Within a general multiscale scheme, it is necessary to define the representative volume element (RVE), over which a measured value becomes representative of the material. In the present work, the RVE size is determined by means of discrete element method (DEM), namely a three-dimensional lattice-particle model. These type of models have been proved to be efficient for simulating fracture processes in quasi-brittle materials. The model is used to perform the numerical simulations for different specimen sizes, aggregate distributions and material regimes. The resulting information is submitted into a statistical analysis and the chi-square test seems to be the best approach to determine the RVE size.