Meso-scale cracking mechanism of semi-flexible pavement: A coupled experimental-numerical study based on cohesive zone modeling

The widespread application of semi-flexible pavement (SFP) is limited by early cracking. To elucidate the meso-scale damage mechanisms, this study combines hydrothermal accelerated testing with micromechanical finite element modeling (FEM) incorporating cohesive zone elements. Experiments identified the hardened cement paste and its interface with aggregates as primary failure zones under environmental stress. Subsequent simulations decoupled the effects of shrinkage and external loading. Results reveal a dual-track cracking mechanism: endogenous shrinkage concentrates tensile stress at the cement–aggregate interface, causing delamination, while external loads primarily damage the aggregate skeleton. Importantly, the simulations indicate a model-based critical shrinkage reference value of approximately 0.5% for the cement paste under the adopted parameter set; as shrinkage approaches this level, the interface enters a near-critical softening state and becomes increasingly prone to crack propagation. These findings provide a mechanism-based framework for interpreting shrinkage-control strategies in SFP grouting materials and for supporting the development of low-shrinkage, high-durability grouting systems. Overall, this study is intended to provide mechanism-oriented insight into damage initiation and propagation in SFP, rather than a fully validated predictive model.