Characterization of waste clay brick powder and its effect on the mechanical properties and microstructure of geopolymer mortar

Fly ash is known as a common geopolymer precursor. However, it is important to search for suitable alternatives as the availability of fly ash will reduce with the move to more renewable energies. This paper evaluates the feasibility of using waste clay brick powder (WCBP) as a partial alternative for fly ash in geopolymer mortars with ground granulated blast furnace slag (GGBFS), under ambient and heat curing conditions. The physical, mechanical, and mineralogical properties of geopolymer mortar with 10 to 40% WCBP were investigated. Microstructural properties of WCBP and geopolymer mortars were investigated using X-ray fluorescence (XRF), X-ray diffraction (XRD), tescan integrated mineral analyzer (TIMA), scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). Reductions of the flow of fresh mortar were observed with the increase of WCBP. The highest 28 days compressive strengths were obtained in the mortars containing 40% WCBP, both at ambient and heat curing conditions. Microstructural analysis highlighted compact structure and reduced porosity, which are attributed to the role of WCBP in enhancing fly ash-GGBFS mortar properties by promoting geopolymer gel formation.