This study considers the production and performance of geopolymer mortars made up of 100% waste ceramic powder and 100% granulated blast furnace slag, specific for achieving the structural values through low-molarity activation. Mixtures were prepared using binder contents of 100%, 75%, 50%, and 25% by weight, activated using sodium hydroxide of 1 M, 2 M, 4 M, and 6 M molarity and sodium silicate/sodium hydroxide content ratio of 1.0, 1.5, and 2.5 and a constant activator/binder ratio of 0.7. Mortars were thermally treated in the range of 60 °C to 100 °C for 48 h and tested using ASTM, ACI, Eurocode, and British Standard tests for compressive strength, flexural strength, splitting tensile strength, direct tensile strength, elasticity modulus, porosity, unit weight, and water absorption. 75% granulated blast furnace slag+25% waste ceramic powder activatable with 6 M sodium hydroxide and 2.5 ratio and heat-treated in 100 °C gave the maximum compressive strength of 58.96 MPa. 50% granulated blast furnace slag+50% waste ceramic powder showed the most balanced mechanical profile having flexural strength of 9.84 MPa, elasticity modulus of 22.56 GPa, a tensile-to-compressive strength ratio of 0.1818 and flexural-to-compressive strength ratio of 0.8029. Curing in 80 °C was optimum in reducing the shrinkage while developing the strength while the heating in 100 °C added up the strength along with slight microcracking. ASTM predictions displayed close correlation to the experiment results while the ACI as well as the Eurocode prediction was less accurate. Multi-criteria decision-making analysis identified the 1.2% polyvinyl alcohol fiber-reinforced series as the most successful having a 24.5% increase in the compressive strength, 77.9% in flexural strength, and lowest porosity value being 20.73% along with water absorption of 10.35%. These results prove that high-strength and durable binders are reliably possible through the low-alkali activation of industrial wastes that not only provide a functional cement replacement in the structural element but also a scalable approach bridging the gap between the material innovation and the pressing need of sustainable construction.