Residential Concrete Driveways and Paths Documents/CCAA... · ResidentiAl Concrete driveways and Paths the bAsiC funCtion of residential pavements such as driveways, paths and patios

5 MAINTENANCE 5.1 Cleaning 10 5.2 Resealing 10 5.3 AssessmentofCracks 10

6 SPECIFICATIONCHECKLIST 10

7 REFERENCES 12

july 2006

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ResidentiAlConcretedrivewaysandPaths

thebAsiCfunCtionof

residentialpavementssuch

asdriveways,pathsandpatios

istoprovidesafe,easyaccess

ontooraroundaproperty.

>

1 INTRODUCTION 2

2 PLANNING 2.1 footpathArea 2 2.2 PavementGrades 2 2.3 drainage 2 2.4 trees 2 2.5 Adjacentstructures 2 2.6 surfacefinish 3

3 DESIGN 3.1 Concrete 3 3.2 Reinforcement 4 3.3 Joints 4 3.4 surfacetolerances 4 3.5 PermeablePavements 4 3.6 segmentalPavements 4

4 CONSTRUCTION 4.1 subgradePreparation 6 4.2 subbase 6 4.3 Reducingfrictionundertheslab 6 4.4 Reinforcementfixing 6 4.5 formwork 6 4.6 AdditionofWatertoConcrete 6 4.7 PlacingofConcrete 7 4.8 CompactionofConcrete 7 4.9 surfacefinishes 7 4.10 CuringofConcrete 7 4.11 Joints 8 4.12 Jointsealants 9 4.13 surfacesealers 9

Page2of12> RESIDENTIAl Concrete Driveways and Paths

1 INTRODUCTIONthebasicfunctionofresidentialpavementssuchasdriveways,pathsandpatiosistoprovidesafe,easyaccessontooraroundaproperty.Concreteistypicallyusedtonotonlyprovideadurablepavingsurface,butonewhichcanalsoincorporateawiderangeofdecorativefinishestocomplementthedesignandlandscapingoftheresidence.Whileprovidingaconcretepavementonthe

groundisrelativelystraightforward,therearemanyaspectsofresidentialpavementdesignandconstructionthatneedtobeconsideredinordertoproduceafinishedproductthatwillsatisfyboththefunctionalandaestheticrequirementsdemandedbyhomeowners.thisdatasheetprovidesguidanceonthe

planning,design,construction,maintenanceandspecificationaspectsthatneedtobeconsideredtoensureasuccessfulconcretepavingproject.

2 PLANNING2.1 FootpathAreaPavementsbetweenthekerb-and-gutterandpropertyboundarywillgenerallyhavetocomplywiththerequirementsofthelocalAuthorityinrespectoflevels,gradesandminimumdetails(thickness,reinforcementandconcretestrength).theseshouldbedeterminedinitially,astheymayaffectthegrades(andpossibleneedfortransitionzones)fortheremainderofthedriveway,especiallyonsteepslopeswithshortdistancesfromtheboundarytothehouse.

2.2 PavementGradestoallowadequatedrainageofthesurface,therecommendedminimumgradeorcrossfallforapavementisgenerally1in100(1%),or10mmpermetre.themaximumgradeshouldnotexceed1in20

(5%)inthefootpathareaor1in4(25%)withinthepropertyboundary.notethatastheactualrequirementsmayvaryfromtheselimits,especiallyinhillyareas,itisalwaysadvisabletocheckwiththerelevantlocalAuthority.Wheregradessteeperthan12.5%arenecessary

fordrivewaysorwherevehicleshavelowgroundclearance,atransitionzoneateitherendofthesteepsectionmayberequiredtopreventvehiclesfrom‘bottoming’onthedriveway,seeFigure1.

2.3 Drainagethestormwaterdrainagesystem(includingpavementlevelsand/orfalls)shouldensurethatthereisnopondingdeeperthan10mmonthesurface15minutesafterthecessationofrainfall.Whereapavementcannotbegradedaway

fromabuilding(egdrivewaysthatslopetowardthehouse),asuitabledrainshouldbeprovidedadjacenttothebuildingtodivertstormwaterrunoff.

2.4 Treesthepresenceoftreesadjacenttothepavementmaycausesoilmovementsthatchangethegroundlevelsandresultincrackingofthepavement.Particularlywithexpansiveclays,themoisturedrawnbytreerootscandrythesoil,causingittoshrinkandaffectthepavementlevels.Moredirectly,treerootsmayfindtheirwayunderthepavementandcausedamagebyliftingsectionsoftheslab.furtherinformationcanbefoundinbtf181.

2.5 AdjacentStructuresWheredrivewaysandpavementsareconstructedadjacenttohousesandotherstructures,anumberofitemsmayneedtobeconsidered:n Termitebarriers.itisimportantnottoconstructthepavementatalevelthatwillobstructanyrequiredvisualtermiteinspectionzone.

n Finishedlevels.thebuildingCodeofAustralia2(bCA)requirespavedareasthathaveaslopeawayfromthebuildingofatleast50mm(25mminsouthAustralia)overthefirst1mfromthebuildingtobeatleast50mm(75mminsouthAustralia)belowthefinishedsurfaceoftheadjacentslab-on-ground.thisminimumheightmayneedtobeincreasediftherequiredslopecannotbeprovided,thereisapossibilityofflooding,orlocalplumbingregulationsrequirespecificheightsbetweentheoverflowreliefgullyanddrainagefittingsandground/pavinglevel.

