6-2 hp concrete

8/6/2019 6-2 Hp Concrete

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Tony Kojundic

Silica Fume Associationc/o Elkem Materials Inc.PO Box 266

Pittsburgh, PA 15230(412)299-7229

[email protected]

Synopsis:

This presentation will provide a fundamental look into the definition of high-performanceconcretes (HPC) of today, and the technology behind silica-fume to produce HPC for bridgeapplications. The presentation will highlight key structural and durability properties of HPCand the life-cycle cost savings from implementing HPC into our nations transportationinfrastructure. Included are HPC bridge applications from around the country and the latestevolving HPC designs employing the lessons learned from 20 years of bridge experiences.One such lesson is a universally accepted construction technique and curing practice to bestutilize the properties HPC brings to the project. The presentation also highlights many

resources for information on HPC technology, application, and practice, provided by industryand the FHWA.

About the Presenter:

Tony Kojundic is a founding Board member of the Silica Fume Association, and BusinessManager for Elkem Materials in Pittsburgh, PA. The Silica Fume Association operates under aco-operative agreement with the FHWA to help provide technology transfer on High-performance Concrete(HPC) to state and local transportation departments. He is active on

numerous committees of the American Concrete Institute(ACI), the Transportation ResearchBoard, the American Society of Testing and Materials, the National Concrete Bridge Council,and the Society of Petroleum Engineers. His ACI duties include secretary of the Silica-fumeConcrete Subcommittee, and chapter author to the High-strength Concrete, ParkingStructures, and Concrete Proportioning Committees. Through his employment at Elkem hesbeen directly involved with silica-fume concrete research and implementation into projectapplications for the past 20 years A 1975 graduate engineer from West Virginia University

SESSION 6.2

Silica Fume High-performance Concretein Bridge Applications


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Eleventh StateEleventh State--wide Conference on Local Bridgeswide Conference on Local Bridges

Silica Fume HighSilica Fume High--performance Concreteperformance Concretein Bridge Applicationsin Bridge Applications

October 28, 2004October 28, 2004


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What is highWhat is high--performance concrete?performance concrete?

HPC is a concrete in which certain characteristicsHPC is a concrete in which certain characteristics

are developed for a particular application andare developed for a particular application and

environmentenvironment -- FHWA,FHWA, BridgeViewsBridgeViews, Issue, #1., Issue, #1.


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Examples of HPC

Ease of placement.Ease of placement.

Compaction without segregation.Compaction without segregation.

EarlyEarly--age strength.age strength.LongLong--term properties.term properties.

PermeabilityPermeability

DensityDensityHeat of hydration.Heat of hydration.

ToughnessToughness

Volume stability.Volume stability.

LongLong--life.life.

http://www.fhwa.dot.gov/bridge/hpcwhat.htmhttp://www.fhwa.dot.gov/bridge/hpcwhat.htm


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1999 National Bridge1999 National Bridge

InventoryInventory

585,000 US bridges,585,000 US bridges,+210,000 are deficient.+210,000 are deficient.

7,623 (48.9%) of NY7,623 (48.9%) of NY

bridges.bridges. #1 repair area#1 repair area -- bridgebridge

decks.decks.

$5 B/yr. dedicated for$5 B/yr. dedicated forbridges.bridges.


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Service Life Estimate

Initiation period,ti Propa gation period,tp

End of service life

D

amage

Time

Cl , CO2 penetration

O2 diffusion,

resistivity

Figure 4.1 Two-Stage Service Life Model Proposed by Tuutti (1982)


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Ceramic: Particle Packing TheoryCeramic: Particle Packing Theory

100% packing100% packing

= 0% voids.= 0% voids.


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Concrete without silica fume with silica fumeConcrete without silica fume with silica fume


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Bridge Deck HPC PhilosophyBridge Deck HPC Philosophy

Implies using the leastImplies using the least

amount of cement possible!amount of cement possible!

Judicious use of pozzolans.Judicious use of pozzolans.Particle packing / reducedParticle packing / reduced

permeability.permeability.

ASR control.ASR control.Less water / lessLess water / less

shrinkage.shrinkage.

Reduced heat of hydration.Reduced heat of hydration.Reduced cracking.Reduced cracking.


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Typical HPC ProportionsTypical HPC Proportions -- Piles, Piers, Caps.Piles, Piers, Caps.

High Strength, HPC.High Strength, HPC.

CementCement 624 pcy624 pcy

Fly ashFly ash 120 cy (15%)120 cy (15%)SFSF 56 pcy (7%)56 pcy (7%)

w/cmw/cm 0.340.34

1d1d 5000 psi5000 psi28d28d 9000 psi9000 psi


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Hoover Dam Bypass - Box Girder Arch, 12,000psi HPC.Hoover Dam Bypass - Box Girder Arch, 12,000psi HPC.

www.hooverdambypass.comwww.hooverdambypass.com


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Deck Concrete Performance GoalDeck Concrete Performance Goal

Extended service life.Extended service life.

Reduce mortar permeability.Reduce mortar permeability.

