## 2 Materials and Methods
### Methods  
All samples passed through a system of complex research; the composition of the liquid and solid components, and the structure of the solid component were studied. The change in the cationic composition of the solution was measured using optical emission spectroscopy on an Agilent 5110 inductively coupled plasma optical emission spectrometer (Agilent Technologies, Santa Clara, CA, USA). The anions were measured using a KAPEL-105M capillary electrophoresis system using the PND F 14.1:2:4 technique 157-99. The separation of the solid phase from the solution was carried out by centrifugation in a Sigma 3-16 L centrifuge (Sigma, Osterode am Harz, Germany) for 10 min in 30 mL tubes with a rotor speed of rpm. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Sample** & **Surface Area S, m\({}^{2}\)/g** &
\begin{tabular}{c} **Pore Volume,** \\ **g\(\cdot\)cm\({}^{-3}\)/Average Pore Size, nm** \\ \end{tabular} \\ \hline \hline \multicolumn{3}{c}{Concrete} \\ \hline Initial & 12.1 & 0.089/29.4 \\
1 month & 16.9 & 0.111/12.6 \\ \hline \hline \multicolumn{3}{c}{Bentonite} \\ \hline Initial & 22.0 & 0.084/6.0 \\
1 month & 32.0 & 0.080/4.0 \\
3 months & 30.0 & 0.086/4.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The surface characteristics of the investigated concrete and bentonite samples. The pH levels of the solutions during the experiments were determined using a pH meter with an IT-1101 (Izmeritelnaya Tekhnika, Moscow, Russian Federation) combined electrode. Studies of the porosities and microstructures of the concrete samples were carried out by scanning electron microscopy and computer microtomography. An electron microscope (SEM) LEO1450 VP (Carl Zeiss, Oberkochen, Germany) was used to study the porosities of the concrete samples. To remove the accumulated electric charge, the sample was subjected to gold sputtering in a vacuum chamber before taking pictures. The thickness of the coating layer with the conductive material was 5-10 nm. The quantitative analysis of the microstructure was carried out using the specialized software STIMAN (Structural Image Analysis) [60]. It is known that the methods of SEM studies are rightly referred to as local, single point studies, obtaining a single SEM image, and do not allow for speaking about the properties of the object under study as a whole. In order to overcome this limitation, STIMAN analyzes a series of different-scale images of an object. As a result of the analysis, an array of quantitative data on the structure of the sample is obtained, covering all scale levels of the structural elements. As a result of the analysis, integral quantitative indicators of porosity are obtained. A Yamato TDM1000 X-ray tomograph (Yamato Scientific, Tokyo, Japan) was used to study the porosity using computed microtomography. Scans were performed at 75 kV and 0.053 mA with a voxel size of 20 \(\upmu\)m. The measuring was carried out under magnification, which made it possible to obtain a 3D model of the sample as a whole. The construction and processing of three-dimensional models of the samples were performed using the VGStudio MAX 2.2 software. As a result, a visualization of the internal structure of the samples was achieved, the distribution of the pores over the volume of the samples was determined, and the total porosity was calculated at a given magnification. The specific surface area (SSA) was determined with a Quadrasorb SI/Kr analyzer (Quantachrome Instruments, Boynton Beach, FL, USA). Adsorption was performed at the temperature of liquid nitrogen (77.35 K). Nitrogen with a purity of 99.999% served as an adsorbate. Helium grade 6.0 (99.9999%) was used for the volume calibration of the measuring cells. The calculation was carried out by the BET multiple-point isotherm in the range of P/P0 from 0.05 to 0.30.