What Is Grade of Concrete & Its Ratio for Mix

What Is the Grade of Concrete?

Grades of concrete are defined by the concrete mix proportion and the minimum strength of concrete at end of 28 day curing period.

The Concrete Grade 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 that 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) Indicating 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 the 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

Resulting 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

Conclusion:

In conclusion reinforced cement concrete is a widely used construction material which combines the strength of concrete and the tensile strength of steel reinforcement, RCC is essential for building bridges, building dams, and foundations.

By utilizing mix proportions, sound construction practices, RCC structure can be constructed to be robust and long lasting..

In conclusion the grade of concrete refers to the quality of the concrete and strength of the concrete mixture used in construction projects, also the concrete grade is denoted by a numerical value such as M7.5, M10, M20, M30 and so on and the letter “M” is stand for mix and the number represent its compressive strength of concrete in unit (MPa).

It is essential to determine the appropriate grade of concrete and to ensure that the structure can withstand the environmental conditions and anticipated loads.

The ratio for the mix concrete plays a crucial role in determining the its grade of concrete, the mix ratio is representing the proportion of different ingredients which is used in the concrete mixture such as cement, fine aggregate, coarse aggregate, sand, water and admixture.

The mix ratio is expressed the weight or volume of each ingredient relative to the total volume or weight of mixture.

The choice of mix ratio is depending on various factors such as desired strength of the concrete, availability of material, nature of work.

Watch Video: What is the Grade of Concrete and Different Types used in Construction

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