A new approach to estimating rheological properties of the rap binder at intermediate temperatures

Determining thermo rheological properties of the aged binder in reclaimed asphalt pavement (RAP) is a challenging problem. In the literature, there are different methods available, but some of them are considered not accurate, others are costly and time consuming. For these reasons, in this paper, a new methodology to evaluate RAP binder properties at intermediate temperatures (0–40°C) is proposed; this is based on the back-calculation of the rheological parameters of the RAP binder from dynamic shear rheometer tests carried out on mortars composed of a selected fine fraction of the RAP mixed with virgin bitumen. For the back-calculation of the parameters, the original formulation of the Nielsen model is modified in order to take into account the effects of frequency and temperature on the mortar stiffness. The Voigt model is used to estimate the complex modulus of the RAP binder from the complex modulus of the blend.