# Study on Slump and Compressive Strength of Gangue Based on Aggregate Size Gradation
###### Abstract  
In order to solve the ecological environment pollution caused by a large amount of coal gauge accumulation and the problems of poor conveying performance and low support strength of paste filling materials. Based on the standard slump test and uniaxial compressive strength test, the slump and compressive strength (post-coagulation) of gangue paste under different aggregate size aggregations were obtained through orthogonal experiments in this study. The results show that the slump of the gangue filling paste with four types of aggregate size gradations is negatively correlated with the mass fraction, and the slump of the filling paste with a coarser aggregate content is more obviously affected by the mass fraction The increase of fine aggregate content has a significant impact on the compressive strength of the filling paste, which shows a trend of first increasing and then decreasing. When the mixing ratio of coarse aggregate and fine aggregate is 5.5, the compressive strength of the paste reaches the best. In addition, different proportions of aggregate mixing cause the filling paste to form different skeleton structures, including the skeleton void structure at 7:3 or 6:4, the skeleton dense structure at 5:5, and the skeleton suspension structure at 4:6, which are decisive for the final performance of the paste. By analyzing the experimental results of the compressive strength and slump of the gangue filling paste, it was found that the relationship between the compressive strength and slump of the gangue filling paste is a power index function. Through data fitting, it was found that the regression coefficient of the fitting function is no less than 0.97, and the fitting effect is good for evaluating the strength of the filling paste under the aggregate size grading. methods for paste slurry fluidity include the slump test, viscometer, L-shaped tube test, and loop tube test [11; 12; 13; 14; 15]. A rheometer is commonly used in the laboratory to test the rheological properties of the tailing slurry, and pressure test instruments are used to test the compressive strength of the paste. However, most mine sites do not have such testing conditions. Therefore, if the relationship between the collapse of the gypsum body and the compressive strength of the paste can be established, it can provide a new way to quickly and accurately evaluate the filling strength of the paste. [PERSON] [16] conducted a stress analysis on the slump cone test for concrete mortar and, for the first time, established a relationship model between the slump of concrete mortar in a cone and the yield stress. Based on the [PERSON] model theory, [PERSON] et al. [17] constructed a simplified formula for dimensionless models of conical and cylindrical cave-in cylinders. [PERSON] [18] used the finite element analysis method to study the flow model of fresh concrete slurry, which was considered a Bingham model. He analyzed the relationship between the flow properties and the collapse of the concrete slurry. The results show a strong correlation between the yield stress and slump, whereas the correlation between the viscosity and slump was weak. [PERSON] et al. [19] explored the effects of saline groundwater or seawater as mix water in cemented fills on the rheological properties (ability to control flow or transportability) and setting time of the cemented backfill. [PERSON] et al. [20] studied the influence of slurry rheometer test method on the yield stress of the whole tailings paste material and compared the dimensionless yield stress calculated by slump with the yield stress measured by rheometer. In this paper, the influence of different mass fraction and aggregate ratio on flowing property and uniaxial compressive strength of filling paste was explored through detailed testing and exploration of 4 aggregates with unique particle size ratios, standard slump testing, and uniaxial compressive strength testing.