Research Article Solidification/Stabilization of Fly Ash from a …downloads.hindawi.com/journals/amse/2016/7101243.pdf · 2019-07-30 · in waste volume, and the concentration of

Research ArticleSolidificationStabilization of Fly Ash from a Municipal SolidWaste Incineration Facility Using Portland Cement

Qiang Tang123 Yang Liu1 Fan Gu4 and Ting Zhou1

1School of Urban Rail Transportation Soochow University Soochow China2Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering Hohai University Nanjing China3Jiangsu Research Center for Geotechnical Engineering Technology Hohai University Nanjing China4Texas AampM Transportation Institute Texas AampM University College Station TX USA

Correspondence should be addressed to Fan Gu tracygufantamuedu

Received 10 April 2016 Accepted 8 September 2016

Academic Editor Jun Liu

Copyright copy 2016 Qiang Tang 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

This study investigated the solidificationstabilization of fly ash containing heavy metals using the Portland cement as a binder Itis found that both the cementfly ash ratio and curing time have significant effects on the mechanical (ie compressive strength)and leaching behaviors of the stabilized fly ash mixtures When the cementfly ash ratio increases from 4 6 to 8 2 the increase ofcompressive strength ratio raises from 4224 to 8036 meanwhile the leaching amount of heavy metals decreases by 233 to8523 When the curing time increases from 3 days to 56 days the compressive strength ratio of mixtures raises from 24000to 41429 meanwhile the leaching amount of heavy metals decreases by 1649 to 8870The decrease of compressive strengthwith the lower cementfly ash ratios and less curing time can be attributed to the increase of fly ash loading which hinders theformation of ettringite and destroys the structure of hydration products thereby resulting in the pozzolanic reaction and fixationof water molecules Furthermore the presence of cement causes the decrease of leaching which results from the formation ofettringite and the restriction of heavy metal ion migration in many forms such as C-S-H gel and adsorption

1 Introduction

Incineration as an effective method to energy recovery andreduction of the volume and weight of waste has been widelyadopted for the treatment of solid waste around the world[1 2] According to the Eurostat yearbook the incinerationpercentages of solid waste in Germany and France were ashigh as 32 [3] In Holland the incineration percentage ofsolid waste already reached 40 in 2000 while such incin-eration percentage was around 60 in Sweden Denmarkand Luxembourg even up to 77 and 80 in Japan andSwitzerland [4 5] During the incineration process heavymetals in the waste were accumulated through absorption byfly ash along the evaporation of the water and the decreasein waste volume and the concentration of heavy metalseventually reaches a relative high level The heavy metalcontents of fly ash from various districts worldwide aredetailed in Table 1 The upper limits of designated heavymetals in soils defined by three listed standards individually

implemented by European union Canada and China arealso shown in Table 1 Thus fly ash is regarded as hazardouswaste in Code 190113 of the Council of the European Unionand has to be pretreated according to ASTM STP 1123 and 40CFR 26124 [1 6ndash8] Similar to pozzolana the composition offly ash also includes high content of Si and Ca which providethe potential possibility for further utilization such as cementand concrete products structural fill cover material androadway and pavement utilization [9] In Germany 50 ofthe ash produced from the incinerated waste was used in themanufacture of sound insulating walls along highways andthe sublayers of city roads In Denmark over 72 of the ashis reused in the construction of parking lots cycling tracksand other roads [10]

For the reutilization in the civil and environmentalengineering fields the fly ash shouldmeet the requirement inboth themechanical and leaching properties of heavymetalsAccording to Choi et al and Song et alrsquos research cement canbe utilized as a binder to effectively reduce the leachability

Hindawi Publishing CorporationAdvances in Materials Science and EngineeringVolume 2016 Article ID 7101243 10 pageshttpdxdoiorg10115520167101243

2 Advances in Materials Science and Engineering

Table 1 Heavy metals in fly ash from various districts and countries

Heavy metal content (mgkg) ReferencesCr Pb Cu Zn Cd Ni Hg

StandardEU 100 100 100 300 1 50 mdash [20]CCME 64 70 63 200 14 50 mdash [21]GB 150 280 50 200 03 70 025 [22]

ChinaWuhan 282 1276 899 4187 36 mdash mdash [23]Shanghai 180 2710 990 4530 90 70 mdash [24]Shenzhen 5662 13564 30808 373835 778 15839 mdash [25]

Spain 790 398 156 15900 le6 90 lt60 [2]Poland 1529 1857 2400 46600 875 786 mdash [26]Japan 235 3750 1800 21000 225 mdash 45 [27]Portugal 185 2462 586 mdash 834 61 mdash [28]Italy 109 964 173 mdash 85 45 mdash [29]Denmark 990 2710 7491 22400 976 mdash mdash [30]Austria 500 4500 890 19000 350 94 mdash [31]India 120 35 100 mdash mdash 150 mdash [32]Belgium 100 2900 500 9400 300 100 lt100 [33]Note EU = European Union Standards (2009) CCME = Canadian Environmental Quality Guidelines (1999) GB = Environmental Quality Standards for Soilsof China (2009)

of As and Pb in mine tailing [11ndash14] Furthermore Voglarand Lestanrsquos and Patel and Pandeyrsquos findings indicated thatwith the presence of cement in sludge and contaminated soilsthe mechanical properties (ie compressive strength) werealso greatly improved [15 16] Considering all above in thisstudy the ordinary Portland cement (OPC) was selected asa binder material utilized for the solidificationstabilization(SS) treatment towards the fly ash Compressive strengthtest and TCLP (Toxicity Characteristic Leaching Procedure)tests were conducted to the cement-stabilized fly ash mix-tures This study investigated the mechanical behavior of themixtures and the leaching behaviors of heavymetal ions (egCr Cd Pb Ni Cu and Mn) The influence factors taken intoaccount in this study include the cementfly ash ratio mois-ture content fly ash-water reaction and curing time VisualMINTEQ was used to simulate the experimental conditionsThe calculation results were used to analyze the leachingbehaviors of heavy metals Based on the calculation resultsfurther discussions were made towards the SS mechanismsand the leaching behaviors of heavymetalswith the assistanceof X-ray diffraction (XRD) pattern and X-ray fluorescence(XRF) results

2 Materials and Methods

21 Materials Since incineration can provide a substantialreduction in volume and weight of the waste landfills usuallyequipped incineration facilities to cut down the cost of wastedisposal The fly ash used in this study was collected frommunicipal solid waste (MSW) incineration facility in theQizi Mountain landfill site Suzhou China The landfill has atotal storage capacity of 47 million m3 Approximately 5000

Figure 1 MSWI fly ash sample collection

tons (t)day of MSW was deposited at this location Amongthem around 3550 tday MSW was incinerated for elec-tricity generation and the incineration temperature insidethe incinerator was controlled at 900∘Cndash1100∘C During theincineration the flue gases were successively purified byan alkaline absorbent spray system (acid gases removal)an activated carbon injection system (heavy metals anddioxin removal) and a fabric filter (dust removal and fly ashgeneration) In Qizi Mountain landfill site over 100 tday flyashes were produced during MSW incineration With theassistance of the staff there original fly ash samples utilizedin this study were collected as shown in Figure 1 As thebinder material the commercially available OPC PO 425was prepared which consisted of 6ndash15 active additive and85ndash94 cement

Advances in Materials Science and Engineering 3

N2-BET adsorption tests were conducted on fly ash

to analyze several parameters including the specific sur-face area total pore volume micropore volume (diameterlt 10212 nm) and average pore size (NOVA2000e Quan-tachromeUS)Moisture content andwater retention capacityweremeasured following JISA 1203 and JGS 0151 respectively[17] The maximum and minimum density and the granuledensity of the fly ash were determined according to JGS0162 JIS A 1224 and JIS A 1202 respectively [17] Plasticlimit was determined according to JIS A 1205 [17] FollowingGBT50123-1999 liquid limit was determined by Photoelec-tric Liquid-Plastic Tester (GYS-2 Turangyiqi China) [18]In accordance with JIS A 1218 hydraulic conductivity wasdetermined using a permeameter (TST-55 JingkeyushengChina) [17] In addition swell index and grain size distri-bution test of fly ash were conducted according to ASTMD5890-06 [19] and GBT50123-1999 [18] respectively Thechemical composition andmineral composition of fly ash andOPC were analyzed by XRF (JSX-3400R JEOL Japan) andXRD (RAD-2B Rigaku Corporation Japan) The electricalconductivity (EC) and pH of the samples were measuredusing a pHEC meter (PH-2603 Lohand China) followingJGS 0212 and JGS 0211 respectively [17]

