Accelerated Healing in Asphalt Concrete via Laboratory Microwave Heating

Abstract

Self-healing of asphalt concrete (AC) is highly dependent on temperature, and its healing capacity increases with elevated temperatures. The main objective of this study is to investigate the effect of microwave heating on promotion of self-healing in AC. With this purpose, two types of AC specimens (neat AC without additives and conductive AC containing steel fiber and graphite) were prepared to for use in thermal conductivity, microwave heating speed tests, four-point bending fatigue, and healing tests. In addition, oscillatory frequency sweep tests were carried out to obtain the flow behavior of asphalt binder. Results indicated that AC containing electrically conductive additives had a higher thermal conductivity and microwave heating speed than neat AC. It was also found that the fatigue resistance and healing capacity of conductive AC after microwave heating were higher than that of neat AC. Moreover, there exists a critical temperature (corresponding to near-Newtonian behavior temperature of asphalt binder) above which healing of AC starts and an optimum heating time (temperature) to maximize the healing effect. Finally, it was found that an intermittent heating mode with a cooling process is more effective than the consecutive heating mode to enhance the healing capacity of AC. Based on these findings, it is concluded that self-healing efficiency of AC can be enhanced via microwave heating.