Ali Akbar Sohanghpurwala. CONCORR, Inc. CONCRETE CORROSION SPECIALISTS

Transcription

1 Ali Akbar Sohanghpurwala CONCORR, Inc. CONCRETE CORROSION SPECIALISTS

2 The Goals of the Synthesis Examine 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.

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

4 Response to Survey Thirty State DOT s from US responded. Five Provincial DOT s from Canada responded. Five responses from industry.

5 Use of Cathodic Protection in North America Figure 20: Number of Cathodic Protection System Installations Per Year Nuimber of Bridges Year

6 Use of Cathodic Protection in North America A total of 287 systems were installed on 200 bridges by The NBIS database list 375 bridges with deck protection systems at present. The survey reported 573 bridges with CP. Nuimber of Bridges Number of Cathodic Protection System Installations Per Year Year

7 Users of CP Systems 23 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 CP 1. Missouri 2.New Brunswick 3. Florida 4.Ontario 5.Alberta 6.Oregon have 1.2 million square feet of concrete under CP

8 Table 2: Use Of CP On Various Bridge Components CP Installed on Bridge Components # of Respondents Deck 21 Superstructure 9 Caps 11 Columns 19 Piles 8 Footers 4

9 Use of CP in North America Table 3: Types of Cathodic Protection Systems Used by Respondents Impressed Current CP Galvanic CP Arc Sprayed Zinc Arc Sprayed Titanium Arc Sprayed Aluminun-Zinc Alloy Conductive Paint Raychem Ferex Ceramic Anode Conductive Polymer Titanium Mesh Titanium Ribbon Other Arc Sprayed Zinc Arc Sprayed Alloys - Corrpro Hockey Puck Zinc Anodes Zinc Foil Anodes Jackets with expanded zinc mesh Bridge Elements Zinc Bulk Anode other Bridge Decks Beams, Girders, & Diaphragms Caps Columns Piles Struts Footers

10 Table 4: Magnitude of the Corrosion Problem Magnitude of Corrosion # of States Not A Problem 1 Minor 4 Moderate 23 Major 7 Total 35

11 Exposure Conditions Table 5: Salt Usage Tons Per Lane- Mile Per Year # of Respondents none 1 0 to to to to 20 2 > 20 2 Note: Table based on results of Question 7 of the Survey

12 % of Bridges Table 6: Distribution of Bridges Based on Exposure Condition Bridge Deck Exposure Deicing Marine Salt Both Exposure Exposure Neither Substructure Exposure Deicing Marine Salt Both Exposure Exposure Neither Note: Table based on results of Questions 5 & 6 of the Survey

13 Table 9: Factors Most Likely To Determine Which Corrosion Control System Will Be Selected Factors # of Respondents Quantity of damage 16 Presence of chloride ions 4 Extension of service life 2 Life cycle costs 2 Cost of repair and rehabilitation 6 Disruptionin bridge operation 0 Structure type 0 Funds available 1 Consultant Familiarity with corrosion control system 0 Past experience with corrosion control system 2 Agency practise 2 Agency research findings 0

14 Table 10: Reasons For Which CP Was Considered Reason # of Respondents Quantity of concrete damage 9 Level of chloride ion contamination 12 Cost of other alternatives 13 Prevention of future damage 22 Agency research and development recommendation 13 Funding available from other sources such as FHWA or Congressional Mandate to use CP 10 Location of Structure 11 Structure Type 8 Severity of exposure 11 Extension of service life provided by CP 22 Life cycle cost analysis 6 Consultant recommendation 1 FHWA recommendation 3 Experience with cathodic protection 7 Other 4 Note: Table based on results of Question 18 of the Survey

15 Table 11: CP Used for the Folowing Reasons Yes Marine environment where exposure is very corrosive and no other corrosion control 8 system provides service life extension of more than 5 years. Deicing salt exposure which has resulted in high and uniform chloride ion contamination and no other corrosion control system is 9 expected to provide service life extension of more than 5 years. Life cycle cost of cathodic protection system was lower than any other corrosion control 3 system. Cathodic protection system was expected to provide service life extension in excess of years. Location of the structure required use of an 10 aggressive corrosion protection system Type of Structure 7 Other 6 Note: Table based on results of Question 29 of the Survey No

16 Reason Table 12: Reasons For Not Including CP As An Alternative Corrosion Control System Exposure environment is not sufficiently corrosive to warrant the use of cathodic protection Cathodic protectection technology is relatively more expensive than other options available Engineers and contractors that serve the Agency do not have any experience with the technology Cathodic protection is too complicated and Agency does not have sufficient understanding to use it Past experience with cathodic protection has been dissapointing Note: Table based on results of Question 15 of the Survey # of Respondents

17 Table 29: Factors that Will Encourage Applciation of CP Systems # of Responses Better understanding of the technology by Agency Staff 14 Education of the consultants 3 Trained applicators and contractors 4 Reduction 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 17 maintenance of CP components Improved design 11 Technical assistance in selection of appropriate CP systems for each application 13 All of the above 8 Note: Table based on results of Question 53 of the Survey

18 Table 17: Number of Bridges Been Monitored Number Monitored Number of Systems Prince Edward Island, Canada 2 2 New Brunswick, Canada N/A 85 California Florida Indiana Missouri Ontario, Canada Oregon 9 11 Vermont 1 1 Note: Table based on results of Question 32 of the Survey

19 Table 19: Resources for Monitoring and Maintenance of CP Systems Yes No Does your agency have any personnel trained to monitor and maintain cathodic protection 9 14 systems? Does your agency have sufficient trained personnel to monitor and maintain all cathodic 6 17 protection systems under your jurisdiction? Does your agency use consultants on regular basis to monitor and maintain cathodic 5 18 protection systems? Does your agency have a program in place to monitor and maintain the cathodic protection 7 16 systems? 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

20 Table 23: Percent of Systems Operational % CP Systems # of Responses Note: Table based on results of Question 42 of the Survey

21 Table 24: Reasons for Failure of CP Systems # of Responses Failure of CP components resulted in the system been not operational for more than 20% 8 of the time. 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 1 Anode not appropriate for the application 0 Vandalism damaged system components 4 Not identified 5 Note: Table based on results of Question 47 of the Survey

22 Table 25: Length of Operation of CP Systems Length of Operation # of Responses Less than 1 year 2 1 to 5 years 3 5 to 15 years 14 Greater than 15 years 3 Note: Table based on results of Question 43 of the Survey

23 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

24 Case History Missouri 161 Deck systems and 6 substructure systems. Majority of deck systems are slotted with platinumniobium 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.

25 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.

26 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.

27 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.

28 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.

29 Conclusions Corrosion 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.

30 Conclusions Agencies 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 Cost 2. Burden of monitoring and maintenance Past 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.