Conservation of Earthen Bricks in Architecture: An Experimental Campaign to Test Different Treatments on Vernacular Built Heritage

Earthen architecture, by its nature, is a fragile because it has a poor resistance toward the action of weathering, which has also increased in recent years through the effects of climate change. The presence of interesting examples of earthen brick buildings, for example, in the Piedmont Region of Italy, is characterised by the absence of rendering, which reveals the need to test treatments for the protection and/or strengthening of the walls of these buildings. This action is of fundamental importance to improve its resistance to the aggressive action of atmospheric agents and avoid their disappearance. A testing campaign adopting protective products with sustainability characteristics and low environmental impact was carried out on earthen brick walls. Different products belonging to various categories (synthetic polymers, natural resins, nano-structured materials) and selected based on previous experiments or tested for the first time on earthen surfaces were selected. The performance assessment of the products was carried out by taking into account the standardised procedures in the field of cultural heritage conservation through the following tests: water absorption, water vapour permeability, drilling resistance, water erosion tests (Geelong and spray), contact angle measurements, colorimetric measurements, and ageing tests. Although the choice of the optimal protective product should be made on a case-by-case basis, where it is not sustainable to proceed in this way, the results of this experimental campaign-in the presence of materials and weathering conditions similar to those of the case study analysed-will provide indications in identifying of the most appropriate product.