Simultaneous effect of ZnO nanoparticles and silica fume on the mechanical properties of the concrete

This work investigates the effects of silica fume (SF) and ZnO nanoparticles in enhancing the mechanical strength and durability of concrete. High-performance concrete specimens (w/b 0.34) were prepared, replacing cement with SF (4–16%) and combining 8% SF with ZnO (0.3–1.2%). Mechanical strengths and resistance to sulphate and chloride attack were assessed. Results identified 8% SF and 0.9% ZnO as the optimal dosage for ternary blends, yielding a 8.96% increase in compressive strength (p < 0.05) and reducing strength loss by 18.86% under sulphate exposure. Microstructural analysis (XRD and SEM-EDX) confirmed that ZnO acts as a nucleation agent, enhancing matrix densification following the initial retardation period, while SF consumes calcium hydroxide through long-term pozzolanic reactions. This synergistic interaction results in a refined, compact cementitious matrix, consistent with improved retention of mechanical performance under aggressive exposure conditions. Consequently, the optimized SF-ZnO composite offers a robust material for sustainable infrastructure in aggressive environments.