Durability of self-cleaning TiO2 coatings on fired clay brick façades: Effects of UV exposure and wet & dry cycles

Environmental pollution is constantly increasing and it causes aesthetical concerns to urban buildings exposed to the atmosphere. Nanometric titanium dioxide (TiO2) has become a promising photocatalytic material owing to its ability to accelerate degradation of many organic contaminants. Application of TiO2 is rising and it found application on building industry. However, photocatalytic properties of this nanotechnology strongly depend on substrate morphology and on its nature. Thus, it is not correct to extrapolate photocatalytic activity on different types of substrate. Moreover, very few information is available about effectiveness of TiO2 coatings after aging phenomena when applied on different substrate. This paper aims to investigate photocatalytic properties of TiO2 applied on clay brick surfaces both after deposition and after aging process. TiO2 characterization was carried out by assessing nano-film morphology, wettability and self-cleaning efficiency before durability test. Self-cleaning ability was also evaluated during aging test in order to evaluate its variation in long term applications. Results show that photocatalytic efficiency of TiO2 remain stable after aging, thus TiO2 shows a good photocatalytic efficiency when it is applied to clay brick substrate. In the long run, photocatalytic efficiency of clay brick specimens treated with TiO2 is seven times higher than untreated specimens.