Electrokinetic and chemical treatment of oil sands mature fine tailings: Dewatering and strengthening

Oil sands tailings have become a major challenge in Canada due to various geotechnical and environmental concerns. Mature fine tailings (MFT) typically contain 70% water and 30% silt- and clay-sized solids and have low hydraulic conductivities, which lead to difficulties in consolidation by nature. Electrokinetics (EK) has been proved to be effective at dewatering and strengthening oil sands tailings, but is only limited to the anode area. Further treatment is needed to improve the tailings around the cathode. Chemical stabilisation is a mature technique for ground improvement. However, there is limited information for the combined effects of EK and chemical treatment on high water content geomaterials such as MFT, slurry, sludge and so forth. This research study was carried out to evaluate the effects of combined EK and chemical treatment of MFT. Quicklime and Portland cement were selected as the chemical additives. The changes in water content, undrained shear strength, plasticity, pore-water pH and electrical conductivity and particle zeta potential after treatment were studied. It was found that the chemical treatment reduced the material property difference between the anode and cathode, whereas it reduced EK-induced water flow. Combined EK and chemical treatment of MFT may be beneficial at a low chemical dosage.