## 4 Performance Enhancement Tests on Fluid-Cured Soil
### Analysis of the Results of Calcium Chloride Doping  
The test results of Ratios I and II are shown in Figure 7. The test was carried out with a gradient of 1.5% calcium chloride doping to analyze the flow degree and strength change rule of the fluid-cured soil at different doping amounts (0%, 1.5%, 3%, 4.5%, 6%, and 7.5%). From the test results, it can be seen that there was a peak interval of about 1.5% in the compressive strength, regardless of the use of Ratio 1 or Ratio 2. However, with calcium chloride doping greater than 1.5%, the compressive strength began to gradually decline, and calcium chloride doped outside the cured soil strength at 3d promoted the largest change compared to the case of un-doped calcium chloride, with year-on-year growth of 33%. However, the strength of the cured soil at 7d and 28d increased by approximately  
Figure 6: Test results of the polycarboxylate superplasticizer.  
12%, which indirectly reflects the characteristic of the \"early strength\" of calcium chloride, the cured soil's flowability, and the strength change rule of the fluid state. It is worth noting that with the increase in dosage, the strength of the cured soil began to decrease, and when the dosage of calcium chloride was more than 4.5%, the compressive strength at 3d, 7d, and 28d was smaller than that in the case of unadulterated calcium chloride [23].  
As the in situ soil was taken from the Hongwan Project of China Railway Construction Port and Navigation Bureau, the soil samples were subjected to seawater infiltration for an extended amount of time. The samples were not treated more than once after the removal of impurities and contained large amounts of seawater. According to previous studies, soft soils are rich in a variety of salts, with chloride ions being the most abundant. Further, cement-industrial slag composites produce C-S-H, CAH, Ca(OH)\({}_{2}\), and other substances during hydration, and an appropriate amount of CaCl\({}_{2}\) can react with tricalcium aluminate (C\({}_{3}\)A) in cement to produce almost insoluble F's salt, accelerating the hydration of C\({}_{3}\)A. At the same time, the generated F's salt and calcium chloride solid phase accelerate the formation of the cement paste structure and provide an early strengthening effect. Soil samples themselves are rich in a large number of chloride ions, and the equations for the reaction between chloride ions in seawater and the hydration products of cement after the admixture of excess calcium chloride are shown in Equations (3) and (4):  
\[\mathrm{Ca(OH)}_{2}+2\mathrm{Cl}^{-}=\mathrm{CaCl}_{2}+2\mathrm{OH}^{-} \tag{3}\]  
\[3\mathrm{CaO}\cdot\mathrm{Al}_{2}\mathrm{O}_{3}\cdot 6\mathrm{H}_{2}\mathrm{O}+3 \mathrm{CaCl}_{2}+25\mathrm{H}_{2}\mathrm{O}=3\mathrm{CaO}\cdot\mathrm{Al}_{2} \mathrm{O}_{3}\cdot 3\mathrm{CaCl}_{2}\cdot 31\mathrm{H}_{2}\mathrm{O} \tag{4}\]  
Chloride ions react with calcium hydroxide to form calcium chloride, which reacts with a large amount of hydrated calcium aluminate to form an abundance of F's salt, which has low strength and does not play a cementing role. The F's salt coats the surface of clay particles and hydration products, preventing the clay minerals from continuing the hard-setting reaction with the calcium hydroxide. Ultimately, it affects the compressive strength of cured soil.  
On the other hand, when mixed with calcium chloride, the soil dissolves in water and forms Ca+ and cl- positive and negative ions. It adsorbs positively and negatively charged hydration products and forms a double-layer structure, which inhibits and destroys the cement flocculation structure. At the same time, a large amount of F's salt is generated, which has a loose structure and does not act as a good cementing agent. Macroscopically, this shows that the flowability increases with an increase in calcium chloride dosage.