PSI - Issue 67

Gabriele Milone et al. / Procedia Structural Integrity 67 (2025) 90–106 G. Milone et al./ Structural Integrity Procedia 00 (2024) 000 – 000

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descending patterns, closely aligned with the expansion and stabilization phases of the cracks, respectively. The rapid crack opening led to an increment in the electric response. On the other hand, a relaxation in the coating’s resistance occurred during the stabilization of crack widening. Such a progression was related to the oxide movements within the matrix. This proved that the various patterns experienced in the FCR response were related to the dominance that either oxide movements or fracture development had. Finally, the sensors experienced a continuity loss in all samples caused by fracture at the coating level when the crack width reached 33 ± 3 μm.

Figure 12. Graphical representation of crack width and FCR development as functions of attack penetration for mortar prisms subjected to accelerated corrosion test with partially confined steel rebar for (a) 4, (b) 8 and (c) 12 cm.

It was observed that a beam with minimal confinement (i.e., 4 cm in Figure 12a) required less time to fracture its surface. In contrast, higher attack penetration was necessary to achieve similar crack widening for longer steel confinements (Figure 12b,c). This difference was attributed to the oxide concentration needed to elevate the state of stress/strain in the substrate beneath the sensor. Thus, a longer confinement range leads in a slower and more gradual fracture development, consequently delaying the FCR response. On the other hand, shorter epoxy sealing slightly reduced the corrosion rate, leading to a more abrupt crack expansion, accordingly influencing the sensing response of the coating. To interpret the obtained results, visualizing oxide propagation (Figure 13) and assessing the epoxy sealing efficiency of steel bars subjected to accelerated corrosion is critical. Figure 13b,d,f highlight that, despite confinement, some oxides were gener ated around the sensors’ region, with a more pronounced effect in shorter confinements compared to longer ones. This behavior was attributed to the larger exposed region of the rebar and the subsequent increase in oxide production. In addition, Figure 13a,c,e present the epoxy's ineffectiveness in completely sealing the rebar's exposure to corrosive agents.