道路工程材料教學(xué)課件Road Engineering Materials ch4

RoadEngineeringMaterials

道路工程材料CollegeofAutomobileandTrafficEngineering汽車與交通學(xué)院QingdaoTechnologicalUniversity青島理工大學(xué)Lecturer:ZHANGZhen主講：張鎮(zhèn)Ch4ConcreteandMortar4.1Propertiesoffreshconcrete（新拌砼）4.2Mixing拌合,Placing澆筑

andCuring養(yǎng)護(hù)4.3PropertiesofHardenedConcrete4.4Mixproportioninganddesign新拌水泥混凝土：指在施工過(guò)程中使用的尚未凝結(jié)硬化的水泥混凝土。ADefinitionofPortlandCementConcrete（PCC）Amixtureof:PortlandCementFineAggregateCoarseAggregateWaterAirCementandwatercombine,changingfromamoist,plasticconsistencytoastrong,durablerock-likeconstructionmaterialbymeansofachemicalreactioncalled“hydration”.VolumetricproportionsofconstituentsofPCC2-8%air25-40%cementpaste60-75%aggregateBasedonapparentdensityBasedonapparentdensity,concretecanbedividedinto:Normalweightconcrete(2350-2500kg/m3)Lightweightconcrete(upto1900kg/m3)Heavyweightconcrete(upto3200kg/m3)4.1Propertiesoffreshconcrete4.1.1Propertiesoffreshconcrete4.1.2FactorsaffectingConsistency(稠度)andWorkability(和易性)4.1.3Segregation(離析)andBleeding(泌水)4.1.1PropertiesoffreshconcreteWorkability（和易性）Consistency（稠度）Slump（坍落度）Workability（和易性）Workabilitycanbedefinedastheeasewithwhichafresh-concretemixcanbehandledfromthemixertothefinalstructure.ExpressedbythreecharacteristicsConsistency稠度Mobility流動(dòng)性Compatibility相容性;

保水性和易性是指新拌混凝土易于各工序施工操作（攪拌、運(yùn)輸、澆灌、搗實(shí)等）并能獲得質(zhì)量均勻、成型密實(shí)的性能。影響和易性的主要因素：1、水泥漿的數(shù)量。與流動(dòng)性以及粘聚性相關(guān)2、水泥漿的稠度。3、砂率此外水泥品種、骨料種類、粒形和級(jí)配、外加劑、時(shí)間、溫度等，都對(duì)混凝土拌和物的和易性有一定影響ConsistencyandSlump

（稠度）（坍落度）Consistencyisameasureofconcrete’swetnessorfluidity,anddependsonthemixproportionsandpropertiesofingredients.MeasuredbySlumptest

坍落度試驗(yàn)SlumptestSlumptestMold:slumpcone坍落度筒Bottomdiameterof200mmtopdiameterof100mmheightof300mmProcedureofSlumptesta.Filltheconeusingstandardprocedureb.Strikeoffexcessc.RaisethemoldandmeasurethedisplacementoftheoriginalcenterofthespecimenSlumpIntheslumptest,thenumberofmmtheoriginalcenteroftheconesinksorsettlesuniformlyismeasuredtothenearest5mm.Themeasurementiscalledslump.E.g.slumpcanbe75,80,85mm,etc.Types

ofslumpNear-zeroslumpVerydrymixNormalslumpProperlyproportionedconcreteShearslumpConcretelacksplasticityandcohesionCollapseslumpLean,harshorextremelywetconcreteRecommendedslumpsforvarioustypeofconstructionTypeofconstructionSlump(mm)MaxMinFootings,caissons,foundationwallsandsubstructurewalls7525Beams,columnsandwalls10025Pavementandslabs7525Massconcrete50254.1.2FactorsaffectingConsistencyandWorkabilityInternalFactorsCementpropertiesProportionofcement,Typesofcement,FinenessAggregatepropertiesSurfaceareaofaggregate,shape,gradation,maximumsizeofaggregateWatercontentWater-to-Cementratio

