research article preparation and stability of inorganic...
TRANSCRIPT
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
4 Advances in Materials Science and Engineering
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
Advances in Materials Science and Engineering 5
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
6 Advances in Materials Science and Engineering
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
Advances in Materials Science and Engineering 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 (
)
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 ()
Stability coefficientFoam expansion ratio
9054
52
50
48
46
44
42
40
88
86
84
82
(b)
Foam
expa
nsio
n ra
tio
WS
Stability coefficientFoam expansion ratio
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
8 Advances in Materials Science and Engineering
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
Advances in Materials Science and Engineering 9
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
10 Advances in Materials Science and Engineering
[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
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Biomaterials
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Journal ofNanomaterials
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
4 Advances in Materials Science and Engineering
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
Advances in Materials Science and Engineering 5
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
6 Advances in Materials Science and Engineering
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
Advances in Materials Science and Engineering 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 (
)
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 ()
Stability coefficientFoam expansion ratio
9054
52
50
48
46
44
42
40
88
86
84
82
(b)
Foam
expa
nsio
n ra
tio
WS
Stability coefficientFoam expansion ratio
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
8 Advances in Materials Science and Engineering
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
Advances in Materials Science and Engineering 9
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
10 Advances in Materials Science and Engineering
[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
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CeramicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CompositesJournal of
NanoparticlesJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Biomaterials
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
NanoscienceJournal of
TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Journal of
NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
CrystallographyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CoatingsJournal of
Advances in
Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Smart Materials Research
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MetallurgyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
BioMed Research International
MaterialsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nano
materials
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofNanomaterials
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
4 Advances in Materials Science and Engineering
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
Advances in Materials Science and Engineering 5
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
6 Advances in Materials Science and Engineering
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
Advances in Materials Science and Engineering 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 (
)
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 ()
Stability coefficientFoam expansion ratio
9054
52
50
48
46
44
42
40
88
86
84
82
(b)
Foam
expa
nsio
n ra
tio
WS
Stability coefficientFoam expansion ratio
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
8 Advances in Materials Science and Engineering
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
Advances in Materials Science and Engineering 9
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
10 Advances in Materials Science and Engineering
[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
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CeramicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CompositesJournal of
NanoparticlesJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Biomaterials
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
NanoscienceJournal of
TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Journal of
NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
CrystallographyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CoatingsJournal of
Advances in
Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Smart Materials Research
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MetallurgyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
BioMed Research International
MaterialsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nano
materials
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofNanomaterials
4 Advances in Materials Science and Engineering
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
Advances in Materials Science and Engineering 5
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
6 Advances in Materials Science and Engineering
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
Advances in Materials Science and Engineering 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 (
)
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 ()
Stability coefficientFoam expansion ratio
9054
52
50
48
46
44
42
40
88
86
84
82
(b)
Foam
expa
nsio
n ra
tio
WS
Stability coefficientFoam expansion ratio
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
8 Advances in Materials Science and Engineering
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
Advances in Materials Science and Engineering 9
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
10 Advances in Materials Science and Engineering
[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
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CeramicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CompositesJournal of
NanoparticlesJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Biomaterials
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
NanoscienceJournal of
TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Journal of
NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
CrystallographyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CoatingsJournal of
Advances in
Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Smart Materials Research
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MetallurgyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
BioMed Research International
MaterialsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nano
materials
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofNanomaterials
Advances in Materials Science and Engineering 5
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
6 Advances in Materials Science and Engineering
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
Advances in Materials Science and Engineering 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 (
)
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 ()
Stability coefficientFoam expansion ratio
9054
52
50
48
46
44
42
40
88
86
84
82
(b)
Foam
expa
nsio
n ra
tio
WS
Stability coefficientFoam expansion ratio
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
8 Advances in Materials Science and Engineering
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
Advances in Materials Science and Engineering 9
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
10 Advances in Materials Science and Engineering
[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
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CeramicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CompositesJournal of
NanoparticlesJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Biomaterials
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
NanoscienceJournal of
TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Journal of
NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
CrystallographyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CoatingsJournal of
Advances in
Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Smart Materials Research
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MetallurgyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
BioMed Research International
MaterialsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nano
materials
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofNanomaterials
6 Advances in Materials Science and Engineering
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
Advances in Materials Science and Engineering 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 (
)
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 ()
Stability coefficientFoam expansion ratio
9054
52
50
48
46
44
42
40
88
86
84
82
(b)
Foam
expa
nsio
n ra
tio
WS
Stability coefficientFoam expansion ratio
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
8 Advances in Materials Science and Engineering
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
Advances in Materials Science and Engineering 9
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
10 Advances in Materials Science and Engineering
[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
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CeramicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CompositesJournal of
NanoparticlesJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Biomaterials
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
NanoscienceJournal of
TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Journal of
NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
CrystallographyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CoatingsJournal of
Advances in
Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Smart Materials Research
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MetallurgyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
BioMed Research International
MaterialsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nano
materials
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofNanomaterials
Advances in Materials Science and Engineering 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 (
)
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 ()
Stability coefficientFoam expansion ratio
9054
52
50
48
46
44
42
40
88
86
84
82
(b)
Foam
expa
nsio
n ra
tio
WS
Stability coefficientFoam expansion ratio
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
8 Advances in Materials Science and Engineering
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
Advances in Materials Science and Engineering 9
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
10 Advances in Materials Science and Engineering
[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
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CeramicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CompositesJournal of
NanoparticlesJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Biomaterials
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
NanoscienceJournal of
TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Journal of
NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
CrystallographyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CoatingsJournal of
Advances in
Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Smart Materials Research
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MetallurgyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
BioMed Research International
MaterialsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nano
materials
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofNanomaterials
8 Advances in Materials Science and Engineering
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
Advances in Materials Science and Engineering 9
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
10 Advances in Materials Science and Engineering
[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
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CeramicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CompositesJournal of
NanoparticlesJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Biomaterials
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
NanoscienceJournal of
TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Journal of
NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
CrystallographyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CoatingsJournal of
Advances in
Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Smart Materials Research
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MetallurgyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
BioMed Research International
MaterialsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nano
materials
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofNanomaterials
Advances in Materials Science and Engineering 9
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
10 Advances in Materials Science and Engineering
[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
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CeramicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CompositesJournal of
NanoparticlesJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Biomaterials
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
NanoscienceJournal of
TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Journal of
NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
CrystallographyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CoatingsJournal of
Advances in
Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Smart Materials Research
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MetallurgyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
BioMed Research International
MaterialsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nano
materials
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofNanomaterials
10 Advances in Materials Science and Engineering
[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
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CeramicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CompositesJournal of
NanoparticlesJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Biomaterials
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
NanoscienceJournal of
TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Journal of
NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
CrystallographyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CoatingsJournal of
Advances in
Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Smart Materials Research
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MetallurgyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
BioMed Research International
MaterialsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nano
materials
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofNanomaterials
Submit your manuscripts athttpwwwhindawicom
ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CorrosionInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Polymer ScienceInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CeramicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CompositesJournal of
NanoparticlesJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Biomaterials
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
NanoscienceJournal of
TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Journal of
NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
CrystallographyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CoatingsJournal of
Advances in
Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Smart Materials Research
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MetallurgyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
BioMed Research International
MaterialsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nano
materials
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofNanomaterials