道路工程材料教学课件Road Engineering Materials ch4

RoadEngineeringMaterials

道路工程材料CollegeofAutomobileandTrafficEngineering汽车与交通学院QingdaoTechnologicalUniversity青岛理工大学Lecturer:ZHANGZhen主讲：张镇Ch4ConcreteandMortar4.1Propertiesoffreshconcrete（新拌砼）4.2Mixing拌合,Placing浇筑

andCuring养护4.3PropertiesofHardenedConcrete4.4Mixproportioninganddesign新拌水泥混凝土：指在施工过程中使用的尚未凝结硬化的水泥混凝土。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(离析)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流动性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（搅拌、运输、浇灌、捣实等）并能获得质量均匀、成型密实的性能。影响和易性的主要因素：1、水泥浆的数量。与流动性以及粘聚性相关2、水泥浆的稠度。3、砂率此外水泥品种、骨料种类、粒形和级配、外加剂、时间、温度等，都对混凝土拌和物的和易性有一定影响ConsistencyandSlump

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

坍落度试验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减水剂、引气剂4.1.2FactorsaffectingConsistencyandWorkabilityExternalFactorsEnvironmentTemperature,humidity,windspeed

TimeDelayinplacingTherelationshipofslumpandtemperatureslumpTemperatureTherelationshipofslumpandtimeTimeSlump4.1.3SegregationandBleedingSegregation离析

andBleeding泌水

resultsinNonhomogeneity

不均匀性Excessivebleeding----WeaktoplayerSegregationSegregationisthetendencyforseparationbetweenlargeandfineparticlesoffreshconcrete.SegregationresultsinRockpocket/honeycomb蜂窝Sandstreaks砂条痕,起砂Crazing龟裂Surfacescaling表面剥落混凝土局部酥松，砂浆少、石子多，石子之间出现空隙，形成的蜂窝状孔洞。Sandstreaks砂条痕,起砂Crazing龟裂SegregationReasonsofsegregationVerywetmixtures,lackoffineparticles,highslumpconcrete,OvervibrationControllingsegregationAir-entrainmentFinelydividedmaterialsDroppedverticallyBleeding

Bleeding----Aconcretemixthatdoesnotpossessproperconsistencyisunabletoholdthemixwater,whichslowlygetsdisplacedandthenrisestothetopoftheform.ReasonsofExcessivebleedingOvervibration,overtroweling,leanmixes,lackoffinesand,prematurefinishing混凝土在运输、振捣、泵送的过程中出现粗骨料下沉，水分上浮的现象称为混凝土泌水。泌水量(混凝土拌和物单位面积的平均泌水量)泌水率(泌水量对混凝土拌和物之比含水量之比)。影响因素：1、混凝土水灰比，2、水泥，3、骨料，4、减水剂，5、含气量，6、施工Bleeding泌水的危害1、对混凝土表面的危害有流砂水纹缺陷的混凝土，表面强度、抗风化和抗侵蚀的能力较差。同时，水分的上浮在混凝土内留下泌水通道，即产生大量自底部向顶层发展的毛细管通道网，这些通道增加了混凝土的渗透性，盐溶液和水分以及有害物质容易进入混凝土中，使混凝土表面损坏。泌水使混凝土表面的水灰比增大，并出现浮浆，即上浮的水中带有大量的水泥颗粒，在混凝土表面形成返浆层，硬化后强度很低，同时混凝土的耐磨性下降。这对路面等有耐磨要求的混凝土是十分有害的。2、对混凝土内部结构及性能的危害在混凝土粗骨料、钢筋周围形成水囊，随着水分的逐渐挥发形成空隙，从而影响混凝土的致密性、骨料的界面强度以及混凝土与钢筋间的握裹力。混凝土泌水造成塑性收缩是一个不可逆的变形。泌水引起混凝土地沉降导致混凝土产生塑性裂纹。塑性裂纹的存在会降低水泥石的强度。由于泌水混凝土产生整体沉降，浇注深度大时靠近顶部的拌合物运动距离更长，沉降受到阻碍，如遇到钢筋等障碍时，则产生塑性沉降裂纹，从表面向下直至钢筋的上方。。分层浇注的混凝土受下层混凝土表面泌水的影响，造成混凝土层间结合强度降低并易形成裂缝。ControllingbleedingAir-entrainmentIncreasethefinenessofcementDecreasewater-to-cementratioRichmixes控制泌水的措施1、混凝土配合比方面适当增加胶凝材料用量，适当提高混凝土的砂率，在不满足其他性能的前提下，使混凝土适量引气。在保证施工性能的前提下，尽量减少单位用水量。

