PSI - Issue 64

Marco Carlo Rampini et al. / Procedia Structural Integrity 64 (2024) 2141–2148 Author name / Structural Integrity Procedia 00 (2019) 000–000

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top/bottom walls of the extracted concrete samples. This tie rod did not present any significant defects on the visible external surface of the cementitious layer. Results for specimen S9 are summarized in Figure 6. In this case, the cementitious layer resulted generally wetter than in the previous member, with resistivity values even around 300 Ω∙m. Corrosion potential, mainly higher than -200 mV vs CSE, experienced two major drops in correspondence of the two tie ends, and a significant reduction at around 6 m of length (-300 mV vs CSE). The latter was found in correspondence to the only defect detected on the external surface of the cementitious layer, i.e. a void due to segregation during casting (see the defect reported in Figure 7a). Carbonation depth was then measured in four different spots (ID.S9-C1 to C4 in Figure 6), chosen similarly to what done in the previous case. No carbonation was generally found, except in the ID.S9-C3 point, in correspondence with the significant casting defect (see the remaining part of the RC tie after the extraction of the concrete core sample in the Figure 7b), where corrosion products were already present. Figure 8 shows the results for S6 tie rod. Resistivity measurements showed that the moisture content of the cementitious layer was similar to that of specimen S9, with lowest recorded values of around 300 Ω∙m. Although several defects were detected in the cementitious layer, with big voids (likely due to segregation in correspondence of subsequent concrete pouring) and the clear presence of corrosion products (mainly on the external Ø8 mm bars), as visible in Figure 8, corrosion potential values were mainly included in the range -200/-100 mV vs CSE. Similarly to the other tie rods, the corrosion potential experienced only minor potential drops in the central positions, and slightly major drops in correspondence of the two ending parts. Carbonation depth still needs to be assessed for this tie rod.

Fig. 6. Electrical resistivity mapping, and corrosion potential results for tie rod S9.

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Fig. 7. Investigation for the most significant spots in tie rod S9 (ID.S9-C2 and C3): concrete core sampling (a) and carbonation depth result (b).