research article preparation and stability of inorganic...

Research ArticlePreparation and Stability of Inorganic SolidifiedFoam for Preventing Coal Fires

Botao Qin12 Yi Lu2 Fanglei Li2 Yuwei Jia2 Chao Zhu2 and Quanlin Shi2

1 State Key Laboratory of Coal Resources and Mine Safety CUMT Xuzhou Jiangsu 221008 China2 Faculty of Safety Engineering China University of Mining and Technology Xuzhou Jiangsu 221116 China

Correspondence should be addressed to Botao Qin qbt2003163com

Received 14 March 2014 Revised 21 May 2014 Accepted 26 May 2014 Published 2 July 2014

Academic Editor Peter Chang

Copyright copy 2014 Botao Qin et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Inorganic solidified foam (ISF) is a novel material for preventing coal firesThis paper presents the preparation process and workingprinciple of main installations Besides aqueous foam with expansion ratio of 28 and 30min drainage rate of 13 was preparedStability of foam fluid was studied in terms of stability coefficient by varying water-slurry ratio fly ash replacement ratio of cementand aqueous foam volume alternatively Light microscope was utilized to analyze the dynamic change of bubble wall of foam fluidand stability principle was proposed In order to further enhance the stability of ISF different dosage of calciumfluoroaluminate wasadded to ISF specimens whose stability coefficient was tested and change of hydration products was detected by scanning electronmicroscope (SEM)The outcomes indicated that calcium fluoroaluminate could enhance the stability coefficient of ISF and compacthydration products formed in cell wall of ISF naturally the stability principle of ISF was proved right Based on above-mentionedexperimental contents ISF with stability coefficient of 95 and foam expansion ratio of 5 was prepared which could sufficientlysatisfy field process requirements on plugging air leakage and thermal insulation

1 Introduction

Coal fires are difficult persistent and costly problems world-wide in coal mining processes [1 2] They lead to seriousenvironmental issues safety problems and considerableeconomic losses [3] Meanwhile spontaneous combustionof coal and heat transfer occurs more frequently due tosubsidence and increased channels of air leakage in thegoaf Air leakage prevention and thermal insulation canlower effectively the spontaneous combustion risk of coal[4 5] Based on the various techniques for control andextinguishment of coal fires developed and applied over past60 years [6ndash8] materials with pore structure are drawinggrowing attention because of their characteristics involvingheat insulation fire resistance lightweight superior fluidityenvironmental friendliness and so on [9 10]

In this work a novel material ISF with high closedporosity and uniform pore distribution was prepared viamixing aqueous foam and composite slurry consisting offly ash cement and compound additives In this process of

preparation the following two points are worthy of consider-ation Firstly stable aqueous foam is required for ISF to plugair leakage in mining applications Furthermore the stabilityof foam may be affected by foam generator parameters sur-factants and their concentration [11] Selection of surfactantshas an impact on the properties of foam as it affects the sur-face tension and gas-liquid interfacial properties Secondlythe foam slurry after mixing is a three-phase system (gas-liquid-solid) which should be uniform and stable But fewscholars have studied the foam formation and stabilizationin this kind of system Current researches mainly focus onthe stabilization of two-phase foam (aqueous foam or otherliquid foam) [12] Just a few scholars such as Gonzenbachet al [13] Hunter et al [14] Sethumadhavan et al [15] andVijayaraghavan et al [16] carried out experimental studiesandmechanism analyses on solid particles stabilized aqueousfoam

In this paper as a first step we studied the preparationprocess of ISF and analyzed the working principles and theeffects of key devices As a next step the aqueous foam with

Hindawi Publishing CorporationAdvances in Materials Science and EngineeringVolume 2014 Article ID 347386 10 pageshttpdxdoiorg1011552014347386

2 Advances in Materials Science and Engineering

low drainage rate and high expansion ratio was preparedbased on sodium dodecyl sulfate (SDS) solution and mod-ified by the foam stabilizers such as cetrimonium bromide(CTAB) sodium chloride (NaCl) and lauryl alcohol (LA)Then the factors influencing the stability coefficient and foamexpansion ratio of ISF were investigated At last throughthe observation on drainage of the bubble wall and thehydration products accelerated by calcium fluoroaluminatethe stabilization mechanism of foam fluid was proposed

2 Experimental

21 Raw Materials Constituent materials are listed below

(1) Portland cement (PC) with the compressive strengthof 645MPa at 28 days conforming toBSEN 197-1 typeI cement [17]

(2) Fly ash (FA) with a median particle size of 35 120583m andloss on ignition (LOI) of 50 conforming to BS EN450 [18]

(3) Calcium fluoroaluminate (11CaO sdot 7Al2O3sdot CaF2) it

influences the rate of cement hydration leading to areduction in setting time

(4) Redispersible polymer powder (PP) it is a kind ofpolymeric powder which can be easily reemulsifiedin water to reform liquid emulsion with essentiallyidentical properties to the original emulsion

(5) Water (W) its percentage was fixed in order to satisfyboth the workability criterion and the controlled lowstrength materials (CLSM) recommendations for theinsulation materials [19]

(6) Lauryl sodium sulfate (SDS) Cetrimonium Bromide(CTAB) NaCl and lauryl alcohol (LA) They werediluted with water in different ratios

22 Preparation Process of ISF The basic preparation processcan be divided into three parts including mixing the com-posite slurry preparing aqueous foam andmixing compositeslurry accelerator and aqueous foam We admixed cementfly ash and redispersible polymer powder together and gotthe blend of these three basic raw materials Then partof water was injected into the blend and composite slurryformed under the work of stirrer The water-solid ratio wascontrolled slightly less than preset ratio At the same timethe rest of the water was used to dilute the surfactant Thenhigh pressure air was pumped into the foam generator andaqueous foam was produced The next procedure was to mixcomposite slurry with aqueous foam in a self-made mixerwith some compound additives added At last foam fluidwas produced and evolved into ISF at room temperatureThe specific preparation procedures of ISF are schematicallyshown in Figure 1 The main installations are shown inFigure 2

23 Test Procedure

231 Drainage Rate Test We chose the drainage rate to be 30minutes since aqueous foam was produced to reflect foamstability After generation of aqueous foam the initial foammass 119898 was measured immediately and then poured fullyinto a Buchner funnel A measuring cylinder was placedunder the Buchner funnel and the mass of liquid drainedfrom aqueous foam 119898

