Suhua Chen

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 (ΔT_c 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.

To further investigate the self‐healing mechanism of microcapsules and exclude the interference of capsule‐wall materials, a bi‐plate test and a molecular model of asphalt and capsule‐core materials were established using dynamic shear rheometer (DSR) and molecular dynamic (MD) simulation. Firstly, the models of asphalt‐rejuvenator‐asphalt and asphalt‐epoxy resin‐asphalt were established to simulate the interface of asphalt and capsule‐core materials. The cross‐linking between poxy resin and curing agent, and tensile tests were then simulated through Perl scripts. Finally, the bi‐plate DSR test was applied to reveal the different action mechanisms between core materials and asphalt materials. The results showed that the cohesive energy of the epoxy resin and asphalt is greater than that of the rejuvenator at the same simulation time. Meanwhile, the maximum stresses generated after stretching for the two models were 69.9 and 34.68 MPa, respectively. The healing indexes HI₁ and HI₂ have a sound linear correlation with the maintenance time. The HI₁ value of the epoxy resin is greater than that of the rejuvenator, and the maximum value exceeds 1. This implies that the capsule core of epoxy resin can recover the strength of damaged asphalt in a short time. Epoxy resin should be considered for asphalt cracks caused by heavy‐load shear.