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

98

9

corrosion can be approximated to ~5.85 mm, resulting in an empirical A.P. of 150 ± 55 μm, slightly higher but still analogous to the theoretical value.

Figure 6. Visual representation of diameter for (a) uncorroded and (b) corroded beam after applying I corr = 100 μA/cm

2 for 24 days.

A critical aspect in validating the accelerated corrosion protocol involves the relationship between fracture width on the mortar’s surface and oxides production and movement. For rebars positioned 4.8 mm below the surface, the first visible crack emerged for an attack penetration of 24 μm (within 5/6 days). Despite a slightly higher empirical A.P. (Figure 6b), the systems experienced the first crack occurrence on the surface at a slower rate than what was expected by theory (Alonso et al. , 1996). Indeed, when currents drive chemical reactions, the efficiency of accelerated corrosion is typically less than 100%, mainly due to simultaneous heat generation (Alonso et al. , 1996; Dzhioev, Kosov, and Von Oppen, 2013). Consequently, higher attack penetrations were necessary to achieve specific crack widths, when applying high corrosion rates (i.e., I corr = 100 μA/cm²), and to compensate for the oxide diffusion through the pores of the cover (Alonso et al. , 1996). Hence, both longitudinal and transversal cross-sections for the corroded specimens are presented in Figure 7 and Figure 8, proving the significant role of oxide propagation in influencing crack formation on the system’s surface. Moreover, Figure 7 reveals that oxides, originating from the rebar, exhibit a random movement toward any of the four surfaces parallel to the reinforcement.

Figure 7. Oxide propagation as visualised along the transversal cross-section of two reinforced mortar beams with c/ ϕ = 0.8.