I live in an old firehouse with a rebar reinforced cement garage floor. I’m guessing that the floor is at least 8 inches thick with I Beams every four feet or so. The floor is cracked in the garage (1 long crack) and water (from melting snow on the car) seeps into the crack and comes out in the cellar. Over time, this has eroded part of the cellar ceiling creating a upside down “divet” with the rebar (rusting) exposed. I was told by the inspector when I bought the place that structurally, this is not a big deal. On the other hand, it bothers me and I’d like to fix it. What is the best way to repair this type of problem. I’m assuming first the crack needs to be sealed on the garage floor. In fact it looks like the crack was made into a “V” and patched, as the patch has now separated from the surrounding slab. Can I patch directly over this old patch or do I need to remove it? Also, should I use cement or a sealer (someone recommended All-Krete)? I’m sure this post exposes my ignorance on this, but I wanted to give as much info as possible.
Also, what is the best way to seal a foundation to the sidewalk which butts up against it.
Thanks.
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I have seen spalled concrete similar to your description left with just the exposed rebar. The leak was sealed, loose concrete removed and lead bridge paint was applied over the exposed bars. This lasted for several years until a real rehabilitation job was let to repair the area. This was in a concrete frame structure at the foot of the Goethals bridge where the PA paint crew stored their remaining stash of lead paint.
First, you need to figure out what is causing the cracks to reopen. Is it continued deterioration from the water (likely with roadway salts) or is it structural?
After sealing the cracks with, clean the exposed rebar to bare metal and remove all of the loose/deteriorated concrete and remove an additional 1/2" into the sound concrete. Expose at least 1/2" beyond the rebar so the patch meaterial can achieve a physical bond with the rebar. It is best if the edge of the concrete patch area is sawcut with a bit of an undercut for a physical bond. Use an epoxy-modified overhead and vertical patching material (5-Star Products are good).
The patch is no good if you don't apply some kind of waterporrofing material over the repaired cracks.
...that's not a mistake, it's rustic
remove an additional 1/2" into the sound concrete...
For crev's situation don't think a full 1/2' is needed (maybe only 3/8<G>), but you sure do have to go to clean concrete, both ceiling and floor sides.
You absolutely need to remove down to bare concrete - defiitely remove the old bad patch. Then, wire brush (wire wheel or cup on 7 or 9' angle grinder ) a thick 100% cement and water grout onto all surfaces. Put a form up against the ceiling, and grout the bottom in with a really stiff grout. The next day, after that has set, pour a thin grout into the carck, and top off the last 1" of the "V" in the floor with a trowel and stiff grout again. The only way I've found to get a waterproff fix other than filling the whole thing with silicone - need to clean down to new concrete with that method also.