Study On Storage Stability And Phase Separation Behavior Of Warm Mix SBS Modified Asphalt Based On Phase Field Method

As a high performance material,warm mix SBS modified asphalt has been widely used in road engineering.In the storage process,the addition of SBS and warm mix additive can greatly improve the performance of asphalt,but there is also a problem of storage stability,which is directly related to the performance of pavement.When the storage stability is poor,SBS and asphalt are not thermodynamically compatible,resulting in phase separation after mixing.Therefore,it is of great significance to study the storage stability and phase separation behavior of warm mix SBS modified asphalt.First of all,this thesis uses the experimental method to prepare warm mix SBS modified asphalt by using No.70 base asphalt,SBS modifier and Sasobit warm mix agent.Through the three indexes,Brookfield viscosity,segregation experiment,DSR experiment and FTIR experiment,the conventional physical properties,rheological properties and modification mechanism of warm-mix SBS modified asphalt were analyzed.In order to further study the microscopic morphology of warm-mix SBSmodified asphalt,this thesis uses a fluorescence microscope to observe the phase separation of warm-mix SBS-modified asphalt over time,and studies the influence of Sasobit content and storage temperature changes on phase separation,and uses image The processing method makes quantitative analysis on the area percentage of SBS and the swelling amount of SBS.Then this thesis uses the simulation method to build a simulation model suitable for phase separation of modified asphalt.Through the study of thermodynamics and phase separation kinetics,a diffusion phase field model suitable for warm-mix SBS modified asphalt was constructed.The Navier-Stokes equation and phase field model were coupled to construct a diffusion-mobile phase field model under the action of gravity to study the microstructure of warm-mix SBS modified asphalt during high-temperature storage.On the basis of the simulation model,the phase separation process of SBS content,matrix asphalt type and SBS type under the action of diffusion is studied,and verified by consulting relevant data.On this basis,the phase separation process under the action of gravity is studied.Through the research on relevant experiments and simulations,the following research results have been obtained:(1)Through the three major indicators,it is found that with the increase of Sasobit content,the penetration of warm-mix SBS modified asphalt decreases,the softening point increases,and the ductility decreases,indicating that the addition of Sasobit improves the hardness of asphalt,but is not conducive to asphalt of extensibility.Through Brookfield viscosity experiments,it was found that when the temperature was higher than the melting temperature of Sasobit,the viscosity of SBS modified asphalt decreased with the increase of Sasobit content.Through segregation experiments,it was found that the segregation degree of modified asphalt increased with the increase of warm mix agent content,indicating that the addition of Sasobit was not conducive to the storage stability of warm mix SBS modified asphalt.Through DSR experiments,it was found that after adding Sasobit,the complex modulus of warm-mix SBS modified asphalt increased,and the phase angle decreased,indicating that after adding Sasobit warm-mix agent,the elastic component in asphalt increased,and at the same time High temperature deformation resistance of asphalt.Through FTIR experiments,it was found that the incorporation of Sasobit did not bring about obvious changes in functional groups,and Sasobit was physically cross-linked with SBS.(2)The fluorescence observation results show that the warm-mix SBS modified asphalt presents a transformation process from the SBS continuous phase to the asphalt continuous phase during the phase separation process.During this process,the SBS phase undergoes volume shrinkage and phase inversion.The results of the effect of warm mix agent content on phase separation showed that with the increase of Sasobit content,the phase separation speed of warm mix SBS modified asphalt was accelerated,but the addition of Sasobit did not have a significant impact on the final phase structure.Effect of temperature on phase separation The results show that when the temperature decreases,the phase separation speed of the modified asphalt slows down,the amount of swelling decreases,and the area percentage of SBS decreases.When the temperature was lowered to near the melting point,the space network structure after Sasobit crystallization appeared during the phase separation process of the warm mix SBS modified asphalt mixed with Sasobit warm mix agent,which greatly slowed down the phase separation speed.(3)The simulation results clearly show the phase separation process of warm-mix SBS modified asphalt under the action of diffusion and the phase separation process under the action of gravity.Through the study of the diffusion phase field model,it is found that when the temperature decreases,the mobility coefficient of the model decreases,the thermal movement rate of molecules slows down,the relative number of interacting molecules in asphalt decreases,the swelling size of SBS decreases,and the swelling effect of polymer in asphalt The worse it is,the smaller the volume fraction of SBS phase is.Through the study of the diffusion-mobile phase field model of gravity,it is found that with the increase of Sasobit content,the segregation degree of warm-mix SBS modified asphalt increases during storage.(4)The simulation study on the SBS content found that with the increase of the SBS content,the SBS phase gradually changed from dispersed particles to connected strips,and then to a network structure.During the phase separation under the action of gravity,the higher content of SBS showed greater aggregation.In the simulation study of different matrix asphalt types and different SBS types,it was found that asphalt and SBS types have an impact on the phase separation velocity,model interaction parameters and swelling coefficient,and have an impact on the phase structure of warm-mix SBS modified asphalt.