## 4 Conclusions  
In this study, the feasibility of using Biobio clam shells as a partial replacement for cement in mortars was investigated, analyzing its impact on the mechanical properties of the material. Comparative tests were performed on samples with different replacement \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Specimen** & **MR-00** & **MR-05** & **MR-10** & **MRC-00** & **MRC-05** & **MRC-10** \\ \hline Replacement percentage & 0\% & 5\% & 10\% & 0\% & 5\% & 10\% \\ Sand (SUSD) & 98.53 & 98.53 & 98.53 & 97.45 & 97.45 & 97.45 \\ Water (SUSD) & 0.37 & 0.37 & 0.37 & 0.40 & 0.40 & 0.40 \\ Cement (SUSD) & 79.08 & 75.12 & 71.17 & 78.21 & 74.30 & 70.39 \\ Residue (SUSD) & 0 & 0.12 & 0.24 & 0 & 2.43 & 4.86 \\ Total (SUSD) & 177.98 & 174.14 & 179.31 & 176.06 & 174.58 & 173.1 \\ Savings compared to the standard mix & 0\% & 2.16\% & 4.31\% & 0\% & 0.84\% & 1.68\% \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Dosing costs in mixture of 1 [m\({}^{3}\)]. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Format** & **Unit** & **Price (SUSD)** & **Unit Price (SUSD/unit)** \\ \hline Cement & 25 & kg & 4.04 [57] & 0.16 \\ Water & 1 & L & 0.0015 [58] & 0.0015 \\ Sand & 25 & kg & 1.68 [59] & 0.067 \\ Uncalcined shells & 1 & kg & 0.0050 & 0.0050 \\ Calcined shells & 1 & kg & 0.096 & 0.096 \\ Energy & 1 & kWh & 2.5 [60] & 2.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Reference values. percentages, both with calcined and non-calcined shells, to evaluate their compressive and flexural tensile strength. The results obtained provide a comprehensive view of the advantages and limitations of this alternative, allowing us to identify key areas for optimization in future works. The main conclusions of the study are presented below:  
The results indicate that, although the use of uncalcined shells at replacement percentages of 5% and 10% shows a slight increase in flexural tensile strength, these increases are not significant enough to ensure consistent improvements compared to the control sample. On the other hand, calcined shells not only do not improve the mechanical strength of the mortar but also show a decrease in compressive and flexural strength. The results obtained in this study differ from some previous studies that reported improvements in strength when using seashells as a partial substitute for cement. In particular, the compressive strength results were lower than those reported in the literature, indicating the need for adjustments in experimental parameters such as calcination temperature and time. To improve the feasibility of using seashells in mortars, it is recommended to optimize the calcination process, reduce the particle size of the shells, and explore the use of additives that improve the internal cohesion of the material. Furthermore, further research is needed to better understand how these factors affect the microstructure and mechanical properties of the mortar. Despite technical challenges, the use of seashells as a partial substitute for cement remains a promising option from an environmental perspective. Reducing the use of Portland cement and valorizing abundant waste such as seashells could contribute to sustainability in construction, provided that processes are optimized to ensure adequate mechanical performance. Conceptualization, M.V.F., B.S.M.T. and L.E.M.Q. ; methodology, B.S.M.T. and L.E.M.Q. ; validation, D.A.P. ; formal analysis, B.S.M.T. and A.F.S.S. ; investigation, M.V.F. and B.S.M.T. ; resources, L.E.M.Q. ; data curation, B.S.M.T. ; writing--original draft preparation, M.V.F. ; writing--review and editing, L.E.M.Q. ; visualization, J.L.V.R. ; supervision, J.L.V.R. ; funding acquisition, J.L.V.R. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.