Fractional Viscoelastic Modeling of Antirutting Response of Bituminous Binders

A three-parameter fractional model, composed by a springpot in series with a dapshpot, was employed to describe the rheological behaviour of a set of polymer-modified bituminous binders obtained by combining a single-base bitumen with different types of syrene-butadiene-styrene copolymers at different concentrations. Experimental strain-time curves gathered from creep-recovery shear tests carried out by means of a dynamic shear rheometer at various temperatures were found to be in good agreement with model predictions. The fractional approach leads to a synthetic yet exhaustive description of the viscoelastic behavior of all materials. Variation of model parameters, each of which with a precise physical meaning, appears to be coherent with different binder compositions and testing conditions, reflecting the variations in terms of polymer concentration and temperature.