concrete mix grades

Concrete mix grades & concrete mix ratios

Are you confused about concrete mix grades? Don’t worry, after reading the post you won’t be confused anymore. Initially i was confused too, but as i have practical experience i knew what is concrete grade & what is concrete mix ratio. In this article, we will discuss different types of concrete mix grades used in construction. Further the composition and strength of different concrete mix ratio.

What are concrete grade?

In concrete gradesM” means mix and the number after “M” represents MPa or N/mm2 compressive strength of concrete. For example M10, M15, M20, M25 concrete mix grade. Here M10 means the concrete mix which can bear 10 MPa or 10 newton load on per square millimeter.

There are different types of concrete mix grade in civil engineering according to their need and use. Grades of concrete are e.g. M5, M10, M15, M20 up to the M80. All the grades have different strength, group and purpose of use.

Some of them are standard and pre designed & calculated but sometimes in special project, need based concrete grades are used. Their use depend upon their strength. According to nature of project we go for a ready mix concrete and sometimes we mix on site. What is concrete grade means?

5N/mm2 means that one mm2 area of concrete cube of 150mm can bear 5N or 5MPa compressive load after curing the 28 days. It can be converted into PSi (by multiplying with 145).

IMPORTANT! C10, C15, C20, C25 etc are British/European standard of “Concrete strength class”.

Where C refers class and numerical values next to “C” represents the compressive strength of Cylinder of (150mm × 300mm) after curing 28 days.

Cylinder Compressive Strength = 0.80 Times of Cube compressive strength.

Read also types of concrete.

Concrete mix ratio:

Basically concrete mix ratio is the ratio of ingredients used in concrete composition. For example 1:5:10, 1:4:8, 1:3:6, 1:2:4 and more. If there’s mentioned to use M15 grade of concrete. You may know the strength of M15 but you need to know how many parts of cement, sand & aggregates gonna be use in M15 grade.

Mostly used concrete grade for beams, floor and slabs is M15 which has concrete mix ratio of 1:2:4. It means 1 part of cement, 2 parts of sand and 4 parts of aggregate is used in M15 grade composition. On other hand you can calculate concrete mix ratio using ballast by 1:6, which means 1 part of cement and 6 parts of ballast (sand & aggregate mixture).

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Further there’s M20 concrete grade, which has mix ratio of 1:1.5:3. Below the table is given where you can read the concrete grade and their mix ratios. Concrete mix ratio is further divided into two categories nominal concrete mix & designed concrete mix.

Nominal concrete mix:

In Nominal concrete mix the ratios of ingredients are predefined. These types of mix ratios are used widely in most of the construction projects so the the ratio are already calculated. Concrete grades M5 to M25 are counted as nominal mix. Below the table is given about the nominal concrete mix ratio.

Concrete GradeMix Ratio (C:S:A)Compressive Strength (MPa)
N/mm2


PSi
M51:5:105 MPa725
M7.51:4:87.5 MPa1087
M101:3:610 MPa1450
M151:2:415 MPa2175
M201:1.5:320 MPa2900
M251:1:225 MPa3625
Nominal concrete grade table

Designed mix:

In designed concrete mix the ratios of ingredients aren’t predefined. Because these concrete mix are used in heavy/mega projects such as high rise buildings, dams, bridges etc. The structural engineer compose & test different concrete mix with different superplasticizer & water reducer and then define what mix ratio+superplasticizer will used.

Concrete GradeMix Ratio (C:S:A)Compressive Strength (MPa)
N/mm2


PSi
M30Design Mix30 MPa4350
M40/40 MPa5800
M50/50 MPa7250
M60/60 MPa8700
M70/7010150
M80/8011603
Designed concrete grade table

Related: How to calculate concrete mix ratio

Concrete grades & mix ratio table:

Below the table is given, there’s the concrete grades and what are their concrete mix ratio & their strength and their uses are mentioned too. These are concrete grades & mix ratio used in USA, India, Sri Lanka and around.

Concrete GradeMix Ratio (C:S:A)Compressive Strength (MPa)
N/mm2


PSi
Group
M51:5:105 MPa725Lean Concrete
M7.51:4:87.5 MPa1087/
M101:3:610 MPa1450Ordinary Concrete
M151:2:415 MPa2175/
M201:1.5:320 MPa2900/
M251:1:225 MPa3625/
M30Design Mix30 MPa4350Standard Concrete
M40/40 MPa5800/
M50/50 MPa7250/
M60/60 MPa8700High Strength Concrete
M70/7010150/
M80/8011603/
Concrete grade table

How to choose concrete grade: Different grades of concrete and their uses

If you are confused, which concrete grade do you need or what grade should you choose. Its not something for decorative purpose to choose but for strength. When choosing a concrete grade be sure to pick right one. First of all specify you area of use, where you are going to use e.g. columns, beams, patio or slab. If there is more load on the area choose a stronger grade. Don’t choose a grade below M15 expect for pity work.

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Basically there are 4 groups of concrete grades. Such as lean concrete, ordinary concrete, standard concrete and high strength concrete. Below all the grades of concrete are mentioned and their uses are briefly explained.

M5 concrete mix grade:

M5 (1:5:10) is lean concrete mix which can bear 5 newton load/pressure on per square millimeter area or 725 Psi. 1:5:10 is a basic concrete mix, where there is no need of more strength but just a smooth surface.

