Materials Performance

OCT 2018

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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OCTOBER 2018 MATERIALSPERFORMANCE: VOL. 57, NO. 10 13 PRE SERV ING BRID GE S In the early interstate era, the time when the structures we are driving on today were designed, there really wasn't a concept of service life or durabil- ity, says NACE International member David Whitmore, president and chief innovation officer with Vector Corrosion Technologies, Ltd. (Winnipeg, Mani- toba, Canada). "Steel and concrete were thought to be semi-permanent materials—when you built something out of concrete, it would be there for- ever. We didn't salt roads then like they do now. Corrosion wasn't a major consideration in the design process." In terms of structural integrity, North America has a very good system of bridge inspection and maintenance, and overall the infrastructure is safe and reliable, Whitmore says. However, he comments that older bridges have their own set of problems given the fact that they're aging and getting closer to the end of their service life—if they haven't already surpassed it. The major- ity of the thousands of bridge structures in the United States that are 50-plus years old already have chloride contamination from exposure to deicing salts or a marine environment, or are suffering from carbonation. They are either corroding or at risk of corroding. "That is the elephant in the room, because they are not going away, and just ignoring them doesn't make them go away. You can decide not to do any- thing and let the problem fester and progress, but eventually you will be forced to do something," Whitmore says. "You don't want to get to the point where a bridge is structurally unsound and there are life safety issues." Tearing down and replacing older structures, however, is not always an option. Most of the bridges in Florida were constructed in the 1950s, and have an expected service life of 50 years, says NACE member Ivan Lasa, state materials administrator with the Florida Department of Transportation (FDOT) Corrosion Research Laboratory (Gainesville, Florida, USA). Because the population in Florida is growing, much of the FDOT budget for highway infrastructure has been expended on new roads and new bridges, which has slowed down the state's ability to replace old bridges that have met or exceeded their expected service life. The cost to replace the total number of structurally deficient bridges in the United States is estimated by the FHWA to be close to $48.8 billion. To rehabilitate the structurally deficient bridges, the FHWA estimated the cost to be around $33.2 billion, roughly 68 percent of the replacement cost. 6 "It's not practical to tear down and replace all older infrastructure—there is too much out there, and we can't afford, as an economy, to demolish and replace everything, Whitmore says. Bridge owners have turned to bridge inspection to identify integrity prob- lems, which provides them with options on how to address issues before they become structurally problematic. In the United States, as mandated by the FHWA, all bridges are to be inspected at least every two years, which puts a state in control of the condition of its bridges at all times, says Lasa. The FDOT has a protocol in place to track any bridge deficiencies and ensure that measures are put in place if a deficiency may create an unsafe situation for the public. If a bridge is structurally deficient, the bridge owner reviews the deficiency. If the deficiency doesn't require immediate attention, the bridge is put into a work program so that the deficiency will be remedi- ated or the bridge be replaced within six years. If necessary for the safety of The Bob Graham Sunshine Skyway Bridge, 7 one of Florida's flagship bridges near St. Petersburg, Florida, USA, opened in 1987. When corrosion of the steel was found in the hollow precast concrete segmental columns on the high-level approaches, workers were able to enter the bridge through the superstructure in 2003 and 2004 and reinforce the corroded sections of the bridge. This was followed by the installation of ICCP on the columns in 2017.

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