22 Preparation of Samples Fly ash and OPC samples wereoven dried at 105∘C for 24 hours (h) (101-A Leao China) toensure the accurate quality during the experiment since theremight be some moisture content in them Subsequently theywere cooled to room temperature in a desiccator In order tomix evenly the fly ash was first homogenized with the cementat five different ratios of cementfly ash (8 2 7 3 6 4 5 5and 4 6 by dry mass) manually for 4-5 minutes (min) in thevessel [1]Thendistilledwater whichwas produced by awaterdistillation apparatus (JYCS-002T China) was added slowlyinto the dry mix for the mixing process

To determine the optimum water content or waterce-ment ratio two preliminary tests were carried out as followsFly ash was mixed with water with the initial moisturecontents maintained at 4286 6667 100 1500023333 and 400 (preliminary test 1) 10 20 3040 50 60 70 80 90 and 100 (preliminarytest 2) During the test period one mixture was exposedto the air in preliminary test 1 meanwhile another mixturewas sealed by a polyethylene membrane in preliminary test2 Then the final moisture contents were determined after15min (preliminary test 1) and 6 h (preliminary test 2) andthe results are presented in Figures 2 and 3 respectivelyFrom Figure 2 the initial water content decreased by 278ndash1300 within 15min which indicates that 325ndash667water evaporated due to the heat released by the reactionbetween fly ash and water In preliminary test 1 the reactionbetween water and fly ash was neglected since the relativeshort period As shown in Figure 3 the initial water contentdecreased by 417ndash110 after 6 h which indicates 722ndash5300 water has reacted with fly ash Since the samples wereall sealed by a polyethylene membrane during experimentperiod the evaporation can be neglected in preliminary test 2Considering the above and the hydration reaction of cementthe water-cement ratio was therefore maintained at 1 1

Initial moisture contentFinal moisture content

6667 10000 15000 233334286 40000Initial moisture content ()

0

50

100

150

200

250

300

350

400

Moi

sture

cont

ent (

)

The mixture was exposed to the air for 15min

Figure 2 Moisture content before and after preliminary test 1


0102030405060708090

100M

oistu

re co

nten

t (

)

20 30 40 50 60 70 80 90 10010Initial moisture content ()

The mixture was sealed for 6h


After the mixing procedure the mixture was transferredinto themoulds (100mmtimes 100mmtimes 100mm Jianyi China)which were then sealed with a polyethylene membrane toavoid severe dehydration Afterwards the mixtures were leftundisturbed for 24 h at room temperature (23plusmn 2∘C) and highrelative humidity (gt50) Three replicates were analyzed foreach trial After the period of the initial setting the mixtureswere demoulded and cured (ge95 humidity 20 plusmn 2∘C) for 37 14 28 and 56 days in a curing box (HBY-15B DonghuaChina)

23 Compressive Strength Test Method Microcomputer Con-trolled Electronic TestingMachine (LDS-50 Chenda China)was used to obtain the compressive strength of samples Theloading platformrsquos diameter was 15 cm and the range wasfixed at 0ndash30 kN during the test Total maximum loads wererecorded at the point of fracture and the compressive strengthwas determined using the formula 119875 = 119865119860 where P is


Table 2 Properties of fly ash

Property Units Standard ValuesMoisture content JIS A 1203 6110Water retention capacity JGS 0151 1178Maximum density gcm3 JGS 0162 067Minimum density gcm3 JIS A 1224 049Granule density gcm3 JIS A 1202 2528Plastic limit JIS A 1205 1596Liquid limit GBT50123-1999 4766Swell index mL2g-solid ASTM D 5890-06 300Hydraulic conductivity ms JIS A 1218 155 times 10minus7

pH mdash JGS 0211 1215EC mScm JGS 0212 5768Grain size distribution GBT 50123-1999Sand fraction (2ndash0075mm) 1210Silt fraction (0075ndash0005mm) 8426Clay fraction (le0005mm) 364Uniformity coefficient mdash 402Coefficient of curvature mdash 112N2-BET

Correlation coefficient (1198772) mdash 0999Specific surface area m2g 7944Average pore size A 1142Total pore volume mLg 2710 times 10minus2

Micropore volume (diameter lt10212 nm) mLg 2516 times 10minus2

the compressive strength (MPa) F is the total maximum load(N) and A is the area of loaded surface (mm2) [34 35] All ofsamples were prepared in triplicate

24 Leaching Test Method for Heavy Metals First of all theextraction buffer was prepared using 1molL acetic acid and1molL sodium hydroxide (pH 288 plusmn 005) The crushedsamples collected after the compressive strength test wereoven dried at 105∘C for 24 h Then the dried samples werefurther crushed manually until the particle size was less than95mm The crushed samples were then leached using thepreviously prepared extraction buffer at a liquidsolid ratioof 20 1 Subsequently the extraction was performed usingFlip-Automatic Extraction Oscillator (KB-W08 Marina BayChina) for 18 plusmn 2 h at 23 plusmn 2∘C and the rotational speedwas fixed at 30 plusmn 2 rmin After the extraction the leachatesamples were filtered through a 045 120583m borosilicate glassfiber filter and the resultant TCLP (US EPA TestMethod 1311)extract (filtrate) was analyzed for heavy metals by AtomicAbsorption Spectroscopy (AAS) (TAS-990 Persee GeneralChina) [36] All the samples were prepared in duplicate

3 Results and Discussion

31 Characterization of the Materials The properties of flyash are detailed in Table 2 As shown in Table 2 the moisturecontent of fly ash is 6110 The maximum and minimum

density are 067 and 049 gcm3 respectively The granuledensity of fly ash is 2528 gcm3 which is lower than that ofthe clay utilized in Tran et al (ie the granule density of flyash is 27 gcm3) [37] The plastic limit and liquid limit offly ash are 1596 and 4766 respectively The swell indexis 300mL2 g solid almost the same as the Fukakusa clayutilized in Tang et al which demonstrates that the fly ashused in the experiment contains little expansive constitute[38] As observed in the grain size accumulation curve offly ash presented in Figure 4 the curve is steep when theparticle size ranges from0067 to 01mmwhich indicates thatthe particle size distribution is dense within this range Theuniformity coefficient and coefficient of curvature are 402and 112 respectively [39] This indicates that the particle sizedistribution is relatively uniformThe hydraulic conductivityof fly ash is 155 times 10minus7ms two orders of magnitude higherthan that of the clay used in Tran et al [37] The diversehydraulic conductivities can be attributed to the differencein the particle size The pH value of fly ash is 1215 becauseof its alkaline nature The EC value of fly ash is 5768mScmwhich is 287 times higher than for the soil used in Taghipourand Jalali [40] This demonstrates that a large amount ofsoluble salt exists in fly ash and thus increases the difficultyin immobilization

The specific surface area of the fly ash used in thisexperiment is 7944m2g This is much higher than thepozzolana utilized in Ghrici et al which is 042m2g [41]


01 0011 1E minus 3

Particle size (mm)

0

20

40

60

80

100

Cum

ulat

ive p

erce

ntag

e (

)

Figure 4 Grain size distribution curve of fly ash

Table 3 Chemical compositions of fly ash and OPC

Chemical composition Unit Fly ash OPCSiO2

1153 2085Al2O3

789 571Fe2O3

257 333CaO 4180 6048MgO 227 228SO3

325 284Na2O 258 143

K2O 574 073

TiO2

068 031Cl 1089 026ZnO 130 mdashPbO 055 mdashCdO 007 mdashMnO 007 mdashCuO 025 mdashCr2O3

001 mdash

This may be because the particle size of fly ash is smallerthan that of the pozzolana In addition the specific surfacearea of the fly ash is smaller than that of the bentoniteutilized in Hua which is 344m2g The reason for thisis due to the special microstructure of bentonite whichconsists of irregular groups that have an average diameter ofapproximately 01 to 10 120583m [42] These groups are composedof a certain number of particles whose lateral dimensionsrange from 8 to 10 nm At the same time these particles aremade up of 5 to 10 layers whose dimensions are 100 to 200 nmin diameter and only 1 nm in thickness [43] Additionally theaverage pore size of fly ash is 1142 A The total pore volumeandmicropore volume of the fly ash are 2710times 10minus2mLg and2516 times 10minus2mLg respectively

