Research Article Chloride Transport of High Alumina Cement...

Research ArticleChloride Transport of High Alumina Cement Mortar Exposed toa Saline Solution

Hee Jun Yang Sung Ho Jin and Ki Yong Ann

Department of Civil and Environmental Engineering Hanyang University Ansan 15588 Republic of Korea

Correspondence should be addressed to Ki Yong Ann kannhanyangackr

Received 7 October 2016 Accepted 6 December 2016

Academic Editor Paulo H R Borges

Copyright copy 2016 Hee Jun Yang 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

Chloride transport in different types of high alumina cement (HAC)mortar was investigated in this studyThreeHAC cement typeswere used ranging from 520 to 811 of aluminum oxides in clinker For the development of the strength the setting time of freshmortar was measured immediately after mixing and the mortar compressive strength was cured in a wet chamber at 25 plusmn 2∘C andthen measured at 1ndash91 days Simultaneously to assess the rate of chloride transport in terms of diffusivity the chloride profile wasperformed by an exposure test in this study which was supported by further experimentation including an examination of the porestructure chloride binding and chemical composition (X-ray diffraction) analysis As a result it was found that an increase in theAl2O3 content in the HAC clinker resulted in an increase in the diffusion coefficient and concentration of surface chloride due toincreased binding of chloride However types of HAC did not affect the pore distribution in the cement matrix except for macropores

1 Introduction

High alumina cement (HAC)mainly consisting of aluminumoxide (Al2O3) from about 50 to 85 in cement clinkercould be often used for a special application due to bothhigh resistance to aggressive chemical ions (ie sewer con-crete) and rapid development of strength within 24 hours[1ndash4] However its use in concrete structures has beenseverely restricted by the loss of strength in the process ofconversion metastable hydrates (CaOsdotAl2O3sdot10H2O CAH102CaOsdotAl2O3sdot8H2O C2AH8) are transformed to stable ones(3CaOsdotAl2O3sdot6H2O C3AH6) as follows [5ndash8]

3CAH10 997888rarr C3AH6 + 2AH3 + 18H (1)

3C2AH8 997888rarr 2C3AH6 + 2AH3 + 9H (2)

Due to the release of water molecules in the conversionhowever further hydration of anhydrous phases in cementmatrix progresses steadily [1 2 9] thereby compensating forthe reduced strength and thus the required performance instructural members Thus HAC may be used for structuralconcrete structures under the condition that rapid hydration

is arrested in situ by any means together with reducedeconomic price

It is also intuitively supported that the high portion ofaluminumoxide inHAC which is in fact related to formationof CA-type hydration for example C3A to remove freechlorides from the concrete pore solution might be preferredto enhance resistance to chloride-induced corrosion of steelin concrete [10] Steel embedment in concrete is usuallyprotected by the passive layer (ie 120574-Fe2O3) formed in ahigh alkaline environment in which the value of pH accountsfor about 120 up to 135 [11] although chloride ions at thedepth of the steel in concrete would subsequently depassivatethe steel surface followed by corrosion propagation to theentire surface of steel [12 13] Simultaneously corrosion ofsteel could be more or less mitigated by the removal of freechloride ions in the pore solution In the majority of previousstudies [14 15] the increased binding capacity of HAC pasteenabled more adsorption and binding of chloride ions inthe pore solution to mitigate the risk of chloride-inducedcorrosion In fact the corrosion resistance of HAC in termsof critical chloride concentration for the onset of corrosionwas increased up to 24 whilst OPC concrete ranged from02 to 10 for the chloride threshold [10]

Hindawi Publishing CorporationAdvances in Materials Science and EngineeringVolume 2016 Article ID 4730616 8 pageshttpdxdoiorg10115520164730616

2 Advances in Materials Science and Engineering

Table 1 Oxide composition and chemical properties of different HAC types

Oxide composition () Ignition loss () Fineness (cm2g) DensityCaO Al2O3 SiO2 Fe2O3 SO3 MgO K2O Na2O MnO

HAC I 3883 5203 502 086 009 042 068 017 003 050 5150 303HAC II 3201 6725 011 008 001 021 001 028 002 061 4800 292HAC III 1835 8109 006 006 001 008 001 032 001 121 8540 319

When it comes to the corrosion-free service life ofstructures the rate of chloride transport in HAC concretehowever is of no concern to date As chloride transportis affected by the distribution of pores and simultaneouslythe reactivity of the cement matrix with chloride ionspredicting the corrosion-free life must be accompanied bythe rate of chloride transport In particular HAC concreteimposes the increased pores in the process of conversionfrom the hexagonal to cubic phases which may acceleratethe chloride permeation and offset the benefit in increasingthe resistance to chloride-induced corrosion Moreover thebinding capacity of HAC concrete may affect the buildupof chloride ions on the surface of concrete when immersedin a salt solution which subsequently would increase thediffusivity of chloride ions

To ensure the characteristics of chloride transport inHAC concrete the rate of chloride transport in terms ofdiffusivity was investigated by an exposure test in this studyRefinement of the pore structure was examined by the intru-sion of mercury into a specimen to quantify the influenceof conversion on the pore distribution Simultaneously thechloride binding capacity of HAC paste was determined toassess its effect on both corrosion resistance and chloridetransport Three different HAC types were used containing520 673 and 811 of aluminum oxides in HAC clinker

2 Experimental Works

21 Compressive Strength and Penetration Resistance Theoxide composition of HAC used in the present study wasdetermined by X-ray fluorescence (XRF) and physical prop-erties of HAC are given in Table 1 For the development ofthe compressive strength mortar specimens were fabricatedin a cylindrical mould (Oslash 100 times 200mm) Mix proportionfor the cement water sand (Grade M) was 100 040 245The specific gravity of sand was 265 This mix proportionfor mortar was subsequently used for the chloride profileand mercury intrusion porosimetry The mortar specimenswere demoulded in 12 hours after casting and then cured ina wet chamber at 25 plusmn 2∘C to reduce the influence on thetransformation of hexagonal to cubic phases in hydrationproducts The compressive strength for mortar specimenswas measured at various ages to monitor the influence ofthe conversion process in the HAC mortar on the strengthdevelopment

