Effects of waste glass sand on the thermal behavior and strength of fly ash and GGBS based alkali activated mortar exposed to elevated temperature

Abstract

This study investigated the thermal behavior of a series of alkali activated mortars (AAm) based on blends of fly ash (FA) and ground granulated blast furnace slag (GGBS) precursors with waste glass (WG) and natural sand (NS) as fine aggregate. Results revealed that with increasing GGBS content, the AAms deteriorate after exposure to elevated temperature owing to dehydration causing mass loss, and weakening binder- aggregate bonding, which in turn decreased residual compressive strength. The efficacy of WG on the thermal behavior and mechanical strength depends on the binder type as well as on the temperature to which the AAms were exposed. In FA rich AAms, increasing WG showed good resistance to elevated temperature (200 –800 °C). Increasing WG in GGBS rich AAms, only showed acceptable performance for AAms exposed to 600 °C and 800 °C as the melted WG formed strong bonds with the matrix. However, for samples with 100 wt% WG and 100 wt% GGBS, surface spalling occurred at 200 °C, 400 °C and 600 °C and explosive spalling at 800 °C mainly caused by the high stresses induced on the expansion of both WG and matrix during exposure to elevated temperature.