Abstract
The aim of this work is to determine the influence of the bitumen chemistry on the rheological performance of bitumen and polymer modified bitumen (PmB), as well as the polymer distribution and storage stability. Six different bitumens and their 5 wt.% SBS mixtures are considered in this work. The bitumen composition was determined by SARA fractioning, which was then correlated with the glass transition temperature, complex modulus |G*|, and phase angle, which were obtained by parallel-plate dynamic shear rheology in the temperature range of −25 to 65 °C. The polymer distribution, which was derived from fluorescence microscopy images and the storage stability (determined by tube test) also correlated with the SARA fractions. It was found that the saturates decrease |G*| and T and increase the phase angle in crude bitumen, while the asphaltenes increase |G*| and the phase angle. For PmB, the amount of swelling was determined by the saturate content of bitumen. The glass transition temperature of PmBs increases for low saturate and decreases for high saturate contents. |G*| and the phase angle of PmBs correlates with the saturate content, with a varying influence depending on a high or low saturate content and the temperature range due to saturate depletion in the bitumen-rich phase and the varying vol% polymer-rich phase. The aromatic and resin fractions show no correlation in the considered bitumens and PmBs.
Highlights
Published: 8 March 2021Bitumen is readily available as a by-product of the crude oil refining process
It is common to refer to the SARA fractions when talking about the chemistry of the bitumen composition
The glass transition temperature shows a reasonable correlation with the saturate content and no correlation for the remaining fractions of the considered bitumens
Summary
Bitumen is readily available as a by-product of the crude oil refining process Since it exhibits convenient mechanical properties, it is widely used as a binder material for paving and sealing applications. It is common to refer to the SARA fractions when talking about the chemistry of the bitumen composition. These fractions represent classes of compounds with similar physicochemical properties such as solubility, aromaticity, molecular weight, and polarity [1,2,3]. Weigel et al used principal component regression to successfully correlate the bitumen composition and the average molecular weights with the softening point, penetration index, complex modulus |G*|, and phase angle [7]. To improve the mechanical and aging related properties, bitumen is often modified with polymers [2,3]
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