Effect Of Three Zeolite-containing Natural Pozzolanic Materials On Alkali-Silica Reaction

Abstract

This paper describes the effect of three natural zeolite-containing pozzolanic admixtures on expansion of mortar bars caused y alkali-silica reaction (ASR). Heulandite is present in all three samples, and clinoptilolite may be also present in one sample. Silica is also present in all three samples, but the mineral form and the amount of silica are significantly different in the different samples. Nevada opal was used as the alkali-expansive mineral in the aggregate, and the three admixtures (I, II, and III) were each blended with Type 10 portland cement at three replacement levels by weight of 6, 12, and 24%. Mortar bars containing 6 and 12% of the pozzolanic admixture tended to expand more than control bars, but when 24% admixture was present, expansion was reduced. The study suggests that the mineral composition and the content of alkali-reactive components in the admixture have an important bearing on their effectiveness in reducing expansion due to ASR.