DSCN5466 DSCN5467 596 DSCN5468 DSCN5469 North Approach Spans DSCN5470 DSCN5471 597 DSCN5472 DSCN5473 North Approach Spans DSCN5474 DSCN5475 598 DSCN5476 DSCN5477 North Approach Spans DSCN5478 DSCN5479 599 DSCN5480 DSCN5481 North Approach Spans DSCN5482 DSCN5483 600 DSCN5484 DSCN5485 North Approach Spans DSCN5486 DSCN5487 601 DSCN5488 DSCN5489 North Approach Spans DSCN5490 DSCN5491 602 DSCN5492 DSCN5493 North Approach Spans DSCN5494 DSCN5495 603 DSCN5496 DSCN5497 North Approach Spans DSCN5498 DSCN5499 604 DSCN5500 DSCN5501 North Approach Spans DSCN5502 DSCN5503 605 DSCN5504 DSCN5505 North Approach Spans DSCN5506 DSCN5507 606 DSCN5508 DSCN5509 North Approach Spans DSCN5510 DSCN5511 607 DSCN5512 DSCN5513 North Approach Spans DSCN5514 DSCN5515 608 DSCN5516 DSCN5517 North Approach Spans DSCN5518 DSCN5519 609 DSCN5520 DSCN5521 North Approach Spans DSCN5522 DSCN5523 610 DSCN5524 North Approach Spans 611 612 613 614 615 616 617 618 619 620 621 622 623 Miscellaneous
624 DSC06671 DSC06672 625 DSC06673 DSC06674 Waterline and Supports DSC06676 DSC06677 626 DSC06928 DSCN5609 Waterline and Supports DSCN5755 DSCN5756 627 Validation Insp 092313 077 Validation Insp 092313 108 Waterline and Supports 628 2013 Inspection Update ‐ 10th Avenue Bridge December 16, 2013 Minneapolis, Minnesota
Appendix C – Corrosion Mitigation Options
10th Avenue Bridge Rehabilitation
Corrosion Mitigation Options
8 November 2013
10th Avenue Bridge Rehabilitation i SRF Consulting Group, Inc.
Executive Summary
In early October 2013, Vector Corrosion Technologies, Inc. conducted a corrosion investigation of the 10th avenue Bridge substructure to assist SRF provide corrosion mitigation recommendations. Primary testing was conducted on the seven spans and on two bents under expansion joints on the north approach spans.
Bridge Description: Originally constructed in 1929, the 10th Avenue Bridge is a seven span, 2,135-foot long, open-spandrel arch bridge across the Mississippi River. The bridge spans a gap between West River Parkway and 2nd Street SE, connecting 10th Avenue SE in the Marcy-Holmes neighborhood of Minneapolis, MN to 19th Avenue South on the West Bank of the University of Minnesota. The bridge is located 300 feet east of Interstate 35W (I-35W), and approximately one-half mile northwest a 55.5-foot roadway and a barrier-protected eight-foot-wide pedestrian facility. This historic arch bridge has a long history of past repairs and it is now time to conduct additional maintenance and rehabilitation repairs. Testing recently conducted on the 10th Ave Bridge indicates that chloride-induced corrosion is one of the primary causes for substructure distress. There are many areas of the structure that are either currently undergoing active corrosion, or are in danger of future corrosion-related damage. Factors informing the selection of a corrosion mitigation system include:
• The structure’s age and historical significance • Aesthetics of the structure • Location and extent of chloride contaminated concrete • Required service life of the rehabilitation • Half-cell potential measurements • Initial cost of corrosion mitigation systems • Life-cycle costs for maintenance and replacement of the system • Electrical continuity of embedded steel reinforcement • Extent of concrete damage • Structural deficiencies or concerns
Corrosion Mitigation Options Vector Corrosion Technologies, Inc. was tasked to conduct a corrosion investigation of the substructure and to recommend corrosion mitigation options for the various bridge elements and provide the associated costs for each system. The corrosion mitigation options considered fall into four broad categories:
1. Topical treatments
10th Avenue Bridge Rehabilitation ii SRF Consulting Group, Inc.
2. Galvanic protection systems 3. Impressed current systems 4. Electrochemical treatments
Topical treatments include the application of barrier coatings, crack sealants, breathable penetrating sealers, and surface applied corrosion inhibitors. Judicial use of topical treatments makes sense when used as part of a proper repair and protection strategy. Galvanic protection options rely on the use of a sacrificial metal producing a small current to counteract the natural electrochemical corrosion process. Galvanic protection involves electrically connecting a sacrificial metal to the reinforcing steel network. This sacrificial metal, predominately zinc, corrodes preferentially to the reinforcing steel and delivers a small electrical current to the reinforcing. This small current forces the cathodic reaction of oxygen reduction to occur on the steel surface. This cathodic reaction increases the local pH on the steel surface, and reduces corrosion activity. Galvanic systems are generally not adjustable after installation and have a defined service life based on the quantity of sacrificial metal provided. Impressed current cathodic protection works on the same principle as galvanic protection, except the power is delivered to the structure from an external source. Impressed current systems use an inert anode system, typically mixed metal oxide coated titanium or ceramic, to distribute the current to the concrete. In this system electrical connections are made to the reinforcing and the anode system, and DC current is supplied through a rectifier. Impressed current systems have the advantage of being adjustable and can have an extended service if regularly maintained. Electrochemical treatments are essentially temporary impressed current systems using an external anode system. These treatments supply a current to the system that is at least an order of magnitude larger than an impressed current system. The primary benefits of these treatments are 1) it removes the source of the problem; and 2) there is no additional maintenance requirement once complete. The primary electrochemical treatments in use today are chloride extraction and realkalization. Both systems require a continuous reinforcing steel network.