XRF results of untreated fly ash and OPC are dis-played in Table 3 Based on the XRD pattern shown inFigure 5 untreated fly ash is composed of calcite (CaCO

3)

and calcium chlorite hydrate (Ca(ClO)2sdot4H2O) which are

H1C1H1 S3M

H2

C1 calcium chlorite hydrate

Inte

nsity

(CPS

)

C1

S1

S3

S2

H1

K

C2

C2 calciteH1 halite

K kyanite

S1 silicon chlorideS2 silicon titanium

H2

M maghemite

M

S3 sylvite

C1

I iron manganese titanium oxide

I

H2 hematite

20 40 60 80 10002120579 (deg)

Figure 5 XRD pattern of fly ash

observed at 2120579 = 2936∘ and (1780∘ 3820∘ 6073∘) XRFresults corroborate the presence of these two substances andCaO accounts for 4180 of the total contents Accordingto Anastasiadou et alrsquos study the calcite was also observed[1] From Table 3 fly ash contains 1153 SiO

2 1089 Cl

and 571 Al2O3 The presences of kyanite (Al

2O3sdotSiO2) and

silicon chlorite (SiCl4) are verified at 2120579 = 4709∘ and 3164∘

as well Faleschini et al also demonstrated that kyanite existsin fly ash [44] Considering the existence of Na

2O and K

2O

shown by XRF results the characteristic peaks at 2120579 = (4538∘5641∘ 8392∘) and (2830∘ 6634∘) shown in the XRD patternindicate the presence of halite (NaCl) and sylvite (KCl) Thisalso agrees with Liu et alrsquos study [45] In addition hematite(Fe2O3) maghemite (Fe

3O4) ironmanganese titanium oxide

(Fe2MnTi3O10) and silicon titanium (TiSi

2) appearing at 2120579

= (6214∘ 7522∘) (4327∘ 5014∘) 2542∘ and 4045∘ are inaccordance with XRF analysis in which 257 Fe

2O3 068

Ti2O and 007 MnO are detected

32 Compressive Strength Test Results The compressivestrength values of the cement-based fly ash mixtures underdifferent curing periods are presented in Figure 6 Atcementfly ash ratios of 4 6 5 5 6 4 7 3 and 8 2 the com-pressive strengths are 045ndash153MPa 063ndash257MPa 049ndash252MPa 060ndash259MPa and 075ndash267MPa respectivelyCompared to 3 days of curing the compressive strength ofmixtures with 28 days of curing time increases by 1578(4 6) 841 (5 5) 1796 (6 4) 1750 (7 3) and 1200(8 2) respectively These results were in good agreementwith the Anastasiadou et alrsquos study where the compressivestrength of mixtures increased by 2000 (4 6) 7000(5 5) and 4040 (6 4) by comparing the values after 28days of curing with 1 day of curing [1] All values of compres-sive strength for the testmixtures exceed the standard (ASTM


8 26 4 7 35 54 6Cement-fly ash ratio

3 days7 days14 days

28 days56 days

00

05

10

15

20

25

Com

pres

sive s

treng

th (M

Pa)

Figure 6 Compressive strength of cemented solidified fly ash

STP 1123) stipulated for solidified waste to be landfilledwhich is 0414MPa [1 7]

Figure 6 shows that the compressive strength of mixturesincreases with the curing time This is because the hydrationreaction will be more complete when the curing time islonger Two processes are involved during the period ofcement hydration reaction One is through-solution hydra-tion which involves several factors including dissolution ofanhydrous compounds into their ionic constituents forma-tion of hydrates in the solution and eventual precipitationof hydrates from the supersaturated solution The other issolid-state hydration of cement and the reactions occurringdirectly at the surface of the anhydrous cement compoundsDuring this period no compounds dissolve into solutionIn the early stage of cement hydration through-solutionhydration is dominant At the poststage of cement hydrationthe hydration of residual cement particles may occur by thesolid-state reactions and the migration of ions in the solutionbecomes restricted [46]

For cementfly ash ratio the attributes of the mixturewill be closer to the pure OPC when cementfly ash ratiois larger Therefore the compressive strength decreases asthe cementfly ash ratio is reduced This phenomenon canbe analyzed from four aspects specifically the formationof ettringite (AFt) the structure of products of hydrationpozzolanic reaction and the fixation of water moleculesFirstly when the addition of fly ash increases the formationof AFt which supports the development of the early strengthwill be reduced [47] Due to the presence of fly ash a part ofthe aluminate which should participate in the formation ofAFt is seized to form Friedelrsquos salt It is inferred that themorethe fly ash that is added the more the aluminate that reacts toform Friedelrsquos salt and the larger the decrease inmagnitude ofstrength Regarding the AFt a more concrete discussion willbe given in Section 33

Secondly the residues in fly ash that are not completelyburnt also influence the compressive strength of the solidified

matrix The products of cement hydration are lapped andbound by the multiple gravitation This is the reason whycement blocks have a high compressive strength Howeverthe high levels of residues in fly ash not only reduce the con-centration of products from cement hydration which haveconnection effect but also destroy the structure of productsof hydration [48]This also explains the phenomenon that thecompressive strength of mixtures decreases with the increaseof fly ash loading

Thirdly when fly ash is added to OPC it will undergo thepozzolanic reaction Due to similar chemical compositionfly ash can be classified as a pozzolan which is one of twomain components used in production of concrete The otheris cement [26] When added to OPC fly ash as a pozzolanundergoes the pozzolanic reaction with calcium hydrox-ide which is slow and the rate of strength developmentwill accordingly slow down Regarding the hydration reac-tion a comparison between Portland cement and Portland-pozzolan cement is given as follows

Portland cement

C3S +Hfast997888997888rarr C-S-H + CH (1)

Portland-pozzolan cement

Pozzolan + CH +H slow997888997888997888rarr C-S-H (2)

where C S and H represents CaO SiO2 and H

2O respec-

tively [46] When the cementfly ash ratio is low the hydra-tion of Portland-pozzolan cement has the higher tendencyto take place following (2) This is another reason for thedecrease of compressive strength associatedwith the decreaseof cementfly ash ratio

Fourthly fly ash will bind water which should participatein the hydration of cement due to its strong ability to fixwater molecules Based on the work by Mitchell and Sogathe surface charges of fly ash particles along with hydrogenbonds on the particle surface and van Der Waals forcesbetween water molecules and fly ash particles contribute tothe fixation of water molecules [49] As shown in Table 2 thespecific surface area of fly ash is 7944m2g which providesa favorable condition for attracting water considering theinteraction between water and fly ash particles That isexpected by the results of the preliminary tests in Section 22For the samples with various initialmoisture contents 722ndash5300 water reacted with fly ash The ability to strongly fixwater molecules is also corroborated by the water retentioncapacity displayed in Table 2 When the water is boundby fly ash the hydration reaction is incomplete This iswhy fly ash loading leads to a decrease of compressivestrength Obviously the more fly ash is added the morewater is attractedThereby the compressive strength of fly ashmixtures decreases accordingly

33 Leaching Test Results The TCLP leaching amounts offly ash samples after 3 7 14 28 and 56 days of curing aredisplayed in Table 4 For treated fly ash the final leachingamount of all measured metals is lower than the US EPAstandard (40 CFR 26124) [8] Compared to the untreated


Table 4 Summary of TCLP leaching results for solidified fly ash samples

Cementfly ash Curing time Concentration of metals in leachate (mgL)Cr Cd Pb Ni Cu Mn

Untreated fly ash 085 640 1550 104 019 mdash40 CFR 26124 5 1 5 100 100 mdash

8 2

3 d 0722 0084 0821 0188 0115 01137 d 0601 0076 0688 0182 0092 009414 d 0541 0073 0465 0176 0084 004028 d 0433 0056 0255 0169 0009 003456 d 0455 0057 0236 0157 0013 0045

7 3

3 d 0843 0148 0907 0200 0189 01947 d 0547 0106 0741 0190 0167 014514 d 0472 0069 0669 0156 0109 003728 d 0361 0044 0321 0140 0099 003456 d 0367 0048 0189 0138 0098 0014

