## 3 Results and Discussion
### SEM Findings  
SEM images of the fracture surface morphologies of cement stone samples with _w/c_ ratios of 0.40, 0.44, 0.50 at one day and seven days are shown in Figure 12. Image J was used to statistically analyze the morphologic characteristics of crystalline CH, 20 CH crystals.  
In Figure 12, with the increase in the _w/c_ ratio, the pore spaces of samples increased obviously, the side length of the formed CH crystals became larger and more regular. The proportion of large capillary pores increased correspondingly. When the _w/c_ ratio is 0.40, only a few well-crystallized hexagonal and tabular CH crystals can be found, while the side length of the hexagonal CH crystals is mainly distributed in the range of 0.8-2.5 \(\upmu\)m (Figure 12a). When the _w/c_ ratio is 0.44, the formed CH crystals are in clusters, and most of them are well crystallized hexagonal and tabular, while the side length of the CH crystals is mainly distributed in the range of 1.3-3.6 \(\upmu\)m (Figure 12b). When the _w/c_ ratio is 0.50, compared to the samples with _w/c_ ratios of 0.40 and 0.44, the formed CH crystals in Figure 11c are larger and looser, while the side length of the CH crystals is mainly distributed in the range of  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Function** & **Measured Results** & **Predicted Results** & **Residual** &
\begin{tabular}{c} **Internally** \\ **Studentized Residuals** \\ \end{tabular} \\ \hline \multirow{8}{*}{Ryshkewitch function} & 47.27 & 40.29 & 6.98 & \(-1.579\) \\  & 37.62 & 35.93 & 1.69 & \(-0.264\) \\  & 30.15 & 32.72 & \(-2.57\) & 0.805 \\  & 34.08 & 32.02 & 2.06 & \(-0.485\) \\  & 30.72 & 28.01 & 2.71 & \(-0.785\) \\  & 24.90 & 26.31 & \(-1.41\) & 0.291 \\  & 23.91 & 22.34 & 1.57 & \(-0.646\) \\  & 19.07 & 19.16 & \(-0.09\) & \(-0.289\) \\  & 11.40 & 13.30 & \(-1.90\) & 0.027 \\  & 8.63 & 11.03 & \(-2.40\) & 0.095 \\  & 5.74 & 10.08 & \(-4.34\) & 0.597 \\  & 49.30 & 52.32 & \(-3.02\) & 1.388 \\  & 47.27 & 40.70 & 6.57 & \(-2.121\) \\  & 37.62 & 36.88 & 0.74 & \(-0.128\) \\  & 30.15 & 33.95 & \(-3.80\) & 1.424 \\  & 34.08 & 33.28 & 0.80 & \(-0.196\) \\  & 30.72 & 29.39 & 1.33 & \(-0.432\) \\  & 24.90 & 27.65 & \(-2.75\) & 0.974 \\  & 23.91 & 23.35 & 0.56 & \(-0.241\) \\  & 19.07 & 19.60 & \(-0.53\) & 0.093 \\  & 11.40 & 11.58 & \(-0.18\) & \(-0.134\) \\  & 8.63 & 7.87 & 0.76 & \(-0.511\) \\  & 5.74 & 6.17 & \(-0.43\) & \(-0.116\) \\  & 49.30 & 48.20 & 1.10 & 0.001 \\  & 47.27 & 40.23 & 7.04 & \(-1.930\) \\  & 37.62 & 37.23 & 0.39 & 0.063 \\  & 30.15 & 34.78 & \(-4.63\) & 1.564 \\  & 34.08 & 34.21 & \(-0.13\) & 0.179 \\  & 30.72 & 30.71 & 0.01 & 0.086 \\ One linear function & 24.90 & 29.07 & \(-4.17\) & 1.343 \\  & 23.91 & 24.78 & \(-0.87\) & 0.272 \\  & 19.07 & 20.76 & \(-1.69\) & 0.466 \\  & 11.40 & 11.22 & 0.18 & \(-0.242\) \\  & 8.63 & 6.31 & 2.32 & \(-0.967\) \\  & 5.74 & 3.96 & 1.78 & \(-0.835\) \\ \hline \hline \end{tabular}
\end{table}
Table 4: \(Cont.\)1.9-5.3 \(\upmu\)m (Figure 12c). Compared to the results in Figure 12c,d, it also can be found that the cement stone trends to be more compact as the hydration time increases.  
The cement particles in the cement slurry with a high _w/c_ ratio have a relatively higher hydration degree compared to the cement stone with a low _w/c_ ratio. However, the proportion of cement decreases as the _w/c_ ratio increases, and the amount of hydration products decreases correspondingly (Figure 8, Figure 9, and Figure 12). Macroscopically, the mechanical properties of the cement stone decrease with the increase in the _w/c_ ratio (Figure 6).