InTrans Project 18-671, IHRB Project TR-757
Iowa Department of Transportation
Iowa Highway Research Board
About the research
Recent developments in nondestructive testing technology have opened the door for innovative inspection methods for infrastructure. One such technology is ultrasound evaluation, specifically in the form of linear arrays. The objective of this project was to explore the potential ability of an ultrasound evaluation device called MIRA to assess the condition of a bridge’s superstructure. To achieve this goal, MIRA was deployed at two bridges with two different sets of objectives. On the first bridge, two concrete overlays had previously been applied, and the bridge was soon to be overlaid for the third time. The second bridge was constructed using concrete box girders, and the condition of the post-tensioning ducts was of interest. For each bridge, multiple test sections were evaluated. Based on the test results, the following conclusions were made:
- When the overlay on the concrete deck was in good condition, MIRA could effectively detect the location and relative size of the rebar in the top layer.
- MIRA scans could not clearly distinguish between the bottom surface of the deck and the bottom layer reinforcement at about 575 mm below the surface.
- When cracks were present in the overlay, MIRA was able to detect these defects. However, since the substrate deck condition of one of the bridges was unknown during this project, the damage seen in the MIRA scans could not be field verified.
- MIRA performed well in detecting voids in post-tensioning ducts.
This project hoped to capture the actual condition of the substrate of the first bridge via field evaluation during overlay placement. Unfortunately, due to delays in the letting of that work, the actual condition was not able to be captured within the timeframe of this project. As such, future research is recommended on an experimental basis to quantitatively evaluate MIRA’s performance related to validating the condition of the substrate.