Cathodic Protection for Life Extension of Existing Reinforced Concrete Bridge Elements (2009) / Chapter Skim
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Pages 24-33
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From page 24... ...
Similarly, if the decision-making processes for repair and rehabilitation either are not sophisticated enough or do not include cathodic protection as an alternative, then the use of the technology would be limited. The design, installation and quality control, and monitoring and maintenance practices have a significant impact on the experience of use of this technology.
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From page 25... ...
It may be noted that for the purpose of the survey, marine exposure was defined to persist 2 miles around a saline body of water. In addition to Mississippi, Washington State has more than 90% of its substructures listed as "Neither." PROCESS FOR SELECTION OF CORROSION MITIGATION ALTERNATIVES To ascertain the compatibility and the cost-effectiveness of a cathodic protection system on a reinforced concrete structure, among other things, it is important that the severity of exposure, the presence of chloride ions in sound concrete, the presence of electrical continuity, the susceptibility of the concrete to alkali–silica reaction and freeze–thaw damage, and the presence of corrosion activity in sound areas be known.
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From page 26... ...
The testing protocol used by the majority of the agencies would provide a good measure of the symptoms of corrosion, rust staining, cracking, delamination, and spalling, and would reasonably indicate the overall condition of the structure and provide a basis for more in-depth evaluation. During an in-depth survey or corrosion condition evaluation, the vast majority of the agencies perform a visual survey, delamination survey, chloride ion content analysis, and half-cell potential survey.
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From page 27... ...
The summary of responses in Table 12 provides some answers to this question; nine agencies do not include cathodic protection as an alternative corrosion mitigation system in their procedures, protocols, and methodologies for selecting repair and corrosion control alternatives owing to disappointing past experience and eight agencies do not use it because it is more Factors No. of Respondents 61egamaDfoytitnauQ 4snoIedirolhCfoecneserP 3efiLecivreSfonoisnetxE 2stsoCelcyC-efiL 6noitatilibaheRdnariapeRfotsoC 0noitarepOegdirBninoitpursiD 0epyTerutcurtS 1elbaliavAsdnuF Consultant Familiarity with Corrosion Control System 0 Past Experience with Corrosion Control System 2ecitcarPycnegA 0sgnidniFhcraeseRycnegA Note: Table based on results of Question 13 of the survey.
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From page 28... ...
On existing structures, localized zinc point anodes, galvanic cathodic protection, impressed current cathodic protection, admixed corrosion inhibitors, and surface-applied corrosion inhibitors are used by a decreasing number of agencies. The trend indicates that agencies are choosing the simplest options with minimal or no monitoring and maintenance requirement.
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From page 29... ...
Remote monitoring units are used by eight agencies. The frequency of remote monitoring; that is, remotely connecting to the system and obtaining a status report, might be performed at least once a month for impressed current cathodic protection systems.
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From page 30... ...
The Traffic Engineers and Signal Electricians use electrical and electronic systems quite similar to those used in impressed current cathodic protection systems and, therefore, are easily trained to perform monitoring and maintenance tasks. The Bridge Maintenance Engineers handle the regular maintenance required on the systems and the Construction Inspectors provide quality control and assurance during installation.
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From page 31... ...
It can evaluate the structure and ascertain the need for corrosion mitigation, provide options for corrosion control, provide quality control and quality assurance services and assistance during construction, and monitor and maintain the cathodic protection systems. The Corrosion Laboratory does not limit itself to cathodic protection technology; it uses all corrosion mitigation technologies depending on their applicability and the need for extension in service life.
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From page 32... ...
Caltrans developed the coke breeze cathodic protection system and experimented with several coating systems including arc sprayed zinc. It has also experimented with a conductive polyester concrete bridge deck cathodic protection system.
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From page 33... ...
All cathodic protection systems installed under this program are impressed current type with titanium-mixed metal oxide mesh or ribbon anodes. The selection and design of the cathodic protection systems were performed in-house by the Research Group with assistance from the FHWA and NACE.
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