Study on the Effect of Natural Aging and PAV Aging on Asphalt Binder Based on Rheology and Microstructural Composition

Laboratory-simulated aging fails to fully replicate the complex aging behavior of asphalt binder under actual environmental conditions. This study aims to preliminarily investigate and analyze the differences between natural aging and PAV aging of asphalt binder. To achieve this objective, the asphalt binder was aged using three distinct methods: PAV aging, natural thermal-oxidative aging, and all-weather aging. The divergence in asphalt binder aging behavior was systematically investigated through encompassing low-temperature performance, chemical structure, elemental composition, molecular weight, and macroscopic and microscopic performance correlation analyses. Key findings include: the harsh environment in the cold and arid regions resulted in inferior low-temperature performance of asphalt binder after 12 months of natural thermal-oxidative and all-weather aging compared to PAV-aged asphalt binder, with the stiffness modulus at -12 °C increasing by 114.8% and 105.3%, respectively. Natural aging induced more significant asphalt binder's chemical structural changes than PAV aging but exhibited less prominent oxidative reactions and macromolecular structure formation. Whether from a macroscopic or microscopic perspective, thermal-oxidative conditions were identified as the primary driver behind both the natural aging behavior and the aging pathway of asphalt binder. The influence of other factors on the aging behavior of asphalt binder was not significant. The poor correlation (R² < 0.62) between oxygen content, molecular weight, and low-temperature performance across different aging modes underscores a fundamental divergence in aging pathways between PAV and natural aging. This study preliminarily identifies the key differences between laboratory-accelerated aging and natural aging of asphalt binder and paves the way for optimizing the parameters of laboratory-accelerated aging protocols.