Author Topic: Getting through 12" of concrete  (Read 3878 times)

Getting through 12" of concrete
« on: May 11, 2014, 03:18:50 pm »
I need to make sure that the enormous pit, aka ex-pond, drains before I start to fill it in with rubble, sand etc. The space will then become useable.

Bought a 400mmx12mm drillbit to drill exploratory, hopefully draining holes.

I now know how thick it is. 12" concrete base. The centre has a sunken bit about 8" across and the concrete at the bottom of that is only 6" thick. Managed to drill about 10 holes in total yesterday - but it still didn't drain. Could be compacted rubble below the concrete, could be clay, could be anything. Ideally I'd remove a chunk a couple of feet square and make sure it can drain, but short of explosives I can't see any practical way of doing that. 12" is too thick for any cutting saw, too thick to break up with an SDS drill or even a jackhammer. Absolutely ludicrous.
<i>Marmite slave</i>

Re: Getting through 12" of concrete
« Reply #1 on: May 11, 2014, 03:26:12 pm »
Interesting one.

All you can realistically do is to use your drill bit to make as many holes in the foot square you want as the drain. If you also use a bolster hammer and a chisel you will hopefully be able to remove a fair bit of material then drill down again. There are longer bits available and you might consider hiring a Kango hammer or similar.

Good luck

PH
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Re: Getting through 12" of concrete
« Reply #2 on: May 11, 2014, 03:42:46 pm »
If it's a pond there's no replenishment, yes?

What's wrong with a pump and a long hose? Get the water out and get it filled in PDQ . . .

Sorry if I haven't understood.
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Well that's the more blunt way of putting it but as usual he's dead right.

Re: Getting through 12" of concrete
« Reply #3 on: May 11, 2014, 03:47:19 pm »
Because it will fill up with water from the rain.
<i>Marmite slave</i>

Re: Getting through 12" of concrete
« Reply #4 on: May 11, 2014, 04:46:39 pm »
A Kango will do the job. If you want to remove the concrete use a spade bit, if you just want to drill holes a chisel bit will go through.

tiermat

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Re: Getting through 12" of concrete
« Reply #5 on: May 11, 2014, 04:50:30 pm »
6" was about the thickness of our kitchen floor, and it was >70 years old.

Make a hole approx 6" across, then break it up from the edges. A small impact driver might not cope, but a two handed job shouldn't cost too muchmore to hire, and should be doable in a day.
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Re: Getting through 12" of concrete
« Reply #6 on: May 11, 2014, 05:14:54 pm »
No need for 2 hander (although obv better at it) Something like: https://www.us.hilti.com/drilling-%26-demolition/demolition-hammers-%26-breakers/r287 will get through just about any domestic situation.

(I have the 15 year old version of the same, I've not found anything it won't get through)

PaulF

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Re: Getting through 12" of concrete
« Reply #7 on: May 11, 2014, 05:45:38 pm »
Surely the standard answer to this sort of problem is "Dust off and nuke it from orbit. It's the only way to be sure."

:D

Re: Getting through 12" of concrete
« Reply #8 on: May 11, 2014, 05:51:36 pm »
12" of concrete doesn't break that easily - I've dug out concrete floors and broken things up.

A kango will chip away, sure, but it won't smash this up.

Anyway, I've re-drained out the rainwater (getting fountained in sludge in the process) and drilled again through the same holes I did yesterday. There was 4" of water in yesterday so I couldn't probe about much.

There is clay under the pond. So no matter how big a hole I make, it isn't going to drain.

There is a 6" pipe leading to the lowest point in the pond. I reckon I can feed a pump down through this, rigged to a float switch. Really not the solution I wanted but looks like it is the only way.
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Tim Hall

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Re: Getting through 12" of concrete
« Reply #9 on: May 11, 2014, 08:38:46 pm »
Hire a diamond core drill from HSS (other tool hire outlets are available)?

like this: http://www.hss.com/g/1121/Light-Duty-Diamond-Driller-Kit.html
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Re: Getting through 12" of concrete
« Reply #10 on: May 11, 2014, 08:41:06 pm »
um - I'd need the heavy-duty version - that is £162 per day :(

As I said tho, still wouldn't drain because of the clay. It's going to have to be a pump
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David Martin

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Re: Getting through 12" of concrete
« Reply #11 on: May 11, 2014, 09:17:34 pm »
Concrete will disintegrate on repeated vibration, such as from a jackhammer. When you have a hole, excavate underneath. Concrete is realtively strong in compression but not in extension - it should be easy to break into a hole.

Obviously the challenge is to get a hole from which you can excavate (possibly through pumping out the water, then washing away the clay into a slurry.)

