OrthogonalExperimentalStudiesonPreparationofMine-Filling … · 2019. 7. 30. · Received 1 April 2018; Accepted 24 June 2018; Published 9 August 2018 ... According to the BS EN (British

Research ArticleOrthogonal Experimental Studies on Preparation of Mine-FillingMaterials from Carbide Slag Granulated Blast-Furnace Slag FlyAsh and Flue-Gas Desulphurisation Gypsum

Mingyue Wu Xiangming Hu Qian Zhang Weimin Cheng and Zunxiang Hu

Key Lab of Mine Disaster Prevention and Control College of Mining and Safety EngineeringShandong University of Science and Technology Qingdao 266590 China

Correspondence should be addressed to Xiangming Hu xiangming0727163com

Received 1 April 2018 Accepted 24 June 2018 Published 9 August 2018

Academic Editor Marco Cannas

Copyright copy 2018 MingyueWu et al +is 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

Environmentally friendly and cheap composite green cementitious materials have been prepared from carbide slag fly ash flue-gas desulphurisation (FGD) gypsum and granulated blast-furnace slag (GBFS) without using cement clinker Orthogonal testingwas used to investigate the effects of the raw materials on the amount of water required for reaching standard consistency andconsistency setting time slump value and strength of the produced materials after curing for 7 d and 28 d Scanning electronmicroscopy (SEM) and X-ray diffraction (XRD) techniques were used for the analysis of the sample microstructure and hydrationproducts as well as for the exploration of possible hydration mechanisms We found that among the utilised raw materials theaddition of FGD gypsum had the most significant effect on the setting time and amount of water required for reaching standardconsistency and consistency while the addition of GBFS deeply affected the slump value +e optimal activation results wereobtained when the mass ratio of carbide slag fly ash GBFS FGD gypsum was equal to 121 606 182 91

1 Introduction

Owing to the increasing depletion of nonrenewable resourcesand effects produced by global warming the high levels ofenergy consumption and pollution generated during theproduction of cement clinker have attracted widespreadconcern +erefore both domestic and international scholarsare currently attempting to identify high-performance ce-mentitious materials whose production involves low levels ofpollution and energy consumption Recovering solid wasterepresents one of the major methods for manufacturing suchldquogreenrdquo cementitious materials +e utilised waste typicallyincludes fly ash (the fine ash collected from the soot producedduring coal combustion) which exhibits a pozzolanic effectand can be activated in an alkaline environment Anothersolid waste material consists of granulated slag (or water-quenched blast-furnace slag) which can potentially exhibithydraulic cementitious properties +e major component ofFGD gypsum is calcium sulphate dihydrate At present theseindustrial wastes are primarily utilised for the production of

cement [1 2] concrete [3ndash7] geopolymers [8ndash10] and ce-mentitiousmaterials formine filling [11 12] For exampleMaet al [13] prepared sulphoaluminate cement that was capableof meeting special structural requirements from fly ash andFGD gypsum Sarkar et al [14] partially substituted cementwith fly ash and GBFS to investigate variations in the concretestrength and determine the optimal ratio of the utilisedcomponents Qin et al [15] prepared a hydraulic cementitiousmaterial using GBFS FGD gypsum and activators as rawmaterials According to the results of these studies the hy-dration reaction that occurs between fly ash GBFS and FGDgypsum can be used for the preparation of cementitiousmaterials However in all the studies on the utilisation of solidwastes such as fly ash and GBFS a certain amount of cementclinker was added during production thus reducing theeconomic benefits of the proposed method

Carbide slag is a waste residue produced during thehydrolysis of calcium carbide its major components includecalcium oxide and calcium hydroxide Without specialtreatment a large amount of carbide slag produces dust and

HindawiAdvances in Materials Science and EngineeringVolume 2018 Article ID 4173520 12 pageshttpsdoiorg10115520184173520

air pollution Additionally if carbide slag is stacked it mayoccupy a large area of the land and put immense pressure onthe ecological environment Hence both domestic and in-ternational researchers have conducted a number of studieson the comprehensive utilisation of carbide slag Wang et al[16] prepared cement clinker using carbide slag as the rawmaterial and studied the formation process of cementclinker minerals Hao et al [17] examined the effects of thefly ash and carbide slag addition on the compressive strengthof the resulting cement paste However it is still unclearwhether carbide slag can effectively activate fly ash Becausecarbide slag is rich in the alkaline calcium oxide and calciumhydroxide components we hypothesised that it wouldprovide a large number of OHminus ions when used as an ad-mixture of cementitious materials +ese ions can effectivelydestroy the acidic film formed on the surfaces of fly ash andGBFS particles leading to the dissolution of various mineralconstituents such as silicon dioxide and aluminium oxide+e latter process in turn promotes the hydration of fly ashand GBFS components and forms hydration productscharacterised by a certain level of strength

Hence in the present study fly ash carbide slag GBFSand FGD gypsum were used to prepare green cementitiousmaterials without cement clinker Afterwards we in-vestigated the mechanical properties and morphology ofthese materials in order to identify the optimal quantities ofcarbide slag fly ash and other industrial waste componentsWe hope that this study will contribute to the preparationand promotion of high-quality inexpensive cementitiousmaterials for mine filling [18ndash24]

2 Materials and Methods

21 Raw Materials +e following raw materials have beenutilised in this study

Fly ash with a density of 178 gcm3 and a specific surfacearea of 219m2kg was purchased from Shandong BinzhouShanshui Cement Co Ltd Its activity index was calculatedas follows

R28 R

R01113888 1113889 times 100 (1)

+e obtained activity index of the fly ash was H28 61(its chemical composition is listed in Table 1)

GBFS with a density of 288 gcm3 and a specific surfacearea of 361m2kg was purchased from Shandong BinzhouShanshui Cement Co Ltd Its chemical composition is listedin Table 1 and the corresponding X-ray diffraction (XRD)pattern is depicted in Figure 1 It shows the existence ofa large peak in the 2θ range of 20ndash38deg and a very smallamount of the gehlenite phase without any distinct crys-talline peaks Hence the GBFS used in this study can beconsidered a completely vitreous material

Carbide slag purchased from Shandong Linzi AcetyleneGas Factory was calcined for 30min at 1000degC It wascharacterised by the calcium oxide mass fraction of 775calcium hydroxide mass fraction of 185 density of264 gcm3 and specific surface area of 419m2kg +e

chemical composition of the utilised carbide slag is listed inTable 1

FGD gypsum that contained more than 90 mass ofcalcium sulphate dihydrate was purchased from ShandongBinzhou Shanshui Cement Co Ltd After the calcination ofFGD gypsum for 2 h at 180degC its major component wasconverted into β-hemihydrate gypsum with a density of264 gcm3 and a specific surface area of 269m2kg

Admixtures of sodium hydroxide (ge960 mass) andnaphthalene superplasticiser (Clminus content lt04 masssulphate content lt9 mass and solid content ge93 mass)were purchased from Chenqi Chemical Technology Co LtdShanghai

+e density of the mixture was 231 gcm3 and itsspecific surface area was 327m2kg

Round siliceous river sand with a silicon dioxide contentexceeding 98 mass was utilised Its particle size is listed inFigure 2

Tap water was used in all experiments

22 Preparation of Test Blocks An orthogonal experimentaldesign was employed for the development of experimentalprocedures +e orthogonal testing parameters included themasses of FGD gypsum (A) GBFS (B) and carbide slag (C)(their corresponding amounts are listed in Table 2)

In accordance with the parameter combinations describedin the L25(56) orthogonal table [11] the fly ash carbide slagFGD gypsum GBFS and admixture components were mixedtogether to form composite cementitious materials Prior tomixing the materials were weighed with an accuracy of 001 gusing an electronic balance (YP1002N Shanghai JingkeTianmei Scientific Instrument Co Ltd) in accordance with thematerial mixing ratios provided in Table 3 +e cementsandratio was 025 and the watercement ratio was 05 Sub-sequently the weighed materials were mixed using the fol-lowing procedure first a specified amount of granular sodiumhydroxide was dissolved in water and the resulting aqueoussodium hydroxide solution was added to the bowl of the mixerwith a capacity of 5 L (JJ-5 Wuxi Xiyi Building MaterialsInstrument Co Ltd) whichwas fixed onto its frame and raisedto a set position Afterwards the materials were immediatelymixed for 30 s at a low speed of 140plusmn5 rpm Sand was con-tinuously added at a uniform rate during the next 30 s ofmixing After the sand addition the mixer was run for another30 s at a high speed of 285plusmn 10 rpm and then stopped for 90 sWithin the first 15 s after the mixer was stopped the mortarthat had adhered to the blades and bowl wall was scraped intothe centre of the bowl After a 90 s interval the mixing processwas continued for another 60 s at a high speed Immediatelyafter mixing the materials were moulded using an empty testmould (with dimensions of 40mmtimes 40mmtimes 160mm) anda bushing fixed onto a vibrating compaction table A scoop wasused to obtain mortar from the mixer bowl which was placedinto the testmould in two layers About 300 g ofmortar was putinto each groove in the first layer which was then compactedvia 60 vibrations +e second layer was added until the mouldwas filled and the mortar was again compacted by 60 vibra-tions Afterwards themould bushingwas removed and the testmould was transferred from the vibrating compaction table

