[2019] Grades of Concrete | Types | Concrete Mix Ratio Table

Grades of concrete

Grades of concrete are related to compressive strength and composition of concrete. Various types of concrete grades are available in Civil Engineering.

GRADES OF CONCRETE

After the completion of this article, you will be able to answer the following questions:

• Can you perfectly define the term"grades of concrete"?
• How many grades of concrete are there in civil engineering?
• What do you mean by M30 concrete?
• What does "M" represent in M30 concrete?
• What is the difference between M30 and C30 grades of concrete?
• What is the concrete mix ratio for different types of concrete grades?

What is meant by "Grades of concrete"?

As a civil engineer, you may have noticed the term "Grades of concrete" or "M20 concrete" many times.

Maybe you could have ignored the term or you don't have detailed knowledge about 'Grades of concrete'.

Hey! don't worry, here I shared everything that a civil engineer must know about "Grades of concrete". 

Let's start together.

Grades of concrete represent the strength of concrete.

More specifically it represents that the compressive strength of a 15cm concrete cube sample after 28 days of curing.

'Grades of concrete' not just define the compressive strength but also define the concrete mix ratio or composition of concrete.

Hold on, everything will be explained thoroughly.

Okay, let's back to the point.

This Grade of concrete denoted by prefixing and followed by the number.

Example: M10, M15, M20, M30, etc...

Where M is prefixing and is stand for "MIX".

Similarly, 10, 15, 20, 30 are the number used to denote the compressive strength in N/mm2.

Now we can easily conclude that meaning of M30 grade of concrete.

M30 GRADE OF CONCRETE →

"Minimum compressive strength of a 15cm concrete cube is 30 N/mm2 after 28 days of curing.

One thing you should keep in mind that Grade of concrete can be denoted by M20 as well as C20.

As per Indian standard "M" is used to denote the grade of concrete. Similarly 'C' is generally used by British standard.

Well, there is one more major difference.

Let me explain through an example.

"C20"- characteristic strength of concrete cylindrical sample (15 cm dia* 30cm of height) after 28 days of curing.

"M20"- characteristic strength of concrete cube (15 cm cube) after 28 days of curing.

Yes, the main difference is based upon the type of sample used in each standard.

In the case of British standard, the cylindrical concrete sample is used whereas Concrete cube sample is used for Indian standard.

Okay, till now we have defined the meaning of grade of concrete.

Now let's move forward.

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Concrete Mix ratio table

I already mentioned above that the grades of concrete also define the composition or mix-ratio of concrete.

And we have recently covered that specific grade of concrete gives us a specific amount of compressive strength.

For an Example, M10 concrete has a strength of 10N/mm2.

But the question that arises is 'How can we determine the mix ratio of concrete from the grade of concrete'?

Well, The Indian standard (IS CODE-456:2000) has given us a table from where we can figure out the proportion of cement, fine aggregates, and coarse aggregate.

CONCRETE  GRADE	MIX RATIO	CHARACTERISTIC-COMPRESSIVE        STRENGTH OF CONCRETE
M5	1:5:10	5 N/mm2
M7.5	1:4:8	7.5 N/mm2
M10	1:3:6	10 N/mm2
M15	1:2:4	15 N/mm2
M20	1:1.5:3	20 N/mm2
M25	1:1:2	25 N/mm2
M30	DESIGN MIX	30 N/mm2
M35	DESIGN MIX	35 N/mm2
M40	DESIGN MIX	40 N/mm2
M45	DESIGN MIX	45 N/mm2
M50	DESIGN MIX	50 N/mm2
M55	DESIGN MIX	55 N/mm2
M60	DESIGN MIX	60 N/mm2
M65	DESIGN MIX	65 N/mm2
M70	DESIGN MIX	70 N/mm2
M75	DESIGN MIX	75 N/mm2
M80	DESIGN MIX	80 N/mm2

As per Indian standard, there are three major groups of concrete such as

1. ordinary concrete (M10, M15, M20)
2. standard concrete (M25, M30, M35, M40, M45, M50, M55)
3. high-strength concrete (M60, M65, M70, M75, M80)

As you can see each grade of concrete represent some specific mix ratio (only for nominal mix).

For an example, M20 grade of concrete defines a mix ratio of 1:1.5:3 which means for every 1 part of cement, 1.5 part of sand and 3 part of coarse aggregates is mixed.

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In concrete technology, there are two types of mixes available-

1. Nominal mix.
2. Design mix.

Nominal mixes are those whose mix ratio is pre-defined which includes grades of concrete up to M25.

Nominal mix-M5, M7.5, M10, M15, M20, M25.

While further breakdown, we can say that the proportion of cement, sand, and coarse aggregates of concrete grade up to M25 are already defined and constant.

Nominal mixes are adopted for the small scale of construction work where the required amount of concrete is not so high.

The nominal mix ratio of different grades of concrete is shown below-

NOMINAL MIX RATIO OF CONCRETE UP TO M25

Similarly, Design mix is those whose mix ratio proportion is obtained from the various lab test.

Design mix- M30, M35, M40, M45, M50, M55, M60, M65, M70, M75, M80.

Here one thing you must remember that the mix proportion of cement, sand and coarse aggregates are not predefined. 

This mix proportions can be obtained by the various lab test.

These proportions can be vary depending upon many Factor such as the process of concreting, properties of concrete, quality of the material, etc.

A large type of construction work highly depends on the design mix of concrete where high strength is the first priority.

Comment below if you still have any unanswered question. Feel free to share.

That's all information regarding Grades of concrete.

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