This paper describes a preliminary study undertaken at the University of Illinois to investigate the impact of contact stiffness properties on aggregate assembly strength. An aggregate particle imaging based Discrete Element Modeling (DEM) methodology was employed to study the effects of normal and shear contact stiffnesses. Using the results of laboratory direct shear box tests on actual aggregate samples, direct shear box DEM simulations were calibrated to identify the effects of different contact stiffness combinations. It was found that as the normal to shear contact stiffness ratio increased, the shear strength of the aggregate assembly also increased. Further, the same stiffness ratio captured the shear behaviour at three different normal stress levels thus validating the DEM simulation results.