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Thread: Vertical slab repair??

  1. #1

    Question Vertical slab repair??

    This past weekend I had to demo a rather large vertical section out of our slab to expose a leak in the cold water line. I would estimate that it is 13-15 inches wide by about 30 inches tall. I did have to cut the rebar to get to the pipe and what I used was a jackhammer to demo the concrete. I know that I need to put the rebar back in roughly the same places. The edges are jagged and should hold well on a vertical plane.

    Is there anyone who can formulate a good game plan with ideal pointers for ensuring I do it right? Forms, material, what not to do, etc.

    Also, the concrete the contrator used for this slab is a lighter gray color and has a brushed rough finish. The concrete is 7 years old and is stable with no visible cracks from the jackhammer. This is about as much info I can think of to supply.

    The work doesn't scare me, but the I don't knows do.
    Last edited by sstgt; 12-14-2006 at 08:22 PM.

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    I'm not a pro, but if I had to do this, I'd drill some holes, epoxy in some rebar, and tie things back together using the appropriate wire prior to refilling it with concrete.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3

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    Thank you for the info Jim. Anyone else have any fine points?

  4. #4
    In the Trades Bob NH's Avatar
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    I would consider breaking back the concrete about a foot on either side so that about a foot of re-bar is exposed on either side of the break. You don't need a clean break.

    Then cut some re-bar long enough to just fit in the gap and overlap the old bar ends. Wire the new re-bar to the old ones. You can get 10 ft lengths of 1/2" rebar at HD and 20 ft lengths as some better supply stores. You can get 10 ft lengths of threaded rod in the electrical conduit area at HD which will also work very well.

    Clamp some plywood against the inside and outside surfaces of the walls, overlapping onto the old wall, using some 1/4" threaded rod with a couple of 2x4s to stiffen the plywood. Use large washers under the nuts on the 1/4" threaded rod. They call them "fender washers".

    If you oil the plywood it will come off cleaner when you strip the forms.

    Then you will need about 8 to 10 bags of the best quality sack-crete or quick-crete (5000 psi grade). Mix it up medium stiff (not sloppy) and put it in the forms. Use a rod as you pour it to make it fill good and whack the forms with a big hammer to vibrate the concrete into place to avoid a honeycomb finish when you strip the forms. Finish it level with the old wall.

    After a couple of days, you can remove the forms. You can cut the 1/4" rods about 1/2" into the surface and fill it with a cement/sand mix.

    If you want to try to match finish, you can rub the surface with a carbide masonry brick and sand/cement mix.

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