The Structural Engineer's Corner

Eng. Onorio Francesco Salvatore

Exposure conditions for concrete according to British Standard 8110

Written By: Lexatus - Sep• 17•14

Exposure conditions

Similarly to other international standards, the British Standard 8110-1 defines different exposure conditions based on the design environment.

The environment can be:

– Mild;
– Moderate;
– Severe;
– Very severe;
– Most severe;
– Abrasive.

 

The mild environment is defined as:
Concrete surfaces protected against weather or aggressive conditions

The moderate environment is defined as:
Exposed concrete surfaces but sheltered from severe rain or freezing whilst wet
Concrete surfaces continuously under non-aggressive water
Concrete in contact with non-aggressive soil (see sulfate class 1 of Table 7a in
BS 5328-1:1997)
Concrete subject to condensation

The severe environment is defined as:
Concrete surfaces exposed to severe rain, alternate wetting and drying or occasional
freezing or severe condensation

The very severe environment is defined as:
Concrete surfaces occasionally exposed to sea water spray or de-icing salts (directly or
indirectly)
Concrete surfaces exposed to corrosive fumes or severe freezing conditions whilst wet

The most severe environment is defined as:
Concrete surfaces frequently exposed to sea water spray or de-icing salts (directly or
indirectly)
Concrete in sea water tidal zone down to 1 m below lowest low water

The abrasive environment is defined as:
Concrete surfaces exposed to abrasive action, e.g. machinery, metal tyred vehicles or
water carrying solids

 

The correct design is based on the correct combination of concrete class and concrete cover.

The following table coming from the BS 8110-1 has to be used for the concrete design:

Cover

So, if we are in a severe environment the minimum choice is to use a C40 concrete class with a nominal cover of 40 mm. If, instead of a C40, we use a C50, then the concrete cover can be reduced to 25 mm.

In case of most severe environment the concrete class to be used is raised to C50 and the minimum cover is 50 mm.

Special analysis on the abrasion are required for the abrasive environment.

 

For any issues or questions, you can contact the author at:

onorio@strutturista.com

Eng. Onorio Francesco Salvatore

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