Grade*5% say

Grade12.5% say(1 in 8)

Grade 0%

Street

Transition

2 m min 2 m min

Pavement grade Transition Garage

Prop

erty

bou

ndar

y

Grade

= 5% + 12.5% 2= 8.75%

Grade

= 12.5% + 0% 2= 6.25%

* The advice of the Local Authority should be sought to obtain grade requirements for the area between the street and property boundary.

Figure1:transitionzonesfordriveways


n Flashingsanddamp-proofingcourses.thebCArequiresthattheheightofadamp-proofingcourseorflashingservingasadamp-proofingcoursebeatleast75mmabovethefinishedsurfacelevelofthepavingadjacenttothewall.

n Sub-floorventilationopenings.ifanyexistingsub-floorventilationopeningsarecoveredbythepaving,thebCArequiresnewopeningstobeprovidedtoreinstatetherequiredventilationarea.

n Groundmovement.inclaysoils,themoisturecontentofthesoilbeneathareasoflargepavingmaychangeovertime,possiblycausingmovementofthesoilandconsequentchangestothepavingandadjacentbuildinglevels.thepossibleeffectsofthismovementonthedrainageandadjacentwallsshouldbeconsidered.

2.6 SurfaceFinishWhiletherangeofsurfacefinishespossiblewithconcreteistooextensivetocoverhere,asurfacefinishappropriatefortheapplicationmustbeselected.itemstobeconsideredwhenselecting/specifyingfinishesinclude:n Gradeofpavement.steeppavementsgenerallyrequireacoarsesurfacetexturetoprovideskidandslipresistance,especiallyifasurfacesealerisapplied.dependingonthegrade,steeltrowelled,polished,stampedandsmoothaggregatetypefinishesmaybeunsuitable.Coarsebroomed,tyned,draggedandstencilledfinisheswouldbemoresuitable.Also,exposedaggregatefinishesmayrequireanangular(crushed)stoneinsteadofasmoothroundedstone.

n Slipresistance.somesurfacetextureisrequiredtoprovideslipresistance,particularlyinwetconditions.notethatifthepavementissubjecttobarefoottraffic(iearoundapool)thetextureshouldnotbetoocoarse.suitablefinishesfortheseapplicationsincludewoodfloat,lightbroomandpebblecrete.

n Cleaning.forpavementssubjecttospills(egbarbeque,outdoorkitchenandeatingareas),smoothfinishesarethemostappropriatesincetheyareeasytocleanandmaintain.useofasurfacesealercanpreventspillagefrompenetratingtheconcreteandfacilitatecleaning.

3 DESIGN3.1 ConcreteStrength–themajorityofconcreteusedinresidentialpavementsis‘Normal’classconcretewithaminimumstrengthof20MPa(ien20concrete).Ahigherstrengthmayberequiredincertainsituations,viz:n HeavierLoads.ifthepavementisbeingusedbyvehiclesbetween3and10tgrossmass,andinfrequentlybyheaviervehiclesthatdonotexceedthestatutorylimitsfortyre,wheelandaxleloads,ann25concreteisrecommended.

n AbrasionResistance.thisistheabilityoftheconcretesurfacetoresistwear;itisdirectlyrelatedtothestrengthofconcreteandthequalityofthesurfacefinish.Ann20concreteissatisfactoryformostresidentialpavingapplications,includingtypicaldriveways.forusebyheavierpneumatic-tyredvehiclesupto3t,ann25concreteisrecommended,andforvehiclesover3t,ann32concrete.

n FreezingandThawing.Ann32concreteshouldbeusedifthepavementissubjectedtooccasionalexposuretofreezing,andann40concretewheremorethan25freezingcyclesoccureachyear.Also,anairentrainingagentshouldbeusedintheconcretemix.(note:airentrainingagentabove5%wouldmaketheconcretespecialclass.)

n Salinity.ifsaltsarepresentinthesoilorgroundwater,increasingtheconcretestrengthtoprovideimproveddurabilityisadvisable3.n25concreteisrecommendedformoderatelysalinesoils,n32forverysalinesoilsandn40forhighlysalinesoils.Also,aplasticmembraneshouldbeprovidedunderthepavementtoreducetheriskofawhitedepositofsalts(efflorescence)developingonthesurface.

OtherProperties–ifpropertiesotherthanstrengtharerequired,a‘Special’class(egs20)ratherthannormal-classconcreteshouldbespecified.forcolouredanddecorativepavementfinishes,someoftheproperties(apartfromthestrength)thatmayberequiredinclude:n Colourpigments.supplier,colourandpercentagebyweightofcementtobeused.

n Aggregates.Anyinformationnecessarytoidentifythestonerequired–size,type,texture,colour(egnominal10-mmaggregateconsistingof90%brownroundedrivergraveland10%crushedwhitequartz).

n Cementcolour.normalgrey,off-whiteorwhite.notethattheavailabilityoftheseshouldbecheckedpriortospecifying.Analternativetoachievealightercolouristheuseofatitaniumwhitecolourpigment.


Thickness–Pavementsforfoottrafficonly(egpathsandpatios)shouldhaveaminimumthicknessof75mm.Pavementsforvehicleslessthan3tgrossmassshouldhaveaminimumthicknessof100mm.Pavementsforvehiclesbetween3and10tgrossmassandinfrequentusebyheaviervehiclesthatdonotexceedthestatutorylimitsfortyre,wheelandaxleloads,shouldhaveaminimumthicknessof150mm.

