Valorization of high-volume crushed waste glass as fine aggregate in foamed geopolymer

The high production and low recycling rate of waste glass (WG) have come under increased scrutiny. While WG can be incorporated into construction materials as a binder or aggregate, its susceptibility to alkali-silica reaction (ASR) expansion restricts its large-scale usage. As a result, WG is typically used in controlled proportions or with reduced particle size, diminishing the environmental benefits. Additionally, investigations on the use of WG in geopolymer applications are less intensive compared to those involving Portland cement-based materials. This work, therefore, explores the feasibility of utilizing 100% crushed waste glass (CWG), crushed and sieved to a size below 4 mm, as fine aggregate in geopolymer applications while investigating the viability of mitigating deleterious ASR expansion using a chemical foaming approach. Results indicate non-foamed geopolymer specimens prepared using CWG exhibited deleterious ASR expansion of 0.54% at 14 days, despite the enhanced compressive strength, suggesting a reaction occurred between geopolymer paste and CWG. In contrast, the ASR expansion of foamed geopolymer specimens with CWG was significantly reduced to 0.09%, meeting the 0.1% threshold specified in ASTM C1260. Notably, the performance of foamed geopolymer specimens prepared with CWG was comparable to those prepared with natural sand. This work demonstrates a viable approach to increase the WG utilization rate without the need to reduce the WG particle size to micron level, while contributing to land conservation. It is estimated that by increasing the recycling rate of WG by 10%, up to 1493.2 hectares of land could be conserved. • Non-foamed geopolymer produced with CWG exhibits higher compressive strength. • Foaming method mitigates ASR expansion of geopolymer made with CWG to within 0.1%. • Foamed geopolymer made with CWG performs comparably to those with natural sand. • Approximately 1493.2 hectares of land could be conserved through this method.