Influence of waste glass powder on the physico-mechanical properties and microstructures of fly ash-based geopolymer paste after exposure to high temperatures

The present study investigated the properties of fly ash-based geopolymer pastes containing waste glass powder (WGP) after being exposed to ambient and high temperatures. The influences of WGP on the workability, setting time, compressive strength and bonding strength of geopolymer pastes were investigated. The results showed that the physical properties such as workability and setting time were changed by adding WGP. The workability of the paste specimens increased with the content of WGP. The setting time decreased with the increased content of WGP. Furthermore, the introduction of WGP changed the Si/Al ratio and thus the mechanical properties. The mechanical properties such as compressive and bonding strengths were enhanced as a result of more reactive silicon and alumina excited by WGP. WPG participated in the geopolymerization and more homogeneous gel matrix was produced. Both of the optimum compressive and bonding strengths were obtained at a certain WGP content (20%). After exposure to high temperatures (up to 1200℃), the unreacted WGP melted to fill the porous microstructures of the geopolymer matrix, which mitigated the increase of pores. The retention ratio of residual strengths obtained higher values after adding WGP, which proved that a proper ratio of WGP could enhance the fire-resistance of geopolymer paste when it was subjected to high temperatures.