In-situ spectroscopic assessment of the conservation state of building materials from a Palace house affected by infiltration water

摘要

The built Heritage constantly suffers different deterioration processes caused by the action of external agents, being one of the main consequences of the formation of soluble salts. These salts appear as efflorescences or subefflorescences that by hydration and dehydration cycles and/or dissolution processes producing crystallization of salts within the pores may promote internal fractures and material loss. The assessment of building material conservation on a 15~(th) century Palace house, located close to the Urola river (Azpeitia, Basque Country, North of Spain), has been performed by in-situ characterization of pathologies on sandstone, mortar and limestone affected by infiltration waters. Portable Raman and X-ray fluorescence spectrometers have been used to characterize the bulk materials as well as the salts present along the different walls of the Palace. The in-situ analysis by those portable equipments has been complemented with laboratory measurements on selected samples, taken close to the spots analysed by the portable instruments. Different carbonates (natrite, termonatrite, natron, calcite and gaylussite), oxides (hematite, limonite and rutile), feldspar (orthoclase) and silicates (quartz) have been identified as original compounds. Furthermore, nitrates (niter, nitrocalcite and nitratine) and sulphates (gypsum and thenardite) have been found as decaying compounds permitting to establish the degradation processes of the attack produced by the infiltration waters on the different building materials. Moreover, the study revealed that certain materials used in a previous restoration produced new degradation processes, evidencing the importance of a proper selection of the materials to be used in the interventions.