Effect of aggregate deformation on alkali-silica reaction

Expansion of mortar specimens prepared with granodiorite, mylonite, phyllon ite, and ultramylonite from the Santa Rosa mylonite zone in southern Califo rnia were studied to investigate the effect of aggregate deformation on the alkali-silica reaction in concrete. While these rocks have basically the s ame chemical and mineralogical composition, they differ in the grain size d istribution, deformation state, and structural organization of polycrystals . ASTM C 1260 expansion tests indicate that mortar expands increasingly whe n made with granite, mylonite, phyllonite, and ultramylonite, respectively. There is a significant correlation between expansion and the development o f foliation and the accompanying reduction in grain size. The results prese nted in this paper suggest that the alkali-silica reaction depends on more factors than simply the crystallinity of quartz. Deformed granitic rocks pr ovide a good system to quantify these parameters. Texture analysis of these rocks indicate that there is a quantitative relationship between the degre e of deformation and reactivity.