Alkali–carbonate reaction

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The alkali–carbonate reaction is a process suspected for the degradation of concrete containing dolomite aggregate.

Alkali from the cement might react with the dolomite crystals present in the aggregate inducing the production of brucite, (MgOH)2, and calcite (CaCO3). This mechanism was tentatively proposed by Swenson and Gillott (1950)[1] and may be written as follows:

CaMg(CO3)2 + 2 NaOH → CaCO3 + Na2CO3 + Mg(OH)2

Brucite (Mg(OH)2), could be responsible for the volumetric expansion after de-dolomotisation of the aggregate, due to absorption of water.

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  1. ^ Swenson, E.G.; Gillott, J.E. (1964). "Alkali–carbonate rock reaction". Highway Research Record 45: 21–40. 
  1. Swenson, E.G. (1957) A reactive aggregate undetected by ASTM test. ASTM Bulletin No. 226, pp. 48–50.
  2. Swenson, E.G. (1957) Cement-aggregate reaction in concrete of a Canadian bridge. ASTM Proceedings, 57: 1043–1056.