Specific corrosion mitigation options considered for the 10th Avenue Bridge are described in the following sections and the body of the report. Each system provides a level of corrosion protection; however some may be better suited for this structure than others based on the final budgetary, service life, and other requirements. Please see summary table in Appendix B for estimated costs and considerations related to this project.
Investigation Findings The corrosion investigation findings indicate the predominant areas of substructure distress include: 1. Deck beams, piers, and spandrel columns exposed to chloride contamination from leaking expansion joints;
10th Avenue Bridge Rehabilitation iii SRF Consulting Group, Inc.
2. Delamination of the arch concrete due to corrosion of the structural steel angle truss and reinforcement embedded within the arches; 3. Spandrel columns are cracked adjacent to the arch connections. This allows chloride laden runoff direct access to the reinforcing steel and can cause severe localized corrosion.
Other key findings indicate that:
1. The reinforcing steel network is mostly discontinuous. This means that the individual reinforcing members are not in contact with each other, or that a layer of rust has developed between contact points. This finding means that reestablishing electrical continuity is a prerequisite to employing global galvanic, impressed current and electrochemical treatment options. Targeted and distributed galvanic solutions can be employed by reestablishing electrical continuity locally. The costs associated with re-establishing electrical continuity within each element are included in the cost matrix. 2. The reinforcement layers were reversed for the spandrel columns investigated. This means that vertical bars are on the exterior layer and are not confined by hoops or ties. This structural deficiency may require enlarging or adding reinforcement to the piers and spandrel columns requiring rehabilitation.
Bridge Deck One of the key areas of concern is preventing further chloride penetration from the bridge deck. Leaking expansion joints are the predominant source of deicing salt contamination to the substructure below and expansion joint distress is evident. It is recommended that: 1. Expansion joint replacement should include a continuous line of Galvanode DAS 0.25 lb/LF anodes along the construction joint on either side of the joint. 2. Deck cracks should be sealed with low viscosity epoxy or methyl methacrylate resin. 3. Sealing the deck with a breathable silane or siloxane to reduce the rate of chloride buildup in the concrete.
Spandrel Columns and Cap Beams under Expansion Joints Large areas of delaminated concrete were noted on the beams under expansion joints. Two options were considered for corrosion mitigation of these beams. 1. Total replacement with a barrier coating 2. Partial depth repairs with distributed galvanic anodes and a barrier coating These two options are essentially equivalent with respect to service life. If the level of reinforcing damage is relatively small, the recommended option should be based on bid pricing. If the level of reinforcing damage is significant, replacement is more appropriate. It is recommended that both scenarios be included in the bid package as alternates. The barrier coating should be a low viscosity penetrating epoxy primer with a pigmented aliphatic urethane top coat for UV resistance.
10th Avenue Bridge Rehabilitation iv SRF Consulting Group, Inc.
Galvanode DAS 0.25 lb/LF distributed galvanic anodes are recommendations for 1. Cap beam top repairs, 3 continuous rows 2. Cap beam soffit repairs, 2 continuous rows 3. Cap beam side repairs, 1 continuous row/side, or 7 for a beam replacement in lieu of coating. 4. Spandrel column encasement repairs, 5 continuous vertical rows per side. 5. Pier encasement repairs, 6 continuous vertical rows per side.
Other Spandrel Cap Beam Repairs Beam repairs other than the expansion joint deck beams should utilize partial-depth patch repairs with targeted galvanic anodes along the perimeter of the repair. The ratio of steel surface area to concrete surface for the beams varies from 0.38 on the cantilever portion to 0.58 between spandrel columns. Based on the observed conditions our data sheet lists a maximum corrosion control spacing of 20 inches on center. However, we recommend a 16-inch spacing to increase the service life and provide reasonable anode arrangement for the anticipated full-side repairs. Anode quantity estimates are based on one anode for every 1.25 square feet of spandrel cap beam repair. Part of the bid package should include pricing for sounding of each beam to identify the outline of each repair area at the time of construction while the access scaffolding is in place.
Other Pier and Spandrel Column Repairs Pier and spandrel column repairs other than the encasement type expansion joint repairs should utilize partial-depth patch repairs with targeted galvanic anodes along the perimeter of the repair. The ratio of steel surface area to concrete surface for the pier and spandrel columns was calculated to be approximately 0.26. Based on the observed conditions we recommend the maximum corrosion control spacing for Galvashield XP2 anodes should not exceed 20 inches on center. Anode quantity estimates are based on one anode for every 2 square feet of spandrel column repair.
