Evaluation of Electrochemical Chloride Extraction, Fiber Reinforced Polymer Wraps, and Concrete Sealers for Corrosion Mitigation in Reinforced Concrete Bridge Structures PDF Download
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Author: Michael S. Murphy
Publisher:
ISBN:
Category : Chlorides
Languages : en
Pages : 155
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Book Description
Reinforced concrete bridge substructures in Minnesota and other northern climates possess an elevated risk for chloride induced corrosion damage, which can reduce capacity and shorten service life. Research was performed in 1997 to investigate new strategies for corrosion mitigation, including electrochemical chloride extraction (ECE) and installation of fiber reinforced polymer (FRP) wrap, which were applied on several corrosion-damaged piers on a 30-year-old bridge in Minneapolis. This report presents the results of follow-up research performed to assess the condition of the treated piers after 20 additional years of service, in order to understand the long-term effectiveness of the strategies implemented. The combination of ECE treatment and FRP wrap installation was found to be very effective, with no concrete distress or probable corrosion activity identified in the treated elements. Poor or mixed performance was observed with all other strategies, including both ECE treatment followed by application of a penetrating sealer and FRP wrap installation that was not accompanied with ECE. In addition, significant chloride contamination occurred in all of the subject piers within the 20 years since the initial study, indicating that neither FRP wrap nor concrete sealers prevented the ingress of new chlorides in the manner in which these systems were installed in the initial study. The findings indicated that performing ECE treatment, or installing FRP wraps, did not alone eliminate the risk of future corrosion activity. The most effective corrosion mitigation strategy to extend the service life of reinforced concrete bridge substructures was to minimize water and chloride exposure.
Author: Michael S. Murphy
Publisher:
ISBN:
Category : Chlorides
Languages : en
Pages : 155
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Book Description
Reinforced concrete bridge substructures in Minnesota and other northern climates possess an elevated risk for chloride induced corrosion damage, which can reduce capacity and shorten service life. Research was performed in 1997 to investigate new strategies for corrosion mitigation, including electrochemical chloride extraction (ECE) and installation of fiber reinforced polymer (FRP) wrap, which were applied on several corrosion-damaged piers on a 30-year-old bridge in Minneapolis. This report presents the results of follow-up research performed to assess the condition of the treated piers after 20 additional years of service, in order to understand the long-term effectiveness of the strategies implemented. The combination of ECE treatment and FRP wrap installation was found to be very effective, with no concrete distress or probable corrosion activity identified in the treated elements. Poor or mixed performance was observed with all other strategies, including both ECE treatment followed by application of a penetrating sealer and FRP wrap installation that was not accompanied with ECE. In addition, significant chloride contamination occurred in all of the subject piers within the 20 years since the initial study, indicating that neither FRP wrap nor concrete sealers prevented the ingress of new chlorides in the manner in which these systems were installed in the initial study. The findings indicated that performing ECE treatment, or installing FRP wraps, did not alone eliminate the risk of future corrosion activity. The most effective corrosion mitigation strategy to extend the service life of reinforced concrete bridge substructures was to minimize water and chloride exposure.
