An extension of the fractional model for construction of asphalt binder master curve

Abstract

Knowledge and prediction of viscoelastic behaviour of asphalt binder is of great interest in order to design asphalt mixtures for civil construction of road and airports with good performances. The capability of a fractional model – requiring a very limited number of parameters – to describe and predict the linear viscoelastic behaviour of asphalt binder subjected to sinusoidal oscillations is investigated. Experimental data of complex modulus, |G*|, and phase angle, δ, are used to validate the proposed constitutive model. Based on the proposed extension of a fractional model, complex modulus isotherms for a range of frequencies can be created simply starting from isochronals at frequency value of 1 Hz. Furthermore, a mathematical procedure derived from the same model is proposed in order to compute the shift factors and automatically create the master curve, thus avoiding further errors due to manual adjustments. This shifting procedure requires only a few isotherms to create a smooth master curve able to describe asphalt binder behaviour under a wide range of temperature and loading conditions. When the fractional model is adopted and the mathematical shifting procedure is applied, only a temperature sweep test at 1 Hz is needed in order to create complex modulus and phase angle master curves.