The Cover provided by the Concrete to the Reinforcement bar is very important to ensure corrosion free long life to the Structure. Let us see some details on cover to reinforcement.
The Cover is the minimum clear distance from the reinforcement to the Phase of the concrete.
It is measure from the outer edge of the studs or tiles of Beams and columns to the outer surface of the concrete. It protects reinforcement from corrosion and provides resistance to fire damage.
The cover enhances the durability of the structure. The Cover distance is ensure by providing cover blocks between the reinforcement and shuttering before pouring concrete.
The Thickness of the cover bears depending on the type of exposure that the concrete has with surrounding environment. If the concrete is exposed to marine or aggressive surrounding or it is inside the soil having harmful chemicals higher cover should be provided, more cover to be provided if concrete has to withstand accidental fire for longer duration, Cover thickness can range from 20 mm to 75 mm.
The cover concrete should be dense and impervious> Stone chips, tile pieces etc should not be used in place of concrete or good quality PVC Cover Blocks. In slabs the spacing of the cover Blocks should be such that the reinforcement does not sag in between and touch the shutter plate under the load of concrete.
Summary of Cover to Reinforcement
Cover is important for protection against corrosion and fire damage.
It should be more in aggressive environments,
Cover depends on type of member & exposure condition.
Concrete Cover Blocks are preferable than those made with other materials.