Abstract
With employment of Atomic Force Microscope (AFM), more knowledge on asphalt surface and mechanical property at micro-scale could be obtained. Yet, aging effect on styrene–butadiene-styrene polymer modified asphalt (SBSMA) has not been well investigated with AFM. In this study, two SBSMAs were prepared by two SBS polymers and one base binder, and then all samples were subjected to Thin Film Oven Test (TFOT), 20-hour Pressure Aging Vessel (PAV), and 40-hour PAV aging. Topographical and phase images of samples at each aging condition were obtained using tapping mode of AFM, and two indices of area ratio of bee structures and surface roughness were obtained to present microstructural evolution as aging severity. Meanwhile, micro-mechanical property was characterized in terms of Young’s modulus and Elastic Index as well as Adhesion, obtained from AFM scanning at contact mode. Additionally, chemical and macro-rheological change were evaluated by ATR-FTIR and DSR tests, including temperature sweep, multiple stress creep recovery (MSCR) and linear amplitude sweep (LAS) tests. Results highlight that the introduction of SBS can make a difference in terms of micro-structure and macro-property, as compared with the base binder. The bee structures and surface roughness of SBSMAs and base binder showed a different behavior trend during aging process, while aging hardening could be observed in both micro- and macro- scale. Also, the adhesion evolution as aging can also be distinguished, with and without SBS polymer. ATR-FTIR results show that the long-term aging (PAV aging) contributes the most of SBS polymer degradation and asphalt binder oxidation during the whole aging process. Moreover, the certain microstructural, micromechanical and rheological properties are well correlated with the chemical change. This study aims to provide insights to better understand aging behavior of SBSMAs from multi-scale aspect.
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