Cross-scale evolution mechanism of microstructure and adhesion performance during the stress relaxation of long-term aged asphalt

Document Type

Article

Publication Date

4-11-2026

Department

Department of Civil, Environmental, and Geospatial Engineering

Abstract

Under prolonged traffic loading and environmental exposure, the microstructure and interfacial properties of asphalt continuously evolve, directly affecting pavement durability and service life. Current studies on asphalt stress relaxation behavior mostly remain at the macroscopic level, lacking nano-scale, controllable in situ dynamic observation methods. To address this issue, a custom in situ loading device adapted to an Atomic Force Microscopy (AFM), combined with QNM mode, to perform real-time characterization of the microstructure, surface roughness, adhesion force, and interfacial response of PAV-aged asphalt under tensile and compressive strain. Molecular dynamics (MD) simulations were also conducted to reveal the evolution mechanism of the asphalt’s molecular structure. The results show that tensile strain causes elongation of the asphalt surface 'bee structures', increased surface roughness, and a rapid strengthening of adhesion, which stabilizes around 10 h. In contrast, compressive strain leads to slower structural changes and a delayed evolution of adhesion, and the trend of molecular free volume fraction is opposite, indicating an asymmetry in stress relaxation between tension and compression. The AFM in situ mechanical loading and multi-scale simulation approach developed in this study provides a novel technical pathway and theoretical support for understanding the stress relaxation evolution mechanism of aged asphalt and its interfacial property changes.

Publication Title

Construction and Building Materials

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