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Concrete durability
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Concrete
Durability
A S P O N B O O K
Concrete
Durability
Thomas Dyer
Cover Artwork: Courtesy of Bill Revie
CRC Press
Taylor & Francis Group
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Boca Raton, FL 33487-2742
© 2014 by Taylor & Francis Group, LLC
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Version Date: 20140307
International Standard Book Number-13: 978-0-203-86211-7 (eBook - PDF)
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v
Contents
Preface xiii
Author xv
1 Introduction 1
References 5
2 Physical mechanisms of concrete degradation 7
2.1 Introduction 7
2.2 Shrinkage 8
2.2.1 Plastic shrinkage 8
2.2.1.1 Avoiding plastic shrinkage cracking 13
2.2.1.2 Avoiding plastic settlement cracking 14
2.2.2 Drying shrinkage 15
2.2.2.1 Capillary pressure 15
2.2.2.2 Gel particle effects 16
2.2.2.3 Aggregate shrinkage 17
2.2.2.4 Shrinkage as a function of time 17
2.2.2.5 Factors controlling drying shrinkage 21
2.2.2.6 Cracks resulting from shrinkage 26
2.2.3 Autogenous shrinkage 34
2.2.4 Reducing the problem of cracking
resulting from shrinkage 36
2.3 Thermal cracking 38
2.3.1 Thermal expansion and contraction 38
2.3.2 Cracks resulting from thermal contraction 41
2.3.3 Factors influencing early-age thermal contraction 42
2.3.3.1 Environmental conditions 42
2.3.3.2 Construction practices 43
vi Contents
2.3.3.3 Concrete composition 45
2.3.4 Preventing thermal cracking 51
2.4 Freeze–thaw attack 53
2.4.1 Volume changes of water 54
2.4.2 Action of ice formation in concrete 54
2.4.2.1 Scaling 58
2.4.2.2 D-cracking 60
2.4.2.3 Pop-outs 63
2.4.3 Avoiding damage from freeze–thaw attack 63
2.4.3.1 Air-entraining admixtures 63
2.4.3.2 Effects of air entrainment 64
2.4.3.3 Loss of entrained air 68
2.4.3.4 Factors affecting air content
and air-void parameters 71
2.4.3.5 Other approaches 73
2.5 Abrasion and erosion 76
2.5.1 Mechanisms of abrasion and erosion 76
2.5.2 Factors influencing resistance
to abrasion and erosion 82
2.5.3 Achieving abrasion resistance 85
References 87
3 Chemical mechanisms of concrete degradation 99
3.1 Introduction 99
3.2 Sulphate attack 99
3.2.1 Sulphates in the environment 99
3.2.1.1 Seawater 99
3.2.1.2 Soil and groundwater 100
3.2.1.3 Other sources 101
3.2.2 Conventional sulphate attack 101
3.2.3 Factors influencing the resistance of
concrete to conventional sulphate attack 105
3.2.3.1 Sulphate concentration 105
3.2.3.2 Temperature 106
3.2.3.3 Cement composition 106
3.2.3.4 Permeation properties 109
3.2.3.5 Cement content 110
3.2.4 Magnesium sulphate attack 110
3.2.5 Factors influencing the resistance of
concrete to magnesium sulphate attack 111
Contents vii
3.2.5.1 Sulphate concentration 111
3.2.5.2 Temperature 111
3.2.5.3 Cement composition 113
3.2.6 Thaumasite formation 113
3.2.7 Factors influencing thaumasite formation 114
3.2.7.1 Temperature 114
3.2.7.2 Groundwater conditions 114
3.2.7.3 Cement composition 116
3.2.8 Avoiding sulphate attack 116
3.2.9 Delayed ettringite formation 119
3.2.9.1 Avoiding delayed ettringite formation 120
3.3 Alkali–aggregate reactions 121
3.3.1 Alkali–silica reaction 121
3.3.2 Alkali–carbonate reaction 122
3.3.3 Alkali–silicate reaction 123
3.3.4 Expansion and cracking caused by
alkali–aggregate reactions 123
3.3.4.1 Alkali content 124
3.3.4.2 Temperature 126
3.3.4.3 Particle size and shape 127
3.3.4.4 Moisture 131
3.3.4.5 W/C ratio 131
3.3.4.6 Timescale for cracking 132
3.3.5 Sources of alkalis 136
3.3.5.1 Portland cement 136
3.3.5.2 Other cementitious constituents 137
3.3.6 Aggregate reactivity 142