Author: Mark Robert Chauvin
Publisher:
ISBN:
Category : Concrete bridges
Languages : en
Pages : 748
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Author: Mark Robert Chauvin
Publisher:
ISBN:
Category : Bridges, Reinforced concrete
Languages : en
Pages : 186
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Book Description
Author: Stephen R. Sharp
Publisher:
ISBN:
Category : Concrete bridges
Languages : en
Pages : 38
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Book Description
Electrochemical chloride extraction (ECE) is an electrochemical bridge restoration method for mitigating corrosion in reinforced concrete structures. ECE does this by moving chlorides away from the reinforcement and out of the concrete while simultaneously increasing the alkalinity of the electrolyte near the reinforcing steel. Despite its proven success, ECE is not used extensively in part because of an incomplete understanding of the following three issues: (1) the time required for ECE with varying water-to-cement ratios (w/c) and cover depths; (2) the cause of the decrease in current flow and, therefore, chloride removal rate during ECE; (3) the additional service life that can be expected following ECE when the treated member is subjected to chlorides. This study addressed the first two issues. Plain carbon steel reinforcing bars were embedded in portland cement concrete slabs of varying w/c and cover depths and then exposed to sodium chloride solutions. A fraction of the slabs contained sodium chloride as an admixture. All slabs were subjected to cyclical ponding with a saturated solution of sodium chloride. ECE was then used to remove the chlorides from the slabs while electrical measurements were made in the different layers between the reinforcing bar (cathode) and the titanium mat (anode) to follow the progress of the ECE process. The resistance of the outer concrete surface layer increased during ECE, inevitably restricting current flow, and the resistance of the underlying concrete either decreased or remained constant. During ECE, a white residue, or surface film, formed on the surface of the concrete. The residue contained calcium carbonate, calcium chloride, and other yet unidentified minor components when calcium hydroxide was used as the electrolyte. The surface film can be removed mechanically or, to some extent, inhibited chemically. There was no obvious relationship among cover depth, w/c, and chloride extraction efficiency, although cover depth did influence the current density. The investigators recommend that the Virginia Department of Transportation's Structure & Bridge Division (1) require that contractors mechanically remove the latent surface layer of concrete prior to treatment using ECE and (2) discuss with corrosion consultants the potential for using a scale inhibitor during ECE to increase the efficiency of chloride removal. The benefits and costs assessment of treating a structure using ECE can not currently be determined, but research currently underway will provide the necessary information for the assessment.
Author: Stephen Sharp
Publisher:
ISBN:
Category : Reinforced concrete
Languages : en
Pages : 63
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Book Description
One of the biggest causes of bridge deterioration is corrosion of the reinforcement in concrete structures. Therefore, repair techniques that mitigate corrosion and extend the service life of reinforced concrete are of great value to the Virginia Department of Transportation (VDOT). One such technique is electrochemical chloride extraction (ECE), which is a temporary in situ restoration method for removing chlorides from reinforced concrete structures that are deteriorating because of corrosion. The results of this study are based on historical and current data gathered during the evaluation of substructure elements in Virginia, i.e., the 5th Street Extended Bridge in Albemarle County and two I-95 bridges in Richmond, and on information from the literature about the earliest bridge substructure treated with ECE, i.e., the Burlington Bay Skyway in Burlington, Ontario, Canada,. Early ECE work on the Burlington Bay Skyway showed favorable results upon reassessment of the treated area after 9 years. With regard to the ECE-treated structures in Virginia, the study determined that if additional service life beyond that provided by ECE alone is desired, the structure must be protected against the reintroduction of chlorides to the repaired elements. Further, the use of ECE techniques should be accompanied by repair or removal of overhead deck expansion joints that exposed the concrete elements to salt-laden water and application of a waterproofing sealer such as silane, methacrylate, or epoxy to the substructure elements. ECE provided an additional 15 to 20 years of service life when a post-treatment silane sealer was also applied. The study also found that in the project specification, the criterion used for determining when to terminate ECE is often the amount of charge passed but difficulties in the field might result in unforeseen construction delays as a result of the attempt to meet this criterion. Therefore, contracts should specify that chloride concentration at the level of the reinforcing bar can be used as an alternative criterion for determining when the ECE is complete, particularly when treatment times become excessive. Specifications should also require that all ECE connections to the steel be completely removed or embedded after completion of the treatment and a highly resistive cementitious repair material should be used to