Hindawi Publishing CorporationThe Scientific World JournalVolume 2013 Article ID 606524 11 pageshttpdxdoiorg1011552013606524

Research ArticleEffect of Metakaolin on Strength and Efflorescence Quantity ofCement-Based Composites

Tsai-Lung Weng1 Wei-Ting Lin23 and An Cheng2

1 Physics Division Tatung University 40 Zhongshan North Road 3rd Section Taipei 104 Taiwan2Deptartment of Civil Engineering National Ilan University 1 Shen-Lung Road Ilan 260 Taiwan3 Institute of Nuclear Energy Research Atomic Energy Council Executive Yuan Taoyuan 325 Taiwan

Correspondence should be addressed to Tsai-Lung Weng wengabcyahoocomtw

Received 8 March 2013 Accepted 8 April 2013

Academic Editors D Aggelis S Chen M Jha and E Lui

Copyright copy 2013 Tsai-Lung Weng et alThis is an open access article distributed under theCreativeCommonsAttribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

This study investigated the basic mechanical and microscopic properties of cement produced with metakaolin and quantified theproduction of residual white efflorescence Cement mortar was produced at various replacement ratios of metakaolin (0 5 10 1520 and 25 by weight of cement) and exposed to various environments Compressive strength and efflorescence quantify (usingMatrix Laboratory image analysis and the curettage method) scanning electron microscopy and X-ray diffraction analysis werereported in this study Specimens with metakaolin as a replacement for Portland cement present higher compressive strength andgreater resistance to efflorescence however the addition of more than 20 metakaolin has a detrimental effect on strength andefflorescenceThis may be explained by the microstructure and hydration productsThe quantity of efflorescence determined usingMATLAB image analysis is close to the result obtained using the curettage method The results demonstrate the best effectivenessof replacing Portland cement with metakaolin at a 15 replacement ratio by weight

1 Introduction

Efflorescence is a fine white powdery deposit of water-soluble salts left on the surface of concrete as the water evap-oratesThis deposit is detrimental to the durability of cemen-titious materials and a stubborn problem for researchersin the field of masonry and concrete [1] Until recentlyit was assumed that calcium hydroxide (Ca(OH)

2 CH)

forming within cement-based composites is responsible forefflorescence however CH does not contribute sufficientlytowards the soluble alkali sulfates required for efflorescenceto occur Alkali sulfates penetrate through pores within thecomposites toward the surface Reducing the number and sizeof these pores restricts the movement of salts to the surfaceOne approach is consolidating grout through mechanicalvibration to reduce voids in the grout while improving thebond between the steel and the masonry wall Producingcomposites with a denser microstructure also reduces the

porous nature of the material making it difficult for salts tomigrate [2 3]

In recent years supplementary cementitious materials(SCMs) such as fly ash slag and silica fume have been usedto replace a portion of the aggregate or cementitious materialin cement-based compositesThe aimhas been to improve themechanical properties by taking advantage of their extremelyfine spherical particles [4ndash7] The pozzolanic reaction ofSCMs produces an additional binder which increases thedensity of the microstructure thereby reducing permeabilityThe problem of efflorescence can be greatly reduced byincluding SCMs in cement-based composites

Metakaolin has been widely studied for its highly poz-zolanic properties suggesting that metakaolin could be usedas an SCM Unlike other SCMs that are secondary productsor by-products metakaolin is a primary product obtainedby calcining kaolin clay within a temperature range of 650 to800∘C [8 9]Metakaolin is increasingly being used to produce

2 The Scientific World Journal

Replacement of metakaolin ()

0

10

20

30

40

50

60

Com

pres

sive s

treng

th (M

Pa)

4022

51345346

5572

5002

3596

0 5 10 15 20 25

Figure 1 Histogram compressive strength versus replacement of metakaolin (age = 28 days)

(M0) (M5) (M10)

(M15) (M20) (M25)

Figure 2 Quantity of efflorescence under normal environmental conditions (7 days)

materials with higher strength denser microstructure lowerporosity higher resistance to ions and improved durability[10ndash12]

Very few researchers have addressed the problem of efflo-rescence in metakaolin cement-based composites This studysought to determine the appropriate quantity of metakaolinrequired (as a replacement for cement) to reduce efflores-cence We employed specimens with various replacementratios of metakaolin (0 5 10 15 20 and 25)at a watercement (wc) ratio of 05 The occurrence ofwhite efflorescence was investigated under various curingenvironments at the curing age of 3 7 and 28 days

2 Experimental Program

21 Materials and Specimens We produced matrices ofASTM Type Ι Portland cement silica sand tap water andmetakaolin The specific gravity and fineness modulus ofthe silica sand were 264 and 240 respectively The physicaland chemical properties of the metakaolin are presented inTables 1 and 2

Metakaolin was added as a replacement for cement at thefollowing percentages 0 5 10 15 20 and 25 of the weightof cement with the watercementitious ratio (wc) set to 050The mixes were then exposed to the following environments

The Scientific World Journal 3

(M0) (M5) (M10)

(M15) (M20) (M25)

Figure 3 Quantity of efflorescence under normal environmental conditions (56 days)

(M0) (M5)

(M15) (M20)

(M10) larr997892

(M25) larr997892

Figure 4 Quantity of efflorescence under carbon dioxide environmental conditions (7 days)

Table 1 Physical properties of metakaolin

Item Specific gravity Color Brightness ( ISO) Surface area (m2g) D10 (120583m) D50 (120583m) D90 (120583m) Bulk density (gcm3)Condition 260 White 79ndash82 15 lt20 lt45 lt25 003sim004

4 The Scientific World Journal

(M0) (M5)

(M15) (M20) (M25)

(M10) larr997892

Figure 5 Quantity of efflorescence under carbon dioxide environmental conditions (56 days)

(M0) (M5)

(M15) (M20)

(M10)

(M25) larr997892

Figure 6 Quantity of efflorescence under low temperature environmental conditions (7 days)

Table 2 Chemical properties of metakaolin

Item SiO2 Al2O3 Fe2O3 Tio2 SO4 P2O5 CaO MgO Na2O K2O LOIMass as oxide 52ndash55 41ndash44 lt19 lt30 lt005 lt02 lt02 lt01 lt005 lt075 lt05

The Scientific World Journal 5

(M0) (M5)

(M15) (M20) (M25)

(M10) larr997892

Figure 7 Quantity of efflorescence under low temperature environmental conditions (56 days)

0

10

20

30

40

50

60

0 5 10 15 20 25Metakaolin ()

7 days (NE)56 days (NE)7 days (CDE)

56 days (CDE)7 days (LTE)56 (LTE)

The p

ropo

rtio

ns o

f effl

ores

cenc

e are

a of t

otal

area

()

Figure 8 Proportional area of efflorescence versus replacement of metakaolin

normal environment (NE) 25∘C with 85 humidity car-bon dioxide environment (CDE) in a carbonization tubwith 100 carbon dioxide at 15 atm pressure 100∘C and90 relative humidity low temperature environment (LTE)refrigerated at minus5sim0∘C with 2 humidity

Themix proportions are presented in Table 3The codingin Table 3 (M0 M5 M10 M15 M20 andM25) represents thepercentage of metakaolin

Cubic specimens (50 times 50 times 50mm) were prepared to testthe compressive strength Additional specimens (150 times 150 times

6 The Scientific World Journal

0 5 10 15 2520Replacement of metakaolin ()

0

10

20

30

40

50

0

10

20

30

40

5060C

ompr

essiv

e stre

ngth

(MPa

)

Efflor

esce

nce a

rea f

or N

E (

)

Compressive strengthEfflorescence area

Figure 9 Curves comparing compressive strength versus replace-ment of metakaolin and area of efflorescence versus replacement ofmetakaolin (NE specimens)

Table 3 Designed mix proportions

Mix Water (g) Cement (g) Metakaolin (g) Sand (g)M0 41747 83494 0 83494M5 41747 79319 4175 83494M10 41747 75145 8349 83494M15 41747 70969 12525 83494M20 41747 66796 16698 83494M25 41747 81419 20875 83494

30mm) were also prepared for the quantification of efflores-cence using image analysis in MATLAB Finally specimens(10 times 10 times 10mm) were sliced from the mortar specimensfor observation under scanning electron microscope (SEM)and samples of mortar powder (3 g) were prepared for X-raydiffraction (XRD)

22 Testing Methods Compressive strength was determinedafter 1 3 7 and 28 days of curing according to ASTM C109-12The extent of white efflorescence was quantified accordingto RGB values using MATLAB (Matrix Laboratory) imageanalysis of photographs (taken at 7 and 56 days) of samplesexposed to the three experimental environments (NE CDEand LTE) MATLAB image analysis was unable to determinethe thickness of efflorescence therefore the specimens wereanalyzed using the curettagemethod to quantify efflorescenceaccording to weight The curettage method indicated that weremoved the efflorescence with a spatula and then weighed it

A petrographic examination of hardened mortar wasperformed using SEM according to ASTM C856-11 specifi-cations The specimens were dried vacuumed and Au ion-sputtered prior to SEM investigation in order to render thesurface conductive By varying the degree of magnification(times1000 and times3000) capillary pores of various sizes (micro-or meso-pore structure) were estimated

We also investigated the compounds of cement-basedmaterials following replacement with metakaolin Becausethe hydration of composite materials is multiphased all ofthe compositions are compounds that is almost no singleelement structures exist As a result we employed XRDanalysis to analyze the chemical compounds within cement-based materials These samples were ground into powderat room temperature under air-dried conditions and XRDpatterns were recorded using Cu-K radiation between 20∘to 80∘ at a scanning speed of 05 s1∘ The composition ofthe compounds was determined by comparing XRD intensitydiagrams with the peak values of corresponding compoundsin the computer database

3 Results And Discussion

31 Compressive Strength Compressive strength and the per-cent of relative compressive strength are presented in Table 4At the curing age of 28 days in the experiment results thehighest compressive strength was obtained from specimenswith 15 metakaolin (as a replacement for cement) asillustrated in Figure 1The compressive strength of specimenswithmetakaolin increased with time however for specimenscontaining 25metakaolin the strength characteristics failedto meet those of standard mortar specimens The inclusionof metakaolin in cement-based composites enhances com-pressive strength through the filler effect in the interfacialtransition zone between the cement paste and aggregateparticles In addition CHgels are quickly removed during thehydration of cement with metakaolin and actually acceleratecementitious hydration

32 Quantification of Efflorescence Using MATLAB ImageAnalysis The specimens were photographed at the curingage of 7 and 56 days to quantify efflorescence usingMATLABimage analysisThe areas affected by efflorescence as a ratio ofthe total area are summarized in Table 5The specimens con-taining 15 metakaolin present a distinctly lower degree ofefflorescence compared to the other specimens according tothe presence of deposits both on and around the specimens

As shown in Figures 2 3 4 5 6 and 7 the most obvi-ous efflorescence was observed on specimens cured underLTE conditions In addition the inclusion of metakaolindecreased the extent of efflorescence in all specimens exceptfor those with 20 and 25 metakaolin specimens with15 metakaolin showed the least efflorescence These resultsverify that the inclusion of metakaolin can accelerate thehydration reaction with CH to produce a denser morehomogeneous material with a narrower transition zonethereby reducing the extent of efflorescenceThese results arein strong agreement with those of the relationship betweenefflorescence area and the replacement of metakaolin asshown in Figure 8

Figure 9 compares the area affected by efflorescencewith compressive strength values the data are fundamen-tally consistent with the visible extents of efflorescence inFigures 2 3 4 5 6 and 7 for NE specimens As shown inFigure 9 cement-based composites produced with higher

The Scientific World Journal 7

(a) times1000

CH

Pore

Pore

(b) times3000

Figure 10 SEM observations for M0 specimens

(a) times1000

Pore

Pore

CH

(b) times3000

Figure 11 SEM images of M5 specimens

(a) times1000

Pore

(b) times3000

Figure 12 SEM images of M10 specimens

8 The Scientific World Journal

(a) times1000

Hydration

(b) times3000

Figure 13 SEM images of M15 specimens

(a) times1000 (b) times3000

Figure 14 SEM images of M20 specimens

(a) times1000

Pore

(b) times3000

Figure 15 SEM images of M25 specimens

The Scientific World Journal 9

Table 4 Compressive strength and percent of relative compressive strength

Mix Compressive strength (MPa) Relative compressive strength ()1 day 3 day 7 day 28 day 1 day 3 day 7 day 28 day

M0 1262 2520 2866 4022 100 100 100 100M5 1431 2846 3296 5134 113 113 115 128M10 1478 3054 3918 5346 117 121 137 133M15 1503 3716 4436 5572 119 147 155 139M20 1468 2834 3646 5002 116 112 127 124M25 1176 2088 2682 3596 93 83 94 89

Table 5 Proportion of white efflorescence over total area (unit )

Mix Exposure environment and age in days7 days (NE) 56 days (NE) 7 days (CDE) 56 days (CDE) 7 days (LTE) 56 days (LTE)

M0 3414 4785 3185 3409 4460 5704M5 3389 4285 3657 3961 3601 5294M10 1587 3442 2190 3159 2053 4138M15 1514 2034 925 1025 1529 2171M20 3329 3522 1588 2504 2865 3227M25 4635 4920 2424 2906 3007 4406

Table 6Quantity of efflorescence using the curettagemethodunderNE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13528 13976 13848 13539 14106 12617Weight after curettage 1352 1397 13842 13535 14101 12607Weight loss 08 06 06 04 05 1

Table 7Quantity of efflorescence using the curettagemethod underCDE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13284 14002 14147 13785 14187 12618Weight after curettage 13278 1400 14145 13784 14186 12614Weight loss 06 02 02 01 01 04

Table 8Quantity of efflorescence using the curettagemethod underLTE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13153 12902 13469 13147 13252 12524Weight after curettage 13141 12894 13463 13142 13245 12513Weight loss 12 08 06 05 07 11

quantities (5 to 20) of metakaolin provide higher strengthand resistance to efflorescence due to a denser microstruc-ture and the controlled concentration of mobile alkalis in thepore solutions respectively

33 Quantification of Efflorescence Using the CurettageMethod The results for the quantification of efflorescenceusing the curettage method are presented in Tables 6 7 and8 Clearly the addition of 15 metakaolin was most effective

in inhibiting efflorescence under any exposure environmentThe specimens cured under LTE conditions had a higherquantity of efflorescence than those under NE or CDEBased on the previous study higher humidity led to a higherquantity of efflorescence and efflorescence increased withan increase in the size of moist particles [13] In additionefflorescence was proportional to alkali leaching perhapsdue to the larger volume of macropores (particularly thosebetween 200 nm and 1000 nm) capable of increasing thediffusion coefficient for themigration ofNa from geopolymerphase into the solution [14]

34 Effect of Metakaolin on Microscopy Characteristics Thisstudy employed SEM observations to characterize the micro-structural compounds produced withwithout replacementmetakaolin Careful analysis ofmicrostructures can reveal thepozzolanic reaction and the gel development SEM magnifi-cation was set at 1000 and 3000 times to directly observe thedevelopment of cement hydration and pore structure SEMobservation was performed on control specimens after 56days of aging shown in Figure 10 large capillary pores CHand pore interconnectivity were observed

SEM observation was also applied to specimens withvarious amounts of replacement metakaolin (5 10 1520 and 25) at 56 days as shown in Figures 11 1213 14 and 15 Clearly cement-based paste specimens withreplacement metakaolin developed a more compact denserpore structure Hydration was formed on the surface of theM5 M10 M15 and M20 specimens the microstructure ofthese samples reduced themobility of chloride and other ionsresulting in higher compressive strength and a reduction incrack stretching

The SEM image in Figure 13 illustrates the relativelydense homogeneous microstructure of M15 specimens with

10 The Scientific World Journal

M25

M20

M15

M10

M5

M0

Sample

10 20 30 40 50 60 70 802120579 (deg)

15CaO SiO2 xH2OAl07Fe3Si03SiO2

Figure 16 XRD results of paste specimens with metakaolin

smooth surfaces and no distinct poresThe densemicrostruc-ture observed in SEM images is consistent with the resultsof compressive strength A number of large capillary poreswere observed in specimens containing 25 metakaolin asillustrated in Figure 15 exceeding those in other samplesThis may be due to the fineness of metakaolin reducingthe workability of the composites resulting in inconsistentdispersion of particles throughout the specimens In additionthe 25 metakaolin specimens contain a lot of unreactedprecursor powder due to the lack of water

A pozzolanic reaction between metakaolin and CHoccurred during the hydration of cement resulting in theconsumption of a portion of the CH The formation ofsecondary calcium-silicate-hydrate (C-S-H) gel (due to poz-zolanic reaction) although less dense than the primary C-S-H gel is effective in filling and segmenting large capillarypores into small discontinuous capillary pores through poresize refinement thereby decreasing the total permeabilityof cement-based composites The filler action of metakaolindue to its fine particle size (approximately 1120583m) comparedto the particle size of cement (approximately 12120583m) furtherincreases the density of the pore structure of metakaolincement-based composites

35 Influence of Metakaolin on Microscopy CharacteristicsThis study employed X-ray diffraction analysis to deter-mine the products of hydration in cement-based materialsFigure 16 illustrates the XRD results of cement-based pastespecimens with replacement metakaolin at 56 days It wasfound that the amounts of the primary hydration productsC-S-H (15CaO-SiO

2-119909H2O) and SiO

2 present a significant

form with the addition of metakaolin (M10 M15 and M20)In contrast Al

07Fe3Si03

content (peak value in Figure 16)increased significantly in the specimens containing 15 and20 metakaolin This is because metakaolin contains highquantities of Al

07Fe3Si03 which verifies that nonhydrated

particles could act as filler changing large capillary poresinto small discontinuous capillary pores The M15 and M20specimens presented superior pozzolanic activity which isconsistent with the compressive strength test results quantityof efflorescence and SEM observations In addition the peakvalue for theM25 specimens dropped significantly indicatingan inferior hydrated reaction compared with the controlspecimens This trend is similar to the results of compressivestrength in which the hydration reaction of specimens ofsamples with more than 20metakaolin is lower than that ofcontrol specimens due to the influence of reduced resistanceto efflorescence

