The term grade refers to the strength of the compression capacity of the concrete after it has aged 28 days. Normally, middle east’s symbol is C followed by numbers. But several other countries use the symbol M instead of C. If one asks which concrete grade is the best? It depends on where or what type of construction you are building. Just be sure you are using concrete with grades not overly designed for economical purposes.
Before we proceed with the discussion of concrete grades, several factors contribute to its strength and quality. Some of which are water-cement ratio, the workmanship like how the cement and its aggregates where mixed, cast, finished and cured.
As to how to assess the quality of concrete, it is best to ask a technical person, say, a quality engineer, for a compression test. A slump test may also be conducted to check the on-site quality and determine the workability of the concrete. But if in doubt, get advises from a technical person.
For the determination of what is a suitable concrete grade to be used, please take note that there are two common types of concrete mixes, the design mix, and the nominal mix.
Nominal mixes are generally used for small construction like a residential house.
Design mixes are used for large-scale construction like buildings and roads. Since we are discussing the concrete grades for building construction, the most suitable mix for this one is the design mix.
Building construction basically uses almost all concrete grades. For Dubai’s setting, here are some of the most commonly used concrete grades for building construction.
Conc. grade C25/20 and C30/20:
These concrete grades are used for blinding, and foundation or road leveling. Generally, these are low-graded concrete with low designed capacity.
Conc. Grade C40/20 and C45/20:
These concrete grades are used for structural members and systems that are directly or indirectly experiencing loads in itself such as slabs, foundations, columns, and footings. Basically, these are middle to high graded concrete with a certain design capacity as these grades have a direct impact on the credibility and integrity of the structure.
Conc. Grade C60/20:
This concrete grade is used for the most important part of the structural concrete element which is “Column” and “Shear wall.” The highest quality concrete grades is the high-strength concrete grade. This is the grade used for beams and girders, columns, and other major structural members. It can be used also for retaining wall. If you can notice that the grade is increasing it means that the most pressured concrete element is column, beam, and wall that needs to possess a huge amount of strength, 60 Megapascal (Mpa or N/mm²). Imagine how much load a column can carry, it means there should be 60 newtons per millimeter square. HUGE!
Again, to save several dimes, it is advisable to use the lowest quality of concrete mix that is C25/20 for leveling of footing instead of 40/20, because that is quite self-explanatory. While for the structural construction elements, the grade as stated by the structural engineer is advised. The required concrete grade for these structural elements falls under the bracket of standard grade concrete or the C40/20 – C45/20 concrete grade. In addition, concrete grade has several mix proportions. These are denoted with 1:2:3 or cement:sand: coarse aggregates.
Normal concrete grades are usually used in the leveling of footing, kerb and blinding mix, domestic floors, and foundations that carry light loads like single-story residential. Standard concrete grades are generally used in commercial and domestic constructions. These are basically multi-purpose concrete grades. It may be used as footings for residential floorings. Under this grade bracket lies the lowest standard design grade for roadways.
Normally, a realized plan signed and sealed by the designer has its own concrete design mixes. If it is not stated, you can ask your designer to provide it to you. But generally, it is already stated in the structural note.
In addition to concrete mixes, some commercial admixtures or additive generally boosts a concrete grade. But it is not advisable to depend on the concrete grade on these admixtures. To be clear, concrete has to attain its designed strength with or without admixture. That is a rule of thumb.
Anyway, the common admixtures available in the market are plasticizers (added to concrete to promote viscosity, thus, free-flowing), Retardants (added to concrete for it to settle way longer than normal concrete), and Accelerants (opposite to retardants, it accelerates the time the concrete settles).
very nice post.
Great post.
What the 20 stands for in C40/20?
what is good slump for C60 CONCRETE ?
Hi Oswald,
It is 150 plus or minus 50mm but if it is SCC it is 500mm to 800mm.
I do not believe you understand how to specify concrete.
Concrete specified in accordance with the Eurocodes use two numbers in a concrete grade (e.g C32/40). The first number is the characteristic compressive strength of a cylinder of concrete at 28 days. The second number is the characteristic compressive strength of a CUBE of the same concrete at 28 days.
There is no such concrete grade as C60/20 – this would imply that the compressive strength of a cylinder of said concrete is 60MPa, whilst the compressive strength of a cube of the same concrete only 20MPa. In practice a cube of concrete has a greater compressive strength than a cylinder.
in c40/20, 20 stands for what?
Grade of concrete at 40Mpa compressive strength.
i think 20 stands for the size of aggregate
Grades of Concrete explained astonishingly!
Thanks for stopping by.
why we are calling it C40/20 can we call only C 40?
Yes.
Hello Noel,
Please tell me the different types of concrete grades used in UAE.
Like in India we use M5,M10,M15……so in UAE what it is….?
You can check this link out https://www.qualityengineersguide.com/concrete-grade-used-in-building-construction
Thanks for being here. Keep on asking.
If the cylinder test failed for 7 and 28 days, then which procedure is next to be followed?
Are we going to conduct hummer test? If so, then the question again if it failed then which steps are needed to go forward? Along with this, if we go for core cutting test and again its failed then what procedure is ahead to follow?
Dear Sir,
kindly provide Method of Statement Pouring of Concrete for Beam and Slab.
Thanks and Best Regards
khaja Zahid
Hi Khaja,
Sorry, it is available only in product section and I cannot post it here. It is unfair to those who bought the MS.
Hoping for your understanding.
Thanks,
Noel