Viscoelastic Properties Of Asphalt At Different Temperatures And Their Effects On Pavement Performance Of Asphalt Mixtures

Asphalt often presents different viscoelastic forms at different temperatures.In order to evaluate rheological properties of asphalt at different temperatures more comprehensively and effectively,based on rheological and viscoelastic theories,dynamic shear rheometer（DSR）was used to test rheological properties of different modified asphalt at high temperature to evaluate the rheological properties of different modified asphalt at high temperature.The low-temperature performance of different modified asphalt was analyzed by using Burgers model to fit the creep compliance through the bent beam rheological test（BBR）.The results show that the ranking of rheological properties of several modified asphalts from best to worst at high temperature is PE modified asphalts>SBS modified asphalts>SBR modified asphalts.Short-term aging can improve the high temperature performance of asphalt,and different types of modifiers can promote or inhibit the improvement effect.Based on the results of BBR test and Burgers model fitting analysis,SBR modified asphalt has the best low-temperature performance,followed by SBS modified asphalt,while PE modified asphalt has poor low-temperature performance and is not suitable for use as road materials in low-temperature areas.In order to deeply explore the evolution of viscoelastic properties of road asphalt at medium temperature,90#and 70#matrix asphalt were used as test materials,and needle penetration tests and temperature scanning tests were designed under multiple temperature conditions.Data analysis methods were used to accurately define the viscoelastic medium temperature zone limits of 90#and70#matrix asphalt.The results show that the middle temperature zone of 90#asphalt of viscoelasticity is[-5±1℃,38±1℃],and the middle temperature zone of 70#asphalt of viscoelasticity is[0±1℃,51±1℃].According to the viscoelastic response of road asphalt in the middle temperature zone of viscoelasticity,the middle temperature zone of viscoelasticity can be subdivided into three evolution stages:weak viscoelastic stage（Ⅰ）,viscoelastic equilibrium stage（Ⅱ）,strong viscoelastic stage（Ⅲ）.Based on the analysis of the intrinsic viscoelastic index,the evolution of viscoelastic properties of asphalt was described from different angles.In view of the limitations of the intrinsic viscoelastic index,a mathematical model was established based on the principal component analysis method.By means of standardization and rotation dimension reduction,A comprehensive evaluation index I_M-T was proposed,which not only integrated the information of the intrinsic viscoelastic index but also accurately evaluated the evolution of viscoelastic characteristics of road asphalt at medium temperature.Finally,this paper analyzes and studies the pavement performance of asphalt mixture at different temperatures by carrying out rutting test at multiple test temperatures,low-temperature beam bending test and four-point fatigue bending test.According to the selected asphalt viscoelastic index and asphalt mixture pavement performance index at the corresponding temperature,the correlation analysis of linear regression is carried out to explore the impact of asphalt viscoelastic characteristics on the pavement performance of asphalt mixture at different temperatures.The results show that the stress response of asphalt mixture with temperature change at high temperature is nonlinear.With the gradual decrease of test temperature,asphalt becomes hard and elastic,and the pavement performance of asphalt mixture also changes.When the asphalt mixture is in the low temperature zone,the asphalt binder often presents the stress state of"strong elasticity and weak viscosity".Too strong elasticity will make the hardness of the asphalt become larger,and brittle failure is easy to occur.And when the asphalt is in the"strong elasticity and weak viscosity"stage,the effect of temperature reduction on the fatigue life of the asphalt mixture is more obvious.The correlation analysis of linear regression shows that some asphalt viscoelastic indexes can reflect and predict the pavement performance of the mixture to a certain extent,that is,the influence of asphalt viscoelastic characteristics on the pavement performance of the mixture at different temperatures is significant.