Photocatalytic Activity and Self-Cleaning Effect of Coating Mortars with TiO2 Added: Practical Cases in Warm Sub-Humid Climates

Abstract

In this study, the photocatalytic activity of coating mortars with synthetized and commercial TiO2 nanoparticles added has been evaluated at 2, 3 and 5% by weight of cement by calculating the degradation efficiency of methyl orange and red wine dyes exposed to both visible-light and UV radiation; also, the self-cleaning effect of coatings exposed to weather conditions (warm sub-humid climate) was assessed. TiO2 nanoparticles were synthesized via the sol–gel method to a low synthesis temperature and characterized via X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The results show synthesized TiO2 particles in anatase phase with a crystallite size of 14.69 nm, and hemispherical particles with sizes of submicron order. The addition percentage with the best performance in the coating mortars was 3%, with both commercial and synthesized TiO2; however, coating mortars with synthesized TiO2 exhibited the highest degradation efficiency for both dyes when they were exposed to visible light, while mortars with commercial TiO2 exhibited the highest degradation efficiency when exposed to UV radiation. In addition, in coating mortars with synthesized TiO2, the self-cleaning effect was evident from the beginning of exposure to weather, reaching the largest dye-free surface at the end of exposure. The compressive strength increased significantly in mortars with TiO2 addition.