Abstract
This paper presents the results of a study on the inhibitory effect of alkali-aggregate reaction by a treatment method of immersing aggregate into solution of hydrogen peroxide（H2O2）. This study was conducted to evaluate expansion of mortars containing H2O2-immersed reactive aggregate（glassy orthopyroxene andesite in Setouchi, Japan）, and to analyze extremely thin layers of the aggregate surface by X-ray photoelectron spectroscopy（XPS）.
The results obtained were as follows：（1）The expansion of the mortar containing H2O2-treated aggregate by mortar bar（ASTM C 227）was extremely smaller than that of mortar with non-treated aggregate after 6 months.（2）The bonding state of silicon oxides on the aggregate surfaces as evaluated by XPS was transformed by the action of H2O2 from active glassy SiO2（102.7eV）to high-crystallinity SiO2（103.2eV）, which improves chemical stability of SiO2. From these results, it was recognized that the solution of H2O2 is effective in inhibiting alkali-silica reaction.
