Enhanced antioxidant activity of lignin for improved asphalt binder performance and aging resistance in sustainable road construction

Lignin, the second most abundant renewable biopolymer, has great potential for utilization. This study enhances lignin’s antioxidant activity through modifying its structure with laccase and evaluate its effect on asphalt binder performance. This study evaluates the effects of reaction conditions (pH, time, temperature, and laccase dosage) on the chemical structure and antioxidant activity of enzymatic hydrolysis lignin (EHL). Waste lignin and EHL modified binders (WLA and ELA) were subjected to chemical and rheological analyses under different aging conditions. Results showed that laccase treatment increases phenolic hydroxy (Ph-OH) groups in lignin, enhancing antioxidant activity. Optimal conditions were pH of 5.0, 25 °C, 6 h, and 1.2 mL/g laccase. FTIR results indicated that EHL inhibits oxidation and decelerates binder aging. Rheological tests demonstrated improved binder’s resistance to aging, deformation, cracking, and fatigue compared to waste lignin. This study supports sustainable road construction by enhancing waste lignin through biomodification and conserving non-renewable resources.