# Influence of Five Additives on No Loading Swelling Potential of Red Clay
## 2 Materials and Methods
### Test Procedures  
The no loading swelling ratio test refers to the National Standard of the People's Republic of China: GB/T 50123-2019 Standard for geotechnical testing method. The red clay specimen and schematic of the test setup used for the no loading swelling ratio test are shown in Figure 1.  
Through the no loading swelling test of red clay, the height of the red clay specimen increased by 1.89 mm three hours after adding water. The swelling of red clay specimens tended to be stable six hours after adding water, and the subsequent height increase was less than 0.1 mm. Therefore, the swelling ratio of the specimen was calculated according to the reading at 12 h after adding water. Three parallel tests were carried out for each specimen with a specific dosage and age, and the average value was taken. The swelling ratio was defined as the height change in the specimen after swelling after water addition divided by the original height of the specimen, and the result was taken as a percentage. The size, manufacturing method, and curing method of the specimen for the direct shear test were the same as those for the no loading swelling ratio test. Four specimens were used for each set of direct shear tests. The vertical pressures appli  
\begin{table}
\begin{tabular}{c c} \hline
**Physical and Index Properties of the Red Clay** & **Quantity** \\ \hline Natural density (g/cm\({}^{3}\)) & 1.92 \\ Dry density (g/cm\({}^{3}\)) & 1.64 \\ Liquid limit (\%) & 63.30 \\ Plastic limit (\%) & 11.31 \\ Plasticity index (\%) & 51.99 \\ Optimum moisture content (\%) & 9.55 \\ Unified soil classification & CH \\ Free swelling ratio (\%) & 68.00 \\ Total cohesion (kPa) & 21.51 \\ Total angle of internal friction (\({}^{\circ}\)) & 30.90 \\ \hline \end{tabular}
\end{table}
Table 1: Properties of the tested red clay.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline
**Chemical Composition** & **Red Clay (\%)** & **Cement (\%)** & **Steel Slag (\%)** & **BFS (\%)** & **Fly Ash (\%)** & **Zeolite (\%)** \\ \hline CaO & 0.74 & 47.40 & 41.22 & 59.31 & 3.60 & 2.80 \\ SiO\({}_{2}\) & 52.99 & 15.82 & 6.32 & 16.31 & 35.71 & 65.41 \\ Al\({}_{2}\)O\({}_{3}\) & 18.78 & 10.67 & 2.88 & 10.24 & 37.34 & 11.02 \\ Fe\({}_{2}\)O\({}_{3}\) & 13.48 & 4.96 & 22.44 & 1.46 & 9.86 & 2.53 \\ MgO & 1.04 & 4.49 & 5.68 & 5.63 & 0.46 & 0.89 \\ SO\({}_{3}\) & - & - & - & 0.59 & - & - \\ Na\({}_{2}\)O & 0.07 & 0.65 & 0.37 & 0.43 & 0.19 & 1.37 \\ K\({}_{2}\)O & 5.06 & 0.96 & 0.33 & 0.57 & 1.66 & 6.85 \\ P\({}_{2}\)O\({}_{5}\) & 0.08 & 0.06 & - & - & 0.43 & 0.04 \\ MnO & 0.17 & 0.37 & 3.80 & 1.00 & 0.09 & 0.13 \\ ZrO\({}_{2}\) & 0.52 & 0.32 & 0.14 & 0.45 & 1.49 & 0.14 \\ Cl & - & 1.24 & 0.06 & 0.06 & - & 0.08 \\ S & 0.02 & 1.78 & - & 1.22 & - & 0.02 \\ SrO & 0.06 & 0.67 & 0.17 & 0.67 & 1.63 & 0.11 \\ Loss of ignition & 4.97 & 8.20 & 12.77 & - & 2.05 & 7.86 \\ \hline \end{tabular}
\end{table}
Table 2: Chemical properties of the red clay, cement, gypsum, steel slag, blast furnace slag, fly ash and zeolite.  
100, 200, 300 and 400 kPa. The cohesion and internal friction angle of the specimen were tested by the fast shear test. XRD tests used an X-ray diffractometer D8 Advance (Bruker, Rheinstetten, Germany) to analyze the relative content of clay. SEM tests used a JSM-IT300 (JEOL, Tokyo, Japan) scanning electron microscope working at 15.0 kV to observe the microstructure of the section after the direct shear test.