Experimental Study On Rheological And Fatigue Characteristics Of Super Hard Asphalt

Hard asphalt is a kind of low-grade heavy-duty asphalt,which is widely used in high-grade highway pavement construction in European countries due to its low penetration and good high-temperature rutting resistance.At present,the hard asphalt represented by 30#asphalt has been preliminarily applied in our country,but the rheological and fatigue characteristics of hard asphalt are not perfect,which affects the popularization and use of hard asphalt.As a kind of hard asphalt,super hard asphalt is very necessary to systematically analyze its evaluation indexes through experimental research on rheological and fatigue characteristics of super-hard asphalt.In this paper,the rheological theory is applied to study the rheological properties and fatigue properties evaluation methods and indexes of super hard asphalt modified asphalt binder.The main work includes:First,to study the preparation process,in this paper,two factors and four levels are formulated through experiments and selected three traditional indicators as evaluation indicators,the preparation process of super hard asphalt modified asphalt binder is obtained from high temperature stability and low temperature crack resistance.On this basis,the high and low temperature rheological properties of super hard asphalt SHA modified asphalt binder in different temperature ranges are systematically studied.The high temperature rheological properties of super hard asphalt binder are studied by dynamic shear rheological test and multiple stress creep-recovery test respectively.The Black curve of super hard asphalt binder is obtained.The Black diagram shows that it is suitable for the time-temperature equivalence principle.The addition of super hard asphalt can effectively improve the rutting factor G*/sin? of asphalt binder,and ? the high temperature performance of asphalt mixture is obviously improved.Wilh the increase of super hard asphalt content,the average strain recovery rate R of asphalt binder increases,while the unrecoverable creep compliance Jnr decreases,indicating that adding super hard asphalt is beneficial to improving the high temperature deformation resistance and deformation recovery ability of asphalt binder.According to the high temperature classification in PG classification,the high temperature classification of SHA8 can reach 82?;The low-temperature creep characteristics of modified asphalt binder with super hard asphalt at-10??-22? were studied by bending beam rheometer test.It was found that with the addition of super hard asphalt SHA,the creep stiffness S and creep stiffness change rate m of asphalt binder changed little,indicating that the low-temperature crack resistance of asphalt binder was not affected much.Aiming at fatigue cracking,the main form of asphalt pavement damage,this paper studies the fatigue cracking performance of asphalt samples after short-term aging by simulating the fatigue aging of asphalt during construction.Using dynamic shear rheometer,The effects of stress level,SHA content of super hard asphalt and evaluation method on fatigue performance of asphalt binder are studied in the stress control mode of time scanning.The fatigue curves of complex shear modulus G*,dissipative energy change rate RDEC and cumulative dissipative energy change rate DER with loading times under different stress levels and different SHA content of super hard asphalt are analyzed,and their corresponding fatigue lives Nf50,Nfm and Np20 are compared,and the indexes are transformed into each other by using discrimination degree.It is found that the change curves of G*-N and RDEC-N can divide the fatigue failure process of aged asphalt into three stages,while DER-N curve compares the deviation degree between fatigue failure degree and nondestructive curve,and finds that the fatigue life determined by the three methods is not much different.With the increase content of super hard asphalt,the number of fatigue life under each index increases greatly,indicating that the addition of super hard asphalt can significantly improve the fatigue life of modified asphalt binder.With the increase of stress level,the discrimination degree between each index is close,indicating that at higher stress level,the three indexes can be converted to each other.To sum up,in the experimental study on the rheological,and fatigue characteristics of modified asphalt binder of super hard asphalt,a systematic study was carried out through evaluation methods and indexes based on rheological theory.It is found that modified asphalt binder with super hard asphalt has excellent rutting resistance at high temperature,low temperature performance remains unchanged compared with PG classification of matrix asphalt,and fatigue life is greatly improved.