## 3 Results
### Compressive Strength  
The results of determining the compressive strength of experimental samples of non-autoclaved aerated concrete are shown in Figure 5.  
The maximum compressive strength was recorded for prototypes of non-autoclaved aerated concrete of type 4A composition, where part of the cement 16% MS was replaced, and amounted to 13.2 MPa. The minimum value of compressive strength was recorded for samples of composition type 5B, where part of the cement was replaced with 20% GBFS and amounted to 5.5 MPa. In general, the compressive strength values of type A compounds are higher than those of type B and AB compounds (Table 9). The dependences of the change in the compressive strength of compositions of types A, B, and AB are shown in Figure 6.  
Figure 4: Statistical density values of non-autoclaved aerated concrete. Figure 5: Statistical values of compressive strength of non-autoclaved aerated concrete. Figure 6: Change in compressive strength of non-autoclaved aerated concrete samples depending on the percentage of binder replacement by various types of additives. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c c} \hline \hline
**Composition number** & C & 1A & 2A & 3A & 4A & 5A & 1B & 2B & 3B & 4B & 5B & 1 AB & 2 AB & 3 AB & 4 AB & 5 AB \\
**Compressive strength, MPa** & 9.0 & 10.1 & 11.4 & 12.1 & 13.2 & 10.0 & 8.5 & 8.4 & 7.2 & 6.3 & 5.5 & 9.1 & 8.5 & 7.4 & 7.2 & 6.7 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Experimental values of compressive strength of non-autoclaved aerated concrete. Figure 6 shows that the addition of microsilica has the most positive effect on the compressive strength of non-autoclaved aerated concrete. Statistical processing of the obtained experimental data made it possible to determine regression curves describing the effect of additives \(x\) on compressive strength \(R_{b}\). \[R_{bMS} =9.11-\ 0.0135\times x+0.0597\times\ x^{2}-\ 0.00282\times x^{3},\ \ \ \ R^{2}=0.936 \tag{3}\] \[R_{b\,GBFS} =9.01-\ 0.0758\times\ x-\ 0.00525\times\ x^{2},\ \ \ \ R^{2}=0.98\] (4) \[R_{b\,MS+GBFS} =9.21-\ 0.0995\times x-\ 0.00156\times x^{2},\ \ \ \ \ R^{2}=0.93 \tag{5}\]  
The significance of the regression coefficients was tested using [PERSON]'s and [PERSON]'s tests. In the above equations, all coefficients are significant. The coefficient of determination is quite high from 0.93 to 0.98. It can also be seen that if the additive \(x\) is equal to zero, the value of the compression strength is approximately the same with an error of \(\pm 5\%\). Therefore, the MS additive, introduced instead of part of the cement in an amount of 4%, provides an increase in strength by 12% compared to the control composition, and replacing part of the cement with an MS additive in an amount of 8%, 12%, 16%, and 20% provides an increase in strength by 27%, 35%, 47%, and 11% respectively. The decrease in strength gained when replacing cement with 20% MS indicates that a further increase will lead to a loss in strength. This increase in the strength of non-autoclaved aerated concrete when replacing part of the MS cement in an amount of 4-16% can be explained by the fact that the addition of MS, due to its pozzolanic activity, provides the formation of additional C-S-H and creates the effect of a denser packing of particles [43,60]. Replacing part of the cement with the addition of ground blast-furnace slag leads to a decrease in the strength of non-autoclaved aerated concrete in comparison with the strength value of the control composition. Thus, when replacing part of the cement with 4% GBFS, the compressive strength decreases by 5%, with the amount of GBFS 8%, the strength decreases by 6%, with the amount of GBFS 12%, the strength decreases by 19%, and the replacement of cement with GBFS in the amount of 16% and 20% leads to a reduction in compressive strength of up to 29% and 39%, respectively. First, the drop in strength characteristics is due to the fact that when using GBFS in concrete, it reduces \"the degree of hydration of the cement due to the lack of cement gel\".