The physical properties of the aggregate base of a pavement system have a significant influence on the bulk mechanical properties of that system. Simulations based on the discrete element method provide a powerful method to investigate the mechanics of granular materials, but they are limited, particularly when it comes to representing moisture and finer particles. Established discrete element method simulations were adapted with additional terms to account for moisture and finer particles to model established tests of the aggregate base of a pavement system. The presence of moisture in unsaturated granular material was modeled by using published experimental work with consideration of the form of the standard liquid bridge model, and the finer particle content was modeled through an effective friction coefficient. This combined model was used to simulate the lightweight deflectometer test, an established in situ test for a measure of the modulus of an aggregate base, and the results were compared with estimated target values of aggregate bases for Minnesota roads. When either the model moisture content or model fines content was increased systematically, there was a decrease in the elastic modulus computed from the simulations, similar to trends seen in existing experimental data.