2 Advances in Materials Science and Engineering

Any mortar exceeding the dimensions of the test mould wasscraped away using a metal ruler and the produced test blockwas numbered e moulded test block was cured at a tem-perature of 20plusmn 2degC in the environment with a relative hu-midity greater than 50 After 24h of curing the mould was

removed and subjected to another curing procedure at 20plusmn 2degCinside the curing chamber with a relative humidity of 95Each test block was cured for either 7 or 28d and its strengthwas measured after the corresponding curing period

23 Testing Parameters

231 Amount of Water and Setting Time Required forReaching Standard Consistency According to the BS EN(British Standard European Norm) 196-3 standard (com-pliant with the EN (European Norm) 196-3 standard)Vicatrsquos apparatus (purchased from Shanghai Shenrui TestEquipment Manufacturing Co Ltd) was used to determinethe amount of water and setting time required for the ce-mentitious materials to achieve standard consistency

232 Consistency An SC-145 mortar consistometer (pur-chased from Beijing Zhongke Luda Instrument Co LtdFigure 3) was used to determine the consistencies of the

Table 1 Chemical compositions of raw materials (in wt)

Raw materials Loss on ignition Silicondioxide

Aluminiumoxide Iron(III) oxide Calcium oxide Magnesium

oxideSulphurtrioxide

Fly ash 422 4598 3179 618 367 090 070Carbide slag 17 316 272 042 6457 072 152GBFS 025 3013 1714 071 3883 738 059

0

0

Inte

nsity

(au

)

200

400

600

800

1000

1200

10 20 30 40

A

50 60 70

A Ca2Al2SiO7

2θ (deg)

Figure 1

01

0 0

5

10

15

20

25

20

40

60

Cum

ulat

ive d

istrib

utio

n (

)

Freq

uenc

y di

strib

utio

n (

)80

100

1Particle size (mm)

10

Figure 2

Table 2 Levels and factors of the orthogonal test

LevelsFactors

FGDgypsum (g) (A) GBFS (g) (B) Carbide

slag (g) (C)1 7 24 122 9 26 143 11 28 164 13 30 185 15 32 20

Table 3 Materials proportioning of the orthogonal test

Number

Raw materials

FGDgypsum(g)

GBFS(g)

Carbideslag (g)

Flyash(g)

Sodiumhydroxide

(g)

Water-reducingadmixture

(g)1 7 24 12 100 75 052 7 26 14 100 78 053 7 28 16 100 79 054 7 30 18 100 82 055 7 32 20 100 84 056 9 24 14 100 77 057 9 26 16 100 79 058 9 28 18 100 82 059 9 30 20 100 84 0510 9 32 12 100 81 0511 11 24 16 100 79 0512 11 26 18 100 82 0513 11 28 20 100 84 0514 11 30 12 100 81 0515 11 32 14 100 83 0516 13 24 18 100 82 0517 13 26 20 100 84 0518 13 28 12 100 81 0519 13 30 14 100 83 0520 13 32 16 100 85 0521 15 24 20 100 84 0522 15 26 12 100 81 0523 15 28 14 100 83 0524 15 30 16 100 85 0525 15 32 18 100 92 05

Advances in Materials Science and Engineering 3

produced cementitious materials First each prepared ce-mentitious material was placed inside a container When thetip of the testing cone touched the material surface theclamping screw was unscrewed allowing the testing cone tofall freely +e falling depth displayed on the consistometerdial corresponded to the consistency value for the cemen-titious material (the results of three tests were averaged foreach studied cementitious material) and the measurementaccuracy was 1mm

233 Slump Testing +e cementitious material was packedinside a tube in three layers with approximately equal volumesEach layer was treated with a tamping rod evenly inserted in theslump cylinder 25 times following the shape of a spiral After thecompletion of the tamping process the slump tube was re-moved and the difference between the centre point of thespecimenrsquos top and the height of the produced slump (corre-sponding to the slump value) wasmeasured by a steel ruler+eduration of the entire testing procedurewas about 150 s and theaccuracy of the obtained results was 1mm If the studied sampleexhibited collapse or shear the results of the slump test wereconsidered negative and the testing procedure was repeated

234 Strength Compressive and flexural strengths (Figure 4)of the cementitiousmaterials weremeasured in accordancewiththe BS EN (British Standard European Norm) 196-1 standardcompliant with the EN (European Norm) 196-1 standard

235 XRD Analysis After the test blocks were cured for 7and 28 d the surfaces that might be possibly carbonated wereremoved with a knife +e samples were removed from theinterior of each test block and cut into 25ndash5mm pieces [25]which were subsequently immersed in a mixture of absoluteethanol and acetone After the hydration reaction was

complete the test blocks were dried for about 48 h at 40degCand then ground into fine powder for XRD analysis

236 Scanning Electron Microscopy Analysis After the testblocks were cured for 7 and 28d additional samples were takenfrom their interior and cut into 25ndash5mm pieces [26] whichwere subsequently dried to a constant weight in a vacuum-drying tube with a vacuum degree of 740mm Hg at 60degC [27]Afterwards the samples were metallised under vacuum placedinto a scanning electron microscope (SEM SX-40 In-ternational Scientific Instruments Japan) for the observation oftheir cross-sectional morphology and photographed

3 Results and Discussion

31 Amounts of Water Required for Reaching StandardConsistency and Consistency Table 4 lists the results of or-thogonal testing Table S1 contains the results of range analysiswhich was conducted to determine the amounts of water re-quired for reaching standard consistency and consistency of thecementitious materials According to the results presented inTable S1 when the raw material combination is A5B2C4 (cor-responding to the mass ratio of FGD gypsum GBFS carbideslag equal to 15 26 18) it exhibits the greatest impact on theamounts of water required for reaching standard consistency(the greater the content of FGD gypsum the higher theamount of the consumed free water in addition carbide slagconsumes a fraction of free water as well) When the rawmaterial combination is A2B1C5 (corresponding to the FGDgypsum GBFS carbide slag mass ratio of 9 24 20) it ex-hibits the greatest impact on the consistency of cementitiousmaterials since carbide slag not only consumes largeamounts of free water but also releases a lot of heat thataccelerates the hydration reaction As shown in Figure 5the raw materials can be ranked in terms of their effect onthe amount of water required to achieve standard consis-tency and consistency as follows FGD gypsumgt carbideslaggtGBFS After high-temperature calcination the majorcomponents of the tested FGD gypsum and carbide slagwere transformed into hemihydrate gypsum and calciumoxide respectively Once hemihydrate gypsum was exposedto water it was hydrated rapidly to produce dihydrategypsum A large amount of free water was consumed duringhydration while calcium oxide species also reacted with waterto generate calcium hydroxide +e amounts of water requiredfor the cementitious materials to reach standard consistencyvaried owing to the large volume of consumed free water (ingeneral consistency is a measure of the fluidity of a cementi-tious system corresponding to a fixed volume of water) +esamples containing large amounts of FGD gypsum and carbideslag consume more free water thus decreasing the consistencyand fluidity of the cementitious system

32 Setting Time Table S2 contains the results of the rangeanalysis conducted for the setting time of the prepared ce-mentitious materials It shows that when the combinations ofthe raw materials correspond to the formulas A1B5C5 andA1B5C3 (for themass ratios of FGDgypsum GBFS carbide slag

Figure 3


of 7 15 20 and 7 15 16 resp) the initial and final setting timesare affectedmost significantly because FGD gypsum inhibits thehydration process of cementitious materials As shown inFigure 6 the rawmaterials can be ranked in terms of their effect

on the initial and final setting times as follows FGD gyp-sumgt carbide slaggtGBFS In general the setting time of ce-mentitious materials is related to their hydration rate Dihydrategypsum a hydration product of hemihydrate gypsum can

(a) (b)

Figure 4

Table 4 Results of the orthogonal test

NumberWater requiredfor standard

consistency (mL)

Consistency(mm)

Slump(mm)