水灰比AdmixturesWater-reducingadmixture,air-entrainingadmixture減水劑、引氣劑4.1.2FactorsaffectingConsistencyandWorkabilityExternalFactorsEnvironmentTemperature,humidity,windspeed

TimeDelayinplacingTherelationshipofslumpandtemperatureslumpTemperatureTherelationshipofslumpandtimeTimeSlump4.1.3SegregationandBleedingSegregation離析

andBleeding泌水

resultsinNonhomogeneity

不均勻性Excessivebleeding----WeaktoplayerSegregationSegregationisthetendencyforseparationbetweenlargeandfineparticlesoffreshconcrete.SegregationresultsinRockpocket/honeycomb蜂窩Sandstreaks砂條痕,起砂Crazing龜裂Surfacescaling表面剝落混凝土局部酥松，砂漿少、石子多，石子之間出現(xiàn)空隙，形成的蜂窩狀孔洞。Sandstreaks砂條痕,起砂Crazing龜裂SegregationReasonsofsegregationVerywetmixtures,lackoffineparticles,highslumpconcrete,OvervibrationControllingsegregationAir-entrainmentFinelydividedmaterialsDroppedverticallyBleeding

Bleeding----Aconcretemixthatdoesnotpossessproperconsistencyisunabletoholdthemixwater,whichslowlygetsdisplacedandthenrisestothetopoftheform.ReasonsofExcessivebleedingOvervibration,overtroweling,leanmixes,lackoffinesand,prematurefinishing混凝土在運(yùn)輸、振搗、泵送的過(guò)程中出現(xiàn)粗骨料下沉，水分上浮的現(xiàn)象稱為混凝土泌水。泌水量(混凝土拌和物單位面積的平均泌水量)泌水率(泌水量對(duì)混凝土拌和物之比含水量之比)。影響因素：1、混凝土水灰比，2、水泥，3、骨料，4、減水劑，5、含氣量，6、施工Bleeding泌水的危害1、對(duì)混凝土表面的危害有流砂水紋缺陷的混凝土，表面強(qiáng)度、抗風(fēng)化和抗侵蝕的能力較差。同時(shí)，水分的上浮在混凝土內(nèi)留下泌水通道，即產(chǎn)生大量自底部向頂層發(fā)展的毛細(xì)管通道網(wǎng)，這些通道增加了混凝土的滲透性，鹽溶液和水分以及有害物質(zhì)容易進(jìn)入混凝土中，使混凝土表面損壞。泌水使混凝土表面的水灰比增大，并出現(xiàn)浮漿，即上浮的水中帶有大量的水泥顆粒，在混凝土表面形成返漿層，硬化后強(qiáng)度很低，同時(shí)混凝土的耐磨性下降。這對(duì)路面等有耐磨要求的混凝土是十分有害的。2、對(duì)混凝土內(nèi)部結(jié)構(gòu)及性能的危害在混凝土粗骨料、鋼筋周圍形成水囊，隨著水分的逐漸揮發(fā)形成空隙，從而影響混凝土的致密性、骨料的界面強(qiáng)度以及混凝土與鋼筋間的握裹力?；炷撩谒斐伤苄允湛s是一個(gè)不可逆的變形。泌水引起混凝土地沉降導(dǎo)致混凝土產(chǎn)生塑性裂紋。塑性裂紋的存在會(huì)降低水泥石的強(qiáng)度。由于泌水混凝土產(chǎn)生整體沉降，澆注深度大時(shí)靠近頂部的拌合物運(yùn)動(dòng)距離更長(zhǎng)，沉降受到阻礙，如遇到鋼筋等障礙時(shí)，則產(chǎn)生塑性沉降裂紋，從表面向下直至鋼筋的上方。。分層澆注的混凝土受下層混凝土表面泌水的影響，造成混凝土層間結(jié)合強(qiáng)度降低并易形成裂縫。ControllingbleedingAir-entrainmentIncreasethefinenessofcementDecreasewater-to-cementratioRichmixes控制泌水的措施1、混凝土配合比方面適當(dāng)增加膠凝材料用量，適當(dāng)提高混凝土的砂率，在不滿足其他性能的前提下，使混凝土適量引氣。在保證施工性能的前提下，盡量減少單位用水量。

