Bartlett - The Bond and Impact Resistance of Gigacrete

8/2/2019 Bartlett - The Bond and Impact Resistance of Gigacrete

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DEPARTMENT OF CIVIL AND ENIVORNMENTAL ENGINEERING, UNIVERISTY OF UTAH

TheBondStrengthandImpactResistanceofGigacreteFacingonExpandedPolystyreneforHighway

Embankments

Technical Report Prepared by

StevenF.Bartlett,Ph.D.,P.E.;AurelianC.Trandafir,Ph.D.;BrianJ.Higley

4/10/2009


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TheBondStrengthandImpactResistanceofGigacreteTMFacingonExpandedPolystyreneforHighway

Embankments Page 2

ContentsListofFigures................................................................................................................................................ 3

Introduction.................................................................................................................................................. 4

TestProceduresandResults......................................................................................................................... 5

ExpandedPolystyrene............................................................................................................................... 5

CompressiveStrengthofGigacreteTM....................................................................................................... 6

InterfaceAxialExtensionAdhesionBondTests........................................................................................ 7

InterfaceBondDirectShearTests............................................................................................................ 9

InterfaceShearStrengthwithCyclicUnaxialCompression.................................................................... 11

ImpactStrengthofGigacreteTM.............................................................................................................. 18

SummaryandConclusions.......................................................................................................................... 26

References..................................................................................................................................................

28

Appendix1.................................................................................................................................................. 29


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Embankments Page 3

ListofFiguresFigure1. UnconfinedUniaxialCompressionStressStrainCurvesforEPS1950mmcubicsamples

(Bartlettetal.2000)...................................................................................................................................... 5

Figure2. Cylinderpreparationforunconfinedcompressivestrengthtests................................................ 6

Figure3. (a)UnconfinedcompressiontestingofGigacreteTMcylinder,(b)FailureofGigacretesample...7

Figure4. GigacreteTM

compressivestrengthgainasafunctionofcuretime.............................................. 7

Figure5. Laminatedmaterialsubjectedtotensilestressnormaltothelaminateplanetodetermine

adhesionbondstrength................................................................................................................................ 8

Figure6. TensilefailureoflaminatedGigacreteTM EPSspecimens............................................................ 9

Figure7. Verticaldeformationversusloadforlaminatedsamples............................................................. 9

Figure8. Laminatedmaterialsubjectedtoshearstressparalleltolaminateplanetodetermineshear

bondstrength............................................................................................................................................... 9

Figure9. UniversityofUtahdirectsheardevicemanufacturedbyELEInternational............................... 10

Figure10. DirectsheartestresultsforGigacreteTM

EPSbond................................................................... 10

Figure11. SamplesofGigacreteTMEPSlaminatetestedindirectshear. EPSsampleislocatedontop

andhasbeencompressedduringshear. Localshearfailurehasoccurredontheleadingedgeofthe

sample......................................................................................................................................................... 11

Figure12. Shearstressesintroducedatlaminateinterfacefromaxialcompressionandextension........11

Figure13. CyclicloadingwithintheEPSresultingfromthermalexpansioncontractionoftheEPSwall

system......................................................................................................................................................... 12

Figure14. CylindricalsampleofGigacreteTMandEPS19casttotestthebondstrengthforcyclicunaxial

compression................................................................................................................................................ 12

Figure15. UniversityofUtahcyclictriaxialtestapparatus....................................................................... 13

Figure16. Plotsofshearstressversusaxialstrainforcyclicuniaxialstresstests,cycles0250.............14

Figure17. Plotsofshearstressversusaxialstrainforcyclicuniaxialstresstests,cycles251500.........15



Figure20. Photographsofthetopofthesamplebefore(top)andafter(bottom)theapplicationof1000

loadingcycles. Nodamagewasobserved attheEPSGigacreteTMinterface......................................... 17

Figure21. Photographsofthebottomofthesamplebefore(top)andafter(bottom)theapplicationof

1000loadingcycles. NodamagewasobservedattheEPSGigacreteTMinterface................................. 17

Figure22. TheGardnerStrikerUsedinImpactTesting............................................................................. 19

Figure23. Photographsofthickglassfiberreinforced1x1and6x6samples............................. 24

Figure24. Photographsofnylonreinforced1x1and6x6samples............................................. 24

Figure

25.

