Rheological Behavior and Aging Resistance of SBS/Lignin Composite Modified Asphalt

The degradation of styrene-butadiene-styrene (SBS) modified asphalt under thermal-oxidative aging can reduce pavement service life. Lignin is a renewable material with active phenolic hydroxyl groups. Incorporating lignin into SBS modified asphalt may provide a potential bio-based auxiliary modification route. To investigate the antioxidative effect and rheological properties of SBS modified asphalt after adding lignin, a molecular dynamics test and experimental tests were employed. The molecular simulation results suggested that lignin preferentially associated with asphaltene and resin molecules and changed the molecular mobility of asphalt components in a component-dependent manner. The SBS/lignin composite modified asphalt was evaluated by temperature sweep (TS), Multiple Stress Creep and Recovery (MSCR), Linear Amplitude Sweep (LAS) and Fourier transform infrared spectroscopy (FTIR). Rheological tests showed that lignin increased the complex shear modulus and rutting factor. LAS results showed that lignin reduced the fatigue life of SBS-modified asphalt in the unaged state due to increased stiffness and embrittlement. However, after long-term aging, the lignin-containing binders retained higher fatigue resistance than the SBS-only control, which may be related to the slower evolution of oxidation-related functional groups and SBS-related spectral indices. FTIR analysis provided semi-quantitative evidence that lignin addition reduced the growth of sulfoxide-related bands and helped maintain the polybutadiene-related index during aging. Overall, lignin may serve as a potential auxiliary antioxidant modifier for SBS modified asphalt, while its exact source-specific molecular mechanism requires further verification.