The alkali–carbonate reaction is an alteration process first suspected in the 1950s in Canada for the degradation of concrete containing dolomite aggregates.
[1][2] 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 (1964)[3] and may be written as follows: Brucite (Mg(OH)2), could be responsible for the volumetric expansion after de-dolomitisation of the aggregates, due to absorption of water.
The alkali–carbonate reaction is also catalyzed by the soluble NaOH produced by the reaction of Na2CO3 with Ca(OH)2 (portlandite) present in the hardened cement paste (HCP), therefore perpetuating the reaction indefinitely as observed by Fournier and Bérubé (2000) and Bérubé et al.
Anyway a chemical coupling between ACR and ASR cannot be ruled out.