Characteristics of Metakaolin Metakaolin and its use in • Calcination of clay mineral (kaolin) at moderately-high temperature (650-800oC) • Breaks down the crystal structure producing a transition phase (silica and amorphous alumina in reactive form) of high surface area • Optimum burning temperature will depend on the base mineral used • Burning at higher temperature will cause recrystallization into quartz and mullite (inert materials)

CANMET Materials Technology Laboratory

Metakaolin Metakaolin

• Pozzolanic reaction in concrete • When used in concrete ! Replacement level of PC will depend on the nature ! C3S / C2S (clinker) + H 2O ----> Calcium Silicate of the constituents and the To and reaction time Hydrates (C-S-H) + Ca(OH) 2 ! Produces significant pore refinement --> modifies water transport properties and diffusion rates of ! Ca(OH) 2 + MK ---> C-S-H pouzz. + crystalline harmful ions products (C2ASH 8, C4AH13, C3AH6) ! Enhances several mechanical (early-age ! Highly-reactive with high specific compressive strength, flexural strength) and surface durability properties (chemical attack, ASR expansion, sulphate resistance, F/T cycles) of concrete

Metakaolin Chemical Analysis of Cementititous Materials ! Increases water demand ==> superplasticizers for workability; may require less SP than SF, Cementitious Materials Chemical Type 1 Silica have better finishability and being less sticky Composition, % Metakaolin than SF concrete Fume • Could be very beneficial in ternary systems Silicon dioxide, SiO 2 20.1 51.34 93.6 ! PC + GGBFS + MK Aluminum oxide, Al 2O 3 4.51 41.95 0.06 ! PC + FA + MK Ferric oxide, Fe2O 3 2.50 0.52 0.45 ! The contrasting behaviours of FA and MK can be utilized with maximum benefit in terms of Calcium oxide, CaO 61.3 0.34 0.50 the finished products with respect to the flow behaviour, strength development and cost Loss on Ignition 2.41 0.72 2.26 Zhang & Malhotra (1995)

1 Microtexture of Products Physical Properties of Cementititous Materials

Cementitious Materials Type 1 Silica Physical Properties Metakaolin Cement Fume Specific gravity 3.09 2.50 2.20 Specific Surface Blaine < 1µm 2 373 fineness, m /kg Silica Fume Nitrogen Absorption, Metakaolin 2 16.8 20.9 m /g Typical median particle size: ~10 µm for PC, 1.3 µm for MK and 0.1 µm for SF Zhang & Malhotra (1995) Zhang & Malhotra (1995)

Metakaolin - Mineralogy Type of concrete Investigated • Type of concrete investigated ? Control ? 10% Metakaolin ? 10% • Mixture proportioning ? W / C + SCM = 0.40 ? Cementititous materials content: 390 kg/m3 • Properties of fresh concrete ? Slump : 80 - 170 mm ? Air Content: 5.5 - 6.1 % Zhang & Malhotra (1995) Zhang & Malhotra (1995)

Setting Times of Concrete Mechanical

Compressive Setting Time, Concrete Strength, Days h:min SF Concrete Mixture Mixture (Mpa) Initial Final MK 1 7 28 90 Set Set Con Control 20.9 28.9 36.4 42.5 Control n/a 5:12 MK, 10% 25.0 37.9 39.9 43.0 Metakaolin, 10% 3:06 4:24 SF, 10% 23.2 34.7 44.4 48.0 Silica Fume, 10% 3:36 4:48

Zhang & Malhotra (1995) Zhang & Malhotra (1995)

2 Mechanical Properties of Concrete Resistance to Chloride- Properties of Hardened Concrete ion Penetration (RCIP) Splitting Flexural, E Concrete Mixture RCIP RCIP tensile, 28 28 days, Modulus, Concrete 28 days, 90 days, days, MPa MPa GPa Mixture Coulombs Coulombs Control 2.7 6.3 29.6 Control 3175 1875 Metakaolin, 10% 3.1 7.4 32.0 Metakaolin, 390 300 10% Silica Fume, 10% 2.8 7.0 31.1 Silica Fume, 410 360 10%

Zhang & Malhotra (1995) Zhang & Malhotra (1995)

Resistance to Freezing and Results of De-icing Salt Scaling Tests Thawing Cycles (ASTM C 666) Visual Scaling Concrete Rating, Residue, 2 Mixture ASTM kg/m Residual Air Durability C 672 Concrete Flexural Content, Factor, Mixture Strength, Control 2 0.3 % % % MK, 10% 3 0.9 Rating 0 Control 6.6 98.3 85 SF, 10% 3 0.8

MK, 10% 4.9 100.3 89

SF, 10% 5.0 100.9 96

Rating 1 Rating 3 Rating 5 Zhang & Malhotra (1995) Zhang & Malhotra (1995)

Drying Shrinkage of Concrete Heat Generation of Concrete

Zhang & Malhotra (1995) Zhang & Malhotra (1995)

3 Conclusion • Metakaolin is a highly pozzolanic and “reactive” material • Metakaolin improves most mechanical and durability properties of concrete • Properties of concrete incorporating MK are comparable and sometimes better than SF concrete.

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