Conservation of tuff-stone with polymeric resins

In this work, the experimentation of protective treatments on yellow and grey tuff-stones, characteristic materials of the historic buildings of Salerno (Italy), was performed. Tuff-stones, due to their high porosity, are often interested by damage phenomena from salt crystallization and other deterioration mechanisms mediated by water. As a consequence, they show a weak durability and require frequent maintenance and restorations. The study was carried out using several commercial polymeric resins, with different chemical composition, as protective coatings suitable for prevent water from entering into the porous material. In particular, siloxane, silicon and fluorinated resins, in solvent and/or in water solution, were considered. The protectiveness of the treatments was evaluated performing capillary absorption and total immersion tests and salts crystallization cycles, both on untreated and treated samples. Moreover, the hydrophobic properties of the surface were determined by static contact angle measurements on the treated samples. In order to estimate the over time effectiveness of the treatments, colorimetric measurements and UV weathering tests were also carried out. Finally, using the experimental data, a static durability indicator was calculated as proposed in the literature, in order to evaluate the effectiveness of each treatment on the potential durability of the treated tuff samples. On the whole, silicon resins in water solution represent the best choice for a protection treatment of tuff-stone, since they showed a good compromise among eco-compatibility, reduction of absorbed water, yellowing of the original substrate, weathering resistance after UV exposure.