Utilization of waste glass as precursor material in one-part alkali-activated aggregates

The increasing demand for glass products has led to a rise in waste glass (WG), which is commonly disposed of in landfills, causing environmental degradation. Moreover, the direct adoption of a high volume of WG as aggregates in concrete can lead to unfavorable ASR expansion due to its high level of reactive silica. This study explores a one-part alkali activation method to produce WG-based aggregates, aiming to reduce the reactive silica content, mitigate ASR expansion and increase the recycling rate of WG. Waste glass powder (WGP) with a replacement ratio of 100% was combined with two different alkalis (sodium metasilicate pentahydrate (Na 2 SiO 3 .5H 2 O) and sodium aluminate (NaAlO 2 )) through the cold-bonded one-part alkali activation method to produce WG-based alkali-activated aggregates (WG-AAAs). The influence of various activator contents (0%, 6%, 9%, 12% and 15%) on the physical and mechanical properties of the WG-AAAs was investigated. The WG-AAAs had a bulk density ranging from 920 to 1010 kg/m 3 , which can be classified as lightweight aggregates. The WG-AAAs with 12% NaAlO 2 showed the best performance, with a water absorption of 8.46% and single particle crushing strength of 3.19 MPa. SEM-EDS and XRD results indicated that WG-AAAs with the supply of alumina from NaAlO 2 exhibited a lower Si/Al ratio, leading to the formation of C-(N)-A-S-H gel, which improved the strength and creating a denser microstructure. Furthermore, the WG-AAAs showed no ASR expansion concerns, conforming to the expansion limit specified in ASTM C1260.