As an alternate, chloride extraction of spandrel columns that only have localized damage can re-establish a passive condition to the entire element. Coating after treatment is recommended. Part of the bid package should include pricing for sounding of each spandrel column to identify the outline of each repair area at the time of construction while the access scaffolding is in place.
Arch Repairs Arch repairs are primarily corner repairs due to corrosion of the embedded structural steel truss angle. The plans indicate the angles are 3.5 x 3.5 x 3/8 inch. This angle has a 14 inch perimeter, which calculates to be 1.16 SF/LF. Corrosion of the flange develops pack rust and breaks the concrete corner off. Removal of the damaged concrete followed by abrasive blast
10th Avenue Bridge Rehabilitation v SRF Consulting Group, Inc.
cleaning and direct connection of a continuous line of Galvanode DAS anodes will prevent recurrence of corrosion activity on the corner. We recommend using the 0.6 lb/LF DAS anode to protect the arch spans, because the steel surface area of the structural steel is large. If 0.25 lb/LF anodes are selected the anode life is estimated at 13 to 18 years, but the service life using the larger 0.6 lb/LF anode is estimated at 25 to 30 years. The incremental cost of the larger anode is trivial compared to the cost of access and repair so we recommend using the larger 0.6 lb/LF anodes for Arch repairs. Arch top and bottom repairs should follow a similar guideline as the corners. The arch trusses are spaced approximately 31 inches apart and are comprised of back to back 3.5 inch angles. The delamination patterns follow this spacing, so corrosion at the tips of the arch truss angles is assumed to be the primary cause for distress. Anode quantity estimates are based on one lineal foot of anode for every lineal foot of arch corner, and one lineal foot of anode per truss angle in top and bottom repairs. Anodes can be grouted in slots in sound areas. An alternate global protection option is to conduct chloride extraction of the arch after repairs are completed without anodes, followed by a penetrating coating.
Arch to Spandrel Column Joint Repair Arch to column joint repair recommendations are preventative in nature. Structural analysis indicates that cracks naturally form between the arch and the spandrel column due to thermal movements. Many spandrel columns have horizontal cracks located just above the arch. These cracks should be replaced with defined joints or by routing and sealing the existing cracks. These cracks provide a direct path for deicing salt to reach the reinforcing steel. This condition can cause severe localized corrosion. Vector recommends that the bid package should address corrosion protection of this hinged joint using drilled-in Galvashield CC 100 galvanic anodes located above and below the joint. The anodes would be attached to every other dowel or 14 anodes per spandrel column. Creating a horizontal slot around the spandrel column to reestablish electrical continuity between all the verticals should be included in the repair plan.
Activated Arc Sprayed Zinc Option One corrosion mitigation option that was considered for this structure is Activated Arc Sprayed Zinc Metalizing. This is a coating of zinc metal sprayed onto the concrete surface similar to galvanizing of steel. This zinc layer acts as the anode for the system and is attached to the reinforcing steel at regular intervals using a zinc mesh that is clamped to the sprayed surface using drilled and tapped or welded studs. In this option all repairs are made without embedded anodes and electrical continuity of the structure has to be reestablished. Once the repairs are complete and threaded studs are in place, the surface is abrasive blasted and metallizing begins. This surface anode cannot be applied to coated elements so removal of coatings is necessary. In addition, once metallized the surface applied anode should only be coated with breathable
10th Avenue Bridge Rehabilitation vi SRF Consulting Group, Inc.
sealers, so the overall appearance is grey. This option has a long track record of successful implementation and is a very effective global corrosion control system, but was not selected because the installation cost to coat the entire substructure is high.
Electrochemical Chloride Extraction Option Chloride extraction was considered for this structure, but was not selected as a primary corrosion mitigation procedure due to budgetary constraints and the extent of damage observed. Chloride extraction is a process that reduces chloride contamination levels in sound concrete cover. This process reduces chloride levels and reestablishes an alkaline environment around the reinforcing steel, halting corrosion. This process requires electrical continuity of the reinforcing steel to be effective. Chloride extraction may still be a viable option for the arches, selected piers, and spandrel columns that are contaminated with chloride but are not damaged to the point where refacing or encasement is required.
10th Avenue Bridge Rehabilitation vii SRF Consulting Group, Inc.
Table of Contents
Executive Summary ...... ii
Introduction ...... 1 Purpose ...... 1
Corrosion Mitigation Strategies ...... 1 Chip and Patch Repairs ...... 1 Discrete Sacrificial Anodes ...... 3 Distributed Galvanic Anodes ...... 4 Surface Applied Galvanic Protection Systems ...... 6 ...... 6 ...... 6 Electrochemical Chloride Extraction (ECE) ...... 8 Impressed Current Cathodic Protection (ICCP) ...... 10 ...... 10
Appendix A: Corrosion Mitigation Options Descriptions
Appendix B: Corrosion Mitigation Summary Table
Appendix C: Product Data
10th Avenue Bridge Rehabilitation viii SRF Consulting Group, Inc. DRAFT Corrosion Mitigation Options
Introduction
Purpose The intent of the 10th Ave Bridge Rehabilitation Project is to provide the owner with a long term repair solution. Corrosion mitigation systems provide a longer service life to the structure when used in conjunction with conventional repair methods.
