Study on the Interlayer Contact Mechanism of Foamed Cold-Recycled Asphalt Mixture Under Static Loads

Highlights: What are the main findings ? A refined DEM model for foam cold-recycled asphalt pavement is developed, with an optimized interface contact model for meso-mechanical simulation. Pavement mechanical indices are verified to increase monotonically and show distinct layered distribution with rising static loads. The rigid support of cement-stabilized macadam base is proven to remarkably mitigate asphalt surface layer deformation. What are the implications of the main findings? The refined DEM model provides a reliable meso-scale tool for analyzing foam cold-recycled asphalt pavement mechanics. The identified mechanical behavior offers theoretical guidance for recycled pavement structural design and load evaluation. The base’s deformation mitigation effect highlights its critical role in enhancing asphalt pavement performance and durability To investigate the interlayer contact mechanism of foamed cold-recycled asphalt mixture under static loads, a three-layer asphalt pavement discrete element model (DEM) was established, with the surface layer composed of asphalt concrete-13 (AC-13), asphalt concrete-20 (AC-20) and asphalt-treated base-25 (ATB-25) foamed cold-recycled asphalt mixture and cement-stabilized macadam as the base. Based on mortar theory, the pavement was divided into coarse aggregate, asphalt mastic and air void phases, and the Burgers Model, Linear Parallel Bond Model and Linear Model were adopted to characterize the bonding of asphalt-aggregate, cement contact interface and subgrade-surface layer, respectively. Static loads of 0.7 MPa, 1.1 MPa, 1.5 MPa and 1.9 MPa were applied to analyze the mechanical responses of asphalt-based and cement-based pavement systems from tensile strain, vertical compressive stress and vertical displacement. Results showed that mechanical indices of the pavement increase monotonically with static load and present obvious layered distribution. The cement-stabilized macadam base provides rigid support, significantly reducing tensile strain (TS) and vertical displacement (VD) of asphalt layers, while the asphalt-based system has flexible stress transfer and superior stress dissipation in the bottom layer. The two systems exhibit respective structural advantages, with the cement-based system outstanding in deformation control and the asphalt-based system suitable for flexible stress adaptation working conditions.