Stress Absorbing Layer Technology Of Crumb Rubber/SBS Modified Asphalt

Generally,cement pavement can be considered as a rigid base on which asphalt pavement can be added.Adding of asphalt on cement can make full use of the structural strength of the cement pavement,save local building materials,improve the driving comfort of the pavement,reduce the bumps,noise as well as make the maintenance of pavement easier.However,due to the difference of mechanical properties between asphalt and cement,loading and temperature load may cause bottom-up reflection cracks from cement to asphalt pavement.Laying stress absorption layer between old cement pavement and asphalt mixture can improve the stress statement and effectively prevent and delay the occurrence and expansion of reflection cracks.In this paper,from the perspective of engineering practice and material composition,the matrix asphalt is modified by rubber powder and styrene butadiene-styrene(SBS)polymer,and the main materials and technological parameters affecting the properties of rubber powder/SBS composite modified asphalt are analyzed by orthogonal test method,and the material composition and preparation technology are determined.Firstly,the creep-recovery test was applied to obtain the recovery characteristics,cumulative strain and other shear resistance characteristics of the crumb rubber / SBS modified asphalt.And Burgers model was used to fit the 50 th and 51 st creep process,and the viscosity part of creep stiffness modulus was studied.The stiffness modulus S and creep deformation rate m of the three kinds of asphalt at low temperature were measured by the bending beam rheological test.Secondly,The two-dimensional plane method and three-dimensional plane surface method are used to determine the asphalt film thickness on the aggregate surface,as well as comparing the actual asphalt film thickness on the aggregate surface with that of predicted by the above two methods.At last,rutting test,high temperature penetration test,low temperature bending test,immersion Marshall test and freeze-thaw test were used to evaluate the high temperature shear resistance,low temperature crack resistance and water damage resistance of STRATA asphalt,crumb rubber/SBS modified asphalt,SBS modified asphalt and rubber asphalt mixture.The results show that with the decrease of test temperature,the advantage of rubber asphalt and crumb rubber/ SBS modified asphalt in low temperature is more prominent.The increase of stiffness modulus and the decrease of creep deformation rate of rubber asphalt and crumb powder/SBS modified asphalt are far less than that of SBS modified asphalt.The error of the asphalt film thickness on the aggregate surface determined by the three-dimensional plane surface method is smaller than two-dimensional method,and the three-dimensional result is close to the actual asphalt film thickness.Gradation has little influence on the volume index of the mixture,but it has a certain influence on the resilient modulus;the ratio of asphalt to stone had significant influence on the volume index and resilient modulus of the mixture.The rutting tests show that the four mixtures are stable at high temperature and the order of qualitative is: strata asphalt > crumb rubber/SBS modified asphalt > SBS modified asphalt > rubber asphalt.The results of low temperature bending tests show that the low temperature bending performance of STRATA asphalt and crumb rubber/SBS modified asphalt mixture is significantly higher than that of rubber asphalt and SBS modified asphalt mixture.The test results of water stability of the four kinds of mixtures are all meet the requirements of the code.The research results can provide theoretical basis and technical support for the promotion and application of rubber powder /SBS composite modified asphalt stress absorption layer.