Performance Study On Aging Resistance Of High Content Crumb Rubber Modified Asphalt Based On Molecular Dynamics Simulation

In the era of transportation power background,the rapid development of transportation industry will inevitably bring the same degree of resource loss.Only for the road transportation industry,the number of tires produced and put into use every year is very large,and the proper disposal of waste tires has become another problem that cannot be ignored.The road construction is often faced with problems such as short life span of pavement materials,time consuming in maintenance and rework.Waste tires are processed and put into road construction,for example,improving the pavement material performance to delay aging.This has become an excellent way of environmental protection and resource recycling.By comparing the effects of different rubber types and rubber mesh on the properties of modified matrix asphalt,40～60 mesh natural rubber or styrene butadiene rubber(SBR)was determined as the best modified rubber material.By optimizing the preparation technology of traditional rubber modified asphalt,high rubber modified asphalt with more than 25% rubber dosage was prepared.The three indexes and elastic recovery properties of the prepared high dosage crumb rubber modified asphalt under the three conditions of short-term thermal oxygen aging,long-term thermal oxygen aging and photooxygen aging were analyzed.The change of data verified the rationality of the performance of modified asphalt after the increase of rubber dosage.Macroscopically,the aging resistance of high dosage of crumb rubber modified asphalt was good.The molecular models of high dosage of crumb rubber modified asphalt before and after aging were constructed.The changes of molecular dynamics energy under different aging environments showed that the molecular structure would be unstable due to the increase of rubber dosage in short-term thermal oxygen aging,and the structure would become stable gradually with the aging process.Based on the change of the inter-molecular RDF value inside the modified asphalt,it is found that the main cause of the aging of modified asphalt is the increase and accumulation of asphaltene content under the conditions of thermal and photooxygen aging.In terms of the effect of aging on the composition changes,long-term aging has the greatest effect,followed by photooxygen aging,and short-term aging has little effect.In the high temperature environment,the best compatible temperature of asphalt and rubber in the high content rubber modified asphalt was determined,and the compatibility of the modified asphalt before and after aging was compared at this temperature point.The compatibility between rubber and asphalt in modified asphalt after aging is better than that before aging,and the high temperature aging resistance of modified asphalt is improved.In the low temperature environment,the method of multi-point piecewise fitting combined with mean square displacement analysis was used to determine the glass point conversion temperature,so as to ensure the compatibility between rubber and asphalt.The physical aging of high dosage of crumb rubber modified asphalt was analyzed by using the mean square displacement curve near the glass transformation temperature point.It was found that the activity of components in modified asphalt increased with the passage of low temperature aging time,and the growth rate decreased gradually.The basic activity of light components ensured the micro-brownian motion at the chain end of asphalt molecules.Combined with the physical properties of SBR rubber powder,the low temperature aging resistance of high dosage of crumb rubber modified asphalt is improved.