PSI - Issue 64

Pascual Saura Gómez et al. / Procedia Structural Integrity 64 (2024) 2125–2132 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 4 Measurements at points without cover cracking (uncracked) and with cover cracking (cracked): (a) Potential, E corr , (b) Resistivity, ρ , (c) Corrosion rate, I corr , (d) Chloride content, [Cl - ]. 4. Discussion In this session, a study on the mutual relationships between the resistivity ρ , the corrosion rate I corr , the potential E corr , and the chloride contents was performed. The Fig. 5(a) shows that most of the measured corrosion rates values in the center of the beams (light blu dots) are ranging from 0.1 to 0.5 μA/cm 2 . The corrosion risk of the beams is moderate, with a current density less than 0.2 μA/cm 2 and an estimated chloride content from 2% to 4%. In addition, the Fig. 5(a) shows that the measured corrosion rates values at the ends of the beams (purple dots) are ranging from 0.02 to 1.3 μA/cm 2 and chloride content from 2% to 5%; hence an higher risk of corrosion can be stated. Fig. 5(b) reports a statistical study obtained by using log-normal distribution, suggesting that the most likely value for the chloride content is around 3%, with mean and standard deviation equal to 3.21% and 1.05%, respectively. In Fig. 6 the statistical population of the measured corrosion rate values, I corr , is described with a log-normal distribution in uncracked and cracked zones of the beams. Fig. 6(b) shows that the corrosion rate in the cracked zones of the beams is higher than in the uncracked zones of the beams (Fig. 6(a)), as well as the standard deviations. For uncracked zones, mean and standard deviation are equal to 0.160 and 0.167 μA/cm 2 , respectively. For cracked zones, mean and standard deviation are equal to 0.57 and 0.37 μA/cm 2 , respectively. When analysing the relationship between I corr and E corr , it is important to distinguish between uncracked and cracked zones. As shown in Fig. 7(a), the values measured in the cracked zones (blue dots) exhibit higher corrosion rates and more negative potentials than in the uncracked zones (yellow dots). The values are also higher with respect to the limits of 0.2 μA/cm² and -424 mV for I corr and E corr , respectively, indicating high probability of corrosion. By comparing I corr and [Cl - ] in Fig. 7(b), it can be observed that for the same values of chloride content, the corrosion rate results higher in cracked zone than in uncracked zones. The Fig. 8(a) illustrates the relationship between I corr and resistivity ρ in concrete, in uncracked and cracked zones. The data show that cracked zones are characterised by higher corrosion rate at lower resistivity than uncracked zones. Fig. 8(b) reports the same values plotted in function of their position along the beam (either in the centre or at the end). The scattering of the values measured in the centre of the beam is lower with respect to the points at beam’s ends, with resistivity values, ρ , mainly ranging from 100 to 200 KΩcm and corrosion rate values, I corr , mainly ranging from 0.1 to 0.2 μA/cm 2 .