Mesoscopic Investigation of Conventional and Weakly Bonded Cement Stabilized Macadam Based on Discrete Element Method: Considering Realistic Particle Shape Effects

Road engineers still face a critical challenge in improving the crack resistance of cement-stabilized macadam (CSM) base courses. This study employs the discrete element method (DEM) with realistic aggregate morphologies from X-ray computed tomography to model normally bonded and weakly bonded CSM. The mesoscopic parameters of normally bonded models were calibrated against laboratory unconfined compressive strength (UCS) tests, and a weakening ratio of bond strength (Wrbs) was introduced to define the weakly bonded model. The results show that UCS decreases monotonically with the reduction in Wrbs and the increase in Rrca. The maximum strength reduction reaches 26.3% at the extreme condition of Rrca = 100% and Wrbs = 50%. Despite this reduction, the UCS of weakly bonded specimens remains compliant with Chinese specifications for base course materials when designed with appropriate parameters. Notably, weakly bonded specimens exhibit a more dispersed crack distribution and a more gradual energy dissipation process. This mechanism is associated with a reduced tendency for macroscopic crack initiation and propagation, suggesting the potential of weakly bonded CSM to enhance crack resistance. This work provides a mesoscopic theoretical foundation for the engineering application and sustainable development of weakly bonded CSM in pavement base courses.