Mechanism of glass powder mitigating alkali-silica expansion of concrete: Synergy control of ion diffusion and adsorption

The alkali-silica reaction (ASR) remains a critical degradation risk threatening concrete infrastructure durability. This study systematically investigates the ASR mitigation mechanisms of glass powder (GP), which is primarily driven by its pozzolanic reactivity. The presence of GP triggers two synergistic effects: microstructural densification and chemical sequestration of alkalis. Results demonstrated that GP effectively reduced ASR expansion below the ASTM C1260 standard threshold. Fine GP particles underwent pozzolanic reaction, formed two distinct C-S-H gel structures: GP-derived gels underwent Q4 to Q1 depolymerization while cement hydration produced Q0 to Q3 polymerization forming long-chain structures. Fine GP reduced mortar porosity and permeability through the micro-filler effect and C-S-H gel densification. Fine GP-derived C-S-H gels with abundant Q1 sites and high specific surface area provided enhanced adsorption sites for Na + ions, reducing the effective mobility and local availability of Na+, which mitigated ASR gel formation. The study reveals a synergistic ASR inhibition strategy, providing a comprehensive theoretical framework for understanding fine GP's multifunctional role in concrete applications.