“2304” Gr75 Duplex Stainless Steel Rebar, From Its Surface To Its Core, Is The Long-Term Alternative To Corrosion Resistant Concrete Reinforcing Steel.
There are four types of stainless steel chemistries per ASTM A276 (PDF). Only two are generally regarded as being suitable for stainless steel rebar:
Austenitic Grade (Non-magnetic such as Type 316LN & XM-28)
Austenitic-Ferritic Grade (Duplex such as Type 2304 & 2205)
All stainless steel bars must conform to the physical specifications of ASTM A955/A955M (PDF).
The current ASTM A955/A955M specification is under review. With the increased interest and use of stainless steel rebar, the specification is being updated with pertinent information relative to information gained with its use.
Although considered an Austenitic Grade, S24100 or XM-28 stainless steel rebar should not be used in applications that absolutely require non-magnetic concrete reinforcement.
By year end 2012, all stainless steel will be required to have ASTM A955/A955M grade marks. GR75 will be designated with two “dots”; GR60 will be designated with one “dot”. It may take some time to purge existing inventories once the specification goes into effect.
Stainless Steel can also be referred to by a UNS (Universal Numbering System) designation such as S24100, S32205, S32304, S31653, etc. These designations are then given a “Type”. Individual chemistries can be listed interchangeably by its UNS designation and/or Type.
There are as many Types (chemistries) of stainless steel as there are in carbon rod! Each chemistry has been created for a specific application.