Upcycling Coal Gasification Slag to Enhance the Self-Healing Performance of Asphalt Mixtures

With the extensive application of coal gasification technology, the production and storage of coal gasification slag continue to increase. Expanding the application scope of coal gasification slag is of positive significance for mitigating environmental pollution. Coal gasification slag has potential in the field of microwave-heated asphalt mixtures; however, there is limited research in this area. This study attempts to investigate the impact of utilizing coal gasification slags as fillers on the self-healing properties of asphalt mixtures. For this purpose, two different types of coal gasification slag in five ratios (within the range of <0.075 mm, 10%, 20%, 30%, 40%, and 50%) were used to replace limestone filler (LF) for preparing the Marshall test samples. Firstly, the micromorphology, chemical composition, and microwave absorption properties of LF, coarse slag (CS), and fine slag (FS) were characterized by scanning electron microscopy, X-ray fluorescence tests, and electromagnetic measurement. Afterward, an infrared camera examined the microwave-heating behaviors of different asphalt mixtures under microwave irradiation. Furthermore, semicircular bending fracture-healing-fracture tests were carried out to evaluate the self-healing properties of the asphalt test samples. Finally, the economical aspects were calculated by the cost analysis. Results indicated that CS and FS exhibited excellent microwave absorption performance. However, the excessive use of CS or FS could potentially weaken the thermal diffusion behavior of asphalt mixtures. Moreover, the microwave-heating capacity and self-healing properties of asphalt mixtures containing coal gasification slag were improved compared to typical specimens. It was possible to find that 50% CS or 40% FS could be considered as the suitable alternative because this rate obtained excellent microwave-heating efficiency, while significantly increasing the self-healing ratio. Moreover, the statistical results demonstrated significant differences in microwave-heating capacity and self-healing properties between CS and FS asphalt mixtures. And the results of cost analysis showed that the utilization process can lead to substantial economic advantages. In general, this study proves the feasibility of utilizing coal gasification slag as a microwave absorber to accelerate the efficiency of microwave healing of asphalt mixture. This finding provides a new methodology for consuming coal gasification slag, enabling the reuse of waste resources.