## 2 Experimental Setup
### Preparation of Specimens  
The ceramsite was pre-wetted with water 1 h before testing. On the one hand, pre-wetted ceramsite alleviates drying shrinkage cracks by providing internal curing, enhancing hydration, and improving early-stage densification [43; 44]. By maintaining sufficient internal moisture, pre-wetted ceramsite reduces shrinkage and early cracking, resulting in denser hydration products and improved mechanical properties [45; 46]. On the other  
\begin{table}
\begin{tabular}{c c c c c c c} \hline
**Serial** & **W/C** & **Water** & **Cement** & **SS** & **Ceramsite** & **Foam** \\
**Number** & **Ratio** & **(kg/m\({}^{3}\))** & **(kg/m\({}^{3}\))** & **(kg/m\({}^{3}\))** & **(kg/m\({}^{3}\))** & **(kg/m\({}^{3}\))** \\ \hline
1 & 0.4 & 172.11 & 430.28 & 61.47 & 122.94 & 13.21 \\
2 & 0.4 & 142.69 & 356.72 & 97.29 & 194.58 & 8.72 \\
3 & 0.4 & 142.35 & 355.88 & 129.41 & 161.76 & 10.59 \\
4 & 0.45 & 168.16 & 373.7 & 62.28 & 186.85 & 9.01 \\
5 & 0.45 & 167.78 & 372.85 & 93.21 & 155.36 & 10.8 \\
6 & 0.45 & 167.40 & 372.01 & 124.00 & 124.00 & 12.59 \\
7 & 0.5 & 193.53 & 387.07 & 59.55 & 148.87 & 10.98 \\
8 & 0.5 & 193.12 & 386.23 & 89.13 & 118.84 & 12.68 \\
9 & 0.5 & 158.33 & 316.66 & 126.67 & 190.00 & 8.34 \\ \hline
10 & 0.4 & 222.59 & 556.48 & 0 & 0 & 20.93 \\
11 & 0.45 & 241.92 & 537.61 & 0 & 0 & 20.46 \\
12 & 0.5 & 259.99 & 519.98 & 0 & 0 & 20.03 \\ \hline \end{tabular}
\end{table}
Table 5: Mix ratio of steel slag and ceramide foam concrete materials.  
hand, it reduces the density difference between ceramsite and concrete paste, partially suppressing ceramsite flotation. It should be noted that in this experiment, the water absorbed during the ceramsite pre-wetting process was not included in the calculation of mixing water content for the mix proportion design. According to Table 5, pre-weighed cement, steel slag, and dry ceramsite were mixed in a container for 2 min, followed by 5 min of additional mixing after water addition. The preformed foam method was adopted, where foam generated by a foaming machine was directly injected into the container and thoroughly mixed with the slurry until achieving homogeneous stability. Repeated trials determined that 2 min of mixing after the injection of foam produced optimal results. Prolonged mixing (>2 min) intensified foam collapse by steel slag particles, reducing the internal porosity and increasing the density. Insufficient mixing (<2 min) caused inadequate foaming and an uneven foam distribution. This process yielded a ceramsite foam mixture with good flowability. Finally, the prepared slurry was cast into \(100\text{ mm}\times 100\text{ mm}\times 100\text{ mm}\) molds, manually compacted, and then covered with an impermeable plastic membrane to prevent moisture evaporation and mitigate ambient drying effects on mix design [47,48]. Specimens were then transferred to a curing chamber that was maintained at 20 \(\pm\) 2 \({}^{\circ}\)C with \(\geq\)95% relative humidity. For each test group, a total of nine specimens were prepared. These were equally divided into three sets, which were then assigned to compressive strength testing at 7 days, 14 days, and 28 days, respectively. The preparation process is illustrated in Figure 4. Subsequent performance testing procedures are shown in Figure 5.  
Figure 4: Preparation process of SSCFC.