# Different Grade of Concrete, their Mix ratio and Uses.

## What is meant by Grade of Concrete?

The grade of concrete is defined as the minimum strength the concrete should have after the completion of 28 days of the construction period with proper quality control. The Grade of Concrete is denoted by MPa, where M stands for Mix and the MPa denotes the overall strength.

For example, for a grade of concrete with a strength of 20 MPa, it would be denoted by M20, where M stands for Mix and 20 is the overall strength of the concrete in Newton.

Major ingredients of concrete are binding material (like cement, lime), fine aggregate (sand), coarse aggregates (crushed stone, jelly), and water.

Depending on the proportion of the material, the strength of the concrete varies. And it is possible to determine the proportion of the ingredients for a particular strength by mix design procedure.

Generally, the grade of concrete is divided into three different categories viz. normal grade of concrete, standard grade of concrete, and high strength grade of concrete. The table below shows the grade of concrete and its mixing ratio and its corresponding compressive strength after 28 days of construction.

#### Characteristic Compressive Strength Fck at 28 days MPa(psi)

M5 1:5:10 05 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
M2o 1:1.5:3 20 MPa 2900 psi

#### Characteristic Compressive Strength Fck at 28 days MPa(psi)

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:

#### Characteristic Compressive Strength Fck at 28 days MPa(psi)

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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## Uses of Different Grades of Concrete

### 1. Ordinary Grade of Concrete Uses:

M5, M10, M15 grades of concrete are mostly used in Plain Cement Concrete (PCC) works as bed concrete below column footing. While M20 grade concrete is used for RCC works (for mild exposure) such as the construction of slabs, beams, columns, footings, etc.

### 2. Standard Grade of Concrete Uses:

M25, M30, M35, M40, M45,  fall in the category of the standard grade of concrete. The concrete grades ranging from M25 to M35 are mostly used to construct RCC works such as footings, columns, slabs, beams, etc. Whereas the higher grades like M40 & M45 are used for the construction of commercial structures, pre-stressed concrete members, Runways, Concrete Roads (PQC), Pressurised Concrete Girders, RCC Columns, Pressurised beams, etc.

### 3. High Strength Grade of Concrete Uses:

High strength grade of concrete is used in RCC work where high compressive strength is required such as tall buildings, long-span bridges, construction in aggressive environments, spillways of dams, etc.