Is alkali–carbonate reaction just a variant of alkali–silica reaction ACR = ASR?

The mechanism of the alkali–carbonate reaction (ACR) has been recognized as being different from that of the more common alkali–silica reaction (ASR). However, the identification of alkali–silica gel in ACR concrete from Cornwall, Ontario, Canada by Katayama, in 1992 raised the possibility that ASR was at least playing a role in the ACR reaction. The acid insoluble residues of the ACR aggregate from Kingston, along with two other aggregates were analyzed to determine what might be contributing to the reaction. The acid insoluble residue of the ACR Kingston rock contains 96% quartz of high solubility in NaOH. Good correlation was found between the amount of quartz and expansion of concrete prisms indicating that the expansion was due mainly to an alkali–silica reaction. This conclusion is supported by observations, in 2008, by Katayama of gel in thin sections of concrete made with the Kingston aggregate. It is concluded that ACR = ASR.