Maintaining our nation’s bridges is important for the construction industry. The workers shown here are making structural repairs under a DOT contract.
Photo credit: Euclid Chemical
Deck maintenance often starts at joint locations where water and corrosion first start.
Photo credit: Minnesota Department of Transportation
Training and certification for contractors doing bridge repair work is sometimes conducted by the product manufacturers who provide the products used.
Photo credit: MAPEI
The American Society of Civil Engineers (ASCE) states the United States owns 607,380 bridges. But 11 percent of them — one out of every nine — are structurally deficient. Each day people in the largest 102 metropolitan city regions make 200 million trips over these bridges that are in serious need of repair. The ASCE predicts the deteriorating nature of our transportation infrastructure will reduce our Gross Domestic Product (GDP) perhaps as much as $897 billion by 2020. That said, we are making some headway. The average age of our nation’s bridges has decreased, from 43 years in 2009 to 42 years today. But there is still a long way to go. The Federal Highway Administration (FHWA) states that 30 percent of our bridges have exceeded their 50-year design life — bridges in metropolitan areas deteriorating faster than rural ones due to the increased amount of traffic.
To eliminate the backlog of “deficient bridges” (the total of structurally deficient and functionally obsolete bridges) by 2028 we would need to invest $20.5 billion per year. Currently, $12.8 billion is being spent from all fund sources. So the need to repair or replace bridges poses a huge problem at a time when governments are struggling financially.
How bridges are rated
Tom DeHaven, the executive vice president of operations for Figg Bridge Inspection, St. Paul, Minn., says the National Bridge Inspection Standard requires that bridges be inspected every two years — the result of federal legislation enacted in 1969. The teams that perform these inspections are trained and certified to do the work, but the team leader is always a structural engineer.
Local Departments of Transportation (DOTs) perform most of the inspections, but they often employ consulting engineering firms such as Figg to inspect bridges with specialized technical construction systems like segmental or cable stay. Contracts for these types of inspection services typically run for several years.
During the inspection process, engineers and inspectors look for signs of corrosion and rust, frozen bearings, scaled concrete, cracking, driving surface problems, and electrical problems. But repair priorities are set by DOTs based on fund allotments for doing repair work. So they might shift allocated funds to repaint a bridge to one requiring the repair of exposed, corroded reinforcing before that issue becomes critical.
Rehab verses preventative
If DOTs had all the money they wanted, most of it would go for new construction and preventative maintenance. However, in our real world, significant funding must go for rehab work to repair bridges rated as structurally deficient. Performing these structural repairs is challenging work for contractors as well as the specified products used in the repairs.
Nancy Daubenberger, state bridge engineer for the MnDOT Bridge Office, St. Paul, Minn., says her office currently spends 78 percent of its bridge construction budget each year for new bridge and replacement construction, 7 percent for rehab work on bridges, and 15 percent for preventative maintenance. When MnDOT builds a new bridge, it bases the type of construction on the need of the location, but its requirement now is a minimum 50-year service life. She adds MnDOT is beginning to require 100-year service lives for more important bridges — the I-35W bridge reconstruction replacing the one that collapsed in 2007 being an example. “But we know that doing preventative work yields an even longer life,” she adds.
Dave Juntunen, a Bridge Development Engineer with the Michigan DOT, Lansing, Mich., says his office’s strategy changed in 1998, the year it decided to fund more preventative maintenance. The office did so hoping the commitment would slow bridge deterioration rates and reduce the amount of funding needed for structurally deficient bridge work over time. He says in 1998, Michigan was judged to be near the bottom of all DOTs in terms of needed repair work, with over 20 percent of its bridges classified as structurally deficient. So the state DOT dedicated itself to sound asset management and decided to spend 18 to 20 percent of its budget each year on preventative maintenance. The strategy worked — currently 94 percent of Michigan bridges are rated in good or fair condition.
Selecting and specifying products for repair
Each DOT is confronted with different environmental conditions. In Florida chloride penetration is a big problem. Freeze-thaw issues and salt applications in northern states cause repair problems. And intense heat in the Southwest can influence product applications. Repair specifications are different throughout the country.
