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NEW GENERATION STAINLESS NEW GENERATION STAINLESS

STEEL REINFORCING BARS FOR STEEL REINFORCING BARS FOR

CONCRETE STRUCTURESCONCRETE STRUCTURES

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CONTENTS

1.1. IntroductionIntroduction2.2. Causes of corrosionCauses of corrosion3.3. Stainless steelStainless steel4.4. Types of stainless steelTypes of stainless steel5.5. Cost of stainless steelCost of stainless steel6.6. ApplicationsApplications7.7. ConclusionConclusion8.8. ReferencesReferences

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IntroductionIntroduction

Construction builds the basic framework and infrastructure of a country Construction builds the basic framework and infrastructure of a country

Reinforced concrete has been used successfully in the construction Reinforced concrete has been used successfully in the construction

industry since the beginning of this centuryindustry since the beginning of this century

One of the products traditionally used to reinforce concrete is plain One of the products traditionally used to reinforce concrete is plain

carbon steelcarbon steel

Large number of reinforced structures are starting to show serious signs Large number of reinforced structures are starting to show serious signs

of deterioration, particularly those over 30 years of age due to corrosion of deterioration, particularly those over 30 years of age due to corrosion

of reinforcementof reinforcement

This necessitates costly and time-consuming repairs and maintenance of This necessitates costly and time-consuming repairs and maintenance of

the structurethe structure

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What Causes Corrosion?What Causes Corrosion?

Chloride ion is the main culpritChloride ion is the main culprit

Chlorides may be incorporated into the original mix due to their Chlorides may be incorporated into the original mix due to their

presence in the sand, aggregate or water. Chlorides penetrate presence in the sand, aggregate or water. Chlorides penetrate

through the "cover" when the external surfaces of the concrete through the "cover" when the external surfaces of the concrete

are exposed to seawater, marine atmospheres or de-icing saltsare exposed to seawater, marine atmospheres or de-icing salts

When steel corrodes, it forms an oxide layer. These corrosion When steel corrodes, it forms an oxide layer. These corrosion

products-oxides-have a larger volume than the original steel. products-oxides-have a larger volume than the original steel.

This expansion puts pressure on the concrete cover. Since the This expansion puts pressure on the concrete cover. Since the

concrete is already set and hard, it causes cracks as it expands to concrete is already set and hard, it causes cracks as it expands to

accommodate the larger volume of steel insideaccommodate the larger volume of steel inside

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Some Pictures Showing the Deterioration of Structures Due to Some Pictures Showing the Deterioration of Structures Due to

Carbon Steel ReinforcementCarbon Steel Reinforcement

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Several Methods Are Currently Employed in an Attempt to Reduce Several Methods Are Currently Employed in an Attempt to Reduce

the Corrosion of Carbon Steel Rebars.the Corrosion of Carbon Steel Rebars. Rebar coatingsRebar coatings

Increased concrete coverIncreased concrete cover

Reduced water/cement ratiosReduced water/cement ratios

Corrosion inhibiting admixtures added to the concrete mixCorrosion inhibiting admixtures added to the concrete mix

Cathodic protectionCathodic protection

Application of waterproofing membranes, penetrants and Application of waterproofing membranes, penetrants and

sealers on concrete surfacessealers on concrete surfaces

Solution lies in providing the stainless steel which is resistant Solution lies in providing the stainless steel which is resistant

to corrosionto corrosion

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What Is Stainless Steel?What Is Stainless Steel? Stainless steel is low carbon steel. It is an alloy of iron with chromium content Stainless steel is low carbon steel. It is an alloy of iron with chromium content

over 10.5%.Also nickel,molybdenum and certain other alloying elements are over 10.5%.Also nickel,molybdenum and certain other alloying elements are

addedadded

Chromium is the alloying element that imparts to stainless steel their corrosion Chromium is the alloying element that imparts to stainless steel their corrosion

resistance qualitiesresistance qualities

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Fig 1.Corrosion Resistance of Stainless steel

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Types Of Stainless SteelTypes Of Stainless Steel

AusteniticAustenitic

FerriticFerritic

Austenitic- ferritic (duplex)Austenitic- ferritic (duplex)

MartensiticMartensitic

Some of the commonly used grades of stainless steel for rebar Some of the commonly used grades of stainless steel for rebar

applications are type 304,316(austenitic) and 2205(duplex).applications are type 304,316(austenitic) and 2205(duplex).

