## 3 Results and Discussion
### Influence of the Type of Binder on the Chloride Penetration Resistance
The \(C_{s}\) increased with the w/b, as suggested in the literature [53; 72; 73], since the porous surface structure may accommodate a higher chloride content [52; 70]. Moreover, a systematic increase of \(C_{s}\) with the incorporation percentage of FA was also observed (Table 5). This is related with the higher binding capacity of FA [39; 52; 70]. It is possible that the reduction of \(D_{cl}\) in FA concrete also contribute to the greater retention of chloride ions at the concrete surface, as well as to the slightly higher volume of binder achieved after the weight replacement of CEM I with FA [52]. The minor variation of \(C_{s}\) in SF concrete confirms the lower chloride binding capacity of these concretes compared to those with FA. In LF concrete, the trend was not clear, because the coarser microstructure and the lower chloride binding capacity have an opposite effect on \(C_{s}\). Due to the above mentioned aspects, the \(K_{cr}\) increased with the w/b, since a coarser pore structure both contributed to the increase of the \(C_{s}\) and the \(D_{cl}\) (Figure 7). In general, the \(K_{cr}\) followed the same trend of \(D_{cl}\) in the IT and the WDT. However, the difference between these tests was higher in \(K_{cr}\), because the \(C_{s}\) tended to increase in the WDT. Regarding the influence of the type of binder, the higher reduction of \(D_{cl}\) was offset by the higher \(C_{s}\) in FA concrete. Therefore, the evolution of \(K_{cr}\) with the FA content was closer to that found in the RCMT. Nevertheless, the chloride penetration resistance increased with the incorporation percentage of FA. Since \(C_{s}\) was less affected by SF and LF, in general, the same trend found in the \(D_{cl}\) was maintained in the \(K_{cr}\). Figure 7: Penetration parameter \(K_{cr,IT}\) (**a–c**) or \(K_{cr,WDT}\) (**d–f**) as a function of percentage incorporation of SF (**a,d**), FA (**b,e**) and LF (**c,f**). The comparisons between the \(D_{cl,IT}\) and the \(D_{cl,RCMT}\), as well as the \(D_{cl,WDT}\) and the \(D_{cl,RCMT}\) are presented in Figure 8. In general, a poor correlation was observed between tests when all compositions were considered, regardless of the type of binder. As mentioned, the contribution of FA in the short duration RCMT was not as significant as in the long-term IT and WDT. However, when concretes with FA were excluded, the \(D_{cl,IT}\) and the \(D_{cl,WDT}\) followed the same trend of the \(D_{cl,RCMT}\). Similar conclusions are reported in literature, when comparing the RCMT and the IT [5,35]. Despite the different test conditions the obtained correlation coefficient (R\({}^{2}\)) was as high as 0.88 for the IT (Figure 8). However, for the WDT, the correlation was poorer, because for high w/b, the chloride penetration was more affected by the convection phenomenon. Therefore, when comparing these methods with distinct transport mechanisms, the correlation tends to be lower. Note that, for all correlations, the regression line was forced to cross the origin, maintaining the physical meaning of the analysis, which reduced the R\({}^{2}\). Moreover, in Figure 8, the concrete with FA appears to be clustered in the bottom of the plot, both for the IT and the WDT. This result emphasises the high efficiency of FA in increasing the chloride penetration resistance, as well as its slower reaction, only contributing to this property at later ages. The relations between \(K_{cr,IT}\) or \(K_{cr,WDT}\) and \(D_{cl,RCMT}\) are presented in Figure 9, taking into account all concretes with or without FA. As discussed, the mentioned impact of slower FA reactivity is mitigated when Kcr is considered instead of \(D_{cl}\). Therefore, the difference between concrete with and without FA becomes smaller (Figure 9). Thus, the penetration parameter related better with \(D_{cl,RCMT}\), especially when time-dependent additions were considered.