Evaluating Asphalt Binder Quality: Point and Shape Rheological Parameters for Assessing Intermediate-Temperature Cracking Susceptibility

This study aims to identify point and shape rheological parameters that can effectively differentiate between high- and low-quality asphalt binders, particularly in their resistance to intermediate-temperature cracking, regardless of binder source or formulation changes. Point parameters assess binder hardness, while shape parameters describe the binder’s overall viscoelastic behavior. A total of 20 asphalt binders were tested, comprising 17 binders from various suppliers and three low-quality binders. Two of the low-quality binders were artificially manufactured, while one was obtained from a supplier. To validate the selected parameters, a Superpave 12.5 mm asphalt mixture was designed using seven of the binders, including the three lower-quality ones. The mixtures’ susceptibility to intermediate-temperature cracking was evaluated using the indirect tensile asphalt cracking test as per ASTM D8225-19. Higher cracking tolerance index (CT Index ) values indicate better resistance to cracking. The CT Index results were compared with binder rankings based on the identified point and shape parameters to verify their effectiveness. Glover–Rowe values at 15°C and 10 rad/s and the phase angle at a specific modulus of 10 MPa (δ 10MPa ) were found to be effective in distinguishing poor-quality binders. A simplified, rapid test method using a dynamic shear rheometer was developed to measure these parameters, showing a strong correlation with traditional master curve analysis. This approach offers a practical tool for routine quality control during production, ensuring consistent binder performance and improved resistance to intermediate-temperature cracking in asphalt mixtures.