The foundation piers of the towers of the Figueira da Foz Bridge showed signs of expansive reactions. The cracking pattern in the capping segment (starting at the construction joint about 1 meter from the top) indicated volumetric fracturing effects resulting from alkali-aggregate reaction. The top section of the piers exhibited an advanced state of rebar corrosion, with delamination of the concrete cover - likely due to high chloride content and rebar depassivation caused by concrete carbonation.

Steps and techniques used

Assuming that the permanently submerged zone did not show signs of rebar corrosion due to the absence of oxygen, the following methodology was adopted:

a) Complete deep repair of a 1-meter-high strip around the entire perimeter of the tops of the eight piers, involving removal and replacement of about 8 cm of the concrete cover using structural dry-process shotcrete applied with double-chamber machines.

b) Localized deep repair of a 4-meter-high strip around the perimeter of the tops of the eight piers - corresponding to the tidal range and the permanently exposed segment showing localized rebar corrosion - by replacing approximately 8 cm of concrete cover using structural dry-process shotcrete with double-chamber machines.

c) Superficial repair by chipping approximately 2 cm and correcting rebar cover to 5 cm in the remaining areas exposed at low tide that were not subject to deep repair.

d) Application of the APE composite encapsulation system from the section centered on mean low tide down to the riverbed, on the north tower piers.

e) Structural strengthening using carbon fiber laminates (60×1.4 mm, low modulus – 200 GPa), including the application of 1.5 cm of sprayed mortar to improve the mechanical protection of the fibers.

f) Epoxy coating of the repaired tidal zone.