The role of particle size optimisation of waste granite powder in cementitious composites

Abstract The utilisation of granite powder (GP) waste in cementitious composites is limited by its low reactivity and adverse effects on mechanical performance. This study investigates the mechanical activation of GP through grinding (GP-M) and sieving (GP-S) to optimise its physical properties and sustainability potential. The modified powders were characterised in terms of specific surface area (SSA), reactivity, loss on ignition, and alkali leachability. Cementitious composites were prepared with 20% and 40% cement replacement and evaluated for slump flow, setting time, strength development, and bulk density. Results show that grinding increases the SSA from 2890 cm 2 /g (raw GP) to 4290 cm 2 /g (GP-M), improving particle packing and enhancing compressive strength by up to 20% compared to unprocessed GP. Despite its low pozzolanic reactivity, GP-M acts as an effective filler, improving microstructure and maintaining compressive strengths above 40 MPa at 28 days for 20% replacement. Alkali leachability was also reduced, supporting long-term durability. A Life Cycle Assessment (LCA) indicates that replacing 40% of cement with GP-M reduces CO 2 emissions by over 50%, while maintaining acceptable mechanical properties. The proposed Mechanical Performance Ratio (MPR) and Environmental Performance Ratio (EPR) demonstrate that the most balanced performance was achieved in the GP-M20 and GP-S20 series, offering up to 12% CO 2 savings with minimal strength reduction. This study confirms that mechanically valorised granite powder is a viable, sustainable SCM, capable of reducing cement content while satisfying structural and environmental requirements in construction applications.