vii TABLE OF CONTENTS CHAPTER NO. TITLE PAGE NO. ABSTRACT LIST OF TABLES LIST OF FIGURES LIST OF SYMBOLS AND ABBREVIATIONS iii xvii xix xxvii 1 INTRODUCTION 1 1.1 GENERAL 1 1.2 OBJECTIVES AND SCOPE OF RESEARCH 4 1.3 SCOPE OF THE WORK 4 2 REVIEW OF LITERATURE 7 2.1 GENERAL 7 2.2 HIGH STRENGTH CONCRETE 8 2.3 HIGH PERFORMANCE CONCRETE 8 2.4 CORROSION 9 2.4.1 Effect of Chloride Ingress in Concrete 13 2.4.2 Mode and Mechanisms of Chloride Ion Ingress in Concrete 13 2.5 IMPROVEMENT OF CONCRETE DURABILITY 14 2.5.1 Effect of Concrete Cover on Durability 14 2.5.2 Effect of Cement Replacement Materials on concrete Durability 15 2.5.3 Effect of Cement Type on Concrete Durability 16
viii CHAPTER NO. TITLE PAGE NO. 2.5.4 Effect of Aggregate Properties on Concrete Durability 16 2.5.5 Importance of Water Binder Ratio for a Durable Concrete 17 2.5.6 Importance of Concrete Mix 18 2.5.7 Effect of Curing Methods 18 2.5.8 Effect of Concrete Cover Thickness on Corrosion Initiation Period 19 2.6 CONCRETE DURABILITY TEST METHODS 20 2.6.1 Test Methods for Determination of Durability Properties 21 2.6.2 Steady State and Non Steady State Chloride Profile 22 2.6.3 Durability Test Parameters 23 2.6.4 Effect of Test Duration 23 2.6.5 Effect of Accelerating Voltage on Chloride Profile 23 2.6.6 Temperature Variations During the Test Period 23 2.6.7 Chloride Profile and Chloride Bindings During the Test Period 24 2.6.8 Concrete Diffusion Co-efficients 25 2.6.9 Diffusion Co-efficient from Profile Method and the Migration Co-efficient from Colorimetric Method 26 2.6.10 Diffusion Co-efficient Based on RCPT 27 2.6.11 Initiation Period Based on Diffusion Co-efficient 28
ix CHAPTER NO. TITLE PAGE NO. 2.6.12 Corrosion Initiation Period Based on Chloride Diffusion Co-efficient 29 2.7 RELATIONSHIP BETWEEN CHLORIDE DIFFUSION RATE AND CHARGE PASSED RATE 30 2.7.1 Model for Concrete Cover Cracking due to Rebar Corrosion in RCC Structures 31 2.7.2 Reinforcement Corrosion in Concrete Structures, its Monitoring and Service Life Prediction 32 2.7.3 Effect of Chloride Binding on Service Life Predictions 33 2.7.4 Critical Review about Service Life Concepts of Reinforced Concrete Structures 34 2.8 CONCLUDING REMARKS 35 3 MATERIALS AND METHODS 36 3.1 MATERIALS 36 3.2 EXPERIMENTAL SETUP 43 3.2.1 Diffusion Setup 44 3.2.2 Rapid Chloride Permeability Test Setup 47 3.2.3 Concrete Resistivity Test 48 3.2.4 Water Permeability Test 50 3.2.5 Polarization test 51 3.3 SPECIMENS DETAILS AND EXPERIMENTAL PROCEDURE 54 3.3.1 Casting and Curing Methods of Concrete Specimens 54
x CHAPTER NO. TITLE PAGE NO. 3.3.2 Preparation of Specimen for Diffusion and RCPT Tests 54 3.3.3 Preparation of Specimen for Chloride Diffusion and RCPT Tests 56 3.3.4 Preparation of Specimen for Polarization Test 57 3.3.5 Specimen Details for Studying the Effect of Cover Thickness under Accelerated Corrosion Test 60 3.3.6 Specimens Preparation with Concrete Surface Coatings 61 3.3.7 Application of Coatings on Specimens 61 3.4 EXPERIMENTAL METHODS 64 3.4.1 Diffusion Test 64 3.4.2 Rapid Chloride Permeability Test 66 3.4.3 Concrete Resistivity Test 67 3.4.4 Polarization Test 68 3.4.5 Depth of Chloride Penetration in Concretes at Marine Environment. 71 3.5 SUMMARY 72 4 RESULTS AND DISCUSSION 73 4.1 GENERAL 73 4.2 DIFFUSION TEST VALUES 73 4.2.1 Chloride Profile 73 4.2.2 Effect of Concrete Grades on Chloride Diffusion 75 4.2.3 Effect of Fly Ash on Chloride Diffusion in Different Grades of Concrete 76
