Normal and tangential interaction between discrete particles immersed in viscoelastic fluids: Experimental investigation as basis for Discrete Element Modelling of fresh concrete

The work presented in this paper has been performed in the framework of the development of a Discrete Element Modelling (DEM) approach for the simulation of fresh concrete flow, currently ongoing at the TU Dresden. In the streamline of the pioneer work by Shyshko and Mechtcherine [1], the interaction between discrete neighbouring particles with some amount of viscoelastic material in between has been experimentally investigated with reference to both normal and tangential direction. As for the viscoelastic material, a variety of fluids has been considered, including cement paste and mortar, with compositions formulated from typical Self Compacting Concrete (SCC) mixes. Effects of thixotropy and deformation rate have been investigated as well. For shear particle-particle interaction, a dedicated experimental set-up has been designed and 3D-printed to be employed with a Mars III Haake rheometer. The force-displacement relationships (FDR) obtained from the experiments provide information on particle-particle and particle-wall contact formation, maximum contact forces and distance at contact breakage. Accordingly, constitutive relationships describing the characteristic behaviour are formulated to be eventually implemented into particle flow codes for the simulation of flow of fresh concrete.