What is characteristic strength (fck) of concrete mix design, what is meant by fck concrete, in this topic we know about what is fck of concrete mix design and what is full form of fck in concrete. There is a need of know about value of characteristic compressive strength (fck) of concrete for every civil engineer or architect designer for building construction work.

fck full form in concrete is characteristic compressive strength of concrete. when we calculate concrete and estimate value and design for their project we need fck value of concrete.

**What is fck of concrete & their full form**

FCK is characteristics of compressive strength of different grade of concrete measured in N/mm2 or mega pascal by CTM machine after casting of 28 days of curing, like fck value for m20 is 20N/mm2.

fck of concrete is the compressive strength of different types of concrete, measured in N/mm2 or MPa with the CTM machine after 28 days of curing.

fck of concrete means the compressive strength of different types of concrete (M20, M25, M30 and etc), measured in N/mm2 or MPa with the CTM machine after 28 days of curing.

**Fck full form** in civil engineering is characteristics of compressive strength.

What is characteristic strength (fck) of concrete,we have different grade of concrete like **M20, m25, M30 ,m35 ,m40 ,m45 ,m50** and so more—-

**fck value for M20**: The fck value for M20 concrete is about 20 MPa (20 N/mm2) after 28 days, 18 MPa (18 N/mm2) after 14 days, 13 MPa (13 N/mm2) after 7 days and 8 MPa (7 N/mm2) after 3 days curing.

M20 grade of concrete, in which M stand for mix and numerical figure 20 is stand for characteristics of compressive strength, so fck value for M20 concrete is 20 N/mm2 or 20 m.pascal.

**fck value for M25: **The fck value for M25 concrete is about 25 MPa (25 N/mm2) after 28 days, 22.5 MPa (22.5 N/mm2) after 14 days, 16.5 MPa (16.5 N/mm2) after 7 days and 10 MPa (10 N/mm2) after 3 days curing.

M25 grade of concrete, in which M stand for mix and numerical figure 25 is stand for characteristics of compressive strength, so fck value for M25 concrete is 25 N/mm2 or 25 m.pascal.

**fck value for M30: **The fck value for M30 concrete is about 30 MPa (30 N/mm2) after 28 days, 27 MPa (27 N/mm2) after 14 days, 19.5 MPa (19.5 N/mm2) after 7 days and 12 MPa (12 N/mm2) after 3 days curing.

M30 grade of concrete, in which M stand for mix and numerical figure 30 is stand for characteristics of compressive strength, so fck value for M30 concrete is 30 N/mm2 or 30 m.pascal.

**fck value for M35: **The fck value for M35 concrete is about 35 MPa (35 N/mm2) after 28 days, 31.5 MPa (31.5 N/mm2) after 14 days, 22.75 MPa (22.75 N/mm2) after 7 days and 14 MPa (14 N/mm2) after 3 days curing.

M35 grade of concrete, in which M stand for mix and numerical figure 35 is stand for characteristics of compressive strength, so fck value for M35 concrete is 35 N/mm2 or 35 m.pascal.

**fck value for M40: **The fck value for M40 concrete is about 40 MPa (40 N/mm2) after 28 days, 36 MPa (36 N/mm2) after 14 days, 26 MPa (26 N/mm2) after 7 days and 16 MPa (16 N/mm2) after 3 days curing.

M40 grade of concrete, in which M stand for mix and numerical figure 40 is stand for characteristics of compressive strength, so fck value for M40 concrete is 40 N/mm2 or 40 m.pascal.

For example we have M20 grade of concrete, in which M stand for mix and numerical figure 20 is stand for its compressive strength, so characteristic compressive strength (fck) of M20 concrete is 20 N/mm2 and their fck concrete value is 20 N/mm2 or 20 M pascal. and for M 25 grade of concrete compressive strength is 25 N/mm2.

fck concrete value for different grade of concrete are following:

● 5N/mm2 or 5MPa – M5

● 7.5N/mm2 or 7.5MPa – M7.5

● 10N/mm2 or 10MPa – M10

● 15N/mm2 or 15MPa – M15

● 20N/mm2 or 20MPa – M20

● 25N/mm2 or 25MPa – M25

● 30N/mm2 or 30MPa – M30

● 35N/mm2 or 35MPa – M35

**fck of concrete compressive strength testing machine (CTM)**

The characteristics of compressive strength (fck) of cube concrete can be tested with the help of compressive testing machine (CTM)in the laboratory.

In the test process of comprehensive strength of concrete cube suppose we have 100 concrete cube of M20 grade of concrete. All the concrete cube tested with compressive testing machine than following result is obtained

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**fck of concrete Test ,Rules and result **

1) if 5% and less of concrete cube of M20 grade of concrete fail to withstand with compression pressure of 20N/mm2 in CTM machine in laboratory and 95% and more of concrete cube of M20 grade of concrete with stand with compression pressure of 20N/mm2 in CTM machine than it is called as successful of your test of concrete and their characteristics of comprehensive strength of M 20 grade of concrete is about 20 N/mm2

2) if more than 5% of concrete cube of M20 grade of concrete fail to withstand with compression pressure of 20N/mm2 in CTM machine in laboratory and less than 95% concrete cube of M20 grade of concrete with stand with compression pressure of 20N/mm2 in CTM machine than it is called as fail of your test of concrete and their characteristics of comprehensive strength of M 20 grade of concrete is less than 20 N/mm2.

**Conclusions:-**

fck of concrete is the compressive strength of different types of concrete, measured in N/mm2 or MPa with the CTM machine after 28 days of curing.