Track 4: This New World: Preservation technology and emerging issues within our historic buildings and built landscapes

General Abstract

3 - Lessons in Cathodic Protection Technology from Soldier Field and the Franklin Avenue Bridge

Tuesday, September 25
10:30 AM - 12:00 PM
Location: BNCC-106BC

Cathodic protection is one of several technologies used to prolong the life of historic concrete structures that are prone to damage from corrosion of embedded reinforcing steel. The author (Johnson) previously published a comprehensive study of corrosion mitigation systems for the historic concrete of Soldier Field, constructed 1922–1926 in Chicago, Illinois (“Soldier Field Stadium: Corrosion Mitigation for Historic Concrete,” APT Bulletin: Journal of Preservation Technology 35: 2–3, 2004). Field trials and testing of the following systems were included in that study: corrosion inhibitors (spray applied and admixed in patches); realkalization (a treatment to mitigate carbonation); and passive cathodic protection using embedded zinc anodes, arc-sprayed zinc and adhered zinc sheets. Although cathodic protection was not implemented across the structure due to the owner’s budgetary limitations, the trial installations were left in place. The studies at Soldier Field were widely recognized, including a reference in National Park Service Preservation Brief 15: Preservation of Historic Concrete (Gaudette and Slaton, 2007).

Annually since that time, the historic concrete surfaces at Soldier Field have been inspected close-up and documented for distress. In 2016, the authors performed follow-up testing to examine how the corrosion mitigation trials were performing 15 years after their installation. Testing revealed that the discrete zinc anodes embedded in the colonnade concrete had afforded little if any long-term protection to the concrete, even though testing in 2001 showed good initial performance. Based on analysis of material samples and consultation with the system manufacturer (Vector Corrosion Technologies), the poor long-term performance was attributed to the following factors that were not known or fully understood at the time: resistivity of the anode embedding mortar; resistivity, density and permeability of the native concrete; and proximity of the anodes to the long-term moisture source, chloride-contaminated concrete, and reinforcing steel.

Recently, the authors designed a cathodic protection system as part of a major rehabilitation of the historic Franklin Avenue Bridge, constructed 1919–1923 over the Mississippi River in Minneapolis, Minnesota. The cathodic protection design, which involves continuous zinc anodes placed along the arch rib corners, illustrates proper consideration of the design factors that hindered the long-term performance of the galvanic anodes at Soldier Field. Rehabilitation of the Franklin Avenue Bridge was recently completed, and ongoing continuous monitoring at permanently embedded test stations has shown excellent performance of the cathodic protection system since it was installed three years ago.

This presentation will summarize the details and performance of these two examples of cathodic protection technology used at historic concrete structures, and then use these examples to explain all of the design factors that must be considered in order to achieve long-term protection of concrete. These factors are particularly relevant to the successful use of this emerging technology at historic structures.

Learning Objectives:

Arne P. Johnson, PE, SE

Principal
Wiss, Janney, Elstner Associates, Inc.

Arne P. Johnson is a structural engineer and Principal with 29 years’ experience at Wiss, Janney, Elstner Associates in Northbrook, Illinois. His practice areas include structural evaluation, testing, and rehabilitation for structures of all types, including historic buildings, museums, stadiums, and bridges. Mr. Johnson received his BS in civil engineering from the University of Illinois at Urbana-Champaign and his MS in structural engineering from the University of California, Berkeley. He is a licensed professional engineer and structural engineer in multiple states. His 2004 paper on protection of historic concrete at Soldier Field received APT’s Oliver Torrey Fuller Award, Honorable Mention.

Presentation(s):

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John S. Lawler, PE, PhD

Associate Principal
Wiss, Janney, Elstner Associates, Inc.

[NOTE: Dr. Lawler will be a co-author but only Mr. Johnson will present at the conference.] John S. Lawler is an Associate Principal with WJE in Northbrook, Illinois. His practice areas include structural evaluation, corrosion, repair design, materials evaluation and research. He is a member of ACI Committees 222, Corrosion of Metals in Concrete, and 365, Service Life Prediction; PCI Technical Activity Council (TAC) and Concrete Materials Technology Committee; and CRSI Durability Committee (Chair). Dr. Lawler received his BS in engineering physics from Hope College, Holland, Michigan, and his MS and PhD in civil engineering from Northwestern University, Evanston, Illinois.

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Dan Worth

Mr. Worth is Principal and Historical Architect with BVH Architecture with offices in Lincoln and Omaha, NE. Dan has 40 years of experience with an emphasis in historic preservation, rehabilitation, urban design, master planning, programming and project management. He has extensive experience with managing public facilitation and community engagement process. Over the last 35 years, Dan has completed dozens of master plans and designed / implemented large complex historically significant projects with civic and institutional clients including the National Park Service, Smithsonian Institution, State of Nebraska, University of Nebraska and the Nebraska State College System. Dan has been a leader locally, regionally and nationally in community and non-profit professional organizations promoting the best practices for planning and preserving our communities.

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