..d
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Re: Getting through 12" of concrete
« Reply #12 on: May 12, 2014, 07:22:32 am »
hire a breaker...  Dad asked me to get rid of a 10' x 10' x 2' concrete block when I was about 18, tried using a sledgehammer and it was stupidly hard work. Persuaded him to hire a pneumatic breaker and it was done in a day - and was quite good fun too (in an 18-yr-old, only for one day, kind of way)

Re: Getting through 12" of concrete
« Reply #13 on: May 12, 2014, 08:11:56 am »
Dyn4mite. 

You need an expert quarryman, demolition expert or maybe a tree surgeon.

May we assume it is not reinforced with steel? :o   After all, they were clearly anxious to do a proper job of it..
Sic transit and all that..

Re: Getting through 12" of concrete
« Reply #14 on: May 12, 2014, 08:20:39 am »
Short of a pneumatic type drill/kubota mini digger, I'd try and remove a plug of concrete by means of closely drilled holes, then excavate a hole into the sub-whatever (as has probably been said).  But 12" of concrete is one super thick pond lining... Our's is 1-2mm butyl sheet, with old carpet underlay.  ;-)
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Re: Getting through 12" of concrete
« Reply #15 on: May 12, 2014, 08:46:09 am »
Could there be a carpet with bones in it underneath?
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Re: Getting through 12" of concrete
« Reply #16 on: May 12, 2014, 08:59:30 am »
Could there be a carpet with bones in it underneath?
It had crossed my mind!

There is absolutely no need for it to be so thick; 4" would have done the job, 6" would have been more than ample. 12" is ridiculous, particularly given that it also has a heavy fibreglass liner.
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jogler

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Re: Getting through 12" of concrete
« Reply #17 on: May 12, 2014, 09:18:33 am »
Is it practical to consider infilling the ex-pond pit with clay?

Re: Getting through 12" of concrete
« Reply #18 on: May 12, 2014, 09:21:23 am »
So your alternative is to report your suspicions to the Police with added local rumour that the previous incumbent's wife/grandfather etc disappeared some years ago.

Job done, you won't have to lift a finger ;)

Re: Getting through 12" of concrete
« Reply #19 on: May 12, 2014, 09:40:36 am »
Is it practical to consider infilling the ex-pond pit with clay?

Well you see it is over 7ft deep (about 1.5ft of which is above lawn level. - and my wife want to use it as a sitting/firepit area, slightly sunken. This weekend I discovered that rendering it in such a state takes priority over all else, even putting up a wardrobe for her clothes.

The whole thing is ludicrous. It is big enough for two hippos to have a bath in. It is visible from space. The garden really isn't large - the pond takes up over a 1/4 of the whole garden.
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vorsprung

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Re: Getting through 12" of concrete
« Reply #20 on: May 12, 2014, 09:45:45 am »
Is it practical to consider infilling the ex-pond pit with clay?

Well you see it is over 7ft deep (about 1.5ft of which is above lawn level. - and my wife want to use it as a sitting/firepit area, slightly sunken. This weekend I discovered that rendering it in such a state takes priority over all else, even putting up a wardrobe for her clothes.

The whole thing is ludicrous. It is big enough for two hippos to have a bath in. It is visible from space. The garden really isn't large - the pond takes up over a 1/4 of the whole garden.

Ignore the drainage problem and cover with decking?
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Re: Getting through 12" of concrete
« Reply #21 on: May 12, 2014, 09:47:22 am »
So your alternative is to report your suspicions to the Police with added local rumour that the previous incumbent's wife/grandfather etc disappeared some years ago.

Job done, you won't have to lift a finger ;)
I worked in the world of underpinning for a while. The foreman of one of our gangs was arrested on suspicion of murder. The police believed they had quite a good case, except they needed the murder weapon, an axe I think it was.

The gang had just finished a large underpinning job and the police came to the conclusion that the axe was in the bottom of one of the bases. They asked him which one. He pointed them at the one, and the police hired his gang to dig it out. It wasn't there. "Oh, perhaps it was that one." It wasn't. I don't know how many they worked through, but it was a great way to have his gang trebly employed for a good period of time.
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Re: Getting through 12" of concrete
« Reply #22 on: May 12, 2014, 10:00:37 am »

There is clay under the pond. So no matter how big a hole I make, it isn't going to drain.


But on top of that will be topsoil - otherwise your garden would be a constant lake surely? So, rather than draining out the bottom, don't you need to drain through the sides at some level between surface and clay subsoil?

Of course, you'll discover the transition will be above the level at which the aforementioned SWMBO will want the sunken level to be.....
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jogler

  • mojo operandi
Re: Getting through 12" of concrete
« Reply #23 on: May 12, 2014, 10:02:06 am »
Is it practical to consider infilling the ex-pond pit with clay?

Well you see it is over 7ft deep

'kin ell :o

that'll be a "no" then

Vince

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Re: Getting through 12" of concrete
« Reply #24 on: May 12, 2014, 10:09:46 am »
Fill it with rubble then cap off with a 12" concrete floor at the desired depth. Then make drainage holes through the side.You should be able to dig a soak away at the side of the pond liner avoiding the clay.
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