## 2 Materials and Methods
\begin{table}
\begin{tabular}{c c c c c} \hline
**Notation** & **MWNT** & **NS** & **W/B** & **SP/B** & **Flow Value (mm)** \\ \hline C0N0 & 0 & 0 & 0.26 & 0.003 & 195 \\ C0N1 & - & 1 & - & - & 166 \\ C0N3 & - & 3 & - & - & 141 \\ C0N5 & - & 5 & - & - & 133 \\ \hline C0.3N0 & 0.3 & 0 & 0.26 & 0.0067 & 163 \\ C0.3N1 & - & 1 & - & - & 131 \\ C0.3N3 & - & 3 & - & - & 127 \\ C0.3N5 & - & 5 & - & - & 126 \\ \hline C0.6N0 & 0.6 & 0 & 0.26 & 0.013 & 150 \\ C0.6N1 & - & 1 & - & - & 139 \\ C0.6N3 & - & 3 & - & - & 130 \\ C0.6N5 & - & 5 & - & - & 135 \\ \hline C1.0N0 & 1.0 & 0 & 0.26 & 0.022 & 131 \\ C1.0N1 & - & 1 & - & - & 127 \\ C1.0N3 & - & 3 & - & - & 127 \\ C1.0N5 & - & 5 & - & - & 127 \\ \hline \end{tabular}
\end{table} 
Table 3: Constituent materials and mixture proportions of the MWNT/NS-incorporated cement composites. loading speed was 0.002 mm/s. Five composite samples for each sample type were tested, and the determined strength values were averaged. The compressive strengths of the composites were measured after 28 days of curing according to the ASTM C 109. Four composite samples were tested for each sample type, and the determined strength values were averaged. To assess the electrical conductivities of the composites, a two-probe method was employed. Before evaluating the conductivity, silver paste was first applied to both sides of the composite sample, and then copper foil was attached to the silver-paste-covered surfaces. The silver paste was used in an effort to decrease the contact resistance produced between the copper foil and the composite. The newly added copper foils were connected to two probes of a digital multimeter (Keysight, DMM34461A; Keysight Technologies, Santa Rosa, CA, USA), and the electrical resistance was assessed. Electrical resistance measurements were conducted for two samples of each composite type, and the determined values were averaged. The electrical resistance was converted to an electrical conductivity with consideration of the composite sample dimension. An equation that converts electrical resistance measured by the two-probe method to electrical conductivity was provided as follows [23; 33]. \[\sigma=\frac{1}{\rho}=\frac{L}{R\times A} \tag{1}\]  
where \(\sigma\) and \(\rho\) denote electrical conductivity and resistivity, respectively. \(R\) indicates electrical resistance measured from the samples. \(L\) and \(A\) denote distance between the electrodes and cross sectional area of sample that is contacted to the electrode, respectively [23; 33]. Details of the electrical conductivity assessment can be found in the publications of [PERSON] et al., 2018 and [PERSON] et al., 2020 [23; 33]. Porosity of the cement composite, which is defined as a ratio of the volume of water and air to total volume of the composite, was measured in accordance with the ASTM C 642 [34]. In porosity measurement, the prismatic parallelepiped cement composites with dimension of 40 mm by 40 mm by 160 mm were used and a following formula having parameters of \(A\), \(B\), and \(C\) was used [34]. \[\text{Porosity (vol.\%)}=\ \frac{C-A}{C-B}\times 100 \tag{2}\]  
where \(A\) indicates mass of the cement samples dried at 110 \({}^{\circ}\)C for 24 h [34]. \(B\) indicates apparent mass of the samples suspended in water after they were immersed and boiled [34]. \(C\) denotes mass of the surface-dried samples after they were immersed and boiled [34]. Details of test procedure can be found in the publication of [PERSON] et al., 2016 [34]. To observe the microstructures of the composites, fractured surface images were obtained by means of SEM (JEOL Ltd. in Tokyo, Japan, Model: JSM-6300). The composite samples for SEM observations were fabricated separately from the composite samples fabricated for the mechanical strength tests. The mixture proportions and fabrication procedure were identical to those mentioned earlier, but product models of the MWNTs and NS were not identical.