Concrete is a versatile building material used in various construction projects. Ranging from roads and bridges to high-rise buildings and dams. One crucial aspects of concrete is its grade of concrete which determines its strength and durability. In this blog we will know more about the different grades of concrete, how to prepare them with the use of proper mix ratios, their proportion and in the last we consider its use cases in different projects.
What are grades of concrete?
Grades of Concrete are standardised classifications that indicate the strength and quality of concrete used in construction. The grade of concrete is typically denoted by a number such as M20, M30, etc., where “M” stands for mix and the number denotes the compressive strength of the concrete mix in megapascals (MPa) after 28 days of curing. Higher grades offer greater strength, with each grade tailored to meet diverse construction needs and structural requirements. Before learning the grades let’s first talk about the Mix Proportion.
What is concrete Mix Ratio and Proportions :
Concrete is a mixture of cement, water and aggregates like sand and gravels. The proper mixture of these ingredients determines the workability of concrete, strength of concrete and other important related factors. Concrete mix ratio or proportioning is the process of mixing the suitable quantity of ingredients to produce the concrete mix having higher strength also durable, and can be easy to use. The proportion of the different material will depend on their characteristics. The following factors must be considered to produce the compete mix of concrete :
- Water cement ratio
- Ratio of fine aggregates (sand) and coarse aggregates (kapchi)
- Use of any admixtures for desired quality of concrete
Generally concrete mix ratios are denoted in a form of a:b:c,
where,
- a is parts of measurement for Cement
- b is parts of measurement for Sand
- c is parts of measurement for Aggregates
Types of Concrete Mix Ratio :
As per IS 10262:2009 code of Indian Standard, following are the concrete mix ratios depending on the proportion of the constituents :
The mix proportion shall be selected to ensure the workability of the fresh concrete and when concrete is hardened, it shall have the required strength, durability and surface finish.
The determination of the proportion of cement, aggregate and water to attain the required strengths shall be made as follows :
a) By designing the concrete mix; such concrete shall be called “Design mix concrete”, or
b) By adopting nominal concrete mix; such concrete shall be called “Nominal mix concrete”.
Design mix concrete is prefered to nominal mix. If design mix concrete cannot be used for any reason on the work for grades of M20 or lower, nominal mixes may be used with the permission of engineer-in-charge which, however, is likely to involve a higher cement content.
Types of Grades of Concrete :
As per IS 456:2000 code of Indian Standard, following are the concrete mix ratios depending on the proportion of the constituents :
| Types of Concrete | Grade of Concrete | Mix Ratio (Cement : Sand : Aggregates) | Characteristic strength of cube at 28 days N/mm2 |
|---|---|---|---|
| Ordinary Concrete | M5 | 1:5:10 | 5 |
| Ordinary Concrete | M7.5 | 1:4:8 | 7.5 |
| Ordinary Concrete | M10 | 1:3:6 | 10 |
| Ordinary Concrete | M15 | 1:2:4 | 15 |
| Ordinary Concrete | M20 | 1:1.5:3 | 20 |
| Standard Concrete | M25 | 1:1:2 | 25 |
| Standard Concrete | M30 | Design Mix | 30 |
| Standard Concrete | M35 | Design Mix | 35 |
| Standard Concrete | M40 | Design Mix | 40 |
| Standard Concrete | M45 | Design Mix | 45 |
| Standard Concrete | M50 | Design Mix | 50 |
| Standard Concrete | M55 | Design Mix | 55 |
| High Strength Concrete | M60 | Design Mix | 60 |
| High Strength Concrete | M65 | Design Mix | 65 |
| High Strength Concrete | M70 | Design Mix | 70 |
| High Strength Concrete | M75 | Design Mix | 75 |
| High Strength Concrete | M80 | Design Mix | 80 |
NOTES:- In the designation of concrete mix M refers to the mix and the number specified a compressive strength of 150 mm size cube at 28 days, expressed in N/mm².
1. Ordinary Concrete :
- In the ordinary concrete, grades of concretes are ranging from M10 to M20
- Low compressive strength range
- Ideal for pavements and garage floor
- Non structural applications
2. Standard Concrete :
- Standard concrete grades varies from M25 to M45
- Higher compressive strength range
- Ideal for high tensile structure
- Used in beams, walls, girders
3. High Strength Concrete :
- High strength concrete grades are over the M50 to M80
- Compressive strength 6.525-9.425 PSI
- Used for water body structures and high rise structure
Applications of Different Grades:
A. Lower-grade concretes:
- M5 and M7.5 are suitable for non-structural elements and small-scale projects. Used for non-structural applications like plastering or leveling.
B. Medium-grade concretes:
- M20 to M25 find use in general construction such as beams, columns, and slabs and also for residential buildings and commercial structures.
C. High-grade concretes:
- M30 and above are essential for critical infrastructure projects requiring exceptional strength and durability.
- Reserved for high-strength applications like bridges, dams, and high-rise buildings.
Conclusion:
At the end from the above discussion now you can easily understanding concrete grades, mix ratios and proportions, which is essential for ensuring the success and longevity of construction projects. By selecting the appropriate grade and mix, builders can achieve the desired strength, durability and performance required for various projects. Whether it’s a small residential project or a massive infrastructure endeavor, choosing the right concrete grade is paramount for project success.
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