How to seal a crumbling concrete floor?

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insane

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#298630 2-Jul-2022 20:09

My workshop/storeroom was an extension to my house, and the thick concrete slab floor is slowly crumbling away as I walk around.

I've tried using a vacuum cleaner, but honestly I could literally suck up the entire slab if I kept going.

Is there a way to seal the concrete to bring the floor to a semi flat surface again?

The two options I've thought of are

1. Wet the floor and lay another layer of concrete to level it and to stop the crumbling.
2. Try use liquid polyurethane to both level out the uneven surface and to stop the crumbling.

I'm wondering what the best way is to go about this?

I don't actually need/ want to do the entire area as I have heavy workbenches etc that I made large than the door.... And have nowhere else to temporarily store things. Just need to do + - 8sqm in the middle of the floor.

Thanks!

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#2937625 2-Jul-2022 20:43

Pics?

davidcole

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#2937626 2-Jul-2022 20:45

Our garage floor has this problem. But it’s reached the point where it needs to be ripped up and re poured. It’s probably over 40 years old - if not older

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insane

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#2937630 2-Jul-2022 21:17

I've been literally sweeping the problem away layer by layer and suspect a full re-pour might be the only permanent fix. For now I've just placed floor protection down and pretended it's okay.

Will have to take another pic for a closeup, but basically the aggregate is super small chucks, perhaps 4mm encased in poudry cement. Vacuuming it does bad things to the vacuum cleaner 😁 and just loosens the next later down. I can never get a clean surface as more crumbles.

tweake

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#2937882 3-Jul-2022 13:54

the floor is stuffed. i will need to be removed.

i doubt any coating would work because it will simply lift due to the concrete coming off. put up with it until you can afford to replace it.

coffeebaron

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#2937889 3-Jul-2022 14:11

Stick some outdoor carpet or artificial grass stuff down. Problem covered up :)

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Journeyman

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#2937902 3-Jul-2022 15:48

So it looks like it's pretty much the entire area rather than some concentrated patches? In my not-a-concrete-expert opinion, I'd say that laying more concrete on top won't last because it'll never bond properly to the crumbly stuff underneath. If you were in the mood for some DIY experimentation you could drill some holes through the concrete, place some rebar into the holes so the top is just sticking above the old concrete and then pour some new concrete on top. That might help anchor it. But, again, I'm not an expert - it might work, it might fail miserably :)

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Bung

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#2937918 3-Jul-2022 16:23

insane: I've been literally sweeping the problem away layer by layer and suspect a full re-pour might be the only permanent fix. For now I've just placed floor protection down and pretended it's okay.

Will have to take another pic for a closeup, but basically the aggregate is super small chucks, perhaps 4mm encased in poudry cement. Vacuuming it does bad things to the vacuum cleaner 😁 and just loosens the next later down. I can never get a clean surface as more crumbles.

The aggregate probably started ok but was mixed with too much water. A sloppy mix allows the bigger gravel to settle at the bottom. If the surface keeps crumbling sealing won't do much. Perhaps cover it in ply flooring. See if you can find 2nds or coversheets .

tweake

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#2937920 3-Jul-2022 16:31

Bung:
insane: I've been literally sweeping the problem away layer by layer and suspect a full re-pour might be the only permanent fix. For now I've just placed floor protection down and pretended it's okay.

Will have to take another pic for a closeup, but basically the aggregate is super small chucks, perhaps 4mm encased in poudry cement. Vacuuming it does bad things to the vacuum cleaner 😁 and just loosens the next later down. I can never get a clean surface as more crumbles.

The aggregate probably started ok but was mixed with too much water. A sloppy mix allows the bigger gravel to settle at the bottom. If the surface keeps crumbling sealing won't do much. Perhaps cover it in ply flooring. See if you can find 2nds or coversheets .

i would have to ask a mate who is a pro, but by mem the cause is most likely lack of cement or to much sand. it was too wet i would expect there to be a lot of cracks.

i had it at work where the concrete guys forgot their tools, so they wet the concrete to make it smooth. which caused a ton of cracking.

tdgeek

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#2937929 3-Jul-2022 17:40

Would pouring epoxy over it not provide a good base? As in it will bind the existing concrete?

Ge0rge

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#2937932 3-Jul-2022 17:53

You don't need to bind to the existing concrete - the slab for a house doesn't bind to the damp-proof layer underneath.

However, whatever you do pour needs to be thick enough so that it is strong enough. I would think you might be able to pour a self-levelling compound over it with good success. Set up some timber or silicone "dams" at the edges of your benches and only do the areas where you walk.

Journeyman

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#2937949 3-Jul-2022 18:39

You don't think it would be an issue pouring concrete over something so crumbly? I'm not criticising, just curious. Agree with you on the thickness.

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Ge0rge

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#2937957 3-Jul-2022 19:12

As long as you wet the original floor to dampen the crumbly material, and prevent it from sucking water out of your concrete, you'd be ok.

However, in this case I don't think concrete over the top of what's there will be appropriate - to make it work, you'd need to pour a pad thick enough that it wouldn't be susceptible to cracking, which would effectively lower your bench and ceiling heights by a noticeable amount.

I do think self-levelling would work. Be easy enough to try a small amount in a corner somewhere to see.

tweake

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#2937962 3-Jul-2022 19:33

self leveling will have the same issue. its to thin.

you either do a thick enough pad on top, or just rip the old concrete out. if its falling apart that much its a fairly straight forward job.

tdgeek

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#2937963 3-Jul-2022 19:34

Ge0rge: You don't need to bind to the existing concrete - the slab for a house doesn't bind to the damp-proof layer underneath.

However, whatever you do pour needs to be thick enough so that it is strong enough. I would think you might be able to pour a self-levelling compound over it with good success. Set up some timber or silicone "dams" at the edges of your benches and only do the areas where you walk.

I meant binding the loose or potentially loose stuff

blackjack17

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#2937967 3-Jul-2022 19:50

Wouldn't it be easier simply to put a false wooden floor over the top? 18/20mm ply leveled with some 10mm strips underneath?

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