There are a number of different chemical compositions for steels that are defined as ‘stainless’. For use in concrete, austenitic stainless steel will provide the required level of durability, particularly in chloride environments. All material should conform to BS 6744. Reinforcement is available both as plain bar with a characteristic strength of 200N/mm2 and ribbed bar with a characteristic strength of 500N/mm2. A full range of bar sizes (3mm to 50mm) is available. In addition bars with a strength of 650N/mm2 can be supplied but only in the smaller sizes (3mm to 25mm).
It should be noted that the cost of stainless steel is significantly more than that of carbon steel. However, it may be a viable alternative in highly aggressive locations with the higher initial cost being justified by reduced maintenance or an extended service life. The normal requirements for concrete quality and cover should not be relaxed.
Some stainless steel reinforcement is non-magnetic and hence is appropriate for applications such as support structures for sensitive electrical equipment (e.g. in hospitals). In general no significant modifications to the usual design methods are required. There are no special requirements on site except that stainless steel tying wire should be used.
Further information may be found in Stainless reinforcing steels, part of The CARES Guide to Reinforcing Steels which is available from UK CARES (www.ukcares.com)