## 3 Results and Discussion
### Rebar Corrosion Resistance Accelerated Test  
Figure 8a,b show the evolutions of concrete resistivity (\(\rho\)) during the corrosion tests of the reinforced specimens of concretes C and C*, respectively. Figure 9 contains the evolutions of the mean values of \(\rho\) for both types of concrete. The graphs contain two vertical lines at 14 and 21 days, which indicate the end of the first phase of the corrosion experiments (permanent ponding with tap water) and the end of the second phase (drying period of 7 days), respectively. At 21 days from the beginning of the tests, the final phase began, consisting of wetting-drying cycles with periodic surface application of an amount of NaCl aqueous solution (see Section 2.8). It is apparent from Figure 9 that both types of concrete show no significant differences regarding the electrical resistivity, except during approximately the first 30 days (see Figure 9). In this initial period the reinforced specimens of C* show higher \(\rho\) values than the corresponding specimens of C. This finding is in line with the behaviors shown in Figure 2. Considering that during the first 14 days of the corrosion tests the specimens are subject to a permanent ponding with tap water, it is likely that the presence of the hydrophilic admixture CCADM in the C* specimens might give rise to a more closed and hence less permeable pore network, as compared to the C specimens. \begin{table}
\begin{tabular}{c c} \hline
**Quality** & \(kT\) **(10\({}^{-16}\) m2)** \\ \hline
1—Very good & \textless{}0.01 \\
2—Good & 0.01–0.1 \\
3—Normal & 0.1–1 \\
4—Poor & 1–10 \\
5—Very poor & \textgreater{}10 \\ \hline \end{tabular}
\end{table} 
Table 7: Quality classification of concretes with respect to permeability to gases. Figure 8: Evolution of resistivity \(\rho\) for the reinforced specimens of concrete C (**a**) and C* (**b**) during the corrosion tests. Figure 7: Nomogram of concrete quality with respect to permeability to gases. Figure 10a,b show the evolutions of steel corrosion potential (\(\varepsilon_{corr}\)) during the corrosion tests of the reinforced specimens of concretes C and C\({}^{*}\), respectively. Figure 11 contains the evolutions of the mean values of \(E_{corr}\) for both types of concrete. The potentials are measured against a saturated Cu/CuSO\({}_{4}\) reference electrode. The graphs contain three horizontal lines at \(-200\), \(-350\), and \(-500\) mV, which indicate the accepted limits separating the domains of low, intermediate, and high risk of corrosion, according to ASTM C876-22B [43], see Table 8.  
A sharp decrease of \(E_{corr}\), below the \(-200\) mV limit, is normally considered as indicative of the depassivation of steel, i.e., the breakdown of the passivating layer on steel  
Figure 11: Evolution of the mean values of steel corrosion potential \(E_{corr}\) for the reinforced specimens of concretes C and C\({}^{*}\) during the corrosion tests. \begin{table}
\begin{tabular}{c c} \hline \hline \(E_{corr}\) **(mV vs. Cu/CuSO\({}_{4}\) (Sat))** & **Corrosion Probability** \\ \hline \(>\)\(-200\) & Low risk of corrosion (10\%) \\ \(-350<E_{corr}<-200\) & Intermediate \\ \(-500<E_{corr}<-350\) & High risk of corrosion (90\%) \\ \(<\)\(-500\) & Severe corrosion \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Corrosion probability according to \(E_{corr}\) values. Figure 10: Evolution of steel corrosion potential \(E_{corr}\) for the reinforced specimens of concrete C (**a**) and C\({}^{*}\) (**b**) during the corrosion tests. Figure 9: Evolution of the mean values of resistivity \(\rho\) for the reinforced specimens of concretes C and C\({}^{*}\) during the corrosion tests. reinforcement embedded in concrete [3; 4]. Figure 10a shows a high scatter for the time of this depassivation event in the cases of concrete C, with 170, 150, and 90 days for samples C1, C2, and C3, respectively. The scattering in the depassivation time is much lower for concrete C* (Figure 10b), where the observed range is from 150 to 170 days.