patch any holes. Another valuable outcome from this study was the discussion on how combining electrochemical techniques, such as cathodic protection and ECE, could theoretically provide additional life beyond that provided by the use of one of these techniques alone. This study gathered baseline data to assess this option. The two I-95 bridges in Richmond, one over Hermitage Road and the other over Overbrook Road, should allow a comparison of how much galvanic anode cathodic protection can extend service life beyond that of ECE treatment alone. The study recommends that VDOT’s Structure and Bridge Division incorporate the lessons learned from assessing the restoration of the substructures of the 5th Street Extended Bridge and the two I-95 bridges. In addition, the Virginia Transportation Research Council should continue to monitor the I-95 bridges to determine the value of combining different electrochemical mitigation techniques to extend service life
Author: University of Minnesota. Center for Transportation Studies
Publisher:
ISBN:
Category : Transportation
Languages : en
Pages : 48
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Author: M. Islam
Publisher:
ISBN:
Category : Environmental monitoring
Languages : en
Pages : 12
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Book Description
Electrochemical methods for controlling corrosion of reinforcing steel in concrete involve techniques that interfere with the electrochemical reactions occurring on the embedded steel surface. Included in this category are cathodic protection, electrochemical chloride extraction, re-alkalization (for carbonation damage), and corrosion inhibitors. Assessing and monitoring the performance of these corrosion protection systems for steel in concrete can sometimes be challenging. Several techniques and devices are available. In recent years different electrochemical techniques have been utilized. The present paper discusses the use of the older devices and the more recently developed devices such as the "ladder" probe and the microprocessor controlled electrical resistance probe for evaluating and monitoring the performance of reinforced concrete corrosion protection systems. Remote monitoring options are also discussed.
Author: Dietrich H. Vogel
Publisher:
ISBN:
Category : Cement composites
Languages : en
Pages : 234
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Book Description
Highway drainage pipes utilize concrete reinforced with steel wire to help mitigate water, earth, and traffic loads. Drainage pipes reinforced with zinc electroplated steel fibers offer a lower steel alternative to traditional steel wire cage reinforcements. The objective of the thesis research was to determine the physical and electrochemical characteristics of zinc electroplated steel fiber corrosion propagation. Experimental programs include: Fracture analysis of zinc electroplated steel fibers embedded in dry-cast concrete pipes exposed to varying chloride concentrations; Visual analysis of zinc electroplated steel fibers embedded in concrete exposed to varying chloride concentrations; Electrochemical analysis of zinc electroplated steel fibers embedded in concrete exposed to varying chlorides; Chloride threshold determination for zinc electroplated steel fibers immersed in simulated pore solution. Between the four experimental programs the most significant conclusion is that oxygen, moisture, and chlorides past the chloride threshold must be present for corrosion to propagate significantly on the zinc electroplated steel fibers.
Author: Yu Jiang
Publisher:
ISBN:
Category : Concrete coatings
Languages : en
Pages :
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Author: Gerardo G. Clemeña
Publisher:
ISBN:
Category : Bridges
Languages : en
Pages : 36
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Book Description
Electrochemical chloride extraction is a new technique for mitigating chloride-induced corrosion of the reinforcing bars in concrete bridges. To demonstrate the feasibility of applying this technique on full-sized concrete bridge members and to identify needed improvements to the technology, the technique was tried on two concrete deck spans and three concrete piers in Virginia. For the two deck spans, an anode system consisting of felt-sandwiched catalyzed titanium mesh kept wet by an electrolyte was used. An electrical charge of 741 to 1077 A-hr/m2 was applied between the anode and the steel bar for 57 or 58 days. Approximately 72 to 82 percent of the chloride ions was removed from the concrete at the depth of the first mat of steel bars. For the three piers, an anode system consisting of wet cellulose fibers and steel or titanium mesh was used. An electrical charge of 249 to 382 A-hr/m2 was applied between the anode and the steel bars for 72 to 77 days. The system for the piers appeared to be relatively less effective than that for the deck spans, removing approximately 13 to 53 percent of the chloride ions from the concrete near the steel bars. In addition, more problems were encountered with this treatment system. No damage to the concrete attributable to the treatment was observed with either system, and it is likely that shorter treatment times would have sufficed. Based on potential surveys, the bars in the concrete piers were still passive at 4 years after treatment. To facilitate the comparison between electrochemical chloride extraction and other corrosion control options, such as impressed-current and galvanic cathodic protection, preliminary information on the costs and projected service lives of all options is provided.