The alloy is selected based on mechanical properties and the The alloy is selected based on mechanical properties and the

expected exposure or corrosivity of the service environment, i.e. the expected exposure or corrosivity of the service environment, i.e. the

level of corrosion resistance required.level of corrosion resistance required.

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AusteniticAustenitic It is made by adding nickel (from 8 to 25 percent) and increasing the It is made by adding nickel (from 8 to 25 percent) and increasing the

chromium level (from 17 to 25 percent). Molybdenum can also be chromium level (from 17 to 25 percent). Molybdenum can also be

added (up to 7 percent) to increase the corrosion resistanceadded (up to 7 percent) to increase the corrosion resistance

Excellent corrosion resistance in organic acid, industrial Excellent corrosion resistance in organic acid, industrial

and and

marine environments.marine environments.

Excellent weldability (all processes)Excellent weldability (all processes)

Excellent formability, fabricability and ductilityExcellent formability, fabricability and ductility

Excellent cleanability, and hygiene characteristicsExcellent cleanability, and hygiene characteristics

Good high and excellent low temperature properties (high Good high and excellent low temperature properties (high

toughness at all temperatures)toughness at all temperatures)

Non magnetic (if annealed)Non magnetic (if annealed)

Hardenable by cold work only Hardenable by cold work only

Basic propertiesBasic properties::

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FerriticFerritic

Ferritic stainless steel has properties similar to mild steel but with Ferritic stainless steel has properties similar to mild steel but with

the better corrosion resistance. These alloys are somewhat less the better corrosion resistance. These alloys are somewhat less

ductile than the austenitic types. These are plain chromium ductile than the austenitic types. These are plain chromium

stainless steels with varying chromium content between 12 and stainless steels with varying chromium content between 12 and

18%, but with low carbon content18%, but with low carbon content

Moderate to good corrosion resistance increasing with Moderate to good corrosion resistance increasing with

chromium contentchromium content

Not hardenable by heat treatment and always used in the annealed Not hardenable by heat treatment and always used in the annealed

condition condition

MagneticMagnetic

Weldability is poorWeldability is poor

Formability not as good as the austeniticFormability not as good as the austenitic

Basic propertiesBasic properties::

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Austenitic-ferritic (Duplex):Austenitic-ferritic (Duplex):

Austenitic-ferritic (duplex) duplex stainless steels have a metallurgical Austenitic-ferritic (duplex) duplex stainless steels have a metallurgical

structure that is a combination of both ferritic and austenitic. They have a high structure that is a combination of both ferritic and austenitic. They have a high

chromium content (from 18 to 26 percent) and a low nickel content (from 4 to 7 chromium content (from 18 to 26 percent) and a low nickel content (from 4 to 7

percent). Most grades also contain some molybdenum (from 2 to 3 percent)percent). Most grades also contain some molybdenum (from 2 to 3 percent)

High resistance to stress corrosion crackingHigh resistance to stress corrosion cracking

Increased resistance to chloride ion attackIncreased resistance to chloride ion attack

Higher tensile and yield strength than austenitic or ferritic Higher tensile and yield strength than austenitic or ferritic

steelssteels

Good weldability and formabilityGood weldability and formability

Basic properties:Basic properties:

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MartensiticMartensitic

Martensitic stainless steel contains mostly 11 to 13% chromium Martensitic stainless steel contains mostly 11 to 13% chromium

and is both strong and hard with moderate corrosion resistance. and is both strong and hard with moderate corrosion resistance.

