## 3 Results and Discussion
### Chlorides and Sulfate Oxidation Profiles and pH  
Static exposure of the mortars to chloride-containing solutions has been carried out following a standardized test. The chlorides that penetrated into HC and HN mortars after the curing and drying processes at different thickness (Figure 1) have been quantified after being submitted to a non-electrically forced, standardized immersion test, and compared with the amount penetrated into the OPC mortar. It can be verified in Figure 9 that the HN mortars show the lowest chloride ingresses. The average chloride concentrations obtained for HN mortars are the lowest, which informs that the fragile phases precipitated in the pores due to nitrate addition (Figures 7 and 8) seem able to decrease chloride penetration. The LDH are well known for their excellent abilities for binding chlorides due to ion-exchange properties [61]. Anions present in the interlayer of LDHs can be exchanged with anions present in the environment. The exchange capability of different synthetic LDH/Afm phases with chlorides has been recently shown [62]. These aspects have also already been shown in traditional [58; 63], alkali activated slag binders [62], and new environmentally friendly cementitious binders [64]. The formation of nitrate-AFMs (Figure 6) with a LDH structure in HN mortars explains the ability of HN to control the chloride ingress (Figure 9) in spite of the fact that their pore volume is not  
Figure 9: Chloride concentration determined after non-electrically forced diffusion test in cured and dried at 40% RH mortars. (Figures 3 and 4a). The addition of synthetic nitrate-LDHs to slag/fly ash binders results in improved chloride resistance [65], although LDH dosage can be critical. Nitrate anions can probably be located in the interlayer of these phases, being able to be exchanged with chlorides during the diffusion test, explaining the better performance of HN compared to OPC. The lower porosity of the HN-4% compared to the HN-8% (Figures 3 and 4), which explains the better mechanical performance of HN-4% in comparison with HN-8%, along with the information obtained up to now about the chloride binding abilities of the formed phases, makes the HN-4% the most interesting ecological alternative for reinforced structures exposed to chlorides among the ones explored in the present investigation. Regarding the dried HC mortars, the chloride penetration is higher than for OPC (Figure 9) in spite of their low porosity (Figure 4). However, the presence of microcracks in HC mortars (Figure 5b,c) but not in OPC (Figure 5a) is the fact that can allow to understand that the chloride penetration is higher than for OPC (Figure 9). It is well-known that microcracks can act as preferential diffusion paths for chlorides [66]. HC mortars also have the smallest fraction of pores with small diameter (Figure 4b), which are the most effective ones for delaying chloride diffusion by physisorption. So, the HC pore distribution and microstructure can favor chloride diffusion. On the other hand, for tidal regions or structures exposed to drying and wetting cycles in chloride-containing environments, the porous structure of the binder can affect the results regarding chloride transport obtained in static conditions [67], and this is a point that deserves further studies. Another factor that could affect the corrosion performance of embedded steel bars in hybrid mortars like the ones considered in this study, is the sulfur content (Table 1) and its chemical form. The use of slags for the hybrid mortar manufacturing adds sulfides into the binder that, with time, could become oxidized due to air exposure [68]. The oxidation of this compound occurs in the presence of water and oxygen, and transforms sulfides into \(\text{SO}_{4}\)2-, which are assumed to be present as iron salts and give the binder a greenish color.