# Monitoring of Reinforced Concrete Corrosion: Active and Passive Bars Exposed to Climate
## 4 Discussion  
The following section analyses the corrosion rate evolution and the impact of environmental or exposure parameters. The analysis focused on the beam due to the type of exposure as the tendon is shielded from the environment. Figure 9 displays the corrosion rate evaluation as a function of the inverse temperature in an Arrhenius plot. It is important to note that there was no correlation between the two parameters. Other parameters have a greater influence than temperature alone, as will be discussed later. Previous results have shown a correlation between the two parameters when other conditions remain constant [23]. The results presented in the figures above demonstrate that the resistivity, and therefore water content, has a greater impact on the corrosion rate than temperature. To accurately determine the effect of temperature, it is essential to maintain constant values for all other parameters. Figure 10 illustrates the correlation between the corrosion rate and resistivity. According to [PERSON] theoretical curve, the correlation between the corrosion current density, \(\log(l_{corr})\), and concrete resistance, \(\log(R_{con})\), can be approximated by an almost ideal linear relationship for a broad range of corrosion current densities. Assuming a fixed geometrical arrangement of anodic and cathodic sites on the steel surface, this linear relationship also applies to concrete resistivity, \(\rho_{con}\)[31, 35, 40, 41, 42]. While resistivity does have an impact on the corrosion rate, it is important to note that this correlation is dependent on the specific system being measured, for instance, whether the system is active or passive. Therefore, it is not possible to establish a universal law for all cases. Additionally, it is important to note that there was a significant variation in the corrosion rate values for the same resistivity  
Figure 8: Record of durability parameters. Tendon. Figure 9: Arrhenius-type plot of corrosion rate versus temperature. value. It is worth considering that the figures are presented on a double logarithmic scale, meaning that this variation represents differences of up to one order of magnitude. Further analysis, as illustrated in Figure 11, demonstrated the relationship between the corrosion potential and the corrosion rate in an Evans-type plot. The potential provides a qualitative indication of the risk of corrosion, as evidenced by previous studies [19; 23; 28; 43; 44], yet it is evident that there was a considerable degree of variation in the corrosion rate measurements. For a given value of corrosion potential, the steel can be either active or passive. In other words, in order to determine the real behaviour of the structure, it is necessary to carry out a correct measurement of the corrosion rate. With regard to the values of the thresholds for the corrosion potential, which are set out in standards and recommendations, it is important to exercise caution in their interpretation. There are studies that demonstrate that it is not possible to establish a universal criterion for these thresholds [45]. Figure 12 shows the corrosion rate results (green-red shaded curve) over a period of nearly 10 months along with the climate exposure data: relative humidity (black dotted curve) and rainfall (blue shaded curve). The data indicate that the corrosion rate and humidity exhibit similar behaviour, but it is the presence of rain that decisively activates corrosion. The corrosion rate measurement of the beam was almo  
Figure 11: Evans-type plot: corrosion rate versus corrosion potential. Figure 10: Corrosion rate versus resistivity. direct exposure to rainwater. The absorption of water was rapid, even over long periods of the structure's life [46; 47]. Therefore, if sufficient rainwater reaches the reinforcement and contains chloride, corrosion will occur. In cases of insufficient chloride concentration, a corrosion rate response is observed, but no depassivation occurs.