Alkali-aggregate reactivity in Quebec (Canada)

In the province of Quebec, due to the particular geology and the historic u se of high-alkali cements, a large number of concrete structures are affect ed by alkali-silica reactivity (ASR). Consequently, tremendous effort was m ade in this province during the last 20 years on (1) the determination in t he laboratory (testing methods) as well as in the field (inspection of stru ctures) of the potential alkali-aggregate reactivity (AAR) of concrete aggr egates, (2) the prevention of AAR in new structures, and (3) the management of existing structures affected by this problem. For new structures, the m ost popular measure used in Quebec in the presence of potentially reactive aggregates consists of limiting the alkali contribution by the cement to 3 kg/m(3) of concrete (Na2Oeq). Also, blended silica fume cements were used o n many occasions against ASR; ternary cements containing fly ash and silica fume, which proved in the laboratory to be effective against ASR, are pres ently available. As concerns the existing structures affected by ASR, many of them were repaired using various techniques ranging from the simple appl ication of a penetrating sealer to the application of post-constraints or s lot cutting.