3.2 Reinforcementtheuseofsteelreinforcementormeshdoesnotincreasetheloadcapacityofthepavement,oraffectitsthickness.itsfunctionismainlytoholdtightlyclosedanycracksthatmayform.ingeneral,theamountofreinforcementrequiredtoprovidetheappropriatedegreeofcrackcontrolwilldependonthethicknessoftheslabandthejointspacing.forfootpathswhichtypicallyhaveclosely-

spacedjoints(upto2m),andhencelittleriskofcracking,eithernoreinforcement,oransl52meshisgenerallyappropriate.for100-mm-thickpavementshavingjointsspacedfurtherapart(upto3m),aminimumsl62meshwouldtypicallybeused,andfor150-mm-thickpavements,sl82mesh.notethatinsomecasesincreasingtheminimum

reinforcementwouldberecommended.forexample,wheredecorativefinishesarerequired,increasingthemeshsizebyoneoreventwosizes,willprovidebettercontrolofcrackingthatmayoccur,sothatitdoesnotsignificantlyaffecttheappearance.

3.3 JointsJointsinconcretepavementsfallintotwobasiccategories:thosethatallowmovement(isolationandexpansionjoints)andthosethatcontrolcrackingoftheconcrete(controlorcontractionjoints).Afurthertype,constructionjoints,usedwhenthereisabreakinconcreteplacement,israrelyrequiredinresidentialpavementwork.isolationjointsareusedtoseparatethe

pavementfromanyabuttingbuildings,existingpavements,orrigidstructuressuchasdrainagepits,accessholesorcolumnswhichmaycauserestraintofthepavementandtherebyincreasetheriskofcracking.expansionjointsareusedinlargeareasofpaving

toaccommodateexpansion,primarilyduetoelevatedtemperaturesduringperiodsofhotweather.theyshouldbeprovidedatmaximum15-mcentres.Controljointstypicallyformaweakenedplane

atwhichtheconcretecracks.Withoutthem,dryingshrinkagewillresultinrandomcracking.theyshouldbeprovidedatmaximum3-mcentres,atanychangesinshape(eganarrowpathattachedtoadriveway),atanychangesindirection(egaround

corners,especiallywhereare-entrantcornermaybeformed),andatanyrigidstructures(egaccessholes,pits,columns)thatmaypreventmovementandincreasetheriskofcracking.Whereverpossible,thelocationofjointsshould

beplanned.AtypicallayoutofjointsinthepavingtoaresidenceisshowninFigure2.notethatoneaimshouldbetomaketheconcretepanelsdefinedbyjointsroughlysquareinshape.theratioofwidthtolengthshouldnotexceed1:1.5.fordecorativework,jointsshouldifpossiblebe

locatedtosuittheproposeddecorativepatternorfinish.Withalljointtypes,theanglesformedat

edgesandintersectionsofjointsshouldnotbetooacute,asthisincreasestheriskofcrackingand/orbreakingoffthetaperedsectionofconcrete.Agooddetailinthesesituationsistokeepatleast500mmofthejointatmorethan75°(andpreferablyatrightangles)totheslabedgeFigure3.

3.4 SurfaceTolerancesPavementsgenerallyhavetomeettwoindependenttolerancecriteria:the‘flatness’ofthesurfaceand‘levelness’orvariationfromthedesignedelevation.bothoftheseshouldbespecified.theflatnesstolerancegivesthepermitted

variationfroma3-mstraightedgeplacedonthesurface.forhand-placedpavements,areasonableflatnesstoleranceisamaximumdeviationorgapof12mmundera3-mstraightedgeplacedanywhereonthepavement,includingonslopes.thelevelnesstolerancegivesthepermitted

variationoftheslabsurfacefromafixedexternalreferencepointordatum.Areasonabletoleranceforthesurfaceofanewly-constructedpavementwouldbe±10mmfromthedesignedlevelorelevation.forslopedsurfaces,amaximumdeviationof10mmfromalinejoiningthe‘control’points(iethelevelsatthetopandbottomoftheslope)isrecommended.notethattheminimumslabthicknessshould

bemaintained.

3.5 PermeablePavementsforenvironmentallysensitiveareas,permeableconcretewhichallowswatertoinfiltratethroughthepavementisavailable.informationonthesetypesofpavementsisoutsidethescopeofthisdocumentbutcanbefoundelsewhere4.

3.6 SegmentalPavementsConcretesegmentalpaversrangingfromsmallbrick-sizedunitstothelargerflagpaversareavailableinavarietyofcolours,finishesandtextures.informationonsegmentalpaversisavailablefromtheConcreteMasonryAssociationofAustralia5.


