Research ArticleExperimental Investigation and Quantitative Calculation of theDegree of Hydration and Products in Fly Ash-Cement Mixtures

Zhiyong Liu12 Dong Xu1 and Yunsheng Zhang3

1State Key Laboratory of Geomechanics amp Deep Underground Engineering China University of Mining and TechnologyXuzhou 221116 China2Jiangsu Key Laboratory of Environmental Impact and Structural Safety in Engineering China University of Mining and TechnologyXuzhou 221116 China3Jiangsu Key Laboratory for Construction Materials Southeast University Nanjing 211189 China

Correspondence should be addressed to Zhiyong Liu liuzhiyong0728163com

Received 10 July 2016 Revised 7 October 2016 Accepted 30 November 2016 Published 9 January 2017

Academic Editor Jun Liu

Copyright copy 2017 Zhiyong Liu 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

To explore the hydration process of fly ash-cement blended mixtures the degrees of the fly ash and cement reactions as well asthe content of nonevaporated water were determined at various water to binder ratios curing ages and fly ash incorporationamounts An equation describing the relationship between the degree of hydration and the effective water to binder ratio wasestablished based on the experimental results In addition a simplified scheme describing a model of the degree of reaction in flyash-cement mixtures is proposed Finally using reaction stoichiometry quantitative equations for the hydration products of flyash-cement blended pastes are proposed by considering the hydration reactions of fly ash and cement as well as their interactionsThe predicted results of the enhanced degree of cement hydration content of calcium hydroxide (CH) and porosity are consistentwith the experimental data

1 Introduction

Along with the scale of industrial production the contentrequirements of concrete used in construction are increasingat the same time due to the shortage of energy and mineralresources the demand for high-performance cement hasbecome much greater One important way of addressing thisdemand is to produce high-performance cement regulatedsupplementary cementitious materials and high cemen-titious clinker composites [1ndash3] Recently supplementarycementitious materials have been widely used in concreteeither in blended cements or added separately in cement-basedmaterials [4]These supplementary cementitiousmate-rials which are powdery industrial by-products such asfly ash from coal combustion silica fume from ferrosiliconalloy manufacture and blast-furnace slag a byproduct of pigiron production have latent hydraulic activity or volcanicproperties Fly ash is known as a pozzolana that possesseslittle or no cementitious value [5] and it accelerates the rateof cement hydration by a surface absorption effect [6] and

a heterogeneous nucleation effect [7] Therefore fly ash cansignificantly improve the curedmechanical properties [8] anddurability [9 10] of cement-based materials In addition dueto their spherical geometry fly ash particles can improve theworkability of fresh pastes [11] Accordingly fly ash mixedwith cement-based composite materials greatly improves theperformance of concrete andmakes themicrostructure of thecomposite material more complex

To accurately investigate the volume fraction of eachphase in cement-fly ash mixtures the degree of hydrationof cement and fly ash must first be determined The exper-imental methods for measuring the degree of hydration ofpure cement mainly include the hydration heat method [12ndash14] the CHmeasurementmethod [15 16] the nonevaporatedwater method [5 17] the backscattered electron microscopymethod [18 19] and the XRD quantitative analysis method[20ndash22] For the fly ash-cement composite cementitioussystem because of the simultaneous presence of the cementhydration reaction and the fly ash reaction the amountof nonevaporated water and CH water hydration products

HindawiAdvances in Materials Science and EngineeringVolume 2017 Article ID 2437270 12 pageshttpsdoiorg10115520172437270

2 Advances in Materials Science and Engineering

Table 1 The chemical composition of raw materials wt

Material SiO2 TiO2 Al2O3 Fe2O3 MnO MgO CaO Na2O K2O SO3 LOI sumCement 2168 028 564 422 012 081 6489 02 076 251 054 9914Fly ash 4786 125 325 452 006 105 409 055 162 000 634 10004

cannot be used to distinguish the hydration degrees of theindividual components To accurately study the hydrationdegree of cement and the reaction degree of fly ash infly ash-cement mixtures Suprenant and Papadopoulos [23]tested the degree of reaction of fly ash-cement blendedpastes using selective dissolution by hydrochloric acid Lamet al [5] studied the hydration process of fly ash-cementcomposites and measured the hydration degree of cementand the reaction degree of fly ash in composite materialsby determining the chemically combined water and usingselective dissolution by hydrochloric acid Bentz et al [24]studied the fly ash reaction in two different blended cement-fly ash systems using a selective dissolution technique basedon ethylene diamine tetra acetic acid (EDTA) combinedwith NaOH dilutedNaOH solution and portlandite contentFor hydration models of fly ash blended cement a kinetichydration model [25] and a synthetic model [26] were usedto simulate hydration of cement-fly ash blends based on amulticomponent concept respectively

However the microstructures of fly ash-cement mixturesare complex and have not been characterized quantitativelyThe unhydrated particles the main hydration product andcalcium silicate hydrate (C-S-H) are complex and changewith time temperature water to cement ratio and fly ashincorporation This paper proposes a hydration model forfly ash-cement blended pastes that is based on the reactiondegree and hydration productsThismodel is not only relatedto the hydration reactions of fly ash and cement but is alsoinfluenced by their interaction

2 Experimental Procedures

21 Materials Themass ratio of Portland cement clinker andgypsum was set at 95 5 These components were mixed andmilled to a specific surface area of 310m2kg Fly ash similartoASTMClass F fly ash was supplied by theNanjingThermalPower Plant The cement and fly ash were dried at 105∘Cand then sieved to remove the coarse particles larger than008mmTheir chemical compositions are shown in Table 1

22 Methods

221 Sample Preparation The mix proportions of blendedmaterials are listed in Table 2 The fresh cement paste wasput into sealed bags and held to a predetermined age ina standard curing chamber (20∘C and 95 humidity) Toprevent bleeding and layering of the pastes the sealed bagswere inverted every 15 minutes prior to the initial setting ofthe fly ash-cement mixtures

Table 2 Mix proportions of blended materials wt

Sample number Cement Fly ash WBPC 100 0 03 04 05FA 10 90 10 05FA 30 70 30 05FA 40 60 40 05

FA 50 50 50 03 035 04 04505

Note WB is water to binder ratio

222 Determination of the Quantity of Nonevaporated WaterThe hardened pastes were crushed and mixed with ethanoland then approximately 1 g of sample was weighed (accurateto 01mg) after drying The initial moisture contents of thesamples were recorded as 1198980 and the samples were thenheated to 900∘C at 10∘Cmin in a high-temperature furnaceand held at this temperature for 30 minutes Next the pasteswere taken out cooled in the dryer and weighed using anelectronic balance Finally the masses of the samples wererecorded as 119898900∘C Each group of samples was analyzed 3times in parallel tests and the average value was determinedThe nonevaporated water values of the hardened pastes werecalculated by the following equation

119882119899 =119871 minus 119871C1 minus 119871C

(1)

where119882119899 is the quantity of nonevaporated water L is loss onignition and 119871 = (1198980 minus 119898900∘C)1198980 119871C is loss on ignition ofraw materials

223 Measurement of Degree of Reaction

(1) Degree of the Cement Reaction Based on the Bogue com-position of the cement calculated using the oxide contentsand the reported chemically bound water contents of thecompounds [27] the degree of cement hydration in a purecement paste can be calculated using the following equation

120572C = 100 times 119882119899023

(2)

where 120572C is the hydration degree of cement

(2) Degree of the Fly Ash Reaction The samples of hardenedpaste were crushed and soaked for 25min in isopropylalcohol The samples were milled so that all passed through a008mm sieve that was equipped with ethanol and a vacuumfilter After filtration the powder samples were dried for 24 h

Advances in Materials Science and Engineering 3

at 80 to 200 kPa and 105∘C in a soda lime vacuum oven Thedetermination of the degree of reaction of the fly ash wasbased on a selective dissolution procedure using a picric acid-methanol solution and water [28]

3 Equations for Quantitative Calculations

31 Reaction Degree Model of Fly Ash-Cement MixturesPowers [29] considered that the nonevaporated water of purecement paste is an important indicator of the degree of thecement reactionThe nonevaporated water ratio of hydrationat different ages (119882119899(119905)) and the cement fully hydrated value(119882119899(infin) = 023) characterized the degree of the cementreaction and the amount of hydration products Nonevapo-rated water comes mainly from the CH and C-S-H gel of thehydration products The addition of fly ash to cement pastesresults in changes in the nonevaporable water content of thepaste Cement hydration generates C-S-H gel and CH whilethe fly ash reaction can also form C-S-H gel by consumingthe CH that is produced by the cement reaction Thereforethe nonevaporated quantity of water is not an appropriatemeasure to distinguish the reaction degree of cement and flyash

The total nonevaporated quantity of water ((119882119899)1198791) forthe fly ash-cement cementitious system can be expressed as

(119882119899)1198791 = (119882119899)c sdot 119898c + (119882119899)f sdot 119898f (3)

where (119882119899)c is the nonevaporable quantity of water for thecement hydration and (119882119899)f is the nonevaporable quantity ofwater for the fly ash reaction119898c represents the mass fractionof cement and 119898f is the mass fraction of fly ash Becausefly ash improves the effective water-cement ratio and leadsto increases in the degree of hydration of the cement thenonevaporated water of the hydration products generated bycement is

(119882119899)c = (119882119899)cminus0 + (119882119899)cminusf (4)

where (119882119899)cminus0 is the nonevaporated quantity of water forpure cement under the same conditions of hydration and(119882119899)cminusf is the nonevaporable quantity of water as a result ofthe enhancement in cement hydration due to the presence offly ash Equation (3) then becomes

(119882119899)1198791 = [(119882119899)cminus0 + (119882119899)cminusf] sdot 119898c + (119882119899)f sdot 119898f (5)

The degree of hydration of the fly ash-cement blendedmaterials can be expressed by the following equation

1205721198791 = 120572c sdot 119898 + 120572cminusf sdot 119898c + 120572f sdot 119898f (6)

where 1205721198791 is the total degree of hydration of fly ash-cementpastes 120572c is the degree of reaction of pure cement 120572f is thedegree of the fly ash reaction and 120572cminusf is the increase inthe degree of hydration of cement due to the presence of flyash 120572c is calculated using the nonevaporated water and thePowersrsquo model and 120572f can be directly determined by selectivedissolution in hydrochloric acidThe nonevaporated water offully hydrated fly ash obtained is 0168 from the stoichiometry

analysis of fly ash reactions [26]The presence of fly ash leadsto an increase in the degree of hydration of the cement (120572cminusf )that can be calculated by the total nonevaporated water thenonevaporated water of pure cement and the nonevaporatedwater of the fly ash 120572cminusf is obtained from

120572cminusf =[(119882119899)1198791 minus (119882119899)cminus0 sdot 119898c minus 0168 sdot 120572f sdot 119898f ]

(023 sdot 119898c)(7)

120572f =(119908119899)f0168

(8)

32 Calculation Model of Each Phase Volume Fraction forFlyAsh-CementMixtures Papadakis [30] considered that theglass phase of fly ash mainly consists of active silicon dioxideand aluminum oxide phases that participate in the hydrationreactions and generate C3S2H3 C4ASH12 and C4AH13 It isassumed that 1m3 of paste includes C kg cementW kg waterand FA kg fly ash respectively 119891119894C and 119891119894FA represent themass fraction of oxide 119894 (119894 = C (CaO) S (SiO2) A (Al2O3)F (Fe2O3) (SO3)) of cement and fly ash respectively 120574119894 is themass fraction of active oxide 119894 (119894 = S A) of fly ash 119877 is theunreacted content of cement and fly ash and119867 is the contentof bound water The model has been proposed according tothe stoichiometric reactions for the fly ash-cement blendedpastes [30]

When the gypsum content is higher than the amountrequired to fully hydrate the cement and the activatedalumina of the fly ash CSH2 gt 0637(C3A) + 1689(A) =(1689119891Ac minus 1078119891Fc)C + 1689120574A119891AFAFA or 119891sc gt(0785119891AC minus 0501119891FC) + 0785120574A119891AFA(FAC)

The cement reaction occurs as follows

2C3S + 106H 997888rarr C34S2H8 + 26CH (9)

2C2S + 86H 997888rarr C34S2H8 + 06CH (10)

C3A + CSH2 + 10H 997888rarr C4ASH12 (11)

C4AF + 2CH + 10H 997888rarr 2C3 (A F)H6 (12)

The fly ash reaction occurs as follows

S + 11H + 28H 997888rarr C11SH39 (13)

A + CSH2 + 3CH + 7H 997888rarr C4ASH12 (14)

The quantities of each phase are

CH = (0422 (C3S) 120572C3S + 0129 (C2S) 120572C2S

minus 0305 (C4AF) 120572C4AF)C minus (1357120574S119891sFA

+ 2176120574A119891AFA) 120572FA (FA)

(15)

4 Advances in Materials Science and Engineering

CSH = C34S2H8 + C11SH39 = (0996 (C3S) 120572C3S

+ 1321 (C2S) 120572C2S)C + 3189120574S119891SFA120572FA (FA)(16)

CASH = 2304 (C3A) 120572C3AC + 6106120574A119891AFA120572FA (FA) (17)

C (AF)H = 1675 (C4AF) 120572C4AFC (18)

119877 = (1 minus (C3S) 120572C3S minus (C2S) 120572C2S

minus 1637 (C3A) 120572C3A minus (C4AF) 120572C4AF)C + (1

minus 120574S119891SFA120572FA minus 2689120574A119891AFA120572FA) (FA)

(19)

119867 = (0418 (C3S) 120572C3S + 0450 (C2S) 120572C2S

+ 0667 (C3A) 120572C3A + 0371 (C4AF) 120572C4AF)C

+ (0840120574S119891SFA120572FA + 1237120574A119891AFA120572FA) (FA)

(20)

When result of (17) is positive the pozzolanic reactions offly ash occur fully otherwise there is not enough CH to reactwith the A and S of the fly ash When CH = 0 the maximumcontent of fly ash FAmax can be obtained

FAmax

=(0422 (C3S) + 0129 (C2S) minus 0305 (C4AF))C

(1357120574S119891sFA + 2176120574A119891AFA)

(21)

The volumes of each phase are

119881CH = (0188 (C3S) 120572C3S + 00576 (C2S) 120572C2S

minus 0136 (C4AF) 120572C4AF)C times 10minus3 minus (0606120574S119891sFA

minus 0971120574A119891AFA) 120572FA (FA) times 10minus3

119881CSH = (0475 (C3S) 120572C3S + 0630 (C2S) 120572C2S)C

times 10minus3 + 1702120574S119891SFA120572FA (FA) times 10minus3

119881CASH = 1182 (C3A) 120572C3AC times 10minus3

+ 3131120574A119891AFA120572FA (FA) times 10minus3

119881C(AF)H = 0627 (C4AF) 120572C4AFC times 10minus3

120601 = 119882120588w

minus Δ120601c minus Δ120601p

Δ120601c = (C3S) 119881C3S + (C2S) 119881C2S + (C3A) 119881C3A

+ (C4AF) 119881C4AF = (0347 (C3S) 120572C3S

+ 0384 (C2S) 120572C2S + 0577 (C3A) 120572C3A

+ 0224 (C4AF) 120572C4AF)C times 10minus3

Δ120601p = 120574S119891SFA120572FA (FA) 119881S + 120574A119891AFA120572FA (FA) 119881A

= (0635120574S119891SFA + 1180120574A119891AFA) 120572FA (FA) times 10minus3

120601 = 119882 times 10minus3 minus (0347 (C3S) 120572C3S + 0384 (C2S) 120572C2S

+ 0577 (C3A) 120572C3A + 0224 (C4AF) 120572C4AF)C

times 10minus3 minus (0635120574S119891SFA + 1180120574A119891AFA) 120572FA (FA)

times 10minus3(22)

(2) When the amount of gypsum in the cement issufficient to hydrate the cement but is not enough to reactwith all the fly ash activated alumina

CSH2 lt 0637(C3A) + 1689(A) = (1689119891Ac minus1078119891Fc)C + 1689120574A119891AFAFA or 119891sc lt (0785119891AC minus0501119891FC) + 0785120574A119891AFA(FAC)

The cement reaction occurs as follows

2C3S + 106H 997888rarr C34S2H8 + 26CH (23)

2C2S + 86H 997888rarr C34S2H8 + 06CH (24)

C3A + CSH2 + 10H 997888rarr C4ASH12 (25)

C4AF + 2CH + 10H 997888rarr 2C3 (A F)H6 (26)

The fly ash reaction occurs as follows

S + 11H + 28H 997888rarr C11SH39 (27)

A + CSH2 + 3CH + 7H 997888rarr C4ASH12 (28)

A + 4CH + 9H 997888rarr C4AH3 (29)

The quantities of each phase are

CH = (0422 (C3S) 120572C3S + 0129 (C2S) 120572C2S

minus 0305 (C4AF) 120572C4AF minus 0274 (C3A) 120572C3A

+ 0925119891SC)C minus (1357120574S119891sFA + 2907120574A119891AFA)

sdot 120572FA (FA)

CSH = (0996 (C3S) 120572C3S + 1321 (C2S) 120572C2S)C

+ 3189120574S119891SFA120572FA (FA)

CASH = 7774119891SCC

C (AF)H = 1675 (C4AF) 120572C4AFC

CAH = (2074 (C3A) 120572C3A minus 6999119891SC)C

+ 5497120574A119891AFA120572FA (FA)

Advances in Materials Science and Engineering 5

119877 = (1 minus (C3S) 120572C3S minus (C2S) 120572C2S minus (C3A) 120572C3A

minus (C4AF) 120572C4AF minus 215119891SC)C + (1 minus 120574S119891SFA120572FA

minus 120574A119891AFA120572FA) (FA)

119867 = (0418 (C3S) 120572C3S + 0450 (C2S) 120572C2S

+ 0800 (C3A) 120572C3A + 0371 (C4AF) 120572C4AF

minus 045119891S119862)C + (0840120574S119891SFA120572FA

+ 1591120574A119891AFA120572FA) (FA) (30)

The volumes of each phase are

119881CH = (0188 (C3S) 120572C3S + 0058 (C2S) 120572C2S

minus 0136 (C4AF) 120572C4AF minus 0122 (C3A) 120572C3A

+ 0413119891SC)C times 10minus3 minus (0606120574S119891sFA

+ 1298120574A119891AFA) 120572FA (FA) times 10minus3

(31)

119881CSH = (0474 (C3S) 120572C3S + 0629 (C2S) 120572C2S)C

times 10minus3 + 1696120574S119891SFA120572FA (FA) times 10minus3(32)

119881CASH = 3987119891SCC times 10minus3 (33)

119881C(AF)H = 0627 (C4AF) 120572C4AFC times 10minus3 (34)

119881CAH = (1001 (C3A) 120572C3A minus 3398119891SC)C times 10minus3

+ 2668120574A119891AFA120572FA (FA) times 10minus3(35)

120601 = 119882120588w

minus Δ120601c minus Δ120601p (36)

Δ120601c = (C3S) 119881C3S + (C2S) 119881C2S + (C3A) 119881C3A

+ (C4AF) 119881C4AF = (0347 (C3S) 120572C3S

+ 0384 (C2S) 120572C2S + 0577 (C3A) 120572C3A

+ 0224 (C4AF) 120572C4AF)C times 10minus3

(37)

Δ120601p = 0635120574S119891SFA120572FA (FA) times 10minus3 + (0075119891SC

minus 0022 (C3A) 120572C3A)C times 10minus3

+ 1121120574A119891AFA120572FA (FA) times 10minus3

(38)

120601 = 119882 times 10minus3 minus (0635120574S119891SFA + 1180120574A119891AFA)

sdot 120572FA (FA) times 10minus3 minus (0347 (C3S) 120572C3S

+ 0384 (C2S) 120572C2S + 0555 (C3A) 120572C3A

+ 0224 (C4AF) 120572C4AF + 0075119891SC)C times 10minus3

(39)

4 Results and Discussion

41 Experimental Results of Fly Ash-Cement Mixtures

411 Degree of Fly Ash Reaction As can be seen in Figure 1the degree of the fly ash reaction increased with increasingcuring age for various water binder ratios and amounts of flyash In the early stage (1sim7 d) the fly ash (3 to 25 massfraction) had a greater level of participation in the pozzolanicreaction Testing the specific surface area and particle sizedistribution of the fly ash revealed that the fly ash particleswere small and their surface area was up to 665m2kg Theouter surface of a large number of fine particles of hydrated flyash was exposed to CH in the early stage and the pozzolanicreactivity of fly ash occurred rapidly One investigation [31]examined cement-fly ash paste by SEM and found that thesurface of many fine fly ash particles appeared to be etched atthe age of 7 d and that hydration products were formed on thesurface of the fly ash particles The present study has shownthat a pozzolanic reaction with some of the fly ash began atthis stage When examined at a later age the degree of thepozzolanic reactions with fly ash had also increased but theincreases gradually slowed

The effect of fly ash incorporation on the degree ofthe fly ash reaction at the same water binder ratio (05)is shown in Figure 2 The degree of the fly ash reactiondecreased with increasing amounts of fly ash When the flyash content increased from 10 to 30 40 and 50 (massfraction) the degree of the fly ash reaction at 28 d decreasedfrom 371 to 290 254 and 206 respectively As theincorporation of fly ash increased the proportion of cementdecreased and thus the consumption of CH increased andits production decreased in the fly ash-cement mixtures Theamount of CH in the pore solution decreased and the degreeof the fly ash reaction declined A 10 content of fly ashshowed the highest reaction degree with 4515 at 180 dayswhereas the reaction degree of the 50 content was only3311 indicating that nearly 67 of the fly ash did not reactTherefore the filling effect and the microaggregate effect arethe major effects when the fly ash amount increases and thepozzolanic reaction is relatively weak

The effect of the WB ratio on the degree of the fly ashreaction at the same fly ash incorporation (50) is shownin Figure 3 When the WB ratio rises from 03 to 05 thedegree of the fly ash reaction exhibited a linearly increasingtrend with increased water binder ratioThe average reactiondegree of fly ash increased by approximately 110 with each005 increase in the water binder ratio

412 Degree of Cement Reaction The nonevaporable watercontent of the pure cement pastes changed with curing ageas shown in Figure 4 Curing age had a greater impact on thenonevaporated water content especially in the early stages(before 28 d) From preparation to the curing time of 7 dthe nonevaporable water content increased rapidly After7 d of hydration the nonevaporable water content increasedslowly After 28 d the nonevaporable water content remainedconstant for the cement paste samples with WB ratios of 03

6 Advances in Materials Science and Engineering

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

5

10

15

20

25

30

35D

egre

e of fl

y as

h re

actio

n (

)

WB = 03

WB = 035

WB = 04

WB = 045

WB = 05

FA50

(a) Different WB ratios

00

20 40 60 80 100 120 140 160 180 200Curing time (d)

5

10

15

20

25

30

35

40

45

50

Deg

ree o

f fly

ash

reac

tion

()

WB = 05

FA50FA40FA30FA10

(b) Different amounts of incorporated fly ash

Figure 1 Effect of curing time on the degree of the fly ash reaction

Deg

ree o

f fly

ash

reac

tion

()

10

10

20

20

30

30

40

40

50

50

600

WB = 05

Fly ash incorporation ()

1 d3 d7 d28 d90 d180 d

Figure 2 Effect of fly ash incorporation on the degree of the fly ashreaction

and 04 while the nonevaporable water content of the pastewith the WB ratio of 05 continued to increase

Based on the experimental results for the nonevaporablewater content in the pure cement pastes the reaction degreeof cement (120572C) can be calculated using (2) In this studythe degree of the cement paste reaction at different WB

5

10

15

20

25

30

35

Deg

ree o

f fly

ash

reac

tion

()

WB

1 d3 d7 d

28 d60 d90 d180 d

030 035 040 045 050 055 0600

14 d

FA50

Figure 3 Effect of WB ratio on fly ash reaction degree

ratios and different curing ages is shown in Figure 5 Thereis no suitable experimental method to measure the degree ofthe cement reaction for fly ash-cement pastes at the presenttime mainly because the fly ash-cement paste containsnot only C2S2H Ca(OH)2 C3AH6 and AFt from cement

Advances in Materials Science and Engineering 7

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

WB = 03

WB = 04

WB = 05

Non

evap

orab

le w

ater

cont

ent (

)

11

12

13

14

15

16

17

18

19

20

Pure cement pastes

Figure 4 Nonevaporable water content of pure cement pastes

hydration but also includes C2S2H C3AH6 and AFt from thepozzolanic reactions of fly ash and Ca(OH)2 There are nosignificant differences in the composition and structure of theC2S2H C3AH6 and AFt that are formed in the fly ash reac-tions from those formed in cement hydration It is difficultto experimentally separate them Therefore the traditionalmethods of determining the hydration degree of pure cementpaste have failed by measuring the nonevaporable water andCa(OH)2 contents of blended pastes However quantifyingthe degree of the cement reaction is the prerequisite forunderstanding the hydration processes of fly ash-cementpastes As shown in Figure 2 the degree of cement hydrationof pure cement paste depends on the water-cement ratio Anequation describing the relationship between the hydrationdegree and water-cement ratio is expressed as follows [5]

120572c = 1199101 (119905) 119890minus(1199102(119905)(WC)) (40)

where 1199101(119905) and 1199102(119905) are the age-related functions and WCis the water-cement ratio

To calculate the degree of cement hydration of the fly ash-cement system the watercement (WC) ratio is replaced bythe effective water binder ratio in (40) In addition the fly ashpozzolanic reactions will occur and generate a new productso the effectivewater binder ratio is replaced byW(C+120572fFA)

120572c = 1199101 (119905) 119890minus(1199102(119905)(W(C+120572f FA))) (41)

The degree of cement hydration of the fly ash-cementsystem can be calculated under various conditions accordingto (41) as shown in Figure 6 It was found by comparing thecuring times in Figure 6 that the degree of cement hydrationwas higher than that of pure cement paste under the sameconditions when fly ash was mixed into the cement pasteWhen the fly ash content increased the hydration degree ofcement increasedThis ismainly because the incorporation of

Deg

ree o

f pur

e cem

ent r

eact

ion

()

WB

1 d3 d7 d

28 d60 d90 d180 d14 d

20

30

40

50

60

70

80

10

03 04 050

Figure 5 Nonevaporable water content of pure cement pastes

fly ash increased the effective water-cement ratio of cementimproving the hydration environment and thus increasingthe hydration degreeThe fly ash contributes to consumptionof the hydration product of cement (Ca(OH)2) and thereforeit is beneficial for the hydration reaction of cement

413 Content of Nonevaporable Water Themeasured resultsof nonevaporable water in fly ash-cement blended pastesunder various conditions are shown in Figure 7 It can beseen in Figure 7 that the nonevaporated water content of flyash-cement pastes with 10 30 and 40 fly ash are higherthan the pure cement paste in addition to the 50 contentAfter 7 d the differences were not significant This may bebecause the nucleation and crystallization of Ca(OH)2 wereinduced by the fine particles of the fly ash thus contributingto cement hydrationWithin a certain range of incorporationthe promotion effects of fly ash exceeded the negative effectsdue to the slow development of the activity of fly ash and asmall number of hydrates The nonevaporable water contentof fly ash-cement pastes will be higher than that of purecement pastes From the nonevaporable water trend theblended pastes of fly ash incorporation of 10sim30 showed thehighest nonevaporable water Zhang et al [32] also found thatfly ash can improve the early hydration rate of cement

