Characterization and Utilization of Cement Kiln Dusts (Ckds) As Partial Replacements of Portland Cement

Characterization and Utilization of Cement Kiln Dusts (CKDs) as Partial Replacements of Portland Cement

Om Shervan Khanna

A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy Department of Civil Engineering University of Toronto

Characterization and Utilization of Cement Kiln Dusts (CKDs) as Partial Replacements of Portland Cement Doctor of Philosophy, 2009

Om Shervan Khanna Department of Civil Engineering University of Toronto

Abstract

The characteristics of cement kiln dusts (CKDs) and their effects as partial replacement of Portland Cement (PC) were studied in this research program. The cement industry is currently under pressure to reduce greenhouse gas (GHG) emissions and solid by- products in the form of CKDs. The use of CKDs in concrete has the potential to substantially reduce the environmental impact of their disposal and create significant cost and energy savings to the cement industry.

Studies have shown that CKDs can be used as a partial substitute of PC in a range of 5 – 15%, by mass. Although the use of CKDs is promising, there is very little understanding of their effects in CKD-PC blends. Previous studies provide variable and often conflicting results. The reasons for the inconsistent results are not obvious due to a lack of material characterization data. The characteristics of a CKD must be well-defined in order to understand its potential impact in concrete.

The materials used in this study were two different types of PC (normal and moderate sulfate resistant) and seven CKDs. The CKDs used in this study were selected to provide a representation of those available in North America from the three major types of cement manufacturing processes: wet, long-dry, and preheater/precalciner. The CKDs have a wide range of chemical and physical composition based on different raw material sources and technologies. Two fillers (limestone powder and quartz powder) were also used to compare their effects to that of CKDs at an equivalent replacement of PC.

ii The first objective of this study was to conduct a comprehensive composition analysis of CKDs and compare their characteristics to PC. CKDs are unique materials that must be analyzed differently from PC for accurate chemical and physical analysis. The present study identifies the chemical and physical analytical methods that should be used for CKDs. The study also introduced a method to quantify the relative abundance of the different mineralogical phases within CKDs. It was found that CKDs can contain significant amounts of amorphous material (>30%) and clinker compounds (>20%) and small amounts of slag and/or flyash (<5%) and calcium langbeinite (<5%). The dissolution of ionic species and composition of the liquid phase play an important role in PC hydration. The dissolved ion contributions from CKDs were compared to PC using dilute stirred suspensions at 10 minutes and it was found that the ion contributions from CKDs are qualitatively the same as the ion contributions from PC, with the exception of chloride ions.

The second objective was to utilize the material characterization analysis to determine the relationships among the composition properties of CKD-PC blends and their effects on fresh and hardened properties. The study found that CKDs from preheater/precalciner kilns have different effects on workability and heat evolution than CKDs from wet and long-dry kilns due to the presence of very reactive and high free lime contents (>20%). The blends with the two CKDs from preheater/precalciner plants had higher paste water demand, lower mortar flows, and higher heat generation during initial hydrolysis in comparison to all other CKD-PC blends and control cements. The hardened properties of CKD as a partial substitute of PC appear to be governed by the sulfate content of the CKD-PC blend (the form of the CKD sulfate is not significant). According to analysis of the ASTM expansion in limewater test results, the CKD-PC blend sulfate content should be less than ~0.40% above the optimum sulfate content of the PC. It was also found that the sulfate contribution of CKD behaves similar to gypsum. Therefore, CKD-PC blends could be optimized for sulfate content by using CKD as a partial substitute of gypsum during the grinding process to control the early hydration of C 3A. The wet and long-dry kiln CKDs contain significant amounts of calcium carbonate (>20%) which could also be used as partial replacement of limestone filler in PC.

iii Acknowledgments

I wish to express my sincere gratitude to Professor Doug Hooton, my supervisor, for his excellent guidance and invaluable advice during this investigation. Thanks are also due to Professor Hooton for the facilities extended to me at University of Toronto.

This project was initiated by the Products and Quality Department of Lafarge North America Centre for Technical Services in Montreal under the guidance of Mr. Bruce Blair, Dr. Anik Delagrave, and Ms. Claude Lauzon. Acknowledgement is made of their generous assistance and valuable cooperation throughout the research program. I wish to extend my deepest thanks and appreciation to Dr. Laurent Barcelo of Lafarge North America for his helpful suggestions and interest in this investigation. Dr. Barcelo also reviewed this manuscript during the preparation of the dissertation. Thanks are also extended to these Lafarge personnel who shared their technical knowledge and expertise via personal meetings and/or email exchanges: Dr. Jean Philippe Perez, Dr. Ellis Gartner, and Mr. Paul Lehoux. Thanks are due to Lafarge laboratory technicians Rino Lisella and Patricia Martin who shared their expertise and helped in preparing many of the specimens. Thanks also to the many other laboratory researchers and staff of Lafarge for providing assistance: Mr. Denis Belanger, Mr. Denis Leblanc, Ms. Sona Babikan, Mr. Claude Verville, Ms. Julie Morissette, Ms. Lorraine Phang, and Mr. Bernard Brochard.

Thanks are also due to my colleagues at the University of Toronto. I wish to extend my gratitude to Dr. Terry Ramlochan for providing technical advice periodically throughout the course of this project, particularly with the CKD phase quantification. I would also like to acknowledge the help provided by other members of the Concrete Materials Group: Dr. Gustavo Julio-Betancourt for his helpful discussions, and Ms. Ursula Nytko and Ms. Olga Perebatova for providing guidance and help with the materials and equipment. Thanks are also due to Dr. S. Petrov from the Department of Chemistry for assisting with the CKD phase quantification and Mr. Dan Mathers from the Department of Chemistry for his help in analyzing some of the solution samples.

iv Sincere thanks to my supervising committee members Dr. Brenda McCabe and Dr. Murray Grabinsky for their insightful questions and comments while the thesis was in progress. I would also like to thank Dr. Daman Panesar for very supportive discussions during my Ph.D and reviewing this dissertation.

Further, the author is indebted to Lafarge North America, the Natural Sciences and Engineering Research Council (NSERC), and the Ontario Graduate Scholarship (OGS) Program for providing financial support throughout the project.

My thanks are also due to my wife, children, and family members for their support and understanding throughout the course of this project.

v Table of Contents

1.0 INTRODUCTION ...... 1 1.1 Background...... 1 1.2 Problem Statement...... 2 1.3 Incentives and Objectives of This Study ...... 4 1.4 Summary of Chapters ...... 6

2.0 LITERATURE REVIEW ...... 8 2.1 CKD Manufacture and Management...... 8 2.1.1 Portland Cement Manufacture Overview ...... 8 2.1.2 CKD Generation ...... 17 2.1.3 Fresh and Landfill CKD...... 20 2.1.4 CKD Applications: Cement Industry Perspective ...... 21 2.1.5 Costs Associated with CKD Disposal...... 22 2.1.6 CKD Environmental Considerations ...... 23 2.2 CKD and Portland Cement ...... 24 2.2.1 Chemical Properties...... 24 2.2.2 Mineralogical Properties...... 26 2.2.3 Physical Properties...... 29 2.2.4 CKD Types ...... 32 2.2.5 Variability of CKD from a Single Plant ...... 34 2.3 Portland Cement Hydration ...... 35 2.3.1 Initial Hydrolysis ...... 37 2.3.2 Induction ...... 38 2.3.3 Acceleration...... 39 2.3.4 Deceleration...... 40 2.3.5 Slow Continued Reaction ...... 41 2.4 Effects of CKD Properties and PC Dilution ...... 41 2.4.1 Calcium Carbonate...... 41 2.4.2 Quartz...... 44 2.4.3 Clays ...... 44

vi 2.4.4 Free Lime and Calcium Hydroxide...... 45 2.4.5 Magnesia...... 48 2.4.6 Sulfate ...... 49 2.4.7 Chloride...... 54 2.4.8 Alkalis...... 57 2.4.9 Clinker Phases...... 58 2.4.10 Physical Properties...... 58 2.5 CKD-PC...... 60 2.5.1 CKD-PC Material Characterization...... 62 2.5.1.1 CKD-PC Chemical Composition...... 62 2.5.1.2 CKD-PC Mineralogical Composition...... 66 2.5.1.3 CKD-PC Physical Composition...... 68 2.5.2 Workability...... 69 2.5.3 Setting Time...... 77 2.5.4 Hydration Kinetics...... 82 2.5.5 Compressive Strength...... 87 2.5.6 Flexural and Tensile Strength...... 103 2.5.7 Volume Stability...... 106 2.5.7.1 Soundness ...... 106 2.5.7.2 Drying Shrinkage...... 108 2.5.7.3 Volume Stability Summary...... 112 2.5.8 Durability...... 113 2.5.8.1 Alkali-Aggregate Reaction ...... 113 2.5.8.2 Steel Corrosion...... 116 2.5.8.3 Permeability...... 121 2.5.8.4 Freezing and Thawing...... 123 2.5.8.5 External Sulfate Resistance...... 125 2.5.8.6 Durability Summary...... 126

vii 3.0 MATERIALS AND EXPERIMENTAL DETAILS...... 127 3.1 Materials ...... 127 3.2 Testing of Raw Materials...... 129 3.2.1 Chemical Properties...... 129 3.2.2 Mineralogical Properties...... 129 3.2.3 Physical Properties...... 130 3.2.4 Dilute Stirred Suspensions...... 130 3.3 CKD-PC Blends...... 131 3.3.1 Heat of Hydration ...... 131 3.3.2 Normal Consistency...... 133 3.3.3 Initial Setting Time ...... 133 3.3.4 Flow ...... 134 3.3.5 Compressive Strength...... 134 3.3.6 Expansion in Limewater ...... 134 3.3.7 Autoclave Expansion ...... 135 3.3.8 Alkali Silica Reactivity...... 135

4.0 RESULTS AND DISCUSSION...... 138 4.1 Material Characterization...... 138 4.1.1 Chemical Properties...... 138 4.1.2 Mineralogical Properties...... 144 4.1.3 Physical Properties...... 151 4.1.4 CKD Dissolution Analysis...... 158 4.2 CKD-PC Blends...... 162 4.2.1 Kinetics ...... 167 4.2.1.1 Heat of Hydration ...... 167 4.2.2 Physical Properties of Hydration ...... 195 4.2.2.1 Normal Consistency...... 195 4.2.2.2 Flow ...... 202 4.2.2.3 Initial Setting Time ...... 210 4.2.2.4 Compressive Strength...... 218 4.2.3 Volume Stability and Durability...... 230

viii 4.2.3.1 Expansion in Limewater ...... 230 4.2.3.2 Autoclave Expansion ...... 236 4.2.3.3 Alkali Silica Reactivity...... 242

5.0 MAIN CONTRIBUTIONS OF THE THESIS ...... 246 5.1 CKD Characterization...... 246 5.2 CKD-PC Blends...... 248

6.0 CONCLUSIONS...... 252

7.0 RECOMMENDATIONS FOR FUTURE WORK ...... 254

8.0 REFERENCES ...... 257

ix List of Tables

Table 2.1 Kiln material transformations (Manias, 2004) 12

Table 2.2 Summary of operation data on different kiln systems (Manias, 2004) 13

Table 2.3 Melting points and relative volatiles of different compounds in the kiln burning zone (Manias, 2004) 18

Table 2.4 Typical costs associated with CKD disposal, $/tonne (Kessler, 1995) 23

Table 2.5 CKD chemical oxide composition, free lime, and loss on ignition, and statistical analysis of 63 published datasets (Sreekrishnavilasam et al., 2006) 25

Table 2.6 Portland cement chemical oxide composition, total alkali content, and loss on ignition (Tennis and Bhatty, 2006) 25

Table 2.7 Mineralogical composition of U.S. CKD samples (Hawkins et al., 2004) 27

Table 2.8 Portland cement average bogue compound and Blaine fineness in 2004 (Tennis and Bhatty, 2006) 29

Table 2.9 CKD oxide composition and statistical analysis of intermittent daily samples collected from a single kiln (long-dry process) over a 3 year period (2005 – 2008) in North America (Lafarge, 2009) 34

Table 2.10 Summary of previous CKD-PC studies from literature review 61

Table 2.11 Chemical and physical composition of CKD: from CKD-PC literature review 64

Table 2.12 Chemical and physical composition of PC: from CKD-PC literature review 65

Table 2.13 Mineralogical composition of CKD: from CKD-PC literature review 67

x Table 2.14 Workability: from CKD-PC literature review 76

Table 2.15 Setting time: from CKD-PC literature review 81

Table 2.16 Hydration: from CKD-PC literature review 86

Table 2.17 Mortar compressive strength of CKD 1 at 0%, 5%, and 10% replacement of PC 3 as a function of time (Maslehuddin et al., 2008a) 89

Table 2.18 Compressive strength: from CKD-PC literature review 100

Table 2.19 Flexural and tensile strength: from CKD-PC literature review 106

Table 2.20 Soundness: from CKD-PC literature review 108

Table 2.21 Mortar drying shrinkage with 0%, 5%, and 10% CKD 1 replacement of PC 3 (Maslehuddin et al., 2008a) 110

Table 2.22 Drying shrinkage: from CKD-PC literature review 112

Table 2.23 Alkali-aggregate reactivity: from CKD-PC literature review 115

Table 2.24 Concrete resistivity and risk of reinforcement corrosion as specified in COST 509 (Maslehuddin et al., 2008b) 118

Table 2.25 Steel corrosion: from CKD-PC literature review 120

Table 2.26 Chloride permeability of PC 1 and PC 2 with CKD 1 replacement at 0%, 5%, 10%, and 15% (Maslehuddin et al., 2008b) 122

Table 2.27 Permeability: from CKD-PC literature review 123

Table 2.28 Freezing and thawing cycles: from CKD-PC literature review 125

Table 2.29 Sulfate resistance: from CKD-PC literature review 125

Table 3.1 CKD kiln process description 128

Table 4.1 Melting points and volatility of compounds in CKDs (Manias, 2004) 139

xi Table 4.2 Chemical and select physical components of PC, CKD, and filler materials (mass %) 142

Table 4.3 Cements TI and TII mineralogical composition (mass %) 145

Table 4.4 CKD mineralogical compositions using direct test methods (mass %) 146

Table 4.5 Mineralogical composition of CKD and filler materials (mass %) 148

Table 4.6 Physical properties of all materials 152

Table 4.7 Ionic concentrations of 10:1 water to solid ratio (by mass) 159

Table 4.8 Range for chemical and physical properties of Cement TI blends at 10% and 20% replacement (Theoretical calculation, mass %) 163

Table 4.9 Range for chemical and physical properties of Cement TII blends at 10% and 20% replacement (Theoretical calculation, mass %) 164

Table 4.10 Iterative process to determine the water requirement for normal consistency of (a) Cement TI and (b) Cement TII 195

Table 4.11 Range of change in water demand for normal consistency of pastes 198

Table 4.12 Range of flow for all mortars 204

Table 4.13 Compressive strength range for CKD-PC blends as percent of PC alone 222

Table 4.14 Compressive strength range for PC-filler blends as percent of PC alone 222

Table 4.15 Autoclave expansions for (a) Cement TI and (b) Cement TII 236

Table 4.16 Range of autoclave expansions for all blends 239

Table 4.17 ASR concrete mix alkali loadings and CKD replacement levels for (a) Test Series I: Cement TI CKD blends and (b) Test Series II: Cement TII CKD blends 243

xii List of Figures

Figure 2.1 Cement manufacturing process (Corish and Coleman, 1995) 9

Figure 2.2 Clinker reactions in kiln feed as a function of temperature (Manias, 2004) 12

Figure 2.3 Schematic of (a) a wet and long-dry pyroprocess and (b) a preheater/precalciner pyroprocess (with a single preheater tower) (Manias, 2004) 15

Figure 2.4 Schematic of electrostatic precipitator (ESP) efficiency (Peethamparan, 2002) 19

Figure 2.5 CKD and PC particle size distribution (Peethamparan et al., 2008) 30

Figure 2.6 CKD and PC particle size distribution from published literature (Sreekrishnavilasam et al., 2006) 31

Figure 2.7 Heat evolution of PC paste during hydration stages: (1) initial reaction, (2) induction, (3) acceleration, (4) deceleration, and (5) slow continued reaction (Gartner et al., 2002) 36

Figure 2.8 Relative volumes of the major compounds in the microstructure of hydrating PC pastes as a function of time (Odler, 1998) 36

Figure 2.9 Effect of firing temperature on the heat evolution of pure free calcium oxide during hydration (Shi et al., 2002) 46

Figure 2.10 Heat of hydration of cement paste determined by isothermal conduction calorimetry, (20°C and w/c = 0.44); (a) PC (b) PC + 0.5% SO 3, (c) PC + 2.5% SO 3 (Lawrence, 1998b) Note: Sulfate added as Gypsum (Calcium Sulfate) 51

Figure 2.11 Optimization of gypsum additions for compressive strength at different ages (Gartner et al., 2002) (Note: this PC required higher SO 3 levels than normal to obtain maximum strength) 53

Figure 2.12 Effect of calcium chloride on heat development in PC (Lerch, 1944) 56

xiii Figure 2.13 Relationship between water demand and specific surface area of PC (Sprung et al., 1985) 59

Figure 2.14 Particle size distribution of CKD 5 and PC 7 (Wang et al., 2002) 69

Figure 2.15 Paste water/binder ratio, initial set, and final set of CKD 2 as a partial substitute of PC 4 at different levels of replacement (El- Aleem et al., 2005) 70

Figure 2.16 Mortar water/binder ratio of CKD 2 as a partial substitute of PC 4 at different levels of replacement (El-Aleem et al., 2005) 71

Figure 2.17 Mortar water/binder ratio of CKD 3 as a partial substitute of PC 5 at different levels of replacement (Al-Harthy et al., 2003) 72

Figure 2.18 Hydration of pastes showing (a) evaporable water content (%), (b) free lime content (%) (calcium oxide and calcium hydroxide), and (c) chemically combined water content, as a function of time at different percentage levels of PC 4 replacement with CKD 2 (El- Aleem et al., 2005) 83

Figure 2.19 Concrete compressive strength of CKD 1 at different replacement levels of (a) PC 1 and (b) PC 2 (Maslehuddin et al., 2008b) 88

Figure 2.20 Mortar compressive strength as a function of time at different percentage levels of CKD 2 replacement of PC 4 (El-Aleem et al., 2005) 90

Figure 2.21 Concrete compressive strengths, w/b (a) 0.70, (b) 0.60, and (c) 0.50, at different percentage levels of CKD 3 replacement of PC 5 (Al-Harthy et al., 2003) 92

Figure 2.22 Concrete drying shrinkage as a function of time at different replacement levels of PC 1 with CKD 1 (Maslehuddin et al., 2008b) 109

Figure 2.23 Concrete drying shrinkage as a function of time at two different w/b ratios with 5% CKD 12 replacement of PC 12 (Wang and Ramakrishnan, 1990) 111

Figure 2.24 Concrete specimen variation of electrical resistivity with moisture content at different percentage levels of CKD 1 replacement of (a) PC 1 and (b) PC 2 (Maslehuddin et al., 2008b) 117

xiv Figure 4.1 Process flow chart for CKD chemical composition analysis 140

Figure 4.2 Particle size distribution of PC, CKD and filler. The materials are in the direction and position of the arrow: LS, D, SLX, TII, TI, A, F, C, E, B, D* 155

Figure 4.3 Particle size distribution of PC, CKD and filler between 0.1 µm and 10 µm. The materials are in the direction of the arrow: LS, SLX, C, D, B, A, F, TII, TI, E, D* 155

Figure 4.4 CKD fineness correlation between (a) Blaine fineness and particle size distribution, and (b) percentage passing 45µm sieve and particle size distribution 156

Figure 4.5 Composition of pore solution w/b 0.5 high alkali PC paste (Gartner et al., 2002) 158

Figure 4.6 Schematic of isothermal conduction calorimetry curve heat liberation characterization 168

Figure 4.7 Cumulative heat of hydration during initial hydrolysis (Ai) of (a) Cement TI blends and (b) Cement TII blends (w/b = 0.4, 23°C) 170

Figure 4.8 Cumulative heat of hydration during initial hydrolysis (Ai) as a function of Free CaO (%) for (a) Cement TI CKD blends and (b) Cement TII CKD blends (w/b = 0.4, 23°C) 171

Figure 4.9 Cumulative heat of hydration during initial hydrolysis (Ai) as a function of (a) sulfate content for Cement TI CKD blends and (b) alkali content for Cement TII CKD blends (w/b = 0.4, 23°C) 173

Figure 4.10 Minimum heat of hydration rate during induction period (Qi) of (a) Cement TI blends and (b) Cement TII blends (w/b = 0.4, 23°C) 175

Figure 4.11 Minimum heat of hydration rate during induction period (Qi) as a function of sulfate content for (a) Cement TI CKD blends and (b) Cement TII CKD blends (w/b = 0.4, 23°C) 176

Figure 4.12 Minimum heat of hydration rate during induction period (Qi) as a function of calcium langbeinite content for (a) Cement TI CKD blends and (b) Cement TII CKD blends (w/b = 0.4, 23°C) 177

xv Figure 4.13 Time of minimum heat of hydration rate during the induction period (ti) of (a) Cement TI blends and (b) Cement TII blends (w/b = 0.4, 23°C) 179

Figure 4.14 Time of minimum heat of hydration rate during the induction period (ti) as a function of total alkali content for (a) Cement TI CKD blends and (b) Cement TII CKD blends (w/b = 0.4, 23°C) 180

Figure 4.15 Main hydration peak relative to the minimum peak rate heat of hydration during the induction period (Qw-Qi) for (a) Cement TI blends and (b) Cement TII blends (w/b = 0.4, 23°C) 182

Figure 4.16 Main hydration peak relative to the minimum peak rate heat of hydration during the induction period (Qw-Qi) as a function of calcium langbeinite content for (a) Cement TI CKD blends and (b) Cement TII CKD blends (w/b = 0.4, 23°C) 184

Figure 4.17 Heat of hydration for Cement TI with (a) CKD A and LS at 10% replacements, (b) CKD C and LS at 10% replacements, (c) 0% and LS at 20% replacements, and (d) CKD B and LS at 20% replacements (w/b = 0.4, 23°C) 186

Figure 4.18 Heat of hydration for Cement TI with (a) 0% and LS at 10% replacements and (b) CKD E and LS at 20% replacements (w/b = 0.4, 23°C) 188

Figure 4.19 Heat of hydration for Cement TII with (a) 0% and LS at 10% replacements, (b) CKD C and LS at 10% replacements, and (c) CKD C and LS at 20% replacements (w/b = 0.4, 23°C) 189

Figure 4.20 The total heat generation from induction period to 7 days hydration (A7d-Ai) for (a) Cement TI blends and (b) Cement TII blends (w/b = 0.4, 23°C) 191

Figure 4.21 Water requirement for normal consistency of (a) Cement TI blends and (b) Cement TII blends 197

Figure 4.22 Correlation between Cement TI and Cement TII blends with the same CKD and replacement level for (a) all CKDs and (b) CKDs A, B, C, and D 199

xvi Figure 4.23 Water requirement for normal consistency as a function of free lime content for (a) Cement TI CKD blends and (b) Cement TII CKD blends 200

Figure 4.24 Mortar flow of (a) Cement TI blends and (b) Cement TII blends 203

Figure 4.25 Mortar flow as a function of free lime content for (a) Cement TI CKD blends and (b) Cement TII CKD blends 206

Figure 4.26 Mortar flow as a function of (a) percentage of volume less than 30.5 µm for Cement TI CKD blends (excluding CKDs E and F) (b) percentage passing 45 µm for Cement TII blends (excluding CKDs E and F) 207

Figure 4.27 Initial set time for (a) Cement TI blends and (b) Cement TII blends 211

Figure 4.28 Initial set time as a function of the time of minimum heat rate during the induction period (ti) for (a) Cement TI CKD blends (excluding circled data points) and (b) Cement TII CKD blends 214

Figure 4.29 Initial set time as a function of soluble alkali content for (a) Cement TI blends (excluding circled data points) and (b) Cement TII blends 216

Figure 4.30 Mortar compressive strength of Cement TI blends at 1, 3, 7, 28, and 90 days (w/b = 0.485) for (a) 10% replacement and (b) 20% replacement (w/b = 0.485) 220

Figure 4.31 Mortar compressive strength of Cement TI blends at 1, 3, 7, 28, and 90 days (w/b = 0.485) for (a) 10% replacement and (b) 20% replacement (w/b = 0.485) 221

Figure 4.32 Mortar compressive strength as a function of total sulfate content for Cement TI CKD blends at (a) 1 day and (b) 3 days (w/b = 0.485) 224

Figure 4.33 Mortar compressive strength as a function of total sulfate content for Cement TII CKD blends at (a) 1 day and (b) 3 days (w/b = 0.485) 226

Figure 4.34 Mortar compressive strength at 28 days as a function of percentage passing 45 µm for Cement TI CKD blends 228

xvii Figure 4.35 Mortar compressive strength at 28 days as a function of calcite for Cement TII CKD blends (w/b = 0.485) 228

Figure 4.36 Expansion in limewater after 14 days for (a) Cement TI blends and (b) Cement TII blends 233

Figure 4.37 Expansion in limewater at 14 days as a function of sulfate content for (a) Cement TI CKD blends and (b) Cement TII CKD blends 234

Figure 4.38 Autoclave Expansions for (a) Cement TI blends and (b) Cement TII blends 238

Figure 4.39 Autoclave expansion as a function of free lime content (excluding data points in the circles) for (a) Cement TI CKD blends and (b) Cement TII CKD blends 240

Figure 4.40 ASR expansions over 2 years for (a) Test Series I: Cement TI CKD blends and (b) Test Series II: Cement TII CKD blends 245

xviii List of Appendices

Appendix A. CKD Chemical Composition Correction Calculations Appendix B. PC and CKD TGA Analysis Appendix C. CKD XRD Scans Appendix D. PC, CKD-PC, and PC-Filler Properties Appendix E. Isothermal Conduction Calorimetry Results Appendix F. Mortar Flow Statistical Analysis Appendix G. Mortar Compressive Strength Statistical Analysis Appendix H. Mortar Expansion in Limewater Statistical Analysis

xix

List of Notation

The following notations are commonly used throughout this thesis:

General AAR Alkali-Aggregate Reaction AASHTO American Association of State and Highway Transportation Officials ANOVA Analysis of Variance ASR Alkali-Silica Reaction ASTM American Society for Testing Materials BS British Standard CKD Cement Kiln Dust CSA Canadian Standards Association EPA Environmental Protection Agency (U.S.) ESP Electrostatic Precipitators GHG Greenhouse Gas ISAT Initial Surface Absorption Test LOI Loss on Ignition NCHRP National Cooperative Highway Research Program PC Portland Cement PCA Portland Cement Association PSD Particle Size Distribution SCM Supplementary Cementitious Material TCLP Toxicity Characteristic Leaching Procedure TGA Thermal Gravimetric Analysis XRD X-ray Diffraction

xx Chemical AFm Aluminate-Ferrite-Monosubstituted, Monosulphoaluminate, or Monosulphate AFt Aluminate-Ferrite-Trisubstituted or Ettringite

C3S Tricalcium Silicate or Alite

C2S Dicalcium Silicate or Belite

C3A Tricalcium Aluminate or Aluminate

C4AF Tetracalcium Aluminate Ferrite or Ferrite CH Calcium Hydroxide C-S-H Calcium Silicate Hydrate

Na 2Oe Equivalent Na 2O (Na 2O + 0.658 K 2O) (mass %)

xxi 1.0 INTRODUCTION

1.1 Background There are currently many challenges to the utilization of by-product cement kiln dusts (CKDs) as partial replacement of Portland cement (PC). CKDs are fine powders (CKDs typically have between 80 and 90% passing a 90 µm sieve) that are generated during the cement manufacturing process, then carried off in the flue gases, and subsequently collected in baghouses or electrostatic precipitators. The portion of CKDs that are not returned back to the cement manufacture process, or otherwise used beneficially, are placed in stockpiles or landfills. A limited number of studies have shown that CKDs removed from the cement manufacturing process could be used as partial replacements of PC in the range of 5 – 15%, by mass. Although standards allow for the use of CKDs at low levels of PC replacement, very little is known about the effects of different CKDs in pastes, mortars, and concrete. The studies that have been published on the use of CKDs as a partial substitute of PC often report conflicting results.

Significant amounts of CKDs are placed in landfills every year. In 2000, the Portland Cement Association (PCA) conducted a United States (U.S.) Cement Industry survey of 92 cement plants. They reported total clinker production to be 68.8 million tonnes (clinker is the major component of PC and is typically 90 – 95% of total cement production). The amount of CKDs removed from the cement kiln process that year for the same 92 cement plants was 2.8 million tonnes (4.1% of clinker production). Almost 80% of the CKDs removed from cement-producing kilns were placed in landfills, while only approximately 20% were beneficially re-used (Hawkins et al., 2004). On a global scale, it is estimated that approximately 30 million tonnes of CKDs are removed from the cement manufacturing process every year (Dyer et al., 1999). Approximately 25 years ago, the CKDs in U.S. landfills were estimated to be greater than 90 million tonnes (Collins and Emery, 1983).

There are many applications of CKDs that continue to be investigated: for example, as a component in cements and masonry products, as an agricultural/soil fertilizer, as a soil stabilizer, as a wastewater stabilizer, as a partial replacement of soda in glass production, as an anti-stripping agent in asphalts, and as a subgrade for highway construction (Bhatty, 1995). From the perspective of the cement industry, however, the most desirable application of CKDs that cannot be recycled back into the process is their use as a partial replacement of PC.

1.2 Problem Statement Four obstacles related to CKD compositions currently inhibit their use in concrete: (i) inadequate CKD characterization, (ii) potentially deleterious interactions between CKD and PC, (iii) unknown interactions of CKD with mineral and/or chemical admixtures, and (iv) CKD-PC conformance to cement and concrete standards. The focus of the thesis is to mainly address the first and second categories. Each category is briefly discussed in this section, however, to provide the reader with a broader understanding of the problem.

In order to understand the effects of CKDs in concrete, it is essential to have a proper characterization of an individual CKD. Comprehensive compositional analysis of a CKD is also important for optimization of a CKD-PC blend for use in concrete field applications. Determining the characteristics of the CKDs used in previous CKD-PC interaction studies was not always possible due to the incomplete compositional analysis provided. This is likely due to the insufficient and sometimes inappropriate application of compositional analysis procedures designed for PC to determine the composition of CKD. CKD is a unique material that has different characteristics from PC. In comparison to PC, CKDs typically contain higher concentrations of free lime, alkalis, sulfates, chlorides, raw materials, and trace heavy metals (Hawkins et al., 2004).

2 CKDs can influence the interactions among the basic components of concrete (PC, water, and aggregate). The effects of the individual components found in CKDs at elevated concentrations in concrete are generally understood. The varying concentrations of these components in combination with each other as found in CKDs, however, are not well understood. Therefore, it is not clear how a particular CKD will interact as a partial replacement of a given PC. The composition of each PC can also have unique characteristics. A given CKD may react differently with dissimilar PCs and, therefore, result in different effects on concrete properties. It is important to understand how the CKD-PC interaction will impact concrete properties such as workability, hydration, setting time, strength, volume stability, and durability for optimization of a mix design in the field.

The impact of a CKD in concrete is not limited to its interaction with PC, aggregate, and water. The use of supplementary cementing materials (SCMs) in concrete has been steadily increasing over the years. The presence of a CKD could influence the mechanisms and effectiveness of SCMs and chemical admixtures in concrete. SCMs such as slag, fly ash, and silica fume contribute to the properties of the hardened concrete through hydraulic and/or pozzolanic action (pozzolanic action occurs when a pozzolan combines with calcium hydroxide to exhibit cementitious properties). It has been reported that the high alkali and sulfate content of a CKD can act as an excellent activator for pozzolanic materials (Konsta-Gdoutos and Shah, 2003).

Chemical admixtures are also commonly used in concrete mixtures. Chemical admixtures can be defined as materials other than water, aggregates, and hydraulic cement that are added immediately before or during mixing of concrete. The most prominent chemical admixtures are used to decrease the quantity of water needed to obtain a given degree of workability or to entrain air in order to increase the resistance of concrete to damage from freezing (Taylor, 1997). Chemical admixtures can also be used to increase workability by dispersion of cement in the aqueous phase of concrete and to accelerate or retard the

3 normal rate of hydration (Dodson, 1990). There is little, if any, published research on the interaction of CKDs and PC with chemical admixtures.

Cement and concrete standards include limitations on the chloride, sulfate, and alkali content in PC and concrete to ensure acceptable performance and durability. If it is shown that the elevated concentrations of these components in CKDs do not compromise performance and durability in concrete, regulatory standards may need to be modified to allow for increased amounts of their replacement of PC. In order to allow for the use of industrial by-products such as CKDs, there is a move away from prescriptive or compositional standards towards performance standards. ASTM C150 allows the use of processing additions meeting the requirements of ASTM C465 for use in the manufacture of hydraulic cements.

1.3 Incentives and Objectives of This Study The use of CKDs as a partial replacement of cement has the potential to substantially reduce the environmental impact of CKD disposal and create significant cost and energy savings to the cement industry. From an environmental perspective, CKD removal from the cement manufacturing process leads to excessive generation of gas emissions and increased need for land disposal sites. Partial substitution of PC with CKDs would decrease the need for clinker production and reduce the amount of energy wasted due to partial pyropressing of CKDs. A reduction of clinker production would also reduce greenhouse gases that are related to fuel burning and limestone decarbonation. As environmental concerns increase, it is also important to recognize that obtaining landfill permits is becoming increasingly difficult. The use of CKDs as a partial replacement of cement could help minimize the size and number of landfill disposal sites.

In addition to the environmental benefits related to CKD-PC blends, reducing the clinker factor in cement would also create several financial benefits. First, the lifespan of the limestone quarry and other natural resources would increase. Second, the reduction of

4 raw materials required for PC production would reduce material costs and energy consumption related to mining, crushing, and grinding. Third, a reduction of clinker production would reduce pyroprocess, dust collection, and landfill disposal costs. Fourth, since the CKD is already a fine powder, there will be less energy consumption in the finish mill to achieve the target fineness compared to the energy needed to interground clinker. Finally, the typical transport costs for other materials used for blend cements would not be incurred since CKD is generated on the same site as the PC. It is important to acknowledge that the cement and concrete industry may need to incur costs related to building and maintaining systems that allow for blending of CKD with cements that meet quality control targets.

The study of CKD as a partial replacement of PC has been a sporadic research area for the past 30 years. The concrete industry has been very successful in utilizing other industrial by-products – such as slag, fly ash, and silica fume – as partial replacements of PC. Once considered to be waste products, these SCMs are now widely used to improve the workability, strength, and durability characteristics of concrete. Although there are many studies that report the effects of different binary and ternary blends of CKDs with PC, silica fume, fly ash, and/or slag, it is very difficult to make conclusions regarding performance due to conflicting results and incomplete CKD characterizations. The reasons for the different effects of CKD-PC blends have not been thoroughly explored.

The interaction between different CKDs and PC must be well understood before introducing chemical admixtures and other SCMs. Understanding the CKD-PC interactions and developing appropriate limits for specific deleterious components could ultimately allow for the standardization and optimization of blended cements with high replacement levels (5 – 15%, by mass) of PC with CKD in concrete, leading to both environmental and economic benefits.

5 The first objective of this study was to compare the chemical, physical, mineralogical, and rapid ion dissolution properties of different CKDs with PC. Since there is a lack of proper CKD characterization in previous CKD-PC blend research, the present study aims to identify the appropriate chemical and physical analytical methods that should be used for CKD composition analysis. Mineralogical composition analysis is a fine complement to chemical composition analysis since the effects of CKD elements in a CKD-PC blend may vary depending upon the form in which they actually exist. Therefore, a method to quantify the relative abundance of the different mineralogical phases within CKDs was introduced. Since the availability of ions in the liquid phase greatly influences PC hydration, the rapid ion dissolutions from CKDs compared to PC were also investigated.

The second objective was to utilize the material characterization analysis to determine the relationships among the composition properties of CKD-PC blends and their effects on hydration, mechanical properties, and volume stability. Paste and mortar tests were used to assess the effects of CKDs on: (i) heat of hydration, (ii) water demand, (iii) flow, (iv) initial setting time, (v) compressive strength, (vi) expansion in limewater, and (vii) autoclave expansion. Regression analysis was performed where possible to examine the relationships among CKD-PC blend properties and various independent variables. Additionally, concrete prisms were used to evaluate the impact of CKDs on a key durability concern – alkali silica reactivity (ASR).

1.4 Summary of Chapters The topics addressed in this study are presented in eight chapters. A brief summary of Chapters 2 to 8 is given below.

Chapter 2 is a literature review that provides an understanding of CKD manufacture and management; a basic understanding of CKD composition and its variability relative to PC; a review of PC hydration and the known effects of the individual components of CKDs in pastes, mortars, and concrete; and a review of previous studies on CKD-PC

6 interaction. All performance parameters in previous CKD-PC blend studies are presented in order to provide a general overview of the subject, although some aspects are not part of the current study.

Chapter 3 describes the materials and test methods used in the current study. The CKDs selected for this study are representative of those available in North America. Various test methods related to material characterization and CKD-PC performance used for the experimental program are described.

Chapter 4 presents the results and discussions of the current study. The first part of this chapter explores the material characterization and analytical methods used to determine accurate CKD characterizations. The second part of this chapter focuses on the effects and relationships of using CKDs as a partial replacement of PC on heat of hydration, workability, setting time, compressive strength, expansion in limewater, and soundness. Additionally, it also discusses the impact of CKDs on ASR.

Chapter 5 highlights the main contributions of the thesis, giving a thorough explanation of the value of the research that was conducted. In Chapter 6 the conclusions of the thesis are presented.

Chapter 7 provides recommendations for future research that will enhance the use of CKDs in concrete. This research study is a first step towards a comprehensive understanding of how CKD-PC blends can be optimized.

Chapter 8 provides the list of the references that were consulted in the process of research for the thesis.

7 2.0 LITERATURE REVIEW

2.1 CKD Manufacture and Management 2.1.1 Portland Cement Manufacture Overview A critical examination of CKD utilization as a partial replacement of PC cannot be conducted without an understanding of basic cement manufacturing. The composition and variability of a CKD produced at a plant is directly related to the cement manufacturing process at that plant. PC is produced by burning ground mixtures of limestone and other materials up to high temperatures (greater than 1450˚C) in a rotary kiln to form clinker (Manias, 2004). The clinker is cooled and then ground in a finish mill along with a small amount of gypsum to make a gray powder called PC. ASTM C219 defines PC as “a hydraulic cement produced by pulverizing Portland-cement clinker, and usually containing calcium sulfate”. Low levels of mineral additives such as limestone, however, are increasingly common in PC. Clinker consists of predominantly crystalline calcium silicates. Hydraulic means that it sets and hardens by chemical interaction with water. Although every plant has significant differences in equipment design and operation, the chemical and physical transformation of raw materials into PC is essentially the same at all cement plants. The basic steps of cement manufacturing are illustrated in Figure 2.1.

The principal raw mix components that are required for the production of clinker are calcium, silica, aluminum, and iron (Taylor, 1997). C alcium carbonate and argillaceous substances (clay) are naturally occurring raw materials that typically contain the principal chemical elements. Limestone, the most common form of calcium carbonate, is the usual calcium source for cement manufacturing. Other forms of calcium carbonate such as chalk, shell deposits, and calcareous muds can also be used. Clays are essentially hydrous aluminum silicates with complete or partial substitution of magnesium and/or iron in

8 place of aluminum in certain minerals. Alkalis or alkaline earths are also present as essential constituents in clays (Chatterjee, 2004). The natural raw materials are traditionally mined at quarries close to the cement plant. At times, auxiliary raw materials that contain iron, alumina, and/or silica are required in order to achieve the proper raw mix proportion. Blast furnace slag, fly ash, iron oxide, bauxite, and spent catalysts are widely used auxiliary raw materials (Bhatty and Gajda, 2004).

Figure 2.1 Cement manufacturing process (Corish and Coleman, 1995)

A finely ground mixture typically consisting of approximately 75% calcium carbonate, 15% silicon dioxide, 3% aluminum oxide, and 2% iron oxide provides the major components in the raw materials. The raw materials also contain a certain amount of volatiles (less then 5% by mass). Some of these volatiles are alkalis (potassium oxide and sodium oxide), sulfur, and chloride (Taylor, 1997). In addition to the major elements

9 which make up cement, smaller concentrations of almost every other element will be present in the raw materials. Magnesium, titanium, manganese, and phosphorous are common but they are minimized to prevent potentially deleterious effects on cement burning and quality. Minor trace metals can also be present in the raw materials but are also kept at low levels to avoid adverse effects (Bhatty, 2004).

In an open quarry, limestone mining operations begin with removal of overburden (waste rock) by bulldozers to expose the top surface of the limestone. Drills are used to create deep holes close to the open face of the limestone quarry for dynamite placement. The limestone rock is then blasted with the dynamite to reduce its maximum diameter to between approximately 1 and 2 metres. Front-end loaders load the blast rock into trucks or railroad cars to be sent to the crushing system. The primary and secondary crushing systems reduce the limestone size to between approximately 10 mm and 50 mm in diameter (Chatterjee, 2004).

The crushed limestone and other raw materials are fed into a grinding mill to obtain the correct size and composition for the raw mix. In the wet process, the raw materials are mixed with approximately 30 – 40% water during grinding to form a slurry. The composition of earth minerals in limestone and clays can be quite variable and may require substantial blending and analysis to maintain a homogenous mixture. Homogeneity of the raw mix is essential for quality control and plant efficiency. The wet process homogenization system utilizes mechanical and/or pneumatic systems to agitate, blend, and store the homogenized raw mix in cylindrical tanks or basins until it is fed into the pyroprocessing system. The most common homogenization system used for dry process cement plants over the past several decades is the pneumatic system based on the air fluidization method. The homogenized raw mix is commonly referred to as kiln feed (Chatterjee, 2004).

10 The pyroprocess is the focal point of the cement manufacturing process. Rotary kilns are long, cylindrical, and slightly inclined (3 – 4%) furnaces that are lined with refractory bricks to protect the steel shell and retain heat within the kiln (Manias, 2004). The kiln feed is fed into the upper end of the kiln that rotates on its longitudinal axis. The fuels for the kiln are burned at the lower end of the kiln. As the kiln feed enters the pyroprocess the materials are gradually heated to form calcium oxide, which combines with silicon dioxide at temperatures exceeding 1400 oC in the kiln. Alumina and iron act as fluxing agents, lowering the reaction temperature of the mix to a practical firing temperature. Although there are many different kiln system designs, all kiln feed undergoes the same reactions during the pyroprocess to form clinker – the hard pellets that typically range in size from 0.3 to 5.1 cm in diameter. The chemical and physical transformations of the kiln feed to clinker are quite complex, but can be viewed conceptually as the sequential events listed in Table 2.1 (Manias, 2004).

The four major compounds of clinker that constitute approximately 95% of the clinker, by mass are: tricalcium silicate (C 3S) (35 – 65%), dicalcium silicate (C 2S) (10 – 40%), tricalcium aluminate (C 3A) (0 – 15%), and tetracalcium aluminoferrite (C 4AF) (5 – 15%)

(Taylor, 1997). C 3S and C 2S are commonly referred to as alite (impure C 3S) and belite

(impure C 2S), respectively. Alite typically contains 3 – 4% of substituent oxides, the most

significant of which are Fe 2O3, MgO, and Al 2O3. Belite may contain 4 – 6% of substituent oxides of which Al 2O3 and Fe 2O3 are most common (Taylor, 1997). Alite and belite constitute about 65 – 75% of PC and the combined total content of the four principal clinker compounds in PC is approximately 85%. Cement chemistry

nomenclature abbreviations are as follows: C = CaO, S = SiO 2, A=Al 2O3, and F=Fe 2O3. Several other compounds – such as alkali sulfate and calcium oxide – are present in minor amounts. Figure 2.2 shows the phase transformation of kiln feed to clinker at different stages within the pyroprocess (Manias, 2004).

Table 2.1 Kiln material transformations (Manias, 2004)

Temperature, ˚C Material Transformation 100 Evaporation of free water 100-300 Removal of adsorbed water in clay materials 450-900 Removal of chemically bound water 700-850 Calcination of carbonate materials

800-1250 Formation of belite (C 2S), aluminates, and ferrites >1250 Formation of liquid phase melt

1330-1450 Formation of alite (C 3S) 1300-1240 Cooling of clinker to solidify liquid phase 1250-100 Clinker cooled in cooler

Figure 2.2 Clinker reactions in kiln feed as a function of temperature (Manias, 2004)

12 The pyroprocess is the most energy intensive component of the overall manufacturing process. The most commonly used fuels are coal, natural gas, and oil. Coal can contain significant quantities of sulfur, trace metals, and other halogens that can influence the clinker composition as well as kiln operation dynamics. Natural gas and oil typically contain less sulfur for an equal amount of calorific energy. The use of supplemental fuels – such as petroleum coke, used tires, impregnated sawdust, waste oils, lubricants, sewage sludge, metal cutting fluids, and waste solvents – has expanded in recent years. Minor trace elements from these supplemental fuels can influence clinker composition and kiln performance (Greco et al., 2004).

The pyroprocess at each cement plant can differ substantially depending on the state of technological advancement and the raw materials used. The three major types of kiln pyroprocessing for cement manufacturing in North America are: wet, long-dry, and preheater/precalciner. The main kiln design, production, and energy consumption characteristics for each process are provided in Table 2.2. An important common aspect of different cement pyroprocesses is the presence of the burning zone where the flame temperatures exceeds 1400 oC (Manias, 2004).

Table 2.2 Summary of operation data on different kiln systems (Manias, 2004)

Specific Fuel Residence Consumption, Time Kiln Systems rpm tpd/m 3 Length/Diameter kcal/kg kWh/t minutes Wet 1 0.45-0.8 30-35 1300-1650 17-25 180-240 Long-dry 1 0.5-0.8 30-35 1100-1300 20-30 180-240 Preheater 2 1.5-2.2 14-16 750-900 25 30-40 Precalciner 3.6 3.5-5.0 10-14 720-850 25 20-30 rpm: revolutions per minute tpd/m 3: clinker produced in tonnes per day cubic metre kWh/t: electric energy consumed in kilowatt hour per tonne of clinker

13 In the wet and long-dry processes the entire pyroprocess occurs in the kiln, as shown in Figure 2.3(a). In the wet process the raw materials are introduced to the kiln as slurry containing 30 – 40% water, which results in a relatively high energy consumption (El- Sayed et al., 1991). The kiln usually has a system of chains near the feed end of the kiln to improve heat transfer from hot gases to the solid materials. Kiln rotation allows the chains to be exposed to the hot gases, and they transfer heat to the cooler materials at the bottom of the kiln. The long-dry kiln process is a newer technology than the wet process; while both processes are similar, the long-dry kiln feed is dry. The long-dry kiln process is the most widely used process for clinker production today and is more energy efficient than the wet process (Manias, 2004).

Due to higher energy prices and improved technology, the design of long-dry kiln systems has evolved into a process consisting of a preheater with a number of cyclone stages (five or, in modern kiln systems, even six) to promote heat exchange between the hot kiln exit gases at 1000°C and the incoming dry kiln feed, as shown in Figure 2.3(b). Calcination (decarbonation) is the decomposition of calcium carbonate to free calcium oxide. The material entering the rotary kiln section is already at around 800°C and partly calcined (20 – 30%) with some of the clinker phases already present. The improved heat transfer allows the length of the kiln to be reduced, relative to the length of kilns in the wet and long-dry kiln processes. In recent decades, the precalcination technology has also been introduced as an energy saving measure and is a modification of the preheater process. In the precalciner process, the combustion air for burning fuel in the preheater no longer passes through the kiln, but is taken from the cooler region by a special tertiary air duct to a specially designed combustion vessel in the preheater tower. Typically, 60% of the total fuel is burnt in the calciner, and the kiln feed is more than 90% decarbonated before it reaches the rotary kiln section allowing for increased efficiency (Manias, 2004).

(a)

(b)

Figure 2.3 Schematic of (a) a wet and long-dry pyroprocess and (b) a preheater/precalciner pyroprocess (with a single preheater tower) (Manias, 2004)

15 The final component of all pyroprocess systems is the clinker cooler. The most common types of clinker coolers are rotary, planetary, and reciprocating grate. The clinker is cooled from approximately 1250°C to 100°C by ambient air. The air passes through the bed of clinker and then passes into the kiln for use as combustion air. Clinker that is cooled rapidly typically results in a higher quality clinker (Peray, 1986).

The last step of PC manufacturing is the blending and grinding of clinker and up to 5% – 6% calcium sulfate in a ball or tube mill (finish mill). Calcium sulfate, typically in the form of gypsum and/or natural anhydrite, is generally acquired from a source external to the cement plant. The finish mill reduces the size of the clinker and calcium sulfate to a maximum diameter of 100 micrometers and co nsumes a large portion of the electric energy in the cement manufacturing process (30 to 50 kWh/ton of cement). The total electric energy consumption to make PC is between 110 and 130 kWh/ton of cement. (Hawkins et al., 2004).

CKDs are removed from the pyroprocess mostly for quality control and/or stable operation of the kiln (CKD removal from the pyroprocess is discussed in further detail in the following section). The U.S. cement plant average rate of CKD removal from the manufacturing process has been reported to be 11.5% of clinker production for wet kilns, 10.5% of clinker production for long-dry kilns, and 4.0% of clinker production for preheater/precalciner kilns (EPA, 1993). It appears that the development of preheater/precalciner systems has resulted in significantly lower amounts of CKDs removed from the pyroprocess per tonne of clinker relative to the wet and long-dry kiln processes.

16 2.1.2 CKD Generation CKDs are a fine by-product of the PC rotary kiln production operation that is captured in the air pollution control dust collection system. As kiln feed travels through the kiln, the finest particles of the raw materials, partially processed feed, and components of the final product are entrained in the combustion gases flowing countercurrent to the feed. The particulates and combustion gas precipitates that are removed from the gas stream by air pollution dust collection systems are collectively referred to as CKD (Hawkins et al., 2004).

Many cement plants return all or a portion of the CKD from the dust collection system to the pyroprocess with kiln feed or at mid-kiln with dust scoops. The most desirable application of CKDs is to introduce as much as possible back into the clinker production cycle. The CKDs that are not returned as a pyroprocess input or otherwise used beneficially are placed in landfills (Hawkins et al., 2004). Although it is difficult to quantify a direct correlation between dust generation and plant operation, the amount of CKD generated strongly depends upon the type of process and design of gas velocities in the kiln. Other factors include kiln feed composition, fuel composition, kiln operation, and type of dust collection system (Bhatty, 1995).

The raw materials and fuel inputs can have a significant impact on the chemical composition and amount of CKD removed from the pyroprocess. If the raw material and/or fuel inputs contain substantial amounts of volatiles (sodium, potassium, chloride, and/or sulfur), a higher quantity of CKD will likely be generated in the pyroprocess. These elements partially or completely volatilize in the sintering/burning zone close to the flame and are collected in the gas stream flowing counter-current to kiln feed (Hawkins et. al., 2004). Some of the volatile compounds cannot readily exit the pyroprocess with the gas stream because they condense in the cooler parts of the system. As volatile compounds pass through the melting, vapourizing, and condensing cycle, their concentration in the pyroprocess can increase to the point where they can be

17 catalysts for undesirable coating buildup and ring formation in the kiln. The melting points and relative volatilities of common kiln volatile compounds are shown in Table 2.3. Materials that volatilize in the burning zone will tend to accumulate onto the surfaces of smaller particles of kiln feed in the cooler parts of the pyroprocess or remain in the gas stream and be collected in the dust collectors as a CKD (Manias, 2004).

Table 2.3 Melting points and relative volatiles of different compounds in the kiln burning zone (Manias, 2004)

Volatile Compounds Melting Point, ˚C Range of volatility*, %

CaCl 2 772 60 to 80 KCl 776 60 to 80 NaCl 801 50 to 60

Na 2SO 4 884 35 to 50 K2SO 4 1069 40 to 60 CaSO 4 1280 --- *Range of volatility: % of compound that will volatilize at melting point

The location at which a CKD is extracted from the pyroprocess also has an impact on its characteristics. For example, preheater and precalciner kilns typically extract the CKDs with an alkali/chloride bypass system that is located between the preheater tower and the kiln feed end of the rotary kiln. The temperatures in this region are very different from the temperatures that CKDs are exposed to in the wet and long-dry kiln processes and this gives it unique characteristics. In the bypass system, a portion of the kiln exit gas stream is removed and quickly cooled by air or water to condense the volatiles to fine particles (Manias, 2004).

18 The CKD particles in the kiln exit gas stream of all pyroprocess are removed by dust collection systems. Common kiln dust collection systems include electrostatic precipitators (ESPs), baghouses, and cyclones. Kiln processes equipped with ESPs separate the CKD in multiple electric fields as illustrated in Figure 2.4. The CKD collected in the subsequent fields are generally smaller in size and tend to have higher concentrations of volatiles than the coarser CKD particles. Therefore, it is possible to return the less volatile CKD from the first fields to the pyroprocess and remove the more volatile CKD in the last fields. Baghouses and cyclones do not allow for segregation of CKD based upon volatile concentration.

Figure 2.4 Schematic of electrostatic precipitator (ESP) efficiency (Peethamparan, 2002)

19 There are three major reasons for removal of CKD from the pyroprocess (Kessler, 1995). First, clinker quality must be maintained. For example, the level of alkalis, chlorides, and/or sulfates in the raw materials may be higher than the quality control targets and, therefore, a portion of CKD would need to be removed to reduce the concentration of volatiles. Second, a portion of CKD may need to be removed to maintain stability of the kiln process. As previously discussed in this section, volatiles at high concentrations in the kiln can cause severe material build-up. This can lead to challenging operational problems such as instability, production loss, and blockage, even to the point where the kiln must be shut down (Peray, 1986). The third major reason for removal of CKD from the pyroprocess is due to the lack of a mechanism to return the CKD to the kiln. This is more prevalent in wet process cement plants that were designed and built when the manufacturing challenges and costs associated with recycling CKD back to the kiln from the dust collection system were greater than the costs of removing CKD from the pyroprocess and placing it in landfills.

2.1.3 Fresh and Landfill CKD Fresh CKDs are generally difficult to handle because of their fine, dry, powdery nature and caustic characteristics. The addition of water to mitigate blowing and dusting problems during transport of fresh CKDs to landfills is common. Adding water at this stage can cause hydration of the free lime and significantly reduce possible cementitious potential for other applications. CKD landfills normally represent many years of cement production. They are usually found in very large above-ground stockpiles or backfill quarries. The surface of the landfill site typically crusts over and becomes hard while the interior of the pile can stay relatively loose. Some of the interior material can remain unhydrated, even after many years, if exposure to moisture is limited. CKD landfills are usually located relatively close to the cement manufacturing plants and vary in age and composition. Exposure to the elements (moisture in particular) reduces the chemical reactivity of the kiln dusts thereby making landfill CKD composition very different from that of fresh CKD.

Fresh CKD and landfill CKD should be assessed independently for their potential use as a partial replacement of PC. Changes in composition can occur when CKDs are subject to weather conditions and compaction procedures. In addition to converting lime to calcium hydroxide, exposure to the natural environment could also decompose calcium langbeinite into syngenite and gypsum. The particle size of a CKD can also change due to hydration and compaction. These changes could have large effects on the hydration of a CKD-PC blend.

There are large amounts of CKDs in stockpiles and landfills that are a potential source for CKD applications. The process of utilizing landfill CKDs, however, can be very challenging. Landfill CKDs will often harden and require crushing and screening equipment to remove over-sized pieces as well as any waste that may have become combined with the CKDs.

2.1.4 CKD Applications: Cement Industry Perspective The cement industry has a keen interest in finding practical applications for CKDs in order to reduce costs and environmental concerns related to managing their removal from the pyroprocess. ASTM D5050 lists several beneficial applications of CKD that include: soil fertilization, soil stabilization, raw material for glass manufacture, sewage and wastewater treatment, and waste pollution control.

Although there have been significant developments in the use of CKDs, large amounts continue to be placed in landfills each year. Researchers continue to investigate the use of CKDs in several fields. In particular, the use of CKDs as a partial replacement of traditional construction materials continues to be an area of active interest. A number of researchers have investigated the use of CKDs for subgrade consolidation for highway construction, cement and masonry products, contaminated soil and sludge stabilization, and partial replacement of asphalt. Most of the previous research on CKD applications

21 has been conducted using fresh CKDs while the issue of using CKDs from landfills and stockpiles has not been explored in great detail (Sreekrishnavilasam et al., 2006).

From the perspective of the cement industry, the most beneficial utilization of CKDs that are removed from the pyroprocess is as partial replacement of PC. ASTM currently authorizes the use of processing additions, including CKDs, as a partial replacement of PC provided that the blend complies with the requirements of ASTM C150 and ASTM C465. The American Association of State Highway and Transportation Officials (AASHTO) limits the amount of processing addition to 1% of the total blend. Canadian Standards Association (CSA) has similar standards as ASTM, but if the processing addition is above 1% of the total blend, the nature and amount of processing addition in the finished product must be provided. At the time of writing this thesis, the National Cooperative Highway Research Program (NCHRP) 18-11 “Improved Specifications and Protocols for Acceptance Tests on Processing Additions in Cement Manufacturing” is preparing a report recommending that up to 5% of a processing addition can be used as a partial replacement of PC provided that the blend complies with the requirements of ASTM C150 and ASTM C465. (CKDs are one of the processing addition materials assessed as part of the NCHRP study.)

2.1.5 Costs Associated with CKD Disposal The typical costs associated with CKD disposal in the U.S. in 1995 are presented in Table 2.4. The average cost for CKD disposal, adjusting for inflation increases over 13 years at approximately 2.62% per year and converting short tons to tonnes, is $21.60/tonne in 2008 U.S. Dollars. The average annual clinker production of a cement plant in the U.S. is approximately 800,000 tonnes. As an example, the cost of CKD disposal for a U.S. long- dry kiln that produces 800,000 tonnes of clinker and removes CKD at 10.5% of clinker production in 2008 is approximately $1.8 million dollars per year. The cost to manage CKD disposal for a Canadian cement plant under the same conditions is comparable.

22 Table 2.4 Typical costs associated with CKD disposal, $/tonne (Kessler, 1995)

Items Low Average High Raw Material Costs $1.50 $4.00 $5.50 Kiln Feed Costs: Crushing, Conveying, Drying, and Grinding $3.00 $4.50 $6.00 Kiln Fuel Costs: Dust Calcination and Sensible Heat $1.00 $1.50 $2.00 CKD Transport: Conveying, Hauling, and Dedusting $0.50 $1.00 $1.50 Landfill Maintenance: Monitoring, Pile Maintenance, and Closing $1.00 $3.00 $5.00 Total $7.00 $14.00 $20.00

2.1.6 CKD Environmental Considerations The United States Environmental Protection Agency (EPA) has conducted extensive studies on the issues of production of fresh CKDs and management of stockpile and landfill CKDs. Fugitive dust emissions, surface water pollution, and groundwater pollution have been addressed in these studies. In recent years, hazardous waste has been used as a fuel in cement kiln operations. The use of waste materials in cement kiln operations has raised concerns regarding the accumulation of heavy metals in CKD generated by plants that use these alternative materials.

