Ali Akbar Sohanghpurwala

CONCORR, Inc.CONCRETE CORROSION SPECIALISTS

The Goals of the SynthesisExamine the extent of the use of cathodic protection technology on reinforced concrete structures.Ascertain why public agencies use or do not use the technology.Explore how to encourage the use of the technology.

Data Collection ProtocolLiterature review.Survey of State and Provincial DOT’s in the US and Canada.Survey of private industry.Interview with select State DOT’s.

Response to SurveyThirty State DOT’s from US responded.Five Provincial DOT’s from Canada responded.Five responses from industry.

Use of Cathodic Protection in  North America

 

15

8

17 6

3 42

10 10

20

56

39

4742

22

0

10

20

30

40

50

60

73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89

Nuim

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Year

Figure 20:  Number of Cathodic Protection System Installations Per Year

Use of Cathodic Protection in  North America

A total of 287 systems were installed on 200 bridges by 1989.The NBIS database list 375 bridges with deck protection systems at present.The survey reported 573 bridges with CP.

15

8

17 6

3 42

10 10

20

56

39

4742

22

0

10

20

30

40

50

60

73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89

Nuimbe

r of B

ridg

es

Year

Number of Cathodic Protection System Installations Per Year

Users of CP Systems23 of the 35 respondents have CP Systems.Of the 586 structures reported, 389 are located in US and 197 are located in Canada

Major users of CP1.

Missouri

2.

New Brunswick3.

Florida

4.Ontario5.

Alberta

6.Oregon have 1.2 million  square feet of concrete 

under CP

CP Installed on Bridge Components

# of Respondents

Deck 21Superstructure 9Caps 11Columns 19Piles 8Footers 4

Table 2: Use Of CP On Various Bridge Components

Use of CP in North America

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Bridge Decks 2 1 0 0 0 3 4 11 4 2 1 1 7 1 0 1 3Beams, Girders, & Diaphragms 1 1 0 1 0 0 1 2 0 0 4 3 4 3 1 1 0Caps 5 0 1 3 0 0 1 2 0 0 4 4 9 3 0 0 0Columns 5 0 1 3 0 1 1 4 0 0 8 5 12 4 2 2 0Piles 0 0 0 1 0 0 0 1 1 1 2 2 2 2 3 7 1Struts 1 0 0 2 0 0 1 1 1 0 3 1 3 0 0 0 0Footers 1 0 0 2 0 1 1 1 1 0 2 1 1 0 0 2 1

Table 3: Types of Cathodic Protection Systems Used by Respondents

Bridge Elements

Impressed Current CP Galvanic CP

Magnitude of Corrosion # of States

Not A Problem 1Minor 4Moderate 23Major 7Total 35

Table 4: Magnitude of the Corrosion Problem

Exposure Conditions

Tons Per Lane-Mile Per Year

# of Respondents

none 10 to 5 136 to 10 7

11 to 15 616 to 20 2

> 20 2

Table 5: Salt Usage

Note: Table based on results of Question 7 of the Survey

Marine Exposure

Deicing Salt

ExposureBoth Neither Marine

Exposure

Deicing Salt

ExposureBoth Neither

5 26 6 32 21 24 8 33 1410 2 1 1 2 3 1 1 120 4 0 1 1 5 2 0 130 0 3 0 2 0 5 0 040 0 1 0 1 0 4 0 350 2 2 0 2 2 4 0 260 0 2 0 1 0 1 0 370 0 2 0 1 0 0 0 380 0 1 0 2 0 2 0 290 0 2 0 1 0 1 0 4

100 1 15 1 1 1 7 1 2Note: Table based on results of Questions 5 & 6 of the Survey

Bridge Deck Exposure Substructure Exposure% of

Bridges

Table 6: Distribution of Bridges Based on Exposure Condition

Factors# of

RespondentsQuantity of damage 16Presence of chloride ions 4Extension of service life 2Life cycle costs 2Cost of repair and rehabilitation 6Disruptionin bridge operation 0Structure type 0Funds available 1Consultant Familiarity with corrosion control system 0

Past experience with corrosion control system 2

Agency practise 2Agency research findings 0

Table 9: Factors Most Likely To Determine Which Corrosion Control System Will Be

Selected

Reason # of Respondents

Quantity of concrete damage 9Level of chloride ion contamination 12Cost of other alternatives 13Prevention of future damage 22Agency research and development recommendation 13

Funding available from other sources such as FHWA or Congressional Mandate to use CP 10

Location of Structure 11Structure Type 8Severity of exposure 11Extension of service life provided by CP 22Life cycle cost analysis 6Consultant recommendation 1FHWA recommendation 3Experience with cathodic protection 7Other 4Note: Table based on results of Question 18 of the Survey

Table 10: Reasons For Which CP Was Considered

Yes NoMarine environment where exposure is very corrosive and no other corrosion control system provides service life extension of more than 5 years.

8

Deicing salt exposure which has resulted in high and uniform chloride ion contamination and no other corrosion control system is expected to provide service life extension of more than 5 years.

9

Life cycle cost of cathodic protection system was lower than any other corrosion control system.

3

Cathodic protection system was expected to provide service life extension in excess of 20 years.

