The document discusses reinforced concrete covering requirements according to the Bangladesh National Building Code. It defines concrete covering as the minimum distance between the surface of embedded steel reinforcement and the outer surface of the concrete. It then provides requirements for the minimum concrete cover thickness for different structural elements like slabs, walls, beams, columns, and footings based on whether the concrete is exposed to weather or the earth. It also discusses methods for maintaining the proper concrete cover and requirements for bundled bars and future considerations like fire protection and corrosive environments.

1. Reinforced Concrete Covering
According to
Bangladesh National Building Code
(BNBC)
Prepared By
GROUP NO.03
121025 121031
121026 121032
121027 121033
121028 121034
121029 121035
121030 121036
Submitted To
DR. MD. MOZAMMEL HOQUE
Associate Professor
Department of Civil Engineering,
DUET
MD. KOBIR HOSSAIN
Lecturer
Department of Civil Engineering,
DUET
Design of Concrete Structure – I
Sessional
Dhaka University of Engineering & Technology,
Gazipur,Bangladesh

2. Contents
1. Definition
2.Methods of maintaining cover
3.Slab Covering
4.Wall Panel Covering
5.Beam Covering
6.Column Covering
7.Footing Covering
8.Shell and Folded Plate Member

3. ❶ To protect the steel reinforcement bars ( rebar’s ) from environmental
effects to prevent their corrosion.
❷ To provide thermal insulation, which protects the reinforcement bars
from fire, and;
❸ To give reinforcing bars sufficient embedding to enable them to be
stressed without slipping.
In reinforced concrete, is the least distance between the surface of
embedded reinforcement and the outer surface of the concrete (ACI 130).
Why need covering ?
Concrete cover

4. Methods of maintaining cover
Plastic under layers.
Metal plastic tipped bar chairs.
Concrete Chairs
Plastic strip bar chairs
supporting heavy rebar on
suspended slab

5. ❶𝑐𝑜𝑛𝑐𝑟𝑒𝑡𝑒 𝑁𝑜𝑡 𝐸𝑥𝑝𝑜𝑠𝑒𝑑 𝑡𝑜 𝑊𝑒𝑎𝑡ℎ𝑒𝑟
𝟎𝟏. 36 mm φ bar and smaller
16 𝑚𝑚 𝑖𝑓 Precast
20 𝑚𝑚 𝑖𝑓 Cast‐in‐place
𝟎𝟐. 40 mm φ to 57 mm φ
30 𝑚𝑚 𝑖𝑓 Precast
40 𝑚𝑚 𝑖𝑓 Cast‐in‐place
❷𝑐𝑜𝑛𝑐𝑟𝑒𝑡𝑒 𝐸𝑥𝑝𝑜𝑠𝑒𝑑 𝑡𝑜 𝐸𝑒𝑎𝑟𝑡ℎ 𝑜𝑟 𝑊𝑒𝑎𝑡ℎ𝑒𝑟
𝟎𝟏. 16 mm φ bar and smaller
30 𝑚𝑚 𝑖𝑓 Precast
40 𝑚𝑚 𝑖𝑓 Cast‐in‐place
𝟎𝟐.19 mm φthrough 36 mm φ
40 𝑚𝑚 𝑖𝑓 Precast
50 𝑚𝑚 𝑖𝑓 Cast‐in‐place
𝟎𝟐. 40 mm φ to 57 mm φ
50 𝑚𝑚 𝑖𝑓 Precast
Slab Covering

6. Wall Covering
*Wall Panels(Precast):
𝐸𝑥𝑝𝑜𝑠𝑒𝑑 𝑡𝑜 𝐸𝑒𝑎𝑟𝑡ℎ 𝑜𝑟 𝑊𝑒𝑎𝑡ℎ𝑒𝑟
1. 40 𝑚𝑚 for 40 mm φ to 57 mm φ bars
2. 20 𝑚𝑚 36 mm φ bar and smaller
❶𝑐𝑜𝑛𝑐𝑟𝑒𝑡𝑒 𝑁𝑜𝑡 𝐸𝑥𝑝𝑜𝑠𝑒𝑑 𝑡𝑜 𝑊𝑒𝑎𝑡ℎ𝑒𝑟
𝟎𝟏. 36 mm φ bar and smaller
16 𝑚𝑚 𝑖𝑓 Precast
20 𝑚𝑚 𝑖𝑓 Cast‐in‐place
𝟎𝟐. 40 mm φ to 57 mm φ
30 𝑚𝑚 𝑖𝑓 Precast
40 𝑚𝑚 𝑖𝑓 Cast‐in‐place
❷𝑐𝑜𝑛𝑐𝑟𝑒𝑡𝑒 𝐸𝑥𝑝𝑜𝑠𝑒𝑑 𝑡𝑜 𝐸𝑒𝑎𝑟𝑡ℎ 𝑜𝑟 𝑊𝑒𝑎𝑡ℎ𝑒𝑟
𝟎𝟏. 16 mm φ bar and smaller
30 𝑚𝑚 𝑖𝑓 Precast
40 𝑚𝑚 𝑖𝑓 Cast‐in‐place
𝟎𝟐.19 mm φ through 36 mm φ
40 𝑚𝑚 𝑖𝑓 Precast
50 𝑚𝑚 𝑖𝑓 Cast‐in‐place
𝟎𝟐. 40 mm φ to 57 mm φ
50 𝑚𝑚 𝑖𝑓 Precast

