The production of Portland cement clinker is associated with substantial energy consumption and significant environmental consequences, driven by raw material extraction and Carbon dioxide (CO₂) emissions. However, its production contributes to approximately 5-8% of anthropogenic CO₂ emissions, with each ton of Portland cement yielding about 1.0-1.2 tons of CO₂. This paper used life cycle assessment (LCA) to compare the environmental impact of three types of blended cement (CEM II A-S, CEM II/B-S and CEM III/A) that use ground granulated blast furnace slag (GGBFS) as a substitute for clinker in the South African cement industry using SimaPro 9.2.0.1 software developed by PRé Consultants, Amersfoort, Netherlands at ReCiPe2016 midpoint (H) V1.04. The study found that CEM III/A cement products with a high proportion of GGBFS had the lowest CO₂-equivalent emissions per ton of cement compared to other blended cement with GGBFS substitution. The CO₂-equivalent emissions of CEM III/A cement were about 74% lower than those of CEM I cement, which has the highest emissions. The global warming potential of CEM II A-S and CEM II/B-S cement was 30% and 24% higher than that of CEM III/A cement. CEM III/A cement is the most environmentally friendly option for cement production.