ABSTRACT The research explores M20 grade concrete performance upgrades through combination methods of cement replacement with ground granulated blast furnace slag (GGBFS) and internal curing usage of superabsorbent polymer (SAP). A combined mix of GGBFS replacing 10% cement content and SAP added at 0.1% and 0.2% and 0.3% weights of cement was used in this research. The research evaluation included testing compressive strength together with flexural strength and Rapid Chloride Penetration Test (RCPT) and carbonation resistance tests. When GGBFS was combined with 10% replacement rate and SAP content set at 0.3% the concrete mixture showed 9% stronger compressive strength and 11% better flexural strength than the standard concrete mix ratio. Internal curing properties of SAP showed effectiveness in minimizing shrinkage behaviour and restricting microcracks thus suggesting potential benefits for improving crack resistance through crack arrest. The addition of GGBFS in concrete mixtures reduced hydration heat thus reducing the potential for thermal cracks when used for mass concrete applications. By using GGBFS the construction process achieved two sustainability goals: it lowered cement usage and produced reduced CO2 emissions. The combined usage of GGBFS with plastic bags optimizes concrete structure retention while maximising its long-term durability so it can withstand harsh environmental conditions.