Establishment Of Rheological Models And Prediction Of Rheological Properties Of Polymer Modified Bitumen

As a kind of typical viscoelastic material,bitumen has the viscosity of fluid and the elasticity of solid,and its viscoelastic properties are closely related to the performance and service life of road under different conditions.The mechanical response and the inherent characteristics of material can be reflected by the explicit equations of rheological model,which is the medium of the experiment,the theory and the application.And combining rheological models with the increasingly advanced computer technology,the viscoelastic properties of asphalt materials can be analyzed from microscopic structure level,which is of great significance for a deeper understanding of viscoelasticity of bitumen.In this paper,the rheological model of SBS and rubber modified asphalt was established by rheological characteristic test and model analyzer.The effect of the content of modifier and temperature on rheological model was researched,the relationship between SBS modified bitumen and microstructure was discussed,and the rheological properties of modified asphalt were predicted based on its rheological model.Moreover,SBS modified asphalt mixture were scanned by X-ray CT lossless,and its three-dimensional numerical sample including asphalt sand,aggregate and gap was constructed through image processing technology.In order to verify the rationality of simulation and investigate the distribution and change of the internal mechanical response among asphalt mixture,the splitting test results of numerical sample were simulated and compared with the actual test based on the rheological model of SBS modified asphalt sand and ANSYS.The main conclusions are as follows:(1)Rheological models of SBS modified bitumen was established by rheological characteristic test and model analyzer.The results showed that rheological models of modified asphalt are respectively Burgers model and five element model(H-(H|N)-(H|N)),when SBS content is 3~5wt% and 7~9wt% at 20℃.And rheological models of modified asphalt are Maxwell model,Burgers model and five element model respectively,when SBS content is 3wt%,5 ~ 7wt% and 9wt% under 60℃.(2)Through comparing the rheological parameters of SBS modified bitumen,the instantaneous elastic deformation and delayed elastic deformation of modified bitumen increase by the increase of SBS content and temperature.The instantaneous elastic deformation and delayed elastic deformation of modified bitumen are increased by 0.773 and 0.87 times respectively with the content of SBS from 0wt%~5wt% under 20℃.The viscous deformation of modified bitumen gradually is decreased with the increase of SBS content,but raised with the increase of temperature.From 20℃ to 60℃,the viscous deformation of 5wt%SBS modified bitumen is increased by 13.86 times,and the growth of this deformation is obvious particularly evident.(3)The microstructure of SBS modified bitumen is closely related to its rheological model.The rheological models of 3wt% SBS modified bitumen are Burgers model at 20℃ and transformed into Maxwell model at 60℃ since its system has sea island structure.The modified bitumen is converted into interpenetrating network structure along with the increase of SBS content to 5~7wt%,so the rheological models are respectively changed to Burgers model and five element model for 5wt% and 7wt% SBS modified bitumen at 20℃,and their models are all Burgers model.As SBS continuous phase is formed when SBS content is 9wt%,its models are changed to five element model(4)Rheological models of rubber modified bitumen was established by rheological characteristic test and model analyzer.The results showed that rheological model is Burgers model for modified bitumen with 10~25wt% rubber.In addition,the rheological model is Burgers model at 20~80℃ and Maxwell model at 100℃ for 15wt% and 20wt% rubber modified bitumen.(5)Through comparing the rheological parameters of rubber modified bitumen,its instantaneous elastic deformation is gradually raised along with the increase of rubber and temperature,and have a clear linear relationship with rubber content.Moreover,the viscous deformation is gradually decreased by the increase of rubber content and this declination is clear when rubber content is 10~20wt%.The viscous deformation of modified bitumen is gradually raised with increasing temperature,and the trend is more obvious from the 20℃to 60℃.(6)The repeated creep of SBS modified bitumen and crumb rubber modified bitumen was predicted based on finite element software ANSYS and modified bitumen’s rheological models and parameters characterizing its viscoelasticity.The results showed that the predicted creep curve is close to the indoor test curve,and it can accurately simulate the residual strain and delay elasticity of modified bitumen,which indicates that the rheological properties of modified bitumen can be predicted accurately by rheological models and parameters.(7)The three-dimensional numerical sample of SBS modified asphalt mixture was obtained by X-ray CT scanning SBS and image processing technology and can show the mesoscopic distribution of mixture.Then the splitting strength of SBS modified asphalt mixture was simulated by rheological model of SBS modified asphalt sand and ANSYS.The results showed that the prediction of under different loading rates is bigger than the splitting strength of actual results,and the errors of them are linear with the loading rate.The maximum corrected error is only 0.007 MPa after the numerical simulation results are corrected by this linear relationship.