DESIGN AND CONSTRUCTION OF AIRPORT PAVEMENTS ON EXPANSIVE SOILS 1976

ReportNo.FAA;RO'76-66 DESIGNANDCONSTRUCTION OFAIRPORTPAVEMENTS ONEXPANSIVESOILS R.GOROONMcKEEN )WEe LI'RA'v . 1 ~ t 7 6JUNE1976 FinalReport Documentisavai labletothepublicthroughthe -,I ~NationalTechnicalInformationService, Springfield,Virginia22161. r Preparedfor u.s.DEPARTMENTOFTRANSPORTATION FEDERALAVIATIONADMINISTRATION SystemsResearch& DevelopmentService Washington,D.C.20590 NOTICE Thisdocumentisdisseminatedunderthesponsorshipof theDepartmentofTransportationintheinterestofinformationexchange.TheUnitedStatesGovernmertassumesno liabilityforitscontentsorusethereof.. TechnicalReportDocumentationPage 3.Recipient $CatalogNo.1.ReportNo. 2.GoYer"me,,'AccessionNo. FAA-RD-76-66 -----..-1...--------------+--.5-."R-epo;ti>.;;;- ----- --- --- -._- .-----June1976 DESIGNANDCONSTRUCTIONOFAIRPORT 6.PerformingO,goni zarianCode PAVEMENTSONEXPANSIVESOILS f----..----------:-:------i1--:-__--;-:- ---1 8 .PerformingOrgonlzationReportNo. 1_Author' .J R.GordonMcKeen CERFAP-18 1-------------------------1--:-=---:------------19.PerlormingOrg...ilo';onNome...dAddress10.Wo,kUnitNo.(TRAISJ EricH.WangCivilEngineeringResearchFacility, \-;-;--:=__--::-_.,.,-- --1 11.Con floe'orG,ontNo.UniversityofNewr1exico,Box25,DOTFA75!.iAI-531 Univ. ersityStation,Albuquerque,Nt187131 J3.TypeofRepprtondPeriodCo"eredIf: Of Afdransporta ti 011-----------.Fi na 1Report Federal' AviationAdministrationApril1975- ;larchlJ76 SystemsResearch& DevelopmentSHvi ce14. Code . .:::-C.:.-.L-.. _ 15.SupplementaryNotes 1---:-,,---:------------------------------------16.Abstract A literaturereview\vasconductecto'lrovidetilebestavailable fordesigningairportpavementssoils.areasstudled includedidentificationandclasSlflcatlon settingofacceptablelevelsofteave,andthedeslgnofstablllzedsOll ,layers.r-1ethodsofidentificaticnandclassificationwerefoundusefulfor qualitativepurposesbutunreliableforquantitativepredictionoffield ratesofheave.Predictionofhraveiscurrentlybasedonswelltestsin consolidationtypeequipmentandti,eseI;lethodsrequireextremecaution.The technicalliteratLirefailedtoprovidesufficientdatafromwhichacceptablelimitsofsubgradeheavebeneathairpoytpavementscouldbeestablished.Stabilizationofexpansivesoilsmaybeaccomplishedwithcementor lime.AprocedureisrrovidedfCTthedesignofstabilizedlayers.Present des i gnsys-cemsdonotprovi deme-l ;lOdsfordes i 0ni ngvolumechanges;therefore,theinfluenceofstabilizersonvolunechangebehaviorisnotprODerlyaccountedforinthisprocedure.Anoutlineoftheresearchneededto a designis!wesented.Thetechnologyrequired lSpresentlyavallablebutaconsiderableeffortisrequiredtoproduceimTheapproachrecommendedconsistsofestablishingthe loadanamOlsturechangesexpectedtooccuratthesiteandevaluationof thesoilresponsetothose 17.KeyWord.18.DistributionSrotement Pavementdesign,Claysoils,Documentisavailabletothepublic Expansivesoils,Ai rrort throughtheTechnicalInforS,'/ellpotenti a1,mationService,Springfield,Virginia Swellpredictions,22151. 19.SecurityClass;" (of thisreport) I FI:-:J - "'rmDOTF1700.7(8-721 Reproducti_of completedpogeauthorized METRICCONVERSIONFACTORS S,.1Io1 ApproximateConversionstoMetricMeasures Whl.Vo.111_M.hill"II,ToFiS,.lIol '" -= = --..,.. .... -.. S,..lIol Apprexi.ateConversionstr lI.tric1I....r.. Whl.V.. lne.M.llill"IIyTeFie'S.et lID--. LEISTH

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I 100 C CONTENTS Section Page. 1INTRODUCTION 5 2EXPANSIVESOILS 7 3EXPANSIVESOILSTESTPROCEDURES16 4IDENTIFICATIONANDCLASSIFICATIONSYSTEMS25 Introduction25 GeneralClassificationSystems26 Expansive-SoilClassificationSystems27 Evaluation 36 5PREDICTIONOFIN-SITUHEAVE45 ConsolidometerTesting45 FactorsInfluencing1n-SituHeave47 PredictionMethods53 6STABILIZATIONOFEXPANSIVI.SOILS65 Introduction65 ChemicalStabilization66 SelectionofStabilizingAgents68 StabilizedSoilDesignandEvaluation69 SubsystemforLimeStabilization69 SUbsystemforCementStabilization77 SoilStabilizationSystemforExpansiveSoils83 .7CONSTRUCTIONOFCHEMICALLYSTABILIZEDSOILS89 8CONCLUSIONSANDRECOMMENDATIONS93 APPENDIXA:SWELLTESTPROCEDURE103 APPENDIXC:ESTIMATIONOFFINALEQUILIBRIUMMOISTURE APPENDIXH:RESIDUALSTRENGTHREQUIREMENTSFORSTABILIZED APPENDIXB:LINEARSHRINKAGETEST111 CONTENTUNDERPAVEMENTS114 APPENDIXD:SOILSUCTION116 APPENDIXE:LIMESTABILIZATIONPROCEDURES121 APPENDIXF:SSISSOILSAflPLES131 APPENDIXG:CEMENTSTABILIZATIONPROCEDURES135 SOILMIXTURES153 REFERENCES 168 ILLUSTRATIONS FigurePage 1NatureofHydrationVolumeChanges12 2SwellIndexVersusPotentialVolumeChange19 3ConsistencyLimitsandIndexes21 4DeterminationofPotentialExpansivenessofSoils30 5InterrelationshipofPlasticityIndexandVolume Shrinkage30 6ApplicabilityofProposedChartforClassificationof Twenty-SevenNaturalSoils32 7CorrelationofSwell,Li-1UidLimit,andDryUnitWeight34 8RelationshipBetweenPla,ticityIndexandPVCSwellIndex39 9ComparisonofMultiplea ldSingleParameter ClassificationSystems40 10EffectsofPlacementConlitionsonStructure49 11StagesofGenesisofNonJalGilgai50 12TypesofSwellTestData55 13SelectionofStabilizer70 14SS ISSubsystemforNonexpedi entSubgradeStabil i zati on withLime71 15pHTestVersusStrength-estasPredictorofOptimum LimeContent73 16Twenty- Ei ght- DayStrengtl\Predi ctedbyAcceleratedCure74 17Des i gnChartforFreezer-hawLoss75 18DesignChartforThree-CycleFreeze/ThawStrengthFrom Vacuum Strength76 19DesignSubsystemforNonexpedientSubgradeStabilization withLime78 20SSISSubsystemforNonexpedientSubgradeStabilization withCement79 21CorrelationBetweenSeveri-DayandTwenty-Eight-DayUnconfinedCompressiveStrength80 22CorrelationBetweenSix-CycleAcceleratedandTwelveCycleStandardFreeze/ThawWeightLoss82 23DesignSubsystemforNonexpedientSubgradeStabilization withCement84 24SelectionofTypeofAdmixtureforExpansiveSoil Stabilization85 2 ILLUSTRATIONS(Conc1'd.) Figure 25 26 27 28 29 30 31 Page SubsystemforExpansi veSoi 1Stabil i zationwi thLime87 SubsystemforExpansiveSoilStabilizationwithCement88 DiagramforComputingAllowableHeave95 RecommendedDesignProcedure96 SuctionMeasurementProcedure98 EvaluationofNaturalandStabilizedSoils100 Heave/RoughnessAmplitudeRelationshipforDesign101 3 TABLES Table 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Page. EstimatedSoi.1PropertiesSignificanttoEngineering8 SchematicDiagramsandPropertiesofClayMinerals10 TypicalSoilProperties17 TypicalResultsofSwellTests17 ApproximateRelationshipofExpansionIndex toOtherTests21 SummaryofExpansive-Soi!ClassificationSystems37 SwellPotentialPredictionMethodsUsedfor StatisticalComparison42 ResultsofStatisticalAnalysisofSwellPotential PredictionMethods43 SummaryofIn-SituHeavePredictionMethods54 SampleCalculationofSOilMovement59 ConversionofVolumeChat'getoPotentialVerticalRise60 VanDerMerwe'sHeavePrf:diction62 CalculationofTotalSweil63 PCASoil/Cement,Freeze/lhawWeightLossCriteria83 4 SECTION1 INTRODUCTION BACKGROUND Thepavementsofairports(i.e.,runways,taxiways,ramps,parkingaprons, etc.)constituteavitalpartoftheoverallfacilityandthereforepavement constructionandmaintenancecostsareimportantintheplanningandoperation ofairports.Prematurefailureofthesepavements(manifestedassurface roughness)effectsoperationallimitations,acceleratesaircraftfatigue,and reducessafety;ontheotherhand,initialconstructionandmaterialcosts prohibitdeliberateoverdesignof pavements. A majorcauseofprematurepavementfailureisunderlyingexpansivesoils whi chbyshri nki ngandswell i ngcausesurfaceroughness.Althoughcurrent FederalAviationAdministration(FilA).designprocedures(ref.1)donotadequatelytreatthedesignofpavemelltsoverexpansivesoils,recognitionofexpansivesoilsasasignificantengineeringproblemtookplacemanyyearsago. A concentratedeffortbytheworldengineeringcommunitytosolvethisproblem wasbegunin1965withtheFirstIliternationalConferenceandhascontinued withthefollowingnationalandinternationalconferences: (1)FirstInternationalResearchandEngineeringConferenceon ExpansiveClaySoils,August30-3,1965,Texas A&MUniversity,CollegeTexas. (2)SecondInternationalResearchandEngineeringConferenceon ExpansiveClaySoils,1969,TexasA&MUniversity,College Station,Texas. (3)ThirdInternationalResearchandEngineeringConferenceon ExpansiveClaySoils,July30- August1,1973,Haifa,Israel. (4)WorkshoponExpansiveClaysandShalesinHighwayDesignand Construction,sponsoredbytheFederalHighwayAdministration, December13- 15,1972,Denver,Colorado. (5)University-IndustryWorkshoponBehaviorofExpansiveEarth Materials,sponsoredbytheNationalScienceFoundation, October1974,Denver,Colorado. 5 Theproceedingsoftheseconferences,specialtysessionsinthemeetingsof theInternationalConferenceonSoilMechanicsandFoundationEngineering (ICSMFE),andseveralsignificantliteraturereviewsformthebasisofthis report.

