## 2 Materials and Methods
### Methods
Before measuring the surface characteristics, the samples were vacuum-pumped using a Flo-Vac Degasser installation, which is an integral part of the Quadrasorb SI/Kr analyzer and allows for the pumping of gases and water from the pore space in the temperature range of 15-400 \({}^{\circ}\)C and the control of the pressure in the system (with the sample) in the range of 101.3 kPa-0.133 Pa. In our work, the pumping of the samples was carried out at 100 \({}^{\circ}\)C (temperature of dehydration) to a residual constant pressure in the system of 0.133 Pa. The pumping time at this temperature was 4 h. The density functional theory (DFT) method was used to calculate the volume and average pore size, and the T-method Halsey was used to calculate the micropore volume and surface area of the micropore powder. The analysis of the chemical composition of the concrete and bentonite samples was carried out by X-ray fluorescence spectroscopy using an Axios mAX X-ray fluorescence spectrometer (PANalytical, Almelo, The Netherlands). The samples were pre-dried at 110 \({}^{\circ}\)C to a constant weight. The phase composition of the concrete before and after the experiment and the mineral composition of the bentonite were studied using a Rigaku Ultima-IV X-ray diffractometer (Rigaku, Tokyo, Japan). The diffractometer configuration was Cu-K\(\alpha\) radiation, detector--D/Tex-Ultra, shooting angle range--3-65\({}^{\circ}\) 2\(\Theta\). The quantitative phase composition was calculated according to the recommendations of [61] by the Rietveld method [62] using the PROFEX software for BGMN [63]. The IR spectra were obtained on a Perkin Elmer Spectrum One FT-IR spectrometer with an InGaAs detector. The IR spectrum was measured in the range 4000-400 cm\({}^{-1}\). For research, tablets were made from 1 mg of the sample and 400 mg of KBr by pressing for 20-25 min. The chemical state of the iron and the arrangement of its atoms in the mineral structure were studied by Mossbauer spectroscopy using an IN 96B inter-technique spectrometer with a \({}^{57}\)Co radiation source (Shared Equipment Center AIRES, IPGG RAS, St. Petersburg, Russia). The apparatus half-width for the spectrum of standard \(\alpha\)-Fe was 0.21 \(\pm\) 0.01 mm/s. The angle between the pallet and the radiation direction was set at 54.7\({}^{\circ}\) to eliminate the asymmetry of quadrupole doublets due to the preferred orientation of the studied particles and to introduce the condition of the equality of intensities and half-widths of lines in the doublet at the computer fitting of the spectrum. The lines of the Mossbauer spectra of the studied bentonitees were fitted into several doublets of the quadrupole splitting of Fe\({}^{3+}\) and Fe\({}^{2+}\)-ions in an octahedral position. Thermal analysis was performed on a TGA/DSC 3+ synchronous thermal analyzer (Mettler Toledo, Greifensee, Switzerland) equipped with an o-DTA sensor. The device was calibrated using the temperature and enthalpy of melting of the materials certified by the device manufacturer--indium, zinc, aluminum, and gold. The samples were taken in synthetic air (composition: 80% N\({}_{2}\), 20% O\({}_{2}\)) with a gas flow rate of 60 mL/min in 70 \(\mu\)L alumina crucibles. The heating program consisted of two dynamic segments (40-110 \({}^{\circ}\)C and 110-1000 \({}^{\circ}\)C) and one isothermal segment (110 \({}^{\circ}\)C, 15 min), the heating rate in the dynamic segments was 10 \({}^{\circ}\)C/min. The sample weight was about 50 mg. The experimental curves were processed using the STAReEvaluation Software (v. 16.40).