Concerned about the grades of concrete mix? You won’t be confused anymore after reading this post, so don’t worry you’ll be able to distinguish between concrete grade and concrete mix ratio. We’ll talk about various concrete mix grades used in this article. The composition and strength of various concrete mix ratios are also discussed.
What is the Standard Strength Concrete Grades?
“M” stands for mix in concrete grades, while the number following “M” denotes the MPa or N/mm2 compressive strength of concrete. M10, M15, M20, and M25 are examples of concrete mix grades. Here, “M10” refers to a concrete mix that can support a load of 10 MPa, or 10 newtons, per square millimeter.
In civil engineering, there are several concrete mix grades depending on the necessity and application. Concrete comes in several grades, such as M5, M10, M15, M20, and M80. Each grade has a unique strength, group, and usage.
Some of them are pre-designed and standard, although need-based concrete grades are occasionally employed in unique projects. Their usefulness depends on their strength. Depending on the project, we either use ready-mix concrete or occasionally mix it on the site. How does concrete grading work?
A concrete cube with a surface area of 5 N/mm2 may withstand a compressive load of 5 N/mm2 or 5MPa after 28 days of curing. It is equivalent to PSi (by multiplying with 145).
IMPORTANT! The British/European standard for “Concrete strength class” is C10, C15, C20, C25, etc.
Where “C” stands for class and the numbers next to “C” indicate the compressive strength of a cylinder measuring 150 mm by 300 mm after 28 days of curing.
Cube compressive strength is equal to 0.80 times that of a cylinder.
Concrete mix proportions
Basically, the ratio of components utilized in the construction of concrete is the concrete mix ratio. An example might be 1:5:10, 1:4:8, 1:3:6, 1:2:4, and more. Whenever concrete of the M15 grade is recommended. You may be aware of the M15 grade’s strength, but you also need to know how many parts of cement, sand, and aggregates will be used.
The most popular concrete grade, M15, has a 1:2:4 concrete mix ratio and is utilized for beams, floors, and slabs. This means that the M15 grade composition uses 1 component cement, 2 parts sand, and 4 parts aggregate. Conversely, you can determine the concrete mix ratio using ballast by multiplying it by 1:6, which equals 1 part cement and 6 parts ballast (sand & aggregate mixture).
There is another M20 concrete grade, which has a 1:1.5:3 mix ratio. You may read the concrete grade and their mix ratios below the table. The nominal concrete mix and planned concrete mix are the next two kinds of concrete mix ratios.
Mix for nominal concrete
The proportions of the elements are predetermined in the nominal concrete mix. These mix ratios are frequently used in construction projects, thus they have already been computed. M5 to M25 concrete grade counts as a nominal mix. Information on the nominal concrete mix ratio is provided below the table.
| Concrete Grade | Mix Ratio (C:S:A) | Compressive Strength (Mpa) | Psi |
| M5 | 1:5:10 | 5 | 725 |
| M7.5 | 1:4:8 | 7.5 | 1087 |
| M10 | 1:3:6 | 10 | 1450 |
| M15 | 1:2:4 | 15 | 2175 |
| M20 | 1:1.5:3 | 20 | 2900 |
| M25 | 1:1:2 | 25 | 3625 |
Designed mix
The ratios of the ingredients are not predetermined in intended concrete mixtures. because heavy/massive constructions like high-rise skyscrapers, dams, bridges, etc. employ this concrete mix. The structural engineer creates and tests various concrete mixes with various water reducers and superplasticizers before deciding on the mix ratio and superplasticizer to be utilized.
Table of concrete grades and mix ratios:
| Concrete Grade | Mix Ratio (C:S:A) | Compressive Strength (Mpa) | Psi |
| M30 | Design mix | 30 | 4350 |
| M40 | Design mix | 40 | 5800 |
| M50 | Design mix | 50 | 7250 |
| M60 | Design mix | 60 | 8700 |
| M70 | Design mix | 70 | 10150 |
| M80 | Design mix | 80 | 11603 |
The concrete grades are listed below the table, along with information on their strength, concrete mix ratios, and intended purposes.
