Study On Performance Identification Index Of Recycled SBS Modified Asphalt Based On Toughness And Tenacity Curve Morphology

SBS modified regeneration is one of the important means to restore the road performance of old asphalt mixture and realize the recycling of resources.The unique viscoelasticity given by SBS modifier is the key to the excellent high temperature and fatigue performance of SBS modified asphalt and its mixture.During the aging process,the degradation of modifier leads to the attenuation of viscoelastic properties,while during the regeneration process of SBS modification,the unique viscoelastic properties are restored.The research can reflect the identification index of viscoelastic property attenuation and recovery of SBS modified asphalt in the aging and regeneration process,which has important theoretical research significance and engineering application value for the evaluation of SBS aging degree and regeneration and recovery effect.In this paper,based on the viscoelastic curve shape,the identification indexes and criteria for the degree of viscoelastic property attenuation and performance recovery of SBS modified asphalt after aging and regeneration were studied.The repeatable rheological test indexes suitable for evaluation of SBS modified asphalt were used to verify the new indexes,and the correlation between the new indexes and rheological indexes and functional group indexes was established.The identification index should reflect the viscoelastic properties of SBS modified asphalt,which has the convenience,high differentiation and universality.By comparing the changes of softening point,elastic recovery,toughness and tenacity and other indexes of SBS modified asphalt caused by aging and regeneration,it is found that the shape changes of viscoelastic test curve are the most significant and the distinction is obvious.Based on the toughness and tenacity curve morphology,the viscous compliance C_sand the ductile deformation rate V_rtwere proposed as the identification indexes to evaluate the regeneration effect of SBS modification.The multiple stress creep recovery test,linear amplitude scan test and their indexes based on rheology are the best test methods and indexes that can reflect the high temperature and fatigue properties of SBS modified asphalt.Grey correlation analysis showed that under various regeneration conditions,the correlation degree of identifiable index and unrecoverable creep compliance J_nr3.2,fatigue life N_f2.5%and N_f5%of rheological index were all about 0.75,which could effectively identify the high temperature and fatigue properties of SBS modified regeneration and had universality.Through the laser scanning confocal microscope and fourier transform infrared spectrometer tests,the aging and growth process of SBS modified asphalt were analyzed qualitatively and quantitatively by using fluorescence image and functional group coefficient.Functional index and rheological index,identification index has good correlation,among them,the olefin functional groups contributed the most to the high temperature and fatigue performance of SBS modification regeneration,and the correlation degree was about 0.79 and0.70,respectively,to identify indicators is biggest,the influence of the correlation is about0.70.The effect of aromatic ring and sulfoxide group is the next,the effect of carbonyl group is the least.Based on the classification standard of medium and high temperature and fatigue performance in AASHTO specification,the classification threshold of high temperature and fatigue performance of identifiable indexes was put forward,which provided the basis for screening new SBS modified asphalt and optimizing the regeneration scheme.In conclusion,the proposed viscous compliance C_sand ductile deformation rate V_rtcan well identify the aging and regeneration properties of SBS modified asphalt based on the toughness and tenacity curve morphology,and have a broad universality,which can be used as the identification index to evaluate the regeneration effect of SBS modified asphalt and guide the concrete recycled pavement engineering.