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 durab

• Author biographiesAcknowledgementsList of symbols and dimensions1: Alkali-Aggregate Reaction (AAR) and its Effects on Concrete - an Overview2: Diagnostic Investigations and Tests and their Interpretation3: Effects of AAR on Engineering Properties of Concrete - Results of Laboratory Determinations4: Assessment of Risk of Structural Failure Based on Results of Laboratory or Field Tests5: Repair and Rehabilitation of AAR-affected Structures6: Epilogue - A Check-list of Important Structural Consequences of AAR