Comparative Evaluation of Used Vegetable Oil and Waste Motor Oil as Rejuvenating Agents for Aged Bitumen

This paper considers the influence of used vegetable oil (UVO) and 10W-40 waste motor oil (WMO) used as agents for restoring the physical and mechanical properties of aged BND 100/130 bitumen. The aging process was simulated in a Rolling Thin-Film Oven (RTFO) for short-term aging (85 min) and long-term aging (225 min). The functional groups in the rejuvenating agents and modified samples were determined using Fourier Transform Infrared (FTIR) spectroscopy. The effect of the rejuvenating agents was confirmed by determining the physical and mechanical properties of bitumen before and after aging (softening point, penetration depth, elongation, brittleness temperature, and flash point). With an increase in the mass fraction of rejuvenating additives, a decrease in the softening point of the samples and an increase in the needle penetration depth and elongation values were observed. This confirms their effectiveness as softeners, softening the oxidized and aged structure of old bitumen. The optimal amount of additives for short-term-aged bitumen was 3 wt.%, and for long-term-aged bitumen samples, 9–12 wt.%. The results of Multiple Stress Creep Recovery (MSCR) and Atomic Force Microscopy (AFM) studies showed that the effectiveness of the rejuvenating agents depends on the degree of bitumen aging and their concentration. An analysis of FTIR spectroscopy curves for bitumens with added rejuvenating agents shows that the rejuvenating agents act as physical plasticizers, without chemical reactions that form new covalent bonds.