## 3 Experimental Results and Analysis
### Failure Process and Morphology  
The failure morphology of a representative specimen from each group, along with a specimen without steel fibres for comparison, is shown in Figure 2. In Figure 2, it can be observed that the compressive failure process of the steel fibre-reinforced prism specimens in each group is generally similar. However, noticeable differences in brittle failure characteristics can be observed due to the varying content of coarse aggregate and steel fibres in the different experimental groups. The compressive failure process of the specimens can be divided into the following three stages:  
1. Elastic Stage: Prior to reaching the ultimate load of 40% to 70%, the stress-strain relationship of the specimen follows a proportional growth pattern. In this stage, the compression-induced deformation of the specimen initiates slowly, and microcracks start to form and propagate within the specimen. The load and displacement exhibit a roughly linear relationship, with the curve's slope remaining relatively constant. 2. Elastic-Plastic Stage: When the load exceeds 70% of the ultimate load, the slope of the load-displacement curve decreases. Fracturing occurs at the prism's corners, accompanied by some surface spalling in the edge region. However, due to the micro-reinforcement effect of the steel fibres, the spalled surface maintains some cohesion with the specimen, preventing complete separation. With continued loading, surface microcracks develop and propagate towards the top and bottom of the specimen. Internal microcracks propagate outward, connecting with the surface cracks and intensifying their extension, resulting in the appearance of new cracks. As the load \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Cube Compressive Strength**} & \multicolumn{2}{c}{**Spliting Strength**} & \multicolumn{2}{c}{**Elastic**} & \multicolumn{2}{c}{**Prism Axial**} & \multicolumn{2}{c}{**Axial Compression**} & \multicolumn{2}{c}{**(Slump/Expansion)**} \\  & & \multicolumn{2}{c}{**/MPa**} & \multicolumn{2}{c}{**(MPa)**} & \multicolumn{2}{c}{**(MPa)**} & \multicolumn{2}{c}{**(MPa)**} & \multicolumn{2}{c}{**(MPa)**} & \multicolumn{2}{c}{**Compressive**} & \multicolumn{2}{c}{**/mm**} \\
**Group** & **Day 3** & **Day 7** & **Day 28** & **Day 28** & **Day 28** & **Day 28** & **Day 28** & **Day 28** & \\ \hline SSP1 & 87.7 & 106.4 & 118.4 & 8.1 & 43.4 & 95.1 & 0.80 & 212/462 \\ SSP2 & 94.4 & 120.8 & 135.1 & 11.2 & 49.1 & 111.5 & 0.83 & 207/451 \\ SSP3 & 109.3 & 113.0 & 120.4 & 9.1 & 44.2 & 98.3 & 0.82 & 188/432 \\ SSP4 & 114.5 & 125.3 & 124.7 & 8.7 & 47.5 & 100.6 & 0.81 & 210/455 \\ SSP5 & 109.7 & 122.2 & 147.5 & 14.7 & 51.4 & 120.6 & 0.82 & 203/450 \\ SSP6 & 109.3 & 113.0 & 130.2 & 12.6 & 46.3 & 105.2 & 0.81 & 194/434 \\ SSP7 & 111.3 & 123.9 & 130.7 & 9.4 & 46.8 & 106.0 & 0.81 & 205/452 \\ SSP8 & 103.3 & 114.5 & 126.7 & 9.8 & 45.7 & 105.3 & 0.83 & 195/438 \\ SSP9 & 111.8 & 117.8 & 121.7 & 9.5 & 45.2 & 103.7 & 0.85 & 180/422 \\ Average value & 105.7 & 117.4 & 128.4 & 10.3 & 46.6 & 105.1 & 0.82 & 199/444 \\ P10 & 91.7 & 103.2 & 112.1 & 5.6 & 40.3 & 90.5 & 0.80 & 220/481 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Compressive strength of cube and prism specimens. increases, more significant fragmentation occurs, and the cracks rapidly extend and penetrate through the specimen until reaching the peak load. 3. Failure Stage: After reaching the peak stress, accompanied by a distinct noise, the specimen undergoes splitting failure. Diagonal cracks emerge on the prism's side surface, intersecting one or multiple concrete specimens. However, due to the reinforcing effect of the steel fibres, even in the event of specimen failure, a certain degree of integrity is maintained. This stands in stark contrast to the failure state of specimen P10 without steel fibres, highlighting the beneficial toughening effect of the steel fibres. The 10 figures in Figure 3 show the failure morphology of the numbered specimen.