Concrete cover means the distance between the outer surface of the concrete and the outermost layer of reinforcement in the concrete. A Concrete 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.
Concrete cover does not have a structural function its purpose is to prevent damage occurring to the building part. It ensures that the concrete encases the steel on all sides so that it is not exposed to the external air. If the cover is insufficient the concrete can flake off. The steel is then no longer covered and may corrode.
The building part is damaged fundamentally in the long term and this can lead to failure. Cover should not be less than 15 mm, and is generally between 20- and 25-mm. Cover Blocks are now becoming more common at constructions sites. As it strengthens the roof top and also beam.