119889 was calculated every ten minutes

until 30 minutes Drainage rate 119889119905 can be expressed by

119889119905=119898119889

119898times 100 (1)

232 Stability Coefficient Test The test instrument was onecylindrical gauge whose inner diameter was 100mm andmeasuring rangewas 315mmThe test procedure is as follows(i) pour the fresh ISF into the test instrument and record theinitial height ℎ

0 (ii) measure the final height (ℎ

119894) when ISF

turns into solidification state The stability coefficient 120595 canbe calculated according to the following

120595 =ℎ119894

ℎ0

times 100 (2)

233 Foam Expansion Ratio Test Test procedure for foamexpansion ratio of aqueous foamor foamfluid is as follows (i)fill a container (volume and mass are known and designatedby 119881119888 119898119888 resp) with surfactant solution or cement slurry

weigh the total mass 119898119871 and calculate the density of

surfactant solution or cement slurry 120588119871 by (3) (ii) overfill the

aforementioned container with aqueous foam or foam fluidand strike off the excess foam weigh the total mass 119898

119865 and

calculate the density of aqueous foam or foam fluid 120588119865 by

(4) (iii) calculate the foam expansion ratio of aqueous foamor foam fluid 119864

119865 by (5) as follows

120588119871=119898119871minus 119898119888

119881119888

(3)

120588119865=119898119865minus 119898119888

119881119888

(4)

119864119865=120588119871

120588119865

(5)

234 Microscopy Observation The microstructure of aque-ous foam and ISF fluid were observed by a Nomarski-typephase contrast interferencemicroscope equipped with a digi-tal camera which can be used to take photomicrograph of thesamples and the foams A drop of sample was brought ontoa microscope slide and the structure of bubble was observedThe bubble wall of ISF was investigated by scanning electronmicroscopy (SEM) (FEI QuantaTM 250 SEM system) withthe size of test specimen being 10 times 10 times 10mm3 prism

235 Particle Contact Angle Measurement The water andsurfactant solution contact angle on the particles was mea-sured using the gravimetric version of theWashburnmethodThe method is based on measuring the penetration rate of

Advances in Materials Science and Engineering 3

Cement

PP

Fly ash

Blend (solids)

Water Surfactant

High pressure airSolutionStirrer

Composite slurry Accelerator Aqueous foam

Mixer

Foam fluid

Foam generator

ISF

Raw materialProcess productFinal productAccelerator

EquipmentWork flowMixingDelay

Figure 1 The schematic of the preparation of ISF

Flow meter

High pressure air

Pressure gauge

Solution

Solution pump

Slurry pump

Accelerator

Mixer

Foam fluid (ISF)

Foam generator

Figure 2 The main installations

a wetting liquid into a packed bed of particles which lead tothe following equation [20]

1198722= 119905 times120574LG1205752 cos 120579120583times11990311987821205762

2 (6)

where119872 is the measured mass of the penetrated liquid 119905 isthe penetration time 120574LG is the gas-liquid surface tension 120575is the liquid density 119878 is the cross-sectional area of the tube120576 is the void fraction of particles 120583 is the viscosity of liquid 119903is the mean radius 120579 is the contact angle

24 Test Design In order to investigate the influencingmech-anism of aqueous foam volume (FV) fly ash replacementfor cement (FA) and water-solid ratio (WS) on the stabilityof ISF we conducted tests on different specimens FV wascontrolled to vary from 2V to 10V with the increment being2V FA changed as 10 20 50 andWS increased from03 to 05with every difference quantity being 005 Accordingto this design we conducted 125 tests

3 Results and Discussion

31 The Key Devices To develop fine uniform and stableinorganic solidified foam the following two points deserveconsideration Firstly the foam generator should be able toproduce aqueous foam with uniform pore structure highexpansion ratio and a certain stabilization time Secondlyaqueous foam and composite slurry should contact thor-oughly and then form stable foam fluid during the mixingprocess in themixerThe schematic of key devices was shownin Figure 3

The main process of generating foams by the home-made foam generator is as follows once foaming agentsolution and high pressure air flow through the T-shapeconduit of foam generator the turbulent eddy is formedafter mixing and enhanced by the porous medium whichcan be composed of multilayer meshes powdered metal


Aqueous foam

Foam fluid

Composite slurryFoam fluid

Surfactant solution

High pressure air

DropletAqueous foam

The porosityincreases gradually

Composite slurry

Direction ofrotation

Mixing gradually

Porous mediumImpellers

Hollow spiral pipe

Aqueous foam outlet Helical blades

Foam generator Mixer

Figure 3 The schematic of foam generator and self-made mixer

or spherical glass particles causing greater pressure dropdue to their impediment The more homogenous and denseraqueous foam is produced from down to up as the porosityof porous medium increases stepwise The aqueous foamproduced by mechanical agitation and home-made foamgenerator was as shown in Figure 4

Mixer consists of chamber and hollow spiral pipe insideit The high-speed composite slurry drives the impellers torotate and then foam slurry is stirred and delivered by hollowspiral pipe with helical blades Vortex streets in this processcan completely go into turbulence and cause vortex accordingto certain frequency The loss of kinetic energy acts on themixtures and a large number of foam fluids are formedAqueous foams pass into the mixer from the left body ofhollow spiral pipe equipped with five aqueous foam outletswith an interval angle Aqueous foams are added to slurry stepby step which reduce the broken rate of foam and increasefoam slurry contact areas This kind of mixing chamber canweaken the shock caused by larger flow of aqueous foam andis conducive for gas-liquid-solid to mix thoroughly

32 Preparation of Aqueous Foam From viewing of thetechnology process for preparing the ISF the stability ismainly dependent on that of aqueous foam Generallyspeaking foam expansion ratio of aqueous foam should bemore than 20 SDS is a widely used surfactant with strongfoaming ability Its change trends of 30min drainage rate andfoam expansion ratio with different SDS concentrations aredepicted in Figure 5

From Figure 5 with increasing concentration of SDSfoam expansion ratio increases firstly and then decreasesfor the reason that the surface tension of surfactant solutiondecreased firstly and then increased due to formation ofsurfactant micelle and the largest foam expansion ratio is 24

under a concentration of 25Drainage rate of aqueous foampresented a reverse trend compared to that of foam expansionratio whose minimum is 35 under a concentration of 2This is for the reason that more micelles formed and theirshape changedwith the increase of SDS contributing tomorestable foam films and less drainage rate However in theother limit that is above 2 the violation of the law athighermicelle concentrations is related to the appearance of afreezing transition in foam films [21] Considering the abovetwo indexes the optimal SDS concentration is 25

