| Asphalt is vulnerable to be aged due to the multiple effect of temperature,light,moisture,load and other factors in the process of production and application,resulting in performance degradation and causing various diseases that adverse to asphalt pavement performance.The layered silicates of two dimensional nanomaterials（organic expanded vermiculite,OEVMT）,which mainly improve thermal oxidative aging,were compounded with inorganic nanoparticles of zero dimensional nanomaterials（nano-Si O2,nano-Zn O,nano-Ti O2）,which focus on improving photo oxidative aging,to enhance both thermal oxidative aging and photo oxidative aging resistance of asphalt.In this paper,the physical and rheological properties of asphalt before and after aging were investigated by Penetration,Softening point,Ductility,Viscosity and Dynamic shear rheometer（DSR）.Atomic force microscope（AFM）,Nuclear magnetic resonance（NMR）,Gel permeation chromatography（GPC）and Fourier transform infrared spectrometer（FTIR）were used to characterize the changes of asphalt before and after aging from the perspective of microstructure and chemical composition.In addition,the correlation coefficient between the microscopic characteristic index and the macroscopic performance index of asphalt is studied by grey correlation analysis.The main conclusions are as follows:（1）The physical and rheological properties of asphalt were analyzed.the modifier reduced the softening point increment,the viscosity aging index and complex modulus aging index of asphalt after aging,and increased the residual penetration index,ductility retention rate index and phase angle aging index of asphalt.Those indicated that the modifier improved the aging performance of asphalt.Among different modifier,Zn O+OEVMT compound modifier has the significant effect.（2）The microstructure and mechanical properties of modified asphalt under different aging conditions were analyzed based on AFM-peak force mode（AFM-PFM）model.The structure of the bee phase of asphalt changed after the addition of the modifier of multi-scale nanomaterials,which indicated that the size and morphology of the bee phase were related to the modifier type.With the deepening of aging process,the number of bee phase structure was decreased but the area was increased,and the roughness and adhesion of asphalt were decreased but Derjaguin-Muller-Toporov（DMT）modulus was increased.Besides,there was a significant correlation between the roughness,adhesion and the DMT modulus.The number and size of bee phase structure were closely related to the content of wax and asphaltene.（3）NMR,GPC and FTIR were used to study the chemical structure,molecular size and characteristic functional groups of multi-dimensional nanomaterials modified asphalt.NMR results showed that,during the aging process,the benzene ring structure of asphalt molecules was replaced,the structure was dissimilated,and the length of the aliphatic side chains was increased.The GPC spectrum showed that the LMS（larger molecular size）of asphalt were increased after aging,and the molecular weight distribution curve was shifted to the left,and the modifier slowed down the increase of macromolecules in asphalt.FTIR test showed that the sulfoxide index increasement rate of modified asphalt decreased significantly after aging,and the anti-aging performance of modified asphalt was improved by the modifier.（4）Grey relational Analysis was used to investigate the correlation among the microstructure,chemical composition index and macroscopic physical and rheological indexes of asphalt.The results showed that the indexes constructed by AFM,NMR and GPC had an apparent rule in the change of physical and rheological indexes,and the feasibility of characterization of asphalt properties by microscopic indexes were proved. |
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