Simulating mixing processes of fresh concrete using the discrete element method (DEM) under consideration of water addition and changes in moisture distribution

The article presents a new model for the use in the framework of the Discrete Element Method to simulate the mixing processes of fresh concrete. The model provides a representation of liquid transfer from fluid entities or moist solid particles to dryer solid particles, including volume adaptation and mass conservation. The parameters and laws of force interactions between two particles are defined locally and depend on the amount and the properties of the liquid phase in the contact area. If two dry particles are in contact, friction and elastic forces are computed based on the Hertz-Mindlin model. If two particles with low moisture content are in contact, additional liquid bridge forces act on the particles. When the suspension state is reached, a Bingham-based model is applied. The simulation enables realistic estimation of the moisture distribution during the mixing processes, the corresponding changes in forces acting on the particles and consequently the effect on the rheological properties of the concrete mixture.