Agencies
Services
IDOT Update - 2022 – Monday, May 23, 2022
Setting the bar for longer-lasting bridges
Transportation made up 29% of total greenhouse gas emissions in 2021, according to the U.S. Environmental Protection Agency, over half of which comes from passenger vehicles and commercial trucks.
The Illinois Center for Transportation and IDOT aim to reduce this percentage in their joint project called “Analyzing the Impacts of a Successful Diffusion of Shared E-Scooters and Other Micromobility Devices and Efficient Management Strategies for Successful Operations in Illinois.”
Abolfazl Mohammadian, the University of Illinois Chicago’s Department of Civil, Materials and Environmental Engineering professor and department head, led the project with IDOT’s Manager of Program Support Chuck Abraham.
Mohammadian and Abraham explored the launch of shared electric scooters in Chicago, one of several micromobility services designed to provide transportation over short distances.
E-scooters may provide additional benefits over other micromobility services, including greater mobility for people with physical limitations, the ability to connect to transit more quickly and more flexible pickup and drop-off locations.
Adding a smooth epoxy coating to rebar, a popular technique since the 1970s, significantly increases its resistance to corrosive materials, but also may generally lead to increased crack width in bridge decks.
Here the researchers investigate adding a roughened texture to the smooth epoxy coating, which increases friction as well as the bond between the concrete and bars.
“One of the issues with bridge decks is that they crack,” Schiff said, “and the expectation with this textured reinforcement is it will have less cracking and also hold the cracks tighter, so that’ll allow less chlorides to get into the bridge deck.”
Their goal? Find the optimal level of texture or roughness to add to the coated rebar.
“It’s like looking for just the right grit of sandpaper to sand your wood,” Tobias said. “We wanted to know if a smoother 220 grit or a rougher 40 grit was the best, or somewhere in between.”
To figure out the optimum texture, Andrawes isolated the conditions that bridge decks would experience in the field and recreated them in UIUC’s Newmark Structural Engineering Laboratory.
Andrawes started with taking microscopic images of various textured rebar and examining their surface profiles.
He and his team then embedded the rebar in concrete cylinders to test the bond between the bar and concrete.
Key to the research were several large-scale tests, where the researchers tested the cracking produced from shrinkage after the concrete was cast as well as thermal movement and flexural behavior. Andrawes’ methods showed that cracks in the bridge were not as wide as those when using nontextured, coated rebar and the bridge deck was stiffer and had smaller deflections.
Ultimately, Andrawes’ team verified the textured rebar improves bridge deck performance by about 33%.
“This is the first time that these bars are applied anywhere in the world,” Andrawes said, “so IDOT is pushing the envelope of the application of epoxy-coated rebar.”
The innovative technology is expected to have a nationwide impact, as many state agencies are searching for a way to reduce the number and severity of cracks in bridge decks.
“Several state DOTs are aware of Illinois’ research on this topic and are eagerly awaiting results for their potential implementation,” said Dan Brydl, Federal Highway Administration’s Illinois Division bridge engineer and a member of the project’s technical review panel.
“FHWA is very pleased with the results of this research,” Brydl said. “This marketable innovation could very possibly lead to a new standard in bridge deck reinforcing steel coatings both regionally and nationally.”
Drivers in Illinois can also expect to see an additional benefit: fewer traffic delays due to fewer closures for bridge maintenance and repair.
“Our goal here is to reduce future maintenance of bridge decks and hopefully reduce costs over the life of a bridge,” Schiff said. “That’s the long-term goal: to help save tax dollars.”