Hindawi Publishing Corporation Advances in Materials Science and Engineering Volume 2014, Article ID 970298, 12 pages http://dx.doi.org/10.1155/2014/970298 Research Article Influence of Styrene-Acrylic Ester Dispersion on the Early Hydration of Cement RuWangandXiaoxinShi KeyLaboratoryofAdvancedCivilEngineeringMaterialsofMinistryofEducation,SchoolofMaterialsScienceandEngineering, TongjiUniversity,4800Cao’anRoad,Shanghai201804,China CorrespondenceshouldbeaddressedtoRuWang;[email protected] Received20May2014;Accepted16July2014;Published11August2014 AcademicEditor:JaehwanKim Copyright©2014R.WangandX.Shi.ThisisanopenaccessarticledistributedundertheCreativeCommonsAttributionLicense, whichpermitsunrestricteduse,distribution,andreproductioninanymedium,providedtheoriginalworkisproperlycited. Early hydration of cement in the presence of styrene-acrylic ester (SAE) dispersion was investigated, and the hydration heat, hydrationdegree,andhydrateswereanalyzedusingisothermalcalorimeter,XRD,andESEM.TheresultsshowthatSAEdispersion prolongstheinductionperiod,postponesandshortenstheacceleratingperiod,andinhibitsthedeceleratingandstableperiodsof cementhydration.ThehydrationheatandhydrationdegreeofcementinthepresenceofSAEdispersionarelessthanthoseofthe control.SAEdispersioninhibitstheformationofC4AH13andthusAFt,andmoreSAEdispersionbringsstrongerinfluence,butit enhancesthestabilityofAFt.AFtgenerationduringtheearlyhydrationperiodiscontrolledgraduallybythereactionofC4AH13 generationwithincreasingSAEdispersion,butthisiscontrolledbythereactionofC4AH13 consumptionforthecontrolpaste. Besides,SAEdispersionretardsandinhibitstheformationofCHandC-S-Handalsochangestheirmorphology. 1.Introduction Differentpolymershavevariousfunctionsonthecement hydration. Some researches [7, 8] found that polyvinyl It is well known that polymers can improve the toughness, alcohol (PVA) or other water-soluble polymers could slow bond strength, impermeability, frost resistance, and many down the early hydration of cement. Pique´ et al. [9] found physicalpropertiesofthecement-basedmaterials[1–5].That thatPVAprolongedcementhydrationbecausethegelformed iswhypolymer-modifiedcementmortarisbeingmoreand by PVA hinders cement hydration. Zhang and Wang [10] morewidelyusedinmanyapplicationssuchastileadhesives, thoughthydroxyethylmethylcellulose(HEMC)retardedthe frontagecoatings,coverings,andrepairmortar.Commonly, hydrationofcementinearlyagesbecauseoftheinteractions applicationofcement-basedmaterialresultedfromitsprop- betweenHEMCandthecementhydratesbuthaslittleeffect erty, whereas the property is related with the structure on cement hydration after the decelerating period. Betioli which depends mostly on the cement hydration. In order et al. [11, 12] found that HMEC could greatly prolong the to develop more advantages of polymer-modified cement- induction period of cement hydration but EVA only has a basedmaterials,manyinvestigationshavebeenconductedto very slight influence on the same period. R. Wang and P. figureoutthehydrationmechanismofcementinthepresence M. Wang [13] observed that SBR dispersion and powder of polymers. At present, styrene-butadiene rubber (SBR), acceleratedtheformationofAFtwithin28daysandgreatly styrene-acrylicestercopolymer(SAE),ethylene-vinylacetate inhibitCHwithin3days.Yangetal.