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TeachMeFinance.com - explain Alkali-aggregate reaction (AAR) Alkali-aggregate reaction (AAR) The term 'Alkali-aggregate reaction (AAR)' as it applies to the area of reclamation can be defined as ' A deterioration of concrete by which the alkali in the cement paste in the concrete reacts chemically with the silica or carbonate present in some aggregates. In the presence of free moisture, the gel (product of the reaction) will expand and manifest into cracking and differential movement in structures as well as other deleterious effects such as reduction in freeze-thaw durability and compressive and tensile strength. Three forms of alkali-aggregate reaction have been identified, see alkali-silica reaction, the slow/late-expanding type of reaction referred to as alkali-silicate reaction, and the alkali-carbonate reaction. Visit the Alkali-Aggregate Reactions database'. Previous 5 Terms: aliform aligerous aliphatic Aliquot Alkali Next 5 Terms: Alkali-carbonate reaction (ACR) alkalimeter alkaline alkalinity Alkali-silica reaction (ASR) About the author Mark McCracken Author: Mark McCracken is a corporate trainer and author living in Higashi Osaka, Japan. He is the author of thousands of online articles as well as the Business English textbook, "25 Business Skills in English". Copyright © 2005-2011 by Mark McCracken, All Rights Reserved. TeachMeFinance.com is an informational website, and should not be used as a substitute for professional medical, legal or financial advice. Information presented at TeachMeFinance.com is provided on an "AS-IS" basis. Please read the disclaimer for details.