Thisinvestigationwasinitiatedtl1reviewthecurrentengineeringliterature andsynthesizefromitadesignprlicedureforstabilizingexpansivesoilsbeneathairportpavements.Todoths,thestudywasbrokendowriintosixspecifi careas: (1)Methodsofidentifyingaridclassifyingthetypesofsoilthat areconsideredexpansiveandcauseearlypavementdistress (2)Laboratoryand/orfieldLestmethodstodeterminethelevel ofexpansionandshrinkal.e (3)Selectionofthetypeancamountofstabilizingagent(lime, cement,asphalt,only) (4).Testmethodstodeterminlthephysicalpropertiesofstab"j 1i zedsoi 1 (5)Testmethodstodeterminfthedurabilityofstabilizedsoil (6)Fieldconstructioncriteriaandprocedures SCOPE Thisreportaddressestheaboveobjectivesandprovidesasummaryofthecurrentliteraturepertainingtothesubject.Conclusionsandrecommendations weremadebasedonthecurrentliterature,withoutlaboratoryverification. Soilvolumechangescausedbyotherfactors(e.g.,frostheave,saltheave) werenotstudied. 6 SECTION2 EXPANSIVESOILS ORIGINANDDISTRIBUTION Expansivesoilsaremadeupofclayparticlesthatresultfromthealteration ofparentmaterials.Alterationtakesplacebyseveralprocesses:weathering, diagenesis,hydrothermalaction,neoformation,andpostdepositionalalteration (ref.2).Mostclaymineralsaretransportedbyairorwatertoareasofaccumulation.Oncedeposited,thematerialsaresubjectedtothelocalconditionsofaccumulation(overburden)1nderosionwhichmakeupthegeologic stresshistoryofthematerials(ref.3).Thus,theexistingclaysoilata siteistheproductofparentmaterial,modeofalteration,andgeologichistory.Interactionbetweenthesoilandthelocalenvironmentproducescontinualchangeinthesoilanddeterminesfuturebehavior. Expansivesoilsaredistributedallovertheworld.Usuallytheareaswith themostsevereproblemsarethose' ~ i t h localclimatesthatproducedesiccation.A recentreport(ref.4)providestheresultsofastudyofthedistributionofexpansivesoilsintheC01tinenta1UnitedStates.Distributionis generallyaresultofgeologichist:Jry,sedimentation,andlocalclimaticconditions.A moredetailedandlocalizedsourceofdistributioninformationis availablethroughsoilsurveyspub1ishedbytheU.S.DepartmentofAgriculture SoilConservationService.Thesesurveysprovidedistributionmapsandconsiderableinformationusefulinengineeringapplications(table1).Inthe initialplanningofairportfacilities,publicationsreflectingthedistributionofsoiltypesintheareashouldbecarefullyconsidered,andthelocationwiththebestsoilconditions3hou1dbeselected.Thethreeclaytypes recognizedinengineeringstudiesexhibitdistinctlydifferentstructures (table2).Kaoliniteismadeupofalternatelayersofsilicatetrahedraand gibbsiteboundtogetherbyrelativelystronghydrogenbonds(ref.6).Therelativelylargeparticlesandstablestructurearenotexpansive.Illiteismade upofa2:1structureconsistingofgibbsitesheetssurroundedbysilicatetrahedra.About20percentofthesi1iconsarereplacedbyaluminum,andtheresultingnegativechargeisbalancedbypotassiumionsbetweenthe2:1sheets. 7 -----Table1.Estimated>oi1PropertiesSignificantto Engineerinl[afterFo'lks(ref.5)J J),pth fe1m Soil series and map symbolsDepthtosurf'ere in bedrock"'I'resentltive profile f--------------,----F,uIII"Rednun:RD, RE, RG_I):{ .,>5 -... 60 TravessillapartofRG,secTranssilla ForPenapart ofRE,HrePenaserirs:fnr ecrics. Riverwash:RH. Toovariable forvalidinterpretation. "Rock outcrop:RK,RL. Tonvariableforvalidintr.rpr('tati(ln.For ChimayopartofRL,sceChimayo series. Rock slides:RO. Toovariable forvalidinterpretation. Roughbrokenland:R U Toovariableforvalidinterpretation. "SantaFe:SF, Sk, SM._01-13 ForLaFondapartofSF,HeeLa. Fonda13 series.RockoutcroppartsofSkand SMaretoovariableforvalidinterpr,,tation, "Silver:SP, SR._ 1-14 ForPojoaquepartofS p.seePojoaqu"II4:' series.4 ',-60 StonY roek land: ST. 'roovariableforvalidinterpretation. "Su!>"rviHnr:S U,SV, _____ 1-23 Rockoutrrop part ofSVistoo variable for validinterpretation,23 "Tapia:T A______________________________>5 "-21 21-60ForDeanpart,secDeanseri-es. 11-10 ForBernalpartofT S,secBernalHerirs. Rockoutcroppart ofT R istoovariable forvalid interpretation, "Trave"ilIa:T S,TR___ ___________________Tuff rock land:T U, Toovariable forvalidinterpretation. Wilcoxson,variant:we____________________2*-3 11-26 21,-31 31 "-10 11'-60 Willard:WL... __ ___ _>5 Witt:WN________________________________>5 "-:l631 .. 60 Zuni,variant:Z LJ.,1'-16 If,-20 20 IInmapping unitAocorrosivityto uncoatedsteelishi(l:h. USDAtextureUnified ClayInam ____________________CL Verytilll' sandyrlayloam..CL or1\11. VeryR",\'''llycillyloam..GC Bedrock. Clay(loam,urfa,'"layer). ______CI. Siltyrlayloam._____________CL Veryfinesandyloam __,___ML Gra\'ellyHandyloamandverySM Rravellylightsandyloam. Bedrock. Clayloam(loamsurface I..yer) _.CL Gravellyloam,.. ____81\1or SC Loam__ ______________________ML clay,clay,andgravellyCH clay.. Coarse sandy loamSM Softbedrock. Loam__ ..ML or CL ClayloamCL Clay loamand sandy clay loam __CLorMI.LoamML orCL Loamand clayloamMLorCL.ClayCH Weatheredbedrock. Inmapping unitBfcorrosivityto uncoated steelishightl,roughout. 8 AASHO A-6 orA-7 A-6 orA-4 A-2 A-6 orA-7 A-6 A-4 A-I A-6 A-4 A-4 A-7 A-2 A-4 orA-6 A-6 A-6 A-4 A-4 orA-6 A-7 CoansPercentage less than 3 inchespassing sieve-fractionAvailable greaterPermea "'ater than 3No.4No.10No.40No,200hilit)holding inches(4.7(2.0(0.42(0.074capacity mm.)mm.)mm.)mm.) lrtdl,.ptr inch Part'''''l r t ( f l ~ ' perhourof .oil .. _------- ---------10090-10080-90O.l)f'-O.2O.IBO.21 --------- ---------10090-1007(1800.1;:1-2.0o.IHI.16 ---------35-5530-5025-4520-35O.1\3-2.00.08-0.10 -----_.--95-10090-10090-10085-950.06-0.2O.14-0.16 -.-------95-10090-10090-10085-9502--0.63O.19-0.21 --------.95-1009010085-9550-6.';O.';3-2.0ll.16-0.18 5-1580-9055-6530-4015-252.0-6.30.06-0.08 ---25.:3595-10090-10085-9575-850.63-2.0O.19-0.21 80-9075-8560-7535-500.1):1-2.0 -------_ .. --0-2590-10085-9565--7550-600.63-2.0O.14-0.18 ......... _- ... -_.90-9585-9575-8565-750.06-0.2O.14-0.16 ..... - ..... - ... 10095-10055-6525-352.0-6.3O.10-0.12 .. - ..- ... -- .. --------.10085-9560-750.63-2.0O.16-0.18 -----------------.10090-10070-850.2-0.630.05-0.07 --------- ---------10080-9065-750.63-2.0O.16-0.\8 --_.... ---- ------_.. - 10085-9560-750.63-2.0 -------------------_. ------- .. 100 I 85-9560-750.2-6.3O.17-0.19 --------..- ..---_ .. - 10090-10075-950.06-0.2O.14-0.16 IIn mapping unitFs corrosivitytouncoatedsteelishighthroughout. 9 ReactionI(I :5 dilution) pH7.9-9.0 7.9-8.4 6.6-7.3 7.9-8.4 7.9-8.4 7.9-8.4 6.1-6.5 7.9-9.0 8.5-9.0 7.4-7.8 6.1-7.3 6.6-7.3 7.9-8.4 8.G-9.0 7.9-8.4 8.5-9.0 6.1-7.3 6.6-7.3 Shrink-swell potential Corrosivity touncoated steel I I High.. _. __. __ Moderate. l\loderate.. _... _.Moderate. Low __._ _.. Moderate... High..........High.:\foderate..... __.Moderate. I.ow...... _.Low. Low____ . __ __ Low. Moderate....... __Moderate.Low __ .. _._ . ___ Low. Lowtomoderate._Low. High .. __ _______ High. Low. _. _____ __ Low. Lowtomoderate._Moderate. Moderate.... _.. _High. Moderate... _. __Moderate.Low__ _ ____ Low. Moderate..... _Moderate.High ... ________ ._ High. Table2.SchematicDiagramsandPropertiesofClay (afterreference6) 11 oni te III ite Kao1i nite Schematic Structure of Clay r'li nera1s

