Study On Rheological Constitutive Model And Properties Of Warm Mix Asphalt

Road asphalt is the most important pavement engineering material at present.Warm mix asphalt is a kind of special asphalt which can reduce the mixing temperature and compaction temperature without changing the road performance.Asphalt and warm mix asphalt are complex viscoelastic materials.The research on their viscoelastic properties has always been a hot topic.But at present,there are some problems,such as the lack of universality of asphalt rheological model and the non-linear viscoelasticity of Sasobit asphalt.Therefore,it is very important to establish a universal model of warm mix asphalt for mastering the law of pavement deformation and predicting pavement performance.In view of the above problems,for two kinds of typical warm mix asphalt(Sasobit asphalt and Evotherm asphalt),firstly,the rheological properties of warm mix asphalt are analyzed by three basic characterization indicators,such as three indexes;secondly,the viscoelastic properties of warm mix asphalt are analyzed comprehensively by using dynamic shear remoter,including the change of creep modulus,dynamic shear modulus and phase angle in the frequency domain and temperature domain;finally,the mathematical relationship of the model is described accurately.The results show that the penetration index of Sasobit asphalt is large and does not follow the principle of time temperature equivalence,so it is nonlinear viscoelastic asphalt;the penetration index of matrix asphalt and evertherm asphalt is small and follows the principle of time temperature equivalence,so it is linear viscoelastic asphalt.When describing the rheological behavior of matrix asphalt and everotherm asphalt under the rheological dynamic condition,the classical model has fluctuation,while the fractional derivative model has no fluctuation;under the static condition,the parameters of the classical model meet the Arrhenius equation,and the parameters of the fractional derivative model have no regularity;only in a certain range,there is a universal model that can meet the static and dynamic requirements at the same time.In other temperature sections,asphalt The green model has no universality.There are two kinds of Sasobit bitumen structure,one is the wax structure complete gel asphalt(G-bitumen).After destroying the gel structure,another type of asphalt(S-asphalt)with incomplete wax structure is formed.The g-state Sasobit matrix asphalt will change from G-state to S-state in the creep process,and there will be obvious nonlinear creep process,which needs to be described by nonlinear model;for S-state Sasobit asphalt,its constitutive equation is the same as that of matrix asphalt,which can be described by six element Burgers model.Under the condition of dynamic shear,the S-Sasobit asphalt should be described by fractional derivative model(1S2A1D model).The G-Sasobit asphalt model can be based on 1S2A1D model and connected with a spring to get 2S2A1D model.All of them have achieved very good fitting results.