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Prescriptive Mixture Design of Self-Consolidating Concrete

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Prescriptive Mixture Design of Self-Consolidating Concrete PRESCRIPTIVE MIXTURE DESIGN OF SELF-CONSOLIDATING CONCRETE NDOT RESEARCH Agreement No: P077-06-803 Report Submitted to Nevada Department of Transportation Research Division ATTN: Dr. Tie He 1263 S. Stewart Street Carson City, NV 89712 By Nader Ghafoori, Ph.D., P.E., Professor and Chairman and Hamidou Diawara, MSc, Doctorate student and Research assistant University of Nevada, Las Vegas Civil and Environmental Engineering Department 4505 Maryland Parkway Box 454015 Las Vegas, Nevada 89154-4015 Phone: (702)895-3701 Fax: (702)895-3936 May 2008 ABSTRACT OF THE REPORT PRESCRIPTIVE MIXTURE DESIGN OF SELF-CONSOLIDATING CONCRETE The research investigation presented herein was intended to study the influence of parameters such as aggregate size, admixture source, hauling time, temperature and pumping on the fresh and hardened properties of three distinct groups of self- consolidating concretes (SCC). Within each group, the selected self-consolidating concretes were made with a constant water-to-cementitious materials ratio, a uniform cementitious materials (cement and fly ash) content, and a constant coarse-to-fine aggregate ratio that provided the optimum aggregate gradation. Three coarse aggregate sizes (ASTM C 33 #8, #7, and #67) obtained from two different quarries were investigated. Four sources of polycarboxylate-based high range water reducing admixtures (HRWRA), along with their corresponding viscosity modifying admixtures (VMA), were used. All raw materials were evaluated for their physico-chemical characteristics. The investigation presented herein was divided into two major phases. The first phase aimed at: (1) comparing the optimum dosage requirement of four different sources of polycarboxylate-based HRWRA and VMA in attaining the target slump flow of 20 inches (508 mm), 25 inches (635 mm), and 28 inches (711 mm), T50 of 2 seconds or more, and a visual stability index (VSI) of 0 (Highly stable concrete) or 1 (Stable concrete), (2) evaluating the flow ability/viscosity, the dynamic stability, the passing ability, the filling ability, and the static segregation resistance of trial self-consolidating concretes, and (3) examining the properties of the selected SCCs as related to air content, bleeding, time of setting, adiabatic temperature, demolded unit weight, compressive strength and modulus of elasticity. In the second phase, the influences of hauling time, temperature and pumping on fresh performances of the selected self-consolidating concretes were evaluated. Seven different temperatures 109, 96, 83, 70, 57, 44 and 31 oF (43, 36, 28, 21, 14, 7 and -0.5 oC) and nine different hauling times (10, 20, 30, 40, 50, 60, 70, 80 and 90 minutes) were used to determine the loss in unconfined workability, dynamic stability, and flowability rate of the designed matrices. The adverse influence of the above-mentioned variables was remediated by providing sufficient initial optimum admixture dosages (overdosing method) that resulted in achieving the intended fresh properties of the designed SCCs for different hauling times and temperatures. Moreover, the second phase of the study addressed the effect of pumping at various distances of 100, 200 and 300 ft (30, 60 and 90 m) on the flow ability, passing ability, stability, rheology (yield stress and plastic viscosity), air content and air void characteristics of the selected self-consolidating concretes. ACKNOWLEDGMENTS The authors would like to acknowledge the financial support of the Nevada Department of Transportation, Grant number P 077-06-803. Special thanks are extended to the NDOT research chief, Dr. Tie He, and the research committee for their valuable suggestions throughout the project. Thanks are also given to a number of admixture manufacturers and concrete suppliers who contributed materials and equipments used in this investigation. Their names are withheld to avoid any concern of commercialization or private interest. TABLE OF CONTENTS i Page No. LIST OF TABLES x LIST OF FIGURES xiii GLOSSARY xix RESEARCH OBJECTIVE xxi TASK 0: LITTERATURE REVIEW 1 0.1. INTRODUCTION 2 0.2. AGGREGATES 3 0.2.1 Grading 4 0.2.2 Shape and texture 4 0.2.3 Bulk density or unit weight 5 0.2.4 Specific gravity 5 0.2.5 Porosity and absorption 6 0.2.6 Bond 6 0.2.7 Strength 6 0.3. PORTLAND CEMENT 7 0.3.1 Definition 7 0.3.2 