Powers [29] proposed that nonevaporable water in purecement paste is one index for the degree of cement hydrationNonevaporable water of the hardened pastes comes mainlyfrom the hydration products Ca(OH)2 and C-S-H gel In thefly ash-cement blended pastes both cement hydration andthe fly ash reaction produce C-S-H and the fly ash can alsoconsume Ca(OH)2 that is produced by the hydration of thecement Therefore it is not appropriate to directly use thenonevaporable water to measure the degree of reaction of theblended pastes

8 Advances in Materials Science and Engineering

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

WB = 03

WB = 035

WB = 04

WB = 045

WB = 05

Deg

ree o

f cem

ent r

eact

ion

()

55

60

65

70

75

80

85

90

FA50

(a) Different WB ratios

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

Deg

ree o

f cem

ent r

eact

ion

()

55

60

65

70

75

80

85

90

WB = 05

FA50FA40FA30FA10

(b) Different fly ash incorporation

Figure 6 The fly ash reaction degree of fly ash-cement system

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

6

8

Non

evap

orab

le w

ater

cont

ent (

)

10

12

14

16

18

WB = 03

WB = 04

WB = 05

FA50

(a) Different WB ratios

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

Non

evap

orab

le w

ater

cont

ent (

)

10

12

14

16

18

20

WB = 05

FA50FA40FA30FA10FA0

(b) Different fly ash incorporation rates

Figure 7 Nonevaporable water contents of the fly ash-cement blended pastes

42 Verifying the Model of Fly Ash-Cement Blended Pastes

421The Equations for the Increased Hydration Degree Valuesof Cement According to the experimental results of the totalamount of nonevaporable water the degree of the fly ashreaction and the degree of increasing cement hydration werecalculated in the fly ash-cement composite systems under

various conditions by (7) and (8) as shown in Figures 8 and9

Figure 8 shows the variation of the degree of hydrationof cement in the blended system with the fly ash addition of50 as the WB ratio changed from 03 to 05 The reactiondegree at every curing age increased linearly with increases oftheWB ratio Figure 9 shows the degree of cement hydration

Advances in Materials Science and Engineering 9

WB

1 d3 d7 d

28 d60 d90 d180 d14 d

055030 035 040 045 050

00

01

02

03

04

05

06

07 FA 50

120572cminus

f

Figure 8 Influence of the WB ratio on the increased degree ofcement hydration

1 d3 d7 d

28 d60 d90 d180 d14 d

00

01

01

02

02

03

03

04

04

05

05

06

06

07

08WB 05

mf

120572cminus

f

Figure 9 Influence of the fly ash content on the increased degree ofcement hydration

with the trend of its fly ash content when the WB ratio was05 It can be observed that the added degree of hydration ofthe cement increased with increases of the fly ash contentWhen the fly ash content was less than 03 the curing agehad little influence on the increased degree of hydration ofthe cementWhen the fly ash content was greater than 03 thedegree of hydration of the cement was significantly improvedwith increasing curing age For example as the curing ageof the fly ash-cement system increased from 1 d to 180 d thevalue of the degree of hydration of the cement increased from007 to 011 when its fly ash content was 01 The increased

value of the degree of hydration of cement improved from034 to 072 when the fly ash content was 05 Clearly theWB ratio fly ash content and curing age can each promotethe degree of hydration of the cement On the one handthis is mainly due to the incorporated fly ash increasing theeffective WB ratio of the cement and improving the cementhydration environment On the other hand this is due to thepostsecondary reactions of fly ash that promptly consume theCa(OH)2 that is generated by the hydration of the cementwhich is advantageous for the hydration reactions of cement

One objective of this study was to predict the increaseddegree of hydration of cement and degree of reaction of flyash in the fly ash-cement blended system with different flyash contents WB ratios and curing periods Based on theresults of Figures 8 and 9 it is concluded that the increasedvalues of the degree of hydration of cement containing addedfly ash and the quantitative relationships among the reactiondegree of fly ash the WB ratio and the fly ash content canbe expressed as follows as determined by multiple regressionanalysis

120572cminusf = 1 minus 119890minus119886(119905minus119887)119888

(42)

119886 = minus305481 + 286722 sdot 119890[034293sdot(WB)] (43a)

119887 = 0 (43b)

119888 = minus1167238 + 113153 sdot 119890[011795sdot(119898f )] (43c)

120572f = 1 minus 119890minus119889(119905minus119891)119892

(44)

119889 = 003869 + 000426 sdot 119890[555391sdot(WB)] (45a)

119891 = 09 (45b)

119892 = minus001487 + 0413 sdot 119890[minus07646sdot(119898f )] (45c)

422 Validation of the Model Figure 10 shows the compar-ison of the experimental results and the predicted valuesfor 120572cminusf The fitted 1198772 coefficient of the regression analysisequation (119910 = 099366119909) is 098849 Figure 11 shows the120572119891 of the experimental and predicted values and the fitted1198772 coefficient of the regression analysis equation (119910 =099552119909) is 099131 The maximum relative errors of Figures10 and 11 are 3096 and 4831 respectively The modelwas consistent with the experimental values Therefore it isreasonable to propose a model for the degree of the fly ashreaction and a model of accelerated hydration of cement forblended systems

The CH content and porosity as key parameters ofthe microstructure were selected to verify the hydrationproducts of fly ash-cement mixtures The results of theexperimental values were obtained from the literature [5] Inthis experiment the CH content of hydrated cement pasteswas determined by thermal gravimetry analysis based onthe ignited weight of the sample The porosity of cement-flyash pastes was obtained by mercury intrusion porosimetryThe CH and porosity values are presented in Section 32Figure 12 presents the comparison between the predicted

10 Advances in Materials Science and Engineering

WB = 03

WB = 04

WB = 05

000000

001

001

002

002

003

003

004

004

Measured value

Pred

icte

d va

lue

Figure 10 The predicted and measured values of the degree ofcement hydration of enhanced cement-fly ash pastes

WB = 03

WB = 035

WB = 04

WB = 045

WB = 05

0000

02

02

04

04

06

06

08

08

10

10

Measured value

Pred

icte

d va

lue

Figure 11 The predicted and measured values of the degree of thefly ash reaction of cement-fly ash pastes

and experimental values of the CH content For differentWB ratios and fly ash content the predicted results camecloser to the experimental values with increasing curingage The maximum relative errors were 135 113 and66 at 7 d 28 d and 90 d respectively Figure 13 showsthe comparison of the predicted and experimental valuesof porosity in fly ash-cement systems For all samples thepredicted values were higher than the measured values Themaximum relative errors were 117 112 and 139 at 7 d28 d and 180 d respectively The main reason is that theporosity of the blended system calculated by the model is

10000

20 40 60 80Age (d)

20

2

4

6

8

10

12

14

16

18

CH (

)

WB = 03 mf = 025 (experiment)WB = 03 mf = 025 (prediction)

(prediction)

(prediction)WB = 03 mf = 055 (experiment)WB = 03 mf = 055

WB = 05 mf = 055 (experiment)WB = 05 mf = 055

Figure 12 The predicted and measured values of CH content ofcement-fly ash pastes

100 150 2000 50Age (d)

20

25

30

35

40

45

50

15

Poro

sity

()

WB = 03 (experiment)WB = 03 (prediction)WB = 04 (experiment)WB = 04 (prediction)WB = 05 (experiment)WB = 05 (prediction)

Figure 13 The predicted and measured values of porosity ofcement-fly ash pastes

the capillary porosity (the porosity contained in the capillarypores and the porosity of the gel) that was obtained bymercury intrusion Therefore with longer curing ages moreC-S-H gel phase was generated by the second hydration of flyash and the differences between the predicted and measuredvalues increased

Advances in Materials Science and Engineering 11

5 Conclusions

(1) The degree of hydration of cement in the pure cementpastes was determined by measuring the nonevap-orablewater contentThedegree of the fly ash reactionin fly ash-cement blended pastes was determinedusing a selective dissolution method

(2) Based on the degree of hydration of cement and theeffectiveWB ratio the degree of hydration of cementin fly ash-cement blended pastes was acquired

(3) A hydration model of fly ash-cement blended pasteshas been established based on the degree of reactionand the hydration products This model incorporatesthe reactions of fly ash and the hydration of cementbut is also influenced by their interactions

Competing Interests

The authors declare that there are no competing interestsregarding the publication of this paper

Acknowledgments

The authors gratefully acknowledge the National Natural Sci-ence Foundation of China (51408597) and the FundamentalResearch Funds for the Central Universities (2014QNA75)

References

[1] K-H Yang Y-B Jung M-S Cho and S-H Tae ldquoEffect ofsupplementary cementitious materials on reduction of CO2emissions from concreterdquo Journal of Cleaner Production vol103 pp 774ndash783 2015

[2] T Sato and J J Beaudoin ldquoEffect of nano-CaCO3 on hydrationof cement containing supplementary cementitious materialsrdquoAdvances in Cement Research vol 23 no 1 pp 33ndash43 2011

[3] Z Liu Y Zhang and Q Jiang ldquoContinuous tracking of therelationship between resistivity and pore structure of cementpastesrdquo Construction and Building Materials vol 53 pp 26ndash312014

[4] R Snellings G Mertens and J Elsen ldquoSupplementary cemen-titious materialsrdquo Reviews in Mineralogy and Geochemistry vol74 pp 211ndash278 2012

[5] L Lam Y L Wong and C S Poon ldquoDegree of hydration andgelspace ratio of high-volume fly ashcement systemsrdquo Cementand Concrete Research vol 30 no 5 pp 747ndash756 2000

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

[7] P Hou S Kawashima D Kong D J Corr J Qian and S PShah ldquoModification effects of colloidal nanoSiO2 on cementhydration and its gel propertyrdquo Composites Part B Engineeringvol 45 no 1 pp 440ndash448 2013

[8] J David Raja Selvam D S Robinson Smart and I DinaharanldquoMicrostructure and some mechanical properties of fly ashparticulate reinforced AA6061 aluminum alloy compositesprepared by compocastingrdquoMaterials amp Design vol 49 pp 28ndash34 2013

[9] R Feldman L R Prudencio Jr and G Chan ldquoRapid chloridepermeability test on blended cement and other concretescorrelations between charge initial current and conductivityrdquoConstruction and Building Materials vol 13 no 3 pp 149ndash1541999

[10] SWM Supit and FU A Shaikh ldquoDurability properties of highvolume fly ash concrete containing nano-silicardquo Materials andStructuresMateriaux et Constructions vol 48 no 8 pp 2431ndash2445 2014

[11] N Neithalath and J Jain ldquoRelating rapid chloride transportparameters of concretes to microstructural features extractedfrom electrical impedancerdquo Cement and Concrete Research vol40 no 7 pp 1041ndash1051 2010

[12] G Land and D Stephan ldquoThe influence of nano-silica on thehydration of ordinary Portland cementrdquo Journal of MaterialsScience vol 47 no 2 pp 1011ndash1017 2012

[13] J Justs M Wyrzykowski F Winnefeld D Bajare and P LuraldquoInfluence of superabsorbent polymers on hydration of cementpastes with low water-to-binder ratiordquo Journal of ThermalAnalysis and Calorimetry vol 115 no 1 pp 425ndash432 2014

[14] Z Liu Y Zhang Q Jiang W Zhang and J Wu ldquoSolid phasespercolation and capillary pores depercolation in hydratingcement pastesrdquo Journal of Materials in Civil Engineering vol 26no 12 Article ID 04014090 2014

[15] B Uzal and L Turanlı ldquoBlended cements containing highvolume of natural zeolites properties hydration and pastemicrostructurerdquo Cement and Concrete Composites vol 34 no1 pp 101ndash109 2012

[16] Y Kocak and S Nas ldquoThe effect of using fly ash on the strengthand hydration characteristics of blended cementsrdquoConstructionand Building Materials vol 73 pp 25ndash32 2014

[17] D D Nguyen L P Devlin P Koshy and C C Sorrell ldquoEffectsof acetic acid on early hydration of Portland cementrdquo Journal ofThermal Analysis and Calorimetry vol 123 no 1 pp 489ndash4992016

[18] D P Bentz R J Detwiler E J Garboczi P Halamickova andM Schwartz ldquoMulti-scale modeling of the diffusivity of mortarand concreterdquo in Proceedings of the Chloride Penetration intoConcrete LONilsson and J POllivier Eds pp 85ndash94 RILEM1997

[19] M W Grutzeck D Shi G Liu and S Kwan ldquoComputer sim-ulation of interfacial packing in concreterdquo Journal of MaterialsScience vol 28 no 13 pp 3444ndash3450 1993

[20] D P Bentz ldquoInfluence of silica fume on diffusivity in cement-based materials II Multi-scale modeling of concrete diffusiv-ityrdquo Cement and Concrete Research vol 30 no 7 pp 1121ndash11292000

[21] M Voltolini M C Dalconi G Artioli et al ldquoUnderstandingcement hydration at the microscale new opportunities fromlsquopencil-beamrsquo synchrotron X-ray diffraction tomographyrdquo Jour-nal of Applied Crystallography vol 46 no 1 pp 142ndash152 2013

[22] Z Liu W Chen Y Zhang and H Lv ldquoA three-dimensionalmulti-scale method to simulate the ion transport behavior ofcement-based materialsrdquo Construction amp Building Materialsvol 120 pp 494ndash503 2016

[23] B A Suprenant and G Papadopoulos ldquoSelective dissolutionof portland-fly-ash cementsrdquo Journal of Materials in CivilEngineering vol 3 no 1 pp 48ndash59 1991

[24] D P Bentz E J Garboczi and K A Snyder ldquoA hard coresoftshell microstructural model for studying percolation and trans-port in three-dimensional compositemediardquo NISTIR 6265 USDepartment of Commerce 1999

12 Advances in Materials Science and Engineering

[25] X-Y Wang H-S Lee and K-B Park ldquoSimulation of low-calcium fly ash blended cement hydrationrdquo ACI MaterialsJournal vol 106 no 2 pp 167ndash175 2009

[26] Q Zeng K Li T Fen-Chong and P Dangla ldquoDeterminationof cement hydration and pozzolanic reaction extents for fly-ashcement pastesrdquo Construction and Building Materials vol 27 no1 pp 560ndash569 2012

[27] AMNeville Properties of Concrete AddisonWesley LongmanEssex UK 4th edition 1996

[28] C C Yang ldquoThe relationship between charge passed and thechloride concentrations in anode and cathode cells using theaccelerated chloride migration testrdquo Materials and Structuresvol 36 no 264 pp 678ndash684 2003

[29] T C Powers ldquoStructure and physical properties of hardenedportland cement pasterdquo Journal of the American Ceramic Soci-ety vol 41 no 1 pp 1ndash6 1958

[30] V G Papadakis ldquoEffect of fly ash on Portland cement systemspart I Low-calcium fly ashrdquoCement and Concrete Research vol29 no 11 pp 1727ndash1736 1999

[31] A Xu and S L Sarkar ldquoMicrostructural development in high-volume fly-ash cement systemrdquo Journal of Materials in CivilEngineering vol 6 no 1 pp 117ndash136 1994

[32] YM ZhangW Sun andHD Yan ldquoHydration of high-volumefly ash cement pastesrdquoCement and Concrete Composites vol 22no 6 pp 445ndash452 2000

Submit your manuscripts athttpswwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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NanoparticlesJournal of

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Biomaterials

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NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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CrystallographyJournal of

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The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

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CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

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BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Advances in Materials Science and Engineering 3

at 80 to 200 kPa and 105∘C in a soda lime vacuum oven Thedetermination of the degree of reaction of the fly ash wasbased on a selective dissolution procedure using a picric acid-methanol solution and water [28]

3 Equations for Quantitative Calculations

31 Reaction Degree Model of Fly Ash-Cement MixturesPowers [29] considered that the nonevaporated water of purecement paste is an important indicator of the degree of thecement reactionThe nonevaporated water ratio of hydrationat different ages (119882119899(119905)) and the cement fully hydrated value(119882119899(infin) = 023) characterized the degree of the cementreaction and the amount of hydration products Nonevapo-rated water comes mainly from the CH and C-S-H gel of thehydration products The addition of fly ash to cement pastesresults in changes in the nonevaporable water content of thepaste Cement hydration generates C-S-H gel and CH whilethe fly ash reaction can also form C-S-H gel by consumingthe CH that is produced by the cement reaction Thereforethe nonevaporated quantity of water is not an appropriatemeasure to distinguish the reaction degree of cement and flyash

The total nonevaporated quantity of water ((119882119899)1198791) forthe fly ash-cement cementitious system can be expressed as

(119882119899)1198791 = (119882119899)c sdot 119898c + (119882119899)f sdot 119898f (3)

where (119882119899)c is the nonevaporable quantity of water for thecement hydration and (119882119899)f is the nonevaporable quantity ofwater for the fly ash reaction119898c represents the mass fractionof cement and 119898f is the mass fraction of fly ash Becausefly ash improves the effective water-cement ratio and leadsto increases in the degree of hydration of the cement thenonevaporated water of the hydration products generated bycement is

(119882119899)c = (119882119899)cminus0 + (119882119899)cminusf (4)

where (119882119899)cminus0 is the nonevaporated quantity of water forpure cement under the same conditions of hydration and(119882119899)cminusf is the nonevaporable quantity of water as a result ofthe enhancement in cement hydration due to the presence offly ash Equation (3) then becomes

(119882119899)1198791 = [(119882119899)cminus0 + (119882119899)cminusf] sdot 119898c + (119882119899)f sdot 119898f (5)

The degree of hydration of the fly ash-cement blendedmaterials can be expressed by the following equation

1205721198791 = 120572c sdot 119898 + 120572cminusf sdot 119898c + 120572f sdot 119898f (6)

where 1205721198791 is the total degree of hydration of fly ash-cementpastes 120572c is the degree of reaction of pure cement 120572f is thedegree of the fly ash reaction and 120572cminusf is the increase inthe degree of hydration of cement due to the presence of flyash 120572c is calculated using the nonevaporated water and thePowersrsquo model and 120572f can be directly determined by selectivedissolution in hydrochloric acidThe nonevaporated water offully hydrated fly ash obtained is 0168 from the stoichiometry

analysis of fly ash reactions [26]The presence of fly ash leadsto an increase in the degree of hydration of the cement (120572cminusf )that can be calculated by the total nonevaporated water thenonevaporated water of pure cement and the nonevaporatedwater of the fly ash 120572cminusf is obtained from

120572cminusf =[(119882119899)1198791 minus (119882119899)cminus0 sdot 119898c minus 0168 sdot 120572f sdot 119898f ]

(023 sdot 119898c)(7)

120572f =(119908119899)f0168

(8)

32 Calculation Model of Each Phase Volume Fraction forFlyAsh-CementMixtures Papadakis [30] considered that theglass phase of fly ash mainly consists of active silicon dioxideand aluminum oxide phases that participate in the hydrationreactions and generate C3S2H3 C4ASH12 and C4AH13 It isassumed that 1m3 of paste includes C kg cementW kg waterand FA kg fly ash respectively 119891119894C and 119891119894FA represent themass fraction of oxide 119894 (119894 = C (CaO) S (SiO2) A (Al2O3)F (Fe2O3) (SO3)) of cement and fly ash respectively 120574119894 is themass fraction of active oxide 119894 (119894 = S A) of fly ash 119877 is theunreacted content of cement and fly ash and119867 is the contentof bound water The model has been proposed according tothe stoichiometric reactions for the fly ash-cement blendedpastes [30]

When the gypsum content is higher than the amountrequired to fully hydrate the cement and the activatedalumina of the fly ash CSH2 gt 0637(C3A) + 1689(A) =(1689119891Ac minus 1078119891Fc)C + 1689120574A119891AFAFA or 119891sc gt(0785119891AC minus 0501119891FC) + 0785120574A119891AFA(FAC)

The cement reaction occurs as follows

2C3S + 106H 997888rarr C34S2H8 + 26CH (9)

2C2S + 86H 997888rarr C34S2H8 + 06CH (10)

C3A + CSH2 + 10H 997888rarr C4ASH12 (11)

C4AF + 2CH + 10H 997888rarr 2C3 (A F)H6 (12)

The fly ash reaction occurs as follows

S + 11H + 28H 997888rarr C11SH39 (13)

A + CSH2 + 3CH + 7H 997888rarr C4ASH12 (14)

The quantities of each phase are

CH = (0422 (C3S) 120572C3S + 0129 (C2S) 120572C2S

minus 0305 (C4AF) 120572C4AF)C minus (1357120574S119891sFA

+ 2176120574A119891AFA) 120572FA (FA)

(15)

4 Advances in Materials Science and Engineering

CSH = C34S2H8 + C11SH39 = (0996 (C3S) 120572C3S

+ 1321 (C2S) 120572C2S)C + 3189120574S119891SFA120572FA (FA)(16)

CASH = 2304 (C3A) 120572C3AC + 6106120574A119891AFA120572FA (FA) (17)

C (AF)H = 1675 (C4AF) 120572C4AFC (18)

119877 = (1 minus (C3S) 120572C3S minus (C2S) 120572C2S

minus 1637 (C3A) 120572C3A minus (C4AF) 120572C4AF)C + (1

minus 120574S119891SFA120572FA minus 2689120574A119891AFA120572FA) (FA)

(19)

119867 = (0418 (C3S) 120572C3S + 0450 (C2S) 120572C2S

+ 0667 (C3A) 120572C3A + 0371 (C4AF) 120572C4AF)C

+ (0840120574S119891SFA120572FA + 1237120574A119891AFA120572FA) (FA)

(20)

When result of (17) is positive the pozzolanic reactions offly ash occur fully otherwise there is not enough CH to reactwith the A and S of the fly ash When CH = 0 the maximumcontent of fly ash FAmax can be obtained

FAmax

=(0422 (C3S) + 0129 (C2S) minus 0305 (C4AF))C

(1357120574S119891sFA + 2176120574A119891AFA)

(21)

The volumes of each phase are

119881CH = (0188 (C3S) 120572C3S + 00576 (C2S) 120572C2S

minus 0136 (C4AF) 120572C4AF)C times 10minus3 minus (0606120574S119891sFA

minus 0971120574A119891AFA) 120572FA (FA) times 10minus3

119881CSH = (0475 (C3S) 120572C3S + 0630 (C2S) 120572C2S)C

times 10minus3 + 1702120574S119891SFA120572FA (FA) times 10minus3

119881CASH = 1182 (C3A) 120572C3AC times 10minus3

+ 3131120574A119891AFA120572FA (FA) times 10minus3

119881C(AF)H = 0627 (C4AF) 120572C4AFC times 10minus3

120601 = 119882120588w

minus Δ120601c minus Δ120601p

Δ120601c = (C3S) 119881C3S + (C2S) 119881C2S + (C3A) 119881C3A

+ (C4AF) 119881C4AF = (0347 (C3S) 120572C3S

+ 0384 (C2S) 120572C2S + 0577 (C3A) 120572C3A

+ 0224 (C4AF) 120572C4AF)C times 10minus3

Δ120601p = 120574S119891SFA120572FA (FA) 119881S + 120574A119891AFA120572FA (FA) 119881A

= (0635120574S119891SFA + 1180120574A119891AFA) 120572FA (FA) times 10minus3

120601 = 119882 times 10minus3 minus (0347 (C3S) 120572C3S + 0384 (C2S) 120572C2S

+ 0577 (C3A) 120572C3A + 0224 (C4AF) 120572C4AF)C

times 10minus3 minus (0635120574S119891SFA + 1180120574A119891AFA) 120572FA (FA)

times 10minus3(22)

(2) When the amount of gypsum in the cement issufficient to hydrate the cement but is not enough to reactwith all the fly ash activated alumina

CSH2 lt 0637(C3A) + 1689(A) = (1689119891Ac minus1078119891Fc)C + 1689120574A119891AFAFA or 119891sc lt (0785119891AC minus0501119891FC) + 0785120574A119891AFA(FAC)

The cement reaction occurs as follows

2C3S + 106H 997888rarr C34S2H8 + 26CH (23)

2C2S + 86H 997888rarr C34S2H8 + 06CH (24)

C3A + CSH2 + 10H 997888rarr C4ASH12 (25)

C4AF + 2CH + 10H 997888rarr 2C3 (A F)H6 (26)

The fly ash reaction occurs as follows

S + 11H + 28H 997888rarr C11SH39 (27)

A + CSH2 + 3CH + 7H 997888rarr C4ASH12 (28)

A + 4CH + 9H 997888rarr C4AH3 (29)

The quantities of each phase are

CH = (0422 (C3S) 120572C3S + 0129 (C2S) 120572C2S

minus 0305 (C4AF) 120572C4AF minus 0274 (C3A) 120572C3A

+ 0925119891SC)C minus (1357120574S119891sFA + 2907120574A119891AFA)

sdot 120572FA (FA)

CSH = (0996 (C3S) 120572C3S + 1321 (C2S) 120572C2S)C

+ 3189120574S119891SFA120572FA (FA)

CASH = 7774119891SCC

C (AF)H = 1675 (C4AF) 120572C4AFC

CAH = (2074 (C3A) 120572C3A minus 6999119891SC)C

+ 5497120574A119891AFA120572FA (FA)

Advances in Materials Science and Engineering 5

119877 = (1 minus (C3S) 120572C3S minus (C2S) 120572C2S minus (C3A) 120572C3A

minus (C4AF) 120572C4AF minus 215119891SC)C + (1 minus 120574S119891SFA120572FA

minus 120574A119891AFA120572FA) (FA)

119867 = (0418 (C3S) 120572C3S + 0450 (C2S) 120572C2S

+ 0800 (C3A) 120572C3A + 0371 (C4AF) 120572C4AF

minus 045119891S119862)C + (0840120574S119891SFA120572FA

+ 1591120574A119891AFA120572FA) (FA) (30)

The volumes of each phase are

119881CH = (0188 (C3S) 120572C3S + 0058 (C2S) 120572C2S

minus 0136 (C4AF) 120572C4AF minus 0122 (C3A) 120572C3A

+ 0413119891SC)C times 10minus3 minus (0606120574S119891sFA

+ 1298120574A119891AFA) 120572FA (FA) times 10minus3

(31)

119881CSH = (0474 (C3S) 120572C3S + 0629 (C2S) 120572C2S)C

times 10minus3 + 1696120574S119891SFA120572FA (FA) times 10minus3(32)

119881CASH = 3987119891SCC times 10minus3 (33)

119881C(AF)H = 0627 (C4AF) 120572C4AFC times 10minus3 (34)

119881CAH = (1001 (C3A) 120572C3A minus 3398119891SC)C times 10minus3

+ 2668120574A119891AFA120572FA (FA) times 10minus3(35)

120601 = 119882120588w

minus Δ120601c minus Δ120601p (36)

Δ120601c = (C3S) 119881C3S + (C2S) 119881C2S + (C3A) 119881C3A

+ (C4AF) 119881C4AF = (0347 (C3S) 120572C3S

+ 0384 (C2S) 120572C2S + 0577 (C3A) 120572C3A

+ 0224 (C4AF) 120572C4AF)C times 10minus3

(37)

Δ120601p = 0635120574S119891SFA120572FA (FA) times 10minus3 + (0075119891SC

minus 0022 (C3A) 120572C3A)C times 10minus3

+ 1121120574A119891AFA120572FA (FA) times 10minus3

(38)