3.3.6.1 Alkali–silica reaction 142
3.3.6.2 Alkali–silicate reaction 143
3.3.6.3 Alkali–carbonate reaction 144
3.3.7 Identifying alkali–aggregate reactions 144
3.3.8 Avoiding alkali–aggregate reaction 146
3.3.8.1 Limiting exposure to moisture 146
3.3.8.2 Limiting alkali levels 147
3.3.8.3 Admixtures 147
3.3.8.4 Pozzolanic and latent
hydraulic materials 148
3.4 Acid attack 151
3.4.1 Leaching of concrete by water 151
3.4.2 Acidic environments 152
viii Contents
3.4.3 Mechanisms of acid attack 153
3.4.4 Factors influencing rates of acid attack 157
3.4.4.1 Environmental factors 157
3.4.4.2 Material factors 159
3.4.5 Action of specific acids 161
3.4.5.1 Nitric acid (HNO3) 162
3.4.5.2 Sulphuric acid (H2SO4) 162
3.4.5.3 Acetic acid (CH3COOH) 163
3.4.5.4 Oxalic acid 163
3.4.5.5 Resorcinol 163
3.4.6 Identifying acid attack 164
3.4.7 Achieving acid resistance 164
3.4.7.1 Standards 164
3.4.7.2 Enhanced acid resistance
through mix design 165
3.4.7.3 Polymer-modified concrete 166
3.4.7.4 Protective coatings 167
References 168
4 Corrosion of steel reinforcement in concrete 183
4.1 Introduction 183
4.2 Corrosion of steel in concrete 183
4.2.1 Corrosion of metals 184
4.2.2 Chemistry of galvanic corrosion 184
4.2.3 Passivation 186
4.2.4 Steel corrosion in reinforced concrete 186
4.3 Chloride ingress into concrete 192
4.3.1 Chlorides in the environment 192
4.3.2 Ingress mechanisms 192
4.3.2.1 Diffusion 192
4.3.2.2 Flow 199
4.3.2.3 Capillary action 201
4.3.3 Chloride binding 204
4.3.4 Role of chloride in corrosion 208
4.3.5 Protection from chloride-induced corrosion 211
4.3.5.1 Mix proportions and depth of cover 211
4.3.5.2 Corrosion inhibitors and
other admixtures 215
4.3.5.3 Alternative reinforcement materials 216
4.3.5.4 Reinforcement coatings 219
Contents ix
4.3.5.5 Fibres 220
4.3.5.6 Surface coatings 220
4.4 Carbonation 221
4.4.1 Carbonation reaction 221
4.4.2 Factors influencing rates of carbonation 224
4.4.3 Changes in physical properties 232
4.4.4 Avoiding carbonation 234
References 238
5 Specification and design of durable concrete 245
5.1 Introduction 245
5.2 Concrete as a permeable medium 245
5.2.1 Porosity 246
5.2.2 Cracks 249
5.2.3 Absorption 250
5.2.4 Flow 251
5.2.5 Diffusion 252
5.3 Cement 253
5.3.1 Portland cement 255
5.3.2 Ground granulated blast-furnace slag 259
5.3.3 Fly ash 260
5.3.3.1 Siliceous FA 260
5.3.3.2 Calcareous FA 262
5.3.4 Silica fume 262
5.3.5 Limestone 263
5.3.6 Pozzolanas 263
5.4 Aggregates 264
5.4.1 Natural aggregate 264
5.4.2 Recycled aggregate 267
5.4.3 Air-cooled blast-furnace slag 268
5.4.4 Lightweight aggregates 269
5.5 Admixtures 271
5.5.1 Water reducers and superplasticisers 271
5.5.2 Air-entraining agents 272
5.5.3 Damp proofers 272
5.5.4 Corrosion inhibitors 275
5.5.5 Alkali–aggregate expansion–reducing
admixtures 275
5.6 Fibres 275
5.7 Specifying durable concrete 276
x Contents
5.7.1 Designated concrete 277
5.7.2 Designed concrete 277
5.7.3 Prescribed concrete, standardised prescribed
concrete and proprietary concrete 278
5.7.4 Specifying for durability: Designated concrete 279
5.7.4.1 Carbonation 279
5.7.4.2 Freeze–thaw attack 281
5.7.4.3 Chemical attack 282
5.7.5 Specifying for durability: Designed concrete 282
5.7.5.1 Chlorides and carbonation 285
5.7.5.2 Freeze–thaw attack 286
5.7.5.3 Chemical attack 287
5.7.6 Specifying for AR 287
5.7.7 Specification for the control of alkali–silica reaction 289
5.7.8 Specification for control of drying shrinkage 289
5.8 Concrete mix design 289
5.9 Special concrete 293
5.9.1 Self-compacting concrete 293
5.9.2 High-strength concrete 294
5.9.3 Foamed concrete 295
5.9.4 Lightweight and heavyweight concrete 296
References 297
6 Construction of durable concrete structures 301
