bartlett - the bond and impact resistance of gigacrete
TRANSCRIPT
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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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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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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
Figure18. Plotsofshearstressversusaxialstrainforcyclicuniaxialstresstests,cycles501750.........15
Figure19. Plotsofshearstressversusaxialstrainforcyclicuniaxialstresstests,cycles501750.........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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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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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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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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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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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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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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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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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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Figure17. Plotsofshearstressversusaxialstrainforcyclicuniaxialstresstests,cycles251500.
Figure18. Plotsofshearstressversusaxialstrainforcyclicuniaxialstresstests,cycles501750.
Figure19. Plotsofshearstressversusaxialstrainforcyclicuniaxialstresstests,cycles501750.
Once1000cycleshadbeenappliedtothesample,weinspectedtheGigacreteTMEPSinterfaceforany
signsofdamagedue tocycling. Nodebondingordamagewasobservedat this interface (Figures20
and21).
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Figure20. Photographsofthetopofthesamplebefore(top)andafter(bottom)theapplicationof1000loadingcycles. No
damagewasobserved attheEPSGigacreteTM
interface.
Figure21. Photographsofthebottomofthesamplebefore(top)andafter(bottom)theapplicationof1000loadingcycles.
NodamagewasobservedattheEPSGigacreteTM
interface.
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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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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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(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
4 280 0.177 N Cracks to edges
5 304 0.080 N Cracks to edges
6 320* 0.037 N Cracks to edges
GigacreteTM thickness: 1/2" Sample Size: 1' x 1' x 2 EPS
Reinforcement: Glass Fiber
Sample Drop Indentation Penetrated
Number Energy (inlbs) Depth (in) Mesh? (Y/N) Observations:
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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GigacreteTM thickness: 3/4" Sample Size: 6" x 6" x 2 EPS
Reinforcement: Glass Fiber
Sample Drop Indentation Penetrated
Number Energy (inlbs) Depth (in) Mesh? (Y/N) Observations:
1 200 N No cracks
248 N Cracked to edges, small chips
2 320* 0.013 N Cracks to edges
3 320* 0.013 N Cracks to edges
4 320* 0.010 N Cracks to edges
5 320* 0.038 N Cracks to edges
6 320* 0.022 N Cracks to edges
GigacreteTM thickness: 3/4" Sample Size: 1' x 1' x 2 EPS
Reinforcement: Glass Fiber
Sample Drop Indentation Penetrated
Number Energy (inlbs) Depth (in) Mesh? (Y/N) Observations:
1 320* 0.076 N Cracks to edges
2 200 0.026 N Cracks to edges
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GigacreteTM thickness: 1/2" Sample Size: 6" x 6" x 2 EPS
Reinforcement: Nylon
Sample Drop Indentation Penetrated
Number Energy (inlbs) Depth (in) Mesh? (Y/N) Observations:
1 248 0.024 N Large Cracks to edges and into EPS
2 200 0.045 N Large Cracks to edges and into EPS
3 152 0.008 N Cracks to edges
4 120 0.012 N Cracks to edges
5 96 0.005 N Cracks to edges
280 N Large Cracks to edges and into EPS
6 320* Y Large Cracks to edges and into EPS
GigacreteTM thickness: 1/2" Sample Size: 1' x 1' x 2 EPS
Reinforcement: Nylon
Sample Drop Indentation Penetrated
Number Energy (inlbs) Depth (in) Mesh? (Y/N) Observations:
1 104 0.019 N No Cracks
200 0.182 N Cracks to edges
304 Y Penetrated into EPS
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GigacreteTM thickness: 3/4" Sample Size: 6" x 6" x 2 EPS
Reinforcement: Nylon
Sample Drop Indentation Penetrated
Number Energy (inlbs) Depth (in) Mesh? (Y/N) Observations:
1 200 N Cracks to edges
248 N Cracks to edges, small chips
2 320* 0.013 N Cracks to edges
3 320* 0.013 N Cracks to edges
4 320* 0.010 N Cracks to edges
5 320* 0.038 N Cracks to edges
6 320* 0.022 N Cracks to edges
GigacreteTM thickness: 3/4" Sample Size: 1' x 1' x 2 EPS
Reinforcement: Nylon
Sample Drop Indentation Penetrated
Number Energy (inlbs) Depth (in) Mesh? (Y/N) Observations:
1 240 0.016 N Cracks to edges
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
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ASTM C297 / C297M, 2004, Standard Test Method for Flatwise Tensile Strength of Sandwich
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International,
West
Conshohocken,
PA,
2004,
DOI:
10.1520/C0297_C0297M
04.
ASTM C578, 2008, Standard Specification for Rigid, Cellular Polystrene Thermal Insulation, ASTM
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Bartlett,S.F.,Negussey,D.,Kimball,M.,2000,DesignandUseofGeofoamontheI15Reconstruction
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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