4 Conclusion

Our results demonstrate that the replacement of cementusing metakaolin at percentages of 5 10 15 and 20increases compressive strength with a peak increase insamples produced using 15 metakaolin However a dis-tinct drop in compressive strength was observed in samplesproduced using 25 metakaolin MATLAB image analysisand the curettage method both indicate that efflorescenceis most pronounced when samples were cured in a lowtemperature environment exceeding that produced undera normal environment or carbon dioxide environment Inthe M5 M10 M15 and M20 samples the area affected byefflorescence was lower than that of the control specimensthe M15 specimens were the least affected by efflorescenceIn SEM micrographs materials produced with metakaolindeveloped denser smoother structures XRD results indicatethat the amount of main hydration products in cement-based materials with replacement metakaolin performed asignificant form Our results conclusively demonstrate thatcement-based materials with 15 replacement metakaolinhave superior performance with considerable potential forapplication in engineering

References

[1] A Aıt-Mokhtar R Belarbi F Benboudjema N Burlion BCapra et al ldquoExperimental investigation of the variability ofconcrete durability propertiesrdquo Cement and Concrete Researchvol 45 pp 21ndash36 2013

[2] E N Kani A Allahverdi and J L Provis ldquoEfflorescence controlin geopolymer binders based on natural pozzolanrdquo Cement andConcrete Composites vol 34 no 1 pp 25ndash33 2012

[3] X Y Wang and H S Lee ldquoModeling of chloride diffusion inconcrete containing low-calcium fly ashrdquo Materials Chemistryand Physics vol 138 pp 917ndash928 2013

[4] V S Ramachandran and J J BeaudoinHandbook of AnalyticalTechniques in Concrete Science and Technology Principles Tech-niques and Applications William Andrew 1st edition 2001

[5] C L Lee R Huang W T Lin and T L Weng ldquoEstablishmentof the durability indices for cement-based composite containingsupplementary cementitious materialsrdquo Materials and Designvol 37 pp 28ndash39 2012

[6] T Y Han W T Lin A Cheng R Huang and C C HuangldquoInfluence of polyolefin fibers on the engineering propertiesof cement-based composites containing silica fumerdquo Materialsand Design vol 37 pp 569ndash576 2012

The Scientific World Journal 11

[7] M I Khan and A M Alhozaimy ldquoProperties of naturalpozzolan and its potential utilization in environmental friendlyconcreterdquo Canadian Journal of Civil Engineering vol 38 no 1pp 71ndash78 2011

[8] A A Ramezanianpour and H B Jovein ldquoInfluence ofmetakaolin as supplementary cementing material on strengthand durability of concretesrdquo Construction and Building Materi-als vol 30 pp 470ndash479 2012

[9] E Guneyisi M Gesoglu S Karaoglu and K MermerdasldquoStrength permeability and shrinkage cracking of silica fumeand metakaolin concretesrdquo Construction and Building Materi-als vol 34 pp 120ndash130 2012

[10] H Paiva A Velosa P Cachim and V M Ferreira ldquoEffectof metakaolin dispersion on the fresh and hardened stateproperties of concreterdquo Cement and Concrete Research vol 42pp 607ndash612 2012

[11] E Guneyisi M Gesoglu F Karaboga and K MermerdasldquoCorrosion behavior of reinforcing steel embedded in chloridecontaminated concretes with and without metakaolinrdquo Com-posites B vol 45 pp 1288ndash1295 2013

[12] A Nadeem S A Memonb and T Y Lo ldquoMechanical per-formance durability qualitative and quantitative analysis ofmicrostructure of fly ash and Metakaolin mortar at elevatedtemperaturesrdquo Construction and Building Materials vol 38 pp338ndash347 2013

[13] Y Gao S B Chen and L E Yu ldquoEfflorescence relativehumidity of airborne sodium chloride particles a theoreticalinvestigationrdquoAtmospheric Environment vol 41 no 9 pp 2019ndash2023 2007

[14] L Zheng W Wang and Y Shi ldquoThe effects of alkaline dosageand SiAl ratio on the immobilization of heavy metals inmunicipal solid waste incineration fly ash-based geopolymerrdquoChemosphere vol 79 no 6 pp 665ndash671 2010

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2 The Scientific World Journal

Replacement of metakaolin ()

0

10

20

30

40

50

60

Com

pres

sive s

treng

th (M

Pa)

4022

51345346

5572

5002

3596

0 5 10 15 20 25

Figure 1 Histogram compressive strength versus replacement of metakaolin (age = 28 days)

(M0) (M5) (M10)

(M15) (M20) (M25)

Figure 2 Quantity of efflorescence under normal environmental conditions (7 days)

materials with higher strength denser microstructure lowerporosity higher resistance to ions and improved durability[10ndash12]

Very few researchers have addressed the problem of efflo-rescence in metakaolin cement-based composites This studysought to determine the appropriate quantity of metakaolinrequired (as a replacement for cement) to reduce efflores-cence We employed specimens with various replacementratios of metakaolin (0 5 10 15 20 and 25)at a watercement (wc) ratio of 05 The occurrence ofwhite efflorescence was investigated under various curingenvironments at the curing age of 3 7 and 28 days

2 Experimental Program

21 Materials and Specimens We produced matrices ofASTM Type Ι Portland cement silica sand tap water andmetakaolin The specific gravity and fineness modulus ofthe silica sand were 264 and 240 respectively The physicaland chemical properties of the metakaolin are presented inTables 1 and 2

Metakaolin was added as a replacement for cement at thefollowing percentages 0 5 10 15 20 and 25 of the weightof cement with the watercementitious ratio (wc) set to 050The mixes were then exposed to the following environments

The Scientific World Journal 3

(M0) (M5) (M10)

(M15) (M20) (M25)

Figure 3 Quantity of efflorescence under normal environmental conditions (56 days)

(M0) (M5)

(M15) (M20)

(M10) larr997892

(M25) larr997892

Figure 4 Quantity of efflorescence under carbon dioxide environmental conditions (7 days)

Table 1 Physical properties of metakaolin

Item Specific gravity Color Brightness ( ISO) Surface area (m2g) D10 (120583m) D50 (120583m) D90 (120583m) Bulk density (gcm3)Condition 260 White 79ndash82 15 lt20 lt45 lt25 003sim004

4 The Scientific World Journal

(M0) (M5)

(M15) (M20) (M25)

(M10) larr997892

Figure 5 Quantity of efflorescence under carbon dioxide environmental conditions (56 days)

(M0) (M5)

(M15) (M20)

(M10)

(M25) larr997892

Figure 6 Quantity of efflorescence under low temperature environmental conditions (7 days)

Table 2 Chemical properties of metakaolin

Item SiO2 Al2O3 Fe2O3 Tio2 SO4 P2O5 CaO MgO Na2O K2O LOIMass as oxide 52ndash55 41ndash44 lt19 lt30 lt005 lt02 lt02 lt01 lt005 lt075 lt05

The Scientific World Journal 5

(M0) (M5)

(M15) (M20) (M25)

(M10) larr997892

Figure 7 Quantity of efflorescence under low temperature environmental conditions (56 days)

0

10

20

30

40

50

60

0 5 10 15 20 25Metakaolin ()

7 days (NE)56 days (NE)7 days (CDE)

56 days (CDE)7 days (LTE)56 (LTE)

The p

ropo

rtio

ns o

f effl

ores

cenc

e are

a of t

otal

area

()

Figure 8 Proportional area of efflorescence versus replacement of metakaolin

normal environment (NE) 25∘C with 85 humidity car-bon dioxide environment (CDE) in a carbonization tubwith 100 carbon dioxide at 15 atm pressure 100∘C and90 relative humidity low temperature environment (LTE)refrigerated at minus5sim0∘C with 2 humidity

Themix proportions are presented in Table 3The codingin Table 3 (M0 M5 M10 M15 M20 andM25) represents thepercentage of metakaolin

Cubic specimens (50 times 50 times 50mm) were prepared to testthe compressive strength Additional specimens (150 times 150 times

6 The Scientific World Journal

0 5 10 15 2520Replacement of metakaolin ()

0

10

20

30

40

50

0

10

20

30

40

5060C

ompr

essiv

e stre

ngth

(MPa

)

Efflor

esce

nce a

rea f

or N

E (

)

Compressive strengthEfflorescence area

Figure 9 Curves comparing compressive strength versus replace-ment of metakaolin and area of efflorescence versus replacement ofmetakaolin (NE specimens)

Table 3 Designed mix proportions

Mix Water (g) Cement (g) Metakaolin (g) Sand (g)M0 41747 83494 0 83494M5 41747 79319 4175 83494M10 41747 75145 8349 83494M15 41747 70969 12525 83494M20 41747 66796 16698 83494M25 41747 81419 20875 83494

30mm) were also prepared for the quantification of efflores-cence using image analysis in MATLAB Finally specimens(10 times 10 times 10mm) were sliced from the mortar specimensfor observation under scanning electron microscope (SEM)and samples of mortar powder (3 g) were prepared for X-raydiffraction (XRD)

22 Testing Methods Compressive strength was determinedafter 1 3 7 and 28 days of curing according to ASTM C109-12The extent of white efflorescence was quantified accordingto RGB values using MATLAB (Matrix Laboratory) imageanalysis of photographs (taken at 7 and 56 days) of samplesexposed to the three experimental environments (NE CDEand LTE) MATLAB image analysis was unable to determinethe thickness of efflorescence therefore the specimens wereanalyzed using the curettagemethod to quantify efflorescenceaccording to weight The curettage method indicated that weremoved the efflorescence with a spatula and then weighed it

A petrographic examination of hardened mortar wasperformed using SEM according to ASTM C856-11 specifi-cations The specimens were dried vacuumed and Au ion-sputtered prior to SEM investigation in order to render thesurface conductive By varying the degree of magnification(times1000 and times3000) capillary pores of various sizes (micro-or meso-pore structure) were estimated

We also investigated the compounds of cement-basedmaterials following replacement with metakaolin Becausethe hydration of composite materials is multiphased all ofthe compositions are compounds that is almost no singleelement structures exist As a result we employed XRDanalysis to analyze the chemical compounds within cement-based materials These samples were ground into powderat room temperature under air-dried conditions and XRDpatterns were recorded using Cu-K radiation between 20∘to 80∘ at a scanning speed of 05 s1∘ The composition ofthe compounds was determined by comparing XRD intensitydiagrams with the peak values of corresponding compoundsin the computer database

3 Results And Discussion

31 Compressive Strength Compressive strength and the per-cent of relative compressive strength are presented in Table 4At the curing age of 28 days in the experiment results thehighest compressive strength was obtained from specimenswith 15 metakaolin (as a replacement for cement) asillustrated in Figure 1The compressive strength of specimenswithmetakaolin increased with time however for specimenscontaining 25metakaolin the strength characteristics failedto meet those of standard mortar specimens The inclusionof metakaolin in cement-based composites enhances com-pressive strength through the filler effect in the interfacialtransition zone between the cement paste and aggregateparticles In addition CHgels are quickly removed during thehydration of cement with metakaolin and actually acceleratecementitious hydration

32 Quantification of Efflorescence Using MATLAB ImageAnalysis The specimens were photographed at the curingage of 7 and 56 days to quantify efflorescence usingMATLABimage analysisThe areas affected by efflorescence as a ratio ofthe total area are summarized in Table 5The specimens con-taining 15 metakaolin present a distinctly lower degree ofefflorescence compared to the other specimens according tothe presence of deposits both on and around the specimens

As shown in Figures 2 3 4 5 6 and 7 the most obvi-ous efflorescence was observed on specimens cured underLTE conditions In addition the inclusion of metakaolindecreased the extent of efflorescence in all specimens exceptfor those with 20 and 25 metakaolin specimens with15 metakaolin showed the least efflorescence These resultsverify that the inclusion of metakaolin can accelerate thehydration reaction with CH to produce a denser morehomogeneous material with a narrower transition zonethereby reducing the extent of efflorescenceThese results arein strong agreement with those of the relationship betweenefflorescence area and the replacement of metakaolin asshown in Figure 8

Figure 9 compares the area affected by efflorescencewith compressive strength values the data are fundamen-tally consistent with the visible extents of efflorescence inFigures 2 3 4 5 6 and 7 for NE specimens As shown inFigure 9 cement-based composites produced with higher

The Scientific World Journal 7

(a) times1000

CH

Pore

Pore

(b) times3000

Figure 10 SEM observations for M0 specimens

(a) times1000

Pore

Pore

CH

(b) times3000

Figure 11 SEM images of M5 specimens

(a) times1000

Pore

(b) times3000

Figure 12 SEM images of M10 specimens

8 The Scientific World Journal

(a) times1000

Hydration

(b) times3000

Figure 13 SEM images of M15 specimens

(a) times1000 (b) times3000

Figure 14 SEM images of M20 specimens

(a) times1000

Pore

(b) times3000

Figure 15 SEM images of M25 specimens

The Scientific World Journal 9

Table 4 Compressive strength and percent of relative compressive strength

Mix Compressive strength (MPa) Relative compressive strength ()1 day 3 day 7 day 28 day 1 day 3 day 7 day 28 day

M0 1262 2520 2866 4022 100 100 100 100M5 1431 2846 3296 5134 113 113 115 128M10 1478 3054 3918 5346 117 121 137 133M15 1503 3716 4436 5572 119 147 155 139M20 1468 2834 3646 5002 116 112 127 124M25 1176 2088 2682 3596 93 83 94 89

Table 5 Proportion of white efflorescence over total area (unit )

Mix Exposure environment and age in days7 days (NE) 56 days (NE) 7 days (CDE) 56 days (CDE) 7 days (LTE) 56 days (LTE)

M0 3414 4785 3185 3409 4460 5704M5 3389 4285 3657 3961 3601 5294M10 1587 3442 2190 3159 2053 4138M15 1514 2034 925 1025 1529 2171M20 3329 3522 1588 2504 2865 3227M25 4635 4920 2424 2906 3007 4406

Table 6Quantity of efflorescence using the curettagemethodunderNE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13528 13976 13848 13539 14106 12617Weight after curettage 1352 1397 13842 13535 14101 12607Weight loss 08 06 06 04 05 1

Table 7Quantity of efflorescence using the curettagemethod underCDE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13284 14002 14147 13785 14187 12618Weight after curettage 13278 1400 14145 13784 14186 12614Weight loss 06 02 02 01 01 04

Table 8Quantity of efflorescence using the curettagemethod underLTE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13153 12902 13469 13147 13252 12524Weight after curettage 13141 12894 13463 13142 13245 12513Weight loss 12 08 06 05 07 11

quantities (5 to 20) of metakaolin provide higher strengthand resistance to efflorescence due to a denser microstruc-ture and the controlled concentration of mobile alkalis in thepore solutions respectively

33 Quantification of Efflorescence Using the CurettageMethod The results for the quantification of efflorescenceusing the curettage method are presented in Tables 6 7 and8 Clearly the addition of 15 metakaolin was most effective

in inhibiting efflorescence under any exposure environmentThe specimens cured under LTE conditions had a higherquantity of efflorescence than those under NE or CDEBased on the previous study higher humidity led to a higherquantity of efflorescence and efflorescence increased withan increase in the size of moist particles [13] In additionefflorescence was proportional to alkali leaching perhapsdue to the larger volume of macropores (particularly thosebetween 200 nm and 1000 nm) capable of increasing thediffusion coefficient for themigration ofNa from geopolymerphase into the solution [14]

34 Effect of Metakaolin on Microscopy Characteristics Thisstudy employed SEM observations to characterize the micro-structural compounds produced withwithout replacementmetakaolin Careful analysis ofmicrostructures can reveal thepozzolanic reaction and the gel development SEM magnifi-cation was set at 1000 and 3000 times to directly observe thedevelopment of cement hydration and pore structure SEMobservation was performed on control specimens after 56days of aging shown in Figure 10 large capillary pores CHand pore interconnectivity were observed

SEM observation was also applied to specimens withvarious amounts of replacement metakaolin (5 10 1520 and 25) at 56 days as shown in Figures 11 1213 14 and 15 Clearly cement-based paste specimens withreplacement metakaolin developed a more compact denserpore structure Hydration was formed on the surface of theM5 M10 M15 and M20 specimens the microstructure ofthese samples reduced themobility of chloride and other ionsresulting in higher compressive strength and a reduction incrack stretching

The SEM image in Figure 13 illustrates the relativelydense homogeneous microstructure of M15 specimens with

10 The Scientific World Journal

M25

M20

M15

M10

M5

M0

Sample

10 20 30 40 50 60 70 802120579 (deg)

15CaO SiO2 xH2OAl07Fe3Si03SiO2

Figure 16 XRD results of paste specimens with metakaolin

smooth surfaces and no distinct poresThe densemicrostruc-ture observed in SEM images is consistent with the resultsof compressive strength A number of large capillary poreswere observed in specimens containing 25 metakaolin asillustrated in Figure 15 exceeding those in other samplesThis may be due to the fineness of metakaolin reducingthe workability of the composites resulting in inconsistentdispersion of particles throughout the specimens In additionthe 25 metakaolin specimens contain a lot of unreactedprecursor powder due to the lack of water

A pozzolanic reaction between metakaolin and CHoccurred during the hydration of cement resulting in theconsumption of a portion of the CH The formation ofsecondary calcium-silicate-hydrate (C-S-H) gel (due to poz-zolanic reaction) although less dense than the primary C-S-H gel is effective in filling and segmenting large capillarypores into small discontinuous capillary pores through poresize refinement thereby decreasing the total permeabilityof cement-based composites The filler action of metakaolindue to its fine particle size (approximately 1120583m) comparedto the particle size of cement (approximately 12120583m) furtherincreases the density of the pore structure of metakaolincement-based composites

35 Influence of Metakaolin on Microscopy CharacteristicsThis study employed X-ray diffraction analysis to deter-mine the products of hydration in cement-based materialsFigure 16 illustrates the XRD results of cement-based pastespecimens with replacement metakaolin at 56 days It wasfound that the amounts of the primary hydration productsC-S-H (15CaO-SiO

2-119909H2O) and SiO

2 present a significant

form with the addition of metakaolin (M10 M15 and M20)In contrast Al

07Fe3Si03

content (peak value in Figure 16)increased significantly in the specimens containing 15 and20 metakaolin This is because metakaolin contains highquantities of Al