It is used in footing/foundations bed to provide smooth and plane surface for foundation and to separate the direct interaction of foundation with surface.

concrete mix grade and ratio table
concrete mix grade and ratio table

M7.5 concrete grade:

M7.5 (1:4:8) is also a lean concrete mix which is used in foundation to provide plain surface and to make a disruption between footing and the ground surface. It is used where there is a little more strength is needed as compare to M5 mix.

M10 concrete grade:

Concrete mix grade M10 (1:3:6) is categorize as ordinary concrete. It bear less load than compare to M15. M10 has 10 N/mm2 or 1450 Psi compressive strength. It is use in plinth beams, slabs, R.C.C walls and road pavements etc. C10 has 8 N/mm2 compressive strength which is 80% of M10.

M15 concrete grade:

M15 has concrete mix ratio (1:2:4) and it is the best and most commonly use concrete grade. Because of its compressive strength and economical conditions in ordinary concrete mix section. M15 grade concrete is use for footings, foundations, slab, driveways & patios. Most sections of the house is constructed with M15 grade.

The M15 has 15 N/mm2 compressive strength per square millimeter or 2175 Psi. This concrete mix used for building columns, beams, slab, for plinth beam, bridge piers, pavements almost for every important section. M15 (1:2:4) is concrete mix ratio for floors as well.

M20 and M25 concrete grade:

The M20 has concrete mix ratio is (1:1.5:3) respectively. M20 has compressive strength of 20 N/mm2 (MPa) or 2900 Psi. C20 is same as M20 but it give 0.80 times strength comparatively. C20 has 16 MPa strength which is 0.80% of M20.

M25/C25 concrete mix ratio is (1:1:2), and M25 has 25 N/mm2 or 3625 Psi compressive strength, while C25 has 20 MPa strength which is 0.80 times to cube.. M15 to M25 is best grade of concrete which are used most commonly. To make a strong concrete you need to decrease the quantity of sand, aggregate & water against cement quantity.

Read also ready mix concrete & precast concrete.

Concrete grade M30, M40, M50:

M30, M40 and M50 Concrete mix are standard concrete grades. It is mixed according to design. That have really high compressive strength. Because of its strength they are used in Septic tanks, Dams, Barrages, Flyovers, Bridges columns etc. They have as high compressive strength of 4350 psi, 5800 psi and 7250 psi.

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C25/30, C32/40 & C40/50 is the same concrete mix grade as of M30, along with C40 & C50. But they have less compressive strength because its British system and they use conc cylinder for test, which is 0.80 times to cube compressive strength. Concrete grade c32/40 is same as M40, with same ratio & strength. M40 is a commercial concrete used in commercial and industrial buildings as well as dams and bridges.

concrete mix grades ratio
Concrete mix grades ratio

M60, M70, M80 concrete mix grades:

M60 to M80 concrete mix are high strength concrete and designed mix. That have 8700 psi to 11603 psi compressive strength, but they are use in special occasions. Which concrete grade is used in burj khalifa? In construction of burj khalifa M50 to M80 (high strength) concrete mix grade is used.

Beside compressive strenth high strength concrete mix grade also have resistance against chemical erosion, acid attacks etc. High strength concrete mix grade is use in chemical labs, nuclear reactors, nuclear weapon ware houses.

C10 concrete:

C10 concrete has 10 N/mm2 or 1450 psi compressive strength after 28 days curing of cylinder. It has 1:4:8 mix ratio, which means 1 part of cement, 4 parts of sand and 8 parts of aggregates. C10, C15, C20, C25 etc are British/European standard of “Concrete strength class”. The basic difference in M & C (mix & class) it both has different mix ratio. C is tested on cylinder, while M is tested on cube and use in USA & India. C has compressive strength 80% to cube.

C15 concrete:

C15 concrete mix has 15 N/mm2 or 2175 psi compressive strength after 28 days curing of cylinder. It has 1:3:6 mix ratio, which means 1 part of cement, 3 parts of sand and 6 parts of aggregates.

C20 concrete:

C20 concrete mix has 20 N/mm2 or 2900 psi compressive strength after 28 days curing of cylinder. It has 1:2:4 mix ratio, which means 1 part of cement, 2 parts of sand and 4 parts of aggregates.

C25 concrete:

C25 concrete mix has 25 N/mm2 or 3625 psi compressive strength after 28 days curing of cylinder. It has 1:1.5:3 mix ratio, which means 1 part of cement, 1.5 parts of sand and 3 parts of aggregates.

C30 concrete:

C30 concrete mix has 30 N/mm2 or 4350 psi compressive strength after 28 days curing of cylinder. It has 1:1:2 mix ratio, which means 1 part of cement, 1 parts of sand and 2 parts of aggregates.

What does C16/20 concrete mean?

You may have seen the concrete grades representation like C16/20, C20/25, C25/30 what does that means. C16/20 concrete grade has ratio of (1:1.5:3) that means it has 16 MPa or 2320 psi compressive strength of cylinder which 80% of cube, while 20 MPa or 2900 psi compressive strength of cube. C16/20 is actually M20 mix.

Same goes for C20/25 concrete grade has mix ratio of (1:1:2) and it has 20 MPa or 2900 psi of cylinder compressive strength, while 25 MPa or 3625 psi of cube strength, which is M25 concrete grade. Don’t be confuse, here only the mix ratios are same but the strength are different, because you know in C we test cylinder which is 80% strength to cube.

Conclusion: You need to know

Abive we discuss all the concrete grades and their mix ratios. There 2 systems of concrete grading USA & British/European. USA use cube for concrete testing and denote the grade by M, while the British/European use concrete cylinder for testing and denote grade by C. If you have any query let us know in the comment section.

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