C25/30 Concrete Mix Design
C25/30 is one of the most commonly specified general reinforced concrete strength classes under EN 206, used across a wide range of building and civil work.
Typical exposure classes
Commonly paired with XC1–XC2 carbonation exposure — reinforced concrete that is dry or occasionally wet. The associated maximum w/c and minimum cement content are EN 206 recommended default values, and can be set differently by the national annex that applies to your project.
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
General reinforced concrete — slabs, beams, foundations and walls in typical building work where exposure is moderate.
Frequently asked questions
Is C25/30 suitable for external exposed elements?
It can be for milder external exposure, but more severe carbonation, chloride or freeze-thaw exposure often calls for a higher class such as C30/37 or C35/45 — check the applicable national annex and the project’s exposure class assessment.
Do the durability limits for C25/30 XC2 differ by country?
The recommended EN 206 default values can be adopted directly or tightened by a national annex; see why national annexes matter.