12

Location of the structure required use of an aggressive corrosion protection system 10

Type of Structure 7Other 6Note: Table based on results of Question 29 of the Survey

Table 11: CP Used for the Folowing Reasons

Reason# of

RespondentsExposure environment is not sufficiently corrosive to warrant the use of cathodic protection

4

Cathodic protectection technology is relatively more expensive than other options available

8

Engineers and contractors that serve the Agency do not have any experience with the technology

5

Cathodic protection is too complicated and Agency does not have sufficient understanding to use it

3

Past experience with cathodic protection has been dissapointing 9

Table 12: Reasons For Not Including CP As An Alternative Corrosion Control System

Note: Table based on results of Question 15 of the Survey

# of ResponsesBetter understanding of the technology by Agency Staff 14

Education of the consultants 3Trained applicators and contractors 4Reduction in cost of the cathodic protections system 22

Availability of consultants to monitor and maintain CP systems 9

Improved technology to monitor and maintain systems 19

Improved quality of the system components which would reduce the frequency of repair and maintenance of CP components

17

Improved design 11Technical assistance in selection of appropriate CP systems for each application 13

All of the above 8

Table 29: Factors that Will Encourage Applciation of CP Systems

Note: Table based on results of Question 53 of the Survey

Number Monitored

Number of Systems

Prince Edward Island, Canada 2 2New Brunswick, Canada N/A 85California 10 20Florida 71 71Indiana 15 15Missouri 96 167Ontario, Canada 40 60Oregon 9 11Vermont 1 1

Note: Table based on results of Question 32 of the Survey

Table 17: Number of Bridges Been Monitored

Yes NoDoes your agency have any personnel trained to monitor and maintain cathodic protection systems?

9 14

Does your agency have sufficient trained personnel to monitor and maintain all cathodic protection systems under your jurisdiction?

6 17

Does your agency use consultants on regular basis to monitor and maintain cathodic protection systems?

5 18

Does your agency have a program in place to monitor and maintain the cathodic protection systems?

7 16

Are remote monitoring units used to monitor some or all of the CP Systems 8 15

Note: Table based on results of Questions 34 to 38 of the Survey

Table 19: Resources for Monitoring and Maintenance of CP Systems

% CP Systems # of Responses5 7

20 040 260 280 4100 6

Table 23: Percent of Systems Operational

Note: Table based on results of Question 42 of the Survey

# of ResponsesFailure of CP components resulted in the system been not operational for more than 20% of the time.

8

CP system not putting out sufficient current due to improper design 0

CP system not operational due to failure of one or more components 1

CP system not putting out sufficient current due to improper settings 10

CP system did not operate due to deficient design 2

CP system not installed as designed 1Anode not appropriate for the application 0Vandalism damaged system components 4Not identified 5

Table 24: Reasons for Failure of CP Systems

Note: Table based on results of Question 47 of the Survey

Length of Operation # of ResponsesLess than 1 year 21 to 5 years 35 to 15 years 14Greater than 15 years 3

Table 25: Length of Operation of CP Systems

Note: Table based on results of Question 43 of the Survey

Case History ‐ Missouri

Has a formal team to handle CP systems.Charged with selection, design, installation oversight, monitoring, and operation.12 full time dedicated personnel for monitoring CP systems.Traffic Signal Electricians, Traffic Engineers, Bridge Engineers, and Construction Engineers trained in CP.Developed standard specifications based on AASHTO

Case History ‐ Missouri

161 Deck systems and 6 substructure systems.Majority of deck systems are slotted with platinum‐niobium wire.In the last 8 years all deck systems have been mixed metal oxide.Oldest mixed metal oxide system is 19 years old and operational.

Case History ‐ Florida

Has 6,000 bridges located in the marine environment.Has a Corrosion Laboratory in Gainesville with 9 full time staff.Hired people with formal training.Perform in‐house material testing.Have developed many of the technologies in use today.Regularly use consultants to supplement their staff. 

Case History ‐ Florida

Corrosion Laboratory has slowly but surely convinced all Districts in the State to utilize CP.Corrosion Laboratory performs all monitoring with the assistance of Consultants.Each project requires a NACE Certified or a qualified CP Specialist during installation.Many Contractors in the State now have experience with installation of CP systems.

Case History ‐ Oregon

Has a Bridge Preservation Group which includes a structural, electrical, hydraulics, and corrosion positions.This group controls the selection, design, installation oversight, and monitoring and operation of the CP systems.Large surface area under protection.Primarily arc sprayed zinc CP systems.

Case History ‐ California

Pioneer in CP.Use CP in extreme cases.Presently has 3 personnel experienced and well versed with CP.Generally uses in‐house developed systems.Maintenance group is not well equipped to perform monitoring and maintenance.  They borrow experienced personnel from other groups.Likely to use more if better guidelines become available and they develop more confidence in the newer products available in the market place.

ConclusionsCorrosion at a minimum is a moderate problem for the majority of the DOT’s.Deicing salt usage is sufficiently high to render CP an appropriate technology for use.CP is included as an alternative only for a few select agencies.  The use of the technology is limited in most instances.Use of the technology is declining.

ConclusionsAgencies that have successfully implemented cathodic protection technology have experienced reduction in the frequency and cost of bridge maintenance and an increase in service life of their bridge structures.  To accomplish this they had to acquire a good understanding of the technology and expertise in the technology.The primary hindrance to the use of the technology are:

1.

Initial Cost2.

Burden of monitoring and maintenancePast disappointing experience has also slowed the use of the technology.Galvanic CP is becoming more attractive due to lower need for monitoring and maintenance.Competition and innovation are required in the industry.