Martensitic stainless steels were the first stainless steels Martensitic stainless steels were the first stainless steels

commercially developed (as cutlery) and have relatively high commercially developed (as cutlery) and have relatively high

carbon content (0.1 - 1.2%) compared to other stainless steelscarbon content (0.1 - 1.2%) compared to other stainless steels

Moderate corrosion resistanceModerate corrosion resistance

Can be hardened by heat treatment and therefore high strength Can be hardened by heat treatment and therefore high strength

and hardness levels can be achievedand hardness levels can be achieved

Poor weldabilityPoor weldability

MagneticMagnetic

Basic propertiesBasic properties

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Is Stainless Steel Costly? Is Stainless Steel Costly? UNEXPECTED COSTUNEXPECTED COST

LOST PRODUCTION COSTLOST PRODUCTION COST

MATERIAL COSTMATERIAL COST

ADDITIONAL OPERATING COST ADDITIONAL OPERATING COST

INSTALLINSTALLAATTTIONTION COST COST

MAINTAINANCE COSTMAINTAINANCE COST

REPLACEMENT COSTREPLACEMENT COST

MATERIAL COSTMATERIAL COST

INSTALLINSTALLATIONATION COST COST

STAINLESS STEELSTAINLESS STEEL CARBON STEELCARBON STEEL

Initial cost of stainless steel products will definitely be higher.Initial cost of stainless steel products will definitely be higher.

However to work out the cost of ownership and usage over the However to work out the cost of ownership and usage over the

design life of the structure, say 50 or 80 years, one has to include design life of the structure, say 50 or 80 years, one has to include

the initial cost and add the cost of maintenance, repair, the initial cost and add the cost of maintenance, repair,

replacement, downtime and other factors. replacement, downtime and other factors.

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This method called as the life cycle costing (LCC) analysis, will This method called as the life cycle costing (LCC) analysis, will

show how much the choice of different materials is actually going to show how much the choice of different materials is actually going to

affect the cost of ownership and use of the structureaffect the cost of ownership and use of the structure

Viewed in this manner stainless steel always proves itself to be Viewed in this manner stainless steel always proves itself to be

the most cost-effective choice over the design life of the structure or the most cost-effective choice over the design life of the structure or

the productthe product

The end result is always the same stainless steel is cost-effective The end result is always the same stainless steel is cost-effective

to the userto the user

EXAMPLESEXAMPLES

Take for instance the repair cost of Old Thane Creek Bridge.A-5 Take for instance the repair cost of Old Thane Creek Bridge.A-5

year life extension after just 10 years of service cost eightyear life extension after just 10 years of service cost eight times the times the

original cost (800% increase)original cost (800% increase)

Partial repair to Janak Sethu Bridge built in 1981 in Delhi cost Rs Partial repair to Janak Sethu Bridge built in 1981 in Delhi cost Rs

32 crore in 1999, whereas the initial cost of the bridge was only Rs 9 32 crore in 1999, whereas the initial cost of the bridge was only Rs 9

crore (250%) increasecrore (250%) increase

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Fig 4

Actual Life Costing Example-Oland Bridge,SwedenActual Life Costing Example-Oland Bridge,Sweden

On an average, most bridges need a repair between 18-22 years, On an average, most bridges need a repair between 18-22 years,

at an average cost of the original cost of the bridge itself. at an average cost of the original cost of the bridge itself.

In the above example, the initial capital cost increase amounts to In the above example, the initial capital cost increase amounts to

4% for Type 304 and 8% for Type 3164% for Type 304 and 8% for Type 316

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The increase in overall cost of the project by the introduction of The increase in overall cost of the project by the introduction of

stainless steel reinforcement bars can vary from 0.5% to 15% stainless steel reinforcement bars can vary from 0.5% to 15%

depending on the design.depending on the design.

Maximum durability is obtained with total substitution of stainless Maximum durability is obtained with total substitution of stainless

steel rebar in the structure.steel rebar in the structure.

