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South Dakota Department of Transportation
Project Synopsis
SD1994-13


Title: Electrochemical Removal of Chloride from Bridge Piers
Project Researcher: Jon Becker, South Dakota Department of Transportation
Project Manager: Jon Becker
Research Period: -
Status: Approved
Cost: $0.00

Problem Statement:In the early 1980s the columnar substructure on a Continuous Concrete Box Beam bridge (Structure No. 64-149-367) at M.R.M. 4.35 on Interstate 29 displayed extensive signs of severe corrosion including concrete spalling. An investigation of the cause for this atypical deterioration revealed the culprit was built into the structure. The bridge was built in 1961 using Calcium Chloride (CaCl2) as an accelerator due to winter construction. The presence of the CaCl2 induced the corrosion and gradual deterioration of the substructure.

The substructure was considered an ideal candidate for cathodic protection (CP) but problems with the failures of experimental cathodic protection applications on substructures prevented the use of this technology as a means of mitigating the problem. The development of Electrochemical Chloride Removal (ECR) as an alternative rehabilitation strategy to CP provides a method of stabilizing the deterioration and reducing the corrosion to a manageable level. ECR was first developed in the mid-1970s but the initial research was not promising. Recent developments with ECR both in Europe and as part of the SHRP research have overcome many of the problems. Electrochemical Chloride Removal consists of installing a temporary anode on the surface of the concrete to be treated encased in a suitable electrolyte. Direct electrical current is applied to the structure with the positive side of the circuit connected to the anode and the steel made the system negative. Current flow forces negative chloride ions (Cl-) to migrate toward the anode and away from the steel while positive ions move inward toward the steel to maintain charge neutrality. ECR is a temporary version of CP with much higher current densities employed to facilitate the rapid migration of the Cl- ions.

Findings:
Title: Electrochemical Removal of Chloride from Bridge Piers
Project Researcher: Jon Becker, DOT
Project Manager: Jon Becker
Research Period: -
Status: Approved
Cost: $0.00

Problem Statement:In the early 1980s the columnar substructure on a Continuous Concrete Box Beam bridge (Structure No. 64-149-367) at M.R.M. 4.35 on Interstate 29 displayed extensive signs of severe corrosion including concrete spalling. An investigation of the cause for this atypical deterioration revealed the culprit was built into the structure. The bridge was built in 1961 using Calcium Chloride (CaCl2) as an accelerator due to winter construction. The presence of the CaCl2 induced the corrosion and gradual deterioration of the substructure.

The substructure was considered an ideal candidate for cathodic protection (CP) but problems with the failures of experimental cathodic protection applications on substructures prevented the use of this technology as a means of mitigating the problem. The development of Electrochemical Chloride Removal (ECR) as an alternative rehabilitation strategy to CP provides a method of stabilizing the deterioration and reducing the corrosion to a manageable level. ECR was first developed in the mid-1970s but the initial research was not promising. Recent developments with ECR both in Europe and as part of the SHRP research have overcome many of the problems. Electrochemical Chloride Removal consists of installing a temporary anode on the surface of the concrete to be treated encased in a suitable electrolyte. Direct electrical current is applied to the structure with the positive side of the circuit connected to the anode and the steel made the system negative. Current flow forces negative chloride ions (Cl-) to migrate toward the anode and away from the steel while positive ions move inward toward the steel to maintain charge neutrality. ECR is a temporary version of CP with much higher current densities employed to facilitate the rapid migration of the Cl- ions.

Findings:

Research Objectives:
1  Mitigate the corrosion of a chloride-contaminated bridge substructure.
2  Investigate the use of Electrochemical Chloride Removal.
3  Monitor the effectiveness of various anodes at promoting the migration of chloride ions.
4  Evaluate the effectiveness of a silane sealant at preventing renewed corrosion after ECR.

Research Tasks:
1  Review literature pertinent to electrochemical chloride removal.
2  Submit a work plan to FHWA Demonstration Projects Division outlining the proposed research and requesting funding.
3  Conduct a condition survey of the substructure including delaminations, physical and chemical properties of concrete, steel depth, chloride distribution and half-cell potential and rate of corrosion measurements.
4  Attend a NACE course on cathodic protection.
5  Develop plans and specifications for an ECR application on the substructure.
6  Observe the installation of ECR on a bridge substructure in Virginia.
7  Instrument the substructure with probes or sensors to monitor the ECR process.
8  Install and energize the ECR system.
9  Monitor ECR operation and determine the effectiveness of different anodes at chloride removal.
10  Apply a silane sealant to the concrete after the ECR treatment is finished.
11  Conduct a post-ECR survey of the substructure to determine changes in moisture and corrosion levels and chloride distribution.
12  Present the results of the research to the Research Review Board.
13  Provide a final report and executive summary detailing a literature summary, research methodology, conclusions and recommendations.

Documents Available:

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