Texas A&M Transportation Institute (TTI) researchers are working with multiple Texas Department of Transportation (TxDOT) districts on case study projects to accelerate overall pavement construction project times. Using a wide variety of pavement forensic evaluation tools and an innovative traffic control plan, the bulk of the work happens before letting a project and is intended to evaluate alternative rehabilitation methods. Developed through previous research and implementation efforts, the tools and processes also help pinpoint the most effective repair for various sections of the corridor under construction.
Using alternatives to the originally planned and recommended pavement design in targeted areas avoids the time-honored practice of using a single pavement design or rehabilitation method for an entire corridor. That allows a targeted focus, tailoring construction solutions to unique problems along a discrete part of the roadway rather than applying a one-size-fits-all method.
“The traditional approach is often not 100 percent successful because different parts of the corridor may have different types of issues and problems underneath the pavement,” says TTI Senior Research Engineer Tom Scullion. “That means different solutions may be quicker and more effective in certain areas of the overall project.”
A key to this analytical approach is segmenting the entire corridor into sections that are then classified and evaluated separately based on the existing pavement conditions noted in the initial evaluation. In this process, the first step is to use a combination of GPR and high-definition video along the entire corridor to quickly identify the specific problem areas where moisture-related damage has occurred. Next, researchers do a structural check of the road by collecting deflection data using either traditional methods employing a falling weight deflectometer or TxDOT’s recently developed rolling deflectometer. Last, field cores are taken in targeted areas and analyzed extensively in the lab.
“We are using all of these nondestructive testing data to significantly reduce the cost and time often involved in traditional field coring practices,” says TTI Research Engineer Darlene Goehl, who leads the project. “This ‘Smart Coring’ strategy is much more beneficial and economical than traditional methods that involve randomly coring every mile of the roadway. We get fewer but more accurately revealing locations to pull the cores.”
The first case study in the Dallas-Kaufman area on I-20 between I-635 and State Highway 34 is nearing completion. Researchers evaluated approximately 20 miles that included two distinct rehabilitation methods done across two projects. For approximately 14 of the 20 miles (sections 1 and 2), the rehabilitation included spot repair and an overlay. For the remaining heavily distressed 6 of the 20 miles (section 3), researchers recommended rubblizing the existing concrete pavement and then adding hot-mix overlays.
“One of the success stories on the I-20 rehabilitation/reconstruction project was the use of rubblization,” confirms Nic Wadlington, TxDOT assistant area engineer in the Kaufman/Rockwall Area Office. “While some sections of the project required a more traditional method, the lower traffic volume in others made it ideal for this method. Working 1 to 2 miles at a time, TxDOT reduced the existing concrete into rubble along the roadway. Rather than remove the rubble, the department used it as a base for the new roadway.”
Overall, the rubblization rehabilitation of the last 6 miles saved time and money, with reduced transportation and material costs compared to the traditional alternative of full-depth reconstruction. By designing the right process for the right section of roadway, the overall project time decreased significantly. Further, rubblization is not a frequently used process by TxDOT; therefore, it would not be unreasonable to assume the design strategy would have included removing and replacing the existing pavement structure, which would have substantially increased the project time and cost.