## 2 Materials and Methods
### Main Research
#### 3.2.6 Chemical Resistance Tests
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Parameter**} & \multirow{2}{*}{**Types**} & \multicolumn{3}{c}{**Values**} & \multicolumn{3}{c}{**Variation Coefficients**} \\ \cline{3-8}  & & **NaCl** & **HCl** & **Na2 SO4** & **NaCl** & **HCl** & **Na2 SO4** \\ \hline \multirow{8}{*}{Loss of} & 1 & 52.0 & 17.8 & 13.3 & 18.93 & 10.14 & 9.23 \\  & 2 & 43.8 & 15.1 & 12.0 & 16.32 & 8.76 & 8.02 \\ \cline{1-1}  & 3 & 43.8 & 14.9 & 11.8 & 17.89 & 8.32 & 7.31 \\ \cline{1-1}  & banding & 4 & 43.5 & 14.6 & 11.6 & 16.23 & 8.48 & 7.29 \\ \cline{1-1}  & strength, \% & 5 & 38.0 & 13.5 & 8.2 & 13.27 & 8.24 & 6.85 \\ \cline{1-1}  & 6 & 35.2 & 13.4 & 7.2 & 14.87 & 8.31 & 7.02 \\ \cline{1-1}  & 7 & 34.3 & 13.2 & 6.7 & 13.04 & 8.18 & 6.47 \\ \hline \hline \end{tabular}
\end{table} 
Table 13: _Cont._  
Figure 9: Results of predicting the change in strength over time in different chemical environments: (**a**) Strength loss prediction curves for samples exposed to NaCl environment; (**b**) Strength loss prediction curves for samples exposed to HCl environment; (**c**) Strength loss prediction curves for samples exposed to Na2 SO4 environment. hardening, does not reduce the amount of free portlandite Ca(OH)2--a mineral in cement stone that facilitates corrosion processes. When the samples were maintained in a solution of hydrochloric acid (HCl), the following changes in weight and strength parameters were observed in the two-component composition samples relative to the reference sample: the weight varied from 8.6 to 13.6%; compressive strength ranged from 12.1 to 19.1%; bending strength fluctuated from 15.2 to 18.0%. For the three-component samples, these same parameters comprised a weight range from 17.1 to 29.3%; compressive strength from 19.7 to 29.5%; flexural strength from 24.2 to 25.8%. When the samples were maintained in Na2 SO4 a sodium sulfate environment, the following changes in weight and strength parameters were observed for the samples of two-component composition relative to the reference samples: mass varied from 6.2 to 9.7%; compressive strength varied from 11.2 to 14.4%; flexural strength varied from 9.8 to 12.8%. For the three-component samples, the same parameters showed a variance in mass from 17.7 to 25.7%; compressive strength from 42.4 to 50.4%; flexural strength from 38.7 to 49.6%. Figure 8 shows the results of strength loss prediction during long-term exploitation of concrete structures in aggressive environments. Prediction calculations were performed according to GOST 58896, based on potentiation of chemical resistance coefficients changing as the samples are maintained in aggressive environments [24]. Figure 9a shows the results when the samples are maintained in NaCl, Figure 9b in HCl, and Figure 9c in Na2 SO4. Example of calculating loss of strength on Type 1 specimens: \(\sum\lg\tau_{\rm i}=11.72\), \(\sum\lg\kappa_{\rm GRI}=-0.244\); \(\sum\lg\overline{\tau_{\rm i}}=1.95\); \(\sum\lg\overline{\rm k_{\rm GRI}}=-0.041\); \(\sum(\lg\kappa_{\rm GRI}-\lg\kappa_{\rm GRI})\times(\lg\overline{\tau_{\rm i} }-\lg\tau_{\rm i})=-0.025\); \(\sum(\lg\overline{\tau_{\rm i}}-\lg\tau_{\rm i})^{2}=0.41\); \(\sum(\lg\kappa_{\rm GRI}-\lg\kappa_{\rm GRI})\times(\lg\overline{\tau_{\rm i }}-\lg\tau_{\rm i})=-0.025\); \(\sum(\lg\overline{\tau_{\rm i}}-\lg\tau_{\rm i})^{2}=0.41\); \(\sum(\lg\kappa_{\rm GRI}-\lg\kappa_{\rm GRI})\times(\lg\overline{\tau_{\rm i }}-\lg\tau_{\rm i})=-0.060\); \(\lg\overline{\rm k_{\rm GRI}}-\lg\cdot\lg\overline{\tau_{\rm i}}=0.078\); Then the equation has the form \(\lg\kappa_{\rm CR}=0.0775-0.06\lg\tau\); For a duration of 100 years \(\tau_{\rm i}=36000\)days: \(\lg\kappa_{\rm CR}=0.0775-0.06\lg 3600=0.0775-0.06\times 4.56=-0.198\); Then \(\rm k_{\rm CR}=0.63\) (Loss of strength = 63%), See data-point on Figure 8c.