Suppressing Effect of Fly Ash Composition on Expansion of Mortar due to Alkali-Silica Reaction

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Title: Suppressing Effect of Fly Ash Composition on Expansion of Mortar due to Alkali-Silica Reaction

Author(s): Y. Kawabata and H. Matsushita

Publication: Special Publication

Volume: 242

Issue:

Appears on pages(s): 279-292

Keywords: accelerated mortar bar test; alkali-silica reaction; amorphous silica; electrical double layer theory; fly ash; specific surface area

Date: 4/1/2007

Abstract:
This study reports the suppressing effect of fly ash on the expansion of mortar due to alkali-silica reaction. In this study, 5 types of fly ash were used. As a result, it became clear that the larger the replacement ratio of fly ash, the less the expansion of mortar became. However, the effectiveness of fly ash to suppress the expansion of mortar was different when the chemical composition or physical property of fly ash was different. It is shown that the suppressing effect of the fly ash was affected by the content of amorphous silica and the specific surface area of fly ash. Suppressing mechanism of fly ash for expansion due to ASR can be explained with electrical double layer theory. It is hypothesized that silanol sites on fly ash surface adsorb alkalis as counter ions and alkali concentration in pore fluid becomes low. This theory corresponds to the proposed index in this study.