Valorization of basalt and ceramic electrical insulator wastes through geopolymerization: Synthesis, mechanical, and microstructural properties

This study examines how curing temperature and sodium hydroxide (NaOH) concentration influence the compressive strength, bond strength, porosity, chloride penetration, and corrosion resistance of geopolymer mortar made from a blend of basalt rubble (BS) and ceramic electrical insulator (CE). The experimental parameters included a sodium silicate-to-sodium hydroxide solution ratio (Na 2 SiO 3 /NaOH) of 1.0 and a liquid-to-binder (L/B) ratio of 0.68, with NaOH concentrations of 5 M, 10 M, and 15 M. Two curing conditions were used: (1) oven curing at 60 °C for 48 h and (2) ambient curing at 25 °C for 48 h. The mechanical and microstructural analysis indicated that geopolymer mortars made from BS and CE with a 10 M NaOH solution achieved the highest compressive and bond strengths. Furthermore, it was noted that porosity decreased as NaOH concentration increased. The enhanced performance of heat-cured samples highlights the importance of elevated temperatures in accelerating the geopolymerization process and enhancing mechanical properties. Furthermore, the geopolymer synthesis with BS and CE demonstrated excellent resistance to chloride penetration and corrosion, thereby underscoring its potential as a durable construction material. By repurposing waste materials into high-performance geopolymer mortar, this research promotes environmental sustainability by reducing waste, adding economic value to discarded materials, and advancing the development of eco-friendly construction solutions with long-term applicability.