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Medium and highly sulfidic tailings are high-volume wastes that can lead to severe environmental damage if not properly managed. Due to the high content of sulfide minerals, these tailings can undergo weathering if put in contact with oxygen and water, generating acid mine drainage (AMD). The moderate-to-high sulfide content is also an important technical limitation for their implementation in the production of construction materials. This paper reviews the use of sulfidic tailings as raw material in construction products, with a focus on cement, concrete, and ceramics. When used as aggregates in concrete, this can lead to concrete degradation by internal sulfate attack. In building ceramics, their implementation without prior treatment is undesirable due to the formation of black reduction core, efflorescence, SOx emissions, and their associated costs. Moreover, their intrinsic low reactivity represents a barrier for their use as supplementary cementitious materials (SCMs) and as precursors for alkali-activated materials (AAMs). Nevertheless, the production of calcium sulfoaluminate (CSA) cement can be a suitable path for the valorization of medium and highly sulfidic tailings. Otherwise difficult to upcycle, sulfidic tailings could be used in the clinker raw meal as an alternative raw material. Not only the SO3 and SiO2-rich bulk material is incorporated into reactive clinker phases, but also some minor constituents in the tailings may contribute to the production of such low-CO2 cements at lower temperatures. Nevertheless, this valorization route remains poorly explored and demands further research.

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Mining and quarrying waste is the second largest waste stream in Europe. Sulfidic ore processing residues (tailings) pose a large challenge, because they contain hazardous metal(loid)s and because they can lead to acid mine drainage. However, mine tailings also contain valuable base, precious, and critical metals, which can be used in different technological applications, as well as silicates and clay minerals that offer possibilities for use in building materials. In the present study, the potential use of mine tailing material, from the inactive Pb-Zn mine of Plombières (Eastern Belgium), in 3 ceramic products (roof tiles, blocks, and pavers) was assessed, taking into account production parameters, product quality, and environmental performance. After a detailed physical, mineralogical, and chemical characterization of the mine tailing material and the original raw materials, different mixtures were prepared on a lab scale, in which primary raw materials (e.g., clay and sand) were replaced by 5, 10, or 20 wt% of the fine tailing material. The technical, chemical, and aesthetical properties of each ceramic body were assessed, as well as their environmental performance, considering a 2 nd life scenario, where shaped building materials are demolished and recycled as aggregates. High additions of tailing material in clay roof tiles (10 and 20 wt%) and clay blocks (20 wt%) resulted in technical and aesthetical problems. On the contrary, paver mixtures containing 10 and 20 wt% of tailing material showed better technical properties and satisfying chemical and aesthetical characteristics.

<p>Mining and quarrying waste is considered the second largest waste stream in Europe. According to Eurostat, in 2018, this extractive waste accounted for over a quarter of all the EU-27 waste output (26.2%). The accumulation of this type of waste in tailing dams or waste rock piles, with no end-use, can pose as a significant environmental and health hazard as well as a resource loss. Sulphidic mine waste processing residues (tailings) pose a large challenge, as their content in hazardous metalloids and sulphates tend to become more chemically available, leading to the generation of acid mine drainage. Apart from the hazardous metalloids and sulphates, these mine tailings contain valuable base, precious and critical metals which can be used in different technological applications. Moreover, silicates and clay minerals are amongst the most common and abundant minerals in sulphidic mine tailings, which indicates that after pre-treatment, if necessary, they can be used in different ceramic building applications (e.g. roof tiles and blocks) for an increasing world’s population.</p><p>Plombières Zn-Pb inactive mine (Eastern Belgium), was exploiting an ore deposit between 1844-1882 and after closure of the mine, imported ores were smelted at the Plombières site until 1922. The dumped material from the mining operations consist of mainly mine waste and metallurgical waste, such as tailings and slags, from the processing plants. The goal of the present study is to evaluate the potential use of (uncleaned) Plombières tailing material in 3 different ceramic products (roof tiles, blocks and pavers), with different compositions and firing temperatures, taking into account production parameters, product quality and environmental compliance in Flanders (Belgium).</p><p>After a detailed physical, mineralogical, chemical, thermal and environmental characterisation of the Plombières mine tailing material, as well as of the replaced raw materials, one company-specific blend has been modified on a lab scale for each ceramic product, by partly or totally replacing some primary raw materials (mainly clay and sand) by 5%, 10% and 20% of Plombières fine tailing material. The shaping, drying and firing behaviour of lab test pieces was assessed and compared to the standard, as well as the required technical, aesthetical and chemical properties of each ceramic product. Furthermore, environmental compliance tests (column leaching test) were performed on the fired test pieces of all the ceramic products. The column leaching test is performed considering a 2<sup>nd</sup> life scenario where shaped building products are demolished and can be recycled as granulates (non-shaped building products).</p>