Validating Concrete Overlay Performance on a Key Interstate Corridor

To ensure the long-term performance of two twin reinforced concrete T-beam bridges carrying Interstate 81 over Tattle Branch Road in Smyth County, Virginia, the Virginia Department of Transportation (VDOT) engaged BDI to evaluate recent concrete repairs. These bridges serve a vital role on a heavily traveled truck route, making structural reliability a top priority.

Following the contractor’s application of latex-modified concrete (LMC) overlays to the bridge decks, BDI was tasked with assessing the effectiveness of the overlays and their contribution to overall structural performance.

BDI deployed a comprehensive evaluation strategy combining non-destructive testing and engineering analysis (NDT-E) with live load testing. Using our proprietary SounDAR technology, we investigated the bond between the LMC overlay and the underlying concrete deck. SounDAR’s advanced acoustic imaging capabilities allowed us to detect delaminations caused by poor bonding. High-resolution drone imaging was also used to identify surface defects and generate detailed delamination maps.

To assess structural behavior, BDI conducted live load testing using controlled vehicle crossings and static loading with reinforced concrete barriers. The resulting strain, rotation, and displacement data were used to calibrate a finite-element model and generate updated load ratings for the as-repaired structures.

Key Findings:

• The overlays were well-bonded and actively participating in load resistance through designed T-beam behavior.
• Only 0.25% of the total deck/overlay area showed defects, localized to a previously patched region.
• Load ratings increased due to improved structural condition, overlay contributions, and more accurate modeling of lateral load distribution.

The results confirmed that the concrete repairs were effective and that the bridges are performing well—providing VDOT with confidence in the safety and serviceability of these critical assets.

BDI delivers trusted structural insights when it matters most. If your agency or firm is planning infrastructure rehabilitation or needs post-repair validation, we’re ready to help you respond with confidence.