Grade of Concrete and Reinforcement Cover

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

Where,

1. IS 456: 2000 is not applicable to M60 and Above.
2. 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 Strength (MPa)
M5	1:5:10	5
M7.5	1:4:8	7.5
M10	1:3:6	10
M15	1:2:4	15
M20	1:1.5:3	20
M25	1:1:2	25

REINFORCEMENT

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-

1. Tension Reinforcement
2. Compression Reinforcement
3. Shear Reinforcement
4. Side Face Reinforcement

REINFORCEMENT COVER-

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.

CLEAR COVER-

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-

Nominal Cover is same as clear cover or we can say that clear cover is also known as Nominal Cover.

EFFECTIVE 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-

These are the nominal cover according to Exposure conditions-

NOTES-

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-