Influence of mix proportions on rheology of cement grouts co(8)

744L.Svermovaetal./Cement&ConcreteComposites25(2003)737–749

mini-slumpreducedwhenthedosageofVAincreasedwhilethedosageofSPandtheproportionofLSPwerekeptconstant(Fig.4(b)).

4.3.2.Platecohesionmeter

AsshowninTable4,platecohesionmeterisin u-enced,intheorderofsigni cance,bythedosagesofSPandVA,theW/BandtheproportionofLSP.Thein-creaseinW/Bhasafairlysimilarin uenceontheplatecohesionmeterastheincreaseintheproportionofLSP()0.37vs.)0.32).Bycomparingthee ectofSPandVAdosagesontheplatecohesionmeter,theincreaseofdosageofSPcanthenbeinterpretedtohaveapproxi-mately1.7timesgreaterin uenceonthereductionoftheplatecohesionvaluethantheincreaseinVA,giventhattheW/BandtheproportionofLSPareheldcon-stant.Fig.5showsanexampleofisopresponsecurvesoftheplatecohesionmetervs.W/Bfor xedvaluesofSPandVAorSPandLSPorLSPandVA.For xedvaluesofSPandVAat0.75%and0.045%,respectively,theplatecohesionmeterdecreasedwhentheW/BincreasedortheproportionofLSPincreased(Fig.5(a)).Thein-creaseofthedosageofSP,foranygivenW/Band xedLSPproportionandVAdosage,ledtoareductionintheplatecohesionmeter(Fig.5(c)).

4.3.3.Yieldvalue

AsshowninTable4,thequadratice ectofW/BLSPisshowntoexhibitthegreateste ectontheyieldvaluefollowingbythedosageofSP(2.7and)1.8).Thein-

creaseofW/BandtheproportionofLSPreducedtheyieldvalue.Themodel(Eq.(3))showsthattheincreaseofthedosageofSPismoree cientinreducingyieldvaluethananincreaseintheproportionofLSP()1.8vs.)1.1).Forexample,thee ectofincreasingW/Bratioonyieldvaluevs.theproportionofLSP,whendosagesofSPandVAwere xedat0.75%and0.05%,respectively,orvs.dosageofSPof0.75%andtheproportionofLSPof28.5%,respectively,orvs.thedosageofVAof0.05%andtheproportionofLSPof28.5%,isshowninFig.6.TheyieldvalueseemedtodecreasewithincreasedW/Bup0.40,thentendedtoincreasebeyondthisthresholdvalue(Fig.6(a)).For xeddosagesofSPandVA,theyieldvalueincreasedsigni cantlyuptoabout0.40ofW/BandhigherproportionofLSP(upto29%).AtlowerproportionsofLSP,however,adecreaseofyieldvaluewasobservedwithanincreaseinW/B(Fig.6(a)).4.3.4.Plasticviscosity

Plasticviscosityisin uenced,inorderofsigni cance,bytheW/B,thedosageofVA,thedosageofSPandtheproportionofLSP.TheW/Bisshowntohavethegreateste ectontheplasticviscosity(Eq.(4)).TheincreaseofW/Bhasapproximately1.3timesgreaterin uenceonreducingtheplasticviscositythanthede-creaseinthedosageofVA()0.56vs.0.42).Themodel(Eq.(4))showsthatthee ectofchangingthedosageofSPontheplasticviscosityissimilartothatofthepro-portionofLSP()0.28vs.0.28).Bycomparingthee ectsofSPandVAontheplasticviscosity,itcanbe

observed

L.Svermovaetal./Cement&ConcreteComposites25(2003)737–749745

thatthee ectofVAishigherthanthatofSP(0.42vs.)0.28).Forexample,thee ectofincreasingW/Bratioonplasticviscosityvs.theproportionofLSP,whendosagesofSPandVAwere xedat0.75%and0.05%respectively,orvs.dosageofSPof0.75%andthepro-portionofLSPof28.5%,respectively,orvs.thedosageofVAof0.05%andtheproportionofLSPof28.5%,isshowninFig.7.TheincreaseinW/Band/orthepro-portionofLSPledtoareductioninplasticviscosity(Fig.7(a)).

