Study on the construction of disulfide bonds in modified asphalt: Enhancing the performance of LLDPE and SBS composite asphalt

Due to increasing road traffic and the frequency of complex climatic conditions, issues such as low-temperature cracking and high-temperature rutting in asphalt pavements have become more severe. Therefore, it is imperative to explore effective methods to enhance pavement performance and extend service life of asphalt pavements. In this research, the reversible characteristics of dynamic disulfide bonds were introduced into styrene-butadiene-styrene (SBS) and linear low-density polyethylene (LLDPE), respectively, to produce modified polymers SBS-g-HD and PE-g-HD. Modified asphalt samples were prepared by incorporating the two modifiers at different ratios to systematically investigate the influence of modifier type and content on asphalt properties. The conventional physical properties of the asphalt, including penetration, ductility, softening point, and viscosity were characterized. In addition, the rheological behavior and thermal stability of the binders were evaluated through thermogravimetric analysis (TGA) tests, dynamic shear rheometry (DSR) tests, and bending beam rheometer (BBR) tests. Compared to BA, the modified binder exhibited reduced penetration and ductility, but increased softening point and viscosity. Among the modifiers, PE-g-HD enhanced high-temperature performance, while SBS-g-HD improved low-temperature properties. Their combination resulted in balanced performance over a wide temperature range. At 135 °C, the viscosity of PSHA-3 increased by 1.152 Pa s and 0.46 Pa s compared with that of SHA and PHA, respectively. At −12 °C, PSHA-2 exhibited a 32.2% decrease in S-value compared to PHA. Meanwhile, the improved compatibility of SBS-g-HD and PE-g-HD with asphalt was studied, with the mechanism investigated by molecular dynamics (MD) simulation.