Nonlinear rheological performance characterization of styrene-butadiene-styrene and crumb rubber composite modified bitumen using large amplitude oscillatory shear tests.

The crumb rubber (CR) recycled from waste tires can improve the mechanical properties of bitumen effectively. For the widely used modified bitumen today, it could work in nonlinear regime in many occasions. This study focuses on the nonlinear properties of styrene-butadiene-styrene (SBS) and CR composite modified bitumen (CMB) by analyzing the results of stress-controlled large amplitude oscillatory shear (LAOS) tests. The results show that the nonlinearity of SBS/CR CMB was significant under low load frequency, high temperature and high stress level. Lissajous curves at these conditions are distorted obviously due to the presence of higher-order harmonics. By analyzing the geometry parameters of Lissajous curves, it can be concluded that the incorporation of CR has a positive influence on the nonlinear properties of bitumen, which effectively improve the stress bearing capacity of bitumen. However, the high-order harmonic analysis indicates that improving the CR content simply does not always improve the performance of bitumen. Besides, the nonlinearity of SBS/CR CMB with lower CR content is similar to that of SBS modified bitumen through the value of I 3 / I 1 and intrinsic nonlinear parameter Q, thus there are two critical CR contents for the prospect of modifying the nonlinearity of bitumen. [ABSTRACT FROM AUTHOR]