In order to strengthen stability of aqueous foam CTABNaCl and LA were utilized as foam stabilizers We studiedmodification effects on SDS aqueous foam under differentconcentrations of foam stabilizers ranging from05 to 40whose concrete effects on foam expansion ratio and drainagerate are shown in Figure 6

From Figure 6(a) the change trends of foam expansionratio for three foam stabilizers are different and with increas-ing concentration that of CTAB declines and NaCl increasesslightly while LA elevates In Figure 6(b) from the viewpointof drainage rate three foam stabilizers wholly could diminishthe drainage rate of aqueous foam specifically with theincrease of concentration the drainage rate firstly falls offsharply and tardily goes up later The minimums of drainagerate and the critical concentrations for CTAB NaCl and LAare (20 25) (26 10) and (13 20) respectivelyThe reasons accounting for the trends mentioned above arespecial as follows

Under the condition that the concentration of SDS is25 its foam expansion ratio decreases with the increas-ing concentration of CTAB Because CTAB is a cationicsurfactant while SDS is an anionic one when these twosurfactants are mixed phase separation will occur due tointense electrostatic interaction and condensation of surfac-tant molecules [22] followed by the ascent of surface tension


500120583m

(a) Produced by mechanical agitation

500120583m

(b) Produced by the home-made foam generator

Figure 4 The optical microscopic analysis diagram of aqueous foam

Dra

inag

e rat

e (

)

Drainage rate

100

80

60

40

20

Foam

expa

nsio

n ra

tio

Foam expansion ratio

25

20

15

10

5

0

SDS concentration ()00 05 10 15 20 25 30

Figure 5 Change trends of drainage rate and foam expansion ratiowith different concentrations

With the increase of CTAB concentration the drainagerate of aqueous foam decreases firstly and then increaseswhich is 20 and the least under a concentration of 25Compared with the individual SDS system the SDS+CTABmixed system had a synergic effect on foam stabilization [23]Surfactant mixtures could create a mixed surfactant layerat gasliquid interfaces When two bubbles are approachingeach other to form a thin liquid film this mixed surfactantlayer can confer disjoining pressures to hinder this approach-ing

The foam expansion ratio enlarges with the increase ofNaCl concentrationmainly because homo-ion could not onlydiminish the Critical Micelle Concentration (CMC) of thesurfactant but also reduce surface tension of the solutionand develop its foaming ability The drainage rate decreasesfirstly and then ascends with the increase of NaCl concen-tration the minimum of which is 26 at a concentrationof 10 The addition of NaCl to SDS solution enlarged itsfoaming ability to some degree and reduced its drainagerate which could be explained that there is a thresholdof added electrolyte on stratification phenomenon of foamfilm above which the phenomenon is not observed [24]

Based on our experimental results we believe that 10was just the threshold Above 10 concentrations of NaClbubbles ruptured asynchronously owing to different surfaceconcentrations of NaCl thus the drainage rate of foam roseslightly with the increased concentrations of NaCl

The addition of LA could both prominently improvethe foam expansion and greatly enhance the stability ofaqueous foam This is because the iceberg structure (aperfectly ordered structure formed by the LA moleculesand water molecules) around the hydrocarbon chain in thealcohol makes it a spontaneous process for the alcohol toparticipate in the formation of micelle and thus bubble filmsare consolidated The drainage rate of foam film will slowdown with the rise of surfactant micelles in certain range ofconcentrations [25]

The prepared foam-forming solution containing SDSconcentration of 25 and LA concentration of 2 possessesexcellent foam expansion ratio with the value being 28 andthe aqueous foam derived from the solution acquires the beststability with the value being 13

33 The Stability of ISF

331 Aqueous FoamVolume Fly Ash Replacement for Cementand Water-Solid Ratio According to the results of 125 testsit can be concluded that when FV is 8V FA is 30 and WSis 04 and the ISF is in the best state with its foam expansionratio and stability coefficient being 5V and 90 respectivelyAt the same time some other test data was shown in Figure 7

From Figure 7(a) it can be seen that when FV increasedfoam expansion ratio and stability coefficient of ISF showdifferent variation trends As the aqueous foam volumeincreases the slurry system becomes more disperse and thefilmbecomes thinner which lead to the bursting of liquid filmeven if the drainage volume is not big Besides cement and flyash particles cannot form a continuum and the setting andthe hydration are slowed down So foam stability decreasesas a function of increasing aqueous foam volume When ISFis used in field ISF is requiredwith high foam expansion ratioand desired stability coefficient But in fact these two targetscannot be achieved simultaneouslyTherefore we expect thatunder the limit of foam expansion ratio which is not less than


35

30

25

20

15

10

Foam

expa

nsio

n ra

tio

Concentration ()

CTABNaClLA

05 10 15 20 25 35 4030

(a)

35

30

25

20

15

10

Dra

inag

e rat

e (

)

Concentration ()

CTABNaClLA

05 10 15 20 25 35 4030

(b)

Figure 6 Modifying effects of foam stabilizer on drainage rate and foam expansion ratio

4 V according to the technological requirements the stabilitycoefficient should be improved as high as possible

To reduce cost we use a small quantity of fly ash to replacecement Figure 7(b) shows the variation in foam expansionratio and stability coefficient with FA The foam expansionratio and stability coefficient both reach themaximumswhenthe FA is 30This phenomenon can be explained as followsWhen the cement particles are irregular geometry there aremany spherical particles (glass beads) in fly ash Glass beadsfunction like ball bearing reducing the friction among cementparticles and increasing the liquidity of foam slurry thusmaking bubbles disperse evenly But the hydration velocityof fly ash is slower than cement If the fly ash replacementlevel is too high it can cause reduction of the early hydrationproducts and rupture of bubbles and reduce the stabilitycoefficient of ISF

It is observed from Figure 7(c) that with the increaseof water cement ratio foam expansion ratio and stabilitycoefficient exhibit the same change trend A possible reasonfor this is that at a too low WS level cement hydrationconsumes the water of foam leading to bubble rupture andfoam slurry instability However when the WS is too largesolid particles may sink and foam can float upward whichcauses the uneven component of foam slurry and affects thestability of ISF

