Trying to stop edge of slab from wearing and chipping

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Old 02-16-10, 03:16 PM
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Trying to stop edge of slab from wearing and chipping

I patched the edge of my garage floor last fall. It's breaking down on the very edge where it meets the driveway. It's not sinking at all, as I recall they put rebar in the slab so sinking wouldn't occur in this area, so they told me.
I put sand down in the crack first, the kind you use between pavers, then I watered it down and used a common patching product like you'd buy at a big box store. I can't even remember what it was exactly, but sounded like what I should use.
One side is already breaking up. I know this is probably a bad area to try to fix, it's right about where the right tires of my truck would roll over as I enter and leave the garage, plus the garage door itself ends up in this area. And we get a lot of freeze/thaw cycles. AND the snow melt from my truck will wet this area down at night and freeze when it reaches this area. So I can't fault anything but "unusual circumstances" right now.
I am including a few pictures of the area. The first is of the side which so far is holding up. The second is the general area I am having more trouble, and the last is a closeup of the specific area that's already breaking.

Any suggestions?
Gilly





 
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Old 02-17-10, 10:33 AM
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Looks like the piece that breaks off is quite shallow. The biggest problem is that you are trying to patch the surface with thin layers of whatever you have used. You can patch these areas if you properly prepare the area first. Clean it, and I mean with a wire brush and vacuum out the debris. Use a bonding agent so that the new patch will adhere to what is underneath. Then use a quality product like Ardex to patch with. You will find this at a commercial supply place and not your local hardware store.
And just an FYI, rebar has no affect at all on sinking or heaving.
 
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Old 02-17-10, 12:39 PM
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OK, it's been awhile, but I thought the rebar was installed so that the section of rebar connects the garage slab to the first slab of driveway, so the driveway slab won't sink? Oh well, just thought I would mention it.

To me, an untrained (or at least undertrained) individual, possibly the problem is that the broken edge sort of "undercuts" under the slab, like a negative angle (like the number "7" where the top of the 7 is the top of the slab). So pressure on it would make the repair more prone to loosening or breaking off. I don't know if there is a way around this, only thought I have is to go at it with a hammer, and possibly a chisel, to make the angle more of a positive angle, so the patch can "rest" on top, rather than having nothing to support it other than the sand I put in.

I did get the gap cleaned out, using a shopvac, as you mentioned. Some of the concrete seemed to flake off (I think that's called spalling?) and I did knock off some of this flakey concrete until I was pretty satisfied that the concrete left was hard stuff. I didn't wire brush or like that though.
Then I put in this paver sand so I thought the depth of the crack was about where the bottom of the slab would be, it took more than I thought it would, I dunno, a couple of cups worth at least? Then I wetted the sand and waited a day for that to "harden". Then I put a piece of wooden paneling in front of the slab and put the patch between the slab and paneling. I waited an hour or so to pull out the panel, and was very very careful to NOT drive over the repair for a number of days. I also wetted the patch down for a few days as well, like they do with new concrete construction (I see they usually keep it wet or cover it in plastic for a few days, I guess that keeps it from curing too fast?).

Main question (in addition to critiquing the job I did), is if it would make sense to get rid of that undercut, so instead of the edge being like a "7" it would angle the other way "\" like that?
Thanks for the reply!
Gilly
 
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