A fresh mortar was poured in a cubic mould (100 times100 times 400mm) to determine the penetration resistance withtime and was subsequently measured by a set of standardneedles (16 32 65 161 312 and 645mm2 in diameter)at a given time interval After interpolating the curve for

the penetration resistance with time the setting time wasdetermined assuming that the initial and final sets aredefined as time for the penetration resistance to reach 343and 2746MPa respectively

22 Chloride Profile The mortar specimens fabricated inthe cylindrical mould (Oslash 100 times 200mm) were cured inan identical wet chamber for 91 days to maximise thehydration degree and then the specimens were cut into50mm thickness in which all the surfaces were coated byepoxy resin except for one surface to induce one-way chloridepenetration Then the mortar disks (Oslash 100 times 50mm) wereimmersed in a 10M NaCl solution for 100 days followedby grinding the specimens every 5mm depth increments upto 20mm from the specimen surface to measure chlorideconcentration in each sample The obtained sample wasstirred for 5min in 50mL distilled water at 50∘C to extractthe water-soluble chloride and then for reaching a chemicalequivalent in solution a further 30min of standing wascarried out After filtering the sample the concentrationof chloride ion in sample was measured by the titrationmethod using ion selective electrode (ISE) for chlorideAn identical procedure was adopted to determine the acidsoluble chloride concentration using 20 nitric acid (HNO3)for solvent instead of distilled water

Once the total and free chloride concentrations wereobtained at all depths the surface chloride (119862119878) and anapparent diffusion coefficient (119863app) were determined byfitting to the error function solution to Fickrsquos second law fornonsteady state given by

119862 (119909 119905) = 119862119878 (1 minus erf 1199092radic119863119905) (3)

where 119862(119909 119905) is chloride concentration at depth 119909 after time119905 (m3) 119862119878 is surface chloride concentration (m3) 119909 isdepth (mm)119863 is apparent diffusion coefficient (m2s) and 119905is time of exposure (s)

When free chloride concentration was determined at agiven total the chloride binding capacity was represented bythe Langmuir isotherm In this study water-soluble chlorideswere taken as free while acid soluble ones were taken astotal chloridesThe concentration of bound chloride ions wasdetermined by subtracting the free chloride concentrationfrom the total

23 Chlorides in the Matrix The X-ray diffraction methodwas used to identify the bound chlorides in the HAC pasteTo react with chlorides from an external environment athin layered HAC paste (Oslash 100 times 5mm) at 04 of a free

Advances in Materials Science and Engineering 3

WC was immersed in 10M NaCl solution for 100 daysThen the specimens were immersed in isopropanol for 7days to prevent further hydration followed by remaining in adessicator for 1 day to removeevaporate the residual water-based solvent After removing water the paste specimenwas ground and sieved with the 300 120583m sieve to obtain thedust sample which was analysed with DMAX-2500 model(Rigaku) and Jade 95 software The scan range was from 5 to45∘ of 2120579 at a scan rate of 4∘min

24 Pore Structure Examination To examine the pore distri-bution at a given pore diameter the HAC mortar specimenswere fabricated in a cylindrical mould (Oslash 10 times 10mm) andcured for 91 days in the wet chamber at 25 plusmn 2∘C Priorto examining the pore structure the residual water in thespecimen was removed by an identical method for the X-ray diffraction test The porosimeter used in this study wasAutopore IV 9500 model (Micromeritics Instrument) to fitthe low and high pressure The first step was applied by lowpressure of mercury (Hg) up to 051 psia using nitrogen gas tomeasuremacroporosity and then themaximumpressure wasgradually increased to 33000 psia formicroporosityTheporevolume versus pore diameter calculated by the Washburnequation at a given pressure was plotted in the cumulativepore volume and incremental curve Hence

119889 = minus4120574 cos 120579119875 (4)

where 119889 is pore diameter (m) 120574 is surface tension (N) 120579 iscontact angle (∘) and 119875 is pressure (MPa)

3 Results and Discussion

31 Compressive Strength and Penetration Resistance Thepenetration resistance of freshHACmortar with time is givenin Figure 1 The initial and final sets were determined bythe best-fitted curve for the penetration resistance with time(119910 = 119886119890119887119909) It was seen that the setting time was stronglydependent on theHAC type an increase in the Al2O3 contentin clinker resulted in an increase in the time for the initialand final sets For example the time for the initial and finalsets of HAC I imposed the rapid hardening accounting for185 and 230min for the initial and final sets respectivelywhile HAC III indicated 291min and 409min respectivelyTheHAC is usually divided into three groups (1) low alumina(50ndash60 in Al2O3) (2)medium alumina (65ndash75 in Al2O3)and (3)high alumina (gt80 inAl2O3)The anhydrous phasesconsist of CA a main hydraulic constituent in HAC 120572-Al2O3 C12A7 and CA2 being significant according to rawmaterials Guirado and Galı [16] showed that an increasein ratio of CaOAl2O3 (hereinafter CA) resulted in bothan increase in CA2 content and a decrease in CA onesmeasured by the Rietveld analysis As the hydration processin HAC is governed by the amount of Ca2+ and Al(OH)4minusions in solution the quantities and solubility in each clinkercould be influencing the development of the strength Klauset al [17] investigated the hydration of mixture of CA andCA2 (WC ratio 045 curing temp 23 plusmn 02∘C) in terms

0

10

20

30

40

Pene

trat

ion

resis

tanc

e (M

Pa)

50 100 150 200 250 300 350 400 4500Time (min)

HAC IHAC IIHAC III

Initial set

Final set

343MPa

2746MPa

273min

230min

205min

185min 291min

409min

Figure 1 Penetration resistance of fresh concrete with time todetermine the setting time for different HAC types

of their dissolution They found that the dissolution of CAprogressively appeared at the initial stage (up to about 6hours) followed by that of CA2 Moreover the dissolutionbehaviour of CA was constant in the presence of variousCA2 content In addition it was reported that CA in HACclinker is reactive more than CA2 at ambient temperature(20ndash30∘C) [18] Consequently as CA leads to rapid settingand hardening at the early stage in the process of hydrationit is possible to control the setting behaviour for HAC bymodifying the CA ratio in clinker at the manufacturing step

