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

Estudio de conservación del material pétreo de la Casa de Cultura del Almirante Oquendo, en San Sebastián

The historical heritage of our country is mainly made up of masonry, playing the sandstones an important role. However, because of the effect of environmental conditions and pollution, these materials can loose their cement, and eventually disintegrate. Chemical consolidants can be applied in order to prevent and stop these decay process, which, when there is a lack of cement, fix the stone grains, enhancing the strength and durability of the In order to ensure the success of the application of these products in restoration works, preliminary studies should he carried out, so as to define the suitability of their use, and select the most appropriate consolidant for each specific case, as the reliability of these products is mainly determined by the microstructure of the stone material under study. This paper describes a study which was carried out on Igueldo sandstone from the main façade of the Casa de Cultura del Almirante Oquendo, in San Sebastian, which aimed at establishing the most suitable consolidation technique for the stone degradation processes observed. Firstly, the study dealt with the diagnosis of the pathologies which affected the stone from this building. Furthermore, 6 commercial consolidants were tested on quarry stone. Finally, the results were validated applying these products in real work conditions, what enabled us to select the most appropriate treatment for the restoration of the main façade of the building.El Patrimonio Histórico-Artístico de nuestro país, está constituido, principalmente, por edificios de piedra de sillería, en los que las areniscas juegan un papel muy importante. Sin embargo, debido, fundamentalmente, a las condiciones medioambientales y a la contaminación, estos materiales pueden perder su matriz cementante y sufrir una desintegración. Para prevenir y frenar estos fenómenos de deterioro, se pueden emplear productos consolidantes que, en ausencia de matriz cementante, fijan los granos del material pétreo, proporcionando resistencia y durabilidad al sillar. Para asegurar la fiabilidad de las intervenciones realizadas con estos productos, es necesario llevar a cabo unos estudios previos, al objeto de definir la idoneidad del empleo de consolidantes y seleccionar el tipo más adecuado para cada caso concreto, ya que la fiabilidad de estos productos depende, en gran medida, de la microestructura del material pétreo considerado. FA presente artículo recoge un estudio llevado a cabo sobre la arenisca de Igueldo de la fachada principal de la Casa de Cultura del Almirante Oquendo, en San Sebastián, con el fin de determinar el tratamiento de consolidación más adecuado para la alteración observada en este material pétreo. FA estudio realizado consistió, en primer lugar, en la diagnosis de las patologías presentadas en el material pétreo de este edificio. Posteriormente, se ensayaron 6 productos consolidantes comerciales sobre piedra inalterada de cantera. Por último, se validaron los resultados obtenidos, mediante ensayos en el monumento de los 3 tipos de consolidantes más adecuados, aplicados en condiciones reales de obra, eligiendo el tratamiento más idóneo para la restauración de la fachada principal del edificio

Estudio comparativo de la variación de las propiedades hídricas y el aspecto de la piedra natural y el ladrillo tras la aplicación de 4 tipos de anti-grafiti

En este artículo se presenta un estudio comparativo del comportamiento de diferentes tipos de anti-graffiti comerciales sobre piedra natural y ladrillo. Para ello se seleccionaron 8 tipos de sustratos porosos de diferentes países europeos, sobre los que se aplicaron 4 anti-graffiti de distinta naturaleza química. Posteriormente se estudiaron las variaciones en sus propiedades hídricas y de aspecto (color y brillo) con respecto a los sustratos no tratados, en el laboratorio. Los resultados obtenidos han permitido evaluar la idoneidad de 4 de los principales tipos de formulaciones químicas más frecuentemente utilizadas como anti-graffiti sobre sustratos porosos. El estudio concluye que el antigraffiti de sacrificio de composición parafínica es el producto que reduce en menor medida las propiedades hídricas de los sustratos porosos estudiados, y que menores cambios de color produce en los mismos

The effect of macrocells between active and passive areas of steel reinforcements

The effects of macrocells formed between active (depassivated) and passive areas on the corrosion rate of steel reinforcements in concrete beams and slabs are studied. With a uniform distribution of current lines on the electrodes, the anodic current density (i.e. the corrosion rate) is a function of the difference in potential, ohmic resistance and polarization resistance. This case is approached when passive and active reinforcements are placed opposite each other. A coplanar location of the anode and cathode areas on the reinforcements results in a non-uniform distribution of the current. These cells are modelled by means of a transmission line circuit. A reasonable concordance is obtained between the theoretical predictions and the experimental data

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

Resultados de SEM/EDX en morteros de restauración aplicados a areniscas del Eoceno de Gipuzkoa utilizadas en la construcción de edificios

The restoration of buildings made of sandstones is a critical problem in the Basque Country, because the wide use of Eocene sandstones that appear as a constructing material very frequently affected by weathering processes. The impossibility to recuperate the original material sometimes leads to complete or even replace the masonry stones with mortars which should have the same physical properties and visual appearance than the original stones. Our research is focused to find the better mortars for the Eocene sandstones, and even to synthesize a mortar having the same resistance to weathering than the original sandstone. In order to improve the research, the first step was to accurately know the intimate textures of several types of mortars for furtherly test their physical behaviour under different experimental techniques in the laboratory. We have compared the textures of three commercial mortars (A, B and C) and a fourth one synthesized by Teusa. The mortar A is an amorphous arid-free alite-mortar, whereas the B and C are composed by quartz, alite and calcite. From all the four studied mortars, the A seems to be the most appropriate to rejoin the Igueldo sandstone masonry stones, without exclude its use for completion. The B and C mortars are suitable for completion because their composition and texture is very similar to that of Eocene sandstones. Finally, the uncommercialized Teusa mortar is thought to have by the moment an excessively resistant behaviour when compared to Eocene sandstones. Being relatively-close the textures of all the four studied mortars, we think that both organic additives or catalysts together with the ratio high-Ca-lime/white-cement should play an important role in the final properties of the mortar

Chemical and mineralógica! study of restoration mortars applied to the Eocene sandstones of Gipuzkoa used for building construction

We have chemically and mineralogically analysed four commercial mortars (A, B, C and D) and a fifth one (synthesised by Teusa) by means of X-ray fluorescence and X-ray diffraction techniques. The mortar A is an amorphous arid-free alite-mortar, whereas the B and C are composed by quartz, alite and calcite. The mortar D is particularly special because of its composition of calcite and zincite together with minor amounts of quartz. The establishment of the precise chemical and mineralogical composition of mortars is an essential tool to enlighten the suitability of each type of mortar when applied to a particular rock for building. Most mortars have alite, quartz and calcite, appearing portlandite after 28 days of hardening. The low cristallinity of the mortar A, together with its chemistry suggests the presence of pozzolan. The mortars B and C have variable amounts of quartz as arid, being the C enriched in Ti, which appears as rutile. Probably the presence of Ti is to color the product. Mortar D is enriched on zincite that becomes simonkolleite after hardening, most probably due to reaction with the binding liquid that is added. The Teusa mortar has been synthesised in four different varieties by modifying the proportions ofhigh-Ca lime, white cement and grey cement. All the four varieties recorded the quartz as the main component together with alite, portlandite and calcit

Corrosion detecting probes for use with a corrosion-rate meter for electrochemically determining the corrosion rate of reinforced concrete structures

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