Corrosion and Protection of Reinforced Concrete

Description

Reinforced concrete is the most widely used construction material in the world, and extended performance is rightly expected. Many structures are in aggressive environments, of critical importance and may be irreplaceable, so repair and protection are vital. This book surveys deterioration of concrete, particularly corrosion of the steel reinforcement, and the various chemical, biological, physical and mechanical causes of deterioration. It outlines condition survey and diagnosis techniques by on-site and laboratory measurements. It sets out mechanical methods of protection and repair, such as patching, inhibitors, coatings, penetrants and structural strengthening as well as cathodic protection and other electrochemical methods. This book also gives guidance on preventative measures including concrete technology and construction considerations, coatings and penetrants, alternate reinforcement, permanent corrosion monitoring and durability planning aspects. Asset managers, port engineers, bridge maintenance managers, building managers, heritage structure engineers, plant engineers, consulting engineers, architects, specialist contractors and construction material suppliers who have the task of resolving problems of corrosion of steel reinforced concrete elements will find this book an extremely useful resource. It will also be a valuable reference for students at postgraduate level. Authors The late Professor Brian Cherry of Monash University, Melbourne, Australia was one of the world’s leading corrosion science and engineering educators and researchers. Warren Green of Vinsi Partners, Sydney, Australia is a corrosion engineer and materials scientist. He is also an Adjunct Associate Professor. Cover Half Title Title Page Copyright Page Table of Contents Preface Authors Chapter 1: Steel-reinforced concrete characteristics 1.1 Concrete and reinforced concrete 1.2 The structure of concrete 1.3 Cements and the cementing action 1.3.1 General 1.3.2 Heat of hydration 1.3.3 Rate of strength development 1.4 Supplementary cementitious materials – blended cements 1.4.1 General 1.4.2 Fly ash 1.4.3 Slag 1.4.4 Silica fume 1.4.5 Triple blends 1.5 Aggregates 1.5.1 General 1.5.2 The design of a concrete mix 1.5.3 Estimation of fine aggregate content and mechanical properties 1.6 Mixing and curing water 1.7 Admixtures 1.7.1 Air entraining admixtures 1.7.2 Set retarding admixtures 1.7.3 Set accelerating admixtures 1.7.4 Water reducing and set retarding admixtures 1.7.5 Water reducing and set accelerating admixtures 1.7.6 High range water reducing admixtures 1.7.7 Waterproofing agents 1.7.8 Other 1.8 Steel reinforcement 1.8.1 Background 1.8.2 Conventional steel reinforcement 1.8.3 Prestressing steel reinforcement 1.9 Fibre-reinforced concrete References Chapter 2: Concrete deterioration mechanisms (A) 2.1 Reinforced concrete deterioration 2.2 Cracking 2.2.1 General 2.2.2 Plastic settlement cracking 2.2.3 Plastic shrinkage cracking 2.2.4 Early thermal contraction cracking 2.2.5 Drying shrinkage cracking 2.2.6 Crazing 2.2.7 Alkali aggregate reaction cracking 2.3 Penetrability 2.4 Chemical deterioration 2.4.1 General 2.4.2 Alkali aggregate reaction 2.4.3 Delayed ettringite formation 2.4.4 Sulphate attack 2.4.5 Acid sulphate soils 2.4.6 Thaumasite sulphate attack 2.4.7 Acid attack 2.4.8 Aggressive (Dissolved) carbon dioxide attack 2.4.9 Seawater attack 2.4.10 Leaching and efflorescence 2.4.11 Physical salt attack 2.4.12 Other chemical attack References Chapter 3: Concrete deterioration mechanisms (B) 3.1 Biological deterioration 3.1.1 Bacteria 3.1.2 Fungi 3.1.3 Algae 3.1.4 Slimes 3.1.5 Biofilms 3.2 Physical deterioration 3.2.1 Freeze-thaw 3.2.2 Fire 3.3 Mechanical deterioration 3.3.1 Abrasion 3.3.2 Erosion 3.3.3 Cavitation 3.3.4 Impact 3.4 Structural deterioration 3.4.1 Overloading 3.4.2 Settlement 3.4.3 Fatigue 3.4.4 Other 3.5 Fire damaged concrete 3.5.1 General 3.5.2 Effects on concrete 3.5.3 Visual concrete fire damage classification 3.5.4 Effect on reinforcement