Setting time (min) 7 d strength (MPa) 28 d strength (MPa)Initialtime

Finaltime

Compressivestrength

Flexuralstrength

Compressivestrength

Flexuralstrength

1 141 14 212 287 397 172 061 379 1352 137 13 143 298 387 181 065 340 1053 128 14 129 265 389 248 095 367 1124 132 13 144 267 364 178 064 323 0985 135 14 165 279 397 214 080 336 1336 126 14 138 259 367 222 084 320 1307 143 13 174 246 387 194 079 292 1298 136 14 158 275 376 232 092 384 1449 134 15 149 289 359 237 093 346 12310 137 14 190 273 378 243 093 339 12411 127 11 147 256 367 189 077 335 11712 147 12 211 265 387 190 078 313 11413 132 15 157 286 398 184 075 314 12614 123 14 138 265 369 181 072 356 12415 128 14 139 254 378 222 083 337 10316 131 12 210 247 367 182 066 349 13317 138 14 200 267 373 229 090 407 14018 121 13 129 256 357 180 066 356 11019 127 13 146 243 363 150 066 340 09820 130 13 178 287 356 215 080 405 14721 145 13 191 267 364 163 057 358 11622 138 9 159 253 352 163 056 347 11523 146 8 148 256 358 171 061 394 14024 141 9 149 278 398 181 066 347 11525 142 7 138 298 378 177 070 372 122


promote the hydration of y ash and generate ettringite (AFt)crystals which in turn cover the surface of y ash particles thusdecreasing the hydration rate of the cementitious system As thehydration reaction progresses the resulting crystallisationpressure produces a signicant amount of AFt crystals on the yash particle surface When the crystallisation pressure becomesrelatively high a local rupture of the coated layer occurs ex-posing the y ash particles and further triggering the hydrationreaction erefore among the utilised raw materials FGDgypsum produced the greatest impact on the material settingtime In addition carbide slag reacted with water to generatecalcium hydroxide which not only provided an alkaline envi-ronment for the hydration reaction but also released a largeamount of heat further promoting hydration us the pres-ence of carbide slag aects the setting time of the preparedcementitious materials to a certain extent

33 Slump Value Table S3 contains the results of the rangeanalysis conducted for the obtained slump values It showsthat when the raw material combination is A4B1C5

(corresponding to the mass ratio of FGD gypsum GBFS carbide slag of 13 24 20) it exhibits the greatest impact onthe slump of the cementitiousmaterial According to Figure 7the resulting slump value is aected by the following factorsGBFSgt carbide slaggtFGD gypsum because the former iscomposed of the spherical vitreous bodies with a smooth andcompact surface which ensure good lubrication of the ce-mentitious material At the same time the size of GBFSparticles is relatively small which makes them easily dis-persible in the matrix Hence some amount of the mixingwater trapped inside the gap is released as a result thepresence of GBFS species produces the greatest impact onthe slump value of the cementitious material In addition thereaction of calcium carbide with water is exothermic and thusaccelerates the hydration of cementitious materials (therebyaecting their slump values)

34 Strength According to the data listed in Table 4 thecompressive strengths of the cementitious material aged

FGD gypsum

Am

ount

of w

ater

requ

ired

for

reac

hing

stan

dard

cons

isten

cy (m

L)

GBFS Carbide slag

9692

1314

12

10

8

6

4

2

0

(a)

FGD gypsum

Con

siste

ncy

rang

e (m

m)

GBFS Carbide slag

2

1

55

4

3

2

1

0

(b)

Figure 5

FGD gypsum

Initi

al se

tting

tim

e (m

in)

GBFS Carbide slag

15615

192

8

10

12

14

16

18

20

6

4

2

0

(a)

FGD gypsum

Fina

l set

ting

time (

min

)

GBFS Carbide slag

8868

23625

20

15

10

5

0

(b)

Figure 6


for 7 and 28 d are equal to 248 and 407MPa respectivelyand the highest material strength is achieved at a mass ratioof FGD gypsum to GBFS to carbide slag of 13 26 20 Asindicated by the range analysis results presented in Table S4at a raw material combination of A2B5C3 (corresponding tothe mass ratio of FGD gypsum GBFS carbide slag equal to9 32 16) it exhibits the greatest impact on the 7 d strengthof the resulting material When the compositions of the rawmaterials are A4B3C1 and A2B3C5 (corresponding to themass ratios of FGD gypsum GBFS carbide slag equal to 13 28 12 and 9 28 20 resp) they exhibit the greatest impacton the 28 d compressive strength and exural strength ofthese materials respectively e observed phenomenon isdue to the eect produced by the presence of silicon dioxideand aluminium oxide species in GBFS in particular theCa2+ ions originated from carbide slag play an importantrole in the formation of calcium silicate hydrate (C-S-H)gel during the entire hydration process According toFigures 8(a) and 8(b) the utilised rawmaterials can be rankedaccording to their eect on the 7 d strength of the cementitiousmaterials as follows FGD gypsumgtGBFSgt carbide slag whilethe results presented in Figure 8(c) and 8(d) reveal that after28 d of aging their eects on the exural and compressivestrengths can be described as GBFSgtFGD gypsumgt carbideslag and GBFSgtFGD gypsumgt carbide slag respectively

In practical applications the strength of cementitiousmaterials is an important index To obtain a more accurateratio of the three raw materials that is FGD gypsum GBFSand carbide slag a nonlinear regression analysis was per-formed on the orthogonal results of the 28 d compressivestrength of the cementitious materials e following re-gression equation was obtainedy minus00011x21 minus 00141x

22 minus 00043x

23 minus 00165x1x2

+ 00295x1x3 + 00221x2x3 + 00702x1+ 06548x2 minus 08262x3

(2)

where y indicates the compressive strength x1 indicates FGDgypsum x2 indicates GBFS and x3 indicates carbide slagHere the residual sum of squares is 1469 e dependentand independent variables in this regression equation areobserved to have a good correlation Plt α indicates that thisequation can satisfy the signicance test rough accurateprediction within the range of the value of the three rawmaterial dosages the optimal ratio of the three raw materialsis FGD gypsum GBFS carbide slag 15 30 20 and thecompressive strength is 42MPa

OH + NaOH ONa + H2OSi Si

(3)

+ 2NaOH + H2OONa2OSi Si Si

(4)

Figure 9 is a hydration mechanism diagram of y ashFly ash and GBFS particles exhibit vitreous structureswhich form a compact acidic lm during their contact withwater is lm prevents the permeation of water into theparticlesrsquo interior and outward dissolution of ions thusmaking it impossible for y ash and GBFS to undergohydration After carbide slag was added to the cementitioussystem it reacted with water and raised the temperature ofthe system e presence of calcium hydroxide increasedthe concentration of OHminus ions in the mixture while theaddition of the sodium hydroxide activator produced a largeamount of OHminus ions which in turn increased its pH usthe addition of carbide slag rapidly destroys the acidic lmlayers on the y ash and GBFS surfaces as well as Si-O-Siand Si-O-Al irregular chain structures which enable thedissolution of various mineral components such as silicondioxide and aluminium oxide [28] e damage of the vit-reous surfaces caused by the sodium hydroxide addition canbe described by (3) and (4)

e Si-O-Na species produced during these reactions aresoluble in water while the subsequent exchange of Na+ withCa2+ leads to the formation of C-S-H gel β-Hemihydrategypsum can react with water to form calcium sulphatedihydrate e SO4

2minus species produced during the dissoci-ation of calcium sulphate dihydrate are adsorbed onto thesurface of the vitreous body breaking the Si-O and Al-Obonds at the active reaction sites and thus assisting OHminus ionsin destroying the acid membrane In addition SO4

2minus ionsreact with AlO2

minus in the reaction system in the presence ofCa2+ ions to form AFt species [3] in accordance with (5)

SO42minus + Ca2+ + AlO2

minus+ OHminus ⟶ 3CaO middot Al2O3 middot 3CaSO4 middot 32H2O

(5)

16

40

35

30

25

20

15

10

5

0

36

29

FGD gypsum GBFS

Slum

p va

lue (

mm

)

Carbide slag

Figure 7


3CaO middot Al2O3 middot 6H2O + 3CaSO4 middot 2H2O + 20H2O⟶ 3CaO middot Al2O3 middot 3CaSO4 middot 32H2O

(6)

A fraction of calcium aluminate hydrate can also reactwith calcium sulphate dihydrate to form AFt in accordancewith (6)

e produced AFt species play the following two roles inthe obtained cementitious system

(1) e swelling of AFt [15] cracks the surface of thevitreous body and exposes the active substanceslocated below thus increasing the concentration ofthe volcano ash reactants in the system AFt particlesmay also ll the gaps in the hydration space whichimproves the compactness of the cementitious sys-tem and enhances its strength

(2) e needle-shaped AFt particles interconnect toform brous or network coatings on the surfaces ofy ash and blast-furnace slag particles Because thecompactness of the C-S-H layer is greater than thatof the AFt coating the Ca2+ ions produced during

calcium hydroxide ionisation tend to diuse intothe interior of the y ash and blast-furnace slagparticles and react with silicon dioxide and alu-minium oxide species is process shortens theplateau of the activation process and furtherstimulates the activity of y ash and blast-furnaceslag particles

In addition SO42minus ions can displace some of the SiO4

4minus

ions in the C-S-H gel e displaced SiO44minus ion species

facilitate further dissolution of aluminium oxide and thereaction with Ca2+ ions thus increasing the produced gelamount ey can react with the active sites of the Al3+network on the surface of the vitreous body cleaving Si-Oand Al-O bonds and accelerating the hydration reaction[29] which in turn causes the secondary hydration eactive materials of y ash and blast-furnace slag are con-sumed in the presence of FGD gypsum and carbide slagresulting in the establishment of a positive cycle thatstimulates their activity to the highest extent possible andtherefore enhances the strength of the produced cementi-tious system

FGD gypsum00

Com

pres

sive s

treng

th a

er 7

d (M

Pa)

