cover block, what is cover block? where cover block should be placed?

Cover block and uses of cover block

Introduction:

RCC members like footing, column, Beam and Roof slab must have clear cover. Clear cover is nothing but a gap between outer edge of concrete surface and outer edge of Reinforcement. Clear cover is not constant for all RCC members.

For Roof slab, it must be 20 mm

For Beam, column and footing, it must be 40 mm.

Clear cover must be greater if section area of particular RCC member is larger and less if section area is small.

If we don’t follow clear cover, Failure at surface of the concrete may occur. So that, so many cracks  will form.

Some examples of failure of roof slab those not using cover block:

no cover block causing damage at early stage 

no cover block causing severe damage

In order to maintain a gap between outer edge of concrete surface and edge of Reinforcement, we should place a small block called cover block.

Below the image of cover block for your reference.

dimension of cover block

Cover block is a small block made of plain cement concrete. it may be vary in size according to types of RCC member( Roof, beam. column. Footing).

It has two straight semi circular hollows at top of the cover block. One is for main rod and other one for distributor in order to  don’t allow them to  move from placed position.

How to use cover block?:

Simply place it below the main rod of Rcc members.

Here I have given some images to describe how to place cover block for various structure.

cover block effectively used at RCC footing.

cover block used for RCC footing

cover block used for RCC footing

In the above image, you can notice some important points.

• Always place cover block of size 40 to 50 mm at bottom of the footing.
• At side of footing leave a space of at least 50 mm to avoid corrosion of steel .Otherwise reinforcement affected by damping earth and corrosion will occur.
• Complete the shuttering work and place the concrete.

cover block effectively used at RCC column.

cover block for column

cover block for column

In the above image, you can understand some important points.

• Place the cover block at the all 4 sides of the column.Then only you can save the column from failure.
• Place the cover block at the rings and bind it with binding wire.
• After placing the cover block,complete the shuttering work and place concrete.

cover block effectively used at RCC beam and Roof slab:

front view of cover block at beam and roof 

perspective view of beam and roof having cover block placed

From the above two image, some points should be followed. 

Always place cover block for all 3 sides (bottom, 2 sides)of a beam. leave top side without placing cover block. but place the concrete for extra height as rings plus clear cover.

Place the cover block  for roof slab bottom randomly as sufficient as possible.

To protect the top  reinforcement at nearer to support, place the chair rod.

What is chair rod?

please refer the following image.

chair rod as cover block to maintain cover at top

How can use chair rod?

Place the chair rod at nearer to support in order to resist the top negative rod from hanging. and It also used to maintain top cover.

chair rod as cover block to prevent hanging

Okay Friends, Now we are at the end of this article. I hope now you understand that the purpose of cover block and how you can effectively use it?. cover block is small thing. but it serve the entire structure from severe damage.

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