and prestressing steel 3.6 Examination of sites References Chapter 4: Corrosion of reinforcement (A) 4.1 Background 4.2 Portland cement and blended cement binders 4.3 Alkaline environment in concrete 4.4 Physical barrier provided by concrete 4.5 Passivity and the passive film 4.5.1 Background 4.5.2 Thermodynamics 4.5.3 Kinetics 4.5.4 Film formation 4.5.5 Film composition 4.5.6 Film thickness 4.5.7 Models and theories 4.6 Reinforcement corrosion 4.6.1 Loss of passivity and corrosion of steel in concrete 4.6.2 Uniform (Microcell) corrosion and pitting (Macrocell) corrosion 4.6.3 Corrosion products composition – chloride-induced corrosion 4.6.4 Corrosion products composition – carbonation-induced corrosion 4.6.5 Corrosion products development – visible damage 4.6.6 Corrosion products development – no visible damage 4.7 Chloride-induced corrosion 4.7.1 General 4.7.2 Passive film breakdown/pit initiation 4.7.3 Metastable pitting 4.7.4 Pit growth/pit propagation 4.7.4.1 General 4.7.4.2 Chemical conditions within propagating pits 4.7.5 Reinforcing steel quality 4.7.5.1 Metallurgy 4.7.5.2 Defects 4.7.6 Chloride threshold concentrations 4.7.7 Chloride/hydroxyl ratio 4.8 Carbonation-induced corrosion 4.9 Leaching-induced corrosion 4.10 Stray and interference current-induced corrosion 4.10.1 General 4.10.2 Ground currents 4.10.3 Interference currents 4.10.4 Local corrosion due to stray or interference currents References Chapter 5: Corrosion of reinforcement (B) 5.1 Thermodynamics of corrosion 5.1.1 Background 5.1.2 The driving potential – the Nernst equation 5.1.3 The potential – pH diagram 5.2 Kinetics of corrosion 5.2.1 Background 5.2.2 Polarisation 5.2.3 Investigation of the corrosion state 5.2.4 Pitting corrosion 5.2.5 Oxygen availability 5.2.6 Polarisation of the anodic process 5.2.7 Resistance between anodic and cathodic sites 5.2.8 Potential difference between anodic and cathodic sites 5.3 Reinforcement corrosion progress 5.4 Modelling chloride-induced corrosion initiation 5.5 Modelling carbonation-induced corrosion initiation 5.6 Modelling corrosion propagation 5.6.1 Background 5.6.2 Corrosion damage criterion 5.6.3 Factors affecting corrosion rates 5.6.4 Corrosion rates – chloride contaminated concrete 5.6.5 Corrosion rates – carbonated concrete 5.6.6 Length of corrosion propagation period 5.6.6.1 Background 5.6.6.2 General model 5.6.6.3 Andrade (2014) model 5.6.6.4 Andrade (2017) model 5.7 Design life achievement References Chapter 6: Condition survey and diagnosis (A) – on-site measurements 6.1 Planning a condition survey 6.2 Visual inspection 6.3 Cracks 6.4 Delamination detection 6.5 Concrete cover 6.6 Electrochemical measurements 6.6.1 Electrode (half-cell) potential mapping 6.6.2 Polarisation resistance 6.7 Concrete resistivity 6.8 Other measurements 6.8.1 Rebound hammer 6.8.2 Ultrasonic pulse velocity 6.8.3 Ultrasonic pulse echo 6.8.4 Impact echo 6.8.5 Ground penetrating radar 6.9 Carbonation depth 6.10 Concrete sampling 6.10.1 General 6.10.2 Wet diamond coring 6.10.3 Drilled Dust Samples 6.11 Representativeness of investigations, testings, and sampling References Chapter 7: Condition survey and diagnosis (B) – laboratory measurements 7.1 General 7.2 Cement (Binder) content and composition 7.3 Air content 7.4 Water/cement (binder) ratio 7.5 SCM content and composition 7.6 Water absorption, sorption, and permeability 7.7 Depth of chloride penetration 7.8 Sulphate analysis 7.9 Alkali aggregate reaction 7.10 Alkali content 7.11 Delayed ettringite formation 7.12 Acid attack 7.13 Chemical attack 7.14 Microbial analysis 7.15 Physical deterioration determination 7.16 Petrographic examination 7.17 Compressive strength 7.18 Reporting 7.18.1 Background 7.18.2 Commission/scope of services 7.18.3 Technical background 7.18.4 Site investigation 7.18.5 Hypothesis 7.18.6 Laboratory testing 7.18.7 Commentary on laboratory results 7.18.8 Conclusions and recommendations References Chapter 8: Repair and protection (A) – mechanical methods 8.1 Introduction 8.2 Crack repair 8.3 Repair and protection options 8.4 Patch