The EPA (1993) has classified CKDs as a non-hazardous material under the Bevill’s Amendment; however, it also stated that the runoff from CKD storage and landfill piles has the potential to generate leachate containing hazardous characteristics. Runoff and precipitation from CKD piles have exhibited pH levels above 12.5, which can be highly corrosive. The EPA has also expressed apprehension regarding uncontrolled transport, storage, and disposal of large volumes of CKDs in uncovered and unlined piles that are easily removed by wind and eroded by water (EPA, 1993). Due to the leachate and fugitive dust concerns, standards and guidelines have been developed for management of CKD stockpiles and landfills.

23 2.2 CKD and Portland Cement A basic understanding of CKD compositions and variabilities is fundamental to any investigation of their use. CKDs never contain just a single component and the range of the components and fineness varies not only with the type of cement kiln operation, but also with the raw materials. The chemical, mineralogical, and physical property differences among CKDs and between CKDs and PC must be well understood in order to understand the potential effects in concrete. CKDs are derived from the same raw materials and pyroprocess as clinker. Since CKDs are only partially burnt (relative to fully burnt clinker), CKD compositions differ from PC (Corish and Coleman, 1995). The fineness of a CKD can also be a factor in its influence on concrete properties and is an additional component to be considered.

2.2.1 Chemical Properties Sreekrishnavilasam et al. (2006) summarized statistics on the chemical oxide composition of CKDs based on 63 published datasets from different cement plants, as shown in Table 2.5. The table presents a statistical analyses of the main oxides present in CKDs as well as the total alkalis (based upon equivalent sodium molar mass), loss on ignition (LOI), and free calcium oxide content (note: free calcium oxide content was not available for all datasets).

The chemical composition of PC is usually given as oxides on a mass percent basis, determined by various analytical tests, such as those in ASTM C114. PC has a typical range for each of the four main oxides: CaO (60 – 66%), SiO 2 (19 – 25%), Al 2O3 (3 –

8%), and Fe 2O3 (1 – 5%) (Taylor, 1997). There are five categories of PC in ASTM C150 with equivalent cement types in CSA: ASTM TI and CSA-GU (normal/general use), ASTM TII and CSA-MS (moderate sulfate resistant), ASTM TIII and CSA-HE (high early strength), ASTM TIV and CSA-LH (low heat of hydration), and ASTM TV and CSA-HS (high sulfate resistant). In 2005, a survey of the 123 cement plants in North America was conducted to determine the chemistry of the different categories of PC

24 manufactured in North America (Tennis and Bhatty, 2006). The data from the 92 cement plants that responded is presented in Table 2.6. The free calcium oxide and chloride contents for PC normally appear in minimal quantities and are therefore, not typically reported. Lawrence (1998a) reported that 132 samples of PC had an average free lime content of 1.24% in a range of 0.03 – 3.68%. PC chloride content is typically less than 0.01%. Tennis and Bhatty (2006) did not present data for TIV, as it is not produced in significant amounts in North America.

Table 2.5 CKD chemical oxide composition, free lime, and loss on ignition, and statistical analysis of 63 published datasets (Sreekrishnavilasam et al., 2006)

Chemical Composition, % fCaO & Loss on Equivalent Alkali Ca(OH) 2 Ignition CaO SiO2 Al 2O3 Fe 2O3 MgO SO 3 Na 2O K2O % % % Average 43.99 15.05 6.75 2.23 1.64 6.02 0.69 4.00 3.32 6.75 21.57 Standard Deviation 8.01 4.74 7.83 1.04 0.68 3.93 1.02 3.01 2.44 7.83 8.50 COV (%) 18 31 116 47 41 65 147 75 74 116 39 Max. 61.28 34.30 27.18 6.00 3.50 17.40 6.25 15.30 11.42 27.18 42.39 Min. 19.4 2.16 0.00 0.24 0.54 0.02 0.00 0.11 0.14 0.00 4.20 COV (%) = Co-variance Equivalent Alkali: Na 2O + 0.658 x K 2O fCaO: free calcium oxide (free lime) Ca(OH) 2: Calcium hydroxide

Table 2.6 Portland cement chemical oxide composition, total alkali content, and loss on ignition (Tennis and Bhatty, 2006)

Chemical Composition, % Loss on Type of Portland Cement (ASTM) Equivalent Alkali Ignition CaO SiO 2 Al 2O3 Fe 2O3 MgO SO 3 % % TI Normal: Average 63.23 20.17 5.07 2.66 2.51 3.26 0.70 1.52 Standard Deviation 1.04 0.66 0.54 0.44 1.02 0.62 0.26 0.48 TII Moderate Sulfate Resistant: Average 63.66 20.85 4.62 3.32 1.98 2.91 0.56 1.39 Standard Deviation 0.84 0.52 0.37 0.40 0.92 0.39 0.26 0.40 TIII High Early Strength: Average 63.33 20.38 4.84 2.86 2.21 3.60 0.61 1.51 Standard Deviation 0.93 0.70 0.64 0.59 0.93 0.55 0.27 0.41 TV Sulfate Resistant: Average 63.85 21.61 3.80 3.87 2.18 2.34 0.45 1.29 Standard Deviation 0.66 0.67 0.35 0.67 0.91 0.28 0.12 0.44

Equivalent Alkali = Na 2O + 0.658 x K 2O

25 The data in Table 2.5 indicates that calcium and silica oxides are the major constituents for CKDs, although these values are lower than what is found for PC in Table 2.6. Free calcium hydroxide can sometimes appear as calcium hydroxide due to exposure to moisture. The CKD combined free calcium oxide and calcium hydroxide contents and LOI are significantly higher than in PC for this dataset. It is also observed that CKDs generally contain higher concentrations of sulfates and total alkalis than PC. These findings are not surprising since volatiles are preferentially drawn towards CKD in the kiln pyroprocess. The alumina, iron, and magnesium concentrations of CKD and PC appear to be similar. The CKDs tend to have higher concentrations of potassium than sodium in this dataset, which is to be expected since there is usually a similar ratio for cement raw materials in North America. Although not included in Table 2.5, chlorides can appear in significant levels in CKDs. In an early study, Haynes and Kramer (1982) reported that 113 CKD samples from 102 cement plants in the U.S had an average chloride content of 0.71% with a range between less than 0.01% to as high as 12.3%.

Similar to other construction materials, PC and CKDs have a wide range of trace metals. Trace metals reported in clinker and CKD analyses are normally present in quantities small enough not to influence the performance of the cement (<0.05%) (Corish and Coleman, 1995). Small quantities of trace metals only leach out of CKDs using vigorous procedures such as the U.S. EPA toxicity characteristic leaching procedure (TCLP) (Corish and Coleman, 1995).

2.2.2 Mineralogical Properties The Portland Cement Association (Hawkins et al., 2004) compiled a mineralogy summary table (Table 2.7) of 113 CKD samples from 102 cement plants in the U.S. by X-ray diffraction using raw data from the research conducted by Haynes and Kramer (1982). Of the 113 CKD samples, 106 had a calcite level greater than 30%, which indicates that the majority of the CKDs were from wet or long-dry kilns (CKDs from preheater and precalciner kilns generally have low calcite and high free lime levels).

26 Additional common minerals found in the 113 CKDs, although to a lesser degree than calcite, were: free lime (CaO), anhydrite (CaSO 4), quartz (SiO 2), dolomite

((CaMg(CO 3)2), mica, and feldspar. Other minerals found in only a number of the

samples were: aphthitalite ((K,Na) 2SO 4), arcanite (K2SO 4), sylvite (KCl), portlandite

(Ca(OH) 2), halite (NaCl), gypsum (CaSO 4.2H 2O), and chlorite

(Mg 3(Si 4O10 )(OH) 2.Mg 3(OH) 6). Althought it is reported that CKDs coming from zones of high temperatures in wet and long-dry kilns often contain silicate compounds (i.e. C2S) (Adaska et al., 1998), it is surprosing that Haynes and Kramer (1982) did not report the presence of PC primary compounds in any of the CKDs.

Table 2.7 Mineralogical composition of U.S. CKD samples (Hawkins et al., 2004)

Alkali chlorides and alkali sulfates in CKDs are of particular interest as they tend to be water soluble and enter solution in the early stages of hydration. Usually potassium is more volatile than sodium in the kiln. The molar ratio of sulfate to water soluble alkalis may indicate which sulfate phases are likely to be present in a CKD. Since chlorides are not always present in the raw materials, very little is discussed in the literature regarding alkali chloride formation in the pyroprocess. Due to the lower volatilization temperature

27 of chlorides as compared to sulfates, it is believed that chlorides will preferentially combine with alkalis before sulfates (Lehoux, 2006).

The formation of the alkali sulfates depends upon the available amounts of the remaining alkali and sulfate ions. Potassium and sulfur have a very high mutual affinity. Alkalis and sulfate will preferentially form the double alkali sulfate, aphthitalite (3K 2SO4.Na 2SO4), and/or the single alkali sulfate, arcanite (K 2SO 4). Arcanite will likely form if there are not

enough available sodium ions to produce aphthitalite. Thenardite (Na 2SO 4) will only likely be present if the amount of sodium is greater than the amount of potassium in the cement raw materials, which is rare in North America. In the cases where sulfate is present in excess of the alkalis, the double salt known as calcium langbeinite

(2CaSO 4.K 2SO 4) will likely form. If there is excess sulfate or a lack of potassium ions,

anhydrite (CaSO 4) may also be present. Anhydrite, although water soluble, does not enter solution as quickly as alkali sulfate compounds. There is no equivalent mineralogical phase for sodium to mimic the potassium in calcium langbeinite (Bhatty, 2004).

The mineralogical composition of PC is most commonly determined using Bogue equations that are described in North American Standards (ASTM C150, AASHTO M85, CSA A3001). The data from the Tennis and Bhatty (2006) survey of the 123 cement plants in North America for average Bogue compound composition and Blaine fineness (surface area) of different PCs is presented in Table 2.8. The remaining 15% of PC composition is the minor compounds that normally consist of gypsum (5%), limestone (5%), magnesia (1%), the sodium equivalent alkali oxides (1%), and free calcium oxide (1%).

28 Table 2.8 Portland cement average bogue compound and Blaine fineness in 2004 (Tennis and Bhatty, 2006)

C3S C2S C3A C4AF Blaine Type of Portland Cement (ASTM) % % % % m2/kg TI Normal 56.9 14.8 8.9 8.2 384 Standard Deviation 4.57 3.71 1.81 1.37 19.3 TII Moderate Sulfate Resistant 56.5 17.1 6.7 10.1 377 Standard Deviation 3.93 3.48 0.88 1.20 20.0 TIII High Early Strength 56.2 16.2 7.8 8.8 556 Standard Deviation 4.13 3.91 2.14 1.80 55.5 TV Sulfate Resistant 57.7 18.4 3.5 11.8 389 Standard Deviation 3.47 3.93 1.17 2.03 42.5

2.2.3 Physical Properties Konsta-Gdoutos and Shah (2003) state that CKDs are generally off-white or light brown in appearance. The limited number of research studies that provide fineness data typically report Blaine fineness, relative density, and/or particle size distribution. The Blaine fineness values of CKDs vary in the literature between 318 and 1400 m2/kg, which is generally higher than the typical range of values for PC, as shown in Table 2.8. Comparing the Blaine fineness values has led some researchers to conclude that CKDs are finer than PC (Lachemi et al., 2008; Wang and Ramakrishnan, 1990; Ravindrarajah, 1982). The relative densities of CKDs have been reported to be typically between 2.6 and 2.8, which is closer to the density of raw material and less than the 3.15 relative density typically assigned to PC (Konsta-Gdoutos and Shah, 2003).

PC consists of individual angular particles that are mostly (approximately 95%) smaller than 45 µm. The average particle size of a PC particle is approximately 15 µm. Peethamparan et al. (2008) presented the particle size distribution for four different fresh CKDs and a Type I PC, as shown in Figure 2.5. CKD-1 (long-dry pyroprocess) and CKD-2 (precalciner pyroprocess) had the finest and coarsest particle size distributions, respectivley. CKD-3 (preheater/precalciner pyroprocess) and CKD-4 (wet pyroprocess) had particle size distributions very similar to that of the Type I PC. CKD-3 and CKD-4

29 had a greater percentage of particles smaller than the PC up to between 10 and 20 µm, but beyond 20 µm there was a smaller percentage of particles smaller than the PC. The

D50 values for the CKDs ranged between approximately 7.5 µm and 30 µm while the D50 value for the PC was approximately 15 µm.

CKD Pyroprocess CKD 1: long-dry CKD 2: precalciner CKD 3: preheater/precalciner CKD 4: wet

Figure 2.5 CKD and PC particle size distribution (Peethamparan et al., 2008)

30 Sreekrishnavilasam et al. (2006) presented the particle size distribution of five fresh CKDs, one PC, two microcements, and one landfill CKD from previous studies, as shown in Figure 2.6. The authors stated that the various CKDs show significant variation

in the mean particle size (D 50 = 2.8 µm to 55 µm) as well as in the gradation (C u = 5 to 25). Each CKD has a greater percentage of particles smaller than the PC between 0 and 8 µm. This shows that the CKDs contain more fine particles (smaller than 8 µm) than the PC. Beyond 8 µm, however, the CKD particle size curves are on both sides of the PC particle size curve.

Figure 2.6 CKD and PC particle size distribution from published literature (Sreekrishnavilasam et al., 2006)

31 2.2.4 CKD Types Inconsistency of any material can inhibit its use in construction applications. In realistic terms, there is no typical or average CKD. The characteristics of CKDs vary from plant to plant depending on the kiln feed composition, kiln design and operation, fuel type, and the type of dust control systems (Hawkins et al., 2004). Therefore, a distinct CKD that is used as a partial substitute of a PC at a given replacement level may perform differently from another CKD that is used as a partial substitute of the same PC at an equivalent replacement level.

The typical composition of CKDs covers a wide range of values as shown in Table 2.5 and Figure 2.6. Despite the fact that PC from cement plants across North America has relatively little variation due to adherence to cement standard specifications, components found in CKDs vary significantly. CKD composition differences among cement plants are due to variations in raw materials, fuels, equipment design, and kiln operations.

As shown in Table 2.5, free calcium oxide content and LOI show large variation in CKDs, although they only appear in minimal amounts in PC. Sreekrishnavilasam et al. (2006) reported that the majority of CKDs in the literature studies have low free calcium oxide contents (less than 5% free calcium oxide for 40 out of 43 samples). This implies that the majority of CKDs in this sample set are from either wet or long-dry kilns. CKDs from the wet and long-dry processes typically have much lower free calcium oxide (free lime) and higher LOI than CKDs from the preheater/precalciner processes (Hawkins et al., 2004). As preheater/precalciner pyroprocesses become more prominent in the cement industry, the number of cement plants generating CKDs with free calcium oxide concentrations greater than 20% will increase.

The concentration of volatiles in CKDs can be influenced by the type of fuel used in the pyroprocess. Coal fuel has more sulfur than oil and gas fuels, which can increase the concentration of volatiles in the pyroprocess. As well, oil and gas fuels tend to volatilize

32 more alkalis as compared to coal fuel. This is perhaps due, at least in part, to the higher hydrogen levels in these fuels, which leads to higher water vapour concentrations in the burning zone. Consequently, CKD from gas or oil fired kilns contain higher proportions of soluble alkalis as compared to those from coal fired kilns (Klemm, 1980).

The variability of CKD particle size distributions can be largely attributed to differences in dust collection systems and pyroprocess technologies. Some dust collection systems are able to separate the fine CKDs from the total CKDs. There are often significant chemical differences between total and separated CKDs, with the finer CKDs usually having higher concentrations of volatiles and a lower free calcium oxide content (Collins and Emery, 1983). CKDs from the bypass of precalciner kilns have also been described to be coarser than CKDs from wet and long-dry kilns (Klemm, 1980).

Bhatty (1984, 1985a, 1985b, 1986) is the only researcher that has studied CKD-PC interaction to categorize CKDs according to their compositions. The CKD classification system used by Bhatty (1985b) was (i) low alkali-low chloride-low sulfate; (ii) low alkali-low chloride-high sulfate; (iii) moderate alkali-low chloride-moderate sulfate; and (iv) high alkali-high chloride-low sulfate. This illustrates the necessity to differentiate CKDs according to their composition in considering their potential impact on cement properties.

33 2.2.5 Variability of CKD from a Single Plant The composition of CKDs not only varies between different cement plants, but CKD can also vary from batch to batch within the same plant (Wang and Ramakrishnan, 1990). It is very difficult to produce a homogenous CKD from the pyroprocess and cement plants do not attempt to do so since a large portion is destined for landfills. Table 2.9 presents summarized statistics on the CKD chemical oxide composition of intermittent daily samples collected from a single kiln (long-dry process) over a 3-year period. Although more variable than PC, the CKDs from a specific cement plant will generally have considerably less compositional variation than the CKDs given in Table 2.5, which are from a wide variety of sources (Corish and Coleman, 1995). As an example, the CKD standard deviation of SO 3 content from the single long-dry process plant is 1.53%, while that from a wide variety of sources is 3.93%.

Component SiO 2 Al 2O3 Fe 2O3 CaO SO 3 MgO K2O Na 2O TiO 2 P2O5 SrO Mn 2O3 Cl Average 14.91 4.11 1.43 43.86 5.78 1.20 2.59 0.13 0.20 0.05 0.06 0.06 0.43 Standard 0.91 0.24 0.13 2.61 1.53 0.22 0.67 0.04 0.01 0.00 0.01 0.01 0.15 Deviation No. of 565 565 565 565 565 565 565 565 565 565 565 565 565 samples

As knowledge regarding the use of CKDs in concrete improves, the cement industry may look to invest in the systems and resources that will be required to produce CKDs with less variability from an individual cement plant. CKDs that will be used as a partial replacement of PC must be handled in a fashion that is similar to conventional PC to ensure a consistent and high quality product (sampling ports for quality monitoring, metering systems, pneumatic handling systems, and silos for storage).

34 2.3 Portland Cement Hydration Any study on the use of CKDs as a partial replacement of PC first requires an understanding of PC hydration. C3S and C 2S both react with water to form calcium silicate hydrate (C-S-H) and calcium hydroxide (CH) (also known as portlandite). The C-

S-H provides most of the strength developed by PC. C3S hydration occurs more rapidly than C 2S hydration. Therefore, C3S provides most of the early age strength while C 2S contributes mostly to the later age strength (Gartner et al., 2002).

The reaction between PC and water is mostly an exothermic reaction that takes place in a sequence of stages. Traditionally, isothermal conduction calorimetry has been used to follow the progression of hydration by monitoring the rate of heat liberation of the cement paste. Most researchers have identified five stages of PC hydration. A typical isothermal conduction calorimetric curve for a Type I PC is shown in Figure 2.7 with the stages of hydration indicated as: (1) initial reaction, (2) induction, (3) acceleration, (4) deceleration, and (5) slow continued reaction (Taylor, 1997). The main hydration peak occurs during stages 3 and 4 and is associated with C 3S hydration that produces C-S-H, the main component that contributes to PC paste strength. The intensity and location of the sulfate depletion peak, characterized by the formation of monosulfate during stages 4

and 5, are normally dependent on the amount of C 3A and sulfate in the cement (Tennis and Kosmatka, 2004). A representation of the relative volumes of the major compounds in the microstructure of hydrating PC pastes as a function of time is shown in Figure 2.8.

C 4

Figure 2.7 Heat evolution of PC paste during hydration stages: (1) initial reaction, (2) induction, (3) acceleration, (4) deceleration, and (5) slow continued reaction (Gartner et al., 2002)

Figure 2.8 Relative volumes of the major compounds in the microstructure of hydrating PC pastes as a function of time (Odler, 1998)

36 It is widely accepted that gypsum is added to PC to control the reaction of C 3A. Most

researchers believe that this allows the setting and hardening to be controlled by the C 3S and water reaction (Gartner et al., 2002). Gypsum and alkali sulfates provide readily

soluble sulfate that surrounds the C 3A and forms ettringite (C3A.3CaSO 4.H 2O32 ). There are other ions that can partially or completely replace sulfate, whereas iron and silica may substitute for alumina. Therefore, ettringite in cement paste should be indicated by the more general AFt (Gartner et al., 2002). The AFt continues to form if sufficient sulfate ions are present in the solution. Once the sulfate is depleted, the remaining C 3A reacts

with the AFt to form monosulphates (AFm). The hydration of the C 4AF forms hydration

products similar to C 3A, both with and without gypsum (Gartner et al., 2002). Without

the presence of calcium and sulfate ions, the C 3A reacts very rapidly with water to

produce calcium aluminate hydrates, such as C3AH 6. The formation of calcium aluminate hydrates at this stage is undesirable as they may cause rapid setting of the PC as a whole (flash set).

Many factors other than the four major components of PC can impact cement paste, mortar, and concrete properties. Besides the clinker composition, the presence of minor oxides may also affect the resultant cement strength. For example, the uptake of elements

(i.e., sulfate or alkali) in the C-S-H formation can occur during hydration of C 3S (Taylor, 1997).

2.3.1 Initial Hydrolysis The first stage of PC hydration is initial hydrolysis. As soon as PC contacts water, an

initial heat peak occurs that mainly involves C 3A, C 4AF, alkali sulfates, free lime, and

calcium sulfates. The C 3A and C 4AF first react very rapidly and exothermally, which results in the contribution of calcium and aluminate ions into solution. Iron is not typically soluble. The aluminate concentration then reduces within seconds due to the precipitation of AFt, which forms a layer over the cement particles. Alkali sulfates, hemihydrates, and gypsum provide the readily soluble sulfates which contribute to AFt

37 formation at this stage. Free lime usually dissolves rapidly and exothermally but the amount varies widely depending upon its reactivity. Reactive free lime in sufficient amounts can lead to portlandite supersaturation (Gartner et al., 2002).

The dissolution of alkali sulfates is very rapid and endothermic. The alkalis enter into solution and reach constant concentration within one minute of hydration. In order to balance the cations and anions in solution as SO 3 begins to combine with other elements to form AFt, the alkali sulfates are replaced by alkali hydroxides which rapidly increase the pH of the solution. Dissolution of calcium sulfate proceeds more slowly (relatively modest amounts dissolve within the first few minutes of hydration) and is mildly exothermic. The rate and amount of calcium sulfate dissolution is affected by its form. At normal temperatures, hemihydrate is the most soluble form of calcium sulfate, dihydrate is less soluble, and anhydrite is the least soluble. PCs that contain high levels of metastable sulfates – such as hemihydrate and calcium langbeinite – often react to form the precipitate phases gypsum and/or syngenite. These phases can lead to observable changes in workability (Gartner et al., 2002).

2.3.2 Induction The second stage of PC hydration is a period of reduced heat evolution after the initial reaction. The lack of heat evolution, however, does not mean there is nothing occurring. The slow formation of early C-S-H and AFt leads to an increase in viscosity. The causes of the induction period and its termination have been the subject of many studies (Taylor,

1997). Many of these studies have used the hydration of C 3S as a model for the hydration of PC. Although there has been much debate, Taylor (1997) stated that the balance of the evidence favours a combination of two hypotheses for the cause and end of induction. The first hypothesis is that the induction phase causes the formation of a protective layer on the C 3S particles, the induction phase ending when this layer is destroyed or rendered more permeable by aging or phase transformation. The second hypothesis states that the

38 rate of reaction in the induction phase is controlled by nucleation and growth of the C-S- H formed in the main reaction; the induction period ends when C-S-H growth begins.

The termination of the induction period coincides with crystallization of calcium hydroxide. The length of the induction period seems to depend upon how quickly the calcium concentration rises to reach the maximum calcium hydroxide supersaturation. This supports the idea that a certain minimum calcium hydroxide concentration is required for the onset of the acceleration stage (Gartner et al., 2002). Setting does not occur during the induction phase unless abnormal setting occurs. Flash set is a common form of abnormal setting and occurs when there is an inadequate supply of calcium and sulfate ions to react with the C 3A, which results in the early formation of monosulfoaluminate (AFm) phases. False set, another common form of abnormal setting, most commonly occurs when there is an excess of sulfate in the liquid phase leading to secondary gypsum formation. A false set paste can be re-mixed to regain its plastic form, while a flash set paste cannot.

2.3.3 Acceleration The acceleration phase of PC typically represents the change from a plastic to rigid consistency (initial and final set) and early strength development. Initial set, as defined in ASTM C150, is the time it takes for the depth of penetration of a needle in paste to be less than 25 mm within 30 seconds. Setting is the formation of a network of partially hydrated cement particles connected by PC hydration products (Nonat, 1994). Therefore, as the water to solid ratio increases, the setting times will also increase. It is generally accepted that initial setting is controlled by the hydration of C 3S. Under normal conditions, initial set and the transition from the induction phase to the acceleration phase are reported to be correlated. The termination of induction will typically not correlate with pastes that undergo abnormal setting (false or flash) since very little heat is evolved during false set. It is important to note that the termination of induction and the beginning

39 of the acceleration are not always well-defined (Gartner et al., 2002). Final setting, as defined in ASTM C150, normally occurs near the mid-point of the acceleration phase.

There is a high rate of heat evolution during this phase. The acceleration phase of C 3S hydration performs very similarly to the acceleration phase of PC. In both instances, the main reaction is the formation of C-S-H and portlandite. It is generally accepted that the rate of hydration in the acceleratory period is controlled by the nucleation and growth of C-S-H. The rapid formation of hydrates leads to solidification and a decrease in porosity. Sulfates, and possibly other ions, are significantly adsorbed and/or entrapped by C-S-H (Gartner et al., 2002). The major heat peak of the PC hydration curve occurs at the end of acceleration (Taylor, 1997).

2.3.4 Deceleration The rate of C-S-H formation and portlandite decreases during the deceleration phase. This results in reduced rate of heat evolution. There is general agreement that the main

reaction (C 3S hydration) makes a transition from chemical control to diffusion control sometime prior to the acceleration peak and continues in the deceleration phase. This is likely due to the precipitation of hydrates surrounding the C 3S particles, although the form of the diffusion barrier is not clear (Gartner et al., 2002).

The sulfate in the liquid solution begins to decline due to continued formation of AFt as well as uptake by the C-S-H. The sulfate depletion typically occurs between 12 and 36 hours and is indicated by a small peak during deceleration. At the time of sulfate depletion there is a conversion of AFt formation to AFm formation. If there is an excess amount of sulfate in the liquid phase and depletion does not occur, AFt will continue to

form until C 3A is depleted.

40 2.3.5 Slow Continued Reaction The continuous strength gain and reduction in porosity of paste, mortar, and concrete occurs during the slow continued reaction phase, but at a continually decreasing rate. Beyond one day, the only ions in solution above concentrations of a few mmol/l are potassium, sodium, and hydroxyl ions. The concentrations of these ions tend to rise slightly approaching a limit after about 28 to 90 days, primarily due to consumption of the fluid phase (from ongoing hydration) (Taylor, 1997). Although the strength and porosity development are important to the long term performance and durability of concrete, hydration studies during this phase are limited (Mostafa and Brown, 2005).

2.4 Effects of CKD Properties and PC Dilution The effects of different CKD-PC blends often provide conflicting and variable results, due in large part to the compositional variability of CKD among different sources. Although the effects of these components in combination and at varying replacement levels are not well understood, there is considerable knowledge of the effects of each individual component at varying replacement levels and dilution of PC. In an attempt to understand the interaction of CKD-PC blends, it is important to appreciate how each component of CKD replacement can individually influence hydration, performance, and durability. In this way, it is possible to appreciate some of the potential effects of CKD. A detailed explanation of the synergistic effects of a combination of the various components within a CKD is beyond the scope of this literature review.

2.4.1 Calcium Carbonate CKDs can consist of up to 50% calcium carbonate. Limestone is the most common form of calcium carbonate in North America. The question of whether limestone additions should be permissible has stimulated a great deal of debate and research. Various national standards have adopted different positions. The European Standard (EN 197) allows up to 35% and North American Standards (CSA, ASTM, and AASHTO) allow up to 5%. CSA will soon allow up to 15% limestone addition. The effects of the limestone as a partial

41 substitute of PC are both physical and chemical (Taylor, 1997). The chemical effects of calcite will be discussed in this section. The physical effects of limestone addition are covered in more detail in Section 2.4.10.

During normal PC hydration, C 3A and calcium sulfate react to form AFt. Sulfate depletion typically occurs before the C 3A consumption is complete, resulting in the conversion of AFt to AFm. The presence of calcium carbonate, however, alters these reactions. First, AFt formation is accelerated in the presence of calcium carbonate (Ramachandran and Zhang, 1986). Second, the conversion of AFt to AFm is delayed or prevented due to the reaction between C 3A and calcium carbonate to form calcium carboaluminates. The formation of calium carboaluminates occurs as some of the sulfate ions are replaced by carbonate ions during C 3A hydration (Vernet and Noworyta, 1992). Bensted (1980) investigated the use of limestone for partial substitution of the gypsum to control the early hydration of C 3A. Although he concluded that sulfate ions are more effective than carbonate ions, Bensted (1980) also stated that it is possible to substitute limestone for up to 50% of the gypsum without a deleterious effect. This has been cited for the optimum sulfate content decrease when limestone addition increases (Cochet and

Sorrentino, 1993). The importance of the reactivity between C 3A and calcium carbonate additions is highlighted by reports that carbonate additions with sulfate resistant cement

(low C 3A) act primarily as an inert diluent (Klemm and Adams, 1990).

Calcium carbonate additions also influence the hydration of C 3S. Taylor (1997) stated that the accelerating effect of carbonates in suitable concentrations appears to be confined

to the initial stage of reaction. The accelerating effect occurs with pure C 3S as well as with PC and is, therefore, associated with the behaviour of that phase. Limestone enhances the rate of formation of C-S-H and CH, probably because it offers nucleation sites for growth. Ramachandran (1988), however, reported that calcium carbonate also forms a complex with the hydrated products of C 3S. More recently, Pera et al. (1999)

42 reported that hydration of C 3S in the presence of CaCO 3 produced calcium carbosilicate hydrate.

Barker and Mathews (1989) reported on the heat evolution of limestone filler cements. Their studies indicated that as the amount of limestone increased, the major heat peak and total amount of heat released both decreased. The time that the major peak appeared, however, was dependent upon the method of limestone-PC blend preparation. Blending the limestone with PC was shown to either have no effect or to retard the time of the major peak, while intergrinding limestone and PC was shown to accelerate the time of the major peak. Hooton (1990) determined the 7-day heat evolution (ASTM C186) for commercially available PCs and limestone-PC blends made from the same clinkers. The author reported that there was no consistent effect of limestone on the total heat of hydration.

Sprung and Siebel (1991) reported reduced water demand with limestone filler cements and attributed this to improved particle packing. Cochet and Sorrentino (1993) stated that the water-reducing action of the fillers is greater for a water to cement ratio (w/c) of less than 0.4, but this effect is dependent upon the quality of the limestone. A limestone from clay rock deposits or soft and porous rock leads to an increase in the water demand and reduces the positive effects of a limestone, discussed in further detail in Section 2.4.3. Researchers have observed that the setting times are marginally reduced as the limestone additions increase (Brookbanks, 1989; Vuk et al., 2001).

Hawkins et al. (2005) assessed the compressive strength data for mortars and concrete made with and without limestone as being up to 6% in PC from various data sources. This data analysis showed that up to 5% limestone addition can provide strengths similar to PCs without limestone. Beyond the 5 – 10 % range of limestone addition to PC, strengths are lower than for PC alone, due to the dilution effect. This effect can be offset to an extent by grinding the limestone-PC blend finer (Sprung and Siebel, 1991).

The presence of calcium carbonate additions may increase the likelihood of thaumasite

(CaSiO 3.CaCO 3.CaSO 4.15H 2O) formation. Thaumasite formation occurs in cold and wet environments by reaction of the C-S-H with sulfates and carbonate ions (Hooton and Thomas, 2002). The thaumasite form of sulfate attack results in the decomposition of the C-S-H and can completely destroy the binding capacity of the cement paste. The conventional form of sulfate attack requires the involvement of C 3A. Sulfate resistant cement (low C 3A), however, does not present any special protection from thauamsite since the attack is in the silicate phase and not the aluminate phase. Although thaumasite can cause severe damage, there are very few cases where it is the primary cause of deterioration (Taylor, 1997).

2.4.2 Quartz CKDs have been reported to contain up to 30% quartz. Quartz is inert (insoluble) and is typically not found in PC. The partial replacement of PC with CKDs may have an impact on cement properties due to the presence of unreactive raw materials within CKD. The physical effects of quartz due to fineness (nucleation and filler effects) are discussed in Section 2.4.10.

2.4.3 Clays CKDs may contain clays or de-hydrated clays, although previous studies have not stated this. PC generally does not contain clays, except those present in mineral additives such as limestone. Since CKDs typically consist of partially decarbonated limestone, clays may be present in CKDs. The presence of clay can lead to an increase in water demand (Cochet and Sorrentio, 1993). The effect on hardened concrete is deleterious to freezing and thawing resistance (Detwiler et al., 1996). Unreacted clay minerals could cause problems in hardened concrete if they swell when exposed to water. There is also a potential for an increase in sorption of certain cations, and no hydration products are generated by clays in the presence of PC (Mattus and Gilliam, 1994). However, heat-

44 treated clays, such as metakaolin, can be pozzolanic. The pozzolanic reaction occurs in the presence of calcium hydroxide and silica from the pozzolan to produce C-S-H, the main PC hydrate that contributes to strength in concrete.

2.4.4 Free Lime and Calcium Hydroxide CKDs generally have higher free limes than PC and have been reported to contain up to 40% free calcium oxide (free lime). A small portion of the free lime in CKDs is sometimes found in the form of calcium hydroxide due to exposure to moisture. Approximately 1.5% or less free lime is generally an advisable quantity for a given PC (Bensted, 1983a). Free lime (uncombined lime) appears in the form of calcium oxide (CaO) in clinker and is typically considered hard burnt. In PC, however, the addition of damp gypsum and use of water spray to control temperature in the grinding mill can hydrate some or all of the free lime to form calcium hydroxide. A large amount of the hard burnt lime is not very reactive chemically towards water, but sufficient calcium and hydroxyl ions are available in the solution phase during PC hydration to enable the various chemical reactions that are influenced by calcium hydroxide to occur (Bensted, 1983a).

The calcium hydroxide formed by the hydration of C 3S and that formed by hydration of free lime are slightly different. The hydration of free lime to calcium hydroxide produces poorly developed crystals that have a lower decomposition temperature using thermal analytical methods such as thermal gravimetric analysis (TGA), differential scanning conduction calorimetry (DSC), or differential thermal analysis (DTA) (Bye, 1999).

The hydration activity of free lime formed at different decarbonation temperatures is variable. The rate of heat evolution of pure free calcium oxide decreases with increase of firing temperature, as shown in Figure 2.9. The difference in microstructure of free calcium oxide fired at various temperatures results in its different hydration activity. When calcium carbonate initially decomposes at approximately 900˚C (Soroka, 1979),

45 the free lime retains its rhombohedral structure of calcite and the crystallite size is small. It is known that reactive free lime (soft burnt lime) can significantly affect the rheological properties of the CKD-PC mixture due to its high affinity for water molecules. With the rise of decarbonation temperature, the crystals of free calcium oxide grow and change to the cubic structure. Industrial free calcium oxide contains small amounts of SiO 2, Al 2O3,

Fe 2O3, and other oxides and, consequently, the hydration reactivity is lower than that of pure free calcium oxide (Shi et al., 2002).

Figure 2.9 Effect of firing temperature on the heat evolution of pure free calcium oxide during hydration (Shi et al., 2002)

46 Gartner et al. (2002) has stated that the presence of free calcium oxide can enhance AFt expansions. It appears that the formation of AFt in the presence of a deficiency of free calcium oxide develops more blocky crystal with much less expansion and can rapidly develop a strong matrix. The presence of calcium hydroxide has been reported to enhance the ability of gypsum to retard the hydration of C 3A (Collepardi et al., 1978; Brown et al., 1984). The delayed formation of AFt and subsequent conversion to AFm has been attributed to the development of a more effective AFt diffusion barrier.

Lime has an important role to play in the initial hydration of PC by supplying calcium ions to the system. Nonat (1994) stated that the lime concentration is the most important parameter during C 3S hydration that determines thermodynamic, kinetic, morphological, and structural formations of C-S-H. Therefore, any change in lime concentration or displacement of the solubility equilibrium of portlandite – such as the addition of calcium salts or alkalis – may change the formation characteristics of C-S-H. Nonat (1994) also reported that the lime concentration in solution determines both the particle interactions and solubility of hydrates that control the origin of setting. The duration of the induction period, however, depends essentially on the number of nuclei of C-S-H precipitated from the solution in its state of maximum supersaturation with respect to C-S-H. Therefore, the lower the lime concentration, the greater the number of nuclei and, as a consequence, the shorter the induction period (Damidot and Nonat, 1992). Since, under normal conditions, initial set and the end of the induction period are reported to have a strong correlation (Gartner et al., 2002), it is likely that an increase in lime concentration would retard the induction period and, hence, the initial setting time. Nonat (1994) also reported that a decrease in the w/b ratio of pastes mixed with saturated limewater shortened the induction period due to the increase in the number of contacts between particles, even though the number of initial nuclei is reduced due to a higher concentration of lime in solution.

47 The free lime that reacts after cement has set will form calcium hydroxide. The volume of calcium hydroxide is greater than the original free calcium oxide, which causes expansion and damages the concrete internally. This type of expansion is called unsoundness (Neville, 1996). Soundness cannot be predicted reliably from the free lime content due to the varying hydration activity of free lime. Soundness issues related to free lime reactivity occur after the paste is set, so it is likely that the hard burnt free lime at high temperatures will cause soundness issues. Soft burnt lime hydrates rapidly before the paste has set and, therefore, does not produce unsoundness.

2.4.5 Magnesia The amount of magnesia oxide in CKDs is characteristically similar to that found in PC. CSA A3001 and ASTM C150 limit the total magnesia content in PC to 6% by mass. Magnesia is mostly present in the main silicate phases of PC, but some may be present as crystalline magnesium oxide (periclase). Similar to free calcium oxide, the reactivity of magnesia oxide depends upon the temperature at which thermal decomposition from magnesium carbonate occurs. At lower temperatures of decomposition (700°C – 1000°C), the magnesia oxide may react with water prior to set, and thus not contribute to expansion in the hardened state. The magnesia oxide in PC that has been exposed to high burning temperatures will react with water slowly over a period of years to form magnesium hydroxide and potentially cause expansion (unsoundness) in the hardened paste (Soroka, 1979). Therefore, the amount of magnesia oxide in CKDs may not be a good indicator of potential unsoundness. The effect of periclase on soundness is also influenced by its particle size and distribution in clinker. Slow cooling of clinker allows large periclase crystals to form such that when these hydrate slowly in concrete, the expansion can cause unsoundness (Manias, 2004). Therefore, rapid cooling of clinker is preferred for smaller and uniformly distributed periclase crystals that have less impact on soundeness (Peray, 1986).

48 2.4.6 Sulfate Most CKDs have higher levels of sulfate in comparison to PC. The sulfates found in

CKDs typically occur as single sulfates (K 2SO 4 and/or Na 2SO 4), apthitalite

(3K 2SO 4.Na 2SO 4), calcium langbeinite (2CaSO 4.K 2SO 4), and/or anhydrite (CaSO 4). The sulfate phases often identified in CKDs are also commonly found in the clinker fraction of PC. Gypsum, which is added to clinker during PC grinding, is the most important source of sulfate in PC. During PC hydration, calcium and sulfate ions are supplied by gypsum to control the reaction of C 3A. Although CKDs do not typically contain gypsum, they could provide readily soluble calcium ions (from free lime and calcium langbeinite) and readily soluble sulfate ions from alkali sulfates during the early stages of hydration. Therefore, the effects of alkalis and calcium in conjunction with sulfate must be considered in this review.

It is generally accepted that the alkali sulfates and combined alkali/calcium sulfates are rapidly (within minutes) dissolved upon hydration, whereas alkalis present in the aluminate, ferrite, and silicate phases are released more slowly (perhaps even over months or years). Sandberg and Roberts (2005) stated that the rate of solubility of the different sulfate forms vary in the following order (highest to lowest rate of dissolution): alkali sulfate and calcium langbeinite > plaster (calcium sulfate hemihydrates) > chemical anhydrite (soluble calcium sulfate anhydrite) > gypsum (calcium sulfate dihydrate) > syngenite > natural anhydrite.

The amount of gypsum addition to PC is very important. The supply of sulfate ions controls the setting and maximizes the early strength development of cement. This

process is disturbed if the renewed hydration of C 3A takes place early. Therefore, it is desirable to suppress the C 3A hydration with an appropriate amount of sulfate so that it does not coincide with the C 3S hydration. The optimum amount of sulfate in PC should

(i) retard C 3A hydration, (ii) inhibit C 3A hydration until C 3S hydration takes place to cause the setting of the cement, and (iii) not form an excessive amount of ettringite to

49 cause deleterious expansion after the cement has set and hardened (Bhattacharja, 1997). Each PC is unique and the optimum amount of gypsum for set control as well as other properties – such as early compressive strength – must be determined individually. It is also important to note that the optimum amount of gypsum is not the same for all performance parameters (Gartner et al., 2002).

Tang and Gartner (1988) reported that the presence of soluble sulfates strongly retards initial C3A hydration. In addition, the chemical and physical form is very important. The interblended mixed alkali/calcium sulfates (calcium langbeinite and syngenite) are more

effective retarders of C 3A than either gypsum or pure alkali sulfates alone. The proposed mechanism takes into account the rate at which the sulfate phases can supply both calcium and sulfate ions to the surfaces of the aluminate phases during early stage hydration. Tang and Gartner (1988) concluded that the use of alkali/calcium double salts increases the rate and chemical potential at which calcium and sulfate ions enter the solution. Single alkali sulfates (K 2SO 4 and Na 2SO 4) and apthitalite (3K 2SO 4.Na 2SO 4), however, are generally not known to be effective retarders of C 3A hydration.

Lawrence (1998b) examined the heat of hydration for a PC with different levels of gypsum addition, shown in Figure 2.10. With 0.5% sulfate addition to the PC, the heat evolution of the aluminate peak that was originally superimposed on the main silicate hydration peak was retarded and weakened, and at 2.5% sulfate addition, the aluminate hydration peak was suppressed. Lawrence (1998b) also observed that the main silicate heat peak is depressed at calcium sulfate levels above optimum.

(a)

(b)

(c) Figure 2.10 Heat of hydration of cement paste determined by isothermal conduction calorimetry, (20°C and w/c = 0.44); (a) PC (b) PC + 0.5% SO 3, (c) PC + 2.5% SO 3 (Lawrence, 1998b) Note: Sulfate added as Gypsum (Calcium Sulfate)

As the amount of gypsum added to a PC increases, the setting time also increases until a level of stability is reached and the setting time becomes insensitive to further additions of gypsum (Frigione, 1983). The hydration of silicate phases is accelerated in the presence of calcium sulfates (Ish-Shalom and Bentur, 1972). The effect of calcium sulfate on compressive strength at various ages of a PC is shown in Figure 2.11. It is clear that the optimum sulfate is different for the three ages of compressive strength. Soroka and Relis (1983) stated that the optimum content in the compressive strength curve for PC at a particular age implies that the addition of gypsum involves two opposing effects. The lower range of sulfate content has a beneficial effect on strength and can be attributed to the allowance of C 3S to hydrate to a beneficial strength by controlling C 3A hydration. The range of sulfate greater than the optimum has an adverse effect on strength. Two suggested mechanisms of excessive sulfate ions are: (i) excessive AFt formation and the associated volume increase cause internal cracking of the hardened paste and (ii) C-S-H formation is accelerated but has lower intrinsic strength due to incorporation of sulfate ions into its structure. Both mechanisms may contribute to the phenomenon caused by excessive calcium sulfate (Gartner et al., 2002).

Abnormal setting behaviour is usually related to chemical reactions involving aluminates and sulfate phases (Gartner et al., 2002). False set generally occurs when there is too much readily soluble sulfate, which can come from plaster and/or alkali sulfates. The liquid phase becomes over-saturated with sulfate and precipitation as secondary gypsum occurs. The crystals of gypsum are needle-shaped and weak, but can still restrict the workability of the mix. It is called false set because upon re-mixing the needles will break-up and the mix will revert to its original consistency. Although not commonly reported, false set may also arise due to precipitation of syngenite or ettringite (Gartner et al., 2002).

Figure 2.11 Optimization of gypsum additions for compressive strength at different ages

(Gartner et al., 2002) (Note: this PC required higher SO 3 levels than normal to obtain maximum strength)

53 Excessive sulfate in PC can also lead to expansion problems due to formation of AFt. The reaction between C 3A and calcium and sulfate ions to form AFt involves increases in the volume of solids. When the appropriate amount of calcium sulfate (optimum sulfate) is present in PC, AFt formation occurs when the paste is plastic and volume increases do not impact the integrity of the paste. At higher levels of sulfate (i.e., greater than optimum sulfate), however, the formation of AFt may take place in the hardened paste and possibly cause expansion and/or cracking (Soroka and Relis, 1983).

2.4.7 Chloride The range of chloride content in CKDs from previous studies is between 0 and 12%. PC, however, generally has less than 0.01% chloride content. The American Concrete Institute (ACI 318) guideline for maximum water soluble chloride ion (Cl -) in concrete, as a percent by mass of cement, is limited to: 1% for reinforced concrete exposed to neither a moist environment nor chlorides, 0.15% for reinforced concrete exposed to a moist environment or chlorides or both, and 0.06% for prestressed concrete.

CKD chloride ions generally appear as alkali chlorides (NaCl and/or KCl). Alkali chlorides are more soluble than alkali sulfates and will enter solution within minutes of hydration. Although calcium chloride in CKDs is rare, it is important to consider its effects as well as those of alkali chlorides. Calcium ions could be present during the early stages of hydration due to the presence of calcium-bearing phases that are readily soluble. Therefore, the effects of alkali and calcium ions in conjunction with chloride ions are also considered in this review. Bhatty (1984) also suggested that the alkali chlorides in CKDs would probably behave similarly to calcium chloride.

Calcium chloride is a highly soluble salt that releases calcium and chloride ions into solution and has long been used to shorten both the setting and hardening time of concrete by accelerating the hydration reactions. Calcium chloride is one of the most effective accelerators of PC pastes but the mechanism is not well understood. A practical

54 dosage is typically between 1 and 2%, by mass of cement, and its acceleration effects increase as the concentration of calcium chloride increases (Juenger et al., 2005). Potassium chloride (KCl) and sodium chloride (NaCl) are less effective accelerators than calcium chloride. At very high concentrations, some salts (such as NaCl) act as retarders of C 3S (Taylor, 1997). Calcium ions are considerably more effective than any other cation in salts used for accelerating hydration, suggesting that a specific effect is superimposed on a general one (Taylor, 1997).

It is well known that the chemical binding of chlorides is influenced by the amount of

aluminate phases. C 3A can react with chlorides to form calcium chloroaluminate hydrate or Friedel’s salt (Taylor, 1990). The presence of sulfate ions in the binder, however, reduces the chloride binding capacity of cement. Holden et al. (1983) attributed the reduction in the chloride binding capacity to the preferential reaction of sulfate ions with

the C3A phase forming AFt. It is generally accepted that chlorides react with C 3A only after AFt formation is complete and sulfate depletion occurs (Taylor, 1997).

The effect of calcium chloride on PC heat evolution is shown in Figure 2.12. The accelerated hydration of PC is indicated by a higher heat liberated at the major peak, the shift of the major peak to the left side, and a narrower curve around the major peak. Early strengths will tend to be higher but the final strengths will be reduced. Shoaib (2002) also stated that the larger amounts of chloride present in CKDs can cause a sort of crystallization of hydration products. The crystallization results in opening the pore system within the hardened samples leading to a reduction in strength. It is well accepted that the acceleration of PC hydration with calcium chloride is mostly due to an acceleration of C-S-H growth. The presence of chlorides is typically associated with higher early strengths (1 and 3 days) and lower later strengths (beyond 28 days). Despite a significant amount of effort to understand the acceleration effect of chloride on PC hydration, however, the detailed mechanism still remains unclear.

Figure 2.12 Effect of calcium chloride on heat development in PC (Lerch, 1944)

The presence of chlorides is a durability concern for steel reinforced concrete. The chlorides that are not bound or that leach from the bound hydrates can contribute to steel corrosion. The corrosion of steel in concrete is an electrochemical process and it is a consequence of this corrosion that the surrounding concrete is damaged (Neville, 1983).

56 2.4.8 Alkalis

The CKD equivalent alkali contents (Na 2O + 0.658 x K 2O) from previous studies range between 0.14 and 11.42%. The equivalent alkali content of PC is typically lower (between 0.5 and 1%). Alkali cations in PC typically occur either as sulfates or in the major clinker phases. The balancing anion sooner or later enters a hydration product of low solubility and an equivalent amount of hydroxyl ion is released (Taylor, 1997). Alkalis (potassium and sodium) in CKD that can greatly impact PC hydration normally occur as readily soluble alkali sulfates and/or alkali chlorides. CKD alkalis can also occur in less soluble form within other mineralogical phases.

In general, soluble alkalis are reported to accelerate hydration at an early age, which is attributed to an increase in the permeability of the layer of hydration product surrounding the alite grains after the reaction has become diffusion controlled (Neville 1983). Set time

may shorten due to the increased C 3S hydration. It is widely reported that increasing alkali content generally increases early strength (1 and 3 days) and decreases late strength (28 day). However, these effects are modified by the gypsum content of PC. Osbaeck and Jons (1980) reported that the alkali effects on strength are diminished or absent at gypsum contents above the optimum sulfate level. Further, Jackson (1998) stated that when alkalis are present as calcium langbeinite (2CaSO 4.K 2SO 4), a reduction in early strength and an increase of the same magnitude of strength at 28 days would not, relative to a PC with less alkali sulfate, be unexpected.

Excess soluble potassium is widely known to precipitate syngenite which may lead to early stiffening and false set. The presence of soluble alkalis can also impact the rate of gypsum consumption and, thus, affects the levels of calcium and sulfate in solution. It has been reported that the optimum gypsum content increases as the alkali content increases. Calcium salts and alkali hydroxides that are both soluble can influence initial dissolution

of C 3S due to the common ion effect (Gartner et al., 2002).

57 Increased alkali content in concrete presents durability concerns (Taylor, 1997). ASR is a reaction between hydroxyl ions and certain forms of silica in aggregate to form ASR gel. ASR gel formation causes durability problems that arise as a result of tensile cracks in concrete. The presence of soluble alkalis can also influence air entrainment in fresh concrete (Greening, 1967). Although the exact nature of this influence has not been determined, it is believed that both the air content and the average size of the air voids tend to increase with the amount of soluble alkalis. This can have an adverse effect on freezing and thawing resistance.

2.4.9 Clinker Phases CKDs can contain some or all of the four major clinker phases. Any changes in the amount of C3A could impact the optimum sulfate balance. Due to the reduced amount of silicates typically found in CKDs relative to PC and assuming all other parameters being equal, the CKD strength gain contribution will be less than the contribution from the replaced PC.

2.4.10 Physical Properties The effect of CKDs as partial replacement of PC can be influenced by the CKD physical properties. The overall particle size distribution of PC and CKDs is called “fineness.” CKDs may tend to have more fine particles than PCs below 8 µm (Section 2.2.3). The densities of CKDs are generally lower than the PC industry standard of 3.15 (Konsta- Gdoutos and Shah, 2003). Consequently, when CKDs are used as a partial replacement of PC by mass, more CKD particles are required to replace the PC, which may affect rheological properties. The fineness of a CKD will likely affect its chemical reactivity, ability to act as a filler material (providing nucleation sites for hydration), and soundness as a partial replacement of PC.

58 There is a strong correlation between fineness of PCs and water demand, as shown in Figure 2.13. As the Blaine fineness (specific surface area) of a PC increases, the water demand also increases, which is likely in part related to increased chemical reactivity during the early stages of PC hydration. Increased Blaine fineness of a CKD may allow it to have more impact on early age hydration in a CKD-PC blend by means of increased ion dissolution. Therefore, a CKD-PC binder that has increased chemical reactivity during early stages of hydration in comparison to the PC alone may also have a higher water demand.

Figure 2.13 Relationship between water demand and specific surface area of PC (Sprung et al., 1985)

CKDs may also contain significant amounts of calcite and quartz, which are both widely known to be fillers (although it is recognized that limestone does chemically react with aluminate phases to form carboaluminates). The presence of fine calcite and quartz particles generally accelerates early PC hydration (Taylor, 1997). Greater fineness of the CKD filler components could increase the hydration rate of the CKD-PC binder, most likely by an increased surface area that also increases the number of active sites for the

59 nucleation of PC hydration products (nucleation effect). Alternatively, CKDs may contain fine calcium carbonate particles that could fill the gaps between the cement particles; improved particle packing of very fine filler has been attributed to reductions in water demand as well as higher compressive strengths (Hawkins et al., 2005; Sprung and Siebel, 1991).

The fineness or specific surface of the PC is one of the factors that influence the autoclave expansion soundness assessment. If all other parameters of a PC are equal, coarser ground cements have always exhibited a greater amount of autoclave expansion (Klemm, 2005). Narang et al. (1981) quantified the effects of PC fineness on autoclave expansion using a high MgO content PC. The PC was initially ground to a fineness of 225 m 2/kg and had an autoclave expansion of 7.06%. When the same PC was ground to a higher fineness of 350 m 2/kg, the autoclave expansion was reduced to 1.39%. At an even higher fineness of 400 m2/kg, the autoclave expansion was reduced to 0.24%. Consequently, a reduction in fineness of a CKD-PC blend in comparison to the PC alone may have an adverse effect on the soundness.

2.5 CKD-PC The study of CKDs as a partial replacement of PC has been an intermittent research area for the past 30 years. A list of the CKD-PC interaction studies, the number of CKD and PC used, CKD replacement levels of PC investigated, the type of specimens used (paste, mortar, and concrete), and the recommended limit of CKD replacement of PC for each study are summarized in Table 2.10. Although these studies have shown that CKDs can be used as a partial replacement of PC in the range of 5% to 15%, very little is known about their exact role in cement paste, mortar, and concrete performance. The studies that have been published on the use of CKDs as a partial substitute for PC often report conflicting effects and mechanisms.

60 This section summarizes the materials, test methods, results, and conclusions of CKD-PC interaction studies conducted over the past 30 years. Performance tests and properties for CKD–PC blends – such as workability and water demand, setting time, hydration, compressive strength, tensile and flexural strength, volume stability, and durability – are presented. In order to focus on understanding the interaction between CKD and PC, the literature review only considers studies of binary mixes.

Table 2.10 Summary of previous CKD-PC studies from literature review

Maximum # of # of % CKD % CKD Replacement Author CKD PC Replacement Tested P / M / C Recommended Maslehuddin et al. (2008b) 1 2 0, 5, 10, 15 C 5% Maslehuddin et al. (2008a) 1 1 0, 5, 10 P, M 10% El-Aleem et al. (2005) 1 1 0, 2, 4, 6, 8, 10 P, M 6% Al-Harthy et al. (2003) 1 1 0, 5, 10, 15, 20, 25, 30 M, C 5% Udoeyo and Hyee (2002) 1 1 0, 20, 40, 60, 80 C N.R. Wang et al. (2002) 1 1 0, 15, 25, 50 P, M 15% Konsta-Gdoutos et al. (2001) 1 1 0, 15, 25 M 15% Shoaib et al.(2000) 1 1 0, 10, 20, 30, 40 C <10% Dyer et al. (1999) 2 1 0, 20, 35, 50, 75 P, M N.R. Batis et al. (1996) 2 1 0, 6 C 6% El-Sayed et al. (1991) 1 1 0, 3, 4, 5, 6, 7, 10 P, M 5% Wang and Ramakrishnan (1990) 1 1 0, 5 P, M, C 5% Ramakrishnan and Balaguru (1987) 1 3 0, 5 C 5% Ramakrishnan (1986) 1 1 0, 5 P, M, C 5% Bhatty (1986) 3 1 0, 10 M N.R. Bhatty (1985b) 4 4 0, 10, 15, 20 P N.R. Bhatty (1985a) 3 1 0, 10, 20 M N.R. Bhatty (1984) 5 5 0, 10, 15, 20 P N.R. Ravindrarajah (1982) 1 1 0, 25, 50, 75, 100 (P) P, C 15% 0, 15, 25, 35, 45 (C) CKD = Cement Kiln Dust; PC = Portland Cement P = Paste; M= Mortar; C = Concrete N.R. = Not Reported

61 2.5.1 CKD-PC Material Characterization To effectively assess the effects of CKD as well as its reaction mechanisms involved as a partial substitution of PC, it is essential to take into account the physical, chemical, and mineralogical properties of both CKD and PC. The impact of CKD in a binary mixture may be affected not only by the characteristics of the kiln dust, but also by the characteristics of the cement.

The composition of CKDs that are removed from the pyroprocess is dependent upon the raw material, fuel, kiln pyro-process, dust collection system, and type of cement being produced. As a result, the composition of CKDs varies with respect to chemical composition, particulate size, and mineralogy. Although there are variations among the CKDs produced by different pyroprocesses and even within the same pyroprocess, there are also similarities across all types of CKDs. All CKDs are a particulate mixture of partially calcined and unreacted raw feed, clinker dust, and ash enriched with alkali sulfates and other volatiles. All CKDs are also small enough to be carried by the pyroprocess exhaust gases (Hawkins et al., 2004).

2.5.1.1 CKD-PC Chemical Composition Bhatty (1984, 1985a, 1985b, 1986), one of the earliest published researchers to study CKDs as a partial replacement of PC, stated that the chemical components of CKDs that can affect cement/mortar/concrete properties are sulfates, alkalis, chlorides, free lime, and calcium carbonate (CKDs typically contain higher concentrations of these chemical components than PC). The chemical composition of the CKDs and PC used in each CKD-PC interaction study over the past 30 years are presented in Table 2.11 and Table 2.12, respectively.

62 Very few researchers have characterized the complete chemical composition of the CKD(s) used in their CKD-PC research study. From Table 2.11, it can be observed that the CKD chemical components Bhatty (1985a) identified as affecting cement/mortar/concrete properties are rarely reported; this is likely due to analyzing the CKDs with the same procedures as for PC. For the chemical components that have been reported, it is clear that the CKDs from different research studies, and even within the same study, vary significantly. CKD chemical composition variabilities are heavily influenced by variabilities in raw feed, fuel type, kiln process type, and product specifications for the PC produced (Konsta-Gdoutos and Shah, 2003).

Table 2.12 shows the chemical composition of the PC that was used in each previous research study to assess the use of CKDs as a partial substitute. The majority of the previous research studies utilized TI cements. PC’s other than TI cement (PC 2, PC 12, PC 13, and PC 14) were excluded from the statistical analyses in Table 2.12.

