Diamond Grinding Concrete Pavement
Diamond Grinding Concrete Pavement
(OP)
I’m reviewing a procedure for repairing a bridge deck overly, 2” thick concrete. Actually, the repair involves replacing the entire overlay, which was recently installed. Here’s what happened, among other things, the contractor didn’t turf drag the bridge, and none of the inspectors seemed to mind. Subsequently, the overlay cracked and debonded.
I recommended that the contractor roughen the bridge surface approximately ¼” . He’s p---ing & moaning that there’s no machine that can do this – I know there are walk behind machines for floors, but it’s slow work, and small milling machines, but these are sometimes hard to find. He wants to bring in a huge machine, something on the order of a Roadtec 900. I think this would do more harm than good.
I think diamond grinding would be the best way to go; just enough to roughen the surface to get some bond. Any thoughts?
Thanks
I recommended that the contractor roughen the bridge surface approximately ¼” . He’s p---ing & moaning that there’s no machine that can do this – I know there are walk behind machines for floors, but it’s slow work, and small milling machines, but these are sometimes hard to find. He wants to bring in a huge machine, something on the order of a Roadtec 900. I think this would do more harm than good.
I think diamond grinding would be the best way to go; just enough to roughen the surface to get some bond. Any thoughts?
Thanks





RE: Diamond Grinding Concrete Pavement
I'd hold them to using a walk behind http://www.edcoinc.com/scabblers-cd-5.html or larger scabbler. Possibly they can do a test area if the bridge is big enough.
RE: Diamond Grinding Concrete Pavement
RE: Diamond Grinding Concrete Pavement
I have used a layer of bedding mortar, nominal 1/4" thick (cement, sand, water, and a water reducing, set-retarding admixture, 7 - 9 inch slump) for bonding roller compacted concrete layers to prevent de-bonding. not on a bridge deck, but on a spillway apron.
http://www.dot.ca.gov/hq/esc/techpubs/manual/bridg...
RE: Diamond Grinding Concrete Pavement
2" structural topping is common in building work. Not sure about bridges, but it does seem a bit thin for existing bridges, considering construction timing and dynamic loading.
My experience is that the most important thing in achieving bond is not roughness, but cleanliness. Normally, this can be achieved with a light shotblast to remove the laitance. Rigorous efforts to achieve roughness do lead to microcracking in the substrate. But if there are contaminants present like you would find in bridge decks, achieving cleanliness might be problematic.
Any chance they used a bonding agent? They are notorious for acting as debonders if the timing is not perfect.
RE: Diamond Grinding Concrete Pavement
RE: Diamond Grinding Concrete Pavement
Perhaps my OP wasn't clear: This is a new bridge; it hasn't been opened to traffic. At first, the overlay cracked; then it was noted that the overlay was "peeling off". It turns out the contractor 1)didn't turf drag or roughen the deck surface; 2) didn't pre-wet the deck before placing the overlay; 3)didn't properly cure the concrete.
cvg - good information about overlay curling.
RE: Diamond Grinding Concrete Pavement
RE: Diamond Grinding Concrete Pavement
RE: Diamond Grinding Concrete Pavement
The 2" thickness is a DOT standard for a reconstructed bridge deck; it's meant to be a bonded overlay. Normal DOT practice is to build in a monolithic overlay. This isn't a DOT project but it is my understanding the owner wanted concrete.
RE: Diamond Grinding Concrete Pavement
My boss is in a panic "what should we do?" I said tell them to hire a engineer to figure out a repair. Hit rebar once, Understandable; hit rebar all day long by doing the same thing, can't fix stupid.
RE: Diamond Grinding Concrete Pavement
RE: Diamond Grinding Concrete Pavement