o

,\"\... \', I\"\ I\', 0I't IOtt";0I'toO#j(}fflS,e Aluminum,0PoloSS/llm o and .5,licoIJS (onelounhreploced byoluminums) OOxyqens,eHyd1oxylS,AJumin/lm,0Po/oss/um o ond SdiCOns (one 10000Ih r(yJlocedbyaluminums) Particle 0I 0.5 to2 llmI 0.003to0.1llmI 9.5AThickness SpecificSurface,I10 - 20I65 - 180I50 - 840 m2 /g CationExchange Capaci ty,I 3 - 15I10 - 40I 80 - 150t4i 11 equi va 1ents 100grams Thepotassiumbondsarestrongandpreventwaterfromenteringbetweenthe layers.Inmontmorillonitea2:1structurelikethatofilliteispresent, butthereischaracteristicallyextensiveisomorphoussubstitution,whichdeterminesthebehaviorofthemineral.Asusedhere,isomorphoussubstitution meansthesubstitutionofonemetallicionforanotherwithinthetetrahedral oroctahedralunit.Theimportanteffectofthelatticesubstitutionsisa netnegativechargethatattractsbipolarwatermoleculesbetweenthelayers; thisresultsinanexpandedlayerstructure(fig.1). MECHANISMSOFSWELL Soilvolumechangesresultfromanimbalanceintheinternalenergyofthesystem(soil/water/plants/air).Energyimbalancesimportantinengineeringresult frommoisturemovementcausedbyloads,desiccation,andtemperaturechanges (refs.7,8).Responsetoaspecificsetofconditionsisdeterminedbythe composition,structure,andgeologichistoryofthesoil.Thelargestcomponentofvolumechangeisthatoftheclaymicellewhichsurroundstheindividual clayparticles"inthesoil(refs.6,9).Waterisforcedoutofthemicelleby loads,desiccation,ortemperaturealongenergygradientsandareductionin volumeresults.Whentheseinfluencesareremovedorreduced,theenergygradientsarereversed;theavailablewaterisforcedintotheclaymicelleand swellisproduced(ref.10).Sinceseveraldetailedstudies(refs.4,6,9, 1])arepresentedintheliterature,discussionhereislimitedtothatrequiredforanunderstandingofexpansivesoilbehavior. WaterFixationbyPolarAdsorption(Hydration) Bipolarwatermoleculesareattractedtotheclayparticlesurfacebytheelectricchargeimbalancecausedbyisomorphoussubstitution,usuallynegative (refs.2,9,12,13).A layerofsolid-likewaterformsanewsurfaceoforientedparticles,whichattractssucceedinglayersoforientedwatermolecules, o 0 uptoathicknessof10to16molecularlayersor25to40A (lA=10-Bcm ). Thewaterbeyondthisboundlayerismobileandmovesfreelyunderanystress gradient(refs.2,13,14).Theboundwaterlayerspermitadjacentparticles toslippastoneanotherwithoutelasticrebound,rupture,orappreciable ,,- uo:>"_mnlo-' 11 LUII:>I.t1I1I..ILI'''II''!''!InterparticleorIntracrystalline C= concentrationinthebulksolution,molesofions/litero Ccanbederivedfromdiffusedoublelayertheory(ref.7):c where v= valenceofion B = temperature-dependentconstant(usuallytakenasl015 cmmi 11i mo1e- 1) d= halfthedistancebetweenclayplatelets,cm X=4/vBG,whereG =surfacechargedensity,coulomb-cm-2 o o valuesofX areasofollows:illite,X ::l/vA;kaolinite,X = oo o 2/vA;montmorillonite,X ::4/vA.Ruiz(refs.9,17)modifiedtheequation o forrealsoilsasfollows: where P= realsoilswellingpressure f= functionofmoisturecontent,f< 1 Osmosisispossibleonlyinpolarfluids,suchaswater,thatareabletodisperseexchangeablecations.SwellingvarieswiththetypeofcationandgenerallydecreasesintheorderNa,Li,K,Ca,Mg,and2HforWyomingbentonite (refs.9,18,19). SurfaceTension Thespacesbetweenclayparticlesinsoilsformcapillarytubes.Aswateris removedfromthesoil,anair/waterinterfaceforms.Attractionofwatermoleculestothewallsofthecapillarytube(soilparticles)producesmenisci (refs.6,9).Tensioninthewater,u(g-cm-2 ),maybeexpressedas (ref.13) Asthewatercontentdecreases t themeniscirecedeintothecapillaries t drawingparticlesclosertogetheruntilnofurthervolumechangeispossiblebecauseofparticlecontact.Thetensioninthewaterisbalancedbycompression "inthesoilparticles.Whenadditionalwaterbecomesavailable t thewatertensionisreleasedandthesoilparticlesreboundastheassociatedcompressive stressisrelieved. Thermoosmosis Themovementofsoilmoisturecausedbytheenergygradientproducedbytemperaturedifferences t whichcausechangesinwatervaporpressure t iscalled thermoosmosis(ref.9).Thisaspectofmoisturemovement t althoughnegligible insaturatedsoils(refs.20 t 21),issignificantinunsaturatedsoils.The swellassociatedwithsuchmoisturemovementissmall(ref.9). ElasticBending Elasticdeformationandreboundofsoilparticlesunderappliedloadsmaycontributetoshrinkageandswellingbehavior t particularlyinsoilswithflat platyparticles(ref.22).UsingmicaanddunesandtGi"lboy(ref.23)illustratesthiseffect.Theresultsofhistestsshowthattheconsolidationand reboundofcompactedmixturesareproportionaltothemicacontent t andthe contributionofelasticbendingdependsonparticlestructureandproperties asshownbelow: VolumeDecreaseIncreaseinVoid Mi ca t%Under10kg/cm2 (142psU t% RatioUponRemoval ofLoad t % 103626 204731 405142 EntrappedAir Whenaninitiallydesiccatedclayisallowedtotakeupwater t airmaybetrappedwithinthesoilmass.Thisairdisplaceswaterinthedoublelayerandinducestensilestressesintheparticlessurroundingtheairpocket.Thisinfluenceisgreaterinsoilswithhigheraircontents(i.e. tdriersoils). 15 SECTION3 EXPANSIVESOILSTESTPROCEDURES Theproceduresdescribedinthissectionhavebeenusedinengineeringstudies ofexpansivesoilsandinsomecasestheliteratureprovidesconsiderabledata derivedfromtheiruse.Table3waspreparedtoshowtheresultsnormallyobtainedforgeneralsoiltypes.Thedifferentproceduresforevaluatingswell potentialarereflectedinthevariationinswellandswellpressurevalues reportedintheliterature(table4).Otherproceduresreportedintheliteraturearetooexpensive,complex,ortimeconsumingforroutineengineeringdesignpurposes.However,fortheinterestedreader,thesetechniquescanbe foundinthefollowingreferences: TechniqueReference X-RayDiffraction2,24,25,26,27 ElectronMicroscopy2,25,26 DifferentialThermalAnalysis2,24 InfraredRadiation27 DyeAdsorption6,27 SpecificSurfaceArea9,28,29 CationExchangeCapacity2,30 DielectricDispersion31 SWELL A remoldedorundisturbedsoilsampleisplaced"inaconsolidometerunderspecifiedconditionsandallowedaccesstowater.Theverticalriseofthespecimenisthen A sampleofthisprocedureispresentedinappendixA; numerousversionsinvolvingvariationsinsamplepreparation,wetting,soaking, specimensize,surchargeloading,etc.,arereportedintheliterature.Because