[14]suggestedthatSBR copolymer(EVA),polyacrylicester(PAE),andvinylacetate ledtodenserandmorerefinedmicrostructureofthecement and versatate copolymer (VA/VeoVa) are widely used in mortar after 28 days, which was also found to promote the polymer-modifiedcement-basedmaterialsinChina.There- formationofAFtandfacilitatechloridebinding.Theresearch fore, it is important to research the physical and chemical of Wang et al. [15] showed that SAE redispersible powder influencesofthesepolymersoncementhydrationduetotheir acceleratestheformationofAFtandenhancesitsstabilityand diversestructuresandphysicalproperties[6]. restrainsCHcontentwithin28days.Ithasalsobeenfound 2 AdvancesinMaterialsScienceandEngineering Table1:ChemicalcompositionoftheP⋅II52.5Portlandcement(%byweight). CaO SiO Al O Fe O MgO SO K O Na O TiO f-CaO 2 2 3 2 3 3 2 2 2 63.72 21.24 6.35 3.40 1.28 2.22 0.62 0.38 0.32 0.28 Table2:MineralcompositionoftheP⋅II52.5Portlandcement(%byweight). C S C S C A C AF CaSO 3 2 3 4 4 58.29 17.12 9.77 10.58 3.96 that the addition of ethylene/lauric acid vinyl ester/vinyl after which they were ground to powders. Samples for chloridecopolymerpostponedtheformationofAFt,CH,and morphology observation using ESEM needed no special C-S-H gel and decreased their content greatly within 1 day treatment,andonlyasmallblockfromthecenterofthecured [16].Silvaetal.[17]researchedthatEVAdispersionpromoted samplewasrequired. thegenerationofAFtanddeclinedCHcontentwithin28days 2+ duetothechemicalreactionofCa withEVA. 2.3. Test Methods. The heat evolution of cement hydration Frompreviousresearches,itcanbefoundthatpolymers wasmeasuredwithSwedenThermalmatTAMAir08isother- havestronginfluencesonthehydrationofcementaswellas malcalorimeter.Thetestingtimeisaslongas3daysanddata hydrates,especiallytheearlyperiods.Thoughsomevaluable isrecordedeveryminute. conclusions have been achieved through the researches, it XRDanalysiswasconductedusingaRigakuD/max2550 is still hard to form a systematic mechanism of the whole X-raydiffractometerwithgraphite-monochromatizedCuK𝛼 cementhydrationprocessusingpresentresults,especiallyfor radiation generated at 40kV and 200mA. Time-fixed step the early hydration. Therefore, this paper will research the scanning was carried out, with a step length of 0.02∘, a 4- earlyhydrationofcementinthepresenceofSAEdispersion, secondsettletimeforeachstep,andascanningrangeof8∘– which is a widely used economic polymer and was found 13∘and17∘–19∘. good at reducing the shrinkage, improving the fracture TheQuanta200FESEMwasusedinthisinvestigationto resistance and increasing the bending and tensile strengths observethemicromorphology. of cement mortar [18, 19]. The functionmechanism of SAE dispersionintheearlyhydrationofcementwillbediscussed 3.ResultsandDiscussions from the point of hydration kinetics in intensive hydra- tion time. The isothermal calorimeter, X-ray diffractometer 3.1.HeatEvolution. Heatevolutionisanimportantmethod (XRD), and environmental scanning electron microscope tocharacterizethecementhydrationprocessandthehydra- (ESEM)wereusedinthisinvestigation. tion heat mainly comes from the reactions of the cement. Figure1 shows the heat evolution rate of cement hydration 2.Experiment withandwithoutSAEdispersion.Theheatevolutionrateof allthecementpastesincreasesimmediatelyaftermixingwith 2.1. Raw Materials. Materials used included P⋅II 52.5 Port- waterandreachesamaximumafter3or4minutesandthen land cement, styrene-acrylic ester (SAE) dispersion, and decreases gradually with the time prolongation. It is found deionizedwater.Thechemicalandmineralcompositionsof thatSAEdispersionhaslittleeffectontheveryinitialperiod the cement are shown in Tables 1 and 2. The