# Analysis of the Effect of Capillary Water Absorption on the Resistivity of Cementitious Materials
## 3 Results and Discussion
### Pore Structure Feature  
Figure 10 shows the MIP test results of the pore volume of the specimen, which can be divided into gel pore (5-10 nm), transition pore (10-100 nm), capillary pore (100-1000 nm), and macropore (>1000 nm) according to pore size [35]. It can be seen from Figure 10 that compared with the JZ group, the pore volumes of the specimens in the FA group and the SL group after 28 days of curing are not very different, while the number of gel pores and transition pores is significantly increased, and the number of capillary pores and macropores is significantly reduced. Combined with the analysis in the Section 3.4, this is because FA and SL have lower activity and a lesser secondary hydration reaction, so their pore volume is very much different from that of the JZ group. Due to its physical filling effect and certain secondary hydration reaction, it has a certain refinement effect on the pores. This increases the tortuous degree of pores in the specimen to a certain extent, so the number of conductive pathways formed in the specimen under the effect of capillary water absorption is reduced and the resistivity of the specimen after capillary water absorption is increased; this phenomenon is more obvious with the increase in the doping amount. Under the same doping amount, the specimen doped with FA is stronger than that doped with SL group due to its secondary hydration effect (as can be seen from the Section 3.4, under the same doping amount, 28 d Ca(OH)\({}_{2}\) in FA group is lower than that in SL group), which leads to more gel pores and transition pores in FA specimens compared with SL group, and a better effect of the refining pore \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Group** & **Equation** & **Correlation** & **Capillary Absorption** \\  & & **Coefficient** & **Coefficient** \\ \hline JZ & m = \(-\)0.0345 + 0.01984 t\({}^{1/2}\) & 0.9976 & 0.01984 \\ FA-1 & m = 0.00953 + 0.01644 t\({}^{1/2}\) & 0.993 & 0.01644 \\ FA-2 & m = \(-\)0.00631 + 0.01462 t\({}^{1/2}\) & 0.999 & 0.01462 \\ FA-3 & m = \(-\)0.0122 + 0.01267 t\({}^{1/2}\) & 0.9917 & 0.01267 \\ FA-4 & m = 0.01224 + 0.00992 t\({}^{1/2}\) & 0.9956 & 0.00992 \\ SL-1 & m = \(-\)0.00323 + 0.01568 t\({}^{1/2}\) & 0.9957 & 0.01568 \\ SL-2 & m = \(-\)0.00718 + 0.01402 t\({}^{1/2}\) & 0.9987 & 0.01402 \\ SL-3 & m = 0.03619 + 0.01105 t\({}^{1/2}\) & 0.99551 & 0.01105 \\ SL-4 & m = \(-\)0.00607 + 0.00983 t\({}^{1/2}\) & 0.991 & 0.00983 \\ SF-1 & m = 0.01867 + 0.00938 t\({}^{1/2}\) & 0.9941 & 0.00938 \\ SF-2 & m = \(-\)0.03766 + 0.00928 t\({}^{1/2}\) & 0.9917 & 0.00928 \\ SF-3 & m = 0.01172 + 0.0089 t\({}^{1/2}\) & 0.99213 & 0.0089 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Capillary water absorption coefficient fitting equation and parameters. Figure 9: Diagram of a cement mortar opening pore: (**a**) Opening pore structure under dry conditions. (**b**) Opening pore structure under capillary water absorption. structure. Therefore, the overall resistivity of FA specimens after capillary absorption is higher than that of SL group. In addition, combined with the test results of the resistivity of the specimens in the JZ group, the FA group, and the SL group, it can be found that when there is little difference in the pore volume, the resistivity of the specimens in the dry state increases with the increase in the number of capillary pores and macropores. According to this phenomenon, it is speculated that capillary pores and macropores contribute more to the resistivity of the specimens in the dry state. It can also be seen from Figure 10 that compared with the JZ group, the pore volume of the specimen in the SF group was reduced by more than half. This is mainly related to the higher activity of silica fume; the stronger secondary hydration leads to a significant reduction in its pore volume. which greatly reduced the number of conductive channels formed in the specimen under the action of capillary water absorption, and greatly improved the resistivity of the specimen after capillary water absorption.