Reduce shrinkage or tendency to crack.Reduce shrinkage or tendency to crack.


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Extended Service LifeExtended Service Life

Reduce permeability.Reduce permeability.

Particle packing and pozzolanic chemistry.Particle packing and pozzolanic chemistry.

Reduced shrinkage and/or tendency to crack.Reduced shrinkage and/or tendency to crack.

Less water per volume (cubic yard) ofLess water per volume (cubic yard) of

concrete.concrete.

Lower cement content.Lower cement content.

Greatest amount of aggregate.Greatest amount of aggregate.

Least amount of mortar.Least amount of mortar.Control evaporation.Control evaporation.


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Typical HPC ProportionsTypical HPC Proportions -- Bridge Decks.Bridge Decks. Low permeable, lowLow permeable, low

cracking.cracking.

CementCement 500 pcy500 pcyFly ash 135 pcyFly ash 135 pcy (20%)(20%)

SFSF 40 pcy40 pcy (6%)(6%)

w/cmw/cm 0.400.40

28d28d 5000 psi5000 psi

Perm.Perm.


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Bridge Deck Concrete Comparison HPCHPC volvol DOT AAA mix.DOT AAA mix.

Cement, pcyCement, pcy 470470 2.392.39 665665 3.393.39

Fly ash, pcyFly ash, pcy 100100 0.640.64 117117 0.750.75

Silica fume, pcySilica fume, pcy 4040 0.290.29 ------

Water, galWater, gal 29.829.8 3.973.97 36.836.8 4.914.91

Total volumeTotal volume (


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Cohesive silica-fume concrete-- OK to increase slump


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Evaporation

Bleeding

If Evaporation > Bleeding Plastic Shrinkage Cracking

Problem: Concrete Surface Drying

ConstructionConstruction


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What is Plastic Shrinkage Cracking?What is Plastic Shrinkage Cracking?Cracking that occurs in the surface of fresh concrete

soon after it is placed and while it is still plastic.

-- ACI 116RPlastic shrinkagecracking


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Test Pours for NeverTest Pours for Never-- evers.evers.

Makes slump appear less.Makes slump appear less.

SilicaSilica--fume concrete doesfume concrete does

not bleed.not bleed. Susceptible to plasticSusceptible to plastic

shrinkage cracking.shrinkage cracking.

Requires immediateRequires immediateevaporation protection.evaporation protection.

No delay in final finishing.No delay in final finishing.

Key to fastKey to fast--track finishingtrack finishing.

Document finishing plan.Document finishing plan.


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Machine FoggingMachine Fogging


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OneOne--Pass FinishingPass Finishing

Under finish, over cure.Under finish, over cure.

Excessive hand finishingExcessive hand finishing

gains no advantage, andgains no advantage, and

harms surface durability.harms surface durability.

Avoid tools thatAvoid tools that stick to thestick to the

HPC surface.HPC surface.

Photos of placement


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OneOne--Pass Finishing.Pass Finishing.

Steel bull floats andSteel bull floats and

FresnosFresnoswork well.work well.

Curing requirements.Curing requirements.

Wet cure begins 10Wet cure begins 10--1515

min. after placementmin. after placement

for a minimum 7d.for a minimum 7d.

Membrane cure afterMembrane cure after

wet cure and texturingwet cure and texturingExpedite placing, finishing, texturing

and use immediate curing


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Cracking Performance of HPC Bridge DecksCracking Performance of HPC Bridge Decks -- NY DOTNY DOT

-- TRB Paper No. 5B0121TRB Paper No. 5B0121

SurveySurvey -- 84 bridges84 bridges

constructed between 95constructed between 95and 98.and 98.

Class E concrete decksClass E concrete decks

(95(95--96).96).60% transverse60% transverse

cracking.cracking.

58% longitudinal58% longitudinalcracking.cracking.

Class HP concrete decks 97Class HP concrete decks 97--

98.98.

39% transverse cracking.39% transverse cracking.

33% longitudinal cracking.33% longitudinal cracking.

The 98 decksThe 98 decks -- 33% and 25%33% and 25%respective cracking.respective cracking.

55% of cracks appeared55% of cracks appeared

between 0between 0 --14 days.14 days. No difference steel andNo difference steel and

concrete bridge structuresconcrete bridge structures..


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FHWAFHWA -- HPC Technology Delivery Program.HPC Technology Delivery Program.

Innovative Bridge Research ProgramInnovative Bridge Research Program

http://ibrc.fhwa.dot.gov/http://ibrc.fhwa.dot.gov/

240 projects, 61 HPC.240 projects, 61 HPC.

HPCHPC -- Technology Delivery TeamTechnology Delivery Team

http://www.fhwa.dot.gov/bridge/hpc.htmhttp://www.fhwa.dot.gov/bridge/hpc.htmhttp://knowledge.fhwa.dot.gov/cops/hpcx.nsf/homehttp://knowledge.fhwa.dot.gov/cops/hpcx.nsf/home

Silica Fume Association.Silica Fume Association.

www.silicafume.orgwww.silicafume.org


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6-2 hp concrete

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