## 3 Results
### Compressive Strength  
Table 4 presents the results of the compression test for the specimens with uncalcined and calcined shells. These results were obtained by testing the halves from the flexural tensile test, which are referred to in the table as P1 and P2. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{3}{*}{**Specimen**} & \multirow{3}{*}{**\#**} & \multicolumn{4}{c}{**Compressive Strength [MPa] at Age:**} & \multirow{3}{*}{**Standard Deviation at 28 Days**} \\ \cline{3-10}  & & & **3 Days 1** & & & **7 Days** & & **14 Days** & **28 Days** & \\ \cline{3-10}  & & **P1** & **P2** & **P1** & **P2** & **P1** & **P2** & **P1** & **P2** & **28 Days** \\ \hline \multirow{3}{*}{MR-00} & 1 & 7.54 & 7.80 & 14.79 & 15.98 & 22.85 & 22.54 & 22.72 & 27.29 & \multirow{3}{*}{2.61} \\  & 2 & 8.03 & 7.85 & 15.63 & 16.02 & 22.97 & 22.32 & 29.61 & 29.86 & \multirow{3}{*}{2.61} \\  & 3 & 7.57 & 8.08 & 15.42 & 15.64 & 21.34 & 20.87 & 28.50 & 28.18 & \\ \hline \multirow{3}{*}{MR-05} & 1 & 6.10 & 6.20 & 14.29 & 13.91 & 19.59 & 19.83 & 25.78 & 26.25 & \multirow{3}{*}{0.98} \\  & 2 & 6.23 & 6.27 & 12.81 & 12.97 & 20.90 & 20.14 & 26.98 & 25.91 & \\  & 3 & 6.18 & 6.37 & 12.63 & 12.86 & 19.38 & 19.33 & 24.22 & 24.90 & \\ \hline \multirow{3}{*}{MR-10} & 1 & 5.54 & 5.57 & 11.65 & 11.38 & 19.11 & 19.24 & 21.95 & 22.00 & \multirow{3}{*}{0.5} \\  & 2 & 5.61 & 5.59 & 12.03 & 11.84 & 20.25 & 17.71 & 22.99 & 22.53 & \\ \cline{1-1}  & 3 & 5.34 & 5.79 & 12.19 & 12.92 & 18.98 & 18.40 & 22.53 & 21.61 & \\ \hline \multirow{3}{*}{MRC-00} & 1 & 3.34 & 3.18 & 9.67 & 11.40 & 15.52 & 15.37 & 19.36 & 20.46 & \multirow{3}{*}{1.03} \\  & 2 & 3.42 & 3.29 & 9.36 & 10.02 & 15.44 & 14.72 & 21.31 & 20.83 & \\ \cline{1-1}  & 3 & 3.73 & 3.31 & 9.82 & 10.80 & 16.11 & 14.53 & 22.44 & 21.41 & \\ \hline \multirow{3}{*}{MRC-05} & 1 & 2.88 & 2.93 & 9.02 & 10.41 & 13.64 & 13.66 & 17.76 & 18.32 & \multirow{3}{*}{1.17} \\  & 2 & 2.64 & 2.97 & 9.55 & 9.40 & 13.34 & 14.30 & 18.74 & 17.71 & \\ \cline{1-1}  & 3 & 2.80 & 2.98 & 10.03 & 9.56 & 13.58 & 13.53 & 17.40 & 15.36 & \\ \hline \multirow{3}{*}{MRC-10} & 1 & 2.91 & 2.88 & 7.73 & 8.64 & 13.46 & 13.08 & 16.64 & 18.10 & \multirow{3}{*}{2.66} \\  & 2 & 2.69 & 2.78 & 9.28 & 9.25 & 12.36 & 12.53 & 12.80 & 13.49 & \\ \cline{1-1}  & 3 & 2.82 & 2.31 & 8.17 & 8.61 & 12.48 & 12.49 & 19.07 & 18.37 & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Compressive strength results. Figure 7: Summary of flexural tensile strength results: (**a**) specimens with uncalcined shell and (**b**) specimens with calcined shell. The compressive strength of the specimens tested at 28 days of age decreased by 0.03% and 0.16% in the specimens with uncalcined shells MR-05 and MR-10, respectively, and by 0.32% and 0.39% in the specimens with calcined shells, MRC-05 and MRC-10, respectively, compared to the control sample MR-00. Considering the dispersion of the data, the results of the standard sample show a clear advantage over the samples with 10% replacement, while for the sample with 5% replacement, the ranges generated with the dispersion partially coincide with MR-00 specimen. A graphical representation of the results is presented in Figure 8. From this, it is perceived that there is no improvement in the compressive strength at 28 days of age in the specimens when cement is replaced with calcined clam shells since the MRC-05 and MRC-10 specimens decreased their strength by 0.32% and 0.26% compared to their MR-05 and MR-10 peers. These results may be due to the effect of calcination, which, when not well controlled, leads to a reduction in strength due to changes in the microstructure and increased porosity, which seems to be in line with what was observed in this study. The results obtained do not coincide with those obtained by [16], where the compressive strength with a 5% replacement of bivalve claims by cement, exceeded the magnitude recorded by the standard sample, reaching up to 101% of this value.