120601 = 119882 times 10minus3 minus (0635120574S119891SFA + 1180120574A119891AFA)

sdot 120572FA (FA) times 10minus3 minus (0347 (C3S) 120572C3S

+ 0384 (C2S) 120572C2S + 0555 (C3A) 120572C3A

+ 0224 (C4AF) 120572C4AF + 0075119891SC)C times 10minus3

(39)

4 Results and Discussion

41 Experimental Results of Fly Ash-Cement Mixtures

411 Degree of Fly Ash Reaction As can be seen in Figure 1the degree of the fly ash reaction increased with increasingcuring age for various water binder ratios and amounts of flyash In the early stage (1sim7 d) the fly ash (3 to 25 massfraction) had a greater level of participation in the pozzolanicreaction Testing the specific surface area and particle sizedistribution of the fly ash revealed that the fly ash particleswere small and their surface area was up to 665m2kg Theouter surface of a large number of fine particles of hydrated flyash was exposed to CH in the early stage and the pozzolanicreactivity of fly ash occurred rapidly One investigation [31]examined cement-fly ash paste by SEM and found that thesurface of many fine fly ash particles appeared to be etched atthe age of 7 d and that hydration products were formed on thesurface of the fly ash particles The present study has shownthat a pozzolanic reaction with some of the fly ash began atthis stage When examined at a later age the degree of thepozzolanic reactions with fly ash had also increased but theincreases gradually slowed

The effect of fly ash incorporation on the degree ofthe fly ash reaction at the same water binder ratio (05)is shown in Figure 2 The degree of the fly ash reactiondecreased with increasing amounts of fly ash When the flyash content increased from 10 to 30 40 and 50 (massfraction) the degree of the fly ash reaction at 28 d decreasedfrom 371 to 290 254 and 206 respectively As theincorporation of fly ash increased the proportion of cementdecreased and thus the consumption of CH increased andits production decreased in the fly ash-cement mixtures Theamount of CH in the pore solution decreased and the degreeof the fly ash reaction declined A 10 content of fly ashshowed the highest reaction degree with 4515 at 180 dayswhereas the reaction degree of the 50 content was only3311 indicating that nearly 67 of the fly ash did not reactTherefore the filling effect and the microaggregate effect arethe major effects when the fly ash amount increases and thepozzolanic reaction is relatively weak

The effect of the WB ratio on the degree of the fly ashreaction at the same fly ash incorporation (50) is shownin Figure 3 When the WB ratio rises from 03 to 05 thedegree of the fly ash reaction exhibited a linearly increasingtrend with increased water binder ratioThe average reactiondegree of fly ash increased by approximately 110 with each005 increase in the water binder ratio

412 Degree of Cement Reaction The nonevaporable watercontent of the pure cement pastes changed with curing ageas shown in Figure 4 Curing age had a greater impact on thenonevaporated water content especially in the early stages(before 28 d) From preparation to the curing time of 7 dthe nonevaporable water content increased rapidly After7 d of hydration the nonevaporable water content increasedslowly After 28 d the nonevaporable water content remainedconstant for the cement paste samples with WB ratios of 03

6 Advances in Materials Science and Engineering

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

5

10

15

20

25

30

35D

egre

e of fl

y as

h re

actio

n (

)

WB = 03

WB = 035

WB = 04

WB = 045

WB = 05

FA50

(a) Different WB ratios

00

20 40 60 80 100 120 140 160 180 200Curing time (d)

5

10

15

20

25

30

35

40

45

50

Deg

ree o

f fly

ash

reac

tion

()

WB = 05

FA50FA40FA30FA10

(b) Different amounts of incorporated fly ash

Figure 1 Effect of curing time on the degree of the fly ash reaction

Deg

ree o

f fly

ash

reac

tion

()

10

10

20

20

30

30

40

40

50

50

600

WB = 05

Fly ash incorporation ()

1 d3 d7 d28 d90 d180 d

Figure 2 Effect of fly ash incorporation on the degree of the fly ashreaction

and 04 while the nonevaporable water content of the pastewith the WB ratio of 05 continued to increase

Based on the experimental results for the nonevaporablewater content in the pure cement pastes the reaction degreeof cement (120572C) can be calculated using (2) In this studythe degree of the cement paste reaction at different WB

5

10

15

20

25

30

35

Deg

ree o

f fly

ash

reac

tion

()

WB

1 d3 d7 d

28 d60 d90 d180 d

030 035 040 045 050 055 0600

14 d

FA50

Figure 3 Effect of WB ratio on fly ash reaction degree

ratios and different curing ages is shown in Figure 5 Thereis no suitable experimental method to measure the degree ofthe cement reaction for fly ash-cement pastes at the presenttime mainly because the fly ash-cement paste containsnot only C2S2H Ca(OH)2 C3AH6 and AFt from cement

Advances in Materials Science and Engineering 7

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

WB = 03

WB = 04

WB = 05

Non

evap

orab

le w

ater

cont

ent (

)

11

12

13

14

15

16

17

18

19

20

Pure cement pastes

Figure 4 Nonevaporable water content of pure cement pastes

hydration but also includes C2S2H C3AH6 and AFt from thepozzolanic reactions of fly ash and Ca(OH)2 There are nosignificant differences in the composition and structure of theC2S2H C3AH6 and AFt that are formed in the fly ash reac-tions from those formed in cement hydration It is difficultto experimentally separate them Therefore the traditionalmethods of determining the hydration degree of pure cementpaste have failed by measuring the nonevaporable water andCa(OH)2 contents of blended pastes However quantifyingthe degree of the cement reaction is the prerequisite forunderstanding the hydration processes of fly ash-cementpastes As shown in Figure 2 the degree of cement hydrationof pure cement paste depends on the water-cement ratio Anequation describing the relationship between the hydrationdegree and water-cement ratio is expressed as follows [5]

120572c = 1199101 (119905) 119890minus(1199102(119905)(WC)) (40)

where 1199101(119905) and 1199102(119905) are the age-related functions and WCis the water-cement ratio

To calculate the degree of cement hydration of the fly ash-cement system the watercement (WC) ratio is replaced bythe effective water binder ratio in (40) In addition the fly ashpozzolanic reactions will occur and generate a new productso the effectivewater binder ratio is replaced byW(C+120572fFA)

120572c = 1199101 (119905) 119890minus(1199102(119905)(W(C+120572f FA))) (41)

The degree of cement hydration of the fly ash-cementsystem can be calculated under various conditions accordingto (41) as shown in Figure 6 It was found by comparing thecuring times in Figure 6 that the degree of cement hydrationwas higher than that of pure cement paste under the sameconditions when fly ash was mixed into the cement pasteWhen the fly ash content increased the hydration degree ofcement increasedThis ismainly because the incorporation of

Deg

ree o

f pur

e cem

ent r

eact

ion

()

WB

1 d3 d7 d

28 d60 d90 d180 d14 d

20

30

40

50

60

70

80

10

03 04 050

Figure 5 Nonevaporable water content of pure cement pastes

fly ash increased the effective water-cement ratio of cementimproving the hydration environment and thus increasingthe hydration degreeThe fly ash contributes to consumptionof the hydration product of cement (Ca(OH)2) and thereforeit is beneficial for the hydration reaction of cement

413 Content of Nonevaporable Water Themeasured resultsof nonevaporable water in fly ash-cement blended pastesunder various conditions are shown in Figure 7 It can beseen in Figure 7 that the nonevaporated water content of flyash-cement pastes with 10 30 and 40 fly ash are higherthan the pure cement paste in addition to the 50 contentAfter 7 d the differences were not significant This may bebecause the nucleation and crystallization of Ca(OH)2 wereinduced by the fine particles of the fly ash thus contributingto cement hydrationWithin a certain range of incorporationthe promotion effects of fly ash exceeded the negative effectsdue to the slow development of the activity of fly ash and asmall number of hydrates The nonevaporable water contentof fly ash-cement pastes will be higher than that of purecement pastes From the nonevaporable water trend theblended pastes of fly ash incorporation of 10sim30 showed thehighest nonevaporable water Zhang et al [32] also found thatfly ash can improve the early hydration rate of cement

Powers [29] proposed that nonevaporable water in purecement paste is one index for the degree of cement hydrationNonevaporable water of the hardened pastes comes mainlyfrom the hydration products Ca(OH)2 and C-S-H gel In thefly ash-cement blended pastes both cement hydration andthe fly ash reaction produce C-S-H and the fly ash can alsoconsume Ca(OH)2 that is produced by the hydration of thecement Therefore it is not appropriate to directly use thenonevaporable water to measure the degree of reaction of theblended pastes

8 Advances in Materials Science and Engineering

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

WB = 03

WB = 035

WB = 04

WB = 045

WB = 05

Deg

ree o

f cem

ent r

eact

ion

()

55

60

65

70

75

80

85

90

FA50

(a) Different WB ratios

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

Deg

ree o

f cem

ent r

eact

ion

()

55

60

65

70

75

80

85

90

WB = 05

FA50FA40FA30FA10

(b) Different fly ash incorporation

Figure 6 The fly ash reaction degree of fly ash-cement system

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

6

8

Non

evap

orab

le w

ater

cont

ent (

)

10

12

14

16

18

WB = 03

WB = 04

WB = 05

FA50

(a) Different WB ratios

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

Non

evap

orab

le w

ater

cont

ent (

)

10

12

14

16

18

20

WB = 05

FA50FA40FA30FA10FA0

(b) Different fly ash incorporation rates

Figure 7 Nonevaporable water contents of the fly ash-cement blended pastes

42 Verifying the Model of Fly Ash-Cement Blended Pastes

421The Equations for the Increased Hydration Degree Valuesof Cement According to the experimental results of the totalamount of nonevaporable water the degree of the fly ashreaction and the degree of increasing cement hydration werecalculated in the fly ash-cement composite systems under

various conditions by (7) and (8) as shown in Figures 8 and9

Figure 8 shows the variation of the degree of hydrationof cement in the blended system with the fly ash addition of50 as the WB ratio changed from 03 to 05 The reactiondegree at every curing age increased linearly with increases oftheWB ratio Figure 9 shows the degree of cement hydration

Advances in Materials Science and Engineering 9

WB

1 d3 d7 d

28 d60 d90 d180 d14 d

055030 035 040 045 050

00

01

02

03

04

05

06

07 FA 50

120572cminus

f

Figure 8 Influence of the WB ratio on the increased degree ofcement hydration

1 d3 d7 d

28 d60 d90 d180 d14 d

00

01

01

02

02

03

03

04

04

05

05

06

06

07

08WB 05

mf

120572cminus

f

Figure 9 Influence of the fly ash content on the increased degree ofcement hydration

with the trend of its fly ash content when the WB ratio was05 It can be observed that the added degree of hydration ofthe cement increased with increases of the fly ash contentWhen the fly ash content was less than 03 the curing agehad little influence on the increased degree of hydration ofthe cementWhen the fly ash content was greater than 03 thedegree of hydration of the cement was significantly improvedwith increasing curing age For example as the curing ageof the fly ash-cement system increased from 1 d to 180 d thevalue of the degree of hydration of the cement increased from007 to 011 when its fly ash content was 01 The increased

value of the degree of hydration of cement improved from034 to 072 when the fly ash content was 05 Clearly theWB ratio fly ash content and curing age can each promotethe degree of hydration of the cement On the one handthis is mainly due to the incorporated fly ash increasing theeffective WB ratio of the cement and improving the cementhydration environment On the other hand this is due to thepostsecondary reactions of fly ash that promptly consume theCa(OH)2 that is generated by the hydration of the cementwhich is advantageous for the hydration reactions of cement

One objective of this study was to predict the increaseddegree of hydration of cement and degree of reaction of flyash in the fly ash-cement blended system with different flyash contents WB ratios and curing periods Based on theresults of Figures 8 and 9 it is concluded that the increasedvalues of the degree of hydration of cement containing addedfly ash and the quantitative relationships among the reactiondegree of fly ash the WB ratio and the fly ash content canbe expressed as follows as determined by multiple regressionanalysis

120572cminusf = 1 minus 119890minus119886(119905minus119887)119888

(42)

119886 = minus305481 + 286722 sdot 119890[034293sdot(WB)] (43a)

119887 = 0 (43b)

119888 = minus1167238 + 113153 sdot 119890[011795sdot(119898f )] (43c)

120572f = 1 minus 119890minus119889(119905minus119891)119892

(44)

119889 = 003869 + 000426 sdot 119890[555391sdot(WB)] (45a)

119891 = 09 (45b)

119892 = minus001487 + 0413 sdot 119890[minus07646sdot(119898f )] (45c)

422 Validation of the Model Figure 10 shows the compar-ison of the experimental results and the predicted valuesfor 120572cminusf The fitted 1198772 coefficient of the regression analysisequation (119910 = 099366119909) is 098849 Figure 11 shows the120572119891 of the experimental and predicted values and the fitted1198772 coefficient of the regression analysis equation (119910 =099552119909) is 099131 The maximum relative errors of Figures10 and 11 are 3096 and 4831 respectively The modelwas consistent with the experimental values Therefore it isreasonable to propose a model for the degree of the fly ashreaction and a model of accelerated hydration of cement forblended systems

The CH content and porosity as key parameters ofthe microstructure were selected to verify the hydrationproducts of fly ash-cement mixtures The results of theexperimental values were obtained from the literature [5] Inthis experiment the CH content of hydrated cement pasteswas determined by thermal gravimetry analysis based onthe ignited weight of the sample The porosity of cement-flyash pastes was obtained by mercury intrusion porosimetryThe CH and porosity values are presented in Section 32Figure 12 presents the comparison between the predicted

10 Advances in Materials Science and Engineering

WB = 03

WB = 04

WB = 05

000000

001

001

002

002

003

003

004

004

Measured value

Pred

icte

d va

lue

Figure 10 The predicted and measured values of the degree ofcement hydration of enhanced cement-fly ash pastes

WB = 03

WB = 035

WB = 04

WB = 045

WB = 05

0000

02

02

04

04

06

06

08

08

10

10

Measured value

Pred

icte

d va

lue

Figure 11 The predicted and measured values of the degree of thefly ash reaction of cement-fly ash pastes

and experimental values of the CH content For differentWB ratios and fly ash content the predicted results camecloser to the experimental values with increasing curingage The maximum relative errors were 135 113 and66 at 7 d 28 d and 90 d respectively Figure 13 showsthe comparison of the predicted and experimental valuesof porosity in fly ash-cement systems For all samples thepredicted values were higher than the measured values Themaximum relative errors were 117 112 and 139 at 7 d28 d and 180 d respectively The main reason is that theporosity of the blended system calculated by the model is

10000

20 40 60 80Age (d)

20

2

4

6

8

10

12

14

16

18

CH (

)

WB = 03 mf = 025 (experiment)WB = 03 mf = 025 (prediction)

(prediction)

(prediction)WB = 03 mf = 055 (experiment)WB = 03 mf = 055

WB = 05 mf = 055 (experiment)WB = 05 mf = 055

Figure 12 The predicted and measured values of CH content ofcement-fly ash pastes

100 150 2000 50Age (d)

20

25

30

35

40

45

50

15

Poro

sity

()

WB = 03 (experiment)WB = 03 (prediction)WB = 04 (experiment)WB = 04 (prediction)WB = 05 (experiment)WB = 05 (prediction)

Figure 13 The predicted and measured values of porosity ofcement-fly ash pastes

the capillary porosity (the porosity contained in the capillarypores and the porosity of the gel) that was obtained bymercury intrusion Therefore with longer curing ages moreC-S-H gel phase was generated by the second hydration of flyash and the differences between the predicted and measuredvalues increased

Advances in Materials Science and Engineering 11

5 Conclusions

(1) The degree of hydration of cement in the pure cementpastes was determined by measuring the nonevap-orablewater contentThedegree of the fly ash reactionin fly ash-cement blended pastes was determinedusing a selective dissolution method

(2) Based on the degree of hydration of cement and theeffectiveWB ratio the degree of hydration of cementin fly ash-cement blended pastes was acquired

(3) A hydration model of fly ash-cement blended pasteshas been established based on the degree of reactionand the hydration products This model incorporatesthe reactions of fly ash and the hydration of cementbut is also influenced by their interactions

Competing Interests

The authors declare that there are no competing interestsregarding the publication of this paper

Acknowledgments

The authors gratefully acknowledge the National Natural Sci-ence Foundation of China (51408597) and the FundamentalResearch Funds for the Central Universities (2014QNA75)

References

[1] K-H Yang Y-B Jung M-S Cho and S-H Tae ldquoEffect ofsupplementary cementitious materials on reduction of CO2emissions from concreterdquo Journal of Cleaner Production vol103 pp 774ndash783 2015

[2] T Sato and J J Beaudoin ldquoEffect of nano-CaCO3 on hydrationof cement containing supplementary cementitious materialsrdquoAdvances in Cement Research vol 23 no 1 pp 33ndash43 2011

[3] Z Liu Y Zhang and Q Jiang ldquoContinuous tracking of therelationship between resistivity and pore structure of cementpastesrdquo Construction and Building Materials vol 53 pp 26ndash312014

[4] R Snellings G Mertens and J Elsen ldquoSupplementary cemen-titious materialsrdquo Reviews in Mineralogy and Geochemistry vol74 pp 211ndash278 2012

[5] L Lam Y L Wong and C S Poon ldquoDegree of hydration andgelspace ratio of high-volume fly ashcement systemsrdquo Cementand Concrete Research vol 30 no 5 pp 747ndash756 2000

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

[7] P Hou S Kawashima D Kong D J Corr J Qian and S PShah ldquoModification effects of colloidal nanoSiO2 on cementhydration and its gel propertyrdquo Composites Part B Engineeringvol 45 no 1 pp 440ndash448 2013

[8] J David Raja Selvam D S Robinson Smart and I DinaharanldquoMicrostructure and some mechanical properties of fly ashparticulate reinforced AA6061 aluminum alloy compositesprepared by compocastingrdquoMaterials amp Design vol 49 pp 28ndash34 2013

[9] R Feldman L R Prudencio Jr and G Chan ldquoRapid chloridepermeability test on blended cement and other concretescorrelations between charge initial current and conductivityrdquoConstruction and Building Materials vol 13 no 3 pp 149ndash1541999

[10] SWM Supit and FU A Shaikh ldquoDurability properties of highvolume fly ash concrete containing nano-silicardquo Materials andStructuresMateriaux et Constructions vol 48 no 8 pp 2431ndash2445 2014

[11] N Neithalath and J Jain ldquoRelating rapid chloride transportparameters of concretes to microstructural features extractedfrom electrical impedancerdquo Cement and Concrete Research vol40 no 7 pp 1041ndash1051 2010

[12] G Land and D Stephan ldquoThe influence of nano-silica on thehydration of ordinary Portland cementrdquo Journal of MaterialsScience vol 47 no 2 pp 1011ndash1017 2012

[13] J Justs M Wyrzykowski F Winnefeld D Bajare and P LuraldquoInfluence of superabsorbent polymers on hydration of cementpastes with low water-to-binder ratiordquo Journal of ThermalAnalysis and Calorimetry vol 115 no 1 pp 425ndash432 2014

[14] Z Liu Y Zhang Q Jiang W Zhang and J Wu ldquoSolid phasespercolation and capillary pores depercolation in hydratingcement pastesrdquo Journal of Materials in Civil Engineering vol 26no 12 Article ID 04014090 2014

[15] B Uzal and L Turanlı ldquoBlended cements containing highvolume of natural zeolites properties hydration and pastemicrostructurerdquo Cement and Concrete Composites vol 34 no1 pp 101ndash109 2012

[16] Y Kocak and S Nas ldquoThe effect of using fly ash on the strengthand hydration characteristics of blended cementsrdquoConstructionand Building Materials vol 73 pp 25ndash32 2014

[17] D D Nguyen L P Devlin P Koshy and C C Sorrell ldquoEffectsof acetic acid on early hydration of Portland cementrdquo Journal ofThermal Analysis and Calorimetry vol 123 no 1 pp 489ndash4992016

[18] D P Bentz R J Detwiler E J Garboczi P Halamickova andM Schwartz ldquoMulti-scale modeling of the diffusivity of mortarand concreterdquo in Proceedings of the Chloride Penetration intoConcrete LONilsson and J POllivier Eds pp 85ndash94 RILEM1997

[19] M W Grutzeck D Shi G Liu and S Kwan ldquoComputer sim-ulation of interfacial packing in concreterdquo Journal of MaterialsScience vol 28 no 13 pp 3444ndash3450 1993

[20] D P Bentz ldquoInfluence of silica fume on diffusivity in cement-based materials II Multi-scale modeling of concrete diffusiv-ityrdquo Cement and Concrete Research vol 30 no 7 pp 1121ndash11292000

[21] M Voltolini M C Dalconi G Artioli et al ldquoUnderstandingcement hydration at the microscale new opportunities fromlsquopencil-beamrsquo synchrotron X-ray diffraction tomographyrdquo Jour-nal of Applied Crystallography vol 46 no 1 pp 142ndash152 2013

[22] Z Liu W Chen Y Zhang and H Lv ldquoA three-dimensionalmulti-scale method to simulate the ion transport behavior ofcement-based materialsrdquo Construction amp Building Materialsvol 120 pp 494ndash503 2016

[23] B A Suprenant and G Papadopoulos ldquoSelective dissolutionof portland-fly-ash cementsrdquo Journal of Materials in CivilEngineering vol 3 no 1 pp 48ndash59 1991

[24] D P Bentz E J Garboczi and K A Snyder ldquoA hard coresoftshell microstructural model for studying percolation and trans-port in three-dimensional compositemediardquo NISTIR 6265 USDepartment of Commerce 1999

12 Advances in Materials Science and Engineering

[25] X-Y Wang H-S Lee and K-B Park ldquoSimulation of low-calcium fly ash blended cement hydrationrdquo ACI MaterialsJournal vol 106 no 2 pp 167ndash175 2009

[26] Q Zeng K Li T Fen-Chong and P Dangla ldquoDeterminationof cement hydration and pozzolanic reaction extents for fly-ashcement pastesrdquo Construction and Building Materials vol 27 no1 pp 560ndash569 2012

[27] AMNeville Properties of Concrete AddisonWesley LongmanEssex UK 4th edition 1996

[28] C C Yang ldquoThe relationship between charge passed and thechloride concentrations in anode and cathode cells using theaccelerated chloride migration testrdquo Materials and Structuresvol 36 no 264 pp 678ndash684 2003

[29] T C Powers ldquoStructure and physical properties of hardenedportland cement pasterdquo Journal of the American Ceramic Soci-ety vol 41 no 1 pp 1ndash6 1958

[30] V G Papadakis ldquoEffect of fly ash on Portland cement systemspart I Low-calcium fly ashrdquoCement and Concrete Research vol29 no 11 pp 1727ndash1736 1999

[31] A Xu and S L Sarkar ldquoMicrostructural development in high-volume fly-ash cement systemrdquo Journal of Materials in CivilEngineering vol 6 no 1 pp 117ndash136 1994

[32] YM ZhangW Sun andHD Yan ldquoHydration of high-volumefly ash cement pastesrdquoCement and Concrete Composites vol 22no 6 pp 445ndash452 2000

Submit your manuscripts athttpswwwhindawicom

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CompositesJournal of

NanoparticlesJournal of

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Biomaterials

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NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

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CrystallographyJournal of

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The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

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Advances in

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BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

4 Advances in Materials Science and Engineering

CSH = C34S2H8 + C11SH39 = (0996 (C3S) 120572C3S

+ 1321 (C2S) 120572C2S)C + 3189120574S119891SFA120572FA (FA)(16)

CASH = 2304 (C3A) 120572C3AC + 6106120574A119891AFA120572FA (FA) (17)

C (AF)H = 1675 (C4AF) 120572C4AFC (18)

119877 = (1 minus (C3S) 120572C3S minus (C2S) 120572C2S

minus 1637 (C3A) 120572C3A minus (C4AF) 120572C4AF)C + (1

minus 120574S119891SFA120572FA minus 2689120574A119891AFA120572FA) (FA)

(19)

119867 = (0418 (C3S) 120572C3S + 0450 (C2S) 120572C2S

+ 0667 (C3A) 120572C3A + 0371 (C4AF) 120572C4AF)C

+ (0840120574S119891SFA120572FA + 1237120574A119891AFA120572FA) (FA)

(20)

When result of (17) is positive the pozzolanic reactions offly ash occur fully otherwise there is not enough CH to reactwith the A and S of the fly ash When CH = 0 the maximumcontent of fly ash FAmax can be obtained

FAmax

=(0422 (C3S) + 0129 (C2S) minus 0305 (C4AF))C

(1357120574S119891sFA + 2176120574A119891AFA)

(21)

The volumes of each phase are

119881CH = (0188 (C3S) 120572C3S + 00576 (C2S) 120572C2S

minus 0136 (C4AF) 120572C4AF)C times 10minus3 minus (0606120574S119891sFA

minus 0971120574A119891AFA) 120572FA (FA) times 10minus3

119881CSH = (0475 (C3S) 120572C3S + 0630 (C2S) 120572C2S)C

times 10minus3 + 1702120574S119891SFA120572FA (FA) times 10minus3

119881CASH = 1182 (C3A) 120572C3AC times 10minus3

+ 3131120574A119891AFA120572FA (FA) times 10minus3

119881C(AF)H = 0627 (C4AF) 120572C4AFC times 10minus3

120601 = 119882120588w

minus Δ120601c minus Δ120601p

Δ120601c = (C3S) 119881C3S + (C2S) 119881C2S + (C3A) 119881C3A

+ (C4AF) 119881C4AF = (0347 (C3S) 120572C3S

+ 0384 (C2S) 120572C2S + 0577 (C3A) 120572C3A

+ 0224 (C4AF) 120572C4AF)C times 10minus3

Δ120601p = 120574S119891SFA120572FA (FA) 119881S + 120574A119891AFA120572FA (FA) 119881A

= (0635120574S119891SFA + 1180120574A119891AFA) 120572FA (FA) times 10minus3

120601 = 119882 times 10minus3 minus (0347 (C3S) 120572C3S + 0384 (C2S) 120572C2S

+ 0577 (C3A) 120572C3A + 0224 (C4AF) 120572C4AF)C

times 10minus3 minus (0635120574S119891SFA + 1180120574A119891AFA) 120572FA (FA)

times 10minus3(22)

(2) When the amount of gypsum in the cement issufficient to hydrate the cement but is not enough to reactwith all the fly ash activated alumina

CSH2 lt 0637(C3A) + 1689(A) = (1689119891Ac minus1078119891Fc)C + 1689120574A119891AFAFA or 119891sc lt (0785119891AC minus0501119891FC) + 0785120574A119891AFA(FAC)

The cement reaction occurs as follows

2C3S + 106H 997888rarr C34S2H8 + 26CH (23)

2C2S + 86H 997888rarr C34S2H8 + 06CH (24)

C3A + CSH2 + 10H 997888rarr C4ASH12 (25)

C4AF + 2CH + 10H 997888rarr 2C3 (A F)H6 (26)

The fly ash reaction occurs as follows

S + 11H + 28H 997888rarr C11SH39 (27)

A + CSH2 + 3CH + 7H 997888rarr C4ASH12 (28)

A + 4CH + 9H 997888rarr C4AH3 (29)