Photographs

of

glass

fiber

reinforced

1

x

1

and

6

x

6

samples.

.....................................

25

Figure26. Photographsofnylonreinforced1x1and6x6samples............................................. 25


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Embankments Page 4

IntroductionThis report discusses the bonding and impact resistant of GigacreteTM used as a nonstructural

permanent facing for Expanded Polystyrene (EPS) geofoam embankments. GigacreteTM is a mineral

cement based proprietary product manufactured and distributed by GigaCrete Inc. of Scottsdale,

Arizona. The intended use of this product is to deploy it as a spray on application (e.g., similar to

shotcreting)forthepermanentfacingandprotectionoffreestandinggeofoamembankments.

The exposed sides of a geofoam embankment must be covered to prevent longterm surface

degradationof theEPS,mainly fromUVdegradationand to incidentaldamageof thegeofoam from

otherenvironmentalfactorsandfromimpact. TheBostonCentralArteryTunnel(BCAT)Project,known

astheBigDigproject,deployedanExteriorInsulationandFinishingSystem(EIFS)tocoverandprotect

theEPSgeofoam. Forthisproject,approximately10,000squarefeetofEPSblockswerecoveredusing

dry mix process shotcrete (http://www.aulson.com/concreterepair.cfm). The EPS was prepared for

shotcreteapplicationbyetching recessednotcheswithaheatweldinggunevery12 inchesalong the

permanentfaceoftheEPSstructureinpreparationforshotcreteadhesion. Awiremeshwasfastened

tothe

EPS

face

with

glass

filled

nylon

fasteners

and

hook

bolts

were

used

to

attach

the

wire

mesh

to

the

castinplaceconcretebarrieralongthetopoftheEPSwall. Subsequently,workersappliedatwoinch

thick layer ofdrymixprocess shotcrete at 400 feet per second along the EPSwall face creating an

appearancesimilartorubbedconcrete.

However, theapplicationexploredherein is thedirectapplicationofaGigacreteTMcoating to theEPS

withoutrecessednotches.Importanttothisapplicationisthebondstrengththatdevelopsbetweenthe

EPSandGigacreteTM. BecauseEPSwall systemsare relativelynew in theU.S.andbecause shotcrete

facing is a developing technology, no AASHTO (American Association of State Highway and

Transportation Officials) guidelines or specifications exist for this application. An EIFS project

specificationwas

developed

for

the

Big

Dig

project

(Appendix

1),

which

can

be

used

aguide

for

evaluatingthedesignandconstructionoffuturesystems. However,thisspecificationwasdevelopedfor

aspecificprojectandproduct. Thus,partsoftheBigDigspecificationmaynotbeapplicabletoother

productsandapplicationmethods.

This report evaluates the bond strength of GigacreteTM when applied to EPS geofoam using test

performance data performed by the University of Utah Departments of Civil and Environmental

EngineeringandGeologyandGeophysics. TestdataweregatheredandevaluatedfortheGigacreteTM

EPS interfacefortension,shearandaxialcompression. Inaddition,testswereperformedontheaxial

compressionstrengthofGigacreteTM.


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TheBond

Embank

Itshould

Youngm

(Figure 1

embank

2000)sh

al.(2000)

Compr

ForEIFS,

Thus the

material.