ofthesevariousprocedures,itisdifficulttocompareonesetofresultsto another.Eventhoughnosingleprocedureiswidelyaccepted,thisisthemost popularandreliabletechniqueforevaluatingswellpotential.Thistestmay bereferredtoasaswelltestorafreeswelltest,dependingonthe 16 Table3.TypicalSoilProperties(afterreference32) TestProceduresHeavyTypi ca1Si 1tySandySoilProperty Soils ClaysClaysSoils ASTMAASHO Gradation(%ofgrainsize 40-100500422T88 80-10030-80showninthesoil) GrainSize(mm)~ O.0050.05-0.0052.0-0.050422T88 :::0.005 I ,Consistency I LiquidLimit(%)80-10025-50Nonplastic0423T89 40-60 Nonplastic0424 PlasticLimit(%)5-305-30T90 -NonplasticT91 PlasticityIndex(%)70-8020-4010-200424 D427T92 ShrinkageLimit(%)15-30NoVolume 6- 14 -Change \ I MaximumOensity(lb/ft 3 )I-Ii 90-105100-115110-135 I 0698T99 0698T99 OptimumMoistureContent(%}]- 20-3015-258-15 I I Table4.TypicalResultsofSwellTests Reference -.Rangeof Swell, % Rangeof SwellPressure, psi SoilsUsedRemarks I 330-13.60-83Texas&Israel1.4-psisurchargein swelltest. 340- 13.60-83TexasGulfCoast1.4-ps isurchargein swelltest. I 350- 15.80-284 I IsraelUSBRProcedures: surcharge. l-ps i 360- 50. 10-147~ ~ e s ternU.S.USBR 371.3- 39.8- WesternU.S.USSR 37 38 O.1-54. 0 --0-69 IpureClay&Mixtures IContinentalU.S. USBR FHA,PVCSwellIndex 17 typeofloadingappliedtothesample.Resultsmaybeexpressedinpercent swellunderthespecificloadused. SWELLPRESSURE A testsimilartothatdescribedabove,exceptthatthesampleisloadedin incrementssothatthevolumeremainsconstant,maybeperformedtodetermine swellpressure--thepressurerequiredforzerovolumechange.Thistestin combinationwiththefreeswelltestisoftenperformedonthesamesamplein sometestprocedures(appendixA).Itisalsoreferredtoasano-volumechangetes t. POTENTIALVOLUMECHANGE Potentialvolumechangeisdeterminedbyano-volume-changetestinaspecified apparatusdevelopedfortheFederalHousingAdministrationandusedforsoil classification(ref.39).Testdurationistwohours.Thepressurerequired forzerovolumechangeiscalledtheswellindex(giveninpoundspersquare foot)anditisusedinclassifyingthesoil.Figure2illustratestheuseof theswellindextoclassifysoilsbasedonthemethodofsamplepreparation (i.e.,wet,dry,moist). EXPANSIONINDEX Theexpansionindex,EI,isanindexpropertyofasoildeterminedinaspecifiedconsolidometerringapparatusdevelopedforevaluationofsoilexpansion (ref.40).TheEIiscalculatedby EI== (lOOO)t.hF where t.h== verticalexpansionmeasured F== fractionofthesample30% PlasticityIndex>12% LinearShrinkage>8% Thesecriteria,whicharebasedontheA-lineoftheplasticitychartdeveloped byCasagrande,areusedintheUnifiedSoilClassificationSystem.Thelinear shrinkagecriteriaareincludedtodetectthosesilt-clayandsiltysoilsthat areexpansive. Skempton,1953(ref.42) Theactivityofsoilsasdeterminedbytheplasticityindexand% 12>8 >1.25 >10>300 >81. 5>5>2030-60 >60 >4>20 W -...J PI I:::Reference Ca tegory VeryLow 50493837554033 %

VI..t:Cl..- Cl.. ro ..t: :::l+-' 0" > >,0::: ,......:::lLO,......uEOVI+-'..0OJ ,......U0C:0'l - V'l or- (]JOr- I/) ro(]Jor- co :::lUrocoUroco:::l ro 000 (/')I/) 1/)-'1/) I/) c::( 0 z:::r::: 0::: z:>::E:> => .;.; --.;.;.;.; .;.;.;.;.;.; .;.;.; .;.;.;.; .;.; xIx xxx xx .; .;.;.; .;.;.;.; .;.; xxxx/1 .;.;.;.;.;.;.; .;.; .;.;.;.; .; x .;.;.;.; .;.;.;.; .;.;.;.;.;xxI .;.;.;.; .;.;.; .;.;.;.;.;.;xx xxx Xxxxxxxxx xxx .;.;.; .;.;.; .;.;.;.;.; .;xx x .;.;.;.;.;x xxx xxxxxx .;.;.;.; .;.;.;.;.;.; .;.; xx x .;.;.;.; .;.; .;.;.;.;.;.;.; x x xxxxxx xxxxxxxxx .;.;xxx xxxxxxx xxx - Factors Involved inHeave .----------ClayThickness WaterTableDepth Initial01 SoilStructure

ClayParticles Particle Arrangement I ClodStructure BulkStructureI Init i a1St res s FinalMoisture IFinalStresses Load/Moisture/Volume Relationship RateofVolume Change SeasonalVariations r------,......(]J -0 0 .-+->U(]J ........Or- ........0.; .; iI /,! .; .; .; x .; I I x .; .; x x

(]J +->(]JE 0 -0(]J (]J ,........0 Note:.;= consideredintheprediction;x= notconsideredinthepredictiono '" o 'r+-' ttl a::: "'0 o >LogofLoad(P) Figure12.TypesofSwellTestData overburdenpressure,(1to2).Thenitissubjectedtoachangeinmoisture conditionandmaintainedatconstantvolumeuntilequilibriumisreached(3). Thispressureiscalledtheswell:n"essure(no-volume-changetest).Thepressureisthenreleasedtoasmallarbitrarilyselectedloadortoaspecific designload,(3to4).Anothertestprocedureloadsthesoiltotheoverburdenpressure(2),allowsittoswellunderconstantloadto(5),andloads thesampletotheoriginalvoidratio(6).Withthiskindoftestprocedure, swellmaybecalculatedasfollows: -.--6._e_(t'lH)s==- e 1 where 6.e== changeinvoidratio(finaltoinitial) e== originalvoidratio 1 6.Hthicknessofsoillayer 55 Thecurve(1to7)illustratesatestinwhichasoilisloadedtotheinitial overburdenpressure,(7),unloadedtoafinaloverburdenpressure;(2),and permittedaccesstowater;thentheswellisdetermined(analysisofcutsections).Ineachsituation,eventsfollowaspecificsequence.Thecloser theseduplicatein-situconditions,thebetterthepredictionofsoilbehavior. Thosemethodsreportedintheliteratureinwhichsomeformoftheconsolidometertestisusedareasfollows: (1)DirectModelMethod,TexasHighwayDepartment(ref.77) (2)JenningsandKnight'sDoubleOedometerTest(refs.65,78) (3)SullivanandMcClelland'sMethod(ref.79) (4)Sampson,Schuster,andBudge'sMethod(ref.80) (5)MississippiMethod(refs.81,82,83,84) (6)SalasandSerratosa'sMethod(ref.20) (7)Noble'sMethod(ref.7) (8)NavyMethod(ref.85) (9)SimpleOedometerMethod(ref.86) (10)USBRMethod(ref.63) (11)Vo1umeter(ref.87) (12)Holtz'sMethod(ref.76) Eachofthesemethodshassomesimilaritywiththeothersaswellassomedifferences.Someinvolvemultiplesamples(e.g.,2and10);othersdonot.No onemethodisclearlybetterthananotherforairportpavementconstruction. Anyprocedurethatisusedmustbeadaptedtoaparticularsituationandan effortmustbemadetosimulatetheseactualin-situconditions.Atbestthese methodsprovideestimatesofquestionableaccuracyunlesstheyareusedwith considerableexperiencewiththespecificsoilandclimaticconditionsunder study(refs.40,63). Predictionsofin-situheavearemadebytestingeachsoillayerinthesystemtodetermineitsresponsetochangesinloadandmoisture.Theindividual layersmayrepresentdifferenttypesofsoil,thesamesoilindifferentmoistureconditions,orthesamesoilatdifferentdensities.Onceeachlayeris 56 identifiedandaswellpercentageisassignedbytestingintheconsolidometer, thecalculationofsurfaceheaveisstraightforwardisshownbelow. ThicknessVerticalRise Depth, ft ofSoi 1 Layer, ft Overburden Pressure,* 1b/ft2 Swell, % VerticalRise DuetoLayer, in atLayer Surface, in 0-2212581. 927.68 2-4237540.965.76 4-10687532. 164.80 10-122137530.722.64 12-208200021. 921. 