Complex Modulus Model Of Asphalt Binder And Mixture And Its Application

Asphalt materials present a viscoelastic behavior, and analysis of mechanical responses of asphalt materials and asphalt pavement structures can be an effective way to reflect the characteristics of mechanical behavior, and then better to solve the problem of pavement distress. The analysis of pavement structure mechanical responses is the core to explain the mechanism of the pavement distress and then the design of pavement structure. Moreover, a viscoelastic model of the pavement materials is the basis of the analysis of mechanical responses.Firstly, the existing three kinds of viscoelastic models of asphalt binders and mixtures (nomograph, mathematical model and mechanical model) were evaluated. The results show that the empirical tests used in the nomograph involve complex stress states and may not be able to obtain fundamental engineering properties of binders.The dynamic modulus and phase angle master curves of mathematical models were developed separately using empirically selected mathematical expressions, and apparently they do not satisfy the KK relations. In addition, these models may result in different time-temperature shift factors for the dynamic modulus and phase angle master curves, which is not consistent with LVE theory. Due to the lack of viscous elements, the mechanical model can not accurately characterize the linear viscoelastic properties of asphalt binders or asphalt mixtures at low frequency.Secondly, the modified Havriliak-Negami model previously proposed for complex modulus of asphalt concrete is extended to account for the steady-state flow behavior of viscoelastic liquid materials. The analytical forms of storage and loss modulus master curves are derived from the complex modulus model through complex algebra, and the model parameters are determined by the nonlinear minimization algorithm. The results show that using the modified MHN model can make the characterization of asphalt binders or mixtures in the complex and frequency domain contain the same information. In addition, the same time-temperature shift factor applies to various LVE functions. The proposed approach provides a unified and consistent way to characterize the LVE properties of asphalt binders and mixtures.Lastly, based on the modified Havriliak-Negami model parameters, the viscoelastic responses were analyzed for typical highway asphalt pavement structure using self-developed APRA (asphalt pavement response analysis) viscoelastic layer system software, analyzing the-?- key mechanical responses of permanent deformation(vertical strains at the middle of the asphalt layer) and the key mechanical responses of fatigue cracking (horizontal strains at the bottom of the asphalt layer) at various temperatures and vehicle speeds. The results show that the peak values of the vertical strains at the middle of the asphalt layer and horizontal strains at the bottom of the asphalt layer increase with increasing of temperature and decreasing of vehicle speed, and larger increases in peak values are obtained for vertical compressive strains. It shows that the permanent deformation of asphalt layer can be increased by increasing of temperature and decreasing of vehicle speed.