Research on the performance changes of the binder of the wear layer of open-graded asphalt mixture under different aging methods

Abstract

In order to study the effect of asphalt aging of open-graded friction course (OGFC) on the performance of high-viscosity styrene-butadiene-styrene(SBS) modified asphalt during the mixing of the asphalt mixtures and the whole life cycle, Thin Film Oven Test (TFOT), Rolling Thin Film Oven Test (RTFOT), and Pressurized Aging Vessel Accelerated Asphalt Aging Test (PAV) were used to conduct aging tests on the high-viscosity SBS modified asphalt. And then the aging of SBS modified asphalt is studied at two levels: microscopic and macroscopic. In the microscopic aspect, first use the fluorescence microscope technology to image the asphalt samples before and after aging. The above images were processed by MATLAB and Image-pro plus software, and the micro-structures of high viscosity SBS modified asphalt before and after aging were obtained. At the same time, use the DSR test to observe the changes in the rheological properties of the SBS modified asphalt before and after aging. On the macro level, the softening point, viscous toughness and pull strength are used to analyse the changes in the mechanical properties of the high-viscosity SBS modified asphalt before and after aging, and the aging conditions of the SBS modified asphalt under the micro and macro indexes are compared. The research shows that after short-term aging (simulation of asphalt aging during the mixing ), RTFOT and TFOT the loss ratio of SBS in modified asphalt are at 78.5% and 68.3%, respectively, the degradation of SBS in modified asphalt is serious, and the SBS modified asphalt aging conditions under the macro and micro indicators are consistent. After long-term aging (simulating the aging of the asphalt during the whole life cycle), the loss ratio of SBS in modified asphalt is 83.4% (RTFOT + PAV) and 84.6% (TFOT + PAV). However, the macroscopic index of SBS modified asphalt shows obvious differences. The aging degree of SBS modified asphalt using RTFOT + PAV aging method is significantly higher than that of TFOT + PAV aging method, indicating that the performance of SBS modified was affected at the degradation of SBS during long-term aging, it is also significantly affected by the aging of the basic asphalt itself. Therefore, when mixing OGFC asphalt mixtures, the mixing time should be strictly controlled, and the mixing time should not be extended. OGFC asphalt mixtures should be maintained properly in time to keep their excellent road performance.