A New Tool for Pavement Evaluation

Repairs and maintenance for the transportation infrastructure of Illinois present a potentially huge cost to the state. In order to test new technology that  could provide “effective, efficient, economical, and rapid data collection” of pavements, bridge decks, and other concrete structural elements for the purpose of evaluation of their condition and the need for repairs, IDOT teamed up with ICT in a recent project, Ultrasonic Imaging for Concrete Infrastructure Condition Assessment and Quality Assurance (R27-146).

Mira Device and laptop

The focus of this project was on evaluating a new piece of technology called MIRA, a portable ultrasonic shear wave tomography device that has the potential to allow field workers to asses these structures quickly and efficiently. A team of researchers, led by principal investigators John Popovics (UIUC), Jeffery Roesler (UIUC), and TRP chair Douglas Dirks (IDOT), recently completed their report evaluating MIRA’s effectiveness in a variety of field applications.

Mira B-scan showing pavement thickness and dowel bar locations

For the project, the researchers evaluated several tasks where MIRA might be able to improve on current methods. They then categorized these tasks in the report as either field ready, potentially ready, or challenging, to indicate which tasks MIRA was best suited for. They found that MIRA was field ready for internal concrete and parapet wall void detection, duct position location, slab thickness determination, and initial condition survey of dowel bars/reinforcement; had potential for use in evaluating concrete delamination, concrete/asphalt bonding, bonding of overlays and fiber reinforced polymer (FRP) wrap, and precise rebar location and sizing; and that several tasks would be challenging to accomplish with MIRA, including distributed cracking/surface-breaking crack depth, duct grout condition, corrosion, and evaluating heavily reinforced structures.

Popovics notes that he “liked the opportunity to implement newly developed technology to meaningful practice in the field.” In support of this effort, they also produced a user’s manual (Appendix E of the report) to “assist in introducing new users to the proper operation and interpretation of the MIRA device” and presented their findings at an implementation training session held for engineers in the transportation sector on February 27, 2017, just before the annual Transportation and Highway Engineering Conference.

According to John Popovics, this project went smoothly thanks to a great working relationship with IDOT and the TRP. “The highlight was the end of project implementation training session that we held for transportation engineering. I believe this really helped broaden the understanding and potential beneficial application of this technology.”

3D reconstruction of MIRA scans showing dowel bars and an embedded strain gauge

Looking forward to the next phases of implementing the technology, Popovics says that they “aim to continue to work with IDOT to ensure optimal field application and analysis of the technology and data that is obtained.” He will be working with IDOT to create a training video on the MIRA, which will be a good way for employees to learn to use the device. TRP chair Douglas Dirks says “the Bureau of Bridges and Structures will take possession of the device, and it should be very helpful for many tasks such as locating reinforcement in very old structures where little information is available.”

While this phase of the work is concluded, Jeff Roesler does see some potential for future research in this area: “More research could be done on how to apply the equipment technology with multiple arrays of sensors to look at other problems not currently done such as the depth of a crack into a slab or bridge deck or reinforced concrete section. I think the research could now be focused on expanding the capabilities of the technology.”

Roesler recently used the MIRA technology to assess ten concrete pavement sections in Champaign-Urbana for slab thickness, presence and spacing of reinforcement and dowels, and presence of stabilized base layer in order to link design features with performance of urban concrete pavements. The MIRA was also demonstrated to the Illinois Tollway in June 2017 to show its capability of locating reinforcement and verifying constructed slab thickness for continuously reinforced concrete pavement.