Compatibility of photocatalytic TiO2-based finishing for renders in architectural restoration: A preliminary study

Self-cleaning finishing treatments based on the use of TiO2 nanoparticles have been recently proposed for the protection of materials in cultural heritage, with the aim of increasing the durability of these materials in polluted environments. The results on stone seem encouraging, but the experimental tests on different porous materials, such as bricks and renders used in historical buildings, are still extremely limited. In the present paper, the application of water dispersion of titania nanoparticles to the repair renders of the former Del Corso hotel (XVIII cent., Bologna, Italy) was evaluated. The building and its environment were first analysed for assessing the appropriateness of such finishing, then samples of painted renders identical to those provided for in the intervention work were manufactured and treated with the dispersion, both by brushing on the dry paint and by brushing on the wet paint (the latter procedure in order to enhance the particles retention by exploiting the mechanism of fresco paintings). The outcome of the different treatments was investigated mainly to evaluate its compatibility with the substrate and its durability, which could be of interest also for the application of photocatalytic finishing to renders in new constructions.