Pérdida del pulido de diferentes mármoles comerciales en ambientes salinos

Este artículo cuantifica la pérdida de pulido que sufren los mármoles cuando entran en contacto con disoluciones salinas. La pérdida de pulido (cuantificada como el incremento de rugosidad superficial) es debida a la disolución que sufren los cristales de calcita, y se compara esta tasa de disolución con la estabilidad de los mármoles dolomíticos.Este trabajo se enmarca en el Proyecto Maternas (S0505-MAT/000094, Comunidad de Madrid)

Electrochemical softening of concentrates from an electrodialysis brackish water desalination plant: Efficiency enhancement using a three-dimensional cathode

The electrochemical softening method to remove hardness from water has not been applied in desalination practice due to a high cathodic area requirement. In this work, the use of a 3D stainless steel wool cathode is proposed to overcome this technical limitation. An extensive comparison between the 3D cathode and a 2D Ti mesh has been presented, showing higher hardness removal for the 3D one. Experiments have been conducted with waters similar to concentrates derived from a brackish water treatment by electrodialysis. In addition, the method has been proved to be efficient for different water compositions in terms of hardness, alkalinity or the presence of an anti-scalant. The main influencing parameters (flow rate and current density) have been studied and it can be concluded that lower flow rates (below 1.2 L h−1) give rise to a better efficiencies and 100 A m−2 is the optimum current density. Moreover, the precipitate was characterised by SEM, EDX and XRD showing that Ca2+ is removed as calcite and aragonite (CaCO3), whereas Mg2+ is precipitated as brucite (Mg(OH)2). Finally, long-term experiments revealed that the 3D stainless steel cathode has a better performance than the 2D Ti mesh, but only at short times

Travertine of Baños de Mula. A stone with sedimentological and archaeological interest

Los travertinos coloreados de Baños de Mula fueron utilizados como roca dimensional entre otros sitios, en el Teatro Romano de Cartagena (Travertino Rojo de Mula). Esta roca tiene buenas propiedades mecánicas y buen comportamiento hídrico. Estas propiedades presentan fuerte anisotropía, relacionada con su característica estructura bandeada definida visualmente por cambios en la coloración y en la distribución de los poros. Sus características texturales, muestran el predominio de niveles constituidos por cristales fibrosos y fibroso-radiados, con una fase cementante tardía de oxihidróxidos de Fe, así como morfologías micríticas del tipo de colonias bacterianas. Ambos rasgos pueden relacionarse con actividad bacteriana. Todos estos datos apuntan a favor de una génesis relacionada con aguas termales. Este hidrotermalismo está en relación con fallas activas y se mantiene activo en la actualidad (Balneario de Baños de Mula).The coloured travertine of the Baños de Mula,were used as dimensional stone among other sites in the Roman Theatre in Cartagena (Red Mula Travertine). This rock has good mechanical properties and water behavior. These properties show strong anisotropy related to the characteristic bedding planes visually defined by changes in the color intensity and pore distribution. Their textural features show the prevalence of layers consisting of fibrous and fibrous-radiated crystals with a late stage cementing Fe oxyhydroxides and micritic aggregates following colonial bacterial morphologies. Both features may be related to bacterial activity. All these data point in favor of a genesis related upwelling of thermal waters. These hydrothermal processes are connected with hydrothermal circulation along the active faults, and are manifested at present in the hot springs of Baños de Mula.Este trabajo ha sido parcialmente subvencionado por el proyecto Geomateriales (P2009/MAT-1629) de la Comunidad de Madrid

Some colored travertines from the Betic Range (SE Iberian Peninsula): their geological setting and petrophysical properties

En la zona Bética Externa, se encuentran depósitos de travertinos coloreados de valor como rocas ornamentales cuyas características petrofísicas son poco conocidas. Están en relación con fallas activas. Las canteras de travertino se sitúan en Alhama de Almería, Albox (Almería) y Baños de Mula (Murcia). Estos travertinos forman parte de la última etapa del relleno de las cuencas terciarias postectónicas béticas (Pleistoceno) y generalmente aparecen espacialmente asociados a episodios tobáceos. El objetivo de este trabajo es definir las facies de estos travertinos y las características petrofísicas que presentan con vistas a su utilización como roca ornamental. Predominan en ellos las facies bandeadas (1 - 10 cm). Su porosidad es variable (5 - 15%) consistente en una microporosidad bastante homogénea, con moda (0.005-0.05 μm) ligada al carbonato micrítico, y una familia de poros menos seleccionada entre 0.05-2 μm asociada a cristales de mayor tamaño. La macroporosidad de tamaño y disposición variable es un rasgo característico de estos travertinos. El coeficiente de absorción capilar es muy anisótropo y varía mucho en los diferentes travertinos estudiados. El valor mínimo encontrado en travertinos comercializados ha sido de 1.42 (g/m2s0.5) en dirección oblicua a la estructura en el travertino Rojo Alhama y el máximo de 10.71(g/m2s0.5) en dirección paralela a la estructura en el travertino de Albox. Su resistencia es notablemente anisótropa, encontrando valores de resistencia a compresión que pueden llegar a alcanzar 68 MPa en dirección perpendicular al bandeado. Cortados en dicha dirección constituyen una roca ornamental de buena calidad dentro de la categoría de mármoles comerciales.The Betic Range contains several colored travertine deposits which were formed during the last stage of the post-tectonic Tertiary-Quaternary (Pleistocene) basin refill. Associated with active faults, these travertines are quarried in Alhama de Almería, Albox (Almería) and Baños de Mula (Murcia) for subsequent use as ornamental stone. The aim of this study was to characterize their facies and physical properties in order to establish their suitability for use as an ornamental stone. The main facies was banded (1-10 cm), and the travertines presented variable porosity ranging from 5-15%. Porosity is related to travertine texture: a) fairly homogeneous microporosity, with a mode between 0.005 and 0.05 μm, is linked to micritic carbonate; and b) a porosity mode varying widely from 0.05 to 2 μm is associated with larger crystals. A characteristic feature of these travertine deposits was their macroporosity of variable size and distribution. The coefficient of capillary absorption was highly anisotropic and presented very different magnitudes in the different travertines studied. A minimum value of 1.42 (g/m2 s0.5) was observed in the commercial Red Alhama travertine, in an oblique direction to the structure, while the maximum value of 10.71 (g/m2 s0.5) was found in Albox travertine deposits, in a parallel direction to the structure. Strength was markedly anisotropic, attaining compressive strength values as high as 68 MPa in the direction perpendicular to the bedding planes. When cut in this direction, the travertines studied yield good quality ornamental stone within the category of commercial marble.Este trabajo ha contado con la ayuda del MEC: Proyecto CGL2006-05027y de la Comunidad de Madrid: Proyectos Geomateriales (S2009/Mat-1629 y S2023/MIT 2914)

