## 2 Development of Conductive Mortar
### Results and Discussions  
#### 2.2.1 Pore Characteristics  
Before measuring the resistivity of the prepared specimens, pore characteristics were analyzed. The specific surface areas, pore volumes, and average pore sizes were measured by adsorbing N\({}_{2}\) and measuring its amount (i.e., Brunauer-Emmett-Teller (BET) method). In other words, N\({}_{2}\) was adsorbed to four admixtures (i.e., activated carbon, bentonite, zeolite, and geopolymer) and sand, and the above properties were evaluated. The Surface Area and Porosity System (TriStar II 3020, Micromeritics, Norcross, GA, USA) was used for this test. N\({}_{2}\) adsorption and desorption isotherms of admixtures were obtained at \(-195.8\)\({}^{\circ}\)C, and overnight degassing was conducted at 105 \({}^{\circ}\)C. We obtained 99 points to determine the adsorption and desorption isotherms.  
Table 2 and Figure 2 provide the measured specific surface areas, pore volumes, and average pore sizes of the four admixtures and sand. In general, it is true that the larger the specific surface area and pore volume, the greater the capacity to store water. The specific surface area of activated carbon is the highest among the five materials, and the four selected admixtures have a higher specific surface area than sand. The pore volume can be used to determine the conductivity of the pores. When the size (diameter) of pores is less than 2 nm, they are classified as micropores; when it is in the range of 2-50 nm, it is classified as mesopores; when it is more than 50 nm, it is traditionally classified as macropores in the field of chemistry according to the International Union of Pure and Applied Chemistry (IUPAC, Zurich, Switzerland). Typically, the mesopore acts as a channel through which moisture can be smoothly supplied into the material, and the micropore adsorbs moisture. While mesopores are developed to some degree, materials with a large volume of micropores play a crucial role in reducing resistivity by adsorbing a large amount of moisture in the pore, which is a favorable condition for conductive mortar. The activated carbon has the largest micropore volume; bentonite, zeolite, and geopolymer follow; and sand has the smallest volumes of mesopores and micropores. Since activated carbon has much larger mesopore and micropore volumes and specific surface area than sand, it can be used as a material for providing large conductivity by mixing a small amount of activated carbon [32]. Based on the results, we can tentatively conclude that activated carbon will be the best material as the conductive mortar, and the resistivity measurement supports this tentative conclusion in the next section.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Item**} & \multirow{2}{*}{
\begin{tabular}{c} **Specific** \\ **Surface Area** \\ **(m\({}^{2}\)/g)** \\ \end{tabular} } & \multicolumn{4}{c}{**Pore Volume**} \\ \cline{3-5}  & & **Micropore** \\  & & **Volume** \\  & & **(cm\({}^{3}\)/g)** & **(cm\({}^{3}\)/g)** & **(cm\({}^{3}\)/g)** \\ \hline Sand (\#6) & 0.239 & 0.000034 & 0.000759 & 0.001 & 13.249 \\ \hline Activated carbon & 939.270 & 0.397324 & 0.023491 & 0.420 & 1.792 \\ \hline Bentonite & 78.548 & 0.023538 & 0.078483 & 0.102 & 5.195 \\ \hline Zeolite & 24.695 & 0.005015 & 0.057684 & 0.062 & 10.155 \\ \hline Geopolymer & 20.337 & 0.000571 & 0.147579 & 0.148 & 29.138 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Specific surface area, total pore volume, and average pore size of admixtures and sand.