Assessment of methods to select optimum doses of rejuvenators for asphalt mixtures with high RAP content

Abstract

ABSTRACT This study explores different methodologies to select proper doses of three palm-oil-based rejuvenators to restore the properties of the effective binder present in asphalt mixtures with high Reclaimed Asphalt Pavement (RAP) content. Two commercial vegetable-based rejuvenators were also used as reference for comparison. The dose selection methods are based on penetration and softening point in unaged, short- and long-term aged states, and High Temperature Superpave Performance Grade (PGH) verified with Fatigue Low-Temperature Superpave Performance Grade (PGFL). In addition, a novel approach based on the thermodynamic properties of the recycled binder blends (i.e. mix of virgin binder, RAP binder and rejuvenator) quantified through the Surface Free Energy (SFE) measurements was also explored. In all cases, the optimum dose selection was determined by the amount of rejuvenator required to provide equivalent or better properties than the virgin binder in its unaged and aged conditions. The results suggest that the PGH approach verified with PGFL is the most appropriate method to determine the optimum rejuvenator dose. This methodology was initially validated by means of rheological and chemical testing conducted on the recycled binder blends at the selected dose in different ageing states.