92 20-2442750000 Bedrock Inthisillustration,thepredictedsurfaceheaveis7.68in.Thedesigner shouldcarefullyevaluatetheproceduresusedinestablishingtheinitialmoistureconditionsandloadaswellasthefinalmoistureconditionsandloadused inthetests.Theseparametersandtheirrelationshiptoin-situconditions willdeterminetoalargedegreetheaccuracyoftheprediction.Withsome methodsalateralrestraint-factormaybeusedtoreduceswellvaluesforcertainsoils(e.g.,particularlyhighlyfissuredclays).Theamountoftesting requiredforthistypeofanalysiscanbegreatintermsoftimeandmoney. Thevariabilityofthesoilsystemmustbestudiedinordertoarriveatthe amountoftestingrequiredtoadequatelyevaluatetheswellpotential.Once thesedataareavailable,theeffectofsoilremoval,stabilization,compaction,etc.maybeevaluatedquantitatively,providedswelldataarealsogatheredforthestabilizedand/orcompactedmaterials. RichardsMethod(ref.88) Usingcurvesofmoisturecontentversusmatrixsuctionplottedfrommeasured values,Richardspredictsmoisturecontentchangesassoilsreachtheir *Averageatcenteroflayer,basedondensityofoverlyingmaterialandstructuralload.A densityof125lb/ft 3 wasassumedforallsoilsinthisillustration. 57 equilibriummoistureconditionsunderpavements.Assumingthevolumechange ofthesoilisequaltotheVolumeofwatertakenup,hegives and where W=initialwatercontent,% o (svl=changeinwatercontent(w - I-'J f ),~ ~o Gspecificgravityofsolids(approximately2.70) s V,L,H= volume,length,height,respectively WithempiricalrelationshipsdevelopedforAustralianconditions,thefinal equilibriummoisturecontentunderapavementispredicted.Withthisrelationship,wf maybepredictedfromthemoisture/suctioncurvespreviously determinedforeachsoillayer.A samplecalculationisshownintable10. McDowellISPVRMethod(ref."Sl) Anundisturbedsampleofeachsoillayerinthesystemisintroducedintoa triaxialcellandthesampleisallowedtoabsorbwaterunderasmall(2psi) lateralpressure.AfterthesamplehasabsorbedwaterforlSdays(oranumberofdaysequaltotheplasticityindex,ifitisgreater)thevolumechange, 6V,isconvertedtoalinearverticalrise,6L,fromanempiricalchart.With anotherempiricalchart,6Lisreducedaccordingtothestressimposedbythe overburdenload.Theremainingpercentageofverticalriseisthensummedfor eachincrement.Anexampleofthisprocedureisshownintable11.Columns show:(1)theincrementsofoverburdenloadsintowhichthesystemisdivided, (2)theaverageoverburdenload,(3)thevolumechangemeasuredundertheexistingoverburdenpressure,(4)thelinearswellcorrespondingtothevolume change,(S)thethicknessofeachincrementinthesystem,and(6)theconversionofcolumn(4)toapercentandthetotalverticalriseatthesurface. S8 --- -----------Table10.SampleCalculationofSoilMovement[afterRichards(ref.88)J FromDriestConditiontoEquilibriumProfile L,em 0-10 10- 20 20-30 30-40 40-60 60-80 Initial Suction (h ) , oemH0 2 90,000 45,000 10,000 5,000 3,200 2,500 1,80080-100 1,500100- 120 1,400120-140 FinalInitialFinalSuctionEffective Stress(00emH 0 ), (hf ) , emH 0 22 90,0001400 45,0001400 10,0001300 5,0001300 3,2001300 2,5001300 1,8001300 1,5001300 1,4001300 L_-l-__._. --------------. ------___ _______ FromDriesttoWettestCondition(i.e.,Seasonal SurfaceMovement3.21em Initial SuctionL,em (ho)' emH0 II 2 0-1090,000 10-2045,000 20-3010,000 30-405,000 40-603,200 60-802,500 80-1001,800 1,500 120- 140 100-120 1,400 Initial Effective Stress(0), ern H00 2 90,000 45,000 10,000 5,000 3,200 2,500 1,800 1,500 1,400 Effective%wo' Stress(of)' emH0 2 140011.5 140014.6 130021.0 130023.3 130024.6 130025. 1 130026.4 130027.1 27.2 1300 Final FinallSuction Effective( hfL Stress(of)' emH0emH0 2 2 --------1---------800800 700700 600600 520520 580580 870870 11201120 13501350 13001300 6w,%6L,em 15.71. 08 12.60.82 6.40.37 4. 10.23 2.80.30 2.30.25 1.00.11 0.30.03 0.20.02 w '%!"I;'/,%o

11.516.7 14.613.8 21. 07.8 23.35.8 24.64.3 2.9 25. 1 26.41.1 27. 1-27.2-6L,em 1. 15 0.90 0.45 0.33 0.46 0.32 0.13 --SurfaceMovement3.73em 59 I VanDerMerwe'sMethod(ref.89) AnotherempiricalapproachinvolvesclassifyingthesoilbytheWilliams' :lethod(ref.50)intothecategoriesshownbelow. Wi11i ams'Criteria PotentialUnitHeave, PI,%Cl ay,%Expansiveness*in/ft 28VeryHigh1. 00 Eachcategoryisassignedaunitheavevalueininchesofheaveperfootof soillayerthickness.Anempiricalrelationshipforthechangeinpotential Table11.ConversionofVolumeChangetoPotentialVerticalRise [after (ref.51)] S\'/e11, l;0 AverageLoad, Load,psi psiVolume Linear(Average) (3 )(4 ) (1)(2) --r-15. a a 1.5-2.52.009. 12.90 3.757.52.40 2.5-5.0 5.0-7.56.255.51. 80 8. 754.5 7.5- 10.01. 50 11.253.51. 1a 10.0-12.5 13.75 12. 5- 15. 02.60.80 16.252.00.60 15.0-17.5 17.5- 20.018.751.50.50 21.250.30 20.0-22.51.0 22.5-25. a 23.750.80.25 26.250.50.20 25.0-27.5 0.2 27.5-31. 029.250.10 _____L--._ DepthofLayer, ft ( 5) LOx1.15::: 2.5x1. 15::: 2.5x1. 15::: 2.5x1. 15::: 2.5x1. 15::: 2.5x 1. 15= 2.5x 1. 15= 2.5x 1. 15= 2.5x 1. 15= 2.5x 1.15 = 2.5x1.15::: 3.5x1.15::: TotalDepth::: 1. 15 2.87 2.87 2.87 2.87 2.87 2.87 2.87 2.87 2.87 2.87 4.03 33.88 L. VerticalMovement, 2. 2.4% 1.8% 1. 1. 1 0.8% 0.6% O.0.3% in (6) x1. 15x12 x2.87x12 x34.40x12 x34.40x12 x34.40x12 x34.40x12 x34.40x12 x34.40x12 x34.40x12 0.25%x34.40x12 0.2% 0.1% x34.40x12 x4.03x12 TotalPVR DuetoSwell ir-----AllsoilswithA =(PI < 2 12.1 Determineamount ofsulfatepresent.(appendixG) Determine after15I-- 40 ./V"l ~/ ./ "'- Second-DegreeCurve ell ./CorrelationCoefficient= 0.96ell 0 .././ Y = 0.002+2.21X- 0.02X 2 ....J ./ +-> ..t:: C"l 30 r ./OJ ::==::: . /// ./ ItS CP..t:: Nt/ First-DegreeCurve ......./OJ 20CorrelationCoefficient= 0.96 N/ Y = 2.41+1.40XOJ / OJ SI..L OJ ..... ~J/U >, 10 U I /eN .lfe oII I I II I o102030405060 6-CycleFreeze/ThawWeightLoss(AcceleratedTest),% Figure22.CorrelationsBetweenSix-CycleAcceleratedandTwelve-CycleStandard Freeze/ThawWeightLoss[afterCurrinetal.(ref.105)] Table14.PCASoil/Cement,Freeze/ThawWeightLossCriteria PCACriteria Accelerated6-Cyc1eFreeze/ThawTest WeightLoss,% AASHOSoilGroup Maximum WeightLoss, % 1st-DegreeCurve2nd-DegreeCurve A-1,A-2-4,A-2-5,A-3 A-2-6,A-2-7,A-4,A-5 A-6,A-7 ermeameter:conditionsof, of-)..... "'0..... E :::::I::I:0 N 40 Q) >..... of-) ItS

Q) e::: 20 HydraulicTensiometers1 o o I 1 I 2 I 3 IIITotal.Suction 10-3 10-2 10-1 10 DonotusePsychrometers psychrometers....I..arepracti ca1. _.. -.,. - - - - - - --....;a-95 % 'k - - - - - - - - - - - - 90%

