Mechanical Properties Research On Asphalt Mortar And Asphalt Mixture Based On The Theory Of Fractional Order Derivative

Asphalt pavements are more and more widely used for good driving comfort,low noise, strong adaptability to uneven settlement and the advantages of easily repair.The mechanical properties of asphalt mixture are affected by the types of raw materials, mineral aggregate gradation composition, temperature, load level and other factors. So, it is difficult to rationally describe the mechanical behavior of asphalt mixture. Asphalt pavement diseases such as rutting and waves are easily appeared when it under repeated loading and at high temperature in summer due to the temperature sensitivity of asphalt mixture. Which will bring huge hidden trouble to safety and reduce the service life. It is very necessary to study the mechanical behaviour of asphalt materials and set up comprehensive constitutive equation so as to reduce rutting disease and prolong the service life of pavement.Asphalt mixture is made up of coarse dispersion, fine dispersion(asphalt mastic)and micro disperse system(asphalt binder) according to the theory of mucilage. The mechanical properties of asphalt mixture are affected by material composition and mechanical properties of disperse system at all levels. It is difficult to accurately describe the mechanical properties of disperse system at all levels with traditional viscoelastic theory and elastoplastic theory. In addition, the characteristics of creep deformation of asphalt mixture have an important influence on the permanent deformation of asphalt pavement. So it is important to study the creep property of asphalt mixture. It can provide reliable basis for asphalt mixture ratio design and performance evaluation by studying the creep property mechanical properties of asphalt mortar and asphalt mixture. Therefore, the mechanical properties of asphalt binder, asphalt mastic and asphalt mixture were studied systematically based on the theory of fractional order derivative. The major contents are summarized as follows:(1) The fractional Maxwell model, fractional Kelvin model and fractional rheological model of five components have been proposed.The rheological characteristics of soft soil are studied based on the fractional five components model.The applications for geotechnical engineering and polymer materials of fractional order derivative constitutive models have been introduced briefly.(2) The relationship between Nutting creep equation of viscoelastic material and creep model of classic fractional derivative Abel sticky pot was set up. Then, afractional order derivative dynamic viscoelasticity constitutive model was built and the concept of deformation factor and viscoelasticity factor were put forwarded for the first time which can respectively characterization of resistance to deformation ability and viscoelasticity. And then, the test-data were presented and the model parameter were determined by fitting test results of dynamic shear rheological tests at different temperatures.(3) A new fractional viscoelastic damage constitutive model was constructed by using Weibull distribution function to describe the rheological properties of asphalt binder at low temperature. The new damage model parameters were determined by making use of the bending beam rheological test results.(4) An improved fractional empirical creep constitutive model of asphalt mortar was put forward based on the fractional order derivative theory to describe creep recovery deformation of asphalt sand. Creep recovery tests of asphalt sand AS-13 and AS-20 under uniaxial static load were performed at different temperature and different levels of stress.The parameters of the model were determined by simulating the experimental results. The mechanical properties and main influencing factors of the model parameters were analyzed.(5) The fractional creep constitutive model for the creep behavior of asphalt mixtures under uniaxial static creep test was proposed considering the effects of factors such as stress level and temperature.Pressure head of uniaxial penetration tester was developed in view of the defect of the shear test of asphalt mixture at high temperature and deformation strength of asphalt mixtures AC-13 C and AC-20 C were performed at different temperatures. Correlation of this static-test property with compressive strength, compressive resilient modulus and dynamic stability were evaluated.The analysis indicates that deformation strength can be as high temperature shear performance evaluation index of asphalt mixtures.(6) A subroutine were written for the fractional empirical creep constitutive model of asphalt mixture based on the second development function of ABAQUS providing for user material subroutine.Then simulated analysis for rutting prediction of asphalt mixtures were carried out using ABAQUS.In this paper, the mechanical properties of asphalt mixture dispersion system were studied based on the the fractional order derivative theory. Fractional dynamic viscoelasticity constitutive model, fractional empirical viscoelastic damage constitutive model, improved fractional empirical creep constitutive model, fractionalcreep constitutive model of asphalt mixtures were introduced. And evaluation index of materials performance were put forward. Such studies is fundamentally important to correctly describe the mechanical properties of asphalt mixture and fully understand the deformation mechanism.