Swelling behavior and mechanism of SBS in high viscoelastic-modified bitumen using fluorescence analysis

High viscoelastic-modified bitumen (HVE-MB) contains a variety of modifiers, with SBS being the primary one, and its swelling state has a significant impact on the viscoelastic properties of bitumen. Based on fluorescence microscopy technology, the phase distribution and swelling state of SBS in HVE-MB under different shear times were studied, and the swelling behavior of SBS in HVE-MB was quantitatively characterized. The results can be used to reveal the swelling mechanism of the SBS modifier in HVE-MB. In addition, the physical properties, rheological properties, and viscoelasticity of HVE-MB were investigated with the physical test, rheological test, dynamic viscosity, and elastic recovery tests. The results show that shear time had a significant impact on the physical properties of HVE-MB, and the rheological properties exhibited a similar change trend. The swollen and developed SBS particles in HVE-MB were quantitatively characterized, indicating a 96% reduction in the number of SBS modifier particles. The ratio of SBS modifier particles to the axial length increased by 16%with particle size is increased from 4-7 um to 8-22 um. The shape of the particles transitioned from circular to elliptical and elongated forms. The area ratio of the SBS particles to bitumen increased by 14.9%, and the average area of SBS particles grew by 1948%. these changes contributes to a 277% increase in the dynamic viscosity of the bitumen. These changes occur because, at the microscopic level, polymers like SBS absorb light components from the bitumen after blending, causing the polymers to swell and form a two-phase structure where the swollen polymer phase coexists with the bitumen phase. The results can be used to optimize the heating temperature and shearing time for the industrial production of HVE-MB, providing reference and theoretical support for understanding the modification mechanism and performance regulation of HVE-MB.