| Concrete Grade | Mix Ratio (C:S:A) | Compressive Strength (Mpa) | Psi | Group |
| M5 | 1:5:10 | 5 | 725 | Lean concrete |
| M7.5 | 1:4:8 | 7.5 | 1087 | |
| M10 | 1:3:6 | 10 | 1450 | Ordinary concrete |
| M15 | 1:2:4 | 15 | 2175 | |
| M20 | 1:1.5:3 | 20 | 2900 | |
| M25 | 1:1:2 | 25 | 3625 | |
| M30 | Design mix | 30 | 4350 | Standard concrete |
| M40 | Design mix | 40 | 5800 | |
| M50 | Design mix | 50 | 7250 | |
| M60 | Design mix | 60 | 8700 | High strength concrete |
| M70 | Design mix | 70 | 10150 | |
| M80 | Design mix | 80 | 11603 |
How to choose a concrete grade: Concrete grades and applications
If you are uncertain, you should decide which grade of concrete you require. It’s important to choose something for strength rather than aesthetics. Choose the proper concrete grade while making your selection. First, describe the area that will be used, such as a patio, slab, or columns. Select a stronger grade if the area is under additional load. A grade below M15 should only be used for simple work.
There are basically 4 categories of concrete grades. such as high-strength concrete, lean concrete, standard concrete, and ordinary concrete. Below, all of the concrete grades are included along with a brief description of each one’s use.
Concrete grade M5
Lean concrete mix M5 (1:5:10) has a 5-newton load/pressure capacity per square millimeter area or 725 PSI. A basic concrete mixture of 1:5:10 is used when a smooth surface is all that is required, not additional strength.
It is used in the footing/foundations bed to give the foundation a smooth, level surface and to prevent the foundation from directly interacting with the surface.
Concrete grade M7.5
Lean concrete M7.5 (1:4:8) is also used in foundations to create a disruption between the footing and the ground surface and to offer a plain surface. It is utilized in situations where a little bit more strength than the M5 mix is required.
Concrete grade M10
Ordinary concrete is defined as concrete with a concrete mix grade of M10 (1:3:6). Compared to M15, it can support less weight. 10 N/mm2 or 1450 psi is the compressive strength of M10. It is used in things like road pavements, R.C.C. walls, and plinth beams and slabs. C10 has a compressive strength of 8 N/mm2, which is 80% greater than M10.
Concrete grade M15
M15 is the best and most widely used concrete grade, and it has a concrete mix ratio of (1:2:4). due to its economical circumstances in the section of standard concrete mix and compressive strength. For footings, foundations, slabs, driveways, and patios, M15 grade concrete is used. The majority of the house’s parts are built using M15 grade.
The M15 has a compressive strength of 15 N/mm2 (or 2175 Psi) per square millimeter. The construction of columns, beams, slabs, plinth beams, bridge piers, and pavements all make use of this concrete mixture. The concrete mix ratio for floors is M15 (1:2:4).
Concrete grades M20 and M25
The concrete mix ratio for the M20 is (1:1.5:3). M20 has a 20 N/mm2 (MPa), or 2900 psi, compressive strength. C20 is identical to M20 but provides 0.80 times the strength in comparison. C20 has a strength of 16 MPa or 0.80% of M20.
The M25/C25 concrete mix ratio is (1:1:2). M25 has a compressive strength of 25 N/mm2 or 3625 psi, but C25 has a strength of 20 MPa or 0.80 times the cube. The best grade of concrete, which is most frequently utilized, is M15 to M25. In order to produce strong concrete, you must use less sand, aggregate, and water in comparison to cement.
Concrete grades M30, M40, and M50
Standard concrete grades include M30, M40, and M50 Concrete Mix. It is mixed as intended in the design and possesses extremely strong compressive strength. They are utilized in septic tanks, dams, barricades, flyovers, bridge columns, and other structures due to their strength. High compressive strengths of 4350 psi, 5800 psi, and 7250 psi are possessed them.
The concrete mix grades of C25/30, C32/40, and C40/50, together with C40 & C50, are the same as those of M30. However, they have less compressive strength because of the British system and the concrete cylinder test, which has a compressive strength of 0.80 times that of a cube. Concrete grade C32/40 has the same ratio and strength as M40. Commercial concrete known as M40 is utilized in dams, bridges, and commercial and industrial buildings.
