To avoid confusion commonly used in the estimate of quantity of cement, sand and gravel is in its dry state without water, that is why if you add up all ratio will be more than 1cu.m.
Based on what you will read online, some explanation says that when you mixed all dry materials together with water, it will decrease the volume size of final concrete about 54% due to evaporation of air voids, with cement and water chemical reaction it fills up all the voids present in your aggregates (sand and gravel).
Therefore, 1 cubic meter for comparison for the dry volume estimate is already in its "concrete" form (wet) less 54% as claimed.
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| concrete byproduct of mixture of cement, sand & gravel + water |
Reason why you may see some professionals using 1.54 factor for their actual concrete "batching" to have more control on number of bags and aggregates to be poured to designated areas.
Other explanation of how 1.54 factor was derived is that at least 2% of cement loss or wasted during construction, with overall percentage of mixture left around 66%.
To which they divide this percentage to 1 cubic meter which requires 1.515 plus 0.02 (% of cement loss) which gives out 1.535 or roughly 1.54 factor as dry volume needed to fill 1 cubic meter when mixed with water.
BOOK REFERENCE by MBFJr
By the book from our dear MaxBFajardoJr let us try to break down one by the different concrete class mixture.
Class AA 1: 1-1/2: 3 mixture
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| Class AA 1: 1-1/2: 3 mixture |
- 1: 1-1/2: 3 divide all with 3 to find other ratio in cu.m
- we use the bigger ratio as divisor to arrive at 0.333cu.m, 0.5cu.m, and 1cu.m
- add all three and we get a total of 1.8333cu.m (cement+sand+gravel)
- 0.333 we multiply with 36 and we get 12 bags (see how we derived 36 number here)
- therefore in 1cu.m we need 12 bags of cement, 0.50cu.m of sand and 1cu.m of gravel
Class A 1: 2: 4 mixture
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| Class A 1: 2: 4 mixture |
- 1: 2: 4 divide all with 4 to find other ratio in cu.m
- we use the bigger ratio as divisor to arrive at 0.25cu.m, 0.5cu.m, and 1cu.m
- add all three and we get a total of 1.75cu.m (cement+sand+gravel)
- 0.25 we multiply with 36 and we get 9 bags
- therefore in 1cu.m we need 9 bags of cement, 0.50cu.m of sand and 1cu.m of gravel
CLASS B 1: 2.5: 5 mixture
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| Class A 1: 2.5: 5 mixture |
- 1: 2.5: 5 divide all with 5 to find other ratio in cu.m
- we use the bigger ratio as divisor to arrive at 0.20cu.m, 0.5cu.m, and 1cu.m
- add all three and we get a total of 1.70cu.m (cement+sand+gravel)
- 0.20 we multiply with 36 and we get 7.2 bags rounded to 7.5 bags
- therefore in 1cu.m we need 7.5 bags of cement, 0.50cu.m of sand and 1cu.m of gravel
To check if you were able to follow the process kindly solve for Class C with 1: 3: 6 ratio
To Summarize from the book
- different class mixture have different factors starting from 1.8333, 1.75, 1.70 etc
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| concrete mix ratio and quantities |
1.54 DRY VOLUME FACTOR COMPARISON vs BOOK
Format:
Cement = (cement ratio/total mix ratio) x 1.54 x 36
Sand = (sand ratio/total mix ratio) x 1.54
Gravel = (gravel ratio/total mix ratio) x 1.54
CLASS AA (1: 1-1/2: 3 =5.5)
- Cement = (1/5.5) x 1.54 x 36 = 10.08 bags
- Sand = (1.5/5.5) x 1.54 = 0.42 cu.m
- Gravel = (3/5.5) x 1.54 = 0.84 cu.m
CLASS A (1: 2: 4 =7)
- Cement = (1/7) x 1.54 x 36 = 7.92 bags
- Sand = (2/7) x 1.54 = 0.44 cu.m
- Gravel = (4/7) x 1.54 = 0.88 cu.m
CLASS B (1: 2-1/2: 5 =8.5)
- Cement = (1/8.5) x 1.54 x 36 = 6.52 bags
- Sand = (2.5/8.5) x 1.54 = 0.453 cu.m
- Gravel = (5/8.5) x 1.54 = 0.906 cu.m
To check if you were able to follow the process kindly solve for Class C with 1: 3: 6 ratio
To Summarize from 1.54 dry factor
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| concrete mix ratio and quantities |
QUESTION: WHEN TO USE THE BOOK and WHEN TO APPLY 1.54 FACTOR?
If trying to get a "quick estimate" on how much cost you will be spending for your project so you can get an ideal budget, use the book.
If you want to control the proper mix for actual pouring of concrete to certain sets of footings, columns, beams or slabs then use the 1.54 factor.
To get the idea:
Say you have a 1 bagger concrete mixer, and you wish to pour concrete on a 1.2m x 1.2m x 0.35m footing of 7 sets, using class AA as per your Structural Engineer design. Compute needed cement, sand gravel for batching.
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| 1 bagger concrete mixer image from imimg.com |
Compute total volume of footing as required:
Volume = 1.2 x 1.2 x 0.35 x 7sets = 3.528cu.m
Cement = 3.528 x 10.08 = 35.56 bags say 36 bags
Sand = 3.528 x 0.42 = 1.48 cu.m
Gravel = 3.528 x 0.84 = 2.96 cu.m
Number of batches = number of bags of cement
Total Batches = 36
Therefore, in every (batch) mix in your 1 bagger concrete mixer will be 1 bag of cement, 0.0416cu.m of sand, and 0.0832cu.m of gravel.
How we get values for sand and gravel per batch: "cu.m/bags"
1.48cu.m/35.56 = 0.0416
2.96cu.m/35.56 = 0.0832
Commonly used in small scale construction of houses instead of "measuring box", uses a 16 liters bucket or pail.
Converting these cu.m of sand and gravel: "(cu.m x 1000)/16"
One cubic meter equals to 1000 liters
Sand = (0.0416 x 1000)/16 = 2.60 pail
Gravel = (0.0832 x 1000)/16 = 5.20 pail
Therefore: 1 bag cement + 2.60 pails sand + 5.20 pails gravel per one batch for 36x
You may wish to use excel calculator (here).
