# Formulation of Alkali-Activated Slag Binder Destined for Use in Developing Countries
## 4 Conclusions  
This paper investigated the alkali activation of slag to be used mainly in developing countries. To do so, various more economical and environmentally friendly contents, such as Na\({}_{2}\)CO\({}_{3}\), were used as activators and compared to the use of NaOH. The highlighted conclusions from this study are:  
1. All the mortars activated with NaOH (SH series) for 28 curing days had compressive strength values of around 20 MPa, while all the mortars activated with Na\({}_{2}\)CO\({}_{3}\) (SC series) had values over 40 MPa at the same curing ages. The mortars with the two activators (SHC series) had intermediate values, between 27 and 40 MPa. All the values obtained by the SC series offered optimum use for nonstructural elements in, for example, blocks, tiles or pavements.
2. Alkali-activated slag with 3.5 M of sodium carbonate led to higher compressive strengths: \(56.5\pm 1.83\) MPa and \(9.3\pm 0.4\) MPa tensile strength at 28 curing days. This mixture can be used for structural elements.
3. Characterization studies by TG/DTG, FTIR, and XRD confirmed the presence of CSH, hydrol calcite, CASH and carbonated phases, such as thermonatrite or calcite/vaterite.
4. The environmental and economic studies showed that the samples activated with Na\({}_{2}\)CO\({}_{3}\) yielded the best results. When comparing the SC with the SH series, reductions over 40% in cost per ton and MPa, and higher than 50% of kgCO\({}_{2}\) emitted per ton and MPa, were obtained.  
Conceptualization, N.B., J.M.M. and E.G.; methodology, M.V.B., J.M.M. and J.P.; formal analysis, A.F., L.S. and M.V.B.; investigation, A.F., L.S., J.P., M.V.B., N.B.; E.G. and J.M.M.; resources, N.B., E.G. and J.M.M.; writing--original draft preparation, N.B.; J.M.M.; L.S. and A.F.; writing--review and editing, J.P. and M.V.B.; visualization, A.F., J.M.M., M.V.B.; J.P., supervision, J.M.M., M.V.B. and J.P.; project administration, J.M.M.; funding acquisition, J.M.M. All authors have read and agreed to the published version of the manuscript.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Na\({}_{2}\)CO\({}_{3}\) from Trona Calcination** & **Na\({}_{2}\)CO\({}_{3}\) by the Solvay Process** \\ \hline
**Mixture** & **kgCO\({}_{2}\) Activator/ton** & **kgCO\({}_{2}\)/ton \(\times\) MPa** & **kgCO\({}_{2}\) Activator/ton** & **kgCO\({}_{2}\)/ton \(\times\) MPa** \\ \hline SH 3 & 12.1 & 0.52 & 12.1 & 0.52 \\ SH 4 & 16.1 & 0.64 & 16.1 & 0.64 \\ SH 5 & 20.0 & 0.77 & 20.0 & 0.77 \\ SC 1.5 & 4.9 & 0.12 & 9.9 & 0.24 \\ SC 2 & 6.5 & 0.14 & 13.2 & 0.28 \\ SC 2.5 & 8.1 & 0.16 & 16.5 & 0.32 \\ SC 3 & 9.7 & 0.18 & 19. & 0.36 \\ SC 3.5 & 11.2 & 0.21 & 22.8 & 0.43 \\ SHC 3/0.5 & 13.7 & 0.41 & 15.3 & 0.46 \\ SHC 2/1 & 11.3 & 0.32 & 14.6 & 0.41 \\ SHC 1/1.5 & 8.9 & 0.21 & 13.9 & 0.32 \\ \hline \hline \end{tabular}
\end{table}
Table 7: Kilograms CO\({}_{2}\) emissions from the activator for each mortar per ton of prepared mortar, and per ton of mortar and megapascal, for Na\({}_{2}\)CO\({}_{3}\) from trona calcination and by the Solvay process.  
Funding:We would also like to thank the Spanish Government MINECO/FEDER (ECOSOST project RTI-2018-097612-B-C21) for supporting this research.  
This investigation was done during the postdoctoral scholarship of Erasmus Mundus EMMAG program second action. For this, the authors would like to thanks Erasmus Mundus and the EMMAG program team and especially [PERSON] and [PERSON] in OAI of UPV for their assistance and help. We would also like to thank the UPV Electronic Microscopy Service and DGRSDT.  
The authors declare no conflict of interest.