Effectiveness of Vegetable Oils as Rejuvenators for Aged Asphalt Binders

Traditional rejuvenators normally have a great deal of heavy fuel oils to supply the light oil component of asphalt binders, which decreases throughout a long-term aging process. However, heavy fuel oils can easily volatilize at a high recycling temperature (above 180°C), and this leads to a limited portion of reclaimed asphalt pavement (RAP) materials utilized in the recycled asphalt mixture (with a recycling rate less than 30%). Vegetable oils are rich in unsaturated fatty acids, which are similar to the light oil components, and have a better temperature resistance. Therefore, there is potential that vegetable oils can be utilized to recover the aged asphalt binder based on the asphalt rejuvenating mechanism. In this study, two rejuvenators with waste cooking vegetable oils (corn oil and soybean oil) to replace heavy oils and a commercial rejuvenator were used to recover the aged asphalt (extracted from RAP materials) with different ratios (by weight of asphalt) of 2, 4, 6, 8, and 10%. Dynamic shear rheometer (DSR) and rotational viscosity (RV) tests were used to evaluate the physical properties of the recovered asphalt binder. The low-temperature performance of the recovered asphalt binder was also evaluated by the bending beam rheometer (BBR) test. The laboratory tests and statistical analysis of variance (ANOVA) results show that the vegetable oil rejuvenators can effectively decrease the viscosity and stiffness of aged asphalt binder, which is beneficial for both fatigue and low-temperature cracking resistance. Furthermore, the rejuvenator can lower the viscosity and stiffness of the aged asphalt binder with a larger amount of vegetable oil. Overall, the vegetable oil content (6% to 8%) in the rejuvenator is proposed for recovering the aged asphalt binder in consideration of the rutting resistance under high temperatures.