The chemical variability of the TI cements is considerably lower than that of the CKDs. Since it is one of the volatile components, chloride (Cl) is not typically present in PC (generally less than 0.01%) and, therefore, not reported. Typically the concentrations of free lime (fCaO) in PC are low (typically less than 1.5%). Both chloride and free lime, however, have a wide variation in CKDs. For the CKD free lime values reported, the literature review does not cover the full range of free lime found in CKDs. The maximum free lime reported in the literature review is 21.7%, whereas some CKDs have been tested to contain as high as 35% free lime (Lafarge, 2005). The alkali (Na 2O, K 2O) and sulfate

(SO 3) contents of the CKDs are generally higher in CKDs than in the TI cements. The calcium oxide (CaO) and silica oxide (SiO 2) contents of the CKD are generally lower than in the TI cements, mainly as a consequence of partial decarbonation .

63 Table 2.11 Chemical and physical composition of CKD: from CKD-PC literature review

CaO SiO 2 Al 2O3 Fe 2O3 MgO SO 3 Na 2O K2O Na 2Oe Cl fCaO LOI Blaine Author Material* % % % % % % % % % % % % m2/kg Maslehuddin et al. (2008a and 2008b) CKD 1 49.3 17.1 4.24 2.89 1.14 3.56 3.84 2.18 5.27 6.9 N.R. 15.8 N.R. El-Aleem et al. (2005) CKD 2 42.99 13.37 3.36 2.29 1.90 5.10 3.32 3.32 5.50 7.50 2.59 15.96 318 Al-Harthy et al. (2003) CKD 3 63.80 15.80 3.60 2.80 1.90 1.70 0.30 3.00 2.27 1.10 N.R. N.R. N.R. Udoeyo and Hyee (2002) CKD 4 52.72 2.16 1.09 0.54 0.68 0.05 N.R. 0.11 0.33 N.R. N.R. 42.39 N.R. Wang et.al. (2002) Konsta-Gdoutos et al. (2001) CKD 5 56.99 17.67 5.06 2.75 0.91 6.55 0.30 3.43 2.56 0.38 N.R. 8.00 N.R. Shoaib et al. (2000) CKD 6 49.75 11.95 1.12 2.45 1.86 6.35 3.87 2.66 5.62 6.80 N.R. 17.92 N.R. Dyer et al. (1999) CKD 7 34.30 34.30 3.50 2.00 0.80 11.40 1.20 8.20 6.60 8.10 0.00 N.R. N.R. Dyer et al. (1999) CKD 8 34.80 12.20 3.20 1.80 0.90 10.60 1.60 7.50 6.54 2.80 1.40 N.R. N.R. Batis et al. (1996) CKD 9 43.95 10.12 4.07 2.89 0.95 0.27 0.18 0.82 0.72 0.38 N.R. N.R. N.R. Batis et al. (1996) CKD 10 42.59 13.68 4.36 2.30 1.23 0.10 0.28 0.79 0.80 0.17 N.R. N.R. N.R. El-Sayed et al. (1991) CKD 11 48.80 13.00 3.33 2.00 2.02 8.70 4.19 2.73 5.99 7.40 18.57 12.59 N.R. Wang and Ramakrishnan (1990) Ramakrishnan and Balaguru (1987) CKD 12 45.71 15.78 3.95 1.09 0.98 2.32 N.R. N.R. N.R. N.R. N.R. N.R. N.R. Ramakrishnan (1986) Bhatty (1984-1986) CKD 13 49.30 14.70 3.31 2.04 1.03 3.07 0.23 2.60 1.94 0.24 10.43 23.43 511 Bhatty (1984-1986) CKD 14 51.70 15.50 3.84 2.13 1.59 11.10 0.22 2.50 1.87 0.26 21.72 10.50 489 Bhatty (1984-1986) CKD 15 41.90 15.40 2.65 1.51 1.35 0.25 0.23 4.90 3.45 3.47 3.00 34.06 439 Bhatty (1984, 1985b) CKD 16 41.70 14.00 2.85 1.51 2.73 5.55 0.27 3.60 2.64 0.29 4.31 27.81 566 Bhatty (1984) CKD 17 44.50 16.50 3.71 1.79 1.43 5.67 0.31 3.50 2.61 0.15 7.46 21.33 718 Ravindrarajah (1982) CKD 18 42.70 12.20 5.80 2.30 1.30 6.50 0.80 4.30 3.63 N.R. 6.10 22.10 528 # samples 18 18 18 18 18 18 16 17 17 15 10 12 7 Average 46.53 14.75 3.50 2.06 1.37 4.94 1.32 3.30 3.43 3.06 7.56 20.99 510 St. Dev. 7.23 5.99 1.15 0.63 0.54 3.82 1.54 2.11 2.10 3.29 7.33 9.97 122 * CKDs are numbered as they are referred to in subsequent discussion N.R. = Not Reported; Na 2Oe = 0.658 x K 2O + Na 2O fCaO = free calcium oxide (free lime) and calcium hydroxide LOI = Loss on Ignition

Table 2.12 Chemical and physical composition of PC: from CKD-PC literature review

CaO SiO 2 Al 2O3 Fe 2O3 MgO SO 3 Na 2O K2O Na 2Oe fCaO LOI Blaine Author Material* Type % % % % % % % % % % % m2/kg Maslehuddin et al. (2008b) PC 1 TI 64.35 22.0 5.64 3.80 2.11 2.10 0.19 0.36 0.33 N.R. 0.7 N.R. Maslehuddin et al. (2008b) PC 2 TV 64.07 20.52 4.08 4.24 2.21 1.96 0.21 0.31 0.41 N.R. 0.8 N.R. Maslehuddin et al. (2008a) PC 3 TI N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. El-Aleem et al. (2005) PC 4 TI 64.00 21.06 5.43 3.41 0.75 2.48 0.10 0.12 0.18 0.22 2.42 300 Al-Harthy et al. (2003) PC 5 TI 62.50 20.60 4.50 3.60 2.60 2.70 0.20 0.50 0.53 N.R. N.R. N.R. Udoeyo and Hyee (2002) PC 6 TI N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. Wang et. al. (2002) Konsta-Gdoutos et al. (2001) PC 7 TI 64.29 20.35 5.24 3.58 1.13 2.56 0.11 0.60 0.50 N.R. 1.10 N.R. Shoaib et al. (2000) PC 8 TI 62.70 21.42 3.30 5.23 2.40 2.35 2.41 0.45 2.71 N.R. 1.22 N.R. Dyer et al. (1999) PC 9 TI 64.90 21.10 5.00 2.70 1.60 3.30 0.30 0.60 0.69 N.R. N.R. N.R. Batis et al. (1996) PC 10 TI 65.50 20.54 4.74 3.74 1.52 2.61 0.10 0.48 0.42 N.R. N.R. N.R. El-Sayed et al. (1991) PC 11 TI 62.66 20.40 5.19 3.26 2.62 2.37 2.48 0.32 2.69 0.30 1.17 366 Wang and Ramakrishnan (1990) PC 12 TIII 63.05 20.98 6.13 2.61 1.39 2.50 N.R. N.R. N.R. 0.43 N.R. 540 Ramakrishnan and Balaguru (1987) PC 13 TII N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. Ramakrishnan and Balaguru (1987) PC 14 TIII N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. Ramakrishnan and Balaguru (1987) Ramakrishnan (1986) PC 15 TI 70.27 19.93 1.83 3.03 1.93 2.58 N.R. 0.90 N.R. N.R. N.R. N.R. Bhatty (1985a & 1986) PC 16 TI 64.60 21.40 5.10 3.50 2.10 1.70 0.23 0.46 0.53 0.70 1.10 326 Bhatty (1984, 1985b) PC 17 TI 63.85 20.16 4.75 2.51 1.46 3.93 0.10 0.47 0.41 0.78 2.13 441 Bhatty (1984, 1985b) PC 18 TI 63.33 21.10 4.90 2.57 2.08 2.78 0.15 0.83 0.70 0.93 1.05 398 Bhatty (1984, 1985b) PC 19 TI 63.02 24.06 4.20 2.68 2.29 2.51 0.15 0.39 0.41 0.60 0.71 313 Bhatty (1984, 1985b) PC 20 TI 62.66 21.12 4.42 2.05 3.95 2.78 0.16 0.93 0.77 0.88 1.74 438 Bhatty (1984) PC 21 TI 64.59 21.44 3.93 2.74 1.81 3.48 0.13 0.35 0.36 0.93 1.47 417 Ravindrarajah (1982) PC 22 TI 63.00 20.00 6.00 3.00 1.50 2.00 N.R. N.R. 1.00 0.00 2.00 N.R. # samples + 16 16 16 16 16 16 14 15 15 9 12 8 Average + 64.14 21.04 4.64 3.21 1.99 2.64 0.49 0.52 0.82 0.59 1.40 375 St. Dev. + 1.88 1.00 1.00 0.74 0.74 0.56 0.83 0.22 0.79 0.34 0.56 57 * PCs are numbered as they are referred to in subsequent discussion N.R. = Not Reported; Na 2Oe = 0.658 x K 2O + Na 2O fCaO = free calcium oxide (free lime) and calcium hydroxide LOI = Loss on Ignition + only includes TI cements (PC 2, PC 12, PC 13, and PC 14 were excluded).

2.5.1.2 CKD-PC Mineralogical Composition In the majority of studies, CKD mineralogical composition data is rarely reported. The composition of a CKD consists of unreacted phases from the raw material, partially calcined raw feed, condensed volatiles (alkalis, chlorides, and sulfates), and/or PC clinker particles. Since CKDs are a by-product resulting from the partial decarbonation of limestone (CaCO 3), either free lime (free CaO) or calcite is expected to be the predominant mineralogical component. Calcium carbonate is an important mineralogical component of CKDs that can affect CKD-PC blend properties (Bhatty, 1985a). The reported mineralogical composition data of CKD in the literature is shown in Table 2.13. Although there are only eight data points for calcite content, the standard deviation reflects its variability in CKDs.

Dyer et al. (1999) used Rietveld Refinement on X-ray diffraction traces over an angular range of 3° to 80° 2 θ using commercially available software program to estimate proportions of the compounds present in CKDs 7 and 8; this is shown in Table 2.13. This analysis, however, cannot be used as an estimate of the actual amount of the compounds in the CKDs due to the lack of consideration for the amorphous content. Also, CKD 7 appears to be out of the ordinary since the free calcium oxide content is 0%.

As stated in the previous section, the CKD chemical components that can affect properties of CKD-PC blends are alkalis, sulfates, chlorides, and free lime (Bhatty, 1985a). The chemical composition, however, is not the only important factor to consider in assessing the potential impact of using a CKD-PC blend. The physical form of these chemical components can also be significant. For example, alkalis are known to impact cement properties, but can behave very differently if present in different forms. Readily soluble alkali (alkali chlorides and alkali sulfates) can impact early hydration of PC much more significantly than alkali found in crystal structures that are less soluble. Further, alkali chlorides and alkali sulfates impact the hydration of PC differently.

Table 2.13 Mineralogical composition of CKD: from CKD-PC literature review

Mineralogical Phase CKD 2 CKD 7 CKD 8 CKD 13 CKD 14 CKD 15 CKD 16 CKD 17 Avg. St.Dev. CaCO 3 (calcite) + 8.9 52.8 50.94 22.65 60.4 44.58 64.68 43.56 20.45 CaO (free calcium oxide) + 0.0 1.4 + + + + + Ca(OH) 2 (portlandite) + 26.5 8.4 CaSO 4 (anhydrite) + 9.8 6.1 + + + + SiO 2 (quartz) + 3.5 6.9 + + + + + Na2SO 4 (thenardite) 7.9 0.0 Ca 2Al(OH) 6Cl 2(H 2O) 2 (Friedel’s salt) 3.1 0.0 Na 0.31 K0.69 Cl (halite, potassium) + 0.0 2.9 K3Na(SO 4)2 (aphthitalite) 0.0 10.2 + K2Al 4(Si 6Al 2O20 )(OH) 4 (Muscovite 2m1) 0.0 3.3 Ca 2Si 12 Al 4O32 (H 2O) 12 (calcium harmotome) 0.0 0.9 KCl (sylvite) 20.4 7.0 + K2Ca(SO 4).H 2O (syngenite) 19.9 0.0 K2SO 4 (arcanite) 0.0 0.0 + + + + alpha C 2S (belite) + 0.0 0.0 CKD 2: El-Aleem (2005); CKD 7-8: Dyer (1999); CKD 13-15: Bhatty (1986), Bhatty (1985b), Bhatty (1985a), and Bhatty (1984); CKD 16: Bhatty (1985b) and Bhatty (1984); CKD 17: Bhatty (1984). +: means it was identified as a component

67 2.5.1.3 CKD-PC Physical Composition The majority of CKD-PC interaction studies do not report the physical characteristics of the materials used. For the studies that did describe the physical properties of the materials, the characterization methods consisted of Blaine fineness, particle size distribution, percentage passing sieve, and density. Blaine fineness was the most prominent method used to characterize the fineness of CKDs and PC, which is presented in Table 2.11 and Table 2.12.

The range of the seven reported CKD Blaine fineness values is between 318 m2/kg and 718 m2/kg. The average Blaine fineness value of the 7 CKDs (510 m2/kg) is higher than the average range of the PCs used in the same research studies (375 m2/kg). The standard variation of the Blaine fineness for CKDs (122 m 2/kg) is also higher in comparison to the standard variation of Blaine fineness values for PC (57 m 2/kg), as Blaine fineness in PC is a process control parameter. The Blaine fineness values reported in the literature have led some researchers to conclude that CKDs are finer than PC.

Wang et al. (2002) and Konsta-Gdoutos et al. (2001) were the only authors to have provided particle size distribution analyses for the materials used in their CKD-PC interaction study. CKD 5 and PC 7 particle size distributions are shown in Figure 2.14 (slag was also used in their research study and is included in the figure). Based upon the particle size distribution curve, Wang et al. (2002) concluded that CKD 5 is coarser than PC 7.

Ramakrishnan and Balaguru (1987) reported CKD 12 to be 98.56% passing a No. 200 sieve (70 µm), which is higher than each reported percentage passing a No. 200 sieve for the three cements used in this research study (PC 13 = 95.20%, PC 14 = 97.90%, PC 15 = 95.50%). Based upon the 75 µm (No. 200 sieve), CKD 12 is finer than PC 14. The density values are reported for CKD 4 (Udoeyo and Hyee, 2002) and CKD 18

68 (Ravindrarajah, 1982), which are 2.65 and 2.72 respectively. PC specific density is generally accepted to be 3.15, although it generally varies between 3.1 and 3.2.

Figure 2.14 Particle size distribution of CKD 5 and PC 7 (Wang et al., 2002)

2.5.2 Workability Maslehuddin et al. (2008a) studied the effect of replacing PC 3 with CKD 1 at 0%, 5%, and 10% replacement by mass in pastes. The water required to maintain normal consistency (ASTM C187) of PC alone was at a water to binder ratio (w/b) of 24.6%. The w/b marginally increased to 24.9% at both 5% and 10% CKD replacement. Therefore, the use of CKD 1 at up to 10% replacement of PC 3 did not significantly change the water requirement.

El-Aleem et al. (2005) studied the workability effect of replacing PC 4 with CKD 2 at 0%, 2%, 4%, 6%, 8%, and 10% replacement by mass in pastes and mortars. The authors observed that the addition of CKD increased the water required to maintain normal consistency of pastes and constant flow of mortars (ASTM C1437), as shown in Figure 2.15 and Figure 2.16, respectively. As the amount of PC replacement with CKD

69 increased, the water demand also increased in both pastes and mortars. For the pastes, the w/b increased almost linearly from 26.5% with no CKD replacement to 29.5% at 10% CKD replacement of PC. For the mortars, the w/b also increased somewhat linearly from 0.485 with no CKD replacement of PC to 0.595 at 10% CKD replacement of PC.

El-Aleem et al. (2005) suggested that the increased water demand may be attributed to the high amounts of alkalis, sulfates and volatile salts, and free lime in CKD 2 in comparison to PC 4. El-Aleem et al. (2005) also mentioned that the slightly higher surface area (Blaine fineness value) of CKD 2 could be a factor in the increased water demand of pastes.

Figure 2.15 Paste water/binder ratio, initial set, and final set of CKD 2 as a partial substitute of PC 4 at different levels of replacement (El-Aleem et al., 2005)

70 0.60

0.55

0.50 Water / binder

0.45 0 2 4 6 8 10 CKD Replacement of PC, %

Figure 2.16 Mortar water/binder ratio of CKD 2 as a partial substitute of PC 4 at different levels of replacement (El-Aleem et al., 2005)

Al-Harthy et al. (2003) determined the water demand of mortar mixes to maintain the same workability using CKD 3 at a 0%, 10%, 20%, 25%, and 30% replacement level of PC 5, as shown in Figure 2.17. As the level of CKD 3 replacement increased in the mortar mixes, the water demand also increased. The w/b increased almost linearly from 0.644 with no CKD to 0.677 at 10% CKD replacement of PC and 0.759 at 25% replacement. At 30% replacement, however, the water requirement decreased to w/b of 0.731. Al-Harthy et al. (2003) stated that the increased cohesiveness of the mortar mixes is caused by the very fine particles of CKD. It is not clear whether the sudden w/b decrease as the CKD increased from 25% to 30% replacement is caused by a chemical or physical effect. Al-Harthy et al. (2003) also reported the workability effect using 0%, 5%, 10%, 15%, 20%, 25%, and 30% CKD 3 replacement by total mass of PC 5 in concrete mixtures. Three w/b ratios of 0.50, 0.60, and 0.70 were used for each concrete mixture. For each level of w/b ratio, the measured slump was the same or it decreased as the amount of CKD replacement level increased. As the w/b ratio increased, the impact of CKD 3 replacement of PC 5 on slump loss became more significant.

0.80

0.75

0.70 Water / binder 0.65

0.60 0 10 20 25 30 CKD Replacement of PC, %

Figure 2.17 Mortar water/binder ratio of CKD 3 as a partial substitute of PC 5 at different levels of replacement (Al-Harthy et al., 2003)

Udoeyo and Hyee (2002) studied the workability effect of CKD 4 substitution at 0%, 20%, 40%, 60%, and 80% of PC 6 in concrete mixes. Each concrete mix was batched according to the mix ratio of 1:3:4:0.65 (binder: sand: coarse aggregate: water). The results show that as the CKD replacement level increases, the measured slump decreases. Udoeyo and Hyee (2002) did not suggest mechanisms for the loss of slump in the CKD- PC concrete mixes.

Wang et al. (2002) conducted viscosity tests on pastes with CKD 5 at partial replacement levels of PC 7 at 0%, 15%, 25%, and 50% with a w/b ratio of 0.50. They further reported that the viscosity of the pastes, measured using a rheometer with coaxial cylinders, increased as the amount of CKD used to replace the cement increased. Wang et al. (2002) suggested three factors that could contribute to increased viscosity. First, CKD 5 is coarser than PC 7, based upon the particle size distribution comparison shown in Figure 2.10 and is, therefore, increasingly viscous. The authors state that coarse particles

72 can behave independently of colloidal particles and act as amplifiers that increase the viscosity of a concentrated suspension system, such as fresh cement paste. The authors cited research conducted by Sengun and Probstein (1997) that used bimodal suspensions containing both colloidal and noncolloidal size particles, where a particle size ratio typically larger than 10 is treated as bimodal. It should be noted, however, that the fine and coarse fraction of a CKD generally has only a small fraction of the particle size ratio greater than 10. Second, there is an increase in rapid ion dissolution during the early stages of hydration due to the presence of CKD, which may result in high viscosity. Third, the size irregularity of CKD particles may increase friction between the cement and CKD particles when compared to paste with cement particles only.

Wang and Ramakrishnan (1990) investigated the workability of pastes and concrete made with a binary blend consisting of 5% CKD (CKD 12) and 95% TIII cement (PC 12). The normal consistency w/b ratio for the plain cement paste was 27.0% and the paste with CKD 12 had a w/b ratio of 28.0%. Although the water content required for normal consistency was 1% higher, the authors did not believe this necessarily meant that the CKD-PC blend needed a higher water content to produce the same concrete slump as a plain cement. Wang and Ramakrishnan (1990) stated that the Vicat paste test measures viscosity whereas the concrete slump test indicates the lubricating ability of the paste. The concrete mixes were tested at three w/b ratios: 0.45, 0.52, and 0.55. Wang and Ramakrishnan (1990) reported there was no significant difference in the slump between the plain and CKD blended concretes.

Ramakrishnan (1986) investigated the workability of pastes and concrete made with a binary blend consisting of 5% CKD (CKD 12) and 95% TI cement (PC 15). The w/b ratio for the plain cement paste was 0.245 and the paste with CKD 12 had a w/b ratio of 0.255. The CKD-PC blend had 1% higher normal consistency than the plain cement. The concrete mixes were tested at a cement content of 386 kg/m 3 and w/b ratio of 0.45. Six

73 sets of each concrete mix were batched. Ramakrishnan (1990) reported there was no significant difference in the slump between the plain and CKD blended concretes.

Bhatty (1985a) used a TI cement (PC 16) with three different CKDs (CKD 13, CKD 14, and CKD 15) to investigate their effect on paste workability. CKD-PC blends were prepared by replacing 0%, 10%, and 20% of cement at a w/b ratio of 0.45. Workability was determined by the size of a mini-slump pat area and was consistently reduced for blends with CKD compared to the control pastes. Although the workability of all CKD- PC blends decreased as the amount of CKD increased from 10% to 20%, the magnitude varied significantly.

Bhatty (1984) also conducted mini-slump pat area studies on pastes using five companion cements and CKD obtained from five different cement plants. The five companion cement kiln dust blends were: PC 17 and CKD 13, PC 18 and CKD 14, PC 19 and CKD 15, PC 20 and CKD 16, and PC 21 and CKD 17. For each CKD-PC blend, the CKD replacement of the cement was 0%, 10%, 15%, and 20% by mass at a w/b ratio of 0.50. As the percentage of CKD replacement increased, the blends containing CKD 13, CKD 14, CKD 16, and CKD 17 generally decreased workability. The opposite trend was observed for blends with CKD 15. Bhatty (1984) stated that as the amount of high chloride from the CKD increased in the CKD blends, workability also increased.

Ravindrarajah (1982) used pastes and concrete to study the workability effect of CKD-PC interaction. For pastes, CKD 18 was used as a partial cement replacement of PC 22 by mass at 0%, 25%, 50%, 75%, and 100%. Water was added to each paste mix to maintain a standard consistency. The author reported that as the percentage of CKD increased in the cement paste, the amount of water had to increase in order to attain a normal consistency. For concrete, CKD 18 was used as a partial cement replacement of PC 22 by mass at 0%, 15%, 25%, 35%, and 45%. Water was added to each concrete mix to maintain the same slump for all concrete mixes. Similar to pastes, Ravindrarajah (1982)

74 determined that as the CKD percentage increased in the concrete mix, the water demand to maintain the same slump also increased. The author attributed the increased water demand in pastes and concrete to the higher surface area (Blaine fineness) of the kiln dust compared to cement and the increased solid volume of the mix (since the density of CKD is lower than that of cement).

A summary of the studies conducted on the workability effects of CKD-PC blends compared to each of the respective reference plain cements is shown in Table 2.14. The majority of researchers found that the workability was reduced as the amount of CKD increased, and that the trend was somewhat linear until a plateau was reached. The suggested reasons for a reduction in workability when CKD is used as a partial substitute for PC vary considerably: CKD alkali content, chloride content, sulfate and volatile salts content, lime content, a high fineness of CKD, rapid ion dissolution, high coarseness of CKD, particle size, and lower density of CKD. It is interesting to note that both higher fineness (based upon Blaine fineness) and higher coarseness (based upon particle size distribution) of CKD compared to cement were suggested to have the same impact of reducing workability of pastes. The researcher with the only CKD-PC blend that increased workability stated that as the amount of high chloride from the CKD increased in the CKD blends, workability also increased. Chlorides, however, are not widely known to impact workability (refer to 2.4.7).

75 Table 2.14 Workability: from CKD-PC literature review

Author(s) Blend Type w/b % CKD General Author Suggested Replacement Effect on Mechanism(s) Workability Maslehuddin et CKD 1/PC 3 P V 0,5,10 N.C. al. (2008a) El-Aleem et al. CKD 2/PC 4 P V 0,2,4,6,8,10 ↓ (1) Higher amounts of (2005) M V 0,2,4,6,8,10 ↓ alkalis, sulfates and volatile salts, and lime in CKD. (2) Higher Blaine fineness in CKD. Al-Harthy et CKD 3/PC 5 M V 0,10,20,25,30 ↓ (3) Increased cohesiveness al. (2003) C K 0,10,20,25,30 ↓ caused by very fine CKD particles in pastes. (4) Impact of CKD replacement in concrete was more dramatic at higher w/b ratios. Udoeyo and CKD 4/PC 6 C 0.65 0,20,40,60,80 ↓ Hyee (2002) Wang et al. CKD 5/PC 7 P 0.50 0,15,25,50 ↓ (5) CKD coarseness (2002) increases viscosity. (6) Rapid ion dissolution due to presence of CKD. (7) CKD particle size irregularity Wang and CKD 12/PC 12 P V 0,5 ↓ Ramakrishnan C 0.45 0,5 N.C. (1990) Ramakrishnan CKD 12/PC 15 P V 0,5 ↓ (1986) C 0.45 0,5 N.C. Bhatty CKD 13/PC 16 P 0.45 0,10,20 ↓ (1985a) CKD 14/PC 16 P 0.45 0,10,20 ↓ CKD 15/PC 16 P 0.45 0,10,20 ↓ Bhatty CKD 13/PC 17 P 0.50 0,10,15,20 ↓ (8) As the amount of high (1984) CKD 14/PC 18 P 0.50 0,10,15,20 ↓ chloride from the CKD CKD 15/PC 19 P 0.50 0,10,15,20 ↑ increased in the CKD CKD 16/PC 20 P 0.50 0,10,15,20 ↓ blends, workability also CKD 17/PC 21 P 0.50 0,10,15,20 ↓ increased. Ravindrarajah CKD 18/PC 22 P V ↓ (9) Higher fineness of the (1982) C V ↓ CKD in comparison to 0,25,50,75,100 the PC 0,15,25,35,45 (10) Increased solid volume (since the density of the CKD is lower than that of the cement).

P = Paste; M = Mortar; C = Concrete. V = varied the w/b ratio to maintain consistent workability K = constant w/b ratio, but more than one w/b ratio was tested. N.C. = No Change

76 2.5.3 Setting Time Maslehuddin et al. (2008a) studied the setting time effect of replacing PC 3 with CKD 1 at 0%, 5%, and 10% replacement by mass in pastes, with water added to maintain a constant normal consistency according to ASTM C187 and ASTM C191. The plain cement paste had an initial setting time of 175 minutes and a final setting time of 256 minutes. The initial and final setting times of the paste with 5% CKD replacement were 10 minutes (6%) and 6 minutes (2%) faster than the control plain cement, respectively. The initial and final setting times of the paste with 10% CKD replacement were 20 minutes (11%) and 18 minutes (7%) faster than the control plain cement, respectively. The authors attributed the decrease in both initial and final setting times to the high amounts of lime and alkalis in the CKD, which accelerate the hydration process leading to faster setting times.

El-Aleem et al. (2005) studied the set time effect of replacing PC 4 with CKD 2 at 0%, 2%, 4%, 6%, 8%, and 10% replacement by mass in pastes, with water added to maintain a constant normal consistency. El-Aleem et al. (2005) reported that as the CKD replacement increases, the water demand increases and the setting time decreases. This is contrary to what many expect since it is well known that an increase in w/b results in longer settings times for a given paste. It is important to note that the established influence of w/b refers to its effect on a single blend and not on blends with different chemical/mineralogical and physical properties. As shown in Figure 2.15, the decrease of both initial and final setting times is almost linear as a function of CKD replacement. The initial set time decreased from approximately 135 minutes with no CKD to approximately 65 minutes with 10% CKD replacement of PC. The final set time decreased from approximately 230 minutes with no CKD to approximately 110 minutes with 10% CKD replacement of PC. Similar to Maslehuddin et al. (2008a), El-Aleem et al. (2005) suggested that this was due to the high amounts of lime and alkalis in CKD.

77 Udoeyo and Hyee (2002) studied the setting time effect of replacing PC 6 with CKD 4 at 20%, 40%, 60%, and 80% replacement by mass in concrete at a w/b ratio of 0.65. Udoeyo and Hyee (2002) reported that at a 20% CKD 4 replacement level of PC 6, the initial setting time increased slightly from 0.72 h to 0.78 h, and the final set time remained unchanged at 1.62 h. As the CKD 4 content increased beyond 20% replacement, the set time increased significantly. At a very high replacement level of 80%, the initial set time was 1.33 h and final set time was 2.5 h. Udoeyo and Hyee (2002) stated that the values of the initial and final setting times were within the relevant BS and ASTM standards, but did not suggest possible mechanisms for the increased setting times.

Wang and Ramakrishnan (1990) used CKD 12 at 5% cement replacement of a TIII cement (PC 12) to determine the impact on paste and concrete setting time. The normal consistency w/b ratio for the plain cement paste was 27.0% and the paste with CKD 11 had a w/b ratio of 28.0%. The plain cement paste had an initial setting time of 122 minutes and a final setting time of 155 minutes. The CKD-PC blend initial and final setting times were 45 minutes (38%) and 53 minutes (34%) longer than the control plain cement, respectively. Wang and Ramakrishnan (1990) attributed the longer setting times of the CKD paste to the higher water content required to maintain normal consistency. The concrete mixes were tested at three w/b ratios: 0.45, 0.52, and 0.55. The effects of CKD on the initial and final setting times of concrete were determined by concrete penetration resistance (ASTM C403). Both the initial and final set of the CKD-PC concrete occurred 30 minutes later than for plain concrete (the w/b ratio for the concrete mixes used to assess setting times was not specified). Wang and Ramakrishnan (1990) did not suggest possible mechanisms for the increase in concrete setting times.

Ramakrishnan (1986) used CKD 12 at 5% cement replacement of a Type I cement (PC 15) to determine the impact on paste (ASTM C191) and concrete setting time (ASTM C403). The w/b ratio for the plain cement paste was 24.5% and the paste with CKD 12

78 had a w/b ratio of 25.5%. Ramakrishnan (1986) stated that the initial and final setting times of the CKD-PC blend were longer than that of the plain cement. The author reported the differences to be 22 minutes and 40 minutes, respectively, for initial and final setting times. The concrete mixes were tested at a cement content of 386 kg/m 3 and w/b ratio of 0.45. Six sets of each concrete mix were batched. Ramakrishnan (1986) reported the initial and final setting time for one of the six concrete mixes for each of the CKD blend and plain cement. The initial and final setting times for the plain cement concrete mix was 5 hours and 42 minutes and 7 hours and 20 minutes, respectively. The initial and final setting times for the concrete mix with CKD 12 were 6 hours and 4 minutes and 7 hours and 48 minutes, respectively. Ramakrishnan (1986) concluded that the setting time of the CKD pastes was slightly longer than the plain cement paste, but the setting time of the CKD concrete mix and plain concrete mix were almost the same (within 5%). It is important to note, however, that the concrete initial and final setting times of the CKD concrete mixes were 22 minutes and 28 minutes, respectively, longer than the plain concrete mix.

Bhatty (1985a) used a TI cement (PC 16) with three different CKDs (CKD 13, CKD 14, and CKD 15) to investigate their effect on paste set time. Cement and CKD blends were prepared by replacing 0%, 10%, and 20% of cement at a w/b ratio of 0.45. Bhatty (1985a) stated that time of initial set was always shorter compared to cement for any blends containing 10% CKD. Longer time of initial set was obtained for blends made with 20% CKD 13 and 20% CKD 15, as compared to blends made with 10% of CKD 13 and 10% of CKD 15 or to cement alone. The blend made with 20% of CKD 14 had a considerably shorter time of initial set when compared to all other CKD blends and cement alone. CKD 14 is characterized by high sulfate (11.10%), high free lime (21.72%), and low chloride (0.26%) contents.

Bhatty (1984) also conducted setting time tests on pastes using five companion cements and dusts obtained from five different cement plants. The five companion cement kiln

79 dust blends are: PC 17 and CKD 13, PC 18 and CKD 14, PC 19 and CKD 15, PC 20 and CKD 16, and PC 21 and CKD 17. For each cement kiln dust blend, the CKD replacement of the cement was 0%, 10%, 15%, and 20% at a w/b ratio of 0.50. As the CKD replacement level increased, the setting time for blends with CKD 13, CKD 14, CKD 16, and CKD 17 decreased. Blends with CKD 15 had the opposite effect and increased setting time. Bhatty (1984) concluded that the time of set generally decreased with increased dust addition levels, although no effects of CKD chemistry were specified.

Ravindrarajah (1982) used cement pastes to assess the set time of partial and complete replacement of cement with CKD 18 and PC 22. Cement was partially replaced by mass at 0%, 25%, 50%, 75%, and 100%. The pastes were mixed with necessary water content to produce a consistent workability. As the percentage of cement replacement increased, the final setting time increased. The data shows that all samples had set within 10 hours, which was the specified limit in the British Standard. The initial setting time also lengthened, but the rate of increase slowed after 50% of cement had been replaced by CKD. Ravindrarajah (1982) stated that the increased set times are opposite to what is expected with CKDs, since a higher alkali concentration promotes shortened setting times. The author suggested the effect of increased set time may be attributed to (i) the physical presence of inactive particles and (ii) the kiln dust that acted as a barrier between the cement particles and water. The nature of the suggested barrier was not specified by the author.

A summary of the studies conducted on the setting time effects of CKD-PC blends compared to each of the respective reference plain cement is shown in Table 2.15. The effect of CKDs on setting times is decidedly mixed. The same CKD at different replacement levels of a PC can have different effects on setting time. The setting time impact of CKD is likely a function of the total composition of the CKD-PC blend.

80 Table 2.15 Setting time: from CKD-PC literature review

Author(s) Blend Type w/b % CKD General Effect Author Suggested Mechanism(s) Replacement on Setting Time Maslehuddin CKD 1/PC 3 P V 0,5,10 ↓ (1) High amounts of lime and et al. (2008a) alkalis in CKD accelerate hydration and lead to fast setting. El-Aleem et al. CKD 2/PC 4 P V 0,2,4,6,8,10 ↓ (2) High amounts of lime and (2005) alkalis in CKD accelerate hydration and lead to fast setting. Udoeyo and CKD 4/PC 6 C 0.65 0,20,40,60,80 ↑ Hyee (2002) Wang and CKD 12/PC 12 P V 0,5 ↑ (3) Higher set times in paste Ramakrishnan C N.R. 0,5 ↑ attributed to higher water (1990) demand due to the CKD.

Ramakrishnan CKD 12/PC 15 P V 0,5 ↑ (1986) C 0.45 0,5 N.C. Bhatty CKD 13/PC 16 P 0.45 0,10,20 10% ↓; 20% ↑ (1985a) CKD 14/PC 16 P 0.45 0,10,20 10% ↓; 20% ↓ CKD 15/PC 16 P 0.45 0,10,20 10% ↓; 20% ↑ Bhatty CKD 13/PC 17 P 0.50 0,10,15,20 ↓ (1984) CKD 14/PC 18 P 0.50 0,10,15,20 ↓ CKD 15/PC 19 P 0.50 0,10,15,20 ↑ CKD 16/PC 20 P 0.50 0,10,15,20 ↓ CKD 17/PC 21 P 0.50 0,10,15,20 ↓ Ravindrarajah CKD 18/PC 22 P V ↑ (1) Physical presence of inactive (1982) C V 0,25,50,75,100 ↑ particles in the kiln dust. 0,15,25,35,45 (2) The dust may act as a barrier between the cement particles and water. P = Paste; M = Mortar; C = Concrete. V = varied w/b ratio to maintain consistent workability K = constant w/b ratio, but more than one w/b ratio was tested. N.C. = No Change

81 2.5.4 Hydration Kinetics El-Aleem et al. (2005) studied the hydration behavior effect of replacing PC 4 with CKD 2 at 0%, 2%, 4%, 6%, 8%, and 10% replacement by mass in pastes with water added to maintain a constant normal consistency. El-Aleem et al. (2005) assessed the hydration behaviour of each mix by determining the free lime as well as evaporable water and chemically combined water contents at 3, 7, 28, and 90 days, as shown in Figure 2.18. The free lime was determined using the alcohol ammonium acetate method, which does not distinguish between calcium oxide and calcium hydroxide. The evaporable water content of the hardened paste was determined by subtracting the total water content (loss on ignition at 1000°C of the saturated sample) from the combined water content (loss on ignition at 1000°C for 2 hours). The authors reported that the quantity of free lime increased with curing time due to the continuous hydration of the main cement phases and leaching from CKD 2.

El-Aleem et al. (2005) also noted that at any given time, the quantity of free lime increased with CKD 2 content in the blend. Continuous hydration of the cement phases led to a decrease in evaporable water. It was reported that the evaporable water content in pastes increased with the CKD 2 content due to the increase in mixing water and low or no hydraulic properties of CKD 2, in comparison to the high hydraulic cement properties of PC 4. Generally, the hydration and accumulation of hydration products mainly as calcium silicate and sulfoaluminate hydrates cause the chemically combined water content to decrease. The cement pastes with CKD 2 and PC 4 exhibited lower values of combined water content than the control PC 4 paste. This indicated to the authors that the C-S-H formed in the blends with CKD 2 and PC 4 blend is lower than that in PC 4 alone.

I.1 Control I.2 2% CKD I.3 4% CKD (a) I.4 6% CKD I.5 8% CKD I.6 10% CKD

(b)

(c)

83 Wang et al. (2002) conducted hydration tests on pastes with CKD 5 at partial replacement levels of PC 7 at 0%, 15%, 25%, and 50% with a w/b ratio of 0.50 using adiabatic calorimetric tests. Wang et al. (2002) reported that during initial hydrolysis the pastes with partial replacement of PC 7 with CKD 5 had a much higher heat of evolution than the pastes with PC 7 alone. The induction period began and ended much later than for the pastes with cement alone. The authors suggested that both of these characteristics may be due to the high alkali content of the CKD, which may accelerate ion dissolution of the silicates in the binder system resulting in a high initial heat evolution and an extended ion dissolution period. The cement paste with 15% CKD and 85% cement produced a higher heat peak value for rate of heat evolution than the paste with cement alone. The authors stated this higher value generally reflects the hydration of C 3S and C 2S in PC and implied that the binder system may have an optimum alkali to silicate ratio. They stated that the alkalis, mainly from the CKD, may facilitate dissolution of the silicates and accelerate the formation of calcium silicate hydrates (C-S-H). The paste with 25% CKD and 75% PC, however, had a lower heat peak value for rate of heat evolution than the paste with 15% CKD and 85% cement. Wang et al. (2002) reported that as the percentage of cement replaced with CKD increased, the heat evolution decreased when the CKD content was greater than a certain proportion. Additionally, excessive amounts of alkalis in the paste may have depressed dissolution and retarded hydration of the silicates. The peak appearance of the 25% CKD paste was delayed when compared to the 15% CKD paste and plain cement paste. Wang et al. (2002) concluded that for a specified CKD content, the peak rate of heat evolution increased as the alkali:silica ratio in the paste also increased. The high peak rate of heat evolution generally indicates early strength development.

Dyer et al. (1999) studied the hydration chemistry of cement pastes using two CKDs (CKD 7 and CKD 8) and one cement (PC 9). Dyer et al. (1999) used isothermal conduction calorimetry to assess the maximum rate heat evolution and the time at which this peak occurs at 0%, 20%, 35%, 50%, and 75% CKD replacement of PC. The w/b ratio

84 was 0.50 for each paste. The results from the magnitude of the maximum heat rate evolution indicated that both types of CKD accelerated the hydration of cement. The results for the time at which the peak occurred, however, indicated that the CKDs had the effect of slowing hydration. Dyer et al. (1999) suggested two possible reasons for the conflicting results. First, the combination of potassium chloride (which accelerates hydration) and sulfate compounds (which generally accelerates the hydration of calcium silicate cement phases while retarding the hydration of calcium aluminate phases) in each CKD could produce this effect. Second, a dense membrane of initial hydration products could be forming on the cement grains as a result of the large amounts of ions released into solution by each CKD. CKDs commonly consist of water soluble compounds – such as alkali chlorides, alkali sulfates, and lime – that result in highly alkaline solutions when mixed with water (Dyer et al., 1999). The high pH levels produced by each CKD dissolving into solution are also likely to promote the formation of hydration products and lead to higher heat evolved values. Dyer et al. (1999) also arrested hydration of the cement pastes at 2, 7, and 28 days. As discussed in the report, the hydration of pastes with cement alone typically involves the reduction of sulfate ions to the point at which further formation of AFt becomes impossible and AFm hydrates begin to form. Dyer et al. (1999) concluded that the increased quantities of sulfate introduced as part of each CKD inhibited the conversion of AFt to AFm phases. This led to increased AFt for these blends. Further, there were two AFm phases identified in the CKD-PC blends at later ages: calcium monosulphoaluminate hydrate (typical) and calcium monochloroaluminate hydrate (Friedel’s salt which is atypical). Dyer et al. (1999) noted that Friedel’s salt only forms when the free sulfate ions have already been largely consumed.

A summary of the limited number of studies conducted on the hydration effects of CKD- PC blends compared to each reference plain cement is shown in Table 2.16. The effects of CKD-PC blends were reported to be higher free lime (calcium oxide and calcium hydroxide) in the paste, less C-S-H formation, higher heat evolution during initial hydrolysis, delayed beginning and end of induction period, higher maximum heat value at

85 15% CKD replacement and lower maximum heat value at 25% CKD replacement, delayed maximum heat value, higher AFt content, and the presence of Friedel’s salt at less than 28 days. The suggested mechanisms of a CKD-PC blend upon hydration are: higher alkali concentration in solution causing acceleration or retardation of silicate dissolution depending upon the alkali/silicate ratio, higher chloride, and higher sulfate contents.

Table 2.16 Hydration: from CKD-PC literature review

Author(s) Blend General Effect on Author Suggested Mechanism(s) Paste Hydration El-Aleem et al. CKD 2/PC 4 (1) Higher free lime content. (1) Higher CKD free lime content. (2005) (2) Less C-S-H formation (2) Lower chemically combined H 2O (3) Higher evaporable H 2O Wang et al. (2002) CKD 5/PC 7 (3) Higher heat evolution during (4) High alkali dissolution during initial initial hydrolysis. hydrolysis cause effects (4) and (5). (4) Induction period began and (5) Optimum alkali:silica ratio at 15% CKD ended later. replacement of PC. (5) Higher maximum heat value at (6) Excessive amounts of CKD depress 15% CKD replacement of PC, dissolution and retard hydration of silicates at but lower maximum heat value 25% CKD replacement of PC. at 25% CKD replacement level. Dyer et al. (1999) CKD 7/PC 9 (6) Higher maximum heat value. (7) Combined effect of potassium chloride and CKD 8/PC 9 (7) Time of maximum heat value sulfate compounds could cause effects (7) and was delayed. (8). (8) Higher ettringite (AFt) (8) Rapid ion dissolution form a dense membrane content. of initial hydration productcs. Higher pH, (9) Friedel’s salt present at < however, is less likely to promote hydration 28days. products and higher heat values. (9) High CKD sulfate content cause effect (8). (10) High chloride content cause effect (9).

86 2.5.5 Compressive Strength Maslehuddin et al. (2008b) studied the compressive strength effect of replacing PC 1 (TI) and PC 2 (TV) with CKD 1 at 0%, 5%, 10%, and 15% replacement by mass in concrete. The compressive strength development after 3, 7, 14, 28, 56, and 90 days of curing were tested, according to ASTM C39. The compressive strength development at the different percentage levels of CKD 1 replacement of PC 1 and PC 2 is shown in Figure 2.19. For PC 1, all of the concrete mixes with CKD 1 at 3 and 7 days had lower compressive strength (>5%) than PC 1 alone. At all other ages, the compressive strength of 0% and 5% CKD concrete mixes with PC 1 was similar (±5%). The PC 1 concrete mixes incorporating 10% and 15% CKD 1 had lower compressive strength (>5%) in comparison to PC 1 alone at ages tested after 7 days. For PC 2, the compressive strength of 0% and 5% CKD concrete mixes with PC 2 was similar (±5%) at all ages tested except 56 days (>10%). However, there was generally a decrease in compressive strength (>5%) in the PC 2 concrete mixes with 10% and 15% CKD 1 at all ages, in comparison to PC 2 alone. The authors concluded that up to 5% CKD could be used without apprehension of the reduction in compressive strength, despite the low compressive strength with PC 1 at 3 and 7 days and low compressive strength with PC 2 at 56 days.

(a)

(b) Figure 2.19 Concrete compressive strength of CKD 1 at different replacement levels of (a) PC 1 and (b) PC 2 (Maslehuddin et al., 2008b)

88 Maslehuddin et al. (2008a) studied the compressive strength effect of replacing PC 3 with CKD 1 at 0%, 5%, and 10% replacement by mass in mortars. The mortar mixes had a w/b ratio of 0.485 and were tested at 1, 3, 7, and 28 days. The compressive strength of all CKD-PC blends was higher than PC alone at all ages, as shown in Table 2.17. At 1 day, the blends with CKD at 5% and 10% replacement had 28% and 34% higher strength than PC alone, respectively. At 3 days, the blends with CKD at 5% and 10% replacement had 44% and 51% higher strength than PC alone, respectively. At 7 days, the blends with CKD at 5% and 10% replacement had 20% and 21% higher strength than PC alone, respectively. Finally, at 28 days, the blends with CKD at 5% and 10% replacement had 5% and 11% higher strength than PC alone, respectively. At all ages, the compressive strength increased as the quantity of CKD in the mortar mixes increased.

Table 2.17 Mortar compressive strength of CKD 1 at 0%, 5%, and 10% replacement of PC 3 as a function of time (Maslehuddin et al., 2008a)

Average Compressive Strength (MPa) 1 day 3 day 7 day 28 day 100% PC 3 6.31 15.04 22.93 33.17 95% PC 3, 5% CKD 1 8.09 21.60 27.60 34.79 90% PC 3, 10% CKD 1 8.43 22.71 27.69 36.89

El-Aleem et al. (2005) studied the compressive strength effect of replacing PC 4 with CKD 2 at 0%, 2%, 4%, 6%, 8%, and 10% replacement in mortars according to ASTM C109. The w/b ratio was increased to maintain a constant flow. The mortar compressive strength tests were conducted at 3, 7, 28, and 90 days, as shown in Figure 2.20. El-Aleem et al. (2005) reported that the compressive strength for mortar cubes decreased slightly at all ages with CKD content of up to 6%. Above this percentage, the compressive strength decreased sharply. The reduction of compressive strength is suggested to be caused by:

89 (i) the reduction in the cement content, (ii) an increase in the w/b ratio as the percentage of CKD in the blend increased, (iii) an increase in free lime content in cement dust; the higher amount of Ca(OH) 2 weakened the hardened matrix, (iv) the formation of chloro- and sulfoaluminate phases leads to the softening and expansion of the hydration products, and (v) the porosity also increases, due to the high chloride (7.5%) and sulfate (5.10%) content of CKD 1 (Note: the formation of these products enhances the crystallization of hydration products leading to an opening of the pore system). El-Aleem et al. (2005) concluded that the substitution of PC with CKD up to 6% has no significant effect on the compressive strength of hardened mortar.

I.1 Control I.2 2% CKD I.3 4% CKD I.4 6% CKD I.5 8% CKD I.6 10% CKD

Figure 2.20 Mortar compressive strength as a function of time at different percentage levels of CKD 2 replacement of PC 4 (El-Aleem et al., 2005)

90 Al-Harthy et al. (2003) investigated the compressive strength effect of using CKD 3 as a partial replacement of PC 5 using mortars. The different mortar levels of CKD replacement of PC by mass were 0%, 10%, 20%, 25%, and 30%. The w/b ratio of each mortar mix varied to maintain constant flow. The mortar mixes were tested at 28 days and showed the CKD blended strengths to be lower than the control (31 MPa). Al-Harthy et al. (2003) attributed the lower strengths to the higher w/b ratios of the CKD blended mortars. The 10% CKD blend had a compressive strength of 27 MPa and the 20% CKD blend had a compressive strength of 23 MPa. It is interesting to note that the 25% CKD blend (24 MPa) and 30% CKD blend (24 MPa) had comparable strengths to the 20% CKD blend.

Al-Harthy et al. (2003) also used seven different concrete mixtures that were prepared using 0 (control), 5, 10, 15, 20, 25, and 30% CKD 3 replacement by total mass of PC 5. For each mixture, three water-binder ratios of 0.70, 0.60, and 0.50 by mass were used and the ages tested were 3, 7, and 28 days, as shown in Figure 2.21. A major observation by the authors was that there is generally a decrease in compressive strength with an increase in CKD replacement for cement. The authors also observed that there is more decrease in compressive strengths in mixes with higher w/b ratios (0.70) than in those mixes with low w/b ratios (0.50). At 5% and 10% CKD 3 substitution for PC 5, the reductions in the 28 day compressive strength were 1.8% and 4.5%, respectively (w/b of 0.50). At higher w/b ratio (0.60) the 28 day compressive strength reductions were more significant (12.4% and 18% decreases in strength for 5% and 10% CKD 3 replacement of PC 5). Al-Harthy et al. (2003) stated that CKD is not highly cementitious and the replacement of cement by CKD will lead to less cement content and, therefore, less strength. However, small amounts of 5% and 10% CKD substitution do not seem to have an appreciable adverse effect on strength, especially at low w/b ratios.

(a)

(b) (b)

(c)

Figure 2.21 Concrete compressive strengths, w/b (a) 0.70, (b) 0.60, and (c) 0.50, at different percentage levels of CKD 3 replacement of PC 5 (Al-Harthy et al., 2003)

92 Udoeyo and Hyee (2002) studied the compressive strength effect of replacing PC 6 with CKD 4 at 20%, 40%, 60%, 80%, and 100% replacement in concrete at a w/b ratio of 0.65. The tests were conducted at 1, 3, 7, and 28 days. Udoeyo and Hyee (2002) reported that the strength decreased with an increase in CKD content at these very high replacement levels. For example, the 28-day reduction in compressive strength compared to the plain concrete was 7.5%, 33.2%, 71.8%, and 85.3%, respectively, for concrete with 20%, 40%, 60%, and 80% replacement levels of PC 6 with CKD 4. The strength results suggest that CKD 4 is poorly hydraulic.

Wang et al. (2002) studied the effect of CKD 5 at partial replacement levels of PC 7 at 0%, 15%, and 25% on 28-day compressive strength with mortars at a w/b ratio of 0.50. Wang et al. (2002) found that the compressive strength of blends with CKD and cement increased with the CKD replacement of cement up to 15% (47.8 MPa) in comparison to cement alone (46.3 MPa). The specimen with 25% CKD (39.4 MPa) had a much lower compressive strength than the plain cement specimen. Wang et al. (2002) stated that it is commonly accepted that the low hydraulic property of CKD causes the compressive strength to decrease as the amount of CKD replacement increases. Wang et al. (2002) also suggested that the increased strength in the specimen with 15% CKD may be attributed to an appropriate alkalinity that increases the dissolution of silicate species and formation of C-S-H. The authors also noted that 15% CKD replacement of PC significantly reduces the volume fraction of pores larger than 3 µm, which may result in improved strength.

Shoaib et al. (2000) conducted compression strength tests on concrete using CKD 6 as a partial replacement of PC 8 at 0%, 10%, 20%, 30%, and 40% and a w/b ratio of 0.5. The tests were conducted at one, three, and six months. The authors reported that the compressive strength decreased with increasing amounts of CKD. Shoaib et al. (2000) concluded that the critical value of CKD replacement of cement for compressive strength requirements is 10%. They attributed the compressive strength loss to the reduction in

93 cement clinker, which is mainly responsible for strength development. They also concluded that the higher concentration of chlorides present in CKD led to a reduction of strength. It was reported that the chlorides caused the hydration products to crystallize, which resulted in an increase in the total porosity of the hardened sample, thus reducing the compressive strength. The authors further stated that the chloride ions take part in chemical reactions (similar to those involving sulfate ions) and yield chloro-aluminate hydrate 3CaO.Al 2O3.CaCl 2.12H 2O, which can cause softening. Shoaib et al. (2000) reported that due to the presence of alkalis, the microstructure of C-S-H phases became heterogeneous and lowered the ultimate compressive strength.

Batis et al. (1996) used PC 10 and two CKDs (CKD 9 and CKD 10) for testing 90-day compressive strength concrete containing CKD. Each CKD was added as a 6% partial cement replacement, and the w/b ratio was varied at 0.65, and 0.75. At w/b ratio of 0.65 the level of 90-day compressive strength of the specimens with CKD was the same as the plain cement specimen. At a w/b ratio of 0.75, however, the concrete specimen with CKD 9 had a 35% reduction in compressive compared to the CKD 10 concrete and plain cement specimens. Batis et al. (1996) concluded that concrete made with CKD 10 at 6% replacement of PC 10 exhibited as good performance as the reference concrete. In addition, the authors noted that the incorporation of CKD 10 reduced the porosity of concrete from approximately 14% (reference) to 10%, as measured with mercury intrusion porosimetry (MIP) at w/b ratios of 0.65 and 0.75 and after 6 months of exposure in NaCl. It is widely accepted that a reduction in porosity improves compressive strength.

El-Sayed et al. (1991) conducted 28-day compressive strength tests on cement pastes consisting of PC 11 and CKD 11. The CKD was blended at 0%, 3%, 5%, 6%, 7%, and 10% replacement of cement. The w/b ratio of pastes was 0.30. El-Sayed et al. (1991) reported that as the percentage of CKD content in the paste increased, the compressive strength measurements decreased. The authors also reported that up to 5% CKD

94 replacement of PC was within the range of the Egyptian Standard Specifications for Ordinary and Rapid Hardening Cement (36 MPa).

Wang and Ramakrishnan (1990) investigated the compressive strength properties of mortar and concrete made with a binary blend consisting of 5% CKD (CKD 12) and 95% TIII cement (PC 12). The mortar mixes had a w/b ratio of 0.485 and were tested at 1, 3, 7, 14, 28, and 90 days. The authors reported that there was no significant difference in the compressive strengths of CKD-PC mortar and plain PC mortar specimens. Most of the CKD-PC mortar strengths fell within plus or minus 1.4% of the strength of plain PC mortar. The concrete mixes were tested at w/b ratios of 0.45, 0.52, and 0.55 at 1, 3, 7, and 28 days. The authors stated that most of the strengths for CKD-PC concrete were 4% higher in the earlier tests and 3.5% lower at 28 days than for plain cement concrete.

Ramakrishnan (1986) also used CKD 12 to determine whether it was suitable as a 5% replacement of TI cement (PC 15). Mortar and concrete testing was conducted to assess compressive strengths. The mortar mixes had a w/b ratio of 0.485 and were tested at 1, 3, 7, 14, 28, and 90 days. Ramakrishan (1986) noted that although the difference in strength between blended and plain cement mortar cubes was very small, the blends with CKD nearly always had the lower strength in comparison to the plain cement. Ramakrishan (1986), therefore, stated that the mortar specimens showed that the CKD did not possess any cementitious property. The concrete mixes were tested at a cement content of 386 kg/m 3 and w/b ratio of 0.45. Six sets of each concrete mix were batched. The concrete mixes were tested at 1, 3, 7, 28, and 90 days. As opposed to the mortar specimens, the concrete with CKD had equal or higher compressive strengths than the plain concrete at all ages of testing, with the exception of the compressive strengths at 28 days. Ramakrishan (1986) therefore concluded that there was no significant difference in the compressive strength of blended and cement concretes. The author did not explore the reasons for the different impact of CKD on compressive strength between mortars and concrete.

Bhatty (1986) used a TI cement (PC 16) with three different CKDs (CKD 13, CKD 14, and CKD 15) to investigate their effect on compressive strength in mortars. The amount of CKD in each blend was fixed at 10% by mass of PC with a w/b ratio of 0.45. Compressive strengths were determined at 1, 7, 28, and 90 days, and one year. Bhatty (1986) reported that the blends of cement and CKD at 10% partial replacement had higher strengths at one day, but were generally lower at 7, 28, and 90 days in comparison to cement alone. The strengths of mortars with CKD after one year, however, were comparable to cement alone.

Bhatty (1985a) used the same CKD (CKD 13, CKD 14, and CKD 15) and cement (PC 16) as Bhatty (1986) to conduct paste compressive strength testing. Cement and CKD blends were prepared by replacing 10% and 20% of cement and a w/b ratio of 0.45. Compressive strengths were determined at 1, 7, 28, and 90 days, and one year. Bhatty (1985a) stated that all blends with CKD had similar or higher strengths compared to cement at one day, with CKD 14 blends producing much higher strengths compared to cement and cement blends with CKD 13 and CKD 15. Blends with CKD 15 generally showed significantly lower strengths at later ages compared to CKD 13 and CKD 14. Bhatty (1985a) also noted that a significantly higher strength at one day was obtained for the blend with 10% CKD 15 compared to that with 20% CKD 15, while the other blends were quite comparable. From seven days to one year, blends made with 10% CKD replacement generally showed higher strengths compared to blends with 20% CKD replacement. This study showed that the strengths are adversely affected when high alkali chloride (potassium chloride) CKD was used. Bhatty (1985a) observed that the higher amounts of calcium carbonate in dusts appeared to be detrimental to strength development, but higher free lime appeared to be beneficial for strength. Blends with CKD containing higher amounts of sulfate developed higher strength compared to blends made with CKD containing lower amounts of sulfate. Also, when sulfate was present in

96 the form of calcium sulfate (CKD 14), better strengths were obtained than when some of the sulfate was also present in the form of alkali sulfates (CKD 13).

Bhatty (1984) also conducted compressive strength testing on pastes using five companion cements and dusts obtained from five different cement plants. The five companion cement kiln dust blends are: PC 17 and CKD 13, PC 18 and CKD 14, PC 19 and CKD 15, PC 20 and CKD 16, and PC 21 and CKD 17. For each CKD blend, the CKD replacement of the PC was 0%, 10%, 15%, and 20% at a w/b ratio of 0.50. Bhatty (1984) stated that at all ages, as the amount of CKD increased, the strength generally decreased except with CKD 15, which consistently showed higher strength at 20% addition compared to 10% and 15% addition levels. CKD 15 contained a much higher chloride and alkali content and much lower sulfate content than the other CKDs. Bhatty (1984) stated that alkali chlorides would probably behave similarly to calcium chloride, and calcium chloride is known to increase concrete strength, especially at one to three days curing. The author also reported that the strengths for blends containing CKD 15 were higher at one and seven days than at 28 and 90 days, when compared to cement at the same ages. Also, strengths increased steadily with the increase in chloride level for blends with CKD 15. The CKD-PC blends not containing CKD 15 decreased in strength as the amount of CKD increased. This trend was more prominent in blends with CKD 16 and CKD 17, which contained moderate amounts of alkali and sulfates in the form of alkali and calcium sulfates than in the blends with CKD 14 where the sulfate was predominantly calcium sulfate. Bhatty (1984) concluded that the compressive strengths for CKD blends containing 10%, 15%, and 20% were lower than cement alone. The highest loss in strength occurred when CKDs with relatively high alkali and chloride contents were used. However, as the amount of this CKD increased in the blend, the strength also increased, likely due to an accelerating effect of alkali chlorides on hydration.

