Nonlinear Modeling of Nanoscaled Properties of Asphalt Binders Recovered from Weathered Asphalt Mixtures

It is important to investigate the aging mechanism of asphalt binders. To simulate the aging of the binders in asphalt pavements, three mixture gradations of Stone Mastic Asphalt (SMA)-13, Asphalt Concrete (AC)-13, and Superpave-13 were first aged in an accelerated weathering machine (AWM) for four durations of 0 (as control), 1,000, 2,000, and 3,000 h. Then, aged asphalt binders were recovered from the weathered asphalt mixtures by the Abson method. The nanosized properties of morphology, adhesion, and elastic modulus of the recovered asphalt binders were measured by atomic force microscopy (AFM). Nonlinear models were used to fit the relationships between aging durations and each of the three properties: morphology, adhesion, and modulus of elasticity. The results indicated that (1) as the weathering duration increased, the roughness of morphology decreased while those of both adhesion and elastic modulus increased; (2) nonlinear models fitted well the nanosized properties of morphology, adhesion, and elastic modulus; and (3) SMA-13 performed the best, and Superpave-13 barely outperformed AC-13 with regard to aging resistance.