The compressive strength of mortar with different HACtypes was measured at 1ndash91 days as shown in Figure 2 Asexpected the strength forHACmortar rapidly increasedwithtime at an early age regardless of types up to 7 days andthen decreased at 14 days except for HAC I In particularthe strength of HAC I mortar showed a considerable highstrength at an early age reaching beyond 663MPa at 7 daysand then gradually decreased to 477MPa at 56 days whileHAC III mortar faced a sudden decease from 651MPa at7 days to 514MPa at 14 days The high early compressivestrength is attributed to an inherent characteristic of HACwhich may be attributed to rapidly elevated heat (up to about90∘C in adiabatic temperature) during hydration within 10ndash12 hours [1] A reduction of the compressive strength mayreflect the conversion process from the hexagonal (CAH10and C2AH8) to cubic (C3AH6) phases during hydration ofHAC paste accompanying the densified matrix and thusin turn increased porosity in the cement matrix [6 7] It isnotable that amarginal increase for compressive strength wasobserved after 14 days of curing in all types It is evident thatfurther hydration of anhydrous phases such as CA CA2 andC12A7 may maintain a certain strength despite a risk of the


HAC IHAC IIHAC III

0

10

20

30

40

50

60

70

80

Com

pres

sive s

treng

th (M

Pa)

20 40 60 80 1000Curing age (days)

Figure 2 Development of compressive strength of mortar fordifferent HAC types with curing age

conversion process which is in fact related to generationof porosity and in turn may decrease the concrete strength[6 7] Substantially all the mortar compressive strengthsachieved a high level of their ultimate compressive strengthexceeding about 50MPa at 91 days which could not seem tofurther increase or decrease Thus it can be said that therewould be no adverse effect in using the HAC for structuralconcrete presumably due to the unstable development of thecompressive strength

32 Chloride Transport After exposure of mortar specimensto the 10 NaCl solution for 100 days the chloride concentra-tion was measured at each depth with increments of 50mmfor the acid- and water-soluble chlorides corresponding tototal and free chlorides respectively Then the chloride pro-filewas used to determine the apparent diffusion coefficient ofchlorides and the surface chloride content for nonsteady stateby fitting to the error function solution to Fickrsquos second lawas shown in Figure 3 It is obvious that an increase in the CAratio (ie lower content of Al2O3 in oxides in HAC clinker)resulted in a decrease in the chloride ingress at every depthIn particular the concentration of total surface chloride wasstrongly dependent on the CA ratio in cement For exampleHAC I at the higher CA ratio produced 084 of the surfacechloride by weight of cement while HAC III increased upto 208 This may be ascribed to the chemical equilibriumfor chloride ions at the interface between specimen surfaceand solution The higher Al2O3 content in cement clinkerwould enhance the formation of chloroaluminate hydrateswhich often would result from a reaction between cementpaste and free chlorides to removeimmobilise them from thepore solution [10 19] The higher chloride binding capacityresulting from increased C3A content may impose increased

concentration of bound chloride on the surface of concreteat a given free chloride concentration due to the chemicalbalance between concrete surface and saline media [20]Thus the lower CA ratio in HAC may enhance the buildupof chlorides on the concrete surface leading to an increase inthe concentration gradient to accelerate the rate of chloridetransport

It is evident that the diffusion coefficient of chlorides wasmuch affected by the CA ratio in HAC In fact an increasein the CA resulted in a decrease in the diffusion coefficientFor example the HAC I produced the lowest diffusivity of161 times 10minus11m2s while HAC II and HAC III indicated 185times 10minus11m2s and 217 times 10minus11m2s respectively Howeverthe diffusion coefficient calculated for free chloride transporthad no significant effect arising from different CA ratiosthe diffusion coefficient for free chlorides in HAC was in asmall range from 131 times 10minus11 to 143 times 10minus11m2s irrespectiveof types of HAC The rate of chloride transport is affectedby the pore structure (ie distribution of capillary pores inthe cement matrix) and chemical reactivity between cementpaste and chloride ions such as chloride binding The HACpaste is always subjected to the conversion process fromthe hexagonal phases (CAH10 and C2AH8) to cubic phases(C3AH6) depending on the curing regime temperature andCA ratio which subsequentlymay govern the pore structureSimultaneously the reactivity between cement paste andchloride ions in HAC would be very accelerated rather thanin OPC due to increased formation of reactive hydrationproducts such as CA CA2 and C12A7 Thus these influ-encing factors must be quantified to determine the chloridetransport in HAC concrete For example examination of thechloride binding capacity and the pore structure must beaccompanied

33 Chloride Binding To render the binding isotherm therelation between free and bound chlorides for differentHAC types was depicted in Figure 4 using the Langmuirisotherm The concentration of free and bound chloride wasdetermined in the process of chloride profiling at differentdepths and at different total chloride concentrations Asexpected an increase in the free chloride concentrationresulted in an increase in the bound chlorides regardlessof the HAC types It is evident that the CA ratio wassignificantly influencing the chloride binding capacity at agiven total chloride concentration In fact HAC III wasranked the highest chloride binding capacity presumablyarising from increasedAl-based clinkers which subsequentlywould form the CA-type hydrates to arrest chlorides intoFriedelrsquos salt Due to a marginal difference in the pH of thepore solution the pH seems to be less influencing on thechloride binding capacity [15] and the conversion process inthe HAC matrix is moreover less affected Substantially thebinding of chlorides into a crystallised form may solely beaffected by the concentration of Al2O3 in clinker althoughother hydration products may contribute to the reaction withchlorides in a limited margin

The HAC paste immersed in the NaCl solution wasanalysed by X-ray diffraction as seen in Figure 5 It isseen that the peaks for hydration products were mostly


TotalFreeBound

Total 084

Free 060

0

05

1

15

2

25Ch

lorid

e con

tent

s (

cem

)

5 10 15 20 250Depth (mm)

CS ( cem) Dapp (m2s)

161 times 10minus11

133 times 10minus11

(a) HAC I

TotalFreeBound

140

064

0

05

1

15

2

25

Chlo

ride c

onte

nts (

c

em)

