## 4 Conclusions  
After the study was completed, the following relevant conclusions were drawn about the activation with carbonates and nitrates of innovative hybrid mortars with ecological interest:  
* The activation of hybrid mortars is more effective when using carbonates than when using nitrates, if porosity reduction or compression strength are considered. After drying, the hybrid mortars activated with 6% of carbonate are less porous and more compression resistant than OPC.
* Microcracks tend to be generated in the hybrid mortar microstructure when carbonate is used for activation.
* Precipitation of nitrate-AFm hinders chloride diffusion into the mortars.
* Mortar activation with moderate amounts of nitrates (4% wt.) promotes higher resistance to chloride penetration than that of the OPC used as reference, and reasonable high mechanical properties.
* The wear performances of the hybrid mortars under study are worse than that of OPC. This weakness, if it is not overcome in future formulations, can limit certain eventual applications.
* pH values of hybrid mortars are highly alkaline, as those of OPC. However, the long-term effect of their lower alkaline reserve warrants further study.  
Supplementary Materials: The following supporting information can be downloaded at [[https://www.mdpi.com/article/10.3390/app15148055/s1](https://www.mdpi.com/article/10.3390/app15148055/s1)]([https://www.mdpi.com/article/10.3390/app15148055/s1](https://www.mdpi.com/article/10.3390/app15148055/s1)), Figure S1. Examples of intrusion-extrusion curves obtained during mercury intrusion porosimetry tests for the 5 studied materials.  
Conceptualization, A.B.; methodology, A.B., M.T.-C. and A.C.-H.; validation, A.B. and F.V.; formal analysis, A.C.-H.; investigation, A.C.-H.; resources, A.B. and M.T.-C.; data curation, A.C.-H.; writing--original draft preparation, A.C.-H. and A.B.; writing--review and editing, A.C.-H., A.B., F.V. and M.T.-C.; supervision, A.B. and F.V.; project administration, F.V. and M.T.-C.; funding acquisition, A.B. and M.T.-C. All authors have read and agreed to the published version of the manuscript.  
This study was funded by PID2021-125810 OB-C22 project \"Development of eco-efficient cementitious materials with low-impact and high durability\" (EcoCeMat), financed by MCIN/AEI/10.13039/501100011033/ and FEDER \"Una manera de hacer Europa\".  
Not applicable.  
The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.  
The authors declare no conflicts of interest.  
The following abbreviations are used in this manuscript:  
\begin{tabular}{l l} AAM & Alkali-Activated Materials \\ ACR & Alkali-Carbonate Reaction \\ AFm & Aluminate Ferrite Monosulfate \\ AFt & Aluminate Ferrite Trisulfate \\ ASTM & American Society for Testing and Materials \\ C-A-S-H & Calcium Aluminum Silicate Hydrate \\ C-S-H & Calcium Silicate Hydrate \\ CH & Calcium Hydroxide (Portlandite) \\ DTA & Differential Thermal Analysis \\ HC & Hybrid Cement activated with Carbonate \\ HN & Hybrid Cement activated with Nitrate \\ LDH & Layered Double Hydroxide \\ N-A-S-H & Sodium Aluminum Silicate Hydrate \\ OPC & Ordinary Portland Cement \\ PC & Portland Cement \\ RH & Relative Humidity \\ SEM & Scanning Electron Microscopy \\ TG & Thermogravimetry \\ UNE-EN & European Standard-Spanish Implementation \\ XRF & X-ray Fluorescence \\ s/b & Sand-to-Binder Ratio \\ \end{tabular}