AAR in North America: Recommended practices for testing aggregates and selecting preventive measures

摘要

Stanton documented the first discovery of alkali-silica reaction (ASR) in California in the USA inl940, and Swenson reported the occurrence of alkali-carbonate reaction (ACR) in Ontario, Canada, in 1957. Since these pioneering works, extensive research has been conducted in both countries to elucidate the mechanisms of the reactions, determine factors that influence them, develop test methods for identifying reactive aggregates, evaluate various preventive measures and assess strategies for controlling damage in AAR affected structures. Both countries now have comprehensive guidelines and/or standard practices for minimising the risk of reaction in new construction. The approaches are similar and involve characterisation of the aggregates, estimation of the risks and consequences of reaction based on aggregate reactivity, exposure condition and the nature of the structure, and identifying appropriate preventive measures. This paper describes the development of these protocols and related test methods, and provides a summary of strategies used for preventing deleterious reaction with potentially reactive aggregates.