A model for the quantitative relationship between temperature and microstructure of Styrene–Butadiene–Styrene modified asphalt

• Coefficient of variation was used as a new quantitative index to feature the distribution of SBS polymer in virgin asphalt.
• The microstructure index of SBS modified asphalt shows an exponential relationship with temperature.
• Temperature sensitivity of SBS modified asphalt with different content of SBS can be expressed by a universal model.

This paper presents a new method to characterize the change of microstructure of Styrene–Butadiene–Styrene (SBS) modified asphalt when temperature changes. MATLAB was employed to process microscopic images and to extract feature index of distribution of polymer modifier under different temperature. The coefficient of standard deviation Vσ was appointed as the feature index. By non-linear fitting, the relationship between Vσ of 3.5% SBS modified asphalt and temperature was proved to be in accordance with an exponential equation. The equation shows that when temperature drops, the feature index Vσ increases. The variation tendency of Vσ means congregation happens in SBS with dropping of temperature, leading to its poorer distribution homogeneity. Furthermore, the absolute value of variation rate of Vσ increases with the drop of temperature, which means the congregation rate of SBS becomes greater under lower temperature. In the last part of this paper, a universal model was put forward after analyzing modified asphalt with different SBS contents. This study lays a foundation for new methods to evaluate the temperature characteristics of SBS modified asphalt.