Digital image correlation-based investigation of self-healing properties of ferrite-filled open-graded friction course asphalt mixture

Abstract

Asphalt-based composites can self-heal, and this ability can be enhanced with induction heating and microwave heating. However, few methods are available to quantitatively analyze and monitor crack propagation in a composite before and after healing to evaluate the efficiency of self-healing. Digital image correlation (DIC) techniques, which are used herein, are widely applied for this purpose because they can directly measure the displacement field and strain field of an object under load. We conducted a three-point bending fatigue test and a three-point bending fracture test to study the influences of microwave heating time and healing time on the self-healing of asphalt-based composites with 5% ferrite and without ferrite. The influence of ferrite on the strain development process of the specimens was discussed based on the indexes of crack initiation time, crack propagation rate, and horizontal strain. The addition of ferrite can significantly delay secondary cracking and decrease the crack propagation rate of an open-graded friction course (OGFC) asphalt mixture. Based on DIC observations, the optimal microwave heating time for the OGFC asphalt mixture with 5% ferrite is 80 s. Meanwhile, the longer the healing time, the stronger is the healing effect, but the influence of healing time is weaker than that of heating time. Moreover, based on the change in the horizontal strain during crack development, it can be concluded that the addition of ferrite significantly improves the healing effect, in addition to improving the mixture toughness.