5 10 15 20 250Depth (mm)

Total

Free


185 times 10minus11

131 times 10minus11

(b) HAC II

TotalFreeBound

208

077

0

05

1

15

2

25

Chlo

ride c

onte

nts (

c

em)

5 10 15 20 250Depth (mm)

Total

Free


217 times 10minus11

143 times 10minus11

(c) HAC III

Figure 3 Chloride profiles of mortar for different HAC types after 100 days of exposure to 10M NaCl solution

identical between HAC pastes imposing similar generationof hydration except for unreactive 120572-Al2O3 in HAC III Itis notable that no metastable crystals (CAH10 and C2AH8)were identified for all the HAC types in the X-ray diffractioncurves implying that the hexagonal phases formed in thecement matrix were completely converted to cubic phasesduring curing consisting of 91 days of wet curing and 100 daysof exposure to a salt solution at 25 plusmn 2∘C The high intensitywas commonly observed at 110ndash112∘ of 2120579 in HAC pastes

indicating that Friedelrsquos salt was quite formed depending onthe CA ratio In fact an increase in the CA resulted ina decrease in Friedelrsquos salt This may confirm that the highcontent of Al2O3 may be of benefit in forming Friedelrsquos saltdue to increased possibilities of the formation of chloride-reactive CA hydration products

34 Pore Structure The pore distribution in the HACmortarwas determined by mercury intrusion porosimetry as given


Type IType IIType III

0

05

1

15

Boun

d ch

lorid

e (

cem

)

05 10Free chloride ( cem)

Cb =341Cf

1 + 142Cf

Cb =227Cf

1 + 155Cf

Cb =072Cf

1 + 131Cf

Figure 4 Relation between free and bound chlorides at a given total chloride concentration in cement mortar with different HAC types after100 days of exposure to 10M NaCl solution (expressed by the Langmuir isotherm)

Friedelrsquos salt

HAC I

HAC II

HAC III

10 15 20 25 30 35 40 45 505Degree (2120579)

CAH10

C3AH6

AH3

120572-Al2O3

Inte

nsity

(CPS

)

(a)

12

HAC III

HAC II

HAC I

0

400

800

1200

1600

Inte

nsity

(CPS

)

10 11Degree (2120579)

(b)

Figure 5 X-ray diffraction pattern of cement paste with different HAC types after 100 days of exposure to 10MNaCl solution (a) Hydrationproducts and (b) Friedelrsquos salt

in Figure 6 together with incremental pores at differentsizes Irrespective of types of HAC the total pore volumewas in the range of 0076ndash0088mLg The distribution ofcapillary pore was not much affected by the types of HACwhich would provide paths for ions to transport in the formof interrelated network However macro pore distributionwas dependent on the HAC types an increase in the CAresulted in an increase in the volume of macro pores whichare not interconnected with the capillary pore and thusmay block the ionic transport [21] As seen in Figure 3 the

HAC III produced the highest rate of chloride transport interms of apparent chloride diffusion coefficient This may beattributed to a lower volume of the macro pores enhancingthe connectivity between pores and thus chloride transportMoreover a reduction of themacro pore volumemay increasethe development of the concrete strength at a given hydrationdegree in fact HAC III was ranked the highest strength asseen in Figure 2 after 14ndash28 days of curing Despite furthergeneration of the pores in the conversion process from thehexagonal to cubic phases a modified pore structure after the


Macro pore

Large capillary

Small capillary

Total pore

r lal

0

002

004

006

008

01

012Cu

mul

ativ

e int

rusio

n (m

Lg)

0

0002

0004

0006

0008

001

0012

Incr

emen

tal i

ntru

sion

(mL

g)

001 01 1 10 100 10000001Pore diameter (120583m)

0067mLg 0014mLg

0007mLg

0088mLg

(a) HAC I

Macro pore

Large capillary

Small capillary

Total pore

rr a

0

002

004

006

008

01

012

Cum

ulat

ive i

ntru

sion

(mL

g)

0

0002

0004

0006

0008

001

0012

Incr

emen

tal i

ntru

sion

(mL

g)

001 01 1 10 100 10000001Pore diameter (120583m)

0061mLg 0010mLg

0005mLg

0076mLg

(b) HAC II

Macro pore

Large capillary

Small capillary

Total pore

a ll

0

002

004

006

008

01

012

Cum

ulat

ive i

ntru

sion

(mL

g)

0

0002

0004

0006

0008

001

0012

Incr

emen

tal i

ntru

sion

(mL

g)

001 01 1 10 100 10000001Pore diameter (120583m)

0009mLg

0085mLg

0005mLg

0071mLg

(c) HAC III

Figure 6 Pore size distribution of mortar to a given pore diameter with different HAC types

conversion was not identified in this study because the poredistribution before the conversion process presumably at avery early age was not obtained

4 Conclusion

In this study the ionic transport in different types of HACmortar was investigated by the chloride profile which wassupported by further experimentation including an exam-ination of the pores structure chloride binding capacityand chemical microscopic analysis (X-ray diffraction anal-ysis) The HAC was classified by the content of Al2O3 incement clinker ranging from 520 to 811 Simultaneouslydevelopment of the compressive strength and setting timewere measured to secure their applicability in situ Detailedexperimental results and conclusion derived from the studyare given as follows

(1) An increase in the Al2O3 in the HAC clinker resultedin an increase in the setting time and moreover the

gap between initial and final sets was also increaseddue to increasedCA2 formationHACmortars gainedrapidly the compressive strength at an early ageaccounting for 663MPa at 7 days which was reducedat 14 days of curing presumably due to the conversionprocess from the hexagonal to cubic phases and thenagain marginally increased orand converged to acertain level up to 91 days ranging from 4936 to5392MPa

(2) The apparent diffusion coefficient and surface chlo-ride concentration of HAC mortars immersed in asalt solution were obtained by profiling of chlorideconcentration at each depth An increase in theAl2O3 in HAC clinker resulted in an increase inthe surface chloride and diffusion coefficient dueto increased chloride binding capacity and modifiedpore structureThe surface chloride ranged from 084to 208 while the diffusion coefficient of chloridesin HAC mortar was in the range of 161ndash217m2s


