Recycling waste glass aggregate in concrete: Mitigation of alkali-silica reaction (ASR) by carbonation curing

Abstract

Concerns on low rate of glass recycling are rising due to the environmental issues caused by landfills of waste glass. Glass utilization in concrete is a promising approach to vastly improve the glass recycling rate. However, the glass in concrete causes deleterious alkali-silica reaction (ASR), which cracks the concrete and weakens its durability and is the biggest challenge for this approach. To address this challenge, this study proposes the use of carbonation curing to mitigate ASR of mortar prepared with recycled glass (named glass mortar, GM) for the first time. The effects of glass content and carbonation curing regime on mechanical properties and the resistance to ASR-induced volume change of GM were experimentally investigated. It was found that although the increase of glass content had negative impact on compressive strength and resistance to ASR of GM, with optimized carbonation curing, the 28-day compressive strength was improved by up to 40%, and the ASR-induced expansions was significantly reduced by up to 85%. In addition, the underlying mechanisms of ASR mitigation by carbonation curing were further elucidated through characterization tests including thermogravimetric analysis, pore structure analysis, and pore solution analysis. The test results demonstrated that carbonation curing mitigated the ASR in GM by reducing calcium hydroxide content and the volume of pore solution, densifying the microstructure, and reducing the pH and free alkali metal content in the pore solution. This research is hopeful to promote the application of recycling glass in the concrete industry.