07Fe3Si03 which verifies that nonhydrated

particles could act as filler changing large capillary poresinto small discontinuous capillary pores The M15 and M20specimens presented superior pozzolanic activity which isconsistent with the compressive strength test results quantityof efflorescence and SEM observations In addition the peakvalue for theM25 specimens dropped significantly indicatingan inferior hydrated reaction compared with the controlspecimens This trend is similar to the results of compressivestrength in which the hydration reaction of specimens ofsamples with more than 20metakaolin is lower than that ofcontrol specimens due to the influence of reduced resistanceto efflorescence

4 Conclusion

Our results demonstrate that the replacement of cementusing metakaolin at percentages of 5 10 15 and 20increases compressive strength with a peak increase insamples produced using 15 metakaolin However a dis-tinct drop in compressive strength was observed in samplesproduced using 25 metakaolin MATLAB image analysisand the curettage method both indicate that efflorescenceis most pronounced when samples were cured in a lowtemperature environment exceeding that produced undera normal environment or carbon dioxide environment Inthe M5 M10 M15 and M20 samples the area affected byefflorescence was lower than that of the control specimensthe M15 specimens were the least affected by efflorescenceIn SEM micrographs materials produced with metakaolindeveloped denser smoother structures XRD results indicatethat the amount of main hydration products in cement-based materials with replacement metakaolin performed asignificant form Our results conclusively demonstrate thatcement-based materials with 15 replacement metakaolinhave superior performance with considerable potential forapplication in engineering

References

[1] A Aıt-Mokhtar R Belarbi F Benboudjema N Burlion BCapra et al ldquoExperimental investigation of the variability ofconcrete durability propertiesrdquo Cement and Concrete Researchvol 45 pp 21ndash36 2013

[2] E N Kani A Allahverdi and J L Provis ldquoEfflorescence controlin geopolymer binders based on natural pozzolanrdquo Cement andConcrete Composites vol 34 no 1 pp 25ndash33 2012

[3] X Y Wang and H S Lee ldquoModeling of chloride diffusion inconcrete containing low-calcium fly ashrdquo Materials Chemistryand Physics vol 138 pp 917ndash928 2013

[4] V S Ramachandran and J J BeaudoinHandbook of AnalyticalTechniques in Concrete Science and Technology Principles Tech-niques and Applications William Andrew 1st edition 2001

[5] C L Lee R Huang W T Lin and T L Weng ldquoEstablishmentof the durability indices for cement-based composite containingsupplementary cementitious materialsrdquo Materials and Designvol 37 pp 28ndash39 2012

[6] T Y Han W T Lin A Cheng R Huang and C C HuangldquoInfluence of polyolefin fibers on the engineering propertiesof cement-based composites containing silica fumerdquo Materialsand Design vol 37 pp 569ndash576 2012

The Scientific World Journal 11

[7] M I Khan and A M Alhozaimy ldquoProperties of naturalpozzolan and its potential utilization in environmental friendlyconcreterdquo Canadian Journal of Civil Engineering vol 38 no 1pp 71ndash78 2011

[8] A A Ramezanianpour and H B Jovein ldquoInfluence ofmetakaolin as supplementary cementing material on strengthand durability of concretesrdquo Construction and Building Materi-als vol 30 pp 470ndash479 2012

[9] E Guneyisi M Gesoglu S Karaoglu and K MermerdasldquoStrength permeability and shrinkage cracking of silica fumeand metakaolin concretesrdquo Construction and Building Materi-als vol 34 pp 120ndash130 2012

[10] H Paiva A Velosa P Cachim and V M Ferreira ldquoEffectof metakaolin dispersion on the fresh and hardened stateproperties of concreterdquo Cement and Concrete Research vol 42pp 607ndash612 2012

[11] E Guneyisi M Gesoglu F Karaboga and K MermerdasldquoCorrosion behavior of reinforcing steel embedded in chloridecontaminated concretes with and without metakaolinrdquo Com-posites B vol 45 pp 1288ndash1295 2013

[12] A Nadeem S A Memonb and T Y Lo ldquoMechanical per-formance durability qualitative and quantitative analysis ofmicrostructure of fly ash and Metakaolin mortar at elevatedtemperaturesrdquo Construction and Building Materials vol 38 pp338ndash347 2013

[13] Y Gao S B Chen and L E Yu ldquoEfflorescence relativehumidity of airborne sodium chloride particles a theoreticalinvestigationrdquoAtmospheric Environment vol 41 no 9 pp 2019ndash2023 2007

[14] L Zheng W Wang and Y Shi ldquoThe effects of alkaline dosageand SiAl ratio on the immobilization of heavy metals inmunicipal solid waste incineration fly ash-based geopolymerrdquoChemosphere vol 79 no 6 pp 665ndash671 2010

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Active and Passive Electronic Components

Control Scienceand Engineering

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

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Chemical EngineeringInternational Journal of Antennas and

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The Scientific World Journal 3

(M0) (M5) (M10)

(M15) (M20) (M25)

Figure 3 Quantity of efflorescence under normal environmental conditions (56 days)

(M0) (M5)

(M15) (M20)

(M10) larr997892

(M25) larr997892

Figure 4 Quantity of efflorescence under carbon dioxide environmental conditions (7 days)

Table 1 Physical properties of metakaolin

Item Specific gravity Color Brightness ( ISO) Surface area (m2g) D10 (120583m) D50 (120583m) D90 (120583m) Bulk density (gcm3)Condition 260 White 79ndash82 15 lt20 lt45 lt25 003sim004

4 The Scientific World Journal

(M0) (M5)

(M15) (M20) (M25)

(M10) larr997892

Figure 5 Quantity of efflorescence under carbon dioxide environmental conditions (56 days)

(M0) (M5)

(M15) (M20)

(M10)

(M25) larr997892

Figure 6 Quantity of efflorescence under low temperature environmental conditions (7 days)

Table 2 Chemical properties of metakaolin

Item SiO2 Al2O3 Fe2O3 Tio2 SO4 P2O5 CaO MgO Na2O K2O LOIMass as oxide 52ndash55 41ndash44 lt19 lt30 lt005 lt02 lt02 lt01 lt005 lt075 lt05

The Scientific World Journal 5

(M0) (M5)

(M15) (M20) (M25)

(M10) larr997892

Figure 7 Quantity of efflorescence under low temperature environmental conditions (56 days)

0

10

20

30

40

50

60

0 5 10 15 20 25Metakaolin ()

7 days (NE)56 days (NE)7 days (CDE)

56 days (CDE)7 days (LTE)56 (LTE)

The p

ropo

rtio

ns o

f effl

ores

cenc

e are

a of t

otal

area

()

Figure 8 Proportional area of efflorescence versus replacement of metakaolin

normal environment (NE) 25∘C with 85 humidity car-bon dioxide environment (CDE) in a carbonization tubwith 100 carbon dioxide at 15 atm pressure 100∘C and90 relative humidity low temperature environment (LTE)refrigerated at minus5sim0∘C with 2 humidity

Themix proportions are presented in Table 3The codingin Table 3 (M0 M5 M10 M15 M20 andM25) represents thepercentage of metakaolin

Cubic specimens (50 times 50 times 50mm) were prepared to testthe compressive strength Additional specimens (150 times 150 times

6 The Scientific World Journal

0 5 10 15 2520Replacement of metakaolin ()

0

10

20

30

40

50

0

10

20

30

40

5060C

ompr

essiv

e stre

ngth

(MPa

)

Efflor

esce

nce a

rea f

or N

E (

)

Compressive strengthEfflorescence area

Figure 9 Curves comparing compressive strength versus replace-ment of metakaolin and area of efflorescence versus replacement ofmetakaolin (NE specimens)

Table 3 Designed mix proportions

Mix Water (g) Cement (g) Metakaolin (g) Sand (g)M0 41747 83494 0 83494M5 41747 79319 4175 83494M10 41747 75145 8349 83494M15 41747 70969 12525 83494M20 41747 66796 16698 83494M25 41747 81419 20875 83494

30mm) were also prepared for the quantification of efflores-cence using image analysis in MATLAB Finally specimens(10 times 10 times 10mm) were sliced from the mortar specimensfor observation under scanning electron microscope (SEM)and samples of mortar powder (3 g) were prepared for X-raydiffraction (XRD)

22 Testing Methods Compressive strength was determinedafter 1 3 7 and 28 days of curing according to ASTM C109-12The extent of white efflorescence was quantified accordingto RGB values using MATLAB (Matrix Laboratory) imageanalysis of photographs (taken at 7 and 56 days) of samplesexposed to the three experimental environments (NE CDEand LTE) MATLAB image analysis was unable to determinethe thickness of efflorescence therefore the specimens wereanalyzed using the curettagemethod to quantify efflorescenceaccording to weight The curettage method indicated that weremoved the efflorescence with a spatula and then weighed it

A petrographic examination of hardened mortar wasperformed using SEM according to ASTM C856-11 specifi-cations The specimens were dried vacuumed and Au ion-sputtered prior to SEM investigation in order to render thesurface conductive By varying the degree of magnification(times1000 and times3000) capillary pores of various sizes (micro-or meso-pore structure) were estimated

We also investigated the compounds of cement-basedmaterials following replacement with metakaolin Becausethe hydration of composite materials is multiphased all ofthe compositions are compounds that is almost no singleelement structures exist As a result we employed XRDanalysis to analyze the chemical compounds within cement-based materials These samples were ground into powderat room temperature under air-dried conditions and XRDpatterns were recorded using Cu-K radiation between 20∘to 80∘ at a scanning speed of 05 s1∘ The composition ofthe compounds was determined by comparing XRD intensitydiagrams with the peak values of corresponding compoundsin the computer database

3 Results And Discussion

31 Compressive Strength Compressive strength and the per-cent of relative compressive strength are presented in Table 4At the curing age of 28 days in the experiment results thehighest compressive strength was obtained from specimenswith 15 metakaolin (as a replacement for cement) asillustrated in Figure 1The compressive strength of specimenswithmetakaolin increased with time however for specimenscontaining 25metakaolin the strength characteristics failedto meet those of standard mortar specimens The inclusionof metakaolin in cement-based composites enhances com-pressive strength through the filler effect in the interfacialtransition zone between the cement paste and aggregateparticles In addition CHgels are quickly removed during thehydration of cement with metakaolin and actually acceleratecementitious hydration

32 Quantification of Efflorescence Using MATLAB ImageAnalysis The specimens were photographed at the curingage of 7 and 56 days to quantify efflorescence usingMATLABimage analysisThe areas affected by efflorescence as a ratio ofthe total area are summarized in Table 5The specimens con-taining 15 metakaolin present a distinctly lower degree ofefflorescence compared to the other specimens according tothe presence of deposits both on and around the specimens

As shown in Figures 2 3 4 5 6 and 7 the most obvi-ous efflorescence was observed on specimens cured underLTE conditions In addition the inclusion of metakaolindecreased the extent of efflorescence in all specimens exceptfor those with 20 and 25 metakaolin specimens with15 metakaolin showed the least efflorescence These resultsverify that the inclusion of metakaolin can accelerate thehydration reaction with CH to produce a denser morehomogeneous material with a narrower transition zonethereby reducing the extent of efflorescenceThese results arein strong agreement with those of the relationship betweenefflorescence area and the replacement of metakaolin asshown in Figure 8

Figure 9 compares the area affected by efflorescencewith compressive strength values the data are fundamen-tally consistent with the visible extents of efflorescence inFigures 2 3 4 5 6 and 7 for NE specimens As shown inFigure 9 cement-based composites produced with higher

The Scientific World Journal 7

(a) times1000

CH

Pore

Pore

(b) times3000

Figure 10 SEM observations for M0 specimens

(a) times1000

Pore

Pore

CH

(b) times3000

Figure 11 SEM images of M5 specimens

(a) times1000

Pore

(b) times3000

Figure 12 SEM images of M10 specimens

8 The Scientific World Journal

(a) times1000

Hydration

(b) times3000

Figure 13 SEM images of M15 specimens

(a) times1000 (b) times3000

Figure 14 SEM images of M20 specimens

(a) times1000

Pore

(b) times3000

Figure 15 SEM images of M25 specimens

The Scientific World Journal 9

Table 4 Compressive strength and percent of relative compressive strength

Mix Compressive strength (MPa) Relative compressive strength ()1 day 3 day 7 day 28 day 1 day 3 day 7 day 28 day

M0 1262 2520 2866 4022 100 100 100 100M5 1431 2846 3296 5134 113 113 115 128M10 1478 3054 3918 5346 117 121 137 133M15 1503 3716 4436 5572 119 147 155 139M20 1468 2834 3646 5002 116 112 127 124M25 1176 2088 2682 3596 93 83 94 89

Table 5 Proportion of white efflorescence over total area (unit )

Mix Exposure environment and age in days7 days (NE) 56 days (NE) 7 days (CDE) 56 days (CDE) 7 days (LTE) 56 days (LTE)

M0 3414 4785 3185 3409 4460 5704M5 3389 4285 3657 3961 3601 5294M10 1587 3442 2190 3159 2053 4138M15 1514 2034 925 1025 1529 2171M20 3329 3522 1588 2504 2865 3227M25 4635 4920 2424 2906 3007 4406

Table 6Quantity of efflorescence using the curettagemethodunderNE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13528 13976 13848 13539 14106 12617Weight after curettage 1352 1397 13842 13535 14101 12607Weight loss 08 06 06 04 05 1

Table 7Quantity of efflorescence using the curettagemethod underCDE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13284 14002 14147 13785 14187 12618Weight after curettage 13278 1400 14145 13784 14186 12614Weight loss 06 02 02 01 01 04

Table 8Quantity of efflorescence using the curettagemethod underLTE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13153 12902 13469 13147 13252 12524Weight after curettage 13141 12894 13463 13142 13245 12513Weight loss 12 08 06 05 07 11

quantities (5 to 20) of metakaolin provide higher strengthand resistance to efflorescence due to a denser microstruc-ture and the controlled concentration of mobile alkalis in thepore solutions respectively

33 Quantification of Efflorescence Using the CurettageMethod The results for the quantification of efflorescenceusing the curettage method are presented in Tables 6 7 and8 Clearly the addition of 15 metakaolin was most effective

in inhibiting efflorescence under any exposure environmentThe specimens cured under LTE conditions had a higherquantity of efflorescence than those under NE or CDEBased on the previous study higher humidity led to a higherquantity of efflorescence and efflorescence increased withan increase in the size of moist particles [13] In additionefflorescence was proportional to alkali leaching perhapsdue to the larger volume of macropores (particularly thosebetween 200 nm and 1000 nm) capable of increasing thediffusion coefficient for themigration ofNa from geopolymerphase into the solution [14]

34 Effect of Metakaolin on Microscopy Characteristics Thisstudy employed SEM observations to characterize the micro-structural compounds produced withwithout replacementmetakaolin Careful analysis ofmicrostructures can reveal thepozzolanic reaction and the gel development SEM magnifi-cation was set at 1000 and 3000 times to directly observe thedevelopment of cement hydration and pore structure SEMobservation was performed on control specimens after 56days of aging shown in Figure 10 large capillary pores CHand pore interconnectivity were observed

SEM observation was also applied to specimens withvarious amounts of replacement metakaolin (5 10 1520 and 25) at 56 days as shown in Figures 11 1213 14 and 15 Clearly cement-based paste specimens withreplacement metakaolin developed a more compact denserpore structure Hydration was formed on the surface of theM5 M10 M15 and M20 specimens the microstructure ofthese samples reduced themobility of chloride and other ionsresulting in higher compressive strength and a reduction incrack stretching

The SEM image in Figure 13 illustrates the relativelydense homogeneous microstructure of M15 specimens with

10 The Scientific World Journal

M25

M20

M15

M10

M5

M0

Sample

10 20 30 40 50 60 70 802120579 (deg)

15CaO SiO2 xH2OAl07Fe3Si03SiO2

Figure 16 XRD results of paste specimens with metakaolin

smooth surfaces and no distinct poresThe densemicrostruc-ture observed in SEM images is consistent with the resultsof compressive strength A number of large capillary poreswere observed in specimens containing 25 metakaolin asillustrated in Figure 15 exceeding those in other samplesThis may be due to the fineness of metakaolin reducingthe workability of the composites resulting in inconsistentdispersion of particles throughout the specimens In additionthe 25 metakaolin specimens contain a lot of unreactedprecursor powder due to the lack of water

A pozzolanic reaction between metakaolin and CHoccurred during the hydration of cement resulting in theconsumption of a portion of the CH The formation ofsecondary calcium-silicate-hydrate (C-S-H) gel (due to poz-zolanic reaction) although less dense than the primary C-S-H gel is effective in filling and segmenting large capillarypores into small discontinuous capillary pores through poresize refinement thereby decreasing the total permeabilityof cement-based composites The filler action of metakaolindue to its fine particle size (approximately 1120583m) comparedto the particle size of cement (approximately 12120583m) furtherincreases the density of the pore structure of metakaolincement-based composites

35 Influence of Metakaolin on Microscopy CharacteristicsThis study employed X-ray diffraction analysis to deter-mine the products of hydration in cement-based materialsFigure 16 illustrates the XRD results of cement-based pastespecimens with replacement metakaolin at 56 days It wasfound that the amounts of the primary hydration productsC-S-H (15CaO-SiO

2-119909H2O) and SiO

2 present a significant

form with the addition of metakaolin (M10 M15 and M20)In contrast Al

07Fe3Si03

content (peak value in Figure 16)increased significantly in the specimens containing 15 and20 metakaolin This is because metakaolin contains highquantities of Al

07Fe3Si03 which verifies that nonhydrated

particles could act as filler changing large capillary poresinto small discontinuous capillary pores The M15 and M20specimens presented superior pozzolanic activity which isconsistent with the compressive strength test results quantityof efflorescence and SEM observations In addition the peakvalue for theM25 specimens dropped significantly indicatingan inferior hydrated reaction compared with the controlspecimens This trend is similar to the results of compressivestrength in which the hydration reaction of specimens ofsamples with more than 20metakaolin is lower than that ofcontrol specimens due to the influence of reduced resistanceto efflorescence

