Rheological response characteristics of polymer modified asphalt microstructure

Key words:  modified asphalt  phase structure  rheological response  microscopy

Abstract:

The microscopic phase states of different SBS modified asphalts were studied by fluorescence microscopy. Then, the viscoelastic parameters of SBS modified asphalts with different phase structures were determined and rheological curves were constructed. Lastly, the relationship between the changes of rheological curves and phase structures was deeply analyzed. It is found that the microscopic phase of SBS modified bitumen shows three phase transitions with the increase of SBS from 3% to 7%. In other words, SBS as dispersed phase evolves to SBS/asphalt bi-continuous phase and then to asphalt as dispersed phase. The dependence curves of storage modulus with frequency for SBS modified asphalt can better reflect the three microscopic phase structures. “Platform area” and the curve slope in low-frequency area α>2 means that the SBS phase is dispersed. The low frequency region of the curve is characterized by power rate and slope α ≤1, which indicates that SBS microscopically forms a network structure. The temperature dependence curves of storage modulus can also distinguish the three microscopic phase states, while the Han plot and Black diagrams have no obvious response characteristics for the three microscopic phase states.