Every manufacturer of products used for bridge repairs wants to be on approved DOT lists. Roger Pratt, the business manager of the concrete repair division for MAPEI, says each DOT has its own product qualifications, so companies like MAPEI must conform to the regulations of each. Andrew Fulkerson, MAPEI’s technical services manager, says MAPEI sends each DOT the product test results related to its work. The company often sends actual products to DOTs so they can verify test results.
DOT specifications are usually generic, stating the type of material required. But they often list product names meeting their requirements for the application. Manufacturers work hard to be listed. The generic types of products used for bridge repairs include the following:
- Sealers and penetrants. These include Silane water repellents, corrosion inhibitors, sealers and coatings, and “healers” — low viscosity resins that fill and seal cracks.
- Grouts. Low shrinkage materials used to set anchor bolts, rebar, and plates.
- Repair cements. Prepackaged products for horizontal, overhead, or vertical applications and repairs.
- Corrosion inhibitors. Galvanic anode products attached to steel reinforcement to protect against corrosion.
- Carbon fiber reinforcement. Reinforcement material secured to the outside of concrete elements with resins to increase structural strength.
- Rebar. Epoxy coated and stainless steel reinforcement.
- Structural crack mending materials. Epoxy and other fluid resins which can be injected into cracks to effect structural repair.
- Joint sealants. Flexible products which prevent water intrusion even when there is structural movement.
- Fast setting concrete. Concrete which can be placed on decks and opened to traffic use within short spaces of time.
- Shotcrete. Either wet or dry concrete used in a shotcrete process to repair structures.
- Bonding agents. Polymers and resins that structurally bond repair materials to bridge concrete.
Both DOT and the manufacturers of products work to develop better bridge repair products, sometimes together. Mike McCloskey, a parking and restoration specialist for BASF, says his company constantly does research and development work for new products — bringing them to DOT with the hopes they will be included in specifications. And Fulkerson says sometimes BASF develops products for an individual DOT.
The process of selecting and specifying products, as well as new product development, is handled differently by DOTs. But Dale Mizer, construction products manager for Euclid Chemical, says DOTs influence each other, so getting approved in specifications by one DOT can lead to approval by others.
Daubenberger says MnDOT is constantly funding and participating in research to discover new products and technologies that work better, working in cooperation with universities and other agencies in research efforts.
Juntunen says the Michigan DOT is also experimenting with performance specifications; telling bidders how the installation should perform over time, giving contractors some latitude with regard to how work is performed but also increasing their responsibility.
Contractor requirements for this work
DeHaven says not all DOT work happens through public lettings. Sometimes a DOT has the expertise in house to install work, and sometimes small contracts are sent directly to contractors — especially those requiring fast repairs.
Each state decides how to select or certify contractors to do the work. It might be as easy as being the low bid for a project in some states. MnDOT is an example of one state that doesn’t typically specify contractor qualifications. There, projects are let on a low-bid basis, but they require payment and performance bonds as assurance a contractor can do the work. Michigan, on the other hand, requires contractors to be prequalified for the type of repair work they are installing. Each DOT defines its requirements. This might involve contractors being trained by the manufacturers of products being used and/or supported by product technical rep jobsite visits to assure installations are proper so product warranties can be honored.
DeHaven adds that once a DOT qualifies a contractor, that DOT typically sends the contractor project notifications or posts on the state websites.
Where repair work is headed
The amount of work needed to repair and update our infrastructure is staggering — clearly more expensive than can be afforded and it will take many years to accomplish. To increase the efficiency and effectiveness of repairs the industry is in a state of change. Here are some of the trends:
- Speed is important. Repairs must be installed faster to avoid traffic disruptions. It’s common now to install patches or overlays on bridge decks and open lanes to traffic a short time later.
- DOTs are experimenting with ultra-high-performing concretes to achieve longer bridge life spans.
- The performance of epoxy-coated rebar over time is very good and its use will increase. But high volume traffic bridge constructions and repairs are trending to stainless steel rebar for even longer lifespans.
- The use of carbon fiber wraps for repair work is increasing.
- Galvanic anode corrosion protection for steel reinforcement is increasing.
- Training labor for everything is on the increase and so are the requirements for certification.
- Increasing budgets for preventative work continues to grow, changing the focus on products used.
Our current spending of $12.8 billion for bridge repair is small in terms of the need, but it’s still very good for the construction industry. It may be worth your while to position your company to do some of this work.