Corrosion Mitigation Strategies
The following sections describe the corrosion mitigation options considered for use on the 10th Avenue Bridge.
Chip and Patch Repairs The first option for repair could be identified as addressing the immediate needs of the structure. These repairs would involve the removal of delaminated and spalled concrete and replacing it with new concrete or mortar. Typical industry guidelines for repair include the International Concrete Repair Institute (ICRI) Technical Guideline No. 310.1R–2008 Guide for Surface Preparation for the Repair of Deteriorated Concrete Resulting from Reinforcing stSteel Corrosion. This Industry 1 - XP Type anodes in a partial depth patch repair document provides excellent guidance to achieve quality repairs. Patch repairs are the least expensive repair option based on initial cost. By following ICRI procedures such as removal of damaged concrete outside the areas of active corrosion, creating saw cut edges and square or rectangular patch areas, and cleaning the reinforcing steel of any residual chloride contaminated cement and oxidation, the active corrosion sites in the repair area will be addressed. The guidance in this document along with the recommendations of a qualified structural engineer is the first step in providing quality repairs.
10th Avenue Bridge Rehabilitation 1 SRF Consulting Group, Inc. DRAFT Corrosion Mitigation Options
While a quality repair will provide great benefit, the prior investigations conducted on the structure indicate that previous repairs have failed, and that chloride contaminated concrete and active corrosion exists in sound concrete areas. Therefore, the repair process will create incompatibilities between the new concrete patch and surrounding chloride contaminated concrete. Experience shows this condition creates new or accelerated (halo) corrosion cells adjacent to the patch. Patching is necessary for this structure. The challenge facing the SRF team is to make those repairs last longer. Typically the longest repair service life you can expect from chip and patch repairs is about 10 years. Adding galvanic corrosion mitigation can more than double the service life. Advantages of this system include:
The lowest initial cost solution Removes damaged concrete and reinforcing ICRI and ACI standards available Maintenance free
Disadvantages of this system include:
Relatively short service life of 5-10 years Potential for accelerated corrosion in adjacent areas
10th Avenue Bridge Rehabilitation 2 SRF Consulting Group, Inc. DRAFT Corrosion Mitigation Options
Discrete Sacrificial Anodes Discrete Sacrificial Anodes may be included in any patch repair performed in the chip and patch solution. The anodes work by providing localized galvanic protection to the area directly surrounding the patch. They may not provide a complete solution, but will address corrosion problems in localized areas and reduce
problems with incompatibilities due to patching. 2: Sacrificial anodes in sound concrete. There is no external power required, making them quick and simple to install. They reduce the rate of corrosion in surrounding areas until they are consumed, lasting anywhere from 10 to 20 years depending on the number of anodes installed and level of corrosion activity. Discrete sacrificial anodes can also be proactively installed in targeted areas where there are no concrete repair is 3: XP-Type Anodes in girder repair. required, but where chloride contamination or corrosion potentials indicate the potential for future corrosion damage.
Advantages of this system include:
The simplest and least labor intensive solution Provides corrosion protection in chloride contaminated concrete Anodes are installed into the patches, or cored holes Galvanic systems self-regulate with changes in moisture and temperature No conduit or wires to disrupt aesthetics Galvanic anode performance can be monitored Maintenance free
Disadvantages of this system include:
Sacrificial anodes have a defined life
10th Avenue Bridge Rehabilitation 3 SRF Consulting Group, Inc. DRAFT Corrosion Mitigation Options
Provides the lowest level of corrosion protection Corrosion protection limited to immediate area (~12-in. radius around anode) Reinforcing must be electrically continuous for system to be effective Does not prevent corrosion damage in other locations.
Distributed Galvanic Anodes
Galvashield N
Galvanode DAS Marine Anodes
4: Left: DAS Anodes in abutment repair. Right: N Type Anodes in new construction Distributed Protection with discrete Galvanic Anodes such as the Galvashiel N, Galvashield XP types, or Galvanode DAS anodes are designed to provide corrosion control or cathodic protection to concrete decks, columns, beams and walls which are being topped or overbuilt. Galvanode DAS galvanic anode system is distributed over concrete and masonry structures to provide global corrosion protection. The quantity of zinc provided, the anode shape, electrical components and installation procedures can be customized to meet 5: DAS Anodes bridge deck application. specific project requirements. Individual Galvanode DAS anode components are typically square, rectangular or circular in cross section and can be supplied in lengths of up to 7.5 ft (2.3 m). The system is quickly and easily installed to provide corrosion protection for a variety of applications. The system can be encased in new concrete, embedded in concrete overlays, grouted in slots, and applied along areas
where new concrete meets existing contaminated 6: DAS Anodes along new to old concrete interface. concrete.
10th Avenue Bridge Rehabilitation 4 SRF Consulting Group, Inc. DRAFT Corrosion Mitigation Options
Galvanode DAS Distributed Anodes are connected to the reinforcing steel and the concrete replaced as normal. This system can provide excellent protection throughout the high corrosion areas with the most significant delaminations, such as the tops of arches. A high level of long-term corrosion control can be provided based on anode spacing, typically between 10 to 25 years or longer.
