Distribution of ASR gel in conventional wet-mix glass mortars and mechanically produced dry-mix glass blocks

Abstract

The alkali-silica reaction (ASR) of recycled glass mortars prepared by the traditional wet-mix and the mechanically compacted dry-mix methods using a same aggregate-to-cement (A/C) ratio was examined based on the ASTM C1260 accelerated mortar bar test method. The test results showed the expansion values of the dry-mix glass blocks were within the threshold of ASTM C1260 while the wet-mix glass mortars were above the threshold. The mercury intrusion porosimetry (MIP) results of the dry-mix blocks showed a new peak in the larger pore size range between 10 µm and 100 µm in the differential curves, and the porosity in this ranges decreased after the ASR test. As revealed by scanning electron microscopy-backscattered electron (SEM-BSE) image analysis, the mitigation of ASR expansion and the decrease of porosity were mainly due to the distinctive different distribution of ASR gel in the dry-mix blocks. Compared to the ASR gel formed within the glass aggregate in the wet-mix mortars, the ASR gel in the dry-mix blocks was mainly observed on the surface of glass aggregates in the larger pores (between 10 and 100 µm). No ASR gel was observed in the interface between the glass aggregates and the cement paste of both the wet-mix mortars and the dry-mix blocks. The release of the swelling pressure of the ASR gel by the large pore in the dry-mix blocks suppressed the further development of cracks caused by ASR expansion.