Estimating Measurement Artifacts in Concrete Rheometers from MRI Measurement on Model Materials

Abstract

Measurement artifacts in concrete or mortar rheometers often prevent the user from having access to absolute correct values of the rheological parameters of the tested material. As there does not exist any rheometer giving access to the “correct” or “real” values of these parameters, it is even not possible to estimate the order of magnitude of the error induced by these artifacts. It is however possible to have access to the local and real rheological behavior law by measuring local velocities and local concentrations of particles through Magnetic Resonance Imaging (MRI) techniques. In this paper, we compare macroscopic measurements and local MRI measurements of the behavior of suspensions of natural sand particles and bi-disperse spherical particles in model yield stress fluids (emulsions). In doing so, we seek to illustrate the potential consequences of artifacts on the measurements of the flow curve of cementitious materials. We reach the conclusions that particle migration is at the origin of the discrepancy between concrete rheometers.