CHARACTERIZATION OF MINING WASTES FOR CIRCULAR ECONOMY INTEGRATION *Maria de Lurdes Dinis1, Aurora Futuro1, Nelson Fernandes1, Maria Cristina Vila1, Flávio Oliveira2, Erika Levei3, Eniko Kovacs3, Ilyes Mathi4, Martina Petranikova4, Maria Paz Sáez-Pérez5, Jorge A. Duran-Suarez5, Ergin Gülcan6 1 CERENA, Faculty of Engineering, University of Porto, Portugal (*Presenting author: mldinis@fe.up.pt) 2 Secil S.A., Fábrica Secil, Setúbal, Portugal 3 National Institute of Research and Development for Optoelectronics, INOE 2000, Research Institute for Analytical Instrumentation Subsidiary, Cluj-Napoca, Romania 4 Chalmers University of Technology, Gothenburg, Sweden 5 Advanced Technical School for Building Engineering, University of Granada 6 Mineral Processing Division, Hacettepe University, Beytepe, Ankara, Türkiye ABSTRACT The increasing demand for primary raw materials raises concerns about the depletion and scarcity of natural resources. Identifying, assessing, and enhancing the value of alternative materials is crucial to mitigating these challenges. One promising approach involves the valorization of mining wastes as a secondary source of valuable elements or through their incorporation in other industries, as they offer potential substitutes for specific applications (e.g. cemented paste backfills for ground support, bricks, geopolymer concrete), thereby supporting the transition to the circular economy and sustainability of resources. This study evaluates the valorization potential of four types of mining waste: sulphide tailings (PT1), granite sludge (PT2), marble sludge (PT3), and limestone sludge (PT4). To establish a scientific basis for selecting suitable valorization pathways, an integrated characterization was conducted that included particle size distribution, chemical composition, mineralogical composition, pH, moisture content, and microstructural characteristics. Additionally, natural leaching tests were conducted to evaluate the chemical stability of the residues. The potential for acid generation was also evaluated. The results highlighted that each waste type has unique compositional and mineralogical features, suggesting different optimal valorization routes. Polymetallic sulphide tailings are rich in iron and sulfur, with pyrite as the main mineral phase, a mildly acidic pH, and a notable acid-generating potential—factors that raise environmental concerns and indicate that reprocessing for metal recovery should be prioritized to extract valuable or potentially harmful elements before other reuse options are considered. Granite sludge, with its high feldspar content and favourable physical and chemical properties, is well-suited for use in construction materials. Marble sludge and limestone sludge are predominantly composed
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