6 4

3 d 0823 0094 1014 0218 0131 01577 d 0746 0092 0547 0207 0112 014814 d 0486 0073 0493 0198 0092 011628 d 0450 0045 0448 0176 0087 009756 d 0530 0057 0494 0188 0097 0078

5 5

3 d 0798 0106 0893 0245 0173 01527 d 0493 0088 0684 0236 0096 013214 d 0444 0066 0220 0225 0079 004628 d 0423 0048 0142 0214 0045 002156 d 0480 0069 0238 0205 0034 0013

4 6

3 d 0828 0104 0944 0241 0123 01477 d 0601 0092 0644 0221 0098 012914 d 0490 0080 0480 0213 0086 007128 d 0357 0070 0390 0215 0062 003156 d 0341 0067 0342 0213 0088 0033

Note ldquomdashrdquo = not available

fly ash from Table 4 the leaching amounts of heavy metalsafter 3 days of curing decrease by approximately 9833(Cd) 9409 (Pb) and 7900 (Ni) The decreases of theleaching amounts of Cr andCu are 082ndash1506 and 053ndash3947 respectively After 56 days of curing the decreasesof the leaching amounts of heavy metals are approximately9891 (Cd) 9852 (Pb) 8217 (Ni) 3765ndash5988 (Cr)and 4842ndash9316 (Cu) The leaching amount of all heavymetals decreaseswith the increase of curing timeThis findingis also proved by Anastasiadou et al [1] In Anastasiadou etalrsquos research comparing the samples after 1 day of curingthe leaching-out heavy metal amount from samples after28 days decreases by a wide margin For example Cr NiCu Cd and Pb decrease by 289 306 306 571and 645 [1] According to Table 4 however the leachingamounts of some heavy metals such as Cr (5 5 6 4) andCu (4 6 6 4 and 8 2) after 56 days of curing are higherthan those after 28 days of curing It indicates that a part ofheavy metals have released from the material again after 28days of curing and two reasons can be concluded as givenbelow First of all as mentioned in Section 22 the humidityduring the curing process is relatively high (ge95)Therefore

the carbon dioxide in the air tends to dissolve in water andforms carbonic acid resulting in the decrease of alkalinityAccording to Beaudoin and Brown C-S-H gel is unstablewhen pH is lower than 100 [50] Thus it is rational to judgethat the barriers provided by C-S-H especially covered at theoutward surface have the tendency to be destroyed due tothe decrease in alkalinity as the curing period increased andcaused the release of fixed heavymetals In addition carbonicacid also redissolves heavy metal ion precipitates makingheavy metals exist in free ion form Table 4 also shows thatthe leaching amount of Cr is much higher than that of Cu(II)According to the results calculated by Visual MINTEQ asshown in Table 5 thatmay be attributed to the soluble form ofCr(VI) in the alkaline environment Table 5 shows that 100Cr exists in the form of soluble ions (CrO4

2minus or HCrO4minus)

when pH ranges from 100 to 120 while 0466ndash11594 Cuexists as the precipitate (Cu(OH)

2)The similar phenomenon

is also observed by Mulligan et al in which Cr(VI) is foundhard to transform into a low soluble hydroxide [51]

The mechanisms of SS can be generally divided into twoprocesses physical encapsulation and chemical immobiliza-tion The former provides barriers generated on the surface


Table 5 The percentage of possible ion forms of Cu(II) and Cr(VI)

pH Percentage of possible ion forms ()A B C D E F

Cr(VI)

100 CrO4

2minus HCrO4

minus mdash mdash mdash mdash99987 0013 mdash mdash mdash mdash

110 CrO4

2minus mdash mdash mdash mdash mdash99999 mdash mdash mdash mdash mdash

120 CrO4


Cu(II)

100 CuOH+ Cu(OH)3

minus Cu(OH)2

Cu2(OH)

2

2+ Cu3(OH)

4

2+ mdash0036 0262 0466 0155 99081 mdash

110 CuOH+ Cu(OH)4

2minus Cu(OH)3

minus Cu(OH)2

Cu2(OH)

2

2+ Cu3(OH)

4

2+

0016 0236 11594 2065 0030 86059120 Cu(OH)

4

2minus Cu(OH)3

minus Cu(OH)2

Cu3(OH)

4

2+ mdash mdash16717 81539 1443 0300 mdash mdash

of the waste to restrict contaminant migration by mechanicalprocesses or chemical reactions The latter refers to the pro-cesses that keep heavy metals in a certain form by chemicalreactions to reduce the leachability The related mechanismsare also validated by Sobiecka et al [26]The importance of flyash solidificationstabilization can be specifically expoundedusing the following three aspects Firstly the migration ofheavy metal ions is hindered by the products of the cementhydration reactions The solidification processes result in theformation of C-S-H gel on the surface of the stabilized fly ashparticles C-S-H gel acts as a barrier between the immobilizedsolid wastes and the surrounding liquids and controls thepotential adsorption of ions present in the liquids onto thesurface of the solid waste as well as the immobilization ofheavy metals in the resulting products [52] Based on theaforementioned theory it can be inferred that the hydrationreaction of OPC is more sufficient and the amount of C-S-Hgel is larger by prolonging the curing time That can explainwhy the leaching amount of heavy metals decreases with theincrease of curing time

Secondly heavy metal ions are absorbed by the productsof the cement hydration reaction The absorption can bedivided into the physical absorption and chemical absorp-tion Physical absorption is caused by van Der Waals forcesbetween particles while chemical absorption is the result ofchemical bond formation [53] Due to the porous structureand small crystal particles the specific surface area of cementhydration reaction products ranges from 10 to 50m2g [54]This creates a favorable condition for physical absorptionAs mentioned before with the increase in cementfly ashratio the products of cement hydration reaction also increaseand the effect of physical absorption will therefore be moreremarkable This is corroborated in Table 4 which demon-strates that the highest leaching levels of heavy metals occurat the smallest cementfly ash ratio (4 6)However accordingto Liu et al Cr cannot be effectively removed through thephysical absorption when pH is over 100 [55] Given thealkaline environment during the cement hydration reactionthis can help explain why the immobilization of Cr is not veryefficient

Thirdly the Ca(II) in the structure of AFt can be replacedby divalent heavymetal ions including Zn(II) Cd(II) Pb(II)and Ni(II) through isomorphous replacement Similarly theAl(III) can be replaced by trivalent or tetravalent heavymetalions including Cr(III) Mn(III) Ti(III) and Ti(IV) [54]These reactions have a certain relationship with the ionicradius For instance the ionic radii of some divalent heavymetal ions are 0074 nm (Zn(II)) 0095 nm (Cd(II)) and0069 nm (Ni(II)) which are relatively smaller and denserthan that of Ca(II) (01 nm)Therefore these heavymetal ionshave the tendency to replace Ca(II) in the AFt due to thestronger attractive force However with an increase in fly ashloading the formation of AFt will be hindered The calciumsulfate and chloride in fly ash can influence the hydration ofcement at the same timeOn the one hand the calcium sulfatein fly ash tends to react with aluminate in cement to generateAFt The chemical reaction can be expressed as follows

[Al(OH)4]minus+ 3[SO4]

2minus+ 6[Ca]2+ + aq

997888rarr C6AS3H32

(3)

where C A S and H represent CaO Al2O3 SO3 and H

2O

On the other hand the large amount of chloride in fly ashdissolves into the solution existing in the pores of cementand tends to form calcium chloride which can react withaluminate in cement and generate Friedelrsquos salt The impactson the hydration reaction of aluminate are the oppositeresulting in a competition between the two reactions As amatter of fact compared with the pure cement paste onlya small amount of aluminate may react with sulfate Thisindicates that the latter reaction is dominant in the process[44] Therefore the addition of fly ash reduces the formationof AFt This explains why the maximum leaching amount ofheavy metal ion occurs at the minimum cementfly ash ratio(4 6)

4 Conclusions

In this study compressive strength test and TCLP test wereconducted on the cement-stabilized fly ash The mechanical


behavior of the fly ashmixtures and the leaching behaviors ofheavy metal ions (Cr Cd Pb Ni Cu and Mn) were investi-gated According to the compressive strength test results thecompressive strength of the mixtures grew with the increaseof cementfly ash ratio and curing time For the TCLP testresults it was shown that the leaching amounts of heavymetals decreased with the increase of cementfly ash ratioand curing time After the cement SS treatment the finalleaching amounts of heavymetals were effectively controlledwhich is lower than the US EPA standard Combined withthe XRF and XRD analysis it was found that the formationof AFt was hindered due to the presence of fly ash andthereby reduced the compressive strength and blocked theimmobilization of heavy metals In addition fly ash loadingdestroyed the structure of the products of cement hydrationThis resulted in the pozzolanic reaction and fixation of watermolecules which further increased the compressive strengthof test samples The formation of C-S-H gel along with theadsorption of products restricted the migration of ions andultimately reduced the total amount of leachate

