Sustainable Geopolymer Mortars from Ceramic Sanitaryware Waste: Impact of Curing Methods on Mechanical and Thermal Behavior

This study investigates the influence of curing conditions on mechanical performance, residual strength after high-temperature exposure, and microstructural evolution of geopolymer mortars based on ceramic sanitaryware waste (CSW). Direct and delayed thermal curing regimes were applied at 60 °C and 80 °C for 48 h and 72 h. The fresh mixtures exhibited adequate workability with a flow diameter of 21 cm, indicating suitable consistency for casting. Results show that direct curing consistently enhances compressive strength, reaching 30.97 MPa at 80 °C for 72 h, compared with 15.88 MPa under delayed curing. Increasing curing temperature and duration improved early-age mechanical performance, particularly under direct curing conditions. After exposure to 800 °C, directly cured specimens retained higher residual compressive strength, with an improvement of approximately 6.6% compared with delayed-cured specimens. Microstructural characterization using scanning electron microscopy coupled with energy-dispersive spectroscopy and X-ray diffraction supported the observed mechanical trends under different curing conditions. The findings highlight the role of curing strategy in optimizing CSW-based geopolymer mortars for construction applications where mechanical performance and high-temperature resistance are required.