Research Article Influence of Styrene-Acrylic Ester Dispersion on the Early Hydration of Cement

13 Pages·2015·5.62 MB·English

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.