Quantification of Recycled Engine Oil Bottoms in Asphalt Binder Using Nuclear Magnetic Resonance Techniques

Recycled engine oil bottoms (REOBs) are widely used in asphalt binders for modification and cost saving. However, more early road failures have appeared on the pavements constructed with REOB-modified asphalt binders in North America, leading to the bans and limits of its use and the interest in REOB's quantification in asphalt binders. This study aims to systematically introduce a quantifying method via liquid-state nuclear magnetic resonance (NMR) techniques. One base asphalt binder, two REOB resources, and eight blend samples were measured by H-1 NMR, C-13 NMR, and heteronuclear single-quantum correlation (HSQC) NMR. Peaks at 1.1 and 1.4 ppm in H-1 spectra and peaks at 31.2, 38.1, and 59.5 ppm in C-13 spectra were found only in REOB samples and asphalt samples containing REOBs and derived from polyisobutylene (PIB). The indexes of peak ratio and area ratio could well characterize the relative contents of REOB within a certain concentration range. Finally, an obvious peak at (1.4 ppm, 59.5 ppm) (F2, F1) was found and suggested as a characteristic peak of REOB via the HSQC NMR test. (C) 2022 American Society of Civil Engineers.