Quality requirements for use of green liquor dregs to construct mine waste covers

Abstract Green liquor dregs are one of the main side streams generated in paper and pulp production. Due to a lack of established applications, the material commonly ends up in landfills. However, research has shown the potential for green liquor dregs to replace bentonite clay as a sealing component in mine waste covers. This would be economically and environmentally beneficial for both industries. Green liquor dregs are resistant to dewatering, a property sought after in material for sealing layers. The challenge as well as the opportunity lies in utilizing industrial waste, with little to no monitoring of compositional variations, in soil structures with determined quality requirements. This study aims to outline material properties to strive for. The water retention curve for eight batches of green liquor dregs were experimentally determined and analyzed in terms of variations in clay-sized particle content, organic carbon and water content. Pressure plate tests with suction range 0–148 mH 2 O were used to evaluate how compositional variations affect green liquor dregs ability to withstand drying. Experimental results are described by the van Genuchten model and illustrate how green liquor dregs are up to 60 % more resistant to drying compared to natural soil with similar grain size distribution.