A Novel Rejuvenating Method for Structural and Performance Recovery of Aged SBS-Modified Bitumen

Both aging hardening of a bitumen matrix and structural degradation of a styrene-butadiene-styrene triblock copolymer (SBS), caused by short- and long-term aging effects, can seriously shorten the service life of SBS-modified bitumen (SBSMB) pavement and consequently produce a large amount of waste road materials. For recycling and reusing of the aged SBS-modified bitumen, a novel three-component compound rejuvenator consisting of epoxy soybean oil (ESO), epoxidized polybutadiene resin (EPR), and maleic anhydride (MA) was developed in this research based on the rejuvenating mechanism of bitumen matrix component regulation combined with polymer structural reconstruction. The proposed double rejuvenating mechanism was demonstrated by comparing the effects of rejuvenators with different compound forms regarding three constituents (ESO, EPR, and MA) on the physical and rheological properties, molecular distribution, and polymer morphological structure of aged SBSMB. The optimal composition proportion for the developed compound rejuvenator was further determined in accordance with its rejuvenating effects and cost efficiency. The results indicate that the three-component compound rejuvenator not only can restore the physical properties (especially ductility) of aged SBSMB but is also able to allow the aged SBSMB to significantly recover the phase angle plateau region and molecular weight peak corresponding to the SBS polymer, which illustrates that bitumen matrix component regulation and SBS structural reconstruction can work together for rejuvenating aged SBSMB. Additionally, the fluorescence microscopy (FM) result further verifies that the damaged polymer network structure is reconstructed by the developed three-component compound rejuvenator. In consideration of both high- and low-temperature properties, the cost efficiency and copolymer structural reconstruction degree of rejuvenated SBSMB, 8% ESO, 2% EPR, and 0.1% MA by the weight of the bitumen matrix are determined as an optimal proportion to produce this novel compound rejuvenator.