Enhancing the anti-aging performance of SBS modified bitumen via lignin/expanded vermiculite/chitosan composites: Unveiling the critical role of lignin types

Styrene-butadiene-styrene copolymer (SBS) modified bitumen is susceptible to aging from heat, oxygen, and UV radiation, leading to pavement deterioration. While Lignin/expanded vermiculite/chitosan (LEC) composites are known to enhance bitumen aging resistance, how different lignin types govern this anti-aging performance remains elusive. This work systematically investigates SBS modified bitumen (SBSMB) modified with LEC composites derived from three lignin types: Sulfonate (SL), Kraft (KL), and Dealkalized (DL). The microstructure and properties of the composite material were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), and ultraviolet-visible spectrophotometry (UV–vis). The performance evolution of modified bitumen was analyzed after short-term, long-term, and UV-simulated aging conditions using multi-scale indicators, including physical properties, rheological behavior, and molecular weight distribution. Results demonstrate that LEC composites significantly enhance the high-temperature rutting resistance of SBSMB. Notably, the SBSMB with the KL-prepared composite (KLEC-SBSMB) exhibited the best anti-aging performance, reducing the increase in softening point increment (SPI) by 80.3% after long-term aging and the complex modulus aging index (CMAI) by 25.3% after UV aging. The enhancement is attributed to the combined barrier effect of EVMT against thermal oxidation and the UV absorption by lignin. This study identifies KL as the optimal feedstock for LEC composites, offering a promising strategy for durable and sustainable bitumen pavements.