The quantities of each phase are

CH = (0422 (C3S) 120572C3S + 0129 (C2S) 120572C2S

minus 0305 (C4AF) 120572C4AF minus 0274 (C3A) 120572C3A

+ 0925119891SC)C minus (1357120574S119891sFA + 2907120574A119891AFA)

sdot 120572FA (FA)

CSH = (0996 (C3S) 120572C3S + 1321 (C2S) 120572C2S)C

+ 3189120574S119891SFA120572FA (FA)

CASH = 7774119891SCC

C (AF)H = 1675 (C4AF) 120572C4AFC

CAH = (2074 (C3A) 120572C3A minus 6999119891SC)C

+ 5497120574A119891AFA120572FA (FA)

Advances in Materials Science and Engineering 5

119877 = (1 minus (C3S) 120572C3S minus (C2S) 120572C2S minus (C3A) 120572C3A

minus (C4AF) 120572C4AF minus 215119891SC)C + (1 minus 120574S119891SFA120572FA

minus 120574A119891AFA120572FA) (FA)

119867 = (0418 (C3S) 120572C3S + 0450 (C2S) 120572C2S

+ 0800 (C3A) 120572C3A + 0371 (C4AF) 120572C4AF

minus 045119891S119862)C + (0840120574S119891SFA120572FA

+ 1591120574A119891AFA120572FA) (FA) (30)

The volumes of each phase are

119881CH = (0188 (C3S) 120572C3S + 0058 (C2S) 120572C2S

minus 0136 (C4AF) 120572C4AF minus 0122 (C3A) 120572C3A

+ 0413119891SC)C times 10minus3 minus (0606120574S119891sFA

+ 1298120574A119891AFA) 120572FA (FA) times 10minus3

(31)

119881CSH = (0474 (C3S) 120572C3S + 0629 (C2S) 120572C2S)C

times 10minus3 + 1696120574S119891SFA120572FA (FA) times 10minus3(32)

119881CASH = 3987119891SCC times 10minus3 (33)

119881C(AF)H = 0627 (C4AF) 120572C4AFC times 10minus3 (34)

119881CAH = (1001 (C3A) 120572C3A minus 3398119891SC)C times 10minus3

+ 2668120574A119891AFA120572FA (FA) times 10minus3(35)

120601 = 119882120588w

minus Δ120601c minus Δ120601p (36)

Δ120601c = (C3S) 119881C3S + (C2S) 119881C2S + (C3A) 119881C3A

+ (C4AF) 119881C4AF = (0347 (C3S) 120572C3S

+ 0384 (C2S) 120572C2S + 0577 (C3A) 120572C3A

+ 0224 (C4AF) 120572C4AF)C times 10minus3

(37)

Δ120601p = 0635120574S119891SFA120572FA (FA) times 10minus3 + (0075119891SC

minus 0022 (C3A) 120572C3A)C times 10minus3

+ 1121120574A119891AFA120572FA (FA) times 10minus3

(38)

120601 = 119882 times 10minus3 minus (0635120574S119891SFA + 1180120574A119891AFA)

sdot 120572FA (FA) times 10minus3 minus (0347 (C3S) 120572C3S

+ 0384 (C2S) 120572C2S + 0555 (C3A) 120572C3A

+ 0224 (C4AF) 120572C4AF + 0075119891SC)C times 10minus3

(39)

4 Results and Discussion

41 Experimental Results of Fly Ash-Cement Mixtures

411 Degree of Fly Ash Reaction As can be seen in Figure 1the degree of the fly ash reaction increased with increasingcuring age for various water binder ratios and amounts of flyash In the early stage (1sim7 d) the fly ash (3 to 25 massfraction) had a greater level of participation in the pozzolanicreaction Testing the specific surface area and particle sizedistribution of the fly ash revealed that the fly ash particleswere small and their surface area was up to 665m2kg Theouter surface of a large number of fine particles of hydrated flyash was exposed to CH in the early stage and the pozzolanicreactivity of fly ash occurred rapidly One investigation [31]examined cement-fly ash paste by SEM and found that thesurface of many fine fly ash particles appeared to be etched atthe age of 7 d and that hydration products were formed on thesurface of the fly ash particles The present study has shownthat a pozzolanic reaction with some of the fly ash began atthis stage When examined at a later age the degree of thepozzolanic reactions with fly ash had also increased but theincreases gradually slowed

The effect of fly ash incorporation on the degree ofthe fly ash reaction at the same water binder ratio (05)is shown in Figure 2 The degree of the fly ash reactiondecreased with increasing amounts of fly ash When the flyash content increased from 10 to 30 40 and 50 (massfraction) the degree of the fly ash reaction at 28 d decreasedfrom 371 to 290 254 and 206 respectively As theincorporation of fly ash increased the proportion of cementdecreased and thus the consumption of CH increased andits production decreased in the fly ash-cement mixtures Theamount of CH in the pore solution decreased and the degreeof the fly ash reaction declined A 10 content of fly ashshowed the highest reaction degree with 4515 at 180 dayswhereas the reaction degree of the 50 content was only3311 indicating that nearly 67 of the fly ash did not reactTherefore the filling effect and the microaggregate effect arethe major effects when the fly ash amount increases and thepozzolanic reaction is relatively weak

The effect of the WB ratio on the degree of the fly ashreaction at the same fly ash incorporation (50) is shownin Figure 3 When the WB ratio rises from 03 to 05 thedegree of the fly ash reaction exhibited a linearly increasingtrend with increased water binder ratioThe average reactiondegree of fly ash increased by approximately 110 with each005 increase in the water binder ratio

412 Degree of Cement Reaction The nonevaporable watercontent of the pure cement pastes changed with curing ageas shown in Figure 4 Curing age had a greater impact on thenonevaporated water content especially in the early stages(before 28 d) From preparation to the curing time of 7 dthe nonevaporable water content increased rapidly After7 d of hydration the nonevaporable water content increasedslowly After 28 d the nonevaporable water content remainedconstant for the cement paste samples with WB ratios of 03

6 Advances in Materials Science and Engineering

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

5

10

15

20

25

30

35D

egre

e of fl

y as

h re

actio

n (

)

WB = 03

WB = 035

WB = 04

WB = 045

WB = 05

FA50

(a) Different WB ratios

00

20 40 60 80 100 120 140 160 180 200Curing time (d)

5

10

15

20

25

30

35

40

45

50

Deg

ree o

f fly

ash

reac

tion

()

WB = 05

FA50FA40FA30FA10

(b) Different amounts of incorporated fly ash

Figure 1 Effect of curing time on the degree of the fly ash reaction

Deg

ree o

f fly

ash

reac

tion

()

10

10

20

20

30

30

40

40

50

50

600

WB = 05

Fly ash incorporation ()

1 d3 d7 d28 d90 d180 d

Figure 2 Effect of fly ash incorporation on the degree of the fly ashreaction

and 04 while the nonevaporable water content of the pastewith the WB ratio of 05 continued to increase

Based on the experimental results for the nonevaporablewater content in the pure cement pastes the reaction degreeof cement (120572C) can be calculated using (2) In this studythe degree of the cement paste reaction at different WB

5

10

15

20

25

30

35

Deg

ree o

f fly

ash

reac

tion

()

WB

1 d3 d7 d

28 d60 d90 d180 d

030 035 040 045 050 055 0600

14 d

FA50

Figure 3 Effect of WB ratio on fly ash reaction degree

ratios and different curing ages is shown in Figure 5 Thereis no suitable experimental method to measure the degree ofthe cement reaction for fly ash-cement pastes at the presenttime mainly because the fly ash-cement paste containsnot only C2S2H Ca(OH)2 C3AH6 and AFt from cement

Advances in Materials Science and Engineering 7

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

WB = 03

WB = 04

WB = 05

Non

evap

orab

le w

ater

cont

ent (

)

11

12

13

14

15

16

17

18

19

20

Pure cement pastes

Figure 4 Nonevaporable water content of pure cement pastes

hydration but also includes C2S2H C3AH6 and AFt from thepozzolanic reactions of fly ash and Ca(OH)2 There are nosignificant differences in the composition and structure of theC2S2H C3AH6 and AFt that are formed in the fly ash reac-tions from those formed in cement hydration It is difficultto experimentally separate them Therefore the traditionalmethods of determining the hydration degree of pure cementpaste have failed by measuring the nonevaporable water andCa(OH)2 contents of blended pastes However quantifyingthe degree of the cement reaction is the prerequisite forunderstanding the hydration processes of fly ash-cementpastes As shown in Figure 2 the degree of cement hydrationof pure cement paste depends on the water-cement ratio Anequation describing the relationship between the hydrationdegree and water-cement ratio is expressed as follows [5]

120572c = 1199101 (119905) 119890minus(1199102(119905)(WC)) (40)

where 1199101(119905) and 1199102(119905) are the age-related functions and WCis the water-cement ratio

To calculate the degree of cement hydration of the fly ash-cement system the watercement (WC) ratio is replaced bythe effective water binder ratio in (40) In addition the fly ashpozzolanic reactions will occur and generate a new productso the effectivewater binder ratio is replaced byW(C+120572fFA)

120572c = 1199101 (119905) 119890minus(1199102(119905)(W(C+120572f FA))) (41)

The degree of cement hydration of the fly ash-cementsystem can be calculated under various conditions accordingto (41) as shown in Figure 6 It was found by comparing thecuring times in Figure 6 that the degree of cement hydrationwas higher than that of pure cement paste under the sameconditions when fly ash was mixed into the cement pasteWhen the fly ash content increased the hydration degree ofcement increasedThis ismainly because the incorporation of

Deg

ree o

f pur

e cem

ent r

eact

ion

()

WB

1 d3 d7 d

28 d60 d90 d180 d14 d

20

30

40

50

60

70

80

10

03 04 050

Figure 5 Nonevaporable water content of pure cement pastes

fly ash increased the effective water-cement ratio of cementimproving the hydration environment and thus increasingthe hydration degreeThe fly ash contributes to consumptionof the hydration product of cement (Ca(OH)2) and thereforeit is beneficial for the hydration reaction of cement

413 Content of Nonevaporable Water Themeasured resultsof nonevaporable water in fly ash-cement blended pastesunder various conditions are shown in Figure 7 It can beseen in Figure 7 that the nonevaporated water content of flyash-cement pastes with 10 30 and 40 fly ash are higherthan the pure cement paste in addition to the 50 contentAfter 7 d the differences were not significant This may bebecause the nucleation and crystallization of Ca(OH)2 wereinduced by the fine particles of the fly ash thus contributingto cement hydrationWithin a certain range of incorporationthe promotion effects of fly ash exceeded the negative effectsdue to the slow development of the activity of fly ash and asmall number of hydrates The nonevaporable water contentof fly ash-cement pastes will be higher than that of purecement pastes From the nonevaporable water trend theblended pastes of fly ash incorporation of 10sim30 showed thehighest nonevaporable water Zhang et al [32] also found thatfly ash can improve the early hydration rate of cement

Powers [29] proposed that nonevaporable water in purecement paste is one index for the degree of cement hydrationNonevaporable water of the hardened pastes comes mainlyfrom the hydration products Ca(OH)2 and C-S-H gel In thefly ash-cement blended pastes both cement hydration andthe fly ash reaction produce C-S-H and the fly ash can alsoconsume Ca(OH)2 that is produced by the hydration of thecement Therefore it is not appropriate to directly use thenonevaporable water to measure the degree of reaction of theblended pastes

8 Advances in Materials Science and Engineering

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

WB = 03

WB = 035

WB = 04

WB = 045

WB = 05

Deg

ree o

f cem

ent r

eact

ion

()

55

60

65

70

75

80

85

90

FA50

(a) Different WB ratios

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

Deg

ree o

f cem

ent r

eact

ion

()

55

60

65

70

75

80

85

90

WB = 05

FA50FA40FA30FA10

(b) Different fly ash incorporation

Figure 6 The fly ash reaction degree of fly ash-cement system

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

6

8

Non

evap

orab

le w

ater

cont

ent (

)

10

12

14

16

18

WB = 03

WB = 04

WB = 05

FA50

(a) Different WB ratios

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

Non

evap

orab

le w

ater

cont

ent (

)

10

12

14

16

18

20

WB = 05

FA50FA40FA30FA10FA0

(b) Different fly ash incorporation rates

Figure 7 Nonevaporable water contents of the fly ash-cement blended pastes

42 Verifying the Model of Fly Ash-Cement Blended Pastes

421The Equations for the Increased Hydration Degree Valuesof Cement According to the experimental results of the totalamount of nonevaporable water the degree of the fly ashreaction and the degree of increasing cement hydration werecalculated in the fly ash-cement composite systems under

various conditions by (7) and (8) as shown in Figures 8 and9

Figure 8 shows the variation of the degree of hydrationof cement in the blended system with the fly ash addition of50 as the WB ratio changed from 03 to 05 The reactiondegree at every curing age increased linearly with increases oftheWB ratio Figure 9 shows the degree of cement hydration

Advances in Materials Science and Engineering 9

WB

1 d3 d7 d

28 d60 d90 d180 d14 d

055030 035 040 045 050

00

01

02

03

04

05

06

07 FA 50

120572cminus

f

Figure 8 Influence of the WB ratio on the increased degree ofcement hydration

1 d3 d7 d

28 d60 d90 d180 d14 d

00

01

01

02

02

03

03

04

04

05

05

06

06

07

08WB 05

mf

120572cminus

f

Figure 9 Influence of the fly ash content on the increased degree ofcement hydration

with the trend of its fly ash content when the WB ratio was05 It can be observed that the added degree of hydration ofthe cement increased with increases of the fly ash contentWhen the fly ash content was less than 03 the curing agehad little influence on the increased degree of hydration ofthe cementWhen the fly ash content was greater than 03 thedegree of hydration of the cement was significantly improvedwith increasing curing age For example as the curing ageof the fly ash-cement system increased from 1 d to 180 d thevalue of the degree of hydration of the cement increased from007 to 011 when its fly ash content was 01 The increased

value of the degree of hydration of cement improved from034 to 072 when the fly ash content was 05 Clearly theWB ratio fly ash content and curing age can each promotethe degree of hydration of the cement On the one handthis is mainly due to the incorporated fly ash increasing theeffective WB ratio of the cement and improving the cementhydration environment On the other hand this is due to thepostsecondary reactions of fly ash that promptly consume theCa(OH)2 that is generated by the hydration of the cementwhich is advantageous for the hydration reactions of cement

One objective of this study was to predict the increaseddegree of hydration of cement and degree of reaction of flyash in the fly ash-cement blended system with different flyash contents WB ratios and curing periods Based on theresults of Figures 8 and 9 it is concluded that the increasedvalues of the degree of hydration of cement containing addedfly ash and the quantitative relationships among the reactiondegree of fly ash the WB ratio and the fly ash content canbe expressed as follows as determined by multiple regressionanalysis

120572cminusf = 1 minus 119890minus119886(119905minus119887)119888

(42)

119886 = minus305481 + 286722 sdot 119890[034293sdot(WB)] (43a)

119887 = 0 (43b)

119888 = minus1167238 + 113153 sdot 119890[011795sdot(119898f )] (43c)

120572f = 1 minus 119890minus119889(119905minus119891)119892

(44)

119889 = 003869 + 000426 sdot 119890[555391sdot(WB)] (45a)

119891 = 09 (45b)

119892 = minus001487 + 0413 sdot 119890[minus07646sdot(119898f )] (45c)

422 Validation of the Model Figure 10 shows the compar-ison of the experimental results and the predicted valuesfor 120572cminusf The fitted 1198772 coefficient of the regression analysisequation (119910 = 099366119909) is 098849 Figure 11 shows the120572119891 of the experimental and predicted values and the fitted1198772 coefficient of the regression analysis equation (119910 =099552119909) is 099131 The maximum relative errors of Figures10 and 11 are 3096 and 4831 respectively The modelwas consistent with the experimental values Therefore it isreasonable to propose a model for the degree of the fly ashreaction and a model of accelerated hydration of cement forblended systems

The CH content and porosity as key parameters ofthe microstructure were selected to verify the hydrationproducts of fly ash-cement mixtures The results of theexperimental values were obtained from the literature [5] Inthis experiment the CH content of hydrated cement pasteswas determined by thermal gravimetry analysis based onthe ignited weight of the sample The porosity of cement-flyash pastes was obtained by mercury intrusion porosimetryThe CH and porosity values are presented in Section 32Figure 12 presents the comparison between the predicted

10 Advances in Materials Science and Engineering

WB = 03

WB = 04

WB = 05

000000

001

001

002

002

003

003

004

004

Measured value

Pred

icte

d va

lue

Figure 10 The predicted and measured values of the degree ofcement hydration of enhanced cement-fly ash pastes

WB = 03

WB = 035

WB = 04

WB = 045

WB = 05

0000

02

02

04

04

06

06

08

08

10

10

Measured value

Pred

icte

d va

lue

Figure 11 The predicted and measured values of the degree of thefly ash reaction of cement-fly ash pastes

and experimental values of the CH content For differentWB ratios and fly ash content the predicted results camecloser to the experimental values with increasing curingage The maximum relative errors were 135 113 and66 at 7 d 28 d and 90 d respectively Figure 13 showsthe comparison of the predicted and experimental valuesof porosity in fly ash-cement systems For all samples thepredicted values were higher than the measured values Themaximum relative errors were 117 112 and 139 at 7 d28 d and 180 d respectively The main reason is that theporosity of the blended system calculated by the model is

10000

20 40 60 80Age (d)

20

2

4

6

8

10

12

14

16

18

CH (

)

WB = 03 mf = 025 (experiment)WB = 03 mf = 025 (prediction)

(prediction)

(prediction)WB = 03 mf = 055 (experiment)WB = 03 mf = 055

WB = 05 mf = 055 (experiment)WB = 05 mf = 055

Figure 12 The predicted and measured values of CH content ofcement-fly ash pastes

100 150 2000 50Age (d)

20

25

30

35

40

45

50

15

Poro

sity

()

WB = 03 (experiment)WB = 03 (prediction)WB = 04 (experiment)WB = 04 (prediction)WB = 05 (experiment)WB = 05 (prediction)

Figure 13 The predicted and measured values of porosity ofcement-fly ash pastes

the capillary porosity (the porosity contained in the capillarypores and the porosity of the gel) that was obtained bymercury intrusion Therefore with longer curing ages moreC-S-H gel phase was generated by the second hydration of flyash and the differences between the predicted and measuredvalues increased

Advances in Materials Science and Engineering 11

5 Conclusions

(1) The degree of hydration of cement in the pure cementpastes was determined by measuring the nonevap-orablewater contentThedegree of the fly ash reactionin fly ash-cement blended pastes was determinedusing a selective dissolution method

(2) Based on the degree of hydration of cement and theeffectiveWB ratio the degree of hydration of cementin fly ash-cement blended pastes was acquired

(3) A hydration model of fly ash-cement blended pasteshas been established based on the degree of reactionand the hydration products This model incorporatesthe reactions of fly ash and the hydration of cementbut is also influenced by their interactions

Competing Interests

The authors declare that there are no competing interestsregarding the publication of this paper

Acknowledgments

The authors gratefully acknowledge the National Natural Sci-ence Foundation of China (51408597) and the FundamentalResearch Funds for the Central Universities (2014QNA75)

References

[1] K-H Yang Y-B Jung M-S Cho and S-H Tae ldquoEffect ofsupplementary cementitious materials on reduction of CO2emissions from concreterdquo Journal of Cleaner Production vol103 pp 774ndash783 2015

[2] T Sato and J J Beaudoin ldquoEffect of nano-CaCO3 on hydrationof cement containing supplementary cementitious materialsrdquoAdvances in Cement Research vol 23 no 1 pp 33ndash43 2011

[3] Z Liu Y Zhang and Q Jiang ldquoContinuous tracking of therelationship between resistivity and pore structure of cementpastesrdquo Construction and Building Materials vol 53 pp 26ndash312014

[4] R Snellings G Mertens and J Elsen ldquoSupplementary cemen-titious materialsrdquo Reviews in Mineralogy and Geochemistry vol74 pp 211ndash278 2012

[5] L Lam Y L Wong and C S Poon ldquoDegree of hydration andgelspace ratio of high-volume fly ashcement systemsrdquo Cementand Concrete Research vol 30 no 5 pp 747ndash756 2000

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

[7] P Hou S Kawashima D Kong D J Corr J Qian and S PShah ldquoModification effects of colloidal nanoSiO2 on cementhydration and its gel propertyrdquo Composites Part B Engineeringvol 45 no 1 pp 440ndash448 2013

[8] J David Raja Selvam D S Robinson Smart and I DinaharanldquoMicrostructure and some mechanical properties of fly ashparticulate reinforced AA6061 aluminum alloy compositesprepared by compocastingrdquoMaterials amp Design vol 49 pp 28ndash34 2013

[9] R Feldman L R Prudencio Jr and G Chan ldquoRapid chloridepermeability test on blended cement and other concretescorrelations between charge initial current and conductivityrdquoConstruction and Building Materials vol 13 no 3 pp 149ndash1541999

[10] SWM Supit and FU A Shaikh ldquoDurability properties of highvolume fly ash concrete containing nano-silicardquo Materials andStructuresMateriaux et Constructions vol 48 no 8 pp 2431ndash2445 2014

[11] N Neithalath and J Jain ldquoRelating rapid chloride transportparameters of concretes to microstructural features extractedfrom electrical impedancerdquo Cement and Concrete Research vol40 no 7 pp 1041ndash1051 2010

[12] G Land and D Stephan ldquoThe influence of nano-silica on thehydration of ordinary Portland cementrdquo Journal of MaterialsScience vol 47 no 2 pp 1011ndash1017 2012

[13] J Justs M Wyrzykowski F Winnefeld D Bajare and P LuraldquoInfluence of superabsorbent polymers on hydration of cementpastes with low water-to-binder ratiordquo Journal of ThermalAnalysis and Calorimetry vol 115 no 1 pp 425ndash432 2014

[14] Z Liu Y Zhang Q Jiang W Zhang and J Wu ldquoSolid phasespercolation and capillary pores depercolation in hydratingcement pastesrdquo Journal of Materials in Civil Engineering vol 26no 12 Article ID 04014090 2014

[15] B Uzal and L Turanlı ldquoBlended cements containing highvolume of natural zeolites properties hydration and pastemicrostructurerdquo Cement and Concrete Composites vol 34 no1 pp 101ndash109 2012

[16] Y Kocak and S Nas ldquoThe effect of using fly ash on the strengthand hydration characteristics of blended cementsrdquoConstructionand Building Materials vol 73 pp 25ndash32 2014

[17] D D Nguyen L P Devlin P Koshy and C C Sorrell ldquoEffectsof acetic acid on early hydration of Portland cementrdquo Journal ofThermal Analysis and Calorimetry vol 123 no 1 pp 489ndash4992016

[18] D P Bentz R J Detwiler E J Garboczi P Halamickova andM Schwartz ldquoMulti-scale modeling of the diffusivity of mortarand concreterdquo in Proceedings of the Chloride Penetration intoConcrete LONilsson and J POllivier Eds pp 85ndash94 RILEM1997

[19] M W Grutzeck D Shi G Liu and S Kwan ldquoComputer sim-ulation of interfacial packing in concreterdquo Journal of MaterialsScience vol 28 no 13 pp 3444ndash3450 1993

[20] D P Bentz ldquoInfluence of silica fume on diffusivity in cement-based materials II Multi-scale modeling of concrete diffusiv-ityrdquo Cement and Concrete Research vol 30 no 7 pp 1121ndash11292000

[21] M Voltolini M C Dalconi G Artioli et al ldquoUnderstandingcement hydration at the microscale new opportunities fromlsquopencil-beamrsquo synchrotron X-ray diffraction tomographyrdquo Jour-nal of Applied Crystallography vol 46 no 1 pp 142ndash152 2013

[22] Z Liu W Chen Y Zhang and H Lv ldquoA three-dimensionalmulti-scale method to simulate the ion transport behavior ofcement-based materialsrdquo Construction amp Building Materialsvol 120 pp 494ndash503 2016

[23] B A Suprenant and G Papadopoulos ldquoSelective dissolutionof portland-fly-ash cementsrdquo Journal of Materials in CivilEngineering vol 3 no 1 pp 48ndash59 1991

[24] D P Bentz E J Garboczi and K A Snyder ldquoA hard coresoftshell microstructural model for studying percolation and trans-port in three-dimensional compositemediardquo NISTIR 6265 USDepartment of Commerce 1999

12 Advances in Materials Science and Engineering

[25] X-Y Wang H-S Lee and K-B Park ldquoSimulation of low-calcium fly ash blended cement hydrationrdquo ACI MaterialsJournal vol 106 no 2 pp 167ndash175 2009

[26] Q Zeng K Li T Fen-Chong and P Dangla ldquoDeterminationof cement hydration and pozzolanic reaction extents for fly-ashcement pastesrdquo Construction and Building Materials vol 27 no1 pp 560ndash569 2012

[27] AMNeville Properties of Concrete AddisonWesley LongmanEssex UK 4th edition 1996

[28] C C Yang ldquoThe relationship between charge passed and thechloride concentrations in anode and cathode cells using theaccelerated chloride migration testrdquo Materials and Structuresvol 36 no 264 pp 678ndash684 2003

[29] T C Powers ldquoStructure and physical properties of hardenedportland cement pasterdquo Journal of the American Ceramic Soci-ety vol 41 no 1 pp 1ndash6 1958

[30] V G Papadakis ldquoEffect of fly ash on Portland cement systemspart I Low-calcium fly ashrdquoCement and Concrete Research vol29 no 11 pp 1727ndash1736 1999

[31] A Xu and S L Sarkar ldquoMicrostructural development in high-volume fly-ash cement systemrdquo Journal of Materials in CivilEngineering vol 6 no 1 pp 117ndash136 1994

[32] YM ZhangW Sun andHD Yan ldquoHydration of high-volumefly ash cement pastesrdquoCement and Concrete Composites vol 22no 6 pp 445ndash452 2000

Submit your manuscripts athttpswwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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CeramicsJournal of

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CompositesJournal of

NanoparticlesJournal of

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International Journal of

Biomaterials

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MaterialsJournal of

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Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Advances in Materials Science and Engineering 5

119877 = (1 minus (C3S) 120572C3S minus (C2S) 120572C2S minus (C3A) 120572C3A

minus (C4AF) 120572C4AF minus 215119891SC)C + (1 minus 120574S119891SFA120572FA

minus 120574A119891AFA120572FA) (FA)

119867 = (0418 (C3S) 120572C3S + 0450 (C2S) 120572C2S

+ 0800 (C3A) 120572C3A + 0371 (C4AF) 120572C4AF

minus 045119891S119862)C + (0840120574S119891SFA120572FA

+ 1591120574A119891AFA120572FA) (FA) (30)

The volumes of each phase are

119881CH = (0188 (C3S) 120572C3S + 0058 (C2S) 120572C2S

minus 0136 (C4AF) 120572C4AF minus 0122 (C3A) 120572C3A

+ 0413119891SC)C times 10minus3 minus (0606120574S119891sFA

+ 1298120574A119891AFA) 120572FA (FA) times 10minus3

(31)

119881CSH = (0474 (C3S) 120572C3S + 0629 (C2S) 120572C2S)C

times 10minus3 + 1696120574S119891SFA120572FA (FA) times 10minus3(32)

119881CASH = 3987119891SCC times 10minus3 (33)

119881C(AF)H = 0627 (C4AF) 120572C4AFC times 10minus3 (34)

