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Naval Air Station

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shim_trans  Summery
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shim_trans  Objective
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shim_trans  Project Background
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shim_trans  Scope of Work
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shim_trans  Bravo 25 Description
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shim_trans  Overview
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shim_trans  Crane Rail Removal
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shim_trans  Loss of Transverse
 Negative Moment
 Capacity over the
 Outboard Crane Rail
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shim_trans  Concrete Repair
 Materials
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shim_trans  Top Deck
 Repair Procedure
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shim_trans  Under Deck Repairs
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arrow_right  Cathodic Protection
 System
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shim_trans  Cathodic Protection
 System Installation
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shim_trans  Grout Resistivity
 Measurements
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shim_trans  Reinforcing Steel
 Lead Wire Installation
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shim_trans  Upgrade Reinforcement
 Introduction
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shim_trans  Analysis of Bravo-25
 Load Response
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shim_trans  Calculation of
 Bravo 25 Resistence
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shim_trans  Modes of Failure
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shim_trans  Bravo 25
 Upgrade Design
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shim_trans  Concrete Surface
 Preparation
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shim_trans  Embedded
 Reinforcement
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shim_trans  Wet Lay-up
 Composite Laminate
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shim_trans  Proof Tests using
 Impact Load Method
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shim_trans  Costs
 Acknowledgements
 References
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Turbine Deck Load Capacity Restored


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Home > Featured Project > Pearl Harbor

Featured Project

 

Cathodic Protection System

NFESC conducted a series of electrical tests including continuity and potential measurements in the spans between Bents 217 and 218 and between Bents 223 to 225 to determine the condition of existing reinforcing and the feasibility of effectively mitigating corrosion by cathodic protection (Reference 1). The reinforcing, steel was found electrically continuous within each span. Continuity was not good between spans across the transverse girders. Applying the criteria of ASTM C876-91 to the electrical potential values, a 90 percent probability of no corrosion existed in the tested areas. However, there were visible rust stains around some of the cracks and potential gradients between anodic to cathodic regions indicated moderate corrosion activity near repair patches and cracks. Since the steel reinforcing is electrically continuous, the alteration of natural electrochemical processes that result in corrosion can be achieved by driving electrical reactions in favorable directions with an impressed current on the concrete surface.

 

Since cathodic protection is the only practical means of mitigating corrosion of concrete reinforcing steel once it has started, NFESC designed an impressed current cathodic protection (ICCP) system for selected deck areas of the upgrade segments. These deck areas are between the curb and the outboard pile girder as well as between the two track slabs. The impressed current system is a low amperage circuit consisting of embedded titanium ribbon as the anode, connections to existing rebar that serves as the cathode, lead wires to a junction box, and a rectifier to supply electrical power. The anode configuration and rectifier sizing was established by the site survey of potential polarization information. The design is detailed in Reference 2. The design provides nominal current density requirements to mitigate current corrosion rates and requires less than 30 volts with a maximum current less than 0.5 mA/ft2 (5 mA/m2) Figure 30 is a graphic of the ICCP design for a typical installation between two transverse girders. It was determined that the rebar cover was sufficient for placement of ½-inch wide(1.25 cm), titanium ribbon anodes into slots cut into the underside of the deck without the anode material making contact with the reinforcing steel. The cover is also sufficient to achieve an adequate current distribution for the embedded ICCP system. The anode layout was configured to provide uniform current distribution over the surface of each area. To offset a somewhat low reinforcing steel connectivity across transverse girders (bents), six electrical connections to the reinforcing steel (three for each anode grid) in each span was required.

 

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Figure 30. Schematic of impressed current cathodic protection system on each end of Bravo-25.

 

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ACE Restoration & Waterproofing, Inc.
620 E. Walnut Ave.
Fullerton, CA 92831
714.526.7366
Fax: 714.526.7965

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  ACE Restoration and Waterproofing Quick Service Overview:
  Concrete repair; concrete restoration, structural upgrade, epoxy injection,
  waterproofing, and more concrete technologies in Fullerton California (CA)
  by ACE Restoration and Waterproofing.

  Concrete Repair, Concrete Restoration, Epoxy Injection, Waterproofing

http://www.acerestoration.net/

 

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