6.1 Introduction 301
6.2 Surface of concrete 301
6.2.1 Controlled permeability formwork 302
6.2.2 Surface finish 304
6.3 Curing 305
6.4 Surface protection systems 313
6.4.1 Surface coatings 313
6.4.2 Surface sealers 315
6.4.3 Hydrophobic impregnants 316
6.4.4 Screeds 318
6.4.5 Protective liners 322
6.5 Cathodic protection 322
6.5.1 Impressed current cathodic protection 323
6.5.1.1 Anodes 324
6.5.1.2 Operation 325
6.5.1.3 Monitoring 326
Contents xi
6.5.2 Galvanic cathodic protection 328
References 330
7 Serviceability, repair and maintenance of
concrete structures 333
7.1 Introduction 333
7.2 Serviceability of structures 333
7.2.1 Limit states 334
7.2.2 Aspects of durability influencing serviceability 336
7.2.3 Durability and performance 336
7.2.4 Repair to maintain serviceability 338
7.3 Appraisal of structures 338
7.3.1 Appraisal process 339
7.3.2 Predicting future deterioration 345
7.4 In situ testing 357
7.4.1 Cover measurement 358
7.4.2 Surface absorption 359
7.4.3 Permeability 364
7.4.4 Half-cell potential 365
7.4.5 Linear polarisation resistance 366
7.4.6 Resistivity 370
7.4.7 Abrasion resistance 371
7.5 Laboratory testing 371
7.5.1 Chemical analysis 371
7.5.1.1 Chloride 374
7.5.1.2 Sulphate 378
7.5.1.3 Alkalis (sodium and potassium) 379
7.5.1.4 Carbonation 380
7.5.2 Air-void characteristics 380
7.5.3 Latent expansion test 381
7.6 Concrete repair products 382
7.7 Repair methods 384
7.7.1 Protection against ingress 385
7.7.2 Moisture control 386
7.7.3 Concrete restoration 386
7.7.4 Structural strengthening 386
7.7.5 Increasing physical and chemical resistance 387
7.7.6 Preserving or restoring passivity 387
7.7.7 Increasing resistivity 387
7.7.8 Cathodic control and cathodic protection 387
xii Contents
7.7.9 Control of anodic areas 388
7.7.10 Devising strategies for repair and rehabilitation 388
7.8 Rehabilitation of concrete structures 388
7.8.1 Electrochemical chloride extraction 388
7.8.2 Realkalisation 393
7.8.3 Migrating corrosion inhibitors 396
References 398
Index 403
xiii
Preface
The increasing importance placed on the whole-life performance of structures means that there is a growing demand for long service lives with
minimal maintenance requirements. Furthermore, the operation of infrastructure beyond the originally intended service life is becoming an increasingly common scenario. Thus, the durability of construction materials is of
more concern to civil engineers than ever before.
Concrete is a highly durable material that is also capable of imparting
protection to steel embedded within it. However, concrete structures are
frequently required to function in a wide range of aggressive environments
for long periods of service. Moreover, measures to optimize the durability
performance of concrete structures often find themselves in conflict with
structural and aesthetic design requirements.
Over the past decade, the introduction of new U.K. and European standards has sought to readdress the issue of the durability of concrete structures in a comprehensive manner. However, negotiating the resulting body
of standards and guidance can be a daunting prospect for anyone unfamiliar with their content.
This book individually examines all of the major physical and chemical mechanisms that threaten the durability of concrete and addresses the
options available for achieving appropriate durability, with emphasis on the
approaches addressed by standards. It also provides a coverage of procedures for durability assessment, testing of structures, and repair and rehabilitation methods.
This book has been written with an audience of graduate students and
young professionals in mind.