Abstract
Deposits composed of hard volcanic rocks such as andesite are widely found in the Hokuriku District. They provide good aggregates as river gravel or crushed stone. On the other hand, the regular supply of alkalis due to salt water splash from the Sea of Japan or the use of deicer mainly during winter may contribute to constant occurrence of alkali-silica reaction (ASR) in concrete using andesitic aggregates. With consideration given to the principle of local production for local consumption in construction materials ("Chisan-chisho" in Japanese) as well as reduction in both environmental impact and consumption of natural resources, the use of blended cements using fly ashes has been regarded as one of the most appropriate means of ASR suppression in the Hokuriku District. This paper examined the suppression effect of locally produced high-quality fly ashes with two typical examples of reactive andesitic aggregates used in the Hokuriku region. It was found that replacement with fly ash up to 20% which was appropriate for practical use could effectively suppress the ASR-induced expansion of the mortars. It was also found that polarizing microscope observation was valid for the evaluation of aggregate reactivity and the determination of the progress of reaction due to ASR.
