Mixture - Concrete

[Guest]

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. Thanks.

[Guest]

It is a bit like boiling a pot of potatoes for dinner
The pot is full of potatoes....yet... you can add 2 or 3 pints of water and the pot is no more full, it may not even then be completely filled.

The ratio od cement, sand and gravel is 1 to 2 to 3.....by volume dry materials.....so 6 parts all together
If one bag of cement is used, then 2 bags of sand, and 3 bags of gravel......6 bags all together

6 bags altogether with water mixed makes 3.9 cu. ft of concrete....an emperical relationship found by experiment or trials

[Guest]

So the principle would be the same as a container of coffee makes x cups of coffee, or a container of detergent will wash x loads of clothes.

Correct ?

[Guest]

Coffee and detergent would be more soluable than cement and aggregate.
With sand, cement, gravel and water its more of a mixing of the smaller particles in the spaces between the larger particles and very little disolving.

Your 1 bag of cement + 2 of sand + 3 of gravel + about 50% water makes 3.9 cuft of concrete.........
OR your 7 bags of cement + 14 sand + 21 gravel, means 42 bags all together for 3.9 x 7 = 27.3 cuft = 1 cu yard approx........
................................that would be very strong coffee.

[Guest]

I meant 1 bag of cement makes 3.9 cu. ft.- 1 container of coffee makes x cups - 1 container of detergent washes x loads of clothes. Are those along the same principle as the 1 bag ?

[Guest]

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[Guest]

Tetleys make tea bags make tea................

??

[Guest]

I asked the question about the same principle because I was trying to understand the solution.

[Guest]

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[Guest]

My error for asking the question.

[Guest]

Your original question - How is the 3.9 cu. ft. calculated from the 1 bag ? I know a cu. yard = 27 cu. ft. Thanks.

I dont think it is calculated directly from the 1 bag of cement............ In the question it is a statement of fact given that 1 bag of cement will make 3.9 cuft of concrete. But as posted earlier 1 bag of cement is really 6 bags of aggregate and cement together as dry material of varying partical size, so the fine particles will "fit" between the particles of the coarse materials. And the water will mix and fill any cavities left. That is why it is found by experiment or trial for various mixes of aggregate
That is why I compared it to a pot of potatoes with lost of space between them where tha water and smaller ones can "fit" and the overall volume does not necessarily increase.

Your comparison with coffee of detergent is more about soluable solutions where the bulk is water and very little else solids.