Gilles Chanvillard Memorial Symposium, ENPC, July 5, 2016 ... · Gilles Chanvillard Memorial...

Institute for Mechanics of Materials and Structures TU Wien – Vienna University of Technology, Austria

GillesChanvillardMemorialSymposium,ENPC,July5,2016

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Frommicrostructuretomacroproper.es:strengthandcreepofcemen..ousmaterials

M.Hlobil,M.Irfan-ul-Hassan,M.Königsberger,R.Reihsner,Ch.Hellmich,B.Pichler

TUWien-ViennaUniversityofTechnology,AustriaInsRtuteforMechanicsofMaterialsandStructures

[email protected]



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Mo.va.on:Ø  cemenRRousmaterialsarehierarchicallyorganizedØ  (sub)micron-sizedhydrateneedlesgoverncreepandstrengthof

cemenRRousmaterials

ChaYerjiandJeffrey,Nature,209,1966 hYp://www.^wa.dot.govhYp://www.^wa.dot.gov

TriYhart&Häußler,CCR,2003



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Outline

Creep1.  Hourly-repeated,3mincreeptesRngatearlyages2.  IdenRficaRonofhydratecreepfuncRon+validaRon

Strength

1.  ElasRclimitmodelforcementpastes



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Early-agetes.ngdilemma:couplingbetweencreepandhydra.onØ  duraRonofcreeptests>>characterisRcRmeofhydraRonØ  Microstructuraldevelopment(“aging”)duringcreeptest

Aim:decouplecreepandhydra.onØ  Characterizecreepofspecific(“non-aging”)microstructures

Solu.on:newtestprotocolØ  3minutecreeptests

…referringtospecificmicrostructuresØ  hourlyrepeated

…successivecreeptestsrefertodifferentmicrostructures

Lit.:[Irfan-ul-Hassanetal.,Cement&ConcreteResearch,82:36-49,2016]



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Materials:OPCcementpastes Testsetup:Rawmaterials•  CEMI42.5N•  disRlledwater

ComposiRons•  w/c=0.42/0.45/0.50

Cylindricalspecimens•  diameter=7cm•  height=30cm

CuringcondiRons•  ambientairtemp=20oC•  sealed(nodrying)

aluminumrings

holdingLVDTs

boYleneckedsteelcylinder

5LVDTsequallyspacedaroundspecimen

compressiveloading

specimen




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Loadinghistory:•  loading:….2MPa/s•  unloading:1MPa/s

permanentloadlevel=0.2kN

force

Rme3min

[PichlerHellmich,CemConRes,41,2011]

sampleage[h]appliedforce[kN]

w/c=0.50

Hourlyrepeated:•  From21hoursaterproducRonupto8days

170creeptestsperspecimen:forcelevel=max.15%ofstrengthatRmeoftesRng,determinedby•  calorimetry•  validatedstrengthmodel




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LVDTreadings:•  smalldifferenceof

5individualLVDTreadingsØ  verysmalleccentricityØ  meanvaluemeaningful

unloading

mod

ulus[G

Pa]

Rme[sec]3min

LVDT

shortening[μ

m]

ageofmaterial[h]

Quan.fica.onofunloadingmodulus:

meanoutof5readings

w/c=0.50

stress[M

Pa]

strain[10-6]

r2=99.7%

Datafrom1test Datafrom170tests




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Quan.fica.onofelas+cmodulus:Ø  QuanRfycreepstrains

Ø  IdenRfyelasRcmodulusbyavoidingtensilecreepstrains El

asRcm

odulus[G

Pa]

ageofmaterial[h]

w/c=0.50

datafrom340tests


creepstrain[1

0-6 ]

“creep

strain”[10-

6 ]

“creep

strain”[10-

6 ]

Rme[s]Rme[s]Rme[s]



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Creepstrainevolu.on:Ø  fiyngbasedonpowerlaw

power-la

w

expo

nent[-]

Rme[sec]3min

creepstrain[1

0-6 ]

ageofmaterial[h]

Evolu.onsofcreepmodulusandofpower-lawexponent:

measurements

w/c=0.50

modeled

w/c=0.50

ageofmaterial[h]

creepmod

ulus

[GP

a]

datafrom2samples

datafrom2samples




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Hydra.ondegreeratherthanmaterialageØ  calorimetryat20oC

ageofmaterial[h]hydraR

ondegree[-]

hydraRondegree[-]

Evolu.onofelas.cmodulus:Ø  ElasRcmodulus

increaseslinearlywithhydraRondegree

measurements

w/c=0.50

modeled

datafrom2samples

w/c=0.50

20oC

elasRcm

odulus

[GP

a]




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power-la

w

expo

nent[-]

Evolu.onsofcreepmodulusandofpower-lawexponent:

w/c=0.50

hydraRondegree[-]

creepmod

ulus

[GP

a]

datafrom2tests

datafrom2samples

hydraRondegree[-]

datafrom2samples

w/c=0.50 w/c=0.50

Ø  Creepmodulus

increasesoverlinearlywithhydraRondegree

Ø  Power-lawexponent

decreaseslinearlywithhydraRondegree




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Summaryoftes.ngac.vi.es:Ø  500non-agingcreepfuncRonsofcementpasteswith

w/c={0.42,0.45,0.50}

hydraRondegree[-] hydraRondegree[-] hydraRondegree[-]ElasRcm

odulus[G

Pa]

