The benefits of stainless steel rebar
Reinforced concrete combines low cost, versatility, and high strength. However, over time the process of carbonation means that concrete loses the high alkalinity that protects carbon steel from corrosion.
Stainless steel does not rely on concrete for its corrosion protection and is a straightforward solution when concrete is subject to the ingress of chlorides from either marine environments or de-icing salts. Stainless rebar is also used for long design life buildings, such as temples or monuments, and when equipment is sensitive to magnetic fields and needs non-magnetic reinforcement.
Specifying stainless rebar
Specifying stainless rebar (SSR) comprises three tasks: where to specify SSR, which designation to specify, and how to specify SSR.
Today, most major reinforced concrete projects require a durability report, which includes a calculation on the likelihood of carbonation in the concrete and/or the extent of the ingress of chlorides. Predictive modeling is used for structures in known high-risk environments or those with service lives greater than 50 years. Designers around the world today mainly use Life 365 or AGEDDCA from the Concrete Society technical Report TR61.
In order to further explain the process of specifying stainless rebar, we have included the following downloads:
Stainless steel reinforcement: the use of predictive models – an Outokumpu-commissioned report written by world expert in concrete durability reports, Bryan K Marsh of Arup Materials Consulting.
Simple Representative Model – an excel spreadsheet model that helps illustrate the main points from the Stainless steel reinforcement report. (Note: The file is tested for compatibility with Microsoft Excel 2010 running on Windows 7. Computer settings must be set to English or a language using the decimal point rather than the comma, and macros must be enabled. Compatibility problems may be experienced if using a different operating system/version.)
Standards for Highways and
Use of Stainless Steel Reinforcement in Bridges – these two reports discuss specifying stainless steel rebar.
Choosing rebar designation
Rebar designation is mainly affected by the Critical Chloride Threshold Level (CCTL), where chlorides travel through concrete, mainly by diffusion, and reach the steel reinforcing bar, eventually reaching sufficient concentration to initiate pitting corrosion in the parent metal. The value generally used for the resistance of carbon steel rebar is 0.4% chlorides by mass of cement. Stainless steel rebar has corrosion resistance in the order of one magnitude more.
Designers use predictive modeling of chloride diffusion to calculate where they need to replace the carbon steel rebar with stainless steel rebar and what level of corrosion resistance they will require the stainless to have at design life.
We have included the following download to give more information about CCTL (available in the Research Papers tab below):
There are two main standards for Stainless Rebar (SSR) in the world today: the British Standard BS6744 and the American Standard ASTM A955. The fundamental differences are that the profiles and grades (strengths) follow their respective carbon steel standards.
The ASTM standard has a corrosion test included. This is manufacturer specific and not alloy designation specific. The report included in the Research papers tab below by Kansas University confirms the suitability of LDX 2101® for ASTM A955 specification.
There are other standards for SSR in the world and as countries revise their carbon steel rebar standard, they often incorporate a SSR standard as well. In Europe the logic is that as BS6744 should comply to any new European SSR standard.
Outokumpu supplies mill test certificates with every bundle delivered.
Outokumpu’s quality assurance scheme is ISO 9001 (2008) certified and we are externally audited by Lloyds. Outokumpu is CARES approved, and also approved by Norway’s own certification authority, Kontrollrådet.