Mild steel reinforcement has a characteristic yield strength of 250 N/mm2 and was designated as Grade 250 in BS 4449 Specification for carbon steel bars for the reinforcement of concrete. It was supplied as plain round bars. Standard diameters were from 6 mm to 16 mm. Other sizes were available by arrangement.
For further information see The CARES Guide to Reinforcing Steels, Part 3, Properties of Reinforcing Steels, which is available from www.ukcares.com or can be ordered by e-mail from email@example.com.
Note that this material has not been included in the 2005 revision of the Standard, as it does not comply with Eurocode 2 nor does it have any economic advantage.