97 Ravindrarajah (1982) used concrete mixes to study the compressive strength effect of CKD 18 as a partial cement replacement of PC 22 at 1, 3, 7, 14, 28, 56, and 90 days. Cement was partially replaced with CKD by mass at 0%, 15%, 25%, 35%, and 45%. The total water content for each mix was different to produce a similar workability. Ravindrarajah (1982) reported that as the percent of cement replaced by CKD increased the compressive strength decreased, and the magnitude of strength reduction was increased with the increase in CKD. The author cited four possible mechanisms to explain the impact of CKD replacement of PC on compressive strength in these tests: (i) alkalis in the CKD may modify the nature and strength of the cement hydration products, (ii) since the CKD dust particles are finer than cement, the hydration of the cementitious particles in the dust may occur at a faster rate than the PC. The author noted this by the development of strength with age expressed as a percentage of its 28 day strength for the control and CKD blended mixes. In general, the concrete with no CKD replacement showed the lowest percentage of the 28-day strength at early ages when compared with the CKD concrete, (iii) the portion of CKD that is not cementitious may act as a fine filler and contribute to an increase in strength through increased compaction or provision of nucleation sites for cement hydration, and (iv) concrete compressive strength is a function of paste strength, aggregate strength, and aggregate-paste bond strength. The presence of CKD causes the paste to become weaker, and as the paste strength weakens, the aggregate-cement paste bond also weakens. Ravindrarajah (1982) concluded that from his limited research, cement in concrete could be safely replaced by up to 15% of CKD by mass from the perspective of short-term strength requirements.

98 A summary of the effects of studies conducted on compressive strength (f’ c) with CKD- PC blends compared to each of the respective reference plain cements is shown in Table 2.18. Although there were variations between researchers, generally the compressive strength of samples with CKD was lower than those of the control cement samples. Some of the suggested mechanisms for the reduction in strength are a reduction in the cement content, an increase in the w/b ratio (for mixes that varied water to maintain the same workability of all mixes), formation of portlandite, formation of chloro- and sulfoaluminate phases, higher porosity, lack of CKD cementitious value (low hydraulic property), weakening of the paste-aggregate bond, and poor formation of C-S-H due to alkalis from CKD. Some researchers reported that there was less of a decrease in compressive strength between plain cement and CKD blends at lower w/b ratios. Some researchers also noted that the CKD blends were higher at early ages and lower at later ages than for plain cement. An appropriate alkalinity that increases the dissolution of silicate species and formation of C-S-H and CKD acting as fine filler were suggested as mechanisms that could cause an increase in the compressive strength of cement with CKD as a partial substitute.

Table 2.18 Compressive strength: from CKD-PC literature review

Author(s) Blend Type w/b % CKD General Author Suggested Replacement Effect on f’c Mechanism(s) Maslehuddin CKD 1/PC 1 C N.R. 0,5,10,15 5% N.C et al. (2008b) CKD 1/PC 2 10-15% ↓ Maslehuddin CKD 1/PC 3 M 0.485 0,5,10 ↑ et al. (2008a)

El-Aleem et CKD 2/PC 4 M V 0,2,4,6,8,10 ↓ (1) Reduction in the al. (2005) cement content (2) An increase in the w/b ratio (3) Increase in free lime content in cement dust; the higher amount of Ca(OH) 2 weakened the hardened matrix. (4) The formation of chloro-and sulfoaluminate phases leads to the softening and expansion of the hydration products. (5) The porosity increases due to the high chloride (7.5%) and sulfate (5.10%) content of the CKD (formation of these products enhances the crystallization of hydration products leading to an opening of the pore system). Al-Harthy et CKD 3/PC 5 M V 0,10,20,25,30 ↓ (6) More decrease in al. (2003) C K 0,10,20,25,30 ↓ compressive strength at higher w/b ratios (7) CKD is not highly cementitious. Udoeyo and CKD 4/PC 6 C 0.65 0,20,40,60,80 ↓ Hyee (2002) P = Paste; M = Mortar; C = Concrete V = varied w/b ratio to maintain consistent workability K = constant w/b ratio, but more than one w/b ratio was tested N.C. = No Change f’c = compressive strength

100 Table 2.18 (continued) Compressive strength: from CKD-PC literature review

Author(s) Blend Type w/b % CKD General Author Suggested Mechanism(s) Replacement Effect on f’c Wang et al. CKD 5 / PC 7 M 0.50 0,15,25 15% ↑ (8) Low hydraulic property of (2002) 25% ↓ CKD causes the compressive strength to decrease. (9) Increased strength of 15% CKD-PC blend may be attributed to an appropriate alkalinity that increases the dissolution of silicate species and formation of C-S-H. (10) At 15% CKD replacement of PC, the reduction of volume fraction of pores larger than 3um may result in improved strength. Shoaib et al. CKD 6 / PC 8 C 0.50 0,10,20,30,40 ↓ (11) Loss of cement clinker (1999) which is mainly responsible for strength development (12) CKD Cl - cause crystallization of hydration products resulting in opening of pore system of the hardened samples leading to strength loss (13) Chloro-aluminate formation causes softening (14) CKD alkalis cause the C-S- H phases to become heterogeneous & lowers strength Batis et. al CKD 9 / PC 10 C K 0,6 ↓ (15) CKD 9 concrete specimen (1996) CKD 10/ PC 10 C K 0,6 N.C. was same as control at w/b of 0.65, but at 0.75 was dramatically lower. (16) CKD 10 concrete specimen had lower porosity (MIP) compared to the concrete specimen without CKD. El-Sayed et al. CKD 11 / PC 11 P 0.30 0, 3,4,5,6,7,10 ↓ (1991) Wang and CKD 12/PC 12 M 0.485 0,5 N.C. (17) Most of the CKD concrete Ramakrishnan C K 0,5 N.C. specimens were 4% higher (1990) at early ages and 3.5% lower at 28 days than for plain concrete specimens. Ramakrishnan CKD 12/PC 15 M 0.485 0,5 ↓ (18) CKD does not possess any (1986) C 0.45 0,5 N.C. cementitious value.

Bhatty CKD 13/PC 16 M 0.45 0,10 1d ↑, rest ↓ (1986) CKD 14/PC 16 M 0.45 0,10 1d ↑, rest ↓ CKD 15/PC 16 M 0.45 0,10 1d ↑, rest ↓ P = Paste; M = Mortar; C = Concrete V = varied w/b ratio to maintain consistent workability K = constant w/b ratio, but more than one w/b ratio was tested N.C. = No Change f’c = compressive strength

101 Table 2.18 (continued) Compressive strength: from CKD-PC literature review

Author(s) Blend Type w/b % CKD General Author Suggested Mechanism(s) Replacement Effect on f’c Bhatty CKD 13/PC 16 P 0.45 0,10,20 1d ↑, rest ↑↓ (19) High alkali chloride (KCl) in (1985a) CKD 14/PC 16 P 0.45 0,10,20 1d ↑, rest ↑↓ CKD reduces f’c. CKD 15/PC 16 P 0.45 0,10,20 1d ↑, rest ↑↓ (20) High calcium carbonate in CKD reduces f’c. (21) Higher free lime in CKD increases f’c. (22) Blends with CKD containing higher amounts of sulfate developed higher strength compared to blends made with CKD containing lower amounts of sulfate. (23) When sulfate was present in the form of calcium sulfate (CKD 14), better strengths were obtained than when some of the sulfate was also present in the form of alkali sulfates (CKD 13). Bhatty CKD 13/PC 17 P 0.50 0,10,15,20 1d N.C., rest (24) Strengths increased steadily (1984) CKD 14/PC 18 P 0.50 0,10,15,20 ↓ with increase in chloride CKD 15/PC 19 P 0.50 0,10,15,20 1d ↑, rest ↓ level for blends with CKD CKD 16/PC 20 P 0.50 0,10,15,20 ↓ 15. CKD 17/PC 21 P 0.50 0,10,15,20 1d N.C., rest (25) The CKD-PC blends not ↓ containing CKD 15 ↓ decreased in strength as the amount of CKD increased. This trend was more prominent in blends with CKD 16 and CKD 17 which contained moderate amounts of alkali and sulfates in the form of alkali and calcium sulfates than in the blends with CKD 14 where the sulfate was predominantly calcium sulfate. (26) The highest loss in strength occurred when CKD with relatively high alkali and chloride contents were used. However, as the amount of this CKD increased in the blend, the strength also increased, likely due to an accelerating effect of alkali chlorides on hydration (acting similar to calcium chloride). Ravindrarajah CKD 18/PC 22 C V 0,15,25,35,45 ↓ (27) Alkalis may modify (1982) hydration products. (28) CKD may act as a fine filler. (29) CKD presence weakens paste and aggregate-paste bond. P = Paste; M = Mortar; C = Concrete V = varied w/b ratio to maintain consistent workability K = constant w/b ratio, but more than one w/b ratio was tested N.C. = No Change f’c = compressive strength

102 2.5.6 Flexural and Tensile Strength Al-Harthy et al. (2003) investigated the flexural strength effect of using CKD 3 as a partial replacement of PC 5 using concrete. Al-Harthy et al. (2003) used seven different concrete mixtures that were prepared using 0 (control), 5%, 10%, 15%, 20%, 25%, and 30% CKD 3 replacement by total mass of cement. For each mixture, three water-binder ratios of 0.50, 0.60, and 0.70 by mass were used (the age at which the specimens were tested was not specified but it is assumed that it was at 28 days). Flexural strength measurements were determined using a two-point loading system. Toughness values, which measure the ability of a material to absorb energy up to fracture, were calculated based on the area under the stress-strain diagram. Similar to the effects on compressive strength, the authors stated that the flexural strength and toughness values decreased with an increase in CKD replacement for cement but at 5% and 10% replacement levels did not have an appreciable adverse effect (especially at low w/b ratios). Al-Harthy et al. (2003) attributed the reduction in flexural strength and toughness values to a reduction in the cement content in the blends as the amount of CKD increased.

Udoeyo and Hyee (2002) studied the split tensile strength and modulus of rupture effects of replacing PC 6 with CKD 4 at 20%, 40%, 60%, 80%, and 100% replacement in concrete at a w/b ratio of 0.65. The tests were conducted at 1, 3, 7, and 28 days. Similar to the results of compressive strength, Udoeyo and Hyee (2002) reported that the split tensile strength and modulus of rupture decreased with an increase in CKD content. The reduction in split tensile strength compared to the plain concrete was approximately 24%, 48%, 65%, and 90%, respectively, for concrete with the very high 20%, 40%, 60%, and 80% replacement levels of PC 6 with CKD 4. The reduction in modulus of rupture compared to the plain concrete was approximately 18%, 70%, and 90%, respectively, for concrete with 20%, 40%, and 60% replacement levels of PC 6 with CKD 4. Udoyeo and Hyee (2002) did not suggest possible mechanisms for CKD-PC effects on split tensile strength and modulus of rupture.

103 Wang et al. (2002) studied the effect of CKD 5 at partial replacement levels of PC 7 at 0%, 15%, and 25% on 28-day flexural strength with mortars at a w/b ratio of 0.50. Wang et al. (2002) found that the flexural strength of blends with CKD and cement increase with the CKD replacement of cement up to 15% (8.5 MPa) in comparison to cement alone (8.2 MPa). The specimen with 25% CKD (7.6 MPa) had a much lower flexural strength than the plain cement specimen. Wang et al. (2002) stated that the increased strength in the specimen with 15% CKD may be attributed to an appropriate alkalinity that increased the dissolution of silicate species and formation of C-S-H. Wang et al. (2002) also reported that 15% CKD replacement of PC significantly reduced the volume fraction of pores larger than 3 µm, which may result in improved strength.

Shoaib et al. (2000) conducted splitting tensile strength tests on concrete using CKD 6 as a partial replacement of PC 8 at 0%, 10%, 20%, 30%, and 40% at a w/b ratio of 0.5. The tests were conducted at one, three, and six months. The authors reported a gradual decrease in the splitting tensile strength for all cylinders of concrete samples as the amount of CKD increased. The reduction in tensile strength was attributed to the lower bond strength between the aggregate and paste. Shoaib et al. (2000) stated that as the amount of CKD increased in the paste, the bond strength between the aggregate and the paste decreased.

Wang and Ramakrishnan (1990) studied the splitting tensile and flexural strength properties of binary blends consisting of 5% CKD (CKD 12) and 95% Type III cement (PC 12). The splitting tensile strength mortar mixes had a w/b ratio of 0.485 and were tested at 1, 3, 7, 14, 28, and 90 days. The 14-day tensile strength of the CKD mortar was 10% higher than for the plain cement mortar. At 28 and 90 days, however, there was no significant difference in the tensile strengths of the plain cement and CKD-PC specimens. The flexural strength concrete mixes were tested at w/b ratios of 0.45, 0.52, and 0.55 at 1, 3, 7, and 28 days. Wang and Ramakrishnan (1990) stated that the results of flexure strength tests of concrete specimens with CKD were within a range of ±4% of those of

104 the plain cement concrete and, therefore, not significant. Wang and Ramakrishnan (1990) did not suggest possible mechanisms for CKD-PC effects on split tensile and flexural strength.

Ramakrishnan (1986) studied the mortar splitting tensile and concrete flexural strength properties made with a binary blend consisting of 5% CKD (CKD 12) and 95% TI cement (PC 15). The splitting tensile strength mortar mixes had a w/b ratio of 0.485 and were tested at 1, 3, 7, 14, 28, and 90 days. Ramakrishnan (1986) reported that for most of the CKD-PC mortar splitting tensile strengths were lower than the corresponding plain cement mortar strengths. The flexural strength concrete mixes were tested at a w/b ratio of 0.45 at 1, 3, 7, and 28 days. Ramakrishnan (1986) reported no significant difference in flexural strength between concretes containing CKD and plain concrete.

Ravindrarajah (1982) used concrete mixes to study the flexural and tensile strength effects of CKD 18 as a partial cement replacement of PC 22 at 1, 3, 7, 14, 28, 56, and 90 days. Cement was partially replaced with CKD by mass at 0%, 15%, 25%, 35%, and 45%. The total water content for each mix was varied to produce similar workability. Ravindrarajah (1982) also conducted tests to determine the flexural and tensile strengths. As in the compressive strength test results, the flexural and tensile strengths decreased with increased replacement of cement with CKD.

A summary of the studies conducted on the flexural and splitting tensile effects of CKD- PC blends compared to the referenced plain cement is shown in Table 2.19. Generally, the flexural and tensile strength effects of samples with CKD were lower than those of the control cement samples, which is similar to the compressive strength effects. Many of the suggested mechanisms for the reduction in flexural and split tensile strengths were the same as the mechanisms for the reduction in compressive strength. The most commonly suggested mechanism was the weakening of the aggregate-paste bond due to the presence of CKD.

105

Table 2.19 Flexural and tensile strength: from CKD-PC literature review

Author(s) Blend Typ w/b % CKD General Author Suggested Mechanism(s) e Replacement Effect on f’ t Al-Harthy et CKD 3/PC 5 C K 0,10,20,25,30 ↓ (1) Reduction in the cement al. (2003) content. (2) Less effect at low w/b ratios. Udoeyo and CKD 4/PC 6 C 0.65 0,20,40,60,80 ↓ Hyee (2002) Wang et al. CKD 5/PC 7 M 0.50 0,15,25 15% ↑ (3) Increased strength 15% CKD (2002) 25% ↓ specimen may be attributed to an appropriate alkalinity that increased the dissolution of silicate species and formation of C-S-H. (4) At 15% CKD replacement of PC, the reduction of volume fraction of pores larger than 3um may result in improved strength. Shoaib et al. CKD 6/ PC 8 C 0.50 0,10,20,30,40 ↓ (5) Weaker aggregate-paste bond (1999) as CKD content increases. Wang and CKD 12/PC 12 M 0.485 0,5 ↑ Ramakrishnan C K 0,5 N.C. (1990) Ramakrishnan CKD 12/PC 15 M 0.485 0,5 ↓ (1986) C 0.45 0,5 N.C. Ravindrarajah CKD 18/PC 22 C V ↓ (6) Alkalis may modify hydration (1982) 0,15,25,35,45 products. (7) CKD may act as a fine filler. (8) CKD presence weakened paste and aggregate-paste bond. P = Paste; M = Mortar; C = Concrete. V = varied w/b ratio to maintain consistent workability f’ t = flexural and/or tensile strength K = constant w/b ratio, but more than one w/b ratio was tested. N.C. = No Change

2.5.7 Volume Stability 2.5.7.1 Soundness Maslehuddin et al. (2008a) studied the soundness effect of replacing PC 3 with CKD 1 at 0%, 5%, and 10% replacement by mass in pastes using autoclave expansion (ASTM C151). The PC alone, PC with 5% CKD replacement, and PC with 10% CKD replacement were 0.0075%, 0.0130%, and 0.3730%, respectively. Although the CKD-PC blends had higher expansions than PC alone and increased as the percentage of CKD replacement increased, the autoclave expansions were below the 0.80% allowed by ASTM C150.

106

Bhatty (1986) used a Type I cement (PC 16) with three different CKD (CKD 13, CKD 14, and CKD 15) to investigate the effect on autoclave expansion (ASTM C151). The amount of CKD in each paste was fixed at 10% by mass of PC, with a w/b ratio of 0.45. Bhatty (1986) stated that the type of CKD used in the binary blend influenced the autoclave expansion. Bhatty (1986) reported that the CKD-PC blend with CKD 14 showed autoclave expansion comparable to cement alone but higher expansions were noted for CKD 13 and CKD 15. Bhatty (1986) also noted that each CKD-PC blend autoclave expansion was well below the ASTM C150 specification of 0.80%. Bhatty (1986) generally noted that when binary, ternary, and quaternary blends were made from PC 16, the three different CKD, fly ash and slag – the blends containing CKD 15 (a high chloride dust) generally produced higher autoclave expansions than blends with CKD 14, which contained high sulfate.

Ravindrarajah (1982) used cement pastes to determine the soundness of PC-CKD blends using the Le Chatelier apparatus (EN 196-3). PC 22 was partially replaced with CKD 18 by mass at 0%, 25%, 50%, 75%, and 100%. The total water content for each mix was varied to produce similar workability. As the CKD percentage increased, so did the expansion of the samples. This was attributed to the higher level of free lime in the CKD in comparison to cement. Although the level of expansion was well within the range of the British Standard, the expansion was much higher than that of cement.

A summary of the studies conducted on the soundness of CKD-PC blends compared to each of the respective reference plain cements is shown in Table 2.20. High free lime, sulfate, and chloride contents in the CKDs were attributed to the increased autoclave expansions.

107

Table 2.20 Soundness: from CKD-PC literature review

Author(s) Blend Type w/b % CKD General Effect on Author Suggested Replacement Soundness Mechanism(s) Maslehuddin et CKD 1/PC3 P V 0,5,10 ↓ al. (2008a) Bhatty CKD 13/PC 16 P 0.45 0,10 ↓ (1) High chloride CKD (1986) CKD 14/PC 16 P 0.45 0,10 ↓ generally produced CKD 15/PC 16 P 0.45 0,10 ↓ higher autoclave expansions than high sulfate CKD (includes mixes with slag, and fly ash). Ravindrarajah CKD 18/PC 22 C V 0,15,25,35,45 ↓ (2) High CKD free lime (1982) content.

P = Paste; M = Mortar; C = Concrete. V = varied w/b ratio to maintain consistent workability N.C. = No Change

2.5.7.2 Drying Shrinkage Maslehuddin et al. (2008b) studied the drying shrinkage effect of replacing PC 1 (TI) and PC 2 (TV) with CKD 1 at 0%, 5%, 10%, and 15% replacement by mass in concrete. The drying shrinkage strain after 3, 7, 14, 28, 56, and 90 days of curing were tested, according to ASTM C157. The drying shrinkage strain at the different percentage levels of CKD 1 replacement of PC 1 is shown in Figure 2.22. For PC 1, the highest shrinkage strain at all ages was with the 15% CKD 1 concrete specimens followed by the concrete specimens with 10% and 5% CKD 1, respectively. The 5% CKD 1 concrete specimens with PC 1, however, were only marginally higher (<5%) than the concrete specimens without CKD 1. Although the test results were not provided for PC 2 concrete specimens, it was reported that the initial shrinkage strain in the concrete specimens with CKD 1 was more than that in the concrete specimens without CKD 1. After 90 days, however, the shrinkage strain of 0%, 5%, and 10% concrete specimens with PC 2 was more or less similar while that of 15% CKD 1 concrete specimens with PC 2 was significantly higher than that of the other concrete specimens with PC 2.

108

Figure 2.22 Concrete drying shrinkage as a function of time at different replacement levels of PC 1 with CKD 1 (Maslehuddin et al., 2008b)

Maslehuddin et al. (2008a) studied the drying shrinkage effect of replacing PC 3 with CKD 1 at 0%, 5%, and 10% replacement by mass in mortars, according to ASTM C157. The w/b ratio for each mortar mix was adjusted to maintain a constant flow. The w/b ratios, however, were not reported. Drying shrinkage tests were conducted at 7, 14, 21, 28, 45, 60, and 75 days, as shown in Table 2.21. The drying shrinkage of mortar mixes with 5% CKD ranged between 19% and 43% higher drying shrinkage than that of the mortar mix with PC alone for the ages tested. The drying shrinkage of mortar mixes with 10% CKD ranged between 38% and 68% higher drying shrinkage than that of the mortar mix with PC alone for the ages tested.

109 Table 2.21 Mortar drying shrinkage with 0%, 5%, and 10% CKD 1 replacement of PC 3 (Maslehuddin et al., 2008a)

Average drying shrinkage (%) 7 days 14 days 21 days 28 days 45 days 60 days 75 days 100% PC 3 0.0380 0.0528 0.0620 0.0694 0.0739 0.0811 0.0847 95% PC 3, 5% CKD 1 0.0481 0.0742 0.0886 0.0918 0.0942 0.0977 0.1008 90% PC 3, 10% CKD 1 0.0532 0.0889 0.0924 0.1043 0.1098 0.1144 0.1173

Wang and Ramakrishnan (1990) compared the drying shrinkage properties of concrete made with a binary blend consisting of 5% CKD (CKD 12) and 95% TIII cement (PC 12). The concrete mixes were tested at w/b ratios of 0.45 and 0.52 and the drying shrinkage results are shown in Figure 2.23. The authors reported no significant difference in drying shrinkage between the concrete mixes at w/b of 0.45. At 0.52 w/b ratio, however, the concrete mix with CKD had considerably higher (22%) drying shrinkage than the plain cement concrete. Wang and Ramakrishnan (1990) stated they did not know the reason for this difference.

110 Mix 2: w/b = 0.52 Mix 3: w/b = 0.45

Figure 2.23 Concrete drying shrinkage as a function of time at two different w/b ratios with 5% CKD 12 replacement of PC 12 (Wang and Ramakrishnan, 1990)

Ramakrishnan (1986) also used CKD 12 to determine whether it was suitable as a 5% replacement of TI cement (PC 15). Concrete testing was conducted to assess drying shrinkage at a w/b ratio of 0.45. Ramakrishnan (1986) reported that the shrinkage deformation for CKD concrete mixes was a little more than that of the plain cement concrete.

Bhatty (1986) used a Type I cement (PC 16) with three different CKDs (CKD 13, CKD 14, and CKD 15) to investigate their effect on drying shrinkage in mortars. The amount of CKD in each blend was fixed at 10% by mass with a w/b ratio of 0.45. Drying shrinkage tests were conducted at 4, 11, 18, and 25 days. For all blends containing CKD 13 and CKD 15 the drying shrinkage increased compared to cement alone. The blends containing the high sulfate CKD 14, however, showed lower shrinkage than cement alone. Bhatty (1986) concluded that the drying shrinkage of binary blends with high sulfate CKD was lower than cement alone or other binary blends with low sulfate CKD.

111 A summary of the studies conducted on the drying shrinkage effects of CKD-PC blends compared to each of the respective reference plain cements is shown in Table 2.22. It appears that adverse effects on drying shrinkage of CKD-PC blends may be more significant at higher w/b ratios. Bhatty (1986) stated that drying shrinkage of CKD-PC blends with high sulfate content was lower than the control and other lower sulfate CKD- PC blends. This was not expected since higher sulfate levels are typically associated with drying shrinkage expansion. One possible explanation is that the high sulfate CKD may have contained less soluble sulfate forms than the PC it replaced and the other CKDs.

Table 2.22 Drying shrinkage: from CKD-PC literature review

Author(s) Blend Type w/b % CKD General Effect Author Suggested Mechanism(s) Replacement on Drying Shrinkage Maslehuddin et CKD 1/PC 1 C N.R. 0,5,10, 15 5% N.C. al. (2008b) CKD 1/PC 2 10-15% ↑ Maslehuddin et CKD 1/PC 3 M V 0,5,10 ↑ al. (2008a) Wang and CKD 12/PC 12 C 0.45 0,5 N.C. (1) Higher drying shrinkage at Ramakrishnan C 0.52 0,5 ↑ higher w/b ratio. (1990) Ramakrishnan CKD 12/PC 15 C 0.45 0,5 ↑ (1986) Bhatty CKD 13/PC 16 M 0.45 0,10 ↑ (2) Drying shrinkage of binary (1986) CKD 14/PC 16 M 0.45 0,10 ↓ blends with high sulfate CKD CKD 15/PC 16 M 0.45 0,10 ↑ was lower than cement alone and other binary blends with low sulfate CKD P = Paste; M = Mortar; C = Concrete. N.C. = No Change V = Varied w/b ratio to maintain consistent workability

2.5.7.3 Volume Stability Summary The volume stability of CKD blends in the literature review was assessed by considering the results of soundness and drying shrinkage. Three researchers reported that as the CKD increased, the autoclave expansion also increased for all five of the CKD-PC blends. One mechanism for this effect was suggested to be related to the high free lime content of CKD. It was also reported that high chloride CKD generally produced higher autoclave expansions than high sulfate CKD. Five researchers reported on drying

112 shrinkage. At 5 % CKD replacement, two CKD-PC blends had no change in drying shrinkage while four other CKD-PC blends had higher drying shrinkage values compared to the control cements. At 10% CKD replacement, five of the six CKD-PC blends had increased drying shrinkage compared to the control cements. The CKD-PC blend that decreased drying shrinkage was a high sulfate CKD, but it is likely that this CKD contained less soluble forms of sulfate than the PC or the other CKDs. At 15 % CKD replacement, the drying shrinkage values of the two CKD-PC blends were higher than that at 10% CKD replacement. It was noted that higher drying shrinkage occurred at higher w/b ratio.

2.5.8 Durability 2.5.8.1 Alkali-Aggregate Reaction Bhatty (1986) used a Type I cement (PC 16) with three different CKDs (CKD 13, CKD 14, and CKD 15) in mortars to investigate their effect on alkali-aggregate reactivity (AAR) according to ASTM C227. The aggregate used consisted of 95% Ottawa sand (non-reactive aggregate) and 5% Beltane Opal (reactive aggregate). Opal contains reactive silica that is used to assess the contribution of hydroxyl ions from the binder to form ASR. In this test method, the mortar specimen bars are stored vertically in a sealed environment above water, which is at the bottom of the container. The amount of CKD in each blend was fixed at 10% by mass of PC with a w/b ratio of 0.45. The expansion measurements were taken at 3 and 6 months. PC 16 contains a total alkali content of 0.53% as sodium oxide equivalent and is considered a low alkali cement according to ASTM C150. The blends with CKD 13, CKD 14, and CKD 15, had total alkali contents of 0.67%, 0.66%, and 0.82%, respectively. The expansions of CKD-PC blends at three and six months were very similar to cement alone and significantly below the ASTM limit of 0.1% at six months.

Bhatty (1985b) also conducted mortar bar expansion tests using four companion cements and dusts obtained from four different cement plants to assess potential alkali-aggregate

113 reactivity using ASTM C227. The w/b ratio was 0.50 and measurements were taken periodically over a one-year period. The four companion cement kiln dust blends are: PC 17 and CKD 13, PC 18 and CKD 14, PC 19 and CKD 15, and PC 20 and CKD 16. Each CKD replacement of PC was at 0%, 10%, 15%, and 20%. Although the PCs and CKDs from individual plants showed significant differences, all CKD blends exhibited higher ASR induced expansions compared to the control PC alone. As the amount of CKD in the blends increased, expansion also increased. Bhatty (1985b) stated that at six months the highest expansion obtained was with CKD 16 blends while the lowest expansion was obtained using CKD 13. Blends with CKD 15 produced lower expansions despite having the same alkali contents as blends containing CKD 16. This is likely due to the fact that a major portion of the alkali in CKD 15 is present as a chloride salt. CKD 14 blends had similar water soluble alkali content to blends made with CKD 13 but showed much higher expansion compared to the latter. Differences in expansion of blends containing similar alkali contents can be attributed to the difference in chemical composition of cements and dusts and to the type of alkali compounds present in these materials. Water soluble alkali showed a more meaningful relationship with expansion than did total alkali with respect to the 0.60% alkali limit for CKD-PC blends. The author concluded that kiln dust is not the only material in a binary blend that can influence alkali-aggregate expansion. Different cements with the same kiln dust can produce different expansion not only due to differences in alkali content but also in other compositional variations.

A summary of the studies conducted on the alkali-aggregate reactivity of CKD-PC blends compared to each of the respective reference plain cements is shown in Table 2.23.

114

Table 2.23 Alkali-aggregate reactivity: from CKD-PC literature review

Author(s) Blend Type w/b % CKD General Effect Author Suggested Mechanism(s) Replacement on AAR

Bhatty CKD 13/PC 16 M 0.45 0,10 N.C. (1986) CKD 14/PC 16 M 0.45 0,10 N.C. CKD 15/PC 16 M 0.45 0,10 N.C. Bhatty CKD 13/PC 17 M 0.50 0,10,15,20 ↑ (1) As the amount of CKD in the (1985b) CKD 14/PC 18 M 0.50 0,10,15,20 ↑ blends increased, expansion also CKD 15/PC 19 M 0.50 0,10,15,20 ↑ increased. CKD 16/PC 20 M 0.50 0,10,15,20 ↑ (2) Water soluble alkali showed a more meaningful relationship with expansion than did total alkali with respect to 0.60% alkali limit for CKD-PC blends. (3) Blends with CKD 15 produced lower expansion despite having the same alkali contents as blends containing CKD 16. This is likely due to the fact that a major portion of the alkali in CKD 15 is present as a chloride salt. (4) CKD 14 blends had similar water soluble alkali content to blends made with CKD 13 but showed much higher expansion compared to the latter. (5) Differences in expansion of blends containing similar alkali contents can be attributed to the difference in chemical composition of cements and dusts and to the type of alkali compounds present in these materials. (6) CKD is not the only material in a binary blend that can influence alkali-aggregate expansion. Different cements with the same kiln dust can produce different expansion not only due to differences in alkali content but other compositional variations as well P = Paste; M = Mortar; C = Concrete N.C. = No Change.

115

2.5.8.2 Steel Corrosion Maslehuddin et al. (2008b) studied the electrical resistivity effect of replacing PC 1 (Type I) and PC 2 (Type V) with CKD 1 at 0%, 5%, 10%, and 15% replacement by mass in concrete. Since electrical resistivity is a function of moisture content in the concrete, resistance measurements were conducted at varying water content in the specimens. The specimen was initially saturated in water for 28 days and afterward the electrical resistivity was measured. The specimen was then allowed to dry and the electrical resistivity measurements were taken periodically. Ultimately, the specimen was oven- dried at 110°C and the moisture content determined. The electrical resistivity after 28 days (water curing) at the different percentage levels of CKD 1 replacement of PC 1 and PC 2 was plotted against the moisture content, as shown in Figure 2.24. The electrical resistivity decreased with increasing moisture content. The authors reported that the electrical resistivity of PC 1 concrete mixes with CKD 1 at 0%, 5%, and 10% was not significantly different. However, there was a significant decrease in electrical resistivity of PC 1 concrete mixes with CKD 1 at 15%. For PC 2, the electrical resistivity decreased significantly for all concrete specimens with CKD, in comparison to the concrete specimens without CKD. The authors suggested that the decrease in electrical resistivity due to the partial substitution of CKD 1 for PC2 in the concrete specimens may be attributed to an increase in free chloride ions. The higher presence of free chloride ions in PC2 concrete specimens with CKD in comparison to PC 1 concrete specimens with CKD is possibly due to PC 2 having low-chloride binding properties (lower C 3A content) compared to PC 1. The authors used an electrical resistivity classification system to assess the risk of reinforcement corrosion, as shown in Table 2.24. At a moisture content of approximately 3%, the electrical resistivity of PC 1 and PC 2 concrete specimens with and without CKD was in the range of approximately 25 – 50 k Ω.cm. Therefore, according to Table 2.24, at approximately 3% moisture content the risk of steel reinforcement corrosion for all of the concrete specimens is of moderate intensity.

116

(a)

(b) Figure 2.24 Concrete specimen variation of electrical resistivity with moisture content at different percentage levels of CKD 1 replacement of (a) PC 1 and (b) PC 2 (Maslehuddin et al., 2008b)

117

Table 2.24 Concrete resistivity and risk of reinforcement corrosion as specified in COST 509 (Maslehuddin et al., 2008b)

Concrete resistivity (k Ω cm) Risk of reinforcement corrosion <10 High 10-50 Moderate 50-100 Low >100 Negligible

Konsta-Gdoutos et al. (2001) completed corrosion tests on mortar specimens using CKD 5 as a partial replacement of PC 7 at 0%, 15%, and 25% by mass. The mortar w/b ratio was 0.50 and was mixed in accordance with EN 196-1. Mortar specimens of 75 x 75 x 300 mm were prepared and reinforced centrally with a 12M steel bar and a 12.7 mm cover. They were cured for seven days in a curing room. To accelerate corrosion of the embedded steel the specimens were immersed half way in a 5% (by mass) NaCl solution. The results were interpreted according to ASTM C876 criteria for corrosion of steel in concrete. The corrosion potential of the binary blends was monitored three times per week. The half cell potential technique was used to measure the risk of corrosion. The corrosion potentials observed for the CKD-PC blends suggest that more than 15% CKD replacement of PC accelerates corrosion. This is possibly due to the introduction of chloride ions in the mix incorporated in the CKD.

Batis et al. (1996) used PC 7 and 2 CKDs (CKD 8 and CKD 9) for testing steel corrosion of concrete containing CKD. Each CKD was added as a 6% partial cement replacement at three w/b ratios: 0.50, 0.65, and 0.75. Each concrete test specimen was reinforced with steel bars and immersed in 3.5% by mass NaCl solution 5 cm from their bottom. The free upper section of rebars were connected to copper cable and covered with epoxy resin. The corrosion potential was measured every seven days. Batis et al. (1996) reported that

118 the blends with CKD 9 had improved corrosion resistance in comparison to the reference mix. The blends with CKD 8 had reduced corrosion resistance in comparison to the reference mix. The protective behavior of CKD 9 against corrosion is attributed to its fineness and relatively higher alkalinity. Batis et al. (1996) also noted that CKD 8 had double the chloride content and three times higher sulfate content compared to CKD 9. The elevated chloride and sulfate ion contents accelerated the corrosion rate in the concrete specimens made with CKD 8 at all w/b ratios.

El-Sayed et al. (1991) conducted steel corrosion tests on cement pastes and mortars consisting of PC 11 and CKD 11. The tests were used to determine the potential level of CKD replacement in pastes and mortars without impairing the passivity of the embedded steel. The CKD was blended at 0%, 3%, 5%, 6%, 7%, and 10% replacement of cement. The w/b ratio was 0.30 for pastes and 0.60 for mortars. For both pastes and mortars, as the amount of CKD increased the passivity of steel decreased. El-Sayed et al. (1991) determined that the steel passivity was maintained at an acceptable level up to 5% CKD by mass of cement. The authors attributed the 5% CKD level of corrosion protection from aggressive sulfate and chloride ions in the mix to the high hydroxide (OH -) content that develops during hydration as a result of the CKD. El Sayed et al. (1991) concluded that the OH - helped in maintaining the passive oxide layer that protected the steel.

A summary of the studies conducted on the steel corrosion of CKD-PC blends compared to each of the respective reference plain cement is shown in Table 2.25.

119

Table 2.25 Steel corrosion: from CKD-PC literature review

Author(s) Blend Type w/b % CKD General Effect Author Suggested Mechanism(s) Replacement on Steel Corrosion Maslehuddin et CKD 1/PC 1 C N.R. 0,5,10,15 ↑ (1) Decrease in electrical al. (2008b) CKD 1/PC 2 resistivity (higher risk of steel reinforcement corrosion) may be due to presence of free chloride ions from CKD Konst-Gdoutos CKD 5/PC 7 M 0.50 0,15,25 ↑ (2) More than 15% CKD et al. (2001) replacement of PC accelerated corrosion possibly due to the introduction of CKD chloride ions. Batis et. al CKD 9 / PC 10 C K 0,6 ↑ (3) Protective behavior of CKD (1996) CKD 10/ PC 10 C K 0,6 ↓ 10 against corrosion was partially attributed to its higher fineness. (4) Protective behavior of CKD 10 was partially attributed to its relatively higher alkalinity. (5) CKD 9 had elevated chloride and sulfate ion contents (compared to CKD 10) – accelerated the corrosion rate. El-Sayed et al. CKD 11/ PC 11 P 0.30 0,3,4,5,6,7,10 ↑ (6) Corrosion protection from (1991) M 0.60 0,3,4,5,6,7,10 ↑ aggressive sulfate and chloride ions in the mix was attributed to the high hydroxide (OH -) content that developed during hydration as a result of the CKD. The OH - helped in maintaining the passivation film that protected the steel. P = Paste; M = Mortar; C = Concrete. K = constant w/b ratio, but more than one w/b ratio was tesed. N.R. = Not Reported

120

2.5.8.3 Permeability Maslehuddin et al. (2008b) studied the chloride permeability effect of replacing PC 1 (Type I) and PC 2 (Type V) with CKD 1 at 0%, 5%, 10%, and 15% replacement by mass in concrete, as shown in Table 2.26. The chloride permeability was measured after 28 days of curing, according to ASTM C1202. The measure of chloride permeability (values in Coulombs) increased with an increase in the CKD replacement of PC. At 5% CKD replacement, the increase in coulomb measurement increased by 6% for PC 1 and 1% for PC 2. At 10% CKD replacement, the increase in coulomb measurement increased by 16% for PC 1 and 13% for PC 2. At 15% CKD replacement, the increase in coulomb measurement increased by 62% for PC 1 and 23% for PC 2. As per ASTM C1202, the PC 1 concrete specimens with 0%, 5%, and 10% CKD were within the low range for chloride permeability while the 15% CKD was in the moderate range. The chloride permeability of the PC 2 concrete specimens with and without CKD replacement was in the moderate chloride permeability classification. The author suggested that the increased chloride content of the CKD may lead to a decrease in the electrical resistivity of concrete which is reflected in an increase in chloride permeability. As the content of CKD increases, more free chloride ions are liberated and cause the measure of chloride permeability to increase.

121 Table 2.26 Chloride permeability of PC 1 and PC 2 with CKD 1 replacement at 0%, 5%, 10%, and 15% (Maslehuddin et al., 2008b)

Al-Harthy et al. (2003) used sorptivity (a measure of the capacity to absorb) and the initial surface absorption test (ISAT) to measure the permeability characteristics of different mortar samples containing CKD. Durability of mortar and concrete largely depends on the ease with which fluids can enter and move through the material, commonly known as permeability. Mixtures were prepared using CKD 3 at 0%, 10%, 20%, 25%, and 30% replacement level of PC 5 by mass. Al-Harthy et al. (2003) gradually added water to each mix to maintain the same workability. Al-Harthy et al. (2003) stated that the sorptivity and ISAT measurements both showed that the sorptivity of mortar decreased with incorporation of CKD in the mortar mixtures. They further noted that since sorptivity is a function of mixture strength, the higher the strength the lower the sorptivity values. The use of CKD improved absorption properties and therefore, can enhance durability. The authors attributed the lower sorptivity values to the very fine particles of CKD, but did not elaborate on the nature of this mechanism. It is assumed that the very fine particles could provide nucleation sites for enhanced cement hydration and/or act as fine filler material between the cement grains.

A summary of the study conducted on the steel permeability effects of CKD-PC blends compared to the respective reference plain cement is shown in Table 2.27.

122

Table 2.27 Permeability: from CKD-PC literature review

Author(s) Blend Type w/b % CKD General Author Suggested Replacement Effect on Mechanism(s) Permeability Maslehuddin et al. CKD 1/PC 1 C N.R. 0,5,10,15 ↑ (1) Increase in coulomb (2008b) CKD 1/PC 2 measured permeability may be due to presence of free chloride ions from CKD Al-Harthy et al. CKD 3/PC 5 M V 0,10,20,25,30 ↓ (2) Very fine particles of (2003) CKD. P = Paste; M = Mortar; C = Concrete. V = varied w/b ratio to maintain consistent workability. N.R. = Not Reported

2.5.8.4 Freezing and Thawing Batis et al. (1996) used PC 10 and two CKDs (CKD 9 and CKD 10) to study rapid freezing and thawing resistance of concrete containing CKD. Each CKD was added as a 6% partial cement replacement at three w/b ratios: 0.50, 0.65, and 0.75. The concrete test specimens were placed in a freezing and thawing test chamber and exposed to a continuous 24-cycle with the following conditions: from 35ºC to -35ºC in three hours, after that the temperature was kept constant at -35ºC for 3 hours, then it increased to 35ºC at which it stayed for 1 hour. Each complete cycle lasted eight hours for a total of three times per day. The mass loss of the specimens was measured at regular intervals of about once per week. According to ASTM C666 (rapid freezing and thawing in water), completion was defined at 300 cycles or when the average of percentage mass loss exceeded 25% (whichever came first). Batis et al. (1996) reported that the CKD 10 concrete specimens had similar mass loss behaviour compared to the reference concrete specimens at all three w/b ratios. The 6% CKD 9 concrete specimens had significantly less resistance to rapid freezing and thawing compared to the reference concrete specimens at all three w/b ratios.

123 Wang and Ramakrishnan (1990) conducted studies on the freezing and thawing performance of concrete made with a binary blend consisting of 5% CKD (CKD 12) and 95% TIII cement (PC 12). The concrete mixes were tested at w/b ratios of 0.45, 0.52, and 0.55. Freezing and thawing performance was evaluated using two sets of two specimens for each type of mix. One set was exposed to the conditions specified in ASTM C666 while the other was used as a reference. In addition to monitoring changes in fundamental transverse frequency to calculate durability factors, changes in length and mass were also recorded. Wang and Ramakrishnan (1990) concluded that the concrete specimens with CKD did not show inferior resistance to rapid freezing and thawing in up to 120 cycles (84 days), but experienced a little more mass loss thereafter compared to the plain cement concrete specimens.

Ramakrishnan and Balaguru (1987) conducted an experimental investigation on the freezing and thawing durability of concretes in which 5% of the cement was replaced with CKD 11. Three types of cement were assessed: Type I (PC 15), Type II (PC 13), and TIII (PC 14). Six sets of concrete with cement contents of 386 kg/m 3 and 332 kg/m 3 were tested. The w/b ratio was 0.45 for the higher cement content and 0.52 for the lower cement content. The air content ranged from 3.1 – 8.4%. The freezing and thawing tests were conducted according to ASTM C666, using 100 x 100 x 375 mm prisms. Mass loss, fundamental resonant transverse, frequency, and pulse velocity were measured at approximate intervals of 30 cycles. The freezing and thawing tests were stopped at 300 cycles. Ramakrishnan and Balaguru (1987) concluded that under freezing and thawing conditions, kiln dust (5% by mass) incorporated behavior is essentially similar to that of plain PC concretes.

A summary of the studies conducted on the freezing and thawing effects of CKD-PC blends compared to each of the respective reference plain cement is shown in Table 2.28.

124

Table 2.28 Freezing and thawing cycles: from CKD-PC literature review

Author(s) Blend Type w/b % CKD General Effect Author Suggested Mechanism(s) Replacement on Freezing and Thawing Deterioration Batis et. al CKD 9 / PC 10 C K 0,6 ↑ (1996) CKD 10/ PC 10 C K 0,6 N.C. Wang and CKD 12/PC 12 C K 0,5 <120 cycles N.C. Ramakrishnan >120 cycles ↑ (1990) Ramakrishnan CKD 12/PC 13 C K 0,5 N.C. and Balaguru CKD 12/PC 14 C K 0,5 N.C. (1987) CKD 12/PC 15 C K 0,5 N.C. P = Paste; M = Mortar; C = Concrete. V = varied w/b ratio to maintain consistent workability K = constant w/b ratio, but more than one w/b ratio was tested.

2.5.8.5 External Sulfate Resistance Bhatty (1986) used a TI cement (PC 16) with three different CKDs (CKD 13, CKD 14, and CKD 15) in mortars to investigate their effect on sulfate resistance (ASTM C1012). The amount of CKD in each blend was fixed at 10% by mass of PC, with a w/b ratio of 0.45. Bhatty (1986) reported that the blends containing cement and CKD resulted in expansions that were lower than cement alone. The author did not provide an explanation for the improved sulfate resistance of the CKD blend. Improved sulfate resistance, however, is often a result of lower permeability.

A summary of the study conducted on the external sulfate resistance effects of CKD-PC blends compared to each of the respective reference plain cement is shown in Table 2.29.

Table 2.29 Sulfate resistance: from CKD-PC literature review

Author(s) Blend Type w/b % Replacement General Effect Author Suggested Level on External Mechanism(s) Sulfate Resistance Bhatty CKD 13/PC 16 M 0.45 0,10 ↑ (1986) CKD 14/PC 16 M 0.45 0,10 ↑ CKD 15/PC 16 M 0.45 0,10 ↑ P = Paste; M = Mortar; C = Concrete.

125

2.5.8.6 Durability Summary Although there are relatively few studies on CKD-PC blend durability, researchers have stated the need to consider potential issues due to the composition of CKD (Wang et al., 2002; Dyer et al., 1999). Since CKD is typically high in sulfur, alkalis, and chlorides, there is the potential for external sulfate expansion, AAR, and steel corrosion. The impact of using CKDs as a substitute of PC on microstructure and air content could affect permeability and resistance to freezing and thawing cycles. One study on AAR reported a potential increase for AAR using CKDs, while another study reported no impact. Differences in expansion of CKD blends with similar alkali contents indicates that factors other than alkali content – such as the type of alkali compound and/or the CKD-PC chemical composition – can play a role in AAR. Steel corrosion increased as the amount of CKD increased. A major contributor to steel corrosion can be the high chloride content of CKD. The high alkali content of CKD, however, can help in maintaining the high passivation film layer that protects steel. One study reported that permeability was reduced with CKD, likely due to the presence of fine particles. Lower permeability indicates higher durability. Three studies using blends with 5% and 6% CKD replacement of PC reported no impact in four blends and increased mass loss in two blends when exposed to freezing and thawing cycles. One study showed that CKD blends improve resistance to external sulfate attack. Possible explanations for the freezing and thawing and sulfate resistance effects of CKD blends were not provided.

126 3.0 MATERIALS AND EXPERIMENTAL DETAILS

This thesis consists of several experiments that were designed to provide data within the context of two main objectives:

1. Investigate the characterization of CKDs using chemical, physical, mineralogical, and dissolution analytical techniques 2. Establish an improved understanding of the effects of CKDs as partial substitution for PC on: a. heat of hydration b. normal consistency c. initial set time d. compressive strength e. expansion in limewater f. soundness g. ASR.

3.1 Materials The materials used in this study were seven different CKDs (identified as A, B, C, D, D*, E, and F) having a wide range of chemical/mineralogical and physical properties based on different raw material sources and technologies, two filler materials (limestone powder and ground silica), and two PCs of high and low alkali content (Cements TI and TII, respectively). Each PC consists of only clinker and gypsum (pure PC). Limestone powder (LS) and ground silica (inert) (SLX) were selected for comparison to the CKDs, based on similar Blaine fineness.

127 All CKDs were fresh, as opposed to coming from a stockpile or landfill. The CKDs in this study were selected to provide a representation of available CKDs in North America from the three major types of cement manufacturing processes: wet, long-dry, and preheater/precalciner, as shown in Table 3.1. The CKDs are from different cement plants except CKDs D and D*, which are from the same plant. Only one sample from each cement plant was planned but due to the uncharacteristically low Blaine fineness value of the original sample (CKD D*), a second sample was collected (CKD D).

Table 3.1 CKD kiln process description

CKDs Kiln Process Dust Collection System A Wet Electrostatic Precipitator B Wet Bag-house C Long-dry Electrostatic Precipitator D, D* Long-dry Bag-house E Precalciner (By-pass) Electrostatic Precipitator F Precalciner (By-pass) Electrostatic Precipitator

Due to the length of the study, all materials were stored in plastic bags that were placed in airtight plastic pails between uses. LOI was performed on all materials periodically to ensure that (i) no moisture had been absorbed and (ii) they had not carbonated. LOI results indicated that the materials did not change over time.

128 3.2 Testing of Raw Materials 3.2.1 Chemical Properties The chemical compositions of the PCs were determined in accordance with ASTM C114. X-ray fluorescence (XRF) was used to determine the major elements likely to be present in PC, with the exception of moisture and carbon dioxide (CO 2). The samples were de- carbonized prior to XRF analysis using LOI. The LOI required igniting the dried sample to a constant mass in a muffle furnace at 950 ± 50˚C in an uncovered porcelain crucible. After the PCs had reached constant mass (in approximately 1 hour), samples were prepared as fused beads using lithium borate. Fused beads were prepared by dissolving the specimen in lithium borate at a high temperature (>1000˚C). Then the fused bead samples were placed in the XRF spectrometer to determine the major elements. The alkali, sulfate, and chloride contents for PCs from the XRF analysis were validated using flame photometry, induction heating (LECO SC-432 Sulfur Analyzer), and potentiometric titration. Water soluble alkali content was determined according to ASTM C114. One gram of material is put in contact with water for 10 minutes and, after filtration, the amount of water soluble alkalis contained in the aliquot was determined by flame photometry. Some testing procedures developed for PC were modified to accurately determine the chemical composition of the CKDs; these are described in Section 4.1.1.

3.2.2 Mineralogical Properties The free lime (free calcium oxide) test that is designed for PC (ASTM C114) using hot benzoic acid titration was used for each PC and CKD. Mineralogical characterization of all materials included X-ray diffraction (XRD) and thermal analyses. XRD was performed with a Rigaku D/MAX 2000 diffractometer on pressed powder samples, except CKD D, which was analyzed using PANalytical’s X’Pert PRO. Scanning was performed in the range of 5º ≤ 2 θ ≤ 65º with a scan rate of 0.02º 2 θ per second. Powder samples were analyzed using standard monochromatic CuKά radiation generated at 20mA and 40 kV. PC gypsum phases were obtained by differential scanning conduction

129 calorimetry (DSC) using the Mettler TA3000 System. CKD samples were analyzed by thermo gravimetric analysis (TGA) in a nitrogen environment using a Netzsch STA 730 thermal analysis apparatus at a heating rate of 10˚C/minute.

3.2.3 Physical Properties The relative density of each material was obtained by air-comparison pycnometer. The relative density of the material is a required input in the calculation to determine the Blaine fineness. The Blaine air permeability test (ASTM C204) and the percentage of material finer than 45 µm (No. 325) sieve (ASTM C430) were used to determine the fineness of all materials in this research program. The Blaine fineness test is the most widely used method to assess the fineness of PC. The Blaine fineness test indirectly measures the surface area of the cement particles per unit mass. Particle size distribution (PSD) of all materials was also determined using the Malvern laser diffraction particle sizer, 2600 Series. Although there is presently no standard specification for determining the particle size distribution of PC, the cement industry commonly uses this test method to determine fineness of materials. The usual procedures for measuring PC fineness were slightly modified to accurately measure the fineness of the CKDs and fillers; these are discussed in Section 4.1.3.

3.2.4 Dilute Stirred Suspensions Dilute stirred suspensions were performed on each PC and CKD. A sample of each material was mixed with water in a glass beaker with a water to solid ratio of 10. Each mixture was stirred vigorously for 10 minutes by hand with a glass rod and the temperature of the solution was maintained at approximately 23ºC. The solid material was then separated using a vacuum filter. The liquid solution was placed in a sample tube for analysis. Hyroxyl ion concentration was measured immediately for each sample. Then the solution filtrate was brought to a pH of less than two using nitric acid. The purpose of adjusting the sample pH to less than two was to minimize metal cation precipitation and adsorption onto the sample container wall. It is known that nitric acid can also cause

130 certain elements from glass ampoules to become soluble. Therefore, appropriate plastic ampoules were used to collect the samples. The balance of the cation and sulfide ionic concentrations of each solution was determined by using Inductively Coupled Plasma Atomic Emission Spectrometry (ICP AES) directly; the model used was the Perkin Elmer Model Optima 3000DV ICP AEOS. The chloride ion concentration was approximated using the U.S. Geological Survey public domain PHREEQC geochemical software package.

3.3 CKD-PC Blends For paste and mortar tests, the amount of CKD (CKD A, B, C, D, E, or F), limestone powder, or silica flour in each blend was either 10% or 20% replacement of PC, by mass. This resulted in 30 binder blends: 2 PC binder blends, 24 CKD-PC binder blends, and 4 PC-filler binder blends. All materials were sieved on a No. 20 sieve and weighed accurately. Each blend was then homogenized by hand with a large spoon in a steel bowl prior to the addition of water and/or fine aggregate (mortar sand). The paste and mortar tests used in this study are described in Sections 3.3.1 to 3.3.7.

For concrete tests, the amount of CKD ranged between 7% and 13% replacement of PC, by mass. CKD D was not available at the time of concrete casting, so the low Blaine fineness CKD D* was used. The concrete CKD-PC blend tests are described in further detail in Section 3.3.8.

3.3.1 Heat of Hydration PC hydration leads to the evolution of heat and, consequently, isothermal conduction calorimetry is commonly used to assess hydration kinetics of different paste blends. In this study, the TAM Air isothermal conduction calorimeter was used to determine the effects of the CKDs and fillers on the early hydration characteristics of the blends in accordance with ASTM C1679. Eight samples can be analyzed at a time and an air thermostat is used to maintain the isothermal temperature, which can be set between 15

131 and 60°C. The TAM Air utilizes heat conduction to transfer heat away from the sample to a heat sink to keep the sample temperature essentially constant. The flow of heat, caused by the temperature gradient across the sensor, creates a voltage signal proportional to the heat flow. The heat output is calibrated by measuring the output from a known heat source under identical conditions to the hydrating material. To minimize disturbances from outside the calorimeter, an inert reference sample is used. The inert sample is placed on a parallel heat flow sensor. Any external disturbances will influence both the sample and the inert sample identically and be nullified. The detection limit of the TAM AIR is 2 µW and the precision is specified to be ±10 µW. The time constant is approximately 100 seconds. The results can be presented as either differential plots showing the rate of heat evolution as a function of time or integral plots showing the total amount of heat liberated as a function of time.

All materials were stored in tightly sealed plastic bags inside containers at a constant temperature of 23 ± 2°C to pre-condition them prior to testing. Paste specimens with 150 g of solids and a w/b of 0.4 were prepared to study the heat of hydration at 23°C. Distilled water was added to the solids and mixed for 2 minutes in a steel bowl using a kitchen hand-blender at low speed. After 2 minutes, approximately 8 g of paste sample were extracted from the bowl using a 10 ml syringe and injected into a glass ampoule. All paste samples were weighed by mass difference between the glass ampoule with the sample and the empty glass ampoule. The sample was then sealed and placed in the calorimeter, five minutes after the distilled water was initially added. A corresponding reference sample containing inert silica sand was also placed into the calorimeter. The amount of silica sand was determined by calculating the equivalent specific heat capacity to 8 g of PC paste. Heat of hydration for each paste specimen was measured over seven days and performed in duplicate. The rates of heat evolution (mW/g) were measured and recorded approximately every 10 seconds using a computer data acquisition system. Since mixing of the constituents was carried out prior to introducing the sample into the calorimeter, the first five minutes of heat evolution were not measured.

132 3.3.2 Normal Consistency Normal consistency is a term that is used to describe the degree of plasticity of a freshly mixed PC paste. The normal consistency (w/b ratio expressed as a percentage) was determined for all binders in accordance with ASTM C187. For each binder blend, 650 g of solid material were mixed with water to make a paste. The amount of water required to bring the paste to a standard condition of wetness was regulated by the condition for which the penetration of a standard needle (Vicat needle) into the paste is 10 ± 1 mm in 30 seconds. In order to gain appreciation for the accuracy of this test, ASTM C187 stipulates that the results of single-operator tests should not differ by more than 0.7%.

3.3.3 Initial Setting Time The initial setting time is often used to evaluate if a paste is undergoing normal hydration reactions. Initial setting time is defined as the time that elapses from the moment water is added until the paste ceases to be fluid and plastic. Most PCs attain initial set within two to four hours. For each binder blend, the paste that was mixed to determine normal consistency was also used to determine initial set time. The time of initial setting of the blended pastes was determined using a Vicat apparatus according to ASTM C191. The time at which the needle penetrates 25 mm into the paste at room temperature was taken to define the initial setting. ASTM C191 specifies that the penetration of the Vicate needle in the paste should be checked 30 minutes after moulding and every 15 minutes thereafter until a penetration of 25 mm or less is obtained. According to ASTM C191, the single operator standard deviation has been found to be ±12 minutes within a range of 49 to 202 minutes initial setting time. To increase the accuracy of the initial set time measurement, the test procedure was modified by increasing the frequency of the Vicat penetrations to every five minutes as the paste approached initial set.

133 3.3.4 Flow Flow is used to describe the relative mobility (ability to flow) of mortar. The flow for each binder blend was determined on a flow table as described in ASTM C230. Mortars were mixed in accordance with ASTM C305 with one part of binder blend, 2.75 parts of graded sand, and deionized water. Mortars were mixed for each binder blend to determine (i) the flow at a fixed w/b ratio of 0.485 and (ii) the water demand to yield a flow of 110 ± 5 according to ASTM C1437. ASTM C1437 states that the results of properly conducted tests should differ by no more than 11% for single-operator testing.

3.3.5 Compressive Strength Compressive strength is the most commonly used method to assess cement quality. The compressive strength for each binder blend was determined according to ASTM C109 (CSA A456.2-C3) at 1, 3, 7, 28, and 90 days. 50 mm mortar cube specimens were prepared by mixing one part of binder blend material, 2.75 parts of graded sand, and deionized water addition (w/b ratio of 0.485). The specimens were cured in a humidity chamber at 23±1 °C for 24 hours, then demoulded and immersed in lime saturated water until tested. The compressive strength result is the average of three test specimens from a single batch at the specified curing time. ASTM C109 states that when three cubes represent a test age, the maximum permissible range between specimens from the same mortar batch at the same test age is 8.7% of the average.

