Twenty -First Annual Westford Symposium on Building ......Twenty -First Annual Westford Symposium on...
Transcript of Twenty -First Annual Westford Symposium on Building ......Twenty -First Annual Westford Symposium on...
Twenty-FirstAnnualWestfordSymposiumonBuildingScience
Westford,MA
VaporBarriersInCompactRoofAssemblies
Presenter:MattDupuisPhDPESRIMiddleton,WI
August1,2017
Topics
• ProblemStatements• ConcreteBasics• ConcreteandMoisture• FieldExamples• Research• Recommendations• Questions
ProblemStatements
• Theroofingindustryhasseenadramaticincreaseinmoisturerelatedfailuresfromroofingoverconcreteroofdecks,bothnewconstructionandreroofs.• ThecompressedschedulesinnewconstructionhaveseenGeneralContractorsdirect(demand)theinstallationovergreenconcrete,afteronlydays.• MostabsurdreporttoSRIwas3days!• Materialsandtechniquesforinstallingroofshaschangedfocusingonlaborefficiencyandenvironmentalfriendlyfactors
ProblemStatements
• Theroofingindustryhaslittletonoguidanceontheacceptanceoftheconcretesubstrateassuitabletobegininstallingaroofsystem.• TheguidancethatdoesexistforindirecttestingofroofdecksistypicallylegacyspecificationlanguagetracingitsoriginstobeforeIwasborn
BasicsofConcrete
BasicsofConcrete
•PortlandCementisnotconcrete• PortlandCementisthebindingagent• Concreteisthecompositematerial• Aggregates• Coarse40%-50%byvolume• Fine20%- 30%byvolume
• PortlandCement15%-20%byvolume• Water15%-20%byvolume• Additional“adds”typically<1%
BasicsofConcrete• Additionalcomponents
• Fibers• Accelerators• Retarders• Water reducers• Air entrainment• Fly Ash• Silica Fume• Waterproofing• Magic Pixie Dust
BasicsofConcrete
• ProductionofConcrete• Eachbatchplantwillhavehundredsoreventhousandsofrecipes• Basedonlocalaggregatesandconditions• Requirementsoforderdictatewhichonetheyuse• Developedovertime• Scienceandtrial&error
• Formsforroofdecks• Strippableforms• Steelformdeck
CuringofConcrete
• Note wearediscussingcuringnotdrying• Chemicalprocessofhydration• Allaboutcompressivestrengthgain• Lossofmoistureduringthisprocesscanhaveadverseeffects• Moistcure• Protectfromfreezing
CuringofConcrete
• StructuralEngineerspecifiedstrength• Typicallyspecifiedat28-daycompressivestrength• i.e.5000psiat28days
• 28-dayshasnothingtodowithmoisturecontentonlycompressivestrength
MoistureinConcrete
FactorsThatAffectDrying
• Climacticconditions• Concretesurfacecondition• Rewettingofconcrete• Rain,snow,ice,condensate
• Capillaryclosure
MoistureinConcrete
• EffectsofCuringandDryingEnvironmentsonSplittingandTensileStrengthofConcrete• J.AHanson• 1968
MoistureinConcrete
EffectsofCuringandDryingEnvironmentsonSplittingandTensileStrengthofConcrete- Hanson
<3)+%.*#,)$,?3$:*#%#
1&##5*D6"@*+#BK*c*6%#*L)I*4"I.%:
1&##5*+#BK
<3)+%.*#,)$,?3$:*#%#1&##5*D6"@*+#BK*c*6%#*L)I*4"I.%:
de)-6"*2#&)"4#"*c*@6.$&,"#*4.$&".?,&.6%
1&##5*+#BK
e)-6"*2#&)"4#"
<3)+%.*#,)$,?3$:*#%#1&".--#4*H6"@$*c*<*L)I*4"I.%:
<3)+%.*#,)$,?3$:*#%#1&".--#4*D6"@$*c*GL6*L)I*4"I.%:
de)-6"*2#&)"4#"*c*6%#*L)I*4"I.%:
MoistureinConcrete
• Howdowemeasuremoisturecontentofplacedconcrete?• Surfaceemission• Electricalresistance• Electricalimpedance• RelativeHumidityatdepth
MoistureinConcrete• ASTMD4263StandardTestMethodforIndicatingMoistureinConcretebythePlasticSheetMethod• Veryqualitative• Environmentalconditionscangreatlyinfluenceresults/signal
