PSI - Issue 78

Irene Matteini et al. / Procedia Structural Integrity 78 (2026) 992–999

998

Scan depth: 30 cm

Scan depth: 35 cm

Scan depth: 40 cm

Fig. 6. C-scan images displaying the first layer of reinforcement and the orthogonal rebars at various depths: (a) 30 cm; (b) 35 cm; (c) 40 cm. The three images above highlight how the orthogonal rebar have been placed at different depths. This could be attributed to poor craftsmanship during construction.

Fig. 7. First layer rebars identified with Auto-picking. Image generated with GPR Insights.

The resulting “Cover Map” (Fig ure 11-a) further confirms the visual indications of the depth-slices indicating a strong variability in the concrete cover values, shallow on the sides of the bridge and deeper along the longitudinal axis. The associated “Deterioration map” (Figure 8-b) provides an overview of the possible areas at risk (red areas), potentially indicating delaminated areas, corroded reinforcement and / or areas with high moisture. It is to be noted that in this case, the red areas displaying lower amplitude values tend to coincide with the areas with a high cover value; it remains to be verified hence whether this recurring anomaly is simply induced by the larger depth of the reflector or rather due to real deterioration or to the presence of moisture or higher level of contaminants. Another important observation includes the fact that some “areas at risk” are located roughly where vehicle tires typically pass — zones likely subject to greater wear and tear, as well as increased accumulation of contaminants such as de-icing salts (Figure 8-b). Consequently, it is expected a higher level of deterioration. A full holistic approach in this case would prescribe direct verification on selected probe openings, chosen in the 'areas at risk' indicated by the GPR investigation. This initial survey is considered as Time 0 and will serve as a baseline reference for comparison with future scans as part of an ongoing monitoring strategy.