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TABLE 4 TABLE 5
MAGNITUDE OF THE SALT USAGE
CORROSION PROBLEM
Tons Per Lane- No. of
Magnitude of Mile Per Year Respondents
Corrosion No. of States
None 1
Not a Problem 1
Minor 4 0 to 5 14
Moderate 23 6 to 10 7
Major 8 11 to 15 6
Total 36 16 to 20 2
Note: Table based on results of Question 4 of the survey.
>20 2
Note: Table based on results of Question
7 of the survey.
EXPOSURE CONDITIONS
For bridge decks the primary chloride exposure is deicing
salts. Twenty-one respondents indicated that more than 70% more corrosive exposure when they are located in a marine
of decks are exposed to deicing salts and 13 of those stated environment. It may be noted that for the purpose of the sur-
that all of their decks (100%) are exposed to deicing salts. A vey, marine exposure was defined to persist 2 miles around
summary of exposure environments is presented in Table 6. a saline body of water. In addition to Mississippi, Washington
The province of Prince Edward Island listed 100% of its State has more than 90% of its substructures listed as
bridges in the "Both" category; that is, exposed to both the "Neither."
deicing salts and the marine environment. Only Mississippi
has more than 90% of its decks categorized as "Neither," PROCESS FOR SELECTION OF CORROSION
which correlates well with their perception of the corrosion MITIGATION ALTERNATIVES
problem.
To ascertain the compatibility and the cost-effectiveness of a
Understandably, the substructure exposure to deicing salts cathodic protection system on a reinforced concrete struc-
is lower than that of the bridge decks; only 6 of the 13 re- ture, among other things, it is important that the severity of
spondents (with 100% of bridge decks exposed to deicing exposure, the presence of chloride ions in sound concrete, the
salts) reported that all of their bridge substructures are exposed presence of electrical continuity, the susceptibility of the
to it. The deicing salt exposure to substructure elements concrete to alkalisilica reaction and freezethaw damage,
comes in two forms: (1) leakage of chloride-contaminated and the presence of corrosion activity in sound areas be
water through joints and (2) drains and splashing of the con- known. Analysis of test methods used by respondent agen-
taminated solution onto the substructure elements by vehi- cies during Routine Bridge Inspection and corrosion condi-
cles in the underpass. The substructure elements confront a tion evaluation was performed and is summarized in Table 7.
TABLE 6
DISTRIBUTION OF BRIDGES BASED ON EXPOSURE CONDITION
Bridge Deck Exposure Substructure Exposure
Marine Deicing Salt Marine Deicing Salt
% of Bridges Exposure Exposure Both Neither Exposure Exposure Both Neither
59 26 6 32 21 24 8 33 14
1019 2 1 1 2 4 1 1 1
2029 4 0 1 1 5 2 0 1
3039 0 3 0 2 0 5 0 0
4049 0 1 0 1 0 4 0 3
5059 2 2 0 2 2 4 0 2
6069 0 2 0 1 0 1 0 3
7079 0 2 0 1 0 0 0 3
8089 0 1 0 2 0 2 0 2
9099 0 2 0 1 0 2 0 4
100 1 16 1 1 1 7 1 2
Note: Table based on results of Questions 5 and 6 of the survey.
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TABLE 7 based on the data collected during the evaluations. Sixteen
TEST METHODS USED agencies include cathodic protection as an alternative in their
No. of Respondents selection process (see Table 8). Of the agencies that cited
Routine Corrosion the corrosion problem as a major one, four, Connecticut, New
Bridge Condition York, Oregon, and Pennsylvania, include cathodic protection
Test Method Inspection Evaluation as one of the options, but Oklahoma, Utah, and Virginia do not.
Eight respondents stated that their agencies included cathodic
Visual Survey 36 29 protection as an alternative because it provides service-life
Crack Survey 19 16 extension desired for many of the high use structures and/or
Delamination Survey 21 29 its agency staff has significant success in the use of the tech-
Chloride Ion Content Analysis 4 28 nology. The province of New Brunswick includes it, as it
does not have any alternatives for the severe exposure condi-
Half-cell Potential Survey 4 23
tions its structures have to withstand.
Carbonation Testing 0 3
Electrical Continuity Testing 2 6 The quantity of damage was reported by 16 agencies to
Corrosion Rate Measurement 0 2 be the determining factor for the selection of a corrosion
Concrete Resistivity Testing 1 3 control system and the cost of application and repair was
None 0 1 identified by 6 agencies (see Table 9). Only four agencies
reported that the presence of chloride ions would be the
Other 0 2
determining factor and, for three respondents, the extension
Note: Table based on results of Questions 8 and 9 of the survey.
in service life was the determining factor. All other choices
in the list were picked by two or fewer respondents. These
All agencies perform a visual survey during the Routine responses suggest that the procedures, protocols, and
Bridge Inspection and a majority of them perform delamina- methodologies used by these agencies may not be effec-
tion and crack surveys. Only a few perform chloride ion con- tively using the data obtained during surveys to properly
tent analysis, half-cell potential survey, electrical continuity select a corrosion mitigation system. The quantity of dam-
testing, and concrete resistivity measurements. The testing age signifies the magnitude of the problem and not its
protocol used by the majority of the agencies would provide cause. It is more appropriate for the selection of the repair;
a good measure of the symptoms of corrosion, rust staining, however, it would have to be the presence and distribution
cracking, delamination, and spalling, and would reasonably of chloride ions in the remaining sound concrete that would
indicate the overall condition of the structure and provide a control which corrosion control system would be the most
basis for more in-depth evaluation. During an in-depth sur- effective and viable in that application.
