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Grade of Concrete
Grades of concrete are defined by the concrete mix proportion and the minimum strength of concrete at end of 28 days curing period. The grade of concrete is can be known by calculating the compressive strength of concrete in Mpa, where M stands for mix and the MPa denotes the overall strength
There are different types of concrete mix which are based on concrete classification according to its compressive strength.
For making concrete we use cement, sand, aggregate, and water which are mixed with a 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 testing machine. The compressive stress result is known as the “grade of concrete“. It is expressed in N/mm²
The concrete grade is denoted by M10, M20, M30, and so on according to their compressive strength.
Read More: Concrete Mix Design Step By Step Full Calculation
Concrete Grade As Per Indian Standards
The “M” refers to 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
Concrete Grade 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 the 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.
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.
Concrete Classification
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 |
| Lower Grade 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 Grade of Concrete | |||
| 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 |
The Selection of the Grade of Concrete Depends on the Situation and Uses:
| Concrete Grade (N/mm2) | Ratio Cement, Sand, and Aggregates | Usage |
| 10 | 1:3:6 | PCC |
| 15 | 1:2:4 | PCC |
| 20 | 1:1.5:3 | Normal Construction 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 |
| 40 | Concrete Mix Design | Very heavy reinforced concrete/pre-cast/prestressed |
| 45 | Concrete Mix Design | Very heavy reinforced concrete/pre-cast/prestressed |
Watch Video: What is Grade of Concrete and Different Types used in Construction
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