Compressive Strength Of Concrete

Written By: Engr Sami Ullah Stanikzai (

In this Article Today I am teaching you That what is the compressive strength of concrete from 7 days to 28 days.

Compressive Strength Of Concrete.

But Remember one thing that the compressive strength of the concrete should be in N/mm2.  I made the also the video Lecture about this Article.Compressive strength has the same degree of importance when it comes to the evaluation of existing structures. Structural engineers used it for modeling different structural properties, such as tensile strength, and to predict the flexural and shear capacity of the elements. Other structural characteristics such as ductility and stiffness can be also defined as a function of compressive strength.

Note : Compressive strength of the concrete is depend on the Grade of concrete. Because different Grade of concrete his different compressive strength in 7 days 14 days or 28 days etc.

What is Grade of Concrete?

Grade of Concrete is denoted by : M5 , M7.5 , M10 , M10 , M15 , M20 , M25 , M30 , M35 , M40 , M45 ect are the compressive strength of concrete.

So here “M” Stands for Mix  And  “Number” shows the Show N/mm2.

For Example M25 Grade of concrete Compressive strength is 25N/mm2.

What is the  Minimum Compressive Strength of Concrete N/mm2 in 7 day’s

Compressive strength of concrete procedure :

For cube test two types of specimens either cubes of 15cm X 15cm X 15cm or 10cm X 10cm x 10cm depending upon the size of aggregate are used. For most of the works cubical moulds of size 15cm x 15cm x 15cm are commonly used.

This concrete is poured in the mould and tempered properly so as not to have any voids. After 24 hours these moulds are removed and test specimens are put in water for curing. The top surface of these specimen should be made even and smooth. This is done by putting cement paste and spreading smoothly on whole area of specimen.

These specimens are tested by compression testing machine after 7 days curing or 28 days curing. Load should be applied gradually at the rate of 140 kg/cm2 per minute till the Specimens fails. Load at the failure divided by area of specimen gives the compressive strength of concrete.

  • Before Starting construction work we have to Test the Concrete compressive strength in different days,
  • For that we have to make the concrete Cube which size should be  150 mm x 150 mm .
  • The concrete cube Should be fully vibrated and fully curing. Than we are able to find out the compressive strength of concrete in compression machine.

Below List for the compressive strength of concrete.

Grade of Concrete                                 Minimum Compressive Strength of concrete N/mm2 after 7 days

M10                                                                                                        7 N/mm2

M15                                                                                                        10 N/mm2

M20                                                                                                        13.5 N/mm2

M25                                                                                                         17 N/mm2

M30                                                                                                         20 N/mm2

M35                                                                                                         23.5 N/mm2

M40                                                                                                         27 N/mm2

M45                                                                                                          30 N/mm2

Compressive strength of concrete N/mm2 after 28 day’s

Grade of Concrete                                 Minimum Compressive Strength of concrete N/mm2 after 28 days

M10                                                                                                        10 N/mm2

M15                                                                                                        15 N/mm2

M20                                                                                                        20 N/mm2

M25                                                                                                         25 N/mm2

M30                                                                                                         30 N/mm2

M35                                                                                                         35 N/mm2

M40                                                                                                         40 N/mm2

M45                                                                                                          45 N/mm2

Note: If the 150 mm x 150 Concrete cube does not give you the above compressive strength of concrete so it mean that you did not fully vibrate the concrete cube therefore it can not able to give you the above Strength.

So the concrete cube Must be vibrate and Fully Curing with water than it will give you the standard strength which is required for any grade.














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