Papers by Keyword: Slate

Abstract: Research and development related to the processing of recycled materials has grown progressively in recent times, as scientists endeavour to integrate sustainability criteria, depletion of natural resources, reducing the energy of technological processes involving extraction and processing of raw materials, etc. When it comes to processing slate, industries have to pass over several steps ranging from the extraction of rock blocks until the final products consisting of plates, leaving behind a considerable amount of waste in the form of a mud composed mainly of water, lubricants and crushed rock. This waste with no defined destination accumulates in yards, reservoirs and streams, affecting the environment. Slate powder has great prospects for recovery, recycling and further applications once it has chemical composition and components similar to raw materials used in ceramic and building construction industries. Therefore, a complete characterization of this powder is important and here we present some results of XRD, SEM, EDS, G3 morphology and thermal analysis of slate powder samples from the southeastern state of Minas Gerais in Brazil.

Abstract: The main objective of this work was to contribute to the knowledge of the geological resources of Trás-os-Montes and Alto Douro (TMAD) region, in particular of its “Xisto” (Portuguese word for “schist”, lato sensum), considering its economic and social impact. The target area is characterized by the abundant occurrence of different types of “schist”, belonging to the Variscan basement. This work is a contribution to improve the knowledge about mineralogy, fabric, chemistry and technology of the “schist”, in order to promote its exploitation and use as a natural stone. It was possible to identify the main factors that have an influence on the characteristics of all types of “schist”, conditioning its use as natural stone.

Abstract: The main purpose of this work was to increase the knowledge about the geological resources of Trás-os-Montes and Alto Douro region (TMAD), particularly about their “schists” (slate, phyllite and schist), due to the economic and social effects that their mining and processing can have, not only on the local economy, but also on a national level. This work presents the results of the study conducted on “schists” from TMAD, aiming for their use as natural stone. Special emphasis is given on the results obtained from the following physical and mechanical tests: compressive strength, flexural strength, apparent density, open porosity, water absorption, abrasion resistance and resistance to ageing by thermal shock. These tests were determinant to define the most suitable applications for each schistose stone that was studied, taking into account the existing groups of natural stone products. For defining the recommended applications for each “schist”, European standards for natural stone products were considered, as well as technical specifications that exist in some European countries, which were the basis for the establishment of a proposal of technical specifications for Portugal, already published by one of the authors of this work.

Abstract: The use of ultra-bright, highly directional, high and variable energy associated to synchrotron radiation beams at SPring-8 when compared with conventional X-Ray diffraction analysis applied to slate powders heat treated at temperatures in the range of 600°C up to 1000°C is reported. Fe K-edge XAFS measurements of the products formed upon heating slate showed that in the temperature range 600-800°C, conversion of FeO present in the as-received slate powder into a mixed -Fe2O3/-Fe2O3 has occurred providing useful information on the short-range order atomic structure of the slate. Above 800°C, mainly -Fe2O3 was identified to be present in the slate. The change of the Fe valences within the slate network is most likely responsible for the detected colour change with the increasing temperature.