properties of ofhydration.However,itdoesprolongtheinductionperiod styrene-acrylicdispersionaredisplayedinTable3. of cement hydration from 0.9 hours of the control paste to about1.6,2.3,2.5,and2.6hoursofthepastesatthe𝑚𝑝/𝑚𝑐of 2.2. Preparation of Specimens. The water/cement ratio by 5%,10%,15%,and20%,respectively(Figure1(a)).Itindicates mass(𝑚𝑤/𝑚𝑐)ofallthesamplesinthisexperimentwaskept thatSAEdispersionprolongstheinductionperiodofcement at0.4.SAEdispersion(onlysolidpartinthedispersionwas hydration. The more the SAE dispersion is, the longer the calculatedandthewaterinthedispersionwascalculatedinto inductionperiodlasts. watertocementratio)/cementratiosbymass(𝑚𝑝/𝑚𝑐)were As shown in Figure1(b), SAE dispersion amount has 0%, 5%, 10%, 15%, and 20%. Specimens to be tested were prominent influence on the accelerating period of cement prepared by mixing the SAE dispersion with water firstly hydration. The more the SAE dispersion is, the shorter this and then adding cement. All specimens were cured at the periodis.Theacceleratingperiodforthecontrolpastelasts environmentof20∘C/RH90±5%todesignedages. about 10 hours while it keeps about 7.5, 5.8, 5.6, and 4.5 After curing, samples for XRD analysis were taken at a hours for the cement pastes at the 𝑚𝑝/𝑚𝑐 of 5%, 10%, 15%, depthofmorethan1mmfromthesurfacesofthespecimens, and20%,respectively.Besides,thecorrespondingexothermic broken into pieces, and immersed in the ethyl alcohol to peakalsodecreasessharplywiththegrowingSAEdispersion. stop the cement hydration. The ethyl alcohol was replaced ItisknownthattheC-S-HgelandCHfromthehydrationof everydaylastingaslongasoneweek.Thesampleswerethen C3Smainlygrowintheacceleratingperiodandthisperiod ∘ vacuum-oven-dried at 45 C until their mass was constant, is decided by the chemical reactions. Therefore, it greatly AdvancesinMaterialsScienceandEngineering 3 Table3:Propertiesofstyrene-acrylic(SAE)dispersion. Solidcontent(%) Averageparticlesize(𝜇m) Viscosity(mPa⋅s) pHvalue Lowestfilm-formingtemp.(∘C) Glasstransitiontemp.(∘C) 57 0.2 300–750 7.0–8.5 1 −6 3.5 3.5 3.0 3.0 g) g) W/ 2.5 W/ 2.5 m m n ( n ( utio 2.0 utio 2.0 ol ol v v at e 1.5 at e 1.5 he he of 1.0 of 1.0 ate ate R R 0.5 0.5 0.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 0 12 24 36 48 60 72 Time (hour) Time (hour) mp/mc: mp/mc: 0% 15% 0% 15% 5% 20% 5% 20% 10% 10% (a) (b) Figure1:Rateofheatevolutionofcementhydrationindifferent𝑚𝑝/𝑚𝑐. demonstrates that SAE dispersion inhibits the chemical the cement hydration. Here is a significant decline of the reactionsandthusthehydrationofC3S. hydrationdegreewhenthe𝑚𝑝/𝑚𝑐 increasesfrom0to15%. In the decelerating and stable periods (Figure1(b)), the However,thedecreasingdegreeisnotbiganymorewhenthe heatevolutionrateofmostpasteswithSAEdispersionisless 𝑚𝑝/𝑚𝑐 increasesfrom15%to20%.Thisstatesthatanexcess than that of the control paste within 3 days and the rate is amount of SAE dispersion when the 𝑚𝑝/𝑚𝑐 is higher than declining with the increasing 𝑚𝑝/𝑚𝑐. According to cement 15%doesnotchangethecementhydrationsignificantlyany hydrationtheory,thetotalhydrationduringthedecelerating more.Consider and stable periods is controlled by the ions diffusion speed 𝐻(𝑡) 𝛼(𝑡)= , andAFtalsotendstotransformtoAFminthisperiod.So,it 𝐻 𝑐 canbeconcludedthattheadditionofSAEdispersionslows downtheionsdiffusionspeedduringtheseperiodsbecause 𝐻𝑐 = 500𝑤(C3S)+260𝑤(C2S)+866𝑤(C3A) (1) oftheabsorptionofSAEdispersiononcementparticlesand formed polymer film, which will be shown later by ESEM +420𝑤(C4AF)+624𝑤(SO3)+1186𝑤(f-CaO) observationsinthepaper. +850𝑤(MgO), Figure2exhibitsthehydrationheatofcementindifferent 𝑚𝑝/𝑚𝑐.Itiseasytoseethat,withmoreSAEdispersioninthe where 𝛼(𝑡) is hydration degree at 𝑡 time, 𝐻(𝑡) is cement cementpaste,thehydrationheatislessandless,showingthe hydrationheatforunitmassofcementat𝑡time(J/g),𝐻𝑐 is negative effect of SAE dispersion on the cement hydration. completecementhydrationheatforunitmassofcement(J/g), Table4isthehydrationdegreeofcementindifferent𝑚𝑝/𝑚𝑐. and𝑤isthemassfractionofthemineraloroxideincement. The hydration degree is calculated according to formula (1) From the heat evolution analysis, it can be drawn that [20].Thecompletecementhydrationheatforunitmassofthe SAE dispersion not only retards the cement hydration but usedcementis493J/gbasedonTables1and2.Thehydration alsoinhibitsitwithin3days. degree of all cement pastes grows with the hydration time indicating that hydration reactions happen continuously 3.2.HydratesofCalciumAluminate. Researchingthecement during the early 3 days. In addition, the hydration degree hydratesishelpfulforunderstandingthehydrationprocess. with increasing SAE dispersion is less and less in the same The hydrates of calcium aluminate are investigated using age showing the retardation effect of SAE dispersion on XRD analysis. XRD patterns of cement pastes with SAE 4 AdvancesinMaterialsScienceandEngineering 300 250 at (J/g) 200 e n h 150 o ati dr 100 y H 50 0 0 12 24 36 48 60 72 Time (hour) mp/mc: 0% 15% 5% 20% 10% Figure2:Hydrationheatofcementindifferent𝑚𝑝/𝑚𝑐. Table4:Hydrationdegreeofcementindifferent𝑚𝑝/𝑚𝑐(%). butinhibitsitathigher𝑚𝑝/𝑚𝑐;inrelativeolderagesofthe experiment,forallused𝑚𝑝/𝑚𝑐theSAEdispersionpromotes Hydrationtime(hours) 12 24 36 48 60 72 the AFt content. The more AFt content in the modified 𝑚 /𝑚 𝑝 𝑐 pastesintheolderagescanbeexplainedthatSAEdispersion 0% 21 33 39 42 45 48 enhances the stability of AFt, inhibiting the transformation 5% 15 26 32 36 39 42 from AFt to AFm. More SAE dispersion means stronger 10% 13 21 25 28 31 33 enhancementofthestability.Thisisbeneficialtothevolume stabilityofcement-basedmaterial. 15% 13 19 22 24 26 28 20% 13 19 22 23 25 26 Another hydrate of calcium aluminate, C4AH13, is the hydrate from the reaction of C3A and Ca(OH)2(CH) like (2) and it is only observed in some pastes and specific ages because it is also involved in the generation of AFt as dispersion in different 𝑚𝑝/𝑚𝑐 at 2𝜃 range of 8∘∼13∘ are (3), showing that it is an intermediate hydrate. But some ∘ displayedinFigure3.Thediffractionpeakatabout9.1 relates interesting phenomena were found during the research. In to the diffraction of (100) crystal plan∘e of AFt [21]. The Figure3,thediffractionpeakofC4AH13 onlyappearsinthe appearingdiffractionpeakatabout11.6 iscorrespondingto followingcases:controlpasteafter10minutes,1,4,6,and8 C4AH13.The∘diffractionpeakof(020)crystalplaneofC4AF hours;modifiedpasteatthe𝑚𝑝/𝑚𝑐of5%after10minutes,1, at about 12.2 is evident in all pastes, which shows the slow 4,6,and8hours;modifiedpasteatthe𝑚𝑝/𝑚𝑐 of10%after hydrationofit.ThereisonlyslightlypromotioneffectofSAE 1,4,6,8,and12hours;modifiedpasteatthe𝑚𝑝/𝑚𝑐 of15% dispersiononC4AFhydration. after6hours.Thepeakhasneverbeenseeninthemodified ThesoftwareMDIJade6.5isusedtoanalyzethespecial paste at the 𝑚𝑝/𝑚𝑐 of 20%. C4AH13 content of the control diffractionpeaksofAFtandC4AH13 quantitativelyandthe paste increases to the highest and then decreases. It means results are listed in Tables 5 and 6. The integrated