Thermal conductivity of porous stones treated with UV light-cured hybrid organic–inorganic methacrylic-based coating. Experimental and fractal modeling procedure

tThis study presents an intermingled fractal model (IFU) capable of simulating the porous microstructureof natural calcareous stone substrate, typical of Apulia Region (Pietra Leccese, PL) used in historical build-ings. The developed model is aimed at predicting, by an analytical approach, the thermal conductivity ofthese materials. To verify the actual ability of the proposed method to predict stone thermal conductiv-ity, the intermingled fractal units model was applied to untreated natural stone, and to the same stone,treated with a novel UV-light curable O–I hybrid coating. The application of hydrophobic polymers tostone materials is, in fact, an effective way to preserve stone artifacts and protect cultural heritage fromdecay. To this aim, a novel experimental photopolymerizable organic–inorganic (O–I) hybrid protectivecoating, mainly intended for the protection of PL stone, was previously developed by some of the authors.The innovative hybrid product evidenced an extraordinary hydrophobicity, able to guarantee a very highpreservation of the stone from water actions, as well as another important property required to a pro-tective, i.e., a high traspirability of the stone substrate. Furthermore, the experimental product proposedwas able to equal the performance of commercial available products, with the adjunctive advantage tobe free-solvent.