Physicochemical properties of bitumens modified with bioflux

Abstract

Five laboratory-produced cut-back bitumens with same target viscosity of 600 mm2/s at 60°C were investigated to determine the effect of chemical composition on the rheological properties. Studied cut-back bitumens comprised four bioflux-modified bitumens and one traditional slow-curing cut-back bitumen as a reference. The generic fractions (saturates, aromatics, resins and asphaltenes) of base bitumens (viscosities of about 1500, 3000, 6000 and 37,000 mm2/s at 60°C) were quantified by thin-layer chromatographic method with flame-ionisation detection (IATROSCAN MK-6s) and the rheological properties of the base bitumens and cut-back bitumens were studied with a Physica 301 rheometer. The soft base bitumens (viscosity≤6000 mm2/s at 60°C) and their biofluxed solutions proved to be rheologically complex, which was witnessed by wax crystallisation and melting phenomena observed at temperatures between 10 and 30°C. The harder base bitumens with higher asphaltene content did not exhibit noticeable crystallisation. The low polarity and low molecular weight of the bioflux solvent reduced the stiffnesses of cut-back bitumens remarkably under 30°C. Thus, the composition of cut-back bitumens had a significant effect on the rheology of blends, although the target viscosities at 60°C were the same.