High temperature performance of wet-mix and dry-mix mortars prepared with different contents and size gradings of glass aggregates: Hot test and cold test

Abstract

This paper presents the mechanical property of wet-mix and dry-mix mortars prepared with different contents and size gradings of glass aggregates after exposure to an elevated temperature of 800 °C. The tests were performed during 800 °C exposure (hot test) and after cooling from 800 °C to room temperature (cold test). In the cold test, the residual compressive strength of both the wet-mix and the dry-mix mortars increased with increasing content and decreasing particle size of glass aggregates. However, for the hot test, when the replacement of river sand by the glass aggregates was above 15%, the residual compressive strength sharply decreased. This was attributed to the glass aggregates were softened and the semi-melted glass acted like “soft” aggregates which were unable to sustain stress (loading) under the hot test. Unlike the improvement mechanism through better bonding between the re-solidifying glass aggregates and the cement matrix after cooling, the optimal performance of the mortars prepared with 15% of glass aggregates to replace river sand in the hot test was attributed to the penetration of the softened glass into the empty pores during loading. Further reducing the percentage of glass aggregates led to decrease in strength due to the excessive thermal expansion of river sand in the mortars. Compared with the cold test, the impact of glass particle size was less obvious on the residual strength for the hot test. Due to their higher porosity, the dry-mix mortars performed better than the wet-mix mortars under both the hot and cold test conditions.