Recycling of waste glass in dry-mixed concrete blocks: Evaluation of alkali-silica reaction (ASR) by accelerated laboratory tests and long-term field monitoring

Abstract

Alkali-silica reaction (ASR) restricts the practical applications of recycled waste glass aggregates in concrete. Recent investigations according to ASTM C1260 (laboratory test) found that ASR expansion of glass aggregates in dry-mixed mortars could be minimized as compared with the excessive ASR expansion in wet-mixed mortars. This study aimed to validate the benefit of the dry-mixed method by a long-term (15 years) field monitoring, as no study had been reported on the long-term ASR behavior of glass based dry-mixed mortars before. The results showed that the development process of the ASR gel of the glass aggregates in the dry-mixed mortars tested by the laboratory tests (ASTM C1260 and ASTM C227) was consistent with the long-term field monitoring results. According to ASTM C227 (laboratory test), after six months of the ASR test, the ASR gel was firstly identified only on the exterior surface of the glass aggregates in the macro pores of the dry-mixed mortars (exterior-glass ASR gel), which did not cause expansion. Later, the ASR gel was observed within the interior pre-existing cracks of the glass aggregates (interior-glass ASR gel). For the long-term tested blocks collected from the field, only exterior-glass ASR gel was detected in the 15 years old blocks because of the much slower ASR rate in the field. No ASR induced crack was observed. The results of the study also showed that the additional use of glass powder as a supplementary cementitious material was effective to control the formation of the deleterious interior-glass ASR gel in the dry-mixed mortars, which could further increase the usage of waste glass in concrete blocks.