(3) The chloride binding capacity rendered by the Lang-muir isotherm was increased by Al2O3 in HACclinker which would form CA-type hydration prod-ucts to react with chloride ions into Friedelrsquos saltHowever types of HAC did not have an influence onthe pore distribution in the cement matrix except formacro pores

Competing Interests

The authors declare that they have no competing interests

Acknowledgments

This research was supported by the research fund of HanyangUniversity (HY-2012-N)

References

[1] P C Hewlett Learsquos Chemistry of Cement and Concrete Elsevier4th edition 2013

[2] J Newman and B S Choo Advanced Concrete TechnologymdashConstituent Materials Elsevier 2003

[3] H Pollmann ldquoCalcium aluminate cementsmdashraw materialsdifferences hydration and propertiesrdquo Reviews inMineralogy ampGeochemistry vol 74 no 1 pp 1ndash82 2012

[4] S M Bushnell-Watson and J H Sharp ldquoThe effect of tempera-ture upon the setting behaviour of refractory calcium aluminatecementsrdquo Cement and Concrete Research vol 16 no 6 pp 875ndash884 1986

[5] A M Neville Properties of Concrete Longman Group 4thedition 1995

[6] H GMidgley andAMidgley ldquoThe conversion of high aluminacementrdquoMagazine of Concrete Research vol 27 no 91 pp 59ndash77 1975

[7] C Bradbury PM Callaway andD D Double ldquoThe conversionof high alumina cementconcreterdquo Materials Science and Engi-neering vol 23 no 1 pp 43ndash53 1976

[8] R J Collins and W Gutt ldquoResearch on long-term properties ofhigh alumina cement concreterdquoMagazine of Concrete Researchvol 40 no 145 pp 195ndash208 1988

[9] J Bensted and P Barnes Structure and Performance of CementsTaylor amp Francis Group 2nd edition 2002

[10] K Y Ann T-S Kim J H Kim and S-H Kim ldquoThe resistanceof high alumina cement against corrosion of steel in concreterdquoConstruction and Building Materials vol 24 no 8 pp 1502ndash1510 2010

[11] C L Page ldquoMechanism of corrosion protection in reinforcedconcrete marine structuresrdquo Nature vol 258 no 5535 pp 514ndash515 1975

[12] M Saremi and E Mahallati ldquoA study on chloride-induceddepassivation of mild steel in simulated concrete pore solutionrdquoCement and Concrete Research vol 32 no 12 pp 1915ndash19212002

[13] K Y Ann and H-W Song ldquoChloride threshold level forcorrosion of steel in concreterdquo Corrosion Science vol 49 no 11pp 4113ndash4133 2007

[14] A Macias A Kindness and F P Glasser ldquoCorrosion behaviourof steel in high alumina cement mortar cured at 5 25 and 55∘C

chemical and physical factorsrdquo Journal of Materials Science vol31 no 9 pp 2279ndash2289 1996

[15] M A Sanjuan ldquoFormation of chloroaluminates in calciumaluminate cements cured at high temperatures and exposed tochloride solutionsrdquo Journal of Materials Science vol 32 no 23pp 6207ndash6213 1997

[16] F Guirado and S Galı ldquoQuantitative Rietveld analysis ofCAC clinker phases using synchrotron radiationrdquo Cement andConcrete Research vol 36 no 11 pp 2021ndash2032 2006

[17] S R Klaus J Neubauer and F Goetz-Neunhoeffer ldquoHydrationkinetics of CA2 andCA-investigations performed on a syntheticcalcium aluminate cementrdquo Cement and Concrete Research vol43 no 1 pp 62ndash69 2013

[18] A Rettel R Seydel W Gessner J P Bayoux and A CapmasldquoInvestigations on the influence of alumina on the hydration ofmonocalcium aluminate at different temperaturesrdquoCement andConcrete Research vol 23 no 5 pp 1056ndash1064 1993

[19] K Y Ann and C-G Cho ldquoCorrosion resistance of calciumaluminate cement concrete exposed to a chloride environmentrdquoMaterials vol 7 no 2 pp 887ndash898 2014

[20] G K Glass and N R Buenfeld ldquoThe influence of chloridebinding on the chloride induced corrosion risk in reinforcedconcreterdquo Corrosion Science vol 42 no 2 pp 329ndash344 2000

[21] G K Glass and N R Buenfeld ldquoChloride-induced corrosionof steel in concreterdquo Progress in Structural Engineering andMaterials vol 2 no 4 pp 448ndash458 2000

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Table 1 Oxide composition and chemical properties of different HAC types

Oxide composition () Ignition loss () Fineness (cm2g) DensityCaO Al2O3 SiO2 Fe2O3 SO3 MgO K2O Na2O MnO

HAC I 3883 5203 502 086 009 042 068 017 003 050 5150 303HAC II 3201 6725 011 008 001 021 001 028 002 061 4800 292HAC III 1835 8109 006 006 001 008 001 032 001 121 8540 319

When it comes to the corrosion-free service life ofstructures the rate of chloride transport in HAC concretehowever is of no concern to date As chloride transportis affected by the distribution of pores and simultaneouslythe reactivity of the cement matrix with chloride ionspredicting the corrosion-free life must be accompanied bythe rate of chloride transport In particular HAC concreteimposes the increased pores in the process of conversionfrom the hexagonal to cubic phases which may acceleratethe chloride permeation and offset the benefit in increasingthe resistance to chloride-induced corrosion Moreover thebinding capacity of HAC concrete may affect the buildupof chloride ions on the surface of concrete when immersedin a salt solution which subsequently would increase thediffusivity of chloride ions

To ensure the characteristics of chloride transport inHAC concrete the rate of chloride transport in terms ofdiffusivity was investigated by an exposure test in this studyRefinement of the pore structure was examined by the intru-sion of mercury into a specimen to quantify the influenceof conversion on the pore distribution Simultaneously thechloride binding capacity of HAC paste was determined toassess its effect on both corrosion resistance and chloridetransport Three different HAC types were used containing520 673 and 811 of aluminum oxides in HAC clinker

