Fly Ash Applicability in Pervious Concrete
Thesis
Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in
the Graduate School of The Ohio State University
By
Na Jin, B. E.
Graduate Program in Civil Engineering
The Ohio State University 2010
Thesis Committee William E. Wolfe, Advisor Fabian Hadipriono Tan Tarunjit Singh Butalia Copyright by
Na Jin
2010
2
ABSTRACT
Pervious concrete has been used in the United State for over 30 years. Because of its high porosity, the most common usages have been in the area of stormwater management, but have been limited to use in pavements with low volume traffic because of its low compressive strength compared to conventional concrete. Fly ash has been shown in numerous post studies to increase the strength and durability of conventional concrete. In this study, six batches of pervious concrete with different amounts of aggregate, cement, and fly ash were prepared to find the mix that generated high compressive strength and study the effect of fly ash on the compressive strength and permeability of pervious concrete.
Materials used in this study were selected based on literature reviews and recommendations from local sources. Unconfined compressive strength tests were carried out on pervious concrete specimens with fly ash contents of 0%, 2%, 9%, 30%, 32% by weight of the total cementitious materials. Falling head permeability tests were carried out on specimens having 2% and 32% fly ash.
The results indicated the pervious concrete containing 2% fly ash can achieve compressive strength greater than 3,000 psi at void content of 12%, and a compressive strength 2,300 psi with a permeability of 0.13 cm/s at a void content of 15%. The pervious concrete with 32% fly ash had a compressive strength of 2,000 psi and the permeability of 0.21 cm/s at a void content of 15.8%. The failure surfaces of specimens
ii with 2% fly ash developed through the coarse aggregates, indicating the high strength of cement bonds. The failure of specimens containing 32% fly ash was observed to be along the coarse aggregates surfaces, indicating a lower strength of the paste. Although it was expected for pervious concrete with 32% fly ash to reach a higher compressive strength at lower void content, the failure mode indicated that it may not reach the value as high as that of pervious concrete with 2% fly ash at the same void content.
iii DEDICATION
Dedicated to my dear parents and husband.
iv ACKNOWLEDGEMENTS
I would like to express my sincere appreciation to my advisor, Dr. William E.
Wolfe, for his guidance, patience, kindness, and encouragement throughout this work. I would also like to thank Dr. Fabian Hadipriono Tan for his suggestions and endless support to me during my study. Without their help, the fulfillment of my master degree would have been impossible.
I would also like to thank Dr. Tarunjit Singh Butalia for his suggestions and help in facilitating the purchase of experimental equipments in this study. I am also grateful to all of the professionals for their expertise, support, and kindness: Mr. Mark Pardi, is of
Ohio Concrete, gave me valuable suggestions and guidance on pervious concrete; Mr.
Dan Hunt, is of Buckeye Ready-Mix, carried out one example mix test on pervious concrete and shared his valuable experience; Mr. Michael Adams, is of Euclid Chemical
Corp., provided with pervious concrete admixtures; Mr. Thomas J. Wissinger, is of the
Olen Corp., provided and delivered coarse aggregates even in bad weather; Mr. Dan Jahn, is of Anderson Concrete, arranged a visit to the concrete company and provided with portions of perivous concrete components.
v
VITA
1998 – 2002…………………. B. E, Construction Engineering, University of Science and Technology of Suzhou
2002 – 2004………...… Zhenjiang Architectural Design & Research Institute, P.R. China
2004 – 2006….…………………….. Guangsha Architectural Design Institute, P.R. China
2008 – Present………………………...…. ..Civil Engineering, The Ohio State University
Fields of Study Major Field: Civil Engineering
vi
Table of Contents
ABSTRACT………………………………………………………………………………ii
DEDICATION……………………………………………………………………………iv
ACKNOWLDEGEMENTS……………………………………………………………….v
VITA……………………………………………………………………………………...vi
List of Figures……………………………………………………………………………..x
List of Tables……...………………………………………………………………...…..xiii
CHAPTER 1: INSTRODUCTION ...... 1
1.1 Background...... 1 1.2 Objectives...... 2 1.3 Organization ...... 3
CHAPTER 2: LITERATURE REVIEW OF PORTLAND CEMENT PERVIOUS CONCRETE ...... 5
2.1 Introduction ...... 5 2.2 Benefits and Problems ...... 6 2.2.1 Benefits...... 6 2.2.2 Problems ...... 8 2.3 Components of Pervious Concrete ...... 11 2.3.1 Coarse Aggregate...... 11 2.3.2 Fine Aggregate...... 12 2.3.3 Cement...... 12 2.3.4 Fly Ash ...... 13 2.3.5 Water ...... 13 2.3.6 Admixtures ...... 14 2.4 Important Properties of Pervious Concrete ...... 16 2.4.1 Permeability...... 16 2.4.2 Compressive Strength...... 20 2.4.3 Freeze-thaw Durability...... 21 2.4.4 Modulus of Elasticity ...... 24
vii 2.5 Factors Affect Compressive Strength and Permeability of Pervious Concrete...... 24 2.5.1 Effect of Void Content ...... 25 2.5.2 Effect of Aggregate ...... 27 2.5.3 Effect of Aggregate/Cement Material Ratio...... 28 2.5.4 Effect of Water/Cement Ratio ...... 28 2.5.5 Effect of fly ash...... 29 2.5.6 Effect of Compaction Energy ...... 29 2.5.7 Effect of Fibers ...... 31 2.5.8 Effect of Other Factors...... 32 2.6 Standard Test Methods...... 33 2.7 Pervious Concrete Design ...... 34 2.7.1 Pervious Concrete Mix Design ...... 34 2.7.2 Pervious Concrete Pavement Hydraulic Design...... 36 2.7.3 Pervious Concrete Pavement Structural Design ...... 37
CHAPTER 3: LITERATURE REVIEW OF FLY ASH...... 44
3.1 Introduction of Coal Combustion Products (CCPs) ...... 44 3.2 Introduction of Fly Ash...... 47 3.2.1 Properties of Fly Ash...... 48 3.2.2 Class C and Class F Fly Ash...... 48 3.2.3 Utilization of Fly Ash in Concrete...... 48 3.2.4 Environmental Benefits of Fly Ash Use...... 50 3.3 Effect of Fly Ash on Concrete...... 51 3.3.1 Thermal Cracking ...... 51 3.3.2 Compressive Strength...... 51 3.3.3 Durability...... 53 3.3.4 Permeability...... 54 3.3.5 Sulfate Attack ...... 55 3.4 Fly Ash in Pervious Concrete...... 56 3.5 Summary ...... 56
CHAPTER 4: LABORATORY MIX AND TEST ...... 59
4.1 Introduction ...... 59 4.2 Mix Preparation ...... 59 4.2.1 Mix Materials...... 59 4.2.2 Mix Design ...... 65 4.2.3 Mixing Equipment ...... 71 4.2.4 Specimen Mold ...... 74 4.3 Mixing Procedure ...... 74 4.4 Compaction Method...... 75 4.5 Curing Method...... 76 4.6 Laboratory Tests ...... 77 4.6.1 Unit Weight and Void Content ...... 77
viii 4.6.2 Compressive Strength...... 79 4.6.3 Permeability...... 80 4.7 Summary of Test Procedure...... 83
CHAPTER 5: DISCUSSION ON TEST RESULTS ...... 86
5.1 Introduction ...... 86 5.2 Void Content vs. Unit Weight ...... 86 5.3 Effect of Compaction Energy...... 87 5.4 Effect of W/C Ratio, A/C Ratio and Fly Ash on Void Content ...... 90 5.5 Compressive Strength ...... 90 5.5.1 Compressive Strength vs. Curing Period...... 91 5.5.2 Compressive Strength vs. Void Content ...... 92 5.5.3 Compressive Strength vs. Unit Weight ...... 94 5.5.4 Compressive Stress-strain Curves vs. Void Content...... 94 5.5.5 Compressive Failure vs. Curing Period...... 98 5.5.6 Failure Modes ...... 99 5.6 Permeability...... 103
CHAPTER 6: SUMMARY, CONCLUSION, AND RECOMMENDATIONS...... 107
6.1 Summary ...... 107 6.2 Conclusion...... 109 6.3 Recommendations for Future Work...... 111
REFERENCES ...... 113
APPENDIX A: EXAMPLES OF PERVIOUS CONCRETEEXPERIMENTS FROM
LITERATURE REVIEWS ...... 121
APPENDIX B: PROPERTIES OF PERVIUOS CONCRETE COMPONENTS ...125
APPENDIX C: LABORATORY TEST RESULT ...... 137
APPENDIX D: PERVIOUS CONCRETE MIX DESIGN PROGRAM CODE .....168
ix
List of Figures
Figure 2.1. Model Resulting from the Nonlinear Fitting of the Saturated Hydraulic Conductivity and Total Porosity Data to the Carman-Kozeny Equation ...... 18 Figure 2.2. Plot of the Ergun Equation and Values Calculated Using the Falling Head Experimental Data from Samples Calculated with Dp = 0.1, Dp = 0.3, and Dp = 0.6.(adapted from Montes and Haselbach )...... 19 Figure 2.3. Relationship between Strength, Void Content and Permeability for Several Trial Mixes of Portland Cement Pervious Concrete...... 26 Figure 2.4. Nomograph to Determine Structural Number (Pavement Strength) ...... 38 Figure 3.1. Uses of Coal Combustion Products in 2008 (AACA adapted from U. S Environmental Protection Agency (EPA)) ...... 45 Figure 3.2. 1966-2007 CCP Beneficial Use vs. Production (AACA) ...... 46 Figure 3.3. Coal Combustion Products Generation and Use (Short Tons) (AACA adapted from EPA)...... 47 Figure 3.4. Top Uses of Coal Fly Ash 2003 (AACA adapted from)...... 49 Figure 3.5. Comparison between Ash Concrete Compressive Strength and Plain Cement Concrete Compressive Strength...... 52 Figure 3.6. Effect of Fly Ash on Permeability of Concrete (adapted from) ...... 55 Figure 4.1. Grain Distribution Curve of Size Number 8 River Gravel (Olen Corp.)...... 61 Figure 4.2. Pervious Concrete Mix Calculation Program...... 68 Figure 4.3. 20 quart Blakeslee Mixer ...... 72 Figure 4.4. Specimen Mixed Using 20 Quart Blakeslee Mixer ...... 72 Figure 4.5. 3.4ft3 capacity Gilson 39555 (drum speed speed 22 ~ 25 RPM) ...... 73 Figure 4.6. INSTRON-5585 Compressive Strength Testing Machine...... 80 Figure 4.7. Falling Head Permeability Test for Pervious Concrete Specimen ...... 82 Figure 4.8. Pervious Concrete Specimen for Permeability Test ...... 82 Figure 5.1. Relationship between Void Content (%) and Unit Weight (lb/ft3)...... 87 Figure 5.2. Void Contents of Specimens Compacted by Different Methods ...... 88 Figure 5.3. The Specimen Compacted by Proctor Hammer ...... 89 Figure 5.4. Pervious Concrete Mix #3~#6 Compressive Strength vs. Curing Period...... 92 Figure 5.5. Relaiton between 28-day Compressive Strength and Void Content ...... 93 Figure 5.6. Relationship between 28-day Compressive Strength and Unit Weight...... 94 Figure 5.7. Stress-strain Curves Tested on Specimens with Different Void Content at 28- day Curing Period, Mix #5...... 96 Figure 5.8. Stress-strain Curves Tested on Specimens with Different Void Content at 28- day Curing Period, Mix #6...... 97 Figure 5.9. Stress-strain Curves Tested on Specimens with Void Content 18% at 7-day, 21-day, and 28-day Curing Periods, Mix #6...... 99
x Figure 5.10. Failure Mode I of Pervious Concrete Samples...... 100 Figure 5.11. Failure Mode II of Pervious Concrete Samples...... 100 Figure 5.12. Failure of Specimen Compacted by Standard Proctor Hammer (Mix #6)..101 Figure 5.13. Failure Surface Comparison between Specimen from Mix #5 and Mix #6102 Figure 5.14. Relationship between Void Content and Permeability of Pervious Concrete Specimens ...... 103 Figure 5.15. Comparison of Permeability Test Results with Previous Studies ...... 106 Figure 6.1. Permeability and 28-day Compressive Strength vs. Void Content ...... 109 Figure B.1. Properties of Coarse Aggregates...... 126 Figure B.2. Properties of Cement (St. Marys) ...... 127 Figure B.3. Properties of High Range Water Reducer (Euclid Chemical Company) .....128 Figure B.4. Properties of Mid-Range Water Reducer (Euclid Chemical Company) ...... 130 Figure B.5. Properties of Mid-Range Water Reducer (Euclid Chemical Company) ...... 132 Figure B.6. Properties of Viscosity Modifying Admixture (Euclid Chemical Company) ...... 134 Figure B.7. Properties of Fiber (Euclid Chemical Company)...... 135 Figure C.1. 11-day Compressive Stress-strain Curve of Specimen with Void Contend of 31% from Mix #3 ...... 147 Figure C.2. 21-day Compressive Stress-strain Curve of Specimen with Void Contend of 31% from Mix #3 ...... 147 Figure C.3. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 31% from Mix #3 ...... 148 Figure C.4. 7-day Compressive Stress-strain Curve of Specimen with Void Contend of 27% from Mix #4 ...... 148 Figure C.5. 21-day Compressive Stress-strain Curve of Specimen with Void Contend of 27% from Mix #4 ...... 149 Figure C.6. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 27% from Mix #4 ...... 149 Figure C.7. 7-day Compressive Stress-strain Curve of Specimen with Void Contend of 12% from Mix #5 ...... 150 Figure C.8. 21-day Compressive Stress-strain Curve of Specimen with Void Contend of 12% from Mix #5 ...... 150 Figure C.9. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 13% from Mix #5 ...... 151 Figure C.10. 7-day Compressive Stress-strain Curve of Specimen with Void Contend of 17% from Mix #6 ...... 151 Figure C.11. 21-day Compressive Stress-strain Curve of Specimen with Void Contend of 18% from Mix #6 ...... 152 Figure C.12. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 18% from Mix #6 ...... 152 Figure C.13. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 16% from Mix #5 ...... 153 Figure C.14. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 15% from Mix #5 ...... 153
xi Figure C.15. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 12% from Mix #5 ...... 154 Figure C.16. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 12% from Mix #5 ...... 154 Figure C.17. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 14% from Mix #5 ...... 155 Figure C.18. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 14% from Mix #5 ...... 155 Figure C.19. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 13% from Mix #5 ...... 156 Figure C.20. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 18% from Mix #6 ...... 156 Figure C.21. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 20% from Mix #6 ...... 157 Figure C.22. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 22% from Mix #6 ...... 157 Figure C.23. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 24% from Mix #6 ...... 158 Figure C.24. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 24% from Mix #6 ...... 158
xii List of Tables
Table 2.1. NMCRA Classification of Regions and Recommendation of Precautions of Utilizing pervious concrete ...... 22 Table 2.2. Compaction Method Conducted by Rizvi et al...... 31 Table 2.3. Recommended Typical Mix Design by National Ready Mixed Concrete Association...... 35 Table 2.4. Recommended Typical Mix Design by the Southern California Ready Mix Concrete Association (adapted from ) ...... 35 Table 2.5. Recommended Typical Mix Design by the Euclid Chemical Company ...... 35 Table 4.1. Physical Properties of #8 River Gravel (Olen Corp.) ...... 61 Table 4.2. Coarse Aggregate Distribution (Olen Corp.)...... 61 Table 4.3. Chemical Properties of St. Marys Type I Cement (St. Marys, Inc.)...... 63 Table 4.4. Physical Properties of fly ash ...... 64 Table 4.5. Admixtures from Euclid Chemical Company ...... 65 Table 4.6. Pervious Concrete Mix Design...... 66 Table 4.7. Mix No. Corresponding to Mix ID...... 67 Table 4.8 Compaction Method ID Explanation ...... 75 Table 4.9. Pervious Concrete Mixes Compacted Using Different Methods Mix ...... 76 Table 4.10. Specific Gravities of Materials in Portland Cement Pervious Concrete Mix.79 Table A.1: Examples of Laboratory Tests on Pervious Concrete...... 122 Table A.2. Examples of Field Projects of Pervious Concrete...... 124 Table C.1. Mix Design of Pervious Concrete Mix #1 ...... 138 Table C.2. Unit Weight and Void Content of 4in x 8in Samples from Pervious Concrete Mix #1...... 138 Table C.3. Mix Design of Pervious Concrete Mix #2 ...... 139 Table C.4. Unit Weight and Void Content of 4in x 8in Samples from Pervious Concrete Mix #2...... 139 Table C.5. Mix Design of Pervious Concrete Mix #3 ...... 140 Table C.6. Unit Weight and Void Content of 4in x 8in Samples from Pervious Concrete Mix #3...... 140 Table C.7. Mix Design of Pervious Concrete Mix #4 ...... 141 Table C.8. Unit Weight and Void Content of 4in x 8in Samples from Pervious Concrete Mix #4...... 141 Table C.9. Mix Design of Pervious Concrete Mix #5 ...... 142 Table C.10. Unit Weight and Void Content of 4in x 8in Samples from Pervious Concrete Mix #5...... 142 Table C.11. Unit Weight and Void Content of 3in x 6in Samples from Pervious Concrete Mix #5...... 143 Table C.12. Mix Design of Pervious Concrete Mix #6 ...... 143
xiii Table C.13. Unit Weight and Void Content of 4in x 8in Samples from Pervious Concrete Mix #6...... 144 Table C.14. Unit Weight and Void Content of 3in x 6in Samples from Pervious Concrete Mix #6...... 144 Table C.15. Compressive Strength of Specimens from Mix #1~#6 at 7, 21, and 28 Days Curing Periods...... 145 Table C.16. 28-day Compressive Strength of Specimens from Mix #1~#6 with Various Void Content ...... 146 Table C.17. Measured and Calculated Permeability of Pervious Concrete Specimens from Literature Review ...... 159 Table C.18. Permeability Calculation Parameters in Falling Head Permeability Test ...161 Table C.19. Permeability Test Data for Specimen with Void Content of 19.5% from Mix #5 ...... 162 Table C.20. Permeability Test Data for Specimen with Void Content of 19.5% from Mix #5 ...... 162 Table C.21. Permeability Test Data for Specimen with Void Content of 17.0% from Mix #5 ...... 163 Table C.22. Permeability Test Data for Specimen with Void Content of 16.0% from Mix #5 ...... 163 Table C.23. Permeability Test Data for Specimen with Void Content of 14.9% from Mix #5 ...... 164 Table C.24. Permeability Test Data for Specimen with Void Content of 27.2% from Mix #6 ...... 164 Table C.25. Permeability Test Data for Specimen with Void Content of 25.0% from Mix #6 ...... 165 Table C.26. Permeability Test Data for Specimen with Void Content of 21.0% from Mix #6 ...... 165 Table C.27. Permeability Test Data for Specimen with Void Content of 21.5% from Mix #6 ...... 166 Table C.28. Permeability Test Data for Specimen with Void Content of 15.8% from Mix #6 ...... 166 Table C.29. Void Contents of Specimens Compacted at Different Compaction Methods ...... 167
xiv CHAPTER 1
INTRODUCTION
1.1 Background
According to National Ready Mixed Concrete Association (NRMCA) 1 ,
“pervious concrete is a special type of concrete with a high porosity used for concrete flatwork applications that allows water from precipitation and other sources to pass through it, thereby reducing the runoff from a site and recharging ground water levels.” It is also known as “no-fines concrete” and is composed of Portland cement, coarse aggregate, water, admixtures, and little or no sand. In the past 30 years, pervious concrete has been increasingly used in the United States, and is among the
Best Management Practices (BMPs) recommended by the Environmental Protection
Agency (EPA)2. By capturing stormwater and allowing it to seep into the ground, pervious concrete is instrumental in recharging groundwater, reducing stormwater runoff, and meeting U.S. EPA stormwater regulations. Other benefits of using pervious concrete are: reduction of downstream flows, erosion and sediment; reduction of large volumes of surface pollution flowing into rivers; decrease of urban heat island effect; eliminating traffic noise; and enhancing safety of driving during raining. The use of pervious concrete in building site design can also aid in the
1 process of qualifying the building for Leadership in Energy and Environmental
Design (LEED) Green Building Rating System credits2.
Due to the advantages of pervious concrete, the utilization and construction properties of pervious concrete have been studied by many researchers3,4,5,6. The characteristic of high permeability of pervious concrete contributes to its advantage in storm water management. However, the mechanical properties such as compressive strength are reduced due to this character, limiting the application of pervious concrete to the roads that have light volume traffic.
The advantage of pervious concrete can be enhanced by substituting some of the cement with other materials, such as fly ash. Fly ash is one of the by-products of coal combustion in power generation plants. Large amount of fly ash are discarded each year, increasing costs for disposal. On the other hand, fly ash has been shown to improve the overall performance of concrete, when substituted for a portion of the cement7. Hence, when fly ash is used in pervious concrete, the occupation of landfill
space can be reduced and CO2 emissions generated during cement production can be decreased, improving the sustainability of pervious concrete.
1.2 Objectives
The objective of this research is to investigate the effects on the important engineering properties of pervious concrete with the use of fly ash. The physical properties examined include compressive strength and permeability of pervious concrete. The parameters that affect the strength and the hydraulic conductivity of
2 pervious concrete will be analyzed. The potential use of pervious concrete containing a large portion of fly ash will also be discussed.
1.3 Organization
This thesis consists of six chapters and four appendices. Chapter 1 is an introduction of pervious concrete background and the study objectives. Chapter 2 presents literature reviews of pervious concrete, including benefits and problems, mix designs, and properties of pervious concrete. Chapter 3 contains a brief literature review of fly ash, introducing the application and effect of fly ash on concrete properties. Chapter 4 introduces the laboratory mixing and laboratory tests, including the selection of materials, mixing equipment, mix design, compaction method, and test equipments. Chapter 5 elaborates on the test results, including void content, compressive strength, and permeability of pervious concrete specimens. Chapter 6 summarizes the conclusions of the study, discusses the applicability of pervious concrete that contains large amounts of fly ash, and provides with recommendations for future work. Appendix A presents examples of pervious concrete experiments taken from literature reviews. Appendix B illustrates the properties of pervious concrete components used in this research. Appendix C presents the laboratory test results. Appendix D shows codes of a program developed for pervious concrete mix design.