Advantages of this system include: Provides high level of corrosion protection to large areas Anodes installed into overlays, encasement, large patches, grouted into slots, and along new and old concrete interface can protect entire elements Galvanic systems self-regulate with changes in moisture and temperature No conduit or wires to disrupt aesthetics Galvanic anode performance can be monitored Maintenance free
Disadvantages of this system include: Sacrificial anodes have a defined life Reinforcing must be electrically continuous for system to be effective The system is not adjustable - requires design
10th Avenue Bridge Rehabilitation 5 SRF Consulting Group, Inc. DRAFT Corrosion Mitigation Options
Surface Applied Galvanic Protection Systems
7: Arc Sprayed Zinc Historic Arch Bridge - Gold Beach, OR
Surface-Applied Galvanic Protection Systems such as activated arc sprayed anode can be applied onto the surface of the concrete and electrically connected to the reinforcing steel. With the activated arc sprayed zinc system, the zinc anode is metalized onto the prepared concrete surface at a thickness appropriate for the service life objectives and activated with a chemical humectant. This galvanic protection system protects the reinforcing steel in both the repaired and unrepaired areas as it provides global protection to the entire structure. This type of system requires replacement in approximately 15 to 20 year intervals depending on the coating thickness and how fast the anode is consumed. The appearance of the structure would be a dull grey and become lighter overtime as the zinc corrodes to protect the steel.
With this option, entire elements like arches, beams, columns, etc are protected and the service life of the structure can be extended for 15-20+ years. Then, because it is surface applied it can be re-applied for future service life extension. While it slightly alters the color of the concrete, it conforms to the shape of the 8: ASZ Application structural elements. Because the form or shapes of the
10th Avenue Bridge Rehabilitation 6 SRF Consulting Group, Inc. DRAFT Corrosion Mitigation Options
structure including any architectural details are preserved, the overall appearance is maintained. As a result, this galvanic system has been found acceptable for use on historic bridges.
Advantages of this system include:
Higher levels of galvanic current and protection are achieved with arc sprayed zinc and surface applied activator Galvanic systems self-regulate with changes in moisture and temperature Provides protection to a broader area than discrete anodes Provides global corrosion protection for the entire structure System conforms easily to structures with complex geometry No electrical conduit, wire, or rectifier equipment is required. System can either be shorted (galvanic) or non-shorted (impressed current) System performance can be monitored Maintenance free except for potential humectant application every 5 years or so System can be reinstalled non-invasively after its service life.
Disadvantages of this system include:
A containment system is required for control of zinc dust produced during the application process Requires concrete repairs to be completed prior to installation. Larger initial cost compared to discrete anodes installed in repairs Reinforcing must be electrically continuous for system to be effective The shorted system is not adjustable Coating options are limited
10th Avenue Bridge Rehabilitation 7 SRF Consulting Group, Inc. DRAFT Corrosion Mitigation Options
Electrochemical Chloride Extraction (ECE)
9: ECE Historic Arch Bridge Application - Idaho 10: ECE Steel Anode Mesh and Electrolyte Installation
Electrochemical Chloride Extraction (ECE) is similar to cathodic protection in that it also applies a charge to the reinforcing steel. ECE is a temporary treatment that is designed to move chloride ions away from the rebar within the concrete matrix and elevate the levels of hydroxyl ions (OH-) on the rebar surface. One of the greatest advantages of ECE is the rebuilding of the hydroxyl ions around the reinforcing steel. This creates a high pH layer and a passive oxide film similar to what forms when fresh concrete and steel come together in the original construction phase. ECE in conjunction with the chip and patch repairs will restore the concrete to like new conditions and extend the lifetime of the structure by 20 to 30+ years if recontamination is prevented through improved drainage and/or a coating. Because ECE is a temporary installation, it has no long-term maintenance or monitoring costs. ECE is most effectively used in combination with a barrier coating or sealer after the process is complete in order to prevent contaminating the concrete with chloride ions. This option in combination with patch repair of damaged areas before the treatment is the most complete repair option to solve all corrosion related issues existing in conventionally reinforced elements. This is an appropriate option for use on historic structures that require the longest possible service life, with minimal future maintenance.
