## 3 Results and Discussion
### Corrosion Current Density (\(i_{\text{corr}}\))
#### 3.2.1 Behavior \(i_{\text{corr}}\)  
Gslavanized Steel and AISI 1018 Carbon Steel in Concrete Exposed to Control Medium  
Figure 6 shows the behavior of the corrosion rate or corrosion current intensity (\(i_{\text{corr}}\)) of the CC and binary sustainable concrete specimens immersed in a control medium (DI-Water), reinforced with CS and GS. All specimens with AISI 1018 CS present values of \(i_{\text{corr}}\) between 0.4 to 0.3 \(\upmu\)A/cm\({}^{2}\) on day 7, progressively decreasing to values between 0.16 to 0.12 \(\upmu\)A/cm\({}^{2}\) on day 28. This agrees with various works reported in the literature, associated with the progressive formation of a passivation layer in the steel rebars embedded in concrete during this period of time or curing stage [97; 98]. As exposure time increases, a tendency of CC-W-CS, BSC1-W-CS and BSC2-W-CS to more noble values of \(i_{\text{corr}}\) is observed. BSC2-W-CS, which is made with binary sustainable concrete, shows the least active values. This specimen presents \(i_{\text{corr}}\) values below 0.10 \(\upmu\)A/cm\({}^{2}\) since day 112, indicating a negligible level of corrosion according to Table 9. This trend maintains until the end of monitoring, when values of 0.04 \(\upmu\)A/cm\({}^{2}\) are observed. The CC-W-CS and BSC1-W-CS specimens, which after day 182 present values of \(i_{\text{corr}}\) lower than 0.10 \(\upmu\)A/cm\({}^{2}\), displayed very similar values, reaching \(i_{\text{corr}}\) values of 0.05 and 0.06 \(\upmu\)A/cm\({}^{2}\) at the end of the monitoring, indicating a negligible level of corrosion.  
For the specimens reinforced with GS, CC-W-GS, BSC1-W-GS and BSC2-W-GS the behavior is very similar, with high \(i_{\text{corr}}\) values at the beginning of the curing stage ranging from 0.28 and 0.23 \(\upmu\)A/cm\({}^{2}\) on day 7, decreasing to values below 0.10 \(\upmu\)A/cm\({}^{2}\) on day 28.  
Figure 6: \(i_{\text{corr}}\) monitoring of GS and CS reinforced concrete exposed to control medium (DI-water).  
\begin{table}
\begin{tabular}{c c} \hline \hline
**icorr (\(\upmu\)A/cm2)** & **Corrosion Level** \\ \hline \(i_{\text{corr}}\leq 0.1\) & Negligible (Passivity) \\ \(0.1<i_{\text{corr}}<0.5\) & Low Corrosion \\ \(0.5<i_{\text{corr}}<1\) & Moderate Corrosion \\ \(i_{\text{corr}}>1\) & High Corrosion \\ \hline \hline \end{tabular}
\end{table}
Table 9: Level of corrosion in accordance with the corrosion current density (\(i_{\text{corr}}\)) [96].  
This behavior is associated with protection offered by the zinc layer of said steels, observed during the 300 days of monitoring. This is observed in the GS specimens that present lower values of \(i_{\mathrm{corr}}\) than the specimens with AISI 1018 CS. It is also found that the specimen made with binary sustainable concrete, using 10% silica fume, BSC2-W-GS specimen, presents the noblest \(i_{\mathrm{corr}}\) values than those reported by the CC-W-GS and BSC1-W-GS specimens. However, it is observed that all the specimens with GS, CC-W-GS, BSC1-W-GS and BSC2-W-GS presented \(i_{\mathrm{corr}}\) values that indicate a negligible level of corrosion according to the Table 9, behavior that agrees with the results of other investigations [99; 100], when evaluating corrosion in control media or media without aggressive agents such as sulfates or chlorides.