Steel Reinforced Concrete Structures Assessment and Repair of Corrosion By Mohamed A El Reedy

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Steel Reinforced Concrete Structures Assessment and Repair of Corrosion By Mohamed A El Reedy

Contents

Preface…………………………………………………………………………………………………….. xiii
The Author…………………………………………………………………………………………………xv
Chapter 1 Introduction……………………………………………………………………………….1
Reference……………………………………………………………………………………………………..3
Chapter 2 Corrosion of Steel in Concrete……………………………………………………..5
2.1 Introduction…………………………………………………………………………………………5
2.2 The Corrosion Process………………………………………………………………………….7
2.3 Black Corrosion……………………………………………………………………………………9
2.4 Pit Formation……………………………………………………………………………………….9
2.5 Bacterial Corrosion……………………………………………………………………………. 10
2.6 Corrosion Rate………………………………………………………………………………….. 10
2.7 Summary………………………………………………………………………………………….. 13
References………………………………………………………………………………………………….. 13
Chapter 3 Causes of Corrosion and Concrete Deterioration………………………….. 15
3.1 Introduction………………………………………………………………………………………. 15
3.2 Carbonation………………………………………………………………………………………. 16
3.3 Spread of Carbonation inside Concrete………………………………………………… 19
3.3.1 Parrott’s Determination of Carbonation Rates from
Permeability……………………………………………………………………………. 21
3.4 Chloride Attack…………………………………………………………………………………. 21
3.5 Chloride Movement inside Concrete……………………………………………………..22
3.6 Corrosion Rates………………………………………………………………………………….23
3.6.1 Statistical Analysis for Initiation of Corrosion and Corrosion
Rate………………………………………………………………………………………..23
3.7 Effect of Age on Concrete Strength………………………………………………………24
3.7.1 Statistical Analysis of Longtime Concrete Strength……………………..26
3.7.2 Code Recommendations……………………………………………………………26
3.7.3 Available Statistical Parameters for Concrete Strength
Considering Age………………………………………………………………………27
3.8 Corrosion’s Effect on Spalling of Concrete Cover…………………………………..27
References………………………………………………………………………………………………….. 32
Chapter 4 Assessment Methods for Reinforced Concrete Structures……………… 33
4.1 Introduction………………………………………………………………………………………. 33
4.2 Preliminary Inspection……………………………………………………………………….34
viii Steel-Reinforced Concrete Structures
4.3 Detailed Inspection…………………………………………………………………………….34
4.4 Methods of Structure Assessment………………………………………………………… 35
4.4.1 Visual Inspection……………………………………………………………………..36
4.4.1.1 Plastic Shrinkage………………………………………………………….36
4.4.1.2 Settlement……………………………………………………………………37
4.4.1.3 Shrinkage from Drying…………………………………………………37
4.4.1.4 Thermal Stresses………………………………………………………….38
4.4.1.5 Chemical Reaction……………………………………………………….39
4.4.2 Concrete Test Data……………………………………………………………………44
4.4.2.1 Core Test……………………………………………………………………..44
4.4.2.2 Rebound Hammer………………………………………………………..48
4.4.2.3 Ultrasonic Pulse Velocity……………………………………………… 51
4.4.2.4 Load Test for Concrete Members……………………………………56
4.4.2.5 Comparison between Different Tests……………………………… 59
4.4.3 Sources of Concrete Failure……………………………………………………….60
4.4.4 Example for Structure Evaluation………………………………………………. 61
4.4.5 Example for Structure Assessment……………………………………………..63
4.5 Test Methods for Corroded Steel in Concrete…………………………………………65
4.5.1 Manual Method………………………………………………………………………..65
4.5.2 Concrete Cover Measurements………………………………………………….. 67
4.5.3 Half-Cell Potential Measurements………………………………………………69
4.5.4 Electrical Resistivity Measurement……………………………………………. 71
4.5.5 Measurement of Carbonation Depth…………………………………………… 74
4.5.6 Chloride Tests…………………………………………………………………………. 74
4.6 Building Assessment………………………………………………………………………….. 75
References………………………………………………………………………………………………….. 76
Chapter 5 Codes and Specification Guides………………………………………………….79
5.1 Introduction……………………………………………………………………………………….79
5.2 Allowable Chloride Content in Concrete……………………………………………….80
5.3 Concrete Cover Specifications…………………………………………………………….. 81
5.3.1 British Standards………………………………………………………………………82
5.3.2 American Codes………………………………………………………………………82
5.3.3 European Code………………………………………………………………………..83
5.3.4 Specifications for Structures Exposed to Very Severe
Conditions……………………………………………………………………………….85
5.3.5 Egyptian Code…………………………………………………………………………85
5.3.6 Executing Concrete Cover…………………………………………………………87
5.4 Maximum Crack Width……………………………………………………………………… 91
5.4.1 Recommended Reinforcement Details of Crack Control……………….92
5.5 Design Precautions in Cases of Carbonation………………………………………….93
5.6 Design Precautions for Chloride Effects………………………………………………..95
5.6.1 Effect of the Diffusion Factor on Chloride Permeability……………….97
5.6.2 Effect of Chloride Concentration on Surface……………………………….98
Contents ix
5.6.3 Effective Chloride Concentration……………………………………………….99
5.6.4 Calculating Structure Lifetime…………………………………………………..99
5.6.5 General Design Considerations……………………………………………….. 101
References………………………………………………………………………………………………… 102
Chapter 6 Controlling Corrosion in Steel Bars………………………………………….. 105
6.1 Introduction…………………………………………………………………………………….. 105
6.2 Carbonation Process Control…………………………………………………………….. 106
