Exploring the recovery of fatigue damage in bituminous mixtures at macro-crack level: the influence of temperature, time, and external loads

Recently, the analysis of the healing capacity of bituminous materials has become an important research topic in pavement engineering. Although many studies have demonstrated the potential of some techniques (e.g. self-healing agents or induced healing) to recover the properties of these materials, there still remain some questions that need to be addressed. One of the most important issues is how to define the optimal moment for inducing healing (at micro or macro-crack levels), along with determining the optimal conditions for using the technique. Accordingly, this paper aims to provide an approach to answer these questions. In this research, several mixtures were tested under various conditions until their fracture, and then healed using a range of healing techniques. Following the healing process, the materials were re-tested and the efficiency of the healing at macro-crack level was assessed. The results indicate that the healing capacity at macro-crack level appears to be sensitive to the service conditions; in general, as the temperature of the healing treatment increases, the rate of recovery increases. Furthermore, it was observed that the recovery potential of conventional binder is higher than modified binders at macro-damage level. Additionally, the presence of external loads during application of the healing treatment could increase the rate of recovery. Nonetheless, it is important to note that the application of heating and/or external force as healing techniques produced low levels of recovery in macro-damaged asphalt materials.