**4. Conclusions**

This work used alkali-activated slag as a raw material to obtain concrete. Monosilicates (Si-OH) and Al-OH groups then formed, which facilitated the polymerization of the silicate chains in the C-S-H gel. These species connected the C-S-H dimers, producing a C-S-H gel richer in Al. This compound contributes to optimizing the mechanisms that control the entry of chlorides into the mixture, reducing the permeability of the concrete during the hydration processes and favoring protection against electrochemical attacks.

It was also established that the protection mechanism in slag concrete improved when it was immersed in saline solution, which evaluated as a function of time. Furthermore, the protection of metal immersed in the concrete is related to the formation of oxide (and hydroxide) layers on the steel due to the low degree of porosity of the samples.

The impedance data increased up to 6 years, and its stabilization at 7.5 years is explained by the simultaneous combination of the uniform formation of protective layers on the steel surface and the restriction of the passage of harmful elements into the system through the ceramic matrix.

**Author Contributions:** Conceptualization, W.A. and J.B.-R.; methodology, J.S.-M.; software, W.A.; validation, J.B.-R.; formal analysis, J.S.-M.; investigation, W.A. and J.B.-R. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research work was funded by Vicerrectoria de Investigaciones Universidad Militar Nueva Granada through the INV\_ING\_3123 project.

**Institutional Review Board Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** W. Aperador acknowledges support from the Universidad Militar Nueva Granada.

**Conflicts of Interest:** The authors declare no conflict of interest.
