## 3 Results and Discussion
### Influence of the Type of Binder on the Chloride Penetration Resistance
As expected, in long-term tests, the \(D_{cl}\) increased with the w/b, regardless of the concrete composition, which demonstrates the major relevance of this parameter in the concrete microstructure. Therefore, the RCMT and the long-term tests showed to be sensitive to significant alterations in concrete microstructure, following the same trend regarding the classification of concrete quality. Similarly to the RCMT, the incorporation of 6% SF led to the reduction of the \(D_{cl,IT}\) and the \(D_{cl,WDT}\), respectively. Comparing to the RCMT, the reduction was of the same order of magnitude in the IT (43.5%, 35.7% and 11.9% for w/b of 0.35, 0.45 and 0.55, respectively), confirming a greater contribution of SF in low w/b concrete. In the WDT, where penetration may also be affected by absorption mechanisms, the incorporation of SF led to different reductions (59%, 53% and 5.4% at w/b of 0.35, 0.45 and 0.55, respectively), although also higher in low w/b concrete. In particular, concrete with high w/b showed an abnormally high \(D_{cl}\), which was even higher than that of concrete with only CEM I, indicating the low efficiency of the poorly dispersed SF. Regarding the lower reactivity of FA, the long-term test results indicate an opposite trend than that of the RCMT. The increase of the incorporation percentage of FA led to a progressive reduction of the \(D_{cl,IT}\) and the \(D_{cl,WDT}\), confirming the greater efficiency of these additions at later ages. As mentioned, after 28 days, the slow pozzolanic reactions are more effective, creating a microstructure densification by capillary pore filling with additional hydration products. Moreover, the above-mentioned chloride binding properties are more significant in long-term tests. In these tests, the \(D_{cl}\) tended to be lower in FA concrete than in SF concrete, especially for high w/b, which should be related with the poor dispersion and low chemical binding capacity of SF. In general, as in the RCMT, the \(D_{cl,IT}\) and \(D_{cl,WDT}\) increased with the incorporation percentage of LF. The replacement of CEM I with this quasi-inert addition led to a reduction on both hydration products and aluminate content, coarsening the microstructure and reducing the chloride binding capacity. However, up to 15%LF incorporation in low w/b concrete, the variation of \(D_{cl}\) was not significant, for both the IT and the WDT. In this case, the filler and nucleation effects of LF could have partly compensated the slight reduction in hydration products and chloride binding capacity. For 30%LF incorporation, \(D_{cl,IT}\) presented an unexpectedly high value, which was not considered in further analysis. The \(K_{cr}\) as a function of w/b and type of binder is presented in Figure 7, for the IT, \(K_{cr,IT}\), and the WDT, \(K_{cr,WDT}\). This parameter may provide a more detailed comparison of the concrete performance, since it also takes the surface chloride content, \(C_{s}\), into account. However, the \(C_{s}\) may vary between specimens due to variations in exposure conditions, justifying why \(K_{cr}\) should not be analysed by itself. Figure 6: Chloride profiles of NWC with CEM I and different w/b, after being subjected to IT (**a**) and WDT conditions (**b**) for 3 months. In general, the C\({}_{s,IT}\) was of the same order of magnitude of the \(C_{s,WDT}\), although the latter tended to be slightly higher (Table 5). This may be related with the enhanced enrichment of chloride ions at the concrete surface caused by wetting-drying cycles [39; 57; 67; 68; 69]. This is in line with the higher \(C_{s}\) usually reported in tidal zone than in submerged conditions [39; 52; 70; 71]. However, as mentioned, in this study the WDT involved short drying periods, approximating the exposure conditions to those of IT. Additionally, note that the values of C\({}_{s}\) indicated in Table 5 are theoretically obtained from chloride profiles, which may deviate from the real \(C_{s}\), especially in the WDT.