## Result and Discussion  
### Air Content, Flow, Compressive Strength  
To examine the physical performance of the cement mortar mixed with the water-repellent powders, the air content, flow, and compressive strength were measured. The measurement results showed that the Sand-Co, Silica-Co, FA-Co, and WR (water repellent)-In(inner) specimens exhibited approximately 60 mm higher flow values and higher air contents than the OPC and ZWR specimens. The compressive strengths of OPC and ZWR exhibited a standard deviation of 2 MPa, whereas those of Sand-Co, Silica-Co, FA-Co, and WR-In showed slightly larger deviations ranging from 3 to 6 MPa. The results are shown in Tables 9 and 10.  
Figure 7 shows the results in a graph. This appears to be because the water-repellent's active ingredient was not accurately attached to each powder, and some of it was lost as the materials were separated due to the different specific gravity of silane/siloxane, while the water-repellent's performance was left in some substances remaining inside mortar. The separated water-repellent active ingredient inhibited cement bonding at early ages, thereby causing somewhat high air content and flow values. It appears that ZWR had the ability to fix the water-repellent's active ingredient as the water-repellent's active ingredient was impregnated on the surface of and inside natural zeolite.  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Name**} & \multicolumn{6}{c}{**Compressive Strength (MPa)**} & \multicolumn{3}{c}{**Normalized**} \\ \cline{2-10}  & \multicolumn{3}{c}{**7 Days**} & \multicolumn{3}{c}{**28 Days**} & \multicolumn{3}{c}{**Values**} \\ \cline{2-10}  & **1 st** & **2 nd** & **3 rd** & **Average** & **1 st** & **2 nd** & **3 rd** & **Average** & OPC 28 Days (\%) \\ \hline OPC & 26 & 27.5 & 28 & 27 & 36 & 35 & 37 & 36 & 100 \\ \hline Sand–Co & 8 & 4 & 5 & 5 & 11 & 6 & 7 & 8 & 22.2 \\ \hline Silica–Co & 13 & 19 & 15 & 16 & 15 & 21 & 17 & 18 & 50 \\ \hline FA–Co & 16 & 12.5 & 13 & 14 & 18 & 12 & 16 & 15 & 41.6 \\ \hline WR–In & 10 & 10 & 13 & 11 & 7 & 9 & 13 & 10 & 27.7 \\ \hline ZWR & 25 & 25 & 23 & 24 & 30 & 29 & 32 & 30 & 83.3 \\ \hline \hline \end{tabular} Fly ash (FA)–Co, WR (water repellent)-In(inner), water-repellent impregnated natural zeolite (ZWR).  
\end{table}
Table 10: Result of compressive strength test.  
\begin{table}
\begin{tabular}{c c c} \hline \hline \multicolumn{1}{c}{**Name**} & \multicolumn{1}{c}{**Flow (mm)**} & \multicolumn{1}{c}{**Air Content (\%)**} \\ \hline OPC & 115 & 5 \\ \hline Sand–Co & 180 & 11 \\ \hline Silica–Co & 170 & 9.5 \\ \hline FA–Co & 170 & 11 \\ \hline WR–In & 160 & 12 \\ \hline ZWR & 110 & 7.5 \\ \hline \hline \end{tabular} Fly ash (FA)–Co, WR (water repellent)-In(inner), water-repellent impregnated natural zeolite (ZWR).  
\end{table}
Table 9: Result of the cement mortar flow test and air content test.  
The OPC exhibited the highest compressive strength followed by ZWR, Silica-Co, FA-Co, WR-In, and Sand-Co. The strength of the ZWR specimen was approximately 83% of that of the reference mortar. The ZWR, which used natural zeolite as a carrier, tended to show slightly lower strength than the reference mortar. This appears to be because the fine particles of ZWR delayed the hydration reaction of cement, as it is hydrophobic and tended to be attached to the surface of the pores inside cement, and because silane/siloxane, which is the water-repellent's active ingredient, was attached to the clinker surface, thereby affecting the strengths of C3S and C2S or delaying the formation of calcium silicate hydrate (CSH) [35]. The ZWR, which used natural zeolite, can improve long-term strength and the pozzolanic reaction can be expected. The ZWR, however, does not completely contribute to the pozzolanic reaction, because the surface and outside of natural zeolite was composed of silane/siloxane through impregnation.