Different Grades of Concrete

Generally, concrete is denoted as M20, M25, M30 so on.

They are decided by their requirements. But what exactly M** concrete is?

What is meant by Grade of Concrete?

The grade of concrete is nothing but their compressive strength measurement after 28 days of setting.

 

Why is it mentioned like M**?

M denotes concrete mix and the number followed by that is known as concrete compressive strength. For instance, M20 means concrete mix ratio that has 20 N/mm² or Mpa compressive strength.

So M30 means concrete mix ratio that has 30 N/mm² compressive strength. As simple as that.

Mix Ratio is a proportion of concrete micro-ingredients such as Cement, Sand, and Coarse Aggregate.

For Example, M20 means a mix ratio of 1:1.5:3 (1 part cement, 1.5 part sand & 3 part coarse aggregate) concrete which has a compressive strength of 20 N/mm².

Concrete Grade And Mix Ratio Table

Type of Concrete	Grade of Concrete	Mix Ratio	Compressive strength of 150mm cube @ 28 Days
Ordinary Concrete	M5	1:5:10	5
	M7.5	1:4:8	7.5
	M10	1:3:6	10
	M15	1:2:4	15
	M20	1:1.5:3	20
Standard Concrete	M25	1:1:2	25
	M30	Design Mix	30
	M35	Design Mix	35
	M40	Design Mix	40
	M45	Design Mix	45
	M50	Design Mix	50
High Strength Concrete	M55	Design Mix	55
	M60	Design Mix	60
	M65	Design Mix	65
	M70	Design Mix	70
	M75	Design Mix	75
	M80	Design Mix	80

As you can see from the table, up to M25 only we can do site mixing. Above that is a design mix since we can’t measure materials infractions by hand measurement.

How to select suitable concrete grade for construction?

The selection of concrete depends on the requirement of structural need.

That means it is based on the types of loads that are going to act on the structure. It includes 

• Dead load
• Live Load
• Earthquake Force
• Snow load
• Wind load

 

As per IS 456, the recommended minimum grade of concrete for RCC is M20.

Grade of Concrete	Uses
M5, M7.5  – Lean Mix concrete	Used as filling material such as basement filling
M10 & M15	Used for PCC and non-structural members such as foundation bed
M20	Used for RCC structural members such as beam, column & footing
M25	Used for small construction residential or 3 floors residential
Other Design Mix	Design mixes are used where high compressive strength is demanded by structure

Up to M20 grade concrete, we use general types of cement.

There are some other special grades of cement available for specific needs. Like seashore building, industrial concrete, precast works, nuclear power plants. In these areas, special grades of concrete will be used which are chemical resistant, corrosion-resistant.

Happy Learning 🙂