Concrete grades M60, M70, and M80
High-strength concrete and intended mix are M60 to M80. They have compressive strengths between 8700 and 11603 psi, however, they are only used on specific occasions. Which type of concrete is utilized in the Burj Khalifa? Concrete mix grades M50 to M80 (high strength) are utilized in the construction of the Burj Khalifa.
High-strength concrete mix grades also offer resistance to chemical erosion, acid assaults, etc. in addition to compressive strength. In chemical laboratories, nuclear reactors, and nuclear weapon storage facilities, high-strength concrete mix grade is used.
Concrete grade types used in the U.S.
Concrete grade C10
After 28 days of cylinder curing, C10 concrete has a compressive strength of 10 N/mm2 or 1450 psi. One part of cement, four parts of sand, and eight pieces of aggregates make up the 1:4:8 mix ratio. The British/European standard for “Concrete strength class” is C10, C15, C20, C25, etc. The main distinction between M and C (mix & class) is that each has a unique mix ratio. While M is tested on a cube and is used in the USA and India, C is tested on a cylinder. C has an 80% cube compressive strength.
Concrete grade C15
After 28 days of cylinder curing, the C15 concrete mix has a compressive strength of 15 N/mm2 or 2175 psi. One portion of cement, three parts of sand, and six parts of aggregates make up the 1:3:6 mix ratio.
Concrete grade C20
After 28 days of cylinder curing, the C20 concrete mix has a compressive strength of 20 N/mm2 or 2900 psi. There are 1 part cement, 2 parts sand, and 4 parts aggregates in the 1:2:4 mix ratio.
Concrete grade C25
After 28 days of cylinder curing, the C25 concrete mix has a compressive strength of 25 N/mm2 or 3625 psi. The mix ratio is 1:1.5:3, which equals 1 part cement, 1.5 parts sand, and 3 parts aggregates.
High-Performance Strength Concrete Grades
Concrete grade C30
After 28 days of cylinder curing, the C30 concrete mix also known as ST3 or PAV1 has a compressive strength of 30 N/mm2 (4350 psi). It has a 1:1:2 mix ratio, which implies that there are equal proportions of cement, sand, and aggregates in this mixture.
Concrete grade C35
The 35 N/mm2/28-day strength of C35 Concrete Grade C35 or PAV2 is intended to withstand. C35 grade can be utilized on bigger commercial structures and foundations for increased support because it has more significant strength than the C30 grade. Additionally, C35 contains unique chemicals that lessen the possibility of air bubbles forming and guard against freezing temperatures’ ability to cause surface fissures.
Concrete grade C40
Commercial-grade concrete with a strength of 40 N/mm2/28 days is known as C40. When building substantial industrial support beams and foundations, C40 is the material of choice. Additionally, it is employed in a number of road construction projects and agricultural yards.
Concrete grade C50
Commercial-grade concrete with a strength of 50 N/mm2/28 days is known as C40 which is usually used in columns.
What does concrete marked C16/20 mean?
It’s possible that you have encountered concrete grade representations like C16/20, C20/25, and C25/30. Exactly what that means C16/20 concrete grade has a ratio of (1:1.5:3), which indicates that the cube’s compressive strength is 20 MPa or 2900 psi and the cylinder’s compressive strength is 16 MPa or 2320 psi. In reality, C16/20 is an M20 mix.
The same is true for C20/25 concrete grade, which has a mix ratio of (1:1:2) with cylinder compressive strengths of 20 MPa or 2900 psi, compared to M25 concrete grade’s cube strengths of 25 MPa or 3625 psi. Don’t be confused; only the mix ratios are the same here, but the strengths are different. As you are aware, cylinders are tested in C since they have an 80 percent greater strength than cubes.
In conclusion, you must understand
The mix ratios for each grade of concrete are provided here. There are 2 systems for grading concrete: American and British/European. While the British/European use concrete cylinder for testing and signify grade by C, the USA utilize cubes for testing and denote grade by M.
Difference between M and C
The main difference between M and C (mix & class) is that each has a unique mix ratio. While M is tested on a cube and is used in the USA and India, C is tested on a cylinder. C has an 80% cube compressive strength.