Study On Viscoelastic Properties Of CA Mortar For CRTS?Slab Ballastless Track

CRTS?slab ballastless track is one of the ballastless tracks used in high-speed railway in China.As the filling layer of track slab,CA mortar plays an important role in adjusting,supporting,carrying,vibration damping and vibration isolation.CA mortar has typical viscoelastic characteristics,but most of the current studies regard the adjustment layer as elastic,which is obviously not accurate and rigorous enough.The large amount of damage occurred in the use of the CA mortar filling layer is obviously deviated from the initial design prediction.Therefore,it is of great engineering significance to study the viscoelastic properties of CA mortar through laboratory tests and to carry out theoretical research to provide basic data for the more accurate design and failure analysis of ballastless track structures.This paper first studied the basic mechanical properties of CA mortar,and then the viscoelastic properties of CA mortar at different temperatures and stress levels before and after freeze-thaw cycle are analyzed under the uniaxial compression creep test.The main research contents and conclusions of this article are as follows:(1)CA mortar was prepared in the laboratory to test its workability and basic mechanical properties.The influence of cement,sand,emulsified bitumen and air entraining agent on the mechanical properties of the mortar was analyzed,and the optimum mix ratio was determined.The effect of mixing speed and time on the gas content of CA mortar was analyzed,and the reasonable mixing process was given.(2)The deformation time curve of CA mortar was drawn by uniaxial compression creep test with different temperature and stress level.The viscoelastic properties of CA mortar were analyzed.The study shows that CA mortar has obvious viscoelastic characteristics.The creep deformation and creep stiffness modulus increase with the increase of stress level,creep deformation is positively correlated with the temperature of the test,and creep stiffness modulus is negatively correlated with temperature.The creep equation of viscoelastic energy of CA mortar is further explored.The results show that the existing Burgers model and the modified Burgers model with four elements and five parameters can better describe the viscoelastic properties of CA mortar,and the modified Burgers model can better fit the properties of CA mortar.(3)The frost resistance of CA mortar was studied by freeze-thaw cycle test.The results showed that the relative dynamic modulus and mass loss rate of CA mortar reached the specifications index at the times of 300 freezing thawing.Furthermore,compression creep tests of CA mortar with different stress levels were carried out after freeze-thaw,and the influence of action history on viscoelastic properties of CA mortar was analyzed.The results show that CA mortar still has viscoelasticity after freezing and thawing,and the viscoelastic curves at different stress levels are basically the same.The deformation and non recoverable variable of CA mortar increase with the increase of the stress level.The classical viscoelastic model is still suitable for the CA mortar after freezing and thawing,in which the modified Burgers model can more accurately fit the creep curve.