In order to pass a 3/4" PVC electrical conduit from inside of the house to
outside of the house below grade, I had to chip out part of the concrete
block wall, and since it's below grade on the outside and then travels
vertically up on the inside wall (to get to a junction box), I had to put
two 45 degree elbows into the hollowed out section and that makes the hole
more than the original drilled out 1" hole. Now I want to fill it back up
with something. I don't want to use those expansion foam I would like to
back fill with concrete. However, the cavity inside the 8" thick concrete
block wall is bigger than the hole. I don't think I can "pour" concrete in.
Is it ok to add more water to get the concrete "soupier" so I can pour it
in? or is there another way? It's not a big cavity I think just about the
size of a milk carton.
The fill isn't going to be structural, right? So even though it's poor
practice to soup-ify concrete, in this case it should be OK; you just
need to get some stuff in there, not develop any strength.
At least that's the way this non-concrete expert sees it.
Personally, I like Vista, but I probably won\'t use it. I like it
because it generates considerable business for me in consulting and
I'd use foam and concrete- foam to make a plug in the cavity in the
block, and then the stiff pack-it-in-by-hand concrete patch mix to plug
the holes in both faces. A lot less messy, and a whole lot less weight
to lug around. The problem is, the cavity you can see probably leads to
the same cavity in the row of block below it, unless you made the hole
in the bottom row. If you don't want to mess with foam, another trick is
to wad up some window screen or other similar material, and stuff it in
as best you can. It doesn't matter if there are some voids inside the
wall- they were there to begin with. You just need something to take up
space, that the concrete can lock into place around, but not flow past.
Main objective is to get the patch on both faces to bind well to the
surrounding concrete, so you don't get water leaks. You want it to be
pretty on the inside wall, and extra solid and leakproof on the outside.
Don't forget to heavily wirebrush the outside, so the patch has fresh
concrete edge to bind to, and after the concrete sets, lots of the black
stuff at the transition with the pipe. The black stuff should completely
hide the patch mix on the outside, including on the bottom of the pipe,
and extend down the pipe a couple of inches. Penetrations in the
envelope like this are a common leak point in heavy rains or the spring
Sure, add some water. That's what they do when doing concrete construction
and they want to fill the top, "U" shaped lintel by pumping "grout" into it.
You might want to enlarge the hole some too in an upwards direction...the
soupy grout will pretty much self level so you won't be able to fill above
the bottom of the hole; once the soupy stuff sets, mix some stiffer mortar
to stuff into the upper part.
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