How many bags of Portland Cement for a CU Yard?

How many bags of Portland Cement for a CU Yard? They are 90lb bags. From what I recall, it was 3 bags per cu yard. Yet I got this guy at the local lumberyard who insists I need 5 bags per... Sounds to me he is trying to make more money...
I am referring to a standard mix of 1 part portland, 2 parts sand and 3 parts stone.
It's been awhile since I made cement so I am asking to be sure. I'm checking into the cost to make my own from scratch rather than truck in some ready mixed stuff in a tub.
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snipped-for-privacy@notmail.com wrote:

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I don't think so.
wrote:

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I don't think so either. It will depend on the size of the aggregate; see: http://www.cement.org/tech/faq_cement.asp
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Looks like they are saying 7 bags. That should be about right. I mixed up a yard of the ready mix and it took about 43 bags. The measurment was not exect but close to a yard. From the above mix , if you say it takes 42 bags and devide by 6 (number of parts) that gives you seven .
Be sure you want to devote the ammount of time to mix up the cement. It will take several hours to mix up that much by hand. Unless a big mixer is used, think of it as about 3 minuits per the bag of premixed that I used. That times about 40 will give you the time it will take. It may take longer if done fully by hand. I used a small electric mixer and only mixed one bag at a time.
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snipped-for-privacy@notmail.com wrote:

4 1/2. Five if you mix it a little stronger. Don't add too much water.
Best regards, Bob
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wrote:

Premix aggregate yields 2/3 cubic FOOT of concrete per 90# bag. That's 27 / (2/3) = 40.5 bags of aggregate per cubic yard.
So if you're making your own mix, with the cement being 1 part in 6, you'd need 40.5 / 6 = just under 7 bags.
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On Tue, 06 Nov 2007 15:08:46 -0600, snipped-for-privacy@notmail.com wrote:

Buy five and take two back; or one.
-- Oren
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On Tue, 06 Nov 2007 15:08:46 -0600, snipped-for-privacy@notmail.com wrote:

Back in the olden days before they ordered concrete by the PSI rating they ordered by "bags" per yard 2500psi was 5 bag, 3000psi was 6 bag and 3500psi was 7 bag
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Note: cement and concrete are not the same thing at all.
Concrete comes in different size bags. Concrete is formulated to different specifications and strengths.
It appears the OP does understand this, but some others may not.

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Joseph Meehan

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Joseph Meehan wrote:

...
It would be the cement that comes in the bags...
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Errm..you can also buy premix (dry) concrete in the bag.
Harry K
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Gfretwell gave you the correct answer.
When ordering or specifying concrete today, it is done by requesting a PSI strength depending on how the concrete is to be used. 2500# for residential footings, minimum; most commercial work is speced at 3500#; tilt up and prestress run 4500-6000#. Each excess gallon on water per yard above the design water/cement ratio reduces the strength by 500#, so you will often see references to not using too much water.
The very old method of ordering, mixing, or thinking about concrete as xxx number of sacks per yard is not used anymore, but most concrete people (at least we old ones) do understand the terminology.
It kinda ends up knowing what you are doing with the concrete, the stresses to which it will be exposed, your expectations for the finish product, etc. 3 sack will set up, get hard, and will crack. 6 sack will set up, get hard, and will crack. The six sack can take a great deal more load before crushing.
Your call. There is an excellent explanation with facts and figures here: http://www.wikihow.com/Make-Concrete
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For a simple feedshed floor, I only need the minimum. It's only for me to walk on. On the other hand, I always make my concrete more durable than that sack-crete. That stuff always seems weak and inferior. (not enough portland in it).
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On Nov 7, 6:29 pm, snipped-for-privacy@notmail.com wrote:

Yep, I buy the sack-crete and add 1 bag of portland. Add about a coffee can of portland per bag when mixing. Excess is kept in one of the ubiquitous white buckets with the sealing top. Seems to keep for years that way.
Harry K
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wrote:

You are wasting your money
http://www.quikrete.com/PDFs/SPEC_DATA-ConcreteMix.pdf
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