2、原材料方面選用較細(xì)的膠凝材料和高品質(zhì)的引氣劑

3、減水劑方面選用混凝土泌水較小、流動(dòng)度大的高效減水劑。如果配合比固定，在滿足標(biāo)準(zhǔn)和使用要求的情況下，選用減水率合適的減水劑摻量，避免減水率過(guò)高造成泌水。4、施工方面嚴(yán)格控制混凝土振搗時(shí)間，避免過(guò)振。另外，對(duì)于現(xiàn)澆混凝土的性能控制，選取適當(dāng)?shù)目刂泣c(diǎn)，使得控制有利于減小混凝土泌水。假如要控制最大含氣量，控制點(diǎn)可選在入倉(cāng)口，將混凝土輸送過(guò)程中含氣量損失對(duì)泌水的影響降到最低。當(dāng)倉(cāng)面內(nèi)已經(jīng)出現(xiàn)了泌水，必須及時(shí)排除，其最有效的方法是真空吸水、人工在倉(cāng)面掏水或用海綿等吸水性強(qiáng)的材料吸水，尤其在混凝土收面時(shí)更應(yīng)該及時(shí)吸去泌水，便于混凝土收面確?；炷镣庥^質(zhì)量。嚴(yán)禁在模板上開(kāi)孔自流，造成膠凝材料流失，影響混凝土的質(zhì)量。尤其在混凝土收面時(shí)更應(yīng)該及時(shí)吸去泌水，以便于混凝土收面。5、通過(guò)外加劑改善混凝土的泌水混凝土外加劑（減水劑）一般是有機(jī)高分子物質(zhì)。有機(jī)高分子的分子量、或者分子鏈長(zhǎng)度直接影響其性能。如果減水劑的分子量較大、分子鏈較長(zhǎng)，會(huì)使混凝土的泌水減少，但是同時(shí)減水劑的減水率較低；如果分子量較小、分子鏈較短，則使減水率增加，同時(shí)使混凝土的泌水率增大。有些減水劑在主分子鏈上存在支鏈，無(wú)論主鏈支鏈，較長(zhǎng)時(shí)會(huì)使混凝土泌水減水，但減水率也相應(yīng)降低，如果主鏈短而支鏈長(zhǎng)，則會(huì)使泌水減少的同時(shí)，對(duì)減水率影響不大。一般情況下，減水劑不是由單一分子量的分子組成，而是各種分子量的分子混合組成。在既要減少泌水又要保證減水率的情況下，需要優(yōu)化減水劑的分子量級(jí)配，使得小分子和大分子物質(zhì)達(dá)到最佳搭配關(guān)系。4.2Mixing,PlacingandCuring4.2.1Mixing4.2.2PumpingandPlacing4.2.3Finishingandtypesoffinishes4.2.4Curing4.2.1Mixing拌合Thepurposeofmixingtheingredients----istoensurethateachparticleofaggregateinfreshconcretewillbecoatedwiththecementpaste.BatchingBatching----Weighingoutalloftheingredientsforabatchofconcrete.Concretebatchplant混凝土拌和樓Transitmixer混凝土攪拌車BatchplantTransitmixer4.2.2Pumping泵送

