Polycyclic aromatic hydrocarbons are increasingly widespread pollutants introduced into the environment via oil spillage and incomplete anthropogenic combustion of fossil fuels. In this work, the capacity of stevensite and sepiolite to adsorb phenanthrene (PHE) has been evaluated experimentally by batch testing. Both clay minerals are distributed widely in the Madrid Basin, are of low cost and can be applied with minimal environmental impact. In the context of few previous studies, adsorption isotherms have been developed to understand the adsorption mechanisms and were fitted to the Freundlich and linear models with virtually the same results. Although stevensite showed greater adsorption capacity than sepiolite, the isotherms were constructed for equilibrium concentrations up to 0.8–1.0 mg/L due to the low solubility of PHE in water. When compared to other adsorbents the ability of stevensite to retain PAHs should be examined further in order to add and complement novel functions in reactive barriers.

A novel method to perform small-scale laboratory experiments that reproduce concrete–bentonite and concrete–groundwater interactions has been developed. Such interfaces will prevail in engineered barrier systems used for isolation of nuclear waste. With the goal of optimizing the experimental method, this work has analysed the geochemical interaction of distilled water, low-pH cement mortar and FEBEX-bentonite for 75 days. Limited but evident reactivity between the materials was observed, mainly decalcification in cement mortar, carbonation at the interface with bentonite and Mg enrichment in bentonite. These results are consistent with the state-of-the-art literature and were used to validate this small-scale pilot laboratory experiment to establish the basis for further studies comparing the behaviour of different buffer and cement materials.

Artificial and singular geochemical environments are created around the engineered barrier systems (EBS) designed to isolate high level nuclear wastes in deep geological repositories. A concrete-bentonite interface takes place within the EBS and it builds a significant chemical gradient (pH), approximately from pH 8 (bentonite) to pH 12 (low alkali concrete), in a few millimetre thickness. This disequilibrium triggers dissolution and precipitation reactions and form a thin altered region. In this area, poorly ordered authigenic clay minerals, mainly hydrated magnesium silicates, are formed adjacent to hydrated calcium silicates and calcite precipitates adhered to the interface with concrete. This paper presents the development of this authigenic mineral layer comparing 6–18 months to 13 years interfaces. Scanning Electron Microscopy with Energy Dispersive X-ray spectroscopy (SEM-EDX) morphological and chemical characterization with the aid of ternary plots, X-ray diffraction (XRD) and infrared (IR) data show the young to old interface evolution from single brucite layers to stevensite-saponite silicates composition. Geochemical calculations indicate that this layer acts as a pH~11 buffer useful to minimize bentonite alteration and to favour the retention of amphoteric metal ions.

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Structural ageing, action by aggressive agents, accidents, etc., all make it increasingly necessary to apply conservation and maintenance programs to building structures. Columns are some of a building's most critical elements, since the failure of a single column can lead to the collapse of the entire structure or a large part of it. Although great strides have been made in recent years in the field of reinforced concrete (RC) column repair and strengthening, there is room for further improvement in certain areas. This paper describes a study carried out in the ICITECH laboratories (Universitat Politècnica de València) on RC columns repaired on all four sides with cementitious-based mortars. A total of 18 specimens were tested, representing a group of square 20x20 mm 2 columns subjected to compressive axial loads. Different repair scenarios were considered in order to study the influence of the type of mortar used and the presence or absence of bonding agents between the mortar and the column concrete. The results obtained showed that bonding agents have no appreciable effect on the behaviour of the repaired columns. Of the two types of mortar used in the study (Classes R3 and R4), the columns repaired with the lower grade mortar (R3) were seen to behave better. The main novelty of this work lies in the fact that this is the first time that two types of mortar are compared in the repair of four column sides, in addition to the possible use of bonding agents between the mortar and the column.