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

Abstract

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.