3.3.6 Expansion in Limewater ASTM C1038 is a test method that is used to determine the expansion of mortar bars made from PC in saturated limewater. The amount of expansion is typically related to the amount of calcium sulfate in the PC. In this study, ASTM C1038 was used to assess the expansion of all binder blends. Mortars were mixed in accordance with ASTM C305 with one part of binder blend, 2.75 parts of graded sand, and deionized water. The amount of water required to yield a flow of 110 ± 5 according to ASTM C1437 was used for each binder blend. Four mortar bar specimens (25 x 25 x 285 mm) were prepared for each

134 binder blend and the expansion was calculated as the mean of four mortar bars. The test method specifies calculating the difference in length of specimens at 24 hours from the time the binder blend was mixed with water and at 14 days. The length change of the mortars made from different blends, however, was also measured up to one year for most blends. An expansion limit of 0.020% in 14 days of limewater immersion is in use in CSA A3001.

3.3.7 Autoclave Expansion Soundness refers to the ability of a paste to retain its volume after it has set. Unsoundness can arise from excessive amounts of hard burned free lime or free magnesia and has the potential to cause delayed destructive expansion. In the autoclave expansion test (ASTM C151), a cement paste specimen (25 x 25 x 285 mm) is placed in an autoclave for three hours at 2 MPa and approximately 216 °C . The difference between measurements of the specimen taken before and after the autoclave treatment represents the expansion due to unsoundness. The autoclave expansion test method was used to measure expansion due to the combined effects of both magnesia and free lime for each binder blend. For each binder blend paste, the same w/b ratio used to attain normal consistency and initial setting time was used for the autoclave test. ASTM C151 states that the results of two properly conducted tests by the same operator for expansion of similar batches should not differ from each other by more than 0.07% expansion.

3.3.8 Alkali Silica Reactivity The concrete prism test is typically used to evaluate the reactivity of aggregate with respect to ASR and also to examine the impact of materials that may be introduced to suppress the expansion due to ASR. The typical test period for evaluating the reactivity of an aggregate is one year, and at least two years with SCM (CSA A23.2-14A and ASTM C1293). For the proposed research study, this test method was modified to assess the direct impact on ASR when using CKD as a partial replacement of PC. The main

135 purpose of this study was to make relative comparison of the binary blends rather than obtaining the absolute values.

The materials used for the ASR concrete durability study were six different CKDs (A, B, C, D*, E and F) and two PCs of high and low alkali content (TI and TII). CKD D and the fillers were unfortunately not available at the time of casting for the concrete prisms. Two series of concrete prisms were cast to assess the effect of CKDs on ASR with Cements TI and TII. The reactive aggregate susceptible to ASR that was used in this study is Sudbury aggregate.

The w/b ratio for all mixes was in the range of 0.42 – 0.45 to maintain a constant slump. The three equal reactive coarse aggregate fractions by mass were of 10, 15, and 20 mm nominal maximum diameter, respectively. The specific gravity of the reactive coarse aggregate was 2.71. The fine aggregate had a fineness modulus of 2.90 and a specific gravity of 2.68. The freshly mixed concrete was tested for slump (ASTM C143), air content (ASTM C231, pressure method), and unit mass (ASTM C138). Two concrete cylinders measuring 100 x 200 mm were prepared from each batch. The cylinders were stored moist at 38 ºC and tested for compressive strength at 28 days. Four concrete specimens from each batch were prepared, measuring 75 x 75 x 300 mm. The expansion of the concrete specimens was measured every three months for a period of 365 days. For each concrete mixture investigated, the expansion (length change divided by the gauge length) was calculated as the mean of four concrete prisms. Mass was also measured for each concrete prism and the mass change was averaged for the four prisms.

ASR Test Series 1: The first set of concrete prisms was cast using 10% replacement of Cement TI with CKD binders (CKD and/or PC). The total alkali content of the concrete was increased to 1.25% Na 2Oe of binder mass by adding sodium hydroxide (NaOH) to the mixing water. Cement TI as the binder material alone was used in two control mixtures (Cements TI CTL 1 and CTL 2). The total solid binder was 420 kg/m 3 for each

136 mix except for Cement TI CTL 2, which was 378 kg/m3. Cement TI CTL 2 contained the same amount of PC as in the concrete blends with CKDs. Due to the reduction in solid

binder material, the Cement TI CTL 2 alkali level was increased to 1.38% Na 2Oe of binder mass to give the same total alkali loading as the other blends in Test Series 1.

ASR Test Series 2: The second set of concrete prisms was cast using Cement TII and varying amounts of PC replacement with CKDs. A constant amount of NaOH was added to each mix. The total alkali content of the concrete was increased to 1.25% (Na 2Oe) of cement mass by adjusting the amount of CKD replacement in each mix. The amount of NaOH addition to each mix was selected to maintain the range of CKD replacement levels generally close to 10%. The total solid binder for each mix was 420 kg/m 3. Cement TII as the binder material alone was used in two control mixtures (Cements TII CTL 1 and CTL 2). Cement TII CTL 2 alkali content was raised using NaOH to a level of 1.03%

Na 2Oe of binder mass, rather than the 1.25% of alkali loading to give the same total alkali loading contribution of NaOH as the other CKD blends in Test Series 2.

137 4.0 RESULTS AND DISCUSSION

4.1 Material Characterization The first objective of this thesis was to characterize the seven CKDs, two PCs, and two filler materials. It was found that some of the analytical methods designed for PC do not always provide accurate compositional analysis for CKDs. Therefore, the analytical methods required for accurate analysis of CKDs were identified. The complete chemical analysis and physical properties (relative density, Blaine fineness, and percentage of fine material below 45 µm) of all materials were performed. In addition to the chemical composition and standard fineness tests, quantitative mineralogical compositions, particle size distributions, and dilute stirred suspension analyses were also performed.

4.1.1 Chemical Properties The characteristics of materials used in cement are traditionally evaluated by an oxide composition based on chemical analysis data. Chemical makeup of a CKD and PC can provide an important indicator of how the CKD-PC blend will perform. It was found that there are very few published works with complete chemical analysis of CKDs in the research of CKD-PC blends. The incomplete CKD chemical composition data provided in previous studies is likely due in part to the application of analytical procedures that are specifically designed for PC, rather than CKDs.

The chemical compositions of the two PCs were determined in accordance with ASTM C114 using X-ray fluorescence (XRF), as stated in Chapter 3. Prior to XRF analysis, loss on ignition (LOI) was performed by igniting the 110˚C dried sample to a constant mass in a muffle furnace at 950 ± 50˚C in an uncovered crucible for 1h. The LOI values obtained result from either exposure to moisture or CO 2 (since each of the two PCs only consists

of clinker and gypsum, there is no contribution of CO 2 from carbonate additions).

138 CKDs usually take between 12 to 24 hours to reach constant mass at 950 ± 50 ˚C. The LOI for CKDs not only reflects prehydration and decarbonization, but also the presence of volatiles (alkali, sulfate, and/or chloride). The ranges of volatilization at the melting point of compounds found in CKDs are shown in Table 4.1. A large percentage of the CKD volatiles will be released from the sample into the atmosphere during the LOI test and during preparation of the fused beads since they are less stable in CKDs than in PC at

950 ± 50 ˚C. This presents two problems: (i) the LOI is not just CO 2 and (ii) the XRF quantification of alkali, sulfate, and/or chloride is underestimated. Therefore, direct testing procedures developed for PC in ASTM C114 were used to accurately determine the volatile composition of the CKDs (Babikan and Verville, 2007). The test methods used to measure the volatiles of CKDs were: flame photometry for alkalis, induction heating for sulfate, and potentiometric titration for chloride. The XRF chemical analysis values were then corrected by accounting for the volatiles that were released during the LOI test. The process that was used for chemical analysis of the CKDs is described in Figure 4.1. The CKD chemical composition calculations are presented in Appendix A.

Table 4.1 Melting points and volatility of compounds in CKDs (Manias, 2004) (Note: This table is the same as Table 2.3)

Volatile Compounds Melting Point, ˚C Range of volatility*, %

CaCl 2 772 60 to 80 KCl 776 60 to 80 NaCl 801 50 to 60

Na 2SO 4 884 35 to 50 K2SO 4 1069 40 to 60 CaSO 4 1280 --- *Range of volatility: % of compound that will volatilize at melting point

139

CKD Sample

CKD CKD CKD CKD Sub-sample 1 Sub-sample 2 Sub-sample 3 Sub-sample 4

LOI and XRF Chloride Content: Sulfate Content: Alkali Content: Analysis Potentiometric Induction Furnace Flame Photometry Titration

Calculate chemical composition by accounting for volatiles released during LOI test

Figure 4.1 Process flow chart for CKD chemical composition analysis

The free lime test for PCs is typically used to determine the free calcium oxide content. This test, however, is also sensitive to calcium hydroxide. The free lime test gives the total of free calcium oxide plus calcium hydroxide contents and does not differentiate between the two. This is generally not an issue for PC free lime analysis since the presence of calcium hydroxide is rare (except in PC that consists of weathered clinker). CKDs, however, can be exposed to moisture during processing to reduce fugitive dust and/or storage outside. Therefore, the results from the free lime test for CKDs should be considered as representative of the combined free calcium oxide and calcium hydroxide contents.

140 The chemical and standard physical properties (relative density, Blaine fineness, and fine material below 45 µm) of all materials are shown in Table 4.2. Cement TI met the specifications for normal PC and is characterized by a relatively high sulfate (4.35%), high total alkali content (0.97%), and high C 3A content (11.3%). Cement TII met the

specification for a moderate sulfate resistant cement and is characterized by its low C 3A (6.1%) and low total alkali (0.57%) contents. The data in Table 4.2 shows the LS and SLX to consist of 95.52% calcite based on 53.49% / 56.00% CaO (by LOI, 42.29% / 44.00% = 96.11%) and 98.15% quartz, respectively.

Comparison of the current CKDs to those from previous research studies as summarized by Sreekrishnavilasm et al. (2006) (Table 2.5) shows that all CKDs were within the maximum-minimum range of the compositions, except for the free lime values for CKDs E and F. CKDs A, B, and C appear to be particularly similar to those in the previously published literature. CKDs A and C were within the standard deviations for each parameter. CKD B had concentrations of calcium oxide, silicon dioxide, and aluminum oxide slightly outside the respective range for standard deviation. CKDs D*, D, E, and F, however, appear to be slightly different from the published dataset. CKDs D*, D, and E

each had values for sulfate above the range for standard deviation. CKDs D*, E, and F had higher free limes than the upper limit of the standard deviation. CKDs E and F also had calcium oxide and magnesium oxide contents above the respective ranges for standard deviation. The chloride levels of the CKDs within this study appear to be lower than the full range of chloride levels found in CKDs from previous studies.

As a note of interest, the CKD oxide composition statistical analysis of intermittent daily samples collected over a 3 year period from the same kiln source as CKD C is presented in Table 2.9. Although more variable than PC, the standard deviation results indicate that the CKD from this kiln source is quite consistent.

141 Table 4.2 Chemical and select physical components of PC, CKD, and filler materials (mass %)

PCs Cement Kiln Dusts (CKDs) Fillers Wet Long-dry PH/PC Components TI TII A B C D* D E F LS SLX CaO 62.03 63.06 44.32 32.70 44.75 51.12 45.51 55.18 55.86 53.49 0.02

SiO 2 19.15 20.39 14.25 24.07 14.30 14.23 14.41 15.25 16.81 2.60 98.15

Al 2O3 5.83 4.21 3.77 9.12 4.02 4.05 4.93 3.78 3.94 0.68 0.47

Fe 2O3 2.46 3.01 1.92 3.78 1.60 2.05 2.16 2.26 1.94 0.21 0.06 MgO 2.18 3.21 1.80 1.82 1.02 2.00 1.68 2.85 3.08 0.55 0.00

SO 3 4.35 2.98 3.03 5.79 7.30 15.05 16.15 11.75 8.97 0.03 0.03

Na 2O 0.30 0.13 0.60 0.53 0.19 0.40 0.66 0.26 0.32 0.02 0.01

K2O 1.01 0.69 3.35 4.81 3.20 3.32 4.47 4.83 3.66 0.21 0.08 a Na 2Oe 0.97 0.58 2.80 3.69 2.30 2.58 3.60 3.43 2.73 0.16 0.06

Na 2O soluble 0.16 0.06 0.38 0.30 0.10 0.21 0.39 0.17 0.14 0.00 0.00

K2O soluble 0.97 0.64 2.66 3.88 1.97 2.13 2.9 3.94 2.42 0.00 0.00 b Na 2Oe soluble 0.80 0.49 2.13 2.85 1.40 1.61 2.30 2.76 1.73 0.00 0.00 b a Na 2Oe / Na 2Oe 0.82 0.84 0.76 0.77 0.61 0.62 0.64 0.80 0.64 0.00 0.00

Ti 2O 0.25 0.26 0.40 0.55 0.21 0.24 0.26 0.24 0.19 0.03 0.03

P2O5 0.26 0.12 0.12 0.11 0.04 0.12 0.15 0.11 0.09 0.01 0.01

Mn 2O 0.09 0.56 0.06 0.06 0.05 0.11 0.08 0.50 0.06 0.01 0.00 Cl - 0.00 0.00 2.49 0.94 0.38 0.22 0.35 2.18 0.85 0.00 0.00 LOI c 1.79 1.28 28.74 17.85 23.76 8.23 9.96 5.88 5.47 42.29 0.20 Total Sum (High) d 99.92 99.88 104.95 102.15 100.84 101.16 100.83 105.07 101.27 100.15 99.06 Total Sum (Real) e 99.92 99.88 99.08 99.79 99.73 100.31 100.02 99.74 99.34 100.15 99.06 Free Lime f 0.70 1.53 4.50 4.04 5.70 18.20 10.59 29.20 38.20 0.00 0.00 a Equivalent Alkali (Na 2O + 0.658 K 2O) b Equivalent Water Sol. Alkali (Water Sol. Na 2O + 0.658 Water Sol. K 2O) c Loss on ignition determined at 950 ± 50 ºC d XRF sum of total oxides e - Sum of total oxides calculated by removing the volatiles that are included in the LOI (Na 2O, K 2O, Cl ) f Free lime: combined CaO & Ca(OH) 2 content

Each CKD has its own characteristics, but there can be some generalization of these particular CKDs based upon the pyroprocess, especially in free lime and chloride contents. As expected, the wet and long-dry kilns had free lime contents that are lower than the precalciner kilns. CKDs D* and D have higher free limes than typical long-dry kiln CKDs due to unique equipment design in the kiln, but they are still lower than the precalciner CKDs E and F free limes. The long-dry kiln CKDs have low chloride and high sulfate contents in comparison to the wet and precalciner CKDs.

142 The CKDs were generally higher in total alkali, sulfate, chloride, LOI, and free lime than Cements TI and TII, as shown in Table 4.1. Water soluble alkalis are not normally reported for PCs, although the test method is described in ASTM C114. The CKDs contained higher levels of water soluble alkalis than the Cements TI and TII. It is interesting to note that although the quantity of soluble alkalis is higher in CKDs, the ratio of water soluble alkalis to total alkalis is higher in Cements TI and TII.

Statements/Observations:

4.i The ASTM C114 techniques specified for PC chemical analysis are not necessarily sufficient and/or appropriate for CKD chemical analysis. The mass of CKD at 950 ± 50 ˚C is not stable until 12 – 24 hours. Therefore, the 1-hour PC standard LOI test duration is not sufficient to determine LOI for CKDs. Further, LOI and fused bead preparation of CKDs can cause the volatile compounds to be released into the atmosphere prior to chemical composition analysis. Babikan and Verville (2007) recommend using the following tests in ASTM C114 to determine the chemical composition of CKD volatile elements: i. Alkalis: flame photometry ii. Sulfates: induction furnace iii. Chloride: potentiometric titration

4.ii Although PC typically only contains free calcium oxide, the PC free lime test is representative of both free calcium oxide and calcium hydroxide. CKDs are more likely to contain calcium hydroxide than PC due to exposure to moisture during handling and storage.

143 4.1.2 Mineralogical Properties CKD mineralogical analysis (determination of the relative abundance of the different phases) is an essential complement of the chemical analysis. The effects of CKD elements in a CKD-PC blend may vary depending on the form in which they actually exist. The characteristics of CKD are traditionally evaluated based on chemical analysis data. Such data does not, however, indicate the ways in which the different elements actually exist within the CKD and how they might be expected to react during hydration. Soluble alkalis, for example, may occur as separate crystalline phases in the form of alkali chlorides or alkali sulfates. The reactivity of elements may, therefore, be expected to vary, depending on the form in which they actually exist.

The traditional methods (Bogue equations, XRD Rietveld analysis, and thermal analysis) were used to assess the PC mineralogical compositions. Although quantifying the mineralogical composition of PC has been thoroughly explored, the data to quantify the mineralogical phases of CKDs is relatively limited. Mineralogical analysis of CKDs has not been thoroughly evaluated due to a lack of quantitative analytical techniques. A method for mineralogical phase quantification of CKDs using XRD diffraction scans, Rietveld refinement, and physical tests (thermal analysis and titration) is introduced in this section.

144 Rietveld analyses of Cements TI and TII were performed using the X-ray diffraction scans and control files developed “in-house” at Lafarge North America. The mineralogical compositions of the PCs were determined by Rietveld quantitative X-ray diffraction analysis, shown in Table 4.3(a). Alite (impure C 3S) typically contains 3 – 4% of substituent oxides, the most significant of which are iron, magnesium, and aluminum.

Belite (impure C 2S) may contain 4 – 6% of substituent oxides of which aluminum and

iron are most common (Taylor, 1997). The potential proportions of C 3S, C 2S, C 3A, and

C4AF compounds in each PC, calculated based on the Bogue equations in ASTM C150, are shown in Table 4.3b. Taylor (1997) has noted that Bogue calculations can differ considerably from the true phase compositions, especially by underestimation of alite and overestimation of belite because the actual composition of these phases differs considerably from those of the pure form.

Table 4.3 Cements TI and TII mineralogical composition (mass %)

(a) XRD Rietveld Analysis (b) Bogue Compound Calculation

Phase TI TII Phase TI TII

Alite, C 3S 68.6 66.5 C3S 51.9 60.7 Belite, C 2S 10.3 15.2 C2S 15.8 12.6 Aluminate, C 3A 8.7 3.0 C3A 11.3 6.1 Ferrite, C 4AF 7.5 8.9 C4AF 7.5 9.1 Lime, CaO 0.0 0.2 Periclase, MgO 1.4 2.5 Gypsum, CaSO 4·2H 2O 1.7 1.0 Hemihydrate, CaSO 4·0.5H 2O 0.5 0.6 Anhydrite, CaSO 4 0.2 0.9 Calcite, CaCO 3 0.7 0.8 Portlandite, Ca(OH) 2 0.1 0.4 Quartz, SiO 2 0.3 0.2

145 Cement TI has considerably more gypsum (readily soluble calcium sulfate) than Cement TII. PC with high aluminate contents typically require a sufficient amount of added calcium sulfate as a set controlling agent, which increases the sulfate content of the PC. It follows that cements low in aluminate require less added calcium sulfate and would tend to have lower sulfate contents.

Thermogravimetric analysis (TGA) is ideally suited to quantify the degree of calcination and amount of calcium hydroxide (portlandite) present in CKDs. Samples were tested in a temperature range from 30˚C to 950˚C. Portlandite decomposed between 400 to 530˚C and calcium carbonate was detected between 700 to 850˚C. The TGA results for Cements TI and TII and the CKDs are presented in Appendix B. An approximate determination of portlandite (Ca(OH) 2) was established using mass balance calculations and the TGA results. The portlandite was then subtracted from the total free lime (calcium oxide and calcium hydroxide) in Table 4.2 (based on equivalent calcium oxide) to determine the free calcium oxide (CaO) portion. The mineralogical composition of calcite, portlandite, and free calcium oxide is shown in Table 4.4.

Table 4.4 CKD mineralogical compositions using direct test methods (mass %)

Components Cement Kiln Dusts (CKDs) A B C D* D E F CaCO 3 52.6 34.7 51.3 17.3 22.7 1.8 6.5 free CaO 4.5 4.0 5.7 18.2 10.6 28.4 34.5 Ca(OH) 2 0.0 0.0 0.0 0.0 0.0 1.0 4.9

146 Rietveld XRD analysis was used to accurately estimate the overall mineralogical phases quantification of each CKD. The CKD crystal phases were identified using XRD scans and Joint Committee on Powder Diffraction Standards (JCPDS) files. CKDs typically contain some phases that cannot be observed by XRD. Clay minerals, glass, and similar poorly crystalline components fall into this class and are called amorphous (without form or crystal structure). Different types of amorphous materials, however, may provide an indication of their presence as broad patterns or “humps”. X-ray powder diffraction is only sensitive to crystalline materials.

During normal Rietveld analysis, the amorphous component of a sample is not considered and the relative mass fractions of the crystalline phases are normalized to 100%. This was corrected using a known amount of either calcite or free lime determined by TGA, as shown in Table 4.4. In deciding which phase quantity to use, the best fit results were achieved using the most abundant phase for each respective CKD Rietveld Refinement. Therefore, CKDs A, B, C, and D were quantified relative to their calcite value, and CKDs D*, E and F were quantified relative to their free calcium oxide content. Adding the known mass of the phase to the Rietveld analysis allowed the amorphous phase to be incorporated in the analysis. Furthermore, absolute mass fractions were obtained for all phases. The results of the quantitative phase analyses using TGA, XRD, and Rietveld are shown in Table 4.5. The XRD scans are presented in Appendix C.

Calcite was identified as the major phase for CKDs A (52.6%), B (34.7%), C (51.3%), and D (22.7%), which are from the wet and long-dry processes. Free lime is the dominant phase in CKDs D* (18.2%), E (28.4%), and F (34.5%). CKDs E and F are from precalciners, while CKDs D and D* have uncharacteristically high free limes for a long- dry kiln process. Quartz was present in all CKDs in a range from 3 – 11%. Periclase was present at approximately 2% for CKDs E and F, but less than 1% for the other CKDs. CKDs A and B contained minor amounts ( ≤5%) of dolomite. CKDs E and F had minor amounts of portlandite, while CKD B had only trace amounts. CKDs E and F are from

147 precalciner kilns that are equipped with water conditioning towers to reduce CKD fugitive dust. The water from the conditioning tower converts a portion of the free lime to calcium hydroxide.

Table 4.5 Mineralogical composition of CKD and filler materials (mass %)

Cement Kiln Dust Wet Long-dry PH/PC Category Phase CKD A CKD B CKD C CKD D* CKD D CKD E CKD F

Calcite, CaCO 3 52.6 34.7 51.3 15 22.7 1 4 Raw Quartz, SiO 2 9 7 11 4 3 7 6 Feed Dolomite, CaMgCO 3 5 3 - - 1 - - Periclase, MgO <1 <1 <1 <1 <1 2 2 Clinker Alite, C 3S 1 - 1 6 2 2 <1 Phases ß-Belite, C 2S 22 8 11 7 6 14 4 Aluminate, C 3A <1 <1 <1 <1 <1 1 <1 Ferrite, C 4AF <1 <1 <1 <1 - 2 <1 Free Lime Lime, CaO 4 3 5 18.2 12 28.4 34.5 Portlandite, Ca(OH) 2 - <1 - - - 1 3

Anhydrite, CaSO 4 2 2 5 12 18 14 6 Calcium Langbeinite, 2CaSO 4.K 2SO 4 - - 2 4 3 1 1 Aphthitalite, K3Na(SO 4)2 - <1 - - 2 - - Sulfates Arcanite, K 2SO 4 - 2 <1 - - <1 <1 Calcium Sulfoaluminate, (AFt, AFm) - - 1 1 <1 1 <1 Chlorides Sylvite, KCl 3 1 <1 - <1 4 <1 Calcium Chloride, CaCl 2 - - <1 - - - - Amorphous <1 32 11 31 29 18 35 Clays, Akermanite, Raw Ca 2Mg(Si 2O7) - - - - - 1 - Materials Calcium (slag, fly Dialuminum Oxide, ash), & CaAl 2O4 - - - - <1 1 1 Intermediate Mullite, Phases Al 6Si 2O13 - 4 - - - - - Note: All values are from XRD analysis except those that are in bold

148 Each CKD consisted of some or all of the four major PC phases. The total sum of cement phases in the CKDs ranged between 4% (CKD F) and 25% (CKD A). Belite was the most prevalent PC phase in each CKD within a range of 4% and 22%. Each CKD contained alite in a range between <1% and 2%, with the exception of the uncharacteristic CKD D* which had 6%. All of the CKDs except CKD E had aluminate and ferrite each with <1%. CKD E had higher amounts of aluminate (1%) and ferrite (2%).

Anhydrite was present in all CKDs, with the highest amounts in CKDs D* (12%), D (18%), and E (14%). Alkali sulfate salts were present in all seven CKDs. Calcium langbeinite was found in all CKDs except CKDs A and B, in a range of 1% and 4%. CKDs B, C, E, and F each contained arcanite in a range of <1 – 2%. Aphtithalite was identified in CKDs B (<1%) and D (2%). Calcium sulfoaluminate, which reacts readily with water, was present in small amounts (<1 – 2%) in all CKDs, except CKDs A and B. CKDs A and E contained sylvite ≥3%, while CKD B contained 1%. Small amounts of sylvite (<1%) were present in CKDs C, D, and F, while no traces of sylvite were found in CKD D*. CKD C was the only sample found to contain calcium chloride (<1%).

Amorphous material is mostly a reflection of clay minerals, partially dehydrated clay minerals, and/or supplementary raw materials such as fly ash or slag. CKDs B, D*, D, and F had amorphous contents within a range of 29% and 35%. CKD E contained 18% and CKD C had 11% amorphous content. CKD A had very little amorphous material (<1%). Small amounts of calcium dialuminum oxide were found in CKDs D, E, and F (≤1%). CKD E contained akermanite (1%) and CKD B contained mullite (4%). Akermanite, calcium dialuminum oxide, and mullite are phases typically found in alumina supplementary raw material sources. Akermanite is typically found in slag and mullite is typically found in fly ash.

149 X-ray diffraction techniques were developed to determine the composition of the CKDs. The composition and quantity of the crystalline and amorphous phases of the seven CKDs differed significantly. The type of crystalline material and the relative proportion of the amorphous and crystalline material in CKDs can significantly affect the hydration of a CKD-PC blend. Also, previous literature studies have not identified significant amounts of calcium langbeinite in CKDs. Tang and Gartner (1988) have reported on the effects of calcium langbeinite on PC hydration. They concluded that calcium langbeinite is a more effective retarder of C 3A than either gypsum or pure alkali sulfates alone. The proposed mechanism takes into account the rate at which the sulfate phases can supply both calcium and sulfate ions to the surfaces of the aluminate phases during early stage hydration. The presence of calcium langbeinite increases the rate and chemical potential at which calcium sulfate enters into solution. Finally, although not previously reported, it appears CKDs can contain fly ash and/or slag if these materials are used as raw meal in clinker production. CKD B contains mullite (typically found in fly ash) and CKD E contains akermanite (typically found in slag).

Statements/Observations:

4.iii Fresh CKDs from precalciners may contain portlandite due to the combination of high free lime and the use of water sprays used to condense materials in the preheater gas stream. TGA can be used to determine the CKD calcium hydroxide content.

4.iv Preheater/precalciner CKDs have very high free limes (28 – 35%) compared to CKDs from wet (3 – 4%) or long-dry (5 – 18%) processes.

4.v XRD and Rietveld refinement, combined with TGA and the free lime test, can be used to quantify the actual CKD crystalline composition and amorphous content.

150 4.vi The amorphous and/or clinker phase contents in CKDs can be as high as approximately 23% and 35%, respectively.

4.vii CKDs can contain calcium langbeinite (up to approximately 4%). Calcium langbeinite is readily soluble and can provide excess sulfate to the system causing early precipitates to form, such as syngenite and secondary gypsum. This can lead to observable changes in workability.

4.viii Fly ash and/or slag may also be present at low levels (1 – 4%) if used as raw materials in clinker production. CKD B contains mullite (typically found in fly ash) and CKD E contains akermanite (typically found in slag).

4.1.3 Physical Properties Important physical properties required to understand the behaviour of binder blends using CKD, PC and fillers are relative density, fineness, and particle size distribution. The relative density, Blaine air-permeability (ASTM C204), and the percent passing a 45 µm sieve are traditional methods that were used to characterize the fineness of all materials in this research program; they are shown in Table 4.6. The usual procedures used to measure PC fineness were slightly modified to accurately measure the fineness of the CKDs and fillers. These modifications are described in this section. The particle size distribution (PSD) analysis is more recently developed technology that was also used.

The PSD results are presented in Figure 4.2 and Figure 4.3. The mean particle size or D50 (the equivalent diameter where 50% by volume of the particles has a smaller diameter

and hence the remaining 50% is coarser) and D10 (the equivalent diameter where 10% by volume of the particles has a smaller diameter and hence the remaining 90% is coarser) for all materials are also presented in Table 4.6.

151 Table 4.6 Physical properties of all materials

PCs Cement Kiln Dusts (CKDs) Fillers

Wet Long-dry PH/PC Properties TI TII A B C D* D E F LS SLX Relative Density 3.11 3.18 2.75 2.65 2.77 2.89 2.86 2.97 2.82 2.71 2.66 Blaine (m 2/kg) 367 377 654 684 681 177 610 350 526 488 638 45µm (% passing) a 95.74 92.01 73.30 63.10 71.10 56.90 87.23 69.00 74.90 99.54 98.09

D50 (µm) 15.51 14.37 14.09 18.31 13.73 36.98 9.71 22.58 15.99 9.22 11.42

D10 (µm) 3.40 2.98 2.25 2.19 1.91 8.62 2.13 4.39 2.35 1.57 1.36 a Fineness: determined as material finer than 45µm mesh sieve

The relative densities of Cements TI (3.11) and TII (3.18) are fairly close to the generally accepted average value of 3.15 for PCs in ASTM. The relative densities of the CKDs range between 2.65 and 2.97, which is lower than PC. As a result, if CKD is used as a partial replacement of PC by mass, a larger volume of CKD particles will replace the PC particles removed (assuming the CKD particles are equivalent in size to the PC particles) and the volume of paste will increase. The filler relative densities were in the lower range of the CKD relative densities.

In order to attain accurate Blaine fineness results, the measured density for all CKDs and fillers was used for the Blaine analysis calculations, rather than the standard 3.15 specified in ASTM for PCs. Also, although PCs typically do not require it, ultrasound treatment was used for all materials during particle size laser diffraction. Since particle size laser diffraction is not able to differentiate between individual particles and agglomerated particles, some fine powders used in the cement industry that have a higher tendency for agglomeration, such as silica fume, require ultrasound treatment. CKDs can have very fine particles that agglomerate affecting the accuracy and precision of the PSD analysis.

152 Cements TI and TII have similar Blaine fineness values to other commercially available PCs given by Tennis and Bhatty (2006). The Blaine fineness values for CKDs A (654 m2/kg), B (684 m2/kg), C (681 m2/kg), and D (610 m2/kg) are similar, while Blaine fineness values for CKDs E (350 m2/kg) and F (488 m2/kg) are lower. CKDs E and F come from preheater/precalciner kiln systems, which are reported to generate coarser CKD than wet and long-dry processes. CKD D* has an uncharacteristically low Blaine fineness (185 m2/kg) for a long-dry kiln and is not considered typical. All CKDs had higher Blaine fineness values than Cements TI and TII except CKDs D* and E. The percentage of materials passing 45 µm sieve for the TI and TII were 95.74% and 92.01%, respectively. Each CKD had considerably lower percentage of material passing the 45 µm sieve, with the range being between 56.90% and 87.23%. The CKDs may have a broader particle size range than found in the PCs since the CKDs are not selected based upon size through a separator. The percentage passing 45 µm sieve for LS (99.54%) and SLX (98.09%) are slightly higher than for the PCs.

The full range of particle size distribution for all materials is shown in Figure 4.2. Cements TI and TII have very similar particle size distributions. The overall trend indicates the CKDs generally straddle both sides of the PCs. The black arrow indicates that in the area of larger particles (between 10 µm and 100 µm), CKDs A, B, C, D*, E, and F, are coarser than the PCs. Both fillers appear to be finer than the PCs. Figure 4.3 is a plot of the particle size distributions up to 10 µm (finer particles). CKDs A, B, C, D, and F appear to have more fine particles than PC or fillers.

153 The Blaine fineness values reflect that the CKDs are generally finer than the PCs, but the percentage passing 45 µm sieve values indicate that the CKDs are coarser than the PCs. The PSDs help to explain the reasons for the conflicting results. The correlation coefficient (r) indicates the strength and direction of a linear relationship between two random variables. The first two random variables are Blaine fineness and PSD, shown in Figure 4.4(a). The second two random variables are percentage passing 45 µm sieve and PSD, shown in Figure 4.4(b). The Blaine fineness value is strongly correlated to the particle size distribution below 10 µm, particularly 3 µm. Therefore, it can be concluded that the CKDs generally have more fine particles (<10 µm) than PCs. Since the Blaine fineness does not correlate well to the particles above 10 µm (r < 0.7), the Blaine fineness indicates very little about the material PSD overall. The percentage of material passing the 45 µm sieve has a good correlation (r > 0.7) to the particle size from approximately 10 µm to approximately 100 µm. Therefore, the Blaine fineness is representative of the < 10 µm portion of the PSD and the percentage passing 45 µm sieve is representative of the > 10 µm portion of the PSD.

154

Figure 4.2 Particle size distribution of PC, CKD and filler. The materials are in the direction and position of the arrow: LS, D, SLX, TII, TI, A, F, C, E, B, D*

Figure 4.3 Particle size distribution of PC, CKD and filler between 0.1 µm and 10 µm. The materials are in the direction of the arrow: LS, SLX, C, D, B, A, F, TII, TI, E, D*

155 Relationship between Blaine and PS D for C KDs

1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 Correlation C oefficient (r) 0.0 0.1 1 10 100 1000

Particle size (µm)

(a)

Relationship between Percentage Passing 45 µm Sieve and PSD for C KDs

1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 Correlation Coefficient (r) 0.0 0.1 1 10 100 1000

Particle size (µm) (b)

Figure 4.4 CKD fineness correlation between (a) Blaine fineness and particle size distribution, and (b) percentage passing 45µm sieve and particle size distribution

156

Statements/Observations:

4.ix There are two ways to modify the current PC analysis methods for accurate Blaine fineness and PSD CKD analyses: i. The relative density of the CKD should be used in determining the Blaine fineness value, as opposed to the relative density of PC (3.15), which is used to determine the Blaine fineness of PCs according to ASTM C114, and ii. The PSD of CKDs should include ultrasound treatment to ensure agglomeration of fine particles does not occur.

4.x CKDs generally have higher Blaine values than PCs. The Blaine fineness test correlates well with the particle size distribution below 10 µm (r > 0.7), particularly 3 µm.

4.xi CKDs have a lower percentage of material passing a 45 µm sieve in comparison to PCs. The CKD percentage of material passing the 45 µm sieve has a good correlation (r > 0.7) to the CKD particle size from approximately 10 µm to 100 µm.

4.xii CKDs have lower relative density (2.65 – 2.97) than that of Cement TI (3.11) and Cement TII (3.18).

4.xiii The CKD mean particle sizes (D 50 ) had a range between 9.71 – 22.58 µm. Cement TI (15.51 µm) and Cement TII (14.37 µm) were within this range.

157

4.1.4 CKD Dissolution Analysis The dissolution of ionic species in water and composition of the liquid phase play an important role in PC hydration. The principal ions dissolved in solution are K +, Na +, Ca 2+ , SO4 2-, and OH -. Silicate and aluminate species dissolve to a much lesser extent. There is a charge balance between the cations and anions in solution. The ion contributions from CKDs may influence the charge balance and ultimately the solubility behaviour of phases during the early stages of PC hydration. The liquid phase composition of a high-alkali PC paste (w/b of 0.5) during hydration over a period of three months is shown in Figure 4.5.

Figure 4.5 Composition of pore solution w/b 0.5 high alkali PC paste (Gartner et al., 2002)

158

Rapid ion dissolution at high water/solid ratios gives an indication of the relative differences between PCs and CKDs. In order to gain appreciation for the ion contributions from CKDs relative to PC, the liquid filtrate ion compositions of CKDs and Cements TI and TII at 10:1 water to solid ratio (by mass) in solution after 10 minutes of mixing were conducted; results are shown in Table 4.7. The total ion contribution from the CKDs ranges from 3779 to 6735 mg/L, which is significantly higher than the total ion contributions from Cement TI (1717 mg/L) and Cement TII (1750 mg/L).

Table 4.7 Ionic concentrations of 10:1 water to solid ratio (by mass) solution analysis @ 10 minutes (concentration mg/L)

TI TII CKD CKD CKD CKD CKD CKD CKD A B C D* D E F Calcium 731 1095 1338 1426 1570 2368 1789 1873 1730 Chloride 0.00 0.00 1003 1402 497 151 301 2150 832 Potassium 782 517 1730 2260 1502 1550 1910 2464 1639 Sodium 104 38 234 197 62 111 213 97 68 Sulfur 63 48 29 122 73 139 120 71 98

Silica 6.39 3.03 1.32 2.11 3.35 1.25 2.80 1.43 1.35 Alumina 0.57 0.67 0.74 1.50 2.37 0.77 1.81 0.97 0.82 Iron 0.34 0.48 0.48 0.88 1.29 0.29 0.68 0.35 0.23 Magnesium 0.27 0.58 0.41 0.72 1.62 0.38 0.63 0.39 0.69

Hydroxyl Ions 29 47 61 62 66 83 77 77 75 Total Ions 1717 1750 4398 5474 3779 4405 4416 6735 4445 pH* 12.5 12.7 12.8 12.8 12.8 12.9 12.9 12.9 12.9 CKD LEGEND Bold: Greater than in both PCs Italics: Greater than in one of the PCs Regular: Less than or equal to both PCs * pH was calculated using hydroxyl ion concentration in the formula’s; pOH = - log ( OH -) & pH = 14- pOH

159 Calcium, chloride, potassium, alumina, and hydroxyl ions were all significantly higher in the liquid filtrate of the CKDs in comparison to the concentrations found in the liquid filtrate of Cements TI and TII. The pH of the CKD liquid filtrates was also higher than that of the control cements. Sulfur ions were higher in the liquid filtrate of the CKDs than that of Cements TI and TII, with the exception of CKD A. This is not surprising since the sulfur content of CKD A was also determined to be lower than that of Cements TI and TII. Sodium, iron, and magnesium ion contribution levels from CKDs varied in comparison to the control cements. Silica ion levels of the liquid filtrates for the CKDs were all lower than the silica ion levels found in the PC liquid filtrates. The lower silica ion contributions from CKDs are likely due to the lower levels of alite and belite, in comparison to PCs.

The dilute stirred suspension test results show that the ions available from CKDs during early stages of hydration will likely be qualitatively the same as the ions available from PCs, with the exception of chloride ions. Chloride ions, however, are commonly used as accelerators in concrete mixtures. It is likely that CKD-PC blends will have significantly higher amounts of ions entering solution during the early stages of hydration, in comparison to PC alone. The elevated amount of alumina ions in the CKD liquid filtrates is somewhat surprising since the chemical composition analyses show that most of the CKDs have lower alumina oxide contents than that found in the PCs. This is an indication that the alumina in CKDs may be more readily soluble than the alumina in PCs.

160 Statements/Observations:

4.xiv The ion contributions from CKDs are qualitatively the same as the ion contributions from PC, with the exception of chloride ions.

4.xv Calcium, chloride, potassium, alumina, and hydroxyl ions were all higher in the CKD liquid filtrates in comparison to the concentrations found in the PC liquid filtrates at 10 minutes. Although the effects of these ions are not uniform, these ions can significantly impact the early stages of hydration.

4.xvi The total ion contribution in liquid filtrate of dilute stirred suspensions is higher from CKDs than PCs at 10 minutes.

4.xvii The pH of the CKD liquid filtrates is higher than that of the PC liquid filtrates at 10 minutes.

161 4.2 CKD-PC Blends The second objective of this research program was to develop an improved understanding of the effects of utilizing CKDs as partial replacements of PC. Although the single effect of any one of the common components found in CKDs can be stated in general terms, specific reactions among the multiple components within CKDs are difficult to contemplate. Since CKDs contain multiple components that affect the properties of blends, it is difficult to separate the effects of the individual components. Further, the influence of the same CKD at equal replacement levels of two different PCs can influence the hydration differently. Therefore, regression analysis was applied where possible to deduce the relationships between CKD-PC binder properties and various independent variables.

The combined compositions for the CKD-PC blends were calculated based upon percentage composition, by mass. All paste and mortar blends were made with 10% and 20% of CKD or filler replacements by total mass of each of Cements TI and TII. The calculated chemical, physical, and mineralogical properties of these blends are shown in Appendix D. Overall, 34 different mixtures were prepared using 0% (control), 10%, and 20% of the seven CKDs and two filler replacements by total mass of Cements TI and TII. As an indication of the composition differences of CKD-PC and PC-filler blends in comparison to PC alone, the range for the chemical and select physical properties of CKD and fillers at 10% and 20% replacement of Cements TI and TII are shown in Tables 4.8 (Cement TI blends) and 4.9 (Cement TII blends). The CKD-PC blend chemical and physical properties that are significantly different from PC alone are in bold and highlighted.

162

Table 4.8 Range for chemical and physical properties of Cement TI blends at 10% and 20% replacement (Theoretical calculation, mass %)

CKDs at 10% CKDs at 20% Fillers at 10% Fillers at 20% Components TI TI replacement TI replacement TI replacement TI replacement Min. Max. Min. Max. Min. Max. Min. Max.

SiO 2 19.15 18.66 19.65 18.17 20.14 17.50 27.05 15.84 34.95 Al 2O3 5.83 5.62 6.16 5.42 6.49 5.29 5.32 4.76 4.80 Fe 2O3 2.46 2.37 2.59 2.28 2.72 2.22 2.23 1.98 2.01 CaO 62.03 59.10 61.41 56.16 60.80 55.83 61.18 49.63 60.32 MgO 2.18 2.07 2.27 1.95 2.36 1.96 2.02 1.75 1.86

SO 3 4.35 4.22 5.53 4.09 6.71 3.92 3.92 3.49 3.49 Na 2O 0.30 0.29 0.34 0.28 0.37 0.27 0.27 0.24 0.24 K2O 1.01 1.23 1.39 1.45 1.78 0.92 0.93 0.83 0.85 Na 2Oe 0.97 1.10 1.24 1.23 1.51 0.88 0.89 0.79 0.80

Sol. Na 2O 0.16 0.15 0.18 0.15 0.21 0.14 0.14 0.13 0.13 Sol. K 2O 0.97 1.07 1.26 1.17 1.56 0.87 0.87 0.77 0.77 Sol. Na 2Oe 0.80 0.86 1.00 0.92 1.21 0.72 0.72 0.64 0.64 TiO 2 0.25 0.24 0.28 0.24 0.31 0.23 0.23 0.21 0.21 P2O5 0.26 0.24 0.25 0.21 0.24 0.23 0.23 0.21 0.21 Mn 2O3 0.09 0.08 0.13 0.08 0.17 0.08 0.08 0.07 0.07 Cl 0.00 0.03 0.25 0.07 0.50 0.00 0.00 0.00 0.00 Ca(OH) 2 0.40 0.36 0.85 0.32 1.30 0.36 0.36 0.32 0.32 fCaO 0.40 0.76 3.81 1.13 7.22 0.36 0.36 0.32 0.32 LOI 1.79 2.15 4.48 2.52 7.18 1.63 5.84 1.47 9.89 pH* 11.9 11.92 11.99 11.94 12.09 11.31 11.66 10.72 11.42 Relative Density 3.11 3.07 3.10 3.02 3.08 3.07 3.07 3.02 3.03 Blaine (m2/kg) 367 365 399 364 430 379 394 391 421 45µm, % passing 95.7 92.5 94.9 89.2 94.0 96.0 96.1 96.2 96.5 Na 2Oe: Na 2O + 0.658 (K2O) fCaO: free lime LOI: Loss on ignition * based on w/b = 10 solution analysis @ 10 minutes

163 Table 4.9 Range for chemical and physical properties of Cement TII blends at 10% and 20% replacement (Theoretical calculation, mass %)

CKDs at 10% CKDs at 20% Fillers at 10% Fillers at 20% Components TII TII replacement TII replacement TII replacement TII replacement Min. Max Min. Max Min. Max Min. Max

SiO 2 20.39 19.77 20.75 19.16 21.12 18.61 28.16 16.83 35.94 Al 2O3 4.21 4.16 4.70 4.12 5.19 3.83 3.85 3.46 3.50 Fe 2O3 3.01 2.86 3.08 2.72 3.16 2.71 2.73 2.42 2.45 CaO 63.06 60.02 62.34 56.99 61.62 56.75 62.10 50.45 61.14 MgO 3.21 2.99 3.20 2.77 3.19 2.89 2.95 2.57 2.68

SO 3 2.98 2.98 4.30 2.99 5.61 2.68 2.68 2.39 2.39 Na 2O 0.13 0.14 0.18 0.14 0.24 0.12 0.12 0.11 0.11

K2O 0.69 0.94 1.10 1.19 1.51 0.62 0.64 0.56 0.59 Na 2Oe 0.58 0.75 0.89 0.92 1.20 0.53 0.54 0.48 0.50

Sol. Na 2O 0.06 0.07 0.10 0.07 0.13 0.06 0.06 0.05 0.05 Sol. K 2O 0.64 0.78 0.97 0.91 1.30 0.58 0.58 0.51 0.51 Sol. Na 2Oe 0.49 0.58 0.72 0.67 0.96 0.44 0.44 0.39 0.39 TiO 2 0.26 0.25 0.29 0.25 0.32 0.24 0.24 0.21 0.21 P2O5 0.12 0.11 0.12 0.10 0.13 0.11 0.11 0.10 0.10 Mn 2O3 0.56 0.51 0.55 0.46 0.55 0.50 0.50 0.45 0.45 Cl 0.00 0.03 0.25 0.07 0.50 0.00 0.00 0.00 0.00

Ca(OH) 2 1.30 1.17 1.66 1.04 2.02 1.17 1.17 1.04 1.04 fCaO 0.55 0.90 3.94 1.24 7.34 0.49 0.49 0.44 0.44 LOI 1.28 1.70 4.02 2.12 6.77 1.17 5.38 1.06 9.48 pH* 11.9 11.92 11.99 11.94 12.09 11.31 11.66 10.72 11.42 Relative Density 3.18 3.13 3.16 3.07 3.14 3.13 3.13 3.08 3.09 Blaine (m2/kg) 377 374 408 372 438 388 403 399 429 45µm, % passing 92.0 89.1 91.5 86.2 91.1 92.6 92.8 93.2 93.5 Na 2Oe: Na 2O + 0.658 (K 2O) fCaO: free lime LOI: Loss on ignition * based on w/b = 10 solution analysis @ 10 minutes

164 An assessment of the CKD-PC blend compositions in comparison to the control PC alone and control PC-filler blends provides insight into the potential influence of partial CKD replacements of PC. The presence of CKDs causes the sulfate, alumina, alkalis, portlandite, free lime, and chloride contents of the CKD-PC blends to generally be the same or higher than that of the control PC alone and of control PC-filler blends. The magnitude of the change for each component is important to consider in assessing the potential impact of each component’s elevated concentration. The physical properties of the CKD-PC blends are also important factors to consider.

PC performance is highly sensitive to small changes in sulfate content which can result in very significant effects on hydration, strength development, and volume stability. The sulfate contents of the CKD-PC blends change relative to the control mixes within a range of -0.13% to +0.98% for the blends with Cement TI and 0.0% to 1.32% for the blends with Cement TII. In relation to the sulfate content, the elevated alumina concentrations could affect the optimum sulfate/alumina balance required for normal set to occur. The factor most influencing the effect of calcium sulfate on the early reactions is the rate at which the calcium and sulfate ions are made available in solution. Elevated calcium concentrations during early stages of hydration due to increased free lime and portlandite may allow the excess sulfates to combine with calcium to behave similarly to calcium sulfate (gypsum).

Alkalis are widely reported to accelerate alite hydration, but this is only when the sulfate levels were optimized. At sulfate levels above optimum, the acceleration effects of alkalis were either reduced or suppressed. The presence of higher calcium, as well as alkali concentrations, during early stages of hydration may also influence the solubility of phases during early age hydration. Increased hydroxyl ions, as a result of portlandite and alkalis, may also increase the potential for ASR.

165 With respect to chlorides, calcium chloride is the most effective for accelerating hydration of C 3S (Taylor, 1997). Bhatty (1984) suggested that CKD alkali chlorides would behave similarly to calcium chloride. Chlorides are known to accelerate PC hydration and dosages between 1 and 2% of PC content (by mass) are generally recommended in the field for non-reinforced concrete. The maximum chloride concentration within the CKD-PC blends, however, is only 0.50%. Therefore, optimal acceleration of alite hydration would not be expected. The presence of chlorides could be a concern for steel reinforcement corrosion in concrete. In EN-197, chloride contents of cements are limited to 0.10%.

Additional free lime and calcium hydroxide has an important role to play in the initial hydration of PC by supplying calcium ions to the system. Any change in the lime concentration or displacement of the solubility equilibrium of portlandite – such as addition of calcium salts or alkalis – may change the formation characteristics of C-S-H. Soft burnt (highly reactive) free lime may increase water demand. Hard burnt free lime raises a concern for soundness due to its delayed hydration.

The relative densities of the CKD-PC blends are similar to those of the control PC-filler blends but lower than that of the control PC alone. An increase in the volume of solid particles may impact rheological properties. The CKD-PC blends generally have higher Blaine fineness values but lower percentage passing 45 µm. This implies that the CKDs have a broader particle size range than PCs, with CKDs having higher amounts of both very fine and coarse particles than PCs. The CKD-PC blends generally have similar Blaine fineness values but lower percentage passing 45 µm in comparison to that of the PC-filler blends. The fineness of the CKD-PC blends can broadly influence chemical reactivity, rheological properties, volume stability, and durability.

166 4.2.1 Kinetics 4.2.1.1 Heat of Hydration The rate of heat liberation on the recorded output is used as a means of measuring the rate of hydration. Isothermal conduction calorimetry was used to assess the heat evolution of pastes at 0%, 10%, and 20% replacement of Cements TI and TII, in accordance with ASTM C1679. Six CKDs from different cement plants, a limestone powder, and a quartz powder were used as the replacement materials. Each sample was performed at a w/b ratio of 0.40 in duplicate to check the repeatability of the heat of hydration tests. The total heat measurements of the duplicate tests were within ±3% of each other. The rates of heat evolution during initial hydrolysis did vary somewhat but after the transition to the induction period, the rates of heat evolution were essentially the same.

In order to create regression models for the influence of composition and fineness on CKD-PC blends, a characterization system was developed for the heat liberation curves as shown in Figure 4.6. The parameters of the heat curve that were used to characterize the behaviour of hydration are: the total heat evolved during initial hydrolysis (Ai), the minimum rate of heat evolution during the induction period (Qi), the time at which Qi occurs (ti), the maximum rate of heat evolution (Qw), the rate of heat evolution between the minimum rate of heat evolution during the induction period and the maximum rate of heat evolution (Qw-Qi), and the cumulative heat evolution after initial hydrolysis over seven days (A7d-Ai) (the cumulative heat evolution is simply the area under the rate curve for the time under consideration).

167 Sulfate Depletion Peak

A7d-Ai

Figure 4.6 Schematic of isothermal conduction calorimetry curve heat liberation characterization

The rate of heat development curves for various time periods over seven days of hydration are shown in Appendix E. The heat liberation curves indicate that the presence of different CKDs is markedly different from the control PC alone and equivalent amounts of limestone or silica flour as partial replacements of PC. The magnitude of the peaks and the times at which they occur depends on the chemical, mineralogical, and/or physical properties of each binder blend.

168 The heat liberation curve of PC consists of a large initial peak represented by Ai. The Ai for each control, CKD-PC blend, and PC-filler blend is presented in Figure 4.7. In agreement with results reported by Wang et al. (2002), the CKD-PC blends had similar or higher heat evolution during initial hydrolysis than the respective control cements. Based upon Ai, it appears there is a similar or higher chemical reactivity during the initial hydrolysis period in the CKD-PC blends than the respective cement alone controls. The CKD-PC blends initial hydrolysis heat evolutions were similar to or higher than the PC- filler blends at equivalent replacement levels. As the percentage of CKD replacement increased from 10% to 20%, the total heat evolution remained similar or increased. The blends with CKDs from preheater/precalciner processes, CKDs E and F, had the highest heat evolution during initial hydrolysis in comparison to the respective PC control and all blends with equivalent replacement of PC.

The main contributing factors that are reported to affect initial hydrolysis heat evolution are (i) hydration of free lime, (ii) hydration of calcium sulfate hemihydrate to gypsum, and (iii) formation of AFt, primarily from the aluminate phase but also from the ferrite phase (Bensted, 1987). Since the initial dissolution of ions from CKDs are qualitatively the same as from PCs, as shown in Section 4.1.4, the same factors that affect initial hydrolysis of heat evolution for PCs are likely the same as those for CKD-PC blends. Further, the mineralogical components of PCs that are known to affect initial hydrolysis are the same as those found in CKDs.

The heat evolution Ai as a function of free lime content of the binder is shown for the two control cements and CKD-PC blends in Figure 4.8. It appears the relationship for Ai is linear with a positive slope for the binders as a function of free lime concentration greater than 2% for both Cements TI and TII CKD blends. Scatter in the data for mixtures with less than 2% free lime, however, indicates that factors other than free lime are also involved.

169 15 TI F TI L S E TI S LX 10 F E TI C K D A D D TI CKD B C C B LS SLX A A B TI CKD C 5 TI TI SLX

Initial Hydrolysis LS TI CK D D (Ai) Heat E volution, J /g TI CKD E 0 TI CKD F 10% replacement 20% replacement

(a)

TII 15 TII L S

TII S L X F 10 E TII CKD A

F E TII CKD B B D D A A B C C TII CKD C 5 TII TII SLX SLX Initial Hydrolysis LS LS TII C K D D (Ai) Heat E volution, J /g TII CKD E 0 TII CKD F 10% replacement 20% replacement

(b) Figure 4.7 Cumulative heat of hydration during initial hydrolysis (Ai) of (a) Cement TI blends and (b) Cement TII blends (w/b = 0.4, 23°C) (The legends are ordered top (left) to bottom (right) for the bar charts)

170

12.5 PC Replacement 10% 20% 10 Control

7.5 Ai, (mW/g.h) Ai, r = 0.987 5

2.5 0 2 4 6 8 Free CaO, %

(a)

PC Replacement 10% 10 20% Control

Ai, mW/g.h Ai, r = 0.956

4 0 2 4 6 8 Free CaO, %

(b)

Figure 4.8 Cumulative heat of hydration during initial hydrolysis (Ai) as a function of Free CaO (%) for (a) Cement TI CKD blends and (b) Cement TII CKD blends (w/b = 0.4, 23°C)

171

In order to determine the influence of CKD-PC blends with less than 2% free lime content, all blends with CKDs E and F were removed from the regression analysis. For Cement TI blends, the initial heat evolution as a function of sulfate content of the binder was linear with a positive slope, as shown in Figure 4.9(a). One possible reason for this is that the increased quantity of sulfate ions from CKDs could lead to increased chemical reaction with the Cement TI aluminate phase to form more AFt.

The Cement TII-CKD blend initial hydrolysis heat evolution as a function of the binder alkali concentration was linear with a positive slope, as shown in Figure 4.9(b). The high rate of dissolution of alkalis from the CKD fraction would likely increase the pH of the liquid phase during initial hydrolysis. Dyer et al. (1999) suggested that the higher pH levels produced by alkalis dissolving into solution from CKDs would likely promote formation of more hydrates and lead to higher heat evolution during early age hydration.

172 8

PC Replacement 7 10% 20% Control 6 Ai, J/g Ai, r = 0.880 5

4 4 4.5 5 5.5 6 6.5 7 Sulfate, %

(a)

6.5 PC Replacement 10% 20% 6 Control

5.5 Ai (J/g) Ai 5 r = 0.866

4.5

4 .4 .6 .8 1 1.2 1.4 Total Alkalis (NaEq), %

(b)

173 The induction period, which follows the initial hydrolysis phase, is characterized by a period of very little heat evolution. The minimum rate of heat evolution during the induction period (Qi) of Cements TI and TII CKD blends is shown in Figure 4.10. The Qi for Cement TI CKD blends were similar to or higher than that of the Cement TI control. The Qi for Cement TII CKD blends, however, were both above and below that of the Cement TII control. It appears the relationship for Qi is linear with a positive slope for the binders as a function of sulfate concentration for both Cements TI and TII CKD blends, as shown in Figure 4.11.

During the induction stage, the influence of increased sulfate concentration on the rate of heat evolution is likely due to increased formation of AFt. The Cement TI CKD blends have a higher correlation to the sulfate content than the Cement TII CKD blends. C3A

reacts with calcium and sulfate ions to form AFt. Since Cement TI has a higher C 3A content than Cement TII, this further indicates the likelihood of AFt formation as a governing factor. The sulfate form of the CKD-PC binder influence on Qi is also important. Figure 4.12 shows that Qi is also linear with a positive slope as a function of calcium langbeinite for both Cement TI and TII blends.

174 2.0

TI TI L S 1.5 D TI S LX E F TI C K D A 1.0 D E F C C TI CKD B Qi, mW/g TI A LS A TI CKD C LS B TI SLX SLX B TI CK D D 0.5 TI CKD E TI CKD F 0.0 10% replacement 20% replacement

(a)

2.0 TII

D F TII L S

1.5 TII S L X D F C E TII CK D A E 1.0 TII TII TII CK D B LS C Qi, mW/g A A SLX LS TII CK D C SLX B B TII CK D D 0.5 TII CKD E

TII CK D F 0.0 10% replacement 20% replacement

(b)

Figure 4.10 Minimum heat of hydration rate during induction period (Qi) of (a) Cement TI blends and (b) Cement TII blends (w/b = 0.4, 23°C) (The legends are ordered top (left) to bottom (right) for the bar charts)

175

1.5

1.25 PC Replacement 10% 20% 1 Control Qi, mW/g Qi,

0.75 r = 0.921

0.5 4 4.5 5 5.5 6 6.5 7 Sulfate, %

(a)

1.75

PC Replacement 1.5 10% 20% 1.25 Control

Qi, mW/g Qi, 1 r = 0.765

0.75

0.5 2.5 3 3.5 4 4.5 5 5.5 6 Sulfate, %

(b)

Figure 4.11 Minimum heat of hydration rate during induction period (Qi) as a function of sulfate content for (a) Cement TI CKD blends and (b) Cement TII CKD blends (w/b = 0.4, 23°C)

176 1.75 PC Replacement 10% 20% 1.5 Control

1.25 r = 0.908

Qi, mW/g 1

0.75

0.5 0 .1 .2 .3 .4 .5 .6 Calcium Langbeinite, %

(a)

1.75 PC Replacement 10% 20% 1.5 Control

1.25 r = 0.873

Qi, mW/g 1

0.75

0.5 0 .1 .2 .3 .4 .5 .6 Calcium Langbeinite, %

(b)

Figure 4.12 Minimum heat of hydration rate during induction period (Qi) as a function of calcium langbeinite content for (a) Cement TI CKD blends and (b) Cement TII CKD blends (w/b = 0.4, 23°C)

177 The time of the minimum rate heat evolution during the induction period (ti) for all control blends is shown in Figure 4.13. The ti for CKD-PC blends occurred later than that of the pastes with PCs alone and/or PC-filler blends. These findings were in agreement with the results reported by Wang et al. (2002) using a CKD at 0, 15%, and 25% replacement of an OPC. The relationship for ti is linear with a positive slope for the binders as a function of total alkali concentration for both Cement TI and Cement TII CKD blends, as shown in Figure 4.14.

