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(My issue is kind of like this question but more of a missing chunk than a thin crack.)

I have a concrete patio in the front of my house that was fixed by a previous owner after a bottom chunk broke off. Unfortunately, that repair doesn't appear to be permanent. I'd like to:

  • Knock out the existing broken area with a hammer and chisel.
  • Drive some Tapcons in partially, such that enough of the Tapcon (say, 1/2" to 1") is sticking out from the old slab to provide some reinforcement (but will be covered completely by the new patch).
  • Clean the area with a pressure washer (and let dry).
  • Maybe wrap some metal wire between the Tapcons for extra reinforcement.
  • Build the area up using some vinyl concrete patcher (based on this guide).
  • Patch all the smaller chips elsewhere on the patio, and cover the whole thing in a nice, thick layer of Concrete Restore.

So:

  • Is this Tapcon reinforcement idea a good one? Is it even necessary with a vinyl concrete patcher compound?
  • Would Bondo be a better in this case than vinyl concrete patcher (keep in mind: it's all going to be painted over with Concrete Restore anyway)?

patio with broken chunk broken chunk detail

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Given the proximity of that railing, I'd see if water is getting under it and causing this problem. If so, be sure to fix the source of the problem. –  BMitch Mar 9 '12 at 23:15
    
@BMitch I can see a crack running from the railing foot to the missing chunk, also the concrete is discolored I'd say there's a moisture problem –  ratchet freak Mar 9 '12 at 23:41
    
@BMitch: If the railing is causing a moisture problem, how might I fix it? Sealing around the base of the railing with silicone, maybe? –  Kevin L. Mar 10 '12 at 2:38
    
@ratchetfreak: Good eye. I just went outside with a flashlight to confirm; there is indeed a tiny but definite crack running from the base of the railing. –  Kevin L. Mar 10 '12 at 2:58
    
@KevinL. Silicone is the best idea I have. If there's a high side, leave a small opening so that any moisture that gets in there can escape. Clean the space as best you can and avoid getting silicone on any surfaces you'd like to paint in the future. –  BMitch Mar 10 '12 at 12:33

2 Answers 2

I have a similar problem, but worse. I think im going to put concrete backer board, like what they use to tile bathrooms, on the outside of the edge of the porch, then cover it up with the morter you see covering the edge of your concrete already. To attach it, ill drill holes and use anchor nails or screws and adhesive.

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Please report back to let us know if your method worked. –  Niall C. Apr 6 at 23:30

You're on the right track. I've repaired chips and missing chunks in 80-100 year old public stairways in similar ways. Start with a hammer and chisel, and be really aggressive like a dentist to find and remove all the soft spots.

I've used the tapcon screws, but generally find it easier to chisel an irregular shape that does the same thing.

For your patch I might chisel a channel all the way to the top, so it is easier to get the patching mortar past temporary formwork. Remove your formwork as the stuff starts to get hard, and brush or trowel to match the old surface. Or ignore that as your "concrete restore" will hide minor surface differences.

You can build up the repair in layers, but that requires mixing a fresh batch of rapid set cement every 15 minutes or so.

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