4 CONSTRUCTION4.1 SubgradePreparationthepreparationofthesubgrade(supportingground)forresidentialpavementsisarelativelysimpleprocessastypicallytheloadsarelight.Alltopsoil(whichmaysettle)shouldberemovedandthearealevelledtoprovideauniformplatformforthepavement.forheavyloads,theabilityofthesubgradetoadequatelysupporttheloadswithoutexcessivedeflectionandcrackingofthepavementneedstobeconsidered.Areasonablyuniformfoundationisessentialto

LEGEND

Double garage

Residence

Property boundary

Isolation joint

Expansion joint

Control jointAccess hole

Centre CJ on access hole

EJ if length greater than 15 m, otherwise CJ

Joints perpendicular to slab edgeto avoid acute angles

Path

3 m wide driveway

Extend pavement here toavoid acute angle

Path

Potential crackif CJ usedinstead of IJ

Potential crackif CJ usedinstead of IJ

W

L (max) = 1.5 x W

3 m max3 m max

3 m max

Provide IJaround access hole

FootpathIJ

IJ

EJ

EJ

IJ

IJ

IJ

IJ

IJIJ

IJ

IJ

IJ

CJ

CJ

CJ

CJ

CJ

CJ

CJ CJ

CJCJ

CJ

CJ

CJ

CJ

IJ

IJ IJ

Kerb and gutter

Figure2:typicaljointlayout

Figure3:Jointperpendiculartoslabedge


thelong-termperformanceofaconcretepavement.Anassumptionthataconcretepavementwillbridgeoverapoorsubgradecouldleadtoafalsesenseofsecurity.thus,anypoor,saturated,highlycompressibleorotherwiseweakareasshouldberemovedandreplacedwithsuitablesubgradeorroadbasematerial,adequatelycompactedwithaplatecompactororsmallroller,toavoidsubsequentsettlement.thesameappliestothebackfillingofservicetrenches.Alevelareaalsominimisesthefrictionbetween

thepavementandground.thisreducestherestraintofthepavement,andinturn,theriskofunplannedcracking.

4.2 Subbaseonhighlyexpansiveclaysubgrades,significantvolumechangescanoccurinthesoilresultinginnon-uniformsupportoftheslab,andsubsequentlyearlyslabfailure.Potentialproblemscanbeminimisedbyappropriatepavementdesign,theprovisionofasubbase,orstabilisationofthesubgradematerial.thefunctionofthesubbase(orcoverlayer)of

low-volume-changesoilistominimisemoisturemigrationunderthepavement,andhencechangesinthemoisturecontentandvolumeoftheunderlyingexpansivesoilFigure4.italsoprovidesmore-uniformslabsupportbyequalisingminorsubgradedefects.theappropriatethicknessofthenon-expansivesubbaselayerdependsonthesiteconditionsandlocalexperience;inthemajorityofcases,a100-mmthicknessisrecommended.Alternatively,alayeroftheexistingclaysoil

maybestabilised(generallywithlimeorcement)toenhanceitsstabilityunderconditionsofalternatewettinganddrying.

4.3 ReducingFrictionUndertheSlabProvidingpolyethylenesheetingora20-mm-thicklayerofsandbeneaththepavementisaneffectivewayofreducingthefrictionbetweentheslabandsubgrade/subbase.Comparedtoplacingthe

concretedirectlyonaplasticsoilsuchasclay,thefrictionalforce–andhencerestraintoftheslab–canbemorethanhalved.thisallowstheconcreteslabtomovemorefreelyasaresultoffactorssuchasdryingshrinkageandthermalvolumechanges,therebyreducingtheriskofcracking.ifusingsand,itisimportantthatthepercentage

offinematerialsuchassiltandclaybelimitedtoabout5%,sothatthematerialdoesnotbindtogether,therebyrestrictingmovementoftheslab.

4.4 ReinforcementFixingthereinforcement(usuallymesh)shouldbelocatedwithinthetophalfofthepavement,andhaveaminimum30mmofconcretecovertothetopoftheslab.itshouldbefixedinpositionusingsuitablesupportsorbarchairs,spacedatmaximum800-mmcentrestopreventsaggingofthereinforcementduringconcreteplacement.notethatforlightmeshes,thespacingmayneedtobereducedtopreventsagging.Meshshouldnotbewalkedintoposition

orliftedtoheightusingahookduringconcreteplacement.norshouldtheconcretetruckbedrivenoverittogainaccessforconcretedischarge.Wheresheetsofmesharejoined,theyshould

haveaminimumoverlapoftwocrosswires(iethetwooutermostcrosswiresofeachsheetareoverlapped).

4.5 Formworkformworkshouldbesecuredaccuratelyinpositiontomaintainlinesand/orshapeduringconcreteplacement,andsettothecorrectlevelssoastoprovideaguideforthefinishedsurfacelevelsandtolerances.

4.6 AdditionofWatertoConcretenowater(inexcessofthemixingwater)shouldbeaddedtotheconcretemixasthiswillincreasethewater-cementratio,resultinginalowerstrengthconcretethatislessabletoresistthesurfaceabrasionandwearcausedbytraffic.Also,excesswaterwillgenerallyincreasethe

dryingshrinkageoftheconcretewhichmayresultineitherunplannedcracking,orcrackwidthswiderthanwouldnormallybeexpected.

Concrete pavement

Subbase (recommended forhighly-expansive clay sites)

Subgrade or natural ground

Polyethelene membraneor sand layer (recommended)

Figure4:typicalpavementcross-section


4.7 PlacingofConcreteConcreteplacementshouldcommencefromonecornerofthepavementandproceedcontinuouslyoutfromthatpoint,withnewconcretealwaysbeingdepositedontothefaceoftheconcretealreadyplacedtoensureinterblendingandavoidsegregation,ietheseparationoftheaggregatefromthecementpastewithinaconcretemixwhichmayleadtohoneycombinginthehardenedconcrete.Whenplacingconcretethefollowingshouldbe

considered:n Transport.themajorityofconcreteismovedfromtheconcretetrucktoitsfinallocationbyaconcretepump.ifawheelbarrowisused,atypicalplacingrateofabout1to1.5m3/hcanbeachieved,thetraveldistanceislimitedtoabout50mforcontinuouswork,andarelativelylevel,smoothaccessisrequiredtoavoidjoltingandpossiblesegregationoftheconcrete.

