The fracture process of concrete involves phenomena of considerable complexity, such as scale effect and softening behavior, which are directly linked to the heterogeneity of this material. These phenomena pose great challenges to the fracture modeling. Probabilistic models that deal directly with heterogeneity are a powerful tool to overcome these challenges, since they consider the natural variability of the mechanical responses. The present work refers to the simulation of concrete fracture by means of a 3D probabilistic finite element model in which interface elements are employed to represent the cracks explicitly. Friction between crack surfaces is also taken into account in the model. The three-dimensional modeling of cracks allows the fracture process to be analyzed in a more realistic way. Different sample sizes were considered to enable the assessment of the scale effect prediction, taking into account empirical reference data. The possibility of occurrence of different softening levels was also investigated.