## 3 Research on Alkali-Activated Grout Materials
### Study on UCS and Fluidity of Alkali-Activated Composite Grouting Material
#### 3.2.3 UCS Test Results and Analysis of Alkali-Activated Composite Grouting Material
When alkaline activators and slaked lime act together on slag and fly ash, they can trigger a series of alkali activation reaction processes, which consists of two core phases: firstly, in the alkaline environment, the key components inside slag and fly ash, such as SiO\({}_{2}\), Al\({}_{2}\)O\({}_{3}\), etc., go through an initial depolymerization reaction phase. During this phase, the original chemical bonds are broken and rearranged in combinations, releasing elements such as reactive silicon, aluminum, and possibly sodium and calcium. The parameter soil-to-binder ratio has a decisive influence on the effective content of reactive metal oxides, which in turn affects the mechanical properties of the final alkali-activated composites. Therefore, the soil-to-binder ratio is the first factor affecting the UCS of alkali-activated grout materials at all maintenance ages. As the reaction process advances, the released reactive elements continue to participate in the subsequent steps of the polymerization reaction through the formation of basic structural units, such as silica-oxygen tetrahedra and aluminum-oxygen tetrahedra. At this point, the presence of free Ca\({}^{2+}\) and Na\({}^{+}\) ions in the system under alkaline conditions promotes the connection and fusion between these units. The amount of slaked lime incorporated enhances the strength of the alkaline environment of the reaction system, which is essential for the polymerization reaction. Ultimately, these chemical reactions led to the generation of two types of gel substances: N-A-S-H type and C-A-S-H type. These gel substances not only fill into the microscopic pore structure of the composite soil material, but also act as an effective bonding medium to firmly bond the soil particles together, thus optimizing the structural integrity and density in the composite soil. Therefore, within the scope of this experimental study, an increase in slaked lime content resulted in an increase in the UCS of alkali-activated grout materials. However, as the reaction proceeds, the water in the alkali-activated grout materials will evaporate from the system, forming small cracks inside the alkali-activated grout materials. Hence, the increase in the water-to-solid ratio will adversely affect the UCS. With the prolongation of the maintenance time, more and more water in the system escapes from the alkali-activated grout materials system, making the cracks continue to increase in size. When the maintenance runs to 7 days and 28 days, the degree of influence of the water-to-solid ratio on the UCS is greater than the slaked lime ratio. The UCS values in all the periods of time decrease with the increase in the water-to-solid ratio. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Level** & **Soil-to-Binder Ratio** & **Slaked Lime Content** & **Water-to-Solid Ratio** \\ \hline
3 days—1 & 0.8073 & 6.5951 & 9.3673 \\
3 days—2 & 2.5204 & 8.1740 & 8.8490 \\
3 days—3 & 8.3469 & 9.3505 & 8.7505 \\
3 days—4 & 22.6053 & 10.1601 & 7.3130 \\
3 days—Delta & 21.7980 & 3.5650 & 2.0543 \\
3 days—Ranking & 1 & 2 & 3 \\
7 days—1 & 1.171 & 12.814 & 14.472 \\
7 days—2 & 5.394 & 13.017 & 13.940 \\
7 days—3 & 20.450 & 13.262 & 14.032 \\
7 days—4 & 27.372 & 15.296 & 11.944 \\
7 days—Delta & 26.201 & 2.482 & 2.528 \\
7 days—Ranking & 1 & 3 & 2 \\
28 days—1 & 1.320 & 13.725 & 17.719 \\
28 days—2 & 7.826 & 15.397 & 16.573 \\
28 days—3 & 23.738 & 15.377 & 13.997 \\
28 days—4 & 28.685 & 17.070 & 13.280 \\
28 days—Delta & 27.365 & 3.344 & 4.439 \\
28 days—Ranking & 1 & 3 & 2 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Analysis table of strength variability of geogel grouting materials at different ages.