Although there are many hypotheses regarding the mechanics of the induction phase, many researchers advance that it is caused by formation of a protective layer on the C 3S particles inhibiting further hydration and terminates when this layer is destroyed or rendered more permeable by aging or phase transformation (Gartner et al., 2002). It is

widely reported that alkalis accelerate hydration of C 3S. It is important to note that this effect, however, is only found in PCs with optimized sulfate content levels. The increased alkali content of the CKD-PC blends, which were not optimized for sulfate content, appeared to delay Qi. This indicates that CKD alkali content retarded the normal

hydration of C 3S. One suggestion that could explain the correlation between the increased alkali concentration and the delayed time of Qi (ti) is reduced solubility of C 3S due to the common ion effect (Gartner et al., 2002).

178 D TI 2.5 E F D F E TI LS B C 2.0 C A TI S LX B SLX LS SLX A TI C K D A 1.5 LS TI TI TI CKD B

ti, hours 1.0 TI CKD C

0.5 TI CKD D

TI CKD E 0.0 10% replacement 20% replacement TI CKD F

(a)

TII 2.5 TII LS

2.0 TII S LX F B E TII CKD A 1.5 D B E F A D C TII CKD B A C SLX ti, hours 1.0 TII SLX TII LS LS TII CKD C

0.5 TII CKD D TII CKD E 0.0 10% replacement 20% replacement TII CKD F

(b)

Figure 4.13 Time of minimum heat of hydration rate during the induction period (ti) of (a) Cement TI blends and (b) Cement TII blends (w/b = 0.4, 23°C) (The legends are ordered top (left) to bottom (right) for the bar charts)

179 2.5

PC Replacement 2.25 10% 20% Control 2

ti, hours ti, 1.75 r = 0.762 1.5

1.25 .9 1 1.1 1.2 1.3 1.4 1.5 1.6 Total Alkalis (NaEq), %

(a)

1.75

PC Replacement 10% 1.5 20% Control

1.25 ti, hours ti, r = 0.825 1

.4 .6 .8 1 1.2 1.4 Total Alkalis (NaEq), %

(b)

Figure 4.14 Time of minimum heat of hydration rate during the induction period (ti) as a function of total alkali content for (a) Cement TI CKD blends and (b) Cement TII CKD blends (w/b = 0.4, 23°C)

180 Following the induction phase, an ascending rate of heat generation leads to the main hydration peak. The ascending curve and the main hydration peak correspond to hydration of the C 3S. The CKDs generally do not possess high amounts of C 3S that could contribute to the main hydration peak. Any pozzolanic reaction that could occur is typically not observed, if at all, until after the main hydration peak in isothermal conduction calorimetry. Therefore, the main hydration peak of the CKD-PC blends can

be assumed to be mostly the C 3S contribution of the PC. The magnitude of the main

hydration peak (Qw) is typically used to assess C 3S hydration between different samples. Since Qi varied significantly among the CKD-PC blends, the main hydration peak

relative to Qi (Qw-Qi) was used to assess the effects on C 3S hydration during the acceleration stage leading to the main hydration peak.

The Qw-Qi for each mix is shown in Figure 4.15. The Qw-Qi for the CKD-PC blends varied widely, as many were both above and below the respective PC control. As the percentage of CKD replacement increased from 10% to 20% for each CKD blend, the Qw-Qi decreased. This effect was more pronounced in the Cement TI CKD blends than in the Cement TII CKD blends. Blends with CKDs A, B, and E had the highest Qw-Qi for both PCs within their respective 10% and 20% replacement categories. These CKDs generally have higher chloride and lower sulfate contents than CKDs C, D, and F. The dilution effect of PC appears as a reduction in the Qw-Qi. The magnitudes of the Qw-Qi for blends with limestone and silica sand as partial replacement of PC were lower than that of the control PCs alone and all CKD-PC blends with the same respective control PC.

181 4.0 TI

3.5 A TI L S B E TI TI A B 3.0 SLX TI S LX LS C D F SLX 2.5 LS C E TI C K D A F 2.0 D TI CKD B 1.5 TI CKD C Qw - Qi, mW/g 1.0 TI CKD D 0.5 TI CKD E 0.0 TI CKD F 10% replacement 20% replacement

(a)

TII 4.0 A B A B 3.5 E TII L S E TII SLX C TII SLX TII S L X 3.0 LS C D F LS 2.5 D TII CKD A F 2.0 TII CKD B 1.5 TII CKD C Qw - Qi, mW/g 1.0 TII CK D D 0.5 TII CKD E 0.0 10% replacement 20% replacement TII CKD F

(b)

Figure 4.15 Main hydration peak relative to the minimum peak rate heat of hydration during the induction period (Qw-Qi) for (a) Cement TI blends and (b) Cement TII blends (w/b = 0.4, 23°C) (The legends are ordered top (left) to bottom (right) for the bar charts)

182

The Qw-Qi had a good correlation with the calcium langbeinite content of the CKD-PC blends, as shown in Figure 4.16. The Qw-Qi has a negative linear slope as a function of calcium langbeinite content for both Cements TI and TII CKD blends. It is known that the main hydration peak is generally depressed at gypsum (calcium sulfate) levels above the optimum sulfate content (Lawrence, 1998b) and that there is significant C-S-H uptake of sulfate ions. The decrease in Qw-Qi as the calcium langbeinite increased suggests that the calcium langbeinite may be providing calcium and sulfate ions, similar to gypsum.

183 4 PC Replacement 10% 20% Control 3.5

3 r = -0.910 Qw-Qi, mW/g 2.5

2 0 .1 .2 .3 .4 .5 .6 Calcium Langbeinite, %

(a)

4 PC Replacement 10% 20% 3.5 Control

3 r = -0.786 Qw-Qi, mW/g 2.5

2 0 .1 .2 .3 .4 .5 .6 Calcium Langbeinite, %

(b)

184 Although calcium langbeinite seems to have a strong influence on the kinetics of C-S-H formation, other components appear to also affect C3S hydration if sulfate levels are low. The increased Qw-Qi for some of the CKD-PC blends is likely due to the presence of chlorides that caused the main hydrate peak to be higher and narrower. As shown in Figure 4.17(a), the high-chloride; low-sulfate CKD A at 10% replacement of Cement TI caused the ascending slope to be steeper and narrower in comparison to LS at 10% replacement of Cement TI. The low-chloride; medium-sulfate CKD C at 10% replacement of Cement TI had little impact on the shape of the hydration curve from the induction phase to the main hydration peak, as shown in Figure 4.17(b). This may be due to low solubility of the sulfate in CKD C.

The heat of hydration curves for Cement TI at 0% (control) and 20% replacement with LS are shown in Figure 4.17(c). The dilution effect of limestone is evidenced by a reduction in the main hydrate peak. CKD B at 20% replacement of Cement TI appeared to have a significant broadening immediately after the main hydration peak indicating pozzolanic reactivity, as shown in Figure 4.17(d). This was likely due to the presence of reactive fly ash in CKD B.

185

5.0 5.0 TI CKD C 10% 4.0 4.0 TI CKD A 10% TI LS 10% 3.0 TI LS 10% 3.0

2.0 2.0

1.0 1.0 heat evolution(mW/g) heatevolution (mW/g) 0.0 0.0 0 4 8 12 16 20 24 0 4 8 12 16 20 24 time (h) tim e (h)

(a) (b)

5.0 5.0 TI CKD B 20% 4.0 TI 4.0 TI LS 20% TI LS 20% 3.0 3.0 2.0 2.0 1.0 1.0 heatevolution (mW/g)

heatevolution (mW/g) 0.0 0.0 0 4 8 12 16 20 24 0 4 8 12 16 20 24 time (h) time (h)

186 The sulfate depletion (aluminate hydrate) peak for a properly retarded PC occurs after the main hydration peak, as shown for Cement TI in Figure 4.18(a). The Cement TII heat evolution aluminate peak, however, was superimposed on the main silicate hydration peak, as shown in Figure 4.19(a). This implies that Cement TII does not have sufficient available gypsum to retard the early hydration of aluminate phase. It appears the presence of CKD retards or suppresses the time of the sulfate depletion peak for the CKD-PC blends, as shown in Figure 4.18(b) and Figure 4.19(b, c). Calcium and sulfate ions in the form of gypsum are known to retard the sulfate depletion peak by forming AFt. This implies that CKD is contributing excess calcium and sulfate ions that are readily available to react with C 3A. Since calcium langbeinite appears to have a significant influence on the early age of hydration during the induction phase, it is reasonable to assume it can also affect the sulfate depletion peak. This is particularly important, since the proposed mechanism for calcium langbeinite takes into account the rate at which the sulfate phase can supply both calcium and sulfate ions to the surfaces of the aluminate phases during early stage hydration (Tang and Gartner, 1988).

187

5.0

4.0 TI TI LS 10% Sulfate depletion (a) 3.0 peak

2.0

1.0

heatevolution (mW/g) 0.0

0 4 8 12 16 20 24 time (h)

5.0

4.0 TI CKD E 20% (b) TI LS 20% 3.0

2.0 1.0

heatevolution (mW/g) 0.0 0 4 8 12 16 20 24

time (h)

Figure 4.18 Heat of hydration for Cement TI with (a) 0% and LS at 10% replacements and (b) CKD E and LS at 20% replacements (w/b = 0.4, 23°C)

188

Sulfate depletion 5.0 peak

(a) 4.0

3.0 TII 2.0 TII LS 10% 1.0 heat evolution (mW/g) 0.0 0 4 8 12 16 20 24

time (h)

5.0

4.0 TII CKD C 10% (b) 3.0 TII LS 10% 2.0

1.0 heatevolution (mW/g) 0.0 0 4 8 12 16 20 24 time (h)

5.0 4.5 4.0 (c) 3.5 TII CKD C 20% 3.0 TII LS 20% 2.5 2.0 1.5 1.0

heatevolution (mW/g) 0.5 0.0 0 4 8 12 16 20 24 time (h)

Figure 4.19 Heat of hydration for Cement TII with (a) 0% and LS at 10% replacements, (b) CKD C and LS at 10% replacements, and (c) CKD C and LS at 20% replacements (w/b = 0.4, 23°C)

189 The heat due to initial hydrolysis was subtracted from the total heat evolution (A7d-Ai) in order to compare effects on C 3S hydration. The total heat generation from the induction period to seven days hydration (A7d-Ai) of all blends is shown in Figure 4.20. At 10% replacement of PC, the CKD-PC blends A7d-Ai were similar to or lower than that of the PC alone and PC-filler blends. At 20% replacement of PC, the CKD-PC blends were all lower than PC alone. The A7d-Ai generally decreased as the amount of CKD and filler replacements increased from 10% to 20%.

190 90 SLX E TI LS TI TI D SLX TI L S C LS 85 F A TI S LX

A F TI C K D A B 80 C TI CKD B B

A 7d - Ai, J /g D TI CKD C 75 E TI CKD D TI CKD E 70 TI CKD F 10% replacement 20% replacement

(a)

90 TII TII L S E TII SLX F TII 85 D TII S L X A F LS E TII CKD A C SLX C B 80 A B LS TII CKD B

A 7d - Ai, J /g TII CKD C 75 D TII C K D D

70 TII CKD E 10% replacement 20% replacement TII CKD F

(b)

Figure 4.20 The total heat generation from induction period to 7 days hydration (A7d-Ai) for (a) Cement TI blends and (b) Cement TII blends (w/b = 0.4, 23°C) (The legends are ordered top (left) to bottom (right) for the bar charts)

191 Statements/Observations:

4.xviii Cumulative heat generation during initial hydrolysis (Ai) increased between 6% and 120% (more than double) at 10% CKD replacement of PC in comparison to the respective PC control. At 20% CKD replacement, the Ai increased between 16% and 208% (more than triple).

4.xix Large and highly reactive amounts of free lime (> 20%), typically found in CKDs from preheater/precalciner pyroprocesses, readily react with water; this results in an exothermic reaction that contributes to higher heat generation during initial hydrolysis in comparison to all other blends and control cements.

4.xx For Cement TI (high C 3A), reactivity with CKD sulfates appears to contribute to higher heat generation during initial hydrolysis. This reaction

is likely to form AFt. For Cement TII (low C3A), the contribution of alkalis from CKDs appears to increase heat generation during initial hydrolysis.

4.xxi For Cement TI CKD blends, the minimum rate of heat evolution during the induction period (Qi) as a function of the binder sulfate content appears to be a linear relationship with a positive slope. At 10% and 20% replacement of Cement TI with CKD A, the Qi values were similar (±3%) to that of Cement TI alone. At 10% and 20% replacement of Cement TI with CKD B, the Qi values decreased by 5% and 10%, respectively, in comparison to Cement TI alone. At 10% and 20% replacement of Cement TI with CKDs C, D, E, and F, the Qi values increased in the range of 25% to 44% and 37% to 104%, respectively. The increased heat evolution is likely due to the formation of additional AFt in the Cement TI CKD blends.

192 4.xxii In contrast to Cement TI CKD blends, the Cement TII CKD blends Qi do not have as strong a relationship with the sulfate content, which is likely due

to the lower C 3A level in Cement TII that inhibits the formation of AFt. At 10% and 20% replacement of Cement TII with CKDs A and B, the Qi values were lower (15-36%) than that of Cement TI alone. At 10% replacement of Cement TII with CKD C, the Qi value decreased by 8% but at 20% replacement increased by 36% in comparison to Cement TII alone. At 10% and 20% replacement of Cement TII with CKDs D, E, and F, the Qi values increased in the range of 15% to 47% and 28% to 81%, respectively.

4.xxiii The Qi as a function of calcium langbeinite content of the binder appears to be a linear relationship with a positive slope. This may indicate that the sulfate form of CKDs contributing to AFt formation during the induction period is largely due to calcium langbeinite.

4.xxiv The time of the minimum rate of heat during the induction period (ti) for CKD-PC blends occurred later than that of the pastes with PCs alone. At 10% and 20% CKD replacement of Cement TI and Cement TII, the ti increased by 13-58% and 29-85%, respectively. In contrast to the CKD-PC blends, the PC-filler blends ti ranged between -5% and +18% in comparison to the PC alone.

4.xxv The time of the minimum rate of heat during the induction period (ti) as a function of the binder alkali content appears to be a linear relationship with a positive slope. This indicates that CKD alkali content retards the normal

hydration of C 3S.

193 4.xxvi The main hydration peak relative to the minimum rate of hydration during the induction period as a function of the calcium langbeinite content is a linear relationship with a negative slope. This indicates that the calcium

langbeinite content from CKD inhibits the hydration of C 3S.

4.xxvii The sulfate depletion peak that occurs as a result of conversion of AFt to AFm formation is delayed or suppressed by partial replacement of CKDs for both PCs with all CKDs, except CKD A. The delay or suppression of AFt to AFm appears to be due to the increased availability of calcium and sulfate ions, which simulates the addition of gypsum to the blends.

4.xxviii At 10% replacement of Cement TI and TII with CKD, heat evolutions over a seven-day period are similar (±5%) or lower (<8%) than the respective PC control. At 20% replacement of Cement TI and TII with CKD, heat evolutions decreased between 4% and 14% in comparison to the respective control PC.

194 4.2.2 Physical Properties of Hydration 4.2.2.1 Normal Consistency The purpose of the normal consistency test (ASTM C187) was to assess whether CKDs varied the water demand of the CKD-PC blend pastes. Normal consistency is the water to binder ratio required to bring the paste to a standard condition of wetness for which the penetration of a standard needle (Vicat needle) into the paste is 10 ± 1 mm at 30 seconds. To provide an indication of the sensitivity of the test, the results of the iterative process to determine the water requirement for normal consistency of Cements TI and TII are presented in Table 4.10. These results show that as little difference as 0.2% in the normal consistency water demand can result in a paste that is outside the required range of 10mm ± 1 penetration at 30 seconds.

Table 4.10 Iterative process to determine the water requirement for normal consistency of (a) Cement TI and (b) Cement TII

(a) Cement w/b ratio (%) Needle Penetration (mm) TI 26.5 12 TI 26.2 8.5 TI 26.4 10

(b) Cement w/b ratio (%) Needle Penetration (mm) TII 24.6 14.5 TII 23.7 6.5 TII 24.1 14 TII 23.8 8 TII 24.0 10

195 The normal consistency water demand results for the PC alone, CKD-PC blends, and PC- filler blends are shown in Figure 4.21. At 10% replacement of Cements TI and TII, all of the CKD-PC blends required more water to maintain a normal consistency penetration in the range of 9 and 11 mm than the respective PC alone. At 20% replacement, each CKD- PC blend required more water than each 10% replacement blend. Some CKD blends at 20% replacement required less water than CKD blends at 10% replacement with equivalent PC. The blends with CKDs from preheater/precalciner processes – CKDs E and F – had the highest water requirement for normal consistency in comparison to the respective PC control and blends with equivalent replacement of PC. Previous researchers (El Aleem et al., 2005; Ramakrishnan, 1990; Bhatty, 1984 and 1985a), who also used normal consistency to study effects of CKD replacement at 10% and/or 20%, had similar results.

Table 4.11 provides the range for increased water demand of blends with CKDs and fillers in comparison to the PCs at equivalent replacement levels. At 10% and 20% replacement of Cements TI and TII, the water requirement increase ranged between 0.1 and 0.7% for SLX and LS. At 10% replacement of Cement TI CKDs A, B, C, and D, the increase in water demand (0.4 – 0.8%) was similar to or higher than the fillers effect on the increase in water demand (0.1 – 0.4%). All other CKDs required more water than that of the fillers as equivalent partial replacements of the same PC.

The blends with CKDs from the preheater/precalciner cement processes were separated from the remaining CKD blends, since the impact was markedly different. For example, Cement TI required 26.4% water to maintain normal consistency. At 10% replacement of Cement TI, the water requirement increase ranged between 0.4 and 0.8% for CKDs A, B, C, and D. CKDs E and F, however, resulted in an increase between 1.3 and 2.1%. The water demand impact of CKD replacements was larger in magnitude in the Cement TII blends than Cement TI blends. This suggests that the magnitude of impact is dependent upon the composition of both the CKD and PC.

196

32% F TI E 30% TI L S

F TI S LX E B C D 28% A A B D LS TI C K D A LS C TI SLX TI SLX 26% TI CKD B TI CKD C 24% TI CKD D 22% TI CKD E TI CKD F Water of Normal Consistency20% (% ) 10% replacement 20% replacement

(a)

32% F TII

30% TII L S E TII S L X F 28% TII CK D A E B D A C 26% D TII CK D B A B C LS SLX TII CK D C 24% TII LS SLX TII TII CK D D 22% TII CK D E TII CK D F

Water of Normal 20%Consistency (% ) 10% replacement 20% replacement

(b)

Figure 4.21 Water requirement for normal consistency of (a) Cement TI blends and (b) Cement TII blends (The legends are ordered top (left) to bottom (right) for the bar charts)

197

Table 4.11 Range of change in water demand for normal consistency of pastes

PC % CKD Fillers CKDs A, B, C, D CKDs E, F and Filler w/b change w/b increase w/b increase Replacement (CKDs from wet (CKDs from and long-dry kilns) preheater/precalciner kilns) TI (26.4%) 10% 0.1% to 0.4% 0.4% to 0.8% 1.3% to 2.1% 20% 0.2% to 0.7% 1.1% to 1.6% 3.9% to 5.2% TII (24.0%) 10% 0.2% 1.2% to 1.6% 2.3 to 2.7% 20% 0.5% 2.3% to 2.7% 5.2% to 7.5%

Figure 4.22(a) shows the correlation of the normal consistency between all Cement TI and Cement TII CKD blends. Figure 4.22(b) shows the same correlation with the exception that blends with CKDs E and F were excluded. The very good correlation of both indicates that the effects on normal consistency are a function of the CKD composition.

Correlations between water demand for consistency of CKD-PC blends and various independent variables were then conducted. The normal consistency water requirement as a function of free lime for both Cement TI and TII CKD blends is shown in Figure 4.23. The CKD-PC blends with the highest free limes also have the highest water demand. The increased water demand, however, is not only due to the presence of high amounts of free lime but also its reactivity. The free lime of preheater/precalciner process CKDs is typically very reactive due to the low de-carbonation temperature, resulting in soft burnt free lime. As discussed in Section 4.2.1.1, CKDs E and F have large amounts of very reactive free lime, which is indicated by isothermal conduction calorimetry in the heat evolved during initial hydrolysis.

198 0.32 PC Replacement 10% 0.3 20% Control 0.28

0.26

TII CKD TII blends r = 0.982

Normal Consistency (%) Consistency Normal 0.24

0.22 .26 .27 .28 .29 .3 .31 .32 TI CKD blends Normal Consistency (%)

(a) Blends with all CKDs

0.32 PC Replacement 10% 0.3 20% Control

0.28 r = 0.967 0.26 TII CKDs TII (A, B,C, D)

Normal Consistency (%) Consistency Normal 0.24

0.22 .26 .265 .27 .275 .28 .285 TI CKDs (A, B, C, D) Consistency (%)

(b) Blends with CKDs A, B, C, and D

Figure 4.22 Correlation between Cement TI and Cement TII blends with the same CKD and replacement level for (a) all CKDs and (b) CKDs A, B, C, and D

199 0.32

PC Replacement 0.3 10% 20% Control 0.28

0.26 r = 0.970 0.24 w/b @ Normal Consistency, % @w/b Consistency, Normal

0.22 0 2 4 6 8 Free CaO, %

(a)

0.32 PC Replacement 0.3 10% 20% Control 0.28

0.26 r = 0.958

0.24 w/b @ Normal Consistency, % @Consistency, Normal w/b

0.22 0 2 4 6 8 Free CaO, %

(b)

Figure 4.23 Water requirement for normal consistency as a function of free lime content for (a) Cement TI CKD blends and (b) Cement TII CKD blends

200 The reason(s) for the effects of long-dry and wet kiln CKDs A, B, C, and D on increased water demand in CKD-PC blends are not as clearly related to free lime. Attempts to correlate water demand of the CKD-PC blends with CKDs A, B, C, and D to other independent variables did not provide clear relationships. Since CKDs vary significantly in composition, it is possible that there is more than one independent variable of CKD that is impacting the water requirement. Besides the presence of free lime, an increase in rate of ion dissolution could lead to greater overall chemical reactivity that requires higher water demand.

Statements/Observations:

4.xxix For Cement TI and Cement TII, 10% replacement with CKDs A, B, C, and D (wet and long-dry kiln CKDs) increased water demand by 1 – 3% and 5 – 7%, respectively. At 20% replacement of Cement TI and Cement TII, water demand increased by 4 – 6% and 10 – 11%, respectively.

4.xxx CKDs with large amounts of highly reactive free lime (CKDs E and F) at 10% replacement of Cement TI and Cement TII increased the water demand by 5 – 8% and 11 – 17%, respectively. At 20% replacement of Cement TI and Cement TII with CKDs E and F, water demand increased by 15 – 20% and 22 – 31%, respectively.

4.xxxi As the percent replacement of PC increased from 10% to 20% for CKDs A, B, C, and D, water demand increased by 2 – 3% for Cement TI and 4 – 5% for Cement TII, in comparison to the PC control. As percent replacement of PC increased from 10% to 20% for CKDs E and F, water demand increased by 9 – 11% for Cement TI and 10 – 12% for Cement TII. As filler replacement levels increased from 10% to 20% of PC, the water demand remained the same (± 1%).

201 4.2.2.2 Flow The purpose of the flow test was to assess the impact of CKDs on the workability of the CKD-PC mortar blends. A minimum of two flow measurements were taken for the PCs and with CKD and filler as partial replacements of the PCs at a constant w/b ratio of 0.485. The average of the measurements for each mortar control and mortar blend is presented in Figure 4.24. The statistical differences among the mortars for Cements TI and TII were assessed using one-way analysis of variance (one-way ANOVA) and results are presented in Appendix F.

Generally, the filler replacements increased flow while the CKD replacements reduced flow. This indicates that the behaviour of the fillers is different from the impact of CKDs. The LS and SLX blends had higher flow measurements at both 10% and 20% replacement than that of the respective control PCs. As the percentage of each filler replacement increased from 10% to 20% for both Cements TI and TII, the flow increased. As the percentage of each CKD replacement increased from 10% to 20%, however, the flow decreased. Some of the CKD blends at 20% replacement, however, had higher flow than some CKD blends at 10% replacement with equivalent PC. The governing influence of using CKD as a partial replacement of PC does not appear to be the percentage of replacement.

At 10% replacement of Cement TI the flow of CKD blends were all lower than the control with the exception of the blend with CKD D. The Cement TI with 10% CKD D had a similar flow measurement to both filler blends at 10% replacement. However, at 20% replacement, all Cement TI CKD blends were lower than both the Cement TI alone and filler blends. All Cement TII CKD blends had similar flow or were lower than that of the Cement TII alone. Blends with CKD D had the highest flow in comparison to the other CKD blends at an equivalent replacement level, while blends with the preheater/precalciner CKDs E and F had significantly reduced flow.

202

TI 120 LS SLX LS 110 SLX D D TI L S TI TI A E A C C TI S LX 100 B F B TI C K D A 90

F low TI CKD B 80 E TI CKD C 70 F TI CKD D 60 TI CKD E 50 TI CKD F 10% replacement 20% replacement

(a)

120 LS LS SLX SLX TII TII TII B D 110 A C D A TII L S E C B 100 F TII S L X

E 90 TII CKD A F low TII CKD B 80 F TII CKD C 70 TII CK D D 60 TII CKD E

50 TII CKD F 10% replacement 20% replacement

(b)

Figure 4.24 Mortar flow of (a) Cement TI blends and (b) Cement TII blends (The legends are ordered top (left) to bottom (right) for the bar charts)

203 The ASTM C109 requirement for mortar flow is 110 ± 5 of blended cement. The range of flows for the filler and CKD blends at 10% and 20% for each PC are presented in Table 4.12. Cement TI control flow was 107, which is close to the lower limit of the required range. Cement TII control flow was 114, however, which is close to the upper limit of the required range. The flows of PC-filler blends were comparable (±3) at equivalent partial replacements of the same PC. Filler replacements at 10% of Cement TI were within the ASTM range, while all other blends with filler replacements were near or slightly above the upper limit.

Blends with CKDs A, B, C, and D were separated from blends with CKDs E and F due to the significant difference in the range of flows. At 10% replacement of Cement TI with CKDs A, B, C, and D the flow measurements were all within the required range or slightly below the lower limit. Cement TII blends with CKDs A, B, C, and D at 10% replacement were all within the required range. At 20% CKD replacements of Cements TI and TII, all blends were slightly above or below the lower limit of 105, with the exception of Cement TI CKD B at 20% that had a flow of 95. Blends with CKDs E and F at 10% replacement of PCs were only slightly below the lower limit, except for Cement TI CKD F at 10% replacement, which was 94. Blends with CKDs E and F at 20% replacement of Cements TI and TII, however, were well below the ASTM specified range. Table 4.12 Range of flow for all mortars

CKD Cement CKDs A, B, C, D CKDs E, F Fillers Replacement Type (CKDs from wet and (CKDs from long-dry kilns) preheater/precalciner kilns) Flow Range Flow Range Flow Range 10 % replacement TI (107) 100 – 110 94 – 102 111 – 112 TII (114) 109 – 113 100 – 103 116 –117 20% replacement TI (107) 95 – 108 66 – 79 114–117 TII (114) 102 – 109 78 – 90 117–118 • Regular: All flows between 105 - 115 • Italic: All flows between 100 – 120 • Bold: Atleast one flow is below 100

204 Correlations between flow of CKD-PC blends and various independent variables were conducted. The flow as a function of free lime for both Cement TI and TII CKD blends is shown in Figure 4.25. Similar to the impact on water requirement for normal consistency, the CKD-PC blends with the highest free lime contents also have the highest water demand, resulting in low flow. As discussed in Sections 4.2.1.1 and 4.2.2.1, high amounts of reactive free lime in CKDs E and F quickly combine with water to form calcium hydroxide precipitates. The reduction in flow is likely due to the formation of these precipitates. Scatter in the data below 2% free lime, however, indicates that factors other than free lime are also involved.

Correlations were then investigated for flow of CKD blends excluding CKDs E and F and other independent variables. As shown in Figure 4.26, the effects of fineness became more pronounced for both Cements TI and TII CKD blends. The most pertinent findings of the analysis are that the flow correlates well with the particle size fraction less than 30 µm for Cement TI CKD blends and less than 45 µm for Cement TII CKD blends. As the percentage of finer particles below the respective size increases, so does the flow. This apparently is in line with the results of the fillers, which also have higher 45 µm passing and higher flow. CKD D also had the highest percentage of particles passing 45 µm and the highest flows.

205 120

110

100 PC Replacement 10% 90

Flow 20% Control 80

60 r = -0.870 0 2 4 6 8 Free CaO, %

(a) Cement TI blends

120 PC Replacement 110 10% 20% 100 Control

90 Flow r = -0.926 80

60 0 2 4 6 8 Free CaO, %

(b)

Figure 4.25 Mortar flow as a function of free lime content for (a) Cement TI CKD blends and (b) Cement TII CKD blends (Encircled data points reflect scatter in the data below 2% free lime content)

206 115

110 PC Replacement 10% 20% 105 Control Flow 100

95 r = 0.960

90 74 75 76 77 78 79 Volume < 30.5 µm, %

(a)

115 PC Replacement 112.5 10% 20% 110 Control

107.5 Flow r = 0.892 105

102.5

100 86 87 88 89 90 91 92 93 45µm, % Passing

(b)

207 The results from the present study indicate that the flows of CKD-PC mortar blends are similar to or lower than PC alone. The role of CKD in reducing flow arises from the fact that reactive free lime hydrates readily to form calcium hydroxide precipitates and/or there is a smaller percentage of particle size less than 30.5 µm for Cement TI CKD blends and 45 µm for Cement TII CKD.

Statements/Observations:

4.xxxii The CKD-PC blends had similar (±5%) or reduced flows (>5% reduction) in comparison to the control PC alone. The PC-filler blends, however, had similar or higher flows (2 – 9%) than PC alone.

4.xxxiii At 10% and 20% replacement of Cement TI with CKDs A, B, and C, flow decreased by 3 – 7% and 5 – 11%, respectively. At 10% and 20% replacement of Cement TI with CKD D, flow was similar to the respective PC control (±3%). At 10% and 20% replacement of Cement TII with CKDs A, B, C, and D, flow decreased by 1 – 4% and 4 – 11%, respectively.

4.xxxiv CKDs with large amounts of highly reactive free lime reduce the flow of a CKD-PC blend significantly in comparison to control PC. At 10% replacement of Cement TI and Cement TII with CKDs E and F, flow decreased by 5 – 12% and 10 – 12%, respectively. At 20% replacement of Cement TI and Cement TII with CKDs E and F, flow decreased by 26 – 38% and 21 – 32%, respectively.

4.xxxv In the absence of large amounts of highly reactive free lime (>20%), it appears the flow is governed by the fineness properties of the blends. Cement TI CKD blend flows as a function of the total particles of less than 30.5 µm by volume is a linear relationship with a positive slope. For Cement

208 TII CKD blends, the flow as a function of percentage of the total particles less than 45 µm by mass is a linear relationship with a positive slope.

4.xxxvi As the percentage of PC replacement with CKDs A, B, C, and D increased from 10% to 20%, the flow remained the same or decreased by 0-5% for Cement TI and decreased by 3 – 9% for Cement TII. As the percentage replacement of PC with CKDs E and F increased from 10% to 20%, the flow decreased by 23 – 30% for Cement TI and 13 – 22% for Cement TII. As the percentage of PC replacement with fillers increased from 10% to 20%, however, the flow marginally increased (1 – 4%).

209 4.2.2.3 Initial Setting Time Concrete is traditionally a mixture of PC, water, and aggregate. The initial setting time of PC is important as, in addition to workability, it provides an indication of how long the mixture will remain in the plastic condition to allow for its transportation, placement, and compaction under a variety of conditions. For economic and logistical reasons, it is generally desirable for concrete to harden and develop strength within a reasonable time after it has been placed. For these reasons, understanding the impact of CKD as a partial replacement of PC on the initial setting time is essential.

The ASTM C191 procedure was modified to attain a setting time at five minute intervals instead of 15 minute intervals. To assess the repeatability of the initial setting time results, three samples for each control PC were tested. The setting times for Cement TI were 120, 115, and 120 minutes. The setting times for Cement TII were 60, 55, and 60 minutes. This provides an indication of the level of repeatability to be expected in the results of the setting times for all blends.

The setting times for the PC alone, CKD-PC blends, and PC-filler blends are shown in Figure 4.27. The blends with LS and SLX had very similar setting times to that of the respective cement alone specimens. Of the 14 Cement TI CKD blends, nine exhibited similar or delayed setting times in comparison to that of the Cement TI control. Cement TI CKD blends that consisted of CKDs C and D at both 10% and 20% replacement had shorter setting times in comparison to Cement TI alone. CKD F at 10% replacement of Cement TI delayed setting time, but at 20% replacement shortened setting time in comparison to the Cement TI control. All of the setting times for the Cement TII CKD blends were delayed in comparison to the control. The setting times of CKD-PC blends increased or stayed the same when the level of CKD replacement increased from 10% to 20%, except blends with CKD F.

210

180 TI B E 160 TI L S A 140 E TI S LX A B F TI SLX 120 LS SLX TI D LS C D F TI C K D A C 100 TI CKD B 80 TI CKD C 60 TI CKD D 40

Initial S et Time (minutes)20 TI CKD E 0 TI CKD F 10% replacement 20% replacement

(a)

140 B TII 120 E TII L S F 100 B E A TII S L X D F A C 80 D TII CKD A LS SLX C LS SLX TII TII 60 TII CKD B TII CKD C 40 TII CK D D 20 Initial S et Time (minutes) TII CKD E

0 TII CKD F 10% replacement 20% replacement

(b)

Figure 4.27 Initial set time for (a) Cement TI blends and (b) Cement TII blends (The legends are ordered top (left) to bottom (right) for the bar charts)

211

ASTM C150 allows the use of processing additions to meet the requirements of ASTM C465 for use in the manufacture of hydraulic cements and states that the time of setting (ASTM C191) shall not vary from that of the control cement by more than 60 minutes or 50%, whichever is the lesser. This requirement for setting time is one parameter that was used to assess the acceptability of using CKDs as a partial replacement of PC in the current standards.

The Cement TI control setting time was 120 minutes and, according to ASTM C465, the acceptable setting time range for Cement TI with processing additions is between 60 and 180 minutes. All of the Cement TI CKD blends at both 10% and 20% replacement were within the ASTM C465 specified range. The setting time with 10% CKD replacement of Cement TI was between 105 and 130 minutes. The range of setting time with 20% CKD replacement of TI was between 110 and 170 minutes.

The Cement TII setting time was 60 minutes and, according to ASTM C465, the acceptable setting time range for Cement TII with processing additions is between 30 and 90 minutes. Three of the six Cement TII blends at 10% CKD replacement and two of the six blends at 20% CKD replacement were within the acceptable range. The range of setting times with 10% CKD replacement of Cement TII was between 70 and 100 minutes. The range of setting times with 20% CKD replacement of Cement TII was between 80 and 125 minutes.

It is generally accepted that initial setting is controlled by the hydration of C 3S to form C- S-H. Under normal conditions, initial setting time and the transition from the heat of hydration induction phase to the acceleration phase are related. Since it is difficult to define this transition phase of the heat of hydration curve, the time at which the minimum rate of heat evolution during the induction period, ti, is used as an indication of the time at which the induction period occurs. The setting time as a function of the time of the

212 minimum rate of heat evolution during the induction period for both Cements TI and TII CKD blends is shown in Figure 4.28.

As shown in Figure 4.28(a), the Cement TI CKD blends setting times correlate well with the time that the minimum peak of the induction period occurred for blends that had longer setting times than the TI control, indicating normal setting. The relationship appears to be linear with a positive slope. The Cement TI CKD blends that resulted in shorter setting times (TI CKD C 10 and 20%, TI CKD D 10 and 20%, and TI CKD F 20%), in comparison to Cement TI control, are circled in Figure 4.28(a). These data points do not correlate well with time of the minimum rate of heat evolution during the induction period. This indicates abnormal setting, which is typically caused by an imbalance between alumina and sulfate ions. False set (a type of abnormal set) in the Cement TI CKD blends with CKDs C and D is likely. This is due to either an excess of sulfate in the liquid phase leading to secondary gypsum formation or excessive AFt formation. CKD F was the only CKD that resulted in shortened settings times as the replacement of both PCs increased from 10% to 20% replacement. These shortened setting time are likely due to the large amount of highly reactive free lime resulting in precipitation of Ca(OH) 2 that causes an abnormal set similar to a flash set.

Figure 4.28(b) shows a strong relationship between the heat of hydration induction period and the setting times for Cement TII CKD blends. Therefore, CKD F at 20% was removed from the data set. The setting time as a function of the time of the minimum rate of heat evolution during the induction period appears to be a linear relationship with a positive slope, unless false or abnormal setting occurs. This indicates the difference between hydration kinetics and the setting mechanism. This further reinforces false setting as the case because normal setting is governed by C-S-H formation, which is exhibited in the heat of hydration curve.

213 180

160 PC Replacement 10% 20% 140 Control

Setting time, minutes 120 r = 0.826

100 1.25 1.5 1.75 2 2.25 2.5 time of induction, hours

Abnormal Set: TI CKD C 10% and 20% TI CKD D 10% and 20% (a) TI CKD F 20%

140 (b) Cement TII blends

120 PC Replacement 10% 20% 100 Control

r = 0.795 Setting time, minutes 60

40 1 1.25 1.5 1.75 time of induction, hours

(b)

Figure 4.28 Initial set time as a function of the time of minimum heat rate during the induction period (ti) for (a) Cement TI CKD blends (excluding circled data points) and (b) Cement TII CKD blends

214 Cement TII had a very short setting time, by industry standards. The paste false set test (ASTM C451) was performed that indicated the short setting time was not due to false set, but simply a quick set. As discussed in Section 4.2.1.1, the heat of hydration curves for Cement TII showed that the sulfate depletion peak was superimposed on the main hydration peak. This is an indication that inadequate soluble sulfate was available to control the hydration of C 3A to allow for normal setting to occur. It is likely that the early

sulfate depletion contributed to the hydration of C3A resulting in the quick set.

The setting time as a function of the soluble alkali content of the binder is shown in Figure 4.29 for Cement TI CKD and Cement TII CKD blends. Although the setting is influenced by many variables, the soluble alkali content of the CKD-PC blend is typically of the greatest significance. Both time of induction from heat of hydration graphs and initial setting times also correlate well with the alkali contents for the respective Cement TI and Cement TII CKD blends. This strengthens the premise that alkalis retard the

normal hydration of C 3S.

While, alkalis are widely reported to accelerate hydration of C 3S, Osbaeck and Jons (1980) stated that the accelerated effects of alkalis are diminished or absent if gypsum (calcium sulfate) levels are above the optimum sulfate content. The present study indicates that the sulfate contribution from CKDs behave similar to gypsum. Since CKDs generally contain higher amounts of soluble sulfate than PC, the CKD-PC blends have sulfate contents that are above the optimum sulfate level. Therefore, the finding that an increase in alkali contribution from CKDs delays, rather than accelerates, hydration of

C3S is reasonable.

It is widely known that an increase in w/b for a given paste results in longer setting times. Although the w/b ratio was higher for all CKD-PC blends than the PC, a relationship between w/b and the setting times was not found. This finding is reasonable, however,

215 since the established influence of w/b refers to its effect on a single blend and not on blends with different chemical/mineralogical and physical properties.

180 PC Replacement 10% 160 20% Control

140 initial

Set time - r = 0.945 120

100 .7 .8 .9 1 1.1 1.2 1.3 Sol. Alkalis (NaEq)

Abnormal Set: TI CKD C 10% and 20% TI CKD D 10% and 20% (a) TI CKD F 20%

140 PC Replacement 10% 120 20% Control

100

initial Set time - 80 r = 0.790

40 .4 .5 .6 .7 .8 .9 1 Sol. Alkalis (NaEq)

(b)

Figure 4.29 Initial set time as a function of soluble alkali content for (a) Cement TI blends (excluding circled data points) and (b) Cement TII blends

216 Statements/Observations:

4.xxxvii All of the Cement TI CKD blends at both 10% and 20% replacement were within the ASTM C465 specified range. At 10% CKD replacement of Cement TI, the initial setting times were ±12.5% of the Cement TI initial setting time. At 20% CKD replacement of Cement TI, the initial setting times were between 8% shorter and 42% longer than the initial setting time of Cement TI. Three of the six Cement TII blends at 10% CKD replacement and two of the six blends at 20% CKD replacement were within the acceptable range. At 10% and 20% CKD replacement of Cement TII, the initial setting times were 17 – 67% and 33 – 108% longer, respectively, than the initial setting time of Cement TII.

4.xxxviii The setting time as a function of the binder alkali content appears to be a linear relationship with a positive slope, unless abnormal setting occurs. This implies that an increase in the CKD alkali content retards the normal setting process that occurs as a result of C-S-H hydration.

4.xxxix Abnormal setting may occur with some CKDs as partial replacements of PCs, which is likely due to excessive amounts of sulfate ions available during early age hydration. The likely precipitates are AFt and/or calcium sulfate. Large amounts of highly reactive free lime in CKDs may cause precipitation of calcium hydroxide and also result in abnormal/early setting times.

4.xl Initial setting time is delayed by the presence of CKDs, unless abnormal initial set occurs. All Cement TI CKD blends met the ASTM C465 standards for setting time at 10% and 20% replacement. For the Cement TII CKD blends, however, only some of the blends at 10% and 20% CKD

217 replacement levels were within the acceptable range. The difference is perhaps due to the relatively large change in alkali content between the Cement TII CKD blends and Cement TII in comparison to the Cement TI CKD blends and Cement TI.

4.xli It is widely known that an increase in w/b for a given paste results in longer setting times. Although the w/b ratio was higher for all CKD-PC blends than for the PC control, a relationship between w/b and the setting times was not found. This finding is reasonable since the established influence of w/b refers to its effect on a single blend and not on blends with different chemical/mineralogical and physical properties.

4.2.2.4 Compressive Strength Compressive strength is perhaps the most important criterion for assessing PC quality. Virtually every PC testing specification stipulates minimum strength requirements at certain ages. The strength development of a cementitious system is influenced by the PC type or, more specifically, the mineralogical and physical properties of the PC. As the effects of CKD-PC blends on strength in comparison to the control PC are considered, it is also important to assess the performance criterion for the CKD-PC blends in meeting industry standards.

The compressive strengths of all mortars were determined at 1, 3, 7, 28, and 90 days. The compressive strength at each age was determined using an average of three cube measurements at a constant w/b ratio of 0.485. The statistical differences among the mixes were assessed using one-way analysis of variance (one-way ANOVA), and they are presented in Appendix G.

The average compressive strengths for each mortar control and blend are presented in Figure 4.30 and Figure 4.31 and tabulated in Table G.2. The range of the CKD-PC and

218 PC-filler blend strengths are presented as a percentage of values for PC alone at each age in Table 4.13 and Table 4.14. ASTM C150 states that PC must meet minimum compressive strength requirements that increase at later ages. ASTM C465 states that mortar compressive strengths (ASTM C109) of blends with partial replacement of PC shall not be less than 95% of the control PC at all ages. Therefore, 95% of PC compressive strength at the same age is considered an adequate level to assess performance of the CKD-PC blends.

At 10% replacement of Cement TI (Figure 4.30a), all CKD-PC blends were more than 95% of the PC control except the blend with CKD D at the age of one day (73%). At 10% replacement of Cement TII (Figure 4.31a), the lowest compressive strength of the CKD- PC blends was only marginally below the 95% threshold of PC alone at all ages, with the lowest at 93%. It should be noted that many of the CKD-PC blends at 10% CKD replacement level of PC were higher than the respective PC alone at the same age, with the highest at 115% for the Cement TI CKD blends and 112% for the Cement TII CKD blends.

At 20% replacement of the PCs with CKDs, the range of CKD-PC compressive strengths is much wider. For the Cement TI blends, all CKD-PC blends at one day were below 95% of the control cement. At all of the other ages, some blends are above and some below the 95% threshold. At 90 days, the CKD-PC blends with Cement TI were only marginally below (93 – 94%) or exceeded the 95% threshold for PC alone compressive strength. For the Cement TII CKD blends, some blends are above and some below the 95% threshold at all ages.

The compressive strengths for Cement TI with LS at 10% and 20% replacement were within the compressive strength range of the CKD-PC blends at equal levels of replacement at all ages. At early ages (one and three days), the Cement TI SLX blend compressive strengths were also within the range of the Cement TI CKD blends at equal

219 levels of replacement. At later ages (28 and 90 days), however, the Cement TI SLX blend compressive strengths were lower than the range of the Cement TI CKD blend compressive strengths at equal levels of replacement.

50.0 TI 45.0 TI L S 10% 40.0 35.0 TI S L X 10%

30.0 TI CK D A 10%

25.0 TI CK D B 10%

20.0 TI CK D C 10%

15.0 TI C K D D 10% Compressive S trength (MPa) 10.0 TI C K D E 10% 1 day 3 day 7 day 28 day 90 day TI C K D F 10% Curing Time

(a)

50.0 TI 45.0 TI L S 20% 40.0 TI S L X 20% 35.0 TI CK D A 20% 30.0 TI CK D B 20%

25.0 TI CK D C 20%

20.0 TI C K D D 20%

15.0 TI C K D E 20% Compressive S trength (MPa) 10.0 TI C K D F 20% 1 day 3 day 7 day 28 day 90 day

Curing Time

(b) Figure 4.30 Mortar compressive strength of Cement TI blends at 1, 3, 7, 28, and 90 days (w/b = 0.485) for (a) 10% replacement and (b) 20% replacement (w/b = 0.485)

220 (The legends are ordered top (left) to bottom (right) for the bar charts)

45.0

40.0 TII TII L S 10% 35.0 TII S L X 10% 30.0 TII C K D A 10%

25.0 TII C K D B 10%

20.0 TII C K D C 10% TII C K D D 10% 15.0

Compressive S trength (MPa) TII C K D E 10% 10.0 TII C K D F 10% 1 day 3 day 7 day 28 day 90 day

Curing Time

(a)

45.0

40.0 TII TII L S 20% 35.0 TII S L X 20% 30.0 TII C K D A 20%

25.0 TII C K D B 20%

20.0 TII C K D C 20% TII C K D D 20% 15.0

Compressive S trength (MPa) TII C K D E 20% 10.0 TII C K D F 20% 1 day 3 day 7 day 28 day 90 day

Curing Time

(b)

Figure 4.31 Mortar compressive strength of Cement TI blends at 1, 3, 7, 28, and 90 days (w/b = 0.485) for (a) 10% replacement and (b) 20% replacement (w/b = 0.485) (The legends are ordered top (left) to bottom (right) for the bar charts)

221

Table 4.13 Compressive strength range for CKD-PC blends as percent of PC alone

TI with 10% TII with 10% TI with 20% TII with 20% CKD CKD CKD CKD replacement replacement replacement replacement 1 day 73 – 112% 93 – 109% 65 – 99% 78 – 102% 3 day 96 – 110% 94 – 106% 71 – 100% 71 – 96% 7 day 104 – 113% 94 – 108% 77 – 107% 74 – 103% 28 day 101 – 114% 93 – 104% 90 – 100% 84 – 102% 90 day 99 – 115% 97 – 100% 94 – 114% 89 – 96% 1. Bold: all CKD-PC blends greater than or equal to 95% f’c of PC alone 2. Regular: at least one CKD-PC blend within 90 to 95% f’c of PC alone 3. Italics: at least one CKD-PC blend less than 90% f’c of PC alone

Table 4.14 Compressive strength range for PC-filler blends as percent of PC alone

TI with 10% TII with 10% TI with 20% TII with filler filler filler 20% filler replacement replacement replacement replacement LS SLX LS SLX LS SLX LS SLX 1 day 93% 96% 93% 88% 78% 83% 80% 80% 3 day 103% 95% 95% 87% 89% 83% 81% 81% 7 day 105% 98% 104% 85% 94% 88% 89% 72% 28 day 103% 97% 97% 83% 92% 88% 82% 74% 90 day 110% 97% 97% 83% 94% 87% 82% 73% 1. Bold: all PC-filler blends greater than or equal to 95% f’c of PC alone 2. Regular: at least one PC-filler blend within 90 to 95% f’c of PC alone 3. Italics: at least one CKD-PC blend less than 90% of f’c of PC alone

222 The compressive strengths for Cement TII with LS at 10% and 20% replacement were within the compressive strength range of the Cement TII CKD blends at equal levels of replacement at all ages. The compressive strengths for Cement TII with SLX at 10% replacement, however, were lower than the compressive strength range of the Cement TII CKD blends at equal levels of replacement. At one and three days, Cement TII with SLX at 20% replacement was within the compressive strength range of the Cement TII CKD blends. At 7, 28, and 90 days, however, Cement TII with SLX at 20% replacement compressive strengths was lower than the compressive strength range of the Cement TII CKD blends at equal levels of replacement.

The CKD-PC blends that had higher strengths at one day generally decreased at 7, 28 and 90 days compared to PC alone. Conversely, the CKD-PC blends that had lower strengths at one day generally increased at 7, 28, and 90 days compared to PC alone. Generally speaking, the CKD-PC blends had comparable compressive strengths to PC-LS blends and higher compressive strengths than PC-SLX blends at equal levels of replacement.

Cement TI CKD blends at one and three day compressive strength have a linear relationship with a negative slope as a function of the binder SO 3 content, as shown in Figure 4.32. The only known sulfate form to have this effect on PC compressive strength is calcium sulfate in the form of gypsum. As discussed in Section 2.4.6, the observed optimum sulfate content in the strength curve implies that the addition of gypsum

involves two opposing effects. The first, which predominates in the lower range of SO 3 content, has a beneficial effect on strength. The second, which predominates in the range

of SO 3 greater than the optimum, has an adverse effect on compressive strength. This

results in a bell-curve relationship for compressive strength as a function of SO 3 content. The heat of hydration analysis shows that Cement TI has normal sulfate levels to control aluminate hydration. Therefore, it is expected that excess calcium and sulfate ions provided by the CKD fraction of the binder will contribute to adverse effects on one day strengths.

223 30

PC Replacement 25 10% 20% Control 20

Mortar Compressive 15

Strength @ 1 day, MPa r = -0.900

10 4 4.5 5 5.5 6 6.5 7 SO3, %

(a)

PC Replacement 10% 25 20% Control

20 r = -0.830

Mortar Compressive 15 Strength @ 3 day, MPa

10 4 4.5 5 5.5 6 6.5 7 SO3, %

(b)

Figure 4.32 Mortar compressive strength as a function of total sulfate content for Cement TI CKD blends at (a) 1 day and (b) 3 days (w/b = 0.485)

224 The one and three day strength relationship with SO3 content for the Cement TII CKD blends also support the finding that CKD can behave in a similar manner to gypsum during early-age hydration, as shown in Figure 4.33. From the heat of hydration analysis, the main hydration and sulfate depletion peaks overlap (occur simultaneously) indicating that insufficient calcium and sulfate ions were available to control aluminate hydration. As the sulfate content of the Cement TII CKD blends increased, the one day strength initially increased but then assumed a negative linear slope. Therefore, the data points suggest a bell curve very similar to that seen with the addition of calcium sulfate in the form of gypsum (see Figure 2.7). Two commonly suggested mechanisms of excessive sulfates are: (i) excessive AFt formation and (ii) accelerated hydration of alite but lower

C-S-H intrinsic strength due to incorporation of SO3 into its structure. Gartner et al., (2002) have stated that both mechanisms may contribute to the phenomenon caused by excessive calcium sulfate. Cement TII has low aluminate content. Therefore, the linear negative slope relationship as a function of increasing sulfate content for the Cement TII CKD blends is most likely due to affects on C-S-H, rather than AFt formation at one day strength.

The effect of increased alkali content is widely reported to increase early strengths and reduce later strengths. This effect is significantly diminished, however, as the gypsum content exceeds the optimum sulfate level. Since the presence of CKD appears to increase the amount of calcium and sulfate ions in solution during early age hydration, it is not surprising that the effect of alkalis from CKDs does not appear to impact early age compressive strength. In the absence of high CKD sulfate content, other contributing factors may govern effects on early age strength. For example, CKD A (low sulfate and high chloride contents) increased early age strengths, likely due to the accelerating effect of chlorides.

225

PC Replacement 10% 20% Control

r = -0.798 (linear fit)

(a)

PC Replacement 10% 20% Control

r = -0.867 (linear fit)

(b)

Figure 4.33 Mortar compressive strength as a function of total sulfate content for Cement TII CKD blends at (a) 1 day and (b) 3 days (w/b = 0.485) Note: Straight line is a linear best fit. Curve is a polynomial best fit.

226

The Cement TI CKD blend 28 day compressive strengths as a function of the percentage of material passing 45 µm sieve is shown in Figure 4.34. Cement TI CKD blend 28 day strengths had a linear relationship with a negative slope as a function of percentage passing the 45 µm sieve. The Cement TI CKD blend 28 day compressive strengths as a function of the calcium carbonate content are shown in Figure 4.33. Cement TII CKD blends had a linear relationship with a negative slope as a function of calcium carbonate content. As discussed previously for the calcite filler, calcium carbonate as a partial replacement of low C3A cements acts as a diluent. The CKD contribution of calcium carbonate likely reacts with the aluminate hydrates in Cement TI, whereas Cement TII has much lower aluminate hydrate content. Scatter in the data for the relationships at 28 day compressive strengths indicates that other factors also influence CKD-PC blend strength at this age.

A linear relationship for 7 day and 90 day strengths was not evident for the CKD-PC blends. It is likely a combination of contributing factors that influence the strength development of CKD-PC blends at these ages.

227 42 PC Replacement 40 10% 20% Control 38

34 r = 0.652 Mortar Compressive

Strength @ 28 day, MPa 32

30 88 90 92 94 96 45µm, % Passing

Figure 4.34 Mortar compressive strength at 28 days as a function of percentage passing 45 µm for Cement TI CKD blends

40 PC Replacement 38 10% 20% Control 36

34 Mortar Compressive Strength @ 28 day, MPa 32 r = -0.789

30 0 2.5 5 7.5 10 12.5 Calcite, %

Figure 4.35 Mortar compressive strength at 28 days as a function of calcite for Cement TII CKD blends (w/b = 0.485)

228 Statements/Observations:

4.xlii The compressive strength measurements for all Cement TI blends with 10% CKD replacement were higher than 95% of the PC mortar control, with the exception of only one blend at the age of one day. All of the compressive strength measurements for Cement TII blends with 10% CKD replacement were higher than 93% of the mortar plain control. Many of the CKD-PC blends compressive strengths were 5 – 15% higher than that of the respective control PC.

4.xliii All blends made with 10% CKD showed higher strengths at all ages compared to the blends made with the same CKD at 20%. Therefore, the replacement level is a factor to consider for the compressive strength effect for a particular CKD. Some of the blends with CKDs at 20% replacement, however, performed better than other CKDs at 10% replacement of PC. For example, CKD A at 20% replacement of Cement TI had higher one day compressive strength than CKDs B, C, D, and E at 10% replacement of Cement TI. This is likely due to the high chloride and low sulfate contents of CKD A. Consequently, the effect on the compressive strength of different CKDs is related to the composition of the CKD-PC blend as well as the replacement level.

4.xliv The blends with CKDs D, E, and F had low early compressive strengths but at later ages had compressive strengths comparable to the PC mixes. Excessive calcium sulfate in the form of gypsum is known to have this effect on compressive strength development. Therefore, the sulfate from CKDs D, E, and F is likely the reason for the lower early strengths and higher late strengths.

229 4.xlv The CKD-PC blends compressive strengths were comparable to that of PC- LS blends and higher than PC-SLX blends at both 10% and 20%.

4.xlvi The early age compressive strength is governed by the presence of soluble calcium and sulfate. The one and three day compressive strength of the Cement TI CKD blends each have a linear relationship with a negative slope

as a function of the binder SO 3 content. The one and three day compressive strength of the Cement TII CKD blends each appear to have a bell-curve

relationship as a function of the binder SO 3 content. It seems the sulfate content of CKD has a similar impact to the sulfate from gypsum (calcium sulfate).

4.xlvii In the absence of high CKD sulfate content (CKD sulfate content ≤ PC sulfate content), chlorides from CKDs increase early age strengths.

4.xlviii Cement TI CKD blend 28 day strengths had a linear relationship with a negative slope as a function of percentage passing 45 µm sieve. Cement TII CKD blends had a linear relationship with a negative slope as a function of calcium carbonate content. The CKD contribution of calcium carbonate likely binds with the aluminate hydrates in Cement TI, whereas Cement TII has much lower aluminate hydrate content.

4.2.3 Volume Stability and Durability 4.2.3.1 Expansion in Limewater The expansion in limewater test (ASTM C1038) is typically used to assess the stability of mortars due to the presence of calcium sulfate. The expansions in limewater of all mortars were determined after 14 days. The expansion for PC alone and for blends with CKD and filler as partial replacements of PC was determined using an average of four

230 mortar specimens. The statistical differences among the mixes were assessed using oneway analysis of variance (one-way ANOVA) and are presented in Appendix H.

The expansion in limewater for each mortar control and blend is presented in Figure 4.36. All of the CKD-PC blends had higher expansions than that of the PC alone and filler blends. The expansion in limewater was similar or higher as the percentage of CKD replacement increased from 10% to 20%. As the percentage of LS and SLX in the blends increased from 10% to 20% the expansions were similar. All blends with fillers had essentially the same levels of expansion (0.003 to 0.008%).

The allowable limit of mortar expansion in limewater is 0.020% for CSA A3001, ASTM C150, and ASTM C1157. CKDs A, B, and C were below the 0.020% threshold at both 10% and 20% replacement levels of Cement TI and TII. At 10% replacement, CKD D with both Cements TI and TII and CKD E with Cement TI were higher than 0.020%. At 20% replacement, CKDs D, E, and F with Cements TI and TII were higher than 0.020%. It is important to note that some of the blends with CKD replacement at 20% had much lower expansion than blends with 10% replacement, for the same control cement.

The expansion is most significantly correlated to sulfate content in both Cement TI CKD and Cement TII CKD blends, as shown in Figure 4.37. The expansion in limewater of CKD-PC blends after 14 days as a function of binder sulfate content is a positive linear slope. The expansion in limewater is mostly due to the formation of AFt in the hardened paste. AFt formation requires the presence of C 3A. CKD blends with Cement TI had higher expansions than blends with Cement TII. This can be explained by the higher

levels of C 3A in Cement TI than in Cement TII. Scatter in the data implies there could be factors other than sulfate content that contribute to expansion in limewater.