01

02

03

04

05

06

GBFS Carbide slag

0546

0288

0176

(a)

FGD gypsum000

Flex

ural

stre

ngth

aer

7d

(MPa

)

005

010

015

020

025

030

GBFS Carbide slag

0262

01220098

(b)

FGD gypsum000

Com

pres

sive s

treng

th a

er 2

8d (M

Pa)

005

010

015

020

025

030

035

045

040

GBFS Carbide slag

0404

0232

0092

(c)

FGD gypsum000

Flex

ural

stre

ngth

aer

28d

(MPa

)

002

004

006

008

010

012

014

016

GBFS Carbide slag

0134

0148

0124

(d)

Figure 8


35 SEM and XRD Analyses Figure 10 shows the SEMphotographs of the 10th and 21st sets of samples whichcontain large amounts of y ash particles served asa framework e hydration products of the cementitiousmaterial obtained after 7 d of aging were primarilycomposed of needle- or rod-like AFt crystals and a smallamount of the brous C-S-H gel while the internal samplestructure contained relatively large pores e hydrationproducts obtained after 28 d of aging included largeramounts of AFt crystals and C-S-H gel which overlappedand interlaced with each other thus lling the pores of thecementitious material and forming a relatively compactstructure with a continuously increasing strength Basedon the obtained SEM results sample no 21 containedsmaller amounts of AFt and C-S-H gel species producedduring hydration as compared to sample no 10 Fur-thermore sample no 21 contained a large amount of akycalcium hydroxide species which were not involved in thehydration reaction It also exhibited large pores and aninsuumlciently compact structure which was consistentwith its strength

Under the action of carbide slag and sodium hydroxideactive silicon dioxide and aluminium oxide species in thecementitious system reacted with SO4

2minus ions in the liquidphase to produce AFt crystals which in turn lled the poresand bound to the y ash particles forming a three-dimensional

network spatial structure with a gradually increasing strength[30] When the y ash particles were surrounded by thehydration products they continued to be hydrated into theC-S-H gel and lled the pores of the cementitious system Asa result the compactness and strength of the resulting ce-mentitious material were enhanced

Figure 11 shows the XRD pattern obtained for sampleno 10 After the cementitious system underwent hydrationfor 7 d several AFt and CSH2 diraction peaks were de-tected along with the diraction peaks of calcium hy-droxide which was not involved in the hydration reactione intensities of the calcium hydroxide diraction peaksgradually decreased with time while a bulging processaccompanied by the formation of a large amount of theC-S-H gel was observed in the 2θ range of 15ndash60deg eobtained results indicate that y ash was gradually activatedduring the rst 7 d of curing In addition prominent C-S-Hgel diraction peaks were observed after 28 d of hydrationwhich could be explained as follows rst aluminium oxidereacted with Ca2+ and SO4

2minus ions in the liquid phase toproduce AFt crystals (which covered the surface of y ashparticles) and a small amount of the C-S-H gel whichsubsequently strengthened the cementitious system After28 d of hydration a substantial amount of Ca2+ ions wereconsumed producing larger amounts of the C-S-H gel eresulting gel species lled the pores of the cementitious

O

Si

Al

Ca2+

SO42ndash

AFt

Fly ash

Fly ash

Fly ash

ndash

SiO2

Al2O3

OHndashndash

ndashndash ndashndash

ndash

ndashndash

Figure 9


system and adhered to each other thereby increasing thematerial strength

4 Conclusion

In this study the activity of fly ash and other industrial wasteslag was stimulated by the presence of carbide slag in thefilling cementitious materials prepared without adding any

cement clinker +e main conclusions can be summarised asfollows

(1) +e utilised raw materials can be ranked dependingon the following parameters (a) the amount of waterconsumed for reaching standard consistency andconsistency FGD gypsumgt carbide slaggtGBFS (b)the setting time FGD gypsumgt carbide slaggtGBFS(c) the slump value GBFSgt carbide slaggtFGDgypsum (d) the material strength after 7 d of hy-dration FGD gypsumgtGBFSgt carbide slag and (e)the material flexural and compressive strengths after28 d of hydration FGD gypsumgtGBFSgt carbide slagand GBFSgtFGD gypsumgt carbide slag respectively

(2) +e optimal activation results were achieved whenthe mass ratio of carbide slag fly ash GBFS FGDgypsum was 121 606 182 91

(3) +e results of SEM and XRD analyses indicated thatthe hydration products obtained after 7 d of curingwere primarily composed of AFt crystals and a smallamount of the C-S-H gel In contrast a relativelylarge amount of the C-S-H gel was produced after28 d of hydration

(4) +emanufacturing of fly ash-carbide slag-GBFS-FGDgypsum cementitious materials utilises substantialamounts of industrial waste (including fly ash andcarbide slag) which can potentially produce sig-nificant social and economic benefits

0

0

50

Inte

nsity

(au

)

100

150

200

250

10 20 30

A

A

D

C

C

D

BD

402θ (deg)

50 60 70 80

7d

28d

A AFtB Ca(OH)2C C-S-HD CSH2

Figure 11

Ca(OH)2

AFt

(a)

C-S-H gel

(b)

Ca(OH)2C-S-H gel

(c)

Ca(OH)2

AFt

(d)

Figure 10


Data Availability

+e data used to support the findings of this study are in-cluded within the supplementary information files

Conflicts of Interest

+e authors declare that they have no conflicts of interest

Acknowledgments

+is study was supported by the National Natural ScienceFoundation of China (Grant nos 51674038 and 51674157)the Shandong Province Natural Science Foundation (Grantno ZR2018JL019) the China Postdoctoral Science Foun-dation (Grant nos 2014M560567 and 2015T80730) theShandong Province Science and Technology DevelopmentPlan (Grant no 2017GSF220003) the State Key Program forCoal Joint Funds of the National Natural Science Founda-tion of China (Grant no U1261205) the Scientific ResearchFoundation of Shandong University of Science and Tech-nology for Recruited Talents (Grant nos 2017RCJJ010 and2017RCJJ037) the Shandong Province First Class SubjectFunding Project (Grant no 01AQ05202) the TaishanScholar Talent Team Support Plan for Advantaged amp UniqueDiscipline Areas and the Graduate Student Science andTechnology Innovation Project of Shandong University ofScience and Technology (Grant no SDKDYC170304)

Supplementary Materials

Table S1 range analysis of the water amount required forreaching standard consistency and consistency Table S2range analysis of the setting time Table S3 range analysis ofthe slump value Table S4 range analysis of the materialstrength (Supplementary Materials)

References

[1] L J Gardner S A Bernal S A Walling C L CorkhillJ L Provis and N C Hyatt ldquoCharacterisation of magnesiumpotassium phosphate cements blended with fly ash andground granulated blast furnace slagrdquo Cement and ConcreteResearch vol 74 pp 78ndash87 2015

[2] J L Pastor J M Ortega M Flor M Pilar Lopez I Sanchezand M A Climent ldquoMicrostructure and durability of fly ashcement grouts for micropilesrdquo Construction and BuildingMaterials vol 117 pp 47ndash57 2016

[3] G Y Chen andW H Huang ldquoInvestigation on blending CFBash with blast furnace slag as replacement for Portland cementused in concrete bindersrdquo Advanced Materials Researchvol 723 pp 623ndash629 2013

[4] Y Chen and Y L Gao ldquoFly ash-desulfurization gypsummortar and concrete part II performancesrdquo Advanced Ma-terials Research vol 243ndash249 pp 6880ndash6886 2011

[5] G Rutkowska K Wisniewski M Chalecki M Gorecka andK Miłosek ldquoInfluence of fly-ashes on properties of ordinaryconcretesrdquo Annals of Warsaw University of Life SciencesndashSGGW Land Reclamation vol 48 no 1 pp 79ndash94 2016

[6] J A Zakeri M Esmaeili S A Mosayebi and O SayadildquoExperimental investigation of the production of sleepersfrom concrete that contains blast furnace slagrdquo Proceedings of

the Institution of Mechanical Engineers Part F Journal of Railand Rapid Transit vol 230 no 1 pp 77ndash84 2016

[7] N Marjanovic M Komljenovic Z Bascarevic V Nikolic andR Petrovic ldquoPhysicalndashmechanical and microstructural prop-erties of alkali-activated fly ashndashblast furnace slag blendsrdquoCeramics International vol 41 no 1 pp 1421ndash1435 2015

[8] X L Guo H S Shi and A D Warren ldquoUtilization ofthermally treated flue gas desulfurization (FGD) gypsum andclass-C fly ash (CFA) to prepare CFA-based geopolymerrdquoJournal of Wuhan University of Technology vol 28 no 1pp 132ndash138 2013

[9] P Pavithra M S Reddy P Dinakar B Hanumantha RaoB K Satpathy and A N Mohanty ldquoA mix design procedurefor geopolymer concrete with fly ashrdquo Journal of CleanerProduction vol 133 pp 117ndash125 2016

[10] H Y Du L N Yang W Q Gao et al ldquoEffects of charac-teristics of fly ash on the properties of geopolymerrdquo Trans-actions of Tianjin University vol 22 no 3 pp 261ndash267 2016