xi CHAPTER NO. TITLE PAGE NO. 4.2.4 Effect of Ground Granulated Blast Furnace Slag (GGBS) on Chloride Diffusion in Different Grades of Concrete 78 4.2.5 Effect of Corrosion Inhibitors (CI) on Chloride Diffusion in M40 Grade Concrete 79 4.2.5.1 Compressive Strength 79 4.2.5.2 Flexural Strength 82 4.2.5.3 Split Tensile Strength 84 4.2.6 Effect of Corrosion Inhibitors on Chloride Diffusion 87 4.2.7 General Observations of Chloride Diffusion Values in Various Concrete Types 90 4.3 RAPID CHLORIDE ION PENETRATION TEST VALUES 90 4.3.1 Effect of Concrete Grades on RCPT 90 4.3.2 Effect of Fly Ash in Concretes of Different Grades on RCPT 91 4.3.3 Effect of Ground Granulated Blast Furnace Slag (GGBS) in Concretes of Different Grades on RCPT 92 4.3.4 Effect of Corrosion Inhibitors (CI) in Concretes of Different Grades on RCPT 93 4.3.5 General Observations of RCPT Values in Different Concrete Types 96
xii CHAPTER NO. TITLE PAGE NO. 4.4 CONCRETE RESISTIVITY TEST VALUES 96 4.4.1 Effect of Concrete Grades on Resistivity 96 4.4.2 Effect of Fly Ash on Resistivity in Different Grades of Concretes 96 4.4.3 Effect of Ground Granulated Blast Furnace Slag (GGBS) on Resistivity in Different Grades of Concretes 98 4.4.4 Effect of Corrosion Inhibitors (CI) on Resistivity in Different Grades of Concretes 99 4.4.5 General Observations of Resistivity Values in Different Concrete Types 102 4.5 WATER PERMEABILITY TEST VALUES 102 4.5.1 Effect of Concrete Grades on Water Permeability 102 4.5.2 Effect of Fly Ash on Water Permeability in Different Grades of Concretes 103 4.5.3 Effect of Ground Granulated Blast Furnace Slag (GGBS) on Water Permeability in Different Grades of Concretes 104 4.5.4 Effect of Corrosion Inhibitors on Water Permeability 105 4.5.5 General Observations of Water Permeability Values in Different Types of Concrete 108 4.6 ACCELARATED CORROSION TEST VALUES 108
xiii CHAPTER NO. TITLE PAGE NO. 4.6.1 Effect of Concrete Grades on Re-bar Corrosion 108 4.6.2 Effect of Fly Ash on Re-bar Corrosion in Different Grades of Concrete 110 4.6.3 Effect of Ground Granulated Blast Furnace Slag (GGBS) on Re-bar Corrosion in Different Grades of Concrete 111 4.6.4 Effect of Corrosion Inhibitors in Concrete on Rebar Corrosion 112 4.6.5 Effect of Concrete Surface Coatings on Corrosion Initiation Period 115 4.6.6 Effect of Concrete Cover Thickness and Grades on Corrosion Initiation Time 118 4.6.7 Effect of Fly ash, Cover Thickness and Grades of Concrete on Corrosion Initiation Time 120 4.6.8 Effect of Ground Granulated Blast Furnace Slag (GGBS), Cover Thickness and Grades of Concrete on Corrosion Initiation Time 121 4.6.9 Effect of Corrosion Inhibitor, Cover Thickness and Grades of Concrete on Corrosion Initiation Time 123 4.7 DEPTH OF CHLORIDE ION PENETRATION IN DEFFERENT GRADES OF CONCRETE AT MARINE ENVIRONMENT 124 4.8 SUMMARY 126 5.0 RELATIONSHIP BETWEEN DURABILITY PROPERTIES AND SERVICE LIFE 130
