Concrete containing low-sulphide waste rocks as fine and coarse aggregates: Preliminary assessment of materials

The reuse of mining waste-rocks as construction material constitutes an innovative management approach consistent with the principles of sustainable development. Nevertheless, the implementation of this approach is still limited by most guidelines due principally to insufficient knowledge of these materials performances and to unjustified presumptions related to their chemical instability (presence of sulfide). This paper approaches these issues by assessing the reuse potential of low-sulfide mining waste rocks as aggregates for concrete regarding to the Quebec (Canada) recycling guidelines of non-hazardous inorganic wastes as construction materials. Toxicity characteristic leaching procedure (TCLP), comprehensive physical, chemical (XRF and ICP-AES) and mineralogical investigations (XRD and SEM) as well as modern automated mineral liberation analyses have been carried out. In addition, UCS results of various concrete mixtures using different binders were then presented to illustrate the reuse potential of the waste-rocks. The TCLP test showed the nonhazardous character of the waste rocks. They contained low sulfide content (0.5 wt%), which classify them as non-acid generating and able to meet the classification in recycling category including concrete production. Moreover, liberation analyses showed that most sulfides are concentrated in the fine fraction as pyrite occurrence with a liberated fraction of only 2%. These results influenced significantly the properties of the resulting concretes, which presented good mechanical performances especially when coarse waste rock above 20 mm and fine one below 80 mu m was removed. (C) 2019 Elsevier Ltd. All rights reserved.