1 NRMCA “CIP 38 – pervious concrete” brochure of National Ready Mixed Concrete Association (NRMCA),
3
2 National Ready Mixed Concrete Association (NRMCA),
3 Offenberg, M. (2008). “Is pervious concrete ready for structural applications?” Structure Magazine, February, p. 48.
4 Johnston, K. (2009). “Pervious concrete: past, present and future.” Green Building, Concrete Contractor,
5 Schaefer, V. R., Suleiman, M. T., Wang, K., Kevern, J. T., and Wiegand, P. (2006). “An overview of pervious concrete applications in stormwater management and pavement systems.” < http://www.rmc- foundation.org/images/PCRC%20Files/Hydrological%20&%20Environmental%2 0Design/An%20Overview%20of%20Pervious%20Concrete%20Applications%20 in%20Stormwater%20Management%20and%20Pavement%20Systems.pdf> (Jun. 16, 2010).
6 Yang, J., and Jiang. G. (2003). “Experimental study on properties of pervious concrete pavement materials.” Cement and Concrete Research, vol. 33, pp. 381- 386.
7 Headwaters Resources (2005). “Fly ash in pervious concrete.” Bulletin No. 29,
4
CHAPTER 2
LITERATURE REVIEW OF PORTLAND CEMENT PERVIOUS CONCRETE
2.1 Introduction
Offenberg3 stated that the first popular usage of pervious concrete was in post-
World War II England where it was used in two-story homes known as the Wimpey
Houses. During World War II, nearly two third of Britain’s houses had been destroyed; and no new buildings had been constructed since 1939. Consequently, the demand for housing was very high, causing a shortage of bricks. In this situation, people were seeking alternate construction materials that were economical, reliable and efficient. No-fine concrete was then used in some parts of the walls by Wimpey8 architects and engineers to decrease the cost.
In the United States, pervious concrete has been used for almost 30 years since it was first introduced in California4. In order to study the factors influencing the performance of pervious concrete, researchers have conducted experiments varing mix proportions of cement, water, coarse aggregate, sand, fly ash, and admixtures.
According to experimental studies6,7,9,10,11,12,13, researchers have found that factors that affect the mechanical properties of pervious concrete are void content, aggregate to cement ratio, fine aggregate amount, coarse aggregate size, coarse aggregate type, compaction energy, and curing period. 5
2.2 Benefits and Problems
Due to the absence of fine aggregate, pervious concrete has high porosity, which brings both benefits and drawbacks to construction.
2.2.1 Benefits
Since the pervious concrete pavement is permeable, water can be captured and flow through the pavement during rainfall. In the mean time, free air is stored in the pavement and allows the communication between the subsurface and the air. These properties offer many advantages for pervious concrete.
2.2.1.1 Storm-water Management
One of the primary uses of pervious concrete is in storm water management.
Due to its high porosity, pervious concrete can capture stormwater and provide a path for water to flow into the subsoil, helping to naturally adjust the ground water level.
Furthermore, instead of being carried into rivers and lakes by rain water, the residues on pavement roads will be absorbed by pervious concrete or underneath soils, and then degraded by microorganisms in soils2. Consequently, the pollution of water resources could be decreased substantially, dramatically saving expense of storm water management.
2.2.1.2 Heat Island Effect
Pervious concrete is much cooler than asphalt and conventional concrete. First of all, the light color reflects more ultraviolet rays from sun and absorbs less heat than
6
asphalt. Secondly, the voids in pervious concrete allow it to store less heat than conventional concrete does. This character benefits the districts in hot weather climates. For instances, the group of National Center of Excellence for Sustainable
Materials and Renewable Technology at Arizona State University recommended the utilization of pervious concrete for minimizing the urban heat-island effect14. Houston
Advanced Research Center (HARC)15 published a report titled “Cool Houston! A
Plan for Cooling the Region,” in which the benefits of reducing heat island effect in high density urban areas by using pervious concrete has been introduced.
2.2.1.3 Traffic Benefits
Pervious concrete shows several advantages on traffic. Firstly, the large amounts of voids in pervious concrete are beneficial to reducing traffic noise. As stated by Kim and Lee 16 , pervious concrete “is applied for sound barriers or pavements to absorb traffic (tire) noise and reduce sound wave reflection”. To investigate this property of absorption, Kim and Lee16 created a model to study the acoustic absorption ability of pervious concrete, considering the gradation and shape of aggregates and void content on pervious concrete pavement. The results calculated by the modeling were compared with experimental and statistical results from previous studies. All results illustrated that the maximum acoustic absorption ability was increased with void content and was hardly affected by the shape of aggregate when pervious concrete was compacted well. Secondly, pervious concrete enhances the safety of driving during raining because of the elimination of ponding.
7
2.2.1.4 LEED
The usage of pervious concrete in building site design can also aid in the process of qualifying for Leadership in Energy and Environmental Design (LEED)
Green Building Rating System credits. LEED was developed by the U.S. Green
Building Concil (USGBC). It provides a concise framework for identifying and implementing practical and measurable green building design, and construction.
LEED for New Construction and Major Renovations version 2.2 has maximum total of 69 points, in which concrete can earn up to 25 points. In addition, with the usage of fly ash or other recycled materials in pervious concrete, up to 5 more credits could be earned2.
2.2.2 Problems
High porosity is the necessary condition that makes pervious concrete permeable, and is the main beneficial characteristic of pervious concrete. However it can cause problems that limit the utilization of pervious concrete.
2.2.2.1 Compressive Strength
The bearing capacity of pervious concrete is decreased because of the existence of large amounts of air voids. The low strength limits the utilization of pervious concrete to parking-lots, side walks, and other low-volume traffic roadways.
Obviously, high porosity and strength are two incompatible features of pervious concrete. This disadvantage initiates the study on pervious concrete aim to improve its compressive strength while maintaining the relative high porosity.
8
2.2.2.2 Freeze-thaw Durability
The usage of pervious concrete in a freeze-thaw environment is also a concern, especially in the northern area of the United States, which are districts experiencing cold weather. The pervious concrete is more vulnerable to be destroyed under freeze- thaw weather. Research has been done to study the suitability of pervious concrete in this type of climate. Regulations have been made to ensure the applicability of the pervious concrete. For example ASTM C 666M-03 17 Standard Test Method for
Resistance of Concrete to Rapid Freezing and Thawing specifies the standard test method to determine the resistance of concrete specimens to rapidly repeated cycles of freezing and thawing in the laboratory following procedure A, Rapid Freezing and
Thawing in Water, and procedure B, Rapid Freezing in Air and Thawing in Water.
2.2.2.3 Abrasion
Abrasion of pervious concrete may limit its utilization. Raveling may happen if aggregate is not sufficiently coated with cement paste. Other factors such as low
Water/Cement (W/C) ratio, dry weather, especially the rough surface also make aggregate vulnerable to the abrasion. Theoretically, the abrasion of surface may make surface more uneven and worsen abrasion over time. However, Hein and Schindler18 studied field projects constructed on the Auburn University campus, and found that after curing of pervious concrete, about only 10% of surface aggregates were displaced. But remaining surface was smooth enough as for a sidewalk and had performed very well for three years.
9
2.2.2.4 Clogging Maintenance
Clogging is an unavoidable problem due to the existence of voids in pervious concrete. The open voids are highly prone to be clogged during the utilization of pervious concrete pavement over time. The U. S. EPA recommends that cleaning need to be done regularly to prevent clogging2. Two methods of cleaning are currently used: vacuum sweeping and high pressure washing. Even though cleaning is performed regularly, not all contaminants are removed and the performance of pervious concrete may lessen over the years. Moreover, the residues may cause contamination of the water that runs through the pervious concrete. Hence, stormwater testing is recommended in critical situations to preserve the quality of ground water and inspect the permeability of pervious concrete.
2.2.2.5 Cost
Typically, the initial cost of pervious concrete is greater than that of conventional concrete. However, because the lifespan of pervious concrete is longer than that of the regular concrete2, some of the added cost is offset. The high initial cost of pervious concrete is partly caused by the construction of the subgrade. A thick layer of open gravel subgrade is usually installed under the pavement to provide the storage and drainage of water. With such subgrade, pervious concrete normally can perform very well even when built on clay soils. An example is presented by Dietz19, who tested a subgrade of 10-in. thick layer of open graded gravel with undrained system below. The subgrade showed good storage and drainage conditions. In general, a thick layer of coarse aggregate “provides greater storage capacity and a longer time
10
allows water to exfiltrate to the native soils before underdarin flow would begin”19.
But the construction of subgrade increases the total cost of the pervious concrete pavement. Another reason is the increased maintenance cost for pervious concrete pavement after construction. As stated before, clogging problems need to be solved to ensure the serviceability of pervious concrete.
2.3 Components of Pervious Concrete
Pervious concrete is mainly composed by coarse aggregate, cement, and water.
Small amount of fine aggregate may be added to obtain higher compressive strength.
Other admixtures such as High/Middle Range Water Reducer (HRWR, MRWR), water retarder, viscosity modifying admixtures, and fibers are usually used. In some cases, fly ash is used as a substitute for Portland cement to enhance the environmental friendliness of pervious concrete.
2.3.1 Coarse Aggregate
Coarse aggregate is the main component of pervious concrete. The gradation, size, and type of coarse aggregate have been found to affect the character of pervious concrete6,9,10,11. In practice, river gravels that have size number of 8 (ASTM C 3320) are widely used in construction. Other sizes of river gravels and limestone have been used in laboratory tests to study the effect of coarse aggregate11.
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2.3.2 Fine Aggregate
A fine aggregate is sometimes used in pervious concrete to improve the mechanical capabilities of pervious concrete. On the other hand, the permeability will typically decrease when fine aggregate is added. Wang et al.10 studied pervious concrete with a fine aggregate amount of 7% of total aggregate by weight. Wang’s tests illustrated that the compressive strength and freeze-thaw ability of pervious concrete were significantly improved with addition of fine aggregate while maintaining adequate water permeability. However, the amount of fine aggregate is recommended to be limited within 7% of the total aggregate by weight so that permeability is satisfied10.
According to the ASTM C 3320, the fine aggregate shall consist of natural or, subject to approval, other inert materials with similar characteristics, or combinations having hard, strong, durable particles. The amount substances such as clay lumps coal and lignite, shale, and other deleterious substance should be limited within a range individually, and the total amount should be less than 2% by dry weight. Soundness loss should be less than 10% by weight. The fine aggregate should be free from organic impurities.
2.3.3 Cement
Portland cement is another main component of pervious concrete. Type I/II cement is normally used in pervious concrete9,10,11,12. The content of cement is dependent on the amount and size of coarse aggregate and the water content. Various
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amounts of cement are recommended by different agencies and will be introduced in section 2.7.1.
2.3.4 Fly Ash
Fly ash can be used in pervious concrete as a substitute for a portion of the cement. Two types of fly ash which are Class C and Class F fly ash are both able to used in pervious concrete. Currently, fly ash can replace 5-65% of the Portland cement2 in conventional concrete. However, according to the publication from
Headwaters Resources7, California Ready Mix Concrete Association (SCRMC) recommended amount of ASTM C-618 fly ash is only 50-116lb/yd3 in pervious concrete. The advantage of using fly ash is obvious: fly ash is a by-product of coal burning in power plants, its utilization saves the energy required to produce the cement. In addition, fly ash improves the flowability and workability of concrete.
2.3.5 Water
Water is a crucial component in pervious concrete. Wanielista and Chopra11 discussed the importance of adding appropriate amount of water in pervious concrete mix. Enough water should be added so that cement hydration is thoroughly developed.
However, too much water will settle the paste at the base of the pavement and clog the pores. Meanwhile, too much water increases the distance between particles, causing higher porosity and lower strength. Wanielista and Chopra11 stated that “the correct amount of water will maximize the strength without compromising the permeability characteristics of the pervious concrete.” 13
2.3.6 Admixtures
Admixtures are sometime necessary for pervious concrete to obtain good properties. Typical admixtures used in pervious concrete include HRWR, MRWR, water retarder, viscosity modifying admixtures, air-entraining and fibers. The admixtures should follow standards of ASTM C 49421 (chemical admixtures) and
ASTM C 26022 (Air-entraining admixtures).
2.3.6.1 High/Middle Range Water Reducer
Based on experimental results, less water is used in pervious concrete than in regular concrete2,9,18. One of the reasons is too much water causes settlement of cement at the bottom resulting in clogging. To decrease the water content, a HRWR or MRWR is often used. The dosages of water reducer used in pervious concrete are various and should closely follow manufacturer’s recommendation.
2.3.6.2 Water Retarder
The National Ready Mixed Concrete Association reports that “because of the rapid setting time associated with pervious concrete, retarders or hydration-stabilizing admixtures are commonly used”2. Water retarder can extend setting time so that the hydration of cement is fully developed.
2.3.6.3 Viscosity Modifying Admixtures
Compared to regular concrete, pervious concrete is very dry and hard to cast.
However with the usage of viscosity modifying admixtures, the workability can be highly improved, and pervious concrete can be more manageable18. In a field project, 14
Hein and Schindler18 found that “The use of water reducing admixtures in combination with viscosity modifying admixtures significantly reduced or eliminated most of the previous difficulties experienced placing pervious concrete pavements”.
Since the usage of viscosity eliminated hard physical labor and improved the smoothness and quality of pavement, Hein and Schindler claimed it as “a major milestone in facilitating successful placement of quality pervious concrete pavements”.
2.3.6.4 Air-entraining Admixtures
Air-entraining admixtures can be used in pervious concrete to improve its freeze-thaw durability. Air-entraining admixtures can produce micro-closed air holes, which can flexibly respond to the forces generated by freeze-thaw cycles. These micro air bubbles are different from the voids in pervious concrete, which are open holes and do not functional to sustain freeze-thaw forces.
2.3.6.5 Fibers
Fibers can be used in pervious concrete if higher compressive strength is required. Experiments by Schaefer et al.23 showed that adding latex fibers increases strength of pervious concrete; Yang and Jiang6 used organic polymer fibers and found that they enhanced the strength of pervious concrete greatly. However, they typically also cause a decrease in hydraulic conductivity.
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2.4 Important Properties of Pervious Concrete
Permeability, compressive strength, freeze-thaw durability are important properties of pervious concrete. They are affected by many factors such as water content, void content, aggregate gradations, W/C ratio, and A/C ratio. Research has been carried out to study the effect of different factors. In this research W/C ratio stands for Water/total Cementitious Material ratio for simplification. A/C ratio stands for total Aggregate/total Cementitious Materials ratio.
2.4.1 Permeability
High permeability is the primary characteristic of pervious concrete. Based on previous studies24,25,26,27 two permeability tests, the falling head tests and constant head tests were both used to measure the hydraulic conductivity of pervious concrete samples taken from sites or made in labs. Some lab testing also simulated the conditions of pervious concrete in actual applications. Experimental and field tests found that the typical permeability is larger than 0.1cm/sec or 140in/hour10, which is considered as the lower limit of pervious concrete permeability.
McCain and Dewoolkar26 published a study on pervious concrete, in which falling head permeability tests were carried out on three sets of specimens with diameter 3 inches, 4 inches, and 6 inches, respectively. The falling head permeability tests also simulated the situation of winter surface, which was covered by sand-salt mixture. The results showed that the hydraulic conductivity ranged from 0.68cm/s to
0.98cm/s. One significant and special contribution of this article was the study on the
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decrease of permeability by simulating the winter surface. The results illustrated 15% average reduction on hydraulic conductivity. However, the permeability was still in the allowable range (greater than 0.1cm/s).
Crouch et al. 27 used a triaxial flexible-wall constant head permeameter to measure the permeability of pervious concrete in the range of 1 to 14,000 inches/hour
(0.001 to 10 cm/sec). Crouch et al. found the constant head permeability was a function of three factors: effective air void content, effective void size, and drain down, where “drain down is a result of too much paste for the applied compactive effort or the paste being too fluid”, sealing the lower surface of pervious concrete sample27.
Montes and Haselbach25 compared the hydraulic conductivity of pervious concrete samples taken from three different field-placed slabs using a falling head permeameter system. To investigate the factors affecting permeability of pervious concrete, samples were collected with different W/C ratios and A/C ratios. Based on previous studies7,24,25,26, the average porosity of the samples range from 15% to 30% is typical for pervious concrete. The results indicated that the hydraulic conductivity is dependent on the porosity. By comparing experimental results with the calculated values from the equation, Montes and Haselbach25 studied the relationship between porosity and hydraulic conductivity and found most fitted value of α=17.9 ± 2.3
3 2 (Figure 2.1) in the Carman-Kozeny equation: ks = α [p /(1-p) ], where: ks = the saturated hydraulic conductivity, p = porosity of pervious concrete (adapted from
Montes and Haselbach25). The effect of cementitious material and the non-spherical shape of particles had been considered in this equation.
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Figure 2.1. Model Resulting from the Nonlinear Fitting of the Saturated Hydraulic Conductivity and Total Porosity Data to the Carman-Kozeny Equation25
Montes and Haselbach25 used the Ergun equation to analyze the flow condition inside the pervious concrete samples. The Ergun equation has the form: f’ =
150/Re’+ 7/4, where f’ is a dimensionless friction factor, Re’ is a modified Reynolds number which indicates the particular fluid porous media flow situation. The results of Ergun model calculation presented for pervious concrete samples with various porosities and saturated hydraulic conductivities were presented by Montes and
Haselbach25 (Figure 2.1). The trial results indicated that most of the samples were in
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the laminar flow region. However, the flow regime may fall into the transition region for higher porosity samples impacted by higher hydraulic head25.
Figure 2.2. Plot of the Ergun Equation and Values Calculated Using the Falling Head Experimental Data from Samples Calculated with Dp = 0.1, Dp = 0.3, and Dp = 0.6.(adapted from Montes and Haselbach 25) Note: Dp=0.1, 0.3, and 0.6cm can be interpreted as particles with different average diameters and sphericities so that Dp would be equal to 0.1, 0.3, or 0.6 cm.
Montes and Haselbach25 established the equation between hydraulic
3 2 conductivity and porosity of pervious concrete sample as kS = 18 p / (1-p) , which show a high coefficient value between experiment and calculated results. However, they also claimed the validation of the equation was for the pervious concrete samples in that specific study, in which the size of aggregate was 3/8 inches ~ 5/8 inches, and 19
the porosity ranged from 15% to 32%. Although the application of equation is limited, the study showed the flow regime in pervious concrete is in the laminar flow region, in which Darcy’s law can be applied. This study is significant because it verified the validation of Darcy’s law, which is assumed to be valid in most study of pervious concrete permeability.
All articles stated above considered the permeability of pervious concrete in freshly cast condition. Researchers rarely discussed the performance of pervious concrete that had been used for a while or had become partially clogged. Haselbach et al.24 studied the permeability of pervious concrete in partially clogged condition.
Considering the in-situ pervious concrete pavement, clogging is one of the important concerns because it will decrease the porosity of pervious concrete, decreasing permeability. In order to study the effect of clogging, Haselbach et al.24 started with predicting the permeability of pervious concrete with formulas based on empirical statistics and theoretical analysis. Then experiments were conducted to simulate the rainfall and clogging situation, and the results were used to compare with predicted values. The comparison showed good agreement between experimental results and calculated values, verifying the validity of the prediction. The specialty of this research is that it proposed models to predict the permeability of pervious concrete under the worst condition of clogging, which is usually ignored in most research.
2.4.2 Compressive Strength
According to ASTM C 3928, a minimum compressive strength of 300psi is required for pervious concrete. According to field and laboratory tests, pervious 20
concrete compressive strength regularly falls in a range of 400psi ~ 4,000psi (2.8MPa
~ 28MPa). But the common strength is from 600psi to 1,500psi (4MPa to 10MPa).
Laboratory studies have found compressive strength ranges from 600 psi to 3,600 psi
(4 MPa to 25 MPa)9,10,11.
Wanielista and Chopra11 summarized previous studies on compressive strength of pervious concrete and stated that researchers agreed that factors affect pervious concrete compressive strength included: A/C ratio, W/C ratio, coarse aggregate size, compaction, and curing. “Researchers disagree as to whether pervious concrete can consistently attain compressive strengths equal to conventional concrete”.
2.4.3 Freeze-thaw Durability
Freeze-thaw durability is a crucial property to evaluate the suitability of pervious concrete in cold weather. Freeze-thaw deterioration happens when concrete is more than 91% saturated, which is generally true for concrete surfaces. When water freezes, its volume will increase. The expansion of volume generates large pressures, which act on concrete. When the pressure is in excess of the tensile strength of concrete or mortar layer at a surface, cracking and scaling will occur.
Although some field projects indicated that pervious concrete performed well in freeze-thaw situations, it must be used carefully in cold weather regions. The
NRMCA29 recommends the utilization of pervious concrete in different areas that have various weather conditions. Table 2.1 shows the classification of different districts and the suitability of using pervious concrete: 21
Region Description Precipitation Pervious Pervious Region in in Winter concrete concrete base USA Dry freeze Annual little no special 4 in to 8 in Many parts and Hard freeze-thaw precaution thick, clean of the dry freeze cycle: 15+ aggregate Western U. S
Wet Annual Normal no special 4 in to 8 in Many parts freeze freeze-thaw precaution thick, clean of the cycle: 15+ aggregate middle part of the Eastern U. S Hard wet Certain wet freeze areas Precautions 8 in to 24 in freeze where the ground stays required thick, clean frozen as a result of a long aggregate; air- continuous period of average entraining daily temperatures below admixtures; freezing place PVC pipe High Ground water level is less Not ground than 3 ft from the top of recommend water surface or where substantial table moisture can flow from higher ground Table 2.1. NMCRA Classification of Regions and Recommendation of Precautions of Utilizing pervious concrete 29
NRMCA29 suggests one method to improve the freeze-thaw resistant ability is to entrain air. The microscopic entrained air bubbles that are evenly distributed in the paste can help to relieve any pressure buildup. Generally for regular concrete, an air entrainment of 4% ~ 8% can help to reach satisfactory performance in freeze-thaw condition. However, no specific content has been investigated for pervious concrete.
