Study On Microstructure And Properties Of Asphalt Based On Infrared Spectroscopy And Atomic Force Microscopy

As the binder of asphalt aggregate in asphalt mixture,the aging of asphalt mixture itself is an important factor affecting the pavement performance of asphalt mixture,which leads to many pavement diseases.In highway maintenance engineering,the aging degree and performance of asphalt are also used as an important basis to determine road maintenance nodes.In order to study how the microstructure of asphalt with aging time affects its macroscopic properties,this paper uses ordinary oven to aging 70#and 90#virgin asphalt.The aging time is 0,5,10,15,25,35,45,55,65,75h,respectively.The functional groups of different asphalt were analyzed and compared by using infrared spectrum,and the composition change characteristics of asphalt were obtained.Atomic force microscope(AFM)was used to test the surface morphology and mechanical behavior of different asphalt,and the 2D and 3D morphologies and mechanical behavior parameters of asphalt were obtained.The number and roughness of asphalt "bee-like structure" and the height,adhesion force,modulus and association degree of different parts in a single "bee-like structure" were statistically analyzed under atomic force microscope.On this basis,the high and low temperature properties of different asphalt samples were tested by dynamic shear rheometer,bending beam rheometer and traditional three index testing methods,and the microstructure characteristics of asphalt and the evolution law of performance were demonstrated at the macro level.The results show that under the infrared spectrum,with the increase of asphalt aging time,the unsaturated carbon atoms and sulfur atoms react with oxygen to generate carbonyl and sulfoxide groups.Because the carbonyl and sulfoxide base bodies have strong polarity,they can increase the crosslinking between the molecular chains,increase the viscosity of asphalt,and enhance the high temperature performance.However,the reduction of carbon chain structure content of asphalt will lead to the instability of the internal structure of asphalt,so that its deformation ability and low temperature performance will be weakened.At the same time,a new characterization method of "bee structure" of asphalt was defined under atomic force microscope.With the increase of aging time,the large molecular weight represented by asphaltene in the asphalt increases,the asphalt hardens,the degree of association of four components in a single group increases,and the high temperature performance is enhanced.However,the small molecular weight represented by aromatic fraction decreases,the bonding force between four components decreases,the bitumen becomes brittle and the low temperature performance deteriorates.The change of asphalt properties at high and low temperature under the test of dynamic shear rheometer,bending beam rheometer and traditional three indexes verified the correctness of asphalt microstructure and property evolution law.The research results have certain theoretical and practical value for further clarifying the microstructure characteristics and high and low temperature performance of asphalt.