# The Preparation of Active Support-Based Sealing Material and Sealing Effect Analysis
## 2 Sealing Material Preparation Based on Orthogonal Test
### Raw Materials and Test Method
#### 2.2.2 Test Method
According to the comprehensive analysis based on the orthogonal test of the borehole sealing material in Figure 4a, the bleeding rate and initial setting time increase with the increase in the water/cement ratio; this is because, with the increase in the water/cement ratio, the water content in the material increases, which speeds up the water emission rate on the surface of the material, so the bleeding rate increases, and the relative contact area between the water and cement particles decreases; the reaction rate between the cement particles will slow down, and the initial setting time \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Factors**} & \multicolumn{2}{c}{**the Water-Cement Ratio**} & \multicolumn{2}{c}{**the Content of Quicklime**} & \multirow{2}{*}{**Fly Ash**} & \multicolumn{2}{c}{**Accelerating Agent**} & \multicolumn{1}{c}{**Expanding Agent**} \\ \hline level 1 & 0.9:1 & 0.12 & 0.20 & 0.05 & 0.05 \\ level 2 & 1:1 & 0.16 & 0.30 & 0.10 & 0.15 \\ level 3 & 1.1:1 & 0.20 & 0.40 & 0.15 & 0.25 \\ level 4 & 1.2:1 & 0.24 & 0.50 & 0.20 & 0.35 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The factors and their levels in the test. Figure 3: Test scheme. of the material will increase. In addition, the expansion rate and compressive strength decrease with the increase in the water-cement ratio; this is because the water/cement ratio increases and the porosity of the material increases, which leads to a reduction in the expansion rate and compressive strength of the concrete. For the borehole sealing grouting material, the smaller the bleeding rate is, the better. Ideally, the material is expected to set and solidify after the end of grouting. Generally, the time from adding the water and mixing material to the end of grouting is 20-40 min, so the water-cement ratio is 0.9:1. As can be seen from Figure 4b, with the increase in the quicklime content, the bleeding rate decreases first and then increases, and the expansion rate increases first and then slowly decreases. When the quicklime content is 0.2, the sealing material performs better in terms of the initial setting time, compressive strength, bleeding rate and expansion rate. Accordingly, the quicklime content is set to 0.2. As is shown in Figure 4c, the impact of the fly ash content on the compressive strength and expansion rate is small, and the initial setting time increases with the increase in the fly ash content. When the fly ash content is 0.3, the bleeding rate is relatively low and the initial setting time short. Therefore, the fly ash content is set to 0.3. From Figure 4d, it can be seen that the content of accelerating agent exerts a relatively weak influence on the compressive strength and expansion rate of the material; by contrast, its influence on the initial setting time and bleeding rate of the material is much stronger. With the increase in the accelerating agent content, the bleeding rate and initial setting time decrease significantly. When the accelerating agent content is greater than 0.15, the downward trend in the initial setting time is weakened. Accordingly, the content of the accelerating agent is set to 0.15. As can be seen from Figure 4e, the expanding agent exerts its greatest influence on the compressive strength and expansion rate. As the content of expanding agent increases, the compressive strength significantly decreases, whereas the expansion rate increases correspondingly. Therefore, the value near the intersection of the two curves of compressive strength and expansion rate should be selected for the expanding agent content. Accordingly, the expansion agent content is set to 0.2. To sum up, the contents of these raw materials are as follows: water-cement ratio: 0.9:1, quicklime: 0.2, fly ash: 0.3, accelerating agent: 0.15, and expanding agent: 0.2.