Determination of Rejuvenator Proportion within the Recycled Bitumen: Empirical Double-Logarithmic Formula and Calibration

Abstract

Rejuvenators as environmentally-friendly materials can restore the properties of aged bitumen physically or chemically. A proper dosage of a rejuvenator can achieve the desired properties of bitumen. Thus, this study proposed a method, the empirical double-logarithmic formula and calibration, based on physical properties to determine the appropriate rejuvenator dosage within aged bitumen for the desired properties. Three different rejuvenators were selected to restore recycled/aged bitumen extracted from reclaimed asphalt pavement (RAP) to a similar level as that of neat bitumen with penetration of 70–100 (reference bitumen). The initial estimation of rejuvenator dosage was determined by the viscosity of rejuvenators and recycled bitumen using an empirical double-logarithmic formula; the penetration and softening point of one rejuvenated bitumen were applied to calibrate the rejuvenator dosage within recycled bitumen. After the determination of the rejuvenator portion within recycled bitumen, rejuvenated bitumen was compared with reference bitumen regarding penetration, softening point, Fraass breaking point, complex modulus, phase angle, and PG upper temperature; the properties of rejuvenated bitumen over aging degree (short-term aging and long-term aging) were also compared with that of reference bitumen using softening point, Fraass breaking point, complex modulus, phase angle, rutting factor, and fatigue factor. It was found that this method can accurately calculate the rejuvenator dosage in recycled bitumen with a few available physical parameters; the rejuvenated bitumen showed similar equivalent properties as reference bitumen, and the three rejuvenators have a lasting effect on recycled bitumen. Therefore, this method is recommended for calculating the rejuvenator dosage of recycled bitumen due to its convenience and less demand for tests.