The effects of vibrations on the rheological behaviour of bentonite muds. Comparison with cement pastes

The bentonite muds, widely used in civil engineering and in the oil industry, have a binghamian and thixotropic behaviour, that impedes their flow (pumping, displacement by a slurry, etc). A mechanical vibration able to reduce this rheological character, as it does with fresh cement pastes, would improve the flow. Unfortunately vibrations, whatever their frequency may be (from 0 to 3000 Hz) and acceleration (from 1 to 55 times the gravity one) reduce neither the yield-value nor the thixotropic activity of the muds. This results from the structure of the solid phase which is not very resistant but particularly deformable, contrary to the fresh cement pastes: vibration amplitude is not enough to break the bonds between bentonite particles.