Rheological characteristics and modification mechanism of rock asphalt compound modified binder based on grey relational analysis

Abstract

To address the limitations of conventional asphalt in resisting high-temperature rutting and oxidative aging, a Rock Asphalt Compound additive (RCA) —comprising natural rock asphalt with surface-treated Nano-TiO2—was investigated as a sustainable modifier. This study systematically evaluates the rheological performance and modification mechanism of RCA-modified A-90# asphalt binders with dosages ranging from 0% to 31.6%. The viscoelastic behaviors were characterized using Dynamic Shear Rheometer (DSR), Bending Beam Rheometer (BBR), and Rotational Viscosity (RV) tests, while the chemical interactions were probed via FTIR spectroscopy. Furthermore, Grey Relational Analysis (GRA) was innovatively introduced to quantify the sensitivity of performance indicators to RCA dosage. Results indicate that RCA fundamentally alters the colloidal structure of the binder, acting as a potent stiffening agent. The high-temperature rutting factor (G*/sinδ) increases exponentially with dosage, and the Penetration Index (PI) improves from −1.392 to −0.354, indicating reduced temperature susceptibility. FTIR analysis confirms the modification is primarily a physical blending process, enhanced by the introduction of polar functional groups (S = O, C = O). Crucially, GRA results quantitatively identify that the dominant function of RCA is the enhancement of aging resistance (R = 4.3430), followed by stiffness (R = 3.7567), surpassing its effect on ductility. However, high dosages negatively impact low-temperature relaxation (m-value). Considering the trade-off between the significant gains in anti-aging/rutting performance and the limitations in thermal cracking, an optimal dosage of 21.8% is recommended. At this dosage, the binder achieves a superior rutting factor of 25.5 kPa (64°C) while maintaining an m-value of 0.311 (−12°C), satisfying Superpave specifications.