Thermal storage stability and rheological properties of multi-component styrene-butadiene-styrene composite modified bitumen

Abstract

It has been reported that a novel multi-component styrene-butadienestyrene composite (SBSC) modifier composed of the SBS as the main content and additional components including ethyl-vinyl-acetate (EVA), maleic anhydride grafted with ethyl-vinyl-acetate (MAH-g-EVA), naphthenic oil, and antioxidant can be produced by melt blending. This SBSC modifier can be directly mixed with bitumen and aggregate to prepare bitumen mixture, thus thoroughly addressing inferior thermal storage stability of SBS-modified bitumen. However, it is necessary to explore the efficient utilization of the SBSC modifier due to its inadequate engineering application and poor dispersion when the SBSC modifier was added directly to the bitumen mixture. The objective of this research was to investigate the feasibility of using the SBSC modifier to obtain modified bitumen with acceptable thermal storage stability and other enhanced properties. Modified bitumens (SBSC-modified bitumens with 3, 4, 5, 6, 7 % SBSC modifier content, SBS-modified bitumen with 4.5 % SBS modifier content as the control sample) were prepared. The thermal storage stability of modified bitumen was investigated by the segregation test. Besides, the basic physical properties of modified bitumen were tested, including penetration, softening point, and ductility. The rheological properties were evaluated by temperature sweep test, multiple stress creep recovery (MSCR) test, rotational viscosity (RV) test and bending beam rheometer (BBR) test, respectively. Meanwhile, fluorescence microscopy and Fourier transform infrared (FTIR) spectrometer were also applied to characterize the microproperties of the modified bitumen. Results show that the difference in softening point of SBSC-modified bitumens with modifier contents ranging from 3 % to 7 % is less than 2.5 °C after 72 h of high temperature storage at 163 °C. The softening point and ductility of SBSC-modified bitumen increase considerably with the addition of the SBSC modifier but the decrements of penetration are not significant. Besides, with the increasing addition of the SBSC modifier, complex modulus, average percent recovery, and viscosity of modified bitumen all improve. Meanwhile, phase angle, non-recoverable creep compliance of modified bitumen decrease. The flexural creep stiffness also decreases with the increasing content of the SBS modifier. When the SBS content is the same, the SBSC-modified bitumen gets better thermal storage stability, high and low temperature properties than the SBS-modified bitumen. The microproperties show that the SBSC modifier can be uniformly dispersed in base bitumen and physically mixed with the base bitumen. The SBSC-modified bitumen obtains preferable thermal storage stability. The high and low temperature properties of the bitumen are also enhanced by the addition of the SBSC modifier. Meanwhile, the melt blending method does not restrict the role of the additional components in the SBSC modifier to improve the performance of bitumen. Based on the above findings, it can be considered that the use of SBSC modifier to prepare modified bitumen with enhanced performance is a promising practice. This research may shed light on the application of SBSC modifier to bitumen pavements.