**Abstract**

Fly ash, as a kind of hazardous by-product at coal-fired power stations, has been produced on a tremendous scale worldwide. Still, the utilization of fly ash is far from 100% despite some industrial sectors consuming a considerable amount. The top three industries that have successfully applied fly ash on a large scale are cement production, backfill mining, and civil engineering construction. However, compared to the other two fly ash disposal methods, the use of fly ash in backfill mining is still being extensively researched. Not only is fly ash a perfect substitute for cement due to its cementitious properties bringing the cost of backfill mining down to an affordable level for enterprises, the carbon sequestration capacity it possesses is generating new research enthusiasm. This chapter provides a comparative analysis of the current status of the use of fly ash in different mining methods and the role it plays in the corresponding mining method, with an emphasis on the mechanisms by which fly ash content affects the rheological properties of the paste and the strength of the fill. Therefore, this chapter can contribute to understanding the potential of fly ash in mining applications and exploring innovative applications of fly ash.

**Keywords:** coal, fly ash, backfill mining, rheological properties, strength analysis
