Study on multiple Damage-Healing properties and mechanism of laboratory simulated recycled asphalt binders

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• The laboratory simulated recycled asphalt was prepared using indoor aging test. • The fatigue behavior of recycled asphalt after multiple damage-healing was tested. • Links of self-healing index with physicochemical features of asphalt were established. In order to solve the fatigue cracking problem in asphalt binder reuse, recycled asphalt was prepared in the study by mixing indoor aged SBS modified asphalt and original SBS modified asphalt, which provides a reference for the damage-healing mechanism when recycling asphalt binder in road engineering. The application feasibility of laboratory simulated recycled asphalt was determined by Brookfield viscosity tests; Dynamic Shear Rheometer (DSR) test was conducted to explore the multiple damage-healing behavior of laboratory simulated recycled asphalt; Fourier Transform Infrared Spectroscopy (FTIR) test, Thermal Gravimetric Analyzer (TGA) test and Gel Permeation Chromatography (GPC) test were used to reveal the intrinsic mechanism of changes in the healing potential of laboratory simulated recycled asphalt. The results show that the viscosity of asphalt is less than 3.0 Pa·s except for PA 100%; the incorporation of aged asphalt increases the temperature sensitivity of laboratory simulated recycled asphalt, and the power function is more accurate than Saal's equation in expressing the viscosity-temperature relationship of asphalt. The times of damage-healing significantly affect the self-healing ability of asphalt, the degree of influence is greater than the healing time, and the decrease in mobility is the macroscopic factor of the weakened healing ability of asphalt. Meanwhile, microscopic test results show that with increasing aging asphalt contents and deepening aging degree, the aromatic ring index (I C=C ) of laboratory simulated recycled asphalt, the initial degradation temperature (IDT), the final residue (FR), and the number of macromolecules such as gum and asphaltene increases, which hinders the flow and diffusion between asphalt molecules and slows down the crack healing. Therefore, the recycling of aged asphalt is an effective way to achieve the sustainable use of asphalt binder, but the content of admixtures should be controlled in a relatively low range to ensure its workability and reduce its impact by early cracking.