# Compression Behavior of Rubber-Bentonite Mixture under Different Salinities
## 2 Results and Discussions
### Compression Coefficient Change of MX80 Bentonite/Rubber Mixture
#### 2.1.1 Influence of Different Mass Ratio on Compression Coefficient  
According to the compression coefficient curve shown in Figure 2, it can be observed that there were differences in the compression coefficients between samples with different mass ratios in the same salt solution concentration environment. When the ion content of the salt solution was zero, the compression coefficients of samples B10 and B8T2 showed an increasing trend in the range of 100 kPa to 200 kPa. As the vertical load increased, the compression coefficient gradually decreased. For sample B6T4, the compression coefficient remained relatively stable when the vertical load reached 200 kPa. However, once the vertical load increased to 300 kPa, the compression coefficient increased significantly and then decreased. On the other hand, the compression coefficient of sample B4T6 remained relatively stable, and increasing the rubber content helped to reduce its compression coefficient. We added rubber fibers to bentonite to study its mechanical properties. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Rubber Content**} & \multirow{2}{*}{\
\begin{tabular}{c} **Solution Concentration-** \\ **tion/Vertical Load** \\ \end{tabular} } & \multirow{2}{*}{**100**} & \multirow{2}{*}{**200**} & \multirow{2}{*}{**300**} & \multirow{2}{*}{**400**} & \multirow{2}{*}{**Mean**} & \multirow{2}{*}{
\begin{tabular}{c} **Standard** \\ **Value** \\ \end{tabular} } & \multirow{2}{*}{**Variance**} \\ \cline{2-2} \cline{6-8}  & 0 & 0.4268 & 0.4546 & 0.402 & 0.3835 & 0.417 & 0.031 & 0.001 \\ \cline{2-8}  & 0.1 & 0.477 & 0.4927 & 0.4833 & 0.3904 & 0.461 & 0.047 & 0.002 \\ \cline{2-8}  & 0.5 & 0.625 & 0.56 & 0.5044 & 0.3991 & 0.522 & 0.096 & 0.009 \\ \cline{2-8}  & 1 & 0.7582 & 0.5096 & 0.55 & 0.3821 & 0.550 & 0.156 & 0.024 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._  
Figure 2: Relationship between compression coefficient and vertical load for different samples in 0 mol/L NaCl (**a**), 0.1 mol/L NaCl (**b**), 0.5 mol/L NaCl (**c**), and 1 mol/L NaCl (**d**) solutions. [PERSON] et al. (2018) analyzed the variation in the compression index for different tire rubber fiber and cement contents by adding rubber fiber to bentonite soil. They found that increasing the tire rubber fiber content by 0.5-2% could increase the compression index of the mixture from a minimum value of 0.25 to a maximum value of 0.85. This experiment focused on studying the compression coefficient of a composite bentonite-rubber material. It is important to note that the compression index and compression coefficient are reciprocals of each other. When the compression index increases, the compression coefficient decreases, and vice versa. Both parameters reflect the compression effect of the data, albeit in different forms. Therefore, based on this research and a comparison with previous experimental results, it can be concluded that increasing the rubber content improves the compressibility of the mixture. Under different salt solution concentrations, the compressibility coefficients of both B10 and B8T2 samples increased from 100 kPa to 200 kPa as the vertical load increased and then gradually decreased. With an increase in the salt solution concentration, the compressibility coefficients of the B6T4 and B4T6 samples tended to increase. When the ion concentration in the salt solution exceeded 0.5 mol/L, the compressibility coefficients of both mass ratios tended to stabilize. In the 0.1 mol/L NaCl and 0.5 mol/L NaCl environments, the B6T4 and B4T6 samples exhibited similar compressibility coefficient values and variations. However, in an external 1 mol/L NaCl solution environment, the B4T6 sample expanded for 48 h under an initial load of 50 kPa, leading to a significant increase in the compressibility coefficient at 100 kPa and a larger internal pore channel.