Effect of TiO2/montmorillonite on the photocatalytic and mechanical properties of cementitious materials

Abstract

The poor dispersion of nano-TiO₂ adversely affects the photocatalytic performance of photocatalytic cementitious materials (PCMs). In this study, a supported composite photocatalyst TiO₂/montmorillonite (TiO₂/Mt) was employed to prepare PCMs, aiming to improve the dispersion behavior of nano-TiO₂. The impact of TiO₂/Mt on the photocatalytic and mechanical properties of cementitious materials was also evaluated. The dispersion state of nano-TiO₂ was assessed through changes in particle size and zeta potential. The hydration process of PCMs was analyzed using hydration heat, X-ray diffractometer (XRD), and ²⁹Si-nuclear magnetic resonance (²⁹Si-NMR), while the microstructure was examined by scanning electron microscope (SEM) and mercury intrusion porosimeter (MIP). Results indicated that, compared to TiO₂-PCMs (P25-PCMs), the methylene blue (MB)/NO removal capacity of TiO₂/Mt-PCMs was promoted, attributed to the improved dispersion state of nano-TiO₂ in cementitious materials. It was observed that TiO₂/Mt exhibited significant agglomeration in the cementitious liquid phase due to the strong electrostatic attraction of calcium ions. However, the presence of PCE effectively mitigated this agglomeration through complexation and spatial site resistance effects. Additionally, the compressive strength of cementitious materials was significantly enhanced with the addition of TiO₂/Mt. The nucleation effect of nanoparticles in TiO₂/Mt shortened the induction period and accelerated hydrate formation. Furthermore, the excellent filling effect of TiO₂/Mt reduced the porosity. This research provides valuable insights into achieving uniform dispersion of nano-TiO₂ in cementitious materials.