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RESUMENLas areniscas miocenas estudiadas han sido y son ampliamente utilizadas en patrimonio histórico y en obra civil moderna, localizándose las canteras actuales en el borde de la depresión del Ebro. Se ha realizado un exhaustivo estudio de las características petrofísicas de estos materiales, que pese a presentar la misma edad y pertenecer a la misma cuenca sedimentaria presentan características mineralógicas y texturales diferentes que les confieren diferentes propiedades físicas, mecánicas y una diferente durabilidad. Las características petrográfi-cas y petrofísicas se han evaluado mediante la realización de ensayos según las normas UNE, NORMAL y ASTM. Para todos los ensayos se ha realizado un tratamiento estadístico de los resultados para evaluar las posibles inhomogeneidades texturales y composicionales presentes en el material y que pueden originar modificaciones en su comportamiento.Los resultados ponen de manifiesto que estas areniscas presentan un importante valor industrial como materiales de usos constructivos, siendo la arenisca de Alcañiz la que presenta una mayor durabilidad como consecuencia de la configuración de su sistema poroso.Palabras clave: arenisca, propiedades físicas, durabilidad, petrofísica, piedra de construcción. SUMMARYMiocene sandstones studied were used extensively to build Aragon's architectural heritage, are still used in modern construction. The quarries presently located on the edge of the Ebro Valley depression. The present paper describes an exhaustive petrophysical study of these materials, which while, of the same age and from the same deposition basin, exhibit different mineralogical and textural characteristics and as a result, different physical and mechanical properties and durability. The petrographic and petrophysical characteristics of these materials were evaluated with tests prescribed in UNE (Spanish), NORMAL and ASTM standards. All the results were subjected to statistical analysis to identify possible textural and compositional nonuniformities in the material that may underlie behavioural changes.The results of the present paper show that their petrophysical characteristics afford these sandstones substantial industrial value as construction materials. Durability was found to be longest in the Alcañiz stone, as a result of the geometry of its pore network.Key yw wor rds: sandstone, physical properties, durability, petrophysics, construction stone. INTRODUCCIÓNLas areniscas miocenas de Uncastillo, Ayerbe y Alcañiz se localizan en el borde exterior del sector central de la depresión terciaria del Ebro. Estos materiales han sido ampliamente utilizados a lo largo de los siglos para la construcción en obras que han dejado una particular impronta en el variado patrimonio cultural y monumental aragonés. Entre otros, son ejemplos de la utilización de la Piedra de Uncastillo, el yacimiento arqueológico de los Bañales (siglo I d.C.), el Mausoleo de los Atilios (monumento funerario del siglo II d.C.) y el castillo de Sádaba (siglo XIII). La Piedra de Ayerbe ha sido ut...

The aim of the present article is to identify the influence of the pore morphology on the physical behaviour and durability of natural stone. Fifteen sedimentary rocks commonly used in the cultural and architectural heritage of Aragon (Spain) were characterized. The petrography, porous structure, fluid transport properties and durability of these rocks were analysed. They were classified into two different groups according to the results of the different tests. For each of these groups the physical behaviour was established. A principal components analysis was used in order to examine the correlation between pore structure, hydric properties and durability. The results show that the percentage of pore throats \0.1 lm control the fluid transport properties, have an important influence on stone durability, and can be used to predict resistance to salt decay while the average pore size does not. Stones with a high percentage of pore throats \0.1 lm are less susceptible to salt decay than stones with higher pore size if their pore network is characterized by high tortuosity and low connectivity.

This research characterizes the weathering of natural building stone using an unsteady-state portable probe permeameter. Variations between the permeability properties of fresh rock and the same rocks after the early stages of a salt weathering simulation are used to examine the effects of salt accumulation on spatial variations in surface rock permeability properties in two limestones from Spain. The Fraga and Tudela limestones are from the Ebro basin and are of Miocene age. Both stone types figure largely in the architectural heritage of Spain and, in common with many other building limestones, they are prone to physical damage from salt crystallization in pore spaces. To examine feedbacks associated with salt accumulation during the early stages of this weathering process, samples of the two stone types were subjected to simulated salt weathering under laboratory conditions using magnesium sulphate and sodium chloride at concentrations of 5% and 15%. Permeability mapping and statistical analysis (aspatial statistics and spatial prediction) before and after salt accumulation are used to assess changes in the spatial variability of permeability and to correlate these changes with salt movement, porosity change, potential rock deterioration and textural characteristics. Statistical analyses of small-scale permeability measurements are used to evaluate the drivers for decay and hence aid the prediction of the weathering behaviour of the two limestones.

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