Improving Properties of Sealing Layers Made of Till by Adding Green Liquor Dregs to Reduce Oxidation of Sulfidic Mine Waste

A common solution to minimize formation of acid rock drainage in sulfide-bearing mine waste is to construct a composite cover comprising till. Due to a shortage of fine-grained till close to mines, other sealant materials must be considered. Here, the feasibility of using green liquor dregs (GLD), an alkaline and inorganic residual waste, as an additive to improve low quality till in the construction of sealing layers in cover system designs was studied. GLD was blended with three types of till in a pilot scale study. 10-15 % (wet weight) GLD was found to be sufficient to take full advantage of the physical properties of the residual waste. Different mixing techniques were also evaluated. The results showed that the quality of till, i.e., hydraulic conductivity and water retention capacity, could be improved by addition of 10 % GLD. Short duration and efficient mixing was preferred as vigorous mixing released water bound in the GLD, resulting in increased w and reduced compaction efficiency, making the blended material difficult to apply and use in sealing layer constructions.