[11] W X Chen F Y Li X H Guan L Chen and W Bo NieldquoResearch on mining water-rich fly-ash-based fillingmaterialrdquo Advanced Materials Research vol 988 pp 201ndash2062014

[12] S G Hu X J Lu H L Niu and Z Q Jin ldquoResearch onpreparation and properties of backfilling cementation ma-terial based on blast furnace slagrdquo Advanced Materials Re-search vol 158 pp 189ndash196 2011

[13] B Ma X Li Y Mao and X Shen ldquoSynthesis and charac-terization of high belite sulfoaluminate cement through richalumina fly ash and desulfurization gypsumrdquo Ceramics Sili-katy vol 57 no 1 pp 7ndash13 2013

[14] A Sarkar A K Sahani D K Singha Roy and A Kr SamantaldquoCompressive strength of sustainable concrete combiningblast furnace slag and fly ashrdquo Social Science ElectronicPublishing vol 9 no 1 pp 17ndash26 2016

[15] H Qin X Liu and G Li ldquoPreparation and properties ofdesulfurization gypsum-slag hydraulic cementitious mate-rialsrdquo Procedia Engineering vol 27 pp 244ndash252 2012

[16] Y L Wang S J Dong L L Liu S P Cui and H B XuldquoStudy formation process of cement clinker minerals by usingcalcium carbide slag as raw materialrdquo Applied Mechanics ampMaterials vol 389 pp 341ndash345 2013

[17] C W Hao and M Deng ldquoSurface modification of fly asheswith carbide slag and its effect on compressive strength andautogenous shrinkage of blended cement pastesrdquo Journal ofWuhan University of Technology-Mater Sci Ed vol 27 no 6pp 1149ndash1153 2012

[18] Q Zhang X-M Hu M-Y Wu Y-Y Zhao and C YuldquoEffects of different catalysts on the structure and properties ofpolyurethanewater glass grouting materialsrdquo Journal ofApplied Polymer Science vol 135 no 27 2018

[19] G Zhou Q Zhang R Bai T Fan and G Wang ldquo+e dif-fusion behavior law of respirable dust at fully mechanizedcaving face in coal mine CFD numerical simulation andengineering applicationrdquo Process Safety and EnvironmentalProtection vol 106 pp 117ndash128 2017

[20] G Zhou Y Ma T Fan and G Wang ldquoPreparation andcharacteristics of a multifunctional dust suppressant withagglomeration and wettability performance used in coalminerdquo Chemical Engineering Research and Design vol 132pp 729ndash742 2018

[21] W Yang H Wang B Lin et al ldquoOutburst mechanism oftunnelling through coal seams and the safety strategy by usingldquostrong-weakrdquo coupling circle-layersrdquo Tunnelling and Un-derground Space Technology vol 74 pp 107ndash118 2018


[22] H Wang W Nie W Cheng Q Liu and H Jin ldquoEffects of airvolume ratio parameters on air curtain dust suppression ina rock tunnelrsquos fully-mechanized working facerdquo AdvancedPowder Technology vol 29 no 2 pp 230ndash244 2017

[23] Q Liu W Nie Y Hua et al ldquo+e effects of the installationposition of a multi-radial swirling air-curtain generator ondust diffusion and pollution rules in a fully-mechanized ex-cavation face a case studyrdquo Powder Technology vol 329pp 371ndash385 2018

[24] W Nie W Wei Q Liu et al ldquoSimulation experiments on thecontrollability of dust diffusion by means of multi-radialvortex airflowrdquo Advanced Powder Technology vol 29no 3 pp 835ndash847 2018

[25] T Fan G Zhou and J Wang ldquoPreparation and character-ization of a wetting-agglomeration-based hybrid coal dustsuppressantrdquo Process Safety and Environmental Protectionvol 113 pp 282ndash291 2018

[26] Z X Hu X M Hu W M Cheng and W Lu ldquoInfluence ofsynthetic conditions on the performance of melaminendashphenolndashformaldehyde resin microcapsulesrdquo High Perfor-mance Polymers 2018

[27] W M Cheng X M Hu J Xie and Y Zhao ldquoAn intelligentgel designed to control the spontaneous combustion of coalfire prevention and extinguishing propertiesrdquo Fuel vol 210pp 826ndash835 2017

[28] X L Guo H S Shi L Chen and W A Dick ldquoAlkali-activated complex binders from class C fly ash and Ca-containing admixturesrdquo Journal of Hazardous Materialsvol 173 no 1-3 pp 480ndash486 2010

[29] F S Fonseca R C Godfrey and K Siggard ldquoCompressivestrength of masonry grout containing high amounts of class Ffly ash and ground granulated blast furnace slagrdquo Con-struction and Building Materials vol 94 pp 719ndash727 2015

[30] Z X Hu X M Hu W M Cheng et al ldquoPerformance op-timization of one-component polyurethane healing agent forself-healing concreterdquo Construction and Building Materialsvol 179 pp 151ndash159 2018


CorrosionInternational Journal of

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Analytical ChemistryInternational Journal of


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Journal ofEngineeringVolume 2018

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High Energy PhysicsAdvances in

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

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TribologyAdvances in



ChemistryAdvances in


Advances inPhysical Chemistry


BioMed Research InternationalMaterials

Journal of


Na

nom

ate

ria

ls


Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom

air pollution Additionally if carbide slag is stacked it mayoccupy a large area of the land and put immense pressure onthe ecological environment Hence both domestic and in-ternational researchers have conducted a number of studieson the comprehensive utilisation of carbide slag Wang et al[16] prepared cement clinker using carbide slag as the rawmaterial and studied the formation process of cementclinker minerals Hao et al [17] examined the effects of thefly ash and carbide slag addition on the compressive strengthof the resulting cement paste However it is still unclearwhether carbide slag can effectively activate fly ash Becausecarbide slag is rich in the alkaline calcium oxide and calciumhydroxide components we hypothesised that it wouldprovide a large number of OHminus ions when used as an ad-mixture of cementitious materials +ese ions can effectivelydestroy the acidic film formed on the surfaces of fly ash andGBFS particles leading to the dissolution of various mineralconstituents such as silicon dioxide and aluminium oxide+e latter process in turn promotes the hydration of fly ashand GBFS components and forms hydration productscharacterised by a certain level of strength

Hence in the present study fly ash carbide slag GBFSand FGD gypsum were used to prepare green cementitiousmaterials without cement clinker Afterwards we in-vestigated the mechanical properties and morphology ofthese materials in order to identify the optimal quantities ofcarbide slag fly ash and other industrial waste componentsWe hope that this study will contribute to the preparationand promotion of high-quality inexpensive cementitiousmaterials for mine filling [18ndash24]

2 Materials and Methods

21 Raw Materials +e following raw materials have beenutilised in this study

Fly ash with a density of 178 gcm3 and a specific surfacearea of 219m2kg was purchased from Shandong BinzhouShanshui Cement Co Ltd Its activity index was calculatedas follows

R28 R

R01113888 1113889 times 100 (1)

+e obtained activity index of the fly ash was H28 61(its chemical composition is listed in Table 1)

GBFS with a density of 288 gcm3 and a specific surfacearea of 361m2kg was purchased from Shandong BinzhouShanshui Cement Co Ltd Its chemical composition is listedin Table 1 and the corresponding X-ray diffraction (XRD)pattern is depicted in Figure 1 It shows the existence ofa large peak in the 2θ range of 20ndash38deg and a very smallamount of the gehlenite phase without any distinct crys-talline peaks Hence the GBFS used in this study can beconsidered a completely vitreous material

Carbide slag purchased from Shandong Linzi AcetyleneGas Factory was calcined for 30min at 1000degC It wascharacterised by the calcium oxide mass fraction of 775calcium hydroxide mass fraction of 185 density of264 gcm3 and specific surface area of 419m2kg +e

chemical composition of the utilised carbide slag is listed inTable 1

FGD gypsum that contained more than 90 mass ofcalcium sulphate dihydrate was purchased from ShandongBinzhou Shanshui Cement Co Ltd After the calcination ofFGD gypsum for 2 h at 180degC its major component wasconverted into β-hemihydrate gypsum with a density of264 gcm3 and a specific surface area of 269m2kg

Admixtures of sodium hydroxide (ge960 mass) andnaphthalene superplasticiser (Clminus content lt04 masssulphate content lt9 mass and solid content ge93 mass)were purchased from Chenqi Chemical Technology Co LtdShanghai

+e density of the mixture was 231 gcm3 and itsspecific surface area was 327m2kg

Round siliceous river sand with a silicon dioxide contentexceeding 98 mass was utilised Its particle size is listed inFigure 2

Tap water was used in all experiments

22 Preparation of Test Blocks An orthogonal experimentaldesign was employed for the development of experimentalprocedures +e orthogonal testing parameters included themasses of FGD gypsum (A) GBFS (B) and carbide slag (C)(their corresponding amounts are listed in Table 2)