However, selective substitution is considered as a means of However, selective substitution is considered as a means of

achieving enhanced durability at minimum increase in initial cost.achieving enhanced durability at minimum increase in initial cost.

For example, enhanced durability can be achieved by substituting For example, enhanced durability can be achieved by substituting

stainless steel for carbon steel rebar in the parts of the bridge stainless steel for carbon steel rebar in the parts of the bridge

considered to be at high risk to corrosion while the remainder of the considered to be at high risk to corrosion while the remainder of the

reinforcement will be normal carbon steel. (Schaffhausen Bridge - reinforcement will be normal carbon steel. (Schaffhausen Bridge -

Only half percent increase in initial project cost). Only half percent increase in initial project cost).

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AdvantagesAdvantages

Corrosion resistance: When embedded in concrete, rebar Corrosion resistance: When embedded in concrete, rebar

made of S31600, for example, shows superior (five to ten times made of S31600, for example, shows superior (five to ten times

better) resistance than that of carbon steel. Stainless steel rebar better) resistance than that of carbon steel. Stainless steel rebar

has been used in several highway overpasses and parapets in has been used in several highway overpasses and parapets in

the U.K., Michigan, Oregon, New Jersey, and Ontario; in the U.K., Michigan, Oregon, New Jersey, and Ontario; in

concrete structures constructed in aggressive marine concrete structures constructed in aggressive marine

environments; and in the repair and renovation of historic environments; and in the repair and renovation of historic

buildings.buildings.

Ease of handling and shipping: Unlike coated rebar, stainless Ease of handling and shipping: Unlike coated rebar, stainless

steel is much easier to work with during shipment and while on steel is much easier to work with during shipment and while on

site. Its inherent protective oxide layer is resistant to damage; it site. Its inherent protective oxide layer is resistant to damage; it

cannot chip, crack or fail. Stainless steel is also easily welded cannot chip, crack or fail. Stainless steel is also easily welded

and can be bent into desired shapes.and can be bent into desired shapes.

Lighter structure (greater strength)Lighter structure (greater strength)

Economical cost (life cycle cost analysis)Economical cost (life cycle cost analysis)

The following benefits of stainless rebarThe following benefits of stainless rebar

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Fire and heat resistanceFire and heat resistance

Impact resistanceImpact resistance

Environmental friendlyEnvironmental friendly

Durability: In composite structures like RCC bridges, 125 years of Durability: In composite structures like RCC bridges, 125 years of

trouble-free service life can be guaranteed. trouble-free service life can be guaranteed.

Available in many different product formsAvailable in many different product forms

Good strength Good strength

Good weldability for common rebar grades Good weldability for common rebar grades

Good ductility for common rebar grades (capable of 3D 180E Good ductility for common rebar grades (capable of 3D 180E

bends) bends)

No coatings to chip, crack, deteriorate No coatings to chip, crack, deteriorate

No coatings to damage and repair No coatings to damage and repair

Good mechanical properties for common rebar grades at high and Good mechanical properties for common rebar grades at high and

low temperatureslow temperatures

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ApplicationsApplications A host of marine structures such as bridge decks, sidewalks, A host of marine structures such as bridge decks, sidewalks,

ramps, parapets, pilings, barriers, retaining walls, anchoring ramps, parapets, pilings, barriers, retaining walls, anchoring systems, parking garages, sea walls, columns, piers, jetties systems, parking garages, sea walls, columns, piers, jetties and mooringsand moorings

Anchorages and any kind of jointsAnchorages and any kind of joints

Offshore platformsOffshore platforms

Tunnels, underpasses and subwaysTunnels, underpasses and subways

Bridges, viaducts, overpassesBridges, viaducts, overpasses

Cement frameworks with magnetic characteristicsCement frameworks with magnetic characteristics

Frameworks which are prone to breaking up due to frost or Frameworks which are prone to breaking up due to frost or because of low temperaturesbecause of low temperatures