n Water.Anywaterpondingonthegroundshouldberemovedpriortoplacingtheconcretetoavoidproblemswithincreasingthewater-cementratio,segregationandwashingoutofcementpastefromtheaggregate,allofwhichcanaffectthestrengthanddurabilityoftheconcrete.

n Segregation.segregationshouldbeavoidedbyplacingconcreteasnearaspossibletoitsfinallocation;concreteshouldnotbemadetoflowintoitsfinalpositionthroughtheuseofsayimmersionvibrators,orbedroppedfromheightsofmorethan2m.

n Slopes.Concreteplacementshouldcommenceatthelowestpoint.

n Hotandcoldweatherconditions.Concreteshouldnotbeplacedatambienttemperatureshigherthan30°Corlowerthan10°Cwithouttakingtheappropriateprecautions;iftemperaturesexceed35°Corfallbelow5°Cconcreteplacementshouldnotbeundertaken.inhotweather,themainconcernsare

crackingofthesurfaceduetorapiddryingandlossofstrengthduetoinadequatecuring.flakingofthesurfacemayalsooccurastherateofdryingmayexceedtherateofbleeding,leadingtoprematurefinishingoftheslabortheapplicationofsubsequentsurfacecoatings/treatments.theuseofwindbreaks,shadecoversandapplicationofanevaporativeretardersuchasaliphaticalcoholshouldbeconsidered.incoldweather,delayedsettingand

finishingtimes,slowerstrengthgainandevenfreezingofthesurfaceareofconcern.Concreteshouldbeprotectedfromfreezingforatleast24hoursafterfinishing.

4.8 CompactionofConcreteAdequatecompactionoftheconcretesignificantlyreducesitsporosity,increasesitsstrength,enhancestheabrasionresistanceandgeneraldurability,andminimisestheriskofcracking.Whileanydeepersectionsofthepavement

suchasedgethickeningsanddownturnsshouldbecompactedusinganimmersionvibrator,forslabsongroundthatare100mmorlessinthickness,adequatecompactioncanusuallybeachievedthroughtheplacing,screedingandfinishingprocesses.sometimes,surfacevibrationwillbeusedintheformofasmallhand-heldvibratingscreed.immersionvibratorsarenotrecommendedfor100-mm-thickslab-on-groundconstructionastheslabdepthdoesnotallowproperimmersionofthevibratorhead,andtheplasticmembrane(ifpresent)maybedamaged.

4.9 SurfaceFinishesslip-andskid-resistantconcretesurfacescanbeachievedbytheappropriatetexturingduringthefinishingoperations.theterm‘slip’referstopedestriantrafficwhile‘skid’isthetermusedforvehiculartraffic.Awoodenorspongefloatfinishisgenerally

suitableforfoottrafficonlevelornear-levelpaving.broomedfinishescanproduceagreaterdegreeofskidresistance,suitableforvehiculartraffic.forgreaterskidresistanceonramps,asteel-tynedcombcanbeusedtogroovetheconcretesurface.Compactingthesurfaceoftheconcretebytrowellingwillimprovethestrengthandabrasionresistance,therebyassistingtomaintaintheskidresistantpropertiesofthesurface.itisimportantthereforethat,wherepossible,thesurfacebetrowelledeitherpriortothefinishbeingapplied(iebroomfinish)orduringtheprocessofapplyingthefinish(iecoloursurfacetoppings).Giventherangeofdecorativeproducts,finishes

andfinishingtechniquesavailable,thesuitabilityofthefinishfortheintendedpurposeshouldbeconfirmedwitheitherthemanufacturerorapplicator.Whereasurfacesealerthatmayaffectthe

textureisapplied,careshouldbetakentoensurethefinishedsurfaceprovidesthenecessaryslipandskidresistance.incorporatingsilicadustorcarborundumdustinanappliedsealerisanothertechniquetoeithermaintainorimprovetheslip/skidresistance.

4.10 CuringofConcreteResidentialpavementsforfootandlightvehiculartrafficshouldbecuredforaminimumperiodof3days.thisshouldbeincreasedto7daysif


locatednearthecoast(within1km)and/orsubjecttoheaviertraffic.Curingallowstheconcretetoachieveitspotentialstrengthanddurability.Whenconcreteisnotcured(ieisallowedtodryoutquickly),asignificantreductioninitsstrengthresults.thereductionofconcretestrengthhasasignificanteffectonabrasionresistanceofthesurfaceofthepavementwhenusedbyvehiculartraffic.oneofthemaincontributorstosurfacewearanddustingproblemsisthereductioninstrengthduetoinadequatecompactionandcuring.typicalmethodsofcuringconcretepavements

include:coveringtheconcretewithanimpermeablemembrane(egplasticsheeting,chemicalcuringcompound);orkeepinganyexposedsurfacescontinuouslywet(egpondingorsprayingwithwater).Wettingatintervals(eginthemorningandafternoon)doesnotkeeptheconcretecontinuouslymoist,particularlyinhotweatherconditionsandisthereforenotregardedasanadequatemethod.blackplasticshouldnotbeusedforcuringofexternalsurfaces,asthismayincreaseheatgainandcauseproblemswithslabcurling.Colouredconcretepavementsshouldnotbe

curedwithplasticsheeting,dampsandorwethessian,asthesematerialsmaypromoteunevencolourorstaining.Chemicalcuringcompoundscompatiblewiththesealer,orthesealeritselfifcomplyingwiththerequirementsofachemicalcuringcompound,shouldbeusedforthesetypesofdecorativepavements.

