Impact of cross-linked network derived from PPA and HRBA on recovery properties and nanomechanics of SBS-modified asphalt

To characterise the altered deformation recovery properties of SBS-modified asphalt induced by the ester-based elastic network of polyphosphoric acid (PPA) and hydroxyl-rich bioasphalt (HRBA), and advance the elastic response evaluation system for high-viscoelasticity modified asphalt, a repeated creep and recovery test (RCRT) was conducted to assess the asphalt's elastic response after multiple loading-unloading cycles. Subsequently, the Burgers model characterised strain composition during the creep stage, while the ExpAssoc model quantified the rate of change in deformation recovery speed during the recovery stage. Additionally, atomic force microscopy (AFM) performed a nanoscale elastic modulus sweep to evaluate the impact of the ester-based elastic network on asphalt nanomechanical properties. Results show both models closely fit all asphalt deformation curves (all R2 > 0.99). Composite-modified asphalt had significantly higher delayed elasticity than SBS-only asphalt; although its rapid deformation recovery decreased, the improved delayed elasticity partially offset this disadvantage. Compared to SBS-only asphalt, composite-modified asphalt required a longer recovery time, but had a higher recovery speed change rate in the late recovery stage. AFM results confirmed that EBEN increased the average elastic modulus by 7.36% (±0.47%) even with 37.5% less SBS.