Why Use Stainless Steel?
Salit Specialty Rebar is a leading supplier of cut and pre-assembled stainless steel rebar and mesh.
Why Use Stainless Steel Rebar?
Because it Works!
Because it Provides Net Savings!
Because it Reduces the Future Tax Burden!
There is a growing trend among North American specifiers which is quite evident in the highway sector to use stainless steel because it is seen as the most economically viable corrosion resistant reinforcing steel alternative for use in service environments typified by chloride attack.
Once a structure built with stainless steel reinforcement is commissioned, there will be a dramatic reduction in repairs for the design life of the project.
For a background teaser on the history of the development of stainless, the textbook definition of this alloyed material and how the chemistry works to resist chlorides, visit Stainless Background in our Stainless Resources section.
The Facts about Stainless Steel
Use Stainless Steel to control the damaging effects of corrosive environments due to the presence of chlorides from de-icing road salts, marine salt spray or from chloride contamination or spillage from chemical processing in industrial environments such as in the mining or petrochemical sectors.
Savings in the Initial Construction Cost
There are a number of potential initial construction cost savings opportunities attributable singularly to the use of stainless steel rebar.
Concrete Cover : Historically, engineers used an increase in concrete cover as a defence mechanism against chloride ingress and ultimately to protect black steel from rusting. As stainless steel self protects, there are substantial savings to be made by reducing excess concrete cover intended for black steel but essentially redundant with the use of stainless. The Michigan DOT and the New York DOT both have policies of reducing cover with stainless.
In Section 5.1.1 of the New York State DOT bridge design manual a 1” reduction of concrete cover and slab thickness for bridge decks is allowed only when constructed with stainless steel rebar. Section 15.12.4 indicates that the cost of stainless will be offset to a degree by the reduction in thickness of the slab and reduction in the foundation cost owing to the reduced dead load. The designer is reminded that reinforcement is a small percentage of the overall cost when deciding the type of reinforcement to use.
In the design of new structures, less cover reduces the dead load which lightens the design loading on supporting members; hence, a savings in concrete costs.
High Strength Steel : As stainless steel rebar is high strength steel at Fy = 75 ksi, there is the potential to reduce the amount of rebar steel. The Minnesota DOT mandates it’s engineers to design their bridge structures, particularly in the transverse deck steel, using this higher level of yield which can result in a 15% saving.
Pavings, Membranes, Deck Sealants, Concrete Additives: The “belt and suspenders” philosophy of protection duplication is unnecessary with stainless. This high performance rebar product is the only protection system required. Secondary systems are potentially a waste of money.
Development Length : Design concepts follow that of conventional black rebar. The development length and splice length is the same as black bar compared to coated products which require 30% more development.
Avoidance of Coating Repairs : There are no repair costs associated with damaged coatings due to poor handling in the shop or at the job site.
Stainless is Vastly More Corrosion Resistant
Chemistry matters and it is the alloy formulation especially designed to effectively resist chlorides which differentiates stainless from other products.
Stainless steel rebar has been extensively tested by publicly and privately funded entities for corrosion resistance against other rebar products and consistently ranks substantially ahead, in fact orders of magnitude better than other rebar products.
There are other corrosion resistant rebar products available but they have proven to be inadequate in that they will not provide the extended service life that Owners require. The standard service horizon was a minimum of 75 years which is now being prolonged for critical structure elements to 100 years.
A substantial pack of alloys gives it a chemistry that clearly differentiates stainless from other products relying either on fragile, ineffective coated black bar offerings or other minimal alloy uncoated products.
References are included in the Stainless Steel Tab under Research.
Increased Concrete Durability
Corroding steel rebar is one of the main reasons for our crumbling infrastructure. The connection between rusting rebar and spalled concrete is well documented as is the associated significant downstream cost of repair and traffic disruption. The logic is false that we can spend less now on low cost, inadequate materials and somehow escape the longer term cost repair consequences.
Stainless steel rebar ensures extended concrete durability because it will not rust. The essential value of stainless steel rebar is its Durability and the benefits which ensue — cost reduction and increased structure uptime.
