The cover is required to protect the reinforcement bars against corrosion, fire, and atmospheric agencies. Concrete cover blocks are essential to keep a gap between concrete and reinforcement to prevent the reinforcement from rusting. 

If the cover blocks are made in the ratio 1:2 (cement: sand), it represents the concrete mixture ratio that follows in the concrete casting to the particular structural member. The thickness of the cover depends on environmental conditions and the type of structural member. 

 The minimum thickness of the reinforced cover is indicated in the structural drawing as follows.

The concrete reinforcement is secured by a sufficiently thick and dense concrete cover. In the case of difficult working conditions if the building construction work is carried out underground or if chemical or mechanical corrosion is expected the concrete cover should be thicker and dense.