4 Conclusion

Our results demonstrate that the replacement of cementusing metakaolin at percentages of 5 10 15 and 20increases compressive strength with a peak increase insamples produced using 15 metakaolin However a dis-tinct drop in compressive strength was observed in samplesproduced using 25 metakaolin MATLAB image analysisand the curettage method both indicate that efflorescenceis most pronounced when samples were cured in a lowtemperature environment exceeding that produced undera normal environment or carbon dioxide environment Inthe M5 M10 M15 and M20 samples the area affected byefflorescence was lower than that of the control specimensthe M15 specimens were the least affected by efflorescenceIn SEM micrographs materials produced with metakaolindeveloped denser smoother structures XRD results indicatethat the amount of main hydration products in cement-based materials with replacement metakaolin performed asignificant form Our results conclusively demonstrate thatcement-based materials with 15 replacement metakaolinhave superior performance with considerable potential forapplication in engineering

References

[1] A Aıt-Mokhtar R Belarbi F Benboudjema N Burlion BCapra et al ldquoExperimental investigation of the variability ofconcrete durability propertiesrdquo Cement and Concrete Researchvol 45 pp 21ndash36 2013

[2] E N Kani A Allahverdi and J L Provis ldquoEfflorescence controlin geopolymer binders based on natural pozzolanrdquo Cement andConcrete Composites vol 34 no 1 pp 25ndash33 2012

[3] X Y Wang and H S Lee ldquoModeling of chloride diffusion inconcrete containing low-calcium fly ashrdquo Materials Chemistryand Physics vol 138 pp 917ndash928 2013

[4] V S Ramachandran and J J BeaudoinHandbook of AnalyticalTechniques in Concrete Science and Technology Principles Tech-niques and Applications William Andrew 1st edition 2001

[5] C L Lee R Huang W T Lin and T L Weng ldquoEstablishmentof the durability indices for cement-based composite containingsupplementary cementitious materialsrdquo Materials and Designvol 37 pp 28ndash39 2012

[6] T Y Han W T Lin A Cheng R Huang and C C HuangldquoInfluence of polyolefin fibers on the engineering propertiesof cement-based composites containing silica fumerdquo Materialsand Design vol 37 pp 569ndash576 2012

The Scientific World Journal 11

[7] M I Khan and A M Alhozaimy ldquoProperties of naturalpozzolan and its potential utilization in environmental friendlyconcreterdquo Canadian Journal of Civil Engineering vol 38 no 1pp 71ndash78 2011

[8] A A Ramezanianpour and H B Jovein ldquoInfluence ofmetakaolin as supplementary cementing material on strengthand durability of concretesrdquo Construction and Building Materi-als vol 30 pp 470ndash479 2012

[9] E Guneyisi M Gesoglu S Karaoglu and K MermerdasldquoStrength permeability and shrinkage cracking of silica fumeand metakaolin concretesrdquo Construction and Building Materi-als vol 34 pp 120ndash130 2012

[10] H Paiva A Velosa P Cachim and V M Ferreira ldquoEffectof metakaolin dispersion on the fresh and hardened stateproperties of concreterdquo Cement and Concrete Research vol 42pp 607ndash612 2012

[11] E Guneyisi M Gesoglu F Karaboga and K MermerdasldquoCorrosion behavior of reinforcing steel embedded in chloridecontaminated concretes with and without metakaolinrdquo Com-posites B vol 45 pp 1288ndash1295 2013

[12] A Nadeem S A Memonb and T Y Lo ldquoMechanical per-formance durability qualitative and quantitative analysis ofmicrostructure of fly ash and Metakaolin mortar at elevatedtemperaturesrdquo Construction and Building Materials vol 38 pp338ndash347 2013

[13] Y Gao S B Chen and L E Yu ldquoEfflorescence relativehumidity of airborne sodium chloride particles a theoreticalinvestigationrdquoAtmospheric Environment vol 41 no 9 pp 2019ndash2023 2007

[14] L Zheng W Wang and Y Shi ldquoThe effects of alkaline dosageand SiAl ratio on the immobilization of heavy metals inmunicipal solid waste incineration fly ash-based geopolymerrdquoChemosphere vol 79 no 6 pp 665ndash671 2010

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

4 The Scientific World Journal

(M0) (M5)

(M15) (M20) (M25)

(M10) larr997892

Figure 5 Quantity of efflorescence under carbon dioxide environmental conditions (56 days)

(M0) (M5)

(M15) (M20)

(M10)

(M25) larr997892

Figure 6 Quantity of efflorescence under low temperature environmental conditions (7 days)

Table 2 Chemical properties of metakaolin

Item SiO2 Al2O3 Fe2O3 Tio2 SO4 P2O5 CaO MgO Na2O K2O LOIMass as oxide 52ndash55 41ndash44 lt19 lt30 lt005 lt02 lt02 lt01 lt005 lt075 lt05

The Scientific World Journal 5

(M0) (M5)

(M15) (M20) (M25)

(M10) larr997892

Figure 7 Quantity of efflorescence under low temperature environmental conditions (56 days)

0

10

20

30

40

50

60

0 5 10 15 20 25Metakaolin ()

7 days (NE)56 days (NE)7 days (CDE)

56 days (CDE)7 days (LTE)56 (LTE)

The p

ropo

rtio

ns o

f effl

ores

cenc

e are

a of t

otal

area

()

Figure 8 Proportional area of efflorescence versus replacement of metakaolin

normal environment (NE) 25∘C with 85 humidity car-bon dioxide environment (CDE) in a carbonization tubwith 100 carbon dioxide at 15 atm pressure 100∘C and90 relative humidity low temperature environment (LTE)refrigerated at minus5sim0∘C with 2 humidity

Themix proportions are presented in Table 3The codingin Table 3 (M0 M5 M10 M15 M20 andM25) represents thepercentage of metakaolin

Cubic specimens (50 times 50 times 50mm) were prepared to testthe compressive strength Additional specimens (150 times 150 times

6 The Scientific World Journal

0 5 10 15 2520Replacement of metakaolin ()

0

10

20

30

40

50

0

10

20

30

40

5060C

ompr

essiv

e stre

ngth

(MPa

)

Efflor

esce

nce a

rea f

or N

E (

)

Compressive strengthEfflorescence area

Figure 9 Curves comparing compressive strength versus replace-ment of metakaolin and area of efflorescence versus replacement ofmetakaolin (NE specimens)

Table 3 Designed mix proportions

Mix Water (g) Cement (g) Metakaolin (g) Sand (g)M0 41747 83494 0 83494M5 41747 79319 4175 83494M10 41747 75145 8349 83494M15 41747 70969 12525 83494M20 41747 66796 16698 83494M25 41747 81419 20875 83494

30mm) were also prepared for the quantification of efflores-cence using image analysis in MATLAB Finally specimens(10 times 10 times 10mm) were sliced from the mortar specimensfor observation under scanning electron microscope (SEM)and samples of mortar powder (3 g) were prepared for X-raydiffraction (XRD)

22 Testing Methods Compressive strength was determinedafter 1 3 7 and 28 days of curing according to ASTM C109-12The extent of white efflorescence was quantified accordingto RGB values using MATLAB (Matrix Laboratory) imageanalysis of photographs (taken at 7 and 56 days) of samplesexposed to the three experimental environments (NE CDEand LTE) MATLAB image analysis was unable to determinethe thickness of efflorescence therefore the specimens wereanalyzed using the curettagemethod to quantify efflorescenceaccording to weight The curettage method indicated that weremoved the efflorescence with a spatula and then weighed it

A petrographic examination of hardened mortar wasperformed using SEM according to ASTM C856-11 specifi-cations The specimens were dried vacuumed and Au ion-sputtered prior to SEM investigation in order to render thesurface conductive By varying the degree of magnification(times1000 and times3000) capillary pores of various sizes (micro-or meso-pore structure) were estimated

We also investigated the compounds of cement-basedmaterials following replacement with metakaolin Becausethe hydration of composite materials is multiphased all ofthe compositions are compounds that is almost no singleelement structures exist As a result we employed XRDanalysis to analyze the chemical compounds within cement-based materials These samples were ground into powderat room temperature under air-dried conditions and XRDpatterns were recorded using Cu-K radiation between 20∘to 80∘ at a scanning speed of 05 s1∘ The composition ofthe compounds was determined by comparing XRD intensitydiagrams with the peak values of corresponding compoundsin the computer database

3 Results And Discussion

31 Compressive Strength Compressive strength and the per-cent of relative compressive strength are presented in Table 4At the curing age of 28 days in the experiment results thehighest compressive strength was obtained from specimenswith 15 metakaolin (as a replacement for cement) asillustrated in Figure 1The compressive strength of specimenswithmetakaolin increased with time however for specimenscontaining 25metakaolin the strength characteristics failedto meet those of standard mortar specimens The inclusionof metakaolin in cement-based composites enhances com-pressive strength through the filler effect in the interfacialtransition zone between the cement paste and aggregateparticles In addition CHgels are quickly removed during thehydration of cement with metakaolin and actually acceleratecementitious hydration

32 Quantification of Efflorescence Using MATLAB ImageAnalysis The specimens were photographed at the curingage of 7 and 56 days to quantify efflorescence usingMATLABimage analysisThe areas affected by efflorescence as a ratio ofthe total area are summarized in Table 5The specimens con-taining 15 metakaolin present a distinctly lower degree ofefflorescence compared to the other specimens according tothe presence of deposits both on and around the specimens

As shown in Figures 2 3 4 5 6 and 7 the most obvi-ous efflorescence was observed on specimens cured underLTE conditions In addition the inclusion of metakaolindecreased the extent of efflorescence in all specimens exceptfor those with 20 and 25 metakaolin specimens with15 metakaolin showed the least efflorescence These resultsverify that the inclusion of metakaolin can accelerate thehydration reaction with CH to produce a denser morehomogeneous material with a narrower transition zonethereby reducing the extent of efflorescenceThese results arein strong agreement with those of the relationship betweenefflorescence area and the replacement of metakaolin asshown in Figure 8

Figure 9 compares the area affected by efflorescencewith compressive strength values the data are fundamen-tally consistent with the visible extents of efflorescence inFigures 2 3 4 5 6 and 7 for NE specimens As shown inFigure 9 cement-based composites produced with higher

The Scientific World Journal 7

(a) times1000

CH

Pore

Pore

(b) times3000

Figure 10 SEM observations for M0 specimens

(a) times1000

Pore

Pore

CH

(b) times3000

Figure 11 SEM images of M5 specimens

(a) times1000

Pore

(b) times3000

Figure 12 SEM images of M10 specimens

8 The Scientific World Journal

(a) times1000

Hydration

(b) times3000

Figure 13 SEM images of M15 specimens

(a) times1000 (b) times3000

Figure 14 SEM images of M20 specimens

(a) times1000

Pore

(b) times3000

Figure 15 SEM images of M25 specimens

The Scientific World Journal 9

Table 4 Compressive strength and percent of relative compressive strength

Mix Compressive strength (MPa) Relative compressive strength ()1 day 3 day 7 day 28 day 1 day 3 day 7 day 28 day

M0 1262 2520 2866 4022 100 100 100 100M5 1431 2846 3296 5134 113 113 115 128M10 1478 3054 3918 5346 117 121 137 133M15 1503 3716 4436 5572 119 147 155 139M20 1468 2834 3646 5002 116 112 127 124M25 1176 2088 2682 3596 93 83 94 89

Table 5 Proportion of white efflorescence over total area (unit )

Mix Exposure environment and age in days7 days (NE) 56 days (NE) 7 days (CDE) 56 days (CDE) 7 days (LTE) 56 days (LTE)

M0 3414 4785 3185 3409 4460 5704M5 3389 4285 3657 3961 3601 5294M10 1587 3442 2190 3159 2053 4138M15 1514 2034 925 1025 1529 2171M20 3329 3522 1588 2504 2865 3227M25 4635 4920 2424 2906 3007 4406

Table 6Quantity of efflorescence using the curettagemethodunderNE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13528 13976 13848 13539 14106 12617Weight after curettage 1352 1397 13842 13535 14101 12607Weight loss 08 06 06 04 05 1

Table 7Quantity of efflorescence using the curettagemethod underCDE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13284 14002 14147 13785 14187 12618Weight after curettage 13278 1400 14145 13784 14186 12614Weight loss 06 02 02 01 01 04

Table 8Quantity of efflorescence using the curettagemethod underLTE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13153 12902 13469 13147 13252 12524Weight after curettage 13141 12894 13463 13142 13245 12513Weight loss 12 08 06 05 07 11

quantities (5 to 20) of metakaolin provide higher strengthand resistance to efflorescence due to a denser microstruc-ture and the controlled concentration of mobile alkalis in thepore solutions respectively

33 Quantification of Efflorescence Using the CurettageMethod The results for the quantification of efflorescenceusing the curettage method are presented in Tables 6 7 and8 Clearly the addition of 15 metakaolin was most effective

in inhibiting efflorescence under any exposure environmentThe specimens cured under LTE conditions had a higherquantity of efflorescence than those under NE or CDEBased on the previous study higher humidity led to a higherquantity of efflorescence and efflorescence increased withan increase in the size of moist particles [13] In additionefflorescence was proportional to alkali leaching perhapsdue to the larger volume of macropores (particularly thosebetween 200 nm and 1000 nm) capable of increasing thediffusion coefficient for themigration ofNa from geopolymerphase into the solution [14]

34 Effect of Metakaolin on Microscopy Characteristics Thisstudy employed SEM observations to characterize the micro-structural compounds produced withwithout replacementmetakaolin Careful analysis ofmicrostructures can reveal thepozzolanic reaction and the gel development SEM magnifi-cation was set at 1000 and 3000 times to directly observe thedevelopment of cement hydration and pore structure SEMobservation was performed on control specimens after 56days of aging shown in Figure 10 large capillary pores CHand pore interconnectivity were observed

SEM observation was also applied to specimens withvarious amounts of replacement metakaolin (5 10 1520 and 25) at 56 days as shown in Figures 11 1213 14 and 15 Clearly cement-based paste specimens withreplacement metakaolin developed a more compact denserpore structure Hydration was formed on the surface of theM5 M10 M15 and M20 specimens the microstructure ofthese samples reduced themobility of chloride and other ionsresulting in higher compressive strength and a reduction incrack stretching

The SEM image in Figure 13 illustrates the relativelydense homogeneous microstructure of M15 specimens with

10 The Scientific World Journal

M25

M20

M15

M10

M5

M0

Sample

10 20 30 40 50 60 70 802120579 (deg)

15CaO SiO2 xH2OAl07Fe3Si03SiO2

Figure 16 XRD results of paste specimens with metakaolin

smooth surfaces and no distinct poresThe densemicrostruc-ture observed in SEM images is consistent with the resultsof compressive strength A number of large capillary poreswere observed in specimens containing 25 metakaolin asillustrated in Figure 15 exceeding those in other samplesThis may be due to the fineness of metakaolin reducingthe workability of the composites resulting in inconsistentdispersion of particles throughout the specimens In additionthe 25 metakaolin specimens contain a lot of unreactedprecursor powder due to the lack of water

A pozzolanic reaction between metakaolin and CHoccurred during the hydration of cement resulting in theconsumption of a portion of the CH The formation ofsecondary calcium-silicate-hydrate (C-S-H) gel (due to poz-zolanic reaction) although less dense than the primary C-S-H gel is effective in filling and segmenting large capillarypores into small discontinuous capillary pores through poresize refinement thereby decreasing the total permeabilityof cement-based composites The filler action of metakaolindue to its fine particle size (approximately 1120583m) comparedto the particle size of cement (approximately 12120583m) furtherincreases the density of the pore structure of metakaolincement-based composites

35 Influence of Metakaolin on Microscopy CharacteristicsThis study employed X-ray diffraction analysis to deter-mine the products of hydration in cement-based materialsFigure 16 illustrates the XRD results of cement-based pastespecimens with replacement metakaolin at 56 days It wasfound that the amounts of the primary hydration productsC-S-H (15CaO-SiO

2-119909H2O) and SiO

2 present a significant

form with the addition of metakaolin (M10 M15 and M20)In contrast Al

07Fe3Si03

content (peak value in Figure 16)increased significantly in the specimens containing 15 and20 metakaolin This is because metakaolin contains highquantities of Al

07Fe3Si03 which verifies that nonhydrated

particles could act as filler changing large capillary poresinto small discontinuous capillary pores The M15 and M20specimens presented superior pozzolanic activity which isconsistent with the compressive strength test results quantityof efflorescence and SEM observations In addition the peakvalue for theM25 specimens dropped significantly indicatingan inferior hydrated reaction compared with the controlspecimens This trend is similar to the results of compressivestrength in which the hydration reaction of specimens ofsamples with more than 20metakaolin is lower than that ofcontrol specimens due to the influence of reduced resistanceto efflorescence

4 Conclusion

Our results demonstrate that the replacement of cementusing metakaolin at percentages of 5 10 15 and 20increases compressive strength with a peak increase insamples produced using 15 metakaolin However a dis-tinct drop in compressive strength was observed in samplesproduced using 25 metakaolin MATLAB image analysisand the curettage method both indicate that efflorescenceis most pronounced when samples were cured in a lowtemperature environment exceeding that produced undera normal environment or carbon dioxide environment Inthe M5 M10 M15 and M20 samples the area affected byefflorescence was lower than that of the control specimensthe M15 specimens were the least affected by efflorescenceIn SEM micrographs materials produced with metakaolindeveloped denser smoother structures XRD results indicatethat the amount of main hydration products in cement-based materials with replacement metakaolin performed asignificant form Our results conclusively demonstrate thatcement-based materials with 15 replacement metakaolinhave superior performance with considerable potential forapplication in engineering

References

[1] A Aıt-Mokhtar R Belarbi F Benboudjema N Burlion BCapra et al ldquoExperimental investigation of the variability ofconcrete durability propertiesrdquo Cement and Concrete Researchvol 45 pp 21ndash36 2013

[2] E N Kani A Allahverdi and J L Provis ldquoEfflorescence controlin geopolymer binders based on natural pozzolanrdquo Cement andConcrete Composites vol 34 no 1 pp 25ndash33 2012

[3] X Y Wang and H S Lee ldquoModeling of chloride diffusion inconcrete containing low-calcium fly ashrdquo Materials Chemistryand Physics vol 138 pp 917ndash928 2013

[4] V S Ramachandran and J J BeaudoinHandbook of AnalyticalTechniques in Concrete Science and Technology Principles Tech-niques and Applications William Andrew 1st edition 2001

[5] C L Lee R Huang W T Lin and T L Weng ldquoEstablishmentof the durability indices for cement-based composite containingsupplementary cementitious materialsrdquo Materials and Designvol 37 pp 28ndash39 2012