In fact, the standard for conventional concrete is unsuitable to quantify the amount of entrainment for pervious concrete29. Another method to improve the freeze-thaw durability is to eliminate the saturation of pavement. By placing pervious concrete on
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a thick layer of 8 to 24 inches (200 to 600mm) of open graded stone base, saturation can be effectively avoided23.
In order to test the freeze-thaw resistance of pervious concrete, some researchers did tests on saturated pervious concrete following procedure A, Rapid
Freezing and Thawing in Water of ASTM C 66617, requiring less than 5% mass loss after 300 freeze-thaw cycles10. However, the fully saturated condition in procedure A is very severe and not representative of field conditions29. Theoretically, partially saturated pervious concrete performs well in freeze thaw region because the voids in concrete can provide sufficient space for water to move. However, a fully saturated condition may exist; and pervious concrete should be avoided in regions where this situation is most likely to happen.
Schaefer et al.23 stated the failure mechanism of pervious concrete when subjected to freeze-thaw cycles is either a result of aggregate deterioration or cement paste matrix failure. Aggregate failure is seen by the deterioration or splitting of the aggregate where a portion (usually 15%) of an aggregate particle becomes separated from the concrete. Cement paste failure is observed by the raveling of entire pieces of aggregate from the concrete. According to the experimental results presented by
Schaefer et al., “in general, mixes containing limestone (i.e. Mix 3/8-LS) failed by the deterioration of the aggregate; however, mixes containing the smaller size No. 4 river gravel failed due to aggregate deterioration and splitting”23.
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2.4.4 Modulus of Elasticity
Dynamic modulus of elasticity is another important mechanical characteristic of pervious concrete. The elastic modulus shows the resistance performance of pervious concrete to fatigue, and is significant for evaluating the durability of pavements, which is one of the most important indices to evaluate the pervious- concrete lifespan.
Crouch et al.9 tested the static moduli of four different pervious concrete mixes with various aggregate sizes and gradations. The results showed that the static elastic modulus was inversely proportional to the void content. And the optimum void range which is from 23% to 31% happened in the mix with uniform gradation.
Crouch et al.9 found that the static elastic modulus decreased with increasing aggregate and decreasing paste. No effect of aggregate sizes on static elastic modulus has been shown.
2.5 Factors Affect Compressive Strength and Permeability of
Pervious Concrete
The compressive strength and permeability of pervious concrete have been investigated and their relationships to void content were found. Higher void content usually leads to higher permeability and lower compressive strength. Other factors have also been found through experiments. These factors include aggregate, W/C ratio, A/C ratio, fly ash, compaction energy9,23,27.
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2.5.1 Effect of Void Content
Schaefer et al.23 studied effects of different proportions of mixture on the properties of pervious concrete, and provided results to show the relationship between strength, void content and permeability for several trial mixes of pervious concrete.
The experimental results showed that the permeability increased and compressive strength decreased with increasing void content. The relationship is illustrated in
Figure 2.3. As shown, when the void content increased from 15% to 32%, the 7-day compressive strength of pervious concrete decreased from 3,200psi to 1,300psi, while the permeability increases from 50in/hour to 2,000in/hour. As can be seen in the figure, the effect of void content on the measured permeability increased when the void content increased from about 25% to 32%. Their tests showed that the increase of permeability became more apparent when the void content was relatively large, while the compressive strength as a function of void content remains linear.
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Figure 2.3. Relationship between Strength, Void Content and Permeability for Several Trial Mixes of Portland Cement Pervious Concrete23
Crouch et al.27 also studied the correlation between void content and permeability in both laboratory and field cored specimens. The results showed agreement with those from Schaefer et al.23. The average values illustrated high strength of bond between void content and permeability with correlation coefficient
0.9737. In addition by comparing the laboratory results with experimental results from prior studies, Crouch et al.27 found that the permeability at low void content showed high consistency with the previous experimental results30,31 than those at high void content. This indicated compressive strength values might be more consistent at low void content.
Void content has been found as the primary factor that determines the properties of pervious concrete. It was found to be determined from the concrete mix, including amount of aggregate, cementitious materials, and water2.
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2.5.2 Effect of Aggregate
The effect of aggregate on compressive strength and permeability of pervious concrete comes from the coarse aggregate size, type, gradation, and the percentage of fine aggregate.
2.5.2.1 Effect of Coarse Aggregate Type, Size and Gradation
Mulligan32 stated that since cement bond is limited in pervious concrete and
“the aggregate rely on the contact surfaces between one another, the aggregate with higher stiffness such as granite or quartz would have higher compressive strength than a softer aggregate such as limestone.
Besides the effect of aggregate type, the size of aggregate is another important factor for compressive strength and permeability of pervious concrete. Yang and
Jiang6 conducted experiments on pervious concrete mixes having various aggregate sizes. The results showed that the compressive strength was improved by decreasing the aggregate size. Yang and Jiang analyzed that the reason that smaller aggregate size generated higher compressive strength might because it enlarged the bond area between aggregates. However, decreasing aggregate size also resulted in a decreasing in the permeability.
The gradation of aggregate also affects the properties of pervious concrete.
Crouch et al.9 found that a more uniform gradation deduced to slightly higher effective void content. Furthermore, the compressive strength was higher at the same void content in mix that having uniform gradation. The effect of gradation on compressive strength and permeability was also studied by Wang et al.10. They 27
showed that a single aggregate size for the pervious concrete had higher permeability than uniformly graded aggregate mixtures at the same void content.
2.5.2.2 Effect of Fine Aggregate
The experiments carried out by Wang et al.10 indicated that replacement of 7% of coarse aggregate by sand can improve the compressive strength up to 50%.
However, the void content is deduced by 10%, decreasing the permeability. Although the permeability decreased in those experiments, it was greater than 140in/hour10.
2.5.3 Effect of Aggregate/Cement Material Ratio
The effect of A/C ratio is illustrated in the research done by Crouch et al.9.
The experimental results showed that increasing the aggregate amount in pervious concrete results in higher effective void content and lower compressive strength.
Crouch et al.9 explained the reason of this phenomenon: “An increased aggregate amount also results in a decreased past amount. Hence, there is less paste to fill up the voids, resulting in higher void contents. Also, less paste is available for aggregate bonding, which lowers the compressive strength and modulus of elasticity.”
2.5.4 Effect of Water/Cement Ratio
Various W/C ratios have been recommended, normally falling in a range between 0.22 and 0.45. In the brochure “CIP 38 – pervious concrete”1 published by
NRMCA, a range of 0.35 to 0.45 of W/C ratio is given as a typical ratio for pervious concrete. However, Wang et al.10 mixed pervious concrete batches with W/C ratios
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0.22 and 0.27, and suggested using the lower value, if workability could be maintained. In contrast, in an actual applicaiton published by NRMCA29 W/C ratio up to 0.55 was used.
W/C should be large enough so that hydration of cementitious materials can fully develop. Yang and Jiang6 pointed out that the cement bond should provide good connection between aggregate so that the failure is by splitting of the aggregate, in which way the mixture most effectively works. However, too much water may decrease the strength, which is known to be the case in conventional concrete.
Furthermore, excessive water will result in settlement of paste, sealing the bottom of pervious concrete.
2.5.5 Effect of fly ash
Generally, fly ash is realized to be able to decrease the permeability of conventional concrete, increase freeze-thaw durability of concrete, and improve the later-age strength of concrete. The effect of fly ash will be thoroughly discussed in
Chapter 3.
2.5.6 Effect of Compaction Energy
Compaction energy has been shown by several researchers12,13,23,27 to affect the compressive strength, freeze-thaw durability, and permeability.
Suleiman et al.12 found the significant effect of compaction energy on freeze- thaw durability and compaction failure mode of pervious concrete based on the experiments conducted by Schaefer et al.23. The specimens compacted at lower 29
energy sustained less cycles of freeze-thaw (110 cycles) at failure than those (failed at
153 cycles and 196 cycles) compacted at higher energy. Suleiman et al.23 also found an interesting phenomenon that samples compacted at regular compaction energy failed through the aggregate, while samples compacted at lower energy failed through both aggregate and paste.
Crouch et al.27 studied the effect of compaction energy on permeability by comparing the experimental results of specimens with the same mixture design while compacted at six different compaction efforts. By investigating the effective air void content and the permeability of both in field and laboratory pervious concrete mixtures, Crouch et al. found that larger compaction effort resulted in less effective void content of pervious concrete.
To further study the effect of compaction energy, various compaction methods were used and compared by Rizvi et al.13. The compaction method is determined from the compaction equipment, compaction cycles, and compaction forces. Widely used compaction equipment includes standard tamping rod, standard Proctor hammer in laboratory and compact roller in field.
In the research reported by Rizvi et al.13, five different consolidation techniques as illustrated in Table 2.2 were used to cast identical 6in x 12in cylinders.
For each consolidation technique, samples were prepared for 7, 14 and 28 day compressive strength testing, permeability, and air void testing. The results revealed the optimum compaction technique was a standard Proctor hammer 10times/layer for
2 layers. Samples compacted by this method achieve both relatively high compressive strength and high permeability. In addition, the cylinders compacted by this method
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“also achieved the most consistent results with the least variance for compressive strength and relatively low standard deviations for permeability and air void”13.
Drops 28Days /Tamping Voids Compressive Permeability Method Layers rod/layer (%) Strength (MPa) (cm/s) Rod 3 25 18.5 18.3 0.719 Rod 3 15 21.2 21 1.03 Rod 3 5 21.8 15.7 1.027 Proctor 2 10 19.9 17.5 0.584 Hammer Proctor Hammer 2 20 17.2 20.7 1.041 Table 2.2. Compaction Method Conducted by Rizvi et al.13
Compared to the lab testing, the field compaction methods have been less studied. However, Hein and Schindler18, when reviewing the projects on Auburn
University campus, mentioned the different compaction results of using vibrating roller and hand roller in field. By observing these field projects, he stated that
“vibrating roller appeared to seal the surface and collapse the pores, providing too great a compactive effort. The hand roller guided by side forms seemed to provide the smoothest finish.”
2.5.7 Effect of Fibers
The positive effect of fibers has been shown in many studies. Yang and Jiang6 added polymer fibers into the pervious concrete and obtained increased compressive
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strength. The increase of compressive strength might because the fiber enhanced the binder6. In addition, the permeability was unaffected, which differed to the effects of other factors and therefore enhanced the advantage of adding fibers in pervious concrete.
2.5.8 Effect of Other Factors
Some factors such as specimen size and testing method have also been studied in a few cases. Although these factors are not critical to determine pervious concrete properties, they were discussed and may be considered in some situations.
The size of specimen is not usually considered because they are generally compacted to the standard size defined by national codes. For example, 4in x 8in cylinders are normally used in the United States for compressive strength test; 6in x
12in cylinders were cast in the University of Waterloo in Canada, while rectangular cylinders were used in China. To study the impact of diameter on cylinder samples,
McCain and Dewoolkar26 tested the compressive strength on three sets of specimens with diameter of 3 inches, 4 inches, and 6 inches. For each set, three identical specimens were tested. The compressive strength drawn from these experiments ranged between 650psi (4.5MPa) and 1,100psi (7.6MPa). Even for specimens that were the same size, the compressive strengths were different with 150 to 260psi. The experimental results showed that the effect of specimen size was unpredictable.
However, the specimens with 4 inches diameters showed higher average compressive strength compared to the 3 inches and 6 inches diameters specimens. However, the
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effect of specimen size could not be distinguished from the effect of inconsistent casting of specimens due to the limited experimental results.
Another factor that affects the compressive strength of pervious concrete is capping. Capping is sometimes used in compressive strength test to smooth the surface of pervious concrete specimen, reducing the effect of stress concentration consequently. The studies on pervious concrete conducted by Kevern33 showed that the specimens with sulfur capping compound has higher compressive strength than those without capping.
2.6 Standard Test Methods
Some tests methods that are required for regular concrete may be unnecessary for pervious concrete. For example, since pervious concrete has low water content and lower fluidity, the slump test is not informative.
Currently, standard test methods for field permeability, compressive strength, hardened concrete density and porosity, and flexural strength of pervious concrete are under development by ASTM C 09/4934. Only ASTM C 1688 with title of Fresh concrete Density (Unit Weight) and Void Content has been published35. Obviously, the progress of developing standard test methods for pervious concrete is only at beginning. No standard ASTM test procedure has been suggested to measure the entrained air content for pervious concrete. In fact, before the finalization of testing/mixing methods for pervious concrete, people are using those designed for conventional concrete, even those methods may not be appropriate in many situations.
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2.7 Pervious Concrete Design
This section introduces pervious concrete mix design, pervious concrete pavement structure and hydraulic design. The mix design of pervious concrete is concerned with the properties of pervious concrete used in the pavement; while the pervious concrete pavement design is the process of designing the whole system of pavement including the pavement surface and the subgrade layer.
2.7.1 Pervious Concrete Mix Design
Pervious concrete mix design should generate batches that satisfy compressive strength and permeability requirements. Typical mix designs of pervious concrete have been recommended by different agencies such as National Ready Mixed concrete Association, the Southern California Ready Mix concrete Association, and the Euclid Chemical Company. The recommended mix designs are shown in Table
2.3, Table 2.4, and Table 2.5. The examples of mix design in laboratory experiments and in field projects have been done and are listed in Appendix I.
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Material Amount (pcy) Cementitious Materials 450 – 700 lbs Aggregate 2000 – 2500 lbs W/C by Mass 0.27 – 0.34 A/C by Mass 4 – 4.5 : 1 Table 2.3. Recommended Typical Mix Design by National Ready Mixed Concrete Association36
Material Amount (pcy) Compacted Voids ≥ 10% Cement ≥580 lbs ASTM C-618 fly ash 50 – 116 lbs Total Cementitious Materials 630 – 696 lbs Aggregate 27 ft3 Table 2.4. Recommended Typical Mix Design by the Southern California Ready Mix Concrete Association (adapted from 1)
Material Amount (pcy) Cement 600 lbs Coarse Aggregate 3/8 Limestone 2600 lbs Water 160 lbs W/C by Mass 0.27 Table 2.5. Recommended Typical Mix Design by the Euclid Chemical Company37
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As shown, there is no single accepted mix design for pervious concrete. Since less water is used than typical for conventional concrete, pervious concrete appears drier and more sensitive to the actual water content. Water reducer and water retarder are used in most cases. In addition, the amount of water and other materials are varied with the mixing condition and may need to be adjusted during mixing process. Hence, the mixing of pervious concrete should be done by a crew who has been trained in a certification program.
2.7.2 Pervious Concrete Pavement Hydraulic Design
The purpose of hydraulic design is to provide a pavement system in which water can easily pass through the top layer, be temporarily stored in the subgrade layer and freely enter a shallow groundwater.
North Carolina Department of Environment and Natural Resources
(NCDENR) 38 introduced process of hydraulic design for permeable pavement as illustrated below:
(1) Select Design Storm
(2) Determine Water Storage Capacity of Pavement
(3) Select Exfiltration Time
(4) Calculate Drawdown (Exfiltration) Time
(5) Compare Actual Drawndown with Design Exfiltration
Following this process, designer can calculate the desirable pavement open space, which can produce the required drainage at a certain rainfall rate. The pavement is then designed to have this open space. 36
In addition, Malcolm et al.39 developed a program to do the hydraulic design based on the pervious concrete hydrological analysis program. Input parameters of the program contains trial thickness of pervious concrete and gravel base, porosity of pervious concrete and gravel base, local rainfall information, and adjacent areas which will drain onto pervious concrete. After analyzing the input parameters, the software can generate a chart to model the flowing situation of rainfall with elapsed time. Hence, a satisfactory thickness of the pavement and subgrade layers can be determined by examining the flowing situation.
2.7.3 Pervious Concrete Pavement Structural Design
NCDENR also developed a structural design worksheet for permeable pavements40. According to the worksheet, the structural design of pervious concrete includes four elements: total traffic, in-situ soil strength, environmental elements, and actual layer design. The primary purpose of the structural design is to examine and finalize the thickness of subgrade layer. The top layer of pavement is set to the pervious concrete block, which is usually 6 inches or more. The thickness of pervious concrete pavement is greater than those of regular concrete that is 4 inches in normal11 because pervious concrete has lower compressive strength than regular concrete.
Before beginning the structural design, the thickness of each layer has been determined from the hydraulic design. Only the thickness of subgrade layer will be checked in the structural design to determine whether or not the pavement is strong enough. A formula is given to determine a calculated Structural Number (SNcalc), 37
which will be compared to the Structural Number (SN) determined from a nomograph design chart40 shown in Figure 2.4. Figure 2.4 gives an example of how to obtain a
SN: 1) from soil support value of 7 and total equivalent 18-kip single-axle load applications of 1500psi, the structural number of 2.3 is obtained by extending a line to the structure number scale; 2) connects the structure number of 2.3 and regional factor of 4.0, and extends the line to the scale of weighted structure number, SN = 3.2 is obtained. If calculated SNcalc is greater than the SN, the thickness of subgrade is satisfied. Otherwise, the thickness needs to be increased. Generally, 6 inches to 12 inches layer of permeable subbase is used in pervious concrete pavement.
Figure 2.4. Nomograph to Determine Structural Number (Pavement Strength) 40
38
The permeable subgrade might be composed of either 1 inch maximum-size aggregate, or a natural subgrade soil that is predominantly sandy with moderate amounts of silt, clay, and poorly-graded soil38. However, the top 6 inches of the subgrade is usually made of #4 granular or gravelly materials with no more than a moderate amount (10%) of silt or clay41. The design of subbase is primarily based on its stormwater storage ability, and the modulus of subgrade reaction (k) is another design criterion. NCDENR suggests a suitable range 150-175 lb/in3 for k value, which can be obtained using theoretical relationship between k values from plate-bearing tests (ASTM D 1196 and AASHTO T 222), or estimated from the elastic modulus of subgrade soil 38.
8 Funding Universe, “George Wimpey plc.”
9 Crouch, L. K., Pitt, J. and Hewitt, R. (2007). “Aggregate effects on pervious Portland cement concrete static modulus of elasticity.” Journal of Materials in Civil Engineering, ASCE. 10 Wang, K., Schaefer, V. R., Kevern, J. T., and Suleiman, M. T. (2006). “Development of mix proportion for functional and durable pervious concrete.” submitted to NRMCA concrete technology forum: focus on pervious concrete.
11 Wanielista, M., and Chopra, M. (2007). “Performance assessment of Portland cement pervious pavement.” Final Report FDOT project BD521-02,
12 Suleiman, M. T., Kevern, J., Schaefer, V. R., and Wang, K., “Effect of compaction energy on pervious concrete properties.” Iowa State University,
39
13 Rizvi, R., Tighe, S., Henderson, V., and Norris, J. (2009). “Laboratory sample preparation techniques for Pervious Concrete.” TRB Annual Meeting. Report No. 09-1962, p. 16.
14 “Rocky Mountain Construction.” Brochure of Associated Construction Publication,
15 Houston Advanced Research Center (HARC) (2004).
16 Kim, H. K., and Lee, H. K. (2010) “Acoustic absorption modeling of porous concrete considering the gradation and shape of aggregates and void content.” Journal of Sound and Vibration, 329(7), 866-879,
17 ASTM C 666 (2009). “Standard test method for resistance of concrete to rapid freezing and thawing.” ASTM international, DOI: 10.1520/C0666_C0666M-03,
18 Hein, M. F, and Schindler, A. K. (2007). “Learning pervious: concrete collaboration on a university campus.”
19 Dietz, M. E. (2007). “Low impact development practices: a review of current research and recommendations for future directions.” Water Air Soil Pollutant, v. 186, p. 351-363.
20 ASTM C 33. (2008). “Standard specification for concrete aggregates.” ASTM international, DOI: 10.1520/C0033_C0033M-08,
21 ASTM C 494. “Standard specification for chemical admixtures for concrete.” ASTM international, DOI: 1520/C0494_C0494M-10,
40
22 ASTM C 260 (2006). “Standard specification for air-engineering admixtures for concrete.” ASTM international, DOI: 10.1520/C0260-06,
23 Schaefer, V. R., Wang, K., Suleiman, M. T., and Kevern, J. T. (2006). “Mix design development for pervious concrete in cold weather climates, final report.” National Concrete Pavement Technology Center, Iowa State University.
24 Haselbach, L. M., Valavala, S., and Montes, F. (2006). “Permeability predictions for sand-clogged Portland cement pervious concrete pavement systems.” Journal of Environmental Management, v. 81, p. 42-49.
25 Montes, F., and Haselbach, L. M.(2006). “Measuring hydraulic conductivity in pervious concrete.” Environmental Engineering Science, 23(6).
26 McCain, G. N., and Dewoolkar, M. M. (2009). “Strength and permeability characteristics of porous concrete pavements.” TRB 88th Annual Meeting Compendium of Papers (CD-ROM), Transportation Research Board 88TH Annual Meeting.
27 Crouch, L. K., Smith, N., Walker, A. C., Dunn, T. R., and Sparkman, A. (2006). “Determining pervious PCC permeability with a simple triaxial flexible-wall constant head permeameter.” TRB 2006 Annual Meeting (CD-ROM),
28 ASTM C 39 (2009). “Standard test method for compressive strength of cylindrical concrete specimens.” ASTM international, DOI: 10.1520/C0039_C0039M-09A,
29 North Carolina Department of Environment and Natural Resources (2004). “Freeze thaw resistance of pervious concrete.” brochure of National Ready Mixed Concrete Association,
30 Wingerter, R., Paine, J. (1989). “Field performance investigation Portland cement pervious pavement.” Florida Concrete and Products Association.
