## 1 Introduction  
Coal mines produce a huge amount of gangue waste during coal mining, the discharge of which accounts for about 15% to 20% of coal production [1, 2]. With regard to its disposal, gangue waste is generally directly discharged and stockpiled on the surface to form gangue dumps, which not only occupy large areas of land but also pollute the air and groundwater and even cause disasters such as landslides and explosions [3, 4, 5]. Therefore, improving the comprehensive utilization of gangue waste and innovating the resource utilization technologies of gangue are fundamental solutions for solving problems pertaining to gangue [6; 7; 8]. In mine engineering, shotcrete support of roadways has become a widely used method [9; 10] and is generally used in conjunction with devices such as anchor-bolt and bolt-mesh-anchor support [11; 12; 13] to achieve the high-strength support of roadways [14; 15]; however, huge amounts of raw materials are needed to make the shotcrete required for this technique [16; 17; 18]. Conventional shotcrete is generally prepared with gravel, sand, and cement [19; 20; 21]. Considering the similar chemical and mineral compositions of most gangue with gravel, gangue can be used as a substitute material for gravel in shotcrete [22; 23], and the modified gangue powder can partially replace cement. This not only reduces the demand for conventional raw materials but also increases the amount of gangue disposed. However, the utilization of gangue powder as a cement substitute in shotcrete production has yet to be implemented, primarily due to insufficient research and the technical and economic challenges associated with costly and complex activation processes. Therefore, it is necessary to study the mechanical performance of shotcrete with cement replaced by gangue powder, in a bid to provide support for the development of novel gangue-based shotcrete. Scholars have conducted extensive laboratory experiments to investigate the properties of shotcrete incorporating waste materials, achieving notable advancements in understanding its performance. By replacing sand with scrap glass, [PERSON] et al. developed novel shotcrete with a higher strength [24]. [PERSON] et al. discussed the feasibility of using tailings as a replacement for a fine aggregate (sand) in shotcrete production. Results indicate that the coal gangue-containing shotcrete achieves comparable or even higher mechanical properties at both early-age and 28-day curing periods [25]. [PERSON] et al. prepared shotcrete specimens by replacing natural aggregates with ferrochrome slag aggregates and thus developed a good gamma-ray and neutron-radiation shielding material [26]. By using graded tailings to replace sandstone as the aggregate in shotcrete, [PERSON] et al. prepared wet-mix shotcrete and significantly improved the strength of the concrete [27]. [PERSON] et al. developed novel shotcrete by replacing conventional aggregates with broken inactive coal gangue, attempting to mitigate environmental problems pertinent to the mining and depletion of raw materials for producing concrete and the disposal of gangue [28]. [PERSON] et al. investigated the sprayability and mechanical properties of geopolymer-based shotcrete prepared with varying ratios of fly ash to silica fume as a cement replacement [29]. [PERSON] et al. developed high-performance shotcrete using solid wastes such as fly ash and identified its optimal mix proportion [30; 31; 32]. [PERSON] developed a shotcrete material using red mud modified through chemical and physical activation methods and determined its optimal replacement ratio [33]. The state of research on utilizing waste materials in concrete production is summarized in Table 1. However, the aforementioned studies did not explore the mechanical performance of shotcrete with the replacement of cement with gangue powder. Considering this, investigating the properties of shotcrete with partial cement replacement with gangue powder in mine roadways can provide theoretical support for promoting its broader application.