Basic methodology for the assessment and selection of water-repellent treatments applied on carbonatic materials

Abstract

In this paper, a basic methodology to assess and select water-repellent treatments applied on carbonatic rocks has been carried out. In order to characterize the substratum—a biosparitic limestone—petrological, mineralogical, chemical and petrophysical properties have been determined. Ten water-repellent products have been applied, selected according to their frequent use in the conservation of stone and to their compositional variety: organic, organosilicic and inorganic products, soluble both in organic solvents and in water. In order to evaluate the effectiveness of the treatments, color determination, water–stone contact angle and water-vapor permeability were carried out. The penetration depth of the treatments into the stone, and their distribution within, were studied through scanning electron microscopy. Conclusions obtained are that treatment efficiency is higher, the higher its capacity to coat the walls of the porous system; treatment penetration in the stone, which depends much more on rock porous system than on pore volume, increase effectiveness but is not as significant as its filming capacity. Best results for carbonatic materials analyzed were obtained from siloxane-based compounds, on organic solvent.