Grade of Concrete and Reinforcement Cover
Characteristic Strength of Concrete
It is that strength below which not more than 5% of test results are expected to fall.
Grade of Concrete
Ordinary Grade- M10, M15, M20
Standard Grade- M25 to M55
High Strength Concrete- M60 to M90
- IS 456: 2000 is not applicable to M60 and Above.
- IS 456: 2000 recommends the minimum grade as M20 for Reinforced Concrete.
Minimum Grade of concrete can be used in RCC, depend on the exposure condition.
Proportions of Concrete
|Grade of Concrete||Mix||Compressive |
IS 456: 2000 recommends 3 type of reinforcement according to their yield strength-
Fe250: Yield Strength- 250 N/mm2
Fe415: Yield Strength- 415 N/mm2
Fe500: Yield Strength- 500 N/mm2
Types of Reinforcement in beams-
- Tension Reinforcement
- Compression Reinforcement
- Shear Reinforcement
- Side Face Reinforcement
In reinforced structures, the reinforcement I surrounded by the sufficient cover to protect the concrete from atmospheric conditions which makes reinforcement to corrode.
Minimum cover of 25mm or not be less than the larger diameter of bar should be provided.
The clear cover is the distance between the exposed concrete surface (without plaster and other finishes) to the nearest surface of the reinforcing bar.
Nominal Cover is same as clear cover or we can say that clear cover is also known as Nominal Cover.
The effective cover is the distance between the exposed concrete surface to the centroid of the main reinforcement.
NOMINAL COVER TO MEET DURABILITY REQUIREMENTS-
For main reinforcement up to 12 mm diameter bar for mild exposure the nominal cover may be reduced by 5mm
Unless specified otherwise, actual concrete cover should not derive from the required nominal cover increased by 10mm.
For exposure condition ‘severe’ And ‘very severe’ reduction of 5mm may be made, where concrete grade is M35 and above.
NOMINAL COVER TO MEET SPECIFIED PERIOD OF FIRE RESISTANCE
These are the nominal cover according to Fire resistance conditions-