Development And Investigation Of Rejuvenator For SBS Modified Asphalt Based On Molecular Structure Repair

Styrene-butadiene-styrene copolymer(SBS)modified asphalt pavement would undergo aging and degradation during service,leading to a variety of road damages.Therefore,asphalt pavements need to be recapped or even repaved,which would produce a large number of waste SBS modified asphalt mixtures.The application of asphalt recycling technology can not only recycle the aggregate and asphalt contained in RAP(Reclaimed asphalt pavement)materials,reducing the engineering cost,but also prevent environmental pollutions.In order to realize effective regeneration and utilization of aged SBS modified asphalt mixtures,the aging mechanism of SBS modified asphalt should be investigated.At present,in most of the aging methods concerning SBS modified asphalt,the composite of SBS and asphalt matrix or single SBS modifier is often regarded as research object.Few research methods have been conducted on SBS modifiers that are extracted from SBS modified asphalt with different aging degree.Significantly,the influence of asphalt matrix on aging degree evaluation of SBS modifier can be eliminated by this method.According to literatures,the current rejuvenators for SBS modified asphalt still aim at physical rejuvenation of base asphalt,and take no account of restoration of aged SBS in asphalt,causing that the properties of aged SBS modified asphalt cannot be recovered comprehensively.This paper aims at investigating aging behaviors on extracted SBS modifier separated from SBSmodified asphalt as a whole,which can eliminate the influence of base asphalt.Based on the SBS extraction system,the relationship between SBS and modified asphalt in terms of aging behaviors would be established.Moreover,a novel catalytic-reactive rejuvenator would be developed to repair damaged network structure of SBS,as a result,the properties of aged SBS-modified asphalt can be recovered comprehensively.The main research conclusions of this paper are as follows:Indoor simulated aging of SBS modified asphalt was conducted and the physical and rheological properties and microstructure of SBS modified asphalt before and after aging were evaluated.It was found that the degradation of SBS during aging affected the physical and rheological properties of modified asphalt.Based on the SBS extraction system,the influence of the matrix asphalt can be eliminated.It can be observed that long-term thermal oxygen aging had the most serious effect on the oxidation of asphalt and the degradation of polybutadiene,while ultraviolet aging had the most significant effect on the degradation of SBS molecules.In addition,the methyl index(MI)can be used as an index to evaluate the aging level of SBS modifier.Based on the aging mechanism of SBS copolymer and the products after aging,this paper developed a novel reactive rejuvenator containing epoxidized soybean oil(ESO)and triphenyl phosphine(TPP)that can be able to repair SBS network structure.According to physical and rheological tests,it was determined that the optimal mixing time for rejuvenation was 30 minutes and the optimal dosage of the catalyst was 1%.In addition,in order to comprehensively recover the properties of the aged SBS modified asphalt,this paper further developed a type of catalytic-reactive compounded rejuvenator.Through physical and rheological tests,the optimal compounding ratio of the catalytic-reactive compounded rejuvenator was determined as Aromatic oil(AO): ESO(TPP)=50%:50%.Microstructure testing technology was applied to analyze the changes of functional groups in rejuvenated asphalt binders and molecular weight of SBS.It was demonstrated that the product of polymerization of epoxy group and hydroxyl group(ether bond absorption peak)in the asphalt rejuvenated by reactive rejuvenator in Fourier-transform infrared spectroscopy test,and the increased SBS molecular peak in the asphalt rejuvenated by catalytic-reactive compounded rejuvenator in Gel permeation chromatography test further confirmed the rejuvenation and repair abilities and the mechanism of reactive rejuvenator.