2017 Volume 71 Issue 1 Pages 272-279
Although it is apparent that the deterioration due to alkali silica reaction is caused by the expansion produced by alkali-silica gel generated by the reaction between alkali and some reactive silicious minerals in alkali-reactive aggregate, there is still controversial for the mechanism of alkali-silica gel staying in the reactive aggregate and producing the expansion pressure and cracks in the concrete. Therefore, this paper tried to identify the mechanism of expansion pressure through some simplified element test using highly reactive andesite, which focuses on alkali-silica gel leaching / staying in the reactive aggregate. A series of experiments, the fluorescent observation of the alkali-silica gel distribution appeared on the cut surface of the reactive aggregate, which immersed into some kind of alkali solutions, hardened gypsum pastes or hardened cement pastes and the crack distribution in the cut surface of the cement paste matrix was carried out. As a result, the alkali-silica gel leached out and did not stay in the reactive aggregate without dense hardened cement paste matrix around. Furthermore, the alkali-silica gel in the dense hardened cement paste seems leach gradually from the reactive aggregate into hardened cement paste matrix without any visible cracking and this trend should be accelerated in case of high temperature or high water to binder ratio.
