Microstructural and geochemical evolution of paste tailings in surface disposal conditions

Surface paste tailings disposal has recently been proposed in the mining industry for the management of mill tailings. This new disposal method can represent an advantageous alternative to traditional tailings impoundments, as it favours water recycling and the control of free water during deposition, reduces the need for costly water-retaining dykes, and facilitates site rehabilitation. In this paper, the microstructural and geochemical properties of surface paste tailings were assessed. Column leaching tests were conducted on sulphide-rich paste tailings deposited under different configurations (cemented and uncemented). The leached samples were characterized and the results were compared to those obtained on the reference (unleached) samples. The paste microstructure was characterized by mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) coupled with energy dispersive spectroscopy (EDS) microanalysis. A part of the study focussed on the impact of cracks, which were found to influence the paste reactivity observed for some disposal configurations. The paper illustrates how to use paste technology and a small amount of ordinary Portland cement (0.66 wt.% in configuration L2) to stabilize sulphide-rich acid generating tailings (AP = 953 kg CaCO3/t).