Because of the carbon emissions (8-10%) from energy-intensive Portland cement, this study investigates environmentally friendly alternatives for concrete production. This study investigates the potential use of ferrochrome slag (FCS) as a geopolymer (GP) precursor and supplemental cementitious material (SCM), as FCS is rich in (SiO2, Al2O3, and Fe2O3) and has pozzolanic characteristics. Both air-cooled (AC) and water-cooled (WC) FCS have been investigated to be used in GP and SCM in this research. The evaluation includes key properties such as compressive/flexural strengths, thermal conductivity, ultrasonic pulse velocity (UPV), chemical resistance, high-temperature behavior, porosity, water absorption, and chloride permeability. Notably, the study assesses geopolymer acid resistance after 12 weeks of exposure to corrosive solutions. The optimal ordinary Portland cement replacement with FCS is 10% when using WC-FCS. On the other hand, AC FCS can be used up to 10% as SCM to get marginal strength enhancement. The ideal blend proportion of geopolymer mortar was 15% WC-FCS replacement with OPC. While FCS as an SCM exhibits gradual strength gain due to weak pozzolanic activity, it improves UPV, increases thermal conductivity, and decreases chloride permeability. The addition of OPC to the geopolymer speeds up the setting process, improves UPV, and marginally increases thermal conductivity. Using 10% water-cooled FCS as SCM improves mix quality and durability significantly, with a compressive strength of 38.68 MPa compared to 33.27 MPa for OPC mortar. Using only FCS as a geopolymer precursor yields 26 MPa GP mortar after 56 days, whereas incorporating 15% OPC yields 33 MPa after 56 days, demonstrating improved properties. Water-cooled FCS as SCM reduces chloride permeability while increasing resistance to elevated temperatures. Both plain geopolymer and OPC-infused geopolymer have better acid resistance. To summarize, this research shows that water-cooled FCS has the potential to be a viable SCM and geopolymer precursor for advancing sustainable concrete production. The significance of precise material selection and optimized mix proportions for improving concrete performance while minimizing environmental impact is emphasized.