Competing Interests

The authors declare that they have no competing interests

Acknowledgments

The research presented herein is supported by the NationalNature Science Foundation of China (Grant no 41630633)China Postdoctoral Science Foundation funded project(Grant no 2016M591756) and the Open Project Program ofMOE Key Laboratory of Soft Soils and GeoenvironmentalEngineering Zhejiang University (Grant no 2016P03) Theresearch is also supported by Jiangsu Provincial TransportBureau Bureau of Housing and Urban-Rural Developmentof Suzhou and Soft Science Research Program from SuzhouAssociation for Science and Technology

References

[1] K Anastasiadou K Christopoulos E Mousios and EGidarakos ldquoSolidificationstabilization of fly and bottom ashfrom medical waste incineration facilityrdquo Journal of HazardousMaterials vol 207-208 no 6 pp 165ndash170 2012

[2] Y L Galiano C F Pereira and J Vale ldquoStabilizationsolidifica-tion of a municipal solid waste incineration residue using flyash-based geopolymersrdquo Journal of Hazardous Materials vol185 no 1 pp 373ndash381 2011

[3] European Commission Eurostat Yearbook 2011 Eurostat 2011[4] H-U Hartenstein and M Horvay ldquoOverview of municipal

waste incineration industry in west Europe (based on theGerman experience)rdquo Journal of Hazardous Materials vol 47no 1ndash3 pp 19ndash30 1996

[5] ldquoWaste treatment in Japanrdquo Ministry of Environment WasteManagement and Recycling Unit 2011 (Japanese)

[6] Q Tang X TangMHu Z Li Y Chen and P Lou ldquoRemoval ofCd(II) from aqueous solution with activated Firmiana SimplexLeaf behaviors and affecting factorsrdquo Journal of HazardousMaterials vol 179 no 1ndash3 pp 95ndash103 2010

[7] American Society for Testing and Materials ldquoStabilization andsolidification of hazardous radioactive and mixed wastesrdquoASTM STP 1123 1992

[8] US Environmental Protection AgencyDefinition of Solid Wasteand Hazardous Waste Recycling 2001

[9] M Ahmaruzzaman ldquoA review on the utilization of fly ashrdquoProgress in Energy and Combustion Science vol 36 no 3 pp327ndash363 2010

[10] L Reijnders ldquoDisposal uses and treatments of combustionashes a reviewrdquo Resources Conservation and Recycling vol 43no 3 pp 313ndash336 2005

[11] W-H Choi S-R Lee and J-Y Park ldquoCement based solidifica-tionstabilization of arsenic-contaminatedmine tailingsrdquoWasteManagement vol 29 no 5 pp 1766ndash1771 2009

[12] F Y Song L Gu NW Zhu andH P Yuan ldquoLeaching behaviorof heavy metals from sewage sludge solidified by cement-basedbindersrdquo Chemosphere vol 92 no 4 pp 344ndash350 2013

[13] I G Richardson andGWGroves ldquoThe incorporation ofminorand trace elements into calcium silicate hydrate (CndashSndashH) gel inhardened cement pastesrdquo Cement and Concrete Research vol23 no 1 pp 131ndash138 1993

[14] F Ziegler A M Scheidegger C A Johnson R Dahn andE Wieland ldquoSorption mechanisms of zinc to calcium silicatehydrate X-ray absorption fine structure (XAFS) investigationrdquoEnvironmental Science and Technology vol 35 no 7 pp 1550ndash1555 2001

[15] G E Voglar and D Lestan ldquoSolidificationstabilisation ofmetals contaminated industrial soil from former Zn smelter inCelje Slovenia using cement as a hydraulic binderrdquo Journal ofHazardous Materials vol 178 no 1ndash3 pp 926ndash933 2010

[16] H Patel and S Pandey ldquoEvaluation of physical stability andleachability of Portland Pozzolona Cement (PPC) solidifiedchemical sludge generated from textile wastewater treatmentplantsrdquo Journal of HazardousMaterials vol 207-208 pp 56ndash642012

[17] ISBN 2nd edition[18] Ministry of Housing and Urban-Rural Development of the

Peoplersquos Republic of China Standard for Soil Test Method 1999[19] American Society for Testing and Materials ldquoStandard test

method for swell index of clay mineral component of geosyn-thetic clay linersrdquo ASTMD5890-06 ASTM International WestConshohocken Pa USA 2006

[20] European Union Heavy Metals in Wastes European Commis-sion on Environment 2009

[21] Canadian Environmental Council of Ministers of the Environ-ment Soil Quality Guidelines for the Protection of Environmentaland Human Health 1999

[22] Ministry of Environmental Protection of the Peoplersquos Republicof China Environmental Quality Standards for Soils 2009

[23] J Yu Y Qiao L Jin C Ma N Paterson and L Sun ldquoRemovalof toxic and alkalialkaline earth metals during co-thermaltreatment of two types of MSWI fly ashes in Chinardquo WasteManagement vol 46 pp 287ndash297 2015

[24] Y Y Hu P F Zhang J P Li and D Z Chen ldquoStabilizationand separation of heavy metals in incineration fly ash duringthe hydrothermal treatment processrdquo Journal of HazardousMaterials vol 299 pp 149ndash157 2015

[25] F-H Wang F Zhang Y-J Chen J Gao and B Zhao ldquoA com-parative study on the heavy metal solidificationstabilizationperformance of four chemical solidifying agents in municipalsolidwaste incineration fly ashrdquo Journal of HazardousMaterialsvol 300 pp 451ndash458 2015


[26] E Sobiecka A Obraniak and B Antizar-Ladislao ldquoInfluenceof mixture ratio and pH to solidificationstabilization processof hospital solid waste incineration ash in Portland cementrdquoChemosphere vol 111 pp 18ndash23 2014

[27] M Kamon T Katsumi and Y Sano ldquoMSW fly ash stabilizedwith coal ash for geotechnical applicationrdquo Journal ofHazardousMaterials vol 76 no 2-3 pp 265ndash283 2000

[28] A T Lima L M Ottosen and A B Ribeiro ldquoAssessing fly ashtreatment remediation and stabilization of heavy metalsrdquoJournal of Environmental Management vol 95 pp S110ndashS1152012

[29] F Lombardi T Mangialardi L Piga and P Sirini ldquoMechanicaland leaching properties of cement solidified hospital solid wasteincinerator fly ashrdquo Waste Management vol 18 no 2 pp 99ndash106 1998

[30] GMKirkelund CMagro PGuedes P E JensenA B Ribeiroand LMOttosen ldquoElectrodialytic removal of heavymetals andchloride from municipal solid waste incineration fly ash andair pollution control residue in suspensionmdashtest of a new twocompartment experimental cellrdquo Electrochimica Acta vol 181pp 73ndash81 2015

[31] B Nowak P Aschenbrenner and F Winter ldquoHeavy metalremoval from sewage sludge ash and municipal solid waste flyashmdasha comparisonrdquo Fuel Processing Technology vol 105 pp195ndash201 2013

[32] S Sushil and V S Batra ldquoAnalysis of fly ash heavymetal contentand disposal in three thermal power plants in Indiardquo Fuel vol85 no 17-18 pp 2676ndash2679 2006

[33] B Van Der Bruggen G Vogels P Van Herck and C Vande-casteele ldquoSimulation of acid washing of municipal solid wasteincineration fly ashes in order to remove heavy metalsrdquo Journalof Hazardous Materials vol 57 no 1ndash3 pp 127ndash144 1998

[34] F Gu Y Zhang C V Droddy R Luo and R L LyttonldquoDevelopment of a new mechanistic empirical rutting modelfor unbound granular materialrdquo Journal of Materials in CivilEngineering vol 28 no 8 Article ID 4016051 2016

[35] F Gu H Sahin X Luo R Luo and R L Lytton ldquoEstimation ofresilient modulus of unbound aggregates using performance-related base course propertiesrdquo Journal of Materials in CivilEngineering vol 27 no 6 Article ID 04014188 2015

