Sustainability evolution of coal gangue- and GGBS-based alkali-activated binder

Alkali-activated binders (AABs), particularly low-calcium systems, are emerging as eco-friendly alternatives to ordinary Portland cement (OPC) by utilizing industrial by-products. This study examines the partial replacement of ground granulated blast furnace slag (GGBS) with coal gangue (CG) at 0–100% levels for the development of AABs. A sodium silicate and sodium hydroxide activator (2:1 ratio, 4 M NaOH) was used. Compressive strength, XRD, SEM, EDAX, and FTIR analyses were conducted to evaluate mechanical and microstructural performance, while life cycle assessment (LCA) was employed to assess environmental impact. The optimized mix with 100% GGBS (C0G100) achieved a maximum compressive strength of 80.60 MPa at 28 days, while C20G80 reached 65.60 MPa. Microstructural studies confirmed uniform geopolymerization. LCA results showed CO2 emission reductions of up to 62.15% (C80G20) and energy savings of 11.29% compared with OPC binders. Overall, CG and GGBS-based AABs demonstrate high strength with significant environmental benefits, highlighting their potential as sustainable construction materials.