Characterizing the rheology of laterite slurries

The viscous behaviour of laterite slurries was characterized by measurements of shear stress at constant and changing shear rates. Steady state stresses were obtained after accounting for the settling solids: the values show that the fluids possess viscosities of order 100 mPa s and are moderately shear-thinning, for solid volume fractions from 0.06 to 0.18 and for shear rates between 10 and 1000 s(-1). Transient stress measurements were made for steps down in shear rate and for ramps down and up in shear rate. It was found that the Bingham-Maxwell model provides good fits to the transient data, both at low concentrations, where yield behaviour is dominant, and at high concentrations, where elasticity is dominant. For volume fractions of 0. 10 or greater, relaxation times were found from step tests to be of order 10 s, but relaxation times found from the ramp tests were generally several times higher. (C) 2003 Elsevier Science B.V. All rights reserved.