Effect of OLED Waste Glass Powder on Early Strength Performance of Rapid-Hardening Concrete

Rapid-hardening concrete is widely used for rapid repairs but can suffer from accelerated hydration, shrinkage-related cracking, and durability concerns. This study evaluates the feasibility of replacing cement with OLED waste glass powder (0-30%) in CSA-type rapid-hardening concrete as a low-impact repair material. Mixtures were prepared at a constant binder content (400 kg/m³) and water-to-binder ratio (0.425), and fresh properties (slump, air content, setting time) and mechanical performance (compressive and bond strength) were tested from 4 h to 56 d. Mercury intrusion porosimetry (MIP) and TG/DTG were additionally used to interpret changes in pore structure and hydration-related thermal indices. Increasing glass powder replacement improved workability but delayed setting. A 10% replacement (O-GP10) maintained 4 h compressive strength and showed slightly higher long-term strength and consistently higher long-term bond strength than the control, whereas 20-30% replacement caused pronounced strength loss due to dilution. MIP results indicated that O-GP10 suppressed large pores (>0.1 μm) and promoted a refined pore structure dominated by finer pores. TG/DTG trends were interpreted using temperature windows as comparative indicators, suggesting age-dependent bound-water development and a reduced apparent contribution in the Al-bearing-hydrate-related region for O-GP10. Overall, roughly 10% OLED waste glass powder is suggested for CSA rapid-hardening concrete to ensure early functioning while enhancing long-term bonding and microstructural stability.