intensity thegenerationofC4AH13 iseasierthantheconsumptionof of AFt has different changing trend with the 𝑚𝑝/𝑚𝑐 with it during this period and AFt content is controlled by the hydration time change. After 10 minutes, AFt content of all reactionin(3).WhenaddingSAEdispersion,theappearance pastes with SAE dispersion is less than that in the control ofC4AH13peakisgraduallyputoffto1hourand6hoursor paste but the difference is not significant. With hydration evenhardtobeobservedwiththe𝑚𝑝/𝑚𝑐increasing.Evenif time passing by, AFt content in the pastes with 𝑚𝑝/𝑚𝑐 of the C4AH13 peaks of the paste at the 𝑚𝑝/𝑚𝑐 of 5% and the 5% and 10% grows more than the control one after 1 hour. controlpasteappearsimultaneously,thepeakintensityofthe When the 𝑚𝑝/𝑚𝑐 is 15%, AFt content becomes more than modifiedpasteisweakerthanthatinthecontrol.Thisshows thatinthecontroloneafter1day.After3days,AFtcontent thatthespeedofreactionin(2)isslowerlittlebylittleuntil in all the modified pastes is higher than that in the control thegenerationofC4AH13isslowerthantheconsumptionof paste.ItexpressesthatintheearlyagesoftheexperimentSAE itinthereactionin(3)atlarger𝑚𝑝/𝑚𝑐,atwhichtimetheAFt dispersion promotes AFt content when the 𝑚𝑝/𝑚𝑐 is lower contentiscontrolledbythereactionin(2)insteadofthatin AdvancesinMaterialsScienceandEngineering 5 1600 1600 −1·Intensity (countss)111468024000000000000 AFt Cummmmmrepppppd///// mmmfmmocccrcc===1==010152m0%5%0%%Ci%n4AHC134AF −1·Intensity (countss) 111468024000000000000 AFt Curemmmmdmpp pfpp//o///mmmrmm1ccccch=====o011u25%05r0%%%C%4AH1C34AF 200 200 8 9 10 11 12 13 8 9 10 11 12 13 2𝜃(deg) 2𝜃(deg) 1600 Cured for4hoursC4AH13 1600 AFt Cured for6hours −1·)Intensity (countss111468024000000000000 AFt mmmmmppppp/////mmmmmccccc=====01125%050%%%% C4AF −1·Intensity (countss)111468024000000000000 mmmmmppppp/////mmmmmccccc=====05112%%050%%%C4AH13C4AF 200 200 8 9 10 11 12 13 8 9 10 11 12 13 2𝜃(deg) 2𝜃(deg) 1600 1600 AFt Cured for8hours C4AF AFt Cured for12hours C4AF 1400 mp/mc=0% C4AH13 1400 mp/mc=0%C4AH13 ) ) −1 1200 −1 1200 ·ntss1000 mp/mc=5% ·ntss1000 mp/mc=5% ensity (cou 680000 mmpp//mmcc==1105%% ensity (cou 680000 mmpp//mmcc==1105%% nt nt mp/mc=20% I 400 mp/mc=20% I 400 200 200 8 9 10 11 12 13 8 9 10 11 12 13 2𝜃(deg) 2𝜃(deg) 1600 1600 AFt Cured for1day C4AF AFt Cured for3days C4AF −1·)Intensity (countss111468024000000000000 mmmmmppppp/////mmmmmccccc=====05112050%%%%% −1·Intensity (countss)111468024000000000000 mmmmmppppp/////mmmmmccccc=====01125%500%%%% 200 200 8 9 10 11 12 13 8 9 10 11 12 13 2𝜃(deg) 2𝜃(deg) Figure3:XRDpatternsofcementpasteswithSAEdispersionat2𝜃rangeof8∘–13∘. 6 AdvancesinMaterialsScienceandEngineering Table5:TheintegratedresultsofXRDpeakofAFtinthepasteswithSAEdispersion. Curingtime 𝑚𝑝/𝑚𝑐 𝑑(A˚) 𝐼max(counts⋅s−1) 𝐼integ(counts⋅s−1) 𝑅 0% 9.696 374 2396 1.00 5% 9.709 255 1623 0.72 10minutes 10% 9.668 311 1983 0.91 15% 9.606 319 2041 0.98 20% 9.704 222 1411 0.71 0% 9.712 461 2783 1.00 5% 9.675 618 3977 1.50 1hour 10% 9.688 471 3023 1.19 15% 9.623 374 2293 0.95 20% 9.525 139 975 0.42 0% 9.762 320 2043 1.00 5% 9.671 473 3452 1.77 4hours 10% 9.667 414 2654 1.42 15% 9.723 276 1832 0.98 20% 9.627 170 1072 0.64 0% 9.692 495 3192 1.00 5% 9.651 825 5320 1.75 6hours 10% 9.565 374 3386 1.17 15% 9.687 459 2672 0.96 20% 9.629 194 1226 0.46 0% 9.795 596 3882 1.00 5% 9.71 742 4783 1.29 8hours 10% 9.688 509 4362 1.24 15% 9.647 321 2527 0.60 20% 9.585 167 1151 0.36 0% 9.711 814 4073 1.00 5% 9.669 1091 7050 1.82 12hours 10% 9.709 672 6032 1.63 15% 9.626 