What Is Clear Cover (or) Cover in Concrete?
The clear cover (or) Cover in RCC, is the distance between the exposed concrete surface (without plaster and other finishes) to the nearest surface of the reinforcement bar i.e., Steel rod.
Mostly, it is known as "clear cover" or "minimum concrete cover" in general terms on a construction site.
Why clear cover is important?
Cover is provided to protect the reinforcing bar (rebar) from corrosion due to weather and fire. If we don't leave a cover, then the reinforcing bar will stick to the surface of the shuttering and cause rust in the bar after we casting the column or beam and also damage the strength of the column or beam.
For example, in the case of fire in a building, the metal begins to melt and lose its strength. Therefore, the clear cover acts as an insulator and prevents from melting.
This gives more strength to the bars, reduces the chances of slipping and also increases the durability of the bars. This provides adequate embedding for the reinforcing bars to withstand stress without loss of grip.
How to Define Nominal Cover
As per IS 456(Clause 26.4.1), the term clear cover has been replaced by the term Nominal cover.
The nominal cover is the distance between the exposed concrete surface to nearest reinforcement bar ( it can be any bar I.e., main bar, longitudinal bar and even links or stirrups).
What Is Effective Cover in Concrete?
The Effective cover is the distance measured betweenthe exposed concrete surface (without plaster and other finishes) to the centre of the area ( centroid ) of reinforcement, i.e., tension or compression reinforcement.
Effective cover = overall depth – effective depth. (Or).
Effective cover = Clear cover + Diameter of Stirrup + (Diameter of main reinforcement bar ÷ 2).
Member | Clear cover (Normal Conditions) | wet climatic environment or sea side location |
Foundation | 75 mm |
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Raft Foundation | Top = 50 mm Bottom = 75 mm Sides = 75 mm |
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Strap Beam | 50 mm |
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Beam | 25 mm | 35 to 40 mm |
Column | 40 mm | 50 mm |
Flat Slab | 20 mm |
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Slab | 15 mm |
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