332 The Enhancement of the Stability The maximum sta-bility coefficient is 90 based on the results of 125 groupsof experiments There are certain changes in its internalstructure of foamfluid during the solidification from the freshstate For amore in-depth study on the changes in the internalstructure of the bubble the fresh state of foam fluid (Figure 8)was observed by optical microscopic system

Figure 8 shows that there are two distinct cases withrespect to the cement particlesrsquo location Most of the particles

are present only inside the film and just a few particles arefirmly attached to the film surface In the first case solidparticles at sufficiently high concentration can form a layeredstructure inside the thinning film and thus stabilize it by theso called oscillatory structural force In the second case afew particles irreversibly adsorb at the gas-liquid interfaceand significantly increase the interfacial elasticity neededto prevent the film rupture and bubble coalescence Thefoam stability has been quantitatively assessed by the particlehydrophobicity measured in terms of the contact angle 120579which is related with the energy 119866 required to remove thesmall particles (radius being 119877

119904) from the interface by the

following [26]

119866 = 120587119877119904

2120574LG(1 minus cos 120579)

2 (7)

According to Binks the optimum contact angle for foamstabilization is about 90∘ as at this value the energy toremove the particle from the interface has the highest valueExperimentally the optimumcontact angle interval ensuringthe highest foam stability was found between 40 and 70∘ [27]and 75 and 85∘ [28] (see also results in [29]) Based on (6)our measurements give a contact angle of 166∘ and 78∘ forthe particles in water and surfactant solution respectivelyTherefore the aqueous foams can be stabilized by solidparticles The adsorption of CTAB and LA molecules onthe surfaces of the particles changes their hydrophobicityThe partially hydrophobic particles are able to attach to theinterfaces which play a crucial role in the high foam stabilityreported here [30] For further investigation the burstingprocess of an unstable bubble was shown in Figure 9

From Figure 9(a) to Figure 9(b) this phenomenon wascalled limited coalescence and was observed with emulsionstabilized by the same type of particles [31] After a drainageperiod the site where the liquid drained is clear (as comparedwith the dispersions which are turbid) and the foam evolves


100

98

96

94

92

90

88

86

84

82

802 4 6 8 10

2

1

3

4

5

6

7

Stab

ility

coeffi

cien

t (

)

Stability coefficientFoam expansion ratio

Foam

expa

nsio

n ra

tio

FV (V)

(a)

10 20 30 40 50

Stab

ility

coeffi

cien

t (

)

Foam

expa

nsio

n ra

tio

FA ()


9054

52

50

48

46

44

42

40

88

86

84

82

(b)

Foam

expa

nsio

n ra

tio

WS


52

50

48

46

44

42

40

38

Stab

ility

coeffi

cien

t (

)

90

88

86

84

82

80

030 035 040 045 050

(c)

Figure 7 The change curves of stability coefficient and foam expansion ratio with different factors (a) Independent variable is FV andconstants are 30wt of FA and WS of 04 (b) Independent variable is FA and constants are 8V of FV and WS of 04 (c) independentvariable is WS and constants are 8V of FV and 30wt of FA

200120583m

Figure 8 The fresh state of foam fluid


200120583m

(a)

200120583m

(b)

Figure 9 The bursting process of an unstable bubble

little with time If initially after creation the bubble surfacesare not sufficiently covered by particles upon coalescence thesurface to volume ratio of the created bubbles decreases andhence eventually the coalescence proceeds [32 33]

Based on the previous analysis the apparent high stabilityagainst disproportionation is themost significant result evenconsidering the coagulated nature of the particles Also aswith foam fluid partial coagulation of particle networks onthe surfaces of the bubbles is found to be advantageous forstability It should be noted that the rate of drainage from thebubble wall is much faster than the rate of precipitation of thehydration products So promoting the formation of hydrationproducts is the correct way to delay and stop the burst ofbubbles

333 The Dynamic Changes of Bubble Wall after AddingCalcium Fluoroaluminate Accelerators influence the rate ofcement hydration leading to particles with a high degreeof internetworking against disproportionation and to occur-rence of greater retardation So we conduct experimentson the concentration of calcium fluoroaluminate (11CaO sdot7Al2O3sdot CaF2) on the foam stability coefficient as shown in

Figure 10 Foam stability first increases and then decreaseswith the content increase of 11CaO sdot 7Al

2O3sdot CaF2and the

maximum stability is 95 under the value of concentrationbeing 12

In cement-based materials (eg ISF) the transformationprocess from a paste phase into a solid phase can beunderstood from the properties of their constituents When11CaO sdot 7Al

2O3sdot CaF

2is added to ISF system Al

2O3

coming from the admixture could react with gypsum to formimmediately ettringite crystals ([Ca

2(Al Fe)(OH)

6]2sdot X3sdot

119899H2O) which will attach to the particle surface At the same

time the consumption of gypsum accelerates the pace oftricalcium silicate (3CaO sdot SiO

2) hydration forming a small

amount of fibrous CndashSndashH filling among the cement particlesThe chemical reaction consists in the transformation of11CaO sdot 7Al

2O3sdotCaF2into [Ca

2(Al Fe)(OH)

6]2sdot X3sdot 119899H2O

via a dissolution precipitation process by (8) The dynamic

Concentration ()0 2 4 6 8 10 12 14 16 18

Stab

ility

coeffi

cien

t (

)

95

94

93

92

91

90

Figure 10 The foam stability coefficient versus concentration ofaccelerators

changes of bubble wall in the stabilization and solidificationprocess were shown in Figure 11 Consider

3 (11CaO sdot 7Al2O3sdot CaF2) + 33CaSO

4+ 382H

2O

997888rarr 11 (3CaO sdot Al2O3sdot 3CaSO

4sdot 32H2O)

+ 3CaF2+ 10 (Al

2O3sdot 3H2O)

(8)

In the SEM image obtained from the sample after solid-ification the evolution of the primary cement hydrationproducts is obvious We can observe the formation ofettringite as rod-like crystals massively fill capillary poresSurface products such as CndashSndashH gel can be observed as themajor ISF microstructure component CH as a pore productwith a polycrystalline shape is another dominant cementhydration product The SEM shows that the cement andfly ash particles are more connected and cement hydrationproducts completely surround the particles

4 Conclusions

(1) This paper presents the manufacturing process ofISF which consists of mixing the composite slurry


Solidification

Ettringite

CHCndashSndashH

200120583m

Figure 11 The SEM images of bubble wall

preparing aqueous foam and mixing them withacceleratorThe foamgenerator can produce homoge-nous and dense aqueous foams due to the turbulenteddy which is formed and enhanced by the porousmediumA large number of foamfluids are formed bythe self-made mixer in which turbulence and vortexwere generated and then aqueous foams were addedstepwise to slurry

