Study On Micro-macro Properties And Regeneration Mechanism Of Vegetable Oil Reclaimed Asphalt

In China,there are more and more asphalt pavements requiring to be repaired and maintained,which would be the main task for the development of road construction industry.Especially,the theoretical researches and engineering practices on the application of vegetable oil in the recycling of asphalt pavement have been attracting much attentions at home and abroad.The objective of this study was to investigate the aging mechanism of virgin asphalt and recycled asphalt and to explore their rheological properties at different stages during the aging and recycling process.Firstly,The fourier transform infrared spectroscopy（FTIR）spectroscopy test characterizes the effects of aging on various functional groups in the original asphalt,aged asphalt,regenerated asphalt and re-aged asphalt.Moreover,the differences in the micro structure of the surface of these asphalts were observed through atomic force microscope（AFM）tests to analyze the main reason for recycling.Secondly,DSR tests were conducted to study the high-temperature characteristics of aging and recycled asphalt by analyzing the variation trends of complex shear modulus,phase angle and rutting factor.In addition,the multiple stress creep and recovery tests were performed to explore the performance of modified asphalt revealed by recovery percentage and unrecoverable creep compliance.Finally,the molecular dynamics method was used to simulate the molecular structure of asphalt and to discuss the impacts of molecular components of asphalt and modifier on the performance of asphalt.The results show that:This paper uses molecular dynamics simulation technology to establish the molecular structure of asphalt components,and analyzes the impact of asphalt molecular components and regenerants on asphalt performance based on changes in performance.The results show that:（1）The Fourier infrared spectrums show that the indexes of I_（C=O）and I_（S=O）of asphalt is increasing during the process of aging,reflecting that the carbonyl and sulfoxide are the main products of oxidation of asphalt.The addition of vegetable oil would not act on these functional groups while increasing light components in asphalt.The Atomic force microscope tests show that the vegetable oil may have the ability to inhibit the phase separation of asphalt surface,which is associated with the"bee structure"of asphalt.The addition of vegetable oil could enhance the roughness of aging asphalt to the original level or even higher,which indicates the softening and recycling effects of vegetable oil from a microscopic perspective.（2）The aging of asphalt leads to the increment of polar components including carbonyl group and sulfoxide group,and molecular weight,which further increases the rigidity of asphalt.Affected by vegetable oil,the strain recovery rate of recycled asphalt improves.It is probably related to the rotation of chemical bonds and the disentanglement of molecules that majorly occur in recycled asphalt.Besides,the slipping among molecules is decreasing,which make the performance of asphalt can be recovered in a certain period of time.（3）The density and component indicators simulated by the molecular mechanics model are in good agreement with the actual density of the base asphalt,which verifies the reliability of the asphalt molecular model.It shows that there occurs the aggregation phenomenon of asphaltene in aging asphalt,while the addition of vegetable oil could influence the aggregation of asphaltene to a certain degree.