Influence of ZnO nanoparticle ratio and size on mechanical properties and whiteness of White Portland Cement

The impact of nanotechnology on the cement industry has been extensively studied. Much work remains needed to improve product quality, decrease cost, and minimize the negative environmental impact. The present study explores the influence of ZnO nanoparticles on physical, chemical, and mechanical properties of White Portland Cement (WPC). Zinc oxide nanoparticles were prepared by simple ball-milling to reach average particle sizes of 70, 37, 27, and 24 nm. For each of the four size groups, ZnO nanoparticles were added to WPC at each of four concentrations (0.1, 0.4, 0.7, and 1.0 wt%). Whiteness, setting time, expansion, and compressive strength of resulting mortars were investigated. The crystal structure and morphology of mortars were respectively characterized using X-ray diffraction and scanning electron microscopy. Hydration progress was inspected using Fourier-transform infrared spectrometry. The results show that addition of ZnO to WPC pastes increases the amount of water required for normal consistency and setting time. The addition of 37 nm ZnO nanoparticles to WPC mortars at a specific weight percentage of 0.4% ZnO enhanced compressive strength at 28 days by up to 28% via filler effects. The characterizations and physicomechanical parameters for high-ZnO (1.0 wt%) mortar indicate less hydration products before 28 days but improved at 28 days.