(2) The aqueous foam with expansion ratio of 28 and30min drainage rate of 13 was obtained as a func-tion of 25 wt SDS and 2wt LA The effects ofFV FA and WS on stability coefficient and foamexpansion ratio were studied And the results showthat the optimum values of foam expansion ratio andstability coefficient were 5V and 90 respectively byvalue of FV being 8V FA being 30 and WS being04

(3) The adsorption of CTAB and LA molecules on thesurfaces of the particles changes their hydrophobic-ity with the contact angle from 166∘ to 78∘ Themechanism concerning accelerating the hydrationand reducing the drainage was proposed and verifiedbased on the analysis of dynamic change of bubblewall

(4) At last ISF with stability coefficient of 95 andfoaming expansion ratio of 5 was fabricated whichcould sufficiently satisfy field process requirements ofair sealing and thermal insulation

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work was supported by the National Natural Sci-ence Foundation of China (no U1361213) the Fundamen-tal Research Funds for the Central Universities (CUMT2014YC04) and the independent study projects of StateKey Laboratory of Coal Resources and Mine Safety (SKL-CRSM13X04)

References

[1] G B Stracher and T P Taylor ldquoCoal fires burning out of controlaround the world Thermodynamic recipe for environmentalcatastropherdquo International Journal of Coal Geology vol 59 no1-2 pp 7ndash17 2004

[2] C Kuenzer and G B Stracher ldquoGeomorphology of coal seamfiresrdquo Geomorphology vol 138 no 1 pp 209ndash222 2012

[3] M A Engle L F Radke E L Heffern et al ldquoGas emissionsminerals and tars associated with three coal fires Powder RiverBasin USArdquo Science of the Total Environment vol 420 pp 146ndash159 2012

[4] F Zhou B Shi Y Liu X Song J Cheng and S Hu ldquoCoatingmaterial of air sealing in coal mine clay composite slurry(CCS)rdquo Applied Clay Science vol 80-81 pp 299ndash304 2013

[5] B Taraba Z Michale V Michalcova T Blejchar M Bojko andM Kozubkova ldquoCFD simulations of the effect of wind on thespontaneous heating of coal stockpilesrdquo Fuel vol 118 no 2 pp107ndash112 2014

[6] T R Jolley and H W Russell ldquoControl of fires in inactivecoaldeposits in Western United States including Alaska 1948ndash1958rdquo Information Circular US Bureau of Mines 7932 1959

[7] J J Feiler and G J Colaizzi IHI Mine Fire Control ProjectUtilizing Foamed Grout Technology Rifle Colorado Bureauof Mines United States Department of the Interior ResearchContract Report 14320395H0002 1996

[8] F B Zhou ldquoApplication of new material as air tight coatingmaterial in entries retained at gob-sidesrdquo Coal Safety SpecialIssue pp 97ndash98 2009

[9] A Kan and H Houde ldquoEffective thermal conductivity of opencell polyurethane foam based on the fractal theoryrdquoAdvances inMaterials Science and Engineering vol 2013 Article ID 1252677 pages 2013

[10] S K Lim C S Tan O Y Lim and Y L Lee ldquoFresh andhardened properties of lightweight foamed concrete with palmoil fuel ash as fillerrdquo Construction and Building Materials vol46 pp 39ndash47 2013

[11] I S Ranjani and K Ramamurthy ldquoRelative assessment ofdensity and stability of foam produced with four syntheticsurfactantsrdquo Materials and Structures vol 43 no 10 pp 1317ndash1325 2010

[12] E Carey and C Stubenrauch ldquoFree drainage of aqueous foamsstabilized by mixtures of a non-ionic (C

12DMPO) and an ionic

(C12TAB) surfactantrdquo Colloids and Surfaces A Physicochemicaland Engineering Aspects vol 419 pp 7ndash14 2013

[13] U T Gonzenbach A R Studart E Tervoort and L J GaucklerldquoStabilization of foams with inorganic colloidal particlesrdquo Lang-muir vol 22 no 26 pp 10983ndash10988 2006


[14] T N Hunter R J Pugh G V Franks and G J Jameson ldquoTherole of particles in stabilising foams and emulsionsrdquo Advancesin Colloid and Interface Science vol 137 no 2 pp 57ndash81 2008

[15] GN SethumadhavanADNikolov andDTWasan ldquoStabilityof liquid films containing monodisperse colloidal particlesrdquoJournal of Colloid and Interface Science vol 240 no 1 pp 105ndash112 2001

[16] K Vijayaraghavan A Nikolov andDWasan ldquoFoam formationand mitigation in a three-phase gas-liquid-particulate systemrdquoAdvances in Colloid and Interface Science vol 123-126 pp 49ndash61 2006

[17] BS EN 197-1 Cement Composition Specifications and Confor-mity Criteria for Common Cements British Standards Institu-tion London UK 1995

[18] BS EN 450 Fly Ash for Concrete Definitions RequirementsandQuality Control British Standards Institution London UK1995

[19] W E Brewer Durability Factors Affecting CLSM SP 150-3American Concrete Institute Detroit Mich USA 1994

[20] A V Nguyen ldquoFlotationrdquo in Encyclopedia of Separation ScienceI D Wilson Ed pp 1ndash27 Elsevier Amsterdam The Nether-lands 2007

[21] S Grandner and S H Klapp ldquoSurface charge induced freezingof colloidal suspensionsrdquo Europhysics Letters vol 90 no 6Article ID 68004 2010

[22] S I Karakashev E D Manev R Tsekov and A V NguyenldquoEffect of ionic surfactants on drainage and equilibrium thick-ness of emulsion filmsrdquo Journal of Colloid and Interface Sciencevol 318 no 2 pp 358ndash364 2008

[23] M Wang H Du A Guo R Hao and Z Hou ldquoMicrostructurecontrol in ceramic foams viamixed cationicanionic surfactantrdquoMaterials Letters vol 88 pp 97ndash100 2012

[24] A D Nikolov and D T Wasan ldquoOrdered micelle structuringin thin films formed from anionic surfactant solutions IExperimentalrdquo Journal of Colloid And Interface Science vol 133no 1 pp 1ndash12 1989

