Mitigating Alkali–Silica Reaction in Concrete

Abstract

This study investigated the effectiveness of using recycled waste glass in portland cement concrete, both as a finely ground powder and as a crushed granular material. For the potential of glass to undergo alkali–silica reactivity (ASR) distress to be assessed, mortar bar and miniature concrete prism tests were conducted with glass as both a powder and a crushed material. Parallel studies were conducted with a crushed natural aggregate. Simultaneously, strength activity index and thermogravimetric analysis tests were conducted on cementitious mixtures to evaluate pozzolanic reactivity of glass powder when used as cement replacement material. Results showed that when glass powder (70 μm average size) was used as cement replacement material, its pozzolanic behavior (measured by thermogravimetric analysis and strength activity index) was minimal. When glass powder was used as aggregate replacement material, the combination of glass powder and ASR-prone coarse aggregates showed significantly lower expansion than did control specimens in accelerated mortar bar and miniature concrete prism tests. This result indicates the beneficial effect of using glass powder in mitigating expansion induced by ASR. The mechanism by which the fine glass powder appeared to alleviate ASR in coarse aggregates, and therefore any significant distress in test specimens, was by rapidly undergoing its own ASR, which depleted alkalinity in the vicinity of reactive coarse aggregates. ASR associated with the fine glass particles was localized, and the reaction product did not appear to generate sufficient expansion to cause global distress. Additional field studies are required to validate study findings before waste glass can be used in concrete on a large scale.