Bridges stainless steel rebars

McDonald et al. studied the performance of solid stainless steel rebars (types 304 and 316) and found that they performed well while ferritic stainless steels (types 405 and 430) developed pitting (15). Studies by McDonald et al. reported investigations on a 10-year exposure of 304 stainless steel in Michigan and Type 304 stainless steel clad rebar in a bridge deck in New Jersey and found no corrosion (15). In a study by Virmani and Clemena, the type 316 stainless steel-clad rebar extended the estimated time to the cracking of the concrete beyond 50 years, but not as much as solid types 304 and 316 stainless steels (100 years) (16). 

In addition, McDonald et al. (15) reported on two highway structures constructed with stainless steel rebar. No corrosion was observed for solid 304 stainless steel rebar in a bridge deck in Michigan as well as in New Jersey. The chloride levels in both bridge decks were below or at the threshold level for corrosion initiation in black steel rebars. It is estimated that the use of solid stainless steel rebar provides an expected life of 75-100 years (15, 16). McDonald et al. estimated the costs, at three installations, of the use of solid stainless steel and found the overall cost to be 6-16% higher than black steel (17). 

From the point of view of cost, it is preferable to use stainless steel-clad rebar instead of stainless steel rebar. It is estimated that the use of stainless steel-clad rebar provides an expected life of 50 years. The cost of stainless steel cladding can vary depending on the raw material market prices just like solid stainless steel, but also depends on the cladding manufacturer, cladding thickness, and the chosen grade of stainless steel. With proper quality control, stainless steel-clad rebar promises to be an effective means of control for bridge deterioration because of corrosion of reinforcing steel. 

Because of the tremendous cost involved in the repair of the existing concrete bridges it is necessary to develop designs that will permit longer life of these structures. One such method is the use of stainless steel rebars that offer the following benefits ... 

The concept of using stainless steel rebars is relatively new. At the present time no design standards or specifications are available however, the Canadian Standards Association expects to have a stainless steel design specification available by the end of 1998 for use in Canada. Since working codes and allowable bridge loadings vary in different political subdivisions, design specifications will have to be developed by each individual political subdivision. 

Naturally, the initial cost of a structure with stainless steel rebar will be higher than that of a conventional structure. However, the overall construction cost increase may actually be relatively modest. The case for stainless steel rebar can be strengthened when a life-cycle cost approach is followed. This approach helps to focus attention on total costs over the lifetime of a structure, including the frequency and cost of future maintenance and replacement work. In such an analysis performed for a bridge, the cost benefits of austenitic stainless steels over carbon steel were clearly apparent after a time period of 18 to 23 years, at which time major repair costs would be incurred for the conventionally reinforced structure. ... 

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