comparat

Gigacrete

recomme

high

(Figu

After curi

(Figure3

daycure

showsho

higher st

determin

perform

Strengthan

ents

benoted th

duliandun

) are genera

entapplicati

wthatend

reportYoun

ssiveStrthefacingm

BCATProjec

However,

ivepurposes

TM samples

ndations.Th

re

2)

and

cur

F

ng, the sam

)inamann

imeswere5

w the comp

rengths tha

ation of the

dditionaltes

ImpactResi

t the result

onfinedco

lly too low

ons. Testing

ndedgeeff

moduli

valu

ngthofGaterialisnot

tdidnot sp

e performe

withothers

were pre

mixturewa

ed

for

4,

10,

igure2. Cylind

leswerepl

rsimilartot

220psi(36

ressive stren

those sho

compressiv

tsforlonger

stanceofGig

shownabo

pressivestr

nd do not

onlargeblo

ctsundulyi

esof

about

igacreteT

placed inco

cifyaperfo

d three unc

otcreteand

ared in i

splacedin4

and

12

days

rpreparationf

ced inana

hatrequired

Pa),7100p

gthofGigac

n in Figure

strength

curetimes.

acreteTM

Faci

eshouldno

ngthscalcul

reflect the p

ksamplesp

fluencemo

0MPa

for

2

mpression,b

mancecrite

onfined com

stuccoprod

door condi

inch(10cm)

t

20

degree

orunconfined

tuator (Figu

byASTMC3

i(49MPa)a

reteTM

increa

4 are poss

as not a pr

ingonExpan

tbeused fo

tedfroms

roperties of

rformedat

ulicalculate

foot(600

m

ecause it is

ion forcom

pressive str

cts.

tions accor

diameterm

C

prior

to

u

ompressivestr

re3a)and l

9. Thecomp

d8190psi(

sesasa fun

ible with lo

imary object

dedPolystyr

rdesignofE

all(i.e.,50

largesized

yracuseUni

dfrom50m

)cube

samp

nonbearin

pressive stre

ngth tests

ding to th

oldsthatwer

confined

co

engthtests.

aded tount

ressivestren

57MPa),res

ctionof cure

ger cure ti

ive of this

neforHigh

P

PSembank

m)cubesa

EPS block us

ersity(Elragi

cubes. Elr

lesfor

EPS2

structuralf

ngthof the

n Gigacrete

manufact

e8inches(2

pression

te

il failureocc

gtha4,10a

ectively. Fi

time. Obvi

es, but be

tudy, we di

ay

age 6

ents.

ples

ed in

etal.

agiet

.

acing.

acingMfor

urers

0cm)

sting.

urred

nd12

ure4

ously,

cause

d not


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Embankments Page 7

Figure3. (a)UnconfinedcompressiontestingofGigacreteTM

cylinder,(b)FailureofGigacretesample.

Figure4. GigacreteTM

compressivestrengthgainasafunctionofcuretime.

InterfaceAxialExtensionAdhesionBondTestsForEIFSapplications,theamountofadhesionbondthatdevelopsbetweenthefacingmaterialandthe

EPS isan importantproperty for the longtermperformanceanddurabilityof thepermanent facing.

TheBCAT

Project

acceptance

criterion

for

EIFS

is:

No

failure

in

the

adhesive

base

coat

or

finish

coat.

The insulation board shall fail cohesively except that 25 percent adhesive failure is acceptable. For

testedvaluesofnineteen(19)psiorgreater,adhesivefailureupto100%isacceptable(Appendix1,p.

8).

0

10000

2000030000

40000

50000

60000

0 2 4 6 8 10 12

,

kPa

Cure Time (days)


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Embankments Page 8

ThetestmethodrecommendedbytheBCATprojectfordeterminingbondstrengthisASTMC297. This

testmethodcoversthedeterminationofthecoreflatwisetensionstrength,orthebondbetweencore

andfacingsofanassembledsandwichpanel.Thetestconsistsofsubjectingasandwichconstructiontoa

tensile load normal to the plane of the sandwich (Figure 5). The tensile load is transmitted to the

sandwichthroughthickloadingblocksbondedtothesandwichfacingsordirectlytothecore.

Figure5. Laminatedmaterialsubjectedtotensilestressnormaltothelaminateplanetodetermineadhesionbondstrength.