In accordance with the parameter combinations describedin the L25(56) orthogonal table [11] the fly ash carbide slagFGD gypsum GBFS and admixture components were mixedtogether to form composite cementitious materials Prior tomixing the materials were weighed with an accuracy of 001 gusing an electronic balance (YP1002N Shanghai JingkeTianmei Scientific Instrument Co Ltd) in accordance with thematerial mixing ratios provided in Table 3 +e cementsandratio was 025 and the watercement ratio was 05 Sub-sequently the weighed materials were mixed using the fol-lowing procedure first a specified amount of granular sodiumhydroxide was dissolved in water and the resulting aqueoussodium hydroxide solution was added to the bowl of the mixerwith a capacity of 5 L (JJ-5 Wuxi Xiyi Building MaterialsInstrument Co Ltd) whichwas fixed onto its frame and raisedto a set position Afterwards the materials were immediatelymixed for 30 s at a low speed of 140plusmn5 rpm Sand was con-tinuously added at a uniform rate during the next 30 s ofmixing After the sand addition the mixer was run for another30 s at a high speed of 285plusmn 10 rpm and then stopped for 90 sWithin the first 15 s after the mixer was stopped the mortarthat had adhered to the blades and bowl wall was scraped intothe centre of the bowl After a 90 s interval the mixing processwas continued for another 60 s at a high speed Immediatelyafter mixing the materials were moulded using an empty testmould (with dimensions of 40mmtimes 40mmtimes 160mm) anda bushing fixed onto a vibrating compaction table A scoop wasused to obtain mortar from the mixer bowl which was placedinto the testmould in two layers About 300 g ofmortar was putinto each groove in the first layer which was then compactedvia 60 vibrations +e second layer was added until the mouldwas filled and the mortar was again compacted by 60 vibra-tions Afterwards themould bushingwas removed and the testmould was transferred from the vibrating compaction table












0

0

Inte

nsity

(au

)

200

400

600

800

1000

1200

10 20 30 40

A

50 60 70

A Ca2Al2SiO7

2θ (deg)

Figure 1

01

0 0

5

10

15

20

25

20

40

60

Cum

ulat

ive d

istrib

utio

n (

)

Freq

uenc

y di

strib

utio

n (

)80

100

1Particle size (mm)

10

Figure 2


LevelsFactors


slag (g) (C)1 7 24 122 9 26 143 11 28 164 13 30 185 15 32 20


Number

Raw materials

FGDgypsum(g)

GBFS(g)

Carbideslag (g)

Flyash(g)

Sodiumhydroxide

(g)


(g)1 7 24 12 100 75 052 7 26 14 100 78 053 7 28 16 100 79 054 7 30 18 100 82 055 7 32 20 100 84 056 9 24 14 100 77 057 9 26 16 100 79 058 9 28 18 100 82 059 9 30 20 100 84 0510 9 32 12 100 81 0511 11 24 16 100 79 0512 11 26 18 100 82 0513 11 28 20 100 84 0514 11 30 12 100 81 0515 11 32 14 100 83 0516 13 24 18 100 82 0517 13 26 20 100 84 0518 13 28 12 100 81 0519 13 30 14 100 83 0520 13 32 16 100 85 0521 15 24 20 100 84 0522 15 26 12 100 81 0523 15 28 14 100 83 0524 15 30 16 100 85 0525 15 32 18 100 92 05











Figure 3




(a) (b)

Figure 4



consistency (mL)

Consistency(mm)

Slump(mm)


Finaltime

Compressivestrength

Flexuralstrength

Compressivestrength

Flexuralstrength

1 141 14 212 287 397 172 061 379 1352 137 13 143 298 387 181 065 340 1053 128 14 129 265 389 248 095 367 1124 132 13 144 267 364 178 064 323 0985 135 14 165 279 397 214 080 336 1336 126 14 138 259 367 222 084 320 1307 143 13 174 246 387 194 079 292 1298 136 14 158 275 376 232 092 384 1449 134 15 149 289 359 237 093 346 12310 137 14 190 273 378 243 093 339 12411 127 11 147 256 367 189 077 335 11712 147 12 211 265 387 190 078 313 11413 132 15 157 286 398 184 075 314 12614 123 14 138 265 369 181 072 356 12415 128 14 139 254 378 222 083 337 10316 131 12 210 247 367 182 066 349 13317 138 14 200 267 373 229 090 407 14018 121 13 129 256 357 180 066 356 11019 127 13 146 243 363 150 066 340 09820 130 13 178 287 356 215 080 405 14721 145 13 191 267 364 163 057 358 11622 138 9 159 253 352 163 056 347 11523 146 8 148 256 358 171 061 394 14024 141 9 149 278 398 181 066 347 11525 142 7 138 298 378 177 070 372 122






FGD gypsum

Am

ount

of w

ater

requ

ired

for

reac

hing

stan

dard

cons

isten

cy (m

L)

GBFS Carbide slag

9692

1314

12

10

8

6

4

2

0

(a)

FGD gypsum

Con

siste

ncy

rang

e (m

m)

GBFS Carbide slag

2

1

55

4

3

2

1

0

(b)

Figure 5

FGD gypsum

Initi

al se

tting

tim

e (m

in)

GBFS Carbide slag

15615

192

8

10

12

14

16

18

20

6

4

2

0

(a)

FGD gypsum

Fina

l set

ting

time (

min

)

GBFS Carbide slag

8868

23625

20

15

10

5

0

(b)

Figure 6




22 minus 00043x

23 minus 00165x1x2

+ 00295x1x3 + 00221x2x3 + 00702x1+ 06548x2 minus 08262x3

(2)



(3)


(4)








(5)

16

40

35

30

25

20

15

10

5

0

36

29

FGD gypsum GBFS

Slum

p va

lue (

mm

)

Carbide slag

Figure 7



(6)







4minus



FGD gypsum00

Com

pres

sive s

treng

th a

er 7

d (M

Pa)

01

02

03

04

05

06

GBFS Carbide slag

0546

0288

0176

(a)

FGD gypsum000

Flex

ural

stre

ngth

aer

7d

(MPa

)

005

010

015

020

025

030

GBFS Carbide slag

0262

01220098

(b)

FGD gypsum000

Com

pres

sive s

treng

th a

er 2

8d (M

Pa)

005

010

015

020

025

030

035

045

040

GBFS Carbide slag

0404

0232

0092

(c)

FGD gypsum000

Flex

ural

stre

ngth

aer

28d

(MPa

)

002

004

006

008

010

012

014

016

GBFS Carbide slag

0134

0148

0124

(d)

Figure 8








O

Si

Al

Ca2+

SO42ndash

AFt

Fly ash

Fly ash

Fly ash

ndash

SiO2

Al2O3

OHndashndash


ndash

ndashndash

Figure 9



4 Conclusion







0

0

50

Inte

nsity

(au

)

100

150

200

250

10 20 30

A

A

D

C

C

D

BD

402θ (deg)

50 60 70 80

7d

28d


Figure 11

Ca(OH)2

AFt

(a)

C-S-H gel

(b)

Ca(OH)2C-S-H gel

(c)

Ca(OH)2

AFt

(d)

Figure 10


Data Availability




Acknowledgments




References




































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls














0

0

Inte

nsity

(au

)

200

400

600

800

1000

1200

10 20 30 40

A

50 60 70

A Ca2Al2SiO7

2θ (deg)

Figure 1

01

0 0

5

10

15

20

25

20

40

60

Cum

ulat

ive d

istrib

utio

n (

)

Freq

uenc

y di

strib

utio

n (

)80

100

1Particle size (mm)

10

Figure 2


LevelsFactors


slag (g) (C)1 7 24 122 9 26 143 11 28 164 13 30 185 15 32 20


Number

Raw materials

FGDgypsum(g)

GBFS(g)

Carbideslag (g)

Flyash(g)

Sodiumhydroxide

(g)


(g)1 7 24 12 100 75 052 7 26 14 100 78 053 7 28 16 100 79 054 7 30 18 100 82 055 7 32 20 100 84 056 9 24 14 100 77 057 9 26 16 100 79 058 9 28 18 100 82 059 9 30 20 100 84 0510 9 32 12 100 81 0511 11 24 16 100 79 0512 11 26 18 100 82 0513 11 28 20 100 84 0514 11 30 12 100 81 0515 11 32 14 100 83 0516 13 24 18 100 82 0517 13 26 20 100 84 0518 13 28 12 100 81 0519 13 30 14 100 83 0520 13 32 16 100 85 0521 15 24 20 100 84 0522 15 26 12 100 81 0523 15 28 14 100 83 0524 15 30 16 100 85 0525 15 32 18 100 92 05











Figure 3




(a) (b)

Figure 4



consistency (mL)

Consistency(mm)

Slump(mm)