41
31 Meininger, R. C. (1998). “No-fines pervious concrete for paving.” Concrete International, 10(8), 20-27.
32 Mulligan, A. M. (2005). “Attainable compressive strength of pervious concrete paving system.” A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, Department of Civil Engineering, University of Central Florida,
33 Kevern, J. T. (2006). “Mix design development for Portland cement pervious concrete in cold weather climates.” A thesis submitted to the graduate faculty in partial fulfillment of the requirements for the degree of Master of Science, Iowa State University.
34 Haselbach, L. (2009). “Standard test methods for pervious pavements.”
35 ASTM C 1688 (2009). “Fresh concrete density (unit weight) and void content.” ASTM international,
36 North Carolina Department of Environment and Natural Resources (NRMCA).
37 Euclid Chemical Company (2009). “Pervious concrete.” Brochure of Euclid Chemical Company,
38 North Carolina Department of Environment and Natural Resources (NCDENR) (1997).
39 Malcolm, H. R., Leming, M. L., and Nunez, R. A. (2006). North Carolina State University, Raleigh, North Carolina, North Carolina Department of Environment and Natural Resources NCRMCA.
40 North Carolina Department of Environment and Natural Resources (NCDENR). (1997),
42
41 ACI Committee 522. (2006). “Pervious concrete.” ACI 522R-06, American Concrete Institute.
43
CHAPTER 3
LITERATURE REVIEW OF FLY ASH
3.1 Introduction of Coal Combustion Products (CCPs)
According to the U. S. Environmental Protection Agency, Coal Combustion
Products (CCPs) “are the byproducts generated from burning coal in coal-fired power plants. These byproducts include fly ash, bottom ash, boiler slag, and flue gas desulfurization gypsum”42. The CCPs are used in many fields such as engineering construction, agriculture, and waste stabilization. The American Coal Ash
Association (ACAA) released statistic of the multiple applications of CCPs in 2008 in the United States, as shown in Figure 3.1. As shown, CCPs are mainly used in concrete products, structure fills, and wallboard43.
44
Figure 3.1. Uses of Coal Combustion Products in 2008 (AACA adapted from U. S Environmental Protection Agency (EPA)43)
Based on statistics from the committee on Promoting & Advancing Coal
Combustion Products (ACAA)44, the utilization of CCPs from 1966 to 2007 increased from 20% to 40% as shown in Figure 3.2. The figure illustrates that the amount of
CCPs produced dropped in 2003 and has remained steady since 2007. According to the EPA, the utilization rate of CCPs was 36.8% in 2008, and is aimed to increase to
45% in 201145.
45
Figure 3.2. 1966-2007 CCP Beneficial Use vs. Production (AACA44)
CCPs are used in various areas depending on their properties. Typically, bottom ash is used as aggregate in concrete and in cold mixed asphalt, and is also used as a structural fill for embankments and cement-stabilized bases for highway construction. Flue Gas Desulfurization (FGD) material is used for wallboard production, structural fill, cement, concrete, and grout. Boiler slag is used for roofing granules, blasting grit, asphalt concreted aggregate, structural fill, granular base material for pavement construction, stabilized base aggregate. Fly ash can be used in several areas: replacing Portland cement in concrete and grout; filling embankments; and being added in aggregate for highway subgrades of road base 46 . Figure 3.3 presents the percentage of CCPs used in 2003 in the United States. As illustrated, 46
except for boiler slag, only 30% to 50% of each type of CCPs is used. Figure 3.3 also indicates that although only around 40% of generated fly ash was used, the total weight of utilized fly ash accounted more than half of the total utilized CCPs in 2004.
Figure 3.3. Coal Combustion Products Generation and Use (Short Tons) (AACA adapted from EPA46)
3.2 Introduction of Fly Ash
Fly Ash is a fine residue powder byproduct from burning pulverized coal in electric power generating plants. It is the finest and is the most broadly used material of all the byproducts. It is called “fly” ash because it is transported from the combustion chamber by exhaust gases47.
47
3.2.1 Properties of Fly Ash
The physical and chemical properties of fly ash have been studied and analyzed by many researchers48. The study of its physical properties origins back to
1930s when the term of fly ash was generated49. According to EPA, fly ash consists of fine, powdery particles that are predominantly spherical in shape, either solid or hollow, and mostly glassy (amorphous) in nature, having similar physical characteristic with silt50. Compared to its physical properties, its chemical properties are more influenced by the type of burned coal and the techniques used for handling and storage51.
3.2.2 Class C and Class F Fly Ash
Class C and Class F fly ash are classified according to the ASTM C 61852.
Class C contains more lime than is present in class F fly ash. Class C fly ash has both pozzolanic and cementitious properties, and is mostly used in the situations where high early strength is important such as prestressed applications. Class F fly ash is considered an ideal pozzolanic material in mass concrete and high strength mixes, and is recommended to be used in concrete exposed to ground water53.
3.2.3 Utilization of Fly Ash in Concrete
As shown in Figure 3.4, the greatest utilization of fly ash in 2003 according to the American Coal Ash Association was in concrete and grout products. The beneficial results of adding fly ash to concrete include: (1) Increased concrete durability and strength of concrete: the lime from cement hydration reacts with fly 48
ash, increasing the long-term strength of concrete. Compared to plain cement concrete, fly ash concrete gains higher strength after 28 days; (2) Improved concrete workability: fly ash produces more cementitious paste, increasing the lubrication between aggregate and flowability of concrete; the spherical shape of fly ash and its dispersive ability provide effects similar to those of water-reducing agents; the usage of fly ash also reduces the amount of sand needed in the mix to produce workability.
Because sand has a greater specific surface area than larger aggregates and therefore requires more paste, reducing the sand means the paste would efficiently coat the surface area of aggregates54.
Figure 3.4. Top Uses of Coal Fly Ash 2003 (AACA adapted from46)
49
The usage of ash in building application can be traced back to thousands of years ago in ancient Rome, when people used volcanic ash in their construction to strengthen the structure. Examples of the buildings are the Roman Pantheon and the
Coliseum. The fly ash has similar function as the volcanic ash, and this function has been realized for decades. In 1930s, fly ash was first used as mineral filler in asphalt mixes; in 1942, fly ash concrete was used to repair a tunnel spillway at the Hoover
Dam49. Fly ash has now been used as an ingredient in concrete for more than 60 years.
In January of 1974, the Federal Highway Administration (FHWA) encouraged the use of fly ash in concrete pavement with the Notice N 5080.4, urging states to allow partial substitution of fly ash for cement whenever feasible55. The FHWA also indicated that “the replacement of cement with fly ash of the order of 10% to 25% can be made giving equal or better concrete strength and durability.” In January 1983, the
EPA published federal procurement guidelines for cement and concrete containing fly ash, encouraging the utilization of fly ash55. Currently, fly ash is used to replace 5-
65% of the Portland cement2. Because the manufacture of cement is highly energy intensive, using fly ash as an element replacement of in concrete can reduce significantly the environmental cost of concrete.
3.2.4 Environmental Benefits of Fly Ash Use
Using fly ash in place of natural materials can yield benefits to the environment, economic, and product performance improvements by saving source materials, reducing energy consumption and greenhouse gas emissions. The LEED assigns up to 5 credits to the combined usage of fly ash and recycled material56. Fly
50
ash also makes economic benefit because it is often less costly than the materials that it replaces, such as sand, gravel, or gypsum.
3.3 Effect of Fly Ash on Concrete
The positive effects of adding fly ash into concrete have been mentioned before. Most of the effects were drawn from experiment and field projects. This section will discuss the influence of fly ash on concrete in detail by referencing the prior studies.
3.3.1 Thermal Cracking
ISG Headwaters Resources Inc. published a brochure and stated that the existence of fly ash could decrease the rapid heat and consequently reduce the risk of thermal cracking 57 . Many applications indicate that rapid heat gain of cement increases the chances of thermal cracking, leading to reduce concrete strength and durability57. With replacement of fly ash, the chance of thermal cracking will be decreased because only 15% to 35% as much heat as compared to cement at early ages are generated by fly ash.
3.3.2 Compressive Strength
Fly Ash can increase the long-term compressive strength of concrete. Figure
3.5 compares the strength of fly ash concrete with plain cement concrete. In this graph, the plain cement concrete strength increase is slower than fly ash concrete strength increase. In both types of concrete, strength increase slows after the initial 7
51
day curing period. The plain cement concrete has higher strength than fly ash concrete before 28 days curing period and lower compressive strength after then.
Figure 3.5. Comparison between Ash Concrete Compressive Strength and Plain Cement Concrete Compressive Strength57.
The increased compressive strength of fly ash concrete compared with plain cement concrete can be explained by examining the chemical reaction taking place in the concrete. Typically, Portland cement and water react to produce durable binder
(Calcium Silicate Hydrate (CSH)) and a nondurable binder (free lime). In fly ash concrete, the free lime continues to react with fly ash to produce more CSH.
According to the Headwater Resources report57, approximately ¼ pounds of free lime will be produced with 1 pound of cement. This indicates that large amount of free lime exists in plain cement concrete and available to react with fly ash to produce more CSH. Hence, the utilization of fly ash can save lots of cement while maintaining
52
the compressive strength of concrete because they generate the same binder with cement does. Fly ash can also reduce W/C ratio with typical 2% to 10% water reduction because of its spherical shape of the individual particles57. The compressive strength might be improved because of the decrease of W/C ratio.
3.3.3 Durability
According to the research by Khunthongkeaw and Tangtermsirikul58, fly ash can promote the carbonation process and consequently improve the long-term serviceability of concrete. The CO2 existing in the atmosphere can react with the calcium hydroxide in concrete and reduce the alkalinity of the pore solution. This carbonation process will cause the erosion of steel. Khunthongkeaw and
Tangtermsirikul stated that fly ash can increase the rate of carbonation, and speed up the reduction of alkalinity so that the alkalinity reduction is done in short period time.
In turn, the long-term serviceability could be improved58.
According to the Headwater Resources bulletin No.959, Fly ash can help to increase the freeze-thaw resistance ability of concrete. By reacting with free lime, the fly ash generates more durable binder materials by reacting with free lime. This not only increases the density of concrete, but also decreases the amount of calcium hydroxide which is generated from free lime. Consequently, the minute voids and the potential voids caused by the leaching of calcium hydroxide are decreased. Fly ash spherical shape may reduce the bleed channel and void space, reducing the possibility of water accumulating59.
53
Fly ash increases the durability of concrete. According to the Headwater
Resources bulletin No.2260, practical testing indicated that the DOT’s concrete for bridge superstructures and decks containing 20% fly ash would likely provide a 75- year service life in a marine environment. Because of its advantages in harsh environment, the Utah and Nevada DOTs mandated 20% fly ash usage in all concrete work60.
3.3.4 Permeability
One advantage of decreased permeability is to reduce the rate of ingress of water, corrosive chemicals and oxygen, thus protecting steel reinforcement from corrosion. As discussed before, when more CSH is formed the bond between aggregates is enhanced. At the same time the capillaries in concrete are blocked off during this process, resulting in decreasing permeability. The characteristic that fly ash decreases the permeability of concrete was studied by Elfert (adapted from
Headwater Resources bulletin No.661), and a Cementing Materials in Concrete vs.
Permeability Rate chart shown as Figure 3.6 was released. It is clear from this work that a 30% fly ash replacement of cement dramatically decreased the permeability of concrete. The amount of decrease varied with the amount of cement in concrete mix.
The less cement that concrete had, the more the permeability was decreased.
54
Figure 3.6. Effect of Fly Ash on Permeability of Concrete (adapted from61)
3.3.5 Sulfate Attack
Fly Ash can increase sulfate resistance and reduces alkali-silica reactivity, and
Class F fly ash is more productive than Class C fly ash on this effect 62 . The mechanism of sulfate attack happens in two ways: (1) sulfate reacts with calcium hydroxide (CaOH) and generates gypsum with the volume increased during the process; (2) sulfate reacts with aluminates in concrete and generate expansive compound. Both processes are combined with the expansion of concrete, which is the source of concrete damage. When fly ash is used, it will tie up free lime, thus reduce
55
calcium hydroxide (CaOH). In turn, the chemical reaction in concrete can be reduced and large expansion and damage can be decreased.
3.4 Fly Ash in Pervious Concrete
Based on the publication of Headwaters Resources63, up to 20% percentage of
Portland cement in pervious concrete can be replaced by fly ash. The usage of fly ash can help to improve the workability of the low slump mix so as to benefit the placing and mixing process. The fly ash used in pervious concrete should satisfy the requirement of ASTM C 61852 as specified in ACI 522R-0641.
3.5 Summary
Overall, the usage of fly ash in plain cement concrete has been shown to improve the long-term strength, freeze-thaw durability, and decrease durability of plain cement concrete. However, the study of fly ash effects on pervious concrete was limited. In the following chapters, portions of cement in pervious concrete will be taken place by fly ash. The unit weight, compressive strength and permeability of mixes with various fly ash content will be measured and compared to study the effect of fly ash on pervious concrete.
42 U. S Environmental Protection Agency (EPA). (2010). “What are coal combustion products?”
43 EPA. (2010). “CCP applications.”
44 ACAA (2009). “1996-2007 CCP Beneficial Use v. Production.” American Coal Ash Association, < http://www.acaa-usa.org/associations/8003/files/ Revised_1966_2007_CCP_Prod_v_Use_Chart.pdf >(July 6, 2009). 56
45 EPA “C2P2 results.”
46 EPA. (2005). “Using coal ash in highway construction: a guide to benefits and impacts.” Report no. EPA-530-K-05-002.
47 Coal Ash Research Committee. (2010). “What is coal ash?” University of North Dakota, < http://www.undeerc.org/carrc/html/WhatisCoalAsh.html> (June 30, 2010).
48 Hassett, D. J., and Heebink, L. V. (2001). “JV task 13 – environmental evaluation for utilization of ash in soil stabilization.” 2001-EERC-08-06, Final report prepared for AAD Document Controal, National Energy Technology Laboratory, U.S Department of Energy. Prepared by Energy & Environmental Research Center, University of North Dakota
49 Coal Ash Research Committee. (2010). “Historical timeline.” University of North Dakota,
50 EPA. (2010). “Fly ash.”
51 EPA (2008). “Identification of nonhazardous secondary materials that are solid waste coal combustion residuals - coal fly ash, bottom ash, and boiler slag,
52 ASTM C 618-08a. (2009). “Standard specification for coal fly ash and raw or calcined natural pozzolan for use in concrete.” ASTM international, DOI: 10. 1520/C0618-08
53 Headwaters Resources. (2005). “Fly ash – types and benefits.” Bulletin No. 1, 1 page,
54 “Fly ash for concrete brochure,” ISG Resources, Headwaters Resources,
55 FHWA. (2010). “Fly ash facts for highway engineers.” 57
56 Headwaters Resources. (2005). “Fly ash and concrete in LEED® - NC version 2.2”, Bulletin No. 28, 1 page,
57 Headwaters Resources. (2005). “Fly ash for concrete.”
58 Khunthongkeaw, J., and Tangtermsirikul, S. (2005) “Model for simulating carbonation of fly ash concrete” Journal of Materials in Civil Engineering, ASCE, 17(5), 570-578.
59 Headwaters Resources. (2005). “Fly ash increase resistance to freezing and thawing.” Bulletin No. 9, 1 page.
60 Headwaters Resources. (2005). “High volume fly ash for concrete paving.” Bulletin No. 22, 1 page.
61 Headwaters Resources. (2005). “Fly ash decreases the permeability of concrete.” Bulletin No. 6, 1 page.
62 Headwaters Resources. (2005). “Fly ash increases resistance to sulfate attack.” Bulletin No. 7, 1 page.
63 Headwaters Resources. (2005). “Fly ash decreases the permeability of concrete.” Bulletin No. 29, 1 page.
58
CHAPTER 4
LABORATORY MIX AND TEST
4.1 Introduction
Laboratory preparation and tests will be introduced in this section. First of all, the type and amount of each material were selected. The selection of various material and values of W/C ratio, A/C ratio was based on the literature reviews presented in
Chapter 2 and Chapter 3. Secondly, the unit weight, void content, compressive strength, permeability of pervious concrete were measured according to the appropriate ASTM standards. Some problems encountered during the process of concrete mixing and laboratory testing will also be discussed.
4.2 Mix Preparation
Since the purpose of this research was to identify mixes with high compressive strengths, optimum mix designs obtained by previous studies were taken as reference in this research.
4.2.1 Mix Materials
This section introduces the properties of materials used in this research. All materials were obtained from local sources.
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4.2.1.1 Coarse Aggregate
After reviewing the literature and investigating actual projects, #8 river gravel was used in this research. This material was provided by the Olen Corp. One of the reasons for choosing this gravel was its wide availability. As discussed in Chapter 2, the size and gradation of coarse aggregate is one of the factors that affect the properties of pervious concrete. Based on the study by Schaefer et al.23, the optimum coarse aggregate type gradation was the single sized river gravel that passed through
3/8 inches and was retained in sieve size No. 4. However, this was less practical in field projects. Normally, the material obtained from aggregate supplies was gradated instead of in single size. Hence, #8 river gravel was chosen because it had closest gradation to the optimum one. In addition, this type of coarse aggregate was also widely used by Buckeye Ready-Mix LLC., and Anderson Concrete Corp, which both produce pervious concrete for field projects. The physical properties were provided by the Olen Corp. and are shown in Table 4.1. The grain size distribution is shown in tabular form in Table 4.2 and depicted in Figure 4.1. The distribution of coarse aggregate follows ASTM20.
60
Soundness Loss 5.6 Specific Gravity 2.517 Specific Gravity SSD 2.585 Absorption 2.72 Unit Weight (pcf) 103.0 Clay Lumps & Friable Particles 0.0% Light Weight Chert 0.0% LA Abrasion 22.4 Table 4.1. Physical Properties of #8 River Gravel (Olen Corp.)
1/2 3/8 Sieve Identification inches inches #4 #8 #16 #50 Sieve Size (in) 0.5 0.375 0.187 0.0929 0.0465 0.0118 Percent Finer by Weight 100 92 17 2 1 0.5 Table 4.2. Coarse Aggregate Distribution (Olen Corp.)
#8 River Gravel
100
80
60
40
20 Percentage Finer by Weight (%) Weight by Finer Percentage
0 1 0.1 0.01 Sieve Size (in)
Figure 4.1. Grain Distribution Curve of Size Number 8 River Gravel (Olen Corp.) 61
4.2.1.2 Fine Aggregate
The sand used in this research was QUIKRETE® all purpose sand No. 1152, which met ASTM C 33 specifications20, 64.
4.2.1.3 Cement
Type I cement from St. Marys Inc. was used in this study. The properties of cement were obtained from the company website and are shown in
Table 4.3. The properties met the requirements specified in ASTM standard C15065
(provided by St. Marys Inc., personal communication).
62
Loss on Ignition 2.9%
SiO2 18.9%
Fe2O3 2.16%
Al2O3 4.8% CaO 61.4% Free CaO 1.3% MgO 2.5%
SO3 3.81%
K2O 1.12%
Na2O 0.24%
TiO2 0.3% Insoluble Residue 0.52%
Total Alkali as Na2O 0.98%
CO2 1.3% Limestone 3.1%
CaCO3 in Limestone 97% Table 4.3. Chemical Properties of St. Marys Type I Cement (St. Marys, Inc.)
4.2.1.4 Fly Ash
The fly ash used in experiments was Class F Cardinal fly ash came from
American Electric Power Co. Inc. The specific gravity of fly ash was 2.1 (Modi, personal communication). The chemical properties is physical properties of fly ash is listed in Table 4.4.
63
Particle size (mm) 0.001-0.1 Compressibility (%) 1.8 Dry Density (lb/ft3) 40-90 Permeability 10-6-10-1 Shear strngth cohision (psi) 0-170 Angle of internal friction 24-45 Table 4.4. Physical Properties of fly ash66
4.2.1.5 Admixture
Admixtures including HRWR, MRWR, water retarder, viscosity modifying admixtures, and fibers were provided by the Anderson Concrete Corp. and the Euclid
Chemical Company37. High efficiency polycarboxylate based HRWR PLASTOL
6200 EXT and MRWR EUCON MRX were used to maintain the low W/C ratio and increase the workability. The addition of viscosity modifying admixture made pervious concrete more manageable and improved the adhesion between cement and aggregate, maintaining the air void structure integrity. Eucon W. O. water retarder helped to prolong the hydration of cement. The typical dosages are indicated in Table
4.5. The dosage of water-reducer was based on total weight of cementitious material.
64
Admixtures Name Typical dosage Polypropylene Micro-Fiber Fiberstrand 100 1lb/yd3 High-Range Water Reduer PLASTOL 6200 EXT 3-12fl.oz/100lb Water Retarder EUCON W.O 4-16fl.oz/100lb Mid-Range Water Reducer EUCON MRX 3-12fl.oz/100lb Viscocity Modifying Admixture Visctrol 1-20fl.oz/yd3 Table 4.5. Admixtures from Euclid Chemical Company37
4.2.2 Mix Design
A total of six batches of pervious concrete as indicated in Table 4.6 were studied in this research. The mix design followed the phase-volume design procedure, as introduced in ACI 211.167,68. The A/C ratio and W/C ratio were calculated by weight. The volume of each material was obtained from the division of weight and density. The design volume of each batch was dependent on the volume of materials and design void content. The amount of coarse aggregate was initialized as
2,400lb/yd3 to 2,700lb/yd3. This was used to calculate cement amount and void content according to the design A/C and W/C ratios.
65
Class F Coarse Fly HRWR/ Water Fiber Mix Cement Aggregate Sand Ash MRWR Retarder Visctrol (oz/c No. (lb/yd3) (lb/yd3) (lb/yd3) (lb/yd3) (oz/cwt) (oz/cwt) (oz/cwt) wt) #1 430 1862 103 0 5* 2* 2* -- #2 325 2025 112 139 5* 2* 3* -- #3** 484 2520 0 46 6 12 1 -- #4 334 2184 114 143 8 8 10 1 #5 620 2563 135 12 8 8 10 1 #6 381 2428 122 180 8 8 10 1
Total Total Class F Fly Aggreg Cementitious Sand/Total Ash/Total Mix ates Materials Aggregate Cementitious No. (lb/yd3) (lb/yd3) (%) Material (%) W/C A/C #1 1965 430 5% 0% 0.27 4.6 #2 2137 464 5% 30% 0.22 4.6 #3** 2520 530 0% 9% 0.37 4.8 #4 2298 477 5% 30% 0.32 4.8 #5 2698 632 5% 2% 0.34 4.3 #6 2550 561 5% 32% 0.34 4.5 Table 4.6. Pervious Concrete Mix Design Note: * from Anderson Concrete Corp. ** from Buckeye Ready Mix Corp.