• Easyandinexpensive• Cangivefalsenegative
MoistureinConcrete
MoistureinConcrete
• ASTMF-1869MeasuringMoistureVaporEmissionRateofConcreteSubfloorUsingAnhydrousCalciumChloride• DishofCalciumChlorideisweighedbeforeandafter24hrexposureunderaclearlid• Returnspoundsofwateremittedper1000ft²per24hours• Veryoldtest
MoistureinConcrete
• CalciumChloridetest
http://www.duraamen.com/images/mv_pic_01_test_kit_01.jpg
MoistureinConcrete
• ASTMF-2420DeterminingRelativeHumidityontheSurfaceofConcreteFloorSlabsUsingRelativeHumidityProbeMeasurementandInsulatedHood• Uncommontest• Usesarelativehumidityprobeplacedontopofslabinsideasmallinsulatedbox• Givesindicationofmoistureatsurfacenotwhatisintheslab• Uncommontest
MoistureinConcrete• HumidityProbeMeasurementandInsulatedHood
http://www.esellersolutions.com/eSellerManager/images/upload/item/Southsurvey/itemImage_111_7_12_11_48_35.gif
MoistureinConcrete
• Electricalresistancemeasurement• Drilltwoholesinconcrete• “brush”probesinsertedandresistancebetweenprobescorrelatedtomoisturecontent• NotseenintheUScurrently
MoistureinConcrete
• Impedancemeasurementofconcretesurface• Electricfieldispassedthroughconcrete• Instrumentreadsoutmoisturecontentpercentage.• Onlyreadstop1.5inchesofslab
MoistureinConcrete
• Tramex CMEXII
http://www.i-sells.co.uk/images/Resize%20of%20Electrodes.JPG
http://i.ytimg.com/vi/JJjEJyK4ia8/0.jpg
MoistureinConcrete
• ASTMF-2170DeterminingRelativeHumidityinConcreteFloorSlabsUsinginsituProbes• Drillholeinconcretedeck• 40%ofdepth
• Relativehumidityprobeinsertedintohole• Sealed• Recovered/readafter72hours
• (24hoursworksjustfine)
MoistureinConcrete
• ASTMF-2170(Continued)• FlooringmanufacturersrequireminimumRHreadingdeliveredviaF-2170beforefloorisallowedtobeinstalled• Wideacceptance• LotsofResearch
http://www.southsurvey.co.uk/img/gi_20_38_466_700.jpg
MoistureinConcrete
• Flooringindustrystruggledwiththeissueconcretefloorsandfailuresattheturnofthecentury• Flooringmanufacturersspecifyatwhattestvalues(moisturecontent)theirproductscanbeinstalledoverconcrete• Typicalvaluesrangefrom80%to90%RHviaF2170
MoistureinConcrete
• Howeverfloorsandroofsexistindrasticallydifferentenvironments• Floorscanbelefttillneartheendoftheconstructioncycle• Roofneedstogoonveryearly• Floortypicallyhasconditionedair
• Temperatureandhumidity• Roofisexposedtoweather
• Rewetting
BadandWorse
• Sotheflooringcontractorhasiteasyright?• RemembertheHansongraphs?
BadandWorse
EffectsofCuringandDryingEnvironmentsonSplittingandTensileStrengthofConcrete- Hanson
BadandWorse• DifferencesbetweenRegularWeightConcrete(RWC)andLightWeightStructuralConcrete(LWSC)• Mass(approximate)• RWC150lb/ft³• LWSC110lb/ft³
• Startingwatercontent• Regularweightaggregateshave8- 15lb/yd³ofconcrete• Lightweightaggregateshave150– 200lb/yd³ofconcrete
• Bothcanachievethesamecompressivestrengths• LWSCdoesitwithlessweight
BadandWorse
• Lightweightaggregates• Expandedshalesandclays• Alternatelyreferredtoas“pre-wettedaggregates”• Needtobepondedorsoakedfordaystomonthsbeforebeingbatchedintoaconcretemix• Waterfillsporesandpreventslightweightaggregatesfrominterferingwithmixpropertiesandperformance
• Lightweightstructuralconcretehasrepeatedlybeenshowntotakemuchlongerthanregularweightconcretetodry.
