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

• Limestone is a building material largely used for architectural surfaces.
• TiO2-nanoparticle coatings were tested so as to assess their self-cleaning effect on it.
• Different durability analyses were carried out and self-cleaning activities were assessed.
• Results seem to encourage the use of nano-structured TiO2 for preserving stone during time.

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.