Influence of moisture conditioning on healing of asphalt binders

The self-healing property of asphalt binder in the asphalt concrete has been reported in recent years. Healing is an important property of asphalt binder as it helps to recover the fatigue damage during rest period. However, the effect of moisture conditioning on asphalt binder healing has not been studied yet. In this study, Moisture Induced Sensitivity Test (MIST) is used to moisture-condition the binders and then tested using a Fourier Transform Infrared (FTIR) and Dynamic Shear Rheometer (DSR) to evaluate the chemical and healing properties respectively. Also, cohesion properties of the binder are calculated from the tack test using DSR. FTIR results show that water is absorbed in the asphalt binder due to the moisture conditioning. Additionally, results show that the healing rate of asphalt binder decreases due to moisture conditioning. A healing model is developed to separate the total healing into instantaneous and long-term healings. The instantaneous healing is the instant healing that occurs just after the loading is removed. Moisture conditioning decreases the amount of instant healing by reducing the cohesion or energy of separation of the binder. The long-term healing occurs only if there is a very long rest period and depends on the activation energy (or diffusion rate). Results show that moisture conditioning reduces the long-term healing rate by increasing the required activation energy for diffusion. Therefore, the overall healing of fatigue damage reduces due to moisture conditioning of the asphalt binder.