American Association of State Highway and Transportation Officials

Special Committee on Research and Innovation

FY2023 NCHRP PROBLEM STATEMENT TEMPLATE

Problem Number: 2023-F-04

Problem Title

Durable and Compatible Repair of Historic Concrete Bridges

Background Information and Need For Research

Many bridges that have been determined eligible for the National Register of Historic Places possess concrete components in need of repair. Repairs commonly needed on historic bridges are related to cracks, spawls and larger fractures in concrete piers, beams, railings and decks, due to collisions, load stress, water and road salt infiltration, temperature contraction or expansion, or other types of weathering. To preserve bridges for transportation use and to extend their service life, transportation departments endeavor to make repairs that will last several years. Concrete repair technology continues to advance, resulting in materials and methods that provide more durable repairs, which have proven effective and have become preferred by state departments of transportation (DOTs).

Many historic bridges possess concrete components that are considered character defining or contribute to the integrity of materials and design. Frequently, in Section 106 of the National Historic Preservation Act reviews of repair projects on concrete bridge elements, the Secretary of the Interior’s (SOI) Standards for Concrete Repair are referenced as the preferred method for repair to minimize effects to the integrity of historic bridges. Briefly stated, concrete repairs meeting the SOI standards will be of similar material, texture, and color. The intent is to provide a repair as visually and texturally similar to the original concrete material as possible. Additionally, the SOI standards call for preservation treatments of exposed metal reinforcement, intending to limit corrosion and further deterioration.

While perhaps appropriate for concrete repairs on many historic buildings, the SOI standards may not be compatible with the otherwise preferable, more modern concrete repair methods. Buildings and bridges are subjected to material expansion and contraction factors due to changes in temperature and various types of weathering. However, concrete structural elements of a building are often under a more or less constant load or tension stress, whereas concrete bridge components are exposed to varying load and tension stress, increasing the importance of flexibility of the repaired concrete. Additionally, metal preservation products may impede the bonding of concrete repair material to the reinforcing metal and surrounding concrete, limiting the effectiveness and longevity of the repair. This results in a situation where the need to make the lasting repairs competes with the need to preserve the historic integrity of the bridge, which in turn requires DOT, FHWA, and SHPO staff time to investigate and negotiate a reasonable compromise. Reconciling the need for durable concrete repairs on historic bridges while making them compatible in appearance with adjacent historic materials will attend to both transportation and historic preservation goals. A comprehensive study of the issue and subsequent guidance would benefit all state DOTs who have an ever-increasing number of repair projects involving the concrete portions of their historic bridges. It would also be a beneficial resource for SHPOs, allowing them to more quickly provide Section 106 review and comment on relevant projects.

Literature Search Summary

No research projects were found in the Research in Progress Database meeting the search criteria Historic Concrete Bridge Repair or Historic Concrete Bridge Maintenance. There were numerous items related to concrete bridge repair and maintenance, however none addressed repair compatibility with the SOI Standards for Concrete Repair. The Transportation Research Integrated Database yielded results from the same search criteria but the results related to historic bridges featured repair discussions of specific bridges, including several in Europe, and included repair to concrete features but did not address comparisons with SOI standards for concrete repair. The search did locate an historic bridge repair handbook, Conservation of Bridges: A Guide to Good Practice (2002 Giford Partners, London) which provided a comprehensive guide to the conservation of older bridges, particularly in the United Kingdom. One paper, “Refurbish and Renovate” (Structural Engineer, 1996 Vol 64A Issue 2) reviewed classic examples of historic bridge refurbishment, considered difficulties arising from the refurbishment of the postwar concrete and steel bridges and identified needs for research and development on the assessment of deterioration and repairs.

Research Objective

The study should consist of three phases:

A. Survey of concrete repair methods utilized by state DOTs: $50,000

The survey of state DOT concrete bridge repair methods could begin by obtaining repair standards employed by each DOT for historic concrete repairs. While it may be possible to gather most state DOT repair standards from published resources, it will be important to contact as many DOTs as possible to discover if there are instances where there are deviations from those standards. Some states may have repairs they specifically apply to historic bridges, which should be a question posed to the DOTs, in a survey questionnaire. As some state DOTs have engaged in such specialized repair projects for historic bridges, gathering the methods used and noting where they differ from standard concrete repair practices will be important to detail, revealing the reasons. Geographic and climate related factors that affect the appropriateness of some repair techniques should be taken into consideration.

