An approach to couple aging to stiffness and permanent deformation modeling of asphalt mixtures

摘要

This work presents an effort to evaluate aging in asphalt mixtures and investigate the evolution of resistance to permanent deformation in aged materials. A phenomenological model from the literature (based on an internal state variable for aging) is adopted and a proposition is made for an experimental procedure for simulation of asphalt mixture aging in laboratory, based on a RILEM protocol. With the model that combines aging and linear viscoelasticity (Prony series were studied in this paper), experimental results for storage (real part of complex modulus) and loss (imaginary part of complex modulus) moduli are predicted for a reference asphalt mixture and for the same mixture, but at three other aging states. Complex modulus tests were used to obtain stiffness properties, while uniaxial repeated load tests were used to obtain permanent deformation characteristics (such as the Flow Number). The evolutions of stiffness and of resistance to permanent deformation with aging are simulated to demonstrate the capabilities of the model. The aging model is also coupled to permanent deformation parameters and their evolution was simulated in the material level. It was observed that aging increased asphalt mixture resistance to permanent deformation faster for more evolved aging states, indicating that permanent deformation is a distress more likely to occur at early ages. When it comes to the linear viscoelastic characterization, it was observed that not only a vertical shift but also an inclination of the master curves for the norm of complex modulus occurs after aging. That phenomenon was also visible when analyzing the discrete spectra (LVE models).