# Nanmodified Concrete with Enhanced Characteristics Based on River Snail Shell Powder
## 4 Discussion  
To obtain a more accurate picture of the change in the characteristics of concrete, depending on the amount of RSSP additive introduced to replace part of the cement, we present them as a percentage in Table 6.  
From Table 5 it can be seen that the most optimal amount of cement to be replaced by the powder of snail shells is 6%. Such an amount of the nanomodifying additive makes it possible to increase the strength characteristics by up to 12% and reduce the deformations by up to 7%. In this case, the elastic modulus increased up to 8%. At the same time, replacing cement with the nanomodifier RSSP, from 0 to 6%, there is a smooth increase in strength characteristics and a decrease in the deformation properties of concrete in comparison with the control composition. It can also be seen that after a further increase in the dosage of RSSP instead of part of the cement from 6 to 12%, there is a sharper decrease in the strength characteristics (up to 18%) and an increase in the deformation properties (up to 17%) of nanomodified concrete compared to conventional concrete. The modulus of elasticity is reduced to 17% at 12% RSSP.  
The obtained optimal dosage of the nanomodifying additive in the form of a powder of snail shells of 6% is in good agreement with the results of other studies [2; 38; 39; 40], in which the most effective dosages of shell powder were 4% [38], 5% [39; 40] and to a lesser degree at 10% [40]. However, at the same time, in [39], an increase in the compressive strength after 28 days of concrete hardening was achieved up to 7.5%, and the axial tensile strength up to 3.5%. The study [2] summarizes the feasibility of using various aquaculture wastes in concrete as a partial replacement for cement. However, it is noted that it is necessary to dose the obtained powder from the waste in a small amount, in which the compressive strength of concrete is only slightly below the strength of the control samples from ordinary concrete, in contrast to high percentages of cement replacement, in which the strength is much lower. Only a slight increase in flexural tensile strength and elastic modulus was observed due to the development of a good bond between the binder matrix and aggregates [2]. In [38], the optimal dosage of powdered ground shells, equal to 4%, did not lead to an increase in the compressive strength of concrete and the elastic modulus. At the same time, the tensile strength in bending and axial tension were increased to 10 and 9%, respectively. In comparison with the other studies [2; 38; 39; 40], it was possible to achieve a more impressive improvement in the strength and deformation characteristics of concrete due to its nanomodification with the powder of snail shells.  
\begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline \multicolumn{1}{c}{\multirow{2}{*}{**Concrete Characteristics**}} & \multicolumn{3}{c}{**\(\Delta\), \%, When the Content of the Powder of the Shells of River Snails in the Amount**} \\ \cline{2-9}  & **0** & **2** & **4** & **6** & **8** & **10** & **12** \\ \hline \(R_{b,\text{chips}}\) MPa & 0 & +3 & +7.1 & +11.9 & +2.0 & \(-\)7.9 & \(-\)16.8 \\ \hline \(R_{b}\), MPa & 0 & +1.3 & +4.3 & +8.0 & +0.7 & \(-\)9.0 & \(-\)18.1 \\ \hline \(R_{b\text{th}}\), MPa & 0 & +2.5 & +5.5 & +9.1 & +1.9 & \(-\)10.0 & \(-\)17.6 \\ \hline \(R_{b\text{th}}\), MPa & 0 & +2.3 & +6.5 & +11.1 & +1.5 & \(-\)9.1 & \(-\)16.4 \\ \hline \(\epsilon_{bR}\), mm/m \(\times\) 10\({}^{-3}\) & 0 & \(-\)1.8 & \(-\)3.9 & \(-\)6.1 & \(-\)0.4 & +8.3 & +14.9 \\ \hline \(\epsilon_{bR}\), mm/m \(\times\) 10\({}^{-4}\) & 0 & \(-\)1.5 & \(-\)4.5 & \(-\)6.7 & 0 & +8.2 & +17.2 \\ \hline \(E\), GPa & 0 & +1.5 & +4.0 & +7.3 & +1.1 & \(-\)8.0 & \(-\)17.1 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Changes in characteristics of concrete depending on the dosage of snail shell powder (\(\Delta\)).