10th Avenue Bridge Rehabilitation 8 SRF Consulting Group, Inc. DRAFT Corrosion Mitigation Options
11: ECE Application on Pier Caps of Washington Ave Bridge - Minneapolis, MN
Advantages of this system include:
Only system that is able to remove the source of the problem - chloride contaminated concrete Increases the local pH at the reinforcing steel (passivating layer) Temporary installation with no long term maintenance or monitoring costs Most complete solution to the corrosion issues Does not alter the structure’s existing appearance
Disadvantages of this system include:
Treatments lasts approximately 8 weeks in addition to the install/remove process Does not repair corroded steel. Requires concrete repairs to be completed prior to installation Reduced success rate on vertical surfaces or structures with complex geometry Full access required to each treated zone for entire duration of installation and monitoring of the system Water and power required 24hrs a day for length of the treatment High current density during treatment may lead to hydrogen embrittlement in prestressed reinforcing steel
10th Avenue Bridge Rehabilitation 9 SRF Consulting Group, Inc. DRAFT Corrosion Mitigation Options
Impressed Current Cathodic Protection (ICCP)
3: Impressed Current Connections for ASZ System 2: Ribbon ICCP Anode Embedded in Concrete Slot
Impressed Current Cathodic Protection (ICCP) is a permanent system applied to concrete to halt corrosion. It does so by applying a charge to the reinforcing steel to overcome its natural tendency to corrode in its current environment. This is achieved by grouting an anode ribbon in a slot, embedding anodes in drilled holes, or applying a conductive overlay or coating over the existing concrete surface and electrically connecting the overlay to the corroding reinforcement after patch repairs are complete. ICCP systems provide global protection and can effectively stop on-going corrosion. ICCP requires a permanent power supply and continual monitoring. Systems may be monitored through on-site visits or remote monitoring systems via the internet. A high level of control and protection can be achieved, however if the system is not monitored and maintained the protection may stop suddenly. Due to their complexity, ICCP systems typically have higher initial and maintenance costs but can provide the highest level of overall corrosion protection for the life of the installation or structure. ICCP systems can last anywhere from 25 to 40+ years depending on the materials used, the environment, and level of operation maintenance.
Although the initial installation costs are typically higher, the long-term effectiveness can more than offset the initial cost. It should be noted that impressed current systems are generally associated with higher operating potentials than sacrificial
10th Avenue Bridge Rehabilitation 10 SRF Consulting Group, Inc. DRAFT Corrosion Mitigation Options
systems. These electrical equipment and variable operating potentials can provide the structure owners with a level of control that is not possible with a galvanic system.
Advantages of this system include:
Higher levels of current output and protection Provides corrosion protection in chloride contaminated concrete System is adjusted to meet the needs for protection Localized or global corrosion protection High concrete resistivity can be overcome with higher current output Regular system monitoring
Disadvantages of this system include:
Requires more substantial system design Does not remove chloride from the concrete Requires full time access to AC Power Requires concrete repairs to be completed prior to installation Long term monitoring and maintenance required Exposed conduit and electrical boxes can impact aesthetics
10th Avenue Bridge Rehabilitation 11 SRF Consulting Group, Inc. Appendix A
Appendix A: Corrosion Mitigation Summary Table
10th Avenue Bridge Rehabilitation 1 SRF Consulting Group, Inc. Appendix B
Appendix B: Product Data
10th Avenue Bridge Rehabilitation 1 SRF Consulting Group, Inc. 10th Ave. Bridge ‐ Corrosion Mitigation Estimate Summary VECTOR'S Estimated Level of Corrosion Protection Estimated System Installation and Control Option # Description Application Recomendation Notes Quantity Unit Unit Price Estimate Estimate Estimated Installation Time/Staging Estimated Service Life (0=None, 5=Best) 1. System Representative Area monitored Entire Structure Shows representative areas of system Installled durring system installation. Monitoring for GALVANIC systems performance for Embedded and Surface May require site visit by a Corrosion (Embeded, Distributed, Arc Spray Applied Anodes. System may be monitored Specialist durring installation and also 5 EA $5000 ‐ $9000 $25,000 ‐ $45,000 Life of the System N/A Zinc) remotely. Estimate one station per structural upon system completion for element: Beam, Column, Pier, Arch, and Deck. commisioning.
2. Continuity Basic Continuity Check Entire Substructure Required prior to installation of any corrosion Conducted prior to or durring system protection system. Each member receiving a installation. Most of the continuity can Included In System corrosion protection system must be checked. As Required ‐ N/A be easily checked and repaired when Life of the System N/A Estimates the steel is exposed durring the repair phase. Establish Continuity Entire Substructure Required prior to installation of any corrosion Conducted prior to or durring system protection system. Weld or tie a king bar/wire installation. Most of the continuity can to reinforcing cage. Typically conducted in the Included In System be easily checked and repaired when As Required ‐ N/A Life of the System N/A repair. May require saw‐cutting/chipping of Estimates the steel is exposed durring the repair continuity groove in sound concrete. phase.
3. Targeted Galvanic Discrete Embedded in Repairs Patches Throuought Entire Lowest level of corrosion protection. Future Embedded anodes are installed durring Protection with (Galvashiled XP2 ‐type) Structure repairs likely required in non‐treated/repaired 80,400 SF $7 ‐ $13 $563K ‐ $1M the concrete repair process. 10‐20 Years 2 Discreet Embedded areas. Anodes Discreet Embedded in Sound Spandrel Column to Arch Discreet anodes drilled into sound concrete at Embedded anodes are installed durring Concrete (Galvashield CC‐type) Rib Joints targeted joints below expansion joints. Future Each the concrete repair process. 38 $500 ‐ $700 $19K ‐ $27K 10‐25 Years 3 repairs likely required in non‐treated/repaired Column areas.
