Integrated Structural Performance and Carbon Footprint Assessment of Reinforced Concrete Incorporating Supplementary Cementitious Material with Multiple Cement Sources

The environmental impact associated with Ordinary Portland Cement (OPC) production necessitates the development of sustainable concrete materials that maintain structural performance while reducing carbon emissions. Supplementary cementitious materials (SCMs) such as Metakaolin, Alccofine, and Biocement have demonstrated potential for improving concrete properties; however, comprehensive studies integrating structural behavior, durability performance, microstructural characteristics, and environmental assessment across multiple cement sources remain limited. This study presents an experimental and analytical investigation on the mechanical properties, durability, flexural behavior, microstructural characteristics, and carbon footprint of reinforced concrete incorporating SCMs as partial replacements for OPC at replacement levels of 5%, 10%, and 15%. Concrete mixes of grades M25–M75 were evaluated through compressive strength, split tensile strength, and modulus of elasticity tests, while structural performance was assessed using flexural testing of reinforced concrete beams under two-point loading conditions. Durability performance was examined through water absorption and carbonation resistance tests, and microstructural characterization was conducted using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Analysis (EDX), and Thermogravimetric Analysis (TGA). A cradle-to-gate Life Cycle Assessment (LCA) was performed using OpenLCA in accordance with ISO 14040 and ISO 14044 standards to quantify embodied carbon emissions. Results indicated that Alccofine-based concrete achieved higher compressive strength (28.2 MPa), lower water absorption (0.565%), and approximately 35–40% greater load-carrying capacity compared to Metakaolin-based concrete, while increasing SCM replacement levels resulted in consistent reductions in CO₂ emissions across all concrete grades. The study establishes an integrated performance–environment framework for the development of sustainable and high-performance reinforced concrete suitable for modern construction applications.