WeevaluatedthebondstrengthbetweenEPSandGigacreteTMinamannersimilartoASTMC297. A3

inch (75mm)concretecylinderwasusedtomoldthe laminatedsample. Aneyeboltwasanchored in

thetoplayeroftheGigacreteTMandathreadedrodwasanchoredinthebottomlayer(Figure5). These

wereusedtoattachtheweightstoapplythenormaltensileforce.

Twosampleswerepreparedanallowedtocurvefor5and6days,respectively. Thespecimensfailedat

atensilestressof39.6psi(273kPa)and39.5psi(272kPa),respectively. Figure6showsthefailureof

specimens,which

is

atensile

failure

of

the

EPS.

In

both

cases,

the

bond

between

the

EPS

and

the

GigacreteTMdidnotdevelopanadhesion failure; insteadacohesive failuredevelopedwith theEPS.

Thus, the GigacreteTMEPS laminate tested meets, or greatly exceeds, the requirements of the BCAT

ProjectperformancecriterionforbondstrengthforEIFS(Appendix1).

3inch(75mm)diameterby

2inch(50mm)highEPS19

samplesandwiched

betweenGigacreteTMlayers.


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Embankments Page 9

Figure6. TensilefailureoflaminatedGigacreteTM

EPSspecimens.

Inadditiontothepeaktensilestrength,wemeasuretheverticaldeformationofthesampleastheload

wasapplied. Thesedataareshown inFigure7. Thesedatasuggestthatthetensile failure intheEPS

occurredat4and20percentaxialstrain.

Figure7. Verticaldeformationversusloadforlaminatedsamples.

InterfaceBondDirectShearTestsTheshearbondthatdevelopsbetweenthefacingmaterialandEPSisalsoimportantforthelongterm

durabilityof thepermanent facing. Sufficientbonding inpure shear is required toprevent slippage

between the facing material and the EPS when the stress is oriented parallel to the plane of the

interface(Figure8).

Figure8. Laminatedmaterialsubjectedtoshearstressparalleltolaminateplanetodetermineshearbondstrength.

NointerfaceshearperformancecriterionortestswererequiredaspartoftheBCATprojectspecification

(Appendix 1). However, this is a common test done in Geotechnical Engineering to determine the

interface shear strengthor bondbetween two dissimilarmaterials and is commonly performed in a

direct shear device (Figure 9). We evaluated the shear bond strength of GigacreteTM and EPS in a

mannersimilartoASTMD3080.

Two2.5inch(62.5mm)diameterby0.5inch(12.5mm)GigacreteTMlayerswerepouredatopanEPS19

sampleof

identical

dimensions.

The

GigacreteTM

was

allowed

to

cure

for

9days

and

then

tested

in

directshearwithanappliednormalstressof2.2psi(15kPa). (Thisnormalstresswasselectedbecause

it representsa typicalnormal stress thatdevelops in theelastic rangeof theEPS.) The samplewas

subjectedtoahorizontaldisplacementrateintheshearboxthatcorrespondsto0.05inches(1.25mm)

perminuteandtesteduntiladisplacementof0.5inches(12.5mm)wasrealized. Figure10showspeak

shearbondstrengthsof51.3and55.2kPaforsamples1and2,respectively.

-2

0

2

4

6

8

10

12

0 50VerticalDeformation

(mm)

Total Added Mass (kg)

Sample 1

Sample 2

Leading

edgeofEPS


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Embankments Page 10

Figure9. UniversityofUtahdirectsheardevicemanufacturedbyELEInternational.

Figure10. DirectsheartestresultsforGigacreteTM

EPSbond.

0

10

20

30

40

50

60

0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00

ShearStrength(kPa)

Horizontal Displacement (mm) Sample 1Sample 2


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Embankments Page 11

Afterthetestswereperformed,thesampleswerevisuallyinspected.Therewasasignificantamountof

compressionoftheEPS,buttheinterfacebondwasnotbrokenbetweenthetwomaterials. Figure11

showsthelocaldeformationandshearthatdevelopedalongtheleadingedgeofthesample(Figure8);

however,alongthetrailingedgeofthesample,thebondwasintact. Acarefulinspectionoftheleading

edgeof the sample showedbeadsofEPSwere stillembedded in theGigacreteTM suggesting that the

failurewas

alocalized

cohesive

failure

and

not

adhesive

failure

of

the

interface

bond.

