The effect of firing temperature on the properties of pozzolanic cement was assessed. A set of specimens were prepared by mixing different mass ratios (40%, 50%, 60% and 70%) of imported granulated blast furnace slag, (IGBFS) with Ordinary Portland cement, (OPC). Different dosages of GBFS were investigated for weight loss, bulk density, total porosity, and mechanical compressive strength. The results show that the weight loss as well as the porosity for all mix proportions increases in the same trend with firing temperature. Quite in contrast, the bulk density and compressive strength gradually decrease with firing temperature. Finally, recrystallization, phase change, distortion, and other hydration products were investigated using XRD. The research also suggested using the specimen with more slag as a fire-resistant bonding material, which has significant environmental and financial benefits