Manufacturing process of Portland cement 7 0.3.3 Chemistry of Portland cement 9 0.3.3.1 Tricalcium silicate (C3S) 12 0.3.3.2 Dicalcium silicate (C2S) 12 0.3.3.3 Tricalcium aluminate (C3A) 12 0.3.3.4 Tetracalcium aluminoferrite (C4AF) 13 0.3.4 Portland cement hydration 14 0.3.4.1 Initial hydration 14 0.3.4.2 Induction period or dormant period 15 0.3.4.3 Acceleration and setting period 16 0.3.4.4 Deceleration and hardening period 16 0.3.4.5 Curing period (1 to several weeks) 16 0.4 CHEMICAL ADMIXTURES 16 0.4.1 Definition 16 ii 0.4.2 Background 17 0.4.3 Nomenclature, specification and classification 17 0.4.4 Surface-active chemicals 18 0.4.4.1 Air-entraining admixtures 19 0.4.4.1.1 Function 19 0.4.4.1.2 Chemical composition 20 0.4.4.1.3 Mechanism of action 20 0.4.4.2 Water-reducing admixtures or normal plasticizers 21 0.4.4.2.1 Function 21 0.4.4.2.2 Chemical composition 22 0.4.4.2.3 Mechanism of action 22 0.4.4.2.3.1 Adsorption 24 0.4.4.2.3.2 Electrostatic repulsion 25 0.4.4.3 Superplasticizers 27 0.4.4.3.1 Function 27 0.4.4.3.2 Chemical composition 27 0.4.4.3.3 Mechanism of action 28 0.4.4.3.4 Superplasticizer in cement hydrate product 29 0.4.4.3.5 Time of addition of superplasticizer 30 0.4.4.3.6 Effect of chemical structure on polycarboxylate polymer 30 0.4.4.3.7 Effect of cement composition on polycarboxylate polymer 31 0.4.4.4 Viscosity modifying admixture (VMA) 32 0.4.4.4.1 Function 32 0.4.4.4.2 Chemical composition 32 0.4.4.4.3 Mechanism of action 33 0.4.4.4.4 Classification 34 0.4.4.4.5 HRWRA and VMA incompatibility 34 0.5 MINERAL ADMIXTURES 35 0.5.1 Nomenclature and Specifications 35 0.5.1.1 Natural materials 35 0.5.1.2 By-product materials 35 iii 0.5.1.2.1 Fly ash 35 0.5.1.2.2 Silica fume 37 0.5.1.2.3 Ground Granulated Blast Furnace Slag (GGBFS) 39 TASK 1: DEVELOPMENT OF SELF-CONSOLIDATING CONCRETE SPECIFICATIONS ACCEPTANCE CRITERIA AND TEST METHODS 40 TASK 2: PREPARATION AND APPRAISAL RAW MATERIALS 42 2.1. INTRODUCTION 43 2.2. MATERIAL PREPARATION AND APPRAISAL 43 2.2.1 Aggregates 43 2.2.1.1 Quarry Q 44 2.2.1.2 Quarry R 44 2.2.1.3 Quarry S 44 2.2.2 Portland cement 49 2.2.3 Fly ash 49 2.2.4 Water 49 2.2.5 Chemical Admixtures 49 TASK 3: MIXTURE DEVELOPMENT OF SELF-CONSOLIDATING CONCRETE 53 3.1 INTRODUCTION 54 3.2 SCOPE 54 3.3 MIXTURE PROPORTION METHODOLGY 54 3.4 EXPERIMENTAL PROGRAM 56 3.4.1 Mixture proportion design 56 3.4.2 Mixing, sampling, curing, and testing procedures 63 3.5 DISCUSSION OF RESULTS 68 3.5.1 Optimum admixtures dosage 68 3.5.1.1 Influence of admixture source on optimum admixture dosage 67 3.5.1.2 Influence of slump flow value on optimum admixture dosage 73 3.5.1.3 Predictive statistical equations of the SCC admixture dosage 75 3.5.2 Fresh characteristics 76 3.5.2.1 Slump flow 76 iv 3.5.2.2 Flow ability/Viscosity 84 3.5.2.2.1 Influence of admixture source on flowability/viscosity 84 3.5.2.2.2 Influence of slump flow on flowability/viscosity 85 3.5.2.3 Stability 85 3.5.2.3.1 Dynamic segregation resistance 85 3.5.2.3.1.1 Influence of admixture source on dynamic segregation resistance 86 3.5.2.3.1.2 Influence of slump flow on dynamic segregation resistance 86 3.5.2.3.2 Static segregation resistance 87 3.5.2.3.2.1 Influence of admixture source on static segregation resistance 87 3.5.2.3.2.2 Influence of slump flow on static segregation resistance 87 3.5.2.4 Passing ability 90 3.5.2.4.1 Influence of admixture source on passing ability 91 3.5.2.4.2 Influence of slump flow on passing ability 92 3.5.2.5 Filling ability 92 3.5.2.6 Air content 92 3.5.2.7 Bleeding 93 3.5.2.8 Setting time 93 3.5.2.9 Adiabatic temperature 94 3.5.2.9.1 Influence of admixture source on adiabatic temperature 95 3.5.2.9.2 Influence of slump flow on adiabatic temperature 97 3.5.3 Bulk characteristics 97 3.5.3.1 Demolded unit weight 97 3.5.3.2 Compressive strength 101 3.5.3.2.1 Influence of admixture source on compressive strength 101 3.5.3.2.2 Influence of slump flow on compressive strength 104 3.5.3.2.3 Strength and aggregate correlation 104 3.5.3.2.4 Predictive statistical equation of the compressive strength v of the selected self-consolidating concretes 104 3.5.3.3 Static modulus of elasticity 106 3.5.3.3.1 Influence of admixture source on static modulus of elasticity 109 3.5.3.3.2 Influence of slump flow on static modulus of elasticity 109 3.5.3.3.3 Measured versus specified modulus of elasticity 109 3.6 CONCLUSIONS 113 TASK 4: INFLUENCE OF HAULING TIME ON FRESH PERFORMANCES OF SELF CONSOLIDATING CONCRETE 114 4.1.
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