Alkali-Aggregate reaction is a an umbrella term for two types of premature concrete deterioration: alkali-silica reaction (most common) and alkali-carbonate reaction (less common). These forms of deterioration encompass a chemical reaction between CERTAIN aggregate types and the host cement paste, most importantly the internal pore solution in concrete.

AAR has been studied since the mid 1930s after the discovery of alkali-silica reaction (ASR) by Thomas Stanton of the California Division of Highways. A conference series devoted to understanding reaction mechanisms, testing methods, prediction, diagnosis and repair has been active since 1974 with a total of 16 conferences held to date. This website provides the first known web presence to consolidate and make available all of the previous ICAAR Conference Proceedings in electronic format.