Alkali-Aggregate Reactions in Concrete

Abstract

In most concretes, aggregates are more or less chemically inert. However, some aggregates react with the alkali hydroxides in concrete, causing expansion and cracking over a period of many years. This alkali-aggregate reaction has two forms: alkali-silica reaction (ASR) and alkali-carbonate reaction (ACR). ASR is the most common form of alkali-aggregate reaction (AAR) in concrete; the other, much less common, form is alkali-carbonate reaction (ACR). If the aggregate is shown to be potentially reactive by the tests, some mitigation measure must be used to control the expansion and cracking. Alkali-silica reaction can be controlled using certain supplementary cementitious materials.