4.11 JointsisolationjointsFigure5shouldnotimpedeanyrelativemovement.thismaybehorizontal,verticalorbothandmayincluderotation.Whilemovementfromconcretedryingshrinkagewillnormallycausethejointtoopenwithtime,temperaturechangesmaygiverisetojointclosingmovements.expansionjointsFigure6typicallyhavedowel

barsconnectingtheslabstoprovideloadtransferandavoidchangesinthelevelsfromoneslabtoanother.Asaguide,for100-mm-thickpavementsintendedforvehicleslessthan3tgrossmass,12-mm-diameterdowelsatmaximum400-mmcentreswouldbesatisfactory.ControljointsFigure7canbemadeby:

n insertingapre-mouldedstripintotheconcreteasitisbeingplaced;

n useofagroovingtoolimmediatelyaftertheconcretehasbeenplaced;or

n sawingagroovewhentheconcretehashardenedsufficientlytopreventraveling.

n usingaproprietarypressedmetalkeyjoint.

Height to allow clearance toweep holes, flashings,damp-proofing course,termite barriers etc

Suitable silicon orpolyurethane sealantto prevent ingress of dirt

10-mm thick compressiblefiller material for full depthof pavement

Abuting structure orother pavement

30 mm cover to mesh

40 mmend cover

Figure5:typicalisolationjoint

30 mm cover to mesh

Bond-breakingcompound

Cap requiredfor expansion

Dowel(length, L)

40

t

0.5 t

0.5L

25

Suitable silicon orpolyurethane sealantto prevent ingress of dirt

10-mm minimum thicknesscompressible filler materialfor full depth of pavement

Figure6:typicalexpansionjoint

30 mm cover to mesh0.25 to 0.33 t

Saw cut, insert or tooled joint(no sealant required)

Induced crack

t

50 50

(a) CRACK-INDUCED JOINT (SAW CUT, INSERT OR TOOLED)

30 mm cover to mesh

Optional coloured cover strip(no sealant required)

Propriety pressed-metalkey joint to suit slab thickness

40 40

(b) KEY JOINT (PRESSED-METAL OR FORMED)Figure7:typicalcontroljoint

30 mm cover to mesh0.25 to 0.33 t

Saw cut, insert or tooled joint(no sealant required)

Induced crack

t

50 50

(a) CRACK-INDUCED JOINT (SAW CUT, INSERT OR TOOLED)

30 mm cover to mesh

Optional coloured cover strip(no sealant required)

Propriety pressed-metalkey joint to suit slab thickness

40 40

(b) KEY JOINT (PRESSED-METAL OR FORMED)


notethat:n ifjointsaresawcut,theseshouldbeinstalledpriortoshrinkagecrackingoccurring.Asaguide,sawcutsshouldbemadenotmorethan12hoursafterfinishingoftheslabiftemperaturesexceed25°C,andnotmorethan16to18hoursafterfinishingoftheslabforlowertemperatures.toavoiddelays,early-agesawcutting(iethesameday)ispossibleusingspecialisedequipment.thesurfaceshouldbethoroughlycleanedaftercutting.

n ifjointsarewet-formedbyscoringtheplasticconcretewithanedgingtool(tooledjoint),ensurethatthegroovedoesnotfillwithcementslurryandrenderthejointlesseffective.

n ifjointsareformedbyusingproprietarypressedmetalkeyjoints,theyshouldbesecurelyfixedinpositiontomaintainstraightlinesduringplacementoftheconcrete.

n Whilereinforcingmeshwillnormallybeterminated50mmawayfromcontroljoints,itmayextendacrossthejointtoprovidebettercontrolofmovementon,say,highlyexpansiveclays.inthiscase,50%ofthemeshshouldbecuttoassistintheformationofaplaneofweaknessatthejointlocation.toallowsometoleranceinthelocationofthesawcut,crackinducerortooledjoint,theendsofcutwiresshouldbeatleast50mmclearoftheproposedjointlocation.AconstructionjointFigure8isusedto

accommodateanunplannedbreakinconcreteplacement.thejointshouldbeformedtoallowadequatecompactionandfinishingoftheconcretealongtheedge.oncetheconcretehashardened,theformworkisremoved,theedgeroughenedtoprovideaggregateinterlockacrossthejointandthenewconcreteplacedagainsttheexistingedge.

4.12 JointSealantsManytypesofjointsealantsareavailable.forpavements,high-performancesealantssuchaspolyurethaneorsiliconeshouldbeused.theyaresuppliedincartridgesforeasyusewithacaulkinggun,comeinarangeofcolourstosuitvariousdecorativefinishesandareuVlightresistant.Whilethelifeofthesealantdependsona

numberoffactors,thefollowingbasicrulesconcerningtheiruseshouldbeobservedtoachieveadequateperformance:n Jointpreparation.thesurfacesshouldbeclean,dryandprimedifnecessary.Applyingsealantsto‘green’concretecanresultinbubblingandlossofadhesion.thesurfacetemperatureshouldbeabove5°C.

n Jointgeometry.fortypicaljoints,thecross-sectionaldepthofthesealshouldbeatleasthalfthewidth,andnevergreaterthanthewidth.

n Backingsystems.toperformadequatelywhenthepavementmoves,sealantsshouldadhereonlytothesidesofthejoint.Whilethejointfillerwillnormallyensurethis,abackingrodmaysometimesbenecessarytoachievetherequiredjointgeometry.

n Settingtime.thesettingtimeofthesealantdetermineswhenitcanbebroughtintoservice,orwhenthepavementcanbeused.Polyurethanesealantswillcureatarateofabout2-3mmofdepthperdayintemperaturesover5°C.fast-curingandtwo-partproductswillbemarginallyfaster.siliconesskinquicklybuthaveaslowercure-through-depthtime.

