2013 Volume 66 Issue 1 Pages 499-506
The deposits composed of hard volcanic rocks such as the andesite are widely spread out along the Hokuriku District. They give good aggregates as a river gravel or crushed stone. On the other hand, the regular supply of alkalis by the water splash in the Sea of Japan and the deicer scattered especially in the winter season may contribute to a steady occurrence of alkali-silica reaction（ASR）in concrete using andesitic aggregates. Taking into account the principles of local production for local consumption in construction materials, so-called “Chisan-chisho”, the reduction in both the environmental impact and the rationalization of natural resources, the use of blended cements using fly ashes has been considered paramount for ASR mitigating countermeasures in the Hokuriku District. This paper examines the restraining effect by the locally produced high-quality fly ashes for the typical two types of reactive andesitic aggregates used in the Hokuriku region. The increase of fly ash replacement ratio suitable for practical use until 20％ has effectively suppressed the ASR-induced expansion of the mortars. In addition, the evaluation about reactivity of aggregates and the progress of reaction due to ASR by polarizing microscope observation, confirmed the validity of the test results. Especially, this petrographic method was very available to recognize reactivity of aggregates and the progress of ASR.
