# The Curing and Strength Properties of Highly Moist Waste Mud from Slurry Shield Tunnel Construction
## 3 Results  
### Strength Properties Analysis  
#### 3.1.1 Curing Effect of Curing Agent  
The effect of the RCSLP curing agent was evaluated based on the visible changes and the moisture content. The visible changes of the mud solidified with cement after different curing times are shown in Figure 3, and the visual changes of the mud solidified with the RCSLP curing agent after different curing times are shown in Figure 4.  
According to the visual results, the RCSLP curing agent was more likely to cause the mud samples to lose their fluidity than cement. The waste mud solidified by the RCSLP curing agent lost fluidity in a short time, which was more effective compared to the traditional method. One of the most important reasons was that absorbent resin was added to the RCSLP curing agent. After incorporating the RCSLP curing agent, the free water in mud is bound to the three-dimensional space grid structure through the different internal and external ion concentrations. Therefore, a large amount of the pore water in the waste mud is converted into bound water. While adding the RCSLP curing agent to the waste mud, the cement, lime, silica powder, and gypsum in the curing agent react with the water  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Test Number** & **Factor** & **Level** \\ \hline B1 & Cement content (\%) & 10, 12, 15, 18, 20 \\ B2 & Additive content (\%) & 7, 10, 12, 15, 18 \\ B3 & Curing time (d) & 3, 7, 14, 28, 60 \\ \hline \hline \end{tabular}  
* Basists of the mix-ratio: cement content 15%; additive content 12%; moisture content 100%; curing time 7 days.  
\end{table}
Table 7: Test scheme for compressive strength properties of RCSLP solidified soil.  
in the pores, thus consuming the free water and causing the solidified soil to quickly loses its fluidity.  
The moisture content of the waste mud was measured by taking samples at 0.5 h, 1 h, 3 h, and 6 h after adding the curing agent. The results are shown in Figure 5. The moisture content of waste mud solidified in the two ways shows relatively small decreases within a short period. The moisture content of cement solidified soil decreased by 3.3%, and that of the RCSLP solidified soil decreased by 5.6%, i.e., the RCSLP curing agent performs better. In general, the moisture content of the waste mud varies in a small range within a short period. Considering the intuitive effect of adding curing agents, the curing effect of the RCSLP curing agent is more significant than that of the cement curing agent.  
Figure 4: Curing effect of RCSLP solidified soil: (a) After 0.5 h; (b) After 1 h; (c) After 3 h; (d) After 6 h.  
Figure 5: Moisture content variation of the solidified soil with curing time.  
Figure 3: Curing effect of cement solidified soil: (a) After 0.5 h; (b) After 1 h; (c) After 3 h; (d) After 6 h.  
The reason is that the free water in the waste mud reacts with the materials in the RCSLP curing agent to form bound water. At the same time, part of the free water in the RCSLP curing agent is bound by the absorbent resin structure due to its electrical neutrality and becomes bound water. However, during moisture content measurement, the temperature is between 105 \({}^{\circ}\)C and 110 \({}^{\circ}\)C, and the drying time is over 8 h, which vaporizes the strong binding water, weak binding water, bound water, and free water in the RCSLP solidified soil. Therefore, the moisture content of the RCSLP solidified soil has not changed significantly in the short term.