Optimizing cement particle size for strength enhancement and CO₂ reduction in lightweight mortars.

This study examines how cement particle size (modified through sieving) affects the fresh and hardened properties of lightweight mortars, with emphasis on early-age microstructural development and environmental performance. The experimental program included three levels of cement fineness and applied advanced characterization techniques such as X-ray diffraction (XRD), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM) during the first 12 h of hydration. Results demonstrate that finer cement particles enhance workability and increase bulk density due to improved particle packing. While tensile strength slightly decreases, compressive strength increases significantly, especially after 7 days, attributed to accelerated hydration kinetics confirmed by microstructural evidence. A comprehensive life cycle assessment (LCA) shows that finer cement requires more energy to process, but the increased strength-to-emission ratio makes it a cost-effective and sustainable option. Screening cement to below 50 μm enabled up to 14% reduction in CO₂ emissions per unit strength. However, increased shrinkage in finer systems may compromise long-term durability due to greater crack susceptibility. The proposed LCA-based framework supports balancing performance gains with environmental costs in cementitious material design.