andPlacing澆筑Pumpingcanbeamethodusedinplacing.1、BasicRequirementsforPlacingConcrete1）PreserveconcretequalityWater-cementratioSlumpAir-contentHomogeneity2）AvoidseparationofaggregateandmortarBasicRequirementsforPlacingConcrete3）Avoidexcessivehorizontalmovement4）Consolidateadequately5）Maintainsufficientplacementcapacity6）Choosetherightequipmentfortheconcrete2、PreparationBeforePlacingIncludes:TrimmingthesubgradePreparationBeforePlacingIncludes:MoisteningthesubgradePreparationBeforePlacingIncludes:Compactingthesubgrade3、DepositingConcreteStartplacingalongperimeteratoneendwitheachbatchdischargedagainstpreviouslyplacedconcreteDonot— (a)dumpinseparatepiles&thenlevelandworktogether (b) depositinlargepiles&thenmovehorizontallyintopositionThesepracticesresultinsegregation(mortarflowsaheadofcoarsermaterial)1）SlabConstructionDepositingConcreteDischargingintopreviouslyplacedconcreteEffectiveuseofwheelbarrows手推車IncorrectPlacementwithConveyorBelt傳送帶BaffleMortarRockMortarMortarRockShallowhopperPlacementwithConveyorBeltBeltScraper輸送帶刮板NoSeparationProvideatleast0.6m(24in.)headroomfordownpipe,elephanttrunkorequivalent提供最少有0.6m凈空的落水管、象鼻管或差不多的東西DepositingConcrete2）Pavement

SlabConcretedepositedinfrontofslipformpaver滑膜攤鋪機(jī)

bydumptrucks自卸車Concretespreadevenlyacrossthesubgradebythepaverbeforeconsolidation搗實(shí)

andfinishing抹平

3）Curb/CurbandGutter路緣石、排水溝DepositingConcreteConcretedepositedintohopperofslipformcurbandguttermachinewhichthenextrudestheconcreteintothedesiredshapeDepositingConcreteDepositinhorizontallayersofuniformthicknessReinforced—150mmto500mmMass—375mmto500mmConsolidateeachlayerbeforenextisplacedTimelyplacement&consolidationpreventsflowlinesandcoldjoints4）Walls4、ConsolidatingConcreteInternalVibration振搗ExternalVibrationInternalVibrationdR1?RVibratorRadiusofActionSystematicVibrationofEachNewLiftCORRECTVerticalpenetrationafewinchesintopreviouslift(whichshouldnotyetberigid)ofsystematicregularintervalswillgiveadequateconsolidationINCORRECTHaphazardrandompenetrationofthevibratoratallanglesandspacingswithoutsufficientdepthwillnotassureintimatecombinationofthetwolayersPlacingConcreteinaSlopingLiftCORRECTStartplacingatbottomofslopesothatcompactionisincreasedbyweightofnewlyaddedconcrete.Vibrationconsolidatestheconcrete.INCORRECTWhenplacingisbegunattopofslopetheupperconcretetendstopullapartespeciallywhenvibratedbelowasthisstartsflowandremovesfromconcreteabove.ExternalVibrationFormvibratorsVibratingtablesSurfacevibratorsVibratoryscreedsPlatevibratorsVibratoryrollerscreedsVibratoryhandfloatsortrowelsConsolidatingConcrete Inadequateconsolidationcanresultin:HoneycombExcessiveamountofentrappedairvoids(bugholes)SandstreaksColdjointsPlacementlinesSubsidencecracking4.2.3FinishingandtypesoffinishesFinishing----Aconcretesurfaceisfinishedtofulfilltherequirementsofaestheticsorservice.TypesoffinishesScreeding刮平Floating抹平Troweling抹光Tining拉毛Screeding(Strikeoff)刮平TheprocessofcuttingoffexcessconcretetobringthetopsurfaceofaslabtopropergradeVibratoryScreedsBullfloatingDarbyingFloating(PowerorHand)ToembedaggregateparticlesjustbeneaththesurfaceToremoveslightimperfections,humps,andvoidsTocompactthemortaratthesurfaceinpreparationforadditionalfinishingoperations.TrowelingCreatessmooth,hard,densesurfaceExteriorconcreteshouldnotbetroweledbecause:itcanleadtoalossofentrainedaircausedbyoverworkingthesurfacetroweledsurfacescanbeslipperywhenwet.BroomingTiningCuringandProtectionCurefor7days4.2.4CuringCuring----isanyprocedurethatmaintainspropermoistureandtemperaturetoensurecontinuoushydration.Age齡期90-daystrengthofconcrete100（%）28-daystrengthofconcrete80（%）7-daystrengthofconcrete45（%）3-daystrengthofconcrete30（%）CuringMoistureTemperatureTimeCuringrequiresadequate—

