ASTM C 1260によるフライアッシュ含有モルタルの安山岩に対するASR抑制効果の評価

概要

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Volcanic rocks such as andesite have popularly been used for aggregates in the Hokuriku District. Therefore, the andesitic aggregates have contributed to a steady occurrence of alkali-silika reaction (ASR) in concrete. Taking into account the effective utilization of local materials, so-called "Chisan-chisho", both the reduction in the environmental impact and the rationalization of natural resources, positive countermeasures for mitigating ASR by using blended cements with fly ash (FA) or blast-furnace slag (BFS) are most expected. This paper examines the mitigating effects of mineral admixtures on ASR of mortars by the accelerated mortar-bar test (ASTM C 1260). As the result of test, the replacement with FA or BFS at normal percentages recommended by JIS A 5308 decreased significantly the expansion of mortar bars using reactive andesitic aggregates in the Noto peninsula. Especially, a high-quality fine FA produced in the Hokuriku District is hopeful in its practical use of concrete mixtures. Furthermore the ASR mitigating effects by mineral admixtures are assessed with a good performance by the test method "ASTM C 1260".