metakoalin

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Characteristics of Characteristics of MetakaolinMetakaolinand its use in concreteand its use in concrete

CANMET Materials Technology Laboratory

MetakaolinMetakaolin•• CalcinationCalcination of clay mineral (kaolin) at of clay mineral (kaolin) at

moderately-high temperature (650-800moderately-high temperature (650-800ooC)C)

•• Breaks down the crystal structure producingBreaks down the crystal structure producinga transition phase (silica and amorphousa transition phase (silica and amorphousaluminaalumina in reactive form) of high surface area in reactive form) of high surface area

•• Optimum burning temperature will dependOptimum burning temperature will dependon the base mineral usedon the base mineral used

•• Burning at higher temperature will causeBurning at higher temperature will causerecrystallizationrecrystallization into quartz and into quartz and mullitemullite(inert materials)(inert materials)

MetakaolinMetakaolin

•• PozzolanicPozzolanic reaction in concrete reaction in concrete

!! CC33S / CS / C22S (clinker) + HS (clinker) + H22O ----> Calcium SilicateO ----> Calcium SilicateHydrates (C-S-H) + Ca(OH)Hydrates (C-S-H) + Ca(OH)22

!! Ca(OH)Ca(OH)22 + MK ---> C-S-H + MK ---> C-S-H pouzz pouzz. + crystalline. + crystallineproducts (Cproducts (C22ASHASH88, C, C44AHAH1313, C, C33AHAH66))

!! Highly-reactive Highly-reactive pozzolan pozzolan with high specificwith high specificsurfacesurface

MetakaolinMetakaolin

•• When used in concreteWhen used in concrete!! Replacement level of PC will depend on the natureReplacement level of PC will depend on the nature

of the constituents and the Tof the constituents and the Too and reaction time and reaction time

!! Produces significant pore refinement --> modifiesProduces significant pore refinement --> modifieswater transport properties and diffusion rates ofwater transport properties and diffusion rates ofharmful ionsharmful ions

!! Enhances several mechanical (early-ageEnhances several mechanical (early-agecompressive strength, flexural strength) andcompressive strength, flexural strength) anddurability properties (chemical attack, ASRdurability properties (chemical attack, ASRexpansion, expansion, sulphatesulphate resistance, F/T cycles) of resistance, F/T cycles) ofconcreteconcrete

MetakaolinMetakaolin!! Increases water demand ==> Increases water demand ==> superplasticizerssuperplasticizers

for workability; may require less SP than SF,for workability; may require less SP than SF,have better have better finishability finishability and being less stickyand being less stickythan SF concretethan SF concrete

•• Could be very beneficial in ternary systemsCould be very beneficial in ternary systems!! PC + GGBFS + MKPC + GGBFS + MK!! PC + FA + MKPC + FA + MK

!! The contrasting The contrasting behaviours behaviours of FA and MK canof FA and MK canbe utilized with maximum benefit in terms ofbe utilized with maximum benefit in terms ofthe finished products with respect to the flowthe finished products with respect to the flowbehaviourbehaviour, strength development and cost, strength development and cost

Chemical Analysis ofChemical Analysis ofCementititousCementititous Materials Materials

Cementitious MaterialsChemicalComposition, % Type 1

CementMetakaolin Silica

Fume

Silicon dioxide, SiO 2 20.1 51.34 93.6

Aluminum oxide, Al 2O 3 4.51 41.95 0.06

Ferric oxide, Fe2O 3 2.50 0.52 0.45

Calcium oxide, CaO 61.3 0.34 0.50

Loss on Ignition 2.41 0.72 2.26

Zhang & Malhotra (1995)

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MicrotextureMicrotexture of Products of Products

< 1µm

MetakaolinSilica Fume

Typical median particle size: ~10 µm for PC, 1.3 µm for MK and 0.1 µm for SF


Physical Properties ofPhysical Properties ofCementititousCementititous Materials Materials

Cementitious MaterialsPhysical Properties Type 1

CementMetakaolin Silica

Fume

Specific gravity 3.09 2.50 2.20

Specific Surface Blainefineness, m

2/kg

373

Nitrogen Absorption,m

2/g

16.8 20.9


MetakaolinMetakaolin - Mineralogy - Mineralogy


Type of concrete InvestigatedType of concrete Investigated

•• Type of concrete investigatedType of concrete investigated?? ControlControl?? 10%10% Metakaolin Metakaolin?? 10% Silica Fume10% Silica Fume

•• Mixture proportioningMixture proportioning?? W / C + SCM = 0.40W / C + SCM = 0.40?? CementititousCementititous materials content: 390 kg/m materials content: 390 kg/m33

•• Properties of fresh concreteProperties of fresh concrete?? Slump : 80 - 170 mmSlump : 80 - 170 mm?? Air Content: 5.5 - 6.1 %Air Content: 5.5 - 6.1 %


Setting Times of ConcreteSetting Times of Concrete

Setting Time,h:min

Concrete Mixture InitialSet

FinalSet

Control n/a 5:12

Metakaolin, 10% 3:06 4:24

Silica Fume, 10% 3:36 4:48


Mechanical Properties of ConcreteMechanical Properties of Concrete

CompressiveStrength, Days

(Mpa)

ConcreteMixture

1 7 28 90

Control 20.9 28.9 36.4 42.5

MK, 10% 25.0 37.9 39.9 43.0

SF, 10% 23.2 34.7 44.4 48.0

SFMKCon


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Mechanical Properties of ConcreteMechanical Properties of Concrete

Properties of Hardened Concrete

Concrete MixtureSplitting

tensile, 28days, MPa

Flexural,28 days,

MPa

EModulus,

GPa

Control 2.7 6.3 29.6

Metakaolin, 10% 3.1 7.4 32.0

Silica Fume, 10% 2.8 7.0 31.1


Resistance to Chloride-Resistance to Chloride-ion Penetration (RCIP)ion Penetration (RCIP)

ConcreteMixture

RCIP28 days,

Coulombs

RCIP90 days,

Coulombs

Control 3175 1875

Metakaolin,10%

390 300

Silica Fume,10%

410 360


Resistance to Freezing andResistance to Freezing andThawing Cycles (ASTM C 666)Thawing Cycles (ASTM C 666)

ConcreteMixture

AirContent,

%

DurabilityFactor,

%

ResidualFlexuralStrength,

%

Control 6.6 98.3 85

MK, 10% 4.9 100.3 89

SF, 10% 5.0 100.9 96


Results of De-icing Salt Scaling TestsResults of De-icing Salt Scaling Tests

ConcreteMixture

VisualRating,ASTMC 672

ScalingResidue,

kg/m2

Control 2 0.3

MK, 10% 3 0.9SF, 10% 3 0.8

Rating 0

Rating 1 Rating 3 Rating 5


Drying Shrinkage of ConcreteDrying Shrinkage of Concrete


Heat Generation of ConcreteHeat Generation of Concrete


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Conclusion• Metakaolin is a highly pozzolanic and

“reactive” material

• Metakaolin improves most mechanical anddurability properties of concrete

• Properties of concrete incorporating MK arecomparable and sometimes better than SFconcrete.

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