# Influence of Five Additives on No Loading Swelling Potential of Red Clay
## 3 Results and Discussion
### X-ray Diffraction Quantitative Analysis of Clay Minerals  
After comprehensively considering the effect and economy of additives, a red clay specimen, a specimen having 15% steel slag content and 28 days curing, and a specimen having 9% cement content and 28 days curing, were selected to make air drying-oriented slices (the glass slides were coated with a clay suspension and dried naturally), ethylene glycol treatment-oriented slices (i.e., air drying-oriented slices after saturation treatment in a ethylene glycol steam), and heat treatment-oriented slices (obtained by natural cooling of ethylene glycol tablets after treatments at a high temperature and a constant temperature), respectively, for the XRD analysis of clay minerals. The XRD patterns of clay minerals in specimens are shown in Figure 3.  
Comparing the relative intensity of each diffraction peak of the XRD pattern, the relative intensity of the theta angles of 12.27\({}^{\circ}\) and 25.00\({}^{\circ}\) in the XRD patterns of the red clay, steel slag-modified, and cement-modified specimens shows a gradually increasing trend. Therefore, it can be concluded that the relative content of kaolinite in the red clay specimen, the steel slag-modified specimen, and the cement-modified specimen increases gradually. The specific relative contents of clay minerals of the red clay, steel slag-modified, and cement-modified specimens are shown in Table 3.  
The content of montmorillonite in the illite-montmorillonite mixed layer in specimen 1 is 10%. The content of montmorillonite in the illite-montmorillonite mixed layer in specimen 2 is 10%. Comparing the relative content of montmorillonite, that of specimen 1 is 5.9%, that of specimen 2 is 5.7%, and that of specimen 3 decreases to 2%. Comparing the relative content of illite, that of specimen 1 is 72.1%, that of specimen 2 is 67.3%, and that of specimen 3 is 48%. It can be seen that, under the condition of 28 days curing, the addition of cement can greatly reduce the content of montmorillonite and illite resulting in strong hydrophilicity, and increase the content of kaolinite resulting in poor hydrophilicity. The addition of steel slag to red clay can also reduce the relative content of montmorillonite and illite in clay minerals, and increase the relative content of kaolinite, but the effect is less than that of cement. From the analysis of XRD test results, it can be inferred that when cement is used to modify the swelling properties of red clay, it can change the relative content of clay minerals in the specimens. The relative content of hydrophilic clay minerals decreases, whereas the relative content of nonhydrophilic clay minerals increases, which reduces the water absorption of red clay.  
Figure 3: _Cont._  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Specimen Number**} & \multirow{2}{*}{**Additives**} & \multicolumn{6}{c}{**The Relative Content of Clay Minerals**} \\ \cline{3-8}  & & **S 1** & **I/S 1** & **It 1** & **Kao 1** & **C 1** & **C/S 1** \\ \hline
1 & - & 1 & 49 & 28 & 22 & - & - \\
2 & 15\% Steel & 1 & 47 & 22 & 30 & - & - \\
3 & 9\% Cement & 2 & - & 48 & 50 & - & - \\ \hline \hline \end{tabular}  
* \({}^{1}\) S is montmorillonite, It is illite, Kao is kaolinite, C is chlorite, I/S is the illite montmorillonite mixed layer, and C/S is the chlorite montmorillonite mixed layer.  
\end{table}
Table 3: The relative content of clay minerals in the red clay, steel slag-modified and cement-modified specimens.  
Figure 3: XRD patterns of clay minerals (smectite, kaolinite, illite, and their mixed layer) in specimens at 28 days: (**a**) red clay; (**b**) 15% steel slag; (**c**) 9% cement.