Flow induced particle migration in fresh concrete: Theoretical frame,numerical simulations and experimental results on model fluids

In this paper, we describe and compare the various physical phenomena which potentially lead to flow induced particle migration in concrete. We show that, in the case of industrial casting of concrete, gravity induced particle migration dominates all other potential sources of heterogeneities induced by flow. We then show, from comparisons between experiments using model materials, dimensional analysis and numerical simulations, that, from a quantitative point of view, the viscous drag force, which prevents particles from migrating during a casting process, shall neither be computed from the apparent viscosity nor from the plastic viscosity of the suspending phase but from its tangential viscosity. Finally, the transfer of this type of numerical prediction tool to real concrete is discussed.