## 1 Introduction  
With the rapid development of industry and urbanization in China, the problem of massive generation of solid waste has become increasingly prominent [1, 2, 3]. Desulfurization ash is a solid waste produced by energy companies such as thermal power plants in order to reduce the air pollution caused by the emission of sulfur oxides and solidify harmful gases using flue gas desulfurization (FGD) technology [4, 5]. China is the largest producer of desulfurization ash in the world, with an annual increment of about 2 million tons [6], and its massive accumulation not only occupies land resources but also pollutes groundwater, soil, and the atmosphere, thus threatening human health [7, 8]. Therefore, exploring methods of resource utilization of solid wastes such as desulfurization ash is of great significance to alleviate the environmental pressure and achieve sustainable development. Desulfurization ash usually contains CaSO\({}_{4}\) and CaSO\({}_{3}\), as well as free calcium oxide (f-CaO) and partially unreacted Ca(OH)\({}_{2}\), with a high calcium content and high alkalinity. Manyexperimental studies have been devoted to the development of desulfurization ash products for diverse applications in different fields [9; 10; 11; 12; 13]. For example, based on the characteristics of wide sources of FGD ash, low energy consumption, and no waste residue or waste water, FGD ash is used as auxiliary admixtures for the production of building materials, cement blending materials, composite wall materials, and road base materials [14; 15; 16; 17]. [PERSON] et al. [18] and [PERSON] et al. [19] developed a highly efficient method for the co-disposal of multiple hazardous solid wastes by applying FGD ash in combination with red mud. [PERSON] et al. [20] used desulfurization ash to prepare highly efficient and environmentally friendly cement-based grouting fireproofing materials. In summary, the application of desulfurization ash in cementitious materials has good energy-saving and environmental protection properties. However, desulfurization ash has a very low content of reactive components such as SiO\({}_{2}\) and Al\({}_{2}\)O\({}_{3}\) and lacks gelling activity, which can hinder the generation of C-S-H gel and ettringite [21; 22]. In addition, when desulfurization ash reacts with water, Ca(OH)\({}_{2}\) is generated from f-CaO, CaSO\({}_{3}\) is generated from CaSO\({}_{3}\)-0.5H\({}_{2}\)O, and ettringite is generated, all of which lead to volume expansion and fracture of the material, reducing stability and durability, and thus limiting the use in engineering applications [23; 24]. Therefore, previous studies usually focus on the use of FGD ash as an additive to cementitious materials, but the utilization rate is limited and not sufficient to absorb the large amount of solid waste. Fewer existing studies have addressed the large-scale utilization of desulfurization ash, such as mine backfilling [25]. Mine backfilling can not only dispose of a large amount of solid waste but also effectively control surface subsidence, reduce damage to the ecological environment, and take into account resource utilization and economic benefits [26; 27; 28; 29; 30]. The selection of cementitious materials in backfill materials is a decisive factor affecting the backfill effect and cost. Currently, mines usually prepare backfill materials by mixing solid wastes as aggregates with binders such as ordinary Portland cement (OPC) [31] or by using reactive solid wastes as admixtures to minimize the amount of binder [32; 33]. The use of OPC leads to an increase in filling costs, and the production process is energy intensive, with high CO\({}_{2}\) emissions [34]. Therefore, the development of a low-cost, high-performance, and green low-carbon all-solid waste mine backfill cementitious material to replace OPC has become a key focus of current researchers [35].