Effect of metallic-waste aggregates on microwave self-healing performances of asphalt mixtures

Some metallic waste, such as steel slag, has great potential for microwave heating to heal asphalt mixtures as an excellent microwave absorbing material. Prior to this study, hot braised steel slag (HBSS) was firstly selected from three kinds of metallic wastes according to the microwave heat releasing test results. Afterwards, the self-healing performance of the purpose-designed asphalt mixtures was evaluated by cyclic crack-healing tests with the semi-circular bending method. During microwave heating, the temperature distribution and thermal diffusion of asphalt mixtures were observed using an infrared camera. The spatial distribution of the HBSS inside the asphalt mixtures was analyzed using X-ray computed tomography (CT). Results indicated that the asphalt mixtures with a 60% replacement in volume by HBSS of coarse aggregate (4.75-9.5 mm) produced better healing performance after 30 s heating. The infrared images indicated thermal diffusion behavior and confirmed the temperature of mixtures can be increased by microwave. The three-dimensional reconstruction data based on X-ray CT scan demonstrated the HBSS was uniformly distributed inside the asphalt mixtures, and as such it converted the energy of microwave irradiation effectively into thermal energy. (C) 2020 Elsevier Ltd. All rights reserved.