Direct Characterization of Aging Diffusion in Asphalt Mixtures Using Micro-Indentation and Relaxation (MIR)

This study serves as proof of concept for using mixture micro indentation and relaxation (MIR) and possible means of capturing mastic rheological properties in place without binder extraction and recovery. This is achieved via analysis of stress relaxation behavior of samples under constant indentation depth on laboratory fabricated mixture samples. For laboratory compacted samples, indentation is applied on mastic within the mix in the radial direction to explore the aging gradient. The results show significant difference in stiffness of mastic depending on location from the surface. Air content in the mix also appears to be a key factor influencing aging diffusion. The results prove the ability of this testing approach to capture rheological properties of asphalt binders within the mix directly. Testing mastic samples in the laboratory using dynamic shear rheometer (DSR) was conducted to validate the results obtained from the mixture samples. The significant contribution of this study is that it provides direct testing of the material rather than rely on chemical extraction and recovery.