xiv CHAPTER NO. TITLE PAGE NO. 5.1 GENERAL 130 5.2 CONSTITUTIONAL RELATIONSHIP BETWEEN RCPT AND CHLORIDE DIFFUSION 130 5.3 CONSTITUTIONAL RELATIONSHIP BETWEEN RESISTIVITY AND RCPT 131 5.4 CONSTITUTIONAL RELATIONSHIP BETWEEN WATER PERMEABILITY AND RCPT 132 5.5 CONSTITUTIONAL RELATIONSHIP BETWEEN WATER PERMEABILITY AND RESISTIVITY 133 5.6 CONSTITUTIONAL RELATIONSHIP BETWEEN CORROSION INITIATION TIME AND RCPT WITH VARIOUS COVER THICKNESS 134 5.7 CONSTITUTIONAL RELATIONSHIP BETWEEN CORROSION INITIATION TIME AND RESISTIVITY 134 5.8 SERVICE LIFE ESTIMATION BASED ON CHLORIDE DIFFUSION CO-EFFICIENT 135 5.9 SUMMARY 140 6 MATHEMATICAL MODELLING FOR SERVICE LIFE ESTIMATION 141 6.1 GENERAL 141 5.2 SOFTWARE HARDWARE REQUIREMENTS (MATLAB) 141
xv CHAPTER NO. TITLE PAGE NO. 6.2.1 Hardware Requirements 142 6.2.2 Software Requirements 142 6.3 INPUT PARAMETERS REQUIRED FOR MODELLING TO ESTIMATE SERVICE LIFE OF RCC STRUCTURE 142 6.4 PREDICTING THE ACTUAL CORROSION INITIATION TIME 144 6.5 ESTIMATION OF PROPAGATION PERIOD AND SERVICE LIFE 145 6.6 EFFECT OF STEEL TYPES ON SERVICE LIFE 145 6.7 EFFECT OF ENVIRONMENT ON SERVICE LIFE 145 6.8 DEVELOPEMENT OF SERVICE LIFE MODEL 146 6.9 SYSTEM FLOW DIAGRAM 148 6.10 DATA FLOW DIAGRAM 149 6.10.1 Single Input Module 149 6.10.2 Double Input Module 150 6.10.3 Triple Input Module 151 6.10.4 Four Input Module 152 6.11 CONSTRUCTION OF INPUT TYPES IN THE MODULES 153 6.12 USER MANUAL 156 6.12.1 Service Life Estimation Model 156 6.12.2 Display Pattern and Operation of Single Input Selection 158 6.12.3 Display Pattern and Operation of Double Input Selection 160
xvi CHAPTER NO. TITLE PAGE NO. 6.12.4 Display Pattern and Operation of Triple Input Selection 161 6.12.5 Display Pattern and Operation of Four Input Selection 163 6.13 VALIDATION OF SOFTWARE MODEL WITH THE EXPERIMENTAL RESULTS 165 7 CONCLUSIONS 168 7.1 INTRODUCTION 168 7.2 CHLORIDE DIFFUSION 168 7.3 RAPID CHLORIDE PENTRATION VALUE 169 7.4 CONCRETE RESISTIVITY 170 7.5 WATER PERMEABILITY 171 7.6 ACCELERATED CORROSION INITIATION TIME 171 7.7 DEPTH OF CHLORIDE ION PENETRATION IN TIDAL ZONE 173 7.8 CORRELATIONS BETWEEN DURABILITTY PROPERTIES AND SERVICE LIFE ESTIMATION 173 7.9 SERVICE LIFE PREDICTION MODEL 174 7.10 VALIDATION OF MODEL 174 7.11 CONTRIBUTIONS 174 7.12 SCOPE FOR FURTHER RESEARCH 174 REFERENCES 176 LIST OF PUBLICATIONS 184 VITAE 186
xvii LIST OF TABLES TABLE NO. TITLE PAGE NO. 2.1 Existing Durability Test Methods 21 3.1 Test Carried Out on Raw Materials 36 3.2 Physical and Engineering Properties of Raw Materials 37 3.3 Chemical Composition of Fly Ash 37 3.4 Chemical Composition of GGBS 38 3.5 Properties of Superplasticizer (As per the Manufacturer) 38 3.6 Details of Concrete Mixtures with out Admixtures 39 3.7 Details of Concrete Mixtures with Fly Ash 39 3.8 Details of Concrete Mixtures with GGBS 39 3.9 Details of Concrete Mixtures with Corrosion Inhibitors 40 3.10 Details of Mix Proportions With out Mineral Admixture 40 3.11 Details of Mix Proportion with Fly Ash 41 3.12 Details of Mix Proportion with GGBS 41 3.13 Details of Mix Proportion with Corrosion Inhibitors 41 3.14 Compressive Strength of Different Mixes 42 3.15 Flexural and Split Tensile Strength of Mixes with Inhibitors (28 days) 43 3.16 Corrosion Risk from Resistivity 49 3.17 Parameters Monitored in Polarization Test 53 3.18 Specimen Details for Studying the Effect of 60
