Stone chips |

Mix design is commonly referred by mix proportion in a selective zone where same materials are used in concrete. Suppose, in Bangladesh, most of the structural designers refer concrete mix design as ratio in drawing. Because materials of same properties are used in all over the Bangladesh.

The question is,

**How do we estimate materials for different ratio concrete?**

The most common ratio referred here in Bangladesh for column concrete 1:1.5:3 and for slab 1:2:4. When we mix cement, sand and stone chips at 1:1.5:3 ratio, the concrete strength of 28 days cube test's result comes around 3500 psi. If we mix cement, sand and brick chips at 1:2:4 ratio the 28 days cube test result will come around 3000 psi, which is referred for slab concrete.

I will estimate materials for 1:1.5:3 ratio concrete. After learning this process you will be able to estimate materials for any concrete ratio.

Now lets estimate the required materials for the volume of 100 cft concrete of 1:1.5:3 ratio:

Wet volume of concrete = 100 cft.

Dry volume of concrete= 100 x 1.54 = 154 cft.Sum of ratio 1:1.5:3, 1 + 1.5 + 3 = 5.5.

So, Cement content in concrete = (154/5.5) x 1=28 cft.

Sand content= (154 / 5.5) x 1.5 = 42 cft.

Stone chips = (154/5.5) x 3 = 84 cft.

As we know, Cement is available as 50 kg bag in the market. The volume of 50 kg cement bag is 1.25 cft. So the required cement is 28 divided by 1.25 equal to 22.4 bag.

**Summary****:**

Sand : 42 cft,

Stone chips: 84 cft.

In this estimation, we use cubic feet as our concrete unit. If you want to use cubic meter, same method can be applied. But that will be time-consuming. The easiest way to estimate concrete materials for different unit is, apply the above result as percentage. That means,

*Cement*content for 100 unit of 1:1.5:3 ratio concrete is 28% (unit will be as concrete unit),

*Sand*is 42% and

*Stone chips*is 84%.

Now lets calculate the water content of concrete. Suppose, water-cement ratio for concrete is specified 0.45. That means, water/cement = 0.45, or W/C = 0.45.

for 1 bag cement, water is, = 0.45 x 1.25 (as we know, 1 bag cement equal to 1.25 cft),

Water = 0.5625 cft.

We know 1 cubic feet water is equal to 28.31685 litre,

So we can write, water = 0.5625 x 28.31685 = 15.92 litre, say, 16 litre.

So One bag cement needs 16 liter of water for 0.45 W/C ratio.

That's it.

Here, one thing should be cleared that someone assume the dry volume of concrete is equal to one and half times of wet volume. But it is better to use 1.54 for calculating dry volume.

**If I did any mistake here please let me know by commenting below....**
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ReplyDeleteRCC Slab 100'x150'x6" and main bars 6# 6"c/c and dis bars 4# 8"c/c

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ReplyDeletePlease provide me calculation of steel bars as same above detail is below

ReplyDeleteRCC Slab 100'x150'x6" and main bars 6# 6"c/c and dis bars 4# 8"c/c

Please provide me calculation of steel bars as same above detail is below

ReplyDeleteRCC Slab 100'x150'x6" and main bars 6# 6"c/c and dis bars 4# 8"c/c

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ReplyDeletethe formula of calculating the steel weight is d^2/162

ReplyDeleted is the diameter of bar

so if you have a bar which is having 10mm dia the weight of steel rod per metre will be .617kg per metre

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ReplyDeleteyour computation is simplified and easy to understand, however I'm interested to know what is the figure of 1.54 stands for when multiplied by 100(wet volume of concrete)

the get the dry volume of concrete.Thank you.

1.54 is constant

Deletehow much amount of water we will add for 150×150×150mm cube if the water cement ratio is 0.45 I want in kgs

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22/1.25=17.6 cement bags

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ReplyDeletewhy we take 1.54 for dry material? please proof it.

ReplyDeletewhy we take 1.54 for dry material? please proof it.

ReplyDelete"1.54" 0.54 is basically shrinkage factor of wet material you want to convert in dry material. 33% is total shrinkage of mixed material so

ReplyDelete1-0.33=0.67

1/0.67 = 1.492537

Wastage of Material is 3% during mixing etc.

0.03/0.67 = 0.044776

1.492537+0.044776 = 1.537313 say 1.54

Thanks

"1.54" 0.54 is basically shrinkage factor of wet material you want to convert in dry material. 33% is total shrinkage of mixed material so

ReplyDelete1-0.33=0.67

1/0.67 = 1.492537

Wastage of Material is 3% during mixing etc.

0.03/0.67 = 0.044776

1.492537+0.044776 = 1.537313 say 1.54

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ReplyDeleteCement, Sand, 10mm, 20mm

1 1.635 1.657 2.031

Bulk Density/m3

1713.58 ---------1566.67 1572.58

Crushed Sand----CA 10MM --------CA 20MM

So now in one m3 Dry material is ?????????

Cement, Sand, 10mm, 20mm

ReplyDelete1 1.635 1.657 2.031

Bulk Density/m3

1713.58 ---------1566.67 1572.58

Crushed Sand----CA 10MM --------CA 20MM

So now in one m3 Dry material is ?????????

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