Portable and Raman imaging usefulness to detect decaying on mortars from Punta Begoña Galleries (Getxo, North of Spain)

Abstract

Punta Begoña Galleries were built in 1918 in Getxo (Basque Country, North of Spain) but were abandoned in 1960. Nowadays, their conservation state is very poor. In this work, portable Raman spectroscopy was applied to evaluate the original composition and possible deterioration products of the mortars used in the inner walls and those covering the concrete of the ceilings allowing us to select the most appropriate sampling points. In the laboratory, Raman microscopy and Raman imaging, assisted with scanning electron microscopy equipped with an energy dispersive spectrometer (SEM‐EDS), X‐ray diffraction and energy dispersive X‐ray fluorescence (ED‐XRF) imaging, allowed to identify the key compounds to understand the deterioration processes taking place in the mortars of the galleries. The main components of the mortars from the walls were calcite and gypsum. In some cases, alite (Ca3SiO5) and belite (Ca2SiO4) were identified; these components are characteristic of Portland cement clinker. The main components of the mortar covering the concrete were calcite, quartz, aragonite and gypsum. The aragonite identification confirmed the use of beach sand as the aggregate in the mortar. The concrete from the ceiling of the lower gallery is covered with three different mortar layers; the outermost layer is covered with a black crust. In the three mortars, the main components are similar to those used in the mortar covering the concrete from the upper gallery. Thanks to Raman, ED‐XRF and SEM‐EDS imaging, it was possible to map the distribution of the main components through the three mortar layers and also to identify the presence of dolomite {[CaMg(CO3)2]}, which was not possible to detect following single‐point micro‐Raman analyses.