Rheophysical classification of concentrated suspensions and granular pastes

On the basis of existing data along with rational arguments we propose an overview, in a conceptual diagram (solid fraction vs shear rate), of the dominant interaction type (Brownian, colloidal, and hydrodynamic) at a mesoscopic scale within flows of concentrated suspensions or granular pastes. Different flow regimes identified by the values of dimensionless numbers are thus distinguished. The main characteristics of the rheological behavior of suspensions within each regime are inferred. A specific domain corresponds to regimes for which dilatancy effects occur which may lead to frictional or collisional processes if an additional (normal) force is applied over the particles.