2 Experimental Works

21 Compressive Strength and Penetration Resistance Theoxide composition of HAC used in the present study wasdetermined by X-ray fluorescence (XRF) and physical prop-erties of HAC are given in Table 1 For the development ofthe compressive strength mortar specimens were fabricatedin a cylindrical mould (Oslash 100 times 200mm) Mix proportionfor the cement water sand (Grade M) was 100 040 245The specific gravity of sand was 265 This mix proportionfor mortar was subsequently used for the chloride profileand mercury intrusion porosimetry The mortar specimenswere demoulded in 12 hours after casting and then cured ina wet chamber at 25 plusmn 2∘C to reduce the influence on thetransformation of hexagonal to cubic phases in hydrationproducts The compressive strength for mortar specimenswas measured at various ages to monitor the influence ofthe conversion process in the HAC mortar on the strengthdevelopment

A fresh mortar was poured in a cubic mould (100 times100 times 400mm) to determine the penetration resistance withtime and was subsequently measured by a set of standardneedles (16 32 65 161 312 and 645mm2 in diameter)at a given time interval After interpolating the curve for

the penetration resistance with time the setting time wasdetermined assuming that the initial and final sets aredefined as time for the penetration resistance to reach 343and 2746MPa respectively

22 Chloride Profile The mortar specimens fabricated inthe cylindrical mould (Oslash 100 times 200mm) were cured inan identical wet chamber for 91 days to maximise thehydration degree and then the specimens were cut into50mm thickness in which all the surfaces were coated byepoxy resin except for one surface to induce one-way chloridepenetration Then the mortar disks (Oslash 100 times 50mm) wereimmersed in a 10M NaCl solution for 100 days followedby grinding the specimens every 5mm depth increments upto 20mm from the specimen surface to measure chlorideconcentration in each sample The obtained sample wasstirred for 5min in 50mL distilled water at 50∘C to extractthe water-soluble chloride and then for reaching a chemicalequivalent in solution a further 30min of standing wascarried out After filtering the sample the concentrationof chloride ion in sample was measured by the titrationmethod using ion selective electrode (ISE) for chlorideAn identical procedure was adopted to determine the acidsoluble chloride concentration using 20 nitric acid (HNO3)for solvent instead of distilled water

Once the total and free chloride concentrations wereobtained at all depths the surface chloride (119862119878) and anapparent diffusion coefficient (119863app) were determined byfitting to the error function solution to Fickrsquos second law fornonsteady state given by

119862 (119909 119905) = 119862119878 (1 minus erf 1199092radic119863119905) (3)

where 119862(119909 119905) is chloride concentration at depth 119909 after time119905 (m3) 119862119878 is surface chloride concentration (m3) 119909 isdepth (mm)119863 is apparent diffusion coefficient (m2s) and 119905is time of exposure (s)

When free chloride concentration was determined at agiven total the chloride binding capacity was represented bythe Langmuir isotherm In this study water-soluble chlorideswere taken as free while acid soluble ones were taken astotal chloridesThe concentration of bound chloride ions wasdetermined by subtracting the free chloride concentrationfrom the total

23 Chlorides in the Matrix The X-ray diffraction methodwas used to identify the bound chlorides in the HAC pasteTo react with chlorides from an external environment athin layered HAC paste (Oslash 100 times 5mm) at 04 of a free




119889 = minus4120574 cos 120579119875 (4)




0

10

20

30

40

Pene

trat

ion

resis

tanc

e (M

Pa)

50 100 150 200 250 300 350 400 4500Time (min)

HAC IHAC IIHAC III

Initial set

Final set

343MPa

2746MPa

273min

230min

205min

185min 291min

409min





HAC IHAC IIHAC III

0

10

20

30

40

50

60

70

80

Com

pres

sive s

treng

th (M

Pa)

20 40 60 80 1000Curing age (days)









TotalFreeBound

Total 084

Free 060

0

05

1

15

2

25Ch

lorid

e con

tent

s (

cem

)

5 10 15 20 250Depth (mm)


161 times 10minus11

133 times 10minus11

(a) HAC I

TotalFreeBound

140

064

0

05

1

15

2

25

Chlo

ride c

onte

nts (

c

em)

5 10 15 20 250Depth (mm)

Total

Free


185 times 10minus11

131 times 10minus11

(b) HAC II

TotalFreeBound

208

077

0

05

1

15

2

25

Chlo

ride c

onte

nts (

c

em)

5 10 15 20 250Depth (mm)

Total

Free


217 times 10minus11

143 times 10minus11

(c) HAC III







0

05

1

15

Boun

d ch

lorid

e (

cem

)


Cb =341Cf

1 + 142Cf

Cb =227Cf

1 + 155Cf

Cb =072Cf

1 + 131Cf


Friedelrsquos salt

HAC I

HAC II

HAC III

10 15 20 25 30 35 40 45 505Degree (2120579)

CAH10

C3AH6

AH3

120572-Al2O3

Inte

nsity

(CPS

)

(a)

12

HAC III

HAC II

HAC I

0

400

800

1200

1600

Inte

nsity

(CPS

)

10 11Degree (2120579)

(b)





Macro pore

Large capillary

Small capillary

Total pore

r lal

0

002

004

006

008

01

012Cu

mul

ativ

e int

rusio

n (m

Lg)

0

0002

0004

0006

0008

001

0012

Incr

emen

tal i

ntru

sion

(mL

g)

001 01 1 10 100 10000001Pore diameter (120583m)

0067mLg 0014mLg

0007mLg

0088mLg

(a) HAC I

Macro pore

Large capillary

Small capillary

Total pore

rr a

0

002

004

006

008

01

012

Cum

ulat

ive i

ntru

sion

(mL

g)

0

0002

0004

0006

0008

001

0012

Incr

emen

tal i

ntru

sion

(mL

g)

001 01 1 10 100 10000001Pore diameter (120583m)

0061mLg 0010mLg

0005mLg

0076mLg

(b) HAC II

Macro pore

Large capillary

Small capillary

Total pore

a ll

0

002

004

006

008

01

012

Cum

ulat

ive i

ntru

sion

(mL

g)

