Grade Of Concrete : Different Grades Of Concrete M25, M30

What is Grade of Concrete?

Grade of concrete denotes the strength required for construction. For example, the M30 grade indicates that the compressive strength required for construction is 30MPa. The very first letter in grade “M” is the mix and 30 is the required strength in MPa.

Based on various laboratory tests, the grade of concrete is presented in Mix Proportions. As an example, for the M15 grade, the mix proportion can be 1:2:4, where 1 is the ratio of cement, 2 is the ratio of sand, and 4 is the ratio of coarse aggregate based on quantity or weight of materials.

The strength is measured with concrete cubes or cylinders by civil engineers at the construction site. Cube or cylinders are made during casting of foundations, columns, beams, slabs, or any other structural member and after setting it is cured for a maximum of 28 days. Then compressive strength test is conducted to find the strength.
Normal grades of concrete are M15, M20, M25, and so on. For plain cement concrete works, usually, M15 is used. For reinforced concrete construction minimum M20 grade of concrete is used.

 

Concrete Grade

 

 Mix Ratio Compressive Strength MPa (N/mm2) Compressive Strength Psi
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
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
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

There are two types of concrete mixes, nominal mix, and design mix. The nominal mix uses for normal construction works such as small residential buildings. One of the most popular nominal mix is the proportion of 1:2:4.

Design mixed concrete is those for which mix proportions finalize based on cylinder or cube lab tests for its compressive strength. This procedure is also called mix design. These tests conduct to choose a suitable mix based on locally available material to get the required strength as per structural design.