Concrete slabs for drainage in environments with corrosive Concrete slabs for drainage in environments with corrosive agentsagents

Supports/restoration for statues, monuments, cement, stone Supports/restoration for statues, monuments, cement, stone and marble worksand marble works

Historic buildingsHistoric buildings

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A Coastal Replacement Bridge at North Bend, Oregon Has Used A Coastal Replacement Bridge at North Bend, Oregon Has Used 2205 Stainless Steel Rebar Instead of Carbon Steel Rebar for 2205 Stainless Steel Rebar Instead of Carbon Steel Rebar for Critical Structural Elements in a Harsh Marine Environment. Critical Structural Elements in a Harsh Marine Environment. ODOT Expects the New Bridge to Provide Maintenance-free ODOT Expects the New Bridge to Provide Maintenance-free Service for an Amazing 120 Years. That Is 2.5 Times the Service Service for an Amazing 120 Years. That Is 2.5 Times the Service Life of the Bridge It Is ReplacingLife of the Bridge It Is Replacing!

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Nuclear Plant In France: Stainless Steel Has Been Used to Build Nuclear Plant In France: Stainless Steel Has Been Used to Build Ferroconcrete Drums for Disposal of Radioactive Nuclear Wastes. In Ferroconcrete Drums for Disposal of Radioactive Nuclear Wastes. In This Application, for Safety Reasons, Is Mandatory the Use Stainless This Application, for Safety Reasons, Is Mandatory the Use Stainless Steel in Order to Avoid Cracks in the Concrete (Caused by Steel in Order to Avoid Cracks in the Concrete (Caused by Reinforcing Bars Corrosion) and Subsequent Waste LeakingReinforcing Bars Corrosion) and Subsequent Waste Leaking

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Stainless Steel Is Also Used in Restoration Works

Colosseum, Rome - Italy The work involved the partial restoration of the arena floor.The foundations in roman concrete was reinforced by stainless steel ribbed bars type AISI 304L in diameters 6, 8, 10, and 14 mm. Total quantity 3 tonnes.

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Glandstone Bridge, Queenslans, AustraliaThe Gladstone Bridge Was Built in 1960 and Showed Corrosion of the Reinforcing Mild Steel on the Deck.The Maintenance Works Have Seen the Use of 12 mm Diameter Stainless Steel Ribbed Bars Type 316L Joined With the Original Carbon Steel

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Conclusions

The primary intention of this presentation is to create an awareness on the

substantial advantage one can get by using stainless steel as reinforcement in

concrete structures

Despite the initial cost, there is considerable potential in savings of life cycle

cost, especially infrastructures, which are exposed to corrosive environment

Best suited material at all temperatures. Also stainless steel are suited for

cryogenic applications

Available in different grades and hence significant savings can be done

Also the material is available in different forms, which is more advantageous

Material is new generation and environmental friendly hence can be very

rightly utilized as a new generation material for all applications

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References

By K mani and P srinivasan-“service life of RC structures in corrosive environment: A comparison of carbon steel And stainless steel bars”- indian concrete journal, volume 75,1-12,2001

By Y sakumoto, T nakazato and A matsuzaki- “properties of stainless steel For building structures”- ASCE journal Of structural engineering, volume 122,1-6,1996

Web site references:

A. Use of stainless steel reinforcement bars for concrete structures-by dr. N.C mathur (president), ramesh R gopal (general manager), nickel development institute & secretary indian stainless steel development association, 55-A, uday park (ff) khel gaon marg, new delhi - 49(published in new building materials & construction world - september 2000)

B. Www.ISSDA.Com-stainless steel assures durability And enhances aesthetics Of structures-by ramesh R gopal, secretary, ISSDA and general manager of nidi

C. Www.SSINA.Com- stainless steel bridge-new bridge uses stainless steel rebar To last 120 years, CNC west feature article, august  september 2002 vol. XX no. 6 An arnold publication

D. Www.Outokumpu.Com

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THANK THANK YOUYOU