Multi-scale study on the high percentage warm-mix recycled asphalt binder based on chemical experiments

Abstract

With the development of the transportation industry, the requirements for the warm mix asphalt (WMA) involving high percentage of reclaimed asphalt pavement (RAP) are becoming increasingly high due to its benefit in energy cost and environment. This paper focuses on the chemical properties and multi-scale research of the high percentage warm-mix recycled asphalt (WMRA) binder. Three contents of RAP binder, 30%, 50% and 70%, and two types of warm-mix asphalt additives i.e., polyethylene wax (R) and surfactant (M) were considered. The Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC) and differential scanning calorimetry (DSC) tests were carried out on the recycled asphalt binders in this paper. The results showed that there was no reverse reaction of aging in the recycling process, and no patterns of change were found between the content of RAP binder and the carbonyl index/sulfoxide index. The increase in the large molecular size (LMS) distribution of the three types of WMRA binders after short-term aging was generally higher than that after long-term aging. After aging, the change in the LMS of the RAP-R binder was relatively large, and the anti-aging performance was weaker than that of the RAP-M binder. The RAP-R binder improved the low-temperature performance of the binder and showed middle-temperature stability, but its anti-aging properties were worse than that of RAP-M binder. There were clear correlations between the glass-transition temperature and the stiffness modulus, between the complex shear modulus and the weight average molecular weight, and between the rotational viscosity and the LMS. However, the correlation between the aging index and the BBR stiffness modulus was not applicable to the recycled binder. This study lays a foundation for evaluating the performance of WMRA binder at the microscopic level and exploring the mechanisms of warm-mix recycling.