Performance-based fatigue parameters for the selection and dosing the rejuvenating agents in field-aged asphalt binders

High-content Reclaimed Asphalt Pavement (RAP) reduces virgin material consumption and greenhouse emissions in road infrastructure. However, aged binder stiffness increases cracking susceptibility, requiring rejuvenating agents (RAs) to restore performance. This research aims to define parameters for RA selection and dosage based on fatigue performance. For two RAP binders using two RAs, the optimal content required to restore fatigue life (6.7% to 9.6%) was lower than for linear viscoelastic (LVE) (7.9% to 16.6%) and permanent deformation (7.4% to 19.3%) parameters. The convergence among 18 fatigue parameters highlights their potential for determining RA dosage. Selecting dosages using LVE or permanent deformation criteria leads to excessive RA levels beyond what is needed to address the primary damage mechanism in RAP mixtures, increasing costs without providing effective performance gains.