, RT./ T=-In pipV\'/0 ----T----------- - ------,-----VeryWet..l.PracticalRangeof- Soi 1s - - - - - - - - -"1Thennocoup1 ePsychrometersL ..J.e\ _____1GypsumJ I \ e""I I 4567 DFiii 101 102 103 101f TotalSuction(T),bars Figure1.RelationshipBetweenRelativeHumidityandSuction APPENDIXE LIMESTABILIZATIONPROCEDURES Thisappendixprovidestheproceduresusedinthelaboratorytestingofsoil stabilizationwithlime.Althoughthesearenotstandardtestsineachcase, theseprocedureswereusedinthedevelopmentofthedataonwhichthesystem inthisreportisbased.Thematerialpresentedistakendirectlyfromthe citedreferences.Onlythosechangesneededforconformancetothisformat havebeenmade. 121 TESTFORpHTODETERMINELIMEREQUIREMENT(REF.103), Materials Limetobeusedforsoilstabilization Apparatus 1.pHmeter(thepHmetermustbeequippedwithanelectrodehavingapH rangeof14) 2.150-ml(orlarger)plasticbottleswithscrew-toplids 3.50-mlplasticbeakers 4.CO 2 - freedistilledwater 5.Balance 6.Oven 7.Moisturecans Procedure 1.StandardizethepHmeterwithabuffersolutionhavingapHof12.45. 2.Weightothenearest0.01grepresentativesamplesofair-driedsoil, passingtheNo.40sieve -andequalto20.0gofoven-driedsoil. 3.Pourthesoilsamplesinto150-mlplasticbottleswithscrew-toplids. 4.Addvaryingpercentagesoflime,weighedtothenearest0.01g,tothe s o i l s ~ (Limepercentagesof0,2,3,4,5,6,8,and10,basedonthe drysoilweight,maybeused.) 5.Thoroughlymixsoilanddrylime. 122 6.Add100mlofCO2 - freedistilledwatertothesoil/limemixtures. 7.Shakethesoil/limeandwaterforaminimumof30secoruntilthereis noevidenceofdrymaterialonthebottomofthebottle. 8.Shakethebottlesfor30secevery10min. 9.After1hr t transferpartoftheslurrytoaplasticbeakerandmeasure thepH. 10.RecordthepHforeachofthesoil/limemixtures.Thelowestpercentof limegivingapHof12.40isthepercentrequiredtostabilizethesoil. IfthepHdoesnotreach12.40t theminimumlimecontentgivingthe highestpHisthatrequiredtostabilizethesoil. MOISTURE/DENSITYRELATIONSHIPSOFLIME/SOILMIXTURES(REF.105) Tofindtheoptimummoisturecontentcorrespondingtothemaximumdrydensity ofalime/soilmixture t amethodsimilartothatfoundinASTM0698.. 70is used.Figure1givestheapprox"imateoptimummoistureandmaximumdrydensity baseduponknownAtterbergLimitsoftheuntreatedsoil.Theoptimummoisturecontentoflime/soilmixturesisalwayshigherthanthesoiluntreated. Themaximumdrydensityislower.A VicksburgMiniatureCompactionApparatus isusedtofabricatespecimens.Theapparatusproducesa2-in-diameterby 4-in-highspecimenwithsimilardensitiesproducedwiththecompactionequipmentemployedinASTM0698-70.Theproceduresusedindeterminingtheoptimum moisturecontentforlime/soilmixturesareasfollows: (1)TheuntreatedsoilisfirstpassedthroughaNo.4sieve.It maybe necessarytoairdrythesoiltopermitpulverizationtothepropersize. (2)Estimatetheapproximatemoisturecontentfromfigure1.Determinethe proportionsofsoil tlime t andwaterrequiredforfabricationofapproximatelyfivespecimens.Approximately2100gofmixwillberequired. Seethelime/soilmixturecalculationsthatfollowtheseprocedures. 123 15 20 +-> .r-25 E .r--l U30 or+-> VI 10 ,...a..35 2840--29-N .j:::o 45 Note: Numbersbetweencurves identifyzonesofoptimummoi sturecontentand max imumdrydens ity. 78 50 , ,LI, :".....71 12 1520 25 30 35 40 45 5055 60 65 70 LiquidLimit Example:Given:PlasticLimit- 20Find:AverageMaximumDryDensityand LiquidLimit- 35OptimumMoistureContent Answer:110lb/ft3 (Density)16percent ( ~ 1 o i stureContent) Figure1.ApproximateMoisture/DensityRelationship[after Ring,etal.(ref.127)] 30- 31-32-33 -34 75808590 (3)WeightheVicksburgMoldtothenearest0.1g andrecordondatasheet.. (4)MeasuretheinsideheightoftheVicksburgMoldwiththeentireassembly inplacetothenearest0.01in(fromthebasetothetopofthecollar). Measuretheinsidediameterofthemoldtothenearest0.01inandrecordthevaluesonthedatasheet. (5)Weighoutthesoil,lime,andwaterrequiredtothenearestg/m1asper calculations. (6)Thoroughlymixsoilandlimetogethereitherbyhandorwithanelectric soilmixeruntilallfreelimeisblendedwiththesoil. (7)Addwaterevenlytotheblendedsoilandlime(caremustbetakento preventexcesslossonthesidesofthemixingpot).Mixtheentire blendthoroughly.Afterthesoilismixed,coverwithadamppaper toweltopreventmoistureloss. (8)Weighapproximatelyfiveequalportionsofthesoilmixturetobecompacted.Approximately75to85gperlayerwillproduceaspecimenof thepropersize. (9)Poursoilintocompactionmold,levelsoil,andcompactthefirstlayer withfiveblowsoftheslidinghammer(takeweighttoitsfullheight ontheslidingrodbeforedropping). (10)Measuretheheightfromthetopofthecollartothetopofthefirst compactedlayerofsoil.Bysubtractingthisvaluefromthetotal height(step4),youwillobtainthethicknessofthecompactedlayer. Multiplythisfigureby5(numberoftotallayers)andthiswillgive youanapproximationofthetotalheightofthespecimen.Adjustthe amountofsoilinthefollowinglayerssothatthefinalspecimenwill be40.25in. (11) Scarifythetopofeachcompactedlayertoadepthof1/8inwithanice picktoinsureadequatebondwithfollowinglayers. 125 (12)Aftercompactingthelastlayer,measurefromthetopofthespecimen tothetopofthecollarusingasteelrulewithO.Ol-inaccuracyand recordonthedatasheet. (13)Removethecollarandmold.Trimtheexcesssoilfromtheinsideof themoldtomakethespecimenlevelacrossthetop. (14)Weighthemoldwiththecompactedsampletothenearest0.1gand record. (15)Extrudethesamplefromthemold. (16)Breakthespecimenintofiveequalpartsandtakeanequalamountof soilfromthecenterofeachportion.Placeallfiveportionsina preweighedtareandweightothenearest0.01g.Placetareinoven andobtainamoisturecontentthefollowingday. (17)Repeatabovestepsforvaryingwatercontents,addingwaterasper calculations.Donotrecompactsamples. (18)Calculatedrydensityofspecimensandmoisturecontent. WetDensityDryDensity= -.--+-;.:.M..:;.o';..- s--7t"'::;u:";';'re;;";""':CC'L- ""-e-n-:-tontWeightofWater100%MoistureContent= WeightofSolidsx0 (19)Plotdataandselectoptimummoisturecontentforthepercentageof 1ime. SampleProblem Given: Percentlime(byweight)required=6% DesiredinitialH20content= 15% 126 H20contentofuntreatedsoil=10% (determinedearlier) Calculations: TotalDesiredMixtureFormula: LimeWaterSoilSolids + += 21009(willmakeapproximatelyfivesamples) SolveforWs 1. 21W = 21009s W =1735.549 s = 0.06W = 104.139 Wl;me s 0.15W =260.339Wwater= s Check21009 ActualWaterRequired(consideringH20contentofnaturalsoil): WaterinUntreatedSoil Ws = 1735.549(fromabove) H20contentofuntreatedsoil= 10% 0.10(1735.54g)= 173.559ofH20naturalsoil 127 x watertoAddforDesiredH20Content Weightofwaterdesired260.33g Weightofwaterinsoil- 173.55g Weightofwatertoadd86.78g TotalSoil,Lime,andWaterRequired: (1)SoilRequired Ws +WwaterUntreatedSoil= SoilRequired 1735.54g+173.55g=1909g (2)LimeRequired W =1049lime (3)WaterRequired Wwater=879 orml WaterRequiredtoIncreaseMoistureContent: No.SpecimensLeftinBatchxOriginalWs 5 % IncreaseDesired= WatertGAdd Example(foradesired2-percentincrease,3specimensleftinbatch) ~ x1735.549x0.02=219 ormlofwater Note:Actualmoisturecontentswillbehigherthancalculateddueto lossofsoilduringfabrication. 