Impact of environmental conditions on deformation amplification effect induced by multi-wheel loads in asphalt mixtures

Pavement deterioration under multi-wheel heavy transportation is closely related to the service environment, but the corresponding mechanisms remain unclear. This research aimed to explore the impact of environmental conditions on the deformation amplification characteristics induced by multi-wheel loads in asphalt mixtures. Four-point penetration tests, X-ray computed tomography-based mesoscale deformation visualization, and discrete element method simulations were employed. Two parameters were defined: the penetration deformation growth rate and the amplification effect coefficient. It was found that freeze-thaw cycles and high temperatures aggravate deformation amplification under multi-wheel loading. Compared with SMA-13, the AC-13 mixture is more sensitive to increasing freeze-thaw cycles and displays higher deformation amplification within the same temperature range. Mesoscale analysis revealed that increased freeze-thaw cycles and temperatures intensify deformation amplification by reducing contact points, promoting aggregate reorientation, decreasing the fractal dimension of voids, and increasing the air void content. Based on changes in tensile chains under various bond strengths, freeze-thaw action and high temperature progressively reduce tensile force chains in the asphalt binder’s internal structure, demonstrating micromechanical characteristics of freeze-thaw and high-temperature-induced deformation amplification damage. These insights advance the understanding of environmental degradation mechanisms in asphalt mixtures under multi-wheel loading and guide performance evaluation methods of heavy-duty pavements.