4.13 SurfaceSealerssealersareusedtopreventstainingandtofacilitatecleaningoftheconcretesurface.theyshouldbeappliedafterthecuringperiodandwhentheconcretehasdriedoutsufficientlytoallowthesealertopenetrateintotheconcretesurface.notethatsomesealersmayalsofunctionasachemicalcuringcompoundandshouldbeappliedafterfinishing.somesealersmayalsobetintedandthusprovidebothasealandacolouredfinish.Asthepenetrationofsealersintotheconcrete

surfacevaries,theirsuitabilityforaparticularapplicationshouldbediscussedwiththemanufacturer.steepdrivewayswarrantspecialconsideration;non-penetratingsealersthatformafilmonthesurfacecanreduceslipandskidresistance,andarethusgenerallynotsuitableforthisapplicationunlessthesurfacetextureappliedtotheconcreteiscoarseenoughtostillprovideadequateslipandskidresistance.Penetratingsealersorthosewithslip-resistantpropertiesarerecommendedforsteepergrades.

30 mm cover to mesh

Stop board to form joint andallow compaction of concrete

Reinforcing meshcontinuous across joint

Roughened first-cast face

Figure8:typicalconstructionjoint


5 MAINTENANCE5.1 CleaningCleaningshouldbeundertakenassoonaspossiblefollowingcontaminationorstaining.extendingtheareatobecleanedmayalsobenecessarytoachieveauniformsurfaceappearance.high-pressurewateristypicallyusedfor

generalcleaning,witharangeofchemicalcleaningproductssuchasbleachingagentsandacid-basedsolutionsavailabletoremovespecifictypesofstains.Considerationneedstobegiventotheenvironmentaleffectsalongwiththecorrosivenessofthechemicalanditseffectonsurfacesealersand/orthecolourandtextureofthesurface.forcolour-sensitivesituations,theuseofmilddetergentandsteamcleaningshouldbeconsideredinitially.Milderchemicalssuchasoxalicacid,shouldthenbetestedbeforeresortingtoharsherchemicals.

5.2 Resealingnumeroussealersinarangeofcategoriesareavailable,eachofferingdifferentdegreesofprotection.dependingontheextentofabrasionandwear,andperformanceofthesealeritself,replacementafteranumberofyearswillberequired.notethatpenetratingsealerspermeateandcloseoffthesmallporesintheconcrete,andarethusprotectedbytheabrasionresistanceoftheconcreteitself.duetothedifferenttypesofsealersavailable,

thesealerusedshouldbenotedsothatacompatiblesealercanbereappliedatalaterstageifrequired.

5.3 AssessmentofCracksWhileadoptinggooddesign,detailingandconstructionpracticesasoutlinedinthisdocumentwillminimisetheriskofcracking,therewillbesituationswherecracksmayoccurasaresultofmovementsinconcreteduetochangesinitsmoisturecontentandtemperature.Pavementsmayalsobesubjectedtoexcessiveloadsthatmayresultincracking.ifcrackingdoesoccurovertime,itisimportant

toidentifythecause,andthenassesswhetherthecrackingisacceptable,orneedsrepair.Whilethevisualacceptabilityofcracksisverysubjective,a0.3-mm-widecrackshouldberegardedasacceptable.Crackswiderthan1mmshouldbeassessedonanindividualbasisintermsofpossibleeffectsondurabilityandperformancerequirementsand,dependingonthesurfacetextureandfinish,alsoonaestheticrequirements.

6 SPECIFICATIONCHECKLISTthefollowingprovidesguidanceonthemainitemsthatmayneedtobeconsideredinthespecificationfortheconstructionofresidentialdrivewaysandpaths.

PlAnninGn thelocalAuthority’srequirementsforgradesandpavementdetailsbetweenthepropertyboundaryandkerbshouldbeascertained.

n Asketchordrawingshouldbepreparedindicatingthelocation,dimensions,levelsandorgradesofthepavementandanyassociateddrainageandlocalAuthorityrequirements.

subGRAden Alltopsoil,vegetation,debrisandotherforeignmattershouldberemovedfromthelocationoftheproposedpavement.

n Anysoft,weak,saturatedorotherwiseunsuitablematerialshouldberemovedandreplacedbygoodqualitymaterialfromthesiteorbyimportedroadbase,andcompactedinlayersusingarammerplate/uprightcompactor.

n Allservicetrenchesandotherexcavationsshouldbebackfilledwithgoodqualitymaterialfromthesiteorothersuitabletrenchfillingmaterialandcompactedinlayersusingarammerplate/uprightcompactor,toavoidfuturesettlement.

n thesubgradeshouldbedampenedpriortoplacementoftheconcrete.notethatthisisnotrequiredifamembraneand/orsubbaseisused.

subbAse(Recommendedforhighlyreactiveclaysites)n Aminimum100-mm-thicklayeroflow-volume-changematerial(roadbaseorsimilarmaterial,butnotsandorgravel)shouldbeprovidedundertheslab.

n subbasematerialshouldbecompactedusingarammerplatecompactororsmallroller.

n thesubbaseshouldbedampenedpriortoplacementoftheconcrete.

