Study On The Phase State And Aging Of SBS Modified Asphalt

A new method for determining the phase morphology of modified asphalt was found by property analysis,which has settled the unitarily problem of method for determing the phase mophology.The phase behavior of modified asphalt with different morphology was explored by using thermodynamics measures and dynamic mechanics method.Also,the aging resistance of those SBS chemical modified asphalt was detected by conventional test and rheological properties test.The results showed that the phase state of SBS modified asphalt can be devided into three phase morphology:polymer phase with particle shape,network-closer shape and long strips shape when the SBS content is among 3wt%and 8wt%.Phase revolution occurred when the SBS content change.Soft point can be the key indicator and penetration is served as auxiliary index to qualitatively determine the phase state of SBS modified asphalt when conventional test is regarded as the only judge foundation for phase state.A sudden change in soft point and penetration means,in a general sense,that the SBS modified asphalt has the polymer phase with long strips shape.The stable region of the penetration curve with high value and the soft point curve with low value represent the polymer phase with particle shape.On the contrary,the curves in opposite case stand for the polymer phase with network-closer shape.The rheological properties can better characterize the phase state compared with conventional properties.The frequency sweep curve and temperature sweep curve of G?and?change rapidly when the SBS modified asphalt is polymer phase with particle shape.Meanwhile,?is close to90°in areas of elevated temperatures.For the other two phase state,the frequency sweep curve and temperature sweep curve of G?are relatively stable in the end area of low frequency and high temperature.The curves of?are almost stable in entire area and there are platform region with the value of?well below 90°.By analyzing the phase transition as well as activation energy in low and high temperature,it was known that the SBS modified asphalt with particle shape has the best low temperature performance and the ones with long strips shape have the worst low temperature performance.From low to high degree of temperature sensitivity are polymer phase with particle shape,long strips shape and network-closer shape in low temperature.Compared with the modified asphalt with particle shape,the SBS modified asphalt with other two phase states shows lower temperature sensitivity in high temperature.The phase separation occurs at low temperature and the phase separation mechanism is the liquid separation mechanism for the SBS modified asphalt with particle shape.While the SBS modified asphalt with other two phase states shows the viscoelastic phase separation features and the phase separation behavior occurs at higher temperature.Compared with the mechanical blending modified asphalt,the phase-transition concentration of sulfur crosslinked modified asphalt was lower when the crosslinker content is high.The softening point increment,residual needle penetration ratio,delay ductility and aging index which represent the aging degree indicated that the modified asphalt with network-closer shape had the higher aging degree than the modified asphalt with particle shape.Accordingly,the former one showed the worse aging resistance performance.In terms of crosslinked modified asphalt with network-closer shape and particle shape,it was found by conventional property test that the former one shows better performance in high temperature performance.The performance degredation in low temperature was obvious after aging,and the former one showed worse low temperature performance than the later one after aging.The aging degree of the crosslinked modified asphalt with particle shape growed approximately linearly.While,the aging degree of crosslinked modified asphalt with network-closer shape increased rapidly before the aging stage of PAV5h,and the increasing rate slowed down in later aging stage.It was also found by rheological test that the two had the close value in G~*,which indicated their close anti-shearing properties.The crosslinked modified asphalt with the network-closer shape showed the higher content of plastic components.