119881CAH = (1001 (C3A) 120572C3A minus 3398119891SC)C times 10minus3

+ 2668120574A119891AFA120572FA (FA) times 10minus3(35)

120601 = 119882120588w

minus Δ120601c minus Δ120601p (36)

Δ120601c = (C3S) 119881C3S + (C2S) 119881C2S + (C3A) 119881C3A

+ (C4AF) 119881C4AF = (0347 (C3S) 120572C3S

+ 0384 (C2S) 120572C2S + 0577 (C3A) 120572C3A

+ 0224 (C4AF) 120572C4AF)C times 10minus3

(37)

Δ120601p = 0635120574S119891SFA120572FA (FA) times 10minus3 + (0075119891SC

minus 0022 (C3A) 120572C3A)C times 10minus3

+ 1121120574A119891AFA120572FA (FA) times 10minus3

(38)

120601 = 119882 times 10minus3 minus (0635120574S119891SFA + 1180120574A119891AFA)

sdot 120572FA (FA) times 10minus3 minus (0347 (C3S) 120572C3S

+ 0384 (C2S) 120572C2S + 0555 (C3A) 120572C3A

+ 0224 (C4AF) 120572C4AF + 0075119891SC)C times 10minus3

(39)

4 Results and Discussion

41 Experimental Results of Fly Ash-Cement Mixtures

411 Degree of Fly Ash Reaction As can be seen in Figure 1the degree of the fly ash reaction increased with increasingcuring age for various water binder ratios and amounts of flyash In the early stage (1sim7 d) the fly ash (3 to 25 massfraction) had a greater level of participation in the pozzolanicreaction Testing the specific surface area and particle sizedistribution of the fly ash revealed that the fly ash particleswere small and their surface area was up to 665m2kg Theouter surface of a large number of fine particles of hydrated flyash was exposed to CH in the early stage and the pozzolanicreactivity of fly ash occurred rapidly One investigation [31]examined cement-fly ash paste by SEM and found that thesurface of many fine fly ash particles appeared to be etched atthe age of 7 d and that hydration products were formed on thesurface of the fly ash particles The present study has shownthat a pozzolanic reaction with some of the fly ash began atthis stage When examined at a later age the degree of thepozzolanic reactions with fly ash had also increased but theincreases gradually slowed

The effect of fly ash incorporation on the degree ofthe fly ash reaction at the same water binder ratio (05)is shown in Figure 2 The degree of the fly ash reactiondecreased with increasing amounts of fly ash When the flyash content increased from 10 to 30 40 and 50 (massfraction) the degree of the fly ash reaction at 28 d decreasedfrom 371 to 290 254 and 206 respectively As theincorporation of fly ash increased the proportion of cementdecreased and thus the consumption of CH increased andits production decreased in the fly ash-cement mixtures Theamount of CH in the pore solution decreased and the degreeof the fly ash reaction declined A 10 content of fly ashshowed the highest reaction degree with 4515 at 180 dayswhereas the reaction degree of the 50 content was only3311 indicating that nearly 67 of the fly ash did not reactTherefore the filling effect and the microaggregate effect arethe major effects when the fly ash amount increases and thepozzolanic reaction is relatively weak

The effect of the WB ratio on the degree of the fly ashreaction at the same fly ash incorporation (50) is shownin Figure 3 When the WB ratio rises from 03 to 05 thedegree of the fly ash reaction exhibited a linearly increasingtrend with increased water binder ratioThe average reactiondegree of fly ash increased by approximately 110 with each005 increase in the water binder ratio

412 Degree of Cement Reaction The nonevaporable watercontent of the pure cement pastes changed with curing ageas shown in Figure 4 Curing age had a greater impact on thenonevaporated water content especially in the early stages(before 28 d) From preparation to the curing time of 7 dthe nonevaporable water content increased rapidly After7 d of hydration the nonevaporable water content increasedslowly After 28 d the nonevaporable water content remainedconstant for the cement paste samples with WB ratios of 03

6 Advances in Materials Science and Engineering

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

5

10

15

20

25

30

35D

egre

e of fl

y as

h re

actio

n (

)

WB = 03

WB = 035

WB = 04

WB = 045

WB = 05

FA50

(a) Different WB ratios

00

20 40 60 80 100 120 140 160 180 200Curing time (d)

5

10

15

20

25

30

35

40

45

50

Deg

ree o

f fly

ash

reac

tion

()

WB = 05

FA50FA40FA30FA10

(b) Different amounts of incorporated fly ash

Figure 1 Effect of curing time on the degree of the fly ash reaction

Deg

ree o

f fly

ash

reac

tion

()

10

10

20

20

30

30

40

40

50

50

600

WB = 05

Fly ash incorporation ()

1 d3 d7 d28 d90 d180 d

Figure 2 Effect of fly ash incorporation on the degree of the fly ashreaction

and 04 while the nonevaporable water content of the pastewith the WB ratio of 05 continued to increase

Based on the experimental results for the nonevaporablewater content in the pure cement pastes the reaction degreeof cement (120572C) can be calculated using (2) In this studythe degree of the cement paste reaction at different WB

5

10

15

20

25

30

35

Deg

ree o

f fly

ash

reac

tion

()

WB

1 d3 d7 d

28 d60 d90 d180 d

030 035 040 045 050 055 0600

14 d

FA50

Figure 3 Effect of WB ratio on fly ash reaction degree

ratios and different curing ages is shown in Figure 5 Thereis no suitable experimental method to measure the degree ofthe cement reaction for fly ash-cement pastes at the presenttime mainly because the fly ash-cement paste containsnot only C2S2H Ca(OH)2 C3AH6 and AFt from cement

Advances in Materials Science and Engineering 7

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

WB = 03

WB = 04

WB = 05

Non

evap

orab

le w

ater

cont

ent (

)

11

12

13

14

15

16

17

18

19

20

Pure cement pastes

Figure 4 Nonevaporable water content of pure cement pastes

hydration but also includes C2S2H C3AH6 and AFt from thepozzolanic reactions of fly ash and Ca(OH)2 There are nosignificant differences in the composition and structure of theC2S2H C3AH6 and AFt that are formed in the fly ash reac-tions from those formed in cement hydration It is difficultto experimentally separate them Therefore the traditionalmethods of determining the hydration degree of pure cementpaste have failed by measuring the nonevaporable water andCa(OH)2 contents of blended pastes However quantifyingthe degree of the cement reaction is the prerequisite forunderstanding the hydration processes of fly ash-cementpastes As shown in Figure 2 the degree of cement hydrationof pure cement paste depends on the water-cement ratio Anequation describing the relationship between the hydrationdegree and water-cement ratio is expressed as follows [5]

120572c = 1199101 (119905) 119890minus(1199102(119905)(WC)) (40)

where 1199101(119905) and 1199102(119905) are the age-related functions and WCis the water-cement ratio

To calculate the degree of cement hydration of the fly ash-cement system the watercement (WC) ratio is replaced bythe effective water binder ratio in (40) In addition the fly ashpozzolanic reactions will occur and generate a new productso the effectivewater binder ratio is replaced byW(C+120572fFA)

120572c = 1199101 (119905) 119890minus(1199102(119905)(W(C+120572f FA))) (41)

The degree of cement hydration of the fly ash-cementsystem can be calculated under various conditions accordingto (41) as shown in Figure 6 It was found by comparing thecuring times in Figure 6 that the degree of cement hydrationwas higher than that of pure cement paste under the sameconditions when fly ash was mixed into the cement pasteWhen the fly ash content increased the hydration degree ofcement increasedThis ismainly because the incorporation of

Deg

ree o

f pur

e cem

ent r

eact

ion

()

WB

1 d3 d7 d

28 d60 d90 d180 d14 d

20

30

40

50

60

70

80

10

03 04 050

Figure 5 Nonevaporable water content of pure cement pastes

fly ash increased the effective water-cement ratio of cementimproving the hydration environment and thus increasingthe hydration degreeThe fly ash contributes to consumptionof the hydration product of cement (Ca(OH)2) and thereforeit is beneficial for the hydration reaction of cement

413 Content of Nonevaporable Water Themeasured resultsof nonevaporable water in fly ash-cement blended pastesunder various conditions are shown in Figure 7 It can beseen in Figure 7 that the nonevaporated water content of flyash-cement pastes with 10 30 and 40 fly ash are higherthan the pure cement paste in addition to the 50 contentAfter 7 d the differences were not significant This may bebecause the nucleation and crystallization of Ca(OH)2 wereinduced by the fine particles of the fly ash thus contributingto cement hydrationWithin a certain range of incorporationthe promotion effects of fly ash exceeded the negative effectsdue to the slow development of the activity of fly ash and asmall number of hydrates The nonevaporable water contentof fly ash-cement pastes will be higher than that of purecement pastes From the nonevaporable water trend theblended pastes of fly ash incorporation of 10sim30 showed thehighest nonevaporable water Zhang et al [32] also found thatfly ash can improve the early hydration rate of cement

Powers [29] proposed that nonevaporable water in purecement paste is one index for the degree of cement hydrationNonevaporable water of the hardened pastes comes mainlyfrom the hydration products Ca(OH)2 and C-S-H gel In thefly ash-cement blended pastes both cement hydration andthe fly ash reaction produce C-S-H and the fly ash can alsoconsume Ca(OH)2 that is produced by the hydration of thecement Therefore it is not appropriate to directly use thenonevaporable water to measure the degree of reaction of theblended pastes

8 Advances in Materials Science and Engineering

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

WB = 03

WB = 035

WB = 04

WB = 045

WB = 05

Deg

ree o

f cem

ent r

eact

ion

()

55

60

65

70

75

80

85

90

FA50

(a) Different WB ratios

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

Deg

ree o

f cem

ent r

eact

ion

()

55

60

65

70

75

80

85

90

WB = 05

FA50FA40FA30FA10

(b) Different fly ash incorporation

Figure 6 The fly ash reaction degree of fly ash-cement system

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

6

8

Non

evap

orab

le w

ater

cont

ent (

)

10

12

14

16

18

WB = 03

WB = 04

WB = 05

FA50

(a) Different WB ratios

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

Non

evap

orab

le w

ater

cont

ent (

)

10

12

14

16

18

20

WB = 05

FA50FA40FA30FA10FA0

(b) Different fly ash incorporation rates

Figure 7 Nonevaporable water contents of the fly ash-cement blended pastes

42 Verifying the Model of Fly Ash-Cement Blended Pastes

421The Equations for the Increased Hydration Degree Valuesof Cement According to the experimental results of the totalamount of nonevaporable water the degree of the fly ashreaction and the degree of increasing cement hydration werecalculated in the fly ash-cement composite systems under

various conditions by (7) and (8) as shown in Figures 8 and9

Figure 8 shows the variation of the degree of hydrationof cement in the blended system with the fly ash addition of50 as the WB ratio changed from 03 to 05 The reactiondegree at every curing age increased linearly with increases oftheWB ratio Figure 9 shows the degree of cement hydration

Advances in Materials Science and Engineering 9

WB

1 d3 d7 d

28 d60 d90 d180 d14 d

055030 035 040 045 050

00

01

02

03

04

05

06

07 FA 50

120572cminus

f

Figure 8 Influence of the WB ratio on the increased degree ofcement hydration

1 d3 d7 d

28 d60 d90 d180 d14 d

00

01

01

02

02

03

03

04

04

05

05

06

06

07

08WB 05

mf

120572cminus

f

Figure 9 Influence of the fly ash content on the increased degree ofcement hydration

with the trend of its fly ash content when the WB ratio was05 It can be observed that the added degree of hydration ofthe cement increased with increases of the fly ash contentWhen the fly ash content was less than 03 the curing agehad little influence on the increased degree of hydration ofthe cementWhen the fly ash content was greater than 03 thedegree of hydration of the cement was significantly improvedwith increasing curing age For example as the curing ageof the fly ash-cement system increased from 1 d to 180 d thevalue of the degree of hydration of the cement increased from007 to 011 when its fly ash content was 01 The increased

value of the degree of hydration of cement improved from034 to 072 when the fly ash content was 05 Clearly theWB ratio fly ash content and curing age can each promotethe degree of hydration of the cement On the one handthis is mainly due to the incorporated fly ash increasing theeffective WB ratio of the cement and improving the cementhydration environment On the other hand this is due to thepostsecondary reactions of fly ash that promptly consume theCa(OH)2 that is generated by the hydration of the cementwhich is advantageous for the hydration reactions of cement

One objective of this study was to predict the increaseddegree of hydration of cement and degree of reaction of flyash in the fly ash-cement blended system with different flyash contents WB ratios and curing periods Based on theresults of Figures 8 and 9 it is concluded that the increasedvalues of the degree of hydration of cement containing addedfly ash and the quantitative relationships among the reactiondegree of fly ash the WB ratio and the fly ash content canbe expressed as follows as determined by multiple regressionanalysis

120572cminusf = 1 minus 119890minus119886(119905minus119887)119888

(42)

119886 = minus305481 + 286722 sdot 119890[034293sdot(WB)] (43a)

119887 = 0 (43b)

119888 = minus1167238 + 113153 sdot 119890[011795sdot(119898f )] (43c)

120572f = 1 minus 119890minus119889(119905minus119891)119892

(44)

119889 = 003869 + 000426 sdot 119890[555391sdot(WB)] (45a)

119891 = 09 (45b)

119892 = minus001487 + 0413 sdot 119890[minus07646sdot(119898f )] (45c)

422 Validation of the Model Figure 10 shows the compar-ison of the experimental results and the predicted valuesfor 120572cminusf The fitted 1198772 coefficient of the regression analysisequation (119910 = 099366119909) is 098849 Figure 11 shows the120572119891 of the experimental and predicted values and the fitted1198772 coefficient of the regression analysis equation (119910 =099552119909) is 099131 The maximum relative errors of Figures10 and 11 are 3096 and 4831 respectively The modelwas consistent with the experimental values Therefore it isreasonable to propose a model for the degree of the fly ashreaction and a model of accelerated hydration of cement forblended systems

The CH content and porosity as key parameters ofthe microstructure were selected to verify the hydrationproducts of fly ash-cement mixtures The results of theexperimental values were obtained from the literature [5] Inthis experiment the CH content of hydrated cement pasteswas determined by thermal gravimetry analysis based onthe ignited weight of the sample The porosity of cement-flyash pastes was obtained by mercury intrusion porosimetryThe CH and porosity values are presented in Section 32Figure 12 presents the comparison between the predicted

10 Advances in Materials Science and Engineering

WB = 03

WB = 04

WB = 05

000000

001

001

002

002

003

003

004

004

Measured value

Pred

icte

d va

lue

Figure 10 The predicted and measured values of the degree ofcement hydration of enhanced cement-fly ash pastes

WB = 03

WB = 035

WB = 04

WB = 045

WB = 05

0000

02

02

04

04

06

06

08

08

10

10

Measured value

Pred

icte

d va

lue

Figure 11 The predicted and measured values of the degree of thefly ash reaction of cement-fly ash pastes

and experimental values of the CH content For differentWB ratios and fly ash content the predicted results camecloser to the experimental values with increasing curingage The maximum relative errors were 135 113 and66 at 7 d 28 d and 90 d respectively Figure 13 showsthe comparison of the predicted and experimental valuesof porosity in fly ash-cement systems For all samples thepredicted values were higher than the measured values Themaximum relative errors were 117 112 and 139 at 7 d28 d and 180 d respectively The main reason is that theporosity of the blended system calculated by the model is

10000

20 40 60 80Age (d)

20

2

4

6

8

10

12

14

16

18

CH (

)

WB = 03 mf = 025 (experiment)WB = 03 mf = 025 (prediction)

(prediction)

(prediction)WB = 03 mf = 055 (experiment)WB = 03 mf = 055

WB = 05 mf = 055 (experiment)WB = 05 mf = 055

Figure 12 The predicted and measured values of CH content ofcement-fly ash pastes

100 150 2000 50Age (d)

20

25

30

35

40

45

50

15

Poro

sity

()

WB = 03 (experiment)WB = 03 (prediction)WB = 04 (experiment)WB = 04 (prediction)WB = 05 (experiment)WB = 05 (prediction)

Figure 13 The predicted and measured values of porosity ofcement-fly ash pastes

the capillary porosity (the porosity contained in the capillarypores and the porosity of the gel) that was obtained bymercury intrusion Therefore with longer curing ages moreC-S-H gel phase was generated by the second hydration of flyash and the differences between the predicted and measuredvalues increased

Advances in Materials Science and Engineering 11

5 Conclusions

(1) The degree of hydration of cement in the pure cementpastes was determined by measuring the nonevap-orablewater contentThedegree of the fly ash reactionin fly ash-cement blended pastes was determinedusing a selective dissolution method

(2) Based on the degree of hydration of cement and theeffectiveWB ratio the degree of hydration of cementin fly ash-cement blended pastes was acquired

(3) A hydration model of fly ash-cement blended pasteshas been established based on the degree of reactionand the hydration products This model incorporatesthe reactions of fly ash and the hydration of cementbut is also influenced by their interactions

Competing Interests

The authors declare that there are no competing interestsregarding the publication of this paper

Acknowledgments

The authors gratefully acknowledge the National Natural Sci-ence Foundation of China (51408597) and the FundamentalResearch Funds for the Central Universities (2014QNA75)

References

[1] K-H Yang Y-B Jung M-S Cho and S-H Tae ldquoEffect ofsupplementary cementitious materials on reduction of CO2emissions from concreterdquo Journal of Cleaner Production vol103 pp 774ndash783 2015

[2] T Sato and J J Beaudoin ldquoEffect of nano-CaCO3 on hydrationof cement containing supplementary cementitious materialsrdquoAdvances in Cement Research vol 23 no 1 pp 33ndash43 2011

[3] Z Liu Y Zhang and Q Jiang ldquoContinuous tracking of therelationship between resistivity and pore structure of cementpastesrdquo Construction and Building Materials vol 53 pp 26ndash312014

[4] R Snellings G Mertens and J Elsen ldquoSupplementary cemen-titious materialsrdquo Reviews in Mineralogy and Geochemistry vol74 pp 211ndash278 2012

[5] L Lam Y L Wong and C S Poon ldquoDegree of hydration andgelspace ratio of high-volume fly ashcement systemsrdquo Cementand Concrete Research vol 30 no 5 pp 747ndash756 2000

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

[7] P Hou S Kawashima D Kong D J Corr J Qian and S PShah ldquoModification effects of colloidal nanoSiO2 on cementhydration and its gel propertyrdquo Composites Part B Engineeringvol 45 no 1 pp 440ndash448 2013

[8] J David Raja Selvam D S Robinson Smart and I DinaharanldquoMicrostructure and some mechanical properties of fly ashparticulate reinforced AA6061 aluminum alloy compositesprepared by compocastingrdquoMaterials amp Design vol 49 pp 28ndash34 2013

[9] R Feldman L R Prudencio Jr and G Chan ldquoRapid chloridepermeability test on blended cement and other concretescorrelations between charge initial current and conductivityrdquoConstruction and Building Materials vol 13 no 3 pp 149ndash1541999

[10] SWM Supit and FU A Shaikh ldquoDurability properties of highvolume fly ash concrete containing nano-silicardquo Materials andStructuresMateriaux et Constructions vol 48 no 8 pp 2431ndash2445 2014

[11] N Neithalath and J Jain ldquoRelating rapid chloride transportparameters of concretes to microstructural features extractedfrom electrical impedancerdquo Cement and Concrete Research vol40 no 7 pp 1041ndash1051 2010

[12] G Land and D Stephan ldquoThe influence of nano-silica on thehydration of ordinary Portland cementrdquo Journal of MaterialsScience vol 47 no 2 pp 1011ndash1017 2012

[13] J Justs M Wyrzykowski F Winnefeld D Bajare and P LuraldquoInfluence of superabsorbent polymers on hydration of cementpastes with low water-to-binder ratiordquo Journal of ThermalAnalysis and Calorimetry vol 115 no 1 pp 425ndash432 2014

[14] Z Liu Y Zhang Q Jiang W Zhang and J Wu ldquoSolid phasespercolation and capillary pores depercolation in hydratingcement pastesrdquo Journal of Materials in Civil Engineering vol 26no 12 Article ID 04014090 2014

[15] B Uzal and L Turanlı ldquoBlended cements containing highvolume of natural zeolites properties hydration and pastemicrostructurerdquo Cement and Concrete Composites vol 34 no1 pp 101ndash109 2012

[16] Y Kocak and S Nas ldquoThe effect of using fly ash on the strengthand hydration characteristics of blended cementsrdquoConstructionand Building Materials vol 73 pp 25ndash32 2014

[17] D D Nguyen L P Devlin P Koshy and C C Sorrell ldquoEffectsof acetic acid on early hydration of Portland cementrdquo Journal ofThermal Analysis and Calorimetry vol 123 no 1 pp 489ndash4992016

[18] D P Bentz R J Detwiler E J Garboczi P Halamickova andM Schwartz ldquoMulti-scale modeling of the diffusivity of mortarand concreterdquo in Proceedings of the Chloride Penetration intoConcrete LONilsson and J POllivier Eds pp 85ndash94 RILEM1997

[19] M W Grutzeck D Shi G Liu and S Kwan ldquoComputer sim-ulation of interfacial packing in concreterdquo Journal of MaterialsScience vol 28 no 13 pp 3444ndash3450 1993

[20] D P Bentz ldquoInfluence of silica fume on diffusivity in cement-based materials II Multi-scale modeling of concrete diffusiv-ityrdquo Cement and Concrete Research vol 30 no 7 pp 1121ndash11292000

[21] M Voltolini M C Dalconi G Artioli et al ldquoUnderstandingcement hydration at the microscale new opportunities fromlsquopencil-beamrsquo synchrotron X-ray diffraction tomographyrdquo Jour-nal of Applied Crystallography vol 46 no 1 pp 142ndash152 2013

[22] Z Liu W Chen Y Zhang and H Lv ldquoA three-dimensionalmulti-scale method to simulate the ion transport behavior ofcement-based materialsrdquo Construction amp Building Materialsvol 120 pp 494ndash503 2016

[23] B A Suprenant and G Papadopoulos ldquoSelective dissolutionof portland-fly-ash cementsrdquo Journal of Materials in CivilEngineering vol 3 no 1 pp 48ndash59 1991

[24] D P Bentz E J Garboczi and K A Snyder ldquoA hard coresoftshell microstructural model for studying percolation and trans-port in three-dimensional compositemediardquo NISTIR 6265 USDepartment of Commerce 1999

12 Advances in Materials Science and Engineering

[25] X-Y Wang H-S Lee and K-B Park ldquoSimulation of low-calcium fly ash blended cement hydrationrdquo ACI MaterialsJournal vol 106 no 2 pp 167ndash175 2009

[26] Q Zeng K Li T Fen-Chong and P Dangla ldquoDeterminationof cement hydration and pozzolanic reaction extents for fly-ashcement pastesrdquo Construction and Building Materials vol 27 no1 pp 560ndash569 2012

[27] AMNeville Properties of Concrete AddisonWesley LongmanEssex UK 4th edition 1996

[28] C C Yang ldquoThe relationship between charge passed and thechloride concentrations in anode and cathode cells using theaccelerated chloride migration testrdquo Materials and Structuresvol 36 no 264 pp 678ndash684 2003

[29] T C Powers ldquoStructure and physical properties of hardenedportland cement pasterdquo Journal of the American Ceramic Soci-ety vol 41 no 1 pp 1ndash6 1958

[30] V G Papadakis ldquoEffect of fly ash on Portland cement systemspart I Low-calcium fly ashrdquoCement and Concrete Research vol29 no 11 pp 1727ndash1736 1999

[31] A Xu and S L Sarkar ldquoMicrostructural development in high-volume fly-ash cement systemrdquo Journal of Materials in CivilEngineering vol 6 no 1 pp 117ndash136 1994

[32] YM ZhangW Sun andHD Yan ldquoHydration of high-volumefly ash cement pastesrdquoCement and Concrete Composites vol 22no 6 pp 445ndash452 2000

Submit your manuscripts athttpswwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

6 Advances in Materials Science and Engineering

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

5

10

15

20

25

30

35D

egre

e of fl

y as

h re

actio

n (

)

WB = 03

WB = 035

WB = 04

WB = 045

WB = 05

FA50

(a) Different WB ratios

00

20 40 60 80 100 120 140 160 180 200Curing time (d)

5

10

15

20

25

30

35

40

45

50

Deg

ree o

f fly

ash

reac

tion

()

WB = 05

FA50FA40FA30FA10

(b) Different amounts of incorporated fly ash

Figure 1 Effect of curing time on the degree of the fly ash reaction

Deg

ree o

f fly

ash

reac

tion

()

10

10

20

20

30

30

40

40

50

50

600

WB = 05

Fly ash incorporation ()

1 d3 d7 d28 d90 d180 d

Figure 2 Effect of fly ash incorporation on the degree of the fly ashreaction

and 04 while the nonevaporable water content of the pastewith the WB ratio of 05 continued to increase

Based on the experimental results for the nonevaporablewater content in the pure cement pastes the reaction degreeof cement (120572C) can be calculated using (2) In this studythe degree of the cement paste reaction at different WB

5

10

15

20

25

30

35

Deg

ree o

f fly

ash

reac

tion

()

WB

1 d3 d7 d

28 d60 d90 d180 d

030 035 040 045 050 055 0600

14 d

FA50

Figure 3 Effect of WB ratio on fly ash reaction degree

ratios and different curing ages is shown in Figure 5 Thereis no suitable experimental method to measure the degree ofthe cement reaction for fly ash-cement pastes at the presenttime mainly because the fly ash-cement paste containsnot only C2S2H Ca(OH)2 C3AH6 and AFt from cement

Advances in Materials Science and Engineering 7

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

WB = 03

WB = 04

WB = 05

Non

evap

orab

le w

ater

cont

ent (

)

11

12

13

14

15

16

17

18

19

20

Pure cement pastes

Figure 4 Nonevaporable water content of pure cement pastes

hydration but also includes C2S2H C3AH6 and AFt from thepozzolanic reactions of fly ash and Ca(OH)2 There are nosignificant differences in the composition and structure of theC2S2H C3AH6 and AFt that are formed in the fly ash reac-tions from those formed in cement hydration It is difficultto experimentally separate them Therefore the traditionalmethods of determining the hydration degree of pure cementpaste have failed by measuring the nonevaporable water andCa(OH)2 contents of blended pastes However quantifyingthe degree of the cement reaction is the prerequisite forunderstanding the hydration processes of fly ash-cementpastes As shown in Figure 2 the degree of cement hydrationof pure cement paste depends on the water-cement ratio Anequation describing the relationship between the hydrationdegree and water-cement ratio is expressed as follows [5]

120572c = 1199101 (119905) 119890minus(1199102(119905)(WC)) (40)

where 1199101(119905) and 1199102(119905) are the age-related functions and WCis the water-cement ratio

To calculate the degree of cement hydration of the fly ash-cement system the watercement (WC) ratio is replaced bythe effective water binder ratio in (40) In addition the fly ashpozzolanic reactions will occur and generate a new productso the effectivewater binder ratio is replaced byW(C+120572fFA)

120572c = 1199101 (119905) 119890minus(1199102(119905)(W(C+120572f FA))) (41)

The degree of cement hydration of the fly ash-cementsystem can be calculated under various conditions accordingto (41) as shown in Figure 6 It was found by comparing thecuring times in Figure 6 that the degree of cement hydrationwas higher than that of pure cement paste under the sameconditions when fly ash was mixed into the cement pasteWhen the fly ash content increased the hydration degree ofcement increasedThis ismainly because the incorporation of