Mix ID as listed in Table 4.7 was assigned to each batch of mix so that the mixing proportions could be easily told by the identification number.
66
Mix No. Mix ID #1 AC46-FA00-WC27-5SD #2 AC46-FA30-WC22-5SD #3 AC48-FA09-WC37-0SD #4 AC48-FA30-WC32-5SD #5 AC43-FA02-WC34-5SD #6 AC45-FA32-WC34-5SD Table 4.7. Mix No. Corresponding to Mix ID. Example: AC48-FA32-WC32-5SD stands for the batch of mix with aggregate/cement ratio 4.8; fly ash content 32%, water/cementitious material ratio is 0.32, and sand content 5% by weight of total aggregates.
A program was developed to do pervious concrete mix design based on the phase-volume design procedure, and is illustrated in Figure 4.2. The input data include total cementitious materials, percentage of fly ash, A/C ratio, W/C ratio, dosages of admixtures, specific gravities of materials, and expected mixed volume.
The calculated results are the amounts of various materials, void content, unit weight, and maximum unit weight. The program can calculate the expected weight of freshly cast specimens in different molds, and helps to inspect the mixing results. By comparing the actual sample weight with the expected sample weight, one can tell if the void content is higher or lower than the expected value. Since the mix volume contains the volume of voids, a change in design total volume will change the void content. Since the program set mix volume is an input, the desired void content is obtained by adjusting the mix volume. Hence, this program can only give expected values, which might be different with the actual results, which varied with compaction method. Nonetheless, it provides a guidance of pervious concrete mix
67
design and helps to evaluate approximate void content immediately after sample being cast.
Figure 4.2. Pervious Concrete Mix Calculation Program
Based on the previous studies, the main index of mix design such as void content, W/C ratio, A/C ratio, amount of fly ash used in this research followed the principles discussed below.
68
4.2.2.1 Void Content
Typically void content between 15% and 20% was the optimum range for pervious concrete to have satisfied permeability and compressive strength23. Most specimens in this research were compacted with void content in this optimum range.
Some samples were compacted to smaller void content.
4.2.2.2 Fine Aggregates
The amount of sand used in these experiments was 5% by weight of total aggregate. This percentage was within the limit proposed by Wang et al.10, who suggested that using a sand content less than 7% by weight improved the compressive strength without affecting the permeability dramatically. The amount of fine aggregate was finally decided after finalizing the A/C, W/C, cement amount and void content.
4.2.2.3 Cement
Since less sand is used in the production of pervious concrete than in conventional concrete, the surface area of the total aggregate is less than in conventional concrete. Hence, the amount of cement could be decreased accordingly.
In addition, if a larger size aggregate is used, the amount of cement can also be decreased because of the decrease of total aggregate surface area. Adjusting the amount of cement made mix design more economic because of the efficient utilization of cement. Moreover, the amount of cement was varied with the amount of fly ash. Typically, the total cementitious material was designed to be between
69
450lb/yd3 to 700lb/yd3,36,37,38. In this research, the amount of total cementitious material ranged between 430lb/yd3 to 630lb/yd3.
4.2.2.4 W/C Ratio and A/C Ratio
In general, A/C ratio can be calculated by either volume or weight. In this study, the A/C ratio was calculated by weight. The optimum W/C and A/C ratio should be determined for the mix so that cement past can cover all surface of aggregate. The amount of paste should be in the range that provides not only enough bond but also high void content, which can develop both high compressive strength and permeability.
Even in conventional concrete, the precise W/C ratio is hard to obtain.
McIntosh (adapted from Kett68) explained the reason for this difficulty: “because the water in the damp aggregate occurs partly on the surface of the particles and partly absorbed into the pores where it is not readily available for affecting the properties of the concrete.” Furthermore, “Even if the absorption characteristics of the aggregated are known in some detail, it is still not possible to assess accurately the amount of water absorbed by the aggregate in a mix: the absorption varies with time and it depends one the degree of saturation of the aggregate before mixing and on whether the particles are surrounded by water, as in the absorption test, or by a cement paste, as in concrete” (McIntosh adapted from Kett68).
The difficulty in achieving a precise W/C ratio is increased in pervious concrete because the “low W/C of these mixtures makes them very sensitive to atmospheric conditions and small changes in moisture conditions, including the
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moisture condition of aggregates before mixing”18. In the brochure published by
NRMCA32, a range of 0.35 to 0.45 of W/C ratio was given as a typical ratio for pervious concrete. It also pointed out that since pervious concrete was very sensitive to the water content, field adjustment of the freshly mixture was usually necessary.
The W/C ratio used in laboratory tests typically ranged from 0.22 to 0.356,9,10,12. By reviewing the values stated above, a W/C ratio ranging from 0.32 to 0.37 was used in this research because pervious concrete with W/C ratio in this range showed satisfied permeability and compressive strength6,9,10,12.
Compared to W/C ratio, A/C ratio was easier to determine. The National
Concrete Ready Mixed Association recommends a typical A/C range of 4.0~4.5:1.
However, based on the laboratory research and actual project statistics, a range of
4.3~7.3:1 is normally used6,9,10,12. In this research, the A/C ratio was limited to a range of 4.2~ 4.8:1.
4.2.3 Mixing Equipment
Two concrete mixers are introduced in this section and the selection of mixer depended on the purpose and the quality of mixing pervious concrete. The first, a 20 quart Blakeslee Mixer, is shown in Figure 4.3. This mixer has advantage of mixing small batches of conventional concrete, especially useful for laboratory purposes.
However, the mixer was not suitable for mixing consistent batches of pervious concrete. The friction between blender and aggregates may decrease the strength of bond between aggregates.
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Figure 4.3. 20 quart Blakeslee Mixer
Uncovered gravel
Balls formed by sand and cement
Figure 4.4. Specimen Mixed Using 20 Quart Blakeslee Mixer
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A sample mixed by the Blakeslee Mixer is shown in Figure 4.4. As shown, some gravel was not covered by cement, and small balls which were composed by cement and sand were distributed through the sample. Although the usage of the
Blakeslee Mixer indicated worse quality than expected, one set of results were listed and compared with those mixed by the other mixer.
The other mixer is a 3.4ft3 capacity Gilson 39555 (drum speed 22 ~ 25 RPM) shown as Figure 4.5. According to the mixing process guidelines, the volume of mixing material should fill in at least 1/3 of the volume of the container so that the materials can be evenly mixed.
Figure 4.5. 3.4ft3 capacity Gilson 39555 (drum speed speed 22 ~ 25 RPM)
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4.2.4 Specimen Mold
The freshly mixed pervious concrete was cast in 4in x 8in cylinders for compressive strength tests and 3in x 6in cylinders for permeability tests.
4.3 Mixing Procedure
The mixing procedure for the pervious concrete is not specified as it is for conventional concrete. However, researchers have modified some conventional concrete mixing procedures to get high quality of pervious concrete. After reviewing articles10,68 and ASTM standards C 19269, the following mixing steps are used in this research:
(1) Mix a small amount of cement (<5% by mass) with coarse aggregate for about
1min;
(2) Add sand, admixtures (disolved in water), and the remaining cement and water;
(3) Mix for 3min, rest for 3min, and finally mix for another 2min;
Before adding the materials, small amount of water and cement with the design W/C ratio was put into the mixer and mix for 5 seconds. In this way, the inside surface of mixer was covered by a thin layer of cement, decreasing amount of material lost during the mixing. The water content was adjusted by observing the fluidity of the mix. The mix was accepted when the concrete could be formed into a ball after being tightly squeezed by hand for 10 seconds, and the ball separated when was thrown onto the mix, and the adhesive residues coated around 50% of the palm; the concrete mix that achieved these two conditions indicated that the mix had appropriate water content (Hunt70, personal communication]). These conditions were 74
important criteria for detecting the quality of pervious concrete mix. Either higher or lower water content may cause worse quality and decrease the permeability or compressive strength of pervious concrete. This method had been routinely used to inspect the quality of pervious concrete mix (Hunt70, personal communication).
4.4 Compaction Method
Different compaction methods as listed in Table 4.8 were used to obtain best compaction results. Rodding, standard Proctor hammer, jigging and dropping methods were all used and their effects were compared. The samples compacted by different methods are shown in Table 4.9.
Compaction Method ID Note Rod-10/3 Rodding 10 times/layer, 3 layers Jig-25/2* Jigging 25times/layer, 2 layers* Proct-5/3 Proctor hammer compacting 5times/layer, 3 layers Drop-5/3 Dropping with 2~3in height 5times/layer, 3 layers Drop-10/3 Dropping with 2~3in height 10times/layer, 3 layers Drop-15/3 Dropping with 2~3in height 15times/layer, 3 layers Table 4.8 Compaction Method ID Explanation Note: *Buckeye Ready-mix Corp.
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Mix ID Compaction Method ID #1 AC46-FA00-WC27-5SD Rod-10/3 #2 AC46-FA30-WC22-5SD Rod-10/3 #3 AC48-FA09-WC37-0SD* Jig-25/3 #4 AC48-FA30-WC32-5SD Drop-10/3 Proct-5/3 Drop-5/3 #5 AC43-FA02-WC34-5SD Drop-10/3 Drop-15/3 Proct-5/3 Drop-5/3 #6 AC45-FA32-WC34-5SD Drop-10/3 Drop-15/3 Table 4.9. Pervious Concrete Mixes Compacted Using Different Methods Mix Note: *Samples Obtained from Buckeye Ready-mix Corp.
4.5 Curing Method
The curing of pervious concrete samples followed ASTM C 19269. The samples were removed from their molds and cured in a water tank at 72.5 ± 3.5 oF
[23.0 ± 2.0 oC]. Two temperature bars and an electronic blower were immersed in water tank to maintain the temperature and uniformed heat distribution. The molds were removed after 7-day curing period (suggestion from Pardi71, personal contact).
In addition, 6 layers of polyethylene plastic sheets were used to cover the surface of molds to prevent water from evaporating. The thickness of plastic coverage was larger than 6mil (0.006in), which satisfies the requirement specified in ASTM C 31 /
C31M - 0972. 76
4.6 Laboratory Tests
Unit weight, void content, compressive strength test, and permeability test were carried out in this study. All the tests followed ASTM standards28,73,74,75,76,77, 78,79.
4.6.1 Unit Weight and Void Content
The unit weight and void content were obtained following the ASTM C
1688/C 1688M35. The unit weight introduced in this study was freshly mixed pervious concrete unit weight, which is obtained right after samples are cast. Equation
4-1 from ASTM C 1688/C 1688M - 0835 was used to calculate the unit weight.
D = (Mc – Mm)/Vm (Equation 4-1) Where:
D = density or unit weight of concrete, lb/ft3.
Mc = mass of mold filled with concrete, lb.
Mm = Mass of mold, lb.
3 Vm = Volume of mold, ft .
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The Void Content was calculated using Equation 4-2:
U = [(T – D)/T] * 100 % (Equation 4-2) Where:
U = percentage of voids in the fresh pervious concrete.
T = theoretical density of the concrete computed on an airfree basis,
lb/ft3.
D = density or unit weight of concrete, lb/ft3.
The air free density was calculated from Equation 4-3
T = MS/VS (Equation 4-3) Where :
MS = total mass of all materials batched, lb.
VS = sum of the absolute volume of the component ingredients in the
batch, ft3.
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Material Specific Gravity #8 River Gravel (SSD) 2.63 Sand 2.61 Cement type I 3.15 Class F Fly Ash 2.1 Fiberstrand 100 0.91 PLASTOL 6200 EXT 1.08 EUCON W.O 1.12 EUCON MRX 1.12 Visctrol 1.21 Table 4.10. Specific Gravities of Materials in Portland Cement Pervious Concrete Mix
The theoretical density was constant for each batch of concrete mix and was calculated in the pervious concrete mix calculation program (Figure 4.2). The total absolute volume was the sum of each material volume, which was calculated by multiplying the mass by the specific gravity. In this study Saturated Surface Dry
(SSD) specific gravity of coarse aggregate and specific gravities of sand, cement, and fly ash listed in Table 4.10 were used.
4.6.2 Compressive Strength
Compressive strength testing followed ASTM C 3928. The testing machine was INSTRON-5585 as shown in Figure 4.6 with maximum capacity of 300kN
(67,400lb).
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Figure 4.6. INSTRON-5585 Compressive Strength Testing Machine
The specimens with curing period of 7, 21, and 28 days were tested for compressive strength. For specimens with uneven surfaces, capping was used to minimize the effect of stress concentration. In addition, two steel caps with rubber cushion were placed on the top and the bottom of each specimen during the compressive strength test.
4.6.3 Permeability
The permeability of pervious concrete was investigated using a modified falling head permeability test. A simple permeameter system as illustrated in
80
Figure 4.7 was developed to measure the hydraulic conductivity of pervious concrete.
The specimen as shown in Figure 4.8 was tightly covered by two layers of side-sealed plastic sheet to prohibit the water from flowing through the side voids. Layers of rubber membranes were placed around the top of specimen to enclose the space between specimen and PVC pipe. Ideally, the specimen was stuck in the pipe at some location, where the bottom of specimen was untouched with the PVC joint 1 so that the hydraulic conductivity was not affected by the change of cross section of PVC joint 1. The rubber membranes and plastic sheets effectively ensured the water flowed vertically through the specimen. The falling head Equation 4-4 was used in the calculation of coefficient of permeability
79 k = (aL/At) * ln(∆h0/∆h1) (Equation 4-4) (ASTM D 5084 )
Where: k = coefficient of permeability, in/sec. a = cross sectional area of the standpipe, in2. L = length of sample, in. A = cross sectional area of specimen, in2. t = time in seconds from ∆h0 to ∆h1. ∆h0 = initial water level, in. ∆h1 = final water level, in.
.
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Inlet
Specimen Position
PVC joint 1
Outlet
PVC valve
Figure 4.7. Falling Head Permeability Test for Pervious Concrete Specimen
Rubber Membranes
Figure 4.8. Pervious Concrete Specimen for Permeability Test
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4.7 Summary of Test Procedure
The pervious concrete mix design and laboratory tests are introduced in this chapter. The mixing materials used in this research were #8 river gravel, type I cement, sand, HRWR, MRWR, water retarder, viscosity modifying admixture and sand. To investigate the effect of substituting fly ash for cement on compressive strength and permeability of pervious concrete, mixes #2 and #6 were designed to contain 30% more fly ash and 30% less cement than mixes #5 and #1. Sand is used in each batch to increase the compressive strength of pervious concrete, and weighted
5% of total aggregates. A pervious concrete mix calculation program was developed to calculate the design values of unit weight and maximum weight of pervious concrete mix.
A 3.4ft3 capacity drum mixer filled with approximate 1.2ft3 of pervious concrete was used in the mix. When mixing process was finished, pervious concrete was casted to 4in x 8in cylindrical samples for compressive strength test, and 3in x
6in cylindrical samples for permeability tests. The unit weight and void content were calculated from the mass, volume, and air free density of each pervious concrete sample, according to ASTM C 168835. Compressive strength tests on specimens with
7, 21, and 28 curing periods were carried out following ASTM C 3931. Capping was used on specimens in the compressive strength test to help the compressive stress be evenly distributed. A modified falling head permeability test was carried out on specimens with various void contents from mixes #5 and #6 so that the relationship between void content and permeability, and the effect of fly ash on permeability of pervious concrete may be obtained from the test results. 83
64 QUIKRETE. (2010). “Sand and gravels material safety data sheet.” QUIKRETE, http://www.quikrete.com/PDFs/MSDS-B1-SandAndGravel.pdf> (June, 2010).
65 ASTM C 150. (2009). “Standard specification for Portland cement.” ASTM international, DOI: 10.1520/C0150_C0150M-09,
66 Walker, H. W., Taerakul, P., Butalia, T. S., Wolfe, W. E., and Dick, W. A. (2001). “Minimizaiton and use of Coal Combustion By-products (CCBs): concepts and applications, adapted from “Handbook of pollution control and waste minimization.” New Mexico State University, Marcel Dekker, Inc., Ghassemi ed., p. 426.
67 ACI Committee 211. (2002). “Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete”, ACI 211.1-91, reapproved 2002.
68 Kett, I. (1999). “Engineered concrete mix design and test methods.” CRC Press, 1st edition, p. 5-10.
69 ASTM C 192. (2007). “Standard practice for making and curing concrete test specimens in the laboratory.” ASTM international, DOI: 10.1520/C0192_C0192M-07,
70 Hunt, D. (2009). “Pervious concrete yield test.” Buckeye Ready Mix, personal communication.
71 Pardi, M. (2010). National Mix Concrete, personal communication.
72 ASTM C31 / C31M. (2008). “Standard practice for making and curing concrete test specimens in the field.” ASTM international, DOI: 10.520/C0031_C0031M- 09,
73 ASTM C 29. (2009). “Standard test method for bulk density (“unit weight”) and voids in aggregate.” ASTM international, DOI: 10.1520/C0029_C0029M-09,
74 ASTM C 94. (2009). “Standard specification for Ready-Mix Concrete.” ASTM international, DOI: 10. 1520/C0094_C0094M-09A,
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75 ASTM C 125. (2009). “Standard terminology relating to concrete and concrete aggregates.” ASTM international, DOI: 10.1520/C0125-09A,
76 ASTM C 127. (2007). “Standard test method for density, relative density (specific gravity) and absorption of coarse aggregate.” ASTM international, DOI: 10.1520/C0127-07,
77 ASTM C 138. (2009). “Standard test method for density (unity weight) yield, and air content (gravimetric) of concrete.” ASTM international, DOI: 10.1520/C0138_C0138M-09,
78 ASTM C 617. (2009). “Standard practice for capping cylindrical concrete specimens.” ASTM international, DOI: 10.1520/C0617-09A,
79 ASTM D 5084-03 (2003). “Standard test methods for measurement of hydraulic conductivity of saturated porous materials using a flexible wall permeameter.” ASTM international, DOI: 10.1520/D5084-03,
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CHAPTER 5
DISCUSSION ON TEST RESULTS
5.1 Introduction
Test results are presented and discussed in this chapter. The compressive strength test results on mixes #1, #2, #3, #4, #5, #6 and permeability test results on mixes #5, #6 are discussed.
5.2 Void Content vs. Unit Weight
The relationship between void content and unit weight is shown in Figure 5.1.
For each batch of pervious concrete, the unit weight decreased with the increase of void content up to 30%, after which it remained approximately stable. As shown in
Figure 5.1, the specimens from mix #1, #3, and #5 had higher predicted unit weight than those from mix #2, #4, and #6 at the same void content. This can be explained by various fly ash and cement content in the mixes. The fly ash in mix #2, #4, #6 substituted 30% amount of cement, while no or very little fly ash was used in mix #1,
#3, and #5. Since cement has higher specific gravity than fly ash, the weight of specimens is correspondingly higher. Furthermore, at the same W/C ratio, mix #5 had lower A/C ratio and higher unit weight than mix #6, indicating that low A/C ratio may generate higher unit weight.
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Void Content (%) vs. Unit Weight (lb/ft3)
150
140 )
3 #1 AC46-FA00-WC27-5SD
130 #2 AC46-FA30-WC22-5SD #3 AC48-FA09-WC37-0SD
120 #4 AC48-FA30-WC32-5SD #5 AC43-FA02-WC34-5SD Unit Weight (lb/ft 110 #6 AC45-FA32-WC34-5SD
100 10% 15% 20% 25% 30% 35% 40% 45% Void Content (%)
Figure 5.1. Relationship between Void Content (%) and Unit Weight (lb/ft3)
5.3 Effect of Compaction Energy
This section discusses the effect of various compaction methods. The average void content of specimens compacted at different methods are illustrated in Figure 5.2.
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Void Content vs. Compaction Method
Rod-10/3 Proct-5/3 Drop-5/3 Drop-10/3 Drop-15/3
45% 40% 35% 30% 25% 20% 15%
VoidContent (%) 10% 5% 0% #1 AC46- #2 AC46- #4 AC48- #5 AC43- #6 AC45- FA00-WC27- FA30-WC22- FA30-WC32- FA02-WC34- FA32-WC34- 5SD 5SD 5SD 5SD 5SD Pervious Concrete Mix ID
Figure 5.2. Void Contents of Specimens Compacted by Different Methods
As shown in Figure 5.2, the specimens compacted by rodding method had higher void content. This void content was out of the typical range of 15%~25% specified by NRMCA2, and was too high for pervious concrete to reach acceptable compressive strength. Hence, the rodding method Rod-10/3 is not recommended to compact the pervious concrete test samples. Comparatively, the Proctor hammer and the dropping methods generated good compaction results with void content ranges from 12% to 25%. In addition, void contents of specimens from mix #5 and #6 indicated that void content was decreasing with the increase of compaction energy generated by method of Drop-5/3, Drop-10/3 and Drop-15/3.
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Compared to standard Proctor hammer compacting, the dropping method was preferred because it caused less disturbance to the cement bond. Proctor hammer may cause low strength of bonding interface between layers. As illustrated in Figure 5.3, the specimen compacted by standard Proctor hammer showed apparent interface between different layers. And at failure, aggregates at the interface popped out, indicating the low strength of bond at the interfaces.
Compact layer interface
Figure 5.3. The Specimen Compacted by Proctor Hammer
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5.4 Effect of W/C Ratio, A/C Ratio and Fly Ash on Void Content
As illustrated in Figure 5.2, specimens from mix #4, #5, and #6 had different average void contents when using the same compaction method Drop-10/3.
