Multi-scale evaluation of adhesion property between warm-mix rejuvenated styrene-butadiene-styrene (SBS) modified asphalt and aggregates: Integrating experiments and molecular dynamics simulations

This study aims to comprehensively evaluate the adhesion properties between warm-mix recycled styrene-butadiene-styrene (SBS) modified asphalt and aggregates. The different types of asphalt materials included virgin (VA), aged (AA), rejuvenated-aged (RA), warm-mix-aged (WA), and warm-mix-rejuvenated-aged (WRA) asphalt binders were used. A multi-scale adhesion characterization approach was employed, namely integrating surface free energy (SFE) theory, binder bond strength (BBS) tests, and molecular dynamics (MD) simulations. Results indicate that long-term aging significantly improves cohesion and adhesion work, attributed to increased polar components. While rejuvenators or warm-mix agents individually reduce these properties, their combined use in WRA leads to the most pronounced decline in both thermodynamic adhesion and macroscopic bond strength. MD simulations further reveal that adhesion is governed mainly by van der Waals energy and is strongest on CaO, followed by MgO and SiO₂. A strong correlation (R²=0.84) was established between SFE-derived adhesion work and BBS-measured strength.