Deg

ree o

f pur

e cem

ent r

eact

ion

()

WB

1 d3 d7 d

28 d60 d90 d180 d14 d

20

30

40

50

60

70

80

10

03 04 050

Figure 5 Nonevaporable water content of pure cement pastes

fly ash increased the effective water-cement ratio of cementimproving the hydration environment and thus increasingthe hydration degreeThe fly ash contributes to consumptionof the hydration product of cement (Ca(OH)2) and thereforeit is beneficial for the hydration reaction of cement

413 Content of Nonevaporable Water Themeasured resultsof nonevaporable water in fly ash-cement blended pastesunder various conditions are shown in Figure 7 It can beseen in Figure 7 that the nonevaporated water content of flyash-cement pastes with 10 30 and 40 fly ash are higherthan the pure cement paste in addition to the 50 contentAfter 7 d the differences were not significant This may bebecause the nucleation and crystallization of Ca(OH)2 wereinduced by the fine particles of the fly ash thus contributingto cement hydrationWithin a certain range of incorporationthe promotion effects of fly ash exceeded the negative effectsdue to the slow development of the activity of fly ash and asmall number of hydrates The nonevaporable water contentof fly ash-cement pastes will be higher than that of purecement pastes From the nonevaporable water trend theblended pastes of fly ash incorporation of 10sim30 showed thehighest nonevaporable water Zhang et al [32] also found thatfly ash can improve the early hydration rate of cement

Powers [29] proposed that nonevaporable water in purecement paste is one index for the degree of cement hydrationNonevaporable water of the hardened pastes comes mainlyfrom the hydration products Ca(OH)2 and C-S-H gel In thefly ash-cement blended pastes both cement hydration andthe fly ash reaction produce C-S-H and the fly ash can alsoconsume Ca(OH)2 that is produced by the hydration of thecement Therefore it is not appropriate to directly use thenonevaporable water to measure the degree of reaction of theblended pastes

8 Advances in Materials Science and Engineering

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

WB = 03

WB = 035

WB = 04

WB = 045

WB = 05

Deg

ree o

f cem

ent r

eact

ion

()

55

60

65

70

75

80

85

90

FA50

(a) Different WB ratios

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

Deg

ree o

f cem

ent r

eact

ion

()

55

60

65

70

75

80

85

90

WB = 05

FA50FA40FA30FA10

(b) Different fly ash incorporation

Figure 6 The fly ash reaction degree of fly ash-cement system

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

6

8

Non

evap

orab

le w

ater

cont

ent (

)

10

12

14

16

18

WB = 03

WB = 04

WB = 05

FA50

(a) Different WB ratios

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

Non

evap

orab

le w

ater

cont

ent (

)

10

12

14

16

18

20

WB = 05

FA50FA40FA30FA10FA0

(b) Different fly ash incorporation rates

Figure 7 Nonevaporable water contents of the fly ash-cement blended pastes

42 Verifying the Model of Fly Ash-Cement Blended Pastes

421The Equations for the Increased Hydration Degree Valuesof Cement According to the experimental results of the totalamount of nonevaporable water the degree of the fly ashreaction and the degree of increasing cement hydration werecalculated in the fly ash-cement composite systems under

various conditions by (7) and (8) as shown in Figures 8 and9

Figure 8 shows the variation of the degree of hydrationof cement in the blended system with the fly ash addition of50 as the WB ratio changed from 03 to 05 The reactiondegree at every curing age increased linearly with increases oftheWB ratio Figure 9 shows the degree of cement hydration

Advances in Materials Science and Engineering 9

WB

1 d3 d7 d

28 d60 d90 d180 d14 d

055030 035 040 045 050

00

01

02

03

04

05

06

07 FA 50

120572cminus

f

Figure 8 Influence of the WB ratio on the increased degree ofcement hydration

1 d3 d7 d

28 d60 d90 d180 d14 d

00

01

01

02

02

03

03

04

04

05

05

06

06

07

08WB 05

mf

120572cminus

f

Figure 9 Influence of the fly ash content on the increased degree ofcement hydration

with the trend of its fly ash content when the WB ratio was05 It can be observed that the added degree of hydration ofthe cement increased with increases of the fly ash contentWhen the fly ash content was less than 03 the curing agehad little influence on the increased degree of hydration ofthe cementWhen the fly ash content was greater than 03 thedegree of hydration of the cement was significantly improvedwith increasing curing age For example as the curing ageof the fly ash-cement system increased from 1 d to 180 d thevalue of the degree of hydration of the cement increased from007 to 011 when its fly ash content was 01 The increased

value of the degree of hydration of cement improved from034 to 072 when the fly ash content was 05 Clearly theWB ratio fly ash content and curing age can each promotethe degree of hydration of the cement On the one handthis is mainly due to the incorporated fly ash increasing theeffective WB ratio of the cement and improving the cementhydration environment On the other hand this is due to thepostsecondary reactions of fly ash that promptly consume theCa(OH)2 that is generated by the hydration of the cementwhich is advantageous for the hydration reactions of cement

One objective of this study was to predict the increaseddegree of hydration of cement and degree of reaction of flyash in the fly ash-cement blended system with different flyash contents WB ratios and curing periods Based on theresults of Figures 8 and 9 it is concluded that the increasedvalues of the degree of hydration of cement containing addedfly ash and the quantitative relationships among the reactiondegree of fly ash the WB ratio and the fly ash content canbe expressed as follows as determined by multiple regressionanalysis

120572cminusf = 1 minus 119890minus119886(119905minus119887)119888

(42)

119886 = minus305481 + 286722 sdot 119890[034293sdot(WB)] (43a)

119887 = 0 (43b)

119888 = minus1167238 + 113153 sdot 119890[011795sdot(119898f )] (43c)

120572f = 1 minus 119890minus119889(119905minus119891)119892

(44)

119889 = 003869 + 000426 sdot 119890[555391sdot(WB)] (45a)

119891 = 09 (45b)

119892 = minus001487 + 0413 sdot 119890[minus07646sdot(119898f )] (45c)

422 Validation of the Model Figure 10 shows the compar-ison of the experimental results and the predicted valuesfor 120572cminusf The fitted 1198772 coefficient of the regression analysisequation (119910 = 099366119909) is 098849 Figure 11 shows the120572119891 of the experimental and predicted values and the fitted1198772 coefficient of the regression analysis equation (119910 =099552119909) is 099131 The maximum relative errors of Figures10 and 11 are 3096 and 4831 respectively The modelwas consistent with the experimental values Therefore it isreasonable to propose a model for the degree of the fly ashreaction and a model of accelerated hydration of cement forblended systems

The CH content and porosity as key parameters ofthe microstructure were selected to verify the hydrationproducts of fly ash-cement mixtures The results of theexperimental values were obtained from the literature [5] Inthis experiment the CH content of hydrated cement pasteswas determined by thermal gravimetry analysis based onthe ignited weight of the sample The porosity of cement-flyash pastes was obtained by mercury intrusion porosimetryThe CH and porosity values are presented in Section 32Figure 12 presents the comparison between the predicted

10 Advances in Materials Science and Engineering

WB = 03

WB = 04

WB = 05

000000

001

001

002

002

003

003

004

004

Measured value

Pred

icte

d va

lue

Figure 10 The predicted and measured values of the degree ofcement hydration of enhanced cement-fly ash pastes

WB = 03

WB = 035

WB = 04

WB = 045

WB = 05

0000

02

02

04

04

06

06

08

08

10

10

Measured value

Pred

icte

d va

lue

Figure 11 The predicted and measured values of the degree of thefly ash reaction of cement-fly ash pastes

and experimental values of the CH content For differentWB ratios and fly ash content the predicted results camecloser to the experimental values with increasing curingage The maximum relative errors were 135 113 and66 at 7 d 28 d and 90 d respectively Figure 13 showsthe comparison of the predicted and experimental valuesof porosity in fly ash-cement systems For all samples thepredicted values were higher than the measured values Themaximum relative errors were 117 112 and 139 at 7 d28 d and 180 d respectively The main reason is that theporosity of the blended system calculated by the model is

10000

20 40 60 80Age (d)

20

2

4

6

8

10

12

14

16

18

CH (

)

WB = 03 mf = 025 (experiment)WB = 03 mf = 025 (prediction)

(prediction)

(prediction)WB = 03 mf = 055 (experiment)WB = 03 mf = 055

WB = 05 mf = 055 (experiment)WB = 05 mf = 055

Figure 12 The predicted and measured values of CH content ofcement-fly ash pastes

100 150 2000 50Age (d)

20

25

30

35

40

45

50

15

Poro

sity

()

WB = 03 (experiment)WB = 03 (prediction)WB = 04 (experiment)WB = 04 (prediction)WB = 05 (experiment)WB = 05 (prediction)

Figure 13 The predicted and measured values of porosity ofcement-fly ash pastes

the capillary porosity (the porosity contained in the capillarypores and the porosity of the gel) that was obtained bymercury intrusion Therefore with longer curing ages moreC-S-H gel phase was generated by the second hydration of flyash and the differences between the predicted and measuredvalues increased

Advances in Materials Science and Engineering 11

5 Conclusions

(1) The degree of hydration of cement in the pure cementpastes was determined by measuring the nonevap-orablewater contentThedegree of the fly ash reactionin fly ash-cement blended pastes was determinedusing a selective dissolution method

(2) Based on the degree of hydration of cement and theeffectiveWB ratio the degree of hydration of cementin fly ash-cement blended pastes was acquired

(3) A hydration model of fly ash-cement blended pasteshas been established based on the degree of reactionand the hydration products This model incorporatesthe reactions of fly ash and the hydration of cementbut is also influenced by their interactions

Competing Interests

The authors declare that there are no competing interestsregarding the publication of this paper

Acknowledgments

The authors gratefully acknowledge the National Natural Sci-ence Foundation of China (51408597) and the FundamentalResearch Funds for the Central Universities (2014QNA75)

References

[1] K-H Yang Y-B Jung M-S Cho and S-H Tae ldquoEffect ofsupplementary cementitious materials on reduction of CO2emissions from concreterdquo Journal of Cleaner Production vol103 pp 774ndash783 2015

[2] T Sato and J J Beaudoin ldquoEffect of nano-CaCO3 on hydrationof cement containing supplementary cementitious materialsrdquoAdvances in Cement Research vol 23 no 1 pp 33ndash43 2011

[3] Z Liu Y Zhang and Q Jiang ldquoContinuous tracking of therelationship between resistivity and pore structure of cementpastesrdquo Construction and Building Materials vol 53 pp 26ndash312014

[4] R Snellings G Mertens and J Elsen ldquoSupplementary cemen-titious materialsrdquo Reviews in Mineralogy and Geochemistry vol74 pp 211ndash278 2012

[5] L Lam Y L Wong and C S Poon ldquoDegree of hydration andgelspace ratio of high-volume fly ashcement systemsrdquo Cementand Concrete Research vol 30 no 5 pp 747ndash756 2000

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

[7] P Hou S Kawashima D Kong D J Corr J Qian and S PShah ldquoModification effects of colloidal nanoSiO2 on cementhydration and its gel propertyrdquo Composites Part B Engineeringvol 45 no 1 pp 440ndash448 2013

[8] J David Raja Selvam D S Robinson Smart and I DinaharanldquoMicrostructure and some mechanical properties of fly ashparticulate reinforced AA6061 aluminum alloy compositesprepared by compocastingrdquoMaterials amp Design vol 49 pp 28ndash34 2013

[9] R Feldman L R Prudencio Jr and G Chan ldquoRapid chloridepermeability test on blended cement and other concretescorrelations between charge initial current and conductivityrdquoConstruction and Building Materials vol 13 no 3 pp 149ndash1541999

[10] SWM Supit and FU A Shaikh ldquoDurability properties of highvolume fly ash concrete containing nano-silicardquo Materials andStructuresMateriaux et Constructions vol 48 no 8 pp 2431ndash2445 2014

[11] N Neithalath and J Jain ldquoRelating rapid chloride transportparameters of concretes to microstructural features extractedfrom electrical impedancerdquo Cement and Concrete Research vol40 no 7 pp 1041ndash1051 2010

[12] G Land and D Stephan ldquoThe influence of nano-silica on thehydration of ordinary Portland cementrdquo Journal of MaterialsScience vol 47 no 2 pp 1011ndash1017 2012

[13] J Justs M Wyrzykowski F Winnefeld D Bajare and P LuraldquoInfluence of superabsorbent polymers on hydration of cementpastes with low water-to-binder ratiordquo Journal of ThermalAnalysis and Calorimetry vol 115 no 1 pp 425ndash432 2014

[14] Z Liu Y Zhang Q Jiang W Zhang and J Wu ldquoSolid phasespercolation and capillary pores depercolation in hydratingcement pastesrdquo Journal of Materials in Civil Engineering vol 26no 12 Article ID 04014090 2014

[15] B Uzal and L Turanlı ldquoBlended cements containing highvolume of natural zeolites properties hydration and pastemicrostructurerdquo Cement and Concrete Composites vol 34 no1 pp 101ndash109 2012

[16] Y Kocak and S Nas ldquoThe effect of using fly ash on the strengthand hydration characteristics of blended cementsrdquoConstructionand Building Materials vol 73 pp 25ndash32 2014

[17] D D Nguyen L P Devlin P Koshy and C C Sorrell ldquoEffectsof acetic acid on early hydration of Portland cementrdquo Journal ofThermal Analysis and Calorimetry vol 123 no 1 pp 489ndash4992016

[18] D P Bentz R J Detwiler E J Garboczi P Halamickova andM Schwartz ldquoMulti-scale modeling of the diffusivity of mortarand concreterdquo in Proceedings of the Chloride Penetration intoConcrete LONilsson and J POllivier Eds pp 85ndash94 RILEM1997

[19] M W Grutzeck D Shi G Liu and S Kwan ldquoComputer sim-ulation of interfacial packing in concreterdquo Journal of MaterialsScience vol 28 no 13 pp 3444ndash3450 1993

[20] D P Bentz ldquoInfluence of silica fume on diffusivity in cement-based materials II Multi-scale modeling of concrete diffusiv-ityrdquo Cement and Concrete Research vol 30 no 7 pp 1121ndash11292000

[21] M Voltolini M C Dalconi G Artioli et al ldquoUnderstandingcement hydration at the microscale new opportunities fromlsquopencil-beamrsquo synchrotron X-ray diffraction tomographyrdquo Jour-nal of Applied Crystallography vol 46 no 1 pp 142ndash152 2013

[22] Z Liu W Chen Y Zhang and H Lv ldquoA three-dimensionalmulti-scale method to simulate the ion transport behavior ofcement-based materialsrdquo Construction amp Building Materialsvol 120 pp 494ndash503 2016

[23] B A Suprenant and G Papadopoulos ldquoSelective dissolutionof portland-fly-ash cementsrdquo Journal of Materials in CivilEngineering vol 3 no 1 pp 48ndash59 1991

[24] D P Bentz E J Garboczi and K A Snyder ldquoA hard coresoftshell microstructural model for studying percolation and trans-port in three-dimensional compositemediardquo NISTIR 6265 USDepartment of Commerce 1999

12 Advances in Materials Science and Engineering

[25] X-Y Wang H-S Lee and K-B Park ldquoSimulation of low-calcium fly ash blended cement hydrationrdquo ACI MaterialsJournal vol 106 no 2 pp 167ndash175 2009

[26] Q Zeng K Li T Fen-Chong and P Dangla ldquoDeterminationof cement hydration and pozzolanic reaction extents for fly-ashcement pastesrdquo Construction and Building Materials vol 27 no1 pp 560ndash569 2012

[27] AMNeville Properties of Concrete AddisonWesley LongmanEssex UK 4th edition 1996

[28] C C Yang ldquoThe relationship between charge passed and thechloride concentrations in anode and cathode cells using theaccelerated chloride migration testrdquo Materials and Structuresvol 36 no 264 pp 678ndash684 2003

[29] T C Powers ldquoStructure and physical properties of hardenedportland cement pasterdquo Journal of the American Ceramic Soci-ety vol 41 no 1 pp 1ndash6 1958

[30] V G Papadakis ldquoEffect of fly ash on Portland cement systemspart I Low-calcium fly ashrdquoCement and Concrete Research vol29 no 11 pp 1727ndash1736 1999

[31] A Xu and S L Sarkar ldquoMicrostructural development in high-volume fly-ash cement systemrdquo Journal of Materials in CivilEngineering vol 6 no 1 pp 117ndash136 1994

[32] YM ZhangW Sun andHD Yan ldquoHydration of high-volumefly ash cement pastesrdquoCement and Concrete Composites vol 22no 6 pp 445ndash452 2000

Submit your manuscripts athttpswwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Advances in Materials Science and Engineering 7

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

WB = 03

WB = 04

WB = 05

Non

evap

orab

le w

ater

cont

ent (

)

11

12

13

14

15

16

17

18

19

20

Pure cement pastes

Figure 4 Nonevaporable water content of pure cement pastes

hydration but also includes C2S2H C3AH6 and AFt from thepozzolanic reactions of fly ash and Ca(OH)2 There are nosignificant differences in the composition and structure of theC2S2H C3AH6 and AFt that are formed in the fly ash reac-tions from those formed in cement hydration It is difficultto experimentally separate them Therefore the traditionalmethods of determining the hydration degree of pure cementpaste have failed by measuring the nonevaporable water andCa(OH)2 contents of blended pastes However quantifyingthe degree of the cement reaction is the prerequisite forunderstanding the hydration processes of fly ash-cementpastes As shown in Figure 2 the degree of cement hydrationof pure cement paste depends on the water-cement ratio Anequation describing the relationship between the hydrationdegree and water-cement ratio is expressed as follows [5]

120572c = 1199101 (119905) 119890minus(1199102(119905)(WC)) (40)

where 1199101(119905) and 1199102(119905) are the age-related functions and WCis the water-cement ratio

To calculate the degree of cement hydration of the fly ash-cement system the watercement (WC) ratio is replaced bythe effective water binder ratio in (40) In addition the fly ashpozzolanic reactions will occur and generate a new productso the effectivewater binder ratio is replaced byW(C+120572fFA)

120572c = 1199101 (119905) 119890minus(1199102(119905)(W(C+120572f FA))) (41)

The degree of cement hydration of the fly ash-cementsystem can be calculated under various conditions accordingto (41) as shown in Figure 6 It was found by comparing thecuring times in Figure 6 that the degree of cement hydrationwas higher than that of pure cement paste under the sameconditions when fly ash was mixed into the cement pasteWhen the fly ash content increased the hydration degree ofcement increasedThis ismainly because the incorporation of

Deg

ree o

f pur

e cem

ent r

eact

ion

()

WB

1 d3 d7 d

28 d60 d90 d180 d14 d

20

30

40

50

60

70

80

10

03 04 050

Figure 5 Nonevaporable water content of pure cement pastes

fly ash increased the effective water-cement ratio of cementimproving the hydration environment and thus increasingthe hydration degreeThe fly ash contributes to consumptionof the hydration product of cement (Ca(OH)2) and thereforeit is beneficial for the hydration reaction of cement

413 Content of Nonevaporable Water Themeasured resultsof nonevaporable water in fly ash-cement blended pastesunder various conditions are shown in Figure 7 It can beseen in Figure 7 that the nonevaporated water content of flyash-cement pastes with 10 30 and 40 fly ash are higherthan the pure cement paste in addition to the 50 contentAfter 7 d the differences were not significant This may bebecause the nucleation and crystallization of Ca(OH)2 wereinduced by the fine particles of the fly ash thus contributingto cement hydrationWithin a certain range of incorporationthe promotion effects of fly ash exceeded the negative effectsdue to the slow development of the activity of fly ash and asmall number of hydrates The nonevaporable water contentof fly ash-cement pastes will be higher than that of purecement pastes From the nonevaporable water trend theblended pastes of fly ash incorporation of 10sim30 showed thehighest nonevaporable water Zhang et al [32] also found thatfly ash can improve the early hydration rate of cement

Powers [29] proposed that nonevaporable water in purecement paste is one index for the degree of cement hydrationNonevaporable water of the hardened pastes comes mainlyfrom the hydration products Ca(OH)2 and C-S-H gel In thefly ash-cement blended pastes both cement hydration andthe fly ash reaction produce C-S-H and the fly ash can alsoconsume Ca(OH)2 that is produced by the hydration of thecement Therefore it is not appropriate to directly use thenonevaporable water to measure the degree of reaction of theblended pastes

8 Advances in Materials Science and Engineering

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

WB = 03

WB = 035

WB = 04

WB = 045

WB = 05

Deg

ree o

f cem

ent r

eact

ion

()

55

60

65

70

75

80

85

90

FA50

(a) Different WB ratios

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

Deg

ree o

f cem

ent r

eact

ion

()

55

60

65

70

75

80

85

90

WB = 05

FA50FA40FA30FA10

(b) Different fly ash incorporation

Figure 6 The fly ash reaction degree of fly ash-cement system

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

6

8

Non

evap

orab

le w

ater

cont

ent (

)

10

12

14

16

18

WB = 03

WB = 04

WB = 05

FA50

(a) Different WB ratios

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

Non

evap

orab

le w

ater

cont

ent (

)

10

12

14

16

18

20

WB = 05

FA50FA40FA30FA10FA0

(b) Different fly ash incorporation rates

Figure 7 Nonevaporable water contents of the fly ash-cement blended pastes

42 Verifying the Model of Fly Ash-Cement Blended Pastes

421The Equations for the Increased Hydration Degree Valuesof Cement According to the experimental results of the totalamount of nonevaporable water the degree of the fly ashreaction and the degree of increasing cement hydration werecalculated in the fly ash-cement composite systems under

various conditions by (7) and (8) as shown in Figures 8 and9

Figure 8 shows the variation of the degree of hydrationof cement in the blended system with the fly ash addition of50 as the WB ratio changed from 03 to 05 The reactiondegree at every curing age increased linearly with increases oftheWB ratio Figure 9 shows the degree of cement hydration

Advances in Materials Science and Engineering 9

WB

1 d3 d7 d

28 d60 d90 d180 d14 d

055030 035 040 045 050

00

01

02

03

04

05

06

07 FA 50

120572cminus

f

Figure 8 Influence of the WB ratio on the increased degree ofcement hydration

1 d3 d7 d

28 d60 d90 d180 d14 d

00

01

01

02

02

03

03

04

04

05

05

06

06

07

08WB 05

mf

120572cminus

f

Figure 9 Influence of the fly ash content on the increased degree ofcement hydration

with the trend of its fly ash content when the WB ratio was05 It can be observed that the added degree of hydration ofthe cement increased with increases of the fly ash contentWhen the fly ash content was less than 03 the curing agehad little influence on the increased degree of hydration ofthe cementWhen the fly ash content was greater than 03 thedegree of hydration of the cement was significantly improvedwith increasing curing age For example as the curing ageof the fly ash-cement system increased from 1 d to 180 d thevalue of the degree of hydration of the cement increased from007 to 011 when its fly ash content was 01 The increased

value of the degree of hydration of cement improved from034 to 072 when the fly ash content was 05 Clearly theWB ratio fly ash content and curing age can each promotethe degree of hydration of the cement On the one handthis is mainly due to the incorporated fly ash increasing theeffective WB ratio of the cement and improving the cementhydration environment On the other hand this is due to thepostsecondary reactions of fly ash that promptly consume theCa(OH)2 that is generated by the hydration of the cementwhich is advantageous for the hydration reactions of cement

One objective of this study was to predict the increaseddegree of hydration of cement and degree of reaction of flyash in the fly ash-cement blended system with different flyash contents WB ratios and curing periods Based on theresults of Figures 8 and 9 it is concluded that the increasedvalues of the degree of hydration of cement containing addedfly ash and the quantitative relationships among the reactiondegree of fly ash the WB ratio and the fly ash content canbe expressed as follows as determined by multiple regressionanalysis

120572cminusf = 1 minus 119890minus119886(119905minus119887)119888

(42)

119886 = minus305481 + 286722 sdot 119890[034293sdot(WB)] (43a)

119887 = 0 (43b)

119888 = minus1167238 + 113153 sdot 119890[011795sdot(119898f )] (43c)

120572f = 1 minus 119890minus119889(119905minus119891)119892

(44)

119889 = 003869 + 000426 sdot 119890[555391sdot(WB)] (45a)

119891 = 09 (45b)

119892 = minus001487 + 0413 sdot 119890[minus07646sdot(119898f )] (45c)

422 Validation of the Model Figure 10 shows the compar-ison of the experimental results and the predicted valuesfor 120572cminusf The fitted 1198772 coefficient of the regression analysisequation (119910 = 099366119909) is 098849 Figure 11 shows the120572119891 of the experimental and predicted values and the fitted1198772 coefficient of the regression analysis equation (119910 =099552119909) is 099131 The maximum relative errors of Figures10 and 11 are 3096 and 4831 respectively The modelwas consistent with the experimental values Therefore it isreasonable to propose a model for the degree of the fly ashreaction and a model of accelerated hydration of cement forblended systems

The CH content and porosity as key parameters ofthe microstructure were selected to verify the hydrationproducts of fly ash-cement mixtures The results of theexperimental values were obtained from the literature [5] Inthis experiment the CH content of hydrated cement pasteswas determined by thermal gravimetry analysis based onthe ignited weight of the sample The porosity of cement-flyash pastes was obtained by mercury intrusion porosimetryThe CH and porosity values are presented in Section 32Figure 12 presents the comparison between the predicted

10 Advances in Materials Science and Engineering

WB = 03

WB = 04

WB = 05

000000

001

001

002

002

003

003

004

004

Measured value

Pred

icte

d va

lue

Figure 10 The predicted and measured values of the degree ofcement hydration of enhanced cement-fly ash pastes

WB = 03

WB = 035

WB = 04

WB = 045

WB = 05

0000

02

02

04

04

06

06

08

08

10

10

Measured value

Pred

icte

d va

lue

Figure 11 The predicted and measured values of the degree of thefly ash reaction of cement-fly ash pastes

and experimental values of the CH content For differentWB ratios and fly ash content the predicted results camecloser to the experimental values with increasing curingage The maximum relative errors were 135 113 and66 at 7 d 28 d and 90 d respectively Figure 13 showsthe comparison of the predicted and experimental valuesof porosity in fly ash-cement systems For all samples thepredicted values were higher than the measured values Themaximum relative errors were 117 112 and 139 at 7 d28 d and 180 d respectively The main reason is that theporosity of the blended system calculated by the model is

10000

20 40 60 80Age (d)

20

2

4

6

8

10

12

14

16

18

CH (

)

WB = 03 mf = 025 (experiment)WB = 03 mf = 025 (prediction)

(prediction)

(prediction)WB = 03 mf = 055 (experiment)WB = 03 mf = 055

WB = 05 mf = 055 (experiment)WB = 05 mf = 055

Figure 12 The predicted and measured values of CH content ofcement-fly ash pastes

100 150 2000 50Age (d)

20

25

30

35

40

45

50

15

Poro

sity

()

WB = 03 (experiment)WB = 03 (prediction)WB = 04 (experiment)WB = 04 (prediction)WB = 05 (experiment)WB = 05 (prediction)

