These grades of concrete are used in the following sectors:
a. Construction of high rise buildings, spillways of dams, long-span bridges, etc.
b. It can be used in the work where the environment is quite aggressive.
1.1.4. Tricks to remember the different mixture of grades of concrete
M5 has 1:5:10
M7.5 has 1:4:8
M10 has 1:3:6
M15 has 1:2:4
M20 has1:1.5:3
M25 has 1:1:2
From this list we can note;
a. The ratio of cement is constantly 1 for M5 to M25.
b. The ratio of sand is in descending order from 5 to 1.(except M20 of 1.5)
c. The ratio of aggregate is equal to 2 times of ratio of sand of grades.
Examples:
For M5,
5 part sand: ( 5×2) part aggregate
For M7. 5,
4 part sand: ( 4×2) part aggregate
And so on.
1.2. Grades of Concrete Based on British Standard (BS)
As per BS 8500-2; the grades of concrete is represented as C10, C20, C40, etc.
{ Note:
In C10 grade concrete
‘C’ represents Concrete Strength Class and 10 represents 10 N/mm² Compressive Strength of Concrete @ 28 days when tested with the 15cm dia & 30cm height cylinder in a direct compression test. }
1.2.1. Standard strength concrete grades
a. C10 Concrete Grade
It is also known as Gen1 concrete.
It gains 10 N/mm² compressive strength in 28 days.
It can be used in trench fills, general floor binding, agricultural formations and drainage.
It is not suitable for structural mass formations.
b. C15 Concrete Grade
It is also known as Gen2 concrete.
It gains 15 N/mm² compressive strength in 28 days.
It can be used in the construction of short walls, residential flooring, temporary structures, etc.
It is not suitable for large scale projects.
c. C20 Concrete Grade
It is also known as Gen3 concrete.
It gains 20 N/mm² compressive strength in 28 days.
It is used in the construction of lightweight foundations, internal floor slabs, driveways, garages, and sheds.
d. C25 Concrete Grade
It is also known as ST2.
It is used in residential and commercial building projects for the construction of foundations, reinforced bases, etc.
1.2.2. High-performance concrete grades
e. C30 Concrete Grade
It is also known as ST3 or PAV1.
It gains 30 N/mm² compressive strength in 28 days.
It is used in reinforced bases, pavement construction, etc.
f. C35 Concrete Grade
It is also known as PAV2.
It gains 35 N/mm² compressive strength in 28 days.
It is used in large scale projects and constructions.
g. C40 Concrete Grade
It gains 40 N/mm² compressive strength in 28 days.
It is used in the construction of large industrial support beams and foundations.
1.3. Grades of Concrete Based on European Standard
The grades of concrete are represented as C16/20, C20/25, C25/30, C30/45, etc. ; which means C represents Concrete Strength Class and the number behind C refers to Compressive strength of Concrete in N/mm² when tested with Cylinder / Cube.
{ Note:
1MPA = N/mm2 }
Concrete Grade
fck (MPa)
fck, cube (MPa)
Ecm (GPa)
C12/15
12
15
27
C16/20
16
20
29
C20/25
20
25
30
C25/30
25
30
31
C30/37
30
37
33
C35/45
35
45
34
C40/50
40
50
35
C45/55
45
55
36
C50/60
50
60
37
C55/67
55
67
38
C60/75
60
75
39
C70/85
70
85
41
C80/95
80
95
42
C90/105
90
105
44
Ecm = Elastic modulus of concrete
1.4. Grades of Concrete Based on American Standard
Concrete Mix
Cylinder Strength (psi)
Cylinder strength (MPa or N/mm²)
2000
2000
13.8
3000
3000
20.7
4000
4000
27.6
5000
5000
34.5
6000
6000
41.3
8000
8000
55.2
10000
10000
68.9
1.5. Grades of Concrete Based on Canadian Standard
The concrete grades of strength 20 Mpa to 40 MPa are listed in Canadian standard for the general use.
The strength of concrete greater than 70 MPa is classified into high strength concrete.
Highest strength of concrete 220 MPa has also been used in building applications.
1.6. Grades of Concrete Based on Australian Standard
Prefix N is used to symbolize concrete grades and value of the strength of concrete ranges from N20 to N100 in Australian standard.
