The service life of a road is to great extent controlled by the performance of the unbound layers. Assessing the constitutive behavior of these layers is thus imperative for a sustainable pavement design. Adequate description and measurement of unbound materials resistance to aggregate crushing is an issue, in terms of the measured response coupled to intrinsic properties of the aggregates and unbound materials gradation. In this study, a new Discrete Element Method (DEM)—based model is developed to investigate aggregate damage in unbound road materials. In order to get better insight into micro-mechanics of aggregate crushing, the developed model incorporates granular mechanics-based particle contact and damage laws. By numerical analysis with the DEM, several unbound granular materials have been examined investigating the effect of the materials gradation and aggregates toughness properties on their performance in crushing tests. The capability of the model to capture the effect of unbound material properties on its crushing performance, is evaluated based on comparison with experimental findings.