Mixture-based rheological evaluation tool for cracking in asphalt pavements

Cracking is a major distress that limits the durability of asphalt pavements. Various fatigue and fracture-based tests and analyses can be used to assess cracking resistance of asphalt mixtures in order to design more economical and durable mixtures. This mixture cracking resistance is affected by the rheological properties of the asphalt binder, both stiffness and relaxation ability as indicated by measured dynamic modulus and phase angle, respectively. One significant breakthrough involves the use of binder Black space (shear modulus versus phase angle) and the Glover–Rowe (G-R) parameter that is a function of these two rheological properties as an indication of cracking resistance. However, binder characterisation is not adequate to fully represent mixture performance and therefore there is a need for a mixture-based evaluation tool. The objectives of this study were to: (1) investigate the applicability of a representative temperature and frequency combination for mixture-based Black space evaluation; (2) evaluate the ability of mixture Black space to track the effect of aging and rejuvenation (when recycling agents are used with recycled materials); (3) explore the use of a mixture-based G-R parameter (G-Rm) for cracking resistance evaluation and (4) investigate a possible correlation between G-Rm and Flexibility Index (FI) from a semi-circular bending (SCB) test. Test results indicate a reliable temperature–frequency combination for G-Rm, which was sensitive to aging, recycled materials content, binder performance grade and recycling agent dose. Test results also indicate a good correlation between the G-Rm parameter and the FI.