Abstract
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.
Highlights
The extraction of metals from their natural occurrences involves several steps, where each step is accompanied by the production of considerable amounts of waste [1]
The authors reported that after removal of fine particles and clay minerals of highly sulfidic tailings by desliming, the SiO2 + Al2 O3 content and specific surface area of the tailings were observed to decrease by 28% and 47%, respectively
Sulfidic tailings usually accumulate near the mining sites forming heaps of deposits or in tailings impoundments, which occupy considerably large areas and may cause serious environmental contamination, especially for rivers, groundwater, and soils, in case of containment failure
Summary
The extraction of metals from their natural occurrences involves several steps, where each step is accompanied by the production of considerable amounts of waste [1]. To mitigate some of the problems related to tailing dam construction and their failures, surface paste disposal (SPD) techniques involving dewatering of the tailings to prepare stacks of dried tailings has been pursued [18,19] While they offer several advantages including water recovery, they introduce additional engineering challenges and costs, such as dust generation, waste liquefaction, control of rheological parameters for paste transportation [2]. While CPB is considered relatively safer compared to tailing dams, instability of the composites, especially due to the reaction of the binders with sulfur, acids, or minor elements like arsenic, and eventual oxidation of the sulfidic tailings in the failed CPB are major concerns [26] Another alternative is to utilize low-permeability dry covers with materials like geotextiles, low sulfide waste rocks, oxide wastes, organic wastes, clay, soils, clay-rich subsoils, etc., [5,12,27].
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