Research On The Microscopic Characteristics Of SBS Modified Asphalt Before And After Aging Based On AFM

SBS modified asphalt has attracted more and more attention because of its excellent road performance.As one of the main factors affecting the performance of asphalt pavement,aging is accompanied by the whole life of asphalt from mixing,storage to paving.Therefore,it is one of great significance to carry out research on the aging behavior of SBS modified asphalt.At present,the macroscopic properties of SBS modified asphalt before and after aging have become more and more mature,but the research on the microscopic scale is not deep enough.Therefore,this paper uses atomic force microscope to study the microscopic characteristics of SBS modified asphalt before and after aging.Firstly,the basic characteristics of matrix asphalt and SBS modified asphalt before and after aging were analyzed by using the penetration,softening point and ductility.Meanwhile,the thermal stability of the asphalt before and after aging was analyzed by different scanning calorimetry.The results show that the addition of SBS modifier can improve the high temperature performance of asphalt to a certain extent,and enhance its low temperature crack resistance,while also improving the thermal stability of asphalt.At the same time,the addition of SBS modifier can reduce the effect of aging on asphalt and improve the anti-aging ability of asphalt.Secondly,qualitative analysis of functional groups of asphalt was carried out by attenuated total reflection Fourier infrared spectroscopy,and the quantitative analysis of functional groups before and after aging was carried out by using carbonyl index and sulfoxide index.The results show that aging causes a significant change in the functional groups of asphalt.As the degree of aging deepens,the carbonyl index and sulfoxide index increase gradually in both the matrix asphalt and the SBS modified asphalt,and this change is most obvious in the matrix asphalt,indicating that matrix asphalt is significantly affected by aging,and SBS modified asphalt has better antiaging properties.The degradation reaction of SBS modifier in the aging process reduces the variation range of carbonyl and sulfoxide group to a certain extent,and reduce the aging degree of asphalt.Finally,with the help of atomic force microscope,the aging behavior of asphalt at microscopic scale were studied from the aspects of apparent morphology and mechanical characteristics.The results show that there is a special “Bee-structure” in the matrix asphalt and SBS modified asphalt.This paper uses the “Bee-structure” area ratio and surface roughness to qualify the microscopic phase of asphalt.As the degree of aging deepens,the number of “Bee-structure” decreases,so does the proportion of “Bee-structure” area and surface roughness,and the microscopic phase difference gradually decreases.In addition,the addition of SBS modifier can improve the microscopic adhesion force and the modulus of asphalt.During the aging process of asphalt,the microscopic adhesion force decreases so that the adhesion performance is reduced.Conversely,the microscopic modulus increases and exhibits more elastic properties.The index change range of SBS modified asphalt is smaller than that of matrix asphalt,indicating that it has strong resistance of aging and excellent anti-aging performance.Using statistical analysis software to analyze the correlation between the micro-mechanical index and macro-mechanical index,it shows that the two have a good correlation.The aging behavior of asphalt at macro and micro scales presents a consistent law.