The environmental impact of concrete production is a primary concern. Because the production process releases carbon gas emissions and absorbs much energy, this increases the problem as the demand for concrete increases. Geopolymer serves as an alternative solution. Geopolymer concrete can significantly reduce CO2 emissions and energy consumption compared to traditional concrete. Geopolymer concrete relies on a polymerization reaction between pozzolanic materials and an activator. Ground Granulate Blast Furnace Slag (GGBFS) is a pozzolanic material. It contains reactive silica and alumina that participate in the polymerization reaction. This property makes them suitable substitutes for cement. The research examines the influence of temperature and curing duration on GGBFS-based geopolymer concrete. GGBFS, as a precursor material, reacts with an alkali activator (74%:26%). The components of the alkali activator ratio of 5:2 are Na2SiO3 (Sodium silicate) and NaOH ((Sodium hydroxide) with 8 M concentration. The curing temperature varied from 60, 90, and 120 °C with curing times of 12, 18, and 24 h. Subsequently, the curing process continues with ambient curing. The testing results of the specimen were optimal after curing for 24 h at 90 °C.