Figure11. SamplesofGigacreteTM

EPSlaminatetestedindirectshear. EPSsampleislocatedontopandhasbeen

compressedduringshear. Localshearfailurehasoccurredontheleadingedgeofthesample.

InterfaceShearStrengthwithCyclicUnaxialCompressionShearstressesatGigacreteTMandEPS interfacecandevelop fromcyclicaxial loadingoftheEPS. Such

loadingscanbea resultofdifferential thermalexpansioncontractionof theEPSblock relative to the

Gigacrete

TM

facing

or

can

be

caused

by

seismic

and

traffic

loadings

(Figure

12).

Figure12. Shearstressesintroducedatlaminateinterfacefromaxialcompressionandextension.

Forexample,datagatheredfromtheI15ReconstructionProject(Figure13)showscyclicalaxialloading

withintheEPSduetoseasonalthermalexpansionandcontractionoftheEPSwallsystem(Bartlettetal.

2001). Thesedatasuggestaseasonalcyclingofabout2psi (13.8kPa). (Note that the initialvertical

stress of about 5 psi (34.5 kPa) results from the initial placement of the load distribution slab and

overlyingpavementmaterials.) It shouldalsobenoted that theyield stress (i.e., stressat2percent

EPSblocks

undergoingaxial

compressionand

extensionfrom

thermal,trafficor

earthquakeloadings

GigacreteTM

facing


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TheBond

Embank

strain) is

Figure13

Fig

Wedevis

case of

environm

Gigacrete

curedfor

Subseque

alternatin

capsfor

ring. Int

Figure

Pressure

(psi)

Strengthan

ents

approximate

arewithinth

re13. Cycliclo

damodifie

n EPS emb

ental loadinTM

was cast

7days.

ntly in a ser

g compressi

heload

fra

ismannero

14. Cylindrical

1.0

0.0

1.0

2.0

3.0

4.0

5.0

6.0

Mar-99

ImpactResi

ly80 to100

eelasticran

adingwithinth

testmetho

ankment wi

s (e.g., ther

arounda3i

ies of stress

onextension

ecompletel

lyverticalst

ampleofGigac

Mar-00

stanceofGig

kPa (Figure

eoftheEPS

eEPSresulting

dtomeasur

h Gigacrete

mal, seismic,

nch (75mm)

controlled c

using a cycl

contacted

resswastra

reteTM

andEPS

Ma

acreteTM

Faci

1); thus the

.

fromthermale

theperforTM

placed i

etc). A4i

outsidedia

yclic uniaxial

ic triaxialde

heEPS

core

sferredtoth

19casttotestt

r-01

ingonExpan

magnitude

pansioncontr

anceofthe

cyclic axia

ch (100m

eterofEP

tests, the

vice (Figure

,but

did

not

eEPS(Figur

hebondstreng

Mar-02

dedPolystyr

f the cyclic

ctionoftheEP

GigacreteTM

l compressi

)outsidedi

19as show

PS central c

15). The 3

contact

the

14).

hforcyclicuna

Mar-03

neforHigh

Pa

loadings sho

Swallsystem.

EPSbondf

nextension

meter cylin

inFigure1

orewaspla

inch (75mm

GigacreteTM

xialcompressio

ay

ge 12

n in

rthe

from

erof

and

ed in

) end

outer

n.


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Embankments Page 13

InitialtestingofanEPS19cylinderwithouttheGigacreteTMcoatingshowedthatcreepdeformationwas

initiatedina3inch(75mm)EPS19samplewhenastaticaxialstressofabout30kPawasappliedtothe

sample. DesignofEPSembankmentrequiresthattheallowableworkingstressintheEPSembankment

tobeapproximately50percentoftheyieldstress,soweselectedan initialaxialcompressivestressof

15kPaforthetesting.

