Alkali-aggregate reaction in concrete:: a review of basic concepts and engineering implications

This paper presents theoretical and applied state-of-the-art information in the field of alkali-aggregate reactivity (AAR) in concrete. The aspects discussed include basic concepts of the reaction and expansion mechanisms, conditions conducive to the development and the sustainability of AAR in concrete, field and laboratory investigation programs for evaluating the potential alkali-reactivity of concrete aggregates, selection of preventive measures against AAR, and the management of structures affected by AAR. The management section includes the diagnosis of AAR in existing concrete structures, evaluation of the potential for future distress due to AAR, and mitigation and repair approaches used on such structures. This is an introductory paper and sets the stage for a special review of the current AAR situation in the various regions of Canada that is presented in seven papers as part of this issue.