Relationship between microstructure and phase morphology of SBS modified bitumen with processing parameters studied using atomic force microscopy

The aging effects of varying processing parameters, mixing time and shear speed, on the morphology and phase structure of styrene-butadiene-styrene (SBS) modified bitumen were studied used atomic force microscopy (AFM). Both inclusion of SBS and varying processing parameters provide differences in topographic and phase images of the bitumen. The contrast between phases becomes more distinct with increasing mixing time and speed, with the amount of dark phase associated with the asphaltene component of the bitumen also increasing. SBS modification of bitumen results in a decrease in the number of 'bumble-bee' like structures and when combined with varying mixing time produced the longest 'bumble-bee' structures. At the lowest mixing speeds (1000 rpm), the mixing was not effective for the SBS to absorb the bitumen oily components. Longer mixing times, 45 min, clearly altered the blend morphology and resulted in shorter 'bumble-bee' structures. (C) 2020 Elsevier Ltd. All rights reserved.