Microwave self-healing characteristics of bituminous mixtures with different steel slag aggregate and waste ferrite filler

To improve crack propagation issues of bituminous mixtures in an eco-friendly way, steel slag (SS) and waste ferrite were partially substituted for aggregate and filler in the bituminous mixtures to enhance the self-healing performance (SHP) of the mixture through microwave heating (MH). Firstly, the electromagnetic parameters of ferrite filler (FF) and SS were tested by the vector network analyzer. Secondly, the thermal conductivity (TC) of ferrite filler bituminous mixtures (FFBM) and steel slag bituminous mixtures (SSBM) was tested based on the transient plane source. Subsequently, the MH surface temperature was measured on FFBM and SSBM, and the MH efficiency and uniformity were analyzed. Finally, the SHP of two types of bituminous mixtures under different conditions was analyzed. The results revealed that both FF and SS have significant magnetic loss, and the absorption performance of FF is better at the same frequency and thickness. The TC of SSBM is higher than FFBM, but due to the porous characteristics of SS, it tends to stabilize. The MH efficiency of FFBM is lower due to its volume ratio, but it has better uniformity. The self-healing rate of SSBM is higher at 40 s MH time, but FFBM can obtain a higher self-healing rate by extending the heating time. This work contributes to understand the difference between different types of suction materials self-healing of bituminous mixtures under MH.