Cast in concrete: Designing high-performing, economical roadways

The number of vehicle miles traveled annually in Illinois has nearly doubled from around 52 billion in 1970 to 103 billion in 2023, according to the Illinois Department of Transportation.

Pavement designs must continue to evolve to meet increasing traffic levels.

Illinois Center for Transportation and IDOT aim to update the agency’s design for continuously reinforced concrete pavements in a joint project, “R27-230: Performance and Design of Continuously Reinforced Concrete Pavements.”

Jeffery Roesler, CEE Ernest Barenberg Professor, and Charles Wienrank, IDOT’s pavement design engineer in the Bureau of Research, led the project.

Continuously reinforced concrete pavement, primarily used on interstates with high volumes of heavy trucks, uses longitudinal steel reinforcing bars throughout the pavement to hold transverse cracks that develop tightly together.

“The main benefit of CRCP is a very long service life and little maintenance and perhaps even a smoother ride than you might get on a jointed concrete pavement,” Wienrank said. “The only reason we’re (IDOT) not really using it more frequently now is the cost, because it uses a lot more steel than regular concrete pavements.”

The researchers examined how IDOT designs CRCP roads to account for growth and traffic on interstates since developing the current design procedure.

“We’re modernizing how we would design reinforced concrete for traffic we expect in the future as well as how we do the design process,” Roesler said.

Researchers used a mechanistic-empirical method to predict performance using a model and validate that model with real-world performance.

“We’re trying to look at performance data from existing pavements to see how much traffic they’ve carried, how long they’ve been in service and how that matched up to what we would have predicted with our design procedure,” Wienrank said.

For new CRCP designs, such as road reconstruction, and a given level of traffic, the new design procedure predicts longer life for a given concrete slab thickness.

They also used the AASHTO Pavement ME software program to predict the performance of CRCP overlays in Illinois and compared the predictions to the real-world performance of seven existing CRCP overlay sections.

The researchers found the amount of punchouts, or localized structural failures, was not as high as the AASHTO design method originally had predicted for the age of the roadway.

The research will help IDOT to design more cost-effective, high-performing roadways, allowing the agency to build more roads with the same amount of money.

“One of the challenges with CRCP is the cost,” Wienrank said. “So, if we can build them maybe a little thinner or take advantage of some other design details to decrease the cost a little bit while maintaining performance, that allows us to continue to use CRCP.”