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# Mixture - Concrete

Sun 1 Mar, 2015 08:43 pm
In a mixture of concrete a 1:2:3 ratio of materials is used for a cubic yard. The materials used are cement, sand, and rocks or gravel. I know the 1:2:3 ratio is 1 part cement, 2 parts sand, and 3 parts rocks or gravel. The materials required are in a table of different ratios. The 1:2:3 ratio is recommended for walkways, floors, and posts. The information says from the table 1 bag of cement will make 3.9 cu. ft. of concrete - the table does not show that - indicates 7 bags of cement, 14 cu. ft. of sand, and 21 cu. ft. of rocks or gravel.

My question - How is the 3.9 cu. ft. calculated from the 1 bag ? I know a cu. yard = 27 cu. ft
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Type: Question • Score: 1 • Views: 1,992 • Replies: 17
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ekename

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Mon 2 Mar, 2015 09:07 pm
@Randy Dandy,
27 cubic feet of concrete is made using 7 bags of cement.
27/7 equals 3.9 cubic feet of concrete.
Do you have a related question?
Randy Dandy

1
Mon 2 Mar, 2015 10:08 pm
@ekename,
Yes. The ratio is 1:2:3 - 1 part cement, 2 parts sand, 3 parts rocks/gravel = 6 total parts.

My question: Would the following be correct - Cement 1/6, Sand 2/6 or 1/3, Rocks/Gravel 3/6 or 1/2 mixtures ?

ekename

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Mon 2 Mar, 2015 10:49 pm
@Randy Dandy,
Yes, that's what the ratios imply. I was sure you were going to ask a more in depth question, a seeming conundrum perchance, possibly about the cubic feet of sand and the cubic feet of gravel, mmm?
Randy Dandy

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Mon 2 Mar, 2015 11:34 pm
@ekename,
I can't think of any more related questions at this time.
ekename

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Tue 3 Mar, 2015 04:03 am
@Randy Dandy,
I thought you might wonder why 27 cubic feet of cement contains 14 cubic feet of sand and 21 cubic feet of gravel and not only but also, 7 bags of cement?

Pretty tricky how that 3.9 cubic feet of cement per bag was calculated would you say?
Randy Dandy

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Tue 3 Mar, 2015 06:54 am
@ekename,
0 Replies

Randy Dandy

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Tue 3 Mar, 2015 08:00 pm
@ekename,
"I thought you might wonder why 27 cubic feet of cement contains 14 cubic feet of sand and 21 cubic feet of gravel and not only but also, 7 bags of cement?"

Why?

Pretty tricky how that 3.9 cubic feet of cement per bag was calculated would you say? Yes - How?
ekename

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Tue 3 Mar, 2015 10:04 pm
@Randy Dandy,
14 cu ft of sand plus 21 cu ft of gravel equals 35 cu ft even before the cement is added and they only end up with a paltry 27 cu ft of concrete, it seems unfair, I thought it might make you ponder upon derivations of that result?

The 3.9 cu ft of concrete must have been pretty tricky because that was your original question, I'm sure you'll agree, however do you think my explanation of how the 3.9 cu ft came about is correct?
Randy Dandy

1
Tue 3 Mar, 2015 10:29 pm
@ekename,
" I thought it might make you ponder upon derivations of that result?"
I don't understand what you mean.

"I'm sure you'll agree, however do you think my explanation of how the 3.9 cu ft came about is correct?"

I agree - Yes- correct.

ekename

1
Tue 3 Mar, 2015 10:35 pm
@Randy Dandy,
14 plus 21 equals 35 yet there is only 27 cu ft of concrete?
Randy Dandy

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Tue 3 Mar, 2015 10:48 pm
@ekename,
Yes.
ekename

1
Tue 3 Mar, 2015 11:00 pm
@Randy Dandy,
How can 14 cu ft of sand plus 21 cu ft of gravel add to equal only 27 cu ft of concrete?
Randy Dandy

1
Tue 3 Mar, 2015 11:25 pm
@ekename,
It can't I guess.
ekename

1
Tue 3 Mar, 2015 11:31 pm
@Randy Dandy,
Best you think about that while looking at my response to your Sizes question.

http://able2know.org/topic/266814-1
Randy Dandy

1
Tue 3 Mar, 2015 11:45 pm
@ekename,
"How can 14 cu ft of sand plus 21 cu ft of gravel add to equal only 27 cu ft of concrete?"

I don't know.
raprap

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Mon 9 Mar, 2015 04:54 am
@Randy Dandy,
Void volumes---aggregrate has a lot of voids; sand, and water fills those voids.
0 Replies

Randy Dandy

1
Mon 9 Mar, 2015 01:21 pm
Thanks.
0 Replies

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