## 3 Research on Alkali-Activated Grout Materials
### Study on the Setting Time of Alkali-Activated Composite Grouting Material
#### 3.3.2 Test Results and Analysis of Alkali-Activated Composite Grouting Material Setting Time  
Figure 11 shows the setting-time test results of alkali-activated grout materials under different soil-to-binder ratios. When the soil-to-binder ratio is 8:2, the setting time of the alkali-activated composite grouting material is the longest at 1098 min. As the ratio decreases to 5:5, the setting time shortens to 43 min. When the soil-to-binder ratio of the alkali-activated composite grouting material is 5:5, it meets the construction requirements for the setting time of the alkali-activated composite grouting material. When the proportion of the curing agent increases from 20% to 50%, the setting rate improves by 36.07%, 51.28%, and 87.43%. Therefore, as the soil-to-binder ratio decreases, the setting time of the alkali-activated composite grouting material shortens, and the setting rate increases. The more curing agent added, the greater the increase in the setting rate. Within the scope of this experiment, the shortest setting time is 43 min. This is because the curing agent plays a primary role in adhesion and strength in the material. Increasing its amount enhances its adhesive effect and accelerates the alkali-activated composites' reaction, thereby shortening the setting time.  
Figure 12 shows the setting-time test results of alkali-activated grout materials with different slacked lime contents. When the slacked lime content is 4.5%, the setting time of the alkali-activated composite grouting material is the shortest; at 0.0%, the setting time is the longest. As the slacked lime content increases from 0.0% to 4.5%, the setting times are 198 min, 108 min, 76 min, and 43 min, with the setting rates increasing by 45.45%, 29.63%, and 43.42%. Therefore, with the increase in slacked lime content, the setting time decreases, ranging from a minimum of 43 min to a maximum of 198 min. This is because slaked lime enhances the alkaline environment of the system, promoting the alkali-activated composites' reaction.  
Figure 13 shows the test results of the setting time of alkali-activated composite grouting material under different water-to-solid ratios. When the water-to-solid ratio is 0.26, the setting time of the alkali-activated composite grouting material is the shortest; when it is 0.32, the setting time is the longest. As the water-to-solid ratio increases from 0.26 to 0.32, the setting times are 43 min, 87 min, 132 min, and 215 min, with setting rates increasing by 50.57%, 34.09%, and 38.60%. Therefore, within the range of this experiment, as the water-to-solid ratio increases, the setting time lengthens. This is because increasing the water-to-solid ratio weakens the alkaline environment of the system, thereby extending the setting time.  
Figure 11: Setting time of copolymer grouting materials with different soil-to-binder ratios.  
In summary, the soil-to-binder ratio is the main factor affecting the setting time; the higher the content of the binder, the shorter the setting time. If the setting time of the alkali-activated composite grouting material is to meet the construction requirements for karst treatment in Shenzhen Metro, the soil-to-binder ratio should be set to 5:5. When the soil-to-binder ratio of the alkali-activated composite grouting material is 5:5, within the scope of this experimental study, altering the slaked lime content and the water-to-solid ratio can adjust the setting time to fall within the appropriate range. Next, the slaked lime content and the water-to-solid ratio also play significant roles: the higher the slaked lime content, the shorter the setting time; the higher the water-to-solid ratio, the longer the setting time.