B25 concrete / C20/25
B25 is a regional concrete-strength label, not a complete universal mix specification. Under EN 206 notation, C20/25 means 20 MPa characteristic cylinder strength and 25 MPa characteristic cube strength at 28 days.
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B25 concrete strength and C20/25
The labels are often compared because the second value in C20/25 is a 25 MPa characteristic cube strength. They are not identical order codes: B25 and C20/25 come from different classification systems, while the EN class explicitly states cylinder and cube test values. Record the governing standard and specified class on the plan and bill of materials.
How to specify concrete instead of copying “B25”
- Start with structural design. Loads, spans, supports and reinforcement determine the required strength rather than the catalogue label.
- Set exposure and working life. Carbonation, chlorides, freeze–thaw, sulfates and wet ground can impose composition, cover and durability limits.
- Confirm the test notation. For C20/25, the characteristic values are 20 MPa on a cylinder and 25 MPa on a cube at 28 days.
- Complete the delivery specification. Include consistency, maximum aggregate size, chloride class and any pumping, finish or curing constraints required by the job.
- Check the batch record. Match the delivery ticket, quantity, time, class and project reference before placement.
The Concrete Centre BS 8500 tool selects limiting values from exposure, design strength and cover. A current Sheffield City Council specification illustrates the C20/25 notation as 25 N/mm² cube strength under BS EN 206 and BS 8500. Neither source makes C20/25 suitable for every foundation.
Common B25 concrete questions
What strength is B25 concrete?
B25 is a regional label associated with 25 MPa characteristic compressive strength. State the governing standard and test specimen because the label alone is not a complete universal specification.
Is B25 the same as C20/25 concrete?
They are often compared because C20/25 has a 25 MPa characteristic cube strength, but they belong to different classification systems. Use the project class and local standard instead of assuming automatic interchangeability.
Is 25 MPa enough for every foundation?
No. Structural design, ground conditions, exposure, reinforcement cover, intended working life and the applicable standard may require another class or additional limits.
Technical specifications
| Thermal conductivity | 1.69 W/(m·K) |
|---|---|
| Density | 2400 kg/m³ |
| Compressive strength | 25 MPa |
| Frost resistance | 200 cycles |
| Combustibility | Non-combustible |
Catalogue values are orientation only. Specify the governing standard, strength and exposure classes, consistency, aggregate size, chloride class and project-specific requirements before ordering.
