Influence of high temperature exposure on compressive strength and microstructure of ultra-high performance geopolymer concrete with waste glass and ceramic

This research evaluates the effect of high temperatures up to 800 °C on the compressive strength and microstructure of the developed ultra-high performance geopolymer concrete (UHPGC) containing waste glass (WG) and ceramic (WC). Fine aggregate was partially substituted with WG and WC in the range of 7.5–22.5% by vol. Samples were heated in the range of 200–800 °C at a heating rate of 5 °C/min for 1.5 h. The visual appearance, mass loss, residual compressive strength, and microscopic investigation of UHPGC mixtures were investigated. The outcomes of the experiments demonstrated that the residual strength of UHPGC containing WG varied from 98% to 97%, 59%–63%, and 27%–32% after being subjected to 300, 600, and 800 °C, respectively. While WC samples had residual strengths varying from 86% to 83%, 51%–45%, and 24%–18%, respectively. Therefore, compressive strength deteriorates more slowly with an increase in WG than WC. Microscopy experiments showed that WC pore structure expanded with temperature, notably above 600 °C, while WG had less pore structure and enhanced residual strength. Finally, the incorporation of WG is more effective in UHPGC thermal stability up to 800 °C than WC. Thermogravimetric analysis (TGA) results revealed that the mixtures containing 22.5% WG maintained about 95% of its weight, while the mixtures incorporating 22.5% WC lost 8% of their weight. It is concluded that WG could be implemented as an eco-friendly material with desirable properties at high temperatures.