Improved microwave heating uniformity and self-healing properties of steel slag asphalt containing ferrite filler

As a preventive maintenance approach, microwave self-healing is an effective method to repair small pavement cracks at early stage and reduce maintenance costs. However, the difference in microwave absorption ability of asphalt pavement engenders the common problem of uneven heating. This study aims to evaluate the feasibility of applying ferrite to replace partial limestone filler in order to enhance the microwave heating uniformity and self-healing properties of steel slag asphalt mixtures. The morphological features and microwave absorption properties of ferrite were firstly characterized. The addition of ferrite content was estimated via rheological tests including Bending Beam Rheometer and Dynamic Shear Rheometer. Finally, the semi-circular bending and thermal analysis tests were performed to determine the optimal ferrite content. Results demonstrated that ferrite displayed excellent microwave absorption properties; nevertheless, excessive use of ferrite may weaken the rheological behavior of asphalt mortar at low temperatures. Moreover, the addition of ferrite can significantly promote the microwave heating uniformity and heating efficiency level of specimens, while slightly increase the self-healing ratio. Overall, replacing 20% limestone filler with ferrite in volume is a promising solution to properly enhance a uniform microwave heating of steel slag asphalt mixtures.