Post on 31-Jan-2018
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
Page3of12> RESIDENTIAl Concrete Driveways and Paths
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.
Page4of12> RESIDENTIAl Concrete Driveways and Paths
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.
Page5of12> RESIDENTIAl Concrete Driveways and Paths
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
Page6of12> RESIDENTIAl Concrete Driveways and Paths
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
Page7of12> RESIDENTIAl Concrete Driveways and Paths
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
Page8of12> RESIDENTIAl Concrete Driveways and Paths
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)
Page9of12> RESIDENTIAl Concrete Driveways and Paths
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
Page10of12> RESIDENTIAl Concrete Driveways and Paths
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.
Page11of12> RESIDENTIAl Concrete Driveways and Paths
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.
Page12of12> RESIDENTIAl Concrete Driveways and Paths
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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