75 yr. Positive Field Performance of Stainless Steel in Salt Water
A Pier built in the Caribbean Sea in 1937-1941 still in Use
The port city of Progreso, in the Mexican state of Yucatán, boasts of the longest pier in the world. The pier is also the first concrete structure in the world constructed between 1937 and 1941 with stainless steel reinforcement. Despite the relatively poor grade of concrete used, the pier has withstood the harsh marine environment and has been in continuous service for over 75 years without any major repair or routine maintenance activities.
Click here to see SSR projects where stainless steel was the preferred choice by engineers.
View the Life cycle analysis of Progreso Pier by the Nickel Institute at https://www.nickelinstitute.org/en/Sustainability/LifeCycleManagement/LifeCycleAssessments/LCAProgresoPier.aspx
Service Life Extension, Repair Cost Savings : Benefits
The unique ability of stainless steel to effectively resist chloride induced corrosion significantly extends the durability of the concrete. This prolongs the service life of the structure while translating into a dramatic reduction in structure repair and maintenance costs compared to building infrastructure with other types of rebar.
Reduction in Structure Downtime : Benefits
Reduction in Repair Costs : Avoided repair and maintenance activities means less disruption in service operations which in the case of a bridge or roadway means less traffic congestion and increased network uptime and throughput.
Reduction in User Costs : The macro economic benefit of reducing the cost of delaying commuters by reducing congestion – user costs – is significant and directly attributable to increased network uptime and throughput.
Guarantees a Dramatic Reduction in Life Cycle Cost
There is a logical cause and effect relationship which flows from superior corrosion resistance, to an increase in concrete durability and service life, to reduced repair and maintenance costs, to increased structure utilization or uptime and less users costs which ultimately results in lower total, all in costs over the life of the structure – life cycle cost.
Superior quality products usually fetch a higher price tag.
But in the case of stainless steel rebar, the life cycle cost of a structure using stainless steel rebar is dramatically less than the cost using other rebar alternative because :
- The cost avoidance benefits, as explained above.
- The incremental project cost of using this product is normally trivial; in many cases, the incremental cost is less than 1% for major projects
- Not taken into consideration are the initial cost savings referred to above and user costs
In other words, the benefits of using stainless vastly exceed the incremental cost associated with this material.
New York State DOT published two studies on the subject of life cycle costing of bridges which were based on their own experiences and were conducted internally.
The first study was titled “Improving Tomorrow’s Infrastructure : Extending the Life of Concrete Structures with Solid Stainless Steel Reinforcing Bar”. The paper looked at the comparative life cycle costs using different types of reinforcement for bridge rehabilitation and for the construction of a new bridge. The conclusions of this study was that the life cycle cost saving of using stainless steel rebar for bridge deck rehabilitations was 20% with respect to the next best alternative. For the construction of a new bridge which involves a much larger scale investment than bridge rehabs, the savings on a life cycle cost basis was 9% for the stainless case.
The second paper published by the DOT titled “Use of Advanced Materials to Extend Bridge Life and Reduce Initial Cost : A Case Study of Three Projects In New York City” studied the savings that could result from a reduction in concrete cover. It concluded that the incremental initial construction cost was “trivial” with stainless and the life cycle cost savings were 10% relative to next best alternative. The paper cites three examples of bridge projects in New York where the use of stainless steel rebar resulted in net project savings not otherwise achievable.
An Investment that Delivers Benefits : It Costs more but it Works!
The Owner has a choice of many types of rebar at various quality levels and prices points which mirrors our consumer society.
One can always pay less for a product but to expect the same or better performance at a lower price is not realistic. Stainless steel rebar delivers unmatched quality and benefits as measured by superior corrosion resistance, concrete durability, cost avoidance, better structure uptime. And ultimately, the least life cycle cost.
Stainless steel works and more than pays for its cost. The raw material may cost more but it works!
Same bar sizes as Conventional Steel
Stainless is available in the same bar sizes as conventional reinforcing bar steel.
Material is Readily Available
Salit Specialty Rebar keeps an inventory of all the common types and sizes of stainless steel reinforcing bar.
Backed by an ASTM Standard
Stainless steel rebar is manufactured to the standard ASTM A955M.
