Ceramic Waste Powder-Derived Dry Activator for Sustainable One-Part Fly Ash-Based Geopolymer Mortars

Ceramic waste powder (CWP) is a silica-rich fired residue with limited reactivity but considerable potential as a precursor for solid alkaline activators. This study investigated the thermochemical conversion of CWP into a dry activator for a one-part fly ash-based geopolymer mortar. A Taguchi L9 design was used to examine the effects of SiO2/Na2O molar ratio (0.5–2.5), activation temperature (150–350 °C), and activation duration (1–3 h). The synthesised powders were characterized by FTIR, while their activation performance was evaluated through 28-day compressive strength testing, supported by the SEM-EDS analysis of selected mortars. Compressive strength ranged from 4.63 to 14.16 MPa, with the highest value obtained at a molar ratio of 0.5, 350 °C, and 3 h. The replicate-based S/N analysis showed the largest main-effect variations for activation temperature and molar ratio, whereas activation duration had a smaller influence. FTIR and microstructural observations indicated more pronounced changes in the principal Si-O-T spectral region and a denser geopolymer matrix in the better-performing systems. The results show that thermochemical processing can convert CWP into a functional dry activator, demonstrating the proof-of-concept feasibility of a powder-based route for one-part geopolymer mortar production.