Influence of the shear stress applied during flow stoppage and rest on the mechanical properties of thixotropic suspensions

We show that the elastic modulus and yield stress of thixotropic suspensions depend strongly on the shear stress applied during their flow stoppage, while they depend negligibly on the preshear history and on the stress applied at rest. We find that the suspensions age with a structuration rate that hardly depends on the stress history. We propose a physical sketch based on the freezing of a microstructure whose anisotropy depends on the stress applied during the liquid/solid transition to explain these features. We finally discuss the consequences of this new phenomenon for rheometry and macroscopic flows.