Development of a hybrid formulation combining copper(II) oxide nanoparticles and carbon fiber for polymer-modified asphalt binders

This study developed a hybrid formulation of copper(II) oxide nanoparticles (nano-CuO) and carbon fiber for a styrene-butadiene-styrene (SBS)-modified asphalt binder. The modifiers were first evaluated separately across physicochemical, rheological, fatigue, and thermal responses to select contents for hybridization. Nano-CuO was added at 2–8 wt% and carbon fiber at 0.1–0.5 wt%. Characterization included X-ray diffraction, Fourier-transform infrared spectroscopy (FTIR), apparent viscosity, continuous high-temperature performance grade, multiple stress creep recovery (MSCR), linear amplitude sweep, and thermal conductivity. A Derringer-Suich desirability analysis integrated these responses to select the additive contents. Nano-CuO increased the continuous high-temperature grade and thermal conductivity but induced FTIR changes consistent with oxidation of the SBS polybutadiene phase, associated with lower percent recovery (%R 3.2 ). Carbon fiber improved thermal conductivity and the MSCR response without measurable changes in the monitored FTIR indices. The analysis selected 4 wt% nano-CuO and 0.1 wt% carbon fiber. Two hybrids combining 4 wt% nano-CuO with 0.1 wt% (H1) or 0.3 wt% (H2) carbon fiber were evaluated. Relative to the nano-CuO base binder (C4), H1 increased thermal conductivity by approximately 23%, with MSCR parameters within test repeatability and RTFOT-aged fatigue factors statistically indistinguishable from C4 in every strain-amplitude band. Among C4, H1 and H2, only H1 showed no detectable loss relative to the reference binder at high strain amplitudes. H2 achieved a larger conductivity increase (42%) but was the only hybrid whose fatigue factors fell significantly below the reference binder at high strain amplitudes. H1 therefore offered the better overall balance and is recommended for subsequent validation.