0

0002

0004

0006

0008

001

0012

Incr

emen

tal i

ntru

sion

(mL

g)

001 01 1 10 100 10000001Pore diameter (120583m)

0009mLg

0085mLg

0005mLg

0071mLg

(c) HAC III



4 Conclusion







Competing Interests


Acknowledgments


References






























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






119889 = minus4120574 cos 120579119875 (4)




0

10

20

30

40

Pene

trat

ion

resis

tanc

e (M

Pa)

50 100 150 200 250 300 350 400 4500Time (min)

HAC IHAC IIHAC III

Initial set

Final set

343MPa

2746MPa

273min

230min

205min

185min 291min

409min





HAC IHAC IIHAC III

0

10

20

30

40

50

60

70

80

Com

pres

sive s

treng

th (M

Pa)

20 40 60 80 1000Curing age (days)









TotalFreeBound

Total 084

Free 060

0

05

1

15

2

25Ch

lorid

e con

tent

s (

cem

)

5 10 15 20 250Depth (mm)


161 times 10minus11

133 times 10minus11

(a) HAC I

TotalFreeBound

140

064

0

05

1

15

2

25

Chlo

ride c

onte

nts (

c

em)

5 10 15 20 250Depth (mm)

Total

Free


185 times 10minus11

131 times 10minus11

(b) HAC II

TotalFreeBound

208

077

0

05

1

15

2

25

Chlo

ride c

onte

nts (

c

em)

5 10 15 20 250Depth (mm)

Total

Free


217 times 10minus11

143 times 10minus11

(c) HAC III







0

05

1

15

Boun

d ch

lorid

e (

cem

)


Cb =341Cf

1 + 142Cf

Cb =227Cf

1 + 155Cf

Cb =072Cf

1 + 131Cf


Friedelrsquos salt

HAC I

HAC II

HAC III

10 15 20 25 30 35 40 45 505Degree (2120579)

CAH10

C3AH6

AH3

120572-Al2O3

Inte

nsity

(CPS

)

(a)

12

HAC III

HAC II

HAC I

0

400

800

1200

1600

Inte

nsity

(CPS

)

10 11Degree (2120579)

(b)





Macro pore

Large capillary

Small capillary

Total pore

r lal

0

002

004

006

008

01

012Cu

mul

ativ

e int

rusio

n (m

Lg)

0

0002

0004

0006

0008

001

0012

Incr

emen

tal i

ntru

sion

(mL

g)

001 01 1 10 100 10000001Pore diameter (120583m)

0067mLg 0014mLg

0007mLg

0088mLg

(a) HAC I

Macro pore

Large capillary

Small capillary

Total pore

rr a

0

002

004

006

008

01

012

Cum

ulat

ive i

ntru

sion

(mL

g)

0

0002

0004

0006

0008

001

0012

Incr

emen

tal i

ntru

sion

(mL

g)

001 01 1 10 100 10000001Pore diameter (120583m)

0061mLg 0010mLg

0005mLg

0076mLg

(b) HAC II

Macro pore

Large capillary

Small capillary

Total pore

a ll

0

002

004

006

008

01

012

Cum

ulat

ive i

ntru

sion

(mL

g)

0

0002

0004

0006

0008

001

0012

Incr

emen

tal i

ntru

sion

(mL

g)

001 01 1 10 100 10000001Pore diameter (120583m)

0009mLg

0085mLg

0005mLg

0071mLg

(c) HAC III



4 Conclusion







Competing Interests


Acknowledgments


References






























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




HAC IHAC IIHAC III

0

10

20

30

40

50

60

70

80

Com

pres

sive s

treng

th (M

Pa)

20 40 60 80 1000Curing age (days)









TotalFreeBound

Total 084

Free 060

0

05

1

15

2

25Ch

lorid

e con

tent

s (

cem

)

5 10 15 20 250Depth (mm)


161 times 10minus11

133 times 10minus11

(a) HAC I

TotalFreeBound

140

064

0

05

1

15

2

25

Chlo

ride c

onte

nts (

c

em)

5 10 15 20 250Depth (mm)

Total

Free


185 times 10minus11

131 times 10minus11

(b) HAC II

TotalFreeBound

208

077

0

05

1

15

2

25

Chlo

ride c

onte

nts (

c

em)

5 10 15 20 250Depth (mm)

Total

Free


217 times 10minus11

143 times 10minus11

(c) HAC III







0

05

1

15

Boun

d ch

lorid

e (

cem

)


Cb =341Cf

1 + 142Cf

Cb =227Cf

1 + 155Cf

Cb =072Cf

1 + 131Cf


Friedelrsquos salt

HAC I

HAC II

HAC III

10 15 20 25 30 35 40 45 505Degree (2120579)

CAH10

C3AH6

AH3

120572-Al2O3

Inte

nsity

(CPS

)

(a)

12

HAC III

HAC II

HAC I

0

400

800

1200

1600

Inte

nsity

(CPS

)

10 11Degree (2120579)

(b)





Macro pore

Large capillary

Small capillary

Total pore

r lal

0

002

004

006

008

01

012Cu

mul

ativ

e int

rusio

n (m

Lg)

0

0002

0004

0006

0008

001

0012

Incr

emen

tal i

ntru

sion

(mL

g)

001 01 1 10 100 10000001Pore diameter (120583m)

0067mLg 0014mLg

0007mLg

0088mLg

(a) HAC I

Macro pore

Large capillary

Small capillary

Total pore

rr a

0

002

004

006

008

01

012

Cum

ulat

ive i

ntru

sion

(mL

g)

0

0002

0004

0006

0008

001

0012

Incr

emen

tal i

ntru

sion

(mL

g)

001 01 1 10 100 10000001Pore diameter (120583m)

0061mLg 0010mLg

0005mLg

0076mLg

(b) HAC II

Macro pore

Large capillary

Small capillary

Total pore

a ll

0

002

004

006

008

01

012

Cum

ulat

ive i

ntru

sion

(mL

g)

0

0002

0004

0006

0008

001

0012

Incr

emen

tal i

ntru

sion

(mL

g)

001 01 1 10 100 10000001Pore diameter (120583m)

