Relationship between thermoreversible and irreversible aging in rejuvenated asphalt binder

Abstract

Rejuvenators are now widely used to restore performance of aged asphalt. A critical factor that controls performance of pavements in service is age hardening of the binder. Hence, both reversible and irreversible processes need to be accounted for in order to ensure durable designs. Thermoreversible processes are affected by irreversible aging, but how the two interact remains largely unexplored for rejuvenated binders. A straight Cold Lake PG 58-28 binder was blended with castor oil residue (COR), soybean oil residue (SOR) and petroleum-based aromatic oil (ARO) rejuvenators. Standard Extended Bending Beam Rheometer (EBBR, AASHTO TP 122) tests were conducted to assess thermoreversible aging. Non-isothermal crystallization kinetics were investigated using Modulated Differential Scanning Calorimetry (MDSC) and Thermogravimetric Analysis (TGA). Standard Rolling Thin-Film Oven (RTFO) followed by 20 h of Pressure Aging Vessel (PAV) conditioning proved sufficient to differentiate thermoreversible aging tendencies. However, EBBR grade losses increased significantly upon extended aging. Rejuvenated compositions fared worse in comparison to straight Cold Lake binder. Three-day grade losses for the PG 58-28 ranged from 1.8 °C (unaged) to 9 °C (100 h PAV). In contrast, the ARO blend lost 0.8 °C (unaged) increasing to a significant 15 °C (100 h PAV).