Comparable Design Concepts
Stainless steel is high strength steel; at Grade 75, the yield of this rebar is 75 ksi. The modulus of elasticity is within 3% of that of conventional mild steel and as such the design concepts are similar. The development length and splice length is the same as black bar compared to coated products which require 30% more development.
Lower Environmental Footprint
Stainless steel significantly extends the service life without major repair or maintenance beyond 100 years which has the effect of lowering the environmental impact and disruption of unnecessary rehabilitation projects well beyond that which otherwise be the case.
Other Unique Properties
- Good high and low temperature mechanical properties
- Excellent fire resistance
- Very ductile product
- Low magnetic permeability (non-magnetic) types of stainless are also available
The Facts: The Independent Research To Back It Up.
Stainless Steel Rebar has been proven to be a superior corrosion resistant reinforcing material. Below are excerpts from independent studies showing stainless steel rebar to be an excellent and cost effective choice. Links to entire studies in .pdf format are provided.
“Improving Tomorrow’s Infrastructure: Extending the Life of Concrete Structures with Solid Stainless Steel Reinforcing Bar” – by Bergmann and Schnell. – Recent advances in concrete technology have provided structural designers with materials which can easily last more than 100 years, and the life of many concrete structures today is limited by the reinforcing. Improvements in the life of the reinforcing can translate directly into extended life of the structure. http://www.stainlessrebar.com/docs/bergmannschnell.pdf
“Corrosion Resistance of Alternative Reinforcing Bars: An Accelerated Test” by Wiss, Janney Elstner Associates – Stainless Steel 316 and 2205 bars were largely free of corrosion except some minor corrosion product near to cut ends. The coating applied to the cut ends may have generated crevices which are at least partially responsible for the observed corrosion. These two types of stainless bars exhibited phenomenal low corrosion rates, approximately 0.1 percent of conventional steel.
“A Pilot Experimental Study on the Low Cycle Fatigue Behavior of Stainless Steel Rebars for Earthquake Engineering Applications” by Yihui Zhou, Yu-Chen Ou, George C. Lee and Jerome S. O’Connor, University at Buffalo – Enduramet 32 has the highest ductility and the best low-cycle fatigue performance among the steels investigated. In general, the three types of stainless steel (Enduramet 32, 2205 duplex and 316LN), are better than A706 G60.
“The Long Term Performance of Three Ontario Bridges Constructed with Galvanized Reinforcement” by F. Pianca and H. Schell, Ontario Ministry of Transportation – …Three Ontario structures were studied, built in 1975 and 1976 using galvanized reinforcement… Findings of the evaluation indicate the long-term (30 year) performance of galvanized reinforcement, while marginally better than conventional black reinforcement, showed evidence of corrosion and resulting delamination of concrete when the chloride content of the concrete exceeded the threshold to initiate corrosion. On one structure approximately 10% of the deck had deteriorated and required rehabilitation before achieving even a twenty-year service life. Based on the structures surveyed, galvanized reinforcement in the Ontario highway environment did not provide the anticipated corrosion protection.
“Effects of Galvanic Coupling between Carbon Steel and Stainless Steel Reinforcement in Concrete” by Bertolini, Gastaldi, Pedeferri and Pedeferri – The coupling of corroding carbon steel with stainless steels are generally modest, and they are negligible with respect those due to the coupling with passive carbon steel which always surround the corroding area.
“Galvanic Coupling between Carbon Steel and Stainless Steel Reinforcements” by Qian, National Research Council Canada, Qu, Hokkaido University, Japan and Coates, NIckel Institute – Based on this investigation, it can be concluded that use of SS and CS reinforcing bars in the same concrete structure will not increase the corrosion risk on CS even when these bars are in direct (electrical) contact. In fact, the increase in the corrosion rate of CS due to galvanic coupling of SS with corroding CS was less than that of the combination of non-corroded CS with corroding CS. Stainless steel, with its ability to resist chloride-induced corrosion, can be used in areas vulnerable to chloride ingress. Therefore, the judicious use of stainless steel with carbon steel in the high-corrosion-risk areas of a concrete structure can be a cost-effective option for reducing corrosion and greatly extending the service life of concrete structures.
Go to the STAINLESS RESOURCES page where technical information is archived.