## 2 Test Design and Test Method
### Test Process
After 10 s, the cone's descent indicated the slurry consistency, and the average of two readings was recorded as the final test result [47]. (4) Fluidity: In accordance with relevant specifications [48], the slurry fluidity was measured utilizing an apparatus of fluidity of cement mortar (NLD-3) employing the reciprocating flow table method, as shown in Figure 5d. Prior to the test, a damp cloth was used to clean the interior of the countertop, rammer, truncated round die, and set die, which were then positioned centrally on the skip table. The slurry was swiftly loaded into the truncated cone mold in two stages. Initially, two-thirds of the mold were filled, and the rammer was pressed 15 times, moving from the edge towards the center. Subsequently, the remaining slurry was added to slightly exceed the height of the test die, and the rammer was pressed another 10 times in the same manner. After removing the sleeve mold and trimming the excess slurry, the truncated cone mold was lifted vertically. The reciprocating flow table was activated for 25 beats, and the diameter of the slurry in two perpendicular directions was recorded. The average of these measurements was taken as the final result of the slurry flow test. (5) Setting time: According to relevant specifications [46], the mortar setting time measuring instrument (ZKS-100) was utilized, as shown in Figure 5e. Prior to testing, a wet cloth was used to clean the interior of the container, and freshly prepared slurry was poured into the container, maintaining a 10 mm distance from the top. The slurry surface was leveled and covered for proper storage. During measurement, the container was positioned on the pressure gauge base, ensuring the penetration test needle touched the grout surface with a 25 mm depth. The pressure gauge reading was noted, and the setting time, ts (min), of the grout was determined as the time taken for the penetration resistance to reach 0.5 MPa. This test required the simultaneous recording of two samples, with an acceptable error margin of no more than 30 min between the results; exceeding this threshold necessitated a repeat of the determination. \begin{table}
\begin{tabular}{c c c c c c c c} \hline
**No.** & **Ratio Level** & **w/b** & **b/s** & **f/c** & **so/b** & **Particle Size** & **SPs** \\ \hline
1 & \(-2\) & 0.6 & 0.5 & 1 & 0.2 & 0.5 mm–0.3 mm & 0 \\
2 & \(-1\) & 0.7 & 0.55 & 1.5 & 0.4 & 0.3 mm–0.1 mm & 1.5\% \\
3 & 0 & 0.8 & 0.6 & 2 & 0.6 & 0.1 mm–0.075 mm & 3\% \\
4 & 1 & 0.9 & 0.65 & 2.5 & 0.8 & 0.075 mm–0.0885 mm & 4.5\% \\
5 & 2 & 1 & 0.7 & 3 & 1.0 & 0.0385 mm–0 mm & 6\% \\ \hline \end{tabular}
\end{table} 
Table 5: Factor-level table. (6) Slurry strength: According to relevant specifications [46], the compressive strength of five 70.7 mm \(\times\) 70.7 mm \(\times\) 70.7 mm cement mortar cube test blocks, as shown in Figure 5f, was measured using the compression testing machine (JYE-2000). This test was performed after 28 days of curing. During the test, the application of load progressed at a rate of 0.25 kN per second. When the test pressure data exhibited a downward trend instead of ascending, the peak pressure value recorded signified the failure load of the grout test block.