Thermal, mechanical and microstructural properties of geopolymer mortars derived from ceramic sanitary-ware wastes: Pathway to net zero emission

In this study, the influence of curing temperatures (60, 80, and 100 °C) and sodium hydroxide concentrations molar (M) of (10 and 16) on the properties of geopolymer mortars, containing ceramic sanitary-ware waste (CSW) as the sole precursor was investigated. Microstructural and compositional properties were analyzed using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). Meanwhile, thermogravimetric analysis and its derivative (TGA/DTA) were conducted to assess the thermal stability of the geopolymer mortars. The compressive strength of the samples ranged from 0.5 MPa to 11.25 MPa, with the highest values recorded in samples with higher alkali concentration cured at 100 °C. Increasing the alkali concentration improved the flowability by 16 % and reduced the porosity from 18.41 % to 15.55 % in samples cured at 100 °C with 10 M and 16 M NaOH, respectively. This reduction in porosity, as confirmed by microstructural analysis, corresponded to a denser, more compact matrix associated with higher alkali concentrations. However, thermogravimetric analysis (TGA) revealed that higher NaOH concentrations led to increased thermal degradation at later ages. In the 16 M NaOH samples the weight loss exhibited a value of 11 % compared with 4 % weight loss of the 10 M NaOH samples. Additionally, curing at 60 °C and 80 °C for 24 h proved insufficient for complete hardening. These results highlight the importance of optimizing curing conditions and alkali concentrations for high-temperature applications. •Ceramic sanitary ware waste is a sustainable precursor for geopolymers.•Higher alkali concentrations enhance strength but increase thermal degradation.•Longer curing times at lower temperatures are needed for complete hardening.