Application of supplementary cementitious materials in improving the environmental performance of concrete towards sustainable development

The present study investigated the influence of partially replacing cement in concrete with supplementary cementitious materials (SCMs) on the environmental performance and negative impacts of concrete. For this purpose, several mix designs including different levels of cement replacement with a combination of silica fume and fly ash were used while maintaining constant amounts of fine and coarse aggregates and other ingredients. To evaluate the environmental performance of the mixtures, the global warming potential (GWP), expressed as carbon emissions, and embodied energy representing total energy consumption, were quantified and analyzed. Then, simultaneous evaluation of the aforementioned indices with the mechanical indices of concrete, including compressive strength and tensile strength, was performed. The results demonstrated that increasing the replacement level of cement with SCMs significantly improved the environmental performance of concrete. Specifically, carbon emissions decreased from 353.48 to 251.17 kg CO₂/m³, while embodied energy declined from 2150 to 1486 MJ/m³. Compared with the control mixture containing 100% cement, these reductions corresponded to decreases of 28.9% in carbon emissions and 30.8% in energy consumption. Furthermore, a combined assessment of environmental and mechanical performance, based on the ratio of environmental indices to mechanical indices, identified the mixture containing 35% cement replacement (25% fly ash and 10% silica fume) as the optimal design. This mixture achieved approximately 31% and 29% reductions in embodied energy and carbon emissions, respectively, while simultaneously increasing the 28-day tensile and compressive strengths by approximately 25% and 34%, respectively.