A 2D image analysis framework for quantifying interfacial and synergistic homogenization in virgin-RAP asphalt blends

Characterization of blending condition between the aged asphalt on reclaimed asphalt pavement (RAP) and the virgin asphalt are critical for advancing asphalt pavement recycling technologies. This study proposes a novel quantitative methodology for assessing the homogenization rates of virgin-RAP asphalt blends through 2D image analysis. Pre- and post-blending RAP asphalt-aggregate morphologies were precisely identified via field emission scanning electron microscopy-backscattered electron (FESEM-BSE) combined with energy-dispersive X-ray spectroscopy (EDS) elemental mapping, and the synergistic homogenization rate and the interfacial homogenization rate were modeled mathematically. 20% TiO 2 was identified as the optimal tracer content ( Δa variation ratio = 0.007, G ⁎ variation ratio = 0.037) due to enhanced EDS detectability and minimal rheological impact. Atomic force microscopy (AFM) analysis revealed a strong positive linear correlation between Derjaguin-Muller-Toporov (DMT) modulus and DSR-derived G ⁎ , and significant negative correlations between G ⁎ and adhesion force, and between G ⁎ and energy dissipation. The RAP asphalt content synergistically influenced microstructural evolution and nanomechanical properties of virgin-RAP asphalt blends. Elevated RAP preheating temperature (200°C) maximized the synergistic homogenization rate (0.798), while extended residence time optimized interfacial homogenization (0.521); mixing time showed comparatively minor influence. • Developed a novel 2D image-based homogenization rate characterization. • Determined optimal TiO₂ tracer content at 20%. • Revealed strong AFM-DSR correlation (R²>0.95). • RAP preheating temperature dominates synergistic homogenization. • Incorporating residence time maximizes interfacial homogenization.