Multi Scale Study On Diffusion Mechanism Of Regenerant In Aged Asphalt

In recent years,with the development of our country’s highway,the highway network has been gradually improved.Asphalt pavement will be affected by environment and driving factors during the use process,which will form various forms of cracks.A large number of pavement life is greatly reduced due to the problem of heavy load overload.In order to make asphalt pavement recover its function,it is an important research topic to choose the regenerator with excellent performance.Therefore,it is necessary to observe the recovery of recycled asphalt through experiments,and also study the mechanism of regeneration agent changing the performance of the aged asphalt.In order to further study the diffusion mechanism and quantitatively characterize the diffusion degree of recycled asphalt mixture system,the diffusion coefficient of the mixture system was calculated by viscosity experiment on the macro scale,and the diffusion behavior was characterized by quantitative analysis of the functional groups of the mixture system by infrared spectroscopy experiment on the micro scale,on the molecular scale,molecular dynamics simulation(MS)technology was used to analyze the diffusion process of the mixture system on the premise of the four component experiment.The regeneration agent molecular group,composite water aging asphalt molecular group and composite UV aging asphalt molecular group were constructed.The aging asphalt diffusion system was simulated under different time,temperature and asphalt components,the MSD(mean square displacement)curve of the diffusion system was obtained,the diffusion coefficient was calculated,and the viscosity experimental results were verified.The results show that:(1)when the diffusion temperature is constant,with the increase of diffusion time,the viscosity and sulfoxide group index of the two kinds of recycled asphalt decrease,and the diffusion coefficient increases gradually,that is,the length of diffusion time affects the diffusion degree of the regenerant;(2)at the same constant diffusion time of 4h,with the increase of diffusion temperature,the diffusion coefficient of recycled asphalt increases continuously,140 It reaches the highest value at 0 ℃;(3)There is a certain linear relationship between the diffusion degree of regenerant and the position of aging asphalt,and the diffusion coefficient is as follows: upper section > middle section >lower section;the heat generated by ultraviolet radiation in the process of UV aging of SBS modified asphalt deepens the degree of thermal aging,resulting in the decrease of diffusion coefficient;(4)The results of molecular dynamics simulation show that with the increase of time,the diffusion coefficient of regenerant in aged asphalt gradually decreases.The diffusion coefficient of regenerant in UV aged asphalt is smaller than that in water aged asphalt,and the increasing speed of diffusion coefficient gradually slows down with the increase of diffusion temperature.This shows that although the diffusion process continues,the diffusion rate slows down.When the four components of regeneration agent diffuse in the aged asphalt,the diffusion coefficients of aromatic phenol and saturated phenol are greater than those of colloid and asphaltene.There is a good correlation between the results of molecular dynamics simulation and viscosity experiment,which indicates that it is feasible to use molecular dynamics to simulate the diffusion behavior of recycled asphalt mixture.