6.2.1 Effect of Environmental Conditions…………………………………………. 106
6.2.2 Components of Concrete Mix………………………………………………….. 109
6.2.3 Curing………………………………………………………………………………….. 110
6.3 Chloride Control……………………………………………………………………………… 112
6.3.1 Weather Factors Affecting Corrosion……………………………………….. 112
6.3.2 Composition of Concrete Mix…………………………………………………. 113
6.3.3 Curing for Chloride Attack……………………………………………………… 114
6.3.4 Execution of Curing……………………………………………………………….. 116
6.3.4.1 The Curing Process in ACI…………………………………………. 119
6.3.4.2 British Standard for Curing…………………………………………. 120
6.4 Protecting Special Structures…………………………………………………………….. 121
References………………………………………………………………………………………………… 122
Chapter 7 Methods for Protecting Steel Reinforcements……………………………. 123
7.1 Introduction…………………………………………………………………………………….. 123
7.2 Corrosion Inhibitors………………………………………………………………………….124
7.2.1 Anodic Inhibitors……………………………………………………………………124
7.2.2 Cathodic Inhibitors………………………………………………………………… 125
7.3 Epoxy Coating of Steel Reinforcement……………………………………………….. 126
7.4 Galvanized Steel Bars………………………………………………………………………. 127
7.5 Stainless Steel…………………………………………………………………………………. 129
7.6 Fiber Reinforcement Bars…………………………………………………………………. 130
7.7 Protecting the Concrete Surface………………………………………………………… 131
7.7.1 Sealers and Membranes………………………………………………………….. 132
7.7.1.1 Coating and Sealing…………………………………………………… 132
7.7.1.2 Pore Lining……………………………………………………………….. 133
7.7.1.3 Pore Blocking……………………………………………………………. 133
7.7.2 Cathodic Protection by Surface Painting…………………………………… 134
7.8 Cathodic Protection System………………………………………………………………. 135
7.8.1 Cathodic Protection……………………………………………………………….. 135
7.8.2 Cathodic Protection Components and Design Consideration……….. 137
7.8.2.1 Source of Impressed Current………………………………………. 138
7.8.2.2 Anode System…………………………………………………………… 138
7.8.2.3 Conductive Layer……………………………………………………….. 140
7.8.2.4 Precautions in Designing the Anode…………………………….. 140
7.8.2.5 Follow-Up Precaution…………………………………………………. 142
x Steel-Reinforced Concrete Structures
7.8.3 Comparison between Cathodic Protection and Other Types
of Protection………………………………………………………………………….. 142
7.8.4 Cathodic Protection for Prestressed Concrete……………………………. 143
7.8.5 Bond Strength in Cathodic Protection………………………………………. 144
7.9 Concrete with Silica Fume………………………………………………………………… 146
References………………………………………………………………………………………………… 146
Chapter 8 Repair of Reinforced Concrete Structures…………………………………. 149
8.1 Introduction…………………………………………………………………………………….. 149
8.2 Main Steps to Executing Repair………………………………………………………… 150
8.2.1 Structure Strengthening………………………………………………………….. 150
8.2.2 Removing Concrete Cracks…………………………………………………….. 151
8.2.2.1 Manual Method…………………………………………………………. 152
8.2.2.2 Pneumatic Hammer Methods………………………………………. 152
8.2.3 Water Jet……………………………………………………………………………….. 153
8.2.4 Grinding Machine………………………………………………………………….. 155
8.3 Clean Concrete Surfaces and Steel Reinforcements……………………………… 155
8.3.1 Concrete……………………………………………………………………………….. 155
8.3.2 Clean Steel Reinforcement Bars………………………………………………. 156
8.4 New Patch Concrete…………………………………………………………………………. 160
8.4.1 Polymer Mortar……………………………………………………………………… 160
8.4.2 Cement Mortar………………………………………………………………………. 161
8.5 Execution Methods…………………………………………………………………………… 161
8.5.1 Manual Method……………………………………………………………………… 161
8.5.2 Grouted Preplaced Aggregate………………………………………………….. 162
8.5.3 Shotcrete………………………………………………………………………………. 163
8.6 Repair Steps……………………………………………………………………………………. 165
8.7 New Methods for Strengthening Concrete Structures…………………………… 165
8.8 Using Steel Sections…………………………………………………………………………. 166
8.9 Fiber-Reinforced Polymer (FRP)……………………………………………………….. 169
8.9.1 CFRP…………………………………………………………………………………… 170
8.9.2 Application On-site………………………………………………………………… 171
8.10 General Precautions…………………………………………………………………………. 172
References………………………………………………………………………………………………… 173
Chapter 9 Risk-Based Maintenance Strategy……………………………………………. 175
9.1 Introduction…………………………………………………………………………………….. 175
9.2 Basic Rules of Cost Calculation…………………………………………………………. 176
9.2.1 Present Value Method…………………………………………………………….. 176
9.2.2 Repair Time………………………………………………………………………….. 176
9.2.3 Capacity Loss in Reinforced Concrete Sections…………………………. 178
9.3 Example…………………………………………………………………………………………. 180
9.3.1 Required Time to Start of Corrosion………………………………………… 181
9.3.2 Time Required to Start of Deterioration……………………………………. 182
9.3.3 Cost Analysis for Different Protection Methods………………………… 183
Contents xi
9.4 Repair and Inspection Strategy and Optimization………………………………… 185
9.4.1 Repair…………………………………………………………………………………… 186
9.4.2 Expected Total Cost……………………………………………………………….. 186
9.4.3 Optimization Strategy…………………………………………………………….. 187
9.5 Maintenance Plan…………………………………………………………………………….. 190
9.5.1 Assessment Process……………………………………………………………….. 190
9.5.2 Risk-Based Inspection Maintenance Plan…………………………………. 193
References………………………………………………………………………………………………… 195
Index……………………………………………………………………………………………………….. 197

