Efficiency and effect of consolidation and water repelent treatments on stone materials case study: buildings restoration at Almudena cemetery

Since a long time ago, some products have been used in order to preserve and protect natural stone monuments as well as bricks and mortars and thus achieve greater resistance to deterioration processes. At first, natural resins of animal and vegetable origin were used but, in the last decades, synthetic polymers have been commercialized to cover the capillary pores of the material, lowering its water suction capacity, coating the material and isolating it from the aggressive environment [1-4]. Regarding to its effect, two main types of products are distinguished: consolidants and water repellents. First ones are substances that --penetrating inside the stone or ceramic material porous network-- improve their internal cohesion and therefore their mechanical behavior. They work attempting to achieve the adhesion between the surface --generally more weathered-- and the unaltered inner base. A water repellent is a product with a behavior that prevents the penetration of water in its liquid state but allows moisture vapor transmission. It can be applied on the surface of the already altered material or under weathering process. These products act in a double way, both narrowing pore radius and thus avoiding liquid water penetration into the pore network on one side, and repelling water due to a chemical hydrophobic behavior on the other side [5]. In recent years, numerous commercial products have emerged in the market for restoration and conservation of architectural and monumental heritage stone materials. It has generated a great confusion among professionals of the sector because of a lack of knowledge of its long-term performance. Therefore, the evaluation of these products is necessary before their use on the materials surfaces.