Once itwasverifiedthatthesamplewasnotundergoingcreepunderthisaxialstress,additionalcyclic

axialstressof11kPawasappliedtothesample. Thus,theamplitudeoftheaxialstressonthesample

varied from +26 kPa to + 4 kPa, where + indicates compression. This is approximately twice the

magnitudeofthethermalstresscyclingoccurringintheEPSembankment(Figure13).

Thesample inFigure14wassubjectto4setsof250cycleseachwithan initialstaticaxialstressof15

kPAandanaxialcyclicstressof11kPaappliedatafrequencyof1Hz. Theresultsforthesetestsare

showninFigures1619.

Figure15. UniversityofUtahcyclictriaxialtestapparatus.

(Intheseplots,theshearstressisplottedinsteadoftheaxialstressontheleftaxisofthefigures. The

shearstressistheaxialstressdividedby2forthecaseofuniaxialloading.) Figure16showsthatslightly

lessthan0.2percent inelastic (i.e.,plastic)axialstrainaccumulated in theEPSsampleduringthe first

250cycleloadingset. Thissuggeststhatthecombinationofinitialstaticandcyclic loadinghadslightly

exceeded the elastic limit of the EPS. However, subsequent sets on the same sample showed less

inelasticbehavior,suggestingtheinelasticdeformationdecreaseswiththenumberofcycles.


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Embankments Page 14

Wenotethatthesamplewascompletelyunloadedaftereachsetof250cycles. (Thiswasdonesothat

thesystemssolenoidcouldcooldownbeforethenextsetof250cycleswasapplied.) Becauseofthis,

the permanent deformations shown in Figures 16 through 19 cannot be added to get the total

permanentaxialstrainduring1000cycles.

Figure16. Plotsofshearstressversusaxialstrainforcyclicuniaxialstresstests,cycles0250.


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Embankments Page 15




Once1000cycleshadbeenappliedtothesample,weinspectedtheGigacreteTMEPSinterfaceforany

signsofdamagedue tocycling. Nodebondingordamagewasobservedat this interface (Figures20

and21).


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Embankments Page 16


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Embankments Page 17

Figure20. Photographsofthetopofthesamplebefore(top)andafter(bottom)theapplicationof1000loadingcycles. No

damagewasobserved attheEPSGigacreteTM

interface.

Figure21. Photographsofthebottomofthesamplebefore(top)andafter(bottom)theapplicationof1000loadingcycles.

NodamagewasobservedattheEPSGigacreteTM

interface.


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Embankments Page 18

ImpactStrengthofGigacreteTMInitially,squaresamplesofEPS19,measuring1footby1foot(0.3mby0.3m)and0.5ft(0.15m)thick,

were coated with inch (12.5 mm) of unreinforced GigacreteTM for impact testing. A striker was

constructedusinga cylindrical shapedweightanda steelballbearing.This strikerwasdropped from

predeterminedheightsandimpactedtheGigacreteTMcoatingappliedtotheEPSbacking. Theseinitial

impacttests

showed

that

even

at

relatively

small

drop

heights,

the

unreinforced

samples

on

EPS

backing

will fracture. After discussing the results of the initial impact tests with the manufacturer, it was

decidedthatreinforcedsamplesshouldbepreparedforadditionalimpacttesting.

Subsequently, two types of reinforcing meshes were used in the samples: glassfiber and nylon

reinforcingmesh. TwelveEPS19samples,measuring0.5ftby0.5ft(0.15mby0.15m)and2in(50mm)

thick, were prepared and coated with GigacreteTM for impact testing. Six of these samples were

reinforced with glassfiber and six were reinforced with a nylon reinforcing mesh. In addition, an

identicalsetofsampleswereprepared,butusingaGigacreteTMcoatingthicknessofinch(18.75mm).

This was done to evaluate how the impact performance may improved as the thickness of the

GigacreteTMis

increased.

It

should

be

noted

that

a2in

(50

mm)

thickness

of

EPS19

was

chosen

for

all

testssothatthesamplespreparedwithaGigacreteTMcoatingcouldfitunderneaththestriker.

