Contrasting decay of historical building stone: relationships between petrophysical features and frontal polymerization treatment suitability on medieval buildings of north Sardinia, Italy

Textural, physical–mechanical, and mineralogical–chemical properties influence the degradation of building stone. These properties also control the efficacy of different preventative treatments to inhibit degradation. In this study, several historic buildings in northern Sardinia, Italy, constructed with a wide variety of building stones were examined in order to contrast degradation effects with and without frontal polymerization. Different types of degradation were observed in carbonate and volcanic lithologies, which compromise their durability and toughness. Among the different lithotypes tested, four revealed a good response to the polymerization treatment. Textural and physical–mechanical evidences show that open porosity and capillary absorption control the suitability of this treatment. Laboratory tests on both untreated and treated specimens revealed a strong reduction of parameters directly related to decay (e.g., open porosity and water absorption), as well as an improvement on crush strength. Moreover, the polymerization treatment retains a residual porosity sufficient to enable the rock to equilibrate with the ambient environmental humidity.