Concrete is prepared by mixing cement, sand (fine aggregate), and aggregate (coarse aggregate) with water. The M20 grade of concrete represents the mix ratio of 1:1.5:3, that is, 1 part of cement, 1.5 parts of sand, and 3 parts of aggregate.
Well, the following procedure is a step-by-step process to calculate how much of each component is required in order to prepare the M20 grade of concrete.
Step by Step Cement calculation for m20 concrete
Q) Calculate cement, sand and aggregate for 1 meter cube of concrete of M20 grade of concrete.
Given,
Grade of concrete = M20 Grade (1:1.5:3)
Volume of Concrete Taken = 1 meter cube
Let’s start,
Step 1: Choose the Mix Ratio of Concrete
The mix proportion in M20 grade concrete is 1:1.5:3 by volume, with cement, sand, and aggregate, respectively. It means that every 1 part of cement needs 1.5 parts of sand and 3 parts of aggregate.
Note: The mix ratio is always calculated with respect to volume and not with respect to weight.
Step 2: Calculate the Total Dry Volume of Concrete
Assume you need to mix 1 m³ of concrete. Increase the concrete volume to take the approx. 52 % of voids and wastage.
Total Volume = 1 + 0.52 =1.52 m³
Note: Additional volume includes the volume of voids between the aggregate and the loss of volume during mixing
Step 3: Calculate the Cement Quantity
This is obtained by multiplying the total volume by the ratio of cement in the mix and dividing by the summation of the mix ratio. Thus,
Cement quantity = 1/5.5 × 1.52 = 0.276 m³
Since 1 m³ of cement = 1440 kg and
1 bag of cement = 50 kg, to change to bags, multiply by 1440 and divide by 50.
Bags of cement = 0.276 × 1440 ÷ 50 = 7.94 bags
Note: Round off to 8 bags for practical purposes.
Step 4: Calculate Sand Quantity
Since the mix is 1:1.5:3 for cement:sand:aggregate, the quantity of sand will be determined just as in the case of cement but using the sand ratio.
Quantity of Sand = (1.5 / 5.5) × 1.52 = 0.414 m³
Convert this volume to weight, because 1 m³ of sand = 1600 kg.
Sand in kg = 0.414 × 1600 = 662.4 kg
Note: Always convert the volume to weight for ease during mixing.
Step 5: Calculate the Aggregate Quantity
Similarly, the aggregate quantity can be determined using the aggregate ratio in the mix given as 3 parts.
Aggregate quantity = (3/5.5) × 1.52 = 0.828 m³
Now, convert this volume to weight since 1 m³ of aggregate = 1450 kg.
Aggregate in kg = 0.828 × 1450 = 1201 kg
Step 6: Water-Cement Ratio
The water-cement ratio for M20 grade concrete is generally 0.5. That is to say, per 1 kg of cement, it requires 0.5 kg of water.
Water required = 0.5 × weight of cement in kg
Water in liters = 0.5 × 7.94 × 50 = 198.5 liters
Note: Water content may vary slightly depending on site conditions and workability requirements.
Conclusion
The mix ratio of concrete may depend on several factors like temperature, humidity, size of ingredient, etc. In short, to prepare 1 cubic meter of M20 grade concrete, you will need approximately:
8 bags of cement – 400 kg
662 kg sand
1201 kg aggregate
198.5 liters water
I hope this article on “Cement calculation for m20 concrete” remains helpful for you.
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