Sustainable development of ternary binder-based mortar using OPC, GGBFS, and Coal Bottom Ash

The production of Ordinary Portland Cement (OPC) is responsible for 5–8 % of global CO₂ emissions and requires 4–5 GJ of energy per ton, emphasizing the need for sustainable alternatives. This study investigates a ternary blended binder mortar system composed of OPC, Ground Granulated Blast Furnace Slag (GGBFS), and Coal Bottom Ash (CBA) to reduce clinker demand while improving performance. Six mixes were developed with a predefined 30 % GGBFS content, and OPC was progressively replaced with 5–25 % CBA. The mixes were evaluated for fresh, mechanical, durability, and microstructural properties, with statistical validation and sustainability assessments. The mix with 15 % CBA (OPC:GGBFS:CBA is 55:30:15) was identified as optimal, achieving an 8–10 % increase in compressive strength (with greater gains at later ages), up to 20 % improvement in durability indices, and denser microstructural development compared to the control mix. Sustainability analysis exhibited a 16.79 % reduction in embodied energy, 19.92 % lower CO₂ emissions, and 10.13 % cost savings. The novelty of this work lies in demonstrating the synergistic role of CBA with GGBFS in ternary systems, where CBA’s utilization improves both performance and sustainability in mortar applications. The findings establish OPC:GGBFS:CBA with a 55:30:15 proportion as an optimized and statistically validated mix; however, it is also revealing that CBA incorporation up to 20 % is permissible without compromising mix-performance. This confirms the potential of OPC–GGBFS–CBA blends as durable, cost-effective, and eco-efficient alternatives for sustainable mortar production.