Recycling waste brick powder in metakaolin–fly ash-based geopolymer mortar toward high-temperature resistance

Abstract

This study develops sustainable and high-temperature resistant metakaolin–fly ash-based geopolymer with recycled brick powder (RBP). The compressive strength, thermogravimetric analysis, X-ray diffraction (XRD) and microstructure of geopolymers are investigated after 20–800 °C exposures. The results show that appropriate RBP contents can improve the compressive strength and environmental benefits of the geopolymer. The strength of the designed geopolymers increases with exposure temperature from 20 to 400 ℃ due to further polymerization reaction, while strength reduction and crack propagation occur at 600 and 800 ℃ because of vapor effect, thermal incompatibility and gel dihydroxylation. After the high-temperature calcination, the pore structures of geopolymer transform into large-diameter pores. An optimum RBP substitution content of 15% is recommended to achieve excellent compressive strength of 58.3 MPa and residual compressive strength of 52.3 MPa after 800 ℃.