The linear slope for the Cement TI CKD blends in Figure 4.37(a) indicates that the expansion in limewater exceeds 0.020% at a sulfate content of approximately 4.75%.

231 Therefore, since the Cement TI sulfate content at 4.35% is optimized according to the heat of hydration analysis (see Section 4.2.1.1), the expansion in limewater exceeds the 0.020% limit when the Cement TI CKD blend sulfate content is approximately 0.40% above the optimum Cement TI sulfate content. The linear slope for the Cement TII CKD blends in Figure 4.37(b) indicates that the expansion in limewater exceeds 0.020% at a sulfate content of approximately 3.75%. The Cement TII sulfate content at 2.98% is under-sulfated according to the heat of hydration analysis (see Section 4.2.1.1). The CKD-PC expansion in limewater exceeds the 0.020% limit when the Cement TII CKD blend sulfate content is approximately 0.75% above the Cement TII sulfate content.

232

0.14 TI D 0.12 TI L S

0.10 TI S LX TI C K D A 0.08 E TI CKD B 0.06

D TI CKD C 0.04 F E TI CK D D F 0.02 A A B C E xpansion in Limewater (% ) TI B C TI SLX TI CKD E LS SLX LS 0.00 TI CKD F 10% replacement 20% replacement

(a)

0.14 TII 0.12 TII L S 0.10 TII S L X 0.08 TII CKD A

0.06 TII CKD B E D TII CKD C 0.04 F TII CK D D D E F 0.02 A A C TII CKD E B C B E xpansion in Limewater (% ) TII LS SLX TII LS SLX 0.00 TII CKD F 10% replacement 20% replacement

(b)

Figure 4.36 Expansion in limewater after 14 days for (a) Cement TI blends and (b) Cement TII blends (The legends are ordered top (left) to bottom (right) for the bar charts)

233

0.14 TI CKD D 10% and 20% 0.12 TI CKD E 10% and 20% PC Replacement TI CKD F 20% 10% 0.1 20% Control 0.08

0.06

0.04 r = 0.936

Expansion Limewater, in % 0.02

0 4 4.5 5 5.5 6 6.5 7 ASTM maximum limit SO3, %

(a)

0.14

0.12 PC Replacement 10% 0.1 20% TII CKD D 20% Control TII CKD E 20% 0.08 TII CKD F 20% 0.06 r = 0.870 0.04

Expansion Limewater, in % 0.02

0 2.5 3 3.5 4 4.5 5 5.5 6 ASTM maximum limit SO3, %

(b)

Figure 4.37 Expansion in limewater at 14 days as a function of sulfate content for (a) Cement TI CKD blends and (b) Cement TII CKD blends

234

Statements/Observations:

4.xlix At 10% CKD replacement of Cement TI the expansions in limewater were 35 – 765% higher than the expansion in limewater of Cement TI. At 20% CKD replacement of Cement TI the expansions in limewater were 115 – 2400% higher than the expansion in limewater of Cement TI. At 10% CKD replacement of Cement TII the expansions in limewater were 110 – 314% higher than the expansion in limewater of Cement TII. At 20% CKD replacement of Cement TII the expansions in limewater were 133 – 914% higher than the expansion in limewater of Cement TII.

4.l Blends with CKDs A, B, and C gave expansions in limewater below the ASTM C1038 maximum limit of expansion at both 10 and 20% replacement of Cements TI and TII. Blends with CKDs D, E, and F, however, exceeded the 0.020% limit. This is due to the significantly higher sulfate contents of CKDs D, E, and F in comparison to CKDs A, B, and C. It appears that the amount of CKD replacement of a PC is limited by the CKD-PC sulfate content, which is to be less than approximately 0.40% above the optimum sulfate content of the PC.

4.li Some blends with 20% CKD replacement had less expansion in limewater after 14 days than other blends with 10% CKD replacement. This indicates that the composition of the CKD-PC blend is more of a governing factor for expansion in limewater than the level of PC replacement with CKD.

4.lii Expansion of CKD-PC mortars in limewater after 14 days as a function of binder sulfate content is a positive linear slope. It is hypothesized that the CKDs contribute excess calcium and sulfate ions to form higher amounts of AFt than the control PC alone.

235

4.liii Cement TII CKD blends had less expansion in limewater after 14 days than the Cement TI CKD blends due to the lower aluminate content in Cement TII, in comparison to Cement TI.

4.2.3.2 Autoclave Expansion Soundness is the ability of hardened cement paste to retain volume after setting. Soundness issues generally result from the delayed or slow hydration of magnesium oxide (MgO) and/or calcium oxide (CaO free lime). It is essential that cement paste, once it has set, does not undergo a large change in volume; in particular there must be no appreciable expansion, which, under condition of restraint, could result in a disruption of the hardened cement paste.

The amount of CKD and filler in each paste was fixed at 10% and 20% by mass of PC, with a w/b ratio that varied to maintain normal consistency. To assess the repeatability of the autoclave expansion tests, repeat samples for each control PC were performed, as shown in Table 4.15. This provides an indication for the level of repeatability to be expected in the results of the autoclave expansion for all tests.

Table 4.15 Autoclave expansions for (a) Cement TI and (b) Cement TII

(a)

Autoclave PC Expansion (%) TI 0.040 TI 0.042 TI 0.038 TI 0.035

(b)

Autoclave PC Expansion (%) TII 0.055 TII 0.057

236 The autoclave expansion for each paste control and blend is presented in Figure 4.38. All of the CKD-PC blends had similar or higher expansion than that of the PC alone or the filler blends. The blends with filler materials had marginally lower expansions than PC alone. The autoclave expansion was similar or higher than the percentage of CKD replacement increased from 10% to 20%. As the percentage of LS and SLX in the blends increased from 10% and 20%, the expansions decreased. Some blends with 20% CKD replacement had less autoclave expansion than other blends with 10% CKD replacement. This indicates that the composition of the CKD-PC blend is more of a governing factor for autoclave expansion than the level of PC replacement with CKD.

The ranges for autoclave expansions of the CKD-PC blends are shown in Table 4.16. The free lime contents of the CKD-PC blends are higher than PC alone. Since the free lime contents of CKD-PC blends vary significantly, however, the results were separated into blends made with high and low free lime CKDs. All of the CKD-PC blends were well below the ASTM C150 limit of 0.80% and CSA A3001 limit of 1.0%. Therefore, all CKD-PC blends are acceptable in terms of long-term soundness/durability from the viewpoint of undesirable autoclave expansion according to ASTM C150.

ASTM C465, the specification for processing additions, however, states that the impact shall not be more than 0.10% greater than the expansion of the control cement. Blends with 10% CKD replacement were generally within this range for the two PCs, as required in ASTM C465. Some blends with 20% CKD replacement were below the 0.10% expansion of the cement alone, while others were higher. The CKD-PC blends that were within the 0.10% expansion range of the PC had low free lime contents. Therefore, CKDs with very high free lime contents may still meet the ASTM C465 requirement for soundness at 10% replacement of PC.

237 0.40 TI

0.35 TI L S

0.30 TI S LX

0.25 E TI C K D A 0.20 TI CKD B

0.15 E TI CKD C D F 0.10 F A TI CK D D D A B TI B TI C Autoclave0.05 E xpansion (% ) SLX C TI CKD E LS LS SLX 0.00 TI CKD F 10% replacement 20% replacement

(a)

0.40 E TII 0.35 TII L S 0.30 TII S L X 0.25 TII CKD A 0.20 D TII CKD B E A F 0.15 TII CKD C A F B 0.10 B D C TII CK D D C TII TII Autoclave E xpansion0.05 (% ) LS TII CKD E LS SLX SLX 0.00 TII CKD F C 10% replacement 20% replacement

(b)

Figure 4.38 Autoclave Expansions for (a) Cement TI blends and (b) Cement TII blends (The legends are ordered top (left) to bottom (right) for the bar charts)

238 Table 4.16 Range of autoclave expansions for all blends

Cement Type CKD CKDs A, B, C, CKDs D, E, F Replacement (low free lime content) (high free lime content) Expansion Change (%) Expansion Change (%) Cement TI 10% -0.009 to 0.021 0.024 to 0.091 20% 0.003 to 0.037 0.057 to 0.192 Cement TII 10% 0.016 to 0.051 0.026 to 0.112 20% 0.029 to 0.105 0.083 to 0.325 Bold: At least 1 sample is greater than 0.10% than the control PC

The autoclave expansion is most significantly correlated to free lime content for both Cement TI CKD and Cement TII CKD blends, as shown in Figure 4.39. The autoclave expansion of CKD-PC blends as a function of binder free lime content is a positive linear slope. The expansion is mostly due to the formation of calcium hydroxide in the hardened paste. It should be noted that CKD-PC blends with CKD F were excluded from the regression analysis, but the data points are still shown (encircled) in Figure 4.39. Although CKD F had the highest free lime, it did not have the highest expansion. Soundness cannot always be predicted reliably from free lime content of a CKD-PC blend, since its hydration reactivity is a function of its decarbonation temperature. CKD F is from a preheater/precalciner pyroprocess which calcinates CKDs at a lower temperature than that of wet and long-dry kiln CKDs. Free lime that has been decarbonated at low temperatures readily reacts with water in the plastic paste (see Figure 2.9) and, therefore, does not contribute to autoclave expansion in the hardened paste. The excessive heat evolution during initial hydrolysis, increased water demand, and decreased flow of blends with CKD F all indicated that the free lime content was very reactive, as is expected for a CKD from a preheater/precalciner.

Scatter in the data implies there could be other factors than free lime content that contribute to autoclave expansion, such as reactivity of free lime (as discussed above).

239

0.4

0.3 PC Replacement 10% 20% Control 0.2

CKD F 0.1 r = 0.975 Autoclave Expansion, % blends

0 0 2 4 6 8 Free CaO, %

(a)

0.4

0.3 PC Replacement 10% 20% 0.2 Control

CKD F 0.1

Autoclave Expansion, % blends r = 0.938

0 0 2 4 6 8 Free CaO, %

(b)

Figure 4.39 Autoclave expansion as a function of free lime content (excluding data points in the circles) for (a) Cement TI CKD blends and (b) Cement TII CKD blends

240 Statements/Observations:

4.liv At 10% CKD replacement of Cement TI the autoclave expansions were between 22% lower and 228% higher than the autoclave expansion of Cement TI. At 20% CKD replacement of Cement TI the autoclave expansions were 7- 480% higher than the autoclave expansion of Cement TI. At 10% CKD replacement of Cement TII the autoclave expansions were 29-191% higher than the autoclave expansion of Cement TII. At 20% CKD replacement of Cement TII the autoclave expansions were 47-591% higher than the autoclave expansion of Cement TII.

4.lv The CKD-PC blends had similar or higher autoclave expansions than PC alone, but all were well below the ASTM C150 specification of 0.80%. PC- filler blends had slightly lower autoclave expansion levels than PC alone.

4.lvi Some blends with 20% CKD replacement had less autoclave expansion than other blends with 10% CKD replacement. This indicates that the composition of the CKD-PC blend is more of a governing factor for autoclave expansion than the level of PC replacement with CKD.

4.lvii Blends with 10% CKD replacement were typically within 0.10% expansion of the two PC controls, as required in ASTM C465. Some blends with 20% replacement CKD were below the 0.10% expansion of the cement alone, while others were higher. The CKD-PC blends that were similar or below 0.10% expansion of the PC alone had low free limes (< ~ 4%).

4.lviii Expansion of CKD-PC pastes in the autoclave expansion as a function of free calcium oxide binder content has a positive linear slope. It is hypothesized that the CKDs contribute hard burnt free lime that hydrates to form higher

241 amounts of calcium hydroxide than from the control PC alone. The expansion

of hydrating lime is caused by crystallization of Ca(OH) 2. Scatter in the linear relationship with free lime content indicates that other factors may contribute to unsoundness, such as the reactivity of the free lime.

4.lix Soundness cannot always be predicted reliably from the free lime content of a CKD-PC blend since its hydration reactivity is a function of its decarbonation temperature. Free lime that has been decarbonated at low temperatures readily reacts with water in the plastic paste and therefore does not contribute to expansion in the hardened paste.

4.2.3.3 Alkali Silica Reactivity This program was designed to develop an understanding of the effects of CKD and is not aimed at addressing the ASR mitigation of mixes incorporating CKDs. The objective was to determine the influence of different types of CKD on ASR expansion tests. One of the concerns with the CSA A23.2-14A ASR test for expansion is that the NaOH is used to 3 offset the sodium equivalent alkali (Na 2Oe) level to a constant value of 5.25 kg/m . This study attempts to assess the impact of CKDs on CSA A23.2-14A concrete prism expansions.

The details of the concrete mixes within the two test series are shown in Table 4.17. For Test Series I, CKD replacement was constant at 10% of Cement TI and the amount of 3 NaOH addition varied to attain the desired Na 2Oe loading of 5.25 kg/m in concrete (based on the alkali content of both the PC and CKD). For Test Series II, the NaOH addition was kept constant for the CKD-PC blends but the amount of CKD replacement varied. Due to its lower alkali content, the TII series of blends required much more NaOH addition to bring the alkali loading of each blend to 5.25 kg/m 3 than the TI series of blends .

242 Table 4.17 ASR concrete mix alkali loadings and CKD replacement levels for (a) Test Series I: Cement TI CKD blends and (b) Test Series II: Cement TII CKD blends

(a)

Cement TI Blends Na 2Oe loading in binder Binder NaOH Expansions (%) (%) (kg/m 3) (kg/m 3) 1 year 2 years Cement TI - CTL 1 1.25 420 1.518 0.130 0.193 CKD A 10% 1.25 420 0.542 0.174 0.262 CKD B 10% 1.25 420 0.054 0.146 0.248 CKD C 10% 1.25 420 0.813 0.157 0.224 CKD D 10% 1.25 420 0.651 0.167 0.224 CKD E 10% 1.25 420 0.163 0.174 0.258 CKD F 10% 1.25 420 0.542 0.163 0.257 Cement TI - CTL 2 1.38 378 2.013 0.142 0.202 3 All blends had 5.25 kg/m of Na 2Oe in concrete mix

(b)

Cement TII Blends Na 2Oe loading in binder Binder NaOH Expansions (%) (%) (kg/m 3) (kg/m 3) 1 year 2 years Cement TII - CTL 1 1.25 420 3.633 0.182 0.262 CKD A 9.8% 1.25 420 2.452 0.173 0.227 CKD B 7.0% 1.25 420 2.452 0.189 0.253 CKD C 12.9% 1.25 420 2.452 0.175 0.240 CKD D 10.9% 1.25 420 2.452 0.197 0.258 CKD E 7.7% 1.25 420 2.452 0.213 0.297 CKD F 10.1% 1.25 420 2.452 0.191 0.247 Cement TII - CTL 2 1.03 420 2.452 0.149 0.211 3 3 All blends had 5.25 kg/m of Na 2Oe in concrete mix except Cement TII CTL 2 which had 4.34 kg/m .

243 The ASR expansion tests for Test Series I and II are shown in Figure 4.40. For Test Series I, the CKD-PC blends had higher expansions after two years in comparison to both of the controls with PC alone. This implies that either (i) the alkali contribution from CKDs causes more ASR expansion than the contribution of alkalis from NaOH addition, or (ii) there are factors other than ASR that cause expansion to occur. It is reasonable to assume that expansions due to high sulfate and free lime contents found in CKDs contribute to expansion during the ASR test. A series of tests using two cement types indicates that CKD can have a pronounced effect on ASR expansion tests, but it is dependent on factors other than alkali level.

For Test Series II, the CKD-PC blends had similar or lower expansions after two years in comparison to Cement TII CTL 1, with the exception of the blend with 7.7% CKD E. The ASR expansion results in the Test TII series indicate that for an equivalent alkali loading, NaOH is more reactive than Cement TII alkalis but less reactive than the alkalis in CKDs or other CKD factors.

Statements/Observations:

4.lx CKDs can increase the expansion in the CSA A23.2-14A ASR concrete prism test. This effect, however, is likely dependent on factors other than alkali level. High sulfate and free lime contents can also influence the amount of expansion during the ASR test.

244

(a)

(b) Figure 4.40 ASR expansions over 2 years for (a) Test Series I: Cement TI CKD blends and (b) Test Series II: Cement TII CKD blends

245 5.0 MAIN CONTRIBUTIONS OF THE THESIS

5.1 CKD Characterization Studies have shown that CKDs can be interground or blended as a partial substitute of PC between 5% and 15%, by mass. Although the use of CKDs is promising, there is very little understanding of their effects on concrete. Previous studies provide variable and often conflicting results. The reasons for the inconsistent results are not obvious due to the lack of compositional data provided in the literature. It was also found that compositional analysis procedures designed for PC are sometimes inappropriate to determine the characteristics of CKDs. The characteristics of a CKD must be well- defined in order to understand its potential impact in concrete.

A wide range of CKDs from different kiln processes were studied to assess overall CKD characterization. Within the range of materials used in this study, the following main contributions towards CKD characterization are:

1. The present study identifies the appropriate chemical and physical analytical methods that should be used for accurate CKD composition analysis. CKDs must be prepared and analyzed differently from PCs for accurate chemical and physical analysis. This will assist other researchers and the industry in properly characterizing their CKDs in future.

2. A greater understanding of the fineness properties of CKDs has resulted from this investigation. Due to the lack of a size selection process, CKDs have a broader particle size range than PCs. Also, the Blaine fineness of a CKD is largely representative of the percentage of particles of less than 10 µm while the percentage passing the 45 µm sieve is more representative of the percentage of particles between 10 and 100 µm. This will help researchers correctly interpret the fineness test results typically used for CKDs.

246

3. A process flow diagram to determine the relative abundance of the different phases within CKDs was introduced. The characteristics of CKDs are traditionally evaluated based on chemical analysis data. Such data does not, however, indicate the ways in which the different elements actually exist within the CKD and how they might be expected to react during hydration. Alkalis, for example, may occur as separate crystalline phases in the form of alkali chlorides or alkali sulfates. The reactivity of elements may therefore be expected to vary, depending on the form in which they actually exist.

4. CKDs consist of clinker phases, calcium carbonate, quartz, clays, free lime, portlandite, periclase, alkali chlorides, alkali sulfates, anhydrite, calcium langbeinite, fly ash, and/or slag. Some of the phases identified in the CKDs had not been previously recognized in the literature (i.e., calcium langbeinite) and can influence hydration significantly.

5. The initial dissolution of ionic species in water and the composition of the liquid phase play an important role in PC hydration. The availability of ions during the initial minutes of hydration was used to assess the differences in reactivity between various types of CKDs and PC. CKDs generally provide the same ions as PC during initial dissolution, except some CKDs may also contribute chloride ions. Calcium chloride, however, is commonly used as an accelerator in non- reinforced concrete in cold weather. Other than the impact of chlorides, this implies that CKD-PC blends could perform in similar manner to PC alone.

247 5.2 CKD-PC Blends CKDs contain various components that affect performance and durability properties when used as a partial replacement of PC. The chemical, physical, and mineralogical properties of CKDs vary considerably between different cement plants and even within the same plant. Therefore, it has been difficult to separate the effects of individual CKD components on CKD-PC blends. Although the single effect of any one of the common components found in CKDs can be stated in general terms, specific reactions among more than one component are sometimes difficult to predict. Improved understanding of the CKD-PC interaction will allow for optimization and increased utilization of these blends in concrete.

The majority of previous CKD-PC research has generally used only one or two CKDs and one PC (Table 2.10). Since CKDs and PCs can vary considerably, it is very difficult to make conclusions on CKD-PC interaction based upon only one or two types of CKD and one PC. The current study utilized seven CKDs with a wide range of composition characteristics, two fillers, and two PCs. Within the range of materials and CKD and filler replacement levels investigated in this study, the following main contributions towards the performance of CKD-PC blends are:

1. CKD-PC blends can show comparable performance properties to PC alone and to PC-filler blends. The components that govern the effects of CKDs as partial replacement of PCs are: free lime, sulfates, chlorides, alkalis, calcium carbonate, and fineness.

2. The most significant contribution to the optimization of CKD-PC blends is the new premise that CKDs can contribute calcium and sulfate ions that are readily available to control aluminate hydration. Many of the adverse effects of CKD-PC blends are related to excessive amounts of calcium and sulfate ions. Therefore, if

248 CKD is used as partial PC replacement, optimum SO 3 should be determined for the CKD-PC blend and that would likely lead to lower gypsum additions.

3. The results of this study have been used to present the effects and relationships of individual CKD-PC blend components using regression analysis techniques. The effects and relationships based upon compositional analysis of the CKD-PC blends are:

i. Water demand for pastes is higher for CKD-PC blends than for PC alone. Very high and reactive amounts of free lime significantly increase water demand. In the absence of high and reactive amounts of free lime, the water demand of CKD-PC blends was similar or higher than the PC alone.

ii. Mortar flow is generally lower for CKD-PC blends than for PC alone. Very high and reactive amounts of free lime significantly increase water demand. In the absence of high and reactive amounts of free lime, it appears that the particle size distribution influences the flow. CKD-PC blend flows decreased linearly as the percentage of particles passing 45 µm (Cement TI blends) and 30.5 (Cement TII blends) µm decreased.

iii. CKDs from preheater/precalciner kilns have high amounts of reactive free lime that cause the impact of water demand and flow to be significantly different in comparison to CKDs from wet and long-dry kilns. Therefore, the preheater/precalciner kiln CKDs may need to be categorized separately from wet and long-dry kiln CKDs.

249 iv. The presence of CKDs generally delays hydration of C3S in CKD-PC blends. The data suggests the magnitude of this delay is linearly related to the increased concentration of alkalis in the CKD-PC blends.

v. Since normal set is generally accepted to be a result of the onset of C3S

hydration, the presence of alkalis that delay C3S hydration will also delay normal initial set. However, accelerated initial set may occur due to the precipitation of hydration products that are not directly related to

C3S hydration (abnormal set). The likely precipitate products are AFt, syngenite, calcium sulfate, and/or calcium hydroxide. vi. CKDs influence the strength development of CKD-PC blends and tend to have low early strengths and higher late age strengths. The increased sulfate contents (beyond the PC optimum sulfate content) of the CKD- PC blends reduced early age strengths. In the absence of high CKD sulfate content, increased chloride content due to CKDs increased early

age strengths. For Cement TI (normal C 3A), later age strengths were adversely affected due to a lower percentage of particles passing the 45

µm sieve. For Cement TII (low C 3A), the calcium carbonate fraction of CKD performed as a diluent and resulted in lower later-age strengths. vii. CKD-PC blends have higher expanions in limewater than PC alone. Increased expansions in limewater of CKD-PC blends are linearly related to increased concentrations of sulfate in the binder, likely due to the formation of AFt in the hardened paste. It is believed that an optimized sulfate content for a CKD-PC blend would mitigate these expansions.

250 viii. CKD-PC blends have higher autoclave expansions than PC alone. Increased autoclave expansions are related to high amounts of hard burnt free lime content as opposed to total free lime content. It appears there are also other contributing factors to autoclave expansion, such as the presence of coarser particles in CKDs.

4. This study provides a contribution to the limited data that exists for the impact of CKD-PC blends on ASR. It appears CKD-PC blends will result in higher ASR expansion and that mitigative measures may have to be increased from those currently recommended in CSA A23.2-27A.

251 6.0 CONCLUSIONS

Within the range of materials and CKD replacement levels investigated in this study, the following conclusions are made.

1. CKD compositions vary with kiln process and the raw materials used. Therefore, the impact of CKD as a partial replacement of PC may not be consistent. Further, a particular CKD may impact CKD-PC blends differently due to varying compositions in PC.

2. Thermal and compositional anaylsis methods used for PC must be modified to use on CKDs by correcting for the volatile compounds that may be released during the LOI test and fused bead preparation.

3. CKDs may contain significant amounts of amorphous material (>30%) and clinker compounds (>20%) and small amounts of slag and/or fly ash (<5%) (if used as raw materials in clinker production) and calcium langbeinite (<5%). Although these materials/compounds do not necessarily govern the impact of CKD in a CKD-PC blend, it is important to recognize they can have an influence on hydration and on the compounds that are formed.

4. CKDs from preheater/precalciners have different effects on workability and heat evolution than CKDs from the wet and long-dry kilns. The blends with the two CKDs from preheater/precalciner plants had higher paste water demand, lower mortar flows, and higher heat generation during initial hydrolysis in comparison to all other blends and control cements. This is due to the high amounts of reactive free lime (>20%) in CKDs from preheater/precalciner processes.

252 5. The effect of CKD as a partial replacement of PC appears to be governed by the sulfate content of the CKD-PC blend (however, the form of the CKD sulfate is not significant). According to the analysis of the ASTM C1038 expansion in limewater test results in this study, the CKD-PC sulfate content should be less than ~0.40% above the optimum sulfate content of the PC.

6. CKD in CKD-PC blends behaved similarly to the addition of gypsum to PC. Therefore, CKD-PC blends could be optimized for sulfate content by using CKD as a partial substitute of the gypsum during the grinding process to control the early

hydration of C 3A. The wet and long-dry kiln CKDs contain significant amounts of calcium carbonate (>20%) which could also be used as partial replacement of limestone filler in PC. The impact of additional CKD components would need to be considered.

7. With the knowledge gained in this thesis and other research studies, there may be efforts directed towards modifying North American industry standards to allow for appropriate utilization of CKDs as partial replacement of PC, between 5 and 10% by mass. These changes would likely require less emphasis on the use of compositional specifications and greater importance on the use of performance standards such as ASTM C1157.

253 7.0 RECOMMENDATIONS FOR FUTURE WORK

1. The current study provides an understanding of the effect of free calcium and

sulfate ions from CKDs on C3S and C 3A hydration in CKD-PC blends. Many of the adverse effects of CKD-PC blends are related to excessive sulfate contents. It would be useful to assess performance of the CKD-PC blends at optimum sulfate content (as a partial substitute of gypsum).

2. The excessive contribution of free calcium and sulfate ions from CKDs appears to dominate the behaviour of CKD-PC blends. Since gypsum (calcium sulfate) is known to have a significant impact on drying shrinkage, this is another volume stability parameter that should be investigated.

3. The two CKDs from preheater/precalciner plants performed significantly differently in comparison to the CKDs from the wet and long-dry kilns with respect to influence on water demand and flow. It would be beneficial to conduct future studies with preheater/precalciner CKDs separate from wet and long-dry kiln CKDs, particularly at PC replacement levels greater than 10%.

4. The current study utilized dry blending to mix the CKD-PC blends. Intergrinding the CKD-PC blends, however, may produce different results. For example, it is important to highlight the potential impact of highly reactive free lime to cause gypsum false set if CKD from preheater/precalciners is interground with PC, as opposed to being blended. Free lime, if too high and/or reactive, enhances gypsum dehydration by its considerable hygroscopity (which allows it to extract water from gypsum molecules during milling when they are in a state of perturbation from the heat generated by frictional forces and liable to be subjected to some decomposition) and also has the effect of delaying rehydration of hemihydrate (Bensted, 1983b). This could enhance the likelihood of a plaster

254 (gypsum) false set. Therefore, the differences between intergrinding and blending CKD-PC blends should be investigated.

5. The stirred suspension dissolution analyses of CKDs and PCs at w/b ratio of 10:1 were very useful to gain an understanding of rapid ion dissolution differences between CKDs and PC during early age hydration. It would be interesting to conduct further investigations of the actual CKD-PC blend pore solutions with more practical w/b ratios, such as 0.4 to 0.7 at various ages. It is recommended that the pore solution extractions be perfomed at very frequent periods during the early stages of hydration. Geochemical software programming (i.e., PHREEQC) could also be used to model and predict the hydration products at each stage.

6. The current study provides a hypothesis for the microstructural development of CKD-PC blends during hydration based upon the effects and relationships among the binder compositions and their performance in various physical tests. Further work is needed to investigate the formation of hydration products as well as morphology changes to C-S-H at various hydration ages.

7. The role of C3A is very important in CKD-PC blends. It would be interesting to

conduct studies on the reactions of C3A in the concomitant presence of calcium sulfate, calcium chloride, and calcium carbonate. Each of these compounds is

known to react with C3A individually, but how they react together, as in CKDs, is not yet clearly defined.

8. The hydration, mechanical properties, and durability effects of CKD-PC blends with SCMs and/or chemical admixtures were not included in this study. This needs to be investigated further.

255 9. The current study shows that CKDs contribute to deleterious ASR expansion based upon the concrete prism tests. Measures to mitigate ASR expansion of CKD-PC blends should be investigated, such as the addition of SCMs.

10. There are other durability concerns of CKD-PC blends, besides ASR. Elevated concentrations of chlorides contribute to steel corrosion in concrete. Excessive amounts of sulfate can contribute to internal sulfate attack. Higher alkali contents can impact freezing and thawing resistance. Permeability may also be increased due to the dilution of PC with CKDs. These durability concerns need to be assessed.

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268

Appendix A. CKD Chemical Composition Correction Calculations

269 270

Appendix B. PC and CKD TGA Analysis

271

Cement TI

Cement TII

272

CKD A

CKD B

273

CKD C

CKD D*

274

CKD D

CKD E

275

CKD F

276

Appendix C. CKD XRD Scans

277

CKDA

278

CKDB

279

CKDC

280

CKDD*

281

CKDD

282

CKD E

283

CKDF

284

Appendix D. PC, CKD-PC, and PC-Filler Properties

285 Table D.1 Chemical and Physical Composition of TI Blends with 10% Replacement

TI CKD A TI CKD B TI CKD C TI CKD D TI CKD E TI CKD F TI CKD TI CKD Components TI 10% 10% 10% 10% 10% 10% LS 10% SLX 10%

SiO 2 19.15 18.66 19.65 18.67 18.68 18.76 18.92 17.50 27.05 Al 2O3 5.83 5.62 6.16 5.65 5.74 5.63 5.64 5.32 5.29 Fe 2O3 2.46 2.40 2.59 2.37 2.43 2.44 2.40 2.23 2.22 CaO 62.03 60.26 59.10 60.30 60.38 61.35 61.41 61.18 55.83 MgO 2.18 2.14 2.15 2.07 2.13 2.25 2.27 2.02 1.96

SO 3 4.35 4.22 4.49 4.65 5.53 5.09 4.81 3.92 3.92 Na 2O 0.30 0.33 0.32 0.29 0.34 0.30 0.30 0.27 0.27 K2O 1.01 1.25 1.39 1.23 1.36 1.39 1.28 0.93 0.92 Na 2Oe 0.97 1.15 1.24 1.10 1.23 1.21 1.14 0.89 0.88

Sol. Na 2O 0.16 0.18 0.17 0.15 0.18 0.16 0.16 0.14 0.14

Sol. K 2O 0.97 1.14 1.26 1.07 1.16 1.26 1.11 0.87 0.87 Sol. Na 2Oe 0.80 0.93 1.00 0.86 0.95 0.99 0.89 0.72 0.72

TiO 2 0.25 0.26 0.28 0.25 0.25 0.25 0.24 0.23 0.23 P2O5 0.26 0.24 0.24 0.24 0.25 0.24 0.24 0.23 0.23

Mn 2O3 0.09 0.09 0.09 0.08 0.09 0.13 0.09 0.08 0.08 Cl 0.00 0.25 0.09 0.04 0.03 0.22 0.08 0.00 0.00 LOI 1.79 4.48 3.39 3.98 2.60 2.19 2.15 5.84 1.63 pH* 11.90 11.92 11.92 11.94 11.95 11.99 11.99 11.66 11.31

Ca(OH) 2 0.40 0.36 0.36 0.36 0.36 0.46 0.85 0.36 0.36 fCaO 0.40 0.81 0.76 0.93 1.42 3.20 3.81 0.36 0.36 Relative Density 3.11 3.08 3.07 3.08 3.09 3.10 3.08 3.07 3.07 Blaine (m2/kg) 367 396 399 398 391 365 383 379 394 45µm, % passing 95.74 93.50 92.48 93.28 94.89 93.07 93.66 96.12 95.98 Na 2Oe: Na 2O + 0.658 (K 2O) LOI: Loss on ignition * based on w/b = 10 solution analysis @ 10 minutes fCaO: free lime

286 Table D.2 Chemical and Physical Composition of TI Blends with 20% Replacement

TI CKD A TI CKD B TI CKD C TI CKD D TI CKD E TI CKD F TI CKD TI CKD Components TI 20% 20% 20% 20% 20% 20% LS 20% SLX 20%

SiO 2 19.15 18.17 20.14 18.18 18.21 18.37 18.68 15.84 34.95 Al 2O3 5.83 5.42 6.49 5.47 5.65 5.42 5.45 4.80 4.76 Fe 2O3 2.46 2.35 2.72 2.28 2.40 2.42 2.35 2.01 1.98 CaO 62.03 58.49 56.16 58.57 58.73 60.66 60.80 60.32 49.63 MgO 2.18 2.11 2.11 1.95 2.08 2.32 2.36 1.86 1.75

SO 3 4.35 4.09 4.64 4.94 6.71 5.83 5.27 3.49 3.49 Na 2O 0.30 0.36 0.35 0.28 0.37 0.29 0.30 0.24 0.24 K2O 1.01 1.48 1.77 1.45 1.70 1.78 1.54 0.85 0.83 Na 2Oe 0.97 1.33 1.51 1.23 1.49 1.46 1.32 0.80 0.79

Sol. Na 2O 0.16 0.20 0.19 0.15 0.21 0.16 0.16 0.13 0.13

Sol. K 2O 0.97 1.31 1.55 1.17 1.35 1.56 1.26 0.77 0.77 Sol. Na 2Oe 0.80 1.06 1.21 0.92 1.10 1.19 0.98 0.64 0.64

TiO 2 0.25 0.28 0.31 0.24 0.25 0.25 0.24 0.21 0.21 P2O5 0.26 0.23 0.23 0.21 0.24 0.23 0.22 0.21 0.21

Mn 2O3 0.09 0.08 0.08 0.08 0.09 0.17 0.08 0.07 0.07 Cl 0.00 0.50 0.19 0.08 0.07 0.44 0.17 0.00 0.00 LOI 1.79 7.18 5.00 6.18 3.42 2.60 2.52 9.89 1.47 pH* 11.90 11.94 11.95 11.98 12.00 12.09 12.09 11.42 10.72

Ca(OH) 2 0.40 0.32 0.32 0.32 0.32 0.52 1.30 0.32 0.32 fCaO 0.40 1.22 1.13 1.46 2.44 6.01 7.22 0.32 0.32 Relative Density 3.11 3.04 3.02 3.04 3.06 3.08 3.05 3.03 3.02 Blaine (m2/kg) 367.00 424 430 430 416 364 399 391 421 45µm, % passing 95.74 91.25 89.21 90.81 94.04 90.39 91.57 96.50 96.21 Na 2Oe: Na 2O + 0.658 (K 2O) LOI: Loss on ignition * based on w/b = 10 solution analysis @ 10 minutes fCaO: free lime

287

Table D.3 Chemical and Physical Composition of TII Blends with 10% Replacement

TII CKD TII CKD TII CKD TII CKD TII CKD TII CKD TII CKD TII CKD DESCRIPTION TII A 10% B 10% C 10% D 10% E 10% F 10% LS 10% SLX 10%

SiO 2 20.39 19.77 20.75 19.78 19.79 19.87 20.03 18.61 28.16 Al 2O3 4.21 4.16 4.70 4.19 4.28 4.16 4.18 3.85 3.83 Fe 2O3 3.01 2.90 3.08 2.86 2.92 2.93 2.90 2.73 2.71 CaO 63.06 61.18 60.02 61.23 61.30 62.27 62.34 62.10 56.75 MgO 3.21 3.07 3.07 2.99 3.06 3.18 3.20 2.95 2.89

SO 3 2.98 2.98 3.26 3.41 4.30 3.86 3.58 2.68 2.68 Na 2O 0.13 0.18 0.17 0.14 0.18 0.14 0.15 0.12 0.12 K2O 0.69 0.95 1.10 0.94 1.06 1.10 0.98 0.64 0.62

Na 2Oe 0.58 0.80 0.89 0.75 0.88 0.87 0.80 0.54 0.53

Sol. Na 2O 0.06 0.09 0.09 0.07 0.10 0.07 0.07 0.06 0.06 Sol. K 2O 0.64 0.84 0.97 0.78 0.87 0.97 0.82 0.58 0.58

Sol. Na 2Oe 0.49 0.65 0.72 0.58 0.67 0.71 0.61 0.44 0.44 TiO 2 0.26 0.27 0.29 0.25 0.26 0.26 0.25 0.24 0.24

P2O5 0.12 0.12 0.12 0.11 0.12 0.12 0.12 0.11 0.11 Mn 2O3 0.56 0.51 0.51 0.51 0.51 0.55 0.51 0.50 0.50 Cl 0.00 0.25 0.09 0.04 0.03 0.22 0.08 0.00 0.00 LOI 1.28 4.02 2.93 3.52 2.14 1.74 1.70 5.38 1.17 pH* 11.90 11.92 11.92 11.94 11.95 11.99 11.99 11.66 11.31

Ca(OH) 2 1.30 1.17 1.17 1.17 1.17 1.27 1.66 1.17 1.17 fCaO 0.55 0.94 0.90 1.06 1.55 3.34 3.94 0.49 0.49 Relative Density 3.18 3.14 3.13 3.14 3.15 3.16 3.14 3.13 3.13 Blaine (m2/kg) 377 405 408 407 400 374 392 388 403 45µm, % passing 92.01 90.14 89.12 89.92 91.53 89.71 90.30 92.76 92.62 Na 2Oe: Na 2O + 0.658 (K 2O) LOI: Loss on ignition * based on w/b = 10 solution analysis @ 10 minutes fCaO: free lime

288

Table D.4 Chemical and Physical Composition of TII Blends with 20% Replacement

TII CKD TII CKD TII CKD TII CKD TII CKD TII CKD TII CKD TII CKD DESCRIPTION TII A 20% B 20% C 20% D 20% E 20% F 20% LS 20% SLX 20%

SiO 2 20.39 19.16 21.12 19.17 19.19 19.36 19.67 16.83 35.94 Al 2O3 4.21 4.12 5.19 4.17 4.35 4.12 4.15 3.50 3.46 Fe 2O3 3.01 2.79 3.16 2.72 2.84 2.86 2.79 2.45 2.42 CaO 63.06 59.31 56.99 59.40 59.55 61.48 61.62 61.14 50.45 MgO 3.21 2.93 2.93 2.77 2.91 3.14 3.19 2.68 2.57

SO 3 2.98 2.99 3.54 3.84 5.61 4.73 4.18 2.39 2.39 Na 2O 0.13 0.22 0.21 0.14 0.24 0.16 0.17 0.11 0.11

K2O 0.69 1.22 1.51 1.19 1.44 1.51 1.28 0.59 0.56 Na 2Oe 0.58 1.02 1.20 0.92 1.18 1.15 1.01 0.50 0.48

Sol. Na 2O 0.06 0.13 0.11 0.07 0.13 0.08 0.08 0.05 0.05

Sol. K 2O 0.64 1.05 1.29 0.91 1.09 1.30 1.00 0.51 0.51 Sol. Na 2Oe 0.49 0.81 0.96 0.67 0.85 0.94 0.73 0.39 0.39

TiO 2 0.26 0.29 0.32 0.25 0.26 0.26 0.25 0.21 0.21 P2O5 0.12 0.12 0.12 0.10 0.13 0.12 0.11 0.10 0.10

Mn 2O3 0.56 0.46 0.46 0.46 0.46 0.55 0.46 0.45 0.45 Cl 0.00 0.50 0.19 0.08 0.07 0.44 0.17 0.00 0.00 LOI 1.28 6.77 4.59 5.77 3.01 2.20 2.12 9.48 1.06 pH* 11.90 11.94 11.95 11.98 12.00 12.09 12.09 11.42 10.72

Ca(OH) 2 1.30 1.04 1.04 1.04 1.04 1.24 2.02 1.04 1.04 fCaO 0.55 1.34 1.24 1.58 2.55 6.13 7.34 0.44 0.44 Relative Density 3.18 3.09 3.07 3.10 3.12 3.14 3.11 3.09 3.08 Blaine (m2/kg) 377 432 438 438 424 372 407 399 429 45µm, % passing 92.01 88.27 86.23 87.83 91.05 87.41 88.59 93.52 93.23 Na 2Oe: Na 2O + 0.658 (K 2O) LOI: Loss on ignition * based on w/b = 10 solution analysis @ 10 minutes fCaO: free lime

289

Table D.5 Mineralogical Composition of TI Blends with 10% Replacement

TI CKD A TI CKD B TI CKD C TI CKD D TI CKD E TI CKD F TI CKD TI CKD Components TI 10% 10% 10% 10% 10% 10% LS 10% SLX 10% Alite 68.60 61.86 61.74 61.84 61.89 61.92 61.83 61.74 61.74 ß-Belite 10.30 11.46 10.04 10.32 9.87 10.62 9.66 9.27 9.27 Aluminate 8.70 7.88 7.88 7.90 7.88 7.97 7.88 7.83 7.83 Brownmillerite 7.50 6.77 6.81 6.81 6.75 6.99 6.80 6.75 6.75 Gypsum 1.70 1.53 1.53 1.53 1.53 1.53 1.53 1.53 1.53 Hemihydrate 0.50 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 Calcite 0.70 5.89 4.10 5.76 2.90 0.75 1.05 10.43 0.82 Quartz 0.30 1.19 0.99 1.35 0.59 0.92 0.87 0.47 10.09 Dolomite 0.00 0.45 0.31 0.00 0.10 0.00 0.00 0.00 0.00 Periclase 1.40 1.32 1.33 1.27 1.29 1.47 1.45 1.26 1.26 Lime 0.00 0.37 0.33 0.50 1.18 2.84 3.45 0.00 0.00 Portlandite 0.10 0.09 0.11 0.09 0.09 0.20 0.41 0.09 0.09 Anhydrite 0.20 0.37 0.41 0.66 1.98 1.56 0.73 0.18 0.18 Calcium Langbeinite 0.00 0.00 0.00 0.16 0.26 0.11 0.14 0.00 0.00 Aphthitalite 0.00 0.00 0.07 0.00 0.17 0.00 0.00 0.00 0.00 Arcanite 0.00 0.00 0.16 0.09 0.00 0.06 0.06 0.00 0.00 Calcium Sulfoaluminate 0.00 0.00 0.00 0.09 0.06 0.14 0.06 0.00 0.00 Sylvite 0.00 0.32 0.11 0.03 0.02 0.39 0.04 0.00 0.00 Calcium Chloride 0.00 0.00 0.00 0.05 0.00 0.00 0.00 0.00 0.00 Amorphous 0.00 0.05 3.21 1.11 2.93 1.83 3.50 0.00 0.00 Akermanite 0.00 0.00 0.00 0.00 0.00 0.11 0.00 0.00 0.00 Calcium Dialuminium Oxide 0.00 0.00 0.00 0.00 0.04 0.14 0.10 0.00 0.00 Mullite 0.00 0.00 0.41 0.00 0.00 0.00 0.00 0.00 0.00

290

Table D.6 Mineralogical Composition of TI Blends with 20% Replacement

TI CKD A TI CKD B TI CKD C TI CKD D TI CKD E TI CKD F TI CKD TI CKD Components TI 20% 20% 20% 20% 20% 20% LS 20% SLX 20% Alite 68.60 55.12 54.88 55.08 55.18 55.24 55.06 54.88 54.88 ß-Belite 10.30 12.62 9.78 10.34 9.44 10.94 9.02 8.24 8.24 Aluminate 8.70 7.06 7.06 7.10 7.06 7.24 7.06 6.96 6.96 Brownmillerite 7.50 6.04 6.12 6.12 6.00 6.48 6.10 6.00 6.00 Gypsum 1.70 1.36 1.36 1.36 1.36 1.36 1.36 1.36 1.36 Hemihydrate 0.50 0.40 0.40 0.40 0.40 0.40 0.40 0.40 0.40 Calcite 0.70 11.08 7.50 10.82 5.10 0.80 1.40 20.16 0.93 Quartz 0.30 2.08 1.68 2.40 0.88 1.54 1.44 0.64 19.87 Dolomite 0.00 0.90 0.62 0.00 0.20 0.00 0.00 0.00 0.00 Periclase 1.40 1.24 1.26 1.14 1.18 1.54 1.50 1.12 1.12 Lime 0.00 0.74 0.66 1.00 2.36 5.68 6.90 0.00 0.00 Portlandite 0.10 0.08 0.12 0.08 0.08 0.30 0.72 0.08 0.08 Anhydrite 0.20 0.54 0.62 1.12 3.76 2.92 1.26 0.16 0.16 Calcium Langbeinite 0.00 0.00 0.00 0.32 0.52 0.22 0.28 0.00 0.00 Aphthitalite 0.00 0.00 0.14 0.00 0.34 0.00 0.00 0.00 0.00 Arcanite 0.00 0.00 0.32 0.18 0.00 0.12 0.12 0.00 0.00 Calcium Sulfoaluminate 0.00 0.00 0.00 0.18 0.12 0.28 0.12 0.00 0.00 Sylvite 0.00 0.64 0.22 0.06 0.04 0.78 0.08 0.00 0.00 Calcium Chloride 0.00 0.00 0.00 0.10 0.00 0.00 0.00 0.00 0.00 Amorphous 0.00 0.10 6.42 2.22 5.86 3.66 7.00 0.00 0.00 Akermanite 0.00 0.00 0.00 0.00 0.00 0.22 0.00 0.00 0.00 Calcium Dialuminium Oxide 0.00 0.00 0.00 0.00 0.08 0.28 0.20 0.00 0.00 Mullite 0.00 0.00 0.82 0.00 0.00 0.00 0.00 0.00 0.00

291

Table D.7 Mineralogical Composition of TII Blends with 10% Replacement

TII CKD TII CKD TII CKD TII CKD TII CKD TII CKD TII CKD TII CKD Components TII A 10% B 10% C 10% D 10% E 10% F 10% LS 10% SLX 10% Alite - M3 66.50 59.97 59.85 59.95 60.00 60.03 59.94 59.85 59.85 ß-Belite 15.20 15.87 14.45 14.73 14.28 15.03 14.07 13.68 13.68 Aluminate 3.00 2.75 2.75 2.77 2.75 2.84 2.75 2.70 2.70 Brownmillerite 8.90 8.03 8.07 8.07 8.01 8.25 8.06 8.01 8.01 Gypsum 1.00 0.90 0.90 0.90 0.90 0.90 0.90 0.90 0.90 Hemihydrate 0.60 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.54 Calcite 0.80 5.98 4.19 5.85 2.99 0.84 1.14 10.52 0.91 Quartz 0.20 1.10 0.90 1.26 0.50 0.83 0.78 0.38 10.00 Dolomite 0.00 0.45 0.31 0.00 0.10 0.00 0.00 0.00 0.00 Periclase 2.50 2.31 2.32 2.26 2.28 2.46 2.44 2.25 2.25 Lime 0.20 0.55 0.51 0.68 1.36 3.02 3.63 0.18 0.18 Portlandite 0.40 0.36 0.38 0.36 0.36 0.47 0.68 0.36 0.36 Anhydrite 0.90 1.00 1.04 1.29 2.61 2.19 1.36 0.81 0.81 Calcium Langbeinite 0.00 0.00 0.00 0.16 0.26 0.11 0.14 0.00 0.00 Aphthitalite 0.00 0.00 0.07 0.00 0.17 0.00 0.00 0.00 0.00 Arcanite 0.00 0.00 0.16 0.09 0.00 0.06 0.06 0.00 0.00 Calcium Sulfoaluminate 0.00 0.00 0.00 0.09 0.06 0.14 0.06 0.00 0.00 Sylvite 0.00 0.32 0.11 0.03 0.02 0.39 0.04 0.00 0.00 Calcium Chloride 0.00 0.00 0.00 0.05 0.00 0.00 0.00 0.00 0.00 Amorphous 0.00 0.05 3.21 1.11 2.93 1.83 3.50 0.00 0.00 Akermanite 0.00 0.00 0.00 0.00 0.00 0.11 0.00 0.00 0.00 Calcium Dialuminium Oxide 0.00 0.00 0.00 0.00 0.04 0.14 0.10 0.00 0.00 Mullite 0.00 0.00 0.41 0.00 0.00 0.00 0.00 0.00 0.00

292

Table D.8 Mineralogical Composition of TII Blends with 20% Replacement

TII CKD TII CKD TII CKD TII CKD TII CKD TII CKD TII CKD TII CKD Components TII A 20% B 20% C 20% D 20% E 20% F 20% LS 20% SLX 20% Alite - M3 66.50 53.44 53.20 53.40 53.50 53.56 53.38 53.20 53.20 ß-Belite 15.20 16.54 13.70 14.26 13.36 14.86 12.94 12.16 12.16 Aluminate 3.00 2.50 2.50 2.54 2.50 2.68 2.50 2.40 2.40 Brownmillerite 8.90 7.16 7.24 7.24 7.12 7.60 7.22 7.12 7.12 Gypsum 1.00 0.80 0.80 0.80 0.80 0.80 0.80 0.80 0.80 Hemihydrate 0.60 0.48 0.48 0.48 0.48 0.48 0.48 0.48 0.48 Calcite 0.80 11.16 7.58 10.90 5.18 0.88 1.48 20.24 1.01 Quartz 0.20 2.00 1.60 2.32 0.80 1.46 1.36 0.56 19.79 Dolomite 0.00 0.90 0.62 0.00 0.20 0.00 0.00 0.00 0.00 Periclase 2.50 2.12 2.14 2.02 2.06 2.42 2.38 2.00 2.00 Lime 0.20 0.90 0.82 1.16 2.52 5.84 7.06 0.16 0.16 Portlandite 0.40 0.32 0.36 0.32 0.32 0.54 0.96 0.32 0.32 Anhydrite 0.90 1.10 1.18 1.68 4.32 3.48 1.82 0.72 0.72 Calcium Langbeinite 0.00 0.00 0.00 0.32 0.52 0.22 0.28 0.00 0.00 Aphthitalite 0.00 0.00 0.14 0.00 0.34 0.00 0.00 0.00 0.00 Arcanite 0.00 0.00 0.32 0.18 0.00 0.12 0.12 0.00 0.00 Calcium Sulfoaluminate 0.00 0.00 0.00 0.18 0.12 0.28 0.12 0.00 0.00 Sylvite 0.00 0.64 0.22 0.06 0.04 0.78 0.08 0.00 0.00 Calcium Chloride 0.00 0.00 0.00 0.10 0.00 0.00 0.00 0.00 0.00 Amorphous 0.00 0.10 6.42 2.22 5.86 3.66 7.00 0.00 0.00 Akermanite 0.00 0.00 0.00 0.00 0.00 0.22 0.00 0.00 0.00 Calcium Dialuminium Oxide 0.00 0.00 0.00 0.00 0.08 0.28 0.20 0.00 0.00 Mullite 0.00 0.00 0.82 0.00 0.00 0.00 0.00 0.00 0.00

293 Table D.9 Particle Size Distributions of CKD-PC and PC-filler Blends

TI CKD A TI CKD B TI CKD C TI CKD D TI CKD E TI CKD F TI CKD TI CKD Description TI 10% 10% 10% 10% 10% 10% LS 10% SLX 10% < 3.0887 8.59 9.12 9.17 9.41 9.24 8.44 9.03 9.59 9.75 <10.4804 36.69 37.19 36.80 37.37 38.30 35.58 36.82 38.58 37.78 < 22.4909 65.02 64.80 63.96 64.70 65.99 63.51 64.56 67.01 65.80 < 30.5252 78.31 77.52 76.55 77.36 78.58 76.58 77.46 79.69 78.83 < 41.4295 89.55 88.32 87.26 88.17 89.22 87.79 88.46 90.26 89.81 < 48.2654 93.65 92.34 91.25 92.21 93.16 91.99 92.55 94.10 93.81 3-30 um 69.72 68.40 67.38 67.95 69.34 68.14 68.43 70.10 69.08 30-48 um 15.34 14.82 14.71 14.85 14.58 15.41 15.09 14.40 14.98

TI CKD A TI CKD B TI CKD C TI CKD D TI CKD E TI CKD F TI CKD TI CKD Description TI 20% 20% 20% 20% 20% 20% LS 20% SLX 20% < 3.0887 8.59 9.66 9.75 10.24 9.90 8.29 9.47 10.58 10.91 <10.4804 36.69 37.68 36.91 38.05 39.92 34.46 36.95 40.47 38.86 < 22.4909 65.02 64.58 62.90 64.37 66.96 61.99 64.11 69.00 66.58 < 30.5252 78.31 76.73 74.78 76.41 78.85 74.86 76.60 81.07 79.35 < 41.4295 89.55 87.10 84.97 86.79 88.90 86.03 87.36 90.97 90.07 < 48.2654 93.65 91.03 88.85 90.77 92.66 90.32 91.45 94.54 93.98 3-30 um 69.72 67.07 65.03 66.17 68.95 66.56 67.14 70.49 68.44 30-48 um 15.34 14.30 14.07 14.36 13.81 15.47 14.84 13.47 14.62

TII CKD TII CKD TII CKD TII CKD TII CKD TII CKD TII CKD TII CKD DESCRIPTION TII A 10% B 10% C 10% D 10% E 10% F 10% LS 10% SLX 10% < 3.0887 10.56 10.89 10.94 11.18 11.01 10.21 10.80 11.36 11.52 <10.4804 39.09 39.35 38.96 39.53 40.46 37.74 38.98 40.74 39.94 < 22.4909 67.39 66.93 66.09 66.83 68.12 65.64 66.69 69.14 67.93 < 30.5252 79.35 78.46 77.48 78.30 79.52 77.52 78.39 80.63 79.77 < 41.4295 89.10 87.92 86.86 87.77 88.82 87.39 88.05 89.86 89.41 < 48.2654 92.73 91.51 90.42 91.38 92.32 91.16 91.72 93.26 92.98 3-30 um 68.80 67.56 66.55 67.11 68.50 67.31 67.60 69.27 68.25 30-48 um 13.38 13.05 12.94 13.08 12.81 13.63 13.32 12.63 13.21

TII CKD TII CKD TII CKD TII CKD TII CKD TII CKD TII CKD TII CKD DESCRIPTION TII A 20% B 20% C 20% D 20% E 20% F 20% LS 20% SLX 20% < 3.0887 10.56 11.23 11.32 11.81 11.47 9.87 11.04 12.16 12.49 <10.4804 39.09 39.60 38.83 39.97 41.83 36.38 38.86 42.39 40.78 < 22.4909 67.39 66.47 64.80 66.27 68.85 63.88 66.00 70.89 68.47 < 30.5252 79.35 77.56 75.61 77.24 79.68 75.69 77.44 81.90 80.19 < 41.4295 89.10 86.74 84.61 86.43 88.54 85.67 87.01 90.62 89.71 < 48.2654 92.73 90.29 88.11 90.03 91.92 89.58 90.71 93.80 93.24 3-30 um 68.80 66.33 64.29 65.43 68.21 65.82 66.40 69.75 67.70 30-48 um 13.38 12.72 12.50 12.78 12.24 13.89 13.27 11.89 13.05

294

Appendix E. Isothermal Conduction Calorimetry Results

295 5.0 5.0

4.0 TI 4.0 TI LS 10% TI SLX 10% 3.0 3.0 TI LS 10%

2.0 2.0

1.0 1.0 heatevolution (mW/g) heatevolution (mW/g) 0.0 0.0 0 4 8 12 16 20 24 0 4 8 12 16 20 24 time (h) time (h)

5.0 5.0

4.0 TI CKD A 10% 4.0 TI CKD B 10% TI LS 10% 3.0 3.0 TI LS 10%

2.0 2.0

1.0 1.0 heatevolution (mW/g) heatevolution (mW/g) 0.0 0.0 0 4 8 12 16 20 24 0 4 8 12 16 20 24 time (h) time (h)

5.0 5.0 TI CKD C 10% TI CKD D2 10% 4.0 4.0 TI LS 10% TI LS 10% 3.0 3.0

2.0 2.0

1.0 1.0 heat evolution (mW/g) heatevolution (mW/g) 0.0 0.0 0 4 8 12 16 20 24 0 4 8 12 16 20 24 time (h) time (h)

5.0 5.0

4.0 4.0 TI CKD E 10% TI CKD F 10%

3.0 TI LS 10% 3.0 TI LS 10%

2.0 2.0

1.0 1.0 heatevolution (mW/g) heatevolution (mW/g)

0.0 0.0 0 4 8 12 16 20 24 0 4 8 12 16 20 24 time (h) time (h)

Figure E.1 Heat of Hydration of TI cement with 10% replacement of limestone (LS), silica flour (SLX), and six CKDs (A, B, C, D, E and F).

296

5.0 5.0

4.0 TI 4.0 TI LS 20% TI SLX 20% 3.0 3.0 TI LS 20%

2.0 2.0

1.0 1.0 heatevolution (mW/g) heatevolution (mW/g) 0.0 0.0 0 4 8 12 16 20 24 0 4 8 12 16 20 24 time (h) time (h)

5.0 5.0 TI CKD B 20% 4.0 TI CKD A 20% 4.0 TI LS 20% TI LS 20% 3.0 3.0

2.0 2.0 1.0 1.0 heatevolution (mW/g)

heatevolution (mW/g) 0.0 0.0 0 4 8 12 16 20 24 0 4 8 12 16 20 24 time (h) time (h)

5.0 5.0 4.0 TI CKD D2 20% 4.0 TI CKD C 20% TI LS 20% TI LS 20% 3.0 3.0

2.0 2.0

1.0 1.0 heat evolutionheat (mW/g) heatevolution (mW/g) 0.0 0.0 0 4 8 12 16 20 24 0 4 8 12 16 20 24 time (h) time (h)

5.0 5.0

4.0 TI CKD E 20% 4.0 TI CKD F 20% TI LS 20% 3.0 3.0 TI LS 20%

2.0 2.0 `

1.0 1.0 heat evolutionheat (mW/g) heatevolution (mW/g)

0.0 0.0 0 4 8 12 16 20 24 0 4 8 12 16 20 24 time (h) time (h)

Figure E.2 Heat of Hydration of TI cement with 20% replacement of limestone (LS), silica flour (SLX), and six CKDs (A, B, C, D, E and F).

297 5.0 5.0

4.0 4.0

3.0 3.0 TII TII SLX 10% 2.0 2.0 TII LS 10% TII LS 10% 1.0 1.0 heatevolution (mW/g) heatevolution (mW/g) 0.0 0.0 0 4 8 12 16 20 24 0 4 8 12 16 20 24 time (h) time (h)

5.0 5.0

4.0 4.0 TII CKD B 10% 3.0 TII CKD A 10% 3.0 TII LS 10% TII LS 10% 2.0 2.0

1.0 1.0 heat evolutionheat (mW/g) heat evolutionheat (mW/g) 0.0 0.0 0 4 8 12 16 20 24 0 4 8 12 16 20 24 time (h) time (h)

5.0 5.0

4.0 4.0 TII CKD D2 10% TII CKD C 10% TII LS 10% 3.0 3.0 TII LS 10% 2.0 2.0

1.0 1.0 heatevolution (mW/g) heatevolution (mW/g) 0.0 0.0 0 4 8 12 16 20 24 0 4 8 12 16 20 24 time (h) time (h)

5.0 5.0

4.0 4.0 TII CKD E 10% TII CKD F 10% 3.0 TII LS 10% 3.0 TII LS 10%

2.0 2.0

1.0 1.0 heat evolutionheat (mW/g) heat evolutionheat (mW/g)

0.0 0.0 0 4 8 12 16 20 24 0 4 8 12 16 20 24 time (h) time (h)

Figure E.3 Heat of Hydration of TII cement with 10% replacement of limestone (LS), silica flour (SLX), and six CKDs (A, B, C, D, E and F).

