Investigating the link between the chemical composition of bitumen and the kinetics of the styrene-butadiene-styrene swelling process

Changes in bitumen production processes and crude sources can affect the chemical composition of the bitumen and the quality of the final polymer-modified binder products. As the rheological properties of the final products are of great importance, this study utilises systemic rheology along with functional indices determined from Fourier transform infrared spectroscopy and bitumen fractions to find a link between the chemical composition of bitumen and the kinetics of the polymer swelling process. The results show that the substitution mode of aromatic rings and the colloidal index significantly correlate with swelling parameters. The presence of weakly condensed aromatic rings reduced the swelling rate and elongated the swelling extent. Furthermore, a lower colloidal index resulted in a lower modification degree. It is possible to conclude that the outcomes of chemical studies conducted on the base bitumen are related to the swelling kinetics of styrene–butadiene-styrene-modified binders.