Why use Stainless – The Rationale

The Rationale is Simple -- for a structure under chloride or chemical attack the use of SSR will likely save the Owner money over the service life of the structure compared to the use other reinforcement bars.

The reasoning is straightforward. SSR’s chemistry is at the core of the rationale for using this bar. A chemistry specifically formulated to resist corrosion increases the durability of concrete which reduces repairs and maintenance costs while extending the service life beyond that achievable with other available reinforcement materials. The utilization rate of these structures increases as repair programs are drastically reduced in terms of time and intensity. Taking all these factors into consideration, the Life Cycle Cost with structures using SSR is the least of any comparable alternative. 

It is not rationale to think that spending less now on low cost, inadequate materials will somehow allow planners to escape the longer term repair cost consequences.

Cost Competitive

The raw material cost of stainless steel reinforcement relative to conventional black carbon reinforcement is NOT SIX TO TEN TIMES MORE!! In fact, the cost of SSR raw material is very competitive with other types of coated and uncoated corrosion resistant reinforcement considering the value of SSR. The fundamental point is that SSR costs have declined in recent years and the small premium to be paid is more than justified on the basis of the benefits it delivers.  

Superior Chemistry = Superior Corrosion Resistance

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 in comparative studies against other rebar products and consistently ranks substantially ahead -- in fact orders of magnitude better than other rebar products. 

Increased Concrete Durability

Corroding steel rebar is one of the main reasons for our crumbling infrastructure. The chlorides reach the surface of conventional rebar which forms rust occupying a volume of 6 times that of the original steel which generates large bursting forces in the concrete causing cracking and spalling. At this point it is a fast track to major structural repairs to the concrete.

Stainless steel reinforcement with its specially alloyed steel types allowing for much higher chloride threshold values for corrosion initiation fundamentally ensures that the concrete will be more durable into the long term.

Unique and Beneficial Material Properties

75 yr. Positive Field Performance of Stainless Steel in Salt Water
The world’s longest pier (now 6 KM long) built in the Caribbean Sea in 1937-1941 still in use today.

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 view the life cycle analysis of Progreso Pier by the Nickel Institute

WHY STAINLESS? MORE REASONS!

Service Life Extension 

The connection between rusting rebar and spalled concrete is well documented. The increased durability which stainless steel reinforcement affords reinforce concrete structures subject to chloride attack results in an extended number of years in which the structure will be functional (service life) relative to that which could be provided by other types of reinforcement. 

The benefit of a small additional upfront investment by specifying SSR is a long lasting structure.

Lower Operating Costs

The direct benefit from longer lasting, more durable structures is a drastic reduction in maintenance and major repairs to structures during the design life. In addition, Owners and users have to bear the significant cost of traffic delays during the repairs which are avoided with implementing the use of SSR in the critical zones of the structure. 

The avoidance of these maintenance and repairs cost is the payoff for using more durable materials in the original construction.  

Reduction in Structure Downtime and Traffic Delays

The utilization rate and throughput for any structure is increased by the factor of the decreasing length and frequency of maintenance and repairs attributable to corroding reinforcement. The effect of reducing traffic congestion by avoiding repairs has the macro-economic benefit of reducing the user costs of delaying commuters.

Dramatic Reduction in Life Cycle Cost

There is a logical cause and effect relationship which flows from superior corrosion resistance which provides for an increase in concrete durability and ultimately results in lower total cost over the life of the structure – the life cycle cost.   

Superior quality products usually fetch a higher price tag. However, 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 are very significant. 

• The incremental total project cost of using this product is normally trivial; in many cases, the incremental cost is less than 1% for major projects

• User costs can be reduced though these are seldom taken into consideration.

the benefits of using stainless vastly exceed the incremental cost associated with this material.

Life Cycle Cost Studies 

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.

Potential to Reduce Initial Costs  

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 defense 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 load on supporting members; hence, a savings in concrete costs.

Additional Load Carrying Capacity: For existing structures rehabilitated with SSR, this weight reduction due to less cover enhances the efficiency of the structure by increasing the live load carrying capacity.   

High Strength Steel: As stainless steel rebar is high strength steel at Fy = 80 ksi, there is the potential for Owners to reduce the amount of rebar steel by mandating their design engineers to design bridge structures using this higher yield point. (The Minnesota DOT has reported a 15% saving by embracing this practice).  

Deck Overlays, 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. 

Ease of Fabrication and Installation

Fabrication of SSR is the same as for uncoated carbon steel reinforcing bars, except for springback, which may require tooling adjustment. As such, there is no specialized equipment or processes that are required to fabricate stainless steel reinforcement other than the need to avoid carbon contamination throughout the plant. In addition, it is a weldable product with no special provisions required for installation.

It’s Steel  

Other non-steel bars made of composite materials are appearing on the market. These bars have different mechanical properties relative to steel notably that the allowable design strength is severely reduced due this material’s characteristic to lose strength over time, the strength in the transverse direction is very limited and the product is susceptible to degradation in humid conditions which calls into question the durability of this material.

Final Word: It May Cost 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!