xviii TABLE NO. TITLE PAGE NO. Cover Thickness Under Accelerated Corrosion Test 3.19 Properties of Coating Materials 61 3.20 Consumption of Coating Materials Applied Over Concrete Specimen Surface 64 3.21 Parameters Monitored for Diffusion Test 65 3.22 Parameters Monitored for RCPT Test 67 3.23 Details of Mixes Chosen for Preparation of Test Specimens Placing in Tidal Zone 72 4.1 Depth of Chloride Penetration in Concretes of Different Types Exposed to Marine Environment 124 4.2 Durability Properties of Concretes of Various Grades with Fly Ash and GGBS and Corrosion Inhibitors 128 5.1 Service Life Estimation of Concrete of Different Mixtures Based on Chloride Diffusion Values 139 6.1 Details of Mixes chosen for validation 166 6.2 Durability Properties of Mixes studied for validation Purposes 166 6.3 Comparison of Experimental Results of Mix- Val-1 with the Data Obtained from the Model 166 6.4 Comparison of Experimental Results of Mix- Val-2 with the Data Obtained from the Model 167 6.4 Comparison of Experimental Results of Mix- Val-2 with the Data Obtained from the Model 167
xix LIST OF FIGURES FIGURE NO. TITLE PAGE NO. 2.1 Corrosion of Steel in Concrete by Chloride 10 Attack 2.2 Service Life Model Design 11 3.1 Details of One Half of the Test Cell 45 3.2 Layout of Diffusion and RCPT Experiment 45 Unit 3.3 Resistivity Measurement 49 3.4 German Water Permeability Apparatus Test 50 Setup 3.5 Test Set Up for Polarization Experiment 52 3.6 Specimen Set for Polarization Study 53 3.7 Concrete specimens Cast Using Cylindrical 55 Mould 3.8 Marking on the Specimen for Identity 55 3.9 Concrete Cylinders after 28 Days of Curing 56 3.10 Sizing of Specimen Using Diamond Saw 56 Concrete Cutter 3.11 Prepared Specimens with Markings for 57 RCPT and Chloride Diffusion Tests 3.12 Steel Bars with Insulation Tape and Coated 58 with Epoxy 3.13 Casting of Concrete Cylindrical Specimen with Re- Bars 58
xx FIGURE NO. TITLE PAGE NO. 3.14 Typical Details of Test Specimen 59 3.15 Specimens for Polarization Test 60 3.16 Preparation of Putty by Mixing Different Ingredients 62 3.17 Application of Putty Over Specimen Surface 62 3.18 Specimens with Primer Coat 63 3.19 Surface Coating in Progress 63 3.20 Specimens with Three Types of Coating 64 3.21 Diffusion Test Setup 65 3.22 Rapid Chloride Permeability Test Setup 67 3.23 Measurement of Concrete Resistivity 68 3.24 Specimens Placed Under Polarization Test (TMT bars) 70 3.25 Specimens Placed Under Polarization Test (CRS bars) 71 4.1 Typical Chloride Profile of M25 Concrete 74 4.2 Chloride Profile of M40 Grade Concrete 75 4.3 Effect of Concrète Grades on Chloride Diffusion 76 4.4 Effect of Fly Ash on Chloride Diffusion in Different Grades of Concretes 77 4.5 Effect of GGBS on Chloride Diffusion in Different Grades of Concretes 78 4.6 Compressive Strength of Concrete with Calcium Nitrate Inhibitors at Different Ages 79 4.7 Compression Strength of Concrete with Sodium Nitrite Inhibitors at Different Ages 80
xxi FIGURE NO. TITLE PAGE NO. 4.8 Compressive Strength of Concrete with Monothanolamine at Different Ages 81 4.9 Flexural Strength of Concrete with Calcium Nitrate at the Age of 28 Days 82 4.10 Flexural Strength of Concrete with Sodium Nitrite at the Age of 28 Days 83 4.11 Flexural Strength of Concrete with Monothanolmine at the Age of 28 Days 84 4.12 Split Tensile Strength of Concrete with and without Calcium Nitrate at the Age of 28 Days 85 4.13 Split Tensile Strength of Concrete with Sodium Nitrite at the Age of 28 Days 86 4.14 Split Tensile Strength of Concrete with Monoethanolamine at the Age of 28 Days 87 4.15 Effect of Calcium Nitrate Inhibitors in Concrete on Chloride Diffusion 88 4.16 Effect of Sodium Nitrite Inhibitors in Concrete on Chloride Diffusion 89 4.17 Effect of Monoethanolamine Inhibitors in Concrete on Chloride Diffusion 89 4.18 Effect of Concrete Grades on RCPT 91 4.19 Effect of Fly Ash on RCPT in Different Grades of Concrete 92 4.20 Effect of GGBS on RCPT in Different Grades of Concrete 93
