ICRI 2011 Project Award Winner
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Award of Merit: Transportation Category

Lester River Bridge Repairs and Corrosion Mitigation
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Duluth, Minnesota

Submitted by Vector Corrosion Technologies, Inc.

Lester River Bridge

Minnesota Department of Transportation
St. Paul, Minnesota

Project Engineer/

Minnesota Department of Transportation
St. Paul, Minnesota

Repair Contractor
PCI Roads
St. Michael, Minnesota

Material Supplier/

Vector Corrosion Technologies, Inc.
Tampa, Florida

Built in 1925, the Lester River Bridge (Minnesota Bridge No. 5772) is a single-span, ribbed reinforced concrete arch bridge that carries T.H. 61 over the Lester River in Duluth, MN, adjacent to Lake Superior. As an excellent example of a small indigenous stone highway bridge designed to blend with its natural surroundings, the bridge is listed in the National Register of Historic Places and has been selected as one of 24 Minnesota bridges to receive a higher level of maintenance and preservation due to its historical significance.

After years of exposure to deicing chemicals, the reinforcing steel was corroding and beginning to affect the integrity of the structure. The repair work included concrete patching, replacement of the waterproofing system on the top of the concrete arch slab and the lower portion of the fascia and tie walls of the concrete arch, construction of a new reinforced concrete roadway slab with a low-slump concrete wearing course, construction of new concrete end posts and light base pylons, and rehabilitation of the reinforced concrete arches. All repairs were completed to replicate the original historic appearance of the bridge.

Rehabilitation to ensure long service life considered various corrosion mitigation options, but ultimately a galvanic corrosion system was implemented to protect the arch slab and ribs, as well as repairs to the exterior walls of the bridge. Discrete embedded galvanic anodes were used around the perimeter of concrete patches on the interior arch ribs to provide localized protection against patch-accelerated corrosion, the exterior arch ribs used drilled-in galvanic anodes to protect the masonry veneer anchors, and embedded activated galvanic anode strips were distributed across the top of the arch to provide distributed protection to the buried reinforced concrete arch slab.

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