[25] S E Anachkov K D Danov E S Basheva P A Kralchevskyand K P Ananthapadmanabhan ldquoDetermination of the aggre-gation number and charge of ionic surfactant micelles fromthe stepwise thinning of foam filmsrdquo Advances in Colloid andInterface Science vol 183-184 pp 55ndash67 2012

[26] B P Binks ldquoParticles as surfactantsmdashsimilarities and differ-encesrdquo Current Opinion in Colloid and Interface Science vol 7no 1-2 pp 21ndash41 2002

[27] G Johansson and R J Pugh ldquoThe influence of particle sizeand hydrophobicity on the stability of mineralized frothsrdquoInternational Journal of Mineral Processing vol 34 no 1-2 pp1ndash21 1992

[28] Y Q Sun and T Gao ldquoThe optimum wetting angle for thestabilization of liquid-metal foams by ceramic particles exper-imental simulationsrdquo Metallurgical and Materials TransactionsA vol 33 no 10 pp 3285ndash3292 2002

[29] S W Ip Y Wang and J M Toguri ldquoAluminum foam stabiliza-tion by solid particlesrdquo Canadian Metallurgical Quarterly vol38 no 1 pp 81ndash92 1999

[30] Q Liu S Zhang D Sun and J Xu ldquoAqueous foams stabilized byhexylamine-modified Laponite particlesrdquo Colloids and SurfacesA Physicochemical and Engineering Aspects vol 338 no 1ndash3 pp40ndash46 2009

[31] E RioW Drenckhan A Salonen and D Langevin ldquoUnusuallystable liquid foamsrdquo Advances in Colloid and Interface Sciencevol 205 pp 74ndash86 2014

[32] S Samanta and P Ghosh ldquoCoalescence of bubbles and stabilityof foams in aqueous solutions of Tween surfactantsrdquo ChemicalEngineering Research and Design vol 89 no 11 pp 2344ndash23552011

[33] W Kracht and H Rebolledo ldquoStudy of the local critical coa-lescence concentration (l-CCC) of alcohols and salts at bubbleformation in two-phase systemsrdquoMinerals Engineering vol 50-51 pp 77ndash82 2013

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


low drainage rate and high expansion ratio was preparedbased on sodium dodecyl sulfate (SDS) solution and mod-ified by the foam stabilizers such as cetrimonium bromide(CTAB) sodium chloride (NaCl) and lauryl alcohol (LA)Then the factors influencing the stability coefficient and foamexpansion ratio of ISF were investigated At last throughthe observation on drainage of the bubble wall and thehydration products accelerated by calcium fluoroaluminatethe stabilization mechanism of foam fluid was proposed

2 Experimental

21 Raw Materials Constituent materials are listed below

(1) Portland cement (PC) with the compressive strengthof 645MPa at 28 days conforming toBSEN 197-1 typeI cement [17]

(2) Fly ash (FA) with a median particle size of 35 120583m andloss on ignition (LOI) of 50 conforming to BS EN450 [18]

(3) Calcium fluoroaluminate (11CaO sdot 7Al2O3sdot CaF2) it

influences the rate of cement hydration leading to areduction in setting time

(4) Redispersible polymer powder (PP) it is a kind ofpolymeric powder which can be easily reemulsifiedin water to reform liquid emulsion with essentiallyidentical properties to the original emulsion

(5) Water (W) its percentage was fixed in order to satisfyboth the workability criterion and the controlled lowstrength materials (CLSM) recommendations for theinsulation materials [19]

(6) Lauryl sodium sulfate (SDS) Cetrimonium Bromide(CTAB) NaCl and lauryl alcohol (LA) They werediluted with water in different ratios

22 Preparation Process of ISF The basic preparation processcan be divided into three parts including mixing the com-posite slurry preparing aqueous foam andmixing compositeslurry accelerator and aqueous foam We admixed cementfly ash and redispersible polymer powder together and gotthe blend of these three basic raw materials Then partof water was injected into the blend and composite slurryformed under the work of stirrer The water-solid ratio wascontrolled slightly less than preset ratio At the same timethe rest of the water was used to dilute the surfactant Thenhigh pressure air was pumped into the foam generator andaqueous foam was produced The next procedure was to mixcomposite slurry with aqueous foam in a self-made mixerwith some compound additives added At last foam fluidwas produced and evolved into ISF at room temperatureThe specific preparation procedures of ISF are schematicallyshown in Figure 1 The main installations are shown inFigure 2

23 Test Procedure

231 Drainage Rate Test We chose the drainage rate to be 30minutes since aqueous foam was produced to reflect foamstability After generation of aqueous foam the initial foammass 119898 was measured immediately and then poured fullyinto a Buchner funnel A measuring cylinder was placedunder the Buchner funnel and the mass of liquid drainedfrom aqueous foam 119898

119889 was calculated every ten minutes

until 30 minutes Drainage rate 119889119905 can be expressed by

119889119905=119898119889

119898times 100 (1)

232 Stability Coefficient Test The test instrument was onecylindrical gauge whose inner diameter was 100mm andmeasuring rangewas 315mmThe test procedure is as follows(i) pour the fresh ISF into the test instrument and record theinitial height ℎ

0 (ii) measure the final height (ℎ

119894) when ISF

turns into solidification state The stability coefficient 120595 canbe calculated according to the following

120595 =ℎ119894

ℎ0

times 100 (2)

233 Foam Expansion Ratio Test Test procedure for foamexpansion ratio of aqueous foamor foamfluid is as follows (i)fill a container (volume and mass are known and designatedby 119881119888 119898119888 resp) with surfactant solution or cement slurry

weigh the total mass 119898119871 and calculate the density of

surfactant solution or cement slurry 120588119871 by (3) (ii) overfill the

aforementioned container with aqueous foam or foam fluidand strike off the excess foam weigh the total mass 119898

119865 and

calculate the density of aqueous foam or foam fluid 120588119865 by

(4) (iii) calculate the foam expansion ratio of aqueous foamor foam fluid 119864

119865 by (5) as follows

120588119871=119898119871minus 119898119888

119881119888

(3)

120588119865=119898119865minus 119898119888

119881119888

(4)

119864119865=120588119871

120588119865

(5)

234 Microscopy Observation The microstructure of aque-ous foam and ISF fluid were observed by a Nomarski-typephase contrast interferencemicroscope equipped with a digi-tal camera which can be used to take photomicrograph of thesamples and the foams A drop of sample was brought ontoa microscope slide and the structure of bubble was observedThe bubble wall of ISF was investigated by scanning electronmicroscopy (SEM) (FEI QuantaTM 250 SEM system) withthe size of test specimen being 10 times 10 times 10mm3 prism

