Located in a highly aggressive and corrosive environment, the tidal sections of the piers in alignments SVP1 to SVP14 of the South Viaduct of the Vasco da Gama Bridge were subject to a protection intervention. This was carried out using a composite encasement system for underwater application (A-P-E™ system).

Steps and techniques used

To install the underwater encasement, two work teams were organized: one was responsible for preparing the jackets onshore, while the other installed the system on the piers. All concrete surfaces to be encased in fiberglass jackets were first prepared using high-pressure freshwater jetting to remove all marine organisms and any loose surface material. Each pier (with a perimeter of approximately 6.5 meters) was encased in three segments joined together by splicing, in accordance with the manufacturer’s specifications, using epoxy resin bonding and stainless steel rivets. After transport to each pier, the fiberglass jackets were sealed and strapped to prevent deformation during injection. Grout was then injected to fill the space between the FGRP jacket and the concrete, forming a permanent encasement.

The concrete surface protection system consisted of polyester shells reinforced with fiberglass, installed 12 mm away from the concrete surface. This gap was subsequently filled with a high-adhesion grout suitable for wet conditions.

Additional information

The main challenge in executing this project was the difficulty of accessing the work areas. Both personnel and materials/equipment were transported by water, using boats and floating platforms, and were subject to the navigability conditions of the Tagus River, including wind, waves, and tides.