Concrete Technology: Diagnosis and Control of Alkali-Aggregate Reactions in Concrete

Aggregates containing certain constituents can react with alkali hydroxides in concrete. The reactivity is potentially harmful only when it produces significant expansion. This alkali-aggregate reactivity (AAR) has two forms--alkali-silica reaction (ASR) and alkali-carbonate reaction (ACR, sometimes called alkali-carbonate rock reaction, or ACRR). ASR is of more concern than ACR because the occurrence of aggregates containing reactive silica materials is more common. Alkali-reactive carbonate aggregates have a specific composition that is not very common. Alkali-silica reactivity has been recognized as a potential source of distress in concrete since the late 1930s. Even though potentially reactive aggregates exist throughout North America, ASR distress in structural concrete is not common. There are a number of reasons for this: Most aggregates are chemically stable in hydraulic cement concrete; Aggregrates with good service records are abundant in many areas; The concrete in service is dry enough to inhibit ASR; The use of certain pozzolans or slags control ASR; In many concrete mixtures, the alkali content of the concrete is low enough to control harmful ASR and; Some forms of ASR do not produce significant deleterious expansion. To reduce ASR potential requires understanding the ASR mechanism; properly using test to identify potentially reactive aggregates; and, if needed, taking steps to minimize the potential for expansion and related cracking. Alkali-carbonate reaction in concrete was not documented until 1957. Although ACR is much less common, this report also briefly reviews the mechanism, visual distress symptoms, identification tests, and control measures.


  • English

Media Info

  • Media Type: Print
  • Features: Figures; References; Tables;
  • Pagination: 25p

Subject/Index Terms

Filing Info

  • Accession Number: 01054775
  • Record Type: Publication
  • ISBN: 0893121460
  • Report/Paper Numbers: PCA R&D Serial No. 2071b, IS413.02
  • Files: TRIS
  • Created Date: Jul 31 2007 12:03PM