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Chloride in concrete (BS 8500)

BS 8500 Concrete – Complementary British Standard to BS EN 206 requires that concrete should have a maximum chloride ion content by mass of cement depending on certain criteria. This is expressed as a chloride class e.g. Cl 0,40  The use of a "," instead of  a "." is how it is expressed in the main Standard BS EN 206.  


BS 8500-1 Table A.8 says:

Prestressed pre-tensioned concrete or concrete containing reinforcement of other embedded metal that is to be  heat cured, should normally be specified as chloride class Cl 0,10.

In prestressed post-tensioned and unbonded prestressed concrete, no particular guidance is given as the appropriate class will depend on the construction and exposure conditions. For internal post-tensioned office construction, Cl 0,40 is considered appropriate.

For reinforced concrete with ordinary carbon steel or other embedded metal it should be specified as chloride class Cl 0,40, or Cl 0,30.


If a class is not specified, BS 8500-1 clause 4.2.3 for designated concrete states:

"where a class has not been specified, Cl 1,0 for the GEN and CB series of designated concretes or Cl 0,40 for other designations for all cements except CEM I+SR0 or SR3, in which case it shall be Cl 0,20."  For designed concrete, Clause 4.3.2 states “ the chloride class will be Cl 0,40“


Sulfate resistance is achieved via composite/combination cements or CEM I+SR0 or 3 to EN 197


Acknowledgement: Concrete Society