Rheology of mature fine tailings

Rheological characteristics of mature fine tailings (MFTs) were examined in both the linear and non-linear viscoelastic regimes. MFT samples exhibited thixotropic behavior as well as apparent slip, which was suppressed by using sandpaper of grit 80 (200 μm) at the wall of the parallel-plate geometry. The real yield stress of MFTs with shear-thinning behavior was retrieved after fitting to a Herschel–Bulkley equation. Creep and oscillatory shear tests are also used to verify the yield stress measurement. The yield stress of two MFT suspensions possessing similar volume fractions was found to be similar; however, a kaolinite suspension (formulated to mimic/match the MFT rheology) showed more shear thinning and less thixotropy. The presence of bitumen remaining in the MFTs (up to 2 wt. %) suppressed the apparent slip to a large extent due to the immobilization of the particles at the interface. Finally, the effect of temperature on MFT rheology was studied in detail over the range of 0–50 °C, showing a minimum viscosity and yield stress at about 20 °C (demonstrating a non-monotonic increase with the increase in temperature).