Expansion of Concrete Due to Alkali-Silica Reaction


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Title: Expansion of Concrete Due to Alkali-Silica Reaction

Author(s): R. Narayan Swamy and M. M. Al-Asali

Publication: Materials Journal

Volume: 85

Issue: 1

Appears on pages(s): 33-40

Keywords: alkali-aggregate reactions; alkalies; cement-aggregate reactions; concrete durability; concretes; cracking (fracturing); deterioration; expansion; silica; temperature; Materials Research

Date: 1/1/1988

Although the phenomenon of alkali-silica reaction (ASR) has been known for several decades, much of the available data are based on cement pastes and mortars. There is only sparse data on the expansion due to ASR in concrete. The paper presents comprehensive information on the expansion of concrete undergoing ASR. Both beltane opal and a synthetic-fused silica were used as reactive aggregates, and the cement used was a portland cement with about one percent sodium oxide equivalent by weight. The effects of temperature, cement content, and the presence of alkali from sources other than cement on the expansion of concrete are reported. It is shown that when all the alkali is cement bound, an alkali content of 3 to 4 kg/m3 represents a critical band of alkalinity above and below which either a dramatic increase or decrease of expansion occurs. When, in addition, external sources of alkali are also present, this range of total alkalinity represents a threshold value above which expansion again increases dramatically, irrespective of the source of alkalinity. When the reactive aggregate is of the type of fused silica, the maximum tolerable alkalinity is about 2.0 kg/m3 if disruptive expansion and cracking are to be avoided. The results showed no relation between expansion and popouts.