 

Preface

Deterioration of reinforced concrete structures has been one of the major challenges
facing civil engineers over the past 20 years. Concrete structures were famous for
being maintenance free. Over time, however, it was found that nothing is free and
that it was necessary to increase spending if one did not know how to deal with
deterioration of concrete structures. The major factor causing concrete deterioration
is corrosion of steel reinforcements, so it is very important to understand this issue
thoroughly.
This book aims to be a handbook for reinforced concrete structure maintenance
to be used as a guide for junior and senior engineers’ work in design, construction,
repair, and maintenance. Moreover, the book has been written so as to be easy for
civil engineers to understand—without any complicated chemical reactions—and to
help researchers with its very strong theoretical background.
The book consists of three main approaches. In the first, chapters 1–3 describe
the corrosion phenomena of steel in concrete, the effect of concrete properties on
the corrosion, and the precautions taken in construction to control corrosion. The
second approach concerns the evaluation of concrete structures and different methods
to protect steel reinforcement from corrosion. The last two chapters describe the
most traditional and advanced repair techniques. Moreover, chapter 9 focuses on
an advanced maintenance plan philosophy as risk-based maintenance for reinforced
concrete structures.
This book provides a practical guide to the art of concrete structure repair and
maintenance. It includes case histories from all over the world to assist the reader in
appreciating the widespread applications and ranges of advanced repair techniques