Concrete
Concrete is defined as composite material created by mixing cement, coarse aggregate (gravel, stone, brick chips, etc), fine aggregate (sand), water, admixture etc in specific mixing proportions.
Concrete is easy to produce and can be formed into various shapes and sizes. Concrete is reasonable, low cost & Instantly mixed material.
What is the Grade of Concrete?
A grade of concrete is a numeric value, which represents the compressive strength of concrete, obtained after 28 days of construction with proper quality control.
M20 represents the compressive strength of that cube having a size (150mm x 150mm x 150mm) at 28 days is 20 Mpa (N/mm^{2}).
As per IS 456:2000, concrete is graded into 15 types as given in the table below.
Group  Designation  Characteristic Compressive Strength (F_{ck}) at 28 days (N/mm^{2}) 
Ordinary Concrete  M 10
M 15 M 20 
10
15 20 
Standard Concrete  M 25
M 30 M 35 M 40 M 45 M 50 M 55 
25
30 35 40 45 50 55 
High Strength Concrete  M 60
M 65 M 70 M 75 M 80 
60
65 70 75 80 
Grades of concrete are represented by the letter M which means mix and, number that is the compressive strength of that concrete at 28 days in Mpa (N/mm^{2}).
Concrete Mix Ratio
Concrete mix ratio is define as the proportion of concrete’s ingredients such as cement, sand, aggregates and water.
As per IS code, there are two types of concrete mix like nominal concrete mix and standard concrete mix.
Nominal Concrete Mix : The nominal concrete mix may be used for grade of concrete such as M5, M10, M 15, M20 and M25.
Designed Concrete Mix : In designed concrete mix, the proportion of ingredients of concrete is found out to get specified properties of concrete.
Various Types of Concrete Grade with Concrete Mix Ratio and Compressive Strength
Normal Concrete Grades
Grade of Concrete  Mix Ratio (Cement : Sand : Aggregates)  Compressive Strength At 28 Days (N/mm^{2} or MPa) 
M5  1:5:15  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 Grades
Grade of Concrete  Mix Ratio (Cement : Sand : Aggregates)  Compressive Strength At 28 Days (N/mm^{2} or MPa) 
M25  1:1:2  25 
M30  Design Mix  30 
M35  Design Mix  35 
M40  Design Mix  40 
M45  Design Mix  45 
High Strength Concrete Grades
Grade of Concrete  Mix Ratio (Cement : Sand : Aggregates)  Compressive Strength At 28 Days (N/mm^{2} or MPa) 
M50  Design Mix  50 
M55  Design Mix  55 
M60  Design Mix  60 
M65  Design Mix  65 
M70  Design Mix  70 
Uses of Different Grades of Concrete
Ordinary Grade of Concrete : M5, M10 and M15 are used as PCC (Plain Cement Concrete) in foundation. M20 is used as RCC work such as beam, column, slab and footing etc.
Standard Grade Concrete : M25, M30 and M35 used for heavy RCC work such as foundation, columnfooting, beams and slabs.
Grade M40 is used for prestressed concrete work. M45 and M50 grades are used for concrete roads, runways, prestressed concrete girders and prestressed beams etc. M55 is used for prestressed concrete girder and bridge piers etc.
High Strength Concrete : M55 is used for prestressed concrete girder and bridge piers etc. M60, M65 and M70 are used for RCC work where high compressive strength is needed like long span bridges, high rise building and coastal construction etc.
So, friends, I hope that you understand different grades of concrete. If you found this article useful, please share it.
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FAQs
What is a grade of concrete?
A grade of concrete is a numeric value, which represents the compressive strength of concrete, obtained after 28 days of construction with proper quality control. M20 represents the compressive strength of that cube having a size (150mm x 150mm x 150mm) at 28 days is 20 Mpa (N/mm2).
What are the different types of grade of concrete?
As IS 456 : 2000, Ordinary Concrete : M10, M15, M20 Standard Concrete : M25, M30, M35, M40, M45, M50, M55 High Strength Concrete : M60, M65, M70, M75, M80
What are the 7 grades of concrete?
As IS 456 : 2000, For Ordinary Concrete : M10, M15, M20 For Standard Concrete : M25, M30, M35, M40, M45, M50, M55 For High Strength Concrete : M60, M65, M70, M75, M80
What is the M20 grade of concrete?
M20 represents the compressive strength of that cube having a size (150mm x 150mm x 150mm) at 28 days is 20 Mpa (N/mm2).
Refference :

Concrete Technology: Theory and Practice – Book by Murari Lal Gambhir
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