The effect of mineral admixtures and micronized calcite on alkali silica reaction expansions in the usage of aggregates from different origin

Abstract

This paper investigates the effectiveness of two zeolites with different reactive silica content, fly ash (FA), blast furnace slag (BFC), silica fume (SF), and micronized calcite (MC) in reducing expansion of concrete due to alkali-silica reaction. Also in this research, effects of three different cement usages were investigated by using accelerated mortar bar method, ASTM C1260. Five different aggregates, three natural sands, and two crushed sands were used for preparing mortar bars. All of these aggregates have been petrographically examined according to ASTM C295 standard and have been found out to be harmful to ASTM C 1260. Performances of the mineral admixtures were compared by examining the expansion due to alkali silica reaction (ASR). The aggregate and cement mixtures were tested with accelerated mortar bar test procedures including 10 and 20% replacement of mineral admixtures by weight of cement. 20% substitution levels of all admixtures were highly effective in inhibiting the ASR. The expansions of test specimens, in which mineral admixtures were used, were within the code-defined acceptable limits of ASTM C1260. According to the standard, different cement usage should not affect expansions in this accelerated test method. However, on contrary to ASTM C1260 statement, this research showed that the mixtures prepared with the same aggregate but different cements displayed different expansions at the end of 14 days. In addition, this different cement usage does not significantly affect the expansions. Key words: Alkali silica reaction (ASR), natural zeolite (NZ), fly ash (FA), blast furnace slag (BFC), silica fume (SF), micronised calcite (MC).