repair 8.4.1 Stages in the process 8.4.2 Breakout 8.4.3 Rebar coatings 8.4.4 Bonding agents 8.4.5 Patching materials 8.4.6 Equipment and workmanship 8.5 Sprayed concrete (Shotcrete/Gunite) 8.6 Recasting with new concrete 8.7 Inhibitors 8.8 Coatings and penetrants 8.8.1 Anti-carbonation coatings 8.8.2 Chloride-resistant coatings 8.8.3 Penetrants 8.9 Structural strengthening 8.10 Pile jacketing References Chapter 9: Repair and protection (B) – cathodic protection 9.1 Introduction 9.2 History of cathodic protection 9.3 Impressed current cathodic protection 9.4 Galvanic cathodic protection 9.5 The application of cathodic protection 9.6 Impressed current anodes 9.6.1 Historic 9.6.2 Soil/water anodes 9.6.3 Mesh anodes 9.6.4 Ribbon/grid anodes 9.6.5 Discrete anodes 9.6.6 Arc sprayed zinc 9.6.7 Conductive organic coatings 9.6.8 Remote (soil/water) anodes 9.7 Galvanic anodes 9.7.1 Remote (soil/water) anodes 9.7.2 Thermally sprayed metals 9.7.3 Zinc mesh with fibreglass jacket 9.7.4 Zinc sheet anodes 9.8 The actions of cathodic protection 9.8.1 General 9.8.2 Thermodynamics 9.8.3 Kinetics 9.9 Criteria for cathodic protection 9.9.1 Background 9.9.2 Potential criterion 9.9.3 Instantaneous off measurements 9.9.4 300 mV shift criterion 9.9.5 100 mV potential decay (polarisation) criterion 9.9.6 AS 2832.5 criteria 9.9.7 ISO 12696 criteria 9.9.8 Other standards 9.9.9 CP criteria are proven 9.10 Selection and design of cathodic protection systems 9.10.1 General considerations 9.10.2 General design considerations 9.10.3 Current density 9.10.4 Anode layout 9.10.5 Power requirements 9.10.5.1 General 9.10.5.2 Anode resistance 9.10.5.3 Circuit resistance 9.10.5.4 Cathodic polarisation (back emf) 9.10.5.5 Power supply 9.11 Stray current and interference corrosion 9.11.1 General 9.11.2 Regulatory requirements 9.12 Commissioning 9.13 System documentation 9.13.1 Quality and test records 9.13.2 Installation and commissioning report 9.13.3 Operation and maintenance manual 9.14 Operational 9.14.1 Warranty period 9.14.2 Monitoring 9.14.3 System registration 9.15 Cathodic prevention References Chapter 10: Repair and protection (C) – electrochemical methods 10.1 Galvanic electrochemical treatments 10.1.1 Background 10.1.2 Discrete zinc anodes in patch repairs 10.1.3 Distributed discrete zinc anodes 10.1.4 Performance limitations 10.1.5 Performance assessment 10.2 Hybrid electrochemical treatments 10.2.1 Background 10.2.2 First generation system 10.2.3 Second generation system 10.2.4 Performance assessment and limitations 10.3 Electrochemical chloride extraction 10.4 Electrochemical realkalisation 10.5 Repair and protection options – costs assessment approaches 10.6 Repair and protection options – technical assessment approaches 10.6.1 General 10.6.2 ‘Do nothing’ option 10.6.3 Scenario analyses approach References Chapter 11: Preventative measures 11.1 Introduction 11.2 Concrete technology aspects 11.2.1 General 11.2.2 Mix design/mix selection 11.2.3 Mix selection process 11.2.4 Binder types 11.2.5 Water/cement (water/binder) ratio 11.2.6 Concrete strength 11.3 Construction considerations 11.3.1 General 11.3.2 The 5 Cs/Pentagon of Cs 11.4 Coatings and penetrants 11.4.1 General 11.4.2 Organic coatings 11.4.3 Penetrants 11.4.4 Pore blocking treatments 11.4.5 Cementitious overlays 11.4.6 Sheet membranes 11.5 Coated and alternate reinforcement 11.5.1 General 11.5.2 Galvanised reinforcement 11.5.3 Epoxy coated reinforcement 11.5.4 Stainless steel reinforcement 11.5.5 Metallic clad reinforcement 11.5.6 Non-metallic reinforcement 11.6 Permanent corrosion monitoring References Chapter 12: Durability planning aspects 12.1 Significance of durability 12.2 Durability philosophy 12.3 Phases in the life of a structure 12.4 Owner requirements 12.5 Designer requirements 12.6 Contractor requirements 12.7 Operator/maintainer requirements 12.8 Limit states 12.9 Service life design 12.10 Durability assessment – buried aggressive exposure – 100-year design life 12.11 Durability assessment – marine exposure – 100-, 150-, & 200-year design lives References Index