| Rubber powder modified asphalt has been widely concerned and studied for its good road performance and comprehensive social benefits.Thermal aging is a problem faced by rubber powder modified asphalt from production to use throughout its life cycle.Therefore,the performance change of rubber powder modified asphalt before and after aging was analyzed from multiple scales and the mechanism of the effect of aging on the performance of rubber powder modified asphalt was studied.Firstly,at the macroscopic scale,the macroscopic dynamic shear rheological experiment(DSR)and the bending beam rheological experiment(BBR)of the rubber powder modified asphalt before and after aging were conducted to analyze the complex modulus G^* of the rubber powder modified asphalt before and after aging.rutting factor G^*/sinδ and creep stiffness S and creep rate m.The results showed that after aging,the high temperature deformation resistance of the rubber powder modified asphalt was improved while the low temperature crack resistance was reduced.During the aging process,a large number of light components were converted into asphaltenes,which made the viscosity decrease and the elasticity rise.The macroscopic resistance to high temperature deformation was enhanced,and the low temperature brittleness was increased.Secondly,at the mesoscale scale,the quantitative Nano-mechanics(QNM)scan based on atomic force microscopy(AFM)was carried out on the matrix asphalt and rubber powder modified asphalt before and after aging.The microstructure and micromechanical properties of the asphalt before and after aging were analyzed.From the surface characteristics,the black-white speckle structure of the rubber powder modified asphalt is more uniform;the roughness of the rubber powder modified asphalt is smaller than that of the matrix asphalt;the influence of aging on the microstructure of the rubber powder modified asphalt is small;the adhesion of the asphalt surface gradually decreases with the aging degree;the addition of the rubber powder and the deepening of the aging degree make the modulus of the asphalt rise and the asphalt is more elastic.Then,on the nanoscale,the molecular model of asphalt and rubber powder were established.The molecular dynamics simulation technology was used to calculate and analyze the compatibility of asphalt and rubber powder in rubber powder modified asphalt at different temperatures before and after aging.At the same time,the change of molecular dynamics energy of asphalt before and after aging was analyzed.The results show that the best compatibility temperature between asphalt molecules and SBR molecules is 160 °C;the overall energy of asphalt molecular model increases but the density does not change significantly after aging;the compatibility between aging asphalt and SBR molecules decreases significantly;the addition of SBR molecules weakens the effect of aging on the asphalt molecular group.Finally,based on the analysis results of three scales,the cross-scale analysis of the rubber powder modified asphalt before and after aging was carried out.The results show that at room temperature,the increase of the macroscopic high temperature resistance to deformation after aging is caused by the aging of the asphalt to make the microstructure uniform and stable,and the microscopic modulus is increased on the mesoscale;the reduction of the microscopic peak structure of the rubber powder modified asphalt after aging is due to the increase of the molecular dynamic energy of the asphalt molecular group,which makes the agglomeration difficult,resulting in the reduction of the microscopic peak structure of the rubber powder modified asphalt and the smooth surface;for asphalt materials,the performance at different scales are related,and the performance of macroscopic performance can be analyzed from the meso and Nano scales to explore its causes and mechanisms. |
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