533 3426 0.97 20% 9.647 301 1921 0.57 0% 9.711 649 3967 1.00 5% 9.711 783 6183 1.64 1day 10% 9.688 714 5971 1.66 15% 9.667 660 5523 1.60 20% 9.646 342 2186 0.66 0% 9.731 572 3594 1.00 5% 9.667 1048 6772 1.98 3days 10% 9.731 1064 6439 1.97 15% 9.646 960 6202 1.98 20% 9.625 586 3766 1.26 𝑑:interplanarspacing;𝐼max,𝐼integ:intensitiesofXRDpatternformaximumandintegrate;𝑅=𝐼integ(1+𝑚𝑝/𝑚𝑐)/(𝐼integ)control. (3) in the control. It can be concluded that SAE dispersion 3.3.HydratesofCalciumSilicate. CHisanimportanthydrate changed the controlling factor of AFt generation. Consider ofcalciumsilicateofthecement,whichcanreflectthehydra- thefollowing: tion of calcium silicate to some extent, so the quantitative analysisofitiscarriedout.CHcancomefromthereactions seenin(4)to(5).ButitismainlythehydrateofC3Swithin C3A+CH+12H=C4AH13 (2) 3 days in (4) because C2S has an extremely slow hydration rate during this period. Figure4 gives XRD patterns of C4AH13+3CSH2+14H=C3A⋅3CS⋅H32+CH (3) cement pastes with SAE dispersion in different curing ages AdvancesinMaterialsScienceandEngineering 7 Table6:TheintegratedresultsofXRDpeakofC AH inthepasteswithSAEdispersion. 4 13 Curingtime 𝑚𝑝/𝑚𝑐 𝑑(A˚) 𝐼max(counts⋅s−1) 𝐼integ(counts⋅s−1) 𝑅 0% 11.539 336 2146 1.00 10minutes 5% 11.621 198 1250 0.62 0% 11.559 708 4676 1.00 1hour 5% 11.600 532 3385 0.79 10% 11.580 164 933 0.22 0% 11.539 941 6045 1.00 4hours 5% 11.598 605 3876 0.68 10% 11.541 122 764 0.14 0% 11.539 180 1140 1.00 5% 11.601 522 3353 3.05 6hours 10% 11.702 195 1933 1.19 15% 11.582 308 1967 1.97 0% 11.619 127 794 1.00 8hours 5% 11.600 498 3195 4.12 10% 11.582 118 739 1.02 12hours 10% 11.618 106 660 — 𝑑:interplanarspacing;𝐼max,𝐼integ:intensitiesofXRDpatternformaximumandintegrate;𝑅=𝐼integ(1+𝑚𝑝/𝑚𝑐)/(𝐼integ)control. and different 𝑚𝑝/𝑚𝑐 at 2𝜃 range of 17∘∼19∘. The special 3.4. Morphology Observation. ESEM is a very useful and diffraction peak at about 18∘ is ascribed to the diffraction visual method to observe the morphology of the cement of (001) crystal plane of CH. The software MDI Jade 6.5 is hydrateswithoutdestroyingitsstructure.Ithasbeenproved alsoappliedtointegratetheintensityofthediffractionpeak thatSAEdispersionhassomeeffectsonthehydrationprocess quantitativelyandtheresultsarelistedinTable7.InFigure4, and hydrates content. Some of these influences can also be thereisnearlynoCHdiffractionpeakafter10minutesand observed by ESEM more vividly. Figure5 shows the ESEM 1 hour, which is because it is in the initial and induction imagesofcementpastesintheabsenceandpresenceofSAE periods of cement hydration proved by the heat evolution dispersion. Some regular and irregular shape hydrates are 2+ measurement.Duringthisperiod,theconcentrationofCa observed on the surface of cement particles in the control islessthanthesaturatedlevelandCHishardtoprecipitate. pasteafter10minutes(Figure5(a)).Mostoftheregularshape Even if there is some CH, it is quickly consumed in the hydrates,coveredonthesurfaceofthecement,belongtoAFt generationofC4AH13.However,thediffractionpeakofCH whichwerealsodetectedusingXRD.Atthesametime,itis startstoemergeafter6hoursandthecontentofCHincreases clearthatSAEdispersionparticlescovernotonlythesurface graduallywiththeprolongationofhydrationtimewhatever ofthecementparticlesbutalsothespaceamongthecement withorwithoutSAEdispersion.Itmeansthatthehydration particlesinthepastewithSAEdispersion(Figure5(b)). degree of C3S of all pastes grows with time passing. The After1hour,muchlamellarC4AH13 canbeobservedin CH peak of