Enhancement of hardness in nanostructured CuO/TiO2–cement composites

Abstract

Concrete has been widely used in pavements and buildings, and it is necessary to increase its hardness in order to resist deformation, penetration, and abrasion for these applications. This study explores the effects of addition of CuO and/or TiO2 nanoparticles on the hardness of cement mortar. Scanning electron microscopy, X-ray diffraction, energy dispersive spectroscopy, and Rockwell hardness testing were used to study the microstructure, chemical and phase composition, and hardness. The results showed that the addition of nanoparticles can effectively improve the hardness of cement mortar by improving the microstructure and hydration process. This is because they offer additional nucleation sites for hydrates to deposit on, producing a more compact microstructure with finer grains. As the concentration of nanoparticles added increases, the enhancement is more obvious and stable. However, after the concentration reaches its maximum level, the hardness starts to decrease due to the formation of defects, mainly voids, caused by excess nanoparticles. CuO and TiO2 nanoparticles show similar effects on the microstructure and hardness, but the addition of both CuO and TiO2 nanoparticles with similar amounts shows denser microstructure and higher hardness as they densify the composites.