## 3 Results
### Effect of Aggregate Size on Compressive Strength
For RFC with aggregate size of 1000 mm, when the load was close to the peak strength (strain of 0.37 \(\times\) 10\({}^{-3}\)), a large number of tensile damage elements developed around the edge of the aggregates, forming micro-cracks (marked as D); during the strain range from 0.40 \(\times\) 10\({}^{-3}\) to 1.00 \(\times\) 10\({}^{-3}\), the tensile damage elements around the aggregates increased, and the micro-cracks expanded into macroscopic cracks distributed around the aggregate (marked as E); when the strain reached 1.00 \(\times\) 10\({}^{-3}\), the SCC no longer bore the load, causing some aggregates to develop through-cracks (marked as F), and the overall failure mode of the RFC was similar to splitting tensile failure. For RFC with aggregate size of 600 mm, due to the relatively uniform distribution of aggregates, their damage elements did not surround the distribution of aggregates, and with the increase in load, tensile damage elements gradually developed, forming inclined micro-cracks at a strain of 0.57 \(\times\) 10\({}^{-3}\) (marked as G); when the loading strain reached 1.00 \(\times\) 10\({}^{-3}\), the micro-cracks expanded into inclined cracks that penetrated the specimen (marked as H), and the RFC was characterized by macroscopic shear failure composed of a large number of tensile damaged elements. As shown in Table 1, this paper used the particle size type as the independent variable to carry out linear fitting on the compressive strength, and the fitting parameters are shown in Table 3. Figure 11 describes some fitting straight lines (the sizes of specimens are 600 mm, 1200 mm, 1800 mm, 2400 mm, and 3000 mm, respectively). The slope of the fitting straight line in Table 3 is positive except for the specimens with sizes of 150 mm and 2400 mm. It  
Figure 10: Crack formation process of RFC with different aggregate sizes. (**a**) Type 1 (aggregate size: 3000 mm), (**b**) Type 3 (aggregate size: 1000 mm), (**c**) Type 5 (aggregate size: 600 mm). is clear that, on the whole, with the increase in particle size type, that is, the decrease in aggregate size, the compressive strength of RFC gradually increases. Further Study on the Effect of Aggregate Size on Compressive Strength  
As there are only five points of data in the above fit on the compressive strength by particle size type, the fitted straight line contradicts the reality. In practical terms, the compressive strength of RFC cannot increase indefinitely with increasing particle size type, and its maximum value cannot exceed the compressive strength of the aggregate. In order to further investigate the relationship between aggregate size and compressive strength, the size of the numerical model was fixed at 3000 mm in this paper, and more particle size  
Figure 11: Linear fitting of particle size type to compressive strength. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Specimen Size (mm)** & **Intercept** & **Slope** \\ \hline
150 & 35.48 & \(-\)0.07 \\  
\hline \hline \end{tabular}
\end{table} 
Table 3: Linear fitting parameter of particle size type against compressive strength. types were added on the basis of the previous ones. The aggregate size and compressive strength corresponding to RFC of each particle size type are shown in Table 4, and some models are shown in Figure 12a. Figure 12b illustrates the post-failure element damage state of RFC of partial particle size types. For type 1 and type 3 RFC with larger aggregate size, cracks mainly developed along the interface, and aggregate failure occurred after the SCC stopped working. For type 5 to type 30 RFC with smaller aggregate size and more uniform distribution, inclined cracks penetrating the specimen occurred after failure, indicating shear failure. In the numerical simulation experiment of RFC, the strain energy in the element was released in the form of acoustic emission. Figure 13a expresses the relationship between particle size type on acoustic emission and compressive strength.