the control paste appears after 6 hours and the control paste (Figure5(c)), showing that the hydration the earliest obvious appearance of CH peak in the pastes of C3A happened greatly at this time. While adding SAE with SAE dispersion is after 12 hours, showing that SAE dispersion,itiseasytoseethatSAEparticlesonthesurface dispersionretardsthehydrationofC3Sandthiscanalsobe ofthecementbutlamellarC4AH13 tendtogrowaroundthe provedbythedelayedappearingtimeofacceleratingperiod spaceamongthecementparticles(Figure5(d)).TheC4AH13 inthemodifiedpastesintheheatevolutioncurves.Whatis contentnowismuchlessthanthatinthecontrolonewhich more,CHcontentdecreaseswiththeincreasing𝑚𝑝/𝑚𝑐.For isinaccordancewithXRDanalysisresults. example,thecontentofCHatthe𝑚𝑝/𝑚𝑐of5%,10%,15%,and After 6 hours, C-S-H gel is more obvious in the con- 20%is0.89,0.69,0.34,and0.24timesthatofthecontrolpaste trol paste indicating it has been in the accelerating period after3days.ItindicatesthattheadditionofSAEdispersion of cement hydration and the shape of it is short cluster restrains the hydration of C3S which is in accordance with theresultsofheatevolutionmeasurement,thatis,theshorter (Figure5(e)).C4AH13ishardtofind,meaningthatmosthas beenconsumed.Onthecontrary,thereisnearlynoobvious accelerating period and smaller corresponding exothermic peak. Therefore, the delayed formation of CH and its less C-S-HgelinthepastewithSAEdispersionbutsomeC4AH13 exists(Figure5(f)).Whatismore,theSAEdispersionparti- content in early ages will result in the slow hardening and clesonthesurfaceofcementparticlesbecomenotclearand strengthdevelopmentofthecement-basedmaterial: formfilmstructurepartly. C3S+𝑛H=C-S-H+(3−𝑥)CH (4) The C-S-H gel continues to develop and cluster-like gel becomes the main component after 12 hours. The outline C2S+𝑚H=C-S-H+(2−𝑥)CH (5) of it is better than that after 6 hours in the control paste 8 AdvancesinMaterialsScienceandEngineering ×103 ×103 12 12 Cured for10min Cured for1hour 10 mp/mc=0% 10 mp/mc=0% −1) 8 mp/mc=5% −1) 8 mp/mc=5% s s ·nts ·nts y (cou 6 mp/mc=10% y (cou 6 mp/mc=10% ntensit 4 mp/mc=15% ntensit 4 mp/mc=15% I I 2 2 mp/mc=20% mp/mc=20% 0 0 17.0 17.5 18.0 18.5 19.0 17.0 17.5 18.0 18.5 19.0 2𝜃(deg) 2𝜃(deg) ×103 ×103 12 12 Cured for6hours Cured for12hours CH CH 10 mp/mc=0% 10 mp/mc=0% −1·Intensity (countss) 864 mmmppp///mmmccc===11505%%% −1·Intensity (countss) 864 mmmppp///mmmccc===51150%%% 2 mp/mc=20% 2 mp/mc=20% 0 0 17.0 17.5 18.0 18.5 19.0 17.0 17.5 18.0 18.5 19.0 2𝜃(deg) 2𝜃(deg) ×103 ×103 12 12 Cured for1day CH Cured for3days CH 10 10 −1) 8 mp/mc=0% −1) 8 ·untss mp/mc=5% ·untss mp/mc=0% ensity (co 64 mp/mc=10% ensity (co 64 mmpp//mmcc==510%% Int 2 mp/mc=15% Int 2 mp/mc=15% mp/mc=20% mp/mc=20% 0 0 17.0 17.5 18.0 18.5 19.0 17.0 17.5 18.0 18.5 19.0 2𝜃(deg) 2𝜃(deg) Figure4:XRDpatternsofcementpasteswithSAEdispersionat2𝜃rangeof17∘–19∘. (Figure5(g)).WhenaddingSAEdispersion,cluster-likeC-S- timeisdelayedfrom6to12hourscomparedwiththecontrol HgelalsoappearswhichreplacesSAEparticlesandC4AH13 one, which confirms the effect trend of SAE dispersion on present after 6 hours, and meantime some polymer films thecalciumsilicatehydratesformationanalyzedbyXRD. are observed on the surface of the hydrates (Figure5(h)). The C-S-H gel gets closer with some rod-like AFt and However,theC-S-Hgelcontentismuchlessanditsappearing these hydrates mutually penetrate to form a composite AdvancesinMaterialsScienceandEngineering 9 Table7:TheintegratedresultsofXRDpeakofCHinthepasteswithSAEdispersion. Curingtime 