4.3.5.Inducedbleeding

Thein uencesoftheproportionofLSPandthedosagesofSPandVAarehighlysigni cantonthein-ducedbleedingaccordingtotheANOVA.Thepropor-tionofLSPisshowntoexhibitthegreateste ectasaprimaryvariableontheinducedbleedingcomparedtothedosagesofSPandVA(0.14vs.)0.05or0.04).However,theANOVAshowsthatthetwo-factorin-teractionofW/BVAishighlysigni cantandhasthegreateste ectoninducedbleeding.TheinteractionsbetweenW/BSPandW/BLSParesigni cantandhaveoppositee ect()0.1vs.0.1).TheincreaseinSPdosagehasagreaterin uenceonreducingtheinducedbleedingthantheincreaseinVAdosage()0.05vs.0.04).Forexample,thee ectofincreasingW/Bratiooninducedbleedingvs.theproportionofLSP,whendosagesofSPandVAwere xedat0.75%and0.05%,respectively,orvs.dosageofSPof0.75%andtheproportionofLSPof28.5%,respectively,orvs.thedosageofVAof0.05%andtheproportionofLSPof28.5%,isshowninFig.8.

For xeddosageofVAandtheproportionofLSP,theincreaseinSPledtoanincreaseininducedbleedingforlowerW/Bupto0.38.However,forhigherW/B(be-tween0.38and0.42),theincreaseofthedosageofSPresultedinareductionintheinducedbleeding(Fig.8(c)).Thisisduetotheimproveddispersionandpack-ingofcementgrainsassociatedwithgreaterSPdosage.Theresultingincreasein uidity(Fig.4)andparticlepacking(versus occulatedcementgrainsthathavealowerpackingdensity)cansubstantiallyreducethetendencyofwatertopercolateamongcementgrainsunderagivenhead,whichre ectsthepermeabilityofthefreshgrout.Theseresultsconcurwiththe ndingsofotherresearchers[3,4].ForlowerW/B(lowerthan0.38),theincreaseinVAdosageexhibitedareductionintheinducedbleeding,howeverforhigherW/Bbeyond0.39,theinducedbleedingseemedtoincreaseasthedosageofVAincreased(Fig.8(b)).

pressivestrength

TheANOVAsgiveninTable4showthatthee ectofW/Bishighlysigni cantoncompressivestrengthat7and28daysandhasthegreateste ectonstrength.Thecompressivestrengthdecreased,asW/Bincreased.TheproportionofLSPandthedosageofSParealsohighlysigni cantoncompressivestrength.TheincreaseoftheproportionofLSPorthedosageofSPledtoareductionincompressivestrengthat28days.Thee ectoftheproportionofLSPoncompressivestrengthwasgreaterthanthatofW/BandSP

dosage.

746L.Svermovaetal./Cement&ConcreteComposites25(2003)737–749

4.4.Trade-o betweenSPandVA

Contourresponsesshowingthein uenceofSPandVAdosagesonmini-slumpandplatecohesionmeter,andmini-slumpandyieldvalueforgroutsmadewith xedW/Bof0.35and12%ofLSParepresentedinFig.9.Asexpected,foragivenSPdosage,thecontourdia-gramsofFig.9(a)indicatethattheincreaseinVAdosagereducesthemini-slumpwhiletheplatecohesionmeterincreases.Forexample,formini-slumpof90mm,amixgroutwith0.6%ofSPand0.02%ofVAcanen-surethe uidityof90mm.TheincreaseinVAdosageto0.042%resultedinareductionofmini-slumpto75mm.However,byincreasingtheSPfrom0.6%to0.97%,themini-slumpcanbere-establishedto90mm.Forthesamemix,with0.6%ofSPand0.02%ofVA,thein-creaseinVAdosageto0.042%increasedtheplateco-hesionmeterfrom0.9to1.4mm.Theplatecohesionmeterc …… 此处隐藏：10466字，全部文档内容请下载后查看。喜欢就下载吧 ……