Stainless steel reinforcement

Stainless steel rebar has been applied in special circumstances but it is a very expensive option. A clad stainless steel with a mild steel core and stainless 

Calcinm nitrite is the principal corrosion inhibitor available to stop corrosion that is compatible with concrete in the casting process. As stated in Section 10.2, it is accepted by FHWA as an alternative to FBECR for protection against chloride induced corrosion. FHWA research shows that if sufficient nitrite is added to the concrete mix to ensure a chloride to nitrite ratio of less than 1.0 at rebar depth, then the nitrite will prevent corrosion. Obviously this is feasible in marine conditions where the chloride level is known (and assuming no concentration effects) but may be more difficult in other situations. 

The advantage of calcinm nitrite is that it can be added to the mix and has no serions effects on the design, construction and performance of the strnctnre other than its effect as a set accelerator. Mix design may require adjusting to include a retarder. Its disadvantage is that there mnst be enough to stop corrosion and it is consnmed with its exposure to chlorides. It is therefore important to calcnlate the chloride exposure for the life of the structure and add snfficient inhibitor. It does not inhibit the application of cathodic protection or chloride extraction in later life of the strnctnre if necessary. 

Other proprietary corrosion inhibiting admixtures, mainly amine based, are also available although there is much discussion about longevity and effectiveness. Some of these issues are covered in Elsener (2001). As an additive to the concrete mix, inhibitors can be used along side other protective measures such as coated reinforcement. 

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McDonald, D.B., Sherman, M.R., Pfeifer, D.W., and Virmani, Y.P., Stainless Steel Reinforcing as Corrosion Protection, Nickel Development Institute, Reprint Series 14034, August 1995. 

Smith, F.N., C.P. Cutler, D.J. Cochrane, Stainless Steel Reinforcing Bars, Proceedings, Conference on Understanding Corrosion Mechanisms in Concrete, Massachusetts Institute of Technology, Cambridge, MA, July 1997. 

The cost of various techniques can only be given very roughly, and any estimate will be incomplete, since the actual cost will vary from one application to another. Furthermore, different types of prevention mechanisms are not directly comparable. Beyond this, it can be said that with respect to normal carbon-steel reinforcement, use of galvanized and epoxy-coated bars costs about twice as much, and the cost of stainless-steel reinforcement is about 5 to 10 times higher. The use of nitrite inhibitors in higher doses costs approximately 30 /m of concrete (volume). Coatings may vary from 7 to 50 /m of concrete surface, hydrophobic treatment costs about 10 /m. Cathodic prevention varies from 50 to 100 /m. ... 

Often the use of stainless-steel reinforcement is hmited to the outer part of the structure (skin reinforcement) or to its most critical parts for economical reasons. Furthermore, when stainless-steel bars are used in the rehabihtation of corroding structures, they are usually connected to the original carbon-steel rebars. Concern has been expressed with regard to the risk of galvanic corrosion of carbon steel induced by coupHng with stainless-steel bars. Actually, the galvanic corrosion that can arise when stainless steel is used in partial substitution of carbon steel has to be compared with that which takes place in the absence of stainless steels [30]. 

In principle, stainless-steel reinforcement can be a viable solution for preventing corrosion in a large number of applications. The chloride threshold is much higher than the chloride content that is normally found in the vicinity of the steel even in structures exposed to marine environment or de-icing salts. There is no objection to using stainless steel only where its improved protection is necessary, combined with normal steel at other areas. Hence, stainless-steel bars can be used in the more vulnerable parts of structures exposed to chloride environments, such as joints of bridges or the splash zone of marine structures. Similarly, they can be used when the thickness of the concrete cover has to be reduced, such as in slender elements. 

A. E. Bauer, D. J. Cochrane, The Actual Implication of Stainless Steel Reinforcement in Concrete Structures,... 

G. Kulessa, Stainless steel reinforcement for concrete , Betonwerk und Fertigteiltechnick, 1988, 54 (3), 58-63. B. L. Brown, D. Harrop,... 

O. Klinghoffer, T. Skovsgaard, Cost-effective enhancement of durability of concrete structures by intelligent use of stainless-steel reinforce-... 

U. Nurnberger, W. Beul, Corrosion of stainless-steel reinforcement in cracked concrete , Otto Graf Journal,... 

Pier in Progreso, Mexico. Evaluation of the Stainless Steel Reinforcement, Inspection report, Arminox,... 

Concrete Society (1998). Guidance on the Use of Stainless Steel Reinforcement. Concrete Society Technical Report, 51. 

Reconstruction, using high-performance stainless steel reinforced concrete, of the 100 external comhs supporting the peripheral slabs. The columns are called combs because they have a wave-breaking effect, in the background you can see the sea and temporary dyke that was built to keep the construction site dry, as well as the tetrapods maintaining the dyke. ( Christine Raynaud - BTPM). 

The hose was fabricated with a Teflon PTFE inner core and a braided stainless steel reinforcement sleeve. Postincident inspections of two stainless steel hoses nse to deliver phosgene identified tmiqne corrosion patterns on the braided stainless. Testing confirmed the hose was fabricated of the correct materials. Investigators learned that most of the braided hoses were identified with tags secured either with plastic ties or... 

Aramid-fiber-reinforced Stainless-steel-reinforced, 7%, 10%... 

MacDonald, D. B., Sherman, M. R., Pfeifer D. W. and Y. P. Virmani (1995) Stainless steel reinforcing as corrosion protection. Concrete International, May 1995. 

Natural weathering steels commonly used for structural steelwork do not perform well in concrete containing moisture and chloride and are not suitable for reinforcement. Stainless steel reinforcement has been used in special applications, especially as hardware for attaching panels in precast concrete construction, but is much too expensive to replace mild-steel reinforcement in most applications. 

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