What is Concrete Cover Block?

A Cover block is basically a spacer that is used to lift the rebar matrix off the ground so that Concrete may flow below the rebar. 

In order to prevent corrosion of the rebar, it has to be totally sheathed in concrete. It usually needs about 2 to 3 inches of coverage on all sides. So the cover block lifts the rebar up by about 2 to 3 inches and becomes a permanent and integral part of the poured concrete, make certain that no part of the rebar sags and minimizes that required concrete coverage throughout the pour.

Why is Cover Block used in the construction?

While doing RCC work it is important to embed the steel in the concrete (also known as cover) so that the rebar doesn’t corrode and to provide fire protection to the rebar. If the cover is not recommended the rebar will corrode with time and will ultimately result in premature failure of the structure .Thus using cover blocks enhances the life of the structure significantly without adding much to the cost.

Why Concrete Spacers? 

Alternatives to concrete spacers are PVC/plastic spacers.

As plastic is a different material than concrete and has different coefficient of thermal expansion than concrete, it does not bond properly with concrete. It is observed that hair cracks develop between plastic and concrete surface, which allow ingress of corrosive gases, which in turn accelerates corrosion.

While concrete spacers are made from high strength concrete, these concrete spacers bond perfectly with the surrounding concrete.

Technical Specifications:

Advantages of Cover Block 

Concrete Spacers prevent rebars from corrosion, protect them from fire to certain length of time and help to provide proper transfer of stresses from concrete to steel rebars, by helping provide proper cover to rebars. 

• a) Protection of the Rebar from the environment by providing a physical barrier.
• b) It provides thermal insulation, which protects the reinforcement bars from fire.
• c) To give reinforcing bars sufficient embedding to enable them to be stressed without slipping.
• d) Ensures that concrete completely encircles Rebar allowing passivation.
• e) Ensures that concrete completely encircles Rebar allowing complete bond to develop. Allows the Rebar to assume position and act as designed.
• f) Prevents staining.
• g) Provides a time lag in case of fire.                                                                 

What is the right amount of cover Block?

The right amount of cover is determined by the application and the environment (e.g., is the RCC under water, etc.)

In normal environments, following are typical covers recommended, 

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