rigid--pavement

RigidPavementLearningtasksfortoday•AfterlearningLessonSeven,youwillbeableto:I.Understandthecomponentlayersofrigidpavements;II.Knowthemajorconstructionstepsofrigidpavement;III.Grasptheexpressionsandtermsusedinthislesson;IV.TranslatesomeEnglishphrasesandsentencesintoChineseandsomeChineseonesintoEnglishaccordingtothelesson.Componentlayersofarigidpavement•Apavement(acementconcreteslabontopofasubbase)superimposeduponthesubgrade.LoaddistributionofrigidpavementToactasabeamandbridgeoveranyminorirregularitieswithconsiderableflexuralstrengthRigidcompositepavement•Anewcontinuouslyreinforcedconcreteroadbase(CRCR)withabituminoussurfacing.Rigidpavement‘with’abituminoussurfacingorabituminousoverlay•Existingrigidpavementcoveredwithabituminoussurfacingorabituminousoverlay.Rigidpavementtypes•Unreinforced(i.e.plain),•ReinforcedReinforcedconcreteslabtypes•JPCP(Jointedplain/unreinforcedconcretepavement)•JRCP(jointedreinforcedconcretepavement)•CRCP(Continuouslyreinforcedconcretepavement)JUCP(Jointedplain/unreinforcedconcretepavment)•Itusescontractionjointstocontrolcrackinganddoesnotuseanyreinforcingsteel.JRCP(jointedreinforcedconcretepavement)•Itusescontractionjointsandreinforcingsteeltocontrolcracking.CRCP(continuouslyreinforcedconcretepavement)•Itdoesnotrequireanycontractionjoints.Separationmembrane•Betweenthebottomoftheconcreteslabandthetopofthesubbase.FunctionsofSeparationmembraneToreducefrictionbetweentheslabandsubbaseandallowfreemovementoftheslab,Topreventunderlyingmaterialfrombeingmixedintothebottomofthefreshly-pouredconcrete,Topreventthelossofmoistureandfinematerialfromtheconcretemixintoaporoussubbase(orthesubgrade).SubbaseFunctionsofsubbaseToprovideauniform,stableandpermanentsupportfortheslab,Topreventfrostactionunderconcreteslabs,Toactasadrainagelayer,Toactasaworkingplatformfortheconstructionequipment.SubgradeFunctionsofsubgrade•Towithstandthestressescausedbyconstructionandcompactiontraffic,•Toprovidetheuniformsupportrequiredbythepavementthroughoutitslife.RigidpavementconstructionConstructionprocedurePlacementConsolidationFinishingCuringJointingPlacement•PCCcanbeplaceddirectlyinthedesiredlocationbytruckortruckattachments,orcanbefedintoaplacementmachineformoreaccurateandevenplacement.SlipformpavingConsolidation•TomakethefreshlyplacedPCCintoamoreuniformandcompactmassbyeliminatingundesirableairvoidsandcausingittomovearoundpotentialobstructions(suchasreinforcingsteel).Finishing•TocreatethefinalsurfacefinishandtextureoffreshPCC.FloatingTexturingFloating•Toeliminatehighandlowspots,embedlargeraggregateparticlesbeneaththesurface,removeslightimperfectionsandtocompactthemortaratthesurfaceinpreparationfortexturing.Texturing•Tocreateaslipresistantsurfacefortraffic.Curing•CuringreferstothemaintenanceofsatisfactorymoistureandtemperaturewithinaPCCmassasitsetsandhardenssuchthatthedesiredpropertiesofstrength,durabilityanddensitycandevelop.Moisture•AhighrelativehumidityaroundahydratingPCCmasswillensureanadequatewatersupplyforhydrationandlimitshrinkagecracking.Temperature•MnimumambienttemperaturesforPCCconstructionarespecifiedtoensureanadequatehydrationrateandthus,strengthgain.Watercuring（喷洒养生）•Pondingwaterontopofaslab,continuouslysprayingaslabwithafinemistorcoveringaslabwithawater-retainingmaterialsuchasburlap.Sealedcuring(保湿覆盖)•Placingawaterproofcoveringoveraslab(suchasplastic)orusingaliquidmembrane-formingchemicalcompound.Jointing•Jointsarepurposefullyplaceddiscontinuitiesinarigidpavementsurfacecourse.Themostcommontypesofpavementjoints,definedbytheirfunction,arecontraction,expansionandconstruction.Contractionjoints•Toregulatethelocationofthecrackingcausedbydimensionalchangesintheslab.Contractionjointsarethemostcommontypeofjointinconcretepavements,thusthegenerictermjointgenerallyreferstoacontractionjoint.Expansionjoints•Toallowthepavementtoexpandwithoutdamagingadjacentstructuresorthepavementitself.However,expansionjointarenottypicallyusedtodaybecausetheirprogressiveclosuretendstocausecontractionjointstoprogressivelyopen.ConstructionJoints•Aconstructionjointisajointbetweenslabsthatresultswhenconcreteisplacedatdifferenttimes.Thistypeofjointcanbefurtherbrokendownintotransverseandlongitudinalconstructionjoints.TranslatethefollowingtermsintoChinese•bituminousoverlay•bituminoussurfacing•bleeding•cappinglayer•cementconcreteslab•coarseaggregate•consolidation•constructionjoint•constructionprocedure•continuouslyreinforcedconcretepavment(CRCP)•curing•finishing整平饰面•flexuralstrength•floating•frostaction•jointedreinforcedconcretepavement(JRCP)•Jointedplain/unreinforcedconcretepavement(URCP)•jointing•longitudinaljoint•mud-pumping•placement/concreting•plainconcrete•reinforcedconcrete•separationmembrane•stabilizedmaterial•texturing•transversejointTranslatethefollowingsentencesintoChinese.•1.Thecross-sectionofarigidroadwaycomprisesapavementsuperimposeduponthesubgrade,andmostusuallythispavementiscomposedofacementconcreteslabontopofasubbase.•2.Hence,anddependinguponthecircumstancesprevailing,thelikelihoodofpumpingisminimizedifthepavement