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What is Grade of Concrete?

Grade of concrete is defined as the minimum strength the concrete must posses after 28 days of construction with proper quality control. Grade of concrete is denoted by prefixing M to the desired strength in MPa. For example, for a grade of concrete with 20 MPa strength, it will be denoted by M20, where M stands for Mix.

These grade of concrete is converted into various mix proportions. For example, for M20 concrete, mix proportion will be 1:1.5:3 for cement:sand:coarse aggregates.

 How to select suitable concrete grade for construction?

Grade of concrete construction is selected based on structural design requirements. There are two types of concrete mixes, nominal mix and design mix.

Nominal mix concrete are those which are generally used for small scale construction and small residential buildings where concrete consumption is not high. Nominal mix takes care of factor of safety against various quality control problems generally occurring during concrete construction.

Design mix concrete are those for which mix proportions are obtained from various lab tests. Use of design mix concrete requires good quality control during material selection, mixing, transportation and placement of concrete. This concrete offers mix proportions based on locally available material and offers economy in construction if large scale concrete construction is carried out.

Thus, large concrete construction projects uses design mix concrete.

So, suitable grade of concrete can be selected based on structural requirements. Nominal mixes for grades of concrete such as M15, M20, M25 are generally used for small scale construction.

Large structures have high strength requirements, thus they go for higher grades of concrete such as M30 and above. The mix proportions of these concretes are based on mix design.

Regular Grades of Concrete and their Uses

Regular grades of concrete are M15, M20, M25 etc. For plain cement concrete works, generally M15 is used. For reinforced concrete construction minimum M20 grade of concrete are used.

Concrete GradeMix RatioCompressive Strength
MPa (N/mm2)psi
Normal Grade of Concrete
M51 : 5 : 105 MPa725 psi
M7.51 : 4 : 87.5 MPa1087 psi
M101 : 3 : 610 MPa1450 psi
M151 : 2 : 415 MPa2175 psi
M201 : 1.5 : 320 MPa2900 psi
Standard Grade of Concrete
M251 : 1 : 225 MPa3625 psi
M30Design Mix30 MPa4350 psi
M35Design Mix35 MPa5075 psi
M40Design Mix40 MPa5800 psi
M45Design Mix45 MPa6525 psi
High Strength Concrete Grades
M50Design Mix50 MPa7250 psi
M55Design Mix55 MPa7975 psi
M60Design Mix60 MPa8700 psi
M65Design Mix65 MPa9425 psi
M70Design Mix70 MPa10150 psi

Read More:

What are the Types of Concrete? What are their Applications?

Concrete Calculator – Calculate Concrete for Slab, Beam, Column and Footings

Concrete – Definition, Components, Manufacture, Construction and Articles

Why Select Reinforced Concrete as Construction Material for a Structure?

What is Foundation in Construction? Purpose and the Functions of Foundations

Quantities of Materials Per Cubic Meter of Concrete and Mortar Mix Proportions

About Gopal MishraVerified

Gopal Mishra is a Civil Engineer from NIT Calicut and has more than 10 years of experience in Civil Engineering and Construction. He is the founder of The Constructor.

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