LAUSR

Abstract Numerical results on a fracture process of a concrete beam with a notch under three-point bending were presented. Calculations were carried out at the concrete aggregate level with the discrete element method (DEM). To explicitly take the heterogeneity into account, concrete was modelled as a four-phase material that included aggregates, cement matrix, interfacial transitional zones (ITZs) and macro-voids. Both the 2D and 3D DEM calculations were performed with the: 1) accurate shape representation of aggregates, based on micro-CT images of concrete and 2) simplified circular/spherical representation of aggregate assuming the same aggregate volume, size and grading curve. In 2D calculations, the positions of circular/spherical aggregate particles were also the same as of real ones. The focus was laid on the impact of the aggregate shape on both the load–displacement curve (strength and brittleness) and fracture geometry (shape, width and length). In addition, the evolutions of broken contacts, contact force networks and tensile stress regions at the crack tip depending upon the aggregate shape were compared with each other. Concrete was proved to be stronger and the macro-crack was less curved for circular/spherical aggregates. Significant dissimilarities regarding the shape of a macro-crack with real aggregates occurred, in particular, for circular/spherical aggregates in 2D simulations.