Laboratory investigation on deicing characteristics of asphalt mixtures using magnetite aggregate as microwave-absorbing materials

• Asphalt mixtures containing magnetite aggregate as microwave absorber were prepared.
• Deicing characteristics of asphalt mixtures with magnetite aggregate were studied in laboratory.
• MHE test, microwave reflection and MDT test of asphalt mixtures were conducted.
• SEM, EDS and XRD were adopted to conduct microscopic analyses.

Natural magnetic components in magnetite are outstanding microwave absorbers, which can be used in asphalt pavement for deicing practice. Therefore, asphalt mixtures containing magnetite aggregate as microwave absorber for different replacements of conventional basalt aggregate were prepared in this work and their deicing characteristics were studied in laboratory. Properties of asphalt mixtures incorporated with magnetite and basalt aggregates were tested, respectively. Microwave heating efficiency (MHE), microwave reflection and microwave deicing time (MDT) tests of asphalt mixtures were conducted. In addition, scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD) were adopted to conduct microscopic analyses. The results show that asphalt mixtures with magnetite aggregate present better performances at high temperature compared to those containing basalt aggregate with the same content, even though slightly lower water and temperature resistance are observed. The MHE of magnetite aggregate is 6.15 times that of basalt aggregate. The minimum reflectivity value of asphalt mixtures containing 80% magnetite content reaches −11.3 dB at 2.45 GHz frequency. Suitable magnetite content can decrease microwave reflectivity and improve microwave absorbing ability. The MHE of asphalt mixtures increases with the increase of magnetite contents when magnetite content is below 80%. Optimum magnetite aggregate content can evidently shorten the MDT. However, the MDT increases with the decrease of surrounding temperature. In a word, magnetite can be used as aggregates and microwave-absorbing materials in asphalt mixtures to achieve microwave deicing function.