Research On Performance Of Nano-graphene Modified Asphalt

With the rapid development of economic in recent years,the traffic volume increases a lot,common modifiers such as SBS and rubber asphalt have gradually been unable to meet the requirements of pavement performance.Nano-modifiers are gradually applied to the road field because they have new characteristics that are different from macroscopic large-size particles,and are also different from microscopic particles such as single atoms and molecules,which can fundamentally improve the performance of materials.Nano-graphene has become the current research hotspot of nano-modifiers because of its excellent mechanical properties,electrical properties,and thermal properties.In this paper,through molecular dynamics simulation and literature research,the influence of graphene content on the mechanical properties of modified asphalt is studied,and theoretical guidance is provided for the setting of graphene content and the selection of graphene types;the modification mechanism of graphene modified asphalt is analyzed by atomic force microscope,Fourier infrared spectroscopy and scanning electron microscope and other microscopic tests;the rheological properties of graphene modified asphalt are studied through conventional dynamic shear rheology test and low temperature bending beam test;to analyze the electrical performance and anti-aging performance of the graphene-modified asphalt,the conductivity test and ultraviolet light aging test have been designed,obtained the threshold value of the graphene content of the modified asphalt from the insulator to the semiconductor,and comprehensively analyze the reasonable content range of graphene modified asphalt.First of all,through molecular dynamics simulation to construct graphene modified asphalt models with different content and different graphene sizes analyze its mechanical properties.It was found that the mechanical properties of graphene modified asphalt continuous improved with the increase of graphene content and graphene size.According to the high temperature performance of three different kinds of graphene modified asphalt,it is found that the 99-5-80 graphene modified asphalt has the largest graphene diameter and the best mechanical properties.And this type of modified asphalt has the best high temperature performance.Therefore,choose99-5-80 graphene to prepare graphene-modified asphalt with different dosages.Then,the modification mechanism of graphene modified asphalt was studied by fluorescence microscope,scanning electron microscope,atomic force microscope,and Fourier infrared spectroscopy.Fluorescence microscopy and scanning electron microscopy images show that the addition of graphene is more of a physical blending effect,no chemical reaction occurs,and the infrared spectrum also proves this because the modified asphalt does not produce new functional groups.Next,a dynamic shear rheometer and a curved beam rheometer were used to analyze the rheological properties of the graphene-modified asphalt.The results of the dynamic shear rheometer show that with the increase of the graphene content,the high-temperature rheological properties of the modified asphalt are improved,and according to the result analysis of the master curve,it can be found that the higher the graphene content,the anti-aging performance of modified asphalt is better.From the results of the low-temperature bending rheological test,it can be found that with the increase of the graphene content,the low-temperature crack resistance of the modified asphalt continues to decrease.When the graphene content is 3% or less,the low-temperature performance only slightly decreases,but when the graphene content reaches 4%,the low temperature performance is significantly reduced,which cannot meet the standard PG classification requirements.Finally,through the electrical performance test,it is found that the addition of graphene improves the conductivity of the modified asphalt.When the content of graphene is 2%-3%,there is a threshold,which makes the graphene modified asphalt change from an insulator to a semiconductor.When the graphene content reaches 6%,the conductivity of the modified asphalt is improved exponentially.Regarding the anti-aging performance of graphene-modified asphalt,infrared spectroscopy tests are used to analyze it.It is found that the addition of appropriate amount of graphene can improve the anti-thermal oxidative and anti-ultraviolet aging properties of the asphalt.The addition of graphene should not exceed 3%.Therefore,the recommended content of graphene in asphalt is 2%-3%.In this case,the electrical properties,thermal oxidative aging resistance,UV aging resistance,and hightemperature rheological properties of the graphene-modified asphalt are significantly improved,and the low-temperature crack resistance has declined but not much.