Durability of nano-engineered TiO2 self-cleaning treatments on limestone

Titanium dioxide (TiO2) colloidal suspensions applied by spray-coating have been used to deposit transparent self-cleaning coatings on stones with the aim of preserving the original aesthetic features of historical and monumental architectures. Travertine was chosen as the reference substrate. Compatibility with travertine and self-cleaning efficiency were analysed by indoor laboratory tests. The self-cleaning ability of TiO2 is mostly dependant on the photocatalysis generated by ultraviolet light. The stones were artificially aged through different procedures and the photo-activity of TiO2 was evaluated before and after the ageing. Results seem to encourage the use of nano-structured TiO2 for preserving stone during time.