C30/37 Concrete Mix Design
C30/37 is a common strength class for reinforced concrete facing more demanding carbonation exposure than C25/30, and is a frequent default choice for general exposed reinforced work.
Typical exposure classes
Often paired with XC4 (cyclic wet and dry carbonation exposure) and sometimes a moderate freeze-thaw class such as XF1, reflecting exposed reinforced elements subject to periodic wetting. See exposure classes and durability.
Designated Concrete equivalent
Closely associated with RC30/37 in the Designated Concrete catalogue. See the designated concrete catalogue.
Typical uses
Exposed reinforced concrete elements, some external structural work, and general reinforced concrete in more demanding but not extreme exposure.
Frequently asked questions
Is C30/37 always needed for external concrete?
Not always — it depends on the actual exposure class assessment for the project; milder, sheltered external elements can sometimes remain at C25/30, while more aggressive exposure needs a higher class again.
What is the BS 8500 designation closest to C30/37?
RC30/37 is the closest Designated Concrete equivalent.