4. Distributed Galvanode DAS in Arch Rib Arch Ribs Provides distributed protection for high risk LF of Arch Embedded anodes are installed durring Galvanic Protection corner repairs members. TBD Corner $115 ‐ $165 TBD the concrete repair process. 10‐25 Years 3 with Embedded Repair Anodes Galvanode DAS in full cap beam Exp. Joint Cap Beams Provides distributed protection for high risk Embedded anodes are installed durring replacement members. 22 Each Beam $10.5K ‐ $11.5K $231K ‐ $253K the concrete repair process. 10‐25 Years 3
Galvanode DAS in full Pier Provides distributed protection for high risk Embedded anodes are installed durring LF of Pier face/corner pier repairs members. TBD $150 ‐ $800 TBD the concrete repair process. 10‐25 Years 3 Repair Galvanode DAS in Spandrel Spandrel Columns Provides distributed protection for high risk LF of Embedded anodes are installed durring Column Repair members. TBD Column $250 ‐ $300 TBD the concrete repair process. 10‐25 Years 3 Repair Galvanode DAS Type Anodes Deck @ Expansion Joint ‐ This is reccomended in conjuction with all other Embedded anodes are installed durring New to Old Concrete options. Best option for repaired expansion 5,250 LF $25 ‐ $30 $131K ‐ $156K the concrete repair process. 10‐25 Years 4 Interface joints.
5. Surface Applied Shorted (Galvanic) ASZ System Entire Substructure Good global protection for the entire structure. All concrete repairs must be completed Protection (Arc Spray Provides good protection for both repaired and substantially cured prior to system Zinc) areas and chloride contaminated sound installation. Installation at a rate of 700 300,000 SF $25 ‐ $30 $7.5M ‐ $9M 15‐20+ years concrete. ‐ 1,500+ SF per day depending on 4 access and crew size.
Shorted (Galvanic) ASZ System Cap Beams Good protection for high risk members. Other system such as embedded anoded required to 116,000 SF $30 ‐ $35 $3.5M ‐ $4.1M " "15‐20+ years 3.5 protect remainder of structure Shorted (Galvanic) ASZ System Spandrel Columns Good protection for high risk members. Other system such as embedded anoded required to 63,000 SF $30 ‐ $35 $1.9M ‐ $2.2M " "15‐20+ years 3.5 protect remainder of structure Shorted (Galvanic) ASZ System Arch Rib Good protection for high risk members. Other system such as embedded anoded required to 82,000 SF $30 ‐ $35 $2.5M ‐ $2.9M " "15‐20+ years 3.5 protect remainder of structure Shorted (Galvanic) ASZ System Piers Good protection for high risk members. Other system such as embedded anoded required to 38,000 SF $30 ‐ $35 $1.1M ‐ $1.3M " "15‐20+ years 3.5 protect remainder of structure Non‐Shorted (Impressed Entire Substructure Allows adjustment to be made to the cathodic Similar to shorted system with added Current) ASZ System protection current. Adjustments can be made time for conduit, wire, and rectifier automatically or manually. Requires power 300,000 SF $35 ‐ $45 $10.5M ‐ $13.5M installation. System short detection 15‐20+ years 4.5 source and regular monitoring/maintenance. and remediation also necessary.
6. Electrochemical Full Structure Treatment Entire Substructure Provides chloride reduction and reinforcing All concrete repairs must be completed Chloride Extraction steel passivizing for the entire structure. and substantially cured prior to system (ECE) installation. System installation time of 300,000 SF $35 ‐ $40 $10.5M ‐ $12M 300‐1,200 SF per day, plus up to 60 25+ Years 5 days of run time. Installed and run in zones of approximately 1,000 SF.
Target Area Cap Beams Good for high risk chloride contaminated members. Other system such as embedded 116,000 SF $40 ‐ $45 $4.6M ‐ $5.2M " " 25+ Years 4 anoded required to protect remainder of structure Target Area Arch Rib Good for high risk chloride contaminated members. Other system such as embedded 82,000 SF $40 ‐ $50 $3.3M ‐ $4.1M " " 25+ Years 4 anoded required to protect remainder of structure Target Area Spandrel Columns Good for high risk chloride contaminated members. Other system such as embedded 63,000 SF $40 ‐ $50 $2.5M ‐ $3.2M " " 25+ Years 4 anoded required to protect remainder of structure Target Area Bridge Deck/Exp. Joints Alternate option for treating repaired expansion All concrete repairs must be completed joints and passivating the steel in the deck. and substantially cured prior to system Alternate to Distributed DAS Type anodes in installation. Deck installation of ECE is expansion joint repairs. Requires lane closure 81,000 SF $20 ‐ $30 $1.6M ‐ $2.4M typically much faster than the 25+ Years 5 for the duration of the treatment. substructure (5,000+ SF per day).
NOTES: Estimated costs do not include safe access or environmental containment Square footage is estimated based on the 2008 report and 1970's estimate for the surface coating 2013 Inspection Update ‐ 10th Avenue Bridge December 16, 2013 Minneapolis, Minnesota
Appendix D – Field Testing
Braun Intertec Corporation Phone: 952.995.2000 11001 Hampshire Avenue S Fax: 952.995.2020 Minneapolis, MN 55438 Web: braunintertec.com
November 29, 2013 Project BL-13-03269
Mr. Larry Erickson SRF Consulting Group Inc. One Carlson Parkway North, Suite 150 Minneapolis, MN 55447
Re: Summary of Test Results 10th Avenue Bridge Minneapolis, Minnesota
Dear Mr. Erikson:
This report is provided to summarize the test results of cores extracted from the 10th Avenue Bridge in Minneapolis, Minnesota.
