feasibility of using recycled burnt clay brick waste in cement-based mortar: mechanical properties, durability, and residual strength after exposure to elevated temperatures

This paper investigates the possibility of utilizing burnt clay brick waste (cbw) as a partial replacement for natural sand (ns). the natural sand was replaced with cbw at five levels: 0%, 25%, 50%, 75%, and 100%. the physical properties, mechanical strength, shrinkage, porosity, and decay of compressive strength due to elevated temperatures (after exposure to 20, 250, 400, and 600 °c) were performed. the results show that the workability and dry density of mortar decrease as the cbw content increases. the mechanical strength of the mortar increases up to 50% replacement level of ns with cbw. the increase represents 17–25% for compression, 25–31% for tensile, and 5–31% for flexural strength relative to the reference mix (100% ns) at all curing ages (7, 14, 28, and 60 days). furthermore, results show that the shrinkage increases with an increase in the content of cbw. a decreasing trend of porosity was observed for the mortar made with up to 50% cbw, which is in good agreement with the mechanical strength of mortar. nevertheless, the residual compressive strength of mortar decreases for all mixes at elevated temperatures, and it was more pronounced for the higher temperatures. this study demonstrates that up to 50% of cbw can be used as fine aggregate in mortar since it enhances the mechanical and durability performances.