Bonding Concrete to Existing Concrete
Bonding Concrete to Existing Concrete
(OP)
Hey there folks, I have a relatively simple quick question here.
My firm has been asked to redesign an outdoor concrete patio type area. This is no big deal, but adjacent to the patio area is a 5" deep concrete slab.
The 5" concrete slab is not very aesthetically pleasing and does not line up well with the patio, so I have recommended to tear it out and replace the entire area. You would think this would be a simple task for a relatively small area, however the client has pushed back saying they cannot do that. Their response was to scrape out the top 3 inches of concrete and essentially just re-pour the top half of the slab. Has anyone heard of any type of coating that would allow placing a couple inches of fresh concrete over existing concrete and bonding them properly? It sounds absurd to me to just re-pour half the depth of the slab, but I wanted to make sure I wasn't missing anything.
Thanks!
My firm has been asked to redesign an outdoor concrete patio type area. This is no big deal, but adjacent to the patio area is a 5" deep concrete slab.
The 5" concrete slab is not very aesthetically pleasing and does not line up well with the patio, so I have recommended to tear it out and replace the entire area. You would think this would be a simple task for a relatively small area, however the client has pushed back saying they cannot do that. Their response was to scrape out the top 3 inches of concrete and essentially just re-pour the top half of the slab. Has anyone heard of any type of coating that would allow placing a couple inches of fresh concrete over existing concrete and bonding them properly? It sounds absurd to me to just re-pour half the depth of the slab, but I wanted to make sure I wasn't missing anything.
Thanks!






RE: Bonding Concrete to Existing Concrete
On your project, removing the top 3" of a 5" slab would leave (theoretically) 2" of concrete. IMHO, the 2" would never survive the removal process. I suppose you could use hydrodemolition, instead of mechanical scabbling, but either way the result could be just very expensive removal of the exiting 5" slab.
Stick with your approach.
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RE: Bonding Concrete to Existing Concrete
Have they spoken to a contractor about this? I can't imagine any contractor would think it was cheaper to chip out 3" from a 5" slab and somehow manage to leave the bottom 2" intact.
You should have them reach out to a contractor. They'll soon agree to your original approach...
RE: Bonding Concrete to Existing Concrete
RE: Bonding Concrete to Existing Concrete
Dik
RE: Bonding Concrete to Existing Concrete
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
https://www.facebook.com/AmericanConcrete/
RE: Bonding Concrete to Existing Concrete
RE: Bonding Concrete to Existing Concrete
But you can demo less concrete thickness, and pour new concrete topping.
RE: Bonding Concrete to Existing Concrete
RE: Bonding Concrete to Existing Concrete
RE: Bonding Concrete to Existing Concrete
Yes, it is technically possible to remove the top 3" ($$$), although expect lots of damage to the 2" that remains. Then, in order to bond properly, you should have the concrete sandblasted ($$), then a bonding agent applied ($$), then reinstate the concrete. Bonding agents such as Sika HiMod 32, Sika Armtec 110, and many others are applicable.
You are correct that partial demo is absurd. Letting the client know that it will cost them at least double to do partial demolition will likely be your best argument.
RE: Bonding Concrete to Existing Concrete
I'll take this as a win for the good guys!