Ifanyofthesefactorsareneglected,thedesired

propertieswillnotdevelopIncreasedStrengthWatertightnessAbrasionresistanceFreeze-thawresistanceVolumestabilityEffectofAdequateCuringonHardenedConcreteEffectofMoistCuringonStrengthEffectofCuringTemperatureonStrengthCuringMethodsMethodsthatmaintainthepresenceofwaterMethodsthatpreventthelossofmixingwaterMethodsthatacceleratehydrationbysupplyingheatandmoistureCuringMethods1. MethodsthatmaintainthepresenceofwaterSupplyadditionalwaterwith:PondingorimmersionSprayingorfoggingSaturatedwetcoveringsCuringofConcretebySupplyingWaterEvaporationfromwatersurfaceConcreteWatersuppliedfromexternalsourceSaturatedCuringMethods2. MethodsthatpreventthelossofmixingwaterSealinmixingwater:PlasticsheetsMembrane-formingcuringcompoundsMembraneCuringofConcreteEvaporationfromwatersurfaceConcreteCuringmembraneSaturatedPartiallysaturatedCuringMethods3. MethodsthatacceleratehydrationbysupplyingheatandmoistureStrengthgainisacceleratedwith:LivesteamHeatingcoilsElectricallyheatedformsorpads4.3PropertiesofHardenedConcreteThemajorpropertiesofhardenedconcrete:StrengthDeformationModulusofelasticityShrinkageCreep(徐變）DurabilityWatertightness(impermeability)1、StrengthCompressivestrengthTensilestrengthFlexuralstrengthCompressivestrengthCompressiontestCubicspecimensofsize150mmEquationWhere,F----appliedloadwhenfailure(N)A----sectionareaofspecimen(mm2)fcu----standardcompressivestrength(MPa)GradeofcompressivestrengthGradeofconcreteC10C15C20C25C30C40C50C60Compressivestrength(MPa)1015202530405060GBJ10-89Influencefactorsofcompressivestrength(1)Effectsofthetypeandamountofcement(2)Effectsofaggregates(3)Effectsofwater-to-cementratio(4)Influenceofvoids(5)Benefitsofcuring(6)Roleofair-entrainment(1)Effectsofthetypeandamountofcement(1)EffectsofthetypeandamountofcementInfluencefactorsofcompressivestrength(1)Effectsofthetypeandamountofcement(2)Effectsofaggregates(3)Effectsofwater-to-cementratio(4)Influenceofvoids(5)Benefitsofcuring(6)Roleofair-entrainment(2)Effectsofaggregates(2)EffectsofaggregatesInfluencefactorsofcompressivestrength(1)Effectsofthetypeandamountofcement(2)Effectsofaggregates(3)Effectsofwater-to-cementratio(4)Influenceofvoids(5)Benefitsofcuring(6)Roleofair-entrainment(3)Effectsofwater-to-cementratio(3)Effectsofwater-to-cementratioInfluencefactorsofcompressivestrength(1)Effectsofthetypeandamountofcement(2)Effectsofaggregates(3)Effectsofwater-to-cementratio(4)Influenceofvoids(5)Benefitsofcuring(6)Roleofair-entrainment(4)InfluenceofvoidsDurabilityWatertightnessCompressivestrengthInfluencefactorsofcompressivestrength(1)Effectsofthetypeandamountofcement(2)Effectsofaggregates(3)Effectsofwater-to-cementratio(4)Influenceofvoids(5)Benefitsofcuring(6)Roleofair-entrainment(5)BenefitsofcuringInfluencefactorsofcompressive