Performance Investigation Of Rejuvenator For Aged SBS Modified Asphalt Based On Asphalt Component Reconciliation And SBS Molecular Structural Repair

Styrene-butadiene-styrene triblock copolymers(SBS)can form three-dimensional polymer-rich network structures in asphalt matrix,and the formed network structures can allow the asphalt binder to present the excellent service performance.Nevertheless,both oxidation hardening of asphalt matrix and aging degradation of SBS copolymer during pavement construction and service period destruct the original polymer-asphalt two phase structure in SBS modified asphalt,which seriously compromises the in-service performance and longevity of SBS modified asphalt pavement.Renovation and reconstruction of aged SBS modified asphalt pavement can produce a large amount of waste road material,which brings a huge environment pollution potential risk.For this case,rejuvenation of waste road material can be an important solution for achieving the environment harmony and resource sustainable use.Currently,most of rejuvenation methods for aged SBS modified asphalt fail to differentiate the disparities in modification mechanism and aging mechanism between SBS modified asphalt and traditional asphalt,still following the thought that the asphalt can be rejuvenated only by component reconciliation,and ignoring the effects of SBS degradation on modified asphalt performance during SBS modified asphalt aging process.As a result,both component reconciliation for aged asphalt matrix and molecular structure repair for damaged SBS are needed to achieve a better rejuvenating effect for aged SBS modified asphalt.This paper explored a reliable and effective method of separating asphalt matrix and SBS modifier from SBS modified asphalt,and further investigated the respective contribution of SBS modifier and asphalt matrix to aging properties of SBS modified asphalt in different aging stages.Based on aging mechanism of SBS modifier and asphalt matrix,a compound rejuvenator for aged SBS modified asphalt was developed by using epoxidized soybean oil as component reconciliation agent and using epoxidized polybutadiene resin as SBS molecular structural repair agent.And the rejuvenating effect of this compound rejuvenator was demonstrated by comparing physical properties,rheological properties,chemical composition and microscopic structure changes of aged SBS modified before and after its rejuvenation,and the optimum proportion ratio for this type of compound rejuvenator was determined as well.The main conclusions are shown as follows:(1)According to different solubility of SBS modifier,maltene and asphaltene in n-heptane,n-hexane and ether agents,a method of separating the asphalt phase and SBS copolymer phase from SBS modified asphalt is proposed.The proposed separation method can effectively avoid the interference of SBS copolymer on complex modulus aging index,and substituting SBS modified asphalt with separated asphalt matrix as aging evaluation object is more objective.(2)The asphalt matrix hardening-copolymer degradation superposition quantitative relationship is suitable for viscosity and complex modulus change of SBS modified asphalt after short-term aging.As far as low-temperature ductility,penetration and softening point are concerned,the asphalt matrix hardening effect outweighs the copolymer degradation softening effect during short-term and long-term aging of SBS modified asphalt.(3)In comparison with other two rejuvenator types,including only use of epoxidized soybean oil or compound of epoxidized polybutadiene resin and maleic anhydride,the compound rejuvenator of epoxidized soybean oil,epoxidized polybutadiene resin and maleic anhydride can better restore the phase angle plateau region of aged SBS modified asphalt,which demonstrates asphalt component reconciliation and SBS molecular structural repair are simultaneously needed to achieve the optimal rejuvenating effect on aged SBS modified asphalt.(4)In terms of compound rejuvenator that is composed of epoxidized soybean oil,epoxidized polybutadiene resin and maleic anhydride,the optimum curing time is60 min.And the best rejuvenating effect for PAV-aged SBS modified asphalt can be achieved when the content of epoxidized soybean oil,epoxidized polybutadiene resin and maleic anhydride is 8%,2% and 0.1%,respectively.