1st Edition

Alkali-Aggregate Reaction and Structural Damage to Concrete Engineering Assessment, Repair and Management

    250 Pages
    by CRC Press

    250 Pages
    by CRC Press

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    Since AAR was first identified in 1940, it has been a subject dominated by studies of the mineralogy of AAR-susceptible aggregates, the chemistry of the AAR and related reactions and laboratory tests used to diagnose AAR and predict potential future swelling. Civil and structural engineers have found the literature bewildering and difficult to apply to their immediate requirements of assessing the present and future effects of AAR on the strength, safety and serviceability of plain and reinforced concrete structures.
    The book discusses methods that can be used for laboratory destructive and in situ non-destructive testing to assess the effects of AAR, and in-service measurements and load-testing to assess the present and future safety of reinforced concrete structures. Methods of repair and rehabilitation and their long-term success are discussed, as are methods of halting or slowing the progress of AAR. At the same time, the fundamentals of AAR are explained in terms intelligible to the civil and structural engineer who is primarily trained in structural mechanics and design, but also needs to have a basic understanding of the AAR process and its effects on concrete.

    Author biographies
    List of symbols and dimensions

    Chapter 1: Alkali-aggregate reaction (AAR) and its effects on concrete – an overview
    1.1 AAR and its visible characteristics
    1.2 The chemical characteristics of AAR
    1.3 Guarding against AAR
    1.4 Main types of AAR and the appearance of fractures caused by AAR
    1.5 Chemical mechanisms of AAR
    1.6 Necessary and sufficient requirements for AAR to occur
    1.7 What is still to come
    1.8 References

    Chapter 2: Diagnostic investigations and tests and their interpretation
    2.1 Investigation of the cause of cracking in a concrete structure
    2.2 Petrology of AAR-susceptible minerals and rock types
    2.3 Assessing aggregates for AAR-potential
    2.4 Aggregate petrography
    2.5 References 

    Chapter 3: Effects of AAR on Engineering Properties of Concrete – Results of Laboratory Determinations
    3.1 Laboratory specimens and cores taken from structures
    3.2 The process of cracking
    3.3 Differences between laboratory specimens and cores taken from AAR-affected structures
    3.4 The testing of cores and laboratory-prepared cylinders or prisms
    3.5 The strength of disrupted or disintegrated concrete
    3.6 Elastic properties, compressive, indirect and direct tensile strengths of AAR-affected concrete
    3.7 Creep of AAR-damaged concrete under sustained load
    3.8 The effects on expansion of compressive stress
    3.9 Fracturing of reinforcing steel in AAR-affected structures
    3.10 The possibility of bond failure in AAR-affected reinforced concrete structures
    3.11 Review and summary of conclusions
    3.12 References

    Chapter 4: Assessment of risk of structural failure based on results of laboratory or field tests
    4.1 Introduction, definitions and examples
    4.2 An acceptable probability of failure
    4.3 Statistical calculation of the probability of failure
    4.4 Assessing demand D and capacity C
    4.5 A simple example of calculating pf
    4.6 Conclusions on statistical assessment of risk
    4.7 Full-scale test loading as a means of assessing risk
    4.8 Instruments used for measurements in laboratory and in situ load testing
    4.9 Planning, preparing and performing an in situ load test on a structure
    4.10 "Special" or "once or twice off" test loadings of complete structures
    4.11 Routine periodic test loading of complete structures
    4.12 Tests on relatively small components removed from site and tested in laboratory
    4.13 Review and conclusions
    4.14 References

    Chapter 5: Repair and rehabilitation of AAR-affected structures
    5.1 Types of repair or remedial treatment
    5.2 Arresting the AAR process – experiments with surface treatments
    5.3 Restoring design properties by resin injection
    5.4 Repair by externally applied stressing
    5.5 Strengthening by glued-on steel plates
    5.6 Repair by partial demolition and reconstruction
    5.7 Repair and rehabilitation of concrete highway pavement
    5.8 Repair or mitigation of effects of AAR in large mass concrete structures
    5.9 Repair of broken reinforcement in AAR-damaged concrete
    5.10 Review and conclusions
    5.11 References 

    Chapter 6: Epilogue – A check-list of important structural consequences of AAR
    6.1 AAR is a durability problem that is unlikely to cause structural failure
    6.2 AAR results in the deterioration of concrete properties
    6.3 In situ concrete properties can usually be expected to be considerably better than properties measured on cores in a laborator
    6.4 Compression members are relatively unaffected by AAR
    6.5 Flexural members need more consideration
    6.6 The performance of structural concrete pavements
    6.7 Compressive stresses in AAR-affected concrete
    6.8 AAR-damaged structures can reach and exceed their design service life


    Geoffrey Blight completed his Bachelor’s and Master’s degrees in Civil Engineering at the University of the Witwatersrand, Johannesburg, and his PhD in Geotechnical Engineering at the Imperial College of Science and Technology, London, in 1961. The early years of his career were spent at the South African National Building Research Institute, Pretoria, where he was engaged in research on design, operation and safety of mine waste storage facilities, including waste rock dumps and hydraulic fill tailings storage facilities. In 1969 Geoff Blight was appointed to the Chair of Construction Materials in the Department of Civil Engineering at Witwatersrand University. The field of study encompassed geotechnical engineering and concrete technology. In 1978 he was commissioned to study and diagnose the cause of cracking occurring in a series of 15- to 17-year-old reinforced concrete structures supporting the Johannesburg motorway system, and diagnosed the cause as AAR. Since then, he has researched and investigated several cases of deterioration by AAR, and has published widely on the subject. He and his co-author, Mark Alexander, spent a number of years in joint research on AAR and other aspects of the durability of concrete. He was a corresponding member of the committee that produced the British Institution of Structural Engineers’ guides on the structural effects of AAR published in 1989 and 1992 and, since 2002, has been a corresponding member of the RILEM* Technical Committees TC 106 and TC 191 – ARP which have been investigating various aspects of AAR.

    Mark Alexander completed his Bachelor’s, Master’s and PhD degrees in Civil Engineering at the University of the Witwatersrand, Johannesburg and lectured in Construction Materials at Witwatersrand University for several years. In 1992 he was appointed to the Chair of Civil Engineering at the University of Cape Town where he has further developed his interests in concrete durability, including repair and rehabilitation of deteriorated concrete structures. He has published extensively and is active in international scientific circles. He co-authored the book, Aggregates in Concrete published by Taylor and Francis in 2005. He is currently Vice President of RILEM* and is scheduled to assume the RILEM Presidency in 2012.

    * Reunion Internationale des Laboratoires et Experts des Materiaux.