Concrete Cover “ing” is the cover provided for the reinforcement in Reinforced Cement Concrete. Cover is defined as the Distance between the outer surface of the concrete to the inserted reinforcement.
Why we provide Concrete Cover?
Covering is provided to arrest the attack of corrosion. Reinforcement is prone to corrosion and fire for atmospheric conditions. If the proper cover isn’t implemented then there is more chance of corrosion and cracks in hardened RCC.
Covering is provided For every element of the building (Slabs, Beams, footings) where the reinforcement is used. In order to maintain the proper arrangement of reinforcement and to provide a covering for reinforcement. covering blocks are used.
Different Types of Concrete Cover Block:-
There are different types of covering blocks based on the type of material used:-
1. Wooden concrete cover Block
2. Steel concrete cover block
3. PVC Block
4. Cement Masonry concrete cover block
5. Aluminium Block
Conditions for Concrete Cover :-
Covering varies according to the dimensions of the elements (Slab, beam, column, footings, etc.) the conditions for providing covering in RCC is tabulated below:-
|If the length of the item is ≤ 0.3||1" or 25mm or 0.025m|
|If the length of the item is in between 0.4m to 0.5m then||2" or 50mm or 0.050m|
|If the length of the item is ≥ 0.6m then||4" or 100mm or 0.1m|
Here the term "item" is referred to either slab or column or beam or retaining wall or footing
From above, The maximum concrete cover is 0.1m or 100cm
Concrete cover for different elements of building:-
1. Concrete Cover in Columns / Beams:-
#1 Below is the top view of a column ( the Same principle is applied for beams too).
From the above figure, The length and Width of the column are 0.5m and 0.45m. It satisfies the second condition in the above table. Then, the covering for reinforcement in the column is 0.050m from all sides and same reinforcement is designed accordingly. The Dimensions of Reinforcement in the column are 0.40m and 0.35m.
#2:- Suppose the length and width of the column are 0.40 and 0.25. From the table, It satisfies both the conditions (2) & (1). Don’t apply two conditions for a single column. Covering should be Symmetrical. Consider the least dimension from the two dimensions. In below figure least dimension is 0.25. For 0.25m the covering of 0.025m is provided. Therefore the covering of 0.025m is provided in all the sides. Hence, dimensions of reinforcement is 0.35m and 0.20m
Total Length of Stirrup from the above figure is 2x [0.35+0.20]+ 9D x 2 (hook length)
2. Concrete Cover for Slabs: –
From the below figure the length and width of the slab are 1.3m and 1.0m. As per the above table, the covering of 0.1m is provided if the length of the bar is more than 0.6m. Apply the same condition as mentioned. The covering of 0.1m is provided from all the sides of the slab.
3. Concrete cover for footings:-
As per the below figure the dimensions of Footing are 0.7m and 0.6m. To length and width of Mesh (reinforcement) used in footings are obtained by deducting the cover. Apply the same principle as above, the below footing is fallen under (3) condition. As per the condition, a concrete cover of 0.1m is deduced from all the sides. Hence, the dimensions of reinforcement are 0.5m and 0.4m.
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