## 3 Results and Discussion
### Biocementation of Fine-Grained Soil Using CA-Cu Nanofluower
#### 3.4.2 Calcium Carbonate Content  
The precipitated calcium carbonate was measured as it is a critical factor in the increase in the strength of biocemented soil. As with the previously reported results on calcium carbonate distribution for bioccementation by injection [65], the amount of calcium carbonate was non-uniform throughout the specimens. High amounts of CaCO\({}_{3}\) were observed at the top, compared to the middle and bottom sections of the specimens. This is due to a significantly high reaction rate at the top, leading to bioclogging so that only the upper  
Figure 9: The typical appearance of the specimens biocemented by injection (**a**) control, (**b**) biocemented by CA only, and (**c**) biocemented by CA-Cu nanoflower.  
soil layers are bioemented. Due to the size of the hybrid carriers, this study did not overcome the uniformity problem; however, had nano-sized carriers been produced, the uniformity challenge could have been addressed. Conversely, the mixing method yielded better uniformity of treatment, with CaCO\({}_{3}\) contents ranging between 6% and 10% for the treated samples. As observed, the optimal CA-Cu mixing ratio is 0.1 M, yielding higher UCS and CaCO\({}_{3}\) content than a 0.2 M or 0.5 M mixing ratio. Similarly, in most other cases, 0.2 M solutions give higher CaCO\({}_{3}\) content and UCS than 0.5 M solutions. Similar observations have been reported in urease enzyme reactions where a highly concentrated solution was undesirable [66].  
Figure 10: The typical appearance of the specimens bioemented by mixing (**a**) control, (**b**) biocemented by CA only, and (**c**) bioemented by CA-Cu nanoflower.  
Figure 11 shows the SEM results of the bioemented soil. The microphotographs show that the untreated soil had no crystal of CaCO\({}_{3}\). Conversely, for the treated specimens, typical CaCO\({}_{3}\) crystals on the surface and between particles are observed, consistent with the bioementation mechanism reported in the literature [(40,41)].  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Treatment**} & \multirow{2}{*}{\
\begin{tabular}{c} **Test** \\ **Category** \\ \end{tabular} } & \multirow{2}{*}{**CaCl\({}_{2}\)/NaHCO\({}_{3}\)(g)**} &
\begin{tabular}{c} **Ca Enzyme** \\ **Concentration** \\ **(mg/mL)** \\ \end{tabular} & \multirow{2}{*}{**q\({}_{\omega}\) (kPa)**} & \multirow{2}{*}{**Average**} & \multirow{2}{*}{**Moisture**} \\ \cline{5-6}  & & & 0.0 M & 0 & 11 & 5\% & 30 \\ \hline \multirow{8}{*}{Mixing} & \multirow{8}{*}{Control} & 0.1 M & 0 & 100 & 6\% & 30 \\ \cline{3-6}  & & 0.2 M & 0 & 108 & 6\% & 30 \\ \cline{3-6}  & & 0.5 M & 0 & 108 & 7\% & 30 \\ \cline{3-6}  & & 0.0 M & 0.1 & 109 & 5\% & 30 \\ \cline{3-6}  & & 0.1 M & 0.1 & 92 & 6\% & 30 \\ \cline{3-6}  & & 0.2 M & 0.1 & 200 & 7\% & 30 \\ \cline{3-6}  & & 0.5 M & 0.1 & 189 & 9\% & 30 \\ \cline{3-6}  & & 0.0 M & 0.1 & 11 & 5\% & 30 \\ \cline{3-6}  & & 0.1 M & 0.1 & 453 & 10\% & 30 \\ \cline{3-6}  & Nano-flower & 0.2 M & 0.1 & 387 & 9\% & 30 \\ \cline{3-6}  & & 0.5 M & 0.1 & 219 & 8\% & 30 \\ \hline \multirow{8}{*}{Control} & 0.0 M & 0 & 11 & 5\% & 30 \\ \cline{3-6}  & & 0.1 M & 0 & 34 & 5\% & 30 \\ \cline{3-6}  & & 0.2 M & 0 & 58 & 6\% & 30 \\ \cline{3-6}  & & 0.5 M & 0 & 11 & 6\% & 30 \\ \cline{3-6}  & & 0.0 M & 0.1 & 11 & 5\% & 30 \\ \cline{3-6}  & & 0.1 M & 0.1 & 44 & 6\% & 30 \\ \cline{3-6}  & & 0.2 M & 0.1 & 125 & 12\% & 30 \\ \cline{3-6}  & & 0.5 M & 0.1 & 11 & 5\% & 30 \\ \cline{3-6}  & & 0.0 M & 0.1 & 11 & 5\% & 30 \\ \cline{3-6}  & & 0.1 M & 0.1 & 80 & 6\% & 30 \\ \cline{3-6}  & Nano-flower & 0.2 M & 0.1 & 60 & 7\% & 30 \\ \cline{3-6}  & & 0.5 M & 0.1 & 34 & 5\% & 30 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Comparison of the UCS and calcium carbonate content.  
Figure 11: The SEM images of EICP bioemented-treated specimens (**a**) control, (**b**) bioemented by CA only, and (**c**) bioemented by CA-Cu nanoflower.