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18 gunite. Between 1985 and 1990, approximately 100 mixed metal oxide systems were installed on bridge decks and more than 3.9 million square feet of concrete surface area were pro- tected (16). Field evaluation of the various mixed metal oxide mesh anodes on twin structures in Virginia was reported after approximately 7 years of operation. The authors concluded that these anodes most likely could have a service life in the range of 60 to 90 years based on the normal current densities required for reinforced concrete bridge decks (41). In 1991, FDOT reported the use of perforated zinc sheets as galvanic anodes, which could be installed in the same fashion as the conductive rubber system (42). The zinc anodes were effective in providing the cathodic protection current; how- ever, the high consumption rate of the zinc at high tide was unacceptable. To overcome this drawback at the next installa- tion, on the B. B. McCormick Bridge in Jacksonville, Florida, FIGURE 19 Activated cylindrical anodes used for a repair. a bulk zinc anode was added under the low water line to pro- vide the majority of the current during high tide. Based on the success of this system, a full-scale installation was designed FHWA provided funding for the installation of many of and installed in 1993 on the Bryant Patton Bridge (43). In 1996, the experimental and trial cathodic protection systems through FDOT reported on another improvement to the system by DP-34. It controlled the implementation of the technology embedding the zinc perforated sheet in a cementitious material from the early stages until the mid-1980s. After the joint com- and creating a jacket. The expanded zinc mesh in a fiberglass mittee of AASHTO, Association of General Contractors of jacket has been commercially available since then and is a America (AGC), and American Road and Transportation standard system of use in Florida. To date these jackets have Builders Association (ARTBA) started the Guide Specifi- been used in 51 projects in Florida and have been installed on cation for Cathodic Protection of Concrete Bridge Decks in 1,782 piles. According to the material supplier, this system has 1989, DP-34 ended. The guide specification prepared by this been installed on more than 4,000 piles in the state of Florida, committee was published in 1994. While the FHWA was most of which are installed on structures that do not belong to involved in the implementation of the cathodic protection, FDOT. A more recent effort evaluated the performance and the it mandated a certain level of design quality, quality control condition of jacketed cathodic protection systems in Florida and assurance during installation, and provided technical and found some evidence to suggest that this system can be assistance, after which, state DOTs became responsible for expected to provide cathodic protection for approximately the design, installation, monitoring and maintenance of the 20 years (44). systems. Several states such as California, Florida, Missouri, and Oregon developed in-house expertise in this technology In 1996, a zinc foil with adhesive system was developed and have been effectively using it to control their maintenance and was later marketed commercially (45). Arc sprayed tita- costs. Similarly, the provinces of Alberta, New Brunswick, and nium with a mixed metal oxide coating was first applied on Ontario are also using this technology to control corrosion- the Depoe Bay Bridge located in Depoe Bay, Oregon, around induced damage on their reinforced concrete bridge structures. 