Alkali-reactivity problems with emphasis on Canadian aggregates: Fid-Bau Portal

Alkali-reactivity problems with emphasis on Canadian aggregates

Gillott, J.E.

Abstract The “classical” form of alkali-aggregate reaction involves the disordered forms of silica particularly opal, chert and chalcedony. The alkali-carbonate reaction involves argillaceous dolomitic limestones and the alkali silicate reaction is found in some grey-wackes, phyllites and argillites. Concrete deterioration due to the alkali-silica reaction has been reported from nearly all major geographic regions of Canada. In the very far north expansive cherts were found on Ellesmere Island. On the Prairies chert is common in the gravels derived from various limestone formations in the Cordillera. These cherts seem to show a low level of alkali-expansivity but when this is combined with other forms of attack on concrete it may contribute to durability failure. Chert containing sands and gravels which show a lowlevel of alkali-expansivity are also known from Quebec. Siliceous limestones, some of whichcontain chalcedony, are known from Ontario and Quebec and in some instances, appear to be a major factor in concrete deterioration. The classical areas of alkali-carbonate reaction occur in Kingston and other parts of Ontario. Greywackes, phyllites and argillites associated with alkali-expansive reactions in concrete have been described particularly from the Maritime Provinces, from parts of the Canadian Shield and from the northern part of Ellesmere Island.