Formulation optimization of a novel amine-based composite anti-stripping agent: From interfacial adhesion to rheological performance

To enhance asphalt-aggregate interfacial adhesion and moisture resistance, this study designed a novel amine-based composite anti-stripping agent (ASA) composed of sodium dodecyl benzene sulfonate (SDBS) and polyamide resin (PA). HY70 and HY90 were used as the base asphalt. The SDBS:PA ratio was optimized through the boiling tests and spectrophotometric colorimetry, and the preliminary recommended dosage was further determined by considering physical properties and workability. The results identified a recommended SDBS:PA ratio of 20:80 and a proposed dosage of 0.4 wt%. Multi-scale microstructural characterization was performed using Fourier transform infrared spectroscopy (FTIR), fluorescence microscopy (FM), and two dimensional ¹H–¹³C heteronuclear single-quantum correlation (HSQC) spectroscopy. Rheological performance was further quantified by dynamic shear rheometer (DSR) temperature sweep and multiple stress creep recovery (MSCR) tests to evaluate high-temperature rutting resistance, linear amplitude sweep (LAS) tests to evaluate intermediate-temperature fatigue resistance, and bending beam rheometer (BBR) to characterize low-temperature cracking resistance. The microstructural characterization results indicated an increase in potential amide-related polar groups and a uniformly dispersed ASA fluorescent phase in the asphalt binder. Rheological tests showed that ASA markedly improved high-temperature rutting resistance, as evidenced by enhanced MSCR responses with higher percent recovery ( 𝑅 ) and lower non-recoverable creep compliance ( 𝐽 𝑛 𝑟 ). ASA also substantially improved intermediate-temperature fatigue resistance; the fatigue life ( 𝑁 𝑓 ) at 5% strain level increased by about 70% when the dosage was increased from 0.3 to 0.4 wt%. However, its improvement in low-temperature cracking resistance was limited, with the low-temperature critical temperature ( 𝑇 𝐿 𝑐 ) decreased slightly by about 2.0–4.0% for HY70 and 1.5–3.5% for HY90. Overall, this study identified a recommended ASA formulation and dosage and provided multi-scale mechanistic evidence for designing durable modified asphalt with improved interfacial adhesion, and improved high- and intermediate-temperature rheological performance.