128 SPECIMENFABRICATION(REF.105) Theproceduregivenaboveisfollowedbyspecimenfabrication.Nomorethan threespecimensmaybecompactedfromabatchofsoil/lime/watermixtureto insurepropermixingandgoodqualitycontrol.Approximately1450g ofsoil isrequiredforfabricationofthreespecimens.A moisturecontentistaken fromtheuncompactedmixduringcompactionofeachspecimen.Eachspecimen height,moisturecontent,anddrydensityisdeterminedandmustmeetthe followingspecifications: SpecimenHei ght4+0.125in MoistureContentOptimum!1% DryDensityMaximumDryDensity!2 lb/ft3 Thespecimensaretriplewrappedinthinplasticmembraneandtapedtopreventmoistureloss. RAPIDCURE(REF.105) Lime/soilspecimensareplacedinanovenfor30hr+15min.Theovenmust becapableofholdingatemperatureof120,!2Fwithquicktemperaturerecoverywhenthedoorisopenedforremovalofspecimens.Aftercompletion ofcuring,thespecimenisallowedtocoolfor15minpriortostrengthtestingand2hrpriortowaterimmersiontesting.Caremustbetakenduring curetototallypreventspecimenmoistureloss. FREEZE/THAW,DURABILITY(REF.'lOS) Thistestisforthedeterminationofthechangeinunconfinedcompressive strengthforcured2-in-diameterby4-in-highlime/soilspecimenswhichhave beensubjectedtorepeatedcyclesofalternatefreezingandthawing.The apparatus,usedconsistsof:(a)aconlmercialwidemouthvacuumflaskwith aninternaldiameterofabout2.5inanddepthofabout6in;(b)aspecimenholderoflowthermalconductivityluciteforholdingthecylindrical 129 specimeninsidethevacuumflask.Thebaseofthespecimenholderwasperforatedtopermittheaccess' ofwatertothebottomofthelime/soilspecimens;(c)demineralizedwater;(d)afreezermaintainedat22+2F. Theprocedureforconductingthefreeze/thawdurabilitytestisasfollows: (1)Thespecimensareplacedintheplasticspecimenholders.Thespecimenholdersaretheninsertedintothevacuumflasks.Enoughdemineral..izedwaterisplacedinthevacuumflaskssothatthebottom1/4inof thelime/soilspecimenswillbeimmersedwhenplacedintheflasks. Thiswaterlevelismaintainedthroughouttheentiretest. (2)Thevacuumflasksandspecimensareplacedinthefreezer(22~ 2F) for16hr. (3)Afterthe16-hrfreezingperiod,thevacuumflasksareremovedfromthe freezer.Thespecimensintheplasticholderareremovedfromtheflasks andallowedtothawfor8hrat77+2F.Thebottom1/4inofthe specimensremainimmersedinwaterduringthethawingperiod.Onefreeze/ thawcyclein16hroffreezingand8hrofthawing. (4)Theprocessisrepeatedforthreecyclesoffreezingandthawing,after whichthespecimenisremovedandtheunconfinedstrengthdetermined (ASTM02166-66). LIMEREACTIVITY(REF.105) Samplesatthreelimepercentages(pHestimatedlimepercent,+2percentand - 2percent)arepreparedusing2-in-diameterby4-in-highmoldsandthe Vicksburgcompactionapparatus.Specimensarethoroughlywrappedtototally preventmoisturelossandthenrapidcuredfor30hrat120F.Afterrapid cureiscomplete,determinetheunconfinedcompressionstrength(ASTM02166-66). Thesoilislimereactiveifthestrengthisinexcessof110psi.Should lowerstrengthsresult,limetreatmentshouldnotbeused. 130 APPENDIXF 5515SOILSAMPLES Inthedevelopmentofanydesignmethodit isdesirabletoincludeawide varietyofmaterialswhicharerepresentativeofmosttypeslikelytobe encounteredinpractice.It was,therefore,desiredtoutilizeawide varietyofsoilsinthetesting.Thesoilsusedinthedevelopmentof theAirForceSoilStabilizationIndexSystem(5515)aredescribedin tables1through3.Examinationofthedatainthesetablesindicates thewiderangeofsoilmaterialsused. 131 ------------Table1.SoilsUsedinInitialValidationofSSIS(ref.103) --Soil TuyHoa AltusSB Dyess AltusSG Ty1 er Houma PerrinB PerrinA PerrinAB PanamaA PanamaB NorthCarolina DallasRegn'l WESClay Buckshot Chenault Consistency LL*,%PI*,% 14.5 40.3 40.7 52.5 63.7 65.0 72.0 69.4 72.5 75.5 61.0 68.0 37.5 67.1 45.6 NP NP 23.2 19.8 21. 1 40.8 41. 7 40.0 43.3 32.8 35.5 26.9 50. 1 13.6 43.0 29.6 *LL= LiquidLimit,PI= PlasticityIndex,Yd OMC= OptimumMoistureContent. Moisture/DensitypH Yl,1b/ft3 OMC*,% -- - 5. 1 -- -7.4 102.719.77.4 97.723.67.5 91. 722.32.3 86.423.76.95 92.424.17.3 97.523.74.5 95.023.96.7 83.435. 15.3 82.835. 16.27 98.623.55.05 -- - 7.73 107.817.8 --- - --- - 7.70 = MaximumDryDensity, Classification AASHOUnified A-1-b A-2-4 A-7-6{l2) A-7-6( 12) A-7- 5( 15) A-7-6(20) A-7-6(20) A-7-6(20) A-7-6(20) A-7-6(20) A-6( 9) A-7-6(20) A-7-6(l7) G SC CL CL OH CH CH CH CH CH CH CH CH CL CH CH 132 Table2.LimeStabilizedSoils.AFACADValidation(ref.105) Soil Dyess Altus Tyler Houma PerrinA PerrinB PerrinAB Bergstrom Carswell Ii nker LeMoore Malmstrom Cannon Estiraodo. Ell i ngton Barksdale Ell sworth Moody Robbins . Classification AASHOUnified A-7-6(l2)CL A-7-6(12)CL . A.,. 7-5( 15)OH A-7-6( 20)CH A-7-6(20)CH A-7-6(20)CH A-7-6(20_CH A-6(7)CL A-7-6(20)CH A-6CL A-7-6( 16)CH A-6CL A-1-bSM A-7-5(8)CL A-7(20)CH. A-2-4CL-ML A-2-7SW-SC A-2-5SM A-2-4ML Consistency AtterbergLimits LL*.%PI*.% 40.323.2 40.719.8 52.521. 1 63.740.8 72.030.0 65.041. 7 69.443.3 32.014. 1 48.618.6 30.012.0 58.433.4 34. 114.9 25.03.5 28.79.7 60.032.5 30.08.3 30.724.0 26.04.8 25.23.6 Moisture/DensitypH Yd*lb/ft 3 OMC*.% 102.719.77.40 97.723.67.50 91. 722.32.30 86.423.76.95 97.523,74.50 92.423.17.30 95.023.96.70 121. 9014.758.70 101.622.68.62 112.816.58.18 8.25 7.50 114.014.08.80 102.725.08.70 114.017. 18.53 8.83 8.00 8.95 *LL= LiquidLimit.PI=PlasticityIndex.Yd=MaximumDryDensity. OMC= OptimumMoistureContent 133 Table3.CementStabilizedSoils,AFACADValidation(ref.105) Soi]Cl ass ifi cati on AASHOUnified ConsistencyMoisture/Density LL*,%PI*,% Yl, lb/ft 3 OMC*,% pH TuyHoa Altus A-l-bNP5.10 SubbaseA-2-4SC14.5NP7.40 Dyess Altus A-7-640.323.2102.719.77.40 SubgradeA-7-6CL40.719.897.723.67.50 TylerA-7-5OH52.521.191. 722.32.30 HoumaA-7-6CH63.740.892.424.1 ;7.30 PerrinBA-7-6CH65.041. 792.424.17.30 PerrinA Clark Patrick Holloman Moody Robbi ns Laughlin Charl eston Norton Vance Ell i ngton George.I Hami 1ton Tinker Kelly A-7-6CH A-l-bSM-SC A-l-b A-l-b A-l-b A-2-7 A-6CL A-l-aGW A-l-bSP A-l-b A-2-4SW A-3 A-4 A-6 A-7-5 _.72.040.097.523.7 NP117.211.2 NP 1 112 . 510.6 NP139.05.9 NP121.011.3 45.222.0122.611. 1 33.213.0105.018.7 NP125.09.8 NP102.516.9 NP8.4 126.29.0 118.012.5 27.45.7112.016.5 37.320.4107.918.6 82.045.289.020.0 4.50 * LL= LiquidLimit,PI= PlasticityIndex,Yd= MaximumDryDensity, OMC= OptimumMoistureContent 134 APPENDIXG CEMENTSTABILIZATIONPROCEDURES Thisappendixprovidestheproceduresusedinthelaboratorytestingofsoil stabilizationwithcement.Theseproceduresaretakendirectlyfromthel i t ~eraturecited.Thedataandproceduresdescribedinthisreportarebasedon testinginaccordancewiththeseprocedures. 