Physical, Rheological, and Anti-Ultraviolet Aging Performance of Layered Double Hydroxides + Styrene Block Copolymer-Modified Asphalt Binders

Abstract

To determine the preparation parameters of layered double hydroxides (LDHs) + styrene butadiene styrene block copolymer (SBS)-modified asphalt binders (MABs) in engineering applications and identify the structure of LDHs used in asphalt modification, this paper investigated the physical, rheological, and UV aging resistance of LDHs + SBS MABs under various preparation parameters. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and an ultraviolet-visible spectrophotometer (UV-vis) were used to characterize the structure and UV resistance of LDHs and D-LDHs (dissolving from LDHs + SBS MABs). The mechanical properties of LDHs + SBS MABs were studied based on penetration, ductility, softening point, and rotational viscosity tests. The rheological performance and UV aging resistance of LDHs + SBS MABs were assessed using the bending beam rheometer (BBR) test, direct tensile test (DTT), dynamic shear rheometer (DSR) test, and FTIR. The results demonstrated that the crystal and chemical structures of LDHs remain unchanged before and after use in asphalt modification. The optimal preparation parameters of LDHs + SBS MABs were as follows: a preparation temperature of 170 °C, a shearing time of 60 min, and a shearing rate of 4000 r/min. The high-temperature performance of LDHs + SBS MABs improved significantly with LDHs added, and the low-temperature performance slightly decreased. The viscosity of LDHs + SBS MABs with 4 wt% LDHs at 135 °C was 1.920 Pa·s, which was 47.4% higher than that of SBS MABs. The DTT results indicated that SBS MABs have the highest fracture energy (FE) value of 4873 J/m2, showing the best low-temperature cracking resistance. In comparison, the FE values of MABs doped with 3 wt% and 4 wt% LDHs are 4518 J/m2 and 4248 J/m2, respectively, just 7.3% and 12.8% lower than that of ABs without LDHs. The complex modulus aging index (CMAI) of MABs doped with 4% LDHs is 14.3%, which is 15.9% lower than that of SBS MABs, indicating that the anti-ultraviolet aging performance of LDHs + SBS MABs has been improved. FTIR analysis demonstrated that the relative content of C=O (RCC) and S=O (RCS) of LDHs + SBS MABs decreased drastically compared with SBS MABs, indicating that the UV aging resistance of LDHs + SBS MABs was largely enhanced. Furthermore, the segregation test result of 3wt% LDHs + SBS-modified asphalt is 0.3 °C, showing the best compatibility with asphalt.