2、原材料方面选用较细的胶凝材料和高品质的引气剂

3、减水剂方面选用混凝土泌水较小、流动度大的高效减水剂。如果配合比固定，在满足标准和使用要求的情况下，选用减水率合适的减水剂掺量，避免减水率过高造成泌水。4、施工方面严格控制混凝土振捣时间，避免过振。另外，对于现浇混凝土的性能控制，选取适当的控制点，使得控制有利于减小混凝土泌水。假如要控制最大含气量，控制点可选在入仓口，将混凝土输送过程中含气量损失对泌水的影响降到最低。当仓面内已经出现了泌水，必须及时排除，其最有效的方法是真空吸水、人工在仓面掏水或用海绵等吸水性强的材料吸水，尤其在混凝土收面时更应该及时吸去泌水，便于混凝土收面确保混凝土外观质量。严禁在模板上开孔自流，造成胶凝材料流失，影响混凝土的质量。尤其在混凝土收面时更应该及时吸去泌水，以便于混凝土收面。5、通过外加剂改善混凝土的泌水混凝土外加剂（减水剂）一般是有机高分子物质。有机高分子的分子量、或者分子链长度直接影响其性能。如果减水剂的分子量较大、分子链较长，会使混凝土的泌水减少，但是同时减水剂的减水率较低；如果分子量较小、分子链较短，则使减水率增加，同时使混凝土的泌水率增大。有些减水剂在主分子链上存在支链，无论主链支链，较长时会使混凝土泌水减水，但减水率也相应降低，如果主链短而支链长，则会使泌水减少的同时，对减水率影响不大。一般情况下，减水剂不是由单一分子量的分子组成，而是各种分子量的分子混合组成。在既要减少泌水又要保证减水率的情况下，需要优化减水剂的分子量级配，使得小分子和大分子物质达到最佳搭配关系。4.2Mixing,PlacingandCuring4.2.1Mixing4.2.2PumpingandPlacing4.2.3Finishingandtypesoffinishes4.2.4Curing4.2.1Mixing拌合Thepurposeofmixingtheingredients----istoensurethateachparticleofaggregateinfreshconcretewillbecoatedwiththecementpaste.BatchingBatching----Weighingoutalloftheingredientsforabatchofconcrete.Concretebatchplant混凝土拌和楼Transitmixer混凝土搅拌车BatchplantTransitmixer4.2.2Pumping泵送

andPlacing浇筑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手推车IncorrectPlacementwithConveyorBelt传送带BaffleMortarRockMortarMortarRockShallowhopperPlacementwithConveyorBeltBeltScraper输送带刮板NoSeparationProvideatleast0.6m(24in.)headroomfordownpipe,elephanttrunkorequivalent提供最少有0.6m净空的落水管、象鼻管或差不多的东西DepositingConcrete2）Pavement

SlabConcretedepositedinfrontofslipformpaver滑膜摊铺机

bydumptrucks自卸车Concretespreadevenlyacrossthesubgradebythepaverbeforeconsolidation捣实

andfinishing抹平

3）Curb/CurbandGutter路缘石、排水沟DepositingConcreteConcretedepositedintohopperofslipformcurbandguttermachinewhichthenextrudestheconcreteintothedesiredshapeDepositingConcreteDepositinhorizontallayersofuniformthicknessReinforced—150mmto500mmMass—375mmto500mmConsolidateeachlayerbeforenextisplacedTimelyplacement&consolidationpreventsflowlinesandcoldjoints4）Walls4、ConsolidatingConcreteInternalVibration振捣ExternalVibrationInternalVibrationdR1½RVibratorRadiusofActionSystematicVibrationofEachNewLiftCORRECTVerticalpenetrationafewinchesintopreviouslift(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龄期90-daystrengthofconcrete100（%）28-daystrengthofconcrete80（%）7-daystrengthofconcrete45（%）3-daystrengthofconcrete30（%）CuringMoistureTemperatureTimeCuringrequiresadequate—

Ifanyofthesefactorsareneglected,thedesired

propertieswillnotdevelopIncreasedStrengthWatertightnessAbrasionresistanceFreeze-thawresistanceVolumestabilityEffectofAdequateCuringonHardenedConcreteEffectofMoistCuringonStrengthEffectofCuringTemperatureonStrengthCuringMethodsMethodsthatmaintainthepresenceofwaterMethodsthatpreventthelossofmixingwaterMethodsthatacceleratehydrationbysupplyingheatandmoistureCuringMethods1. MethodsthatmaintainthepresenceofwaterSupplyadditionalwaterwith:PondingorimmersionSprayingorfoggingSaturatedwetcoveringsCuringofConcretebySupplyingWaterEvaporationfromwatersurfaceConcreteWatersuppliedfromexternalsourceSaturatedCuringMethods2. MethodsthatpreventthelossofmixingwaterSealinmixingwater:PlasticsheetsMembrane-formingcuringcompoundsMembraneCuringofConcreteEvaporationfromwatersurfaceConcreteCuringmembraneSaturatedPartiallysaturatedCuringMethods3. MethodsthatacceleratehydrationbysupplyingheatandmoistureStrengthgainisacceleratedwith:LivesteamHeatingcoilsElectricallyheatedformsorpads4.3PropertiesofHardenedConcreteThemajorpropertiesofhardenedconcrete:StrengthDeformationModulusofelasticityShrinkageCreep(徐变）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