Finaltime

Compressivestrength

Flexuralstrength

Compressivestrength

Flexuralstrength

1 141 14 212 287 397 172 061 379 1352 137 13 143 298 387 181 065 340 1053 128 14 129 265 389 248 095 367 1124 132 13 144 267 364 178 064 323 0985 135 14 165 279 397 214 080 336 1336 126 14 138 259 367 222 084 320 1307 143 13 174 246 387 194 079 292 1298 136 14 158 275 376 232 092 384 1449 134 15 149 289 359 237 093 346 12310 137 14 190 273 378 243 093 339 12411 127 11 147 256 367 189 077 335 11712 147 12 211 265 387 190 078 313 11413 132 15 157 286 398 184 075 314 12614 123 14 138 265 369 181 072 356 12415 128 14 139 254 378 222 083 337 10316 131 12 210 247 367 182 066 349 13317 138 14 200 267 373 229 090 407 14018 121 13 129 256 357 180 066 356 11019 127 13 146 243 363 150 066 340 09820 130 13 178 287 356 215 080 405 14721 145 13 191 267 364 163 057 358 11622 138 9 159 253 352 163 056 347 11523 146 8 148 256 358 171 061 394 14024 141 9 149 278 398 181 066 347 11525 142 7 138 298 378 177 070 372 122






FGD gypsum

Am

ount

of w

ater

requ

ired

for

reac

hing

stan

dard

cons

isten

cy (m

L)

GBFS Carbide slag

9692

1314

12

10

8

6

4

2

0

(a)

FGD gypsum

Con

siste

ncy

rang

e (m

m)

GBFS Carbide slag

2

1

55

4

3

2

1

0

(b)

Figure 5

FGD gypsum

Initi

al se

tting

tim

e (m

in)

GBFS Carbide slag

15615

192

8

10

12

14

16

18

20

6

4

2

0

(a)

FGD gypsum

Fina

l set

ting

time (

min

)

GBFS Carbide slag

8868

23625

20

15

10

5

0

(b)

Figure 6




22 minus 00043x

23 minus 00165x1x2

+ 00295x1x3 + 00221x2x3 + 00702x1+ 06548x2 minus 08262x3

(2)



(3)


(4)








(5)

16

40

35

30

25

20

15

10

5

0

36

29

FGD gypsum GBFS

Slum

p va

lue (

mm

)

Carbide slag

Figure 7



(6)







4minus



FGD gypsum00

Com

pres

sive s

treng

th a

er 7

d (M

Pa)

01

02

03

04

05

06

GBFS Carbide slag

0546

0288

0176

(a)

FGD gypsum000

Flex

ural

stre

ngth

aer

7d

(MPa

)

005

010

015

020

025

030

GBFS Carbide slag

0262

01220098

(b)

FGD gypsum000

Com

pres

sive s

treng

th a

er 2

8d (M

Pa)

005

010

015

020

025

030

035

045

040

GBFS Carbide slag

0404

0232

0092

(c)

FGD gypsum000

Flex

ural

stre

ngth

aer

28d

(MPa

)

002

004

006

008

010

012

014

016

GBFS Carbide slag

0134

0148

0124

(d)

Figure 8








O

Si

Al

Ca2+

SO42ndash

AFt

Fly ash

Fly ash

Fly ash

ndash

SiO2

Al2O3

OHndashndash


ndash

ndashndash

Figure 9



4 Conclusion







0

0

50

Inte

nsity

(au

)

100

150

200

250

10 20 30

A

A

D

C

C

D

BD

402θ (deg)

50 60 70 80

7d

28d


Figure 11

Ca(OH)2

AFt

(a)

C-S-H gel

(b)

Ca(OH)2C-S-H gel

(c)

Ca(OH)2

AFt

(d)

Figure 10


Data Availability




Acknowledgments




References




































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls













Figure 3




(a) (b)

Figure 4



consistency (mL)

Consistency(mm)

Slump(mm)


Finaltime

Compressivestrength

Flexuralstrength

Compressivestrength

Flexuralstrength

1 141 14 212 287 397 172 061 379 1352 137 13 143 298 387 181 065 340 1053 128 14 129 265 389 248 095 367 1124 132 13 144 267 364 178 064 323 0985 135 14 165 279 397 214 080 336 1336 126 14 138 259 367 222 084 320 1307 143 13 174 246 387 194 079 292 1298 136 14 158 275 376 232 092 384 1449 134 15 149 289 359 237 093 346 12310 137 14 190 273 378 243 093 339 12411 127 11 147 256 367 189 077 335 11712 147 12 211 265 387 190 078 313 11413 132 15 157 286 398 184 075 314 12614 123 14 138 265 369 181 072 356 12415 128 14 139 254 378 222 083 337 10316 131 12 210 247 367 182 066 349 13317 138 14 200 267 373 229 090 407 14018 121 13 129 256 357 180 066 356 11019 127 13 146 243 363 150 066 340 09820 130 13 178 287 356 215 080 405 14721 145 13 191 267 364 163 057 358 11622 138 9 159 253 352 163 056 347 11523 146 8 148 256 358 171 061 394 14024 141 9 149 278 398 181 066 347 11525 142 7 138 298 378 177 070 372 122






FGD gypsum

Am

ount

of w

ater

requ

ired

for

reac

hing

stan

dard

cons

isten

cy (m

L)

GBFS Carbide slag

9692

1314

12

10

8

6

4

2

0

(a)

FGD gypsum

Con

siste

ncy

rang

e (m

m)

GBFS Carbide slag

2

1

55

4

3

2

1

0

(b)

Figure 5

FGD gypsum

Initi

al se

tting

tim

e (m

in)

GBFS Carbide slag

15615

192

8

10

12

14

16

18

20

6

4

2

0

(a)

FGD gypsum

Fina

l set

ting

time (

min

)

GBFS Carbide slag

8868

23625

20

15

10

5

0

(b)

Figure 6




22 minus 00043x

23 minus 00165x1x2

+ 00295x1x3 + 00221x2x3 + 00702x1+ 06548x2 minus 08262x3

(2)



(3)


(4)








(5)

16

40

35

30

25

20

15

10

5

0

36

29

FGD gypsum GBFS

Slum

p va

lue (

mm

)

Carbide slag

Figure 7



(6)







4minus



FGD gypsum00

Com

pres

sive s

treng

th a

er 7

d (M

Pa)

01

02

03

04

05

06

GBFS Carbide slag

0546

0288

0176

(a)

FGD gypsum000

Flex

ural

stre

ngth

aer

7d

(MPa

)

005

010

015

020

025

030

GBFS Carbide slag

0262

01220098

(b)

FGD gypsum000

Com

pres

sive s

treng

th a

er 2

8d (M

Pa)

005

010

015

020

025

030

035

045

040

GBFS Carbide slag

0404

0232

0092

(c)

FGD gypsum000

Flex

ural

stre

ngth

aer

28d

(MPa

)

002

004

006

008

010

012

014

016

GBFS Carbide slag

0134

0148

0124

(d)

Figure 8








O

Si

Al

Ca2+

SO42ndash

AFt

Fly ash

Fly ash

Fly ash

ndash

SiO2

Al2O3

OHndashndash


ndash

ndashndash

Figure 9



4 Conclusion







0

0

50

Inte

nsity

(au

)

100

150

200

250

10 20 30

A

A

D

C

C

D

BD

402θ (deg)

50 60 70 80

7d

28d


Figure 11

Ca(OH)2

AFt

(a)

C-S-H gel

(b)

Ca(OH)2C-S-H gel

(c)

Ca(OH)2

AFt

(d)

Figure 10


Data Availability




Acknowledgments




References




































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls






(a) (b)

Figure 4



consistency (mL)

Consistency(mm)

Slump(mm)


Finaltime

Compressivestrength

Flexuralstrength

Compressivestrength

Flexuralstrength

1 141 14 212 287 397 172 061 379 1352 137 13 143 298 387 181 065 340 1053 128 14 129 265 389 248 095 367 1124 132 13 144 267 364 178 064 323 0985 135 14 165 279 397 214 080 336 1336 126 14 138 259 367 222 084 320 1307 143 13 174 246 387 194 079 292 1298 136 14 158 275 376 232 092 384 1449 134 15 149 289 359 237 093 346 12310 137 14 190 273 378 243 093 339 12411 127 11 147 256 367 189 077 335 11712 147 12 211 265 387 190 078 313 11413 132 15 157 286 398 184 075 314 12614 123 14 138 265 369 181 072 356 12415 128 14 139 254 378 222 083 337 10316 131 12 210 247 367 182 066 349 13317 138 14 200 267 373 229 090 407 14018 121 13 129 256 357 180 066 356 11019 127 13 146 243 363 150 066 340 09820 130 13 178 287 356 215 080 405 14721 145 13 191 267 364 163 057 358 11622 138 9 159 253 352 163 056 347 11523 146 8 148 256 358 171 061 394 14024 141 9 149 278 398 181 066 347 11525 142 7 138 298 378 177 070 372 122






FGD gypsum

Am

ount

of w

ater

requ

ired

for

reac

hing

stan

dard

cons

isten

cy (m

L)

GBFS Carbide slag

9692

1314

12

10

8

6

4

2

0

(a)

FGD gypsum

Con

siste

ncy

rang

e (m

m)

GBFS Carbide slag

2

1

55

4

3

2

1

0

(b)

Figure 5

FGD gypsum

Initi

al se

tting

tim

e (m

in)

