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Carbon Fiber Strands for PrestressedConcrete PilesH. Celik Ozyildirim, Ph.D., PE.Principal Research Scientist, VCTIRandStephen R. Sharp, Ph.D., PE.Senior Research Scientist, VCTIRVirginia Concrete Conference: March 8, 2013
Outline Corrosion in reinforced concrete structures– concrete is expected to protect steel.– conventional steel reinforcement can corrode. Corrosion resistant reinforcement (CRR) in– conventional concrete: SS, MMFX2, etc.– prestressed concrete: carbon fiber compositecable (CFCC): corrosion free, examples Piles with CFCC for a VDOT Bridge: 2 test piles(completed), 16 production piles in 2013. Concrete Issues: bond, consolidation, curing5/21/20132
Corrosion5/21/20133
Corrosion Resistance inConventional Concrete Low permeability concrete, however, cracks area problem Coated reinforcements: research in Virginia andelsewhere has shown their limitations5/21/2013Corrosion undercoatingLeakingconstruction joint4
VDOT Approach to ReinforcementCorrosion Resistant Reinforcement (CRR) VDOT has discontinued the use of epoxy coatedand galvanized bars and adopted CRR in bridgedecks. All projects advertised after September 1, 2010shall be with metallic CRR.CoatedAlloyed5
CRR in VDOT Past 2 years, VDOT hasused about 8.8 million lbsof CRR 20% of CRR used wasstainless steel.I-95 Precast ConcreteStainless Steel6
Corrosion Resistance inPrestressed Concrete Metallic CRR (alloyed, not coated) withmechanical properties (strength, relaxation)meeting the needs of prestressed concreteindustry is not commercially available. Corrosion free CFCC has been introduced byTokyo Rope and has been used in excess of200 structures around the world over the past 2decades.5/21/20137
Carbon Fiber Composite Cable (CFCC)Advantages Excellent corrosion resistance: high acid and alkaliresistance. Light weight: about 1/5th of steel weight (SG 1.5) Low relaxation loss: nearly same as low relaxation steel. High tensile strength: equal to that of steel strand. High tensile fatigue performance: fatigue performance ofCFCC is superior to that of steel strands. Low linear expansion: coefficient of linear expansion isabout 1/20 of that of steel. Non s/APFIS 2012/pdf/F1B03.pdf8
Carbon Fiber Composite Cable(CFCC) IS CORROSION FREEHas high strength: 270 ksiBond to concrete twice better than steelAcceptable elongation: 1.5 to 2%Can be formed into shape: spiralsIs cut by a grinderCareful handling due to brittle nature5/21/20139
CFCC - Carbon Fiber Composite Cable:60% carbon fiber and 40% resin5/21/201310
Examples from USAFirst Application Bridge Street Bridge, Southfield, Michigan, 2001 External cable for post-tensioningTransverseLongitudinal11
Maine Cable Stayed Bridge20075/21/201312
Examples from AbroadFirst CFCC Application in a BridgeShinmiya Bridge, Japan 1988No distress at present time13
Shinmiya BridgeFormer Bridge [After-construction 20 years]New Shinmiya Bridge[After-construction 20 years]
Hisho Bridge in Japan1993Both pre-tensioned and post-tensioned with CFCC15
Cable Stayed Bridge in Denmark1999Herningfootbridge16
VDOT Project Nimmo Bridge in Virginia Beach, VA, is underconstruction and will contain18 piles with CFCC in placeof traditional steel strand and spiral. Two of the piles were test piles. Each pile is 24-in square; piles will be placed in 2 bents,and there are16 strands per pile5/21/201317
Test Piles with CFCC Two Test piles (76 and 82-ft long) were fabricated duringthe week of November 12th, 2012 at the BayshoreConcrete Products facility in Cape Charles, VA.5/21/2013180-ft long bedwith steam curing pipes18
End PreparationMesh sheet4-part wedge5/21/2013Braided gripEvenly push 4-partwedges into chuck barrel19
CFCC Strand Coupled to SteelStrandCouplerCFCCSteelIn one end of the coupler is the CFCCchuck and the other end steel chuck.Couplers staggered.20
PrestressingStressedincrementally 5 kips 15 kips 25 kips 34 kipsOnce stressed it was left overnight.The next morning final preparations for concrete started21
Concrete Placement and ConsolidationConsolidation with Internal Vibrators22
CFCC Handling: Consolidation Internal vibrators with rubber heads5/21/201323
Piles and Specimens Steam CuredResearch Specimens Cured with the Piles24
Curing Temperature sensitive Maximum concrete temperature of theelement same as for the conventionalconcrete: 190 F For couplers to prevent slippage maximumtemperature 50 C (122 F)5/21/201325
ThermocouplePlastic tieCFCC SpiralCFCC strand26
Temperature Matched Cure (TMC)Thermocouple wire27
TMC Specimens in the Lab28
Temperature Data29
Fresh Concrete PropertiesTestTime sampledSlump (in)Air content (%)Density (lb/ft3)Concrete temp (F)5/21/2013B111:25 am4.57.0138.560B212:10 pm6.756.2139.46030
Hardened Concrete Properties at28 DaysTestCompressive Str. (psi)B1B27,740 7,530Splitting Tensile (psi)635635Permeability3,226 4,382Permeability w 100F (C) 570767Spec5,000 min------1,500 maxRelease strength (Spec: 3,500 psi min):at 18 hr B1: 4,200 psi and B2: 4080 psi5/21/201331
Strands DetensionedCutting of Steel Strands with a Torch32
CFCC CutCutting of CFCC Strandswith a Cutting Blade33
Pile Removed From FormsPiles Lifted from Forms34
Finished PileBugholes, but no unusual large visible defects35
Conclusion Corrosion free CFCC is used successfully in twoprestressed piles. Concrete is handled carefully using conventionalmethods (i.e. consolidation with rubber tippedvibrators) When steam curing couplers are kept attemperature below 50C (122F) to avoid slippage5/21/201336
Future Production Piles Longer bed (370 ft) for more piles Self consolidating concrete for improvedworkability37
Acknowledgment VDOT’s use of CFCC has been possible throughclose cooperation between the– FHWA– Industry– VDOT Structure and Bridge Division– VDOT Materials Division– VDOT Construction Division– Hampton Roads District– VCTIR.5/21/201338
Thank you.Virginia Concrete Conference: March 8, 2013
Test Piles with CFCC Two Test piles (76 and 82-ft long) were fabricated during the week of November 12 th, 2012 at the Bayshore Concrete Products facility in Cape Charles, VA. 5/21/2013 18 180-ft long bed with steam curing pipes
