Conservation of earthen constructions

Earthen constructions, built in many European, American, Asian and African countries, represent an interesting and important architectural heritage, whose conservation is necessary in order to make possible the transmission of a technological culture which keeps values of the uniqueness of the landscape as well as of their history. A study of the conditions of preservation of many unplastered earthen buildings revealed the need to set-up and test out treatments for the protection of the walls of such kind of buildings, which are still in good conditions, in order to improve their resistance against the aggressive action of external agents. The preservation of this heritage calls for the definition of effective techniques able to mitigate and, if possible, to prevent processes of alteration and ruin in order to guarantee their long-term conservation. Accordingly, it was deemed worthwhile to carry out activities designed to assess the effectiveness of different surface protection methods whose intent is to prevent the arising of defects. The application of plasters on earthen constructions, even if it makes it difficult to appreciate their real material consistence, it can guarantee their adequate safeguard. Used since ancient times, it certainly is the protection method more diffused worldwide. A testing campaign was conducted on different plasters prepared mixing earth and gypsum (the so-called plaster of Paris) or earth, gypsum and additives, real sacrifice surfaces which, trying to guarantee the readability of the actual aspect of the walls, intend to offer an effective way of protection against the atmospheric agents characterising the environment in which the constructions to be protected are located. The testing campaign, including chemical and mineralogical characterization (XRD and FTIR), colour evaluation (spectrophotometry) and performance tests as capillary absorption, erosion spray tests and Geelong tests made it possible to assess effectiveness and performances of the different plasters.