Research On Damage Characteristics Of Rubber Powder-SBS Compound Modified Asphalt And Mixture Based On Viscoelastic Mechanics

The performance of asphalt mixtures has a crucial influence on the quality and service life of asphalt pavements under different servicing conditions.Under heavy traffic loads,repeated loads,and extreme temperature drops,asphalt mixtures are prone to bending and tensile cracking damage,creep damage,fatigue damage,and thermal shrinkage cracking damage,all of which are closely related to the viscoelastic properties of asphalt and asphalt mixtures themselves.In view of this,relying on the National Natural Science Foundation project,this study takes rubber powder-SBS modified asphalt and asphalt mixtures as research carriers,and analyzes the damage and failure characteristics of rubber powder-SBS compound modified asphalt and asphalt mixtures from the perspectives of viscoelastic mechanics and mesostructure.The study aim is to provide new research ideas and analysis methods for the structural design and maintenance of asphalt pavements in different grades and climatic conditions to resist cracking damage.The main research work is as follows:(1)Preparing the rubber powder and SBS compound modified asphalts and evaluating their high-and low-temperature performance,temperature sensitivity performance,construction workability,and storage stability.Subsequently,the multi temperature gradient dynamic shear rheological(DSR)frequency sweep tests and bending beam rheological(BBR)tests were implemented.the high-and low-temperature viscoelastic properties of compound modified asphalt were studied by combining viscoelastic constitutive model with time-temperature equivalence principle.The results show that adding rubber powder can improve the hightemperature deformation resistance,low-temperature toughness,temperature sensitivity,and high-and low-temperature viscoelastic properties of compound modified asphalt.The recommended amount of rubber powder is 10%-20%.(2)The multiple stress creep recovery(MSCR)tests,time sweep tests,and linear amplitude sweep tests were conducted.The creep and fatigue damage of compound modified asphalt were analyzed combing with a five parameter viscoelastic constitutive model and viscoelastic continuous damage theory.Furthermore,the elastic doping finite element model of rubber powder microparticles in asphalt binder was constructed,and the enhancing and toughening mechanism of partially undissolved rubber powder elastic core for the viscoelastic response of compound modified asphalt was simulated and analyzed.The results show that rubber powder can significantly improve the high and low temperature creep damage resistance and fatigue damage resistance of compound modified asphalt,and increase the linear viscoelastic range;Rubber powder microparticles can improve the proportion of elastic properties and the ability to resist shear creep deformation of compound modified asphalt.(3)The optimal mix ratio of compound modified asphalt mixture and mortar was determined using multi-objective grey correlation degree.Under the optimal mix ratio,adding20% rubber powder can respectively increase the dynamic stability of compound modified asphalt mixture by 3.36 times,increase low-temperature bending strain by 57.32%,and improve water damage resistance by 9.86%.Subsequently,the creep and relaxation characteristics of compound modified asphalt mixtures were analyzed using multi-temperature gradient compression creep tests combined with viscoelastic constitutive models and convolution integrals,which can lay the foundation for subsequent research on the evolution of cracking damage,creep damage,and fatigue damage of mixtures based on viscoelastic mechanics’ theory and mesoscopic perspectives.(4)The cracking and failure characteristics of compound modified asphalt mixtures were analyzed using indirect tensile tests(IDT),compression tests,and penetration tests.Subsequently,the multiple stress creep tests,indirect tensile fatigue tests,and notched semicircular bending(SCB)tests were performed.The evolution of crack and damage failure of compound modified asphalt mixtures were studied by combing with acoustic emission technology,viscoelastic damage theory,and digital speckle correlation method.The results indicate that the adding rubber powder can significantly enhance the creep,cracking,and fatigue damage resistance of compound modified asphalt mixture,and can prolong the crack initiation and propagation process of compound modified asphalt mixture,increase the effective bearing range,reduce the stress concentration and crack extension rate at the SCB notch.(5)2D heterogeneous mesoscopic finite element models of IDT,notch SCB tests,and thermal stress restrained specimen tests were constructed using image scanning recognition technology.The cracking damage failure process of the compound modified asphalt mixture was simulated and analyzed in the undamaged(IDT)state,damaged(notch SCB)state,and temperature shrinkage load.And the Weibull probability distribution was used to establish damage probability failure functions for different cross-section mesoscopic finite element models,and the correlation between aggregate and void morphology characteristics and damage performance in compound modified asphalt mixtures was analyzed.The results indicate that the2 D heterogeneous mesoscopic finite element model can better characterize the crack propagation path,load evolution trend,horizontal stress field variation pattern,and horizontal displacement of the crack tip during the cracking and damage process of compound modified asphalt mixture;The damage failure strength of different cross-section microscopic models meets the Weibull probability distribution,which can be used to predict the damage strength of compound modified asphalt mixtures at a certain failure rate;The irregularity of aggregates and the weak areas introduced by voids are the main reasons that affect the damage resistance of asphalt mixtures.