This paper presents the results of computer simulations of a three-point bending test of a notched beam. The numerical model was built to resemble concrete, consisting of a matrix with mortar characteristics and aggregate grains contained in it. The simulation was performed using own method for predicting the direction of crack propagation, implemented in the Abaqus FEA system to cooperate with the XFEM (eXtended Finite Element Method) fracture simulation method. The direction of crack propagation is determined by the procedure based on the stresses at the integration points around the crack tip propagating during the test. The crack is guided in the direction of the greatest decrease in the maximum principal stresses around the crack tip. The goal of this work was to introduce improvements to the existing algorithm so that it could simulate a crack in a heterogeneous material such as concrete. Currently, the implemented algorithm works only for materials modeled as homogeneous. In the literature available to date, no attempts have been found to model crack propagation using the XFEM method in simulations with heterogeneous material. The expected result was that a crack heading towards the grain of the aggregate would surround the grain. To verify the effectiveness of the method, it was first verified on several models with one large aggregate grain or two grains occurring in the path of the predicted crack. The paper also contains a description of the simulation with actual grain distribution and the problems associated with such simulation. It turned out that in simulations with one or two grains the algorithm copes correctly - the crack bypasses the grain. With actual graining there are problems related to the too complicated stress field in the vicinity of the grains and the crack does not reach the end of the sample. The paper discusses several ways to solve this problem, which will be taken up in future publications.