[36] US Environmental Protection Agency ldquoToxicity characteristicleaching procedurerdquo US EPA Test Method 1311 1984

[37] T D Tran Y-J Cui A M Tang M Audiguier and R CojeanldquoEffects of lime treatment on the microstructure and hydraulicconductivity of Hericourt clayrdquo Journal of Rock Mechanics andGeotechnical Engineering vol 6 no 5 pp 399ndash404 2014

[38] Q Tang T Katsumi T Inui and Z Li ldquoMembrane behavior ofbentonite-amended compacted clayrdquo Soils and Foundations vol54 no 3 pp 329ndash344 2014

[39] T Qiang K Heejong E Kazuto K Takeshi and I Toru ldquoSizeeffect on lysimeter test evaluating the properties of constructionand demolition waste leachaterdquo Soils and Foundations vol 55no 4 pp 720ndash736 2015

[40] M Taghipour and M Jalali ldquoEffect of clay minerals andnanoparticles on chromium fractionation in soil contaminatedwith leather factory wasterdquo Journal of Hazardous Materials vol297 pp 127ndash133 2015

[41] M Ghrici S Kenai and M Said-Mansour ldquoMechanical prop-erties and durability of mortar and concrete containing naturalpozzolana and limestone blended cementsrdquo Cement and Con-crete Composites vol 29 no 7 pp 542ndash549 2007

[42] J Hua ldquoSynthesis and characterization of bentonite basedinorgano-organo-composites and their performances forremoving arsenic from waterrdquo Applied Clay Science vol 114 pp239ndash246 2015

[43] H Han and Y Zhu ldquoStudy on modification and application ofbentoniterdquo Inorganic Chemicals Industry vol 43 pp 5ndash8 2011(Chinese)

[44] F Faleschini M A Zanini K Brunelli and C Pellegrino ldquoVal-orization of co-combustion fly ash in concrete productionrdquoMaterials and Design vol 85 pp 687ndash694 2015

[45] Y Q Liu W P Zhu and E H Yang ldquoAlkali-activated groundgranulated blast-furnace slag incorporating incinerator fly ashas a potential binderrdquo Construction and Building Materials vol112 pp 1005ndash1012 2016

[46] P K Mehta and P J M Monteiro Concrete MicrostructureProperties and Materials McGraw-Hill Education 4th edition2014

[47] S Remond D P Bentz and P Pimienta ldquoEffects of theincorporation of municipal solid waste incineration fly ash incement pastes andmortars II modelingrdquo Cement and ConcreteResearch vol 32 no 4 pp 565ndash576 2002

[48] H-Q Liu G-X Wei S-G Zhang and J-J Cai ldquoEffect ofactivated carbon on cement solidification of hospital wasteincineration fly ashrdquoTheChinese Journal of Process Engineeringvol 8 no 5 pp 953ndash956 2008 (Chinese)

[49] J K Mitchell and K Soga Fundamentals of Soil Behavior JohnWiley amp Sons New York NY USA 3rd edition 2005

[50] J J Beaudoin and P W Brown ldquoThe structure of hardenedcement pasterdquo in Proceedings of the 9th International Congresson the Chemistry of Cement pp 1485ndash1525 1992

[51] C N Mulligan R N Yong and B F Gibbs ldquoRemediationtechnologies for metal-contaminated soils and groundwater anevaluationrdquo Engineering Geology vol 60 no 1ndash4 pp 193ndash2072001

[52] A Pariatamby C Subramaniam S Mizutani and H TakatsukildquoSolidification and stabilization of fly ash frommixed hazardouswaste incinerator using ordinary Portland cementrdquo Environ-mental Sciences vol 13 no 5 pp 289ndash296 2006

[53] Q Tang X W Tang Z Z Li et al ldquoZn(II) removal with acti-vated firmiana simplex leaf kinetics and equilibrium studiesrdquoJournal of Environmental Engineering vol 138 no 2 pp 190ndash199 2012

[54] X He H Hou and D Zhang ldquoStudy on cement solidificationof municipal solid waste incineration fly ashrdquo EnvironmentalPollution and Control vol 28 pp 425ndash428 2006 (Chinese)

[55] H Liu S Liang J Gao et al ldquoEnhancement of Cr(VI) removalby modifying activated carbon developed from Zizania caduci-flora with tartaric acid during phosphoric acid activationrdquoChemical Engineering Journal vol 246 pp 168ndash174 2014

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


Table 1 Heavy metals in fly ash from various districts and countries

Heavy metal content (mgkg) ReferencesCr Pb Cu Zn Cd Ni Hg

StandardEU 100 100 100 300 1 50 mdash [20]CCME 64 70 63 200 14 50 mdash [21]GB 150 280 50 200 03 70 025 [22]

ChinaWuhan 282 1276 899 4187 36 mdash mdash [23]Shanghai 180 2710 990 4530 90 70 mdash [24]Shenzhen 5662 13564 30808 373835 778 15839 mdash [25]

Spain 790 398 156 15900 le6 90 lt60 [2]Poland 1529 1857 2400 46600 875 786 mdash [26]Japan 235 3750 1800 21000 225 mdash 45 [27]Portugal 185 2462 586 mdash 834 61 mdash [28]Italy 109 964 173 mdash 85 45 mdash [29]Denmark 990 2710 7491 22400 976 mdash mdash [30]Austria 500 4500 890 19000 350 94 mdash [31]India 120 35 100 mdash mdash 150 mdash [32]Belgium 100 2900 500 9400 300 100 lt100 [33]Note EU = European Union Standards (2009) CCME = Canadian Environmental Quality Guidelines (1999) GB = Environmental Quality Standards for Soilsof China (2009)

of As and Pb in mine tailing [11ndash14] Furthermore Voglarand Lestanrsquos and Patel and Pandeyrsquos findings indicated thatwith the presence of cement in sludge and contaminated soilsthe mechanical properties (ie compressive strength) werealso greatly improved [15 16] Considering all above in thisstudy the ordinary Portland cement (OPC) was selected asa binder material utilized for the solidificationstabilization(SS) treatment towards the fly ash Compressive strengthtest and TCLP (Toxicity Characteristic Leaching Procedure)tests were conducted to the cement-stabilized fly ash mix-tures This study investigated the mechanical behavior of themixtures and the leaching behaviors of heavymetal ions (egCr Cd Pb Ni Cu and Mn) The influence factors taken intoaccount in this study include the cementfly ash ratio mois-ture content fly ash-water reaction and curing time VisualMINTEQ was used to simulate the experimental conditionsThe calculation results were used to analyze the leachingbehaviors of heavy metals Based on the calculation resultsfurther discussions were made towards the SS mechanismsand the leaching behaviors of heavymetalswith the assistanceof X-ray diffraction (XRD) pattern and X-ray fluorescence(XRF) results

2 Materials and Methods

21 Materials Since incineration can provide a substantialreduction in volume and weight of the waste landfills usuallyequipped incineration facilities to cut down the cost of wastedisposal The fly ash used in this study was collected frommunicipal solid waste (MSW) incineration facility in theQizi Mountain landfill site Suzhou China The landfill has atotal storage capacity of 47 million m3 Approximately 5000

Figure 1 MSWI fly ash sample collection

tons (t)day of MSW was deposited at this location Amongthem around 3550 tday MSW was incinerated for elec-tricity generation and the incineration temperature insidethe incinerator was controlled at 900∘Cndash1100∘C During theincineration the flue gases were successively purified byan alkaline absorbent spray system (acid gases removal)an activated carbon injection system (heavy metals anddioxin removal) and a fabric filter (dust removal and fly ashgeneration) In Qizi Mountain landfill site over 100 tday flyashes were produced during MSW incineration With theassistance of the staff there original fly ash samples utilizedin this study were collected as shown in Figure 1 As thebinder material the commercially available OPC PO 425was prepared which consisted of 6ndash15 active additive and85ndash94 cement








0

50

100

150

200

250

300

350

400

Moi

sture

cont

ent (

)




0102030405060708090

100M

oistu

re co

nten

t (

)



















01 0011 1E minus 3

Particle size (mm)

0

20

40

60

80

100

Cum

ulat

ive p

erce

ntag

e (

)




1153 2085Al2O3

789 571Fe2O3

257 333CaO 4180 6048MgO 227 228SO3

325 284Na2O 258 143

K2O 574 073

TiO2


001 mdash



3)


