ABSTRACT:

Department of Defense piers and wharves, most of which are over 50 years old, are often supported by reinforced concrete piles. These piles, when exposed to seawater, can incur severe corrosion of the steel and concrete spalling. This type of damage contributes to an annual maintenance cost of $99M for the waterfront structures that they support. Fiber reinforced polymeric composite wrapping systems have been evolving and are now a viable solution to repair concrete structural piles. These wrap systems, in marine applications, have not proven to be completely successful since some FRP wrap systems may contain the concrete but not fully arrest the corrosion. Other systems are limited in their structural capabilities and abrasion resistance. This paper describes a hybrid pile repair system that uses a FRP wrap that can be placed and cured underwater and is integrated with galvanic cathodic protection. The system will provide corrosion and impact resistance and greatly reduce maintenance costs. Demonstration of the system on the support piles for two dolphin pier structures in Kawaihae Harbor, HI is documented. Monitoring of the corrosion potential of the reinforcing steel and the effectiveness of the wrap in protecting both the concrete and steel will be assessed over the coming years and reported on.

INTRODUCTION:

Waterfront facilities such as piers and wharves are critical elements to the operation, safety, and security of many Department of Defense (DoD) Installations. They are utilized for loading water vessels as part of daily operations and are also used during mobilization and training maneuvers. Most of these facilities are over fifty years old and in need of repair, with the DoD spending roughly $100 million annually1 for their upkeep and maintenance. Of this expenditure, more than $14.5 million is estimated to be due to corrosion problems. Reinforced concrete piles are typically used to provide the structural support for these facilities. The piles are exposed to harsh seawater environment which can cause severe corrosion of the reinforcement steel resulting in cracking and spalling of the concrete (Figure 1). Because the piles are necessary for structural stability, failure of even one pile can have a catastrophic effect on the structure and could impact the availability of the entire facility. If any of these structures are taken out of service because of a corrosion-induced failure of the support piles, it could have far reaching negative impact on the DoD mission. Simple patching of the deteriorated concrete is usually only a temporary solution because it does not stop the corrosion of the rebar caused by the continued presence of chlorides, moisture and oxygen from the seawater. In fact, corrosion rates may be accelerated in the vicinity of new patches. Fiber reinforced polymeric (FRP) composite wrapping systems have been evolving over the last twenty years and are now a viable solution for structural repair to physically damaged piles in marine environments2, 3. However, use of these systems for repairing corrosion damage has not been completely successful. The composite wraps may contain the concrete.

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