235 Particle Contact Angle Measurement The water andsurfactant solution contact angle on the particles was mea-sured using the gravimetric version of theWashburnmethodThe method is based on measuring the penetration rate of


Cement

PP

Fly ash

Blend (solids)

Water Surfactant



Mixer

Foam fluid

Foam generator

ISF




Flow meter

High pressure air

Pressure gauge

Solution

Solution pump

Slurry pump

Accelerator

Mixer

Foam fluid (ISF)

Foam generator




2 (6)







Aqueous foam

Foam fluid


Surfactant solution

High pressure air

DropletAqueous foam


Composite slurry


Mixing gradually


Hollow spiral pipe













500120583m


500120583m



Dra

inag

e rat

e (

)

Drainage rate

100

80

60

40

20

Foam

expa

nsio

n ra

tio


25

20

15

10

5

0












35

30

25

20

15

10

Foam

expa

nsio

n ra

tio

Concentration ()

CTABNaClLA

05 10 15 20 25 35 4030

(a)

35

30

25

20

15

10

Dra

inag

e rat

e (

)

Concentration ()

CTABNaClLA

05 10 15 20 25 35 4030

(b)









following [26]

119866 = 120587119877119904

2120574LG(1 minus cos 120579)

2 (7)




100

98

96

94

92

90

88

86

84

82

802 4 6 8 10

2

1

3

4

5

6

7

Stab

ility

coeffi

cien

t (

)


Foam

expa

nsio

n ra

tio

FV (V)

(a)

10 20 30 40 50

Stab

ility

coeffi

cien

t (

)

Foam

expa

nsio

n ra

tio

FA ()


9054

52

50

48

46

44

42

40

88

86

84

82

(b)

Foam

expa

nsio

n ra

tio

WS


52

50

48

46

44

42

40

38

Stab

ility

coeffi

cien

t (

)

90

88

86

84

82

80

030 035 040 045 050

(c)


200120583m



200120583m

(a)

200120583m

(b)






2O3sdot CaF2and the



2O3sdot CaF


2O3


2(Al Fe)(OH)

6]2sdot X3sdot





2O3sdotCaF2into [Ca

2(Al Fe)(OH)



Concentration ()0 2 4 6 8 10 12 14 16 18

Stab

ility

coeffi

cien

t (

)

95

94

93

92

91

90




4+ 382H

2O


4sdot 32H2O)

+ 3CaF2+ 10 (Al

2O3sdot 3H2O)

(8)


4 Conclusions



Solidification

Ettringite

CHCndashSndashH

200120583m








Acknowledgments


References












































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Cement

PP

Fly ash

Blend (solids)

Water Surfactant



Mixer

Foam fluid

Foam generator

ISF




Flow meter

High pressure air

Pressure gauge

Solution

Solution pump

Slurry pump

Accelerator

Mixer

Foam fluid (ISF)

Foam generator




2 (6)







Aqueous foam

Foam fluid


Surfactant solution

High pressure air

DropletAqueous foam


Composite slurry


Mixing gradually


Hollow spiral pipe













500120583m


500120583m



Dra

inag

e rat

e (

)

Drainage rate

100

80

60

40

20

Foam

expa

nsio

n ra

tio


25

20

15

10

5

0












35

30

25

20

15

10

Foam

expa

nsio

n ra

tio

Concentration ()

CTABNaClLA

05 10 15 20 25 35 4030

(a)

35

30

25

20

15

10

Dra

inag

e rat

e (

)

Concentration ()

CTABNaClLA

05 10 15 20 25 35 4030

(b)









following [26]

119866 = 120587119877119904

2120574LG(1 minus cos 120579)

2 (7)




100

98

96

94

92

90

88

86

84

82

802 4 6 8 10

2

1

3

4

5

6

7

Stab

ility

coeffi

cien

t (

)


Foam

expa

nsio

n ra

tio

FV (V)

(a)

10 20 30 40 50

Stab

ility

coeffi

cien

t (

)

Foam

expa

nsio

n ra

tio

FA ()


9054

52

50

48

46

44

42

40

88

86

84

82

(b)

Foam

expa

nsio

n ra

tio

WS


52

50

48

46

44

42

40

38

Stab

ility

coeffi

cien

t (

)

90

88

86

84

82

80

030 035 040 045 050

(c)


200120583m



200120583m

(a)

200120583m

(b)






2O3sdot CaF2and the



2O3sdot CaF


2O3


2(Al Fe)(OH)

6]2sdot X3sdot





2O3sdotCaF2into [Ca

2(Al Fe)(OH)



Concentration ()0 2 4 6 8 10 12 14 16 18

Stab

ility

coeffi

cien

t (

)

95

94

93

92

91

90




4+ 382H

2O


4sdot 32H2O)

+ 3CaF2+ 10 (Al

2O3sdot 3H2O)

(8)


4 Conclusions



Solidification

Ettringite

CHCndashSndashH

200120583m








Acknowledgments


References












































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Aqueous foam

Foam fluid


Surfactant solution

High pressure air

DropletAqueous foam


Composite slurry


Mixing gradually


Hollow spiral pipe













500120583m


500120583m



Dra

inag

e rat

e (

)

Drainage rate

100

80

60

40

20

Foam

expa

nsio

n ra

tio


25

20

15

10

5

0












35

30

25

20

15

10

Foam

expa

nsio

n ra

tio

Concentration ()

CTABNaClLA

05 10 15 20 25 35 4030

(a)

35

30

25

20

15

10

Dra

inag

e rat

e (

)

Concentration ()

CTABNaClLA

05 10 15 20 25 35 4030

(b)









following [26]

119866 = 120587119877119904

2120574LG(1 minus cos 120579)

2 (7)




100

98

96

94

92

90

88

86

84

82

802 4 6 8 10

2

1

3

4

5

6

7

Stab

ility

coeffi

cien

t (

)


Foam

expa

nsio

n ra

tio

FV (V)

(a)

10 20 30 40 50

Stab

ility

coeffi

cien

t (

)

Foam

expa

nsio

n ra

tio

FA ()


9054

52

50

48

46

44

42

40

88

86

84

82

(b)

Foam

expa

nsio

n ra

tio

WS


52

50

48

46

44

42

40

38

Stab

ility

coeffi

cien

t (

)