Purpose
The purpose of this project is to provide information concerning the current condition of the concrete on the 10th Avenue Bridge and review the results from Braun Intertec’s report dated January 27, 2009.
Background
In 2008, SRF Consulting Group Inc. retained Braun Intertec to conduct field testing and conduct laboratory analysis of the concrete. The testing conducted included compressive strengths, modulus of elasticity, chloride ion content, petrographic observations, corrosion potential and ground penetrating radar. It is our understanding the results of the testing was used to layout a repair process for the bridge. The information from the current study will be used to assess if significant changes have occurred to the chloride ion contents, determination of the electrical resistivity as well as observe the coating and freeze thaw damage in specified areas.
Core Samples
The following table provides the cores which were extracted from the bridge and their locations.
Table 1. Core Locations Core Location 31 From Barrier wall, span 5 between columns P and Q 32 From Arch, Bass of Arch of as it connects to pier 3 in span 2 33 From Pier 2, 6 feet above grade on the upstream side 30A Pier 5 between water line and drain. “Good” area of concrete 30B Pier 5 between water line and drain. “Bad” area of concrete
AA/EOE Providing engineering and environmental solutions since 1957 SRF Consulting Group Inc. Project BL-13-03269 November 29, 2013 Page 2
Core Location 15A From Arch Span 5 between P and Q, upstream side 29A From Span 6, Beam C, Downstream side 20A Span 2, Beam A, Downstream side – this core was too short 20B Span 2, Beam A, Downstream side
Chloride Ion Contents
Chloride Ion Contents were measured in accordance with ASTM C1218, "Standard Test Method for Water-Soluble Chloride in Mortar and Concrete." Results are presented in Table 2 alongside results documented in our 2009 report for the same location.
Table 2. Water Soluble Chloride Contents Core 29 (2008 Chlorides % Core 29A (2013 Chlorides % Horizon (Depth in inches) by mass of concrete) by mass of concrete)
0 to 3/4 0.372 0.435
3/4 to 1-1/2 0.099 0.351
1-1/2 to 2 0.021 0.241
2 to 2-3/4 0.003 0.140
Electrical Resistivity
Several cores were tested for electrical resistivity. The cores were conditioned to be vacuum saturated using the same procedure for conditioning in ASTM C1202, "Standard Test Method for Electrical Indication of Concrete's Ability to Resist Chloride Ion Penetration." The samples were then tested for electrical resistivity using a Giatec RCONTM resistivity meter. Results are presented in Table 3.
Table 3. Electrical Resistivity Results Core (Location) Resistivity (KOhm-cm)
15A (From arch span 5 between P and Q, upstream side) 5.4
29A (From span 6, Beam C, Downstream side) 6.9
20B Span 2, Beam A, Downstream side) 9.8
30A (Pier 5 between water line and drain. “Good” area of concrete) 10.8
30B (Pier 5 between water line and drain. “Bad” area of concrete) 13.0
Sample: 31 PPhotograph 1 Project: BL-13-03269 Description: Profile of Sample. Outer surface is to the left.
Sample: 31 PPhotograph 2 Project: BL-13-03269 Description: Cut surface. Note the coating on outer surface of core approximately 0.0029 inches thick.
Sample: 32 PPhotograph 3 Project: BL-13-03269 Description: Outer surface of Sample.
Sample: 32 PPhotograph 4 Project: BL-13-03269 Description: Cut surface. Note coat on the surface approximately 0.0303 inches thick.
Sample: 33 PPhotograph 5 Project: BL-13-03269 Description: Outer surface of core.
Sample: 33 PPhotograph 6 Project: BL-13-03269 Description: Cut face of core. Note coating on the surface approximately 0.0091 inches think.
Sample: 30A PPhotograph 7 Project: BL-13-03269 Description: Note core was miss-labeled in the field. Outer surface of core is to the left.
Sample: 30B PPhotograph 8 Project: BL-13-03269 Description: Note core was miss-labeled in the field. Outer surface of core is to the left.
Sample: 15A PPhotograph 9 Project: BL-13-03269 Description: Outer surface of concrete is to the left.
Sample: 29A PPhotograph 10 Project: BL-13-03269 Description: Sample was miss-labeled in the field. Outer edge of concrete is to the left and contains a coating approximately 0.0277 inches think.
Sample: 20A PPhotograph 11 Project: BL-13-03269 Description: Outer surface of concrete is to the left
Sample: 20A PPhotograph 12 Project: BL-13-03269 Description: Outer surface of core. The surface of the core contains a coating approximately 0.0084 inches think.
Sample: 20B PPhotograph 13 Project: BL-13-03269 Description: Profile of core, outer surface is to the left.
Sample: 20B PPhotograph 14 Project: BL-13-03269 Description: Outer surface of core containing a coating approximately 0.0080 inches think.