Effects of Thermal Activation on Mechanical Performance and Sustainability of Slag-Based Geopolymers

Ground granulated blast furnace slag (GBFS)-based geopolymers represent a viable binder system that combines mechanical efficiency with a significantly lower carbon footprint when compared to conventional Portland cement. This work examines how thermal curing between 20 °C and 80 °C affects setting time, mechanical performance, shrinkage, and porosity of GBFS-based geopolymers. Curing at 40 °C accelerated gel formation, yielding compressive strengths up to 71.9 MPa. This regime also reduced shrinkage and porosity. In contrast, curing at ≥60 °C caused structural degradation and reduced long-term performance. Statistical analysis (ANOVA and Tukey post hoc) confirmed significant effects of curing regime and age on performance. These findings provide key insights for optimizing thermal curing of slag-based geopolymers, supporting their deployment in environmentally responsible construction practices.