𝑚𝑝/𝑚𝑐 𝑑(A˚) 𝐼max(counts⋅s−1) 𝐼integ(counts⋅s−1) 𝑅 0% 4.935 1793 11619 1.00 5% 4.934 850 5488 0.50 6hours 10% 4.887 484 3107 0.29 15% 4.925 433 2775 0.27 20% 4.919 224 1425 0.15 0% 4.934 2944 19117 1.00 5% 4.924 1568 10151 0.56 12hours 10% 4.929 1237 8002 0.46 15% 4.903 1512 6794 0.41 20% 4.904 875 5651 0.35 0% 4.935 11123 72423 1.00 5% 4.930 5482 35650 0.52 1day 10% 4.919 3660 23780 0.36 15% 4.913 2246 14568 0.23 20% 4.908 2165 14042 0.23 0% 4.935 13424 87422 1.00 5% 4.913 11530 75080 0.89 3days 10% 4.925 9087 59146 0.69 15% 4.913 4044 26276 0.34 20% 4.903 2777 18023 0.24 𝑑:interplanarspacing;𝐼max,𝐼integ:intensitiesofXRDpatternformaximumandintegrate;𝑅=𝐼integ(1+𝑚𝑝/𝑚𝑐)/(𝐼integ)control. microstructureinthecontrolpasteafter1day(Figure5(i)). theveryinitialperiodofcementhydrationbutprolongsthe But SAE dispersion changes the morphology of C-S-H gel, induction period, postpones and shortens the accelerating making it become curly in the modified paste (Figure5(j)). period, and inhibits the hydration during the decelerating The C-S-H gel is also inserted by different hydrates such as andstableperiods.Thehydrationheatandhydrationdegree AFtbutitisnoteasytodistinguish.Somepolymerfilmscan ofcementwithSAEdispersionarelessthanthecontrolones beseenclearly. within 3 days. The bigger 𝑚𝑝/𝑚𝑐 is, the less hydration heat Whenthehydrationtimelastsaslongas3days,thereis andhydrationdegreeare. nogreatchangeofthestructureinthecontrolpastecompared SAEdispersionhasbiginfluenceontheformationofthe withtheoneat1dayexceptthatthewholestructurebecomes alittlemorecompact(Figure5(k)).However,inthemodified hydrates.ItinhibitstheformationofC4AH13 andthusAFt, paste AFt is more evident after 3 days than that after 1 day and more SAE dispersion brings stronger influence, but it (Figure5(l)).Inaddition,AFtandC-S-Hgelpenetratewith enhancesthestabilityofAFt,makingitscontenthigherthan eachothertodevelopthewholestructure.TheC-S-Hgeland thatinthecontrolpasteatrelativelylongerages.AFtgener- AFtinthemodifiedpastelookthickerandstrongercompared ationiscontrolledgraduallybythereactionofC4AH13 gen- withthoseinthecontrolpaste. erationwithincreasingSAEdispersion,butthisiscontrolled Another big difference between the modified paste and bythereactionofC4AH13consumptionforthecontrolpaste. the control paste is the content and morphology of CH. It Besides,SAEdispersionretardsandinhibitstheformationof is easy to find CH in the control paste after 3 days and CHandC-S-Handalsochangestheirmorphology.Itmakes its shape is very clear with an apparent sheet structure theC-S-HandAFtlookthickerandstrongercomparedwith (Figure5(m)). Though sheet-like CH also appears in the thoseinthecontrolpasteafter3days,andthesurfaceofthe pastewithSAEdispersion,itscontentislessanditssurface CHbecomesrougherwithsomeotherhydratesonit. is rougher with some hydrates on it (Figure5(n)). This attributestotheeffectoftheSAEdispersion. 4.Conclusions ConflictofInterests SAE dispersion does have effects on the early hydration of The authors declare that there is no conflict of interests cement. The addition of SAE dispersion has little effect on regardingthepublicationofthispaper. 10 AdvancesinMaterialsScienceandEngineering AFt SAE particle (a) Controlpaste,10minutes (b) 𝑚𝑝/𝑚𝑐of10%,10minutes C4AH13 C4AH13 SAE particle (c) Controlpaste,1hour (d) 𝑚𝑝/𝑚𝑐of10%,1hour C–S–H gel C4AH13 SAE film (e) Controlpaste,6hours (f) 𝑚𝑝/𝑚𝑐of10%,6hours C–S–H gel C–S–H gel (g) Controlpaste,12hours (h) 𝑚𝑝/𝑚𝑐of10%,12hours Figure5:Continued.