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(This copyright material originally appeared in CONCRETE, March 2003, and is reported by permission of The Concrete Society, Century House, Telford Avenue, Crowthorne, Berkshire RG45 6YS, UK.) The Highways Agency code BA 84/02, Use of stainless steel reinforcement in highway structures is briefly outlined. Where stainless and carbon steel bars are in contact, it is noted that there is no need for electrical insulation as tests have shown that there is negligible galvanic, (bimetallic), reaction in concrete. European stainless steel reinforcement bar producers are obtaining UK CARES certification. The implementation of BA 84/02 along with the latest issue, (2001), of BS 6744 for bridge structures is discussed. Finally examples of the successful application of stainless steel reinforcement are given. The relevance of BS 8666 to the bending of stainless steel is noted.
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Terne coatings are hot dip lead-tin alloys on a stainless steel substrate strip. Alternatively electroplated tin coatings are allowed by EN 502 and EN 508-3. The strip thicknesses are usually between 0.4 and 0.8 mm. The main application for terne and tin-coated strip is external cladding and roofing.
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The potential use of stainless steel for roofing has only recently become more widely recognised, despite an early example of the use of stainless steel for the art deco spire of the Chrysler Building in New York, completed in 1930. In addition to a growing appreciation of stainless steel as an architectural material, other factors such as the introduction of low reflective, matt finishes and the development of improved methods of construction have played an important part in this process.
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This BSSA Special Report summarises the report prepared by Arup Research and Development prepared to take account of developments in the use of stainless steel in concrete reinforcement since the publication of BS 6744:2001 and the Highways Agency note BA 84/02. The issue of corrosion of reinforcement is discussed and followed by a summary of the use of stainless steel in concrete reinforcement. Guidance on selection criteria of the BS 6744 grades is shown and followed by notes from the BA 84/02 on cover, design crack width and the need for silane treatments. Finally design examples are shown and the cost calculation model discussed.
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This 12 page paper by Chris Baxter, Group Technical Market Support, AvestaPolarit Ltd. covers the issues of distortion during fabrication and welding, control of stainless steel welding processes and post fabrication cleaning. Buckling distortion can result from either poor design or welding practices. The key factors for good welding are clearly defined welding procedures, (BS EN 1011 and BS EN 287 and BS EN 288 are mentioned), control of heat input, temperature control and cleanliness. Welding electrode selection and methods including TIG, MMA, FCA, plasma, submerged arc and stud welding are covered. Finally, the importance of careful heat tint removal, (temper coloured areas), is discussed by either mechanical abrasion or chemical pickling cleaning methods is discussed. Although this establishes the corrosion resistance for the particular grade welded, care is needed with chemical pickling as it can change, (dull), the aesthetic appearance of the surfaces.
