Combined FEM-DEM approach for concrete mesoscale modeling

A Discrete Element Method (DEM) framework is employed to generate mesoscale representations of concrete specimens using fully three-dimensional polyhedral aggregates, which are seldom adopted due to their high computational cost. The proposed approach addresses two distinct limitations of existing methods. First, it overcomes the geometric constraints of X-ray computed tomography-based reconstructions, including size limitations and voxelized aggregate surfaces. Second, it achieves high aggregate volume fractions (up to 51%), which are difficult to attain with conventional random generation algorithms, particularly when filling complex-shaped containers. Validation is performed by generating multiple standard specimens and verifying their agreement with the target Fuller grading curve. Finite Element Method (FEM) simulations are subsequently conducted using an in-house nonlinear constitutive model for confined concrete to evaluate the compressive mechanical response.