Diffusion Characteristics and Mechanism of Waste Cooking Oil Rejuvenator in Ultraviolet Aged Asphalt Using Multi-Scale Evaluation Method

Abstract One of the challenges of using the regenerator in reclaimed asphalt pavement (RAP) is estimating the blending degree between the RAP and the regenerator. The extent of this blending is crucial because the road performance of the recycled asphalt mixture will be improved with the increase of diffusion degree. To this end, this study focuses on the diffusion and fusion phenomena between waste cooking oil (WCO) rejuvenator and ultraviolet (UV) aged asphalt. First, the improved softening point test was used to characterize the macroscopic diffusion and fusion law between the UV aged asphalt and the regenerator. Then, the Fourier Transform Infrared test and molecular dynamics (MD) simulation were conducted to obtain the microscopic mechanism of diffusion. Finally, the correlations between the macro experiment and the MD simulation and between the micro experiment and the MD simulation were established. The results show that, with the increase of diffusion time, the softening point of recycled asphalt decreases. In addition, the corrected peak areas of methylene (CH2) antisymmetric stretching decreases, whereas the corrected peak area of saturated fatty acid ester C = O and aromatic acid ester C-O increase. The mean squared displacement shows an upward trend, and the diffusion coefficient decreases. Besides, the increase of the diffusion temperature could enhance the diffusion coefficient. There was a preferential relation between the macro tests and simulations and between micro tests and simulations. The results from this research indicate MD can simulate the diffusion between the WCO rejuvenator and UV aged asphalt. The findings in this work provide a possible guideline for the evaluation of the performance of the recycled asphalt that might improve the way this recycled asphalt is used.