PlAstiCundeRlAy(optional–toreducefrictionundertheslaboringressofsaltsinsalineenvironments)n A200-μm(0.2-mm)thickpolyethylenefilmshouldbeprovidedundertheentireslabarea.

n Anyjoinsintheplasticmembraneshouldbelapped200mmminimumandtaped.


sAndlAyeR(Recommended–toreducefrictionundertheslab)n A20-mmlayerofsandshouldbeprovidedundertheentireslabarea.

n thesandshouldhavenomorethan5%ofsiltandclayparticles.

foRMWoRkn edgeformworkshouldextendthefulldepthoftheslab.

n theverticalalignmentshouldbewithin5mmforeach100mmofheight.

n formworkshouldbefixedrigidlywithpegstopreventmovementduringplacementofconcrete.

n thepositionofformworkshouldbewithin±5mmofthelocationshownonthedrawing(s).

n theformworklevelsshouldbesettoatoleranceof±5mmfromthedesignedlevel.

ReinfoRCeMentn theappropriatemeshsizefortheparticularslabthicknessandjointspacingshouldbeprovided.

n themeshshouldbelocatedinthetophalfoftheslabwithminimum(30mm)cover.

n themeshshouldbesupportedonbarchairsatmaximum(800-mm)centres.

n Meshshouldhaveaminimumoverlapof2crosswires(iethetwooutermostcrosswiresofeachsheetareoverlapped).

n onen12trimmerbarshouldbeprovidedaroundallpenetrationssuchasaccessholes.

n 40mmofcovershouldbeprovidedtoallisolationandexpansionjoints,andtoallslabedges.

n ifthemeshisdiscontinuousatcontroljoints,itshouldbeterminated40–50mmawayfromthejointFigure7dependingonthejointtype.

ConCReten theconcretestrengthshouldbenominated(n20minimum).

n forspecial-classconcreteallrequiredpropertiessuchasstrength(s20,etc),colour,aggregatesandcementcolourshouldbespecified.

n theminimumslabthicknessshouldbespecified(100mmusually).

n slabsandareasthickerthan100mmshouldbecompactedusinganimmersionvibrator.

n Concreteshouldbecontinuouslycuredforatleast3daysfromthecompletionoffinishingoperations,andthenallowedtograduallydryout.

n excesswatershouldnotbeaddedtotheconcreteonsite.

finishinGn thetypeofsurfacefinishshouldbespecified.ifproprietaryproductsareinvolvedsuchasdryshakecolourhardeners,thecoverageandapplicationshouldbeinaccordancewiththemanufacturer’s/supplier’srecommendations.

n thesurfacelevelsandflatnessshouldbespecified.Asaguide,thedeviationinlevelnesscanbespecifiedas±10mmfromthedesignedlevel,andflatnessbyamaximumdeviationorgapundera3-mstraightedgeof12mm.

Jointsn isolationjointsasshownFigure5shouldbeprovidedwherevertheslababutsexistingbuildings,pavements,orrigidstructuressuchasdrainagepits,accessholesorcolumns.specifycolourofsealantifrequired.

n expansionjointsasshownFigure6shouldbeprovidedatmaximum15-mcentresinanydirection.Colourofjointsealantifrequiredanddowelsizeandspacingshouldbespecified.for100-mm-thickdriveways,12-mm-diameterdowelsatmaximum400-mmcentresalongthejointwouldbesatisfactory.

n ControljointsasshownFigure7shouldbeprovidedatmaximum3-mcentres,andatlocationswherethereisalikelihoodofacrackoccurring(egatre-entrantcorners).thetypeofcontroljointshouldbenominated,alongwithanyrequirementsforsawcutting,orcuttingofthemeshifcontinuousacrossthejoint.

n Jointsshouldbelocatedsothatthelongerdimensionofanyslabpanelisnomorethan1.5timestheshorterdimension.

n Anyangleformedbetweenjoints,orajointandtheslabedge,shouldnotbelessthan75°toavoidtaperedandnarrowsectionsofpavement.

seAlinGofthesuRfACen thesealershouldbespecified,alongwithitsuseinaccordancewiththemanufacturer’srecommendations.


7 REFERENCES1 buildingtechnologyfile(btf)18foundationMaintenanceandfootingPerformance:Ahomeowner’sGuide,CsiRo(formerlyinformationsheet10–91).

2 buildingCodeofAustralia,Volume2,housingProvisions,AustralianbuildingCodesboard,2005.

3 GuidetoResidentialslabsandfootingsinsalineenvironments(t56)CementConcrete&AggregatesAustralia,2005.

4 PermeableConcretePavementsdatasheet,CementConcrete&AggregatesAustralia,2004.

5 ConcreteMasonryAssociationofAustraliawebsitewww.cmaa.com.au.informationonConcretesegmentalPavementsandConcreteflagPavementscanbefoundundertechnicalpublications.

FURTHERINFORMATIONCCAAdatasheets:hotWeatherConcretingColdWeatherConcretingdownloadfromwww.concrete.net.au.

thehousingConcretehandbook(t53)CementandConcreteAssociationofAustralia,2000.

GuidetoConcreteConstruction(t41/hb64)CementandConcreteAssociationofAustraliaandstandardsAustralia,2002.

july 2006

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