Factors Influencing the Low-Temperature Properties of Styrene-Butadiene-Styrene Modified Asphalt Based on Orthogonal Tests

Styrene-butadiene-styrene (SBS) is widely used in asphalt modification to obtain superior high-temperature performance. Nevertheless, studies on the low-temperature properties of SBS-modified asphalt are not satisfactory. Orthogonal tests are valid in analysing the results. In this paper, the main factors (SBS content, sulfur content, and the addition of rubber processing oil) for improving the low-temperature performance of SBS-modified asphalt were analyzed base on the orthogonal tests. Firstly, the frequency sweep test, bending beam rheometer (BBR) test, and force-ductility test were conducted to evaluate the low-temperature properties of SBS-modified asphalt. Investigation of low-temperature parameters obtained through these tests was conducted base on the orthogonal analysis method. The G-R parameter was abandoned in the analysis of the orthogonal method for the result that the increase of SBS content was negative to the low-temperature properties by the Glover-Rowe (G-R) parameter, which were contrary to the results of BBR and force-ductility tests. Moreover, the other parameters (ΔTc and toughness) sorted according to the orthogonal analysis method indicated the effect on low-temperature performance of the SBS-modified asphalt as SBS content > rubber processing oil > sulfur. As shown above that both SBS and rubber processing oil play a critical role in improving the low-temperature properties of SBS-modified asphalt, for SBS could resist the generation and subsequent propagation of cracks while the rubber processing oil could supplement the maltene loss

Rheological and chemical indices to characterize long-term oxidative aging of SBS/rubber composite-modified asphalt binders

Oxidative aging of asphalt binders seriously affects the durability of asphalt pavements and causes early damage. Hence, appropriate indices that could track the extent of asphalt binder aging are of great importance to the material selection, design, and maintenance of asphalt pavement. This paper aims to select the applicable rheological and chemical indices to characterize oxidative aging degrees of polymer-modified asphalt binders. Styrene–butadiene–styrene (SBS)-modified asphalt and two kinds of SBS/crumb rubber compound-modified asphalt were subjected to a rolling thin-film oven (RTFO) test and 20 h, 40 h, and 60 h pressure aging vessel (PAV) tests. Various rheological experiments at different temperature ranges were applied to obtain rheological indices, including complex shear modulus (|G*|), G–R parameter, and J′ (derivative of creep compliance). A range of chemical indices were determined by Fourier transform infrared spectroscopy (FTIR). The results indicate that the carbonyl index is strongly correlated with PAV aging time. |G*| at 52°C and J′ values at −18°C are the two most promising rheological indices to track the oxidative aging of asphalt binders and relate well to the chemical changes induced by PAV aging. In addition, the G–R parameter is problematic in some instances when used as the rheological index because its accuracy depends on the precise fitting of master curves