H1C1H1 S3M

H2


Inte

nsity

(CPS

)

C1

S1

S3

S2

H1

K

C2

C2 calciteH1 halite

K kyanite


H2

M maghemite

M

S3 sylvite

C1


I

H2 hematite

20 40 60 80 10002120579 (deg)



2 1089 Cl


2O3sdotSiO2) and



2O and K

2O






2O3 068





3 days7 days14 days

28 days56 days

00

05

10

15

20

25

Com

pres

sive s

treng

th (M

Pa)








Portland cement





2O respec-








8 2

3 d 0722 0084 0821 0188 0115 01137 d 0601 0076 0688 0182 0092 009414 d 0541 0073 0465 0176 0084 004028 d 0433 0056 0255 0169 0009 003456 d 0455 0057 0236 0157 0013 0045

7 3

3 d 0843 0148 0907 0200 0189 01947 d 0547 0106 0741 0190 0167 014514 d 0472 0069 0669 0156 0109 003728 d 0361 0044 0321 0140 0099 003456 d 0367 0048 0189 0138 0098 0014

6 4

3 d 0823 0094 1014 0218 0131 01577 d 0746 0092 0547 0207 0112 014814 d 0486 0073 0493 0198 0092 011628 d 0450 0045 0448 0176 0087 009756 d 0530 0057 0494 0188 0097 0078

5 5

3 d 0798 0106 0893 0245 0173 01527 d 0493 0088 0684 0236 0096 013214 d 0444 0066 0220 0225 0079 004628 d 0423 0048 0142 0214 0045 002156 d 0480 0069 0238 0205 0034 0013

4 6

3 d 0828 0104 0944 0241 0123 01477 d 0601 0092 0644 0221 0098 012914 d 0490 0080 0480 0213 0086 007128 d 0357 0070 0390 0215 0062 003156 d 0341 0067 0342 0213 0088 0033












Cr(VI)

100 CrO4

2minus HCrO4


110 CrO4


120 CrO4


Cu(II)

100 CuOH+ Cu(OH)3

minus Cu(OH)2

Cu2(OH)

2

2+ Cu3(OH)

4

2+ mdash0036 0262 0466 0155 99081 mdash

110 CuOH+ Cu(OH)4

2minus Cu(OH)3

minus Cu(OH)2

Cu2(OH)

2

2+ Cu3(OH)

4

2+

0016 0236 11594 2065 0030 86059120 Cu(OH)

4

2minus Cu(OH)3

minus Cu(OH)2

Cu3(OH)

4







997888rarr C6AS3H32

(3)


2O


4 Conclusions




Competing Interests


Acknowledgments


References
































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










0

50

100

150

200

250

300

350

400

Moi

sture

cont

ent (

)




0102030405060708090

100M

oistu

re co

nten

t (

)



















01 0011 1E minus 3

Particle size (mm)

0

20

40

60

80

100

Cum

ulat

ive p

erce

ntag

e (

)




1153 2085Al2O3

789 571Fe2O3

257 333CaO 4180 6048MgO 227 228SO3

325 284Na2O 258 143

K2O 574 073

TiO2


001 mdash



3)


H1C1H1 S3M

H2


Inte

nsity

(CPS

)

C1

S1

S3

S2

H1

K

C2

C2 calciteH1 halite

K kyanite


H2

M maghemite

M

S3 sylvite

C1


I

H2 hematite

20 40 60 80 10002120579 (deg)



2 1089 Cl


2O3sdotSiO2) and



2O and K

2O






2O3 068





3 days7 days14 days

28 days56 days

00

05

10

15

20

25

Com

pres

sive s

treng

th (M

Pa)








Portland cement





2O respec-








8 2

3 d 0722 0084 0821 0188 0115 01137 d 0601 0076 0688 0182 0092 009414 d 0541 0073 0465 0176 0084 004028 d 0433 0056 0255 0169 0009 003456 d 0455 0057 0236 0157 0013 0045

7 3

3 d 0843 0148 0907 0200 0189 01947 d 0547 0106 0741 0190 0167 014514 d 0472 0069 0669 0156 0109 003728 d 0361 0044 0321 0140 0099 003456 d 0367 0048 0189 0138 0098 0014

6 4

3 d 0823 0094 1014 0218 0131 01577 d 0746 0092 0547 0207 0112 014814 d 0486 0073 0493 0198 0092 011628 d 0450 0045 0448 0176 0087 009756 d 0530 0057 0494 0188 0097 0078

5 5

3 d 0798 0106 0893 0245 0173 01527 d 0493 0088 0684 0236 0096 013214 d 0444 0066 0220 0225 0079 004628 d 0423 0048 0142 0214 0045 002156 d 0480 0069 0238 0205 0034 0013

4 6

3 d 0828 0104 0944 0241 0123 01477 d 0601 0092 0644 0221 0098 012914 d 0490 0080 0480 0213 0086 007128 d 0357 0070 0390 0215 0062 003156 d 0341 0067 0342 0213 0088 0033












Cr(VI)

100 CrO4

2minus HCrO4


110 CrO4


120 CrO4


Cu(II)

100 CuOH+ Cu(OH)3

minus Cu(OH)2

Cu2(OH)

2

2+ Cu3(OH)

4

2+ mdash0036 0262 0466 0155 99081 mdash

110 CuOH+ Cu(OH)4

2minus Cu(OH)3

minus Cu(OH)2

Cu2(OH)

2

2+ Cu3(OH)

4

2+

0016 0236 11594 2065 0030 86059120 Cu(OH)

4

2minus Cu(OH)3

minus Cu(OH)2

Cu3(OH)

4







997888rarr C6AS3H32

(3)


2O


4 Conclusions




Competing Interests


Acknowledgments


References
































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials
















01 0011 1E minus 3

Particle size (mm)

0

20

40

60

80

100

Cum

ulat

ive p

erce

ntag

e (

)




1153 2085Al2O3

789 571Fe2O3

257 333CaO 4180 6048MgO 227 228SO3

325 284Na2O 258 143

K2O 574 073

TiO2


001 mdash



3)


H1C1H1 S3M

H2


Inte

nsity

(CPS

)

C1

S1

S3

S2

H1

K

C2

C2 calciteH1 halite

K kyanite


H2

M maghemite

M

S3 sylvite

C1


I

H2 hematite

20 40 60 80 10002120579 (deg)



2 1089 Cl


2O3sdotSiO2) and



2O and K

2O






2O3 068





3 days7 days14 days

28 days56 days

00

05

10

15

20

25

Com

pres

sive s

treng

th (M

Pa)








Portland cement





2O respec-








8 2

3 d 0722 0084 0821 0188 0115 01137 d 0601 0076 0688 0182 0092 009414 d 0541 0073 0465 0176 0084 004028 d 0433 0056 0255 0169 0009 003456 d 0455 0057 0236 0157 0013 0045

7 3

3 d 0843 0148 0907 0200 0189 01947 d 0547 0106 0741 0190 0167 014514 d 0472 0069 0669 0156 0109 003728 d 0361 0044 0321 0140 0099 003456 d 0367 0048 0189 0138 0098 0014

6 4

3 d 0823 0094 1014 0218 0131 01577 d 0746 0092 0547 0207 0112 014814 d 0486 0073 0493 0198 0092 011628 d 0450 0045 0448 0176 0087 009756 d 0530 0057 0494 0188 0097 0078

5 5

3 d 0798 0106 0893 0245 0173 01527 d 0493 0088 0684 0236 0096 013214 d 0444 0066 0220 0225 0079 004628 d 0423 0048 0142 0214 0045 002156 d 0480 0069 0238 0205 0034 0013

4 6

3 d 0828 0104 0944 0241 0123 01477 d 0601 0092 0644 0221 0098 012914 d 0490 0080 0480 0213 0086 007128 d 0357 0070 0390 0215 0062 003156 d 0341 0067 0342 0213 0088 0033












Cr(VI)

100 CrO4

2minus HCrO4


110 CrO4


120 CrO4


Cu(II)

100 CuOH+ Cu(OH)3

minus Cu(OH)2

Cu2(OH)

2

2+ Cu3(OH)

4

2+ mdash0036 0262 0466 0155 99081 mdash

110 CuOH+ Cu(OH)4

2minus Cu(OH)3

minus Cu(OH)2

Cu2(OH)