0009mLg

0085mLg

0005mLg

0071mLg

(c) HAC III



4 Conclusion







Competing Interests


Acknowledgments


References






























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




TotalFreeBound

Total 084

Free 060

0

05

1

15

2

25Ch

lorid

e con

tent

s (

cem

)

5 10 15 20 250Depth (mm)


161 times 10minus11

133 times 10minus11

(a) HAC I

TotalFreeBound

140

064

0

05

1

15

2

25

Chlo

ride c

onte

nts (

c

em)

5 10 15 20 250Depth (mm)

Total

Free


185 times 10minus11

131 times 10minus11

(b) HAC II

TotalFreeBound

208

077

0

05

1

15

2

25

Chlo

ride c

onte

nts (

c

em)

5 10 15 20 250Depth (mm)

Total

Free


217 times 10minus11

143 times 10minus11

(c) HAC III







0

05

1

15

Boun

d ch

lorid

e (

cem

)


Cb =341Cf

1 + 142Cf

Cb =227Cf

1 + 155Cf

Cb =072Cf

1 + 131Cf


Friedelrsquos salt

HAC I

HAC II

HAC III

10 15 20 25 30 35 40 45 505Degree (2120579)

CAH10

C3AH6

AH3

120572-Al2O3

Inte

nsity

(CPS

)

(a)

12

HAC III

HAC II

HAC I

0

400

800

1200

1600

Inte

nsity

(CPS

)

10 11Degree (2120579)

(b)





Macro pore

Large capillary

Small capillary

Total pore

r lal

0

002

004

006

008

01

012Cu

mul

ativ

e int

rusio

n (m

Lg)

0

0002

0004

0006

0008

001

0012

Incr

emen

tal i

ntru

sion

(mL

g)

001 01 1 10 100 10000001Pore diameter (120583m)

0067mLg 0014mLg

0007mLg

0088mLg

(a) HAC I

Macro pore

Large capillary

Small capillary

Total pore

rr a

0

002

004

006

008

01

012

Cum

ulat

ive i

ntru

sion

(mL

g)

0

0002

0004

0006

0008

001

0012

Incr

emen

tal i

ntru

sion

(mL

g)

001 01 1 10 100 10000001Pore diameter (120583m)

0061mLg 0010mLg

0005mLg

0076mLg

(b) HAC II

Macro pore

Large capillary

Small capillary

Total pore

a ll

0

002

004

006

008

01

012

Cum

ulat

ive i

ntru

sion

(mL

g)

0

0002

0004

0006

0008

001

0012

Incr

emen

tal i

ntru

sion

(mL

g)

001 01 1 10 100 10000001Pore diameter (120583m)

0009mLg

0085mLg

0005mLg

0071mLg

(c) HAC III



4 Conclusion







Competing Interests


Acknowledgments


References






























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





0

05

1

15

Boun

d ch

lorid

e (

cem

)


Cb =341Cf

1 + 142Cf

Cb =227Cf

1 + 155Cf

Cb =072Cf

1 + 131Cf


Friedelrsquos salt

HAC I

HAC II

HAC III

10 15 20 25 30 35 40 45 505Degree (2120579)

CAH10

C3AH6

AH3

120572-Al2O3

Inte

nsity

(CPS

)

(a)

12

HAC III

HAC II

HAC I

0

400

800

1200

1600

Inte

nsity

(CPS

)

10 11Degree (2120579)

(b)





Macro pore

Large capillary

Small capillary

Total pore

r lal

0

002

004

006

008

01

012Cu

mul

ativ

e int

rusio

n (m

Lg)

0

0002

0004

0006

0008

001

0012

Incr

emen

tal i

ntru

sion

(mL

g)

001 01 1 10 100 10000001Pore diameter (120583m)

0067mLg 0014mLg

0007mLg

0088mLg

(a) HAC I

Macro pore

Large capillary

Small capillary

Total pore

rr a

0

002

004

006

008

01

012

Cum

ulat

ive i

ntru

sion

(mL

g)

0

0002

0004

0006

0008

001

0012

Incr

emen

tal i

ntru

sion

(mL

g)

001 01 1 10 100 10000001Pore diameter (120583m)

0061mLg 0010mLg

0005mLg

0076mLg

(b) HAC II

Macro pore

Large capillary

Small capillary

Total pore

a ll

0

002

004

006

008

01

012

Cum

ulat

ive i

ntru

sion

(mL

g)

0

0002

0004

0006

0008

001

0012

Incr

emen

tal i

ntru

sion

(mL

g)

001 01 1 10 100 10000001Pore diameter (120583m)

0009mLg

0085mLg

0005mLg

0071mLg

(c) HAC III



4 Conclusion







Competing Interests


Acknowledgments


References






























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Macro pore

Large capillary

Small capillary

Total pore

r lal

0

002

004

006

008

01

012Cu

mul

ativ

e int

rusio

n (m

Lg)

0

0002

0004

0006

0008

001

0012

Incr

emen

tal i

ntru

sion

(mL

g)

001 01 1 10 100 10000001Pore diameter (120583m)

0067mLg 0014mLg

0007mLg

0088mLg

(a) HAC I

Macro pore

Large capillary

Small capillary

Total pore

rr a

0

002

004

006

008

01

012

Cum

ulat

ive i

ntru

sion

(mL

g)

0

0002

0004

0006

0008

001

0012

Incr

emen

tal i

ntru

sion

(mL

g)

001 01 1 10 100 10000001Pore diameter (120583m)

0061mLg 0010mLg

0005mLg

0076mLg

(b) HAC II

Macro pore

Large capillary

Small capillary

Total pore

a ll

0

002

004

006

008

01

012

Cum

ulat

ive i

ntru

sion

(mL

g)

0

0002

0004

0006

0008

001

0012

Incr

emen

tal i

ntru

sion

(mL

g)

001 01 1 10 100 10000001Pore diameter (120583m)

0009mLg

0085mLg

0005mLg

0071mLg

(c) HAC III



4 Conclusion







Competing Interests


Acknowledgments


References






























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





Competing Interests


Acknowledgments


References






























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



Research Article Chloride Transport of High Alumina Cement...

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Transcript of Research Article Chloride Transport of High Alumina Cement...