90

88

86

84

82

80

030 035 040 045 050

(c)


200120583m



200120583m

(a)

200120583m

(b)






2O3sdot CaF2and the



2O3sdot CaF


2O3


2(Al Fe)(OH)

6]2sdot X3sdot





2O3sdotCaF2into [Ca

2(Al Fe)(OH)



Concentration ()0 2 4 6 8 10 12 14 16 18

Stab

ility

coeffi

cien

t (

)

95

94

93

92

91

90




4+ 382H

2O


4sdot 32H2O)

+ 3CaF2+ 10 (Al

2O3sdot 3H2O)

(8)


4 Conclusions



Solidification

Ettringite

CHCndashSndashH

200120583m








Acknowledgments


References












































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




500120583m


500120583m



Dra

inag

e rat

e (

)

Drainage rate

100

80

60

40

20

Foam

expa

nsio

n ra

tio


25

20

15

10

5

0












35

30

25

20

15

10

Foam

expa

nsio

n ra

tio

Concentration ()

CTABNaClLA

05 10 15 20 25 35 4030

(a)

35

30

25

20

15

10

Dra

inag

e rat

e (

)

Concentration ()

CTABNaClLA

05 10 15 20 25 35 4030

(b)









following [26]

119866 = 120587119877119904

2120574LG(1 minus cos 120579)

2 (7)




100

98

96

94

92

90

88

86

84

82

802 4 6 8 10

2

1

3

4

5

6

7

Stab

ility

coeffi

cien

t (

)


Foam

expa

nsio

n ra

tio

FV (V)

(a)

10 20 30 40 50

Stab

ility

coeffi

cien

t (

)

Foam

expa

nsio

n ra

tio

FA ()


9054

52

50

48

46

44

42

40

88

86

84

82

(b)

Foam

expa

nsio

n ra

tio

WS


52

50

48

46

44

42

40

38

Stab

ility

coeffi

cien

t (

)

90

88

86

84

82

80

030 035 040 045 050

(c)


200120583m



200120583m

(a)

200120583m

(b)






2O3sdot CaF2and the



2O3sdot CaF


2O3


2(Al Fe)(OH)

6]2sdot X3sdot





2O3sdotCaF2into [Ca

2(Al Fe)(OH)



Concentration ()0 2 4 6 8 10 12 14 16 18

Stab

ility

coeffi

cien

t (

)

95

94

93

92

91

90




4+ 382H

2O


4sdot 32H2O)

+ 3CaF2+ 10 (Al

2O3sdot 3H2O)

(8)


4 Conclusions



Solidification

Ettringite

CHCndashSndashH

200120583m








Acknowledgments


References












































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




35

30

25

20

15

10

Foam

expa

nsio

n ra

tio

Concentration ()

CTABNaClLA

05 10 15 20 25 35 4030

(a)

35

30

25

20

15

10

Dra

inag

e rat

e (

)

Concentration ()

CTABNaClLA

05 10 15 20 25 35 4030

(b)









following [26]

119866 = 120587119877119904

2120574LG(1 minus cos 120579)

2 (7)




100

98

96

94

92

90

88

86

84

82

802 4 6 8 10

2

1

3

4

5

6

7

Stab

ility

coeffi

cien

t (

)


Foam

expa

nsio

n ra

tio

FV (V)

(a)

10 20 30 40 50

Stab

ility

coeffi

cien

t (

)

Foam

expa

nsio

n ra

tio

FA ()


9054

52

50

48

46

44

42

40

88

86

84

82

(b)

Foam

expa

nsio

n ra

tio

WS


52

50

48

46

44

42

40

38

Stab

ility

coeffi

cien

t (

)

90

88

86

84

82

80

030 035 040 045 050

(c)


200120583m



200120583m

(a)

200120583m

(b)






2O3sdot CaF2and the



2O3sdot CaF


2O3


2(Al Fe)(OH)

6]2sdot X3sdot





2O3sdotCaF2into [Ca

2(Al Fe)(OH)



Concentration ()0 2 4 6 8 10 12 14 16 18

Stab

ility

coeffi

cien

t (

)

95

94

93

92

91

90




4+ 382H

2O


4sdot 32H2O)

+ 3CaF2+ 10 (Al

2O3sdot 3H2O)

(8)


4 Conclusions



Solidification

Ettringite

CHCndashSndashH

200120583m








Acknowledgments


References












































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




100

98

96

94

92

90

88

86

84

82

802 4 6 8 10

2

1

3

4

5

6

7

Stab

ility

coeffi

cien

t (

)


Foam

expa

nsio

n ra

tio

FV (V)

(a)

10 20 30 40 50

Stab

ility

coeffi

cien

t (

)

Foam

expa

nsio

n ra

tio

FA ()


9054

52

50

48

46

44

42

40

88

86

84

82

(b)

Foam

expa

nsio

n ra

tio

WS


52

50

48

46

44

42

40

38

Stab

ility

coeffi

cien

t (

)

90

88

86

84

82

80

030 035 040 045 050

(c)


200120583m



200120583m

(a)

200120583m

(b)






2O3sdot CaF2and the



2O3sdot CaF


2O3


2(Al Fe)(OH)

6]2sdot X3sdot





2O3sdotCaF2into [Ca

2(Al Fe)(OH)



Concentration ()0 2 4 6 8 10 12 14 16 18

Stab

ility

coeffi

cien

t (

)

95

94

93

92

91

90




4+ 382H

2O


4sdot 32H2O)

+ 3CaF2+ 10 (Al

2O3sdot 3H2O)

(8)


4 Conclusions



Solidification

Ettringite

CHCndashSndashH

200120583m








Acknowledgments


References












































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




200120583m

(a)

200120583m

(b)






2O3sdot CaF2and the



2O3sdot CaF


2O3


2(Al Fe)(OH)

6]2sdot X3sdot





2O3sdotCaF2into [Ca

2(Al Fe)(OH)



Concentration ()0 2 4 6 8 10 12 14 16 18

Stab

ility

coeffi

cien

t (

)

95

94

93

92

91

90




4+ 382H

2O


4sdot 32H2O)

+ 3CaF2+ 10 (Al

2O3sdot 3H2O)

(8)


4 Conclusions



Solidification

Ettringite

CHCndashSndashH

200120583m








Acknowledgments


References












































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Solidification

Ettringite

CHCndashSndashH

200120583m








Acknowledgments


References












































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



research article preparation and stability of inorganic...

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