The purpose of this research was to examine the fresh and mechanical properties of self-compacting geopolymer concrete (SCGPC) based on ground-granulated blast-furnace slag (GGBFS) cured at room temperatures. SCGPC was manufactured at various molarities of sodium hydroxide solution (8M, 10M, 12M, and 14M) and by replacing the GGBFS with fly ash at a fixed superplasticizer dose of 5%. For all SCGPC mixes, the total binder content was maintained at 440 kg/m3 , the water-to-geopolymer solid ratio of 0.23 and Sodium Silicate to Sodium Hydroxide ratio of 2.5, while the alkaline activator solution (AAS) to binder ratio was retained at 0.45 by mass. The fresh properties of SCGPC concrete for different mixes were examined, and hardened properties tests such as compressive strength test, flexural strength test, and split tensile strength test were executed. The findings of the investigations demonstrated that the concentration of sodium hydroxide solution and the GGBFS content had a significant effect on the efficacy of SCGPC. All mix proportions of SCGPC met the EFNARC (2005) workability standards (passing ability, flowability, and segregation resistance), and the GGC3 trial mix has the best compressive, split tensile, and flexural strengths at 28 days (44.28 MPa, 3.08 MPa, and 3.28 MPa, respectively).