grade of concrete

Grade of Concrete – Their Ratio, Uses & Suitability

Grade of Concrete is the classification of concrete according to its compressive strength.

For making concrete we use cement, sand, aggregate, and water which are mixed with certain ratio and concrete is cast and put in a cube of 150 mm size and put in a water bath for 28 days and afterward, it is tested in a compression test. The compressive stress result is known as “grade of concrete’. It is expressed in N/mm²

Concrete grades are denoted by M10, M20, M30 and so on according to their compressive strength.

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As Per Indian Standards:

Grade of Concrete

The “M” refers Mix and Number after M (M10, M20) Indicates the compressive strength of concrete after 28 days of curing and testing.

M indicates the proportion of materials like Cement: Sand: Aggregate (1:2:4) or Cement: Fine Aggregate: Coarse Aggregate.

If we mention M10 concrete, it means that the concrete has 10 N/mm2 characteristic compressive strength at 28 days.

In the designation of concrete mix M  to the mix and the number to the specified compressive strength of 150 mm size cube at 28 days, expressed in N/mm^2.

Read More: HOW TO CHECK COMPRESSIVE STRENGTH OF CONCRETE

Grade of Concrete as Per British/European standards:

As per  BS 8500-2 British/European standards The grade of concrete is  denoted as C10, C15, C20, C25, etc., ‘C’ which means ‘Concrete Strength class’ and number behind C refers to characteristic Compressive strength of Concrete in N/mm2 @ 28 days when tested with the 15 cm dia. & 30 cm height cylinder in a direct compression test.

Grade of Concrete

The grade of concrete is also denoted as C16/20, C20/25, C25/30, etc., which means Concrete Strength Class (C) the number behind C refers to Compressive strength of Concrete in N/mm2 when tested with Cylinder / Cube.

Different mix proportions of the materials used to make concrete namely

  • Cement
  • Coarse aggregate
  • Fine aggregate
  • Water

Result in concretes with different properties.

Following are the standard concrete grade with their mix proportions and strength.

Grades of  Concrete Mix Ratio (cement : sand : aggregates) Compressive Strength
MPa (N/mm2)
psi
Grades of  Concrete    
M5 1 : 5 :10 5 MPa 725 psi
M7.5 1 : 4 : 8 7.5 MPa 1087 psi
M10 1 : 3 : 6 10 MPa 1450 psi
M15 1 : 2 : 4 15 MPa 2175 psi
M20 1 : 1.5 : 3 20 MPa 2900 psi
Standard Grade of Concrete    
M25 1 : 1 : 2 25 MPa 3625 psi
M30 Design Mix 30 MPa 4350 psi
M35 Design Mix 35 MPa 5075 psi
M40 Design Mix 40 MPa 5800 psi
M45 Design Mix 45 MPa 6525 psi
High Strength Concrete Grades    
M50 Design Mix 50 MPa 7250 psi
M55 Design Mix 55 MPa 7975 psi
M60 Design Mix 60 MPa 8700 psi
M65 Design Mix 65 MPa 9425 psi
M70 Design Mix 70 MPa 10150 psi

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The selection of the concrete grade depends on the situation and uses:

Concrete Grade N/mm2 Ratio  Cement, Sand and Aggregates   Usage
10 1:3:6 Blinding concrete
15 1:2:4 Mass concrete
20 1:1.5:3 Light reinforced concrete
25 1:1:2 Reinforced concrete/precast
30 Concrete Mix Design Heavy Reinforced concrete/pre-cast
35 Concrete Mix Design Pre-stressed/pre=cast concrete
45 Concrete Mix Design Very heavy reinforced concrete/pre-cast/prestressed

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