アルカリシリカ反応における塩化ナトリウムと水酸化ナトリウムの複合効果

抄録

The relationship between the alkali-silica reaction and the initial current intensity of mortars under the combined influence of NaCl and NaOH was investigated by using φ10×20cm cylindrical mortar specimens. The mortars were prepared with three types of aggregates, i.e., reactive andesite sand, siliceous sand, and Toyoura standard sand and an ordinary Portland cement. The water-cement ratio of all mortars was 0.50 and NaOH was added to the mortars at the stage of mixing. The initial current intensity of mortars was evaluated by applying a rapid chloride permeability test method (AASHTO T277). The results showed that reactive andesite sand mortars and Toyoura standard sand mortars had the lowest and the highest initial current intensity, respectively, among the mortars using three types of sands, when they were stored in a moist environment at>95% R.H. and immersed in 1N NaCl solution at 40°C for 4 weeks. These results indicate that the initial current intensity of mortars decreases with increasing alkali reactivity of sands used. It was also found that the initial current intensity of mortars at the age of 16 weeks decreased as the expansion increased except for siliceous sand mortars. The siliceous sand mortars having a relatively high equivalent percentage of Na₂O exhibited large expansion and extremely high initial current intensity at the age of 16 weeks. The mechanism of expansion behavior of the mortars was also discussed.