1996. This was an attempt to apply a successful anode material in a different form. The conductive ceramic anodes were devel- In 1990, NACE developed a Standard Recommended Prac- oped in the United Kingdom and are now available in North tice for Cathodic Protection of Reinforcing Steel in Atmo- America. Under an FHWA research project, the aluminum spherically Exposed Concrete Structures. The Strategic High- zincindium alloy for use in galvanic cathodic protection sys- way Research Program (SHRP) published the SHRP-S-337 tems was developed around 1998 (46). Around the same time, "Cathodic Protection of Reinforced Concrete Bridge Elements: the activated zinc anodes became available commercially. A-State-of-the-Art-Report" in 1993 (16). These anodes use zinc as the core and encapsulate it with pro- prietary material. This ensures that the zinc remains active PRESENT USE OF CATHODIC PROTECTION throughout its service life. They come in several different IN NORTH AMERICA geometries for application in various different reinforced concrete components. The smaller anodes, designed for use A 1992 SHRP report documented the growth of the cathodic in concrete repairs commonly known as hockey pucks, are protection industry from 1973 until 1989, which is presented increasingly being used in bridge repairs. Other geometries in Figure 20. Their survey results tallied a total of 287 such as the cylindrical anodes for use in larger repair areas, as cathodic protection systems applied to 200 bridges in North depicted in Figure 19, are now available. America (8). They estimated that the agencies that had not
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19 60 56 has 22 bridges with a deck cathodic protection system; how- ever, the survey response lists no bridges with cathodic pro- Number of Bridges 50 47 42 tection systems. Similarly, for Illinois, the NBI lists 25 bridges 39 40 with a deck cathodic protection system and the state reports 8 for the bridge decks. Missouri has 32 more deck systems than 30 20 22 the listing in the NBI database. Ohio has coded a total of 20 29 bridges in the database. However, the state DOT at present 8 7 10 10 does not have any information on the status of any impressed 10 5 6 4 1 1 3 2 current cathodic protection system installed. At present they 0 only use localized anodes in repairs. It is possible that some 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 of the localized anodes installed in repairs have been coded as cathodic protection systems. There is no simple way to judge Year which of the two sets of numbers is more accurate, the NBI FIGURE 20 Number of cathodic protection system installations listing or the numbers reported by the states in the survey. It per year (19731989). is assumed that the state responses are more accurate and that the coding in the NBI database may not reflect the actual con- ditions on the ground. responded to the survey had an additional 20 systems installed on their bridges. In 1989, five states, California, Florida, A total of 586 structures have cathodic protection sys- New Jersey, Ohio, and Pennsylvania had between 6 and tems installed in North America with 389 located in the 20 cathodic protection systems installed and two agencies, United States and 197 in Canada. Of the 586 structures, 375 Missouri and Ontario had more than 20 cathodic protection have cathodic protection systems installed on decks, 47 on systems. Missouri had the most with 121 systems, and was superstructure elements such as beams and girders, 49 on followed by Ontario (44), New Jersey (18), California (17), caps, 83 on columns, 107 on piles, and 15 on footers. Twenty- and Ohio (14). five of the 36 respondents have cathodic protection systems installed on bridge structures. One respondent has no infor- To determine the extent of use of cathodic protection sys- mation available on the installed systems and, therefore, is tems at the time of this synthesis, two approaches were used; not included in the count. in the first approach, the NBI database was queried, and the second approach was to request the inventory of cathodic pro- According to survey responses, Missouri has the highest tection systems from the public agencies in the survey. It may number of bridges with deck cathodic protection systems, be noted that the NBI only contains information on structures 161 of 375 (43%) and Ontario, New Brunswick, and Alberta located in the United States. Item 108C of the NBI database have 40, 35, and 20 bridges, respectively. For superstructure requires the deck protection type to be listed. One of the elements, Oregon has 11 bridges and Alberta and Ontario several deck protection types that can be coded for is cathodic have 10 bridges each out of a total of 47. Cathodic protection protection. The code for cathodic protection in this database has been installed on caps of 49 structures, 