Test evaluating the effectiveness of hydrofugation in the protection of handmade brick walls against rainwater

Abstract

The soaking of rainwater into brick walls of cultural heritage can be the source of various injuries due to the processes of migration and crystallization of salts, the formation of ice inside them in rainy and cold areas, as well as the growth of organisms in humid areas. The ancient handmade bricks and the mortar used in the construction of these walls are porous materials in which water penetrates easily and is therefore very exposed to these deterioration processes. One of the most usual solution to avoid it is to apply a surface treatment by water-repellent products to prevent the entry of rainwater. The handmade bricks are orthohedrons with more or less flat faces, which do not present grooves, recesses or perforations like mechanical bricks, meaning that at the interface between brick and mortar there may be discontinuities that facilitate the entry of rainwater. The values of water absorption and brick and mortar are high, which also favours the entry of direct rainwater through the materials. The hydrophobic facade treatments are usually applied by projection on the surface of the facade and the discontinuities that the surface of the facade presents could have the result that the application of the water repellent would not be effective. For this reason, a test procedure was designed and executed on four walls built in a garden. Above them, water was projected imitating rain. The data was captured by infrared thermography and humidity probes, in order to analyse the efficiency and hydrophobicity and to study if the test method was valid.