Meso-Structural Validation of a Macro-Equivalent Tribological Model for Predicting the Wear of Modified BA16 Asphalt Mixtures

When used to analyze the wear of rough surfaces, Archard’s law implicitly assumes that the surface subjected to wear is homogeneous and that its hardness is equal to that of the bulk material, an assumption that does not apply to asphalt mixtures, where, in the case of road pavements, the wearing surface is a mosaic of aggregate particles and binder (bitumen). This study examines this assumption by comparing two models of the wheel–asphalt pavement contact for four BA16 asphalt mixtures: a reference specimen (M0), a modified specimen (M1, characterized by high porosity), a specimen with aggregate replacement in its composition (M2, containing 3% plastic material in flake form), and a specimen with aggregate replacement in its composition (M3, containing 3% cellulosic material in pellet form). The macro-equivalent model treats the specimens as homogeneous media, whereas the meso-structural model explicitly incorporates 93 polyhedral aggregate particles within a representative volume element of 30 mm × 30 mm × 30 mm, under three loading scenarios: severe dry, wet, and thermal conditions, with extreme temperatures of 5 and 40 °C, respectively. The results were assessed using two independent indicators: a composite tribological degradation indicator and an indicator derived from Archard’s law. The explicit modeling shows that the wearing surface contains 16.2% mineral aggregate, compared with 25.2% in the bulk asphalt mixture, while the effective elastic modulus at the wearing surface is 10.5% lower than that of the bulk asphalt mixture. This ratio remains nearly constant (0.894–0.897) for all mixtures and loading scenarios. Both analyses yield the same ranking of wear susceptibility—M0 < M3 < M2 < M1—in all scenarios, with deviations below 4.3%. Tangential loading at the wearing surface triples the stress in the binder and has a predominant effect on wear compared with the normal tire pressure, while the maximum stress occurs precisely at the aggregate–binder interface.