Sustainable concrete with waste glass and pond ash: durability and life cycle assessment

Crushed waste glass as fine aggregate (GFA) is increasingly utilised in concrete to address environmental issues from glass waste accumulation and reduce dependency on natural river sand, which is rapidly depleting and harming river systems. However, GFA presents a significant challenge due to Alkali-Silica Reaction (ASR), which causes concrete expansion and cracking, thereby limiting its broader application. Pond ash (PA), the residual ash from coal-fired power plants stored in ash ponds or silos, is employed as a supplementary cementitious material owing to its pozzolanic properties and is viewed as a potential alternative to fly ash (FA), which mitigates ASR but faces supply shortages due to coal plant closures. This study explores the viability of PA in reducing ASR expansion and enhancing the durability of GFA concrete. Concrete mixes with varying levels of GFA and PA replacements were tested for compressive strength, shrinkage, creep, moisture absorption, permeability, sorption and ASR expansion over short- and long-term curing periods, with PA performance compared to that of FA. Key findings indicate that GFA enhances both short-term and long-term strength while increasing the risk of ASR expansion. In contrast, PA effectively eliminates ASR expansion and performs similarly to FA. Furthermore, PA demonstrated comparable performance to FA in all other durability tests, confirming its viability as an alternative to FA. Life cycle assessment results reveal that while GFA alone does not substantially improve the environmental impacts of concrete, the addition of PA markedly enhances its sustainability by significantly reducing impacts in major categories.