[6] T Y Han W T Lin A Cheng R Huang and C C HuangldquoInfluence of polyolefin fibers on the engineering propertiesof cement-based composites containing silica fumerdquo Materialsand Design vol 37 pp 569ndash576 2012

The Scientific World Journal 11

[7] M I Khan and A M Alhozaimy ldquoProperties of naturalpozzolan and its potential utilization in environmental friendlyconcreterdquo Canadian Journal of Civil Engineering vol 38 no 1pp 71ndash78 2011

[8] A A Ramezanianpour and H B Jovein ldquoInfluence ofmetakaolin as supplementary cementing material on strengthand durability of concretesrdquo Construction and Building Materi-als vol 30 pp 470ndash479 2012

[9] E Guneyisi M Gesoglu S Karaoglu and K MermerdasldquoStrength permeability and shrinkage cracking of silica fumeand metakaolin concretesrdquo Construction and Building Materi-als vol 34 pp 120ndash130 2012

[10] H Paiva A Velosa P Cachim and V M Ferreira ldquoEffectof metakaolin dispersion on the fresh and hardened stateproperties of concreterdquo Cement and Concrete Research vol 42pp 607ndash612 2012

[11] E Guneyisi M Gesoglu F Karaboga and K MermerdasldquoCorrosion behavior of reinforcing steel embedded in chloridecontaminated concretes with and without metakaolinrdquo Com-posites B vol 45 pp 1288ndash1295 2013

[12] A Nadeem S A Memonb and T Y Lo ldquoMechanical per-formance durability qualitative and quantitative analysis ofmicrostructure of fly ash and Metakaolin mortar at elevatedtemperaturesrdquo Construction and Building Materials vol 38 pp338ndash347 2013

[13] Y Gao S B Chen and L E Yu ldquoEfflorescence relativehumidity of airborne sodium chloride particles a theoreticalinvestigationrdquoAtmospheric Environment vol 41 no 9 pp 2019ndash2023 2007

[14] L Zheng W Wang and Y Shi ldquoThe effects of alkaline dosageand SiAl ratio on the immobilization of heavy metals inmunicipal solid waste incineration fly ash-based geopolymerrdquoChemosphere vol 79 no 6 pp 665ndash671 2010

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

The Scientific World Journal 5

(M0) (M5)

(M15) (M20) (M25)

(M10) larr997892

Figure 7 Quantity of efflorescence under low temperature environmental conditions (56 days)

0

10

20

30

40

50

60

0 5 10 15 20 25Metakaolin ()

7 days (NE)56 days (NE)7 days (CDE)

56 days (CDE)7 days (LTE)56 (LTE)

The p

ropo

rtio

ns o

f effl

ores

cenc

e are

a of t

otal

area

()

Figure 8 Proportional area of efflorescence versus replacement of metakaolin

normal environment (NE) 25∘C with 85 humidity car-bon dioxide environment (CDE) in a carbonization tubwith 100 carbon dioxide at 15 atm pressure 100∘C and90 relative humidity low temperature environment (LTE)refrigerated at minus5sim0∘C with 2 humidity

Themix proportions are presented in Table 3The codingin Table 3 (M0 M5 M10 M15 M20 andM25) represents thepercentage of metakaolin

Cubic specimens (50 times 50 times 50mm) were prepared to testthe compressive strength Additional specimens (150 times 150 times

6 The Scientific World Journal

0 5 10 15 2520Replacement of metakaolin ()

0

10

20

30

40

50

0

10

20

30

40

5060C

ompr

essiv

e stre

ngth

(MPa

)

Efflor

esce

nce a

rea f

or N

E (

)

Compressive strengthEfflorescence area

Figure 9 Curves comparing compressive strength versus replace-ment of metakaolin and area of efflorescence versus replacement ofmetakaolin (NE specimens)

Table 3 Designed mix proportions

Mix Water (g) Cement (g) Metakaolin (g) Sand (g)M0 41747 83494 0 83494M5 41747 79319 4175 83494M10 41747 75145 8349 83494M15 41747 70969 12525 83494M20 41747 66796 16698 83494M25 41747 81419 20875 83494

30mm) were also prepared for the quantification of efflores-cence using image analysis in MATLAB Finally specimens(10 times 10 times 10mm) were sliced from the mortar specimensfor observation under scanning electron microscope (SEM)and samples of mortar powder (3 g) were prepared for X-raydiffraction (XRD)

22 Testing Methods Compressive strength was determinedafter 1 3 7 and 28 days of curing according to ASTM C109-12The extent of white efflorescence was quantified accordingto RGB values using MATLAB (Matrix Laboratory) imageanalysis of photographs (taken at 7 and 56 days) of samplesexposed to the three experimental environments (NE CDEand LTE) MATLAB image analysis was unable to determinethe thickness of efflorescence therefore the specimens wereanalyzed using the curettagemethod to quantify efflorescenceaccording to weight The curettage method indicated that weremoved the efflorescence with a spatula and then weighed it

A petrographic examination of hardened mortar wasperformed using SEM according to ASTM C856-11 specifi-cations The specimens were dried vacuumed and Au ion-sputtered prior to SEM investigation in order to render thesurface conductive By varying the degree of magnification(times1000 and times3000) capillary pores of various sizes (micro-or meso-pore structure) were estimated

We also investigated the compounds of cement-basedmaterials following replacement with metakaolin Becausethe hydration of composite materials is multiphased all ofthe compositions are compounds that is almost no singleelement structures exist As a result we employed XRDanalysis to analyze the chemical compounds within cement-based materials These samples were ground into powderat room temperature under air-dried conditions and XRDpatterns were recorded using Cu-K radiation between 20∘to 80∘ at a scanning speed of 05 s1∘ The composition ofthe compounds was determined by comparing XRD intensitydiagrams with the peak values of corresponding compoundsin the computer database

3 Results And Discussion

31 Compressive Strength Compressive strength and the per-cent of relative compressive strength are presented in Table 4At the curing age of 28 days in the experiment results thehighest compressive strength was obtained from specimenswith 15 metakaolin (as a replacement for cement) asillustrated in Figure 1The compressive strength of specimenswithmetakaolin increased with time however for specimenscontaining 25metakaolin the strength characteristics failedto meet those of standard mortar specimens The inclusionof metakaolin in cement-based composites enhances com-pressive strength through the filler effect in the interfacialtransition zone between the cement paste and aggregateparticles In addition CHgels are quickly removed during thehydration of cement with metakaolin and actually acceleratecementitious hydration

32 Quantification of Efflorescence Using MATLAB ImageAnalysis The specimens were photographed at the curingage of 7 and 56 days to quantify efflorescence usingMATLABimage analysisThe areas affected by efflorescence as a ratio ofthe total area are summarized in Table 5The specimens con-taining 15 metakaolin present a distinctly lower degree ofefflorescence compared to the other specimens according tothe presence of deposits both on and around the specimens

As shown in Figures 2 3 4 5 6 and 7 the most obvi-ous efflorescence was observed on specimens cured underLTE conditions In addition the inclusion of metakaolindecreased the extent of efflorescence in all specimens exceptfor those with 20 and 25 metakaolin specimens with15 metakaolin showed the least efflorescence These resultsverify that the inclusion of metakaolin can accelerate thehydration reaction with CH to produce a denser morehomogeneous material with a narrower transition zonethereby reducing the extent of efflorescenceThese results arein strong agreement with those of the relationship betweenefflorescence area and the replacement of metakaolin asshown in Figure 8

Figure 9 compares the area affected by efflorescencewith compressive strength values the data are fundamen-tally consistent with the visible extents of efflorescence inFigures 2 3 4 5 6 and 7 for NE specimens As shown inFigure 9 cement-based composites produced with higher

The Scientific World Journal 7

(a) times1000

CH

Pore

Pore

(b) times3000

Figure 10 SEM observations for M0 specimens

(a) times1000

Pore

Pore

CH

(b) times3000

Figure 11 SEM images of M5 specimens

(a) times1000

Pore

(b) times3000

Figure 12 SEM images of M10 specimens

8 The Scientific World Journal

(a) times1000

Hydration

(b) times3000

Figure 13 SEM images of M15 specimens

(a) times1000 (b) times3000

Figure 14 SEM images of M20 specimens

(a) times1000

Pore

(b) times3000

Figure 15 SEM images of M25 specimens

The Scientific World Journal 9

Table 4 Compressive strength and percent of relative compressive strength

Mix Compressive strength (MPa) Relative compressive strength ()1 day 3 day 7 day 28 day 1 day 3 day 7 day 28 day

M0 1262 2520 2866 4022 100 100 100 100M5 1431 2846 3296 5134 113 113 115 128M10 1478 3054 3918 5346 117 121 137 133M15 1503 3716 4436 5572 119 147 155 139M20 1468 2834 3646 5002 116 112 127 124M25 1176 2088 2682 3596 93 83 94 89

Table 5 Proportion of white efflorescence over total area (unit )

Mix Exposure environment and age in days7 days (NE) 56 days (NE) 7 days (CDE) 56 days (CDE) 7 days (LTE) 56 days (LTE)

M0 3414 4785 3185 3409 4460 5704M5 3389 4285 3657 3961 3601 5294M10 1587 3442 2190 3159 2053 4138M15 1514 2034 925 1025 1529 2171M20 3329 3522 1588 2504 2865 3227M25 4635 4920 2424 2906 3007 4406

Table 6Quantity of efflorescence using the curettagemethodunderNE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13528 13976 13848 13539 14106 12617Weight after curettage 1352 1397 13842 13535 14101 12607Weight loss 08 06 06 04 05 1

Table 7Quantity of efflorescence using the curettagemethod underCDE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13284 14002 14147 13785 14187 12618Weight after curettage 13278 1400 14145 13784 14186 12614Weight loss 06 02 02 01 01 04

Table 8Quantity of efflorescence using the curettagemethod underLTE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13153 12902 13469 13147 13252 12524Weight after curettage 13141 12894 13463 13142 13245 12513Weight loss 12 08 06 05 07 11

quantities (5 to 20) of metakaolin provide higher strengthand resistance to efflorescence due to a denser microstruc-ture and the controlled concentration of mobile alkalis in thepore solutions respectively

33 Quantification of Efflorescence Using the CurettageMethod The results for the quantification of efflorescenceusing the curettage method are presented in Tables 6 7 and8 Clearly the addition of 15 metakaolin was most effective

in inhibiting efflorescence under any exposure environmentThe specimens cured under LTE conditions had a higherquantity of efflorescence than those under NE or CDEBased on the previous study higher humidity led to a higherquantity of efflorescence and efflorescence increased withan increase in the size of moist particles [13] In additionefflorescence was proportional to alkali leaching perhapsdue to the larger volume of macropores (particularly thosebetween 200 nm and 1000 nm) capable of increasing thediffusion coefficient for themigration ofNa from geopolymerphase into the solution [14]

34 Effect of Metakaolin on Microscopy Characteristics Thisstudy employed SEM observations to characterize the micro-structural compounds produced withwithout replacementmetakaolin Careful analysis ofmicrostructures can reveal thepozzolanic reaction and the gel development SEM magnifi-cation was set at 1000 and 3000 times to directly observe thedevelopment of cement hydration and pore structure SEMobservation was performed on control specimens after 56days of aging shown in Figure 10 large capillary pores CHand pore interconnectivity were observed

SEM observation was also applied to specimens withvarious amounts of replacement metakaolin (5 10 1520 and 25) at 56 days as shown in Figures 11 1213 14 and 15 Clearly cement-based paste specimens withreplacement metakaolin developed a more compact denserpore structure Hydration was formed on the surface of theM5 M10 M15 and M20 specimens the microstructure ofthese samples reduced themobility of chloride and other ionsresulting in higher compressive strength and a reduction incrack stretching

The SEM image in Figure 13 illustrates the relativelydense homogeneous microstructure of M15 specimens with

10 The Scientific World Journal

M25

M20

M15

M10

M5

M0

Sample

10 20 30 40 50 60 70 802120579 (deg)

15CaO SiO2 xH2OAl07Fe3Si03SiO2

Figure 16 XRD results of paste specimens with metakaolin

smooth surfaces and no distinct poresThe densemicrostruc-ture observed in SEM images is consistent with the resultsof compressive strength A number of large capillary poreswere observed in specimens containing 25 metakaolin asillustrated in Figure 15 exceeding those in other samplesThis may be due to the fineness of metakaolin reducingthe workability of the composites resulting in inconsistentdispersion of particles throughout the specimens In additionthe 25 metakaolin specimens contain a lot of unreactedprecursor powder due to the lack of water

A pozzolanic reaction between metakaolin and CHoccurred during the hydration of cement resulting in theconsumption of a portion of the CH The formation ofsecondary calcium-silicate-hydrate (C-S-H) gel (due to poz-zolanic reaction) although less dense than the primary C-S-H gel is effective in filling and segmenting large capillarypores into small discontinuous capillary pores through poresize refinement thereby decreasing the total permeabilityof cement-based composites The filler action of metakaolindue to its fine particle size (approximately 1120583m) comparedto the particle size of cement (approximately 12120583m) furtherincreases the density of the pore structure of metakaolincement-based composites

35 Influence of Metakaolin on Microscopy CharacteristicsThis study employed X-ray diffraction analysis to deter-mine the products of hydration in cement-based materialsFigure 16 illustrates the XRD results of cement-based pastespecimens with replacement metakaolin at 56 days It wasfound that the amounts of the primary hydration productsC-S-H (15CaO-SiO

2-119909H2O) and SiO

2 present a significant

form with the addition of metakaolin (M10 M15 and M20)In contrast Al

07Fe3Si03

content (peak value in Figure 16)increased significantly in the specimens containing 15 and20 metakaolin This is because metakaolin contains highquantities of Al

07Fe3Si03 which verifies that nonhydrated

particles could act as filler changing large capillary poresinto small discontinuous capillary pores The M15 and M20specimens presented superior pozzolanic activity which isconsistent with the compressive strength test results quantityof efflorescence and SEM observations In addition the peakvalue for theM25 specimens dropped significantly indicatingan inferior hydrated reaction compared with the controlspecimens This trend is similar to the results of compressivestrength in which the hydration reaction of specimens ofsamples with more than 20metakaolin is lower than that ofcontrol specimens due to the influence of reduced resistanceto efflorescence

4 Conclusion

Our results demonstrate that the replacement of cementusing metakaolin at percentages of 5 10 15 and 20increases compressive strength with a peak increase insamples produced using 15 metakaolin However a dis-tinct drop in compressive strength was observed in samplesproduced using 25 metakaolin MATLAB image analysisand the curettage method both indicate that efflorescenceis most pronounced when samples were cured in a lowtemperature environment exceeding that produced undera normal environment or carbon dioxide environment Inthe M5 M10 M15 and M20 samples the area affected byefflorescence was lower than that of the control specimensthe M15 specimens were the least affected by efflorescenceIn SEM micrographs materials produced with metakaolindeveloped denser smoother structures XRD results indicatethat the amount of main hydration products in cement-based materials with replacement metakaolin performed asignificant form Our results conclusively demonstrate thatcement-based materials with 15 replacement metakaolinhave superior performance with considerable potential forapplication in engineering

References

[1] A Aıt-Mokhtar R Belarbi F Benboudjema N Burlion BCapra et al ldquoExperimental investigation of the variability ofconcrete durability propertiesrdquo Cement and Concrete Researchvol 45 pp 21ndash36 2013

[2] E N Kani A Allahverdi and J L Provis ldquoEfflorescence controlin geopolymer binders based on natural pozzolanrdquo Cement andConcrete Composites vol 34 no 1 pp 25ndash33 2012

[3] X Y Wang and H S Lee ldquoModeling of chloride diffusion inconcrete containing low-calcium fly ashrdquo Materials Chemistryand Physics vol 138 pp 917ndash928 2013

[4] V S Ramachandran and J J BeaudoinHandbook of AnalyticalTechniques in Concrete Science and Technology Principles Tech-niques and Applications William Andrew 1st edition 2001

[5] C L Lee R Huang W T Lin and T L Weng ldquoEstablishmentof the durability indices for cement-based composite containingsupplementary cementitious materialsrdquo Materials and Designvol 37 pp 28ndash39 2012

[6] T Y Han W T Lin A Cheng R Huang and C C HuangldquoInfluence of polyolefin fibers on the engineering propertiesof cement-based composites containing silica fumerdquo Materialsand Design vol 37 pp 569ndash576 2012

The Scientific World Journal 11

[7] M I Khan and A M Alhozaimy ldquoProperties of naturalpozzolan and its potential utilization in environmental friendlyconcreterdquo Canadian Journal of Civil Engineering vol 38 no 1pp 71ndash78 2011

[8] A A Ramezanianpour and H B Jovein ldquoInfluence ofmetakaolin as supplementary cementing material on strengthand durability of concretesrdquo Construction and Building Materi-als vol 30 pp 470ndash479 2012

[9] E Guneyisi M Gesoglu S Karaoglu and K MermerdasldquoStrength permeability and shrinkage cracking of silica fumeand metakaolin concretesrdquo Construction and Building Materi-als vol 34 pp 120ndash130 2012

[10] H Paiva A Velosa P Cachim and V M Ferreira ldquoEffectof metakaolin dispersion on the fresh and hardened stateproperties of concreterdquo Cement and Concrete Research vol 42pp 607ndash612 2012

[11] E Guneyisi M Gesoglu F Karaboga and K MermerdasldquoCorrosion behavior of reinforcing steel embedded in chloridecontaminated concretes with and without metakaolinrdquo Com-posites B vol 45 pp 1288ndash1295 2013

[12] A Nadeem S A Memonb and T Y Lo ldquoMechanical per-formance durability qualitative and quantitative analysis ofmicrostructure of fly ash and Metakaolin mortar at elevatedtemperaturesrdquo Construction and Building Materials vol 38 pp338ndash347 2013

[13] Y Gao S B Chen and L E Yu ldquoEfflorescence relativehumidity of airborne sodium chloride particles a theoreticalinvestigationrdquoAtmospheric Environment vol 41 no 9 pp 2019ndash2023 2007

[14] L Zheng W Wang and Y Shi ldquoThe effects of alkaline dosageand SiAl ratio on the immobilization of heavy metals inmunicipal solid waste incineration fly ash-based geopolymerrdquoChemosphere vol 79 no 6 pp 665ndash671 2010

