Contribution of IR Thermography to the Performance Evaluation of Water Repellent Treatments

The study presents two innovative applications of Infrared Thermography (IRT) –referred to as “Spilling drop” and “Moisture ring”– that aim to examine moisture diffusion in porous materials. IRT effectively contributes to evaluate both heat and vapour exchanges between stone surface and surrounding air, by localizing the diffusion of water through the pore system at the surface. Changes measured after the application of a hydrophobic product are related to the performance of the product itself and should serve to evaluate the ability of the water-repellent product to keep liquid water away from the stone surface. The evaluation methods were used both in laboratory and in the field, the latter will be addressed in a subsequent paper. Measurements were carried out before and after the application of well known water repellent protective products, i.e., Paraloid B72 and Silirain 50 (PMMA and PDMS respectively) on Noto calcarenite, Dorata sandstone and Macedonia marble. The products were chosen mainly because of the vast bibliography that reports their use, so that knowing their advantages and disadvantages it would be easier to understand the contribution of these new techniques when evaluating their performance. Damp areas were studied by IRT and by other established methods, such as capillary absorption, drying index, contact sponge, and the results were used to evaluate the performances of water repellent treatments thus allowing to compare the effectiveness of the innovative techniques with traditional ones.