This investigation studies the effect of varying sodium silicate to sodium hydroxide (SS/SH) ratios on key mechanical properties of geopolymer concrete (GPC) produced with Class F fly ash and ground granulated blast furnace slag as binder materials. Fine and coarse aggregate from river sand and basalt rock were assessed individually to evaluate their effect on the GPC’s mechanical characteristics such as strength and workability. Compressive strength, splitting tensile strength, and slump were measured at SS/SH ratios ranging from 1, 2, 2.5, and 3. The results indicate that the optimal SS/SH ratio for maximizing compressive and tensile strength is 2.5. Slump values demonstrate a direct relationship with increasing SS/SH ratio, suggesting improved workability at higher ratios. The findings reveal that SS/SH ratio is a critical parameter that can be tailored to enhance the mechanical performance of GPC compared to traditional Portland cement concrete. Identifying ideal SS/SH ratios provides opportunities for optimizing geopolymer concrete mix design for various applications.