Specimens from mix #5 had the lowest void content; while those from mix #4 had the largest void content. This can be explained by different A/C ratio, W/C ratio and fly ash content in these mixes. The mix #5 had lowest A/C ratio, lowest fly ash content and higher W/C ratio, which could be expected to results in the lowest void content.
Mix #6 had A/C ratio that was greater than mix #5 and less than mix #4, fly ash content that was less than mix #5 and similar to mix #4, and W/C ratio that was higher than mix #4. These differences generated void content that was higher than in
#5 and lower than in #4 for specimens in #6. The results showed that lower A/C ratio, lower fly ash content, and higher W/C ratio resulted in lower void contents.
Furthermore, the effects of A/C, W/C and fly ash content on void content were consistent with those for unit weight as discussed in section 4.2.
5.5 Compressive Strength
This section discusses the effect of curing period, void content and mix design on compressive strength of pervious concrete. The compressive strength results of specimens from two sets of mix batches mix #5 and mix #6 are discussed and compared in detail. The comparison helps to investigate the compressive property of the pervious concrete that had large fly ash content which was 32% of the total cementitious material.
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5.5.1 Compressive Strength vs. Curing Period
The increasing compressive strengths with curing period of representative specimens are shown in Figure 5.4. The specimens were from batches of mix #3, #4,
#5, #6, and had different void contents. The compressive strength of specimens from each mix indicated similar trends. However, the strength increased slightly different for specimens with different fly ash content. For the curing period of 7 and 21 days, the compressive strength of specimens from mix #3 and #5 had higher rate of increase than did those from mix #4 and #6. However, from 21-day curing period to 28-day curing period, the compressive strength of specimens from mix #3 and #5 increased more slowly than those from mixes #4 and #6, which had approximate 30% more amount of fly ash than mix #3 and mix #5, respectively. This indicates that the addition of fly ash improved the long-term strength of the pervious concrete mix. The trendlines in Figure 5.4 are consistent with those illustrated in Figure 3.5.
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Compressive Strength vs. Curing Period at Different Void Content
3200
2800 #3 AC48-FA09- WC37-0SD (Buckeye 2400 Readymix) e=31% #4 AC48-FA30- 2000 WC32-5SD e=27% 1600 #5 AC43-FA02- 1200 WC34-5SD e=14%
800 #6 AC45-FA32- 400 WC34-5SD e=18%
Unconfined Compressive Strength (psi)Unconfined Strength Compressive 0 0 7 14 21 28 Curing Period (Days)
Figure 5.4. Pervious Concrete Mix #3~#6 Compressive Strength vs. Curing Period
5.5.2 Compressive Strength vs. Void Content
The relationship between 28-day compressive strength and void content is demonstrated in Figure 5.5. The compressive strength fell in a range between 800psi and 3,200psi. The pervious concrete with 2% of fly ash reached the highest compressive strength which was greater than 3,200psi; while the highest value that the mix with 32% fly ash achieved was only 1700psi. The compressive strength of the specimen with 2% fly ash exceeded the capacity of the load, from so the strength reported is actually at lower bound number. However an earlier test on the same modified indicated a compressive strength of 3,114 psi. So it was acceptable that the specimen had compressive strength close to 3,200psi.
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Although six batches had different mix designs, the compressive strength tests on all specimens indicated the same trend that the compressive strength decreased with increase in void content, as indicated in Figure 5.5. One reason that the specimens from mix #5 had the higher compressive strength was they had the lower void contents. By observing the trend of compressive strength, it was possible for specimens from mix #6, in which fly ash content counted for 32% of total cementitious material, to reach the compressive strength over 2,000psi with void content around 15%. The tests do not indicate the void content at which the compressive strength would reach 3,000psi. Although the compressive strength could reach to 3,000psi, the void content might be too small to satisfy the requirement of permeability.
28-day Compressive Strength vs. Void Content
3500
3000
2500 #1 AC46-FA00-WC27-5SD 2000 #2 AC46-FA30-WC22-5SD #3 AC48-FA09-WC37-0SD 1500 #4 AC48-FA30-WC32-5SD 1000 #5 AC43-FA02-WC34-5SD #6 AC45-FA32-WC34-5SD 500
28-day Compressive28-day Strength (psi) 0 10% 15% 20% 25% 30% 35% 40% 45% Void Content (%)
Figure 5.5. Relaiton between 28-day Compressive Strength and Void Content
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5.5.3 Compressive Strength vs. Unit Weight
28-day Compressive Strength vs. Unit Weight
3500
3000
2500 #3 AC48-FA09-WC37-0SD 2000 #4 AC48-FA30-WC32-5SD 1500 #5 AC43-FA02-WC34-5SD #6 AC45-FA32-WC34-5SD 1000
500
28-day Compressive28-dayStrength(psi) 0 100.0 120.0 140.0 Unit Weight (lb/ft3)
Figure 5.6. Relationship between 28-day Compressive Strength and Unit Weight
The relationship between 28-day compressive strength and unit weight is shown in Figure 5.6. Apparently, the compressive strength increased with the increment of unit weight, corresponding to the decrease of void content.
5.5.4 Compressive Stress-strain Curves vs. Void Content
Stress-strain curves of specimens from mix #5 and mix #6 are presented in this section. However, the strains shown in curves were not actual values of the strains of pervious concrete specimens. As introduced in Chapter 4, since two rubber caps were used to decrease the effect of stress concentration, large strains were developed due to the high elasticity of rubber during the process of compression,
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especially at the initial status. In another word, the strains shown in stress-strain curves were the total strains from both rubber and specimens. As illustrated in Figure
5.7 and Figure 5.8, the stress-strain curves showed dramatic increases after experienced relatively large strains under low stresses. The large strains were expected caused by the rubbers, which have lower elastic modulus than that of pervious concrete. The strains caused by rubbers were expected to be the strain values at the point, at which stress began to increase faster with smaller strains generated. As shown in Figure 5.7 and Figure 5.8, the strains caused by rubbers were approximately expected to be 1%~2%. Hence, the strains of concrete specimens were obtained by subtracting the total strains by 1%~2%.
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28-day Stress vs. Strain Curves, Mix #5
U=12% U=12% U=13% U=14%
3500 U=12% Su=3114psi U=12% Su>3183psi 3000 U=13% Su=2705psi
2500 U=14% Su=1989psi
2000
1500 Stress (psi) Stress
1000
500
0 0.0% 1.0% 2.0% 3.0% 4.0% 5.0% 6.0% 7.0% Strain (%)
Figure 5.7. Stress-strain Curves Tested on Specimens with Different Void Content at 28-day Curing Period, Mix #5
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28-day Stress vs. Strain Curves, Mix #6
U=18% U=20% U=24%
2000 U=18% Su=1714psi
U=20% Su=1432psi
1500 U=24% Su=1296psi
1000 Stress(psi)
500
0 0.0% 1.0% 2.0% 3.0% 4.0% 5.0% 6.0% 7.0% Strain (%)
Figure 5.8. Stress-strain Curves Tested on Specimens with Different Void Content at 28-day Curing Period, Mix #6
Figure 5.7 and Figure 5.8 demonstrate the different failure process of specimens with 28-day cured period from mix #5 and mix #6, respectively. As shown, for those results from the same batch of mix, brittle failures happened in specimens with lower void contents; while the specimens that had greater void content behaved in a plastic manner. The representative examples were specimen with U=12% from mix #5, and the specimen with U=24% from mix #6. The specimen with U=12% failed suddenly after it had reached to the strength; while the stress-strain curves of the later one rebounded several times before and after reaching to the maximum stress.
This ductile failure mode might be explained by the rearrangement of particles during
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compression. Since voids existed in pervious concrete specimens, the aggregates were rearranged and filled some voids after initial peak. This helped specimens to sustain higher loads after partial failure. Consequently, when load kept increasing, the process occurred again. Therefore, these recycling processes formed serrated stress- strain curves. However, for specimens with low initial void content, specimen had already experienced very high compressive load at initial peak. Although some stress may be released by cracks, the load was still out of the capacity of rearranged structure of the specimen. Hence, failure happened in brittle mode when loads reached to the strength.
5.5.5 Compressive Failure vs. Curing Period
Figure 5.9 illustrates the failure modes of specimens with 18% void content at
7-day, 21-day, and 28-day curing periods. The compressive strength of specimens with 7-day curing period showed more apparent rebounds than those with longer curing periods. The difference in failure modes may be caused by the difference in the strength of the cement bond. At the early age, the strength of cement bond had not been fully developed due to the uncompleted cement hydration process. Hence, breaks were easier to occur at the interface between aggregate, followed by the release of stress and rearrangement of aggregates. Consequently, the compressive capacity increased and rebound line occurred.
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7-day, 21-day, and 28-day Stress vs. Strain Curves (U = 18%), Mix #6
7-day 21-day 28-day
2000 28-day Su = 1714psi
21-day Su = 1413psi 1500 7-day Su = 1323psi
1000 Stress(psi)
500
0 0.0% 1.0% 2.0% 3.0% 4.0% 5.0% 6.0% 7.0% 8.0% Strain (%)
Figure 5.9. Stress-strain Curves Tested on Specimens with Void Content 18% at 7- day, 21-day, and 28-day Curing Periods, Mix #6
5.5.6 Failure Modes
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Figure 5.10. Failure Mode I of Pervious Concrete Samples
Figure 5.11. Failure Mode II of Pervious Concrete Samples
Figure 5.10 and Figure 5.11 illustrate the typical failure modes for the pervious concrete specimens. Failure mode I and II matched the ASTM C 3928 well- 100
defined fracture patterns of Type 1 (reasonably well-formed cones on both ends, less than 1 in. of cracking through caps) and Type 2 (well-formed cone on one end, vertical cracks running through cracks running through caps, no well-defined cone on the other end), respectively.
Figure 5.12. Failure of Specimen Compacted by Standard Proctor Hammer (Mix #6)
Figure 5.12 illustrates the unacceptable failure of specimen from mix #6. The failure indicated the low strength of interface between compacted layers caused by
Proctor hammer.
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Exposed gravel surface
Mix #5 Mix #6
Figure 5.13. Failure Surface Comparison between Specimen from Mix #5 and Mix #6
Figure 5.13 illustrates the difference of failure surfaces between the specimens from mix #5 in which fly ash counted for 2% of total cementitous materials and the one from mix #6 that had 32% of fly ash. As shown in mix #5, the failure surface mainly passed through coarse aggregates instead of the interface between aggregate, indicating the good bonding effect generated by cement. In contrast, the failure surface of specimen from mix #6 showed more separation between aggregates, which implied lower strength of bond than that in mix #5. This might be caused by two reasons: firstly, the spherical shape of fly ash may cause poor bonding characteristics; secondly, the cement content was not enough for fly ash to form more CSH bond.
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5.6 Permeability
Permeability tests were conducted on specimens from mix #5 and mix #6. The permeability fell in a range of 0.13~0.5cm/s for specimens with void content in a range of 14.8% to 25.6%. The values satisfied the general minimum requirement for pervious concrete permeability which is 0.1cm/s. In addition, the permeability was proportional with the void content of specimens as shown in Figure 5.14. This agreed with the studies from pervious studies as discussed in Chapter 2.
Void Content (%) vs. Permeability (cm/s)
#5 AC43-FA02-WC34-5SD #6 AC45-FA32-WC34-5SD
0.60
0.50
0.40
0.30
0.20
Permeability (cm/s) 0.10
0.00 10.0 15.0 20.0 25.0 30.0 Void Content (%)
Figure 5.14. Relationship between Void Content and Permeability of Pervious Concrete Specimens
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Figure 5.14 shows consistent relationship between void content and permeability of specimens from mix #5 and #6. This indicated that except for fly ash content, the permeability may be determined from the void content, regardless of other differences in mix designs except fly ash content. The main difference between mix #5 and mix #6 was the fly ash and cement content. Mix #6 had 30% more fly ash and 30% less cement than mix #5. The permeability tests result indicated that the fly ash content did not significantly affect the permeability of pervious concrete. This was different with the effect of fly ash on conventional concrete. As discussed in
Chapter 3, fly ash decreases the permeability of concrete because it blocks the capillaries when reacting with free lime to form CSH. However, this effect might be minimal in pervious concrete because it has capillaries with large diameters. In addition, the replacement of large portion of fly ash for cement may improve the permeability of pervious concrete. Since large portion of cement has been replaced by fly ash, not enough free lime could be developed during the process of the cement hydration. Consequently, portions of fly ash can not react with free lime to form CSH bond and block the capillaries in pervious concrete. The spherical shape of fly ash may also contribute to the improvement of the permeability. This possibility was demonstrated by the permeability test results on specimens with void content that approximately equaled to 16%, as shown in Figure 5.14.
In order to further examine the permeability test, the results were compared with those from pervious studies. As shown in Figure 5.15, the measured values were in coordinating with the results from previous studies. Among these studies, Montes and Haselbach25 proposed permeability as a function of void content as discussed in
104
Chapter 2. The calculated values are presented in Figure 5.15 and show relatively good prediction of permeability for most specimens with void content in a range of
10% ~ 30%. Although the measured values of permeability in this research were generally higher than the calculated results, they showed approximate agreement.
Hence, the formula presented by Montes and Haselbach25 can be used in this study.
Although Montes and Haselbach25 declared the application of the formula to be limited to that specific research, in which the size of aggregate was 3/8 inches~5/8 inches and the porosity was in a range of 15%~32%, this study showed the formula can also be used for the size of aggregate between 3/8 inches and ½ inches . Although no existing standards are available to investigate the permeability test of pervious concrete, the testing method used in this research generated reasonable values that fell in the range of previous testing results. Figure 5.15 indicates the validity of the test method.
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Void Content (%) vs. Permeability (cm/s)
Literature Review Montes(2006) Ks = 18 *p3 / (1-p)2 #5 AC43-FA02-WC34-5SD #6 AC45-FA32-WC34-5SD Power (Montes(2006) Ks = 18 *p3 / (1-p)2) 4.00
3.00
2.00
Permeability (cm/s) Permeability 1.00
0.00 0 5 10 15 20 25 30 35 40 45 Void Content (%)
Figure 5.15. Comparison of Permeability Test Results with Previous Studies
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CHAPTER 6
SUMMARY, CONCLUSION, AND RECOMMENDATIONS
6.1 Summary
The use of pervious concrete is encouraged by the NRMCA2 because of its benefits in stormwater management, reduction of heat island effect, decreased traffic noise, and potential for earning LEED credits. Furthermore, fly ash is used to replace portion of Portland cement, enhancing the sustainability of pervious concrete. This study was oriented by the large portion replacement of cement by fly ash, including the investigation of the effects of factors on the bearing capacity and hydraulic conductivity of the pervious concrete.
Several mix designs were proposed, containing different W/C ratios, A/C ratios, and fly ash content. The mix design that contained 2% fly ash was carried out to obtain the desirable mechanical properties and satisfied permeability. High compressive strength was obtained, and the mix design was taken as the base for the other batch of pervious concrete, in which 32% of cement by weight was replaced by fly ash. Meanwhile, the W/C ratio and A/C ratio were remained constant or slightly different. Moreover, specimens from two mix designs were compacted with the same compaction energy. With all these restrictions, the test results from these two mix
107
batches were compared and the applicability of large portion of fly ash in pervious concrete will be discussed.
Although the six batches of pervious concrete had different mix designs, another reason that the compressive strength showed scattered values was because of the limited knowledge and experience in pervious concrete mixing. The operation of mixing pervious concrete is more challengeable than that of conventional concrete.
Crew should be trained with certified program to obtain the pervious concrete acknowledge and minimize the failure of placement80. In 2005, the NRMCA created the pervious concrete Contractor Certification Program with three levels of certification, including technician, installer and craftsman based on the level of experience that the contractor has in pervious concrete installation81.
The correlations between compressive strength, permeability, and void content are illustrated in Figure 6.1. The figure indicates that at permeability of
0.1cm/s, the void content of specimens from mix #6 is predicted to be approximate
12.5%, at which the compressive strength may reach to 2,500psi.
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Figure 6.1. Permeability and 28-day Compressive Strength vs. Void Content
6.2 Conclusion
The following conclusions were drawn from this study.
(1) The compressive strength increased with the decrease of void content. The
compressive strength of specimens with 2% fly ash (mix #5) and those with
32% of fly ash (mix #6) increased at different rates. For specimens from mix
#5, compressive strength reached to 2,300psi at the void content of 15%, and
over 3,000psi at void content of 12%; while for specimens from mix #6,
pervious concrete only reached to compressive strength around 2,000psi at
void content of 15%. This indicated that pervious concrete that had large
portion of fly ash (≥ 32%) should be limited to use in low volume traffic road.
109
In this specific study, the mix with 32% fly ash in total cementitious material
was restricted for pavement that sustained load larger than 2000psi.
(2) The laboratory test results showed that less A/C ratio and less fly ash content
generated lower void content and higher unit weight.
(3) The existence of fly ash influenced the increase of compressive strength of
pervious concrete along curing period. Compared to the concrete mix with
2% fly ash, the mix in which 32% of cement was replaced by fly ash had
lower growth rate of compressive strength at the first 21-day curing period;
while had higher rate after that. This indicated that fly ash helped to increase
the late-age compressive strength of pervious concrete.
(4) The permeability decreased with the increase of void content. For specimens
from mix #5, the minimum permeability of 0.13cm/s corresponded to the
void content of 14.9% and the compressive strength of 2,300psi. The
measured permeability was slightly higher than the minimum requirement
which was 0.1cm/s for pervious concrete10. The minimum permeability of
specimen from mix #6 was 0.21cm/s at the void content of 15.8%, indicating
good permeability of pervious concrete that had large portion of fly ash.
(5) The unit weight of pervious concrete decreased with the increase of void
content; while remained constant or slightly changed when void content was
larger than 30%. At the same void content, higher W/C ratio and lower A/C
ratio may generate higher unit weight.
(6) The void content of pervious concrete decreases with the increment of
compaction energy. Compact rodding method was inappropriate to use for
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pervious concrete. The compaction technique of using Proctor hammer
provided with most constant compaction results. However, the segregation
occurred at the interface of layers during compression. The compaction
method of drop-5/3, drop-10/3, and drop-15/3 method presented in this study
generated relatively consistent value of void contents for specimens, without
forming apparent separation between layers.
6.3 Recommendations for Future Work
As discussed before, due to the difficulty to obtain design void content in pervious concrete, the compacted specimens may have actual void content that are different from the design value. Compacted specimens used for compressive strength test and permeability test may have different void contents. To obtain more precise conclusions on void content, compressive strength, and permeability, more tests need to be carried out. In addition, the mix with 32% fly ash had minimum permeability of
0.21cm/s at void content of 15.8%, which had more space to reach to the limit of
0.1cm/s for pervious concrete. A new batch of mix is recommended to perform, in which the specimens could be compacted with void contents less than 15.8%.
Consequently, the greater compressive strength is expected to be obtained from specimen that has lower void content and acceptable permeability.
The failure mode of specimens with 32% fly ash showed low strength of paste bond due to large portion replacement of cement by fly ash. According to the mechanism that fly ash reacts with free lime to form CSH, free lime is recommended to use in pervious concrete with large portion of fly ash substitute for Portland cement.
111
Otherwise, extreme high cement content may be required to develop more free lime during the process of hydration.