10 of which are for Item 108C is 4. Only cathodic protection systems installed located in Alberta and 9 in Oregon. On piles, Florida has the on bridge decks can be input into the NBI database; systems most with 50 bridges (46%), followed by New Brunswick installed on any other elements are not accounted for. with 40 bridges (37%) out of a total of 107 bridges reported. Also, on footers, Florida has the most with 10 bridges out of The results of the NBI query and the response of the survey the total 15 (67%). are combined in Table 1. Of the 36 states in the Unites States which are known to have a cathodic protection system in the Over the next 5 years, 159 new cathodic protection systems NBI database, 24 responded to the survey. Eight states that did are being planned for installation by the responding agencies. not have any cathodic protection systems listed in the NBI database also responded. The state of Ohio responded; how- Table 2 provides the number of agencies that have a catho- ever, it did not have any information on inventory to provide. dic protection system on each type of bridge component. Bridge decks and columns appear to be the elements on A total of 375 deck cathodic protection systems are listed which the vast majority of agencies have installed cathodic in the NBI database for structures located in the United States. protection systems. These are followed by caps, superstructure The number of deck cathodic protection systems listed in the elements, piles, and footers in descending order. NBI database for states that responded to the survey is 309. However, the states in the survey reported a total of 279 deck The distribution of the use of the various types of cathodic cathodic protection systems. The difference in the numbers protection systems on various bridge components is listed may be accounted for by cathodic protection systems that have in Table 3. This table documents the number of respondents been decommissioned, have failed, or the bridge decks have using the particular system on each type of bridge element. In been replaced. For the state of New Jersey, the NBI database the impressed current category, the titanium mesh was found
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TABLE 1 NUMBER OF CATHODIC PROTECTION SYSTEMS IN EACH STATE OR PROVINCE State/Province Responded to Reported State Code NBI Deck Superstructure Caps Columns Piles Footers Survey Total Alabama AL No 0 Alaska AK No 2 Arizona AZ Yes 0 1 0 0 0 0 0 0 Arkansas AR Yes 0 0 0 0 0 0 0 0 California CA Yes 6 20 12 1 0 6 1 1 Colorado CO Yes 13 6 6 0 0 1 0 0 Connecticut CT Yes 12 13 12 1 Delaware DE No 1 District of Columbia DC No 0 Florida FL Yes 1 71 3 5 6 10 50 10 Georgia GA No 0 Hawaii HI Yes 0 0 0 0 0 0 0 0 Idaho ID No 2 Illinois IL Yes 25 15 8 3 2 1 1 0 Indiana IN Yes 20 15 15 0 0 0 0 0 Iowa IA Yes 13 6 3 2 0 1 0 0 Kansas KS No 5 Kentucky KY No 0 Louisiana LA No 0 Maine ME No 1 Maryland MD Yes 13 15 14 0 0 1 0 0 Massachusetts MA No 3 Michigan MI No 5 Minnesota MN No 1 Mississippi MS Yes 1 0 0 0 0 0 0 0 Missouri MO Yes 129 167 161 0 0 2 0 0 Montana MT Yes 1 0 0 0 0 0 0 0 Nebraska NE No 8 Nevada NV No 0 New Hampshire NH No 2 (continued )
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TABLE 1 (continued ) New Jersey NJ Yes 22 0 0 0 0 0 0 0 New Mexico NM Yes 1 0 0 0 0 0 0 0 New York NY Yes 2 4 3 0 0 1 0 0 North Carolina NC Yes 0 3 0 0 2 2 1 2 North Dakota ND Yes 0 0 0 0 0 0 0 0 Ohio OH Yes 29 Oklahoma OK Yes 2 0 2 0 5 15 0 0 Oregon OR Yes 8 11 9 11 9 7 0 0 Pennsylvania PA Yes 12 11 11 0 0 1 0 0 Puerto Rico PR No 0 Rhode Island RI No 0 South Carolina SC Yes 0 0 0 0 0 0 0 0 South Dakota SD Yes 3 12 8 0 3 1 0 0 Tennessee TN Yes 7 0 0 0 0 0 0 0 Texas TX Yes 8 1 1 4 5 5 3 2 Utah UT Yes 0 2 2 0 0 0 0 0 Vermont VT Yes 0 1 0 0 1 1 0 0 Virginia VA Yes 6 12 7 0 4 7 1 0 Washington WA Yes 3 3 2 1 0 0 0 0 West Virginia WV No 4 Wisconsin WI No 3 Wyoming WY Yes 1 0 0 0 0 0 0 0 Prince Edward Island, Canada PEI-CA 2 1 1 1 New Brunswick, Canada NB-CA 85 35 10 40 Nova Scotia, Canada NS-CA Ontario, Canada ONT-CA 60 40 10 10 Alberta, Canada AL-CA 50 20 10 10 0 10 0 Totals 375 586 375 47 49 83 107 15 Note: Table based on results of Questions 20 and 21 of the survey and data mined from the NBI Database.