GBFS Carbide slag

15615

192

8

10

12

14

16

18

20

6

4

2

0

(a)

FGD gypsum

Fina

l set

ting

time (

min

)

GBFS Carbide slag

8868

23625

20

15

10

5

0

(b)

Figure 6




22 minus 00043x

23 minus 00165x1x2

+ 00295x1x3 + 00221x2x3 + 00702x1+ 06548x2 minus 08262x3

(2)



(3)


(4)








(5)

16

40

35

30

25

20

15

10

5

0

36

29

FGD gypsum GBFS

Slum

p va

lue (

mm

)

Carbide slag

Figure 7



(6)







4minus



FGD gypsum00

Com

pres

sive s

treng

th a

er 7

d (M

Pa)

01

02

03

04

05

06

GBFS Carbide slag

0546

0288

0176

(a)

FGD gypsum000

Flex

ural

stre

ngth

aer

7d

(MPa

)

005

010

015

020

025

030

GBFS Carbide slag

0262

01220098

(b)

FGD gypsum000

Com

pres

sive s

treng

th a

er 2

8d (M

Pa)

005

010

015

020

025

030

035

045

040

GBFS Carbide slag

0404

0232

0092

(c)

FGD gypsum000

Flex

ural

stre

ngth

aer

28d

(MPa

)

002

004

006

008

010

012

014

016

GBFS Carbide slag

0134

0148

0124

(d)

Figure 8








O

Si

Al

Ca2+

SO42ndash

AFt

Fly ash

Fly ash

Fly ash

ndash

SiO2

Al2O3

OHndashndash


ndash

ndashndash

Figure 9



4 Conclusion







0

0

50

Inte

nsity

(au

)

100

150

200

250

10 20 30

A

A

D

C

C

D

BD

402θ (deg)

50 60 70 80

7d

28d


Figure 11

Ca(OH)2

AFt

(a)

C-S-H gel

(b)

Ca(OH)2C-S-H gel

(c)

Ca(OH)2

AFt

(d)

Figure 10


Data Availability




Acknowledgments




References




































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls








FGD gypsum

Am

ount

of w

ater

requ

ired

for

reac

hing

stan

dard

cons

isten

cy (m

L)

GBFS Carbide slag

9692

1314

12

10

8

6

4

2

0

(a)

FGD gypsum

Con

siste

ncy

rang

e (m

m)

GBFS Carbide slag

2

1

55

4

3

2

1

0

(b)

Figure 5

FGD gypsum

Initi

al se

tting

tim

e (m

in)

GBFS Carbide slag

15615

192

8

10

12

14

16

18

20

6

4

2

0

(a)

FGD gypsum

Fina

l set

ting

time (

min

)

GBFS Carbide slag

8868

23625

20

15

10

5

0

(b)

Figure 6




22 minus 00043x

23 minus 00165x1x2

+ 00295x1x3 + 00221x2x3 + 00702x1+ 06548x2 minus 08262x3

(2)



(3)


(4)








(5)

16

40

35

30

25

20

15

10

5

0

36

29

FGD gypsum GBFS

Slum

p va

lue (

mm

)

Carbide slag

Figure 7



(6)







4minus



FGD gypsum00

Com

pres

sive s

treng

th a

er 7

d (M

Pa)

01

02

03

04

05

06

GBFS Carbide slag

0546

0288

0176

(a)

FGD gypsum000

Flex

ural

stre

ngth

aer

7d

(MPa

)

005

010

015

020

025

030

GBFS Carbide slag

0262

01220098

(b)

FGD gypsum000

Com

pres

sive s

treng

th a

er 2

8d (M

Pa)

005

010

015

020

025

030

035

045

040

GBFS Carbide slag

0404

0232

0092

(c)

FGD gypsum000

Flex

ural

stre

ngth

aer

28d

(MPa

)

002

004

006

008

010

012

014

016

GBFS Carbide slag

0134

0148

0124

(d)

Figure 8








O

Si

Al

Ca2+

SO42ndash

AFt

Fly ash

Fly ash

Fly ash

ndash

SiO2

Al2O3

OHndashndash


ndash

ndashndash

Figure 9



4 Conclusion







0

0

50

Inte

nsity

(au

)

100

150

200

250

10 20 30

A

A

D

C

C

D

BD

402θ (deg)

50 60 70 80

7d

28d


Figure 11

Ca(OH)2

AFt

(a)

C-S-H gel

(b)

Ca(OH)2C-S-H gel

(c)

Ca(OH)2

AFt

(d)

Figure 10


Data Availability




Acknowledgments




References




































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls






22 minus 00043x

23 minus 00165x1x2

+ 00295x1x3 + 00221x2x3 + 00702x1+ 06548x2 minus 08262x3

(2)



(3)


(4)








(5)

16

40

35

30

25

20

15

10

5

0

36

29

FGD gypsum GBFS

Slum

p va

lue (

mm

)

Carbide slag

Figure 7



(6)







4minus



FGD gypsum00

Com

pres

sive s

treng

th a

er 7

d (M

Pa)

01

02

03

04

05

06

GBFS Carbide slag

0546

0288

0176

(a)

FGD gypsum000

Flex

ural

stre

ngth

aer

7d

(MPa

)

005

010

015

020

025

030

GBFS Carbide slag

0262

01220098

(b)

FGD gypsum000

Com

pres

sive s

treng

th a

er 2

8d (M

Pa)

005

010

015

020

025

030

035

045

040

GBFS Carbide slag

0404

0232

0092

(c)

FGD gypsum000

Flex

ural

stre

ngth

aer

28d

(MPa

)

002

004

006

008

010

012

014

016

GBFS Carbide slag

0134

0148

0124

(d)

Figure 8








O

Si

Al

Ca2+

SO42ndash

AFt

Fly ash

Fly ash

Fly ash

ndash

SiO2

Al2O3

OHndashndash


ndash

ndashndash

Figure 9



4 Conclusion







0

0

50

Inte

nsity

(au

)

100

150

200

250

10 20 30

A

A

D

C

C

D

BD

402θ (deg)

50 60 70 80

7d

28d


Figure 11

Ca(OH)2

AFt

(a)

C-S-H gel

(b)

Ca(OH)2C-S-H gel

(c)

Ca(OH)2

AFt

(d)

Figure 10


Data Availability




Acknowledgments




References




































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls





(6)







4minus



FGD gypsum00

Com

pres

sive s

treng

th a

er 7

d (M

Pa)

01

02

03

04

05

06

GBFS Carbide slag

0546

0288

0176

(a)

FGD gypsum000

Flex

ural

stre

ngth

aer

7d

(MPa

)

005

010

015

020

025

030

GBFS Carbide slag

0262

01220098

(b)

FGD gypsum000

Com

pres

sive s

treng

th a

er 2

8d (M

Pa)

005

010

015

020

025

030

035

045

040

GBFS Carbide slag

0404

0232

0092

(c)

FGD gypsum000

Flex

ural

stre

ngth

aer

28d

(MPa

)

002

004

006

008

010

012

014

016

GBFS Carbide slag

0134

0148

0124

(d)

Figure 8








O

Si

Al

Ca2+

SO42ndash

AFt

Fly ash

Fly ash

Fly ash

ndash

SiO2

Al2O3

OHndashndash


ndash

ndashndash

Figure 9



4 Conclusion







0

0

50

Inte

nsity

(au

)

100

150

200

250

10 20 30

A

A

D

C

C

D

BD

402θ (deg)

50 60 70 80

7d

28d


Figure 11

Ca(OH)2

AFt

(a)

C-S-H gel

(b)

Ca(OH)2C-S-H gel

(c)

Ca(OH)2

AFt

(d)

Figure 10


Data Availability




Acknowledgments




References




































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls










O

Si

Al

Ca2+

SO42ndash

AFt

Fly ash

Fly ash

Fly ash

ndash

SiO2

Al2O3

OHndashndash


ndash

ndashndash

Figure 9



4 Conclusion







0

0

50

Inte

nsity

(au

)

100

150

200

250

10 20 30

A

A

D

C

C

D

BD

402θ (deg)

50 60 70 80

7d

28d


Figure 11

Ca(OH)2

AFt

(a)

C-S-H gel

(b)

Ca(OH)2C-S-H gel

(c)

Ca(OH)2

AFt

(d)

Figure 10


Data Availability




Acknowledgments




References




































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls





4 Conclusion







0

0

50

Inte

nsity

(au

)

100

150

200

250

10 20 30

A

A

D

C

C

D

BD

402θ (deg)

50 60 70 80

7d

28d


Figure 11

Ca(OH)2

AFt

(a)

C-S-H gel

(b)

Ca(OH)2C-S-H gel

(c)

Ca(OH)2

AFt

(d)

Figure 10


Data Availability




Acknowledgments




References




































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls




Data Availability




Acknowledgments




References




































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls
















Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls






Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls




Documents

OrthogonalExperimentalStudiesonPreparationofMine-Filling … · 2019. 7. 30. · Received 1 April 2018; Accepted 24 June 2018; Published 9 August 2018 ... According to the BS EN (British