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

6 The Scientific World Journal

0 5 10 15 2520Replacement of metakaolin ()

0

10

20

30

40

50

0

10

20

30

40

5060C

ompr

essiv

e stre

ngth

(MPa

)

Efflor

esce

nce a

rea f

or N

E (

)

Compressive strengthEfflorescence area

Figure 9 Curves comparing compressive strength versus replace-ment of metakaolin and area of efflorescence versus replacement ofmetakaolin (NE specimens)

Table 3 Designed mix proportions

Mix Water (g) Cement (g) Metakaolin (g) Sand (g)M0 41747 83494 0 83494M5 41747 79319 4175 83494M10 41747 75145 8349 83494M15 41747 70969 12525 83494M20 41747 66796 16698 83494M25 41747 81419 20875 83494

30mm) were also prepared for the quantification of efflores-cence using image analysis in MATLAB Finally specimens(10 times 10 times 10mm) were sliced from the mortar specimensfor observation under scanning electron microscope (SEM)and samples of mortar powder (3 g) were prepared for X-raydiffraction (XRD)

22 Testing Methods Compressive strength was determinedafter 1 3 7 and 28 days of curing according to ASTM C109-12The extent of white efflorescence was quantified accordingto RGB values using MATLAB (Matrix Laboratory) imageanalysis of photographs (taken at 7 and 56 days) of samplesexposed to the three experimental environments (NE CDEand LTE) MATLAB image analysis was unable to determinethe thickness of efflorescence therefore the specimens wereanalyzed using the curettagemethod to quantify efflorescenceaccording to weight The curettage method indicated that weremoved the efflorescence with a spatula and then weighed it

A petrographic examination of hardened mortar wasperformed using SEM according to ASTM C856-11 specifi-cations The specimens were dried vacuumed and Au ion-sputtered prior to SEM investigation in order to render thesurface conductive By varying the degree of magnification(times1000 and times3000) capillary pores of various sizes (micro-or meso-pore structure) were estimated

We also investigated the compounds of cement-basedmaterials following replacement with metakaolin Becausethe hydration of composite materials is multiphased all ofthe compositions are compounds that is almost no singleelement structures exist As a result we employed XRDanalysis to analyze the chemical compounds within cement-based materials These samples were ground into powderat room temperature under air-dried conditions and XRDpatterns were recorded using Cu-K radiation between 20∘to 80∘ at a scanning speed of 05 s1∘ The composition ofthe compounds was determined by comparing XRD intensitydiagrams with the peak values of corresponding compoundsin the computer database

3 Results And Discussion

31 Compressive Strength Compressive strength and the per-cent of relative compressive strength are presented in Table 4At the curing age of 28 days in the experiment results thehighest compressive strength was obtained from specimenswith 15 metakaolin (as a replacement for cement) asillustrated in Figure 1The compressive strength of specimenswithmetakaolin increased with time however for specimenscontaining 25metakaolin the strength characteristics failedto meet those of standard mortar specimens The inclusionof metakaolin in cement-based composites enhances com-pressive strength through the filler effect in the interfacialtransition zone between the cement paste and aggregateparticles In addition CHgels are quickly removed during thehydration of cement with metakaolin and actually acceleratecementitious hydration

32 Quantification of Efflorescence Using MATLAB ImageAnalysis The specimens were photographed at the curingage of 7 and 56 days to quantify efflorescence usingMATLABimage analysisThe areas affected by efflorescence as a ratio ofthe total area are summarized in Table 5The specimens con-taining 15 metakaolin present a distinctly lower degree ofefflorescence compared to the other specimens according tothe presence of deposits both on and around the specimens

As shown in Figures 2 3 4 5 6 and 7 the most obvi-ous efflorescence was observed on specimens cured underLTE conditions In addition the inclusion of metakaolindecreased the extent of efflorescence in all specimens exceptfor those with 20 and 25 metakaolin specimens with15 metakaolin showed the least efflorescence These resultsverify that the inclusion of metakaolin can accelerate thehydration reaction with CH to produce a denser morehomogeneous material with a narrower transition zonethereby reducing the extent of efflorescenceThese results arein strong agreement with those of the relationship betweenefflorescence area and the replacement of metakaolin asshown in Figure 8

Figure 9 compares the area affected by efflorescencewith compressive strength values the data are fundamen-tally consistent with the visible extents of efflorescence inFigures 2 3 4 5 6 and 7 for NE specimens As shown inFigure 9 cement-based composites produced with higher

The Scientific World Journal 7

(a) times1000

CH

Pore

Pore

(b) times3000

Figure 10 SEM observations for M0 specimens

(a) times1000

Pore

Pore

CH

(b) times3000

Figure 11 SEM images of M5 specimens

(a) times1000

Pore

(b) times3000

Figure 12 SEM images of M10 specimens

8 The Scientific World Journal

(a) times1000

Hydration

(b) times3000

Figure 13 SEM images of M15 specimens

(a) times1000 (b) times3000

Figure 14 SEM images of M20 specimens

(a) times1000

Pore

(b) times3000

Figure 15 SEM images of M25 specimens

The Scientific World Journal 9

Table 4 Compressive strength and percent of relative compressive strength

Mix Compressive strength (MPa) Relative compressive strength ()1 day 3 day 7 day 28 day 1 day 3 day 7 day 28 day

M0 1262 2520 2866 4022 100 100 100 100M5 1431 2846 3296 5134 113 113 115 128M10 1478 3054 3918 5346 117 121 137 133M15 1503 3716 4436 5572 119 147 155 139M20 1468 2834 3646 5002 116 112 127 124M25 1176 2088 2682 3596 93 83 94 89

Table 5 Proportion of white efflorescence over total area (unit )

Mix Exposure environment and age in days7 days (NE) 56 days (NE) 7 days (CDE) 56 days (CDE) 7 days (LTE) 56 days (LTE)

M0 3414 4785 3185 3409 4460 5704M5 3389 4285 3657 3961 3601 5294M10 1587 3442 2190 3159 2053 4138M15 1514 2034 925 1025 1529 2171M20 3329 3522 1588 2504 2865 3227M25 4635 4920 2424 2906 3007 4406

Table 6Quantity of efflorescence using the curettagemethodunderNE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13528 13976 13848 13539 14106 12617Weight after curettage 1352 1397 13842 13535 14101 12607Weight loss 08 06 06 04 05 1

Table 7Quantity of efflorescence using the curettagemethod underCDE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13284 14002 14147 13785 14187 12618Weight after curettage 13278 1400 14145 13784 14186 12614Weight loss 06 02 02 01 01 04

Table 8Quantity of efflorescence using the curettagemethod underLTE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13153 12902 13469 13147 13252 12524Weight after curettage 13141 12894 13463 13142 13245 12513Weight loss 12 08 06 05 07 11

quantities (5 to 20) of metakaolin provide higher strengthand resistance to efflorescence due to a denser microstruc-ture and the controlled concentration of mobile alkalis in thepore solutions respectively

33 Quantification of Efflorescence Using the CurettageMethod The results for the quantification of efflorescenceusing the curettage method are presented in Tables 6 7 and8 Clearly the addition of 15 metakaolin was most effective

in inhibiting efflorescence under any exposure environmentThe specimens cured under LTE conditions had a higherquantity of efflorescence than those under NE or CDEBased on the previous study higher humidity led to a higherquantity of efflorescence and efflorescence increased withan increase in the size of moist particles [13] In additionefflorescence was proportional to alkali leaching perhapsdue to the larger volume of macropores (particularly thosebetween 200 nm and 1000 nm) capable of increasing thediffusion coefficient for themigration ofNa from geopolymerphase into the solution [14]

34 Effect of Metakaolin on Microscopy Characteristics Thisstudy employed SEM observations to characterize the micro-structural compounds produced withwithout replacementmetakaolin Careful analysis ofmicrostructures can reveal thepozzolanic reaction and the gel development SEM magnifi-cation was set at 1000 and 3000 times to directly observe thedevelopment of cement hydration and pore structure SEMobservation was performed on control specimens after 56days of aging shown in Figure 10 large capillary pores CHand pore interconnectivity were observed

SEM observation was also applied to specimens withvarious amounts of replacement metakaolin (5 10 1520 and 25) at 56 days as shown in Figures 11 1213 14 and 15 Clearly cement-based paste specimens withreplacement metakaolin developed a more compact denserpore structure Hydration was formed on the surface of theM5 M10 M15 and M20 specimens the microstructure ofthese samples reduced themobility of chloride and other ionsresulting in higher compressive strength and a reduction incrack stretching

The SEM image in Figure 13 illustrates the relativelydense homogeneous microstructure of M15 specimens with

10 The Scientific World Journal

M25

M20

M15

M10

M5

M0

Sample

10 20 30 40 50 60 70 802120579 (deg)

15CaO SiO2 xH2OAl07Fe3Si03SiO2

Figure 16 XRD results of paste specimens with metakaolin

smooth surfaces and no distinct poresThe densemicrostruc-ture observed in SEM images is consistent with the resultsof compressive strength A number of large capillary poreswere observed in specimens containing 25 metakaolin asillustrated in Figure 15 exceeding those in other samplesThis may be due to the fineness of metakaolin reducingthe workability of the composites resulting in inconsistentdispersion of particles throughout the specimens In additionthe 25 metakaolin specimens contain a lot of unreactedprecursor powder due to the lack of water

A pozzolanic reaction between metakaolin and CHoccurred during the hydration of cement resulting in theconsumption of a portion of the CH The formation ofsecondary calcium-silicate-hydrate (C-S-H) gel (due to poz-zolanic reaction) although less dense than the primary C-S-H gel is effective in filling and segmenting large capillarypores into small discontinuous capillary pores through poresize refinement thereby decreasing the total permeabilityof cement-based composites The filler action of metakaolindue to its fine particle size (approximately 1120583m) comparedto the particle size of cement (approximately 12120583m) furtherincreases the density of the pore structure of metakaolincement-based composites

35 Influence of Metakaolin on Microscopy CharacteristicsThis study employed X-ray diffraction analysis to deter-mine the products of hydration in cement-based materialsFigure 16 illustrates the XRD results of cement-based pastespecimens with replacement metakaolin at 56 days It wasfound that the amounts of the primary hydration productsC-S-H (15CaO-SiO

2-119909H2O) and SiO

2 present a significant

form with the addition of metakaolin (M10 M15 and M20)In contrast Al

07Fe3Si03

content (peak value in Figure 16)increased significantly in the specimens containing 15 and20 metakaolin This is because metakaolin contains highquantities of Al

07Fe3Si03 which verifies that nonhydrated

particles could act as filler changing large capillary poresinto small discontinuous capillary pores The M15 and M20specimens presented superior pozzolanic activity which isconsistent with the compressive strength test results quantityof efflorescence and SEM observations In addition the peakvalue for theM25 specimens dropped significantly indicatingan inferior hydrated reaction compared with the controlspecimens This trend is similar to the results of compressivestrength in which the hydration reaction of specimens ofsamples with more than 20metakaolin is lower than that ofcontrol specimens due to the influence of reduced resistanceto efflorescence

4 Conclusion

Our results demonstrate that the replacement of cementusing metakaolin at percentages of 5 10 15 and 20increases compressive strength with a peak increase insamples produced using 15 metakaolin However a dis-tinct drop in compressive strength was observed in samplesproduced using 25 metakaolin MATLAB image analysisand the curettage method both indicate that efflorescenceis most pronounced when samples were cured in a lowtemperature environment exceeding that produced undera normal environment or carbon dioxide environment Inthe M5 M10 M15 and M20 samples the area affected byefflorescence was lower than that of the control specimensthe M15 specimens were the least affected by efflorescenceIn SEM micrographs materials produced with metakaolindeveloped denser smoother structures XRD results indicatethat the amount of main hydration products in cement-based materials with replacement metakaolin performed asignificant form Our results conclusively demonstrate thatcement-based materials with 15 replacement metakaolinhave superior performance with considerable potential forapplication in engineering

References

[1] A Aıt-Mokhtar R Belarbi F Benboudjema N Burlion BCapra et al ldquoExperimental investigation of the variability ofconcrete durability propertiesrdquo Cement and Concrete Researchvol 45 pp 21ndash36 2013

[2] E N Kani A Allahverdi and J L Provis ldquoEfflorescence controlin geopolymer binders based on natural pozzolanrdquo Cement andConcrete Composites vol 34 no 1 pp 25ndash33 2012

[3] X Y Wang and H S Lee ldquoModeling of chloride diffusion inconcrete containing low-calcium fly ashrdquo Materials Chemistryand Physics vol 138 pp 917ndash928 2013

[4] V S Ramachandran and J J BeaudoinHandbook of AnalyticalTechniques in Concrete Science and Technology Principles Tech-niques and Applications William Andrew 1st edition 2001

[5] C L Lee R Huang W T Lin and T L Weng ldquoEstablishmentof the durability indices for cement-based composite containingsupplementary cementitious materialsrdquo Materials and Designvol 37 pp 28ndash39 2012

[6] T Y Han W T Lin A Cheng R Huang and C C HuangldquoInfluence of polyolefin fibers on the engineering propertiesof cement-based composites containing silica fumerdquo Materialsand Design vol 37 pp 569ndash576 2012

The Scientific World Journal 11

[7] M I Khan and A M Alhozaimy ldquoProperties of naturalpozzolan and its potential utilization in environmental friendlyconcreterdquo Canadian Journal of Civil Engineering vol 38 no 1pp 71ndash78 2011

[8] A A Ramezanianpour and H B Jovein ldquoInfluence ofmetakaolin as supplementary cementing material on strengthand durability of concretesrdquo Construction and Building Materi-als vol 30 pp 470ndash479 2012

[9] E Guneyisi M Gesoglu S Karaoglu and K MermerdasldquoStrength permeability and shrinkage cracking of silica fumeand metakaolin concretesrdquo Construction and Building Materi-als vol 34 pp 120ndash130 2012

[10] H Paiva A Velosa P Cachim and V M Ferreira ldquoEffectof metakaolin dispersion on the fresh and hardened stateproperties of concreterdquo Cement and Concrete Research vol 42pp 607ndash612 2012

[11] E Guneyisi M Gesoglu F Karaboga and K MermerdasldquoCorrosion behavior of reinforcing steel embedded in chloridecontaminated concretes with and without metakaolinrdquo Com-posites B vol 45 pp 1288ndash1295 2013

[12] A Nadeem S A Memonb and T Y Lo ldquoMechanical per-formance durability qualitative and quantitative analysis ofmicrostructure of fly ash and Metakaolin mortar at elevatedtemperaturesrdquo Construction and Building Materials vol 38 pp338ndash347 2013

[13] Y Gao S B Chen and L E Yu ldquoEfflorescence relativehumidity of airborne sodium chloride particles a theoreticalinvestigationrdquoAtmospheric Environment vol 41 no 9 pp 2019ndash2023 2007

[14] L Zheng W Wang and Y Shi ldquoThe effects of alkaline dosageand SiAl ratio on the immobilization of heavy metals inmunicipal solid waste incineration fly ash-based geopolymerrdquoChemosphere vol 79 no 6 pp 665ndash671 2010

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

The Scientific World Journal 7

(a) times1000

CH

Pore

Pore

(b) times3000

Figure 10 SEM observations for M0 specimens

(a) times1000

Pore

Pore

CH

(b) times3000

Figure 11 SEM images of M5 specimens

(a) times1000

Pore

(b) times3000

Figure 12 SEM images of M10 specimens

8 The Scientific World Journal

(a) times1000

Hydration

(b) times3000

Figure 13 SEM images of M15 specimens

(a) times1000 (b) times3000

Figure 14 SEM images of M20 specimens

(a) times1000

Pore

(b) times3000

Figure 15 SEM images of M25 specimens

The Scientific World Journal 9

Table 4 Compressive strength and percent of relative compressive strength

Mix Compressive strength (MPa) Relative compressive strength ()1 day 3 day 7 day 28 day 1 day 3 day 7 day 28 day

M0 1262 2520 2866 4022 100 100 100 100M5 1431 2846 3296 5134 113 113 115 128M10 1478 3054 3918 5346 117 121 137 133M15 1503 3716 4436 5572 119 147 155 139M20 1468 2834 3646 5002 116 112 127 124M25 1176 2088 2682 3596 93 83 94 89

Table 5 Proportion of white efflorescence over total area (unit )

Mix Exposure environment and age in days7 days (NE) 56 days (NE) 7 days (CDE) 56 days (CDE) 7 days (LTE) 56 days (LTE)

M0 3414 4785 3185 3409 4460 5704M5 3389 4285 3657 3961 3601 5294M10 1587 3442 2190 3159 2053 4138M15 1514 2034 925 1025 1529 2171M20 3329 3522 1588 2504 2865 3227M25 4635 4920 2424 2906 3007 4406

Table 6Quantity of efflorescence using the curettagemethodunderNE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13528 13976 13848 13539 14106 12617Weight after curettage 1352 1397 13842 13535 14101 12607Weight loss 08 06 06 04 05 1

Table 7Quantity of efflorescence using the curettagemethod underCDE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13284 14002 14147 13785 14187 12618Weight after curettage 13278 1400 14145 13784 14186 12614Weight loss 06 02 02 01 01 04

Table 8Quantity of efflorescence using the curettagemethod underLTE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13153 12902 13469 13147 13252 12524Weight after curettage 13141 12894 13463 13142 13245 12513Weight loss 12 08 06 05 07 11

quantities (5 to 20) of metakaolin provide higher strengthand resistance to efflorescence due to a denser microstruc-ture and the controlled concentration of mobile alkalis in thepore solutions respectively

33 Quantification of Efflorescence Using the CurettageMethod The results for the quantification of efflorescenceusing the curettage method are presented in Tables 6 7 and8 Clearly the addition of 15 metakaolin was most effective

in inhibiting efflorescence under any exposure environmentThe specimens cured under LTE conditions had a higherquantity of efflorescence than those under NE or CDEBased on the previous study higher humidity led to a higherquantity of efflorescence and efflorescence increased withan increase in the size of moist particles [13] In additionefflorescence was proportional to alkali leaching perhapsdue to the larger volume of macropores (particularly thosebetween 200 nm and 1000 nm) capable of increasing thediffusion coefficient for themigration ofNa from geopolymerphase into the solution [14]

