## 3 Results and Discussion
### Influence of the Type of Binder on the Chloride Penetration Resistance  
Figure 3 presents the variation of \(D_{cl,RCMT}\) with the w/b, according to the results of the present study and of other authors [10; 31; 54; 55]. The \(D_{cl,RCMT}\) was essentially dependent on the concrete microstructure, thus having increased with the w/b, regardless of the type of binder and aggregate (Figures 3 and 4, Table 5), similarly to the literature [10; 31; 54; 55]. Furthermore, the results obtained in this study as a function of the w/b for CEM I were in the same range as those reported by other authors [10; 31; 54; 55] (Figure 3). Figure 4 presents the variation of \(D_{cl,RCMT}\) with the type and replacement percentage of binder in NWC with different w/b. As reported in literature, for the same w/b, the \(D_{cl,RCMT}\) was affected by the type and amount of mineral admixture [54; 56; 57]. The incorporation of 6% SF led to a significant reduction of \(D_{cl,RCMT}\), of 41%, 33.3% and 16.5%, for w/b of 0.35, 0.45 and 0.55, respectively. According to the classification of  
Figure 4: Chloride migration coefficient, \(D_{cl,RCMT}\), as a function of percentage incorporation of SF (**a**), FA (**b**) and LF (**c**). Figure 3: Chloride migration coefficient, \(D_{cl,RCMT}\), versus w/b, considering this study and other authors [10; 31; 54; 55]. [PERSON] [33], the chloride penetration resistance of concrete increased one level with the addition of 6% SF (Table 5). This significant improvement is not only attributed to a possible refinement of the porous structure, but also to the alteration of the pore solution composition [54; 58], which may affect the interaction of ionic species and chloride migration. This is in line with the insignificant contribution of the SF found in the compressive strength (Table 5). One reason for the unexpectedly low contribution of SF to the microstructure refinement and strength improvement should be related to the poor dispersion of this high-finiteness addition, which was supplied in an agglomerated state (Table 3). As indicated, the efficiency of this pozzolanic addition was higher in low w/b concrete. Contrarily, [PERSON] et al. [59] found that the effect of SF on the pore refinement tended to decrease with the reduction of w/b. This opposite trend may be related to the use of SP in low w/b concrete, helping the better dispersion of mineral additions. Another reason may be related to a greater influence of these admixtures on the pore solution and ionic interaction of low w/b concrete. The influence of the incorporation of FA on the \(D_{cl,RCMT}\) depended on the w/b. Once more, the FA was more effective in low w/b concrete, showing similar \(D_{cl,RCMT}\) to those of reference concrete with only CEM I, regardless of the replacement percentage. The \(D_{cl,RCMT}\) increased up to 27% and 33% with the incorporation of FA, for w/b of 0.45 and 0.55, respectively. This is related to the reduced wet curing period (7 days), early testing age (28 days) and low activity index of FA (Section 2.1) [54; 60; 61; 62; 63]. [PERSON] and [PERSON] [57] also documented a lower influence of FA at early age. A greater contribution of this slow-reactive addition is thus expected to occur at later ages [64; 65]. A correspondent reduction of the compressive strength was also found with the incorporation of FA, having been 27%, 23% and 36% lower than those of reference concrete with w/b of 0.35, 0.45 and 0.55, respectively. This confirms the lower volume of hydration products formed in FA concrete at 28 days. The results also suggest that the incorporation of FA led to a less dense microstructure in low w/b concrete, supporting the idea that other factors contribute to the reduction of \(D_{cl,RCMT}\) in these concretes. A significant reduction of the \(D_{cl,RCMT}\) over 28 days is documented by [PERSON] et al. [62] and [PERSON] et al. [54]. [PERSON] et al.