Influence of mix proportions on rheology of cement grouts co(2)

738L.Svermovaetal./Cement&ConcreteComposites25(2003)737–749

compressivestrengtharehighlyin uencedbywater/binderratio(W/B),VAandSPdosages[7–9].Thewash-outresistanceimprovesasVAcontentincreasesforagivenW/BdespitethegreaterdosageofSPnecessarytomaintain uidity[7–9].ForagivenW/Bof0.40,anin-creaseinmini-slumpduetoagreaterdosageofSPcanincreasethewashoutmasslossandreduceresidualstrength,regardlessofthedosageofVA[9].Anoptimi-sationisthereforenecessarytoestablishabalancebe-tweenthedosagesofVAandSP,theW/Bratioandtheproportionofmineraladmixture(limestonepowder, yash,silicafume,etc.)toensuresuitable owandpene-trationandreducethebleeding.ThemixoptimisationofgroutoftennecessitatesseveraltrialbatchestoachieveabalancebetweenthemineralandchemicaladmixturesandW/Btoensuresuitable uidity,stabilityandme-chanicalproperties,someofwhichparametershaveoppositee ects.Forthisreasonthestatisticalmodellingapproachwasusedinordertoreducethenumberoftrialbatches.Nehdiandco-workers[11,12]reportedthatthelimestonemicro llerreplacementofcementslightlyincreasedtheyieldvalueofcementpasteanddecreaseditsplasticviscosity,whichimpliesbetterstabilityand owabilityofthecementpaste.However,increasingthelimestonemicro llercontentsreducedtheinducedbleedingofcementpasteonlyathighW/Bratiosanddidnotseemtohaveasigni cante ectatlowW/B[11,12].Theaimofthisstudyistoevaluatethee ectoftheW/B,thedosagesofSPandVA,andtheproportionoflimestonepowderreplacementofcementontherhe-ologicalpropertiesandthecompressivestrength(fc0)at7and28daysofgroutsusingastatisticaldesignapproachandanalysisofexperiments[13].Themini-slumptest,Marshcone,Lombardiplatecohesionmeter,inducedbleedingtest,andcoaxialrotatingcylinderviscometer

Table1

Mixproportionforgroutsusedinthetwo-levelfractionalfactorialdesign

Codedvalues

W/B

Levelsoffactors

1234567891011121314151617

)11)11)11)1100000.140.430.710.43)0.14

SP)1)111)1)11100000.000.330.440.33)0.56

LSP)1)1)1)1111100000.09)0.820.390.24)0.52

wereusedfortestingthebehaviouroffreshcementgrouts.Thecompressivestrengthsofgroutsat7and28daysofagewerealsomeasured.Theestablishedmodelscanidentifyparametersandthetwo-wayinteractionsthathavesigni cante ectontherheologicalpropertiesandcompressivestrengthofgrouts.Themodelscanbeusedtoevaluatethepotentialin uenceofadjustingmixvariablesongroutpropertiesrequiredtoensuresuc-cessfuldevelopmentofgrout.Suchsimulationcanfa-cilitatethetestprotocolneededtooptimizegroutwithagivensetofperformancecriteriathatcanbetriedinthelaboratory.

2.Statisticaldesignapproach

Thetechniqueofanalysisusedwasastatisticalanalysisoftheresultsobtainedfromasetofexperiments[13].Thistechniqueappliedtocementmaterialgroutcangivealotofinformationfromafewexperiments.A24À1fractionalstatisticalexperimentaldesign(2kÀ1¼8)wasusedtoevaluatethein uenceoftwodi erentlevelsforeachindependentvariableontherelevantgroutproperties.Fourkeyparameters(k¼4)thatcanhavesigni cantin uenceonmixcharacteristicsofcementgroutwereselectedtoderivemathematicalmodelsforevaluatingrelevantproperties.ThefourvariableswereW/B,dosagesofSPandVA,andproportionofLSPasreplacementofcement.Themodelledexperimentalre-gionconsistedofmixesrangingbetweencodedvariablesof)1toþ1.ThederivedstatisticalmodelsarevalidformixesmadewithrangesofW/Bof0.35–0.42,dosagesofVAof0.02–0.07%,bymassofbinder(or0.057–0.166%ofwater),SPof0.3–1.2%,bymassofbinder,andtheproportionofLSPfrom12to45%(Table1).Themodel

Actualvalues

VA

W/B

SP(%)

LSP(%)

VA(%)

)10.350.312.00.0210.420.312.00.0710.351.212.00.07)10.421.212.00.0210.350.345.00.07)10.420.345.00.02)10.351.245.00.021.042.12.45.00070.0385.075.28.500450.0385.075.28.500450.0385.075.28.500450.0385.075.28.50045)0.60)0.201.00)0.20)0.60

0.390.400.410.400.38

0.750.900.950.900.50

30.015.035.032.520.0

0.030.040.070.040.03

Centrepoints

Pointsofveri cation