Potential Use of Sandy Mining Wastes as Raw Material in Road Construction

Sustainable programs are increasingly stimulating the use of industrial wastes, minimizing economic and environmental impacts. This use is especially notable in the mining industry, in which the amount of discarded material is exaggeratedly higher than the amount of obtained product. In this context, the aim of this paper is to study the sandy wastes generated from beneficiation processes of scheelite (CaWO₄) to determine its potential use as a raw material in pavements. First, a physical, chemical and mineralogical characterization of the sandy wastes was performed. Subsequently, geotechnical characterization tests (grain size analysis, specific gravity, compaction, CBR and direct shear) were performed. The waste presented a heterogeneous mineralogical composition which is consistent with the mineralogical composition of the scheelite host rocks. The main minerals are calcite, quartz, micas and silicates of the garnet group and the pyroxene group that commonly occur in calcium-rich metamorphosed sediments. This resulted in a sandy and non-plastic material, positively influencing the geotechnical behaviour. The results show that the residual strength envelope exhibits zero cohesion for compaction energies, but the residual friction angle increases with the increasing energy. The values obtained for the strength parameters indicate that this material can be used as road embankment layers.