The European concrete standard EN 206-1 was internationally adopted in 2000 as a non-harmonised EN-standard. With regard to the use of different constituent materials, EN 206-1 carries out:

"Constituent materials shall not contain harmful ingredients in such quantities as may be detrimental to the durability of the concrete or cause corrosion of the reinforcement and shall be suitable for the intended use in concrete.
Where general suitability is established for a constituent material, this does not indicate suitability in every situation and for every concrete composition.
…
General suitability is established for cement conforming to EN 197-1."

In the absence of European standards for absolute performance testing of concrete, due to different long term experience, requirements for the method of specification to resist environmental actions are given in EN 206-1 in terms of established concrete properties and limiting values of composition.

The environmental actions are classified as exposure classes. A differentiation is made between the exposure classes XO (no attack), XC (carbonation), XD (de-icing salt), XS (chloride from sea water), XF (freezing and freeze-thaw with de-icing salt) and XA (chemical attack). By using examples, a classification into up to 4 levels is allowed. The given examples are informative. The exposure classes to be selected depend on the provisions valid in the place of use of the concrete. This exposure classification does not exclude consideration of special conditions existing in the place of use of the concrete or the application of protective measures such as the use of stainless steel or other corrosion resistant metal and the use of protective coatings for the concrete or the reinforcement.

A recommendation for the choice of limiting values for concrete composition and properties is given in Annex F (informative) of EN 206-1 when using CEM I cement conforming to EN 197 1 and aggregate with maximum nominal upper size in the range of 20 mm to 32 mm. The values are based on the assumption of an intended working life of the structure of 50 years. The minimum strength classes were derived from the relationship between water/cement ratio and the strength class of concrete made with cement of strength class 32,5.

Due to the lack of experience on how the classification of the environmental actions on concrete reflect local differences in the same nominal exposure class, the specific values of these requirements for the applicable exposure classes are given in the provisions valid in the place of use (National application documents NAD).

The requirements for each exposure class shall be specified in terms of:

• permitted types and classes of constituent materials;
  
• maximum water/cement ratio;
  
• minimum cement content;
  
• minimum concrete compressive strength class (optional);
  

and if relevant

• minimum air-content of the concrete.
  

The provisions valid in the place of use of the concrete should include requirements under the assumption of an intended working life of at least 50 years under the anticipated maintenance conditions. For shorter or longer working life, less onerous or more severe requirements may be necessary. In these cases or for specific concrete compositions or specific corrosion protection requirements for the concrete cover of the reinforcement (e.g. in the case of cover less than that specified in the relevant parts of ENV 1992-1 for corrosion protection), special considerations should be made by the specifier for a specific site or by national provisions in general.

Examples of application of blended cements

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