Concrete Mix Ratio For Various Grade Of Concrete
Cement concrete may be defined as building material obtained by mixing cement, sand, aggregates and water in suitable proportion and then curing this plastic mixture to a hard mass. It can be easily moulded to durable structure members. The volume of aggregates in concrete varies from 60 to 78%.
Concrete mixes are classified by its grade having specified crushing strength at 28 days as measured in standard condition with 150mm x150mm x 150mm size cube, that means the grade of concrete corresponds to its characteristic compressive strength.
M20 shows the crushing strength of that cube having size 150mm at 28 days is 20 N/mm2.
Type of Concrete Mix
1. Nominal Concrete Mix2. Designed Concrete Mix
1. Nominal Concrete Mix
The Nominal concrete mix may be used for concrete of grade M5, M10, M15 and M20. The proportion of its ingredients are given below:
Grade of Concrete 
Maximum
Quantity of Dry Coarse and Fine Aggregates by Mass per 50 kg of Cement (kg)

Proportion
of Fine Aggregates to Coarse Aggregates by Mass

Maximum
Quantity of water per 50 kg of Cement (Litres)

M5
M7.5
M10
M15
M20

800
625
480
350
250

Generally,
1:2 but subject to an upper limit of 1:1.5 and lower limit 1: 2.5

60
45
34
32
60

The proportion of fine to coarse aggregates should be adjusted from the upper limit to lower limit progressively, as the grading of fine aggregates become finer and the maximum size of coarse aggregate become larger. Graded coarse aggregate should be used.
2. Designed Concrete Mix
In designed concrete mixes, the proportion of ingredients of concrete are determined to obtain concrete of specified properties with the overall economy.
Concrete is graded according to its compressive strength given in the table below:
Grade of Concrete

Mix Ratio
(Cement: Sand: Aggregate)

Compressive Strength At 28 Days


MPa (N/mm^{2})

psi


Normal Grade of Concrete


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

Standard Grade of Concrete


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

High Strength Concrete Grades


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

Application of Different Grades of Concrete:
 M5,M7.5,M10,M15 : PCC ( Plain cement concrete ) e.g. Levelling course, bedding for footing,etc.
 M20, M25, M30, M35 : RCC ( Reinforced Cement Concrete ) e.g. Slab, Beams, Columns ,footing etc ( for mild exposure).
 M40: RCC e.g. Prestressed concrete slabs, beams, column, footing etc.
 M45, M50: RCC e.g. Runways, Concrete Roads( POQ ) Prestressed concrete girders, RCC columns, Prestressed beams etc.
 M55 : RCC e.g. Prestressed concrete girders and piers etc.
 M60, M65, M80: RCC work where high compressive strength is required such as high rise building, long Span bridges, ultrathin white topping and spillways of dams, coastal construction etc.
Also, Read  Compressive strength of cement concrete.
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