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You have helped me in the past with some questions that I had on some crash testing results for the Midwest 12.5’ K-Wall Temporary Concrete Barrier wall. The information you provided was very helpful and instrumental in South Carolina’s approval of the concrete anchoring system. I appreciate the help that you provided on that. Now, I am contacting you to get an opinion on a method that I do not believe to have been tested. While pinning some wall through asphalt, a contractor hit some old concrete that is about 10 inches below the surface which is a lot shallower than the 46 inches that we require for asphalt pinning. The concrete that was hit has rebar in it at 3 inches deep. In an effort to not have to core an additional 36 inches through the concrete to achieve the necessary depth,  the contractor is proposing an option to drive through the asphalt and then core an additional 5 ¼ inches into the concrete and using epoxy to anchor as done in our approved concrete anchoring standard. This appears to be able to work but I am unsure of how the wall will react if struck. My concerns are that I don’t know if the wall would tilt over due to the portion of the rod in the asphalt yielding more than the portion of the rod in the concrete. Attached is a copy of our standard that the contractor has modified to represent the requested changes. I welcome any thoughts that you may have on this regarding whether the wall would react similar to the approved concrete anchoring. Please let me know if you have any questions.

The tie-down system shown int the detail was intended for use on reinforced concrete bridge decks that did not include asphalt overlays. With asphalt overlays in place, the loaded barrier may allow the vertical anchor bolts to plow through the asphalt roadway material instead of being restrained by the rigid concrete deck, thus resulting in a longer moment arm and increased bending moment for the bolt region found at the asphalt-concrete interface. This change in loading and capacity may potentially decrease the safety performance of the existing, crashworthy tied-down barrier design. As such, we cannot at this time recommend using this detail on paved roadways or decks that contain an asphalt overlay. Although it may be possible that this design, or one very similar to it, may provide acceptable performance, we believe that more research is needed to investigate and evaluate various temporary tied-down barrier systems for this special application.

The only other temporary barrier solutions for bridge decks with asphalt overlays I can recall is a system that was developed for PCB’s with a cross-bolt connection by Safe Roads R&D with the Powell company in Canada.  https://saferoadsrd.com/

They had an asphalt anchorage that was tested to MASH TL-3 that was only embedded 6”. It might be applicable. However, Our MASH testing with asphalt anchorage showed some concerns for vehicle snag at the barrier joints. This likely had to do with the connection difference – pin and loop versus cross-bolt. As such, the Safe Roads solution may not be directly applicable.

Thanks!

I do have another question. Currently we are addressing this issue by having the contractor follow our asphalt pinning standard which calls for a 46 inch pin to be driven through the asphalt. So would pushing the pin through the asphalt and concrete to the required 46 inches react in a similar manner as their proposed method?

I believe that putting the pin through both the asphalt and concrete would be acceptable.