C35/45 Concrete Mix Design
C35/45 is specified under EN 206 where exposure is more severe than typical carbonation conditions — commonly chloride exposure from de-icing salts, or significant freeze-thaw risk.
Typical exposure classes
Often paired with XD1–XD2 (chloride exposure other than seawater) or XF2–XF3 (freeze-thaw, often with de-icing salt). The exact durability limiting values for these classes are EN 206 recommended defaults, and the national annex that applies to your project can set stricter or differently structured requirements.
A note on national annexes
The exposure classes above are generic EN 206 associations; the exact maximum water-cement ratio, minimum cement content and minimum strength class figures for each are EN 206 recommended default values, and can be set stricter, or structured differently, by the national annex that actually applies to your project — for example BS 8500 in the UK or DIN 1045-2 in Germany. See why national annexes matter for why this matters, and use this site’s UK or Germany calculator directly if your project sits in one of those countries.
Typical uses
Car parks, bridge elements, roads-adjacent structures exposed to de-icing salts, and other elements in more demanding chloride or freeze-thaw environments.
Frequently asked questions
Does C35/45 need air entrainment?
Where the exposure class includes a freeze-thaw class (XF), yes — a minimum air content is required in addition to the strength class, with the exact minimum set by the applicable national annex; see air entrainment.
Are XD and XF limits the same across EN 206 countries?
No — these are exactly the kind of durability limiting values EN 206 leaves to national annexes; see why national annexes matter.