## 4 Conclusions  
To address the economic cost and social issues associated with traditional shotcrete materials applied to roadways, this study utilized typical gangue as the raw material. The laboratory experimental method was employed to design single-factor rotational experimental schemes and processes. Based on these findings, the study explored the effects of the mix proportions of materials on the slump and the mechanical properties of the gangue-based shotcrete material applied to roadways. These properties have a significant impact on the conveying properties and mechanical properties of the gangue-based shotcrete slurry applied to roadways. The study drew the following conclusions:  
1. The gangue size and sand content have an impact on the slump of the gangue-based shotcrete slurry applied to roadways. Increasing the size of the gangue and sand content leads to a decrease in slump, followed by an increase due to the plasticity of the aggregate. The slump is negatively correlated with the mass concentration and is least affected by changes in the cement content;  
Figure 12: Influences of different cement contents on the compressive strength of the gangue-based shotcrete material applied to roadways.  
2. The compressive strengths of the specimens prepared under schemes A\({}_{1}\)-D\({}_{4}\) all increase with prolonged curing. In a curing period of 28 d, the compressive strengths of the specimens all reach a maximum under the corresponding experimental conditions;
3. When the curing period is 28 d, specimens under scheme A\({}_{2}\) (gangue size: 2.5-5 mm) exhibit the highest compressive strength. This is due to the fact that smaller gangue is stressed more uniformly and has a larger bound area cementing the aggregates. Additionally, increasing the mass concentration reduces the water/cement ratio of specimens, which in turn decreases the number of pores and fractures in the specimens. As a result, specimens under scheme B\({}_{4}\) (mass concentration: 78%) also exhibit high compressive strength. Sand has a certain mechanical bearing capacity. However, excessive sand results in voids in the specimens. Therefore, specimens prepared under scheme C\({}_{3}\) (with 35% sand content) have the highest compressive strength. As the cement content increases, the porosity of the specimens decreases, the density increases, and the bound area increases. Therefore, specimens prepared under scheme D\({}_{4}\) (with 18% cement content) exhibit the largest compressive strength.  
The conveying and mechanical properties of the gangue-based shotcrete material applied to roadways vary significantly depending on the mix proportions of materials in the experiment. In practical engineering applications, the ability of shotcrete material is determined by various factors, such as gangue lithologies, geological conditions, and strength. Therefore, the results of this experiment are also significant in guiding the specific mix proportions of materials used in field gangue-based shotcrete applied on roadways. Furthermore, the addition of a rapid-setting admixture and other chemicals during the preparation of the gangue-based shotcrete material applied to roadways will also be studied in subsequent research.  
All the authors contributed to this paper. [PERSON] provided theoretical and methodological guidance in the research process; [PERSON] prepared the test materials and conducted the test; [PERSON] participated in the literature search, investigation, and manuscript preparation; [PERSON] prepared the manuscript; [PERSON] conducted the experiments; [PERSON] and [PERSON] participated in revising the manuscript and figure plotting. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the National Natural Science Foundation of China [52274142], the Natural Science Foundation of Jiangsu Province [BK20231498].  
Not applicable.  
Dataset available on request from the authors.  
The authors declare no conflicts of interest.