34 Effect of Metakaolin on Microscopy Characteristics Thisstudy employed SEM observations to characterize the micro-structural compounds produced withwithout replacementmetakaolin Careful analysis ofmicrostructures can reveal thepozzolanic reaction and the gel development SEM magnifi-cation was set at 1000 and 3000 times to directly observe thedevelopment of cement hydration and pore structure SEMobservation was performed on control specimens after 56days of aging shown in Figure 10 large capillary pores CHand pore interconnectivity were observed

SEM observation was also applied to specimens withvarious amounts of replacement metakaolin (5 10 1520 and 25) at 56 days as shown in Figures 11 1213 14 and 15 Clearly cement-based paste specimens withreplacement metakaolin developed a more compact denserpore structure Hydration was formed on the surface of theM5 M10 M15 and M20 specimens the microstructure ofthese samples reduced themobility of chloride and other ionsresulting in higher compressive strength and a reduction incrack stretching

The SEM image in Figure 13 illustrates the relativelydense homogeneous microstructure of M15 specimens with

10 The Scientific World Journal

M25

M20

M15

M10

M5

M0

Sample

10 20 30 40 50 60 70 802120579 (deg)

15CaO SiO2 xH2OAl07Fe3Si03SiO2

Figure 16 XRD results of paste specimens with metakaolin

smooth surfaces and no distinct poresThe densemicrostruc-ture observed in SEM images is consistent with the resultsof compressive strength A number of large capillary poreswere observed in specimens containing 25 metakaolin asillustrated in Figure 15 exceeding those in other samplesThis may be due to the fineness of metakaolin reducingthe workability of the composites resulting in inconsistentdispersion of particles throughout the specimens In additionthe 25 metakaolin specimens contain a lot of unreactedprecursor powder due to the lack of water

A pozzolanic reaction between metakaolin and CHoccurred during the hydration of cement resulting in theconsumption of a portion of the CH The formation ofsecondary calcium-silicate-hydrate (C-S-H) gel (due to poz-zolanic reaction) although less dense than the primary C-S-H gel is effective in filling and segmenting large capillarypores into small discontinuous capillary pores through poresize refinement thereby decreasing the total permeabilityof cement-based composites The filler action of metakaolindue to its fine particle size (approximately 1120583m) comparedto the particle size of cement (approximately 12120583m) furtherincreases the density of the pore structure of metakaolincement-based composites

35 Influence of Metakaolin on Microscopy CharacteristicsThis study employed X-ray diffraction analysis to deter-mine the products of hydration in cement-based materialsFigure 16 illustrates the XRD results of cement-based pastespecimens with replacement metakaolin at 56 days It wasfound that the amounts of the primary hydration productsC-S-H (15CaO-SiO

2-119909H2O) and SiO

2 present a significant

form with the addition of metakaolin (M10 M15 and M20)In contrast Al

07Fe3Si03

content (peak value in Figure 16)increased significantly in the specimens containing 15 and20 metakaolin This is because metakaolin contains highquantities of Al

07Fe3Si03 which verifies that nonhydrated

particles could act as filler changing large capillary poresinto small discontinuous capillary pores The M15 and M20specimens presented superior pozzolanic activity which isconsistent with the compressive strength test results quantityof efflorescence and SEM observations In addition the peakvalue for theM25 specimens dropped significantly indicatingan inferior hydrated reaction compared with the controlspecimens This trend is similar to the results of compressivestrength in which the hydration reaction of specimens ofsamples with more than 20metakaolin is lower than that ofcontrol specimens due to the influence of reduced resistanceto efflorescence

4 Conclusion

Our results demonstrate that the replacement of cementusing metakaolin at percentages of 5 10 15 and 20increases compressive strength with a peak increase insamples produced using 15 metakaolin However a dis-tinct drop in compressive strength was observed in samplesproduced using 25 metakaolin MATLAB image analysisand the curettage method both indicate that efflorescenceis most pronounced when samples were cured in a lowtemperature environment exceeding that produced undera normal environment or carbon dioxide environment Inthe M5 M10 M15 and M20 samples the area affected byefflorescence was lower than that of the control specimensthe M15 specimens were the least affected by efflorescenceIn SEM micrographs materials produced with metakaolindeveloped denser smoother structures XRD results indicatethat the amount of main hydration products in cement-based materials with replacement metakaolin performed asignificant form Our results conclusively demonstrate thatcement-based materials with 15 replacement metakaolinhave superior performance with considerable potential forapplication in engineering

References

[1] A Aıt-Mokhtar R Belarbi F Benboudjema N Burlion BCapra et al ldquoExperimental investigation of the variability ofconcrete durability propertiesrdquo Cement and Concrete Researchvol 45 pp 21ndash36 2013

[2] E N Kani A Allahverdi and J L Provis ldquoEfflorescence controlin geopolymer binders based on natural pozzolanrdquo Cement andConcrete Composites vol 34 no 1 pp 25ndash33 2012

[3] X Y Wang and H S Lee ldquoModeling of chloride diffusion inconcrete containing low-calcium fly ashrdquo Materials Chemistryand Physics vol 138 pp 917ndash928 2013

[4] V S Ramachandran and J J BeaudoinHandbook of AnalyticalTechniques in Concrete Science and Technology Principles Tech-niques and Applications William Andrew 1st edition 2001

[5] C L Lee R Huang W T Lin and T L Weng ldquoEstablishmentof the durability indices for cement-based composite containingsupplementary cementitious materialsrdquo Materials and Designvol 37 pp 28ndash39 2012

[6] T Y Han W T Lin A Cheng R Huang and C C HuangldquoInfluence of polyolefin fibers on the engineering propertiesof cement-based composites containing silica fumerdquo Materialsand Design vol 37 pp 569ndash576 2012

The Scientific World Journal 11

[7] M I Khan and A M Alhozaimy ldquoProperties of naturalpozzolan and its potential utilization in environmental friendlyconcreterdquo Canadian Journal of Civil Engineering vol 38 no 1pp 71ndash78 2011

[8] A A Ramezanianpour and H B Jovein ldquoInfluence ofmetakaolin as supplementary cementing material on strengthand durability of concretesrdquo Construction and Building Materi-als vol 30 pp 470ndash479 2012

[9] E Guneyisi M Gesoglu S Karaoglu and K MermerdasldquoStrength permeability and shrinkage cracking of silica fumeand metakaolin concretesrdquo Construction and Building Materi-als vol 34 pp 120ndash130 2012

[10] H Paiva A Velosa P Cachim and V M Ferreira ldquoEffectof metakaolin dispersion on the fresh and hardened stateproperties of concreterdquo Cement and Concrete Research vol 42pp 607ndash612 2012

[11] E Guneyisi M Gesoglu F Karaboga and K MermerdasldquoCorrosion behavior of reinforcing steel embedded in chloridecontaminated concretes with and without metakaolinrdquo Com-posites B vol 45 pp 1288ndash1295 2013

[12] A Nadeem S A Memonb and T Y Lo ldquoMechanical per-formance durability qualitative and quantitative analysis ofmicrostructure of fly ash and Metakaolin mortar at elevatedtemperaturesrdquo Construction and Building Materials vol 38 pp338ndash347 2013

[13] Y Gao S B Chen and L E Yu ldquoEfflorescence relativehumidity of airborne sodium chloride particles a theoreticalinvestigationrdquoAtmospheric Environment vol 41 no 9 pp 2019ndash2023 2007

[14] L Zheng W Wang and Y Shi ldquoThe effects of alkaline dosageand SiAl ratio on the immobilization of heavy metals inmunicipal solid waste incineration fly ash-based geopolymerrdquoChemosphere vol 79 no 6 pp 665ndash671 2010

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

8 The Scientific World Journal

(a) times1000

Hydration

(b) times3000

Figure 13 SEM images of M15 specimens

(a) times1000 (b) times3000

Figure 14 SEM images of M20 specimens

(a) times1000

Pore

(b) times3000

Figure 15 SEM images of M25 specimens

The Scientific World Journal 9

Table 4 Compressive strength and percent of relative compressive strength

Mix Compressive strength (MPa) Relative compressive strength ()1 day 3 day 7 day 28 day 1 day 3 day 7 day 28 day

M0 1262 2520 2866 4022 100 100 100 100M5 1431 2846 3296 5134 113 113 115 128M10 1478 3054 3918 5346 117 121 137 133M15 1503 3716 4436 5572 119 147 155 139M20 1468 2834 3646 5002 116 112 127 124M25 1176 2088 2682 3596 93 83 94 89

Table 5 Proportion of white efflorescence over total area (unit )

Mix Exposure environment and age in days7 days (NE) 56 days (NE) 7 days (CDE) 56 days (CDE) 7 days (LTE) 56 days (LTE)

M0 3414 4785 3185 3409 4460 5704M5 3389 4285 3657 3961 3601 5294M10 1587 3442 2190 3159 2053 4138M15 1514 2034 925 1025 1529 2171M20 3329 3522 1588 2504 2865 3227M25 4635 4920 2424 2906 3007 4406

Table 6Quantity of efflorescence using the curettagemethodunderNE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13528 13976 13848 13539 14106 12617Weight after curettage 1352 1397 13842 13535 14101 12607Weight loss 08 06 06 04 05 1

Table 7Quantity of efflorescence using the curettagemethod underCDE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13284 14002 14147 13785 14187 12618Weight after curettage 13278 1400 14145 13784 14186 12614Weight loss 06 02 02 01 01 04

Table 8Quantity of efflorescence using the curettagemethod underLTE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13153 12902 13469 13147 13252 12524Weight after curettage 13141 12894 13463 13142 13245 12513Weight loss 12 08 06 05 07 11

quantities (5 to 20) of metakaolin provide higher strengthand resistance to efflorescence due to a denser microstruc-ture and the controlled concentration of mobile alkalis in thepore solutions respectively

33 Quantification of Efflorescence Using the CurettageMethod The results for the quantification of efflorescenceusing the curettage method are presented in Tables 6 7 and8 Clearly the addition of 15 metakaolin was most effective

in inhibiting efflorescence under any exposure environmentThe specimens cured under LTE conditions had a higherquantity of efflorescence than those under NE or CDEBased on the previous study higher humidity led to a higherquantity of efflorescence and efflorescence increased withan increase in the size of moist particles [13] In additionefflorescence was proportional to alkali leaching perhapsdue to the larger volume of macropores (particularly thosebetween 200 nm and 1000 nm) capable of increasing thediffusion coefficient for themigration ofNa from geopolymerphase into the solution [14]

34 Effect of Metakaolin on Microscopy Characteristics Thisstudy employed SEM observations to characterize the micro-structural compounds produced withwithout replacementmetakaolin Careful analysis ofmicrostructures can reveal thepozzolanic reaction and the gel development SEM magnifi-cation was set at 1000 and 3000 times to directly observe thedevelopment of cement hydration and pore structure SEMobservation was performed on control specimens after 56days of aging shown in Figure 10 large capillary pores CHand pore interconnectivity were observed

SEM observation was also applied to specimens withvarious amounts of replacement metakaolin (5 10 1520 and 25) at 56 days as shown in Figures 11 1213 14 and 15 Clearly cement-based paste specimens withreplacement metakaolin developed a more compact denserpore structure Hydration was formed on the surface of theM5 M10 M15 and M20 specimens the microstructure ofthese samples reduced themobility of chloride and other ionsresulting in higher compressive strength and a reduction incrack stretching

The SEM image in Figure 13 illustrates the relativelydense homogeneous microstructure of M15 specimens with

10 The Scientific World Journal

M25

M20

M15

M10

M5

M0

Sample

10 20 30 40 50 60 70 802120579 (deg)

15CaO SiO2 xH2OAl07Fe3Si03SiO2

Figure 16 XRD results of paste specimens with metakaolin

smooth surfaces and no distinct poresThe densemicrostruc-ture observed in SEM images is consistent with the resultsof compressive strength A number of large capillary poreswere observed in specimens containing 25 metakaolin asillustrated in Figure 15 exceeding those in other samplesThis may be due to the fineness of metakaolin reducingthe workability of the composites resulting in inconsistentdispersion of particles throughout the specimens In additionthe 25 metakaolin specimens contain a lot of unreactedprecursor powder due to the lack of water

A pozzolanic reaction between metakaolin and CHoccurred during the hydration of cement resulting in theconsumption of a portion of the CH The formation ofsecondary calcium-silicate-hydrate (C-S-H) gel (due to poz-zolanic reaction) although less dense than the primary C-S-H gel is effective in filling and segmenting large capillarypores into small discontinuous capillary pores through poresize refinement thereby decreasing the total permeabilityof cement-based composites The filler action of metakaolindue to its fine particle size (approximately 1120583m) comparedto the particle size of cement (approximately 12120583m) furtherincreases the density of the pore structure of metakaolincement-based composites

35 Influence of Metakaolin on Microscopy CharacteristicsThis study employed X-ray diffraction analysis to deter-mine the products of hydration in cement-based materialsFigure 16 illustrates the XRD results of cement-based pastespecimens with replacement metakaolin at 56 days It wasfound that the amounts of the primary hydration productsC-S-H (15CaO-SiO

2-119909H2O) and SiO

2 present a significant

form with the addition of metakaolin (M10 M15 and M20)In contrast Al

07Fe3Si03

content (peak value in Figure 16)increased significantly in the specimens containing 15 and20 metakaolin This is because metakaolin contains highquantities of Al

07Fe3Si03 which verifies that nonhydrated

particles could act as filler changing large capillary poresinto small discontinuous capillary pores The M15 and M20specimens presented superior pozzolanic activity which isconsistent with the compressive strength test results quantityof efflorescence and SEM observations In addition the peakvalue for theM25 specimens dropped significantly indicatingan inferior hydrated reaction compared with the controlspecimens This trend is similar to the results of compressivestrength in which the hydration reaction of specimens ofsamples with more than 20metakaolin is lower than that ofcontrol specimens due to the influence of reduced resistanceto efflorescence

4 Conclusion

Our results demonstrate that the replacement of cementusing metakaolin at percentages of 5 10 15 and 20increases compressive strength with a peak increase insamples produced using 15 metakaolin However a dis-tinct drop in compressive strength was observed in samplesproduced using 25 metakaolin MATLAB image analysisand the curettage method both indicate that efflorescenceis most pronounced when samples were cured in a lowtemperature environment exceeding that produced undera normal environment or carbon dioxide environment Inthe M5 M10 M15 and M20 samples the area affected byefflorescence was lower than that of the control specimensthe M15 specimens were the least affected by efflorescenceIn SEM micrographs materials produced with metakaolindeveloped denser smoother structures XRD results indicatethat the amount of main hydration products in cement-based materials with replacement metakaolin performed asignificant form Our results conclusively demonstrate thatcement-based materials with 15 replacement metakaolinhave superior performance with considerable potential forapplication in engineering

References

[1] A Aıt-Mokhtar R Belarbi F Benboudjema N Burlion BCapra et al ldquoExperimental investigation of the variability ofconcrete durability propertiesrdquo Cement and Concrete Researchvol 45 pp 21ndash36 2013

[2] E N Kani A Allahverdi and J L Provis ldquoEfflorescence controlin geopolymer binders based on natural pozzolanrdquo Cement andConcrete Composites vol 34 no 1 pp 25ndash33 2012

[3] X Y Wang and H S Lee ldquoModeling of chloride diffusion inconcrete containing low-calcium fly ashrdquo Materials Chemistryand Physics vol 138 pp 917ndash928 2013

[4] V S Ramachandran and J J BeaudoinHandbook of AnalyticalTechniques in Concrete Science and Technology Principles Tech-niques and Applications William Andrew 1st edition 2001

[5] C L Lee R Huang W T Lin and T L Weng ldquoEstablishmentof the durability indices for cement-based composite containingsupplementary cementitious materialsrdquo Materials and Designvol 37 pp 28ndash39 2012

[6] T Y Han W T Lin A Cheng R Huang and C C HuangldquoInfluence of polyolefin fibers on the engineering propertiesof cement-based composites containing silica fumerdquo Materialsand Design vol 37 pp 569ndash576 2012

The Scientific World Journal 11

[7] M I Khan and A M Alhozaimy ldquoProperties of naturalpozzolan and its potential utilization in environmental friendlyconcreterdquo Canadian Journal of Civil Engineering vol 38 no 1pp 71ndash78 2011

[8] A A Ramezanianpour and H B Jovein ldquoInfluence ofmetakaolin as supplementary cementing material on strengthand durability of concretesrdquo Construction and Building Materi-als vol 30 pp 470ndash479 2012

[9] E Guneyisi M Gesoglu S Karaoglu and K MermerdasldquoStrength permeability and shrinkage cracking of silica fumeand metakaolin concretesrdquo Construction and Building Materi-als vol 34 pp 120ndash130 2012

[10] H Paiva A Velosa P Cachim and V M Ferreira ldquoEffectof metakaolin dispersion on the fresh and hardened stateproperties of concreterdquo Cement and Concrete Research vol 42pp 607ndash612 2012

[11] E Guneyisi M Gesoglu F Karaboga and K MermerdasldquoCorrosion behavior of reinforcing steel embedded in chloridecontaminated concretes with and without metakaolinrdquo Com-posites B vol 45 pp 1288ndash1295 2013

[12] A Nadeem S A Memonb and T Y Lo ldquoMechanical per-formance durability qualitative and quantitative analysis ofmicrostructure of fly ash and Metakaolin mortar at elevatedtemperaturesrdquo Construction and Building Materials vol 38 pp338ndash347 2013

[13] Y Gao S B Chen and L E Yu ldquoEfflorescence relativehumidity of airborne sodium chloride particles a theoreticalinvestigationrdquoAtmospheric Environment vol 41 no 9 pp 2019ndash2023 2007

[14] L Zheng W Wang and Y Shi ldquoThe effects of alkaline dosageand SiAl ratio on the immobilization of heavy metals inmunicipal solid waste incineration fly ash-based geopolymerrdquoChemosphere vol 79 no 6 pp 665ndash671 2010

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

The Scientific World Journal 9

Table 4 Compressive strength and percent of relative compressive strength

Mix Compressive strength (MPa) Relative compressive strength ()1 day 3 day 7 day 28 day 1 day 3 day 7 day 28 day

