The fundamental difference between B420C and B500C is the characteristic yield strength: 420 MPa and 500 MPa respectively. The letter "C" at the end shows the ductility class and matters for the earthquake code.
Higher strength means the same load can be carried with less cross-section; but the choice is not free, it depends on the structural calculation for the project.
How the code reads
| B | Reinforcing steel for concrete (Betonstahl) |
|---|---|
| 500 | Characteristic yield strength, MPa |
| C | Ductility class — high ductility |
Why ductility matters
Ductility shows how far the steel can stretch before it breaks. A structure's ability to absorb energy under earthquake loads depends on this property.
Class "C" means high ductility, and its use is essential in earthquake regions.
Which is chosen
The choice belongs to the structural calculation for the project. Because B500C gives higher strength it can reduce the amount of reinforcement; but that is not an automatic advantage in every project.
A change of grade changes the calculation; do not change the grade written in the project on your own initiative.
Certificates and verification
A quality certificate comes with the rebar consignment; the grade, diameter and batch number appear on it.
On acceptance at site, check that the certificate matches the marking on the bar.