In this Article, We shown the definition of various exposure conditions for concrete as per IS 456, Minimum Grade of concrete and nominal concrete cover for different exposure condition as per IS456, etc.
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Exposure Conditions as per IS 456
There are major 5 environmental exposure condition as par IS 456 code that is listed below.
- Very Severe
The Concrete Surfaces which are protected against weather or aggressive conditions, except those situated in coastal area are considered in mild exposure condition.
Moderate Exposure Condition considered when,
- Concrete surface sheltered from severe rain or freezing whilst wet
- Concrete surface exposed to condensation and rain
- Concrete continuously under water
- Concrete in contact or buried under non-aggressive soil/ground water
- Concrete surface sheltered from saturated salt air in coastal area.
Also Read: Load Combination as per IS 456
Severe Exposure Condition considered when,
- Concrete surface exposed to severe rain, alternate wetting and drying or occasional freezing whilst wet or sever condensation
- Concrete completely immersed in sea water
- Concrete exposed to coastal environment.
4. Very Severe
Very Severe Exposure Condition considered when,
- Concrete surface exposed to sea water spray, corrosive fumes or severe freezing condition whilst wet
- Concrete in contact with or buried under aggressive sub soil-soil/ground water.
5. Extreme Severe
Extreme Severe Exposure Condition considered when, surface of concrete member s in tidal zone or member in direct contact with liquid solid aggressive chemicals.
Exposure Condition for Concrete Map of India
Minimum Grade of Concrete for Different Exposure Condition
|Exposure Condition||Minimum Grade of Concrete for PCC|
|Exposure Condition||Minimum Grade of Concrete for RCC|
Also Read: Development length of bar as per IS 456
Minimum Cement Content for Different Exposure Condition
Here we tabulated minimum cement content for various exposure condition as per IS456.
|Exposure Condition||Minimum Cement Content for PCC|
|Very Severe||260 Kg/m3|
|Exposure Condition||Minimum Cement Content for RCC|
|Very Severe||340 Kg/m3|
Maximum Water-Cement Ratio for Different Exposure Condition
Here we tabulated Maximum water/cement ratio for various exposure condition as per IS456.
|Exposure Condition||Maximum Water/Cement for PCC|
|Exposure Condition||Maximum Water/Cement for RCC|
Also Read: What is Expansion joint in building
Nominal Cover of Concrete for Different Exposure Condition
Here we tabulated Nominal Cover of Concrete for various exposure condition as per IS456.
|Exposure Condition||Nominal Concrete Cover Not Less Than|
- For Main reinforcement up to 12mm diameter bar for mild exposure, the nominal cover may be reduced by 5mm.
- Unless specified otherwise, actual concrete cover should not deviate from the required nominal by +10mm/0mm.
- For Exposure condition ‘severe’ and ‘very severe’, reduction of 5mm may be made, where concrete grade is M35 and above.