Concrete cover for reinforcement is essential for safeguarding the rebar against erosion as well as fire. The depth of the cover is based on ecological conditions and type of structural member. The slightest thickness of reinforcement cover is specified in the drawings, or achieved from the related code of practice. The specifications for reinforcement cover for various structural members in diverse conditions are explained below :-
a) To each end of reinforcing bar, not below 25 mm or below twice the diameter of the bar.
b) In case of a longitudinal reinforcing bar in a column, not under 40 mm not less than the diameter of such bar. For columns of least dimension of 20 cm or below, whose reinforcing bards should not surpass 12 mm, a cover of 25 mm should be applied.
c) For longitudinal reinforcing bars in a beam, not under 30 mm or below the diameter of the bar.
d) For tensile, compressive shear or other reinforcements in a slab or wall not below 15 mm, not less than the diameter of such bar.
e) For any other reinforcement not below 15 mm, not less than the diameter of such bar.
f) For footings and other major structural members in which the concrete is placed directly alongside the ground, cover to the bottom reinforcement must be 75 mm. If concrete is discharged on a layer of thin concrete, the bottom cover is curtailed to 50 mm.
g) For concrete surfaces uncovered to the weather or the ground once forms are separated - like retaining walls, grade beams, footing sides and top etc. below 50 mm.
h) Expanded cover thickness is offered as specified on the drawings, for surfaces uncovered to the action of injurious chemicals (or uncovered to earth polluted by such chemicals), acid, alkali, saline atmosphere, sulphorone, smoke etc.
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Published By
Rajib Dey
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