Chemical Characterization and Field Aging Behavior of Bio- and Petroleum-Based Spray-on Rejuvenators on Asphalt Pavements

This study investigates the chemical composition and field-aging behavior of 12 spray-on rejuvenators applied to asphalt pavement test sections at the Minnesota Road Research facility. The products (seven bio-based, one hybrid, and four petroleum-based) were classified by gas chromatography–mass into eight chemical groups and applied to pavements constructed with PG 58S-28 (unmodified) and PG 58H-34 (polymer-modified) binders. Over 24 months, binder samples from control and treated sections were evaluated using saturates, aromatics, resins, and asphaltenes fractionation, Colloidal Instability Index, and Fourier transform infrared (FTIR) spectroscopy. The CII for bio-based products was highly variable, likely owing to polar carboxylate functionalities from the fatty acids bonding to and precipitating from the heptane solvent as asphaltenes. Petroleum-based products dissolved in heptane and were later separated into maltene fractions. For bio-based formulations, strong ester absorbances overlapped the carbonyl (C = O) region in FTIR spectra, requiring a modified FTIR approach to accurately distinguish ester content from oxidation products. Accurate evaluation of oxidative aging using typical FTIR analyses without such differentiation is unreliable when bio-oils are present. Using the supplier-recommended application rate resulted in very different residual oil masses for each product. Chemical properties of aged residues were generally improved with higher oil dosages. PG 58S-28 exhibited greater treatment differentiation owing to higher oxidative susceptibility. Overall, results highlight the importance of product formulation, binder type, and tailored analysis methods in selecting effective spray-on rejuvenators for pavement preservation.