80 National Ready Mixed Concrete Association (NRMCA),
81 Aggregate & Ready Mix Association of Minnesota,
112
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(2001). “JV task 13 – environmental evaluation for utilization of ash in soil stabilization.” 2001-EERC-08-06, Final report prepared for AAD Document Controal, National Energy Technology Laboratory, U.S Department of Energy. Prepared by Energy & Environmental 117 Research Center, University of North Dakota 49 Coal Ash Research Committee. (2010). “Historical timeline.” University of North Dakota, 50 EPA. (2010). “Fly ash.” 51 EPA (2008). “Identification of nonhazardous secondary materials that are solid waste coal combustion residuals - coal fly ash, bottom ash, and boiler slag, 52 ASTM C 618-08a. (2009). “Standard specification for coal fly ash and raw or calcined natural pozzolan for use in concrete.” ASTM international, DOI: 10. 1520/C0618-08 53 Headwaters Resources. (2005). “Fly ash – types and benefits.” Bulletin No. 1, 1 page, 54 “Fly ash for concrete brochure,” ISG Resources, Headwaters Resources, 55 FHWA. (2010). “Fly ash facts for highway engineers.” 56 Headwaters Resources. (2005). “Fly ash and concrete in LEED® - NC version 2.2”, Bulletin No. 28, 1 page, 57 Headwaters Resources. (2005). “Fly ash for concrete.” 58 Khunthongkeaw, J., and Tangtermsirikul, S. (2005) “Model for simulating carbonation of fly ash concrete” Journal of Materials in Civil Engineering, ASCE, 17(5), 570-578. 59 Headwaters Resources. (2005). “Fly ash increase resistance to freezing and thawing.” Bulletin No. 9, 1 page. 118 60 Headwaters Resources. (2005). “High volume fly ash for concrete paving.” Bulletin No. 22, 1 page. 61 Headwaters Resources. (2005). “Fly ash decreases the permeability of concrete.” Bulletin No. 6, 1 page. 62 Headwaters Resources. (2005). “Fly ash increases resistance to sulfate attack.” Bulletin No. 7, 1 page. 63 Headwaters Resources. (2005). “Fly ash decreases the permeability of concrete.” Bulletin No. 29, 1 page. 64 QUIKRETE. (2010). “Sand and gravels material safety data sheet.” QUIKRETE, http://www.quikrete.com/PDFs/MSDS-B1-SandAndGravel.pdf> (June, 2010). 65 ASTM C 150. (2009). “Standard specification for Portland cement.” ASTM international, DOI: 10.1520/C0150_C0150M-09, 66 Walker, H. W., Taerakul, P., Butalia, T. S., Wolfe, W. E., and Dick, W. A. (2001). “Minimizaiton and use of Coal Combustion By-products (CCBs): concepts and applications, adapted from “Handbook of pollution control and waste minimization.” New Mexico State University, Marcel Dekker, Inc., Ghassemi ed., p. 426. 67 ACI Committee 211. (2002). “Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete”, ACI 211.1-91, reapproved 2002. 68 Kett, I. (1999). “Engineered concrete mix design and test methods.” CRC Press, 1st edition, p. 5-10. 69 ASTM C 192. (2007). “Standard practice for making and curing concrete test specimens in the laboratory.” ASTM international, DOI: 10.1520/C0192_C0192M-07, 70 Hunt, D. (2009). “Pervious concrete yield test.” Buckeye Ready Mix, personal communication. 71 Pardi, M. (2010). National Mix Concrete, personal communication. 72 ASTM C31 / C31M. (2008). “Standard practice for making and curing concrete test specimens in the field.” ASTM international, DOI: 10.520/C0031_C0031M- 09, 73 ASTM C 29. (2009). “Standard test method for bulk density (“unit weight”) and voids in aggregate.” ASTM international, DOI: 10.1520/C0029_C0029M-09, 74 ASTM C 94. (2009). “Standard specification for Ready-Mix Concrete.” ASTM international, DOI: 10. 1520/C0094_C0094M-09A, 75 ASTM C 125. (2009). “Standard terminology relating to concrete and concrete aggregates.” ASTM international, DOI: 10.1520/C0125-09A, 76 ASTM C 127. (2007). “Standard test method for density, relative density (specific gravity) and absorption of coarse aggregate.” ASTM international, DOI: 10.1520/C0127-07, 77 ASTM C 138. (2009). “Standard test method for density (unity weight) yield, and air content (gravimetric) of concrete.” ASTM international, DOI: 10.1520/C0138_C0138M-09, 78 ASTM C 617. (2009). “Standard practice for capping cylindrical concrete specimens.” ASTM international, DOI: 10.1520/C0617-09A, 79 ASTM D 5084-03 (2003). “Standard test methods for measurement of hydraulic conductivity of saturated porous materials using a flexible wall permeameter.” ASTM international, DOI: 10.1520/D5084-03, 80 National Ready Mixed Concrete Association (NRMCA), 81 Aggregate & Ready Mix Association of Minnesota, 120 APPENDIX A EXAMPLES OF PERVIOUS CONCRETE EXPERIMENTS FROM LITERATURE REVIEW 121 28-day Compressiv Class C Water Unit Void e Permea Mix Cement Fly Ash (lb/yd3 Aggregat Weight Content Strength(ps bility Author ID (lb/yd3) (lb/yd3) ) e (lb/yd3) W/C A/C (lb/ft3) (%) i) (in/sec) Crouch, A 450 131 177 2,599 0.3 4.47 - 12~33 1800~7500 - L. K., B 450 131 177 2,599 0.3 4.5 - 23~37 1450~4600 - et al. C 375 109 147 2,731 0.3 5.6 - 27~39 1000~3500 - (2007) D 375 109 147 2,731 0.3 5.6 - 26~37 870~2900 - Wang, 1 600 - 162 2700 0.27 4.5 116.9 28.8 - - 122 K. et al. 2 600 - 162 2700 0.27 4.5 117.5 25.3 2506 0.1 (2006) 3 600 - 162 2700 0.27 4.5 104.1 33.6 1722 0.57 1A 571 - 154 2500 0.27 4.4 130.9 20.5 - 0.19 1B 520 - 114 2500 0.22 4.8 - - - - 2A 571 - 154 2500 0.27 4.4 127.7 18.3 3661 0.04 2B 520 - 116 2500 0.27 4.8 - - - - 2C 520 - 114 2500 0.22 4.8 126.8 19 2969 0.07 2D 542 - 114 2500 0.22 4.6 120.3 26 1307 - 2E 485 - 114 2500 0.22 5.2 232.2 14.1 2735 0.02 2F 600 - 162 2700 0.27 4.5 120.4 18.9 3106 0.11 2G 600 - 162 2700 0.27 4.5 119.4 22.1 3106 0.27 2H 571 - 154 2500 0.27 4.4 122.5 19 3849 0.12 3A 571 - 154 2500 0.27 4.4 119.8 23 - 0.09 3B 571 - 126 2500 0.22 4.4 - - - - Continued Table A.1: Examples of Laboratory Tests on Pervious Concrete. 122 Table A.1. continued T1 - - - - 0.33 - 114.8 - 1030 3.07 T2 - - - - 0.35 - 121.5 - 1420 3.27 T3 - - - - 0.35 - 115.6 - 2000 3.5 T4 - - - - 0.28 - 131.1 - 2900 0.74 Yang T5 - - - - 0.22 - 128 - 5150 1.14 and T6 - - - - 0.2 - 117.4 - 3872 7.87 Jiang, et al. T7(+S (2003) F) - - - - 0.2 - 134.5 - 8200 0.67 T8(+ VAE) - - - - 0.28 - 144.5 - 8800 0.12 T9(+P AF) - - - - 0.35 - 138 - 7550 0.9 123 Fortes 1BT 510 - 148 - 0.29 - 164 - 1700 0.01 (2008) 2BT 607 - 158 - 0.26 - 164 - 3870 - 3BT 627 - 257 - 0.41 - 158 - 3870 0.39 R2T - - - - 0.39 - 139 - 2550 0.43 R3T 617 - 222 - 0.36 - 144 - 3050 1.14 R4T 617 - 210 - 0.34 - 154 - 3280 - 123 Fine 28-day Project Class C Coarse Coarse Aggreg Fine Compressive Informa Water Cement Fly Ash Aggrega Aggregat ate aggregate Strength tion (lb/yd3) (lb/yd3) (lb/yd3) te e (lb/yd3) (lb/yd3) (%) A/C W/C (psi) Hein and No. 7 Schindle 183 600 - gravel 2391 170 7% 4.27 0.31 - r (2006), No. 78 Auburn 200 451 113 stone 2605 313 11% 6.47 0.44 - Universi No. 7 124 ty 183 600 - gravel 2391 170 7% 4.27 0.31 - No. 78 150 508 56 stone 2410 146 6% 5.03 0.30 - Euclid 3/8'' Chemica round l gravel or Compan limeston y 160 600 - e 2600 0 0% 4.33 0.27 1970 1997 172 400 - - 2700 - - - 0.43 1000 1991 167 300 - - 2570 - - - 0.56 1000 1993 167 300 - - 2570 - - - 0.56 1000 1994 167 300 - - 2570 - - - 0.56 1000 Table A.2. Examples of Field Projects of Pervious Concrete. 124 APPENDIX B PROPERTIES OF PERVIOUS CONCRETE COMPONENTS 125 Figure B.1. Properties of Coarse Aggregates 126 Figure B.2. Properties of Cement (St. Marys) 127 Continued Figure B.3. Properties of High Range Water Reducer (Euclid Chemical Company) 128 Figure B.3. continued 129 Continued Figure B.4. Properties of Mid-Range Water Reducer (Euclid Chemical Company) 130 Figure B.4. continued 131 Continued Figure B.5. Properties of Mid-Range Water Reducer (Euclid Chemical Company) Error! Reference source not found.. continued 132 133 Figure B.6. Properties of Viscosity Modifying Admixture (Euclid Chemical Company) 134 Continued Figure B.7. Properties of Fiber (Euclid Chemical Company) 135 Figure B.7. continued 136 APPENDIX C LABORATORY TEST RESULT (UNIT WEIGHT, VOID CONTENT, UNCONFINED COMPRESSIVE STRENGTH, PERMEABILITY) 137 Mix #1: AC46-FA00-WC27-5SD Mixture Component Weight Density/SG Volume Cement, lb 7.01 3.15 0.04 Coarse Aggregate, SSD, lb 30.34 2.63 0.18 Fine Aggregate, SSD, lb 1.67 2.61 0.01 Water, lb 1.88 1.00 0.03 Poly fibers, 1#/cy HRWR, oz/cwt. 4.43 Water Reducer, oz/cwt. 1.86 Viscosity oz/cwt. 2.06 Void 41% W/C Ratio 0.27 Total weight, lbs 49.26 Total volume, ft3 0.44 Solids Volume, ft3 0.26 Design Unit weight, lb/ft3 111.95 Maximum Theoretical density, lb/ft3 188.77 Table C.1. Mix Design of Pervious Concrete Mix #1 Volume Unit weight Void 4in x 8in Weight (lb) (ft3) (lb/ft3) Content Sample (1) 6.6 0.058 112.8 40.2% Sample (2) 6.6 0.058 113.1 40.1% Sample (3) 6.5 0.058 111.5 40.9% Sample (4) 6.5 0.058 112.1 40.6% Sample (5) 7.3 0.058 125.1 33.7% Table C.2. Unit Weight and Void Content of 4in x 8in Samples from Pervious Concrete Mix #1 Note: compaction method: Rod-10/3 (rodding 10 times/layer, 3 layers ) 138 Mix #2: AC46-FA30-WC22-5SD Mixture Component Weight Density/SG Volume Cement, lb 15.05 3.15 0.08 Class F fly ash 6.45 2.10 0.05 Coarse Aggregate, SSD, lb 93.75 2.63 0.57 Fine Aggregate, SSD, lb 5.18 2.61 0.03 Water, lb 4.73 1.00 0.08 Poly fibers, 1#/cy HRWR, oz/cwt. 5.00 Water Reducer, oz/cwt. 2.00 Viscosity oz/cwt. 3.00 Void 42% W/C Ratio 0.22 Total weight, lbs 135.16 Total volume, ft3 1.25 Solids Volume, ft3 0.73 Design Unit weight, lb/ft3 108.13 Maximum Theoretical density, lb/ft3 185.44 Table C.3. Mix Design of Pervious Concrete Mix #2 Volume Unit weight Void 4in x 8in Weight (lb) (ft3) (lb/ft3) content Sample (1) 6.1 0.058 105.2 43.3% Sample (2) 6.2 0.058 106.7 42.5% Sample (3) 6.2 0.058 105.8 43.0% Sample (4) 6.2 0.058 106.5 42.6% Sample (5) 6.2 0.058 106.2 42.7% Sample (6) 6.1 0.058 105.2 43.3% Sample (7) 6.2 0.058 106.8 42.4% Sample (8) 6.2 0.058 107.3 42.2% Sample (9) 6.2 0.058 106.1 42.8% Sample (10) 6.2 0.058 106.7 42.5% Sample (11) 6.1 0.058 105.6 43.1% Sample (12) 6.2 0.058 106.0 42.8% Table C.4. Unit Weight and Void Content of 4in x 8in Samples from Pervious Concrete Mix #2 Note: compaction method: Rod-10/3 (rodding 10 times/layer, 3 layers ) 139 Mix #3: AC48-FA09-WC37-0SD Mixture Component Weight Density/SG Volume Cement, lb 29.40 3.15 0.15 Class F fly ash 2.80 2.10 0.02 Coarse Aggregate, SSD, lb 152.99 2.63 0.93 Fine Aggregate, SSD, lb 0.00 2.61 0.00 Water, lb 11.79 1.00 0.19 Poly fibers, 1#/cy Eucon WO, oz/cwt. 6.00 Eucon MRX, oz/cwt. 12.00 Visctrol oz/cwt. 1.00 Void 26% W/C Ratio 0.37 Total weight, lbs 215.98 Total volume, ft3 1.74 Solids Volume, ft3 1.29 Design Unit weight, lb/ft3 124.27 Maximum Theoretical density, lb/ft3 167.15 Table C.5. Mix Design of Pervious Concrete Mix #3 Volume Unit weight Void 4in x 8in Weight (lb) (ft3) (lb/ft3) content Sample (1) 6.4 0.058 109.7 34.4% Sample (2) 6.7 0.058 114.7 31.4% Table C.6. Unit Weight and Void Content of 4in x 8in Samples from Pervious Concrete Mix #3 Note: this mix is from Buckeye Ready-mix Corp; compaction method: Jig-25/2 (jigging 25times/layer, 2 layers) 140 Mix #4: AC48-FA30-WC32-5SD Mixture Component Weight Density/SG Volume Cement, lb 4.20 3.15 0.02 Fly Ash, lb 1.80 2.10 0.01 Coarse Aggregate, SSD, lb 27.50 2.63 0.17 Fine Aggregate, SSD, lb 1.44 2.61 0.01 Water, lb 1.92 1.00 0.03 Fiberstrand 100 (g) 5.72 0.91 0.0002 PLASTOL 6200 EXT (g) 13.44 1.08 0.0004 EUCON W.O, (g) 13.44 1.12 0.0004 EUCON MRX, (g) 13.44 1.12 0.0004 Visctrol oz/cwt. (g) 16.80 1.21 0.0005 Void 27% W/C Ratio 0.32 Total weight, lbs 37.00 Total volume, ft3 0.34 Solids Volume, ft3 0.24 Design Unit weight, lb/ft3 110.44 Maximum Theoretical density, lb/ft3 151.42 Table C.7. Mix Design of Pervious Concrete Mix #4 Volume Unit weight Void 4in x 8in Weight (lb) (ft3) (lb/ft3) content Sample (1) 6.991 0.058 120.2 20.6% Sample (2) 6.398 0.058 110.0 27.4% Sample (3) 6.372 0.058 109.5 27.7% Sample (4) 6.648 0.058 114.3 24.5% Table C.8. Unit Weight and Void Content of 4in x 8in Samples from Pervious Concrete Mix #4 Note: compaction method: Drop-10/3 (dropping with 2~3in height 5times/layer, 3 layers) 141 Mix #5: AC43-FA02-WC34-5SD Mixture Component Weight Density/SG Volume Cement, lb 26.40 3.15 0.13 Fly Ash, lb 0.50 2.10 0.00 Coarse Aggregate, SSD, lb 109.14 2.63 0.67 Fine Aggregate, SSD, lb 5.74 2.61 0.04 Water, lb 9.00 1.00 0.14 Fiberstrand 100 (g) 20.18 0.91 0.0008 PLASTOL 6200 EXT (g) 55.90 1.08 0.0019 EUCON W.O, (g) 56.30 1.12 0.0018 EUCON MRX, (g) 55.50 1.12 0.0018 Visctrol oz/cwt. (g) 69.40 1.21 0.0021 Void 14% W/C Ratio 0.34 Total weight, lbs 151.35 Total volume, ft3 1.15 Solids Volume, ft3 0.99 Design Unit weight, lb/ft3 131.61 Maximum Theoretical density, lb/ft3 152.74 Table C.9. Mix Design of Pervious Concrete Mix #5 Unit Weight Volume weight Void Compaction 4in x 8in (lb) (ft3) (lb/ft3) content Method Sample (1) 7.48 0.058 128.6 15.8% Sample (2) 7.64 0.058 131.4 14.0% Sample (3) 7.46 0.058 128.3 16.0% Drop-5/3 Sample (4) 7.52 0.058 129.3 15.3% Sample (5) 7.55 0.058 129.8 15.0% Sample (6) 7.45 0.058 128.1 16.1% Sample (7) 7.45 0.058 128.1 16.1% Sample (8) 7.85 0.058 135.0 11.6% Drop-10/3 Sample (9) 7.80 0.058 134.1 12.2% Drop-15/3 Sample (10) 7.61 0.058 130.8 14.3% Proct-5/3 Sample (11) 7.61 0.058 130.8 14.3% Sample (12) 7.75 0.058 133.2 12.8% Proct-10/3 Table C.10. Unit Weight and Void Content of 4in x 8in Samples from Pervious Concrete Mix #5 142 Unit Weight Volume weight Void Compaction 3in x 6in (lb) (ft3) (lb/ft3) content Method Sample (1) 3.09 0.025 125.9 17.6% Sample (2) 3.02 0.025 123.0 19.4% Proct-5/3 Sample (3) 3.11 0.025 126.7 17.0% Sample (4) 3.15 0.025 128.3 16.0% Sample (5) 3.19 0.025 130.0 14.9% Proct-10/3 Table C.11. Unit Weight and Void Content of 3in x 6in Samples from Pervious Concrete Mix #5 Mix #6: AC45-FA32-WC34-5SD Mixture Component Weight Density/SG Volume Cement, lb 16.22 3.15 0.08 Fly Ash, lb 7.65 2.10 0.06 Coarse Aggregate, SSD, lb 103.40 2.63 0.63 Fine Aggregate, SSD, lb 5.20 2.61 0.03 Water, lb 8.11 1.00 0.13 Fiberstrand 100 (g) 20.18 0.91 0.0008 PLASTOL 6200 EXT (g) 52.47 1.08 0.0017 EUCON W.O, (g) 52.47 1.12 0.0017 EUCON MRX, (g) 52.47 1.12 0.0017 Visctrol oz/cwt. (g) 65.59 1.21 0.0019 Void 18% W/C Ratio Total weight, lbs 141.12 Total volume, ft3 1.15 Solids Volume, ft3 0.94 Design Unit weight, lb/ft3 122.71 Maximum Theoretical density, lb/ft3 150.01 Table C.12. Mix Design of Pervious Concrete Mix #6 143 Weight Volume Unit weight Void Compaction 4in x 8in (lb) (ft3) (lb/ft3) content Method Sample (1) 7.24 0.058 124.5 17.0% Sample (2) 7.15 0.058 122.9 18.1% Proct-5/3 Sample (3) 7.24 0.058 124.5 17.0% Sample (4) 7.05 0.058 121.2 19.2% Sample (5) 7.09 0.058 121.9 18.7% Sample (6) 7.19 0.058 123.6 17.6% Drop-15/3 Sample (7) 7.43 0.058 127.7 14.8% Sample (8) 6.97 0.058 119.8 20.1% Sample (9) 7.01 0.058 120.5 19.7% Drop-10/3 Sample (10) 6.95 0.058 119.5 20.3% Sample (11) 6.81 0.058 117.1 21.9% Sample (12) 6.79 0.058 116.7 22.2% Drop-5/3 Sample (13) 6.61 0.058 113.7 24.2% Sample (14) 6.61 0.058 113.7 24.2% Table C.13. Unit Weight and Void Content of 4in x 8in Samples from Pervious Concrete Mix #6 Weight Volume Unit weight Void Compaction 3in x 6in (lb) (ft3) (lb/ft3) content Method Sample (1) 2.68 0.025 109.2 27.2% Drop-5/3 Sample (2) 2.76 0.025 112.4 25.0% Sample (3) 2.91 0.025 118.6 21.0% Drop-10/3 Sample (4) 2.89 0.025 117.7 21.5% Sample (5) 3.10 0.025 126.3 15.8% Proct-5/3 Table C.14. Unit Weight and Void Content of 3in x 6in Samples from Pervious Concrete Mix #6 144 Curing Compressive Void Period Strength Mix ID Content (days) (psi) 7 260.7 #1 AC46-FA00-WC27-5SD 41% 21 585.1 28 554.3 9 99.5 #2 AC46-FA30-WC22-5SD 42% 21 160.0 28 190.2 11 686.8 #3 AC48-FA09-WC37-0SD 31% 21 827.5 28 899.9 7 505.4 #4 AC48-FA30-WC32-5SD 27% 21 591.8 28 791.1 7 1947.7 #5 AC43-FA02-WC34-5SD 14% 21 2504.9 28 2705.0 7 1323.4 #6 AC45-FA32-WC34-5SD 18% 21 1413.0 28 1713.9 Table C.15. Compressive Strength of Specimens from Mix #1~#6 at 7, 21, and 28 Days Curing Periods 145 Unit 28-day Weight Void Compressive Mix ID (lb/ft3) Content Strength (psi) #1 AC46-FA00-WC27-5SD 111.5 41% 554 #2 AC46-FA30-WC22-5SD 106.7 42% 190 #3 AC48-FA09-WC37-0SD 114.7 31% 900 #4 AC48-FA30-WC32-5SD 109.5 27% 791 128.3 16% 2221 129.3 15% 2258 135.0 12% 3183 #5 AC43-FA02-WC34-5SD 134.1 12% 3114 130.8 14% 2206 130.8 14% 1989 133.2 13% 2705 123.6 18% 1714 119.8 20% 1432 #6 AC45-FA32-WC34-5SD 117.1 22% 1125 113.7 24% 821 113.7 24% 1296 Table C.16. 28-day Compressive Strength of Specimens from Mix #1~#6 with Various Void Content 146 Mix #3: U=31%: 11-day curing period 800 700 600 500 400 Stress(psi) Stress(psi) 300 200 100 0 0.0% 0.5% 1.0% 1.5% 2.0% 2.5% 3.0% 3.5% Strain (%) Figure C.1. 11-day Compressive Stress-strain Curve of Specimen with Void Contend of 31% from Mix #3 Mix #3: U=31%: 21-day curing period 900 800 700 600 500 400 Stress(psi) Stress (psi)Stress 300 200 100 0 0.0% 0.5% 1.0% 1.5% 2.0% 2.5% 3.0% 3.5% 4.0% 4.5% Strain (%) Figure C.2. 