Time-Dependent Rheological Behavior of Flow-plastic Bentonite: Effect of solid concentration and salt solution

Effects of NaCl solution and solid concentration were investigated for time-dependent rheological properties of flow-plastic bentonite. Under constant bentonite concentration, flow curves of five groups added with the NaCl concentration range of 0.01–0.1 mol/L were obtained by rheometer over a range of aging time from 0h up to 120h. As solid concentration increases, the shear stress increased significantly in the initial stage of aging time under the same shear rate, and the growth rate gradually slowed down and became stable with the increase of aging time. This phenomenon was attributed to this period being enough for full hydration, and the development of flow-plastic bentonite structure was relatively limited after 48h. While the addition of NaCl solution significantly reduced the shear stress of flow-plastic bentonite regardless of aging time. Besides, all flow curves were found to be well fitted with the Herschel-Bulkley model, the flow behavior index, which characterizes the rheological properties of the fluid-plastic bentonite in the model, gradually decreases with increasing NaCl concentration, indicating that the higher the NaCl concentration, the more obvious the shear-thinning behavior. Finally, the proposed stretched exponent model for predicting the time-dependent behavior of yield stress is consistent with experimental results by data extrapolation of full rheograms using the Herschel-Bulkley model. These findings will be beneficial for revealing further reliable information for future engineering reality.