Comparación analítica de dos consolidantes comerciales aplicados en areniscas eocenas de monumentos de los siglos XVI y XIX en San Sebastián (norte de España)

The conservation of buildings in the Basque Country made of Eocene sandstone is somewhat problematical, because this type of rock is relatively unstable. This instability is due to the variable content of carbonate cement (0-28%) and the presence of K-feldspar grains (1-13%) which appear to have been dissolved by both diagenetic and environmental processes. We have compared the results of the application of two commercial consolidating products: Sicof SM 296 (product A) and Consistone FS-hA (product B), both ethylsilicates, on Eocene sandstones of the Oquendo Admiral House (16th century) and the Gipuzkoa Provincial Government Palace (19th century), which are both located in the city of San Sebastián (Province of Gipuzkoa, Basque Country, Northern Spain). On the basis of different chemical and physical laboratory tests, together with Scanning Electron Microscopy (SEM) analysis, product A seems to be more efficient in consolidating such Eocene sandstone materials, since it penetrates into the first 8 mm of the rock, occupies very homogeneously even the smallest pore spaces and leaves a certain degree of remaining porosity which allows ventilation of the rock. In contrast, product B seems to be more appropriate for larger pore-sized rocks, because it only penetrates into the first 3 mm of the Eocene sandstone samples due to the thin pores of the matter. Our results demonstrate that the suitability of a commercial product depends not only on its own chemical composition, but also on the textural and lithological features of the rock material upon which it is to be applied.La conservación de los edificios del País Vasco construidos con areniscas del Eoceno es problemática porque este tipo de roca es relativamente inestable debido a su contenido variable en cemento carbonatado (0-28%) y a la presencia de granos de feldespato potásico (1-13%) disueltos tanto por procesos diagenéticos como ambientales. Hemos aplicado dos consolidantes comerciales: Sicof SM 296 (producto A) y Consistone FS+A (producto B), ambos silicatos de etilo, sobre las areniscas de la Casa del Almirante Oquendo (siglo XVI) y el Palacio de la Diputación Foral de Gipuzkoa (siglo XIX), ambos edificios en San Sebastián (País Vasco, norte de España). Los diferentes ensayos físicos y químicos junto con las observaciones al microscopio electrónico de barrido (SEM) revelan que el producto A es más eficiente para la consolidación de este tipo de areniscas, dado que penetra los primeros 8 mm de la roca, ocupa muy regularmente incluso los poros más pequeños y deja un cierto grado de porosidad remanente que permite la aireación de la roca. Por el contrario, el producto B parece más adecuado para rocas con mayor tamaño de poro, dado que sólo penetra los primeros 3 mm. Con ello, queda claro que la eficiencia de un consolidante comercial depende no sólo de su composición química, sino, en gran medida, de las características texturales y litológicas de la roca sobre la que se va a aplicar

S.E.M. Applications to the study of the damage and restoration of historic buildings: the Oquendo House (16th century) and the Deputation Palace (19th century) (San Sebastián, Basque Country)

The studies on the deterioration and restoration of buildings have increased in the last decades. The role of Scanning Electron Microscopy (S.E.M.) as a tool for textural studies of both damaged and restored rocks is important since it enables to us to identify both the style of penetration of consolidating products inside altered rocks and the solidification textures into pore spaces. We have compared the results of the application of the products Sicof SM 296 and Consistone FS+A on Eocene sandstones of the Oquendo House and of the Deputation Palace, both buildings at San Sebastián city. As observed from S.E.M. and different laboratory tests, the Sicof SM 296 seems to be the most efficient consolidating product for the restoration of such Eocene sandstone materials since it occupies even the smallest pore spaces very homogeneously and leaves a certain degree of remaining porosit