676 KEYWORDS Mining tailings; Circular economy integration; Waste valorization; Material characterization; Sustainable construction 1. INTRODUCTION The mining sector is essential to global economic growth, providing the raw materials needed for industry, infrastructure, and energy systems (Hamaroui et al., 2024; Cotrina-Teatino et al., 2025). However, mining operations are associated with considerable environmental impacts, mainly due to the generation and prolonged storage of large volumes of solid waste and effluents (Kinnunen et al., 2022; Kinnunen et al., 2021). Significant amounts of tailings and other by-products are typically deposited in tailings storage facilities, which demand ongoing oversight, water management, and long-term stewardship. Inadequate handling of mining waste can lead to environmental hazards, such as acid mine drainage and the leaching of potentially toxic elements into soil and water (Coles and Yong, 2002; Khalil et al., 2013; Dinis et al., 2020). At the same time, the rising demand for raw materials—driven by population growth, digital transformation, and the shift to new energy technologies—cannot be met solely through recycling, making continued primary extraction necessary (Lèbre et al., 2017). As a result, achieving a sustainable supply of resources requires a balanced approach that combines both primary and secondary sources (Beylot et al., 2022). Embracing the circular economy (CE) framework supports this goal by encouraging the recovery of value from industrial by-products and keeping materials in productive use. Within mining, CE approaches promote both the retrieval of metals and the reuse of mineral residues in construction and other industries (Tayebi-Khorami et al., 2019). Beyond minimizing environmental risks, finding ways to valorize mining waste offers new opportunities for its use in the construction industry. Construction is a major consumer of natural resources and a significant source of energy use and emissions, especially in cement and concrete manufacturing (Scrivener et al., 2018). Partial replacement of conventional raw materials can reduce the need for virgin extraction and enhance resource efficiency (Argane et al., 2016). However, mining waste is highly variable, with its characteristics determined mainly by the geological source, extraction methods, and processing techniques used (Hamaroui et al., 2024; Fernández-Pereira, 2024). Such variability influences their technical and environmental behaviour, making direct reuse challenging (Barroso et al., 2026). Therefore, the effective use of mining residues in construction requires careful control of their physical, chemical, and mineralogical properties to guarantee technical quality and environmental safety (Simonsen et al., 2020). On the other hand, a comprehensive characterization enables the selection of appropriate recovery or reuse options for mining wastes. Within this context, the current research explores the potential for valorizing four types of mining waste: sulphide tailings (PT1), granite sludge (PT2), marble sludge (PT3), and limestone sludge (PT4). Conducted as part of the ValorWaste project, this work aims to identify sustainable pathways for both fresh and stored metallic and non-metallic mining residues, contributing to advancing circular resource management and enhancing material efficiency in the mining sector. 2. MATERIALS AND METHODS 2.1 Origin of Materials and Sampling Locations Four mining waste samples were collected within the framework of the ValorWaste project from different extractive industry sites and geographical locations in Portugal. The collected materials include fresh sulphide tailings (PT1), granite sludge (PT2), marble sludge (PT3), and limestone sludge (PT4), representing both metallic and non-metallic residues. Fresh sulphide tailings were collected from the flotation
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