how to fill this gap with concrete?

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Old 04-19-14, 12:58 PM
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Question how to fill this gap with concrete?

hi,
I recently had some basement leaking issues, before i found out where the problem was(now that i know), i removed a large area of flooring (installed by previous owner). Then I found this(see pics), a piece of 2x4 between 2 sections of concrete floor (the squares are probably the leftover marks from removing tiles from before). what's worse is that the center part of wood has rotten in and i easily punched a hole through it (dirt soil underneath, no gravel)

my questions are:
what could be the reason for the wood to be here?
should i remove it?(i get the answer is yes, but still want to get some option)
after i remove the wood, do i pour concrete to fill the gap?
how to prepare the surfaces (both for soil underneath and existing concrete floor beside the gap)?
what concrete product should i use (i'm noob to concrete,cement...)?
and finally, what are the steps to do this job?

Thanks in advance for any help! I guess i could get someone to come and do this for me, but i'm poor and want to save money DIYing...






 
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Old 04-19-14, 01:10 PM
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I do agree that you should remove the wood. I also wonder why it was there, maybe it is part of the form and they just left it there.

If it is wide enough to fill with concrete, that would be your best, least expensive, option. Just run of the mill concrete should work. Just smooth it out with a trowel to the adjacent concrete.

What will your new flooring be?
 
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Old 04-19-14, 01:22 PM
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will the concrete stick to the existing slab? i was reading about hydraulic cement, looks like it's good for water proofing, should i use that? also, will concrete stick to wood(i may not be able to remove the entire piece of wood because the 1. the end goes into/below the drywall and i don't wanna remove the wall and 2. the end is still pretty dry after been there for over 50 yrs )?

laminate flooring i think. for now i'm think just putting the ones i removed back to where they were(the flooring didnt really get wet because of the vapor barrier under the underlayment), i'm gonna put in new underlayment though.
 
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Old 04-19-14, 03:07 PM
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It may not "stick" but there is not going to be much that will dislodge it in the first place unless you have water the seeps up through the crack. There is also products out there that help concrete to bond to other concrete, but again, you not driving cars over it.
You could use a floor leveler, but that is quite expensive.

I would just get as much wood out as you can without tearing up the walls.
 
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Old 04-19-14, 03:59 PM
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that's very helpful.

should i lay sand or gravel before pouring concrete?
 
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Old 04-22-14, 02:00 AM
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Depends on what's there after you remove the wood. If it's more concrete, just clean it and place new concrete on top of it. If it's dirt, compact it as best you can before adding a shallow layer of gravel, tamp it down, and then place the concrete.
 
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Old 04-22-14, 08:54 PM
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If you can pull it all out and there's concrete under it, it would be easiest to just replace it with pressure treated lumber and then a high quality caulk to prevent excess moisture rising between the seal. Chisel away at it etc to get it all out. Looks like a 2x4 will fit right in without cutting.
Not sure why that's there, seems to large of a piece for someone to have used to pour the slab, they might have even used it as the footer plate for that finished wall, and considering the amount of damage that piece has, rot might creep up that finished wall into electrical etc.

If using concrete to fill, it's such a small piece that it could crumble without adding bonder to strengthen it which will also make it adhere to the existing cement and create a better seal, but bonder's like $20 a gallon the smallest I've seen. Cement might be less likely to crumble as such a small piece. If it crumbles under the floor after set in, you might not notice or care but moisture will just get under your vapor barrier and make it's way to that finished wall especially if it's just dirt underneath.
 
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Old 04-22-14, 09:07 PM
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I've had just one experience with preservative pressure-treated lumber being exposed to constant moisture (i.e., wet) conditions. The stuff started to stink terribly after a few years, and can also harbor certain strains of mold.

A quality, prebagged concrete product will work well, and won't crumble or fail if properly mixed, placed and finished. It shouldn't need a bonding agent, but if you insist on using one, a neat Portland cement slurry (consistency of thick cream) will make the new concrete stick like glue. Cost for a whole 94-lb. sack is less than $10 in the U.S., and you'll have a lot left over to use for "sweetening" the concrete as you mix it.
 
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Old 04-23-14, 10:35 PM
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it usually says right on the bag that regular concrete isn't for applications under 2.5" I think, and this looks only like 1.5" deep. But bonder should prevent cracking if you use concrete. And something like cement might not crack. I say only use PT lumber if you just want to cut a piece and put it in instead of carrying, mixing and cleaning cement/concrete mix. The real problem now seems to be whatever rot might be going on in that finished wall.

Yes, I've seen pressure treated lumber left under a deck on dirt only a few years and it was so rotted, crumbling, that's why I say only use it if there's concrete under what's there. It might only be rotten because it's not pressure treated in contact with cement. There are millions of basements finished with PT lumber on the floor with no problems.
 
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