Characterization, weathering and protection of sandstones: the case of "Agro d'Ardesia"

The conservation of roofing and cladding materials has both environmental and cultural heritage bearing. Our research aimed at comparing the performances of some polymeric products used for the protection of a typical Italian sandstone, the ‘Agro d’Ardesia’, used mostly as cladding, paving, roofing, and building material. These products belong to three different classes: polysiloxanes, acrylics, and fluoropolymers. In addition, an acrylic–silicone mixture was chosen for testing. After the application onto the Agro sandstone by capillary absorption, both efficacy and durability were assessed. Particularly, two types of weathering tests were performed to check the stability over time of the protective products: the exposure to ultraviolet radiation in a climatic chamber and the ageing by exposure to acid rain, expressly designed to represent realistically natural and anthropogenic changes. Detailed information on treatment performances was obtained. The polysiloxane was shown to be the most effective protective material for the Agro sandstone.