Different Exposure Condition for Concrete as per IS 456

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.

So Please Read the article till the end, and if you get any information from this than please share with your friends, Because sharing is caring.

Exposure Conditions as per IS 456

There are major 5 environmental exposure condition as par IS 456 code that is listed below.

  • Mild
  • Moderate
  • Severe
  • Very Severe
  • Extreme

1. Mild

The Concrete Surfaces which are protected against weather or aggressive conditions, except those situated in coastal area are considered in mild exposure condition.

2. Moderate

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

3. Severe

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.

Also Read: Arrangement of Transverse Reinforcement in Column as per IS 456

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

exposure condition map of india
Image Source: Sefindia.org

Minimum Grade of Concrete for Different Exposure Condition

Here we tabulated minimum grade of concrete for various exposure condition as per IS456.

Exposure ConditionMinimum Grade of Concrete for PCC
Mild
ModerateM15
SevereM20
Very SevereM20
ExtremeM25
For Plain Concrete
Exposure ConditionMinimum Grade of Concrete for RCC
MildM20
ModerateM25
SevereM30
Very SevereM35
ExtremeM40
For Reinforced Cement Concrete

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 ConditionMinimum Cement Content for PCC
Mild220 Kg/m3
Moderate240 Kg/m3
Severe250 Kg/m3
Very Severe260 Kg/m3
Extreme280 Kg/m3
For Plain Concrete
Exposure ConditionMinimum Cement Content for RCC
Mild300 Kg/m3
Moderate300 Kg/m3
Severe320 Kg/m3
Very Severe340 Kg/m3
Extreme360 Kg/m3
For Reinforced Cement Concrete

Maximum Water-Cement Ratio for Different Exposure Condition

Here we tabulated Maximum water/cement ratio for various exposure condition as per IS456.

Exposure ConditionMaximum Water/Cement for PCC
Mild0.60
Moderate0.60
Severe0.50
Very Severe0.45
Extreme0.40
For Reinforced Cement Concrete
Exposure ConditionMaximum Water/Cement for RCC
Mild0.55
Moderate0.50
Severe0.45
Very Severe0.45
Extreme0.40
For Reinforced Cement Concrete

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 ConditionNominal Concrete Cover Not Less Than
Mild20mm
Moderate30mm
Severe45mm
Very Severe50mm
Extreme75mm
  • 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.

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