Effect of exposure conditions on alkali-silica reactions in glass incorporated mortars: Importance of sodium ion

In this study, the alkali-silica reaction (ASR) in glass-incorporated mortar (GIM) under various types of Na⁺-contained exposure conditions were investigated by analyzing ASR expansion, compressive strength, and microstructure. As a key result, in comparison to the exposure condition with the same hydroxide OH⁻ concentration, a dramatic increase in ASR-induced expansion can be observed under the mixture condition of 0.5 N-NaOH + 0.5 N-NaCl. SEM/EDX results reveales that Na⁺ can improve Na/Si ratio of ASR gel, resulting in a higher swelling capacity. The variation of compressive strength under different exposure conditions was also studied, and then interpreted by analysis of pore structure characteristics. This work highlights the role of Na⁺ ion on ASR under alkaline conditions, leading to more precautions in the manufacture of GIM.