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Old 10-04-2007, 06:58 AM   #1
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Concrete Mix


Looking for opinions on a concrete mix of sand and pea-gravel for 16 x 8 footers. The project site is in an area inaccessible by redi-mix trucks and the concrete will need to be mixed by hand. The footers will support 3 rows of 8" block topped by a standard 8 ft framed wall.

The local stone/gravel supplier has on hand a combo of pea-gravel and sand - for the convenience of a large company who does driveways and sidewalks. Instead of me buying separate loads of #8 stone and sand for the footers on my project and then mixing 1 part cement/2 parts sand/3 parts stone ... how would the premixed pea-gravel and sand work instead for my footers?

Are the stones larger than pea-gravel required in the concrete mix if I use adequate re-bar?

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Old 10-06-2007, 01:52 PM   #2
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Read a little about concrete, available online, and then you will understand the point of the mix....like 1/2/3...and so on. Footings should have a mix of at least 5 sacks to the yard.....

If possible, I would avoid pea gravel, and use stone and sand.

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Old 10-06-2007, 05:43 PM   #3
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Hi powrus,
As joasis has said, read up on the web. Concrete mixes and mixing is a very complex subject, not easily answered here.
For footings you should use good concrete and adequate rebar.

I don't like the sound of pea gravel etc, but if that's all that's available, talk o the supplier and even though he can't get a pre-mix truck to your site, he may give details of the mix that they use. Local aggregates etc vary so talk to someone in your area who is in the know.

A couple of pointers here that apply to concrete in general, and they are only my opinion.
* Most concrete laid by non professionals does not reach it's full potential strength. That is they pay good money for a product and then they waste half of that money.
* They add too much water (to make it easy to handle), thus changing the water-cement ratio and weakening the mix.
* They don't cure the concrete. You can loose up to 80% of concrete strength by not curing.
* Lets say you have poured a slab and it has taken on the initial set. You and your mates are sat around having a well earned beer. If I came along and said "listen boys, I'll give you $300 to cover that concrete up". (start the curing process). You'd jump at the offer eh! and yet all the time you see good curing neglected. Throwing money away.

In the case of batching by hand it is very hard to keep the right proportions if you just count shovels. Most concrete is weigh batched.

I'd say an easy way for you is to volume batch, say using steel drums. (empty paint tins or whatever is available). It is a pain in the bum to do, but it will give you a better mix. (We used to make up ply boxes, with two battens either side so two men could lift and tip them into the mixer).

Best of luck with it,
Cheers
Bill.
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Old 10-06-2007, 05:50 PM   #4
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If this is just a home with footings, the mix is really not that important. You just have to get a 3000 psi which in not that difficult if you have a reasonable amount of cement.

If this is a basement footing or a stem wall, you really don't have much load on it. Slabs are a different story becaue the concrete properties become important.
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Old 10-06-2007, 08:54 PM   #5
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500PSI is overkill for most foundation footings.
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Old 10-07-2007, 08:16 AM   #6
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Thanks for all the replies. Everybody's input was appreciated. All good info. I'll probably end up using #8 stone and sand.

Wonder if anybody ever adapted an ATV to make runs between the big trucks and remote sites? The little vehicle could navigate through the underbrush and might be able to carry a wheelbarrow full on each run.
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Old 10-07-2007, 09:40 AM   #7
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A tracked skid steer with a concrete bucket would be my choice....you can rent one of those, and your back won't hurt at the end of the day like batching 8 yards of concrete would make you feel.
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Old 10-07-2007, 11:55 AM   #8
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Good idea. Thanks.

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