Simulating the behaviour of fresh concrete with the Distinct Element Method - Deriving model parameters related to the yield stress

This article describes a numerical approach based on the Distinct Element Method (DEM) as a means of simulating fresh concrete during its different working processes. First, a rheological model for fresh concrete and its implementation into a DEM code are presented. Then the main focus is directed at establishing an algorithm to derive the model parameters related to yield stress according to the Bingham model. For this an analytical prediction of stress distribution at the beginning of the slump-flow test is used as reference for the corresponding numerical analysis. For the sake of validation, the analytical and numerical predictions of the final shape of the concrete cake in the slump-flow test are compared. The validation was performed for three different reference values of yield stress. Additionally, the numerical and analytical results of the so-called LCPC-box test were evaluated for the same sets of parameters. The results of the numerical analysis agreed well with the results predicted by analytical solutions for all parameter combinations. Therefore, the proposed algorithm was shown to be a sound procedure in linking yield stress of the simulated concrete to the bond strength, which is the main parameter of the model suggested.