USE OF CORROSION RESISTANT USE OF CORROSION RESISTANT REINFORCING MATERIALSREINFORCING MATERIALS

Ray Bottenberg, P.E.Ray Bottenberg, P.E.Oregon Department of TransportationOregon Department of Transportation

IntroductionIntroduction

Iron reinforcing bar first used in Iron reinforcing bar first used in France in 1850s France in 1850s Steel reinforcing bar first used in Steel reinforcing bar first used in England in 1864England in 1864First concrete building reinforced First concrete building reinforced with steel in the U.S. was in 1893 with steel in the U.S. was in 1893 in Los Angelesin Los AngelesCarbon steel reinforcing bar is uniquely Carbon steel reinforcing bar is uniquely compatible with concretecompatible with concrete

Steel provides tension load path in concreteSteel provides tension load path in concreteThermal expansion rates are similarThermal expansion rates are similarHigh pH in concrete High pH in concrete passivatespassivates surface of steelsurface of steel

Effect of Salt on Reinforced ConcreteEffect of Salt on Reinforced Concrete

Salt destroys protective Salt destroys protective passivatedpassivated surface on reinforcing bars surface on reinforcing bars Salt acts as a catalyst and electrolyte for galvanic corrosionSalt acts as a catalyst and electrolyte for galvanic corrosionCorrosion products from reinforcing bars expand to 6Corrosion products from reinforcing bars expand to 6--11 times the 11 times the original metal thicknessoriginal metal thicknessExpansion of corrosion products causes Expansion of corrosion products causes spallingspalling of concrete and loss of concrete and loss of protective coverof protective cover

Sources of Salt ContaminationSources of Salt Contamination

Marine environment Marine environment Deicing chemicalsDeicing chemicalsSome concrete admixturesSome concrete admixtures

Solutions: Epoxy Coated Reinforcing Solutions: Epoxy Coated Reinforcing BarBar

Fusion Bonded Epoxy Coating Fusion Bonded Epoxy Coating Susceptible to nicks & other mechanical damageSusceptible to nicks & other mechanical damageDevelopment lengths are longerDevelopment lengths are longerSevere corrosion at flaws due to small anode effectSevere corrosion at flaws due to small anode effectPrevents future cathodic protectionPrevents future cathodic protectionSupported by ODOT Bridge Engineering for applications per BDDMSupported by ODOT Bridge Engineering for applications per BDDM

Solutions: Stainless Steel Reinforcing Solutions: Stainless Steel Reinforcing BarBar

Solid 316L (Austenitic) or 2205 (Duplex) Solid 316L (Austenitic) or 2205 (Duplex) DescaledDescaled & pickled to provide ideal & pickled to provide ideal passivatedpassivated surface (high pH not surface (high pH not required) required) Resistant to damageResistant to damageHigher initial costHigher initial costCurrently available with ODOT Special Specification 00530Currently available with ODOT Special Specification 00530Supported by ODOT Bridge Engineering for applications per BDDMSupported by ODOT Bridge Engineering for applications per BDDM

Solutions: HotSolutions: Hot--Dip Galvanized Dip Galvanized Reinforcing BarReinforcing Bar

Carbon steel reinforcing bar, hotCarbon steel reinforcing bar, hot--dip galvanizeddip galvanizedZinc is Zinc is amphotericamphoteric (i.e. susceptible to corrosion in high (i.e. susceptible to corrosion in high oror low pH) low pH) Not currently recommended by ODOT Bridge EngineeringNot currently recommended by ODOT Bridge Engineering

Solutions: Solutions: ““ZbarZbar””

Carbon steel reinforcing barCarbon steel reinforcing bar0.0020.002”” thick layer of arcthick layer of arc--sprayed zincsprayed zincFusion bonded epoxy coating Fusion bonded epoxy coating Vendor claims Vendor claims ““synergisticsynergistic”” corrosion corrosion protection protection Vendor claimed it can be bent like any other barVendor claimed it can be bent like any other barCoating failed during bar bendingCoating failed during bar bendingVendor then claimed that it requires special bending radius and Vendor then claimed that it requires special bending radius and bending temperaturebending temperatureNot currently recommended by ODOT Bridge EngineeringNot currently recommended by ODOT Bridge Engineering

Solutions: Solutions: ““NX CladNX Clad””

Carbon steel reinforcing barCarbon steel reinforcing bar316 stainless steel cladding by powder metal process316 stainless steel cladding by powder metal processCost about 60% of solid 316 reinforcingCost about 60% of solid 316 reinforcingClad layer cracked during bendingClad layer cracked during bendingNot currently recommended by ODOT Bridge EngineeringNot currently recommended by ODOT Bridge Engineering

Solutions: FRP RebarSolutions: FRP Rebar

Fiber reinforced polymer Fiber reinforced polymer reinforcing barreinforcing barDesign specifications existDesign specifications exist

ACI 440.1RACI 440.1R--0303AASHTO LRFD Bridge Design Specifications for GFRP AASHTO LRFD Bridge Design Specifications for GFRP Reinforced Concrete Decks and Deck SystemsReinforced Concrete Decks and Deck Systems

Not susceptible to saltNot susceptible to saltCan be damaged if moisture penetrates outer layersCan be damaged if moisture penetrates outer layersBent bars have to be fabricated in factoryBent bars have to be fabricated in factoryAppears cost effective on Millport Slough BridgeAppears cost effective on Millport Slough Bridge

Solutions: Economical Stainless SteelsSolutions: Economical Stainless Steels

EndurametEnduramet 32 (32 (NitronicNitronic 40) austenitic alloy with manganese, 40) austenitic alloy with manganese, approximately 50% cost of 316approximately 50% cost of 316ArminoxArminox Alloy 2304 duplex alloy, approximately 60% cost of 316Alloy 2304 duplex alloy, approximately 60% cost of 316Similar surface corrosion as 316Similar surface corrosion as 316Stress corrosion cracking test underway by ODOT Research (bent Stress corrosion cracking test underway by ODOT Research (bent bars can be susceptible)bars can be susceptible)

Solutions: Solutions: ““MMFXMMFX””

Proprietary Proprietary ““microalloyedmicroalloyed”” reinforcing barreinforcing barCurrently not recommended by ODOT Bridge EngineeringCurrently not recommended by ODOT Bridge EngineeringPotential for test in moderate environment Potential for test in moderate environment

Summary Summary

BDDM provides current guidelines for use of carbon steel, epoxy BDDM provides current guidelines for use of carbon steel, epoxy coated steel, and stainless steel reinforcing barscoated steel, and stainless steel reinforcing barsTwo economical stainless steel alloys are being tested, will be Two economical stainless steel alloys are being tested, will be added added to specs if suitableto specs if suitableAASHTO design specifications support FRP reinforcing bars for AASHTO design specifications support FRP reinforcing bars for bridge deck applications bridge deck applications

Questions? Questions?