298 5.0 5.0

4.0 4.0

3.0 3.0 TII TII SLX 20% 2.0 2.0 TII LS 20% TII LS 20% 1.0 1.0 heat evolutionheat (mW/g) heatevolution (mW/g) 0.0 0.0 0 4 8 12 16 20 24 0 4 8 12 16 20 24 time (h) time (h)

5.0 5.0

4.0 4.0 TII CKD A 20% TII CKD B 20% 3.0 3.0 TII LS 20% TII LS 20%

2.0 2.0

1.0 1.0 heatevolution (mW/g) heatevolution (mW/g)

0.0 0.0 0 4 8 12 16 20 24 0 4 8 12 16 20 24 time (h) time (h)

5.0 5.0 4.5 4.5 4.0 4.0 TII CKD D2 20% 3.5 TII CKD C 20% 3.5 TII LS 20% 3.0 TII LS 20% 3.0 2.5 2.5 2.0 2.0 1.5 1.5 1.0 1.0 heatevolution (mW/g) heat evolutionheat (mW/g) 0.5 0.5 0.0 0.0 0 4 8 12 16 20 24 0 4 8 12 16 20 24 time (h) time (h)

5.0 5.0

4.0 TII CKD E 20% 4.0 TII CKD F 20% TII LS 20% 3.0 3.0 TII LS 20%

2.0 2.0

1.0 1.0 heat evolutionheat (mW/g) heat evolutionheat(mW/g) 0.0 0.0 0 4 8 12 16 20 24 0 4 8 12 16 20 24 time (h) time (h)

Figure E.4 Heat of Hydration of TII cement with 20% replacement of limestone (LS), silica flour (SLX), and six CKDs (A, B, C, D, E and F).

299

Appendix F. Mortar Flow Statistical Analysis

300 Table F.1 Mortar Flow Raw Data TI Blends flow TII Blends flow TI 109 TII 112 TI 107 TII 113 TI 105 TII 116 TI 107 TII 115 TI 109 TII 115 TI 108 TII 118 TI 102 TII 113 TI CKD LS 10% 110 TII CKD LS 10% 116 TI CKD LS 10% 114 TII CKD LS 10% 117 TI CKD SLX 10% 112 TII CKD SLX 10% 115 TI CKD SLX 10% 111 TII CKD SLX 10% 117 TI CKD A 10% 108 TII CKD A 10% 108 TI CKD A 10% 103 TII CKD A 10% 110 TI CKD A 10% 100 TII CKD B 10% 109 TI CKD B 10% 102 TII CKD B 10% 115 TI CKD B 10% 101 TII CKD C 10% 106 TI CKD B 10% 98 TII CKD C 10% 112 TI CKD C 10% 101 TII CKD D 10% 111 TI CKD C 10% 101 TII CKD D 10% 116 TI CKD D 10% 110 TII CKD E 10% 100 TI CKD D 10% 110 TII CKD E 10% 106 TI CKD E 10% 101 TII CKD F 10% 98 TI CKD E 10% 107 TII CKD F 10% 102 TI CKD E 10% 106 TII CKD LS 20% 116 TI CKD E 10% 96 TII CKD LS 20% 120 TI CKD E 10% 101 TII CKD SLX 20% 114 TI CKD F 10% 96 TII CKD SLX 20% 120 TI CKD F 10% 98 TII CKD A 20% 105 TI CKD F 10% 87 TII CKD A 20% 108 TI CKD F 10% 94 TII CKD B 20% 100 TI CKD LS 20% 117 TII CKD B 20% 105 TI CKD LS 20% 117 TII CKD C 20% 103 TI CKD SLX 20% 113 TII CKD C 20% 107 TI CKD SLX 20% 114 TII CKD D 20% 109 TI CKD A 20% 101 TII CKD D 20% 109 TI CKD A 20% 103 TII CKD E 20% 82 TI CKD B 20% 93 TII CKD E 20% 98 TI CKD B 20% 97 TII CKD F 20% 70 TI CKD C 20% 100 TII CKD F 20% 86 TI CKD C 20% 103 (b) TI CKD D 20% 107 TI CKD D 20% 109 TI CKD E 20% 80 TI CKD E 20% 76 TI CKD E 20% 80 TI CKD F 20% 63 TI CKD F 20% 74 TI CKD F 20% 61 TI CKD F 20% 69 (a)

301 Oneway Analysis of Flow By Cement TI Blends 120

110

100

90 flow

60 TI TI CKD TI A 10% CKD TI A 20% CKD TI B 10% CKD TI B 20% CKD TI E 10% CKD TI E 20% CKD TI 10% F CKD TI 20% F TI CKD TI C 10% CKD TI C 20% CKD TI D 10% CKD TI D 20% TI CKD TI 10% LS CKD TI 20% LS TI CKD TI SLX 10% CKD TI SLX 20% TI Blends

Oneway Anova Summary of Fit

Rsquare 0.958229 Adj Rsquare 0.937343 Root Mean Square Error 3.363037 Mean of Response 99.63776 Observations (or Sum Wgts) 49

Analysis of Variance Source DF Sum of Squares Mean Square F Ratio Prob > F TI Blends 16 8302.4621 518.904 45.8800 <.0001 Error 32 361.9205 11.310 C. Total 48 8664.3827

Means for Oneway Anova Level Number Mean Std Error Lower 95% Upper 95% TI 7 106.571 1.2711 103.98 109.16 TI CKD A 10% 3 103.583 1.9417 99.63 107.54 TI CKD A 20% 2 101.750 2.3780 96.91 106.59 TI CKD B 10% 3 100.333 1.9417 96.38 104.29 TI CKD B 20% 2 94.625 2.3780 89.78 99.47 TI CKD C 10% 2 101.000 2.3780 96.16 105.84 TI CKD C 20% 2 101.250 2.3780 96.41 106.09 TI CKD D 10% 2 109.750 2.3780 104.91 114.59 TI CKD D 20% 2 108.000 2.3780 103.16 112.84 TI CKD E 10% 5 102.050 1.5040 98.99 105.11 TI CKD E 20% 3 78.417 1.9417 74.46 82.37 TI CKD F 10% 4 93.563 1.6815 90.14 96.99 TI CKD F 20% 4 66.313 1.6815 62.89 69.74 TI CKD LS 10% 2 112.000 2.3780 107.16 116.84 TI CKD LS 20% 2 116.500 2.3780 111.66 121.34 TI CKD SLX 10% 2 111.250 2.3780 106.41 116.09 TI CKD SLX 20% 2 113.625 2.3780 108.78 118.47

Std Error uses a pooled estimate of error variance

302 Oneway Analysis of Flow By Cement TI Blends 120

110

100

90 flow

Means and Std Deviations Level Number Mean Std Dev Std Err Mean Lower 95% Upper 95% TI 7 106.571 2.37484 0.8976 104.38 108.77 TI CKD A 10% 3 103.583 3.66003 2.1131 94.49 112.68 TI CKD A 20% 2 101.750 1.06066 0.7500 92.22 111.28 TI CKD B 10% 3 100.333 2.08167 1.2019 95.16 105.50 TI CKD B 20% 2 94.625 2.65165 1.8750 70.80 118.45 TI CKD C 10% 2 101.000 0.00000 0.0000 101.00 101.00 TI CKD C 20% 2 101.250 2.47487 1.7500 79.01 123.49 TI CKD D 10% 2 109.750 0.35355 0.2500 106.57 112.93 TI CKD D 20% 2 108.000 1.41421 1.0000 95.29 120.71 TI CKD E 10% 5 102.050 4.49444 2.0100 96.47 107.63 TI CKD E 20% 3 78.417 2.55359 1.4743 72.07 84.76 TI CKD F 10% 4 93.563 4.70981 2.3549 86.07 101.06 TI CKD F 20% 4 66.313 5.94199 2.9710 56.86 75.77 TI CKD LS 10% 2 112.000 2.82843 2.0000 86.59 137.41 TI CKD LS 20% 2 116.500 0.00000 0.0000 116.50 116.50 TI CKD SLX 10% 2 111.250 1.06066 0.7500 101.72 120.78 TI CKD SLX 20% 2 113.625 0.88388 0.6250 105.68 121.57

303 Oneway Analysis of flow By Cement TII Blends 130

120

110

100

flow 90

60 TII TII CKD TII A 10% CKD TII A 20% CKD TII B 10% CKD TII B 20% CKD TII E 10% CKD TII E 20% CKD TII 10% F CKD TII 20% F TII CKD TII C 10% CKD TII C 20% CKD TII D 10% CKD TII D 20% TII CKD TII LS10% CKD TII LS20% TII CKD TII SLX 10% CKD TII SLX 20% TII Blends

Oneway Anova Summary of Fit

Rsquare 0.902038 Adj Rsquare 0.830793 Root Mean Square Error 4.337334 Mean of Response 107.8205 Observations (or Sum Wgts) 39

Analysis of Variance Source DF Sum of Squares Mean Square F Ratio Prob > F TII Blends 16 3810.9643 238.185 12.6610 <.0001 Error 22 413.8743 18.812 C. Total 38 4224.8386

Means for Oneway Anova Level Number Mean Std Error Lower 95% Upper 95% TII 7 114.429 1.6394 111.03 117.83 TII CKD A 10% 2 108.750 3.0670 102.39 115.11 TII CKD A 20% 2 106.375 3.0670 100.01 112.74 TII CKD B 10% 2 111.625 3.0670 105.26 117.99 TII CKD B 20% 2 102.375 3.0670 96.01 108.74 TII CKD C 10% 2 108.950 3.0670 102.59 115.31 TII CKD C 20% 2 104.750 3.0670 98.39 111.11 TII CKD D 10% 2 113.375 3.0670 107.01 119.74 TII CKD D 20% 2 109.000 3.0670 102.64 115.36 TII CKD E 10% 2 103.000 3.0670 96.64 109.36 TII CKD E 20% 2 89.625 3.0670 83.26 95.99 TII CKD F 10% 2 99.625 3.0670 93.26 105.99 TII CKD F 20% 2 77.500 3.0670 71.14 83.86 TII CKD LS 10% 2 116.375 3.0670 110.01 122.74 TII CKD LS 20% 2 117.875 3.0670 111.51 124.24 TII CKD SLX 10% 2 116.000 3.0670 109.64 122.36 TII CKD SLX 20% 2 116.800 3.0670 110.44 123.16

Std Error uses a pooled estimate of error variance

304 Oneway Analysis of flow By Cement TII Blends 130

120

110

100

flow 90

Means and Std Deviations Level Number Mean Std Dev Std Err Mean Lower 95% Upper 95% TII 7 114.429 1.9133 0.7232 112.7 116.20 TII CKD A 10% 2 108.750 1.4142 1.0000 96.0 121.46 TII CKD A 20% 2 106.375 2.6517 1.8750 82.6 130.20 TII CKD B 10% 2 111.625 4.4194 3.1250 71.9 151.33 TII CKD B 20% 2 102.375 3.7123 2.6250 69.0 135.73 TII CKD C 10% 2 108.950 3.9598 2.8000 73.4 144.53 TII CKD C 20% 2 104.750 2.8284 2.0000 79.3 130.16 TII CKD D 10% 2 113.375 4.0659 2.8750 76.8 149.91 TII CKD D 20% 2 109.000 0.0000 0.0000 109.0 109.00 TII CKD E 10% 2 103.000 3.8891 2.7500 68.1 137.94 TII CKD E 20% 2 89.625 11.1369 7.8750 -10.4 189.69 TII CKD F 10% 2 99.625 2.6517 1.8750 75.8 123.45 TII CKD F 20% 2 77.500 11.3137 8.0000 -24.1 179.15 TII CKD LS 10% 2 116.375 0.5303 0.3750 111.6 121.14 TII CKD LS 20% 2 117.875 3.3588 2.3750 87.7 148.05 TII CKD SLX 10% 2 116.000 1.7678 1.2500 100.1 131.88 TII CKD SLX 20% 2 116.800 4.5255 3.2000 76.1 157.46

305

Appendix G. Mortar Compressive Strength Statistical Analysis

306 Table G.1 Individual Compressive Strength (MPa)

TI Blends 1d 3d 7d 28d 90d TII Blends 1d 3d 7d 28d 90d TI 15.9 26.4 27.6 36.6 40.2 TII 13.8 23.1 27.8 36.5 42.8 TI 16.0 25.2 29.3 35.5 42.1 TII 13.3 23.7 28.2 36.7 42.2 TI 15.9 24.3 29.4 36.5 39.8 TII 14.3 21.6 27.1 37.7 42.0 TI CKD LS 10% 15.1 26.8 31.5 36.0 45.3 TII CKD LS 10% 13.1 21.5 29.1 36.8 42.2 TI CKD LS 10% 15.1 26.2 30.1 38.8 44.1 TII CKD LS 10% 12.5 21.7 28.8 35.1 41.1 TI CKD LS 10% 14.4 26.2 29.3 36.9 42.6 TII CKD LS 10% 12.8 21.5 28.3 35.3 40.5 TI CKD SLX 10% 15.5 24.5 27.8 34.4 39.2 TII CKD SLX 10% 11.7 19.2 22.7 30.7 35.2 TI CKD SLX 10% 15.2 24.7 29.0 35.9 38.6 TII CKD SLX 10% 12.0 19.8 24.6 31.5 37.2 TI CKD SLX 10% 15.1 24.2 27.6 34.8 38.5 TII CKD SLX 10% 12.9 20.3 24.3 31.9 36.0 TI CKD A 10% 17.9 27.4 32.2 37.5 44.4 TII CKD A 10% 15.6 23.6 28.9 34.6 39.9 TI CKD A 10% 17.9 28.6 32.5 37.3 43.7 TII CKD A 10% 14.8 23.8 29.3 37.1 42.6 TI CKD A 10% 17.8 27.9 32.6 38.4 44.9 TII CKD A 10% 14.8 23.3 27.8 36.5 43.4 TI CKD B 10% 16.0 26.8 30.5 35.8 42.0 TII CKD B 10% 14.3 22.2 28.3 35.6 43.2 TI CKD B 10% 16.4 25.7 30.1 38.0 42.6 TII CKD B 10% 14.1 23.5 29.3 34.8 42.2 TI CKD B 10% 16.1 26.6 29.3 37.2 39.7 TII CKD B 10% 15.6 24.2 26.3 35.6 40.8 TI CKD C 10% 15.3 26.6 29.6 36.1 40.6 TII CKD C 10% 14.4 23.0 27.8 34.2 42.2 TI CKD C 10% 14.8 26.3 28.9 35.8 38.8 TII CKD C 10% 14.6 23.4 25.8 34.0 41.8 TI CKD C 10% 15.1 26.5 30.7 38.2 38.9 TII CKD C 10% 15.1 23.7 27.9 35.1 40.4 TI CKD D 10% 11.9 24.5 32.5 41.7 43.3 TII CKD D 10% 12.7 21.2 25.9 34.7 40.6 TI CKD D 10% 11.5 24.5 31.4 39.9 47.1 TII CKD D 10% 12.7 21.6 26.4 34.2 43.4 TI CKD D 10% 11.6 24.0 32.6 41.9 47.6 TII CKD D 10% 13.0 21.3 26.0 35.4 42.7 TI CKD E 10% 15.2 26.2 33.0 36.2 44.3 TII CKD E 10% 14.7 24.0 28.9 36.4 43.0 TI CKD E 10% 14.2 26.8 32.4 36.9 43.6 TII CKD E 10% 15.2 23.5 30.1 36.1 42.3 TI CKD E 10% 14.9 27.0 31.8 36.4 43.5 TII CKD E 10% 15.1 24.3 30.2 38.4 44.2 TI CKD F 10% 14.4 27.2 33.1 37.9 41.1 TII CKD F 10% 13.3 22.0 27.7 40.0 43.6 TI CKD F 10% 14.5 27.6 31.4 40.2 41.5 TII CKD F 10% 13.8 22.7 29.6 38.3 41.2 TI CKD F 10% 14.0 27.3 31.0 39.8 41.6 TII CKD F 10% 14.1 23.9 30.1 36.9 42.3 TI CKD LS 20% 12.4 23.2 26.4 33.9 37.2 TII CKD LS 20% 11.1 19.4 25.5 31.1 35.6 TI CKD LS 20% 12.5 22.9 27.8 32.6 37.1 TII CKD LS 20% 11.0 18.1 24.1 30.2 34.0 TI CKD LS 20% 12.6 23.3 27.0 32.8 38.5 TII CKD LS 20% 10.9 17.8 24.5 29.9 35.0 TI CKD SLX 20% 13.4 21.7 24.9 32.3 33.5 TII CKD SLX 20% 11.2 18.5 19.8 28.1 31.1 TI CKD SLX 20% 12.9 21.7 26.3 31.4 35.2 TII CKD SLX 20% 10.9 18.8 20.4 27.6 31.2 TI CKD SLX 20% 13.5 21.4 25.0 31.0 35.8 TII CKD SLX 20% 11.1 17.7 21.2 28.5 32.6 TI CKD A 20% 15.5 25.1 28.7 34.4 40.1 TII CKD A 20% 13.7 22.5 26.1 32.8 39.3 TI CKD A 20% 16.2 24.6 29.2 33.9 40.7 TII CKD A 20% 12.9 21.5 26.4 32.5 37.4 TI CKD A 20% 15.6 26.1 29.2 34.7 40.9 TII CKD A 20% 13.3 21.5 25.6 32.0 37.0 TI CKD B 20% 14.2 24.0 27.3 33.3 39.7 TII CKD B 20% 13.9 21.8 27.2 31.1 38.0 TI CKD B 20% 14.2 24.0 28.0 33.6 38.9 TII CKD B 20% 13.9 21.2 26.5 30.8 40.2 TI CKD B 20% 14.6 23.3 27.8 34.6 40.0 TII CKD B 20% 14.4 22.1 26.8 31.0 36.6 TI CKD C 20% 13.0 24.8 28.4 33.9 37.5 TII CKD C 20% 12.6 20.4 24.2 30.5 37.4 TI CKD C 20% 13.7 24.8 29.0 33.0 37.9 TII CKD C 20% 11.6 21.4 26.2 31.5 39.3 TI CKD C 20% 13.2 24.2 28.1 29.9 37.3 TII CKD C 20% 12.3 21.2 25.5 30.8 37.1 TI CKD D 20% 10.7 18.2 22.4 37.8 46.8 TII CKD D 20% 11.1 15.9 20.5 31.7 42.1 TI CKD D 20% 10.2 17.9 23.9 37.7 45.2 TII CKD D 20% 10.6 16.6 19.4 35.1 43.1 TI CKD D 20% 10.4 17.6 21.6 34.0 44.2 TII CKD D 20% 10.5 15.8 21.5 32.8 40.5 TI CKD E 20% 10.9 21.4 28.3 36.8 42.6 TII CKD E 20% 11.1 18.1 24.1 35.3 41.3 TI CKD E 20% 10.6 21.4 27.8 35.4 42.9 TII CKD E 20% 10.6 18.4 25.9 33.1 38.3 TI CKD E 20% 11.0 23.6 29.6 35.9 42.5 TII CKD E 20% 11.6 17.4 25.0 32.8 39.4 TI CKD F 20% 11.8 24.5 30.7 35.4 42.5 TII CKD F 20% 11.8 19.8 28.5 36.1 40.8 TI CKD F 20% 11.4 22.8 32.1 36.7 42.5 TII CKD F 20% 11.7 20.7 28.2 37.0 40.8 TI CKD F 20% 11.3 23.7 33.1 35.9 42.2 TII CKD F 20% 12.0 20.8 28.5 35.6 39.2

(a) (b)

307 Table G.2 Average Compressive Strengths

MPa Percentage of TI 1d 3d 7d 28d 90d 1d 3d 7d 28d 90d TI 15.9 25.3 28.7 36.0 40.0 100% 100% 100% 100% 100% TI LS 10% 14.9 25.9 30.3 37.2 44.0 93% 103% 105% 103% 110% TI SLX 10% 15.2 24.0 28.1 35.0 38.8 96% 95% 98% 97% 97% TI CKD A 10% 17.9 27.9 32.4 37.7 44.3 112% 110% 113% 105% 111% TI CKD B 10% 16.2 26.4 30.0 37.0 41.5 102% 104% 104% 103% 104% TI CKD C 10% 15.1 26.5 29.7 36.7 39.4 95% 105% 104% 102% 99% TI CKD D 10% 11.7 24.3 32.1 41.2 46.0 73% 96% 112% 114% 115% TI CKD E 10% 14.8 26.7 32.4 36.5 45.4 93% 105% 113% 101% 114% TI CKD F 10% 14.3 27.4 31.8 39.3 41.4 90% 108% 111% 109% 104% TI LS 20% 12.5 22.6 27.1 33.1 37.6 78% 89% 94% 92% 94% TI SLX 20% 13.2 21.1 25.4 31.6 34.8 83% 83% 88% 88% 87% TI CKD A 20% 15.7 25.3 29.0 34.3 40.6 99% 100% 101% 95% 102% TI CKD B 20% 14.3 23.8 27.7 33.8 39.5 90% 94% 96% 94% 99% TI CKD C 20% 13.3 24.6 28.5 32.3 37.6 84% 97% 99% 90% 94% TI CKD D 20% 10.4 17.9 22.2 35.7 45.4 65% 71% 77% 99% 114% TI CKD E 20% 10.8 22.1 27.3 36.0 42.7 68% 87% 95% 100% 107% TI CKD F 20% 11.5 23.7 30.7 36.0 42.3 72% 94% 107% 100% 106%

MPa Percentage of TII 1d 3d 7d 28d 90d 1d 3d 7d 28d 90d TII 13.8 22.6 27.6 37.0 42.5 100% 100% 100% 100% 100% TII LS 10% 12.8 21.5 28.7 35.7 41.2 93% 95% 104% 97% 97% TII SLX 10% 12.2 19.8 23.4 30.7 35.4 88% 87% 85% 83% 83% TII CKD A 10% 15.0 23.6 28.7 36.1 42.0 109% 104% 104% 98% 99% TII CKD B 10% 14.6 23.3 28.0 35.3 42.1 106% 103% 101% 96% 99% TII CKD C 10% 14.7 23.3 27.2 34.4 41.5 107% 103% 98% 93% 98% TII CKD D 10% 12.8 21.3 26.1 34.8 41.4 93% 94% 94% 94% 97% TII CKD E 10% 15.0 23.9 29.7 36.9 42.3 109% 106% 108% 100% 100% TII CKD F 10% 13.7 22.9 29.2 38.4 42.4 99% 101% 105% 104% 100% TII LS 20% 11.0 18.4 24.7 30.4 34.9 80% 81% 89% 82% 82% TII SLX 20% 11.1 18.3 20.0 27.5 31.0 80% 81% 72% 74% 73% TII CKD A 20% 13.3 21.8 26.0 32.4 37.9 96% 96% 94% 88% 89% TII CKD B 20% 14.1 21.7 26.8 31.0 38.3 102% 96% 97% 84% 90% TII CKD C 20% 12.2 21.0 25.3 30.9 37.9 88% 93% 92% 84% 89% TII CKD D 20% 10.7 16.1 20.5 33.2 41.0 78% 71% 74% 90% 96% TII CKD E 20% 10.9 18.0 25.4 33.7 38.8 79% 79% 92% 91% 91% TII CKD F 20% 11.8 20.5 28.4 37.7 40.3 86% 90% 103% 102% 95%

308 Oneway Analysis of 1d By Cement TI Blends 18

1d 14 13

10 TI TI CKD TI A 10% CKD TI A 20% CKD TI B 10% CKD TI B 20% CKD TI E 10% CKD TI E 20% CKD TI 10% F CKD TI 20% F TI CKD TI C 10% CKD TI C 20% CKD TI D 10% CKD TI D 20% TI CKD TI LS10% CKD TI LS20% TI CKD TI SLX 10% CKD TI SLX 20% TI Blends

Oneway Anova Summary of Fit

Rsquare 0.986739 Adj Rsquare 0.980499 Root Mean Square Error 0.285478 Mean of Response 13.99275 Observations (or Sum Wgts) 51

Analysis of Variance Source DF Sum of Squares Mean Square F Ratio Prob > F TI Blends 16 206.18427 12.8865 158.1217 <.0001 Error 34 2.77091 0.0815 C. Total 50 208.95518

Means for Oneway Anova Level Number Mean Std Error Lower 95% Upper 95% TI 3 15.9338 0.16482 15.599 16.269 TI CKD A 10% 3 17.8681 0.16482 17.533 18.203 TI CKD A 20% 3 15.7455 0.16482 15.411 16.080 TI CKD B 10% 3 16.1906 0.16482 15.856 16.526 TI CKD B 20% 3 14.3424 0.16482 14.007 14.677 TI CKD C 10% 3 15.0781 0.16482 14.743 15.413 TI CKD C 20% 3 13.3155 0.16482 12.981 13.650 TI CKD D 10% 3 11.6558 0.16482 11.321 11.991 TI CKD D 20% 3 10.4066 0.16482 10.072 10.742 TI CKD E 10% 3 14.7875 0.16482 14.453 15.122 TI CKD E 20% 3 10.8339 0.16482 10.499 11.169 TI CKD F 10% 3 14.3085 0.16482 13.974 14.643 TI CKD F 20% 3 11.5306 0.16482 11.196 11.866 TI CKD LS 10% 3 14.8897 0.16482 14.555 15.225 TI CKD LS 20% 3 12.4937 0.16482 12.159 12.829 TI CKD SLX 10% 3 15.2493 0.16482 14.914 15.584 TI CKD SLX 20% 3 13.2472 0.16482 12.912 13.582

Std Error uses a pooled estimate of error variance

309 Oneway Analysis of 1d By Cement TII Blends 16

1d 13

10 TII TII CKD TII A 10% CKD TII A 20% CKD TII B 10% CKD TII B 20% CKD TII E 10% CKD TII E 20% CKD TII 10% F CKD TII 20% F TII CKD TII C 10% CKD TII C 20% CKD TII D 10% CKD TII D 20% TII CKD TII LS10% CKD TII LS20% TII CKD TII SLX 10% CKD TII SLX 20% TII Blends

Oneway Anova Summary of Fit

Rsquare 0.949956 Adj Rsquare 0.926405 Root Mean Square Error 0.40549 Mean of Response 12.94315 Observations (or Sum Wgts) 51

Analysis of Variance Source DF Sum of Squares Mean Square F Ratio Prob > F TII Blends 16 106.11768 6.63235 40.3373 <.0001 Error 34 5.59036 0.16442 C. Total 50 111.70804

Means for Oneway Anova Level Number Mean Std Error Lower 95% Upper 95% TII 3 13.8112 0.23411 13.335 14.287 TII CKD A 10% 3 15.0448 0.23411 14.569 15.521 TII CKD A 20% 3 13.2991 0.23411 12.823 13.775 TII CKD B 10% 3 14.6336 0.23411 14.158 15.109 TII CKD B 20% 3 14.0512 0.23411 13.575 14.527 TII CKD C 10% 3 14.7186 0.23411 14.243 15.194 TII CKD C 20% 3 12.1514 0.23411 11.676 12.627 TII CKD D 10% 3 12.8365 0.23411 12.361 13.312 TII CKD D 20% 3 10.7483 0.23411 10.273 11.224 TII CKD E 10% 3 15.0121 0.23411 14.536 15.488 TII CKD E 20% 3 11.0906 0.23411 10.615 11.566 TII CKD F 10% 3 13.7256 0.23411 13.250 14.201 TII CKD F 20% 3 11.8091 0.23411 11.333 12.285 TII CKD LS 10% 3 12.8187 0.23411 12.343 13.295 TII CKD LS 20% 3 11.0223 0.23411 10.547 11.498 TII CKD SLX 10% 3 12.1864 0.23411 11.711 12.662 TII CKD SLX 20% 3 11.0740 0.23411 10.598 11.550

Std Error uses a pooled estimate of error variance

310 Oneway Analysis of 3d By Cement TI Blends 30

24 3d 22

16 TI TI CKD TI A 10% CKD TI A 20% CKD TI B 10% CKD TI B 20% CKD TI E 10% CKD TI E 20% CKD TI 10% F CKD TI 20% F TI CKD TI C 10% CKD TI C 20% CKD TI D 10% CKD TI D 20% TI CKD TI LS10% CKD TI LS20% TI CKD TI SLX 10% CKD TI SLX 20% TI Blends

Oneway Anova Summary of Fit

Rsquare 0.962887 Adj Rsquare 0.945423 Root Mean Square Error 0.577871 Mean of Response 24.55801 Observations (or Sum Wgts) 51

Analysis of Variance Source DF Sum of Squares Mean Square F Ratio Prob > F TI Blends 16 294.57345 18.4108 55.1331 <.0001 Error 34 11.35377 0.3339 C. Total 50 305.92722

Means for Oneway Anova Level Number Mean Std Error Lower 95% Upper 95% TI 3 25.2785 0.33363 24.601 25.957 TI CKD A 10% 3 27.9824 0.33363 27.304 28.660 TI CKD A 20% 3 25.2596 0.33363 24.582 25.938 TI CKD B 10% 3 26.3738 0.33363 25.696 27.052 TI CKD B 20% 3 23.7899 0.33363 23.112 24.468 TI CKD C 10% 3 26.5110 0.33363 25.833 27.189 TI CKD C 20% 3 24.5945 0.33363 23.917 25.273 TI CKD D 10% 3 24.3378 0.33363 23.660 25.016 TI CKD D 20% 3 17.9020 0.33363 17.224 18.580 TI CKD E 10% 3 26.6649 0.33363 25.987 27.343 TI CKD E 20% 3 22.1123 0.33363 21.434 22.790 TI CKD F 10% 3 27.3708 0.33363 26.693 28.049 TI CKD F 20% 3 23.6871 0.33363 23.009 24.365 TI CKD LS 10% 3 26.4255 0.33363 25.747 27.103 TI CKD LS 20% 3 23.1220 0.33363 22.444 23.800 TI CKD SLX 10% 3 24.4745 0.33363 23.796 25.153 TI CKD SLX 20% 3 21.5995 0.33363 20.921 22.277

Std Error uses a pooled estimate of error variance

311 Oneway Analysis of 3d By Cement TII Blends 25 24 23 22 21

3d 20 19 18 17 16 15 TII TII CKD TII A 10% CKD TII A 20% CKD TII B 10% CKD TII B 20% CKD TII E 10% CKD TII E 20% CKD TII 10% F CKD TII 20% F TII CKD TII C 10% CKD TII C 20% CKD TII D 10% CKD TII D 20% TII CKD TII LS10% CKD TII LS20% TII CKD TII SLX 10% CKD TII SLX 20% TII Blends

Oneway Anova Summary of Fit

Rsquare 0.949156 Adj Rsquare 0.92523 Root Mean Square Error 0.627122 Mean of Response 21.07458 Observations (or Sum Wgts) 51

Analysis of Variance Source DF Sum of Squares Mean Square F Ratio Prob > F TII Blends 16 249.62152 15.6013 39.6696 <.0001 Error 34 13.37159 0.3933 C. Total 50 262.99311

Means for Oneway Anova Level Number Mean Std Error Lower 95% Upper 95% TII 3 22.7969 0.36207 22.061 23.533 TII CKD A 10% 3 23.5504 0.36207 22.815 24.286 TII CKD A 20% 3 21.8217 0.36207 21.086 22.558 TII CKD B 10% 3 23.3109 0.36207 22.575 24.047 TII CKD B 20% 3 21.7017 0.36207 20.966 22.438 TII CKD C 10% 3 23.3448 0.36207 22.609 24.081 TII CKD C 20% 3 21.0005 0.36207 20.265 21.736 TII CKD D 10% 3 21.3422 0.36207 20.606 22.078 TII CKD D 20% 3 16.0878 0.36207 15.352 16.824 TII CKD E 10% 3 23.9438 0.36207 23.208 24.680 TII CKD E 20% 3 17.9704 0.36207 17.235 18.706 TII CKD F 10% 3 22.8825 0.36207 22.147 23.618 TII CKD F 20% 3 20.4526 0.36207 19.717 21.188 TII CKD LS 10% 3 21.5484 0.36207 20.813 22.284 TII CKD LS 20% 3 18.4160 0.36207 17.680 19.152 TII CKD SLX 10% 3 19.7674 0.36207 19.032 20.503 TII CKD SLX 20% 3 18.3299 0.36207 17.594 19.066

Std Error uses a pooled estimate of error variance

312 Oneway Analysis of 7d By Cement TI Blends 34

28 7d 26

20 TI TI CKD TI A 10% CKD TI A 20% CKD TI B 10% CKD TI B 20% CKD TI E 10% CKD TI E 20% CKD TI 10% F CKD TI 20% F TI CKD TI C 10% CKD TI C 20% CKD TI D 10% CKD TI D 20% TI CKD TI LS10% CKD TI LS20% TI CKD TI SLX 10% CKD TI SLX 20% TI Blends

Oneway Anova Summary of Fit

Rsquare 0.936064 Adj Rsquare 0.905977 Root Mean Square Error 0.823119 Mean of Response 29.20319 Observations (or Sum Wgts) 51

Analysis of Variance Source DF Sum of Squares Mean Square F Ratio Prob > F TI Blends 16 337.26034 21.0788 31.1114 <.0001 Error 34 23.03587 0.6775 C. Total 50 360.29621

Means for Oneway Anova Level Number Mean Std Error Lower 95% Upper 95% TI 3 28.7704 0.47523 27.805 29.736 TI CKD A 10% 3 32.3989 0.47523 31.433 33.365 TI CKD A 20% 3 29.0099 0.47523 28.044 29.976 TI CKD B 10% 3 29.9851 0.47523 29.019 30.951 TI CKD B 20% 3 27.6918 0.47523 26.726 28.658 TI CKD C 10% 3 29.7117 0.47523 28.746 30.677 TI CKD C 20% 3 28.4964 0.47523 27.531 29.462 TI CKD D 10% 3 32.1422 0.47523 31.176 33.108 TI CKD D 20% 3 22.6258 0.47523 21.660 23.592 TI CKD E 10% 3 32.4000 0.47523 31.434 33.366 TI CKD E 20% 3 28.5820 0.47523 27.616 29.548 TI CKD F 10% 3 31.7999 0.47523 30.834 32.766 TI CKD F 20% 3 31.9705 0.47523 31.005 32.936 TI CKD LS 10% 3 30.2762 0.47523 29.310 31.242 TI CKD LS 20% 3 27.0756 0.47523 26.110 28.041 TI CKD SLX 10% 3 28.1364 0.47523 27.171 29.102 TI CKD SLX 20% 3 25.3813 0.47523 24.416 26.347

Std Error uses a pooled estimate of error variance

313 Oneway Analysis of 7d By Cement TII Blends 32

26 7d 24

18 TII TII CKD TII A 10% CKD TII A 20% CKD TII B 10% CKD TII B 20% CKD TII E 10% CKD TII E 20% CKD TII 10% F CKD TII 20% F TII CKD TII C 10% CKD TII C 20% CKD TII D 10% CKD TII D 20% TII CKD TII LS10% CKD TII LS20% TII CKD TII SLX 10% CKD TII SLX 20% TII Blends

Oneway Anova Summary of Fit

Rsquare 0.935972 Adj Rsquare 0.905841 Root Mean Square Error 0.856028 Mean of Response 26.25454 Observations (or Sum Wgts) 51

Analysis of Variance Source DF Sum of Squares Mean Square F Ratio Prob > F TII Blends 16 364.20427 22.7628 31.0634 <.0001 Error 34 24.91466 0.7328 C. Total 50 389.11893

Means for Oneway Anova Level Number Mean Std Error Lower 95% Upper 95% TII 3 27.7091 0.49423 26.705 28.713 TII CKD A 10% 3 28.6676 0.49423 27.663 29.672 TII CKD A 20% 3 26.0320 0.49423 25.028 27.036 TII CKD B 10% 3 27.9807 0.49423 26.976 28.985 TII CKD B 20% 3 26.8016 0.49423 25.797 27.806 TII CKD C 10% 3 27.1790 0.49423 26.175 28.183 TII CKD C 20% 3 25.3302 0.49423 24.326 26.335 TII CKD D 10% 3 26.0923 0.49423 25.088 27.097 TII CKD D 20% 3 20.4697 0.49423 19.465 21.474 TII CKD E 10% 3 29.7289 0.49423 28.725 30.733 TII CKD E 20% 3 24.9839 0.49423 23.980 25.988 TII CKD F 10% 3 29.1638 0.49423 28.159 30.168 TII CKD F 20% 3 28.4448 0.49423 27.440 29.449 TII CKD LS 10% 3 28.7359 0.49423 27.732 29.740 TII CKD LS 20% 3 24.6962 0.49423 23.692 25.701 TII CKD SLX 10% 3 23.8588 0.49423 22.854 24.863 TII CKD SLX 20% 3 20.4526 0.49423 19.448 21.457

Std Error uses a pooled estimate of error variance

314 Oneway Analysis of 28d By Cement TI Blends 42

28d 34

28 TI TI CKD TI A 10% CKD TI A 20% CKD TI B 10% CKD TI B 20% CKD TI E 10% CKD TI E 20% CKD TI 10% F CKD TI 20% F TI CKD TI C 10% CKD TI C 20% CKD TI D 10% CKD TI D 20% TI CKD TI LS10% CKD TI LS20% TI CKD TI SLX 10% CKD TI SLX 20% TI Blends

Oneway Anova Summary of Fit

Rsquare 0.872309 Adj Rsquare 0.812218 Root Mean Square Error 1.107147 Mean of Response 35.90854 Observations (or Sum Wgts) 51

Analysis of Variance Source DF Sum of Squares Mean Square F Ratio Prob > F TI Blends 16 284.70643 17.7942 14.5167 <.0001 Error 34 41.67630 1.2258 C. Total 50 326.38273

Means for Oneway Anova Level Number Mean Std Error Lower 95% Upper 95% TI 3 36.1636 0.63921 34.865 37.463 TI CKD A 10% 3 37.7039 0.63921 36.405 39.003 TI CKD A 20% 3 34.3148 0.63921 33.016 35.614 TI CKD B 10% 3 37.0026 0.63921 35.704 38.302 TI CKD B 20% 3 33.8198 0.63921 32.521 35.119 TI CKD C 10% 3 36.7120 0.63921 35.413 38.011 TI CKD C 20% 3 32.2796 0.63921 30.981 33.579 TI CKD D 10% 3 41.1957 0.63921 39.897 42.495 TI CKD D 20% 3 36.4965 0.63921 35.197 37.796 TI CKD E 10% 3 36.5164 0.63921 35.217 37.815 TI CKD E 20% 3 36.0209 0.63921 34.722 37.320 TI CKD F 10% 3 39.3131 0.63921 38.014 40.612 TI CKD F 20% 3 35.9924 0.63921 34.693 37.291 TI CKD LS 10% 3 37.2421 0.63921 35.943 38.541 TI CKD LS 20% 3 33.1007 0.63921 31.802 34.400 TI CKD SLX 10% 3 35.0168 0.63921 33.718 36.316 TI CKD SLX 20% 3 31.5541 0.63921 30.255 32.853

Std Error uses a pooled estimate of error variance

315 Oneway Analysis of 28d By Cement TII Blends 42

34 28d 32

30 28

26 TII TII CKD TII A 10% CKD TII A 20% CKD TII B 10% CKD TII B 20% CKD TII E 10% CKD TII E 20% CKD TII 10% F CKD TII 20% F TII CKD TII C 10% CKD TII C 20% CKD TII D 10% CKD TII D 20% TII CKD TII LS10% CKD TII LS20% TII CKD TII SLX 10% CKD TII SLX 20% TII Blends

Oneway Anova Summary of Fit

Rsquare 0.929448 Adj Rsquare 0.896247 Root Mean Square Error 0.926892 Mean of Response 33.87856 Observations (or Sum Wgts) 51

Analysis of Variance Source DF Sum of Squares Mean Square F Ratio Prob > F TII Blends 16 384.81536 24.0510 27.9946 <.0001 Error 34 29.21035 0.8591 C. Total 50 414.02571

Means for Oneway Anova Level Number Mean Std Error Lower 95% Upper 95% TII 3 36.9510 0.53514 35.863 38.038 TII CKD A 10% 3 36.0786 0.53514 34.991 37.166 TII CKD A 20% 3 32.4334 0.53514 31.346 33.521 TII CKD B 10% 3 35.3429 0.53514 34.255 36.430 TII CKD B 20% 3 30.9643 0.53514 29.877 32.052 TII CKD C 10% 3 34.4182 0.53514 33.331 35.506 TII CKD C 20% 3 30.9103 0.53514 29.823 31.998 TII CKD D 10% 3 34.7772 0.53514 33.690 35.865 TII CKD D 20% 3 33.1863 0.53514 32.099 34.274 TII CKD E 10% 3 36.9343 0.53514 35.847 38.022 TII CKD E 20% 3 33.7336 0.53514 32.646 34.821 TII CKD F 10% 3 38.3890 0.53514 37.302 39.477 TII CKD F 20% 3 36.2433 0.53514 35.156 37.331 TII CKD LS 10% 3 35.7363 0.53514 34.649 36.824 TII CKD LS 20% 3 30.4135 0.53514 29.326 31.501 TII CKD SLX 10% 3 31.3548 0.53514 30.267 32.442 TII CKD SLX 20% 3 28.0686 0.53514 26.981 29.156

Std Error uses a pooled estimate of error variance

316 Oneway Analysis of 90d By Cement TI Blends 50

90d 40

35 TI TI CKD TI A 10% CKD TI A 20% CKD TI B 10% CKD TI B 20% CKD TI E 10% CKD TI E 20% CKD TI 10% F CKD TI 20% F TI CKD TI C 10% CKD TI C 20% CKD TI D 10% CKD TI D 20% TI CKD TI LS10% CKD TI LS20% TI CKD TI SLX 10% CKD TI SLX 20% TI Blends

Oneway Anova Summary of Fit

Rsquare 0.927228 Adj Rsquare 0.892982 Root Mean Square Error 1.012278 Mean of Response 41.20939 Observations (or Sum Wgts) 51

Analysis of Variance Source DF Sum of Squares Mean Square F Ratio Prob > F TI Blends 16 443.91665 27.7448 27.0758 <.0001 Error 34 34.84005 1.0247 C. Total 50 478.75670

Means for Oneway Anova Level Number Mean Std Error Lower 95% Upper 95% TI 3 40.7386 0.58444 39.551 41.926 TI CKD A 10% 3 44.3447 0.58444 43.157 45.532 TI CKD A 20% 3 40.5623 0.58444 39.375 41.750 TI CKD B 10% 3 41.4524 0.58444 40.265 42.640 TI CKD B 20% 3 39.5360 0.58444 38.348 40.724 TI CKD C 10% 3 39.4153 0.58444 38.228 40.603 TI CKD C 20% 3 37.5844 0.58444 36.397 38.772 TI CKD D 10% 3 46.0068 0.58444 44.819 47.195 TI CKD D 20% 3 45.4000 0.58444 44.212 46.588 TI CKD E 10% 3 43.8101 0.58444 42.622 44.998 TI CKD E 20% 3 42.6517 0.58444 41.464 43.839 TI CKD F 10% 3 41.4140 0.58444 40.226 42.602 TI CKD F 20% 3 42.3845 0.58444 41.197 43.572 TI CKD LS 10% 3 44.0357 0.58444 42.848 45.223 TI CKD LS 20% 3 37.6005 0.58444 36.413 38.788 TI CKD SLX 10% 3 38.7789 0.58444 37.591 39.967 TI CKD SLX 20% 3 34.8438 0.58444 33.656 36.032

Std Error uses a pooled estimate of error variance

317 Oneway Analysis of 90d By Cement TII Blends 45

42.5

37.5 90d

32.5

30 TII TII CKD TII A 10% CKD TII A 20% CKD TII B 10% CKD TII B 20% CKD TII E 10% CKD TII E 20% CKD TII 10% F CKD TII 20% F TII CKD TII C 10% CKD TII C 20% CKD TII D 10% CKD TII D 20% TII CKD TII LS10% CKD TII LS20% TII CKD TII SLX 10% CKD TII SLX 20% TII Blends

Oneway Anova Summary of Fit

Rsquare 0.909702 Adj Rsquare 0.867209 Root Mean Square Error 1.195474 Mean of Response 39.72669 Observations (or Sum Wgts) 51

Analysis of Variance Source DF Sum of Squares Mean Square F Ratio Prob > F TII Blends 16 489.53341 30.5958 21.4083 <.0001 Error 34 48.59138 1.4292 C. Total 50 538.12478

Means for Oneway Anova Level Number Mean Std Error Lower 95% Upper 95% TII 3 42.3254 0.69021 40.923 43.728 TII CKD A 10% 3 41.9659 0.69021 40.563 43.369 TII CKD A 20% 3 37.8923 0.69021 36.490 39.295 TII CKD B 10% 3 42.0681 0.69021 40.665 43.471 TII CKD B 20% 3 38.2518 0.69021 36.849 39.654 TII CKD C 10% 3 41.4524 0.69021 40.050 42.855 TII CKD C 20% 3 37.9267 0.69021 36.524 39.329 TII CKD D 10% 3 42.2565 0.69021 40.854 43.659 TII CKD D 20% 3 41.8803 0.69021 40.478 43.283 TII CKD E 10% 3 43.1467 0.69021 41.744 44.549 TII CKD E 20% 3 39.6382 0.69021 38.236 41.041 TII CKD F 10% 3 42.3891 0.69021 40.986 43.792 TII CKD F 20% 3 40.2544 0.69021 38.852 41.657 TII CKD LS 10% 3 41.2468 0.69021 39.844 42.650 TII CKD LS 20% 3 34.8633 0.69021 33.461 36.266 TII CKD SLX 10% 3 36.1504 0.69021 34.748 37.553 TII CKD SLX 20% 3 31.6454 0.69021 30.243 33.048

Std Error uses a pooled estimate of error variance

318

Appendix H. Mortar Expansion in Limewater Statistical Analysis

319 Table H.1 Individual Expansions in Limewater of TI Blends

TI Blends Sample ID 14d TI Blends Sample ID 14d TI 1 0.001 TI CKD D 10% 1 0.043 TI 2 0.000 TI CKD D 10% 2 0.040 TI 3 0.002 TI CKD D 10% 3 0.046 TI 4 0.001 average 0.001 TI CKD D 10% 4 0.044 average 0.043 TI 1 0.010 TI CKD E 10% 1 0.031 TI 2 0.008 TI CKD E 10% 2 0.029 TI 3 0.007 TI CKD E 10% 3 0.030 TI 4 0.009 average 0.008 TI CKD E 10% 4 0.029 average 0.030 TI 1 0.008 TI CKD F 10% 1 0.015 TI 2 0.008 TI CKD F 10% 2 0.017 TI 3 0.008 TI CKD F 10% 3 0.017 TI 4 0.009 average 0.008 TI CKD F 10% 4 0.017 average 0.016 TI 1 0.003 TI CKD LS 20% 1 0.006 TI 2 0.005 TI CKD LS 20% 2 0.006 TI 3 0.005 TI CKD LS 20% 3 0.006 TI 4 0.005 average 0.004 TI CKD LS 20% 4 0.006 average 0.006 TI 1 0.005 TI CKD LS 20% 1 0.003 TI 2 0.004 TI CKD LS 20% 2 0.004 TI 3 0.005 TI CKD LS 20% 3 0.003 TI 4 0.005 average 0.005 TI CKD LS 20% 4 0.003 average 0.003 TI 1 0.004 TI CKD SLX 20% 1 0.002 TI 2 0.004 TI CKD SLX 20% 2 0.004 TI 3 0.004 TI CKD SLX 20% 3 0.004 TI 4 0.003 average 0.004 TI CKD SLX 20% 4 0.004 average 0.004 TI CKD LS 10% 1 0.009 TI CKD SLX 20% 1 0.005 TI CKD LS 10% 2 0.010 TI CKD SLX 20% 2 0.005 TI CKD LS 10% 3 0.010 TI CKD SLX 20% 3 0.005 TI CKD LS 10% 4 0.009 average 0.009 TI CKD SLX 20% 4 0.006 average 0.005 TI CKD LS 10% 1 0.004 TI CKD A 20% 1 0.014 TI CKD LS 10% 2 0.006 TI CKD A 20% 2 0.015 TI CKD LS 10% 3 0.004 TI CKD A 20% 3 0.014 TI CKD LS 10% 4 0.004 average 0.004 TI CKD A 20% 4 0.014 average 0.014 TI CKD SLX 10% 1 0.005 TI CKD B 20% 1 0.011 TI CKD SLX 10% 2 0.006 TI CKD B 20% 2 0.010 TI CKD SLX 10% 3 0.005 TI CKD B 20% 3 0.010 TI CKD SLX 10% 4 0.006 average 0.006 TI CKD B 20% 4 0.012 average 0.011 TI CKD SLX 10% 1 0.006 TI CKD C 20% 1 0.012 TI CKD SLX 10% 2 0.006 TI CKD C 20% 2 0.012 TI CKD SLX 10% 3 0.005 TI CKD C 20% 3 0.013 TI CKD SLX 10% 4 0.005 average 0.005 TI CKD C 20% 4 0.012 average 0.012 TI CKD A 10% 1 0.009 TI CKD D 20% 1 0.1390 TI CKD A 10% 2 0.012 TI CKD D 20% 2 0.1330 TI CKD A 10% 3 0.009 TI CKD D 20% 3 0.1260 TI CKD A 10% 4 0.009 average 0.010 TI CKD D 20% 4 0.1270 average 0.131 TI CKD B 10% 1 0.007 TI CKD D 20% 1 0.124 TI CKD B 10% 2 0.007 TI CKD D 20% 2 0.126 TI CKD B 10% 3 0.009 TI CKD D 20% 3 0.124 TI CKD B 10% 4 0.008 average 0.008 TI CKD D 20% 4 0.126 average 0.125 TI CKD C 10% 1 0.007 TI CKD E 20% 1 0.067 TI CKD C 10% 2 0.007 TI CKD E 20% 2 0.062 TI CKD C 10% 3 0.006 TI CKD E 20% 3 0.071 TI CKD C 10% 4 0.007 average 0.007 TI CKD E 20% 4 0.070 average 0.068 TI CKD D 10% 1 0.058 TI CKD F 20% 1 0.033 TI CKD D 10% 2 0.059 TI CKD F 20% 2 0.034 TI CKD D 10% 3 0.056 TI CKD F 20% 3 0.033 TI CKD D 10% 4 0.055 average 0.057 TI CKD F 20% 4 0.034 average 0.034 TI CKD D 10% 1 0.059 TI CKD D 10% 2 0.057 TI CKD D 10% 3 0.058 TI CKD D 10% 4 0.059 average 0.058

320 Oneway Analysis of 14d By Cement TI Blends

0.13

0.11

0.09

0.07 14d 0.05

0.03

0.01

-0.01 TI TI CKD TI A 10% CKD TI A 20% CKD TI B 10% CKD TI B 20% CKD TI E 10% CKD TI E 20% CKD TI 10% F CKD TI 20% F TI CKD TI C 10% CKD TI C 20% CKD TI D 10% CKD TI D 20% TI CKD TI LS10% CKD TI LS20% TI CKD TI SLX 10% CKD TI SLX 20% TI Blends

Oneway Anova Summary of Fit

Rsquare 0.991545 Adj Rsquare 0.990179 Root Mean Square Error 0.003338 Mean of Response 0.024043 Observations (or Sum Wgts) 116

Analysis of Variance Source DF Sum of Squares Mean Square F Ratio Prob > F TI Blends 16 0.12937762 0.008086 725.6601 <.0001 Error 99 0.00110317 0.000011 C. Total 115 0.13048078

Means for Oneway Anova Level Number Mean Std Error Lower 95% Upper 95% TI 24 0.005125 0.00068 0.00377 0.00648 TI CKD A 10% 4 0.009750 0.00167 0.00644 0.01306 TI CKD A 20% 4 0.014250 0.00167 0.01094 0.01756 TI CKD B 10% 4 0.007750 0.00167 0.00444 0.01106 TI CKD B 20% 4 0.010750 0.00167 0.00744 0.01406 TI CKD C 10% 4 0.006750 0.00167 0.00344 0.01006 TI CKD C 20% 4 0.012250 0.00167 0.00894 0.01556 TI CKD D 10% 12 0.052833 0.00096 0.05092 0.05475 TI CKD D 20% 8 0.128125 0.00118 0.12578 0.13047 TI CKD E 10% 4 0.029750 0.00167 0.02644 0.03306 TI CKD E 20% 4 0.067500 0.00167 0.06419 0.07081 TI CKD F 10% 4 0.016500 0.00167 0.01319 0.01981 TI CKD F 20% 4 0.033500 0.00167 0.03019 0.03681 TI CKD LS 10% 8 0.007000 0.00118 0.00466 0.00934 TI CKD LS 20% 8 0.004625 0.00118 0.00228 0.00697 TI CKD SLX 10% 8 0.005500 0.00118 0.00316 0.00784 TI CKD SLX 20% 8 0.004375 0.00118 0.00203 0.00672

Std Error uses a pooled estimate of error variance

321 Table H.2 Individual Expansions in Limewater of TII Blends

TII Blends Sample 14d TII 1 0.0070 TII 2 0.0080 TII 3 0.0080 TII 4 0.0080 average 0.008 TII 1 0.0040 TII 2 0.0060 TII 3 0.0050 TII 4 0.0060 average 0.005 TII CKD LS 10% 1 0.0060 TII CKD LS 10% 2 0.0050 TII CKD LS 10% 3 0.0050 TII CKD LS 10% 4 0.0060 average 0.005 TII CKD SLX 10% 1 0.0080 TII CKD SLX 10% 2 0.0070 TII CKD SLX 10% 3 0.0080 TII CKD SLX 10% 4 0.0070 average 0.008 TII CKD A 10% 1 0.0140 TII CKD A 10% 2 0.0140 TII CKD A 10% 3 0.0150 TII CKD A 10% 4 0.0150 average 0.015 TII CKD B 10% 1 0.0110 TII CKD B 10% 2 0.0110 TII CKD B 10% 3 0.0100 TII CKD B 10% 4 0.0120 average 0.011 TII CKD C 10% 1 0.0120 TII CKD C 10% 2 0.0120 TII CKD C 10% 3 0.0110 TII CKD C 10% 4 0.0110 average 0.012 TII CKD D 10% 1 0.0170 TII CKD D 10% 2 0.0170 TII CKD D 10% 3 0.0190 TII CKD D 10% 4 0.0160 average 0.017 TII CKD E 10% 1 0.0210 TII CKD E 10% 2 0.0230 TII CKD E 10% 3 0.0210 TII CKD E 10% 4 0.0220 average 0.022 TII CKD F 10% 1 0.0190 TII CKD F 10% 2 0.0170 TII CKD F 10% 3 0.0180 TII CKD F 10% 4 0.0180 average 0.018 TII CKD LS 20% 1 0.0050 TII CKD LS 20% 2 0.0060 TII CKD LS 20% 3 0.0050 TII CKD LS 20% 4 0.0050 average 0.005 TII CKD SLX 20% 1 0.0050 TII CKD SLX 20% 2 0.0060 TII CKD SLX 20% 3 0.0060 TII CKD SLX 20% 4 0.0060 average 0.006 TII CKD A 20% 1 0.0150 TII CKD A 20% 2 0.0150 TII CKD A 20% 3 0.0140 TII CKD A 20% 4 0.0150 average 0.015 TII CKD B 20% 1 0.0130 TII CKD B 20% 2 0.0130 TII CKD B 20% 3 0.0120 TII CKD B 20% 4 0.0110 average 0.012 TII CKD C 20% 1 0.0140 TII CKD C 20% 2 0.0140 TII CKD C 20% 3 0.0160 TII CKD C 20% 4 0.0150 average 0.015 TII CKD D 20% 1 0.0490 TII CKD D 20% 2 0.0470 TII CKD D 20% 3 0.0490 TII CKD D 20% 4 0.0500 average 0.049 TII CKD E 20% 1 0.0550 TII CKD E 20% 2 0.0530 TII CKD E 20% 3 0.0520 TII CKD E 20% 4 0.0530 average 0.053 TII CKD F 20% 1 0.0280 TII CKD F 20% 2 0.0290 TII CKD F 20% 3 0.0290 TII CKD F 20% 4 0.0290 average 0.029

322 Oneway Analysis of 14d By Cement TII Blends 0.06

0.05

0.04

0.03 14d

0.02

0.01

0 TII TII CKD TII A 10% CKD TII A 20% CKD TII B 10% CKD TII B 20% CKD TII E 10% CKD TII E 20% CKD TII 10% F CKD TII 20% F TII CKD TII C 10% CKD TII C 20% CKD TII D 10% CKD TII D 20% TII CKD TII LS10% CKD TII LS20% TII CKD TII SLX 10% CKD TII SLX 20% TII Blends

Oneway Anova Summary of Fit

Rsquare 0.99626 Adj Rsquare 0.995172 Root Mean Square Error 0.000949 Mean of Response 0.016861 Observations (or Sum Wgts) 72

Analysis of Variance Source DF Sum of Squares Mean Square F Ratio Prob > F TII Blends 16 0.01318511 0.000824 915.6327 <.0001 Error 55 0.00004950 9e-7 C. Total 71 0.01323461

Means for Oneway Anova Level Number Mean Std Error Lower 95% Upper 95% TII 8 0.006500 0.00034 0.00583 0.00717 TII CKD A 10% 4 0.014500 0.00047 0.01355 0.01545 TII CKD A 20% 4 0.014750 0.00047 0.01380 0.01570 TII CKD B 10% 4 0.011000 0.00047 0.01005 0.01195 TII CKD B 20% 4 0.012250 0.00047 0.01130 0.01320 TII CKD C 10% 4 0.011500 0.00047 0.01055 0.01245 TII CKD C 20% 4 0.014750 0.00047 0.01380 0.01570 TII CKD D 10% 4 0.017250 0.00047 0.01630 0.01820 TII CKD D 20% 4 0.048750 0.00047 0.04780 0.04970 TII CKD E 10% 4 0.021750 0.00047 0.02080 0.02270 TII CKD E 20% 4 0.053250 0.00047 0.05230 0.05420 TII CKD F 10% 4 0.018000 0.00047 0.01705 0.01895 TII CKD F 20% 4 0.028750 0.00047 0.02780 0.02970 TII CKD LS 10% 4 0.005500 0.00047 0.00455 0.00645 TII CKD LS 20% 4 0.005250 0.00047 0.00430 0.00620 TII CKD SLX 10% 4 0.007500 0.00047 0.00655 0.00845 TII CKD SLX 20% 4 0.005750 0.00047 0.00480 0.00670

Std Error uses a pooled estimate of error variance

323