Implementing the utilization of industrial by-products in lieu of natural resources represents a dual-pronged approach towards fostering sustainability. The construction industry stands as a significant domain wherein vast quantities of natural resources are excavated incessantly to satiate the ever-growing demands associated with what is often referred to as ‘development’. In this article, we have presented a unique solution to decrease the natural resource over exploitation. We have used granulated blast furnace slag (GBFS) as fine aggregate from Iron and steel Industries along with fly ash which is a by-product of thermal power industries to create high strength geopolymer mortar. Our approach minimizes the contribution of conventional cements and contribute to the sustainability in the construction industry. The main challenge behind the idea is optimization of GBFS concentration. Other parameter that needs optimality are, sodium hydroxide to sodium silicate ratio, geopolymer binder to fine aggregate ratio, molarity etc. In this study we have only focussed on GBFS optimal concentration. We have taken four different mixtures based on different concentrations of GBFS ranging from 0 to 100% (0 indicate 0% GBFS and 100 river sand). We note that, the compressive strength of 25GBFS enhance by 12.5% from 0GBFS batch. Granulated blast furnace slag sand exhibits potential as a viable alternative to river sand for partial substitution. Additionally, the utilization of fly ash geopolymeric mortar, incorporating GBFS sand, presents an emerging and environmentally friendly option for sustainable construction materials. Such innovative solutions can be effectively employed in the production of precast building components, contributing to a more eco-conscious manufacturing process