21-day Compressive Stress-strain Curve of Specimen with Void Contend of 31% from Mix #3 147 Mix #3: U=31%: 28-day curing period 1000 900 800 700 600 500 Stress(psi) Stress (psi)Stress 400 300 200 100 0 0.0% 0.5% 1.0% 1.5% 2.0% 2.5% Strain (%) Figure C.3. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 31% from Mix #3 Mix #4: U= 27% 7-day curing period 600. 500. 400. 300. Stress Stress (psi) 200. 100. 0. 0.00% 0.50% 1.00% 1.50% 2.00% 2.50% 3.00% 3.50% Strain (%) Figure C.4. 7-day Compressive Stress-strain Curve of Specimen with Void Contend of 27% from Mix #4 148 Mix #4: U= 27% 21-day curing period 700 600 500 400 Stress Stress (psi)Stress 300 200 100 0 0.0% 0.5% 1.0% 1.5% 2.0% 2.5% 3.0% 3.5% 4.0% Strain (%) Figure C.5. 21-day Compressive Stress-strain Curve of Specimen with Void Contend of 27% from Mix #4 Mix #4: U= 27% 28-day curing period 900 800 700 600 500 400 Stress Stress(psi) 300 200 100 0 0.0% 0.5% 1.0% 1.5% 2.0% 2.5% 3.0% Strain (%) Figure C.6. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 27% from Mix #4 149 Mix #5: U= 12%: 7-days curing period 2000 1800 1600 1400 1200 1000 Stress Stress(psi) 800 600 400 200 0 0.0% 0.5% 1.0% 1.5% 2.0% 2.5% 3.0% 3.5% 4.0% Strain (%) Figure C.7. 7-day Compressive Stress-strain Curve of Specimen with Void Contend of 12% from Mix #5 Mix #5: U= 12%: 21-days curing period 3000 2500 2000 1500 Stress 21days(psi) Stress(psi) 1000 500 0 0.0% 1.0% 2.0% 3.0% 4.0% 5.0% 6.0% 7.0% Strain (%) Figure C.8. 21-day Compressive Stress-strain Curve of Specimen with Void Contend of 12% from Mix #5 150 Mix #5: U= 13%: 28-days curing period 3000 2500 2000 1500 Stress 28days(psi) Stress (psi) 1000 500 0 0.0% 1.0% 2.0% 3.0% 4.0% 5.0% 6.0% Strain (%) Figure C.9. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 13% from Mix #5 Mix #4: U= 27% 7-day curing period 1400 1200 1000 800 Stress 600 Stress (psi) 400 200 0 0.0% 1.0% 2.0% 3.0% 4.0% 5.0% 6.0% 7.0% 8.0% Strain (%) Figure C.10. 7-day Compressive Stress-strain Curve of Specimen with Void Contend of 17% from Mix #6 151 Mix #6: U=18% 21-day curing period 1600 1400 1200 1000 800 Stress 21days(psi) Stress(psi) 600 400 200 0 0.0% 0.5% 1.0% 1.5% 2.0% 2.5% 3.0% 3.5% 4.0% Strain (%) Figure C.11. 21-day Compressive Stress-strain Curve of Specimen with Void Contend of 18% from Mix #6 Mix #6: U=18% 28-day curing period 2000 1500 1000 Stress Stress (psi) 28days(psi) 500 0 0.0% 1.0% 2.0% 3.0% 4.0% 5.0% 6.0% 7.0% Strain (%) Figure C.12. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 18% from Mix #6 152 28-day Stress vs. Strain Curve (U = 16%), Mix #5 2500 2000 1500 1000 500 0 0.0% 2.0% 4.0% 6.0% Figure C.13. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 16% from Mix #5 28-day Stress vs. Strain Curve (U = 15%), Mix #5 2500 2000 1500 1000 500 Compressive Stress (psi) 0 0.0% 2.0% 4.0% 6.0% 8.0% Strain (%) Figure C.14. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 15% from Mix #5 153 28-day Stress vs. Strain Curve (U = 12%), Mix #5 3500 3000 2500 2000 1500 1000 CompressiveStress (psi) 500 0 0.0% 1.0% 2.0% 3.0% Strain (%) Figure C.15. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 12% from Mix #5 28-day Stress vs. Strain Curve (U = 12%), Mix #5 3500 3000 2500 2000 1500 1000 Compressive Stress (psi) 500 0 0.0% 1.0% 2.0% 3.0% 4.0% Strain (%) Figure C.16. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 12% from Mix #5 154 28-day Stress vs. Strain Curve (U = 14%), Mix #5 2500 2000 1500 1000 500 Compressive Stress (psi) 0 0.0% 2.0% 4.0% 6.0% Strain (%) Figure C.17. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 14% from Mix #5 28-day Stress vs. Strain Curve (U = 14%), Mix #5 2500 2000 1500 1000 500 Compressive Stress (psi) 0 0.0% 2.0% 4.0% 6.0% 8.0% Strain (%) Figure C.18. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 14% from Mix #5 155 28-day Stress vs. Strain Curve (U = 13%), Mix #5 3000 2500 2000 1500 1000 500 Compressive Stress(psi) 0 0.0% 2.0% 4.0% 6.0% Strain (%) Figure C.19. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 13% from Mix #5 28-day Stress vs. Strain Curve (U = 18%), Mix #6 2000 1500 1000 Stress (psi) 500 0 0.0% 1.0% 2.0% 3.0% 4.0% 5.0% 6.0% 7.0% Strain (%) Figure C.20. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 18% from Mix #6 156 28-day Stress vs. Strain Curve (U = 20%), Mix #6 2000 1500 1000 Stress(psi) 500 0 0.0% 1.0% 2.0% 3.0% 4.0% Strain (%) Figure C.21. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 20% from Mix #6 28-day Stress vs. Strain Curve (U = 22%), Mix #6 1500 1000 500 Stress (psi) Stress 0 0.0% 1.0% 2.0% 3.0% 4.0% 5.0% Strain (%) Figure C.22. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 22% from Mix #6 157 28-day Stress vs. Strain Curve (U = 24%), Mix #6 1500 1000 Stress (psi) 500 0 0.0% 1.0% 2.0% 3.0% 4.0% 5.0% Strain (%) Figure C.23. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 24% from Mix #6 28-day Stress vs. Strain Curve (U = 24%), Mix #6 1500 1000 Stress (psi) 500 0 0.0% 1.0% 2.0% 3.0% 4.0% 5.0% 6.0% Strain (%) Figure C.24. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of 24% from Mix #6 158 Measured Calculated Water Permeability (Montes Void Permeability (2006): ks = 18 *p3 / Author Contend (cm/sec) (1-p)2) 14.1 0.04 0.05 18.3 0.10 0.11 18.9 0.27 0.13 19 0.18 0.13 Wang, K., 19 0.30 0.13 Schaelfer, V. R., 20.2 0.24 0.15 Kevern, J. T., and 20.5 0.49 0.16 Suleiman, M. T 22.1 0.68 0.20 23 0.23 0.23 25.3 0.254 0.31 25.7 0.47 0.33 33.6 1.45 0.77 11 0.03 0.02 Kajio et al. 2003 15 0.18 0.06 15 0.20 0.06 Tennis et al. 2004 25 0.53 0.30 15.8 0.014 0.07 16.1 0.025 0.08 17.7 0.132 0.10 18.5 0.237 0.12 15.6 0.18 0.07 24.4 0.272 0.28 Montes, F., and 17.7 0.145 0.10 Haselbach, 22.4 0.154 0.21 L.(2006) 24.9 0.404 0.30 25.5 0.457 0.32 29.9 0.783 0.53 26.8 0.869 0.37 29.5 0.941 0.51 32 1.317 0.66 30.1 1.19 0.54 Continued Table C.17. Measured and Calculated Permeability of Pervious Concrete Specimens from Literature Review 159 Table C.17 continued 27.8 0.46 0.42 Crouch, L. K., et 25.2 0.14 0.31 al. 24.4 0.07 0.28 27.3 0.3 0.40 19 0.18 0.13 23.2 0.66 0.24 23 0.23 0.23 Suleiman, M. T 33.2 1.50 0.74 25.7 0.48 0.33 28.8 0.64 0.47 34.8 1.20 0.86 36.1 3.32 0.97 35.5 6.03 0.92 32.3 0.43 0.68 39.8 3.10 1.35 31.9 0.73 0.65 33.3 1.15 0.75 33.4 1.88 0.75 28.9 0.13 0.47 34.1 1.80 0.81 25.5 0.15 0.32 Crouch, L. K., 27.6 0.17 0.41 Smith, N., Walker, 26.3 0.44 0.35 A. C., Dunn, T. R., and Sparkman, A. 24.6 0.04 0.29 (2006) 30.2 0.01 0.55 22.8 0.08 0.23 25.4 0.07 0.32 19.3 0.01 0.13 31.1 0.06 0.60 18.3 0.01 0.11 24.3 0.07 0.27 29.9 0.07 0.53 13.2 0.00 0.04 18.1 2.12 0.11 21.2 0.01 0.18 27.4 0.03 0.40 160 Falling head test Height of top surface of water level: 1220 mm Height of bottom surface of water level: 410 mm Difference height of water level: 810 mm a = 7.07 in = 4560.37 mm2 L = 6.00 in = 152.40 mm A = 7.07 in2 = 4560.37 mm2 ∆h0 810.00 mm = 810.00 mm ∆h1 = ∆h0 - Q/A 3 2 kS = 18 p / (1-p) k = (aL/At) * ln(∆h0/∆h1) Table C.18. Permeability Calculation Parameters in Falling Head Permeability Test 161 Mix No. #5 Testing date 3/13/2010 Smaple No. 2 Void content 19.4% Time (s) Q (ml) ∆h1 (mm) k (in/hour) k(cm/s) 4.48 330 738 451.2 0.32 3.26 255 754 473.9 0.33 5.29 370 729 431.0 0.30 5.52 380 727 424.8 0.30 6.15 420 718 423.9 0.30 6.78 460 709 423.7 0.30 4.54 330 738 445.2 0.31 5.36 370 729 425.3 0.30 6.2 420 718 420.5 0.30 5.91 400 722 418.9 0.30 0.30 ks = 0.20 Table C.19. Permeability Test Data for Specimen with Void Content of 19.5% from Mix #5 Mix No. #5 Testing date 3/13/2010 Void Smaple No. 1 content 17.6% Time (s) Q (ml) ∆h1 (mm) k (in/hour) k(cm/s) 6.4 330 738 315.8 0.22 5.33 280 749 319.5 0.23 7.4 360 731 299.3 0.21 8.45 405 721 296.9 0.21 7.2 350 733 298.6 0.21 7.98 390 724 302.0 0.21 7.61 320 740 257.2 0.18 4.99 250 755 303.3 0.21 9.54 440 714 287.2 0.20 10.61 495 701 292.9 0.21 8.92 420 718 292.3 0.21 0.21 ks = 0.14 Table C.20. Permeability Test Data for Specimen with Void Content of 19.5% from Mix #5 162 Mix No. #5 Testing date 3/13/2010 Smaple No. 3 Void content 17.0% Time (s) Q (ml) ∆h1 (mm) k (in/hour) k(cm/s) 6.74 295 745 266.7 0.19 9.33 405 721 268.9 0.19 6.11 270 751 268.3 0.19 5.34 240 757 271.7 0.19 6.5 290 746 271.7 0.19 7.93 340 735 263.0 0.19 6.92 310 742 273.6 0.19 6.89 310 742 274.8 0.19 8.6 380 727 272.7 0.19 6.1 275 750 273.9 0.19 0.19 ks = 0.13 Table C.21. Permeability Test Data for Specimen with Void Content of 17.0% from Mix #5 Mix No. #5 Testing date 3/13/2010 Smaple No. 4 Void content 16.0% Time (s) Q (ml) ∆h1 (mm) k (in/hour) k(cm/s) 5.48 240 757 264.8 0.19 7.23 305 743 257.5 0.18 7.27 310 742 260.4 0.18 9.39 390 724 256.7 0.18 9.14 380 727 256.5 0.18 7.1 300 744 257.7 0.18 4.17 190 768 273.5 0.19 7.04 290 746 250.9 0.18 9.78 400 722 253.1 0.18 5.86 260 753 269.0 0.19 0.18 ks = 0.10 Table C.22. Permeability Test Data for Specimen with Void Content of 16.0% from Mix #5 163 Mix No. #5 Casting date 2/26/2010 Void Smaple No. 5 content 14.9% Time (s) Q (ml) ∆h1 (mm) k (in/hour) k(cm/s) 8.71 250 755 173.8 0.12 8.22 265 752 188.5 0.14 6.46 210 764 190.1 0.14 8.93 280 749 183.3 0.13 14.48 430 716 173.6 0.13 11.34 350 733 180.5 0.13 12.24 380 727 181.5 0.14 4.16 130 781 182.7 0.13 4.98 180 771 211.4 0.15 10.5 310 742 172.6 0.13 9.45 338 736 209.1 0.15 0.13 ks = 0.08 Table C.23. Permeability Test Data for Specimen with Void Content of 14.9% from Mix #5 Mix No. #6 Testing date 4/19/2010 Smaple No. 1 Void content 27.2% Time (s) Q (ml) ∆h1 (mm) k (in/hour) k(cm/s) 2.83 370 729 805.6 0.57 2.86 340 735 729.3 0.51 3.78 430 716 707.2 0.50 4.98 545 690 692.4 0.49 1.93 280 749 882.2 0.62 3.05 350 733 705.0 0.50 3.92 440 714 698.9 0.49 2.61 300 744 701.0 0.49 3.36 375 728 688.2 0.49 2.2 270 751 745.2 0.53 3.17 360 731 698.7 0.49 0.50 ks = 0.69 Table C.24. Permeability Test Data for Specimen with Void Content of 27.2% from Mix #6 164 Mix No. #6 Testing date 4/19/2010 Smaple No. 2 Void content 25.0% Time (s) Q (ml) ∆h1 (mm) k (in/hour) k(cm/s) 3.28 320 740 596.7 0.42 3.17 375 728 729.4 0.51 3.21 325 739 619.7 0.44 3.27 380 727 717.1 0.51 4.69 510 698 684.3 0.48 4.2 450 711 668.1 0.47 5.61 580 683 657.7 0.46 4.17 425 717 633.1 0.45 3.98 360 731 556.5 0.39 4.63 395 723 527.6 0.37 3.62 330 738 558.4 0.39 0.45 ks = 0.50 Table C.25. Permeability Test Data for Specimen with Void Content of 25.0% from Mix #6 Testing Mix No. #6 date 4/19/2010 Void Smaple No. 3 content 21.0% Time (s) Q (ml) ∆h1 (mm) k (in/hour) k(cm/s) 2.35 225 761 577.6 0.41 3.01 240 757 482.1 0.34 2.78 220 762 477.1 0.34 3.23 255 754 478.4 0.34 4.79 365 730 469.2 0.33 3.83 300 744 477.7 0.34 3.46 270 751 473.8 0.33 3.08 240 757 471.1 0.33 4.45 332 737 457.1 0.32 4.04 310 742 468.6 0.33 0.34 ks = 0.27 Table C.26. Permeability Test Data for Specimen with Void Content of 21.0% from Mix #6 165 Mix No. #6 Testing date 4/19/2010 Smaple No. 4 Void content 21.5% Time (s) Q (ml) ∆h1 (mm) k (in/hour) k(cm/s) 3.41 270 751 480.8 0.34 3.05 255 754 506.6 0.36 3.16 320 740 619.4 0.44 4.05 325 739 491.2 0.35 3.21 205 765 384.2 0.27 3.69 310 742 513.1 0.36 3.72 330 738 543.4 0.38 3.22 260 753 489.6 0.35 3.08 200 766 390.4 0.28 3.45 286 747 504.5 0.36 0.35 ks = 0.29 Table C.27. Permeability Test Data for Specimen with Void Content of 21.5% from Mix #6 Mix No. #6 Testing date 4/19/2010 Void Smaple No. 5 content 15.8% Time (s) Q (ml) ∆h1 (mm) k (in/hour) k(cm/s) 4.6 300 744 397.7 0.28 4.01 200 766 299.8 0.21 4.33 210 764 292.0 0.21 6.86 315 741 280.7 0.20 1.87 110 786 349.2 0.25 3.8 190 768 300.2 0.21 9.84 430 716 271.7 0.19 9.56 420 718 272.7 0.19 4.04 200 766 297.6 0.21 4.73 220 762 280.4 0.20 0.21 ks = 0.10 Table C.28. Permeability Test Data for Specimen with Void Content of 15.8% from Mix #6 166 Void content vs. compaction methods on all samples Average Compaction Void Method Mix ID Void Content Content #1 AC46-FA00-WC27-5SD 41% 41% Rod-10/3 #2 AC46-FA30-WC22-5SD 42% 42% #5 AC43-FA02-WC34-5SD 14% 14% 17% 18% Proct-5/3 #6 AC45-FA32-WC34-5SD 17% 18% 19% 19% 14% 16% 15% #5 AC43-FA02-WC34-5SD 15% 15% Drop-5/3 16% 16% 22% #6 AC45-FA32-WC34-5SD 22% 22% #4 AC48-FA30-WC32-5SD 27% 27% #5 AC43-FA02-WC34-5SD 12% 12% Drop-10/3 20% #6 AC45-FA32-WC34-5SD 20% 20% 20% #5 AC43-FA02-WC34-5SD 12% 12% Drop-15/3 18% #6 AC45-FA32-WC34-5SD 16% 15% Table C.29. Void Contents of Specimens Compacted at Different Compaction Methods 167 APPENDIX D PERVIOUS CONCRETE MIX DESIGN PROGRAM CODE using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; namespace concrete_mix_design { public partial class Form1 : Form { public Form1() { InitializeComponent(); } double Cementitious, HRWR_cwt, WR_cwt, Viscosity_cwt, A_C, W_C, Volume; double CASG, SandSG, FASG, CementSG; double Cement, FA, TA, CA,Sand, Water, HRWR, WR, Viscosity, FApercent; double Cement_f, FA_f, CA_f, Sand_f, Water_f; double CAVol, SandVol, FAVol, CementVol, WaterVol, ARVol, SolVol, SolW; double AR, UnitW, UnitW_f, UnitW_Max, UnitW_Max_f; double MoldW, SamplW,SamplWMax, MandSampl, MandSamplMax; string output = " "; private void button1_Click(object sender, EventArgs e) { Cementitious = Convert.ToDouble(textBox_cement.Text); HRWR_cwt = Convert.ToDouble(textBox_HRWR.Text); WR_cwt = Convert.ToDouble(textBox_WR.Text); Viscosity_cwt = Convert.ToDouble(textBox_Viscosity.Text); A_C = Convert.ToDouble(textBox_A_C.Text); W_C = Convert.ToDouble(textBox_W_C.Text); FApercent = Convert.ToDouble(textBox_FApercent.Text); CASG = Convert.ToDouble(textBox_CASG.Text); 168 SandSG = Convert.ToDouble(textBox_SandSG.Text); FASG = Convert.ToDouble(textBox_FASG.Text); CementSG = Convert.ToDouble(textBox_CementSG.Text); Volume = Convert.ToDouble(textBox_Volume.Text); HRWR = HRWR_cwt * Cementitious *28.35*Volume/ 100; WR = WR_cwt * Cementitious *28.35*Volume/ 100; Viscosity = Viscosity_cwt * Cementitious*28.35*Volume/ 100; HRWR = Math .Round (HRWR ,2); WR = Math .Round (WR,2); Viscosity = Math .Round (Viscosity ,2); label_HRWR.Text = output + HRWR; label_WR.Text = output + WR; label_Viscosity.Text = output + Viscosity; FA = Cementitious * FApercent /100; Cement = Cementitious *(100-FApercent)/100; TA = Cementitious * A_C; Sand = TA * 0.05; CA = TA * 0.95; //Water = W_C * Cementitious - CA * Moisture / 100; Water = W_C * Cementitious; //CA = CA + CA * Moisture / 100; SolW = CA + Sand + Cementitious + Water + HRWR/453.6 +WR/453.6 +Viscosity/453.6 ; CAVol = CA / CASG / 62.4; SandVol = Sand / SandSG / 62.4; FAVol = FA / FASG / 62.4; CementVol = Cement / CementSG / 62.4; WaterVol = Water / 62.4; SolVol = CAVol + SandVol + FAVol + CementVol + WaterVol; ARVol = Volume - SolVol; AR = ARVol*100/Volume; UnitW = SolW; UnitW_Max = SolW / SolVol; AR = Math.Round(AR, 1); label_VR.Text = output + AR; } private void comboBox_Unit_SelectedIndexChanged_1(object sender, EventArgs e) { if (comboBox_Unit.Text == "lb") { 169 CA_f = CA; Sand_f = Sand; Cement_f = Cement; FA_f = FA; Water_f = Water; } else if (comboBox_Unit.Text == "g") { CA_f = CA * 453.6; Sand_f = Sand * 453.6; Cement_f = Cement * 453.6; FA_f = FA * 453.6; Water_f = Water * 453.6; } CA_f = Math.Round(CA_f, 1); Cement_f = Math.Round(Cement_f, 1); Sand_f = Math.Round(Sand_f, 1); FA_f = Math.Round(FA_f, 1); Water_f = Math.Round(Water_f, 1); label_Cement.Text = output + Cement_f; label1_CA.Text = output + CA_f; label1_Sand.Text = output + Sand_f; label_FA.Text = output + FA_f; label1_water.Text = output + Water_f; } private void comboBox_Unit2_SelectedIndexChanged(object sender, EventArgs e) { if (comboBox_Unit2.Text == "lb/ft3") { UnitW_f = UnitW; UnitW_Max_f = UnitW_Max; } else if (comboBox_Unit2.Text == "kN/m3") { UnitW_f = UnitW / 6.37; UnitW_Max_f = UnitW_Max / 6.37; } UnitW_f = Math.Round(UnitW_f, 1); UnitW_Max_f = Math.Round(UnitW_Max_f, 1); SolVol = Math.Round(SolVol, 1); label_UnitW.Text = output + UnitW_f; label_UnitW_Max.Text = output + UnitW_Max_f; label_SolidVol.Text = output + SolVol; 170 } private void button2_Click(object sender, EventArgs e) { MoldW = Convert.ToDouble(textBox_Mold.Text); if (comboBox_Mold.Text == "3 x 6 in") { SamplW = 453.6 * UnitW_f * Math.PI * 9 * 6 / 4/12/12/12; SamplWMax = 453.6 * UnitW_Max_f * Math.PI * 9 * 6 / 4 / 12 / 12 / 12; } if (comboBox_Mold.Text == "4 x 8 in") { SamplW = 453.6 * UnitW_f * Math.PI * 16 * 8 / 4 / 12 / 12 / 12; SamplWMax = 453.6 * UnitW_Max_f * Math.PI * 16 * 8 / 4 / 12 / 12 / 12; } if (comboBox_Mold.Text == "4 x 4 x 16 in") { SamplW = 453.6 * UnitW_f * 4 * 4 * 16 / 12 / 12 / 12; SamplWMax = 453.6 * UnitW_Max_f * 4 * 4 * 16 / 12 / 12 / 12; } MandSampl = MoldW + SamplW; MandSamplMax = MoldW + SamplWMax; MandSampl = Math.Round(MandSampl, 1); MandSamplMax = Math.Round(MandSamplMax, 1); label_SamplW.Text = output + MandSampl; label_SamplMW.Text = output + MandSamplMax; } } } 171