A. Rodríguez-Rey

Characterization by X-ray computed tomography of water absorption in a limestone used as building stone in the Oviedo Cathedral (Spain)

Abstract Water plays a fundamental role in rock weathering processes. Its penetration and movement inside rocks greatly influences the nature and intensity of damage affecting building stones. X-ray computed tomography (CT) is a useful technique for non-destructive mapping of water penetration. For the reported study, CT was used to investigate the internal structure and water penetration patterns for the Piedramuelle Stone, a Cretaceous limestone used as building material in the Oviedo Cathedral (North of Spain). X-ray CT provides good images of the internal structure of the samples: the sedimentary layering due to differences in composition and porosity is clearly seen, as well as other textural features. The movement and penetration rate of water was monitored during standard free absorption water tests. The images that were obtained show a clear difference between dry and wet zones in the interior of the sample. Water movement is related to the petrographic characteristics of the rock, mainly to layering which controls the direction of water penetration. Hounsfield Unit numbers provide a quantitative approach for assessing the penetration rate of water.

Durabilidad en ambientes húmedos de la Arenisca de La Marina (Jurásico superior de Asturias)

Se ha estudiado la alterabilidad de dos variedades (gris y amarilla) de una roca ornamental asturiana, denominada Arenisca de la Marina, perteneciente a la Formacion Lastres (Jurasico Superior). Ademas de las clasicas tecnicas de microscopia, para el estudio textural se han utilizado la velocidad de propagacion de ondas elasticas y la tomografia axial computerizada de rayos-X. Se ha determinado la variacion de algunas propiedades fisicas (densidad, porosidad abierta y velocidad de propagacion de ondas elasticas) antes y despues de los ensayos de alterabilidad (humedad-sequedad, hielo-deshielo y cristalizacion de sales), comprobandose que los ciclos de cristalizacion de sales son los mas agresivos y que la variedad amarilla es mas susceptible al deterioro que la variedad gris. La textura ejerce una gran influencia en la durabilidad de ambas muestras, de modo que las bandas con mas matriz y mayor porosidad presentan una mayor desagregacion superficial, determinandose la existencia de un comportamiento anisotropo, mas marcado en el caso de la variedad amarilla que en la gris.