The sustainability of partial and total replacement of Ordinary Portland Cement: A deep dive into different concrete mixtures through life cycle assessment

The construction sector significantly impacts environmental sustainability, with cement production being a major source of carbon emissions. Ordinary Portland Cement (OPC) manufacturing is highly energy-intensive due to limestone calcination and fossil fuel consumption. To mitigate these environmental effects, this study evaluates the sustainability of literature based alternative concrete mixtures through a Life Cycle Assessment (LCA), considering both partial and total cement replacement strategies. The study examines OPC blended with Supplementary Cementitious Materials (SCMs) such as fly ash (FA), silica fume (SF), metakaolin (MK), and ground granulated blast furnace slag (GGBS), as well as geopolymer concrete as a complete substitute for OPC. Findings indicate that SCMs significantly reduce the environmental footprint of OPC concrete, with GGBS-blended OPC achieving the highest CO₂ reduction (28.7 %), followed by SF (28.3 %), FA (17.25 %), and MK (15.1 %). Geopolymer concrete demonstrated an even greater CO₂ reduction, with FA-based and GGBS-based geopolymers reducing emissions by 67 % and 54 %, respectively. However, geopolymers showed higher environmental impacts in categories such as fossil depletion, human toxicity, and ozone depletion, mainly due to the production of sodium silicate and sodium hydroxide. Notably, MK-based geopolymer concrete exhibited the highest overall environmental burden, performing worse than OPC concrete in all impact categories. The results highlight that the optimal choice of concrete depends on specific environmental goals. SCM-blended OPC presents a feasible and effective solution for lowering CO₂ emissions, while geopolymer concrete offers a more sustainable alternative if challenges related to chemical activators are addressed. This study underscores the importance of optimizing raw material sourcing, production processes, and transportation logistics to enhance the sustainability of concrete in real-world applications.