Application of the exponential stretching theory in studying el Barkan bentontte thixotropy

The exponential stretching theory was used to investigate the thixotropic character of mixes prepared from local el barkan bentonit. the received raw clay was split into four size fractions and pastes were prepared by mixing with different percents of water and curing for 6 hours. apparent viscosity and shear rate were measured using a brookfield rotary viscometer. results revealed that the mode of flow of all mixes investigated was of the non-newtonian bingham type,the yield stress increasing with bentonite concentration. a time constant was calculated that represents the thixotropic character of pastes. this time constant was found to increase with increased bentonite concentration and on using finer particle size.