M0 1262 2520 2866 4022 100 100 100 100M5 1431 2846 3296 5134 113 113 115 128M10 1478 3054 3918 5346 117 121 137 133M15 1503 3716 4436 5572 119 147 155 139M20 1468 2834 3646 5002 116 112 127 124M25 1176 2088 2682 3596 93 83 94 89

Table 5 Proportion of white efflorescence over total area (unit )

Mix Exposure environment and age in days7 days (NE) 56 days (NE) 7 days (CDE) 56 days (CDE) 7 days (LTE) 56 days (LTE)

M0 3414 4785 3185 3409 4460 5704M5 3389 4285 3657 3961 3601 5294M10 1587 3442 2190 3159 2053 4138M15 1514 2034 925 1025 1529 2171M20 3329 3522 1588 2504 2865 3227M25 4635 4920 2424 2906 3007 4406

Table 6Quantity of efflorescence using the curettagemethodunderNE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13528 13976 13848 13539 14106 12617Weight after curettage 1352 1397 13842 13535 14101 12607Weight loss 08 06 06 04 05 1

Table 7Quantity of efflorescence using the curettagemethod underCDE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13284 14002 14147 13785 14187 12618Weight after curettage 13278 1400 14145 13784 14186 12614Weight loss 06 02 02 01 01 04

Table 8Quantity of efflorescence using the curettagemethod underLTE (unit g)

M0 M5 M10 M15 M20 M25

Weight before curettage 13153 12902 13469 13147 13252 12524Weight after curettage 13141 12894 13463 13142 13245 12513Weight loss 12 08 06 05 07 11

quantities (5 to 20) of metakaolin provide higher strengthand resistance to efflorescence due to a denser microstruc-ture and the controlled concentration of mobile alkalis in thepore solutions respectively

33 Quantification of Efflorescence Using the CurettageMethod The results for the quantification of efflorescenceusing the curettage method are presented in Tables 6 7 and8 Clearly the addition of 15 metakaolin was most effective

in inhibiting efflorescence under any exposure environmentThe specimens cured under LTE conditions had a higherquantity of efflorescence than those under NE or CDEBased on the previous study higher humidity led to a higherquantity of efflorescence and efflorescence increased withan increase in the size of moist particles [13] In additionefflorescence was proportional to alkali leaching perhapsdue to the larger volume of macropores (particularly thosebetween 200 nm and 1000 nm) capable of increasing thediffusion coefficient for themigration ofNa from geopolymerphase into the solution [14]

34 Effect of Metakaolin on Microscopy Characteristics Thisstudy employed SEM observations to characterize the micro-structural compounds produced withwithout replacementmetakaolin Careful analysis ofmicrostructures can reveal thepozzolanic reaction and the gel development SEM magnifi-cation was set at 1000 and 3000 times to directly observe thedevelopment of cement hydration and pore structure SEMobservation was performed on control specimens after 56days of aging shown in Figure 10 large capillary pores CHand pore interconnectivity were observed

SEM observation was also applied to specimens withvarious amounts of replacement metakaolin (5 10 1520 and 25) at 56 days as shown in Figures 11 1213 14 and 15 Clearly cement-based paste specimens withreplacement metakaolin developed a more compact denserpore structure Hydration was formed on the surface of theM5 M10 M15 and M20 specimens the microstructure ofthese samples reduced themobility of chloride and other ionsresulting in higher compressive strength and a reduction incrack stretching

The SEM image in Figure 13 illustrates the relativelydense homogeneous microstructure of M15 specimens with

10 The Scientific World Journal

M25

M20

M15

M10

M5

M0

Sample

10 20 30 40 50 60 70 802120579 (deg)

15CaO SiO2 xH2OAl07Fe3Si03SiO2

Figure 16 XRD results of paste specimens with metakaolin

smooth surfaces and no distinct poresThe densemicrostruc-ture observed in SEM images is consistent with the resultsof compressive strength A number of large capillary poreswere observed in specimens containing 25 metakaolin asillustrated in Figure 15 exceeding those in other samplesThis may be due to the fineness of metakaolin reducingthe workability of the composites resulting in inconsistentdispersion of particles throughout the specimens In additionthe 25 metakaolin specimens contain a lot of unreactedprecursor powder due to the lack of water

A pozzolanic reaction between metakaolin and CHoccurred during the hydration of cement resulting in theconsumption of a portion of the CH The formation ofsecondary calcium-silicate-hydrate (C-S-H) gel (due to poz-zolanic reaction) although less dense than the primary C-S-H gel is effective in filling and segmenting large capillarypores into small discontinuous capillary pores through poresize refinement thereby decreasing the total permeabilityof cement-based composites The filler action of metakaolindue to its fine particle size (approximately 1120583m) comparedto the particle size of cement (approximately 12120583m) furtherincreases the density of the pore structure of metakaolincement-based composites

35 Influence of Metakaolin on Microscopy CharacteristicsThis study employed X-ray diffraction analysis to deter-mine the products of hydration in cement-based materialsFigure 16 illustrates the XRD results of cement-based pastespecimens with replacement metakaolin at 56 days It wasfound that the amounts of the primary hydration productsC-S-H (15CaO-SiO

2-119909H2O) and SiO

2 present a significant

form with the addition of metakaolin (M10 M15 and M20)In contrast Al

07Fe3Si03

content (peak value in Figure 16)increased significantly in the specimens containing 15 and20 metakaolin This is because metakaolin contains highquantities of Al

07Fe3Si03 which verifies that nonhydrated

particles could act as filler changing large capillary poresinto small discontinuous capillary pores The M15 and M20specimens presented superior pozzolanic activity which isconsistent with the compressive strength test results quantityof efflorescence and SEM observations In addition the peakvalue for theM25 specimens dropped significantly indicatingan inferior hydrated reaction compared with the controlspecimens This trend is similar to the results of compressivestrength in which the hydration reaction of specimens ofsamples with more than 20metakaolin is lower than that ofcontrol specimens due to the influence of reduced resistanceto efflorescence

4 Conclusion

Our results demonstrate that the replacement of cementusing metakaolin at percentages of 5 10 15 and 20increases compressive strength with a peak increase insamples produced using 15 metakaolin However a dis-tinct drop in compressive strength was observed in samplesproduced using 25 metakaolin MATLAB image analysisand the curettage method both indicate that efflorescenceis most pronounced when samples were cured in a lowtemperature environment exceeding that produced undera normal environment or carbon dioxide environment Inthe M5 M10 M15 and M20 samples the area affected byefflorescence was lower than that of the control specimensthe M15 specimens were the least affected by efflorescenceIn SEM micrographs materials produced with metakaolindeveloped denser smoother structures XRD results indicatethat the amount of main hydration products in cement-based materials with replacement metakaolin performed asignificant form Our results conclusively demonstrate thatcement-based materials with 15 replacement metakaolinhave superior performance with considerable potential forapplication in engineering

References

[1] A Aıt-Mokhtar R Belarbi F Benboudjema N Burlion BCapra et al ldquoExperimental investigation of the variability ofconcrete durability propertiesrdquo Cement and Concrete Researchvol 45 pp 21ndash36 2013

[2] E N Kani A Allahverdi and J L Provis ldquoEfflorescence controlin geopolymer binders based on natural pozzolanrdquo Cement andConcrete Composites vol 34 no 1 pp 25ndash33 2012

[3] X Y Wang and H S Lee ldquoModeling of chloride diffusion inconcrete containing low-calcium fly ashrdquo Materials Chemistryand Physics vol 138 pp 917ndash928 2013

[4] V S Ramachandran and J J BeaudoinHandbook of AnalyticalTechniques in Concrete Science and Technology Principles Tech-niques and Applications William Andrew 1st edition 2001

[5] C L Lee R Huang W T Lin and T L Weng ldquoEstablishmentof the durability indices for cement-based composite containingsupplementary cementitious materialsrdquo Materials and Designvol 37 pp 28ndash39 2012

[6] T Y Han W T Lin A Cheng R Huang and C C HuangldquoInfluence of polyolefin fibers on the engineering propertiesof cement-based composites containing silica fumerdquo Materialsand Design vol 37 pp 569ndash576 2012

The Scientific World Journal 11

[7] M I Khan and A M Alhozaimy ldquoProperties of naturalpozzolan and its potential utilization in environmental friendlyconcreterdquo Canadian Journal of Civil Engineering vol 38 no 1pp 71ndash78 2011

[8] A A Ramezanianpour and H B Jovein ldquoInfluence ofmetakaolin as supplementary cementing material on strengthand durability of concretesrdquo Construction and Building Materi-als vol 30 pp 470ndash479 2012

[9] E Guneyisi M Gesoglu S Karaoglu and K MermerdasldquoStrength permeability and shrinkage cracking of silica fumeand metakaolin concretesrdquo Construction and Building Materi-als vol 34 pp 120ndash130 2012

[10] H Paiva A Velosa P Cachim and V M Ferreira ldquoEffectof metakaolin dispersion on the fresh and hardened stateproperties of concreterdquo Cement and Concrete Research vol 42pp 607ndash612 2012

[11] E Guneyisi M Gesoglu F Karaboga and K MermerdasldquoCorrosion behavior of reinforcing steel embedded in chloridecontaminated concretes with and without metakaolinrdquo Com-posites B vol 45 pp 1288ndash1295 2013

[12] A Nadeem S A Memonb and T Y Lo ldquoMechanical per-formance durability qualitative and quantitative analysis ofmicrostructure of fly ash and Metakaolin mortar at elevatedtemperaturesrdquo Construction and Building Materials vol 38 pp338ndash347 2013

[13] Y Gao S B Chen and L E Yu ldquoEfflorescence relativehumidity of airborne sodium chloride particles a theoreticalinvestigationrdquoAtmospheric Environment vol 41 no 9 pp 2019ndash2023 2007

[14] L Zheng W Wang and Y Shi ldquoThe effects of alkaline dosageand SiAl ratio on the immobilization of heavy metals inmunicipal solid waste incineration fly ash-based geopolymerrdquoChemosphere vol 79 no 6 pp 665ndash671 2010

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

10 The Scientific World Journal

M25

M20

M15

M10

M5

M0

Sample

10 20 30 40 50 60 70 802120579 (deg)

15CaO SiO2 xH2OAl07Fe3Si03SiO2

Figure 16 XRD results of paste specimens with metakaolin

smooth surfaces and no distinct poresThe densemicrostruc-ture observed in SEM images is consistent with the resultsof compressive strength A number of large capillary poreswere observed in specimens containing 25 metakaolin asillustrated in Figure 15 exceeding those in other samplesThis may be due to the fineness of metakaolin reducingthe workability of the composites resulting in inconsistentdispersion of particles throughout the specimens In additionthe 25 metakaolin specimens contain a lot of unreactedprecursor powder due to the lack of water

A pozzolanic reaction between metakaolin and CHoccurred during the hydration of cement resulting in theconsumption of a portion of the CH The formation ofsecondary calcium-silicate-hydrate (C-S-H) gel (due to poz-zolanic reaction) although less dense than the primary C-S-H gel is effective in filling and segmenting large capillarypores into small discontinuous capillary pores through poresize refinement thereby decreasing the total permeabilityof cement-based composites The filler action of metakaolindue to its fine particle size (approximately 1120583m) comparedto the particle size of cement (approximately 12120583m) furtherincreases the density of the pore structure of metakaolincement-based composites

35 Influence of Metakaolin on Microscopy CharacteristicsThis study employed X-ray diffraction analysis to deter-mine the products of hydration in cement-based materialsFigure 16 illustrates the XRD results of cement-based pastespecimens with replacement metakaolin at 56 days It wasfound that the amounts of the primary hydration productsC-S-H (15CaO-SiO

2-119909H2O) and SiO

2 present a significant

form with the addition of metakaolin (M10 M15 and M20)In contrast Al

07Fe3Si03

content (peak value in Figure 16)increased significantly in the specimens containing 15 and20 metakaolin This is because metakaolin contains highquantities of Al

07Fe3Si03 which verifies that nonhydrated

particles could act as filler changing large capillary poresinto small discontinuous capillary pores The M15 and M20specimens presented superior pozzolanic activity which isconsistent with the compressive strength test results quantityof efflorescence and SEM observations In addition the peakvalue for theM25 specimens dropped significantly indicatingan inferior hydrated reaction compared with the controlspecimens This trend is similar to the results of compressivestrength in which the hydration reaction of specimens ofsamples with more than 20metakaolin is lower than that ofcontrol specimens due to the influence of reduced resistanceto efflorescence

4 Conclusion

Our results demonstrate that the replacement of cementusing metakaolin at percentages of 5 10 15 and 20increases compressive strength with a peak increase insamples produced using 15 metakaolin However a dis-tinct drop in compressive strength was observed in samplesproduced using 25 metakaolin MATLAB image analysisand the curettage method both indicate that efflorescenceis most pronounced when samples were cured in a lowtemperature environment exceeding that produced undera normal environment or carbon dioxide environment Inthe M5 M10 M15 and M20 samples the area affected byefflorescence was lower than that of the control specimensthe M15 specimens were the least affected by efflorescenceIn SEM micrographs materials produced with metakaolindeveloped denser smoother structures XRD results indicatethat the amount of main hydration products in cement-based materials with replacement metakaolin performed asignificant form Our results conclusively demonstrate thatcement-based materials with 15 replacement metakaolinhave superior performance with considerable potential forapplication in engineering

References

[1] A Aıt-Mokhtar R Belarbi F Benboudjema N Burlion BCapra et al ldquoExperimental investigation of the variability ofconcrete durability propertiesrdquo Cement and Concrete Researchvol 45 pp 21ndash36 2013

[2] E N Kani A Allahverdi and J L Provis ldquoEfflorescence controlin geopolymer binders based on natural pozzolanrdquo Cement andConcrete Composites vol 34 no 1 pp 25ndash33 2012

[3] X Y Wang and H S Lee ldquoModeling of chloride diffusion inconcrete containing low-calcium fly ashrdquo Materials Chemistryand Physics vol 138 pp 917ndash928 2013

[4] V S Ramachandran and J J BeaudoinHandbook of AnalyticalTechniques in Concrete Science and Technology Principles Tech-niques and Applications William Andrew 1st edition 2001

[5] C L Lee R Huang W T Lin and T L Weng ldquoEstablishmentof the durability indices for cement-based composite containingsupplementary cementitious materialsrdquo Materials and Designvol 37 pp 28ndash39 2012

[6] T Y Han W T Lin A Cheng R Huang and C C HuangldquoInfluence of polyolefin fibers on the engineering propertiesof cement-based composites containing silica fumerdquo Materialsand Design vol 37 pp 569ndash576 2012

The Scientific World Journal 11

[7] M I Khan and A M Alhozaimy ldquoProperties of naturalpozzolan and its potential utilization in environmental friendlyconcreterdquo Canadian Journal of Civil Engineering vol 38 no 1pp 71ndash78 2011

[8] A A Ramezanianpour and H B Jovein ldquoInfluence ofmetakaolin as supplementary cementing material on strengthand durability of concretesrdquo Construction and Building Materi-als vol 30 pp 470ndash479 2012

[9] E Guneyisi M Gesoglu S Karaoglu and K MermerdasldquoStrength permeability and shrinkage cracking of silica fumeand metakaolin concretesrdquo Construction and Building Materi-als vol 34 pp 120ndash130 2012

[10] H Paiva A Velosa P Cachim and V M Ferreira ldquoEffectof metakaolin dispersion on the fresh and hardened stateproperties of concreterdquo Cement and Concrete Research vol 42pp 607ndash612 2012

[11] E Guneyisi M Gesoglu F Karaboga and K MermerdasldquoCorrosion behavior of reinforcing steel embedded in chloridecontaminated concretes with and without metakaolinrdquo Com-posites B vol 45 pp 1288ndash1295 2013

[12] A Nadeem S A Memonb and T Y Lo ldquoMechanical per-formance durability qualitative and quantitative analysis ofmicrostructure of fly ash and Metakaolin mortar at elevatedtemperaturesrdquo Construction and Building Materials vol 38 pp338ndash347 2013

[13] Y Gao S B Chen and L E Yu ldquoEfflorescence relativehumidity of airborne sodium chloride particles a theoreticalinvestigationrdquoAtmospheric Environment vol 41 no 9 pp 2019ndash2023 2007

[14] L Zheng W Wang and Y Shi ldquoThe effects of alkaline dosageand SiAl ratio on the immobilization of heavy metals inmunicipal solid waste incineration fly ash-based geopolymerrdquoChemosphere vol 79 no 6 pp 665ndash671 2010

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

The Scientific World Journal 11

[7] M I Khan and A M Alhozaimy ldquoProperties of naturalpozzolan and its potential utilization in environmental friendlyconcreterdquo Canadian Journal of Civil Engineering vol 38 no 1pp 71ndash78 2011

[8] A A Ramezanianpour and H B Jovein ldquoInfluence ofmetakaolin as supplementary cementing material on strengthand durability of concretesrdquo Construction and Building Materi-als vol 30 pp 470ndash479 2012

[9] E Guneyisi M Gesoglu S Karaoglu and K MermerdasldquoStrength permeability and shrinkage cracking of silica fumeand metakaolin concretesrdquo Construction and Building Materi-als vol 34 pp 120ndash130 2012

[10] H Paiva A Velosa P Cachim and V M Ferreira ldquoEffectof metakaolin dispersion on the fresh and hardened stateproperties of concreterdquo Cement and Concrete Research vol 42pp 607ndash612 2012

[11] E Guneyisi M Gesoglu F Karaboga and K MermerdasldquoCorrosion behavior of reinforcing steel embedded in chloridecontaminated concretes with and without metakaolinrdquo Com-posites B vol 45 pp 1288ndash1295 2013

[12] A Nadeem S A Memonb and T Y Lo ldquoMechanical per-formance durability qualitative and quantitative analysis ofmicrostructure of fly ash and Metakaolin mortar at elevatedtemperaturesrdquo Construction and Building Materials vol 38 pp338ndash347 2013

[13] Y Gao S B Chen and L E Yu ldquoEfflorescence relativehumidity of airborne sodium chloride particles a theoreticalinvestigationrdquoAtmospheric Environment vol 41 no 9 pp 2019ndash2023 2007

[14] L Zheng W Wang and Y Shi ldquoThe effects of alkaline dosageand SiAl ratio on the immobilization of heavy metals inmunicipal solid waste incineration fly ash-based geopolymerrdquoChemosphere vol 79 no 6 pp 665ndash671 2010

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of