A cover block is essentially a spacer that lifts the rebar matrix off the ground to allow concrete to flow beneath the rebar.
Code requires different cover to slab, beam, column, pile,footing, pile cap based on the environmental exposure condition and fire resistance requirement. As a result, the cover block raises the rebar by cover required and becomes a permanent and integral part of the poured concrete, ensuring that no part of the rebar sags and reducing the amount of concrete coverage required during the pour.
The purpose of a concrete cover is to prevent damage to a building part rather than to provide structural support. It ensures that the steel is completely covered in concrete and is not exposed to the elements. Concrete can flake off when the cover is insufficient. The steel is no longer covered and may corrode as a result.
In the long run, the design can be fundamentally damaged, if the cover is not enough.
The concrete cover also ensures fire safety because it directs heat away from the sensitive steel. As with the outside cover, a space between the steel bars within the building part must be maintained.
