An Experimental Study on Evaluation of Suppression Effect Against ASR in Steam-Cured Fly Ash Concrete

It has been pointed out that the use of fly ash in concrete is effective in controlling the expansion due to ASR (alkali silica reaction). In Japan, the total amounts of alkalies in concrete has been kept up to 3.0kg/m3 as one of the major countermeasures for ASR suppression. Recently, it is reported that ASR may be accelerated by the steam curing of PCa concrete even in the case of low alkalies content of less than 3.0kg/m3. On the other hand, the effectiveness of fly ash on the suppression of ASR in concrete is often evaluated by means of the mortar bar method according to JIS A1146, however there are some problems that it takes the long time of 3 or 6 months in assessment, and that it can't take the pessimum content of reactive aggregate in mix proportions of mortar into considerations. In this study, the effectiveness of fly ash in steam-cured concrete was experimentally investigated. For this purpose, the steam-cured fly ash concrete with the replacement percentages by fly ashes was exposed to the accelerated test conditions which were selected as the factor, the temperature, the water supply, the immersion in saturated NaCl solution and so on. As the result of tests, it has been found that the accelerated condition exposed to the saturated NaCl solution at 50°C is most suitable as the rapid test method for the steam-cured fly ash concrete.