vey or corrosion condition evaluation, the vast majority of
the agencies perform a visual survey, delamination survey, Twenty-three agencies have or would consider cathodic
chloride ion content analysis, and half-cell potential survey. protection for its ability to prevent future damage and to sub-
Thus, information on the extent of chloride contamination stantially extend the service life (Table 10). Recommenda-
and the presence of active corrosion is also being determined tions of their own agency research and development efforts
during these evaluations. Only a few agencies conduct elec- have encouraged the use of cathodic protection for many
trical continuity; three perform carbonation testing, one con- agencies. The cost of other alternatives, the level of chloride
siders petrographic analysis on select projects, and one uses
corrosion rate measurements. North Dakota does not perform TABLE 8
corrosion condition evaluation and only performs the visual USE OF PROCEDURES, PROTOCOLS, AND METHODOLOGIES
survey during the Routine Bridge Inspection. Generally rein- Questions Yes No
forcing steel on a bridge deck is electrically continuous, and 18 18
Are there agency-wide standard procedures, protocols,
therefore, electing to test for continuity during the installa- or methodologies for conducting corrosion condition
tion of the cathodic protection system is acceptable. How- evaluations of reinforced concrete structures?
ever, ascertaining the susceptibility to alkalisilica reaction Does your agency have procedures, protocols, or 20 16
could be performed during the selection process, unless based methodologies to analyze the data collected during
on materials used in standard concrete mixes the susceptibil- condition evaluation?
ity is already known. Similarly, susceptibility to freezethaw Does your agency have procedures, protocols, or 20 16
could be ascertained during the selection of the alternative methodologies to select repair and corrosion control
corrosion mitigation systems. alternatives based on data collected from condition
evaluations?
A majority of the agencies have standard procedures, pro- If your agency has procedures, protocols, and/or 16 17
tocols, or methodologies for conducting corrosion condition methodologies to select repair and corrosion control
evaluations, analyzing the data collected during the evalua- alternatives, does it include cathodic protection?
tions, and selecting repair and corrosion control alternatives Note: Table based on results of Questions 10 to 12 and 14 of the survey.
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TABLE 9 TABLE 11
FACTORS MOST LIKELY TO DETERMINE WHICH CATHODIC PROTECTION USED FOR THE FOLLOWING
CORROSION CONTROL SYSTEM WILL BE SELECTED REASONS
No. of No. of
Factors Respondents Reason Respondents
Quantity of Damage 16 Marine environment where exposure is very 8
corrosive and no other corrosion control
Presence of Chloride Ions 4 system provides service life extension of more
Extension of Service Life 3 than 5 years
Life-Cycle Costs 2 Deicing salt exposure that has resulted in high 9
Cost of Repair and Rehabilitation 6 and uniform chloride ion contamination and
no other corrosion control system is expected
Disruption in Bridge Operation 0 to provide service life extension of more than
Structure Type 0 5 years
Funds Available 1 Life-cycle cost of cathodic protection system 3
Consultant Familiarity with Corrosion Control 0 was lower than any other corrosion control
System system
Cathodic protection system was expected to 13
Past Experience with Corrosion Control System 2
provide service life extension in excess of
Agency Practice 2 20 years
Agency Research Findings 0 Location of the structure required use of an 10
Note: Table based on results of Question 13 of the survey. aggressive corrosion protection system
Type of structure 7
ion contamination, and the location of the structure were Other 6
also considered by several agencies as reasons for its use. Note: Table based on results of Question 29 of the survey.
The summary in Table 11 indicates cathodic protection has
been used when service life in excess of 20 years was desired Funding from other sources has encouraged the use of the
if the structure was located in a very aggressive environment, technology for some agencies and their experience with the
if no other alternatives are available, or if it is located in a technology only encouraged its use in seven agencies. This
marine environment. last response raises a question; what has been the experience
of user agencies with cathodic protection systems? The sum-
TABLE 10 mary of responses in Table 12 provides some answers to this
REASONS FOR WHICH CATHODIC PROTECTION question; nine agencies do not include cathodic protection
WAS CONSIDERED
as an alternative corrosion mitigation system in their proce-
dures, protocols, and methodologies for selecting repair and
No. of corrosion control alternatives owing to disappointing past
Reason Respondents
experience and eight agencies do not use it because it is more
Quantity of Concrete Damage 9
TABLE 12
Level of Chloride Ion Contamination 12
REASONS FOR NOT INCLUDING CATHODIC PROTECTION
Cost of Other Alternatives 13 AS AN ALTERNATIVE CORROSION CONTROL SYSTEM
Prevention of Future Damage 22 No. of
Agency Research and Development Recommendation 13 Reason Respondents
Funding Available from Other Sources such as 10 Exposure environment is not sufficiently 4
FHWA or Congressional Mandate to Use corrosive to warrant the use of cathodic
Cathodic Protection protection
Location of Structure 11 Cathodic protection technology is relatively 8
Structure Type 8 more expensive than other options
available
Severity of Exposure 11
Engineers and contractors that serve the 5
Extension of Service Life Provided by Cathodic 23
agency do not have any experience with
Protection
Life-Cycle Cost Analysis 6 the technology
Cathodic protection is too complicated and 3
Consultant Recommendation 1
the agency does not have sufficient
FHWA Recommendation 3 understanding to use it
Experience with Cathodic Protection 7 Past experience with cathodic protection has 9
Other 4 been disappointing
Note: Table based on results of Question 18 of the Survey Note: Table based on results of Question 15 of the survey.
