Marginal road materials such as construction waste are used in unbound granular layers of pavements in order to utilize the landfill waste caused by demolitions of constructions. However, there is lack of research on these marginal materials crushing performance in unbound layers. Inadequate resistance of the particles to crushing may have severe consequences for the unbound pavement layers, as particle crushing may result in excessive permanent deformations and reduce the layers stiffness. Accordingly, the structural and functional performance of the pavement may be compromised. Therefore, understanding the mechanics of aggregate crushing is an important issue in context of implementing marginal materials in pavement engineering. In this study, aggregate breakage of unbound granular materials (UGMs) consisting of crushed rock mixed with brick is investigated both experimentally and numerically. Experimentally, different UGMs that differ in their size and percentage of bricks and varying maximum applied load levels are investigated under monotonic uniaxial compression tests. Numerically, Discrete Element Method (DEM) based models are used to capture how the marginal material behaviour would change at different loads, different blends of materials and different gradations. The DEM model incorporates granular mechanics particle contact and failure laws proposed by [1, 2], and a simplified breakage model to account for the effect of aggregate breakage on macro-mechanics response of UGMs. Single particle breakage tests are conducted to obtain failure law parameters; and a simple procedure to identify the contact law parameters is applied. The DEM models’ capability to capture aggregate breakage of marginal road materials based on mechanical properties is evaluated through the comparison with the experimental results.