Modeling of capillary fluid flow in concrete using a DEM-CFD approach

Abstract

A novel coupled approach to modelling hydraulicand capillary-driven two-phase water flow in unsaturated concrete was formulated. The flow process was numerically analyzed at meso-scale in twodimensional (2D) conditions by combining the discrete element method (DEM) with computational fluid dynamics (CFD) under isothermal conditions. Fully coupled hydro-mechanical simulation tests were carried out on small concrete specimens of a simplified particulate meso-structure. The pure DEM represented by bonded spheres was calibrated with the aid of uniaxial compression while the pure CFD was calibrated with the aid of a permeability and sorptivity test for a sphere assembly. DEM/CFD calculations were successively performed for specimens of the pure cement matrix, cement matrix including aggregate and cement matrix including aggregate and interfacial transition zone (ITZ) of a defined thickness. The major goal of investigations was to show the effect of ITZs on fluid flow in unsaturated concrete driven by hydraulic/capillary pressure.