Anadditiontothe0.5ft(0.15m)squaresamples,largersizedsquareEPS19sampleswerealsoprepared

andtested. Thesesamplesmeasured1 footby1 foot (0.3mby0.3m)and2 in (50mm)thick. One

samplewaspreparedforeachthicknessofGigacreteTM(i.e.,12.5and18.75mmthickness)andforeach

meshtypeforatotalof4samples.

For all of samples, the reinforcing mesh was placed at middepth within the GigacreteTM coating.

However,forthenylonmeshwitha12.5mmcoatingofGigacreteTM,thesmallmeshopeningsizemade

preparationofthesesamplesdifficult. TheGigacreteTMcoatingwasbarelysufficienttofullycoverthe

nylonmesh.

Allsampleswerecuredforsevendaysandthentestedusingvariousimpactenergies. Afterimpacting,

eachspecimenwasinspectedforcracks,breaks,depthofindentationandtoseeifthemeshhadbeen

penetrated or broken by the impact. A Gardner Striker (ASTM D 5420) apparatus was used for the

impact testing (Figure 22). This shape of head producesmore concentrated impact than the larger

diametersteelballsorweightedbagsadaptedfromothermethodsandproducesagoodcompromise

betweenpuncturingandcrackingaction. Inthistest,thesamplerestsonabaseplateoveranopening.

An impactorsitsontopofthetestsampleandaweight israisedtoapredeterminedheight,then it is

released todroponto the top of the sample. Thedropheight,dropweight, and the test result are

recorded.


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Embankments Page 19

Figure22. TheGardnerStrikerUsedinImpactTesting.

The0.5ftby0.5 ft (0.15mby0.15m)samplesweretested first.Becauseoftheirsmallersize, itwas

assumed thatcrackswould format lower impactenergies; therefore theobjectiveof thispartof the

testing was to evaluate the approximate impact energy required to penetrate or break the mesh.

Subsequently, the1 footby1 foot (0.3mby0.3m) sampleswere tested to find the impact energy

requiredtocrackthecoating. TheresultsareshowninTable2below.

Thetestresultsshowedthatforthethickfiberreinforcedsamples,theimpactstrengthrequiredto

crackthesamplesisestimatedtobe280inlbs.Theimpactstrengthrequiredtopenetratethemeshis

consistentlyhigher than themaximumavailableof320 inlbsenergydeliveredby theGardnerStriker

(Figure23).

Incomparison,thethicknylonreinforcedsamplesof1x1dimensionscrackedat200inlbs. Alsoat

304inlbs,thestrikerpenetratedthroughthemeshandintotheEPS(Figure24). Inaddition,atimpact

energyof 200 inlbs,ormore, thedamage to the 6 x 6 sampleswas severe, including cracks that

propagated into theEPS. Also, thebondbetween theEPSandGigacreteTM failedat thecornersand

edges (Figure24).However,thenylonmeshwasnotpenetrateduntil impactsofover300 inlbswere

used.

Whenthethick1x1sampleswithglassfiberreinforcementwasstruckwith200inlbs,smallcracks

formed;butat thehighestenergyof320 inlbs, themeshwasnot ruptured (Figure25). Also, it is

interestingtonotethatforsample1ofthe6x6samplesdidnotcrackat200inlbsofimpactenergy


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Embankments Page 20

(Table 2). Furthermore, none of the 6 x 6 glassfiber samples were penetrated at the maximum

impactenergyof320inlbs(Table2).

Incomparison,thenylonreinforced1x1samplehadsmallcracksat240inlbsbutthemeshwas

notpenetratedwhenstruckagainat320inlbs(seeFigure26).The6x6samplesalsocrackedatlower

energies,but

the

mesh

remained

un

penetrated

at

maximum

impact

or

320

in

lbs.

