Binder Source Matters: A Simplified DSR Approach for Identifying Performance Variability at Intermediate and Low Temperatures

This study validated two rheological parameters, the Glover–Rowe (G–R) parameter at 15°C and 10 rad/s and the phase angle δ at a complex modulus G * of 10 MPa δ 10MPa , as tandem indicators of asphalt binder quality with respect to intermediate-temperature cracking susceptibility. Seven binders were evaluated: four good-quality and three poor-quality. A Superpave 12.5 mm dense-graded mixture was prepared with each binder and tested using the Indirect Tensile Asphalt Cracking Test, Texas Overlay, dynamic modulus, and cyclic fatigue tests. Across all tests, G–R and δ 10MPa together consistently differentiated good from poor-quality binders, validating their combined use as a reliable cracking resistance indicator. This study also extended a simplified Dynamic Shear Rheometer (DSR) protocol, originally developed for intermediate-temperature grading, to low temperatures as a practical alternative to the Bending Beam Rheometer (BBR). BBR stiffness ( S = 300 MPa) and m -value (0.300) thresholds were converted into equivalent DSR values ( G * ≈ 111 MPa and δ ≈ 27.0°) in the high-stiffness range most critical to thermal cracking. Using time–temperature superposition, the BBR loading frequency (0.0167 rad/s) was shifted to 10 rad/s in the DSR, corresponding to an 18°C warmer test temperature while maintaining equivalent rheological behavior. For example, a binder tested at –18°C in the BBR (PGXX-28) could be evaluated at 0°C in the DSR. Integrating these tandem parameters with the simplified DSR method into Balanced Mix Design and quality assurance can improve binder selection and reduce cracking, particularly when binder sources or formulations change without altering the performance grade.