7. ❶𝑐𝑜𝑛𝑐𝑟𝑒𝑡𝑒 𝑁𝑜𝑡 𝐸𝑥𝑝𝑜𝑠𝑒𝑑 𝑡𝑜 𝑊𝑒𝑎𝑡ℎ𝑒𝑟
1. 40 𝑚𝑚 𝑓𝑟𝑜𝑚 Primary reinforcement, Ties,
stirrups, spirals 𝑖𝑓 Cast‐in‐place
2. 20 ≤ 𝒅 𝒃≤ 40 Primary reinforcement
𝑖𝑓 Cast‐in‐place
3. 16 𝑚𝑚 from Ties, stirrups, spiral
𝑖𝑓 Precast
❷𝑐𝑜𝑛𝑐𝑟𝑒𝑡𝑒 𝐸𝑥𝑝𝑜𝑠𝑒𝑑 𝑡𝑜 𝐸𝑒𝑎𝑟𝑡ℎ 𝑜𝑟 𝑊𝑒𝑎𝑡ℎ𝑒𝑟
Primary reinforcement
𝟎𝟏. 36 mm φ bar and smaller
16 𝑚𝑚 𝑖𝑓 Precast
20 𝑚𝑚 𝑖𝑓 Cast‐in‐place
𝟎𝟐. 40 mm φ to 57 mm φ
30 𝑚𝑚 𝑖𝑓 Precast
40 𝑚𝑚 𝑖𝑓 Cast‐in‐place
Beam Covering

8. Column Covering
❶𝑐𝑜𝑛𝑐𝑟𝑒𝑡𝑒 𝑁𝑜𝑡 𝐸𝑥𝑝𝑜𝑠𝑒𝑑 𝑡𝑜 𝑊𝑒𝑎𝑡ℎ𝑒𝑟
1. 40 𝑚𝑚 𝑓𝑟𝑜𝑚 Primary reinforcement, Ties,
stirrups, spirals 𝑖𝑓 Cast‐in‐place
2. 20 ≤ 𝒅 𝒃≤ 40 Primary reinforcement
𝑖𝑓 Cast‐in‐place
3. 16 𝑚𝑚 from Ties, stirrups, spiral
𝑖𝑓 Precast
❷𝑐𝑜𝑛𝑐𝑟𝑒𝑡𝑒 𝐸𝑥𝑝𝑜𝑠𝑒𝑑 𝑡𝑜 𝐸𝑒𝑎𝑟𝑡ℎ 𝑜𝑟 𝑊𝑒𝑎𝑡ℎ𝑒𝑟
Primary reinforcement
𝟎𝟏. 36 mm φ bar and smaller
16 𝑚𝑚 𝑖𝑓 Precast
20 𝑚𝑚 𝑖𝑓 Cast‐in‐place
𝟎𝟐. 40 mm φ to 57 mm φ
30 𝑚𝑚 𝑖𝑓 Precast
40 𝑚𝑚 𝑖𝑓 Cast‐in‐place
Same as beam

9. * Minimum concrete cover for
concrete cast against and
permanently exposed to earth
shall be 75 mm.
Footing Covering

10. ❶ 𝑐𝑜𝑛𝑐𝑟𝑒𝑡𝑒 𝑁𝑜𝑡 𝐸𝑥𝑝𝑜𝑠𝑒𝑑 𝑡𝑜 𝑊𝑒𝑎𝑡ℎ𝑒𝑟
1. 19 mm φ bar and larger
20 𝑚𝑚 𝑖𝑓 Cast‐in‐place
16 𝑚𝑚 𝑖𝑓 Precast
2. 16mm φ bar and smaller
16 𝑚𝑚 𝑖𝑓 Cast‐in‐place
10 𝑚𝑚 𝑖𝑓 Precast
Shell and Folded Plate Member
Folded Plate Member
Shell Member

11. Bundled Bars
=
*Minimum concrete cover shall be equal to
the equivalent diameter of the bundle, but
need not be greater than 50 𝑚𝑚

12. Future Extension : Exposed reinforcement, inserts, and plates intended for bonding with future
extensions shall be protected from corrosion.
Fire Protection : If a thickness of cover for fire protection greater than the concrete covers specified in
8.1.7.1 through 8.1.7.6 is required, such greater thicknesses shall be specified.
Corrosive Environments: If a thickness of cover for corrosive environment or other severe exposure
conditions greater than the concrete covers specified in 8.1.7.1 through 8.1.7.6 is required, such greater
thicknesses shall be specified. For corrosion protection, a specified concrete cover for reinforcement
not less than 50 mm for walls and slabs and not less than 65 mm for other members may be used. For
precast concrete members a specified concrete cover not less than 40 mm for walls and slabs and not
less than 50 mm for other members may be used.
Others

13. Reference
1. http://en.wikipedia.org/wiki/Concrete_cover
2. Bangladesh National Building Code (BNBC) http://buildingcode.gov.bd

14. Thanks
to
Everyone