Effects of antioxidants on the evolution of colloidal structure and oxidative development in bitumen during aging

This study investigates the role of kraft lignin and zinc diethyldithiocarbamate (ZDC) in mitigating oxidative aging in bitumen and asphalt mixtures. Two base binders (20/30 and 70/100) were modified with each antioxidant and aged under controlled conditions. The chemical evolution of binders was assessed using Zenke asphaltene fractionation, SARA analysis via solid-phase extraction, and FTIR spectroscopy, with results interpreted through multivariate discriminant analysis. Results demonstrated that ZDC effectively suppressed asphaltene formation and reduced carbonyl index development, particularly in softer binders. Conversely, kraft lignin exhibited complex, binder-dependent effects with limited efficacy and occasional promotion of asphaltene formation. FTIR-based markers confirmed the carbonyl band (1747–1675 cm−1) as a reliable oxidation indicator. Comparison of aged binders versus samples recovered from aged mixtures revealed traces of filler components in the latter. Overall, the study highlights ZDC as a chemically robust antioxidant, whereas lignin’s behavior warrants further investigation.