Bitumen has long been a material used in the construction of roadways, yet new pavement only consists of low fractions of recycled materials due to poor compatibility of aged bitumen and new materials. Thus, rejuvenators, chemical additives, have been used in an attempt to re-balance the chemical composition and restore the physical properties of aged bitumen back to its virgin state. A fundamental understanding of how one particular rejuvenator, soybean oil, revitalizes bitumen was investigated using a multi-scale approach.
Fourier-transform infrared spectroscopy (FTIR) was used to determine the changes in chemical properties of pure and rejuvenated virgin and aged samples. Samples were artificially short term aged using a rolling thin film oven (RTFO) procedure or long term aged using a pressure aging vessel (PAV). Rejuvenator concentrations were tested at both 7.5% and 15%. FTIR results reveal carbonyl (IC=O), sulfoxide (IS=O), branched aliphatic (IB), and aromatic (IAr) indices decrease in RTFO and PAV samples from rejuvenation with soybean oil, suggesting that the aging process in the aged bitumen has been reversed.
A linear amplitude sweep (LAS), a mechanical procedure using a dynamic shear rheometer (DSR), was employed to investigate rheological properties. LAS analysis of PAV samples manifests fatigue resistances of bitumen samples increase at every applied shear strain as a result of increasing concentration of rejuvenator.
The relation of FTIR and LAS results indicates rejuvenation of aged bitumen with soybean oil reverses the aging process at a molecular level and, as a result, increases the fatigue life of the bitumen
