Comparative Evaluation of Short-Term PAV and Conventional Short-Term Aging Protocols for Thermoplastic-Modified Asphalt Binders

Standard laboratory protocols for simulating short-term asphalt aging, including the Thin-Film Oven Test (TFOT) and Rolling Thin-Film Oven Test (RTFOT), are widely adopted but frequently lack sensitivity to the distinct thermo-oxidative kinetics of high-viscosity and polymer-modified systems. This study evaluates a severity-graded aging matrix incorporating the Pressure Aging Vessel (PAV) at variable durations (2, 5, and 10 h at 163 °C/2.1 MPa) as a potential alternative to conventional thin-film methods. Three binder systems BA-70 (PG 64-22), SBS-modified, and compatibilized functional thermoplastic (CFT)-modified asphalt were subjected to TFOT, RTFOT, and PAV variants. Comprehensive rheological characterization (DSR frequency/temperature sweeps, rutting parameter, MSCR) and SARA fractionation were employed to quantify oxidative stiffening, permanent deformation resistance, and compositional evolution. An Aging Severity Index (ASI) was developed to normalize multi-parameter responses and establish quantitative protocol equivalence thresholds. BA and SBS-modified binders exhibited pronounced protocol-dependent stiffening, with PAV-5h vs. RTFOT ASI gaps of 30.0% and 33.0%, respectively, confirming distinct aging severity under the tested conditions. Conversely, the CFT-modified binder demonstrated a compressed aging signature, maintaining stable complex modulus, minimal non-recoverable compliance escalation, and near-complete elastic recovery across all protocols. The ASI gap between PAV-5h and RTFOT for CFT was 6.0%, falling within the pre-defined ≤7% equivalence threshold established from combined rheological test uncertainty, specification-aligned engineering tolerance, and empirical gap clustering. SARA analysis corroborated these findings, showing CFT retained higher aromatic/resin fractions while limiting asphaltene accumulation compared to BA-70 and SBS. Importantly, the observed interchangeability between PAV-5h and RTFOT is strictly limited to the specific CFT-modified binder formulation tested under laboratory conditions. Broader specification adoption requires targeted validation across diverse modifier chemistries, dosages, and field-aged binders before generalization.