2

2+ Cu3(OH)

4

2+

0016 0236 11594 2065 0030 86059120 Cu(OH)

4

2minus Cu(OH)3

minus Cu(OH)2

Cu3(OH)

4







997888rarr C6AS3H32

(3)


2O


4 Conclusions




Competing Interests


Acknowledgments


References
































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




01 0011 1E minus 3

Particle size (mm)

0

20

40

60

80

100

Cum

ulat

ive p

erce

ntag

e (

)




1153 2085Al2O3

789 571Fe2O3

257 333CaO 4180 6048MgO 227 228SO3

325 284Na2O 258 143

K2O 574 073

TiO2


001 mdash



3)


H1C1H1 S3M

H2


Inte

nsity

(CPS

)

C1

S1

S3

S2

H1

K

C2

C2 calciteH1 halite

K kyanite


H2

M maghemite

M

S3 sylvite

C1


I

H2 hematite

20 40 60 80 10002120579 (deg)



2 1089 Cl


2O3sdotSiO2) and



2O and K

2O






2O3 068





3 days7 days14 days

28 days56 days

00

05

10

15

20

25

Com

pres

sive s

treng

th (M

Pa)








Portland cement





2O respec-








8 2

3 d 0722 0084 0821 0188 0115 01137 d 0601 0076 0688 0182 0092 009414 d 0541 0073 0465 0176 0084 004028 d 0433 0056 0255 0169 0009 003456 d 0455 0057 0236 0157 0013 0045

7 3

3 d 0843 0148 0907 0200 0189 01947 d 0547 0106 0741 0190 0167 014514 d 0472 0069 0669 0156 0109 003728 d 0361 0044 0321 0140 0099 003456 d 0367 0048 0189 0138 0098 0014

6 4

3 d 0823 0094 1014 0218 0131 01577 d 0746 0092 0547 0207 0112 014814 d 0486 0073 0493 0198 0092 011628 d 0450 0045 0448 0176 0087 009756 d 0530 0057 0494 0188 0097 0078

5 5

3 d 0798 0106 0893 0245 0173 01527 d 0493 0088 0684 0236 0096 013214 d 0444 0066 0220 0225 0079 004628 d 0423 0048 0142 0214 0045 002156 d 0480 0069 0238 0205 0034 0013

4 6

3 d 0828 0104 0944 0241 0123 01477 d 0601 0092 0644 0221 0098 012914 d 0490 0080 0480 0213 0086 007128 d 0357 0070 0390 0215 0062 003156 d 0341 0067 0342 0213 0088 0033












Cr(VI)

100 CrO4

2minus HCrO4


110 CrO4


120 CrO4


Cu(II)

100 CuOH+ Cu(OH)3

minus Cu(OH)2

Cu2(OH)

2

2+ Cu3(OH)

4

2+ mdash0036 0262 0466 0155 99081 mdash

110 CuOH+ Cu(OH)4

2minus Cu(OH)3

minus Cu(OH)2

Cu2(OH)

2

2+ Cu3(OH)

4

2+

0016 0236 11594 2065 0030 86059120 Cu(OH)

4

2minus Cu(OH)3

minus Cu(OH)2

Cu3(OH)

4







997888rarr C6AS3H32

(3)


2O


4 Conclusions




Competing Interests


Acknowledgments


References
































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





3 days7 days14 days

28 days56 days

00

05

10

15

20

25

Com

pres

sive s

treng

th (M

Pa)








Portland cement





2O respec-








8 2

3 d 0722 0084 0821 0188 0115 01137 d 0601 0076 0688 0182 0092 009414 d 0541 0073 0465 0176 0084 004028 d 0433 0056 0255 0169 0009 003456 d 0455 0057 0236 0157 0013 0045

7 3

3 d 0843 0148 0907 0200 0189 01947 d 0547 0106 0741 0190 0167 014514 d 0472 0069 0669 0156 0109 003728 d 0361 0044 0321 0140 0099 003456 d 0367 0048 0189 0138 0098 0014

6 4

3 d 0823 0094 1014 0218 0131 01577 d 0746 0092 0547 0207 0112 014814 d 0486 0073 0493 0198 0092 011628 d 0450 0045 0448 0176 0087 009756 d 0530 0057 0494 0188 0097 0078

5 5

3 d 0798 0106 0893 0245 0173 01527 d 0493 0088 0684 0236 0096 013214 d 0444 0066 0220 0225 0079 004628 d 0423 0048 0142 0214 0045 002156 d 0480 0069 0238 0205 0034 0013

4 6

3 d 0828 0104 0944 0241 0123 01477 d 0601 0092 0644 0221 0098 012914 d 0490 0080 0480 0213 0086 007128 d 0357 0070 0390 0215 0062 003156 d 0341 0067 0342 0213 0088 0033












Cr(VI)

100 CrO4

2minus HCrO4


110 CrO4


120 CrO4


Cu(II)

100 CuOH+ Cu(OH)3

minus Cu(OH)2

Cu2(OH)

2

2+ Cu3(OH)

4

2+ mdash0036 0262 0466 0155 99081 mdash

110 CuOH+ Cu(OH)4

2minus Cu(OH)3

minus Cu(OH)2

Cu2(OH)

2

2+ Cu3(OH)

4

2+

0016 0236 11594 2065 0030 86059120 Cu(OH)

4

2minus Cu(OH)3

minus Cu(OH)2

Cu3(OH)

4







997888rarr C6AS3H32

(3)


2O


4 Conclusions




Competing Interests


Acknowledgments


References
































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials







8 2

3 d 0722 0084 0821 0188 0115 01137 d 0601 0076 0688 0182 0092 009414 d 0541 0073 0465 0176 0084 004028 d 0433 0056 0255 0169 0009 003456 d 0455 0057 0236 0157 0013 0045

7 3

3 d 0843 0148 0907 0200 0189 01947 d 0547 0106 0741 0190 0167 014514 d 0472 0069 0669 0156 0109 003728 d 0361 0044 0321 0140 0099 003456 d 0367 0048 0189 0138 0098 0014

6 4

3 d 0823 0094 1014 0218 0131 01577 d 0746 0092 0547 0207 0112 014814 d 0486 0073 0493 0198 0092 011628 d 0450 0045 0448 0176 0087 009756 d 0530 0057 0494 0188 0097 0078

5 5

3 d 0798 0106 0893 0245 0173 01527 d 0493 0088 0684 0236 0096 013214 d 0444 0066 0220 0225 0079 004628 d 0423 0048 0142 0214 0045 002156 d 0480 0069 0238 0205 0034 0013

4 6

3 d 0828 0104 0944 0241 0123 01477 d 0601 0092 0644 0221 0098 012914 d 0490 0080 0480 0213 0086 007128 d 0357 0070 0390 0215 0062 003156 d 0341 0067 0342 0213 0088 0033












Cr(VI)

100 CrO4

2minus HCrO4


110 CrO4


120 CrO4


Cu(II)

100 CuOH+ Cu(OH)3

minus Cu(OH)2

Cu2(OH)

2

2+ Cu3(OH)

4

2+ mdash0036 0262 0466 0155 99081 mdash

110 CuOH+ Cu(OH)4

2minus Cu(OH)3

minus Cu(OH)2

Cu2(OH)

2

2+ Cu3(OH)

4

2+

0016 0236 11594 2065 0030 86059120 Cu(OH)

4

2minus Cu(OH)3

minus Cu(OH)2

Cu3(OH)

4







997888rarr C6AS3H32

(3)


2O


4 Conclusions




Competing Interests


Acknowledgments


References
































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






Cr(VI)

100 CrO4

2minus HCrO4


110 CrO4


120 CrO4


Cu(II)

100 CuOH+ Cu(OH)3

minus Cu(OH)2

Cu2(OH)

2

2+ Cu3(OH)

4

2+ mdash0036 0262 0466 0155 99081 mdash

110 CuOH+ Cu(OH)4

2minus Cu(OH)3

minus Cu(OH)2

Cu2(OH)

2

2+ Cu3(OH)

4

2+

0016 0236 11594 2065 0030 86059120 Cu(OH)

4

2minus Cu(OH)3

minus Cu(OH)2

Cu3(OH)

4







997888rarr C6AS3H32

(3)


2O


4 Conclusions




Competing Interests


Acknowledgments


References
































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





Competing Interests


Acknowledgments


References
































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



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