Carbonates and Sulfates in Hot Spring Microbialites (Baños de Mula, Betic Range)

In this paper the association of various minerals, mainly carbonates, to microbial mats that cover the surfaces of a hot spring is documented. In addition, the influence of microorganisms in the formation of the travertine is discussed.This study was financed by the Spanish Ministry of Economy and Competitivity (Projects CGL2011-25162 and CGL2011-26781)

Análisis geoambiental en medios hipogeos

8 páginas, 1 figura. Ed. Miguel Ángel Rogerio Candelera y Cesáreo Sáiz Jiménez. Primera Reunión de la Red de Ciencia y Tecnología para la Conservación del Patrimonio (Madrid, 28-29 de junio de 2011).Los coordinadores de los dos grupos de trabajo localizados actualmente en dos instituciones independientes (CSIC, Universidad de Alicante) se iniciaron científica y profesionalmente en el equipo de investigación de Geología - Geoquímica - Microclima aplicados a la Conservación del Patrimonio que se formó bajo la dirección de Manuel Hoyos Gómez a principios de la década de los 90. En el campo de la Conservación del Patrimonio, las investigaciones de ese grupo se centraron especialmente en la protección del arte rupestre y actualmente se enfocan al estudio integrado de ambientes subterráneos (cuevas, catacumbas,túneles, etc.) y de los procesos de deterioro del patrimonio que albergan. Los proyectos en los que los dos grupos trabajan abitualmente en estrecha relación incluyen datos de los parámetros climáticos y microclimáticos que caracterizan los sitios de estudio, de las características mineralógicas, geoquímicas y petrofísicas de los soportes y de las aguas de infiltración, y de los aspectos geomicrobiológicos de la interacción entre microoorganismos y los diferentes sustratos existentes (rocas, materiales de construcción, espeleotemas, etc.).Peer reviewe

Influence of anisotropy on rock hydrical properties. Analysis of brecciated dolostones from Betic Cordillera (Spain)

The purpose of this study is to determine the influence of anisotropy on hydrical properties of brecciated dolostones (BD). The present investigation involving BD has revealed, on the one hand, at meso-scale, four types of fractures. On the other hand, mercury intrusion porosimetry (MIP) has delimited two main porous families: pores of rock matrix and micro-fracture systems. Capillary transport and permeability tests were performed on four types of BD in order to establish the correlation between these parameters and the porous-fracture systems. The results show strong anisotropy in capillary absorption measured on prismatic samples in their three orthogonal directions. At the same time, our study has demonstrated that permeability correlates with both capillary absorption, as well as fracture density. Finally, the porous system of BD can be described in two ways: as a tri-continuum medium that consists of pores belonging to the pore matrix, fractures and cavities or as a dual-porosity model embedding fractures and vein intercrystalline porositie

Impact of salt and frost weathering on the physical and durability properties of travertines and carbonate tufas used as building material

This study aims to understand the effect of salt and frost crystallisation on the petrophysical and durability properties of representative types of travertine and carbonate tufas. Results demonstrate that the studied travertines and tufas exhibit a very high durability against salt and ice crystallisation cycles, compared to carbonates rocks with similar porosity values. The variation of the loss of mass, effective porosity, capillary absorption coefficient, ultrasonic wave velocity and attenuation, and compressive strength was scarce during weathering tests. The evolution of petrophysical properties was slightly more intense after 30 cycles of salt crystallisation than 100 cycles of freeze–thaw. Petrophysical and durability properties of the travertines and carbonate tufas depend on porosity fraction and on the manner in which the vuggy porosity is connected. In the travertine facies, vuggy macropores show little connection and can be considered as separate-vug porosity. Their addition to interparticle porosity increases effective porosity and reduces their mechanical strength but does not significantly increase capillary transport and the effectiveness of salt and ice action over the stone. On the contrary, in the carbonate tufas, vugs act as touching-vug pores, as capillary imbibition coefficients reveal. However, scanning electron microscopy displays that they underwent microcracking processes related mainly to both thermal stresses and/or ice and salt pressures. These microcracks present little connection, and they do not enhance noticeably the water flow or decrease the mechanical properties. These results are finally discussed in terms of a nonlinear decay pattern, which with long periods of apparent stability might be followed by rapid and catastrophic decay.This study was financed by the Spanish Ministry of Education and Science (MEC) through the Research Project CGL2006-05027/BTE and Community of Madrid (S2023/MIT 2914). A pre-doctoral research fellowship was awarded to N. Cueto by the MEC