RecommendedReading
• EngineeringBulletin119:ConcreteFloorsandMoisture• HowardM.Kanare• 2008,PortlandCementAssociation
Fieldexamples(TrainWrecks)
FieldExample#1
• Plazadeckoncorporatecampus• Lightweightstructuralconcreteoversteeldeck• Toolateindesigntoswitchtoregularweightconcrete
• IRMAdesignwithfluidappliedandself-adhesivewaterproofingsheets• Deckallowedtocure/“dry”insummerheatforjustover3months
FieldExample#2
• Eastcoasthospital• Roofdeckdesignedtobefloorforfutureverticalexpansion• Operatingsuitesbelowroofdeck
• LightWeightStructuralConcreteonmetaldeck• FullyadheredEPDMwithtaperedISO• Lowrisefoamadhesiveinribbons
• Inplacefor3years
FieldExample#3
• HospitalintheupperMidwest• Roofdeckintendedtobeafloorforfutureverticalexpansion• LightWeightStructuralConcreteonmetaldeck• FullyadheredEPDMwithtaperedISO• Lowrisefoamadhesiveribbon
FieldExample#3
• Topfloorunoccupied• Noleaksreported• Firstindicationwasfullyadheredmembranebillowinginwind• Belowdesignwinds• 9monthsafteroccupancy
• Manufacturerdeniedwarrantycoverageduetotrappedmoisture(interiormoisture)• Insurancecompanydeniedclaimasdefectiveconstruction
ResearchPhase1
ResearchSponsors
ResearchGoals
• PrimaryGoal• Determinewhatmoisturelevelinconcretedecksisappropriateforroofingoperations• Newconstructionandreroof
• SecondaryGoals• Studyinstrumentationcapabilitiesforspeedandaccuracyinthedeterminationofmoisturelevelsinconcreteroofdecks• Studyimpactofweatherandthephenomenaof“rewetting”onmoisturelevelsinconcreteroofdecks
ResearchPlan
• 4ModulesofthePhase1• BeganpreparationandplanningSpring2016• ConcretepoursoccurredJuly11,2016• Studyisongoing• Newinformationlearnedreshapeshypothesesanddirectionofresearch• Phase2startingAugust-September2017
ResearchProgress
• Phase1Fullscaleconcreteweatheringfarmandlabsamples• Received20.43inchesofrainduringthe16weekperiod• TramexCMEXII- ConcreteMoistureMeterused
• Nodiscernabledifferencebetweeninside,outside,normalweight,lightweight
• Onlywasanindicatorofrecentrain
ResearchProgress
0.0
1.0
2.0
3.0
4.0
5.0
6.0
A B C D E F G H I J
Readingon
Tramex
Slabs
TramexCMEXII- ConcreteMoistureMeterReadings
9/5/2016
9/8/2016
9/20/2016
10/2/2016
10/15/2016
10/21/2016
3.25.1
SurfaceisDry
Moistureisdownhere!
• Phase1• UseofF-2170probes• WagnerMetersinRogueRiver,Oregonprovidedhundredsofprobesandaccessoriesforthisstudy.• Calibratedbeforeuse• Readingstypicallytaken1,2,3,6,and24hoursafterplacementweekly• Pans• Slabs• Replicates• Exteriorpansbroughtinlabandprobeagain
• Thousandsofreadingswithconfoundingvariables• Promisingdataneedmoretimetostudy
ResearchProgress
ResearchProgress
ResearchProgress
40
50
60
70
80
90
100
12:00:00AM 3:00:00AM 6:00:00AM 9:00:00AM 12:00:00PM 3:00:00PM 6:00:00PM 9:00:00PM 12:00:00AM
RelativeHu
midity
(%)
Time
F-2170InsertedintoNormalWeightConcrete(15daysafterpour)
ResearchProgress
• Phase2Hygrothermalcharacterizationofconcrete• E96VaporPermeability• C1794WaterAbsorptionCoefficient• C1498HygroscopicIsotherm• C1699MoistureRetention
ResearchProgress
• Module2Hygrothermalcharacterizationofconcrete
ASTME96calculatedPerm·inLightWeightStructural
ConcreteNormalWeight
ConcreteAge WetCup DryCup WetCup DryCup
28Day 1.48 0.78 3.42 1.0560Day 1.45 0.47 2.03 1.13
ResearchProgress
• Module3Hygrothermalmodeling• WUFI5.3ProHygrothermalprogramutilized
• ConsultingwithjustSmartSolutions theU.S.partneroftheGermansoftwarevendor• ThedataoutputfromthemodelinghasbeenvalidatedwithModule1data• Letuslookatsomeofthethingwecanopinefromjustthesimplegraphs!
NormalWeightConcrete– LabDryDown(4Months)
Top1inchofslab
NormalWeightConcrete– OutdoorDryDown(4Months)
Top1inchofslab
TotalWaterContentperFt2 ofslabRegularWeightConcreteChicago,IL(4Mo.)
TotalWaterContentperFt2 ofslabRegularWeightConcretePhoenix,AZ
(4Mo.)
TotalWaterContentperFt2 ofslabRegularWeightConcreteEdmonton,CAN
(4Mo.)
Research
• Usedhygrothermaldataforcurrentgenerationroofingmaterials• Simulatedroofslabsoutdoorsfor28daysthenroofed• Withandwithoutvaporretarders• 100’sofcombinations
Research
• Desertsouthwestgenerallyokwithoutavaporretarder• Canada…justplanonavaporretarder• Southerntierstates…maybe• AtlantaslabgoesdownJuly1=okwithnovaporretarder• AtlantaslabgoesdownDecember1=failwithoutavaporretarder
• So…doIneedavaporretarder…itdepends
Recommendations
• Preliminaryfindingsofconcreteresearchprogrampointtoadistinctissuewithslabsinnorthernandhumidclimates.• Workonhygrothermalsimulationsandtheirvalidationisongoing(Phase2).• Butgiventhecurrentlyavailableresearchdataandobservationsfromit,thisresearcherisrecommendingthat:• UnlesstheDesignerofRecordapprovesinwritingotherwise,avaporretarderoflessthan0.01permisnecessaryovernewconcreteroofdecks.
• Theimpactofrewettingonexistingconcretedecks(reroof)andmoistureladenroofsystemsisbeingdetermined.
ThankYou
ContactInfo:[email protected]