Figure 13 The predicted and measured values of porosity ofcement-fly ash pastes

the capillary porosity (the porosity contained in the capillarypores and the porosity of the gel) that was obtained bymercury intrusion Therefore with longer curing ages moreC-S-H gel phase was generated by the second hydration of flyash and the differences between the predicted and measuredvalues increased

Advances in Materials Science and Engineering 11

5 Conclusions

(1) The degree of hydration of cement in the pure cementpastes was determined by measuring the nonevap-orablewater contentThedegree of the fly ash reactionin fly ash-cement blended pastes was determinedusing a selective dissolution method

(2) Based on the degree of hydration of cement and theeffectiveWB ratio the degree of hydration of cementin fly ash-cement blended pastes was acquired

(3) A hydration model of fly ash-cement blended pasteshas been established based on the degree of reactionand the hydration products This model incorporatesthe reactions of fly ash and the hydration of cementbut is also influenced by their interactions

Competing Interests

The authors declare that there are no competing interestsregarding the publication of this paper

Acknowledgments

The authors gratefully acknowledge the National Natural Sci-ence Foundation of China (51408597) and the FundamentalResearch Funds for the Central Universities (2014QNA75)

References

[1] K-H Yang Y-B Jung M-S Cho and S-H Tae ldquoEffect ofsupplementary cementitious materials on reduction of CO2emissions from concreterdquo Journal of Cleaner Production vol103 pp 774ndash783 2015

[2] T Sato and J J Beaudoin ldquoEffect of nano-CaCO3 on hydrationof cement containing supplementary cementitious materialsrdquoAdvances in Cement Research vol 23 no 1 pp 33ndash43 2011

[3] Z Liu Y Zhang and Q Jiang ldquoContinuous tracking of therelationship between resistivity and pore structure of cementpastesrdquo Construction and Building Materials vol 53 pp 26ndash312014

[4] R Snellings G Mertens and J Elsen ldquoSupplementary cemen-titious materialsrdquo Reviews in Mineralogy and Geochemistry vol74 pp 211ndash278 2012

[5] L Lam Y L Wong and C S Poon ldquoDegree of hydration andgelspace ratio of high-volume fly ashcement systemsrdquo Cementand Concrete Research vol 30 no 5 pp 747ndash756 2000

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

[7] P Hou S Kawashima D Kong D J Corr J Qian and S PShah ldquoModification effects of colloidal nanoSiO2 on cementhydration and its gel propertyrdquo Composites Part B Engineeringvol 45 no 1 pp 440ndash448 2013

[8] J David Raja Selvam D S Robinson Smart and I DinaharanldquoMicrostructure and some mechanical properties of fly ashparticulate reinforced AA6061 aluminum alloy compositesprepared by compocastingrdquoMaterials amp Design vol 49 pp 28ndash34 2013

[9] R Feldman L R Prudencio Jr and G Chan ldquoRapid chloridepermeability test on blended cement and other concretescorrelations between charge initial current and conductivityrdquoConstruction and Building Materials vol 13 no 3 pp 149ndash1541999

[10] SWM Supit and FU A Shaikh ldquoDurability properties of highvolume fly ash concrete containing nano-silicardquo Materials andStructuresMateriaux et Constructions vol 48 no 8 pp 2431ndash2445 2014

[11] N Neithalath and J Jain ldquoRelating rapid chloride transportparameters of concretes to microstructural features extractedfrom electrical impedancerdquo Cement and Concrete Research vol40 no 7 pp 1041ndash1051 2010

[12] G Land and D Stephan ldquoThe influence of nano-silica on thehydration of ordinary Portland cementrdquo Journal of MaterialsScience vol 47 no 2 pp 1011ndash1017 2012

[13] J Justs M Wyrzykowski F Winnefeld D Bajare and P LuraldquoInfluence of superabsorbent polymers on hydration of cementpastes with low water-to-binder ratiordquo Journal of ThermalAnalysis and Calorimetry vol 115 no 1 pp 425ndash432 2014

[14] Z Liu Y Zhang Q Jiang W Zhang and J Wu ldquoSolid phasespercolation and capillary pores depercolation in hydratingcement pastesrdquo Journal of Materials in Civil Engineering vol 26no 12 Article ID 04014090 2014

[15] B Uzal and L Turanlı ldquoBlended cements containing highvolume of natural zeolites properties hydration and pastemicrostructurerdquo Cement and Concrete Composites vol 34 no1 pp 101ndash109 2012

[16] Y Kocak and S Nas ldquoThe effect of using fly ash on the strengthand hydration characteristics of blended cementsrdquoConstructionand Building Materials vol 73 pp 25ndash32 2014

[17] D D Nguyen L P Devlin P Koshy and C C Sorrell ldquoEffectsof acetic acid on early hydration of Portland cementrdquo Journal ofThermal Analysis and Calorimetry vol 123 no 1 pp 489ndash4992016

[18] D P Bentz R J Detwiler E J Garboczi P Halamickova andM Schwartz ldquoMulti-scale modeling of the diffusivity of mortarand concreterdquo in Proceedings of the Chloride Penetration intoConcrete LONilsson and J POllivier Eds pp 85ndash94 RILEM1997

[19] M W Grutzeck D Shi G Liu and S Kwan ldquoComputer sim-ulation of interfacial packing in concreterdquo Journal of MaterialsScience vol 28 no 13 pp 3444ndash3450 1993

[20] D P Bentz ldquoInfluence of silica fume on diffusivity in cement-based materials II Multi-scale modeling of concrete diffusiv-ityrdquo Cement and Concrete Research vol 30 no 7 pp 1121ndash11292000

[21] M Voltolini M C Dalconi G Artioli et al ldquoUnderstandingcement hydration at the microscale new opportunities fromlsquopencil-beamrsquo synchrotron X-ray diffraction tomographyrdquo Jour-nal of Applied Crystallography vol 46 no 1 pp 142ndash152 2013

[22] Z Liu W Chen Y Zhang and H Lv ldquoA three-dimensionalmulti-scale method to simulate the ion transport behavior ofcement-based materialsrdquo Construction amp Building Materialsvol 120 pp 494ndash503 2016

[23] B A Suprenant and G Papadopoulos ldquoSelective dissolutionof portland-fly-ash cementsrdquo Journal of Materials in CivilEngineering vol 3 no 1 pp 48ndash59 1991

[24] D P Bentz E J Garboczi and K A Snyder ldquoA hard coresoftshell microstructural model for studying percolation and trans-port in three-dimensional compositemediardquo NISTIR 6265 USDepartment of Commerce 1999

12 Advances in Materials Science and Engineering

[25] X-Y Wang H-S Lee and K-B Park ldquoSimulation of low-calcium fly ash blended cement hydrationrdquo ACI MaterialsJournal vol 106 no 2 pp 167ndash175 2009

[26] Q Zeng K Li T Fen-Chong and P Dangla ldquoDeterminationof cement hydration and pozzolanic reaction extents for fly-ashcement pastesrdquo Construction and Building Materials vol 27 no1 pp 560ndash569 2012

[27] AMNeville Properties of Concrete AddisonWesley LongmanEssex UK 4th edition 1996

[28] C C Yang ldquoThe relationship between charge passed and thechloride concentrations in anode and cathode cells using theaccelerated chloride migration testrdquo Materials and Structuresvol 36 no 264 pp 678ndash684 2003

[29] T C Powers ldquoStructure and physical properties of hardenedportland cement pasterdquo Journal of the American Ceramic Soci-ety vol 41 no 1 pp 1ndash6 1958

[30] V G Papadakis ldquoEffect of fly ash on Portland cement systemspart I Low-calcium fly ashrdquoCement and Concrete Research vol29 no 11 pp 1727ndash1736 1999

[31] A Xu and S L Sarkar ldquoMicrostructural development in high-volume fly-ash cement systemrdquo Journal of Materials in CivilEngineering vol 6 no 1 pp 117ndash136 1994

[32] YM ZhangW Sun andHD Yan ldquoHydration of high-volumefly ash cement pastesrdquoCement and Concrete Composites vol 22no 6 pp 445ndash452 2000

Submit your manuscripts athttpswwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

8 Advances in Materials Science and Engineering

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

WB = 03

WB = 035

WB = 04

WB = 045

WB = 05

Deg

ree o

f cem

ent r

eact

ion

()

55

60

65

70

75

80

85

90

FA50

(a) Different WB ratios

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

Deg

ree o

f cem

ent r

eact

ion

()

55

60

65

70

75

80

85

90

WB = 05

FA50FA40FA30FA10

(b) Different fly ash incorporation

Figure 6 The fly ash reaction degree of fly ash-cement system

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

6

8

Non

evap

orab

le w

ater

cont

ent (

)

10

12

14

16

18

WB = 03

WB = 04

WB = 05

FA50

(a) Different WB ratios

0 20 40 60 80 100 120 140 160 180 200Curing time (d)

Non

evap

orab

le w

ater

cont

ent (

)

10

12

14

16

18

20

WB = 05

FA50FA40FA30FA10FA0

(b) Different fly ash incorporation rates

Figure 7 Nonevaporable water contents of the fly ash-cement blended pastes

42 Verifying the Model of Fly Ash-Cement Blended Pastes

421The Equations for the Increased Hydration Degree Valuesof Cement According to the experimental results of the totalamount of nonevaporable water the degree of the fly ashreaction and the degree of increasing cement hydration werecalculated in the fly ash-cement composite systems under

various conditions by (7) and (8) as shown in Figures 8 and9

Figure 8 shows the variation of the degree of hydrationof cement in the blended system with the fly ash addition of50 as the WB ratio changed from 03 to 05 The reactiondegree at every curing age increased linearly with increases oftheWB ratio Figure 9 shows the degree of cement hydration

Advances in Materials Science and Engineering 9

WB

1 d3 d7 d

28 d60 d90 d180 d14 d

055030 035 040 045 050

00

01

02

03

04

05

06

07 FA 50

120572cminus

f

Figure 8 Influence of the WB ratio on the increased degree ofcement hydration

1 d3 d7 d

28 d60 d90 d180 d14 d

00

01

01

02

02

03

03

04

04

05

05

06

06

07

08WB 05

mf

120572cminus

f

Figure 9 Influence of the fly ash content on the increased degree ofcement hydration

with the trend of its fly ash content when the WB ratio was05 It can be observed that the added degree of hydration ofthe cement increased with increases of the fly ash contentWhen the fly ash content was less than 03 the curing agehad little influence on the increased degree of hydration ofthe cementWhen the fly ash content was greater than 03 thedegree of hydration of the cement was significantly improvedwith increasing curing age For example as the curing ageof the fly ash-cement system increased from 1 d to 180 d thevalue of the degree of hydration of the cement increased from007 to 011 when its fly ash content was 01 The increased

value of the degree of hydration of cement improved from034 to 072 when the fly ash content was 05 Clearly theWB ratio fly ash content and curing age can each promotethe degree of hydration of the cement On the one handthis is mainly due to the incorporated fly ash increasing theeffective WB ratio of the cement and improving the cementhydration environment On the other hand this is due to thepostsecondary reactions of fly ash that promptly consume theCa(OH)2 that is generated by the hydration of the cementwhich is advantageous for the hydration reactions of cement

One objective of this study was to predict the increaseddegree of hydration of cement and degree of reaction of flyash in the fly ash-cement blended system with different flyash contents WB ratios and curing periods Based on theresults of Figures 8 and 9 it is concluded that the increasedvalues of the degree of hydration of cement containing addedfly ash and the quantitative relationships among the reactiondegree of fly ash the WB ratio and the fly ash content canbe expressed as follows as determined by multiple regressionanalysis

120572cminusf = 1 minus 119890minus119886(119905minus119887)119888

(42)

119886 = minus305481 + 286722 sdot 119890[034293sdot(WB)] (43a)

119887 = 0 (43b)

119888 = minus1167238 + 113153 sdot 119890[011795sdot(119898f )] (43c)

120572f = 1 minus 119890minus119889(119905minus119891)119892

(44)

119889 = 003869 + 000426 sdot 119890[555391sdot(WB)] (45a)

119891 = 09 (45b)

119892 = minus001487 + 0413 sdot 119890[minus07646sdot(119898f )] (45c)

422 Validation of the Model Figure 10 shows the compar-ison of the experimental results and the predicted valuesfor 120572cminusf The fitted 1198772 coefficient of the regression analysisequation (119910 = 099366119909) is 098849 Figure 11 shows the120572119891 of the experimental and predicted values and the fitted1198772 coefficient of the regression analysis equation (119910 =099552119909) is 099131 The maximum relative errors of Figures10 and 11 are 3096 and 4831 respectively The modelwas consistent with the experimental values Therefore it isreasonable to propose a model for the degree of the fly ashreaction and a model of accelerated hydration of cement forblended systems

The CH content and porosity as key parameters ofthe microstructure were selected to verify the hydrationproducts of fly ash-cement mixtures The results of theexperimental values were obtained from the literature [5] Inthis experiment the CH content of hydrated cement pasteswas determined by thermal gravimetry analysis based onthe ignited weight of the sample The porosity of cement-flyash pastes was obtained by mercury intrusion porosimetryThe CH and porosity values are presented in Section 32Figure 12 presents the comparison between the predicted

10 Advances in Materials Science and Engineering

WB = 03

WB = 04

WB = 05

000000

001

001

002

002

003

003

004

004

Measured value

Pred

icte

d va

lue

Figure 10 The predicted and measured values of the degree ofcement hydration of enhanced cement-fly ash pastes

WB = 03

WB = 035

WB = 04

WB = 045

WB = 05

0000

02

02

04

04

06

06

08

08

10

10

Measured value

Pred

icte

d va

lue

Figure 11 The predicted and measured values of the degree of thefly ash reaction of cement-fly ash pastes

and experimental values of the CH content For differentWB ratios and fly ash content the predicted results camecloser to the experimental values with increasing curingage The maximum relative errors were 135 113 and66 at 7 d 28 d and 90 d respectively Figure 13 showsthe comparison of the predicted and experimental valuesof porosity in fly ash-cement systems For all samples thepredicted values were higher than the measured values Themaximum relative errors were 117 112 and 139 at 7 d28 d and 180 d respectively The main reason is that theporosity of the blended system calculated by the model is

10000

20 40 60 80Age (d)

20

2

4

6

8

10

12

14

16

18

CH (

)

WB = 03 mf = 025 (experiment)WB = 03 mf = 025 (prediction)

(prediction)

(prediction)WB = 03 mf = 055 (experiment)WB = 03 mf = 055

WB = 05 mf = 055 (experiment)WB = 05 mf = 055

Figure 12 The predicted and measured values of CH content ofcement-fly ash pastes

100 150 2000 50Age (d)

20

25

30

35

40

45

50

15

Poro

sity

()

WB = 03 (experiment)WB = 03 (prediction)WB = 04 (experiment)WB = 04 (prediction)WB = 05 (experiment)WB = 05 (prediction)

Figure 13 The predicted and measured values of porosity ofcement-fly ash pastes

the capillary porosity (the porosity contained in the capillarypores and the porosity of the gel) that was obtained bymercury intrusion Therefore with longer curing ages moreC-S-H gel phase was generated by the second hydration of flyash and the differences between the predicted and measuredvalues increased

Advances in Materials Science and Engineering 11

5 Conclusions

(1) The degree of hydration of cement in the pure cementpastes was determined by measuring the nonevap-orablewater contentThedegree of the fly ash reactionin fly ash-cement blended pastes was determinedusing a selective dissolution method

(2) Based on the degree of hydration of cement and theeffectiveWB ratio the degree of hydration of cementin fly ash-cement blended pastes was acquired

(3) A hydration model of fly ash-cement blended pasteshas been established based on the degree of reactionand the hydration products This model incorporatesthe reactions of fly ash and the hydration of cementbut is also influenced by their interactions

Competing Interests

The authors declare that there are no competing interestsregarding the publication of this paper

Acknowledgments

The authors gratefully acknowledge the National Natural Sci-ence Foundation of China (51408597) and the FundamentalResearch Funds for the Central Universities (2014QNA75)

References

[1] K-H Yang Y-B Jung M-S Cho and S-H Tae ldquoEffect ofsupplementary cementitious materials on reduction of CO2emissions from concreterdquo Journal of Cleaner Production vol103 pp 774ndash783 2015

[2] T Sato and J J Beaudoin ldquoEffect of nano-CaCO3 on hydrationof cement containing supplementary cementitious materialsrdquoAdvances in Cement Research vol 23 no 1 pp 33ndash43 2011

[3] Z Liu Y Zhang and Q Jiang ldquoContinuous tracking of therelationship between resistivity and pore structure of cementpastesrdquo Construction and Building Materials vol 53 pp 26ndash312014

[4] R Snellings G Mertens and J Elsen ldquoSupplementary cemen-titious materialsrdquo Reviews in Mineralogy and Geochemistry vol74 pp 211ndash278 2012

[5] L Lam Y L Wong and C S Poon ldquoDegree of hydration andgelspace ratio of high-volume fly ashcement systemsrdquo Cementand Concrete Research vol 30 no 5 pp 747ndash756 2000

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

[7] P Hou S Kawashima D Kong D J Corr J Qian and S PShah ldquoModification effects of colloidal nanoSiO2 on cementhydration and its gel propertyrdquo Composites Part B Engineeringvol 45 no 1 pp 440ndash448 2013

[8] J David Raja Selvam D S Robinson Smart and I DinaharanldquoMicrostructure and some mechanical properties of fly ashparticulate reinforced AA6061 aluminum alloy compositesprepared by compocastingrdquoMaterials amp Design vol 49 pp 28ndash34 2013

[9] R Feldman L R Prudencio Jr and G Chan ldquoRapid chloridepermeability test on blended cement and other concretescorrelations between charge initial current and conductivityrdquoConstruction and Building Materials vol 13 no 3 pp 149ndash1541999

[10] SWM Supit and FU A Shaikh ldquoDurability properties of highvolume fly ash concrete containing nano-silicardquo Materials andStructuresMateriaux et Constructions vol 48 no 8 pp 2431ndash2445 2014

[11] N Neithalath and J Jain ldquoRelating rapid chloride transportparameters of concretes to microstructural features extractedfrom electrical impedancerdquo Cement and Concrete Research vol40 no 7 pp 1041ndash1051 2010

[12] G Land and D Stephan ldquoThe influence of nano-silica on thehydration of ordinary Portland cementrdquo Journal of MaterialsScience vol 47 no 2 pp 1011ndash1017 2012

[13] J Justs M Wyrzykowski F Winnefeld D Bajare and P LuraldquoInfluence of superabsorbent polymers on hydration of cementpastes with low water-to-binder ratiordquo Journal of ThermalAnalysis and Calorimetry vol 115 no 1 pp 425ndash432 2014

[14] Z Liu Y Zhang Q Jiang W Zhang and J Wu ldquoSolid phasespercolation and capillary pores depercolation in hydratingcement pastesrdquo Journal of Materials in Civil Engineering vol 26no 12 Article ID 04014090 2014

[15] B Uzal and L Turanlı ldquoBlended cements containing highvolume of natural zeolites properties hydration and pastemicrostructurerdquo Cement and Concrete Composites vol 34 no1 pp 101ndash109 2012

[16] Y Kocak and S Nas ldquoThe effect of using fly ash on the strengthand hydration characteristics of blended cementsrdquoConstructionand Building Materials vol 73 pp 25ndash32 2014

[17] D D Nguyen L P Devlin P Koshy and C C Sorrell ldquoEffectsof acetic acid on early hydration of Portland cementrdquo Journal ofThermal Analysis and Calorimetry vol 123 no 1 pp 489ndash4992016

[18] D P Bentz R J Detwiler E J Garboczi P Halamickova andM Schwartz ldquoMulti-scale modeling of the diffusivity of mortarand concreterdquo in Proceedings of the Chloride Penetration intoConcrete LONilsson and J POllivier Eds pp 85ndash94 RILEM1997

[19] M W Grutzeck D Shi G Liu and S Kwan ldquoComputer sim-ulation of interfacial packing in concreterdquo Journal of MaterialsScience vol 28 no 13 pp 3444ndash3450 1993

[20] D P Bentz ldquoInfluence of silica fume on diffusivity in cement-based materials II Multi-scale modeling of concrete diffusiv-ityrdquo Cement and Concrete Research vol 30 no 7 pp 1121ndash11292000

[21] M Voltolini M C Dalconi G Artioli et al ldquoUnderstandingcement hydration at the microscale new opportunities fromlsquopencil-beamrsquo synchrotron X-ray diffraction tomographyrdquo Jour-nal of Applied Crystallography vol 46 no 1 pp 142ndash152 2013

[22] Z Liu W Chen Y Zhang and H Lv ldquoA three-dimensionalmulti-scale method to simulate the ion transport behavior ofcement-based materialsrdquo Construction amp Building Materialsvol 120 pp 494ndash503 2016

[23] B A Suprenant and G Papadopoulos ldquoSelective dissolutionof portland-fly-ash cementsrdquo Journal of Materials in CivilEngineering vol 3 no 1 pp 48ndash59 1991

[24] D P Bentz E J Garboczi and K A Snyder ldquoA hard coresoftshell microstructural model for studying percolation and trans-port in three-dimensional compositemediardquo NISTIR 6265 USDepartment of Commerce 1999

12 Advances in Materials Science and Engineering

[25] X-Y Wang H-S Lee and K-B Park ldquoSimulation of low-calcium fly ash blended cement hydrationrdquo ACI MaterialsJournal vol 106 no 2 pp 167ndash175 2009

[26] Q Zeng K Li T Fen-Chong and P Dangla ldquoDeterminationof cement hydration and pozzolanic reaction extents for fly-ashcement pastesrdquo Construction and Building Materials vol 27 no1 pp 560ndash569 2012

[27] AMNeville Properties of Concrete AddisonWesley LongmanEssex UK 4th edition 1996

[28] C C Yang ldquoThe relationship between charge passed and thechloride concentrations in anode and cathode cells using theaccelerated chloride migration testrdquo Materials and Structuresvol 36 no 264 pp 678ndash684 2003

[29] T C Powers ldquoStructure and physical properties of hardenedportland cement pasterdquo Journal of the American Ceramic Soci-ety vol 41 no 1 pp 1ndash6 1958

[30] V G Papadakis ldquoEffect of fly ash on Portland cement systemspart I Low-calcium fly ashrdquoCement and Concrete Research vol29 no 11 pp 1727ndash1736 1999

[31] A Xu and S L Sarkar ldquoMicrostructural development in high-volume fly-ash cement systemrdquo Journal of Materials in CivilEngineering vol 6 no 1 pp 117ndash136 1994

[32] YM ZhangW Sun andHD Yan ldquoHydration of high-volumefly ash cement pastesrdquoCement and Concrete Composites vol 22no 6 pp 445ndash452 2000

Submit your manuscripts athttpswwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Advances in Materials Science and Engineering 9

WB

1 d3 d7 d

28 d60 d90 d180 d14 d

055030 035 040 045 050

00

01

02

03

04

05

06

07 FA 50

120572cminus

f

Figure 8 Influence of the WB ratio on the increased degree ofcement hydration

1 d3 d7 d

28 d60 d90 d180 d14 d

00

01

01

02

02

03

03

04

04

05

05

06

06

07

08WB 05

mf

120572cminus

f

Figure 9 Influence of the fly ash content on the increased degree ofcement hydration

with the trend of its fly ash content when the WB ratio was05 It can be observed that the added degree of hydration ofthe cement increased with increases of the fly ash contentWhen the fly ash content was less than 03 the curing agehad little influence on the increased degree of hydration ofthe cementWhen the fly ash content was greater than 03 thedegree of hydration of the cement was significantly improvedwith increasing curing age For example as the curing ageof the fly ash-cement system increased from 1 d to 180 d thevalue of the degree of hydration of the cement increased from007 to 011 when its fly ash content was 01 The increased

value of the degree of hydration of cement improved from034 to 072 when the fly ash content was 05 Clearly theWB ratio fly ash content and curing age can each promotethe degree of hydration of the cement On the one handthis is mainly due to the incorporated fly ash increasing theeffective WB ratio of the cement and improving the cementhydration environment On the other hand this is due to thepostsecondary reactions of fly ash that promptly consume theCa(OH)2 that is generated by the hydration of the cementwhich is advantageous for the hydration reactions of cement

One objective of this study was to predict the increaseddegree of hydration of cement and degree of reaction of flyash in the fly ash-cement blended system with different flyash contents WB ratios and curing periods Based on theresults of Figures 8 and 9 it is concluded that the increasedvalues of the degree of hydration of cement containing addedfly ash and the quantitative relationships among the reactiondegree of fly ash the WB ratio and the fly ash content canbe expressed as follows as determined by multiple regressionanalysis

120572cminusf = 1 minus 119890minus119886(119905minus119887)119888

(42)

119886 = minus305481 + 286722 sdot 119890[034293sdot(WB)] (43a)

119887 = 0 (43b)

119888 = minus1167238 + 113153 sdot 119890[011795sdot(119898f )] (43c)

120572f = 1 minus 119890minus119889(119905minus119891)119892

(44)

119889 = 003869 + 000426 sdot 119890[555391sdot(WB)] (45a)

119891 = 09 (45b)

119892 = minus001487 + 0413 sdot 119890[minus07646sdot(119898f )] (45c)

422 Validation of the Model Figure 10 shows the compar-ison of the experimental results and the predicted valuesfor 120572cminusf The fitted 1198772 coefficient of the regression analysisequation (119910 = 099366119909) is 098849 Figure 11 shows the120572119891 of the experimental and predicted values and the fitted1198772 coefficient of the regression analysis equation (119910 =099552119909) is 099131 The maximum relative errors of Figures10 and 11 are 3096 and 4831 respectively The modelwas consistent with the experimental values Therefore it isreasonable to propose a model for the degree of the fly ashreaction and a model of accelerated hydration of cement forblended systems

The CH content and porosity as key parameters ofthe microstructure were selected to verify the hydrationproducts of fly ash-cement mixtures The results of theexperimental values were obtained from the literature [5] Inthis experiment the CH content of hydrated cement pasteswas determined by thermal gravimetry analysis based onthe ignited weight of the sample The porosity of cement-flyash pastes was obtained by mercury intrusion porosimetryThe CH and porosity values are presented in Section 32Figure 12 presents the comparison between the predicted

10 Advances in Materials Science and Engineering

WB = 03

WB = 04

WB = 05

000000

001

001

002

002

003

003

004

004

Measured value

Pred

icte

d va

lue

Figure 10 The predicted and measured values of the degree ofcement hydration of enhanced cement-fly ash pastes

WB = 03

WB = 035

WB = 04

WB = 045

WB = 05

0000

02

02

04

04

06

06

08

08

10

10

Measured value

Pred

icte

d va

lue

Figure 11 The predicted and measured values of the degree of thefly ash reaction of cement-fly ash pastes

and experimental values of the CH content For differentWB ratios and fly ash content the predicted results camecloser to the experimental values with increasing curingage The maximum relative errors were 135 113 and66 at 7 d 28 d and 90 d respectively Figure 13 showsthe comparison of the predicted and experimental valuesof porosity in fly ash-cement systems For all samples thepredicted values were higher than the measured values Themaximum relative errors were 117 112 and 139 at 7 d28 d and 180 d respectively The main reason is that theporosity of the blended system calculated by the model is

10000

20 40 60 80Age (d)

20

2

4

6

8

10

12

14

16

18

CH (

)

WB = 03 mf = 025 (experiment)WB = 03 mf = 025 (prediction)

(prediction)

