Coating's influence on water vapour permeability of porous stones typically used in cultural heritage of Mediterranean area: Experimental tests and model controlling procedure

Water vapour flux into the porous microstructure represents a crucial factor capable of influencing the degradation of porous materials. This fact is of utmost importance especially considering materials installed in cultural heritage. The necessity to preserve stone artworks pushes to perform surface protective coatings that create an intermediate sacrificial layer between stone and the environment. High hydrophobicity and high permeability of water vapour must be one of the most important requirements of a protective film. These features depend upon the nature of coatings as well as the porous microstructures. In order to control coatings’ effects and their influence on final water vapour permeability (δ) properties, a new modelling procedure has been proposed. The study is conducted on a porous limestone, namely Pietra Leccese, which is being largely used for historical constructions in Mediterranean. The average experimental water vapour permeability δexpis 4.83 × 10−4and 3.86 × 10−4(g/m d Pa) respectively for untreated and treated PL stone, while the average model prediction δIFUis 4.87 × 10−4and 3.77 × 10−4(g/m d Pa) respectively for untreated and treated PL stone. The good agreement between experimental and calculated data shows that the proposed modelling procedure could represent a good tool for designing and controlling protection activity on cultural heritage.