Research On Fatigue Damage Properties And Creep Behavior Of Cement Asphalt Composite Mastic

Cement asphalt composite mastic is a new kind of organic-inorganic composite cementitious materials.It is made of cement,asphalt,water and a variety of admixture after cementation hardening.Cement asphalt composite mastic is mainly used as cementitious materials for cement asphalt mortar(CA mortar)of high-speed rail plate type ballastless track,and can also be used in semi flexible base course and road maintenance material.The fatigue damage and creep behavior of cement asphalt composite mortar have important influence on the service performance of cement.The fatigue damage and creep behavior of cement asphalt composite mortar are studied.Based on the basic principle of continuum damage mechanics,the fatigue damage variable and damage evolution equation of cement asphalt composite mortar were determined,and the fatigue and creep test program was determined.Damage variables are defined by using complex modulus and cumulative dissipation energy.The nonlinear fatigue damage evolution model and the damage evolution model based on energy dissipation rate function are used to describe the fatigue damage evolution process of cement asphalt composite mastic.Fatigue tests and creep tests are carried out by using dynamic rheological shear apparatus,and a creep test method based on initial fatigue damage degree is proposed.Based on fatigue theory and dynamic viscoelastic principle,the fatigue characteristics and the change law of dynamic viscoelastic mechanical parameters of cement asphalt composite mastic are analyzed.The fatigue equation of cement asphalt composite mortar was established,and the influence of material ratio and temperature on fatigue behavior of composite mastic was analyzed.The change law and influence factors of dynamic mechanical parameters such as complex modulus,phase angle,dissipated energy,cumulative dissipated energy and cumulative energy consumption ratio are studied.Based on the damage variable defined by complex modulus and cumulative dissipation energy,the fatigue damage evolution process of cement asphalt composite mastic is studied by combining the damage evolution equation.The change law of fatigue damage degree defined by complex modulus and cumulative dissipation energy with loading times is analyzed.Nonlinear fatigue damage evolution model and damage evolution model based on energy dissipation rate function were adopted to fit the damage variable evolution curve.The influence of temperature,material ratio and other factors on the damage characteristics and damage evolution law was studied.Based on the viscoelastic theory,a mechanical model describing the creep and creep damage of cement asphalt composite mastic is established,and the influence of initial fatigue damage on the creep characteristics of composite mastic is analyzed.The creep compliance equation considering creep damage is established by using the fractional derivative Burgers model and the Hoff ductile creep fr acture damage factor.The evolution process of creep and creep damage of composite mastic was analyzed,and the influence of initial fatigue damage and material ratio on creep behavior of composite mastic was studied.