135 TESTFORpHOFSOIL/CEMENTMIXTURES(REF.103) Materials Portlandcementtobeusedforsoilstabilization Apparatus 1.pHmeter(thepHmetermustbeequippedwithanelectrodehavingapH rangeof14) 2.150-mlplasticbottleswithscrew-toplids 3.50-mlplasticbeakers 4.Di sti 11 edwater 5.Balance 6.Oven 7.Moisturecans Procedure 1.StandardizethepHmeterwithabuffersolutionhavingapHof12.00. 2.Weightothenearest0.01g,representativesamplesofair-driedsoil, passingtheNo.40sieveandequalto25.0gofoven-driedsoil. 3.Pourthesoilsamplesinto150-mlplasticbottleswithscrew-toplids. 4.Add2.5gofthePortlandcement. 5.ThoroughlymixsoilandPortlandcement. 136 6.Addsufficientdistilledwatertomakeathickpaste.(C'aut10n:too muchwaterwi 11reducett1epHand;producean7.Stirthesoil,cement,andwateruntilthoroughb1end1ngisachieved. 8.After15mi n,transferpartofthe:pastetoaplasti cbeakerandmeasure thepH. 9.Ifthe pHis12.1orgreater,thesoilorganicmattercOntents.hou1d not withthecementstabilizingmechanism.Todeterminethe requi redpercentofcement,refertodes i gn methodsoutl tnedinsecti on 6ofthisreport. DETERMINATIONOFSULFATEINSOILS- GRAVIMETRICMETHOD(REF.103) Scope Thismethodisapplicabletoallsoil typ,eswiththeP9ssib1eexceptionof' soi 1scontai ni ngcertai n organi ccompounds.Thi s . methodshou1 dp.ermi tthe ,'.'. detectionofaslittle as0.05percent'sulfa.teas504, Reagents 1.Bar.iumch10r-ide,10-percentsoJutionofBaC1 2 . (Add 1m1of 2percentHe1toeach100mlofsolutionto.preventformationofcarbonate. ) 2.Hydroch1ori caci d,2- sQ:1uti on- (0.55'N) 3...Magnesiumchloride,10-percentsolutionof'MgC1 2 .6H20. 4.Demineralizedwater 5.Silverriitrate,0.1Nsolution 137 Apparatus 1.Beaker,1000ml 2.Burnerandringstand 3.Filteringflask,500ml 4.Buchnerfunnel,9cm 5.FilterNo. 40,9 cm 6.Filterpaper,WhatmanNo.42,9cm 7.Saranwrap 8.Crucible,ignition,oraluminumfoil,heavygrade 9.Analyticalbalance 10.Aspiratororothervacuumsource Procedure (1)Selectarepresentativesampleofair-driedsoilweighingapproximately 10g.Wetgh.tothenearest0.01g.(Note:Whensulfatecontentis anticipatedtobelessthanO.1percent,asampleweighing20gormore maybeused.)(Themoisturecontentoftheair-driedsoilmustbeknown forlaterdeterminationof.dryweightofthesoil.) (2)Boilfor1-1{2hrinbeakerwithmixtureof300mlwaterand15mlHel. (3)FilterthroughWhatmanNo.40paper,washwithhotwater,dilutecombinedfiltrateandwashingsto50ml. (4)Take100mlofthissolutionandaddMgC1 2 solutionuntilnomoreprecipitateisformed. 138 (5)FilterthroughWhatmanNo.42paper.washwithhotwater.dilutecom.. binedfiltrateandwashingsto200ml. (6)Heat100mlofthissolutiontoboilingandaddBaC1 2 solutionvery slowlyuntilnomoreprecipitateisformed.Continueboilingfor about5 minandletstandovernightinwarmplace.coveringbeaker wi thSaranwrap. .' (7)FilterthroughWhatmanNo.42paper.Washwithhotwateruntilfree fromchlorides(filtrateshouldshownoprecipitatewhenadropof AgN03 solutionisadded). (8)Dryfilterpaperincrucibleoronsheetofaluminumfoil.Ignite paper.WeighresidueonanalyticalbalanceasBaS04. Calculation P0WeightofResidue4116ercentS4=Oven-DryWeightofInitialSamplex. where oven-dryweightofinitialsample=Air-DryWeightofInitialSample 1+Air-DryMoistureContent(percent)100percent Note:Ifprecipitatedfromcoldsolution.bariumsulfateissofinelyd i s ~persedthatit cannotberetainedwhenfilteringbytheabovemethod.Precipitationfromawarm.dilutesolutionwillincreasecrystalsize.Dueto theabsorption(occlusion)ofsolublesaltsduringtheprecipitationof BaS04 asmallerror isintroduced.Thiserrorcanbeminimizedbypermitting theprecipitatetodigestinawarm.dilutesolutionforanumberofhours. ThisallowsthemoresolublesmallcrystalsofBaS04todissolveandrecrystallizeonthelargercrystals. 139 DETERMINATIONOFSULFATEINSOILS- TURBIDIMETRICMETHOD(REF.103) Reagents 1.Bariumchloridecrystals(Grindanalyticalreagentgradebariumchloride topassl-mmsieve.) 2.Ammoniumacetatesolution(0.5N)(Adddilutehydrochloricaciduntil thesolutionhasapHof4.2.) 3.Distilledwater Apparatus 1.Moisturecan 2.Oven 3.200-mlbeaker 4.Burnerandringstand 5.Fil teri ngfl ask 6.Buchnerfunnel,9cm 7.Fi 1terpaper,WhatmanNo.40,9cm 8.Vacuumsource. . 9.Spectrophotometerandstandardtubes(BauschandLombeSpectronic20or equivalent) 10.pHmeter 140 Procedure (1)Takearepresentativesampleofair-driedsoilweighingapproximately 10gandweightothenearest0.01g.(Themoisturecontentofthe air-driedsoilmustbeknownforlaterdeterminationofdryweightof thesoil.) (2)AddtheaR11lOniumacetatesolutiontothesoil.(Theratioofsoilto solutionshouldbeapproximately1:5byweight.) (3)Boilforabout5 min. (4)FilterthroughWhatmanNo.40filterpaper.Iftheextractingsolution isnotclear,filteragain. (5)Take10m1ofextractingsolution(thismayvarydependingontheconcentrationofsulfateinthesolution)anddilutewithdistilledwater toabout40m1.Addabout0.2gofbariumchloridecrystalsanddilute tomakethevolumeexactly50m1.Stirfor1min. (6)Immediatelyafterthestirringperiodhasended,pouraportionofthe solutionintothestandardtubeandinsertthetubeintothecellofthe spectrophotometer.Measuretheturbidityat30-secintervalsfor4min. Maximumturbidityisusuallyobtainedwithin2minandthereadingsremainconstantthereafterfor3to10min.Considertheturbiditytobe themaximumreadingobtainedinthe4-mininterval. (7)Comparetheturbidityreadingwithastandardcurveandcomputethesulfateconcentration(asS04)intheoriginalextractingsolution.(The standardcurveissecuredbycarryingouttheprocedurewithstandard potassiumsulfatesolutions.) (8)Correctionshouldbemadefortheapparentturbidityofthesamplesby runningblanksinwhichnobariumchlorideisadded. 141 SampleProblem Given: Weightofair-driedsample= 10.12g WaterContent= 9.36% Weightofdrysoil= 9.27g Totalvolumeofextractingsolution= 39.1ml 10mlofextractingsolutionwasdilutedto50mlafteraddition ofbariumchloride(step5).Thesolutiongaveatransmission readingof81. Calculations: Fromthestandardcurve,atransmissionreadingof81corresponds to16.0ppm(fig.1).Therefore,concentrationoforiginalextractingsolution=16.0x5= 80.0ppm. -- 80.0 x 39.1x 100%PercentS04=1000x1000x9.27= 0.0338 DeterminationofStandardCurve: (1)Preparesulfatesolution.of0,4,8,12,16,20,25,30,35,40, 45,50ppminseparatetesttubes.Thesulfatesolutionismade frompotassiumsulfatesaltdissolvedin0.5N arnnoniulTIacetate (withpHadjustedto4.2). (2)Continuesteps5and6oftheprocedure. (3)Drawstandardcurveasshowninfigure1byplottingtransmission readingsforknownconcentrationsofsulfatesolutions. 142 10 0 1 r - - ~ - - - - - - - - - - - - - - - - - - - - - - - .~\90- 0\ 80:--+---\ .. I0s:: o .,... VI VI .,... 70E :\VI s:: ~ 277psi Thelaboratory28-dayqumustbe369psitodeveloptherequiredfieldstrength of110psiafterfivefreeze/thawcycles.(Note:Foraplantmix.operation,the laboratorystrengthrequirementwouldbereducedto249psibecauseofincreased mixingefficiencyandreducedfieldvariability.) 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