水泥体积安定性（英文）

DETERMINATIONOFSOUNDNESSOFCEMENTLecturer:Dr.WangChuang26May,2018TRAININGMODULEOFCEMENTITIOUSMATERIALPERFORMANCETEST1.SoundnessofCement2.TestMethods3.TestProcedures4.EvaluationoftheResults5.AfterClassContents1.SoundnessofCement1.1Def：Thestabilityofvolumechangeafterhardeningofcementpaste1.2ThreeReasons:(1)Excessiveamountoffreecalciumoxide(detectedbyboilingmethod)(2)ExcessiveamountoffreeMagnesiumoxide(detectedbyautoclavemethod)(3)Excessiveamountofplaster/sulfurtrioxide(detectedbychemicalanalysis)Whatissoundnessofcement?2.Testmethods：(1)Standardmethod

(Lechateliersoundnesstest):Thesoundnessofthecementstandardconsistencypasteischaracterizedbymeasuringtherelativedisplacementoftestneedlesafterboiling.(2)

Substitutivemethod(Trialcakemethod):Thesoundnessischaracterizedbyobservingtheappearancechangeofthetestcakeofthecementstandardconsistencyafterboiling.Howtodeterminethesoundnessofcement?Now,letustakeanexampleintheXi'an-Tongguanexpressway.Intheconstruction,acementstabilizedmacadamstructureisusedforroadbaseandsubbase.Tomixthecement-stabilizedmaterial,anewbatchofcommonPortlandcement42.5ispurchasedandneedstobeinspected.Fig.1AconstructionsiteinXi'an-TongguanexpresswayWearegoingtotestthesoundnessofcementtoseewhetheritisqualifiedornot!3.TestProcedures3.1PreparationofInstrumentsOperating!PreparingstandardconsistencycementpasteFig.2CementpastemixerFig.3VicatapparatusTheclipismadeofcoppermaterial.Therootofaneedleisfirstsuspendedinawireornylonthread,andtherootoftheotherneedlehangsontheweightof300gmass.Atthismoment,thedistancebetweenthetwoneedletipsshouldbeincreasedbetween15--20mm.Whentheweightisremoved,thedistancebetweenthetwotipscanberestoredtotheoriginalstatebeforeweighting.3.1CorrectionofLechatelierclipJudgmentontheLechatelierclipqualifiedornot:1.Madeofcoppermaterial;2.Hang300gweight,thepointerincreasesbetween15--20mm;3.Aftertheweightisunloaded,thedistancebetweenthetwopointertipsisrestored.StandardmethodFirst:verticalSecond:horizontalThird:verticalFig.4CorrectionofLechatelierclip3.2PreparationandtestofsamplesFig.5Insert&SmashFig.6Curing:Temperature:20±1ºCRelativehumidity:≥90%Fivestepsareinvolvedinthetest:Step1.Preparestandardconsistencypastebyaddingwateraccordingtothewaterconsumptionforstandardconsistency.Step2.PutthecalibratedLechateliercliponaglassplatecoatedwithathinlayerofoil.Holdthetestmoldbyonehand.Andasmallknifeisusedbytheotherhandtoinsertandsmashthepastefor3timestoensurecompaction.Coverthemoldwiththeoiledglassplateandputitinamoisturecuringboxfor24±2h.Step3.TakeouttheLechatelierclipandmeasurethedistancebetweenthetwopointertips.ThevalueisrecordedasA.Normallyitis10mm.Fig.7

MeasurementofAvalueStep4.

Boiling!Putthemoldinaboilingbox.Thewatermustbeboiledwithin30±5min,boilingfor180±5min.Thenimmediatelyletoutthehotwaterinthebox.Removetheboxcoverandlettheboxcooldowntoroomtemperature.Takeoutthesample.Fig.8BoilingthesampleinaboilingboxStep5.Re-determinethedistancebetweenthetwopointertipsandrecordthevalueasC.Iftheaveragevalueof(C-A)isnotgreaterthan5.0mm,itisconsideredthatthecementsoundnessisqualified.Whenthe(C-A)valueofthetwosamplesexceeds4.0mm,thetestmustbedoneimmediatelyagainwiththesamesample.Theresultsareaccurateto0.5mm.Fig.9

MeasurementofCvalueNo.DistancebetweenpointersbeforeboilingA/mmDistancebetweenpointersafterboilingC/mmDistanceincreaseafterboiling

(C-A)/mm(C-A)/2110.011.5210.511.04.EvaluationoftheResultsJudgmentCriterionC-A＜5.0:QualifiedC-A＞5.0:UnqualifiedIntheconstruction,thetestresultoft