xxii FIGURE NO. TITLE PAGE NO. 4.21 Effect of Calcium Nitrate on RCPT in Concrete 94 4.22 Effect of Sodium Nitrite on RCPT in Concrete (28 days) 95 4.23 Effect of Monoethanolamine on RCPT in Concrete (28 days) 95 4.24 Effect of Concrete Grades on Resistivity 97 4.25 Effect of Fly Ash on Resistivity in Different Grades of Concrete 97 4.26 Effect of GGBS on Resistivity in Different Grades of Concrete 99 4.27 Effect of Calcium Nitrate on Resistivity in Concrete 99 4.28 Effect of Sodium Nitrite on Resistivity in Concrete 100 4.29 Effect of Monoethanolamine on Resistivity in Concrete 101 4.30 Effect of Concrete Grades on Water Permeability 102 4.31 Effect of Fly Ash on Water Permeability in Different Grades of Concretes 104 4.32 Effect of GGBS on Water Permeability in Different Grades of Concretes 105 4.33 Effect of Calcium Nitrate Inhibitor on Water Permeability in Concrete 106 4.34 Effect of Sodium Nitrite Inhibitor on Water Permeability in Concrete 107
xxiii FIGURE NO. TITLE PAGE NO. 4.35 Effect of Monoethanolamine Inhibitor on Water Permeability in Concrete 107 4.36 Current Intensity for Concrete of M25 and M35 Under Accelerated Corrosion Test (29.5 mm cover thickness) 108 4.37 Effect of Concrete Grades on Corrosion Initiation Time 109 4.38 Current Intensity of Concrete of M25 and M35 with Fly Ash as CRM Under Accelerated Corrosion Test (29.5 mm cover thickness) 110 4.39 Effect of Fly Ash on Corrosion initiation Time in Different Grades of Concrete 111 4.40 Current Intensity of Concrete of M40 and M60 with 40% GGBS as CRM Under Accelerated Corrosion Test (29.5 mm cover thickness) 112 4.41 Effect of Ground Granulated Blast Furnace Slag on Corrosion Initiation Time in Different Grades of Concrete 113 4.42 Effect of Calcium Nitrate on Corrosion Initiation Time in Concrete 113 4.43 Effect of Sodium Nitrite on Corrosion Initiation Time in Concrete 114 4.44 Effect of Monoethanolamine on Corrosion Initiation Time in Concrete 115 4.45 Condition of Un-Coated Specimens at the End of Corrosion Initiation Period 116
xxiv FIGURE NO. TITLE PAGE NO. 4.46 Condition of Un-Coated Specimens Continued Till the Coated Specimens to Reach the End of Corrosion Initiation Period 116 4.47 Condition of Coated Specimens at the End of Corrosion Initiation Period 116 4.48 Current Vs Rime for Coated and Un-Coated Specimens 117 4.49 Corrosion Initiation Period for Concrete Specimens with and with out Coating 118 4.50 Effect of Concrete Cover Thickness on Corrosion Initiation Time 119 4.51 Effect of Concrete Cover Thickness on Corrosion Initiation Time in Different Grades 119 4.52 Effect of Fly Ash and Concrete Cover Thickness on Corrosion Initiation Time 120 4.53 Effect of Fly Ash on Corrosion Initiation Time in Concrete of Different Grades and Cover Thickness 121 4.54 Effect of GGBS in Concrete and Cover Thickness on Corrosion Initiation Time 121 4.55 Effect of GGBS on Corrosion Initiation Time in Concrete of Different Grades and Cover Thickness 122 4.56 Effect of Corrosion Inhibitor and Concrete Cover Thickness on Corrosion Initiation Time 123
