Abstract
In the Hokuriku District, a serious alkali-silica reaction（ASR） has sometimes occurred, which still continues around the Toyama city. Taking into considerations of this local condition, the use of fly ash cement is considered to be the most useful countermeasure for ASR mitigation. This paper describes the mitigating effect of classified fly ash 15％ and blast furnace slag 42％ in the typical reactive aggregate-bearing mortars, the Jouganji river gravel, in the Hokuriku District by both accelerated mortar bar tests according to JIS A 1146 and Danish method. As the result of test, the classified fly ash 15％ showed more significant mitigating effect of ASR compared with blast furnace slag 42％. By SEM-EDS analysis, it was found out that the reaction area of fly ash was limited to 1 to 2 microns only on their surfaces, but that the Ca/Si atomic ratio of formed C-S-H was very low around 0.9. Therefore, the superiority of ASR mitigation by classified fly ash 15％ especially in JIS A 1146 may be mainly attributable to the reduction in OH－ ion of pore solution caused by the adsorption of alkali ions due to large amounts of formation of C-S-H with the low Ca/Si atomic ratio.