Creepmod

ulus[G

Pa]

Creepexpo

nent[-]




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Karteetal.(2014)ultrasound

Quasi-sta.cYoung’smodulivs.dynamicYoung’smoduli

hydraRondegree[-]

w/c=0.42w/c=0.50

Youn

g’sm

odulus[G

Pa]

hydraRondegree[-]Yo

ung’sm

odulus[G

Pa]

w/c=0.42

w/c=0.50

presentstudyquasistaRc

Conclusion:Quasi-staRcYoung’smoduli=dynamicYoung’smoduli




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Outline


Strength




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Mul.scaleexploita.onofcreeptestdata1.  IdenRfycreepofmicron-sizedhydrateneedles

Creephomogeniza.on:Correspondenceprinciplea.  Laplace-CarsontransformaRonofRme-dependentproblem

b.  Quasi-elasRcupscalingusingconRnuummicromechanics,i.e.Eshelby-basedhomogenizaRonschemes

c.  Back-transformaRontoRmespace

hYp://www.^wa.dot.gov

cementpaste

ChaYerji&Jeffrey,Nature,209,1966

hydratefoam

1

hydrateneedle

Literature:[Königsbergeretal.,JournalofEngineeringMechanics,accepted]



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1.Iden.fica.onofcreepofhydrateneedlesØ  PhasevolumefracRons:Powers-AckerhydraRonmodel

Powers,Brownyard,Res.Lab.Port.Cem.Ass.Bull,22101-992,1948

Ackeretal.inConcreteatEarlyAges,ACI,33-48,1986




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1.   Iden.fica.onofcreepofhydrateneedles

Ø  Ansatz:isochoriccreepofneedle-shapedhydrates

Ø  ElasRcproperRes:Ø  CreepproperRes:??

cementpaste hydratefoam


hydrateneedle



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Experimentaldatavs.homogeniza.onresults:creepofcementpaste

Iden.fiedconstants:




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IshydratecreepwithconstantPoisson’sra.omorerealis.c?Ø  AlternaRveansatzforhydratecreepfuncRon

Ø  IdenRficaRonresults:isochoriccreepvs.constantPoisson’sraRo

Ø  IsochoriccreepandcreepwithconstantPoisson’sraRodeliverthesamecreepmodulusandthesamecreepexponent


hydrateneedle



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Modelvalida.onbasedontestsbyTamtsiaandBeaudoin(2000)Ø  ComposiRonofcementpaste:w/c=0.50Ø  Curing:30yearsunderwater->hydraRondegree=87%Ø  CreeptestduraRon:30days

CreepfuncRo

n

[10-

6 /MPa]

CreeptestduraRon[days]

experiments

modelpredic.ons




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Outline


Strength




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Mul.scalemodeling:con.nuummicromechanics

ChaYerjiandJeffrey,Nature,209,1966 hYp://www.^wa.dot.govhYp://www.^wa.dot.gov

Materialphasesinscale-separatedhierarchicalorganiza.on

Strengthmodelingidea:•  CemenRRousmaterialsareintact,ifdeviatoric

stresspeaksinhydrates<hydratestrength

RVE of shotcrete RVE of cement paste RVE of hydrate foam RVE of concrete

Lit.:[Pichler&Hellmich,CementandConcreteResearch,2011]



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Mul.scalemodelingofstrengthofcementpaste

•  Cementpasteisintact,ifdeviatoricstresspeaksinhydrates<hydratestrength

•  Microscopichydratefailure=macroscopicmaterialstrength

Scaletransi.ontostresspeaks:via2ndorderstressaverages

Iden.fica.onofhydratestrengthØ NanoindentaRontesRngonlow-densityC-S-H:

•  cohesionc=50MPa•  angleofinternalfricRonφ=12o

Ø  Thisimplies:•  Uniaxialcompressivestrengthofhydratesfcu,hyd=123.5MPa•  vonMises-typedeviatoricstrength=71.3MPa

ConstanRnidesandUlm,MITReport(2006)SarrisandConstanRnides,CCC(2013)

Pichleretal.Concreep,(2013)

macroscopicstress

Lit.:[Pichler&Hellmich,CementandConcreteResearch,2011]



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Modelvalida.on Pichleretal.,Concreep,(2013)

Modelvs.testsperformedinVienna

...atLCR

...atEMPA

Pichleretal.,CCR(2013)

Pichleretal.,CCR(2013)

Samemodelperformanceforhydratefailure

accordingtoMohr-Coulombcriterion

Wyrzykowskietal.COSTacRonTU1404

hydraRondegree[-]

Compr.stren

gth[M

Pa]

hydraRondegree[-]Compr.stren

gth[M

Pa]

Compr.stren

gth[M

Pa]

Literature:[Hlobiletal.,ManuscriptinpreparaRon,2016]

hydraRondegree[-]

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Gilles Chanvillard Memorial Symposium, ENPC, July 5, 2016 ... · Gilles Chanvillard Memorial...

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