Bio-based reactive rejuvenation systems for aged SBS modified asphalt and its mixture based on component replenishment and molecular chain repair

With the dual goals of advancing sustainable rejuvenation technologies for road asphalt materials and lessening reliance on petroleum resources, the bio-oil (cardanol) was combined with bio-based reactive rejuvenators (dimeric fatty acid diisocyanate (DDI) or L -lysine diisocyanate (LDI)) to construct two fully bio-based reactive rejuvenation systems. These systems were designed to achieve high-quality rejuvenation of the aged styrene-butadiene-styrene (SBS) modified asphalt (PMA) and its mixture. Results from Fourier transform infrared spectroscopy, gel permeation chromatography, and fluorescence morphology indicated that DDI and LDI reacted with the hydroxyl/carboxyl groups on the aged SBS segments, reconstructing the molecular structure and restoring the SBS cross-linked network area from nearly 0% in aged asphalt to 11.5% and 19.3%, respectively. Then, different bio-based reactive rejuvenators slightly reduced the low-temperature ductility of the rejuvenated PMA due to the introduction of rigid carbamate groups, while simultaneously increasing its softening point. Rheological testing showed that the reactive systems restored the complex modulus, phase angle, and low-temperature creep stiffness of aged PMA to levels close to those of unaged PMA. The critical rutting temperature of B- L -PMA reached 81.46 °C, close to 82.85 °C for virgin PMA. Mixture performance further demonstrated that, compared with the use of bio-oil alone, the reactive systems substantially improved high-temperature stability (dynamic stability increased from 6211 to 7658 and 8031 times/mm), low-temperature cracking resistance (flexural tensile strain increased from 2865 με to 3385 and 3153 με), and moisture stability (tensile strength ratio increased from 77.57% to 87.52% and 92.03%) of aged mixtures. Notably, LDI exhibited higher reactivity than DDI and achieved superior overall rejuvenation, offering a promising fully bio-based solution for sustainable pavement recycling.