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

102

13

resulting in critical FCR values (> 500%).

Figure 11. Visual representation of (a,e,i) longitudinal and (b,c,d,f,g,h,j,k,l) transversal cross-sections of fully corroded reinforced prisms: (a,b,c,d) sample #1; (e,f,g,h) sample #2; (i,j,k,l) sample #3.

On the other hand, sample #3 was characterized by a minimal oxide propagation to the top surface, leading to a fracture opening at an attack penetration of 47 μm (Figure 11i -l). The initial crack width of 19 μm remained stable throughout the corrosion period, which resulted in a constant FCR of approximately 92%. This finding confirms the challenges in predicting the direction tendency of oxide propagation through the matrix and provides additional evidence of the smart coatings' capability to monitor strain in multiple sections of a prism, indirectly measuring corrosion progress. In summary, the experimental investigation demonstrated the efficacy of CB-based sensing coatings in monitoring the corrosion process within chloride-contaminated reinforced mortar elements with minimal cover depth. Even when the oxides propagated in opposite directions, the sensors provided an electrical response correlated to the compression on their application surface. While a complete corrosion of steel rebar allowed for assessing oxide production in relation to strain and damage monitoring, the coatin gs’ sensing response focused on a specific section of the rebar. Hence, the next section assesses the corrosion sensing capability of smart coatings when applied at varying distances from the steel bar experiencing chloride-induced damage, in view of practical on-site applications. 3.2.2. Confined rebar Expanding upon the corrosion sensing results of unconfined rebars, this section examines the smart coatings’ ability to measure corrosion development at a growing distance from the steel bar. The graphs presented in Figure 12 depict the evolution of crack width in the vicinity of the coating and the FCR corresponding to the sensor located in the midspan (sensor Y). While the crack propagation exhibited similar amplitudes and patterns, there were distinct variations in their temporal developments. The electric responses of the sensors were characterized by ascending and