xxv FIGURE NO. TITLE PAGE NO. 4.57 Effect of Various Corrosion Inhibitors in Concrete and Cover Thickness on Accelerated Corrosion Initiation Time 123 4.58 Chloride Ion Penetration Depth of Concretes Placed in Tidal Zone 125 4.59 Comparison of Chloride Diffusion Values Arrived Based on Marine and Accelerated Tests Conditions 126 5.1 Relationship Between RCPT and Chloride Diffusion Values 131 5.2 Relationship Between RCPT and Resistivity Values 131 5.3 Relationship Between Water Permeability and RCPT 132 5.4 Relationship Between Water Permeability and Resistivity 133 5.5 Relationship Between Corrosion Initiation Time and RCPT 134 5.6 Relationship Between Corrosion Initiation Time and Resistivity 135 5.7 Relation Between RCPT and the Corrosion Initiation Time 139 6.1 Modules Pattern 148 6.2 Flow Diagram of Single Input Module for Service Life Prediction of RCC Structures 149 6.3 Flow Diagram of Double Input Module for Service Life Prediction of RCC Structures 150
xxvi FIGURE NO. TITLE PAGE NO. 6.4 Flow Diagram of Triple Input Module for Service Life Prediction of RCC Structures 151 6.5 Flow Diagram of Four Input Module for Service Life Prediction of RCC Structures 152 6.6 Starting Screen of the Service Life Prediction Model 157 6.7 Selection Screen for Input Data 157 6.8 Display Screen for the RCPT Selection Mode 158 6.9 Display Screen After Entering the RCPT, Cover Thickness, Steel Type and the Environmental Condition 159 6.10 Graphical and Numerical Results 159 6.11 Display Screen for the RCPT and Diffusion Values Selection 160 6.12 Graphical and Numerical Results 161 6.13 Display Screen for the RCPT, Diffusion and Resistivity Values Selection 162 6.14 Graphical and Numerical Results 163 6.15 Display Screen for the RCPT, Diffusion, Resistivity and Water Permeability Values Selection 164 6.16 Graphical and Numerical Results 165
xxvii LIST OF SYMBOLS AND ABBREVIATIONS A - Ampere ASTM - American Society for Testing Materials BS - Black Steel Bar cm - Centimeter cm 2 - Square centimeter cm 2 / sec - Square centimetre per second CRM - Cement Replacement Materials EC - Epoxy Coated Bar CR - Corrosion Resistant Bar D C(Q) - Chloride Diffusion based on RCPT D C(R) - Chloride Diffusion based on Resistivity D C(P) - Chloride Diffusion based on Permeability Dc - Diffusion Coefficient Env. - Environment FA - Fly ash Fig. - Figure g - Gram GGBS - Ground Granulated Blast furnace Slag HPC - High Performance Concrete kg - Kilogram M - Molarity m 2 / s - Square meter per second Max. - Maximum ma - milli Ampère Min. - Minimum
xxviii mm - milli metre mmol/cm 3 - milli mole per cubic centimeter mmol/ cm 3 s - milli mole per cubic centimeter second mol/l - mole per liter MA - Mineral Admixture N - Normality OPC - Ordinary Portland Cement P - Permeability Q - RCPT RCPT - Rapid Chloride Permeability Test R - Resistivity SCM - Supplementary Cementing Materials SP - Superplasticizer SF - Silica Fume SS - Stainless Steel Bar T i - Accelerated Corrosion Initiation Time ACIT - Actual Corrosion Initiation Time t p - Propagation Period S l - Service Life T a (Q) - Actual Corrosion Initiation Time based on RCPT T a (D) - Actual Corrosion Initiation Time based on Chloride Diffusion T a (R) - Actual Corrosion Initiation Time based on Resistivity T a (P) - Actual Corrosion Initiation Time based on Permeability V - Volt w/b Ratio - Water-Binder ratio w/c Ratio - Water-Cement ratio