High-Efficiency Heating Characteristics of Ferrite-Filled Asphalt-Based Composites under Microwave Irradiation

Abstract

Asphalt concrete is a typical self-healing material, and its self-healing rate is influenced by the temperature. Since microwave irradiation is an efficient way of heating, its use could be a novel approach to heating asphalt pavement. In this study, ferrite particles were mixed into asphalt-based composites to upgrade the microwave absorbing efficiency and then further accelerate the self-healing rate of the composites. The microwave-absorbing capability of three kinds of aggregate and three kinds of filler were studied first. It was found that NiZn ferrite has an excellent microwave-absorbing capability under 2.45 GHz compared to other tested materials. Then the heating rate of asphalt mastic, asphalt matrix, and asphaltic concrete mixture with and without NiZn ferrite fillers were tested. The microwave heating rates of these composites all increase significantly with an increase in NiZn ferrite content. Third, the temperature uniformity of asphalt composites was investigated using an infrared thermal imager and a statistical analysis method. It was found that adding adequate amounts of ferrite fillers could notably improve temperature uniformity. Then, through electromagnetic measurement, it was confirmed that the addition of NiZn ferrite particles to mastic confers an excellent microwave-absorbing capability in a frequency range of 1–2.5 GHz compared to plain asphalt mastic. Finally, a fatigue–rest–fatigue test was used to investigate the effect of microwave heating on the self-healing behavior of ferrite-filled asphaltic concrete mixtures. It can be concluded that the healing capability of asphalt concrete can be significantly increased by ferrite particles’ superior microwave absorption properties, leading to the extension of fatigue life.