B. Comparison of concrete repair methods with Secretary of the Interior’s Standards: $100,000

Once the survey information regarding repair method is compiled, the practices can be assessed in terms of how they met the Secretary of the Interior’s Standards for Concrete Repair and their effectiveness, longevity and cost. This part of the research will require more intense scrutiny which may involve site visits to specific bridge locations. It will also require gathering input from SHPOs, the NPS, architectural historians and others familiar with historic bridge concrete repair and specific case studies to identify gaps between SOI Standards for Concrete Repair and specific repair techniques needed for concrete on historic bridges.

C. Historic Bridge Concrete Repair Recommendations: $100,000

From this above comparison, recommendations can be developed, again, taking geographic and climate conditions into consideration. The resulting report will present the results of the survey information with the specific examples of case studies and the recommendations for best practices for historic bridge concrete repair, with geographical considerations, if warranted. The report will be made available to state DOTs through the Transportation Research Board publications and available to the public via online downloadable PDF available through TRB. The results should be organized into a guide that can be readily incorporated into the bridge repair manuals for state DOTs and quickly put to use.

Urgency and Potential Benefits

Many state DOTs possess historic bridges with concrete components in need of repair, making the issue extremely common nationally. Historic bridges are subject to increasing transportation demands and continue to deteriorate. As DOTs make provisions to repair historic bridges, either due to historic preservation goals or simply because repair is more feasible than replacement, the method of repair will become increasingly of concern. Providing comprehensive assessment and guidance to this ubiquitous issue will allow state DOTs and their transportation partners to quickly adopt lasting repair techniques for historic bridge concrete components and save much time that would otherwise be spent researching and negotiating repair techniques on a per case basis. The time and costs spent researching and coming to an agreement with historic preservation interests is great, especially multiplied by the dramatically increasing number of repairs by the number of historic bridges in each state. State DOTs, SHPOs and historic preservation interests reaching consensus regarding concrete bridge assessment guidance and acceptable SOI-compliant repair techniques will reduce money and time spent in the Section 106 process.

Failure to address this quickly growing concern will result in costly delays to project development while the issue is addressed within the realm of Section 106 on a state by state, or more likely, a case-by-case basis. Many state DOTs and SHPOs do not possess the in-house expertise to assess the issue, compounding the time it would take to come to an agreement. As the recognition that repair is needed is often quickly followed with mobilization to make the repair, time needed for case-by-case analysis is frequently longer than what DOTs can accept. This could culminate in concrete repairs to historic bridges being carried out without a Section 106 nexus and to less favorable standards with decreases to historic integrity, both of which can be avoided with a comprehensive study and subsequent guidance.

Implementation Considerations

The resulting research recommendations will largely be used by state DOT and municipality maintenance and rehabilitation project staff and consultant contractors. State DOTs can determine which recommendations will be appropriate for their geographic locations and can adopt the recommendations into their maintenance and rehabilitation standards and specifications, when a historic bridge is concerned. Dissemination through the Transportation Research Board and AASHTO, through online publication and conferences would introduce the recommendations to all state DOTs for consideration. State DOTs may test the recommendations for applicability through their testing labs and facilities and adjust specific techniques accordingly. State DOTs may hold training workshops for relevant staff and consultants to convey specific methods and materials they determine most effective. This will also be useful to SHPOs by giving them a resource that specifically addresses repair of historic bridges with concrete components that will greatly aid them in carrying out their Section 106 review and commenting obligations more quickly, especially if they lack expertise in the subject.

Recommended Research Funding and Research Period

A. Survey of concrete repair methods utilized by state DOTs: $50,000; 6 months

B. Comparison of concrete repair methods with Secretary of the Interior’s Standards: $100,000; 12 months

C. Historic Bridge Concrete Repair Recommendations: $100,000; 14 months

Total Research Cost and Time: $250,000; 32 months

Problem Statement Author(s): For each author, provide their name, affiliation, email address and phone.

Carey Coxe, Louisiana Department of Transportation and Development, carey.coxe@la.gov, 225-242-4520

Kristina Thompson, Pennsylvania Department of Transportation, Krthompson@pa.gov, 610-871-4459

Robert Hadlow, Oregon Department of Transportation, Robert.W.HADLOW@odot.state.or.us, 503-731-8239

Potential Panel Members: For each panel member, provide their name, affiliation, email address and phone.

Person Submitting the Problem Statement: Name, Affiliation, Email Address And Phone.