Three-dimensional mesostructure model of coupled electromagnetic and heat transfer for microwave heating on steel slag asphalt mixtures

Abstract

Steel slag as a special type of aggregate in asphalt mixture owns excellent potential for microwave heating. To gain high heating performance, the determinant of the optimal content of steel slag in asphalt mixture becomes a key problem. This paper develops a numerical model of the mesostructure of the three-phase asphalt mixture (aggregate, steel slag, and asphalt mortar) with coupled electromagnetic field and heat transfer process. Firstly, the model generates spherical aggregates by the random placement method based on the given grading. Then, the limestone aggregate particles are replaced by steel slag with the same volume. Finally, microwave heating analysis of asphalt mixtures with different steel slag contents is performed by FEM. The comparison between our numerical simulations and the reported experimental data demonstrates that the proposed model is reliable and effective. This research can characterize well the heat transfer among components of asphalt mixture during microwave heating and show the details of the inner temperature distribution. The results also indicate that the microwave heating performance of asphalt mixture enhances with the increase of steel slag content. However, excessive steel slag content can lead to overheating in most areas of the asphalt mixture, and the temperature distribution is more uniform and suitable when steel slag replaces coarse aggregate (4.75 – 9.5 mm) with an equal volume about 60 %.