Nanodispersed TiO2 hydrosol modified Portland cement paste: The underlying role of hydration on self-cleaning mechanisms

The self-cleaning performance of photocatalytic cement paste is related to the dispersion of nano-TiO2 in the hardened matrix. This work aims to study the influences of Portland cement hydration on the self-cleaning behaviour of acidic anatase TiO2 hydrosol modified hardened Portland cement paste (HPCP), and the working mechanisms. The presence of TiO2 hydrosol results in the retardation of hydration at early age and better self-cleaning performance of HPCP. The additional surface defects of TiO2 in HPCP are the main reason of self-cleaning performance enhancement. The morphology and the pore size distribution of hydration products also contribute to the enhancement of self-cleaning performance by the surface electron capture effect, which are supported by the analyses of Confocal Raman Microscopy and Scanning Electron Microscope. A new mechanism is suggested to explain the role of photocatalytic property and cement hydration on the enhancement of self-cleaning performance of HPCP with different concentration of TiO2 hydrosol.