(prediction)WB = 03 mf = 055 (experiment)WB = 03 mf = 055

WB = 05 mf = 055 (experiment)WB = 05 mf = 055

Figure 12 The predicted and measured values of CH content ofcement-fly ash pastes

100 150 2000 50Age (d)

20

25

30

35

40

45

50

15

Poro

sity

()

WB = 03 (experiment)WB = 03 (prediction)WB = 04 (experiment)WB = 04 (prediction)WB = 05 (experiment)WB = 05 (prediction)

Figure 13 The predicted and measured values of porosity ofcement-fly ash pastes

the capillary porosity (the porosity contained in the capillarypores and the porosity of the gel) that was obtained bymercury intrusion Therefore with longer curing ages moreC-S-H gel phase was generated by the second hydration of flyash and the differences between the predicted and measuredvalues increased

Advances in Materials Science and Engineering 11

5 Conclusions

(1) The degree of hydration of cement in the pure cementpastes was determined by measuring the nonevap-orablewater contentThedegree of the fly ash reactionin fly ash-cement blended pastes was determinedusing a selective dissolution method

(2) Based on the degree of hydration of cement and theeffectiveWB ratio the degree of hydration of cementin fly ash-cement blended pastes was acquired

(3) A hydration model of fly ash-cement blended pasteshas been established based on the degree of reactionand the hydration products This model incorporatesthe reactions of fly ash and the hydration of cementbut is also influenced by their interactions

Competing Interests

The authors declare that there are no competing interestsregarding the publication of this paper

Acknowledgments

The authors gratefully acknowledge the National Natural Sci-ence Foundation of China (51408597) and the FundamentalResearch Funds for the Central Universities (2014QNA75)

References

[1] K-H Yang Y-B Jung M-S Cho and S-H Tae ldquoEffect ofsupplementary cementitious materials on reduction of CO2emissions from concreterdquo Journal of Cleaner Production vol103 pp 774ndash783 2015

[2] T Sato and J J Beaudoin ldquoEffect of nano-CaCO3 on hydrationof cement containing supplementary cementitious materialsrdquoAdvances in Cement Research vol 23 no 1 pp 33ndash43 2011

[3] Z Liu Y Zhang and Q Jiang ldquoContinuous tracking of therelationship between resistivity and pore structure of cementpastesrdquo Construction and Building Materials vol 53 pp 26ndash312014

[4] R Snellings G Mertens and J Elsen ldquoSupplementary cemen-titious materialsrdquo Reviews in Mineralogy and Geochemistry vol74 pp 211ndash278 2012

[5] L Lam Y L Wong and C S Poon ldquoDegree of hydration andgelspace ratio of high-volume fly ashcement systemsrdquo Cementand Concrete Research vol 30 no 5 pp 747ndash756 2000

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

[7] P Hou S Kawashima D Kong D J Corr J Qian and S PShah ldquoModification effects of colloidal nanoSiO2 on cementhydration and its gel propertyrdquo Composites Part B Engineeringvol 45 no 1 pp 440ndash448 2013

[8] J David Raja Selvam D S Robinson Smart and I DinaharanldquoMicrostructure and some mechanical properties of fly ashparticulate reinforced AA6061 aluminum alloy compositesprepared by compocastingrdquoMaterials amp Design vol 49 pp 28ndash34 2013

[9] R Feldman L R Prudencio Jr and G Chan ldquoRapid chloridepermeability test on blended cement and other concretescorrelations between charge initial current and conductivityrdquoConstruction and Building Materials vol 13 no 3 pp 149ndash1541999

[10] SWM Supit and FU A Shaikh ldquoDurability properties of highvolume fly ash concrete containing nano-silicardquo Materials andStructuresMateriaux et Constructions vol 48 no 8 pp 2431ndash2445 2014

[11] N Neithalath and J Jain ldquoRelating rapid chloride transportparameters of concretes to microstructural features extractedfrom electrical impedancerdquo Cement and Concrete Research vol40 no 7 pp 1041ndash1051 2010

[12] G Land and D Stephan ldquoThe influence of nano-silica on thehydration of ordinary Portland cementrdquo Journal of MaterialsScience vol 47 no 2 pp 1011ndash1017 2012

[13] J Justs M Wyrzykowski F Winnefeld D Bajare and P LuraldquoInfluence of superabsorbent polymers on hydration of cementpastes with low water-to-binder ratiordquo Journal of ThermalAnalysis and Calorimetry vol 115 no 1 pp 425ndash432 2014

[14] Z Liu Y Zhang Q Jiang W Zhang and J Wu ldquoSolid phasespercolation and capillary pores depercolation in hydratingcement pastesrdquo Journal of Materials in Civil Engineering vol 26no 12 Article ID 04014090 2014

[15] B Uzal and L Turanlı ldquoBlended cements containing highvolume of natural zeolites properties hydration and pastemicrostructurerdquo Cement and Concrete Composites vol 34 no1 pp 101ndash109 2012

[16] Y Kocak and S Nas ldquoThe effect of using fly ash on the strengthand hydration characteristics of blended cementsrdquoConstructionand Building Materials vol 73 pp 25ndash32 2014

[17] D D Nguyen L P Devlin P Koshy and C C Sorrell ldquoEffectsof acetic acid on early hydration of Portland cementrdquo Journal ofThermal Analysis and Calorimetry vol 123 no 1 pp 489ndash4992016

[18] D P Bentz R J Detwiler E J Garboczi P Halamickova andM Schwartz ldquoMulti-scale modeling of the diffusivity of mortarand concreterdquo in Proceedings of the Chloride Penetration intoConcrete LONilsson and J POllivier Eds pp 85ndash94 RILEM1997

[19] M W Grutzeck D Shi G Liu and S Kwan ldquoComputer sim-ulation of interfacial packing in concreterdquo Journal of MaterialsScience vol 28 no 13 pp 3444ndash3450 1993

[20] D P Bentz ldquoInfluence of silica fume on diffusivity in cement-based materials II Multi-scale modeling of concrete diffusiv-ityrdquo Cement and Concrete Research vol 30 no 7 pp 1121ndash11292000

[21] M Voltolini M C Dalconi G Artioli et al ldquoUnderstandingcement hydration at the microscale new opportunities fromlsquopencil-beamrsquo synchrotron X-ray diffraction tomographyrdquo Jour-nal of Applied Crystallography vol 46 no 1 pp 142ndash152 2013

[22] Z Liu W Chen Y Zhang and H Lv ldquoA three-dimensionalmulti-scale method to simulate the ion transport behavior ofcement-based materialsrdquo Construction amp Building Materialsvol 120 pp 494ndash503 2016

[23] B A Suprenant and G Papadopoulos ldquoSelective dissolutionof portland-fly-ash cementsrdquo Journal of Materials in CivilEngineering vol 3 no 1 pp 48ndash59 1991

[24] D P Bentz E J Garboczi and K A Snyder ldquoA hard coresoftshell microstructural model for studying percolation and trans-port in three-dimensional compositemediardquo NISTIR 6265 USDepartment of Commerce 1999

12 Advances in Materials Science and Engineering

[25] X-Y Wang H-S Lee and K-B Park ldquoSimulation of low-calcium fly ash blended cement hydrationrdquo ACI MaterialsJournal vol 106 no 2 pp 167ndash175 2009

[26] Q Zeng K Li T Fen-Chong and P Dangla ldquoDeterminationof cement hydration and pozzolanic reaction extents for fly-ashcement pastesrdquo Construction and Building Materials vol 27 no1 pp 560ndash569 2012

[27] AMNeville Properties of Concrete AddisonWesley LongmanEssex UK 4th edition 1996

[28] C C Yang ldquoThe relationship between charge passed and thechloride concentrations in anode and cathode cells using theaccelerated chloride migration testrdquo Materials and Structuresvol 36 no 264 pp 678ndash684 2003

[29] T C Powers ldquoStructure and physical properties of hardenedportland cement pasterdquo Journal of the American Ceramic Soci-ety vol 41 no 1 pp 1ndash6 1958

[30] V G Papadakis ldquoEffect of fly ash on Portland cement systemspart I Low-calcium fly ashrdquoCement and Concrete Research vol29 no 11 pp 1727ndash1736 1999

[31] A Xu and S L Sarkar ldquoMicrostructural development in high-volume fly-ash cement systemrdquo Journal of Materials in CivilEngineering vol 6 no 1 pp 117ndash136 1994

[32] YM ZhangW Sun andHD Yan ldquoHydration of high-volumefly ash cement pastesrdquoCement and Concrete Composites vol 22no 6 pp 445ndash452 2000

Submit your manuscripts athttpswwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

10 Advances in Materials Science and Engineering

WB = 03

WB = 04

WB = 05

000000

001

001

002

002

003

003

004

004

Measured value

Pred

icte

d va

lue

Figure 10 The predicted and measured values of the degree ofcement hydration of enhanced cement-fly ash pastes

WB = 03

WB = 035

WB = 04

WB = 045

WB = 05

0000

02

02

04

04

06

06

08

08

10

10

Measured value

Pred

icte

d va

lue

Figure 11 The predicted and measured values of the degree of thefly ash reaction of cement-fly ash pastes

and experimental values of the CH content For differentWB ratios and fly ash content the predicted results camecloser to the experimental values with increasing curingage The maximum relative errors were 135 113 and66 at 7 d 28 d and 90 d respectively Figure 13 showsthe comparison of the predicted and experimental valuesof porosity in fly ash-cement systems For all samples thepredicted values were higher than the measured values Themaximum relative errors were 117 112 and 139 at 7 d28 d and 180 d respectively The main reason is that theporosity of the blended system calculated by the model is

10000

20 40 60 80Age (d)

20

2

4

6

8

10

12

14

16

18

CH (

)

WB = 03 mf = 025 (experiment)WB = 03 mf = 025 (prediction)

(prediction)

(prediction)WB = 03 mf = 055 (experiment)WB = 03 mf = 055

WB = 05 mf = 055 (experiment)WB = 05 mf = 055

Figure 12 The predicted and measured values of CH content ofcement-fly ash pastes

100 150 2000 50Age (d)

20

25

30

35

40

45

50

15

Poro

sity

()

WB = 03 (experiment)WB = 03 (prediction)WB = 04 (experiment)WB = 04 (prediction)WB = 05 (experiment)WB = 05 (prediction)

Figure 13 The predicted and measured values of porosity ofcement-fly ash pastes

the capillary porosity (the porosity contained in the capillarypores and the porosity of the gel) that was obtained bymercury intrusion Therefore with longer curing ages moreC-S-H gel phase was generated by the second hydration of flyash and the differences between the predicted and measuredvalues increased

Advances in Materials Science and Engineering 11

5 Conclusions

(1) The degree of hydration of cement in the pure cementpastes was determined by measuring the nonevap-orablewater contentThedegree of the fly ash reactionin fly ash-cement blended pastes was determinedusing a selective dissolution method

(2) Based on the degree of hydration of cement and theeffectiveWB ratio the degree of hydration of cementin fly ash-cement blended pastes was acquired

(3) A hydration model of fly ash-cement blended pasteshas been established based on the degree of reactionand the hydration products This model incorporatesthe reactions of fly ash and the hydration of cementbut is also influenced by their interactions

Competing Interests

The authors declare that there are no competing interestsregarding the publication of this paper

Acknowledgments

The authors gratefully acknowledge the National Natural Sci-ence Foundation of China (51408597) and the FundamentalResearch Funds for the Central Universities (2014QNA75)

References

[1] K-H Yang Y-B Jung M-S Cho and S-H Tae ldquoEffect ofsupplementary cementitious materials on reduction of CO2emissions from concreterdquo Journal of Cleaner Production vol103 pp 774ndash783 2015

[2] T Sato and J J Beaudoin ldquoEffect of nano-CaCO3 on hydrationof cement containing supplementary cementitious materialsrdquoAdvances in Cement Research vol 23 no 1 pp 33ndash43 2011

[3] Z Liu Y Zhang and Q Jiang ldquoContinuous tracking of therelationship between resistivity and pore structure of cementpastesrdquo Construction and Building Materials vol 53 pp 26ndash312014

[4] R Snellings G Mertens and J Elsen ldquoSupplementary cemen-titious materialsrdquo Reviews in Mineralogy and Geochemistry vol74 pp 211ndash278 2012

[5] L Lam Y L Wong and C S Poon ldquoDegree of hydration andgelspace ratio of high-volume fly ashcement systemsrdquo Cementand Concrete Research vol 30 no 5 pp 747ndash756 2000

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

[7] P Hou S Kawashima D Kong D J Corr J Qian and S PShah ldquoModification effects of colloidal nanoSiO2 on cementhydration and its gel propertyrdquo Composites Part B Engineeringvol 45 no 1 pp 440ndash448 2013

[8] J David Raja Selvam D S Robinson Smart and I DinaharanldquoMicrostructure and some mechanical properties of fly ashparticulate reinforced AA6061 aluminum alloy compositesprepared by compocastingrdquoMaterials amp Design vol 49 pp 28ndash34 2013

[9] R Feldman L R Prudencio Jr and G Chan ldquoRapid chloridepermeability test on blended cement and other concretescorrelations between charge initial current and conductivityrdquoConstruction and Building Materials vol 13 no 3 pp 149ndash1541999

[10] SWM Supit and FU A Shaikh ldquoDurability properties of highvolume fly ash concrete containing nano-silicardquo Materials andStructuresMateriaux et Constructions vol 48 no 8 pp 2431ndash2445 2014

[11] N Neithalath and J Jain ldquoRelating rapid chloride transportparameters of concretes to microstructural features extractedfrom electrical impedancerdquo Cement and Concrete Research vol40 no 7 pp 1041ndash1051 2010

[12] G Land and D Stephan ldquoThe influence of nano-silica on thehydration of ordinary Portland cementrdquo Journal of MaterialsScience vol 47 no 2 pp 1011ndash1017 2012

[13] J Justs M Wyrzykowski F Winnefeld D Bajare and P LuraldquoInfluence of superabsorbent polymers on hydration of cementpastes with low water-to-binder ratiordquo Journal of ThermalAnalysis and Calorimetry vol 115 no 1 pp 425ndash432 2014

[14] Z Liu Y Zhang Q Jiang W Zhang and J Wu ldquoSolid phasespercolation and capillary pores depercolation in hydratingcement pastesrdquo Journal of Materials in Civil Engineering vol 26no 12 Article ID 04014090 2014

[15] B Uzal and L Turanlı ldquoBlended cements containing highvolume of natural zeolites properties hydration and pastemicrostructurerdquo Cement and Concrete Composites vol 34 no1 pp 101ndash109 2012

[16] Y Kocak and S Nas ldquoThe effect of using fly ash on the strengthand hydration characteristics of blended cementsrdquoConstructionand Building Materials vol 73 pp 25ndash32 2014

[17] D D Nguyen L P Devlin P Koshy and C C Sorrell ldquoEffectsof acetic acid on early hydration of Portland cementrdquo Journal ofThermal Analysis and Calorimetry vol 123 no 1 pp 489ndash4992016

[18] D P Bentz R J Detwiler E J Garboczi P Halamickova andM Schwartz ldquoMulti-scale modeling of the diffusivity of mortarand concreterdquo in Proceedings of the Chloride Penetration intoConcrete LONilsson and J POllivier Eds pp 85ndash94 RILEM1997

[19] M W Grutzeck D Shi G Liu and S Kwan ldquoComputer sim-ulation of interfacial packing in concreterdquo Journal of MaterialsScience vol 28 no 13 pp 3444ndash3450 1993

[20] D P Bentz ldquoInfluence of silica fume on diffusivity in cement-based materials II Multi-scale modeling of concrete diffusiv-ityrdquo Cement and Concrete Research vol 30 no 7 pp 1121ndash11292000

[21] M Voltolini M C Dalconi G Artioli et al ldquoUnderstandingcement hydration at the microscale new opportunities fromlsquopencil-beamrsquo synchrotron X-ray diffraction tomographyrdquo Jour-nal of Applied Crystallography vol 46 no 1 pp 142ndash152 2013

[22] Z Liu W Chen Y Zhang and H Lv ldquoA three-dimensionalmulti-scale method to simulate the ion transport behavior ofcement-based materialsrdquo Construction amp Building Materialsvol 120 pp 494ndash503 2016

[23] B A Suprenant and G Papadopoulos ldquoSelective dissolutionof portland-fly-ash cementsrdquo Journal of Materials in CivilEngineering vol 3 no 1 pp 48ndash59 1991

[24] D P Bentz E J Garboczi and K A Snyder ldquoA hard coresoftshell microstructural model for studying percolation and trans-port in three-dimensional compositemediardquo NISTIR 6265 USDepartment of Commerce 1999

12 Advances in Materials Science and Engineering

[25] X-Y Wang H-S Lee and K-B Park ldquoSimulation of low-calcium fly ash blended cement hydrationrdquo ACI MaterialsJournal vol 106 no 2 pp 167ndash175 2009

[26] Q Zeng K Li T Fen-Chong and P Dangla ldquoDeterminationof cement hydration and pozzolanic reaction extents for fly-ashcement pastesrdquo Construction and Building Materials vol 27 no1 pp 560ndash569 2012

[27] AMNeville Properties of Concrete AddisonWesley LongmanEssex UK 4th edition 1996

[28] C C Yang ldquoThe relationship between charge passed and thechloride concentrations in anode and cathode cells using theaccelerated chloride migration testrdquo Materials and Structuresvol 36 no 264 pp 678ndash684 2003

[29] T C Powers ldquoStructure and physical properties of hardenedportland cement pasterdquo Journal of the American Ceramic Soci-ety vol 41 no 1 pp 1ndash6 1958

[30] V G Papadakis ldquoEffect of fly ash on Portland cement systemspart I Low-calcium fly ashrdquoCement and Concrete Research vol29 no 11 pp 1727ndash1736 1999

[31] A Xu and S L Sarkar ldquoMicrostructural development in high-volume fly-ash cement systemrdquo Journal of Materials in CivilEngineering vol 6 no 1 pp 117ndash136 1994

[32] YM ZhangW Sun andHD Yan ldquoHydration of high-volumefly ash cement pastesrdquoCement and Concrete Composites vol 22no 6 pp 445ndash452 2000

Submit your manuscripts athttpswwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Advances in Materials Science and Engineering 11

5 Conclusions

(1) The degree of hydration of cement in the pure cementpastes was determined by measuring the nonevap-orablewater contentThedegree of the fly ash reactionin fly ash-cement blended pastes was determinedusing a selective dissolution method

(2) Based on the degree of hydration of cement and theeffectiveWB ratio the degree of hydration of cementin fly ash-cement blended pastes was acquired

(3) A hydration model of fly ash-cement blended pasteshas been established based on the degree of reactionand the hydration products This model incorporatesthe reactions of fly ash and the hydration of cementbut is also influenced by their interactions

Competing Interests

The authors declare that there are no competing interestsregarding the publication of this paper

Acknowledgments

The authors gratefully acknowledge the National Natural Sci-ence Foundation of China (51408597) and the FundamentalResearch Funds for the Central Universities (2014QNA75)

References

[1] K-H Yang Y-B Jung M-S Cho and S-H Tae ldquoEffect ofsupplementary cementitious materials on reduction of CO2emissions from concreterdquo Journal of Cleaner Production vol103 pp 774ndash783 2015

[2] T Sato and J J Beaudoin ldquoEffect of nano-CaCO3 on hydrationof cement containing supplementary cementitious materialsrdquoAdvances in Cement Research vol 23 no 1 pp 33ndash43 2011

[3] Z Liu Y Zhang and Q Jiang ldquoContinuous tracking of therelationship between resistivity and pore structure of cementpastesrdquo Construction and Building Materials vol 53 pp 26ndash312014

[4] R Snellings G Mertens and J Elsen ldquoSupplementary cemen-titious materialsrdquo Reviews in Mineralogy and Geochemistry vol74 pp 211ndash278 2012

[5] L Lam Y L Wong and C S Poon ldquoDegree of hydration andgelspace ratio of high-volume fly ashcement systemsrdquo Cementand Concrete Research vol 30 no 5 pp 747ndash756 2000

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

[7] P Hou S Kawashima D Kong D J Corr J Qian and S PShah ldquoModification effects of colloidal nanoSiO2 on cementhydration and its gel propertyrdquo Composites Part B Engineeringvol 45 no 1 pp 440ndash448 2013

[8] J David Raja Selvam D S Robinson Smart and I DinaharanldquoMicrostructure and some mechanical properties of fly ashparticulate reinforced AA6061 aluminum alloy compositesprepared by compocastingrdquoMaterials amp Design vol 49 pp 28ndash34 2013

[9] R Feldman L R Prudencio Jr and G Chan ldquoRapid chloridepermeability test on blended cement and other concretescorrelations between charge initial current and conductivityrdquoConstruction and Building Materials vol 13 no 3 pp 149ndash1541999

[10] SWM Supit and FU A Shaikh ldquoDurability properties of highvolume fly ash concrete containing nano-silicardquo Materials andStructuresMateriaux et Constructions vol 48 no 8 pp 2431ndash2445 2014

[11] N Neithalath and J Jain ldquoRelating rapid chloride transportparameters of concretes to microstructural features extractedfrom electrical impedancerdquo Cement and Concrete Research vol40 no 7 pp 1041ndash1051 2010

[12] G Land and D Stephan ldquoThe influence of nano-silica on thehydration of ordinary Portland cementrdquo Journal of MaterialsScience vol 47 no 2 pp 1011ndash1017 2012

[13] J Justs M Wyrzykowski F Winnefeld D Bajare and P LuraldquoInfluence of superabsorbent polymers on hydration of cementpastes with low water-to-binder ratiordquo Journal of ThermalAnalysis and Calorimetry vol 115 no 1 pp 425ndash432 2014

[14] Z Liu Y Zhang Q Jiang W Zhang and J Wu ldquoSolid phasespercolation and capillary pores depercolation in hydratingcement pastesrdquo Journal of Materials in Civil Engineering vol 26no 12 Article ID 04014090 2014

[15] B Uzal and L Turanlı ldquoBlended cements containing highvolume of natural zeolites properties hydration and pastemicrostructurerdquo Cement and Concrete Composites vol 34 no1 pp 101ndash109 2012

[16] Y Kocak and S Nas ldquoThe effect of using fly ash on the strengthand hydration characteristics of blended cementsrdquoConstructionand Building Materials vol 73 pp 25ndash32 2014

[17] D D Nguyen L P Devlin P Koshy and C C Sorrell ldquoEffectsof acetic acid on early hydration of Portland cementrdquo Journal ofThermal Analysis and Calorimetry vol 123 no 1 pp 489ndash4992016

[18] D P Bentz R J Detwiler E J Garboczi P Halamickova andM Schwartz ldquoMulti-scale modeling of the diffusivity of mortarand concreterdquo in Proceedings of the Chloride Penetration intoConcrete LONilsson and J POllivier Eds pp 85ndash94 RILEM1997

[19] M W Grutzeck D Shi G Liu and S Kwan ldquoComputer sim-ulation of interfacial packing in concreterdquo Journal of MaterialsScience vol 28 no 13 pp 3444ndash3450 1993

[20] D P Bentz ldquoInfluence of silica fume on diffusivity in cement-based materials II Multi-scale modeling of concrete diffusiv-ityrdquo Cement and Concrete Research vol 30 no 7 pp 1121ndash11292000

[21] M Voltolini M C Dalconi G Artioli et al ldquoUnderstandingcement hydration at the microscale new opportunities fromlsquopencil-beamrsquo synchrotron X-ray diffraction tomographyrdquo Jour-nal of Applied Crystallography vol 46 no 1 pp 142ndash152 2013

[22] Z Liu W Chen Y Zhang and H Lv ldquoA three-dimensionalmulti-scale method to simulate the ion transport behavior ofcement-based materialsrdquo Construction amp Building Materialsvol 120 pp 494ndash503 2016

[23] B A Suprenant and G Papadopoulos ldquoSelective dissolutionof portland-fly-ash cementsrdquo Journal of Materials in CivilEngineering vol 3 no 1 pp 48ndash59 1991

[24] D P Bentz E J Garboczi and K A Snyder ldquoA hard coresoftshell microstructural model for studying percolation and trans-port in three-dimensional compositemediardquo NISTIR 6265 USDepartment of Commerce 1999

12 Advances in Materials Science and Engineering

[25] X-Y Wang H-S Lee and K-B Park ldquoSimulation of low-calcium fly ash blended cement hydrationrdquo ACI MaterialsJournal vol 106 no 2 pp 167ndash175 2009

[26] Q Zeng K Li T Fen-Chong and P Dangla ldquoDeterminationof cement hydration and pozzolanic reaction extents for fly-ashcement pastesrdquo Construction and Building Materials vol 27 no1 pp 560ndash569 2012

[27] AMNeville Properties of Concrete AddisonWesley LongmanEssex UK 4th edition 1996

[28] C C Yang ldquoThe relationship between charge passed and thechloride concentrations in anode and cathode cells using theaccelerated chloride migration testrdquo Materials and Structuresvol 36 no 264 pp 678ndash684 2003

[29] T C Powers ldquoStructure and physical properties of hardenedportland cement pasterdquo Journal of the American Ceramic Soci-ety vol 41 no 1 pp 1ndash6 1958

[30] V G Papadakis ldquoEffect of fly ash on Portland cement systemspart I Low-calcium fly ashrdquoCement and Concrete Research vol29 no 11 pp 1727ndash1736 1999

[31] A Xu and S L Sarkar ldquoMicrostructural development in high-volume fly-ash cement systemrdquo Journal of Materials in CivilEngineering vol 6 no 1 pp 117ndash136 1994

[32] YM ZhangW Sun andHD Yan ldquoHydration of high-volumefly ash cement pastesrdquoCement and Concrete Composites vol 22no 6 pp 445ndash452 2000

Submit your manuscripts athttpswwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

12 Advances in Materials Science and Engineering

[25] X-Y Wang H-S Lee and K-B Park ldquoSimulation of low-calcium fly ash blended cement hydrationrdquo ACI MaterialsJournal vol 106 no 2 pp 167ndash175 2009

[26] Q Zeng K Li T Fen-Chong and P Dangla ldquoDeterminationof cement hydration and pozzolanic reaction extents for fly-ashcement pastesrdquo Construction and Building Materials vol 27 no1 pp 560ndash569 2012

[27] AMNeville Properties of Concrete AddisonWesley LongmanEssex UK 4th edition 1996

[28] C C Yang ldquoThe relationship between charge passed and thechloride concentrations in anode and cathode cells using theaccelerated chloride migration testrdquo Materials and Structuresvol 36 no 264 pp 678ndash684 2003

[29] T C Powers ldquoStructure and physical properties of hardenedportland cement pasterdquo Journal of the American Ceramic Soci-ety vol 41 no 1 pp 1ndash6 1958

[30] V G Papadakis ldquoEffect of fly ash on Portland cement systemspart I Low-calcium fly ashrdquoCement and Concrete Research vol29 no 11 pp 1727ndash1736 1999

[31] A Xu and S L Sarkar ldquoMicrostructural development in high-volume fly-ash cement systemrdquo Journal of Materials in CivilEngineering vol 6 no 1 pp 117ndash136 1994

[32] YM ZhangW Sun andHD Yan ldquoHydration of high-volumefly ash cement pastesrdquoCement and Concrete Composites vol 22no 6 pp 445ndash452 2000

Submit your manuscripts athttpswwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Submit your manuscripts athttpswwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials