### Concrete Mix Design

Concrete is a composite mix consisting of cement, sand, and aggregates. Concrete mix design is the procedure for finding the right amounts of these materials to achieve the desired strength.

The exact design of the concrete mix makes concrete construction economical. Large constructions such as bridges and dams require a large amount of concrete, using the correct number of components makes the structure economical.

To calculate or find the correct amount of cement, sand and aggregates needed in **1m3** of concrete; you need to know the different grades of concrete.

**According to IS456: 2000,** different grades of concrete are classified into M5, M7.5, M10, M15, etc., while M stands for Mix and the number after M stands for Characteristic Compressive Strength (fck) of concrete in N / mm2. @ 28 days when verified with a 15 cm × 15 cm × 15 cm cube in the direct compression test.

#### Volume Of Concrete = 1m³

Now let us consider M20 grade concrete

1 -> Cement

1.5 -> fine Aggregates ( Sand)

3 -> Course Aggregates (gravel)

Then we have to add all the valume to know the Valume = 1+1.5+3 = 5.5

As we know that during concreting when we place wet concrete, it gets harden after certain standard time. Considering the same it had be decided upon by Civil design Engineers to take a factor of safety ranging from 1.54 to 1.57 to counter that shrinkage.

Volume of dry Concrete = 1.54 to 1.57 times of wet concrete.

Dry volume of Concrete = 1m³× 1.54

= 1.54 m³

Note -> For dry volume Multiply by 1.54

test.

#### Volume of Cement:

=(Cement / cement +sand+Aggregates)1.57 =(1 /1+1.5+3)×1.57

= 0.28 M³

1M³ Cement = 1440kgs

0.28 m³ cement = 0.28 x 1440
= 403.2 kgs

No. Of Cement Bags Required
For 1m³ Of Concrete = 403.2/50

=8.06 ~ 8 Bags

#### Valume Of Sand :

= (Sand / Cement+Sand+Aggregates) × 1.57

=(1.5/1+1.5+3)×1.57

= 0.42 m³

1m³ Sand = 1600kg

0.42 m³Sand = 0.42 x 1600

= 672 kgs

Weight Of 1 cft Sand -> 43.30Kg
= 672/43.30

= 15.51 ~ 16 cft.

test.

#### Volume Of Aggregate:

= (Aggregates /Cement +Sand +Aggregates)×1.57 =(3/1.1.5+3) x 1.57

= 0.85 m³

1M³ Aggregates = 1800kg

0.85 m³ Weight ofAggregates = 0.85 x 1800

=1356 kgs

Weight of 1 cft Aggregates = 68.15 kg

= 1356/68.15 =21.47 ~ 21 cft.

test.

###
Amount of water required for 1 m³ of concrete:

To make concrete, Required amount of water is added. The amount of water depends on climatic factors and the required workability. Generally, we

maintain a water-cement ratio of 0.35-0.50.

Remember, the above values may change depending on the moisture content present in the sand and aggregate.

Cement required for 1m³ of concrete = 400Kgs
Assume that the ratio A / C = 0.50 (50% of the cement)
Water needed for 1m3 of concrete.

= 400 x 0.50

Amount of water required for 1 m3 of concrete = 200 kg = 200 liters

**Summary**:

8 bags of cement required for 1 m³ of M20 grade concrete.
672 kg of Sand required for 1 m³ of M20 grade concrete.
1356 kg of 20mm Aggregate is required for 1 m³ of M20 grade concrete.
200 litres of water is required for 1 m³ of M20 grade concrete

test.

Materials Calculation