Table2.ImpactTestingResultsforGigacreteTM

coating,

GigacreteTM thickness: 1/2" Sample Size: 6" x 6" x 2 EPS

Reinforcement: Glass Fiber

Sample Drop Indentation Penetrated

Number Energy (inlbs) Depth (in) Mesh? (Y/N) Observations:

1 152 N No cracks

200 0.162 N Cracked to edges, small chips

2 200 0.015 N No cracks, no chips

224 0.078 N Cracked to edges, small chips

3 224 0.171 N Cracks to edges



6 320* 0.037 N Cracks to edges

GigacreteTM thickness: 1/2" Sample Size: 1' x 1' x 2 EPS




1 280 0.184 N 1 small crack

304 0.386 N Cracked to edges

320* 0.201 N Cracked to edges


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1 200 N No cracks

248 N Cracked to edges, small chips













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Reinforcement: Nylon



1 248 0.024 N Large Cracks to edges and into EPS

2 200 0.045 N Large Cracks to edges and into EPS




280 N Large Cracks to edges and into EPS

6 320* Y Large Cracks to edges and into EPS





1 104 0.019 N No Cracks

200 0.182 N Cracks to edges

304 Y Penetrated into EPS


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1 200 N Cracks to edges

248 N Cracks to edges, small chips











304 N Cracks to edges, small chips


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Figure23. Photographsofthickglassfiberreinforced1x1and6x6samples.

Figure24. Photographsofnylonreinforced1x1and6x6samples.


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Figure25. Photographsofglassfiberreinforced1x1and6x6samples.

Figure26. Photographsofnylonreinforced1x1and6x6samples.


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SummaryandConclusionsTheimpacttestingresultsaresummarizedinTable3.Becauseofthesmallnumberofsamplestestedfor

eachcase (i.e.,maximumofsixsamples),theresultsbelowarenotstatisticallyrobust,butdosuggest

therelativeperformanceforeachcase.

Table3.

Summary

of

Impact

Testing

GigacreteTM

Thickness: Reinforcement

Impact to

Crack (inlbs)*

Impact to

Penetrate Mesh

(inlbs)

1/2" GlassFiber >280 >320

1/2" Nylon 200


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ReferencesASTC39,StandardTestMethod forCompressiveStrengthofCylindricalConcreteSpecimens, ASTM

International,WestConshohocken,PA,2005,DOI:10.1520/C0039_C0039M05E01.

ASTM C297 / C297M, 2004, Standard Test Method for Flatwise Tensile Strength of Sandwich

Constructions,ASTM

International,

West

Conshohocken,

PA,

2004,

DOI:

10.1520/C0297_C0297M

04.

ASTM C578, 2008, Standard Specification for Rigid, Cellular Polystrene Thermal Insulation, ASTM

International,WestConshohocken,PA,2008,DOI:10.1520/C057808.

ASTMD080,2004, StandardTestMethod forDirectShearTestofSoilsUnderConsolidatedDrained

Conditions,ASTMInternational,WestConshohocken,PA,2004,DOI:10.1520/D308004.

Bartlett,S.F.,Negussey,D.,Kimball,M.,2000,DesignandUseofGeofoamontheI15Reconstruction

Project,TransportationResearchBoard,January9thto13th,2000,Washington,D.C.,20p.

BartlettS.F.,Farnsworth,C.,Negussey,D.,andStuedlein,A.W.,2001,InstrumentationandLongTerm

MonitoringofGeofoamEmbankments,I15ReconstructionProject,SaltLakeCity,Utah,EPSGeofoam

2001,3rdInternationalConference,Dec.10thto12th,2001,SaltLakeCity,Utah,23p.

Elragi,A.F.,Negussey,D.andKyanka,G.,2000,SampleSizeEffectsontheBehaviorofEPSGeofoam,

ProceedingsoftheSoftGroundTechnologyConference,ASCESpecialPublication112,theNetherlands.


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The Bond Strength and Impact Resistance of GigacreteTM Facing on Expanded Polystyrene for Highway

Appendix1Section909.300

Exterior

Insulation

and

Finish

Systems

(EIFS)

Boston'sCentralArteryTunnelProject

Bartlett - The Bond and Impact Resistance of Gigacrete

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