Sixteen years after initial construction, the Kwai Chung Container Berth in Hong Kong was exhibiting extensive delamination of the concrete wharf soffit. Corrosion was attributed to the ingress of chloride ions from the sea- water splashing and spray. A condition survey determined that delamination had exceeded 50% of the total concrete beam area. The survey, however, revealed no particular deficiency in concrete material properties from the relevant design standards.
Structural engineering consultant Maunsell determined that cathodic protection (CP) was the best method to control the ongoing corrosion problem associated with the reinforcement. A restoration program incorporating CP was initiated in 1992. The second phase was completed in 1993 and the third phase in 1995. The ELGARD™ 210 Anode Mesh system was applied to the beam sides and ELGARD™ 300 to the beam soffits. A zone around the junction between the beams and tubular sheet piles was provided with a double layer of anode mesh. The anode variations were designed to correspond with changes in the embedded steel surface area.
A sand cement shotcrete layer was applied over the system to fully encapsulate the mesh. A high level of quality control was provided during concrete surface preparation and throughout the shotcrete application.
The transformer rectifiers, which power the cathodic protection system, are housed in stainless steel cabinets rated for +50° C operating temperature. The enclosures also house terminals for reference cells and the remote monitoring system.
CP arrests corrosion in marine structures by eliminating the corroding areas on the rebar and making the steel more passive. Corrpro, the worldwide licensee of the ELGARD™ system for cathodic protection of reinforced concrete structures, provides CP system design, materials, installation, testing and supervision.
Project Data:
Location: |
Kwai Chung, Hong Kong |
Consultant: |
Taywood Engineering
(sub-consultant to Maunsell) |
Contractor: |
Freyssinet (HK) Ltd. |
Anode Type |
ELGARD™ 210 Anode Mesh - beam sides
ELGARD™ 300 Anode Mesh - beam soffits |
Installation Date/Size: |
1992 - 2,508 m2
1993 - 3,438 m2
1994 - 10,800 m2 |
Leading governmental and independent trade organizations have monitored, tested, and reported on corrosion control strategies over the past three decades. These groups include the American Concrete Institute, National Association of Corrosion Engineers, and Federal Highway Administration. They advocate CP as the only rehabilitation technique that effectively stops corrosion in salt-contaminated structures, regardless of the chloride content of the concrete.
ELGARD™ is a trademark of Eltech Systems Corporation. |
