Civil MDC

Report on Alkali-Aggregate Reactivity 2

Report on Alkali-Aggregate Reactivity


In many parts of the world, precautions must be taken to avoid excessive expansion due to alkali-aggregate reactivity(AAR) in many types of concrete construction. AAR may involve siliceous aggregates (alkali-silica reactivity, ASR)or carbonate aggregates (alkali-carbonate reactivity, ACR),and failure to take precautions may result in progressive deterioration, requiring costly repair and rehabilitation ofconcrete structures to maintain their intended function.

Extensive knowledge is available regarding the mechanisms of the reactions, the aggregate constituents that may react deleteriously, and precautions that can be taken to avoidresulting distress. However, deficiencies still exist in our knowledge of both ASR and ACR. This is particularly true with respect to the applicability of test methods to identify the potential for reactivity, methods to repair affected concrete, and means to control the consequences of thereactions in existing structures.

Intensive research has been conducted to develop this needed information. As a result, concrete structures can now be designed and built with a high degree of assurance that excessive expansion due to AAR will not occur and cause progressive degradation of the concrete. This report provides information for those involved with the design and construction of concrete, to make them aware of the factors involved in AAR and the means that are availableto control it.

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