Hi,
I need to demolish an elevated concrete slab deck. It's 8 by 16 and weighs about 4 tons.
My currrent thinking is to use scaffolding to support the slab while I carve it up using a concrete saw.
Do you have better ideas?
Thanks.
Jack
How thick is it? Seems like between 6" and 1 foot. You *could* use a concrete saw, but it is real messy: w/o water, you got dust *everywhere*; second person could hold a vacuum, tho. With water, it's just, well, messy, and miserable in the cold. If it doesn't cut all the way through, you'll still have to break it up. If there's rebar in there, the saw might actually be a big help. Or you could demo hammer it, cut the rebar w/ a sawzall or oxyacetylene.
I took out a 9" thick poured wall, no rebar, partially w/ a saw, but when down, just broke it up w/ the big Bosch Demo hammer. Actually didn't take that long.
With the saw, tho, you could cut nice square blocks, and use it for something else.
Sounds like you have an excuse to rent a big toy like a small excavator with a hydraulic breaker. I recently rented a mid sized Bobcat with a breaker to obliterate a couple protruding boulders in a gravel driveway. Made short work of it and had a lot of fun.
Pete C.
Use expanding concrete in drilled holes to break it up. A hammer drill and an afternoons work then sit back sip beer while the cement cures and breaks up the slab.
Google on Dexpan for one brand of expansive demolition agent.
John
Thanks, everyone. It's wonderful to be able to ask a question and get so much back.
John. I'm interested in expansive demolition although I wonder if they work when rebar is involved.
In my earlier post I forgot to mention that heavy equipment is out due to access issues.
I seem to recall "Bentoblast" is one brand name for the bentonite clay based expansive "blasting" agent. I've seen it stocked at some tool / equipment rental places.
Even if there is rebar, the bentoblast should fracture the concrete and if you're lucky collapse the slab, breaking it up further. You should then be able to go at it with a sledge to get more access to the rebar and cut them off with an abrasive demo saw. Hauling the debris out if you can't get heavy equipment in will not be fun.
Pete C.
"In demolition. concrete cutting & excavating industry, Dexpan helps you to break reinforced concrete and rock into chunks, so you may easily cut off rebar, haul it away with a crane or truck without damage remaining part"
All the more reason to go with this route: the jackhammer or diamond saw route will be very messy and loud, not to mention back breaking.
John
So nobody's mentioned the scaffolding idea. It seems necessary since I want a controlled demolition. I can imagine worst case scenarios where the slab begins to break up and is no longer supported by it's piers, but the rebar causes it to slam into my house or, worst, pulls my brick away from my house.
Any thoughts on a control decent?
Thanks.
Might be a good idea to scaffold, and do an initial saw cut right next to the house, to completely isolate subsequent operations from the house--vibration, etc. But this would require an even stronger scaffolding, as you have introduced another degree of freedom to the slab. Places rent this type stuff, bolt-together, or you could build your own, if you think you might have use for the mat'ls later on. Shit, if you were by me, I got a ton of 5x3 I-beams.... :)
I think we were kind of going on the assumption that you would make appropriate cuts first to separate the slab from anything that was supposed to remain. If the house side needs support where you will cut it away I'd think just some cut and wedged 2x4s would be adequate and would safely fall away once the slab started to collapse from the expansive "blasting". Were it my scaffolding I wouldn't want slab chunks damaging it. 2x4s are a lot cheaper and more disposable than scaffolding.
Pete C.
Put an A frame of steel under the edge nearest the house, saw it loose, and then pull it down with a truck?
I think he might have in mind a scaffolding that would actually cover the whole area *under* the deck (about 1 foot under), to catch the debris as it comes off.
If that's the case, how will he manage to break up the slab, cut the rebar and remove the concrete without damaging the scaffolding? It would need some sort of sacrificial CDX plywood deck on top of it or similar to protect the scaffolding and that is in all probability not worth the effort.
Pete C.
That's sorta what I see around here. yeah, some sacrificial stuff, hopefully it can be used later. The OP is gonna have to pick one poison or another! :)
Can't you just paint it or cover it with vines?
And, yeah, I was think of using rough cut lumber on top of the scaffolding. By the appearance of the concrete, it looks like that's how it was poured.
You guys are great! Thanks for all the help! :)
I'm going to use scaffolding topped with rough lumber, covering the entire slab bottom. I'll press it up against the slab. I'll use Dexpan to crack it up. Then I'll use my sawsall to cut the rebar.
Will a little luck I can remove the concrete one square foot at a time.
Forget about using a sawzall to cut rebar, it simply doesn't work, at least not in any reasonable time frame. Rebar is hard, nasty shit to cut, trust me, I've tried with a sawzall and good blade and gave up about 1/4 of the way through a piece of 1/2" rebar. Use an abrasive cutoff wheel on either an angle grinder, or a demo saw and have plenty of spare wheels.
Pete C.
Or a torch. Torch = more fun.
Yes, however then he will likely set the planks on top of the scaffolding that the whole slab is resting on on fire which is probably not a good thing, especially if it's adjacent to his house.
Pete C.
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