Metakaolin is a material shaped from a natural raw-material kaolinite Al2O3.2SiO2.2H2O by means of its calcination at temperatures above 500 oC. It is a transition metastable phase. On the contrary to the mineral kaolinite the metakaolin shows a very little expressive crystal structure similar to kaolinite – it has more or less amorphous character. At the same time a partial consolidation caused by dehydration of the original material shows up.
Usage of metakaolin
- Technology of concrete
All over the world metakaolin is used in building industry as a partial replacement of cement. Advantage of the partial replacement of cement by metakaolin is the increased mechanical strength of the finished concrete products (up to 20 % after 28 days – usage in HSC-high Strength Concrete), considerably increased resistance against the chemically dissolvable substance (decrease by a half) and last but not least is the increased resistance against percolation of pressure water. With regards to reactivity of metakaolin with calcium hydrate it participates in prevention of efflorescence of loose lime. Further metakaolin is used as a aerating agent, which is especially required by concretes necessitating very high frost resistance. All above-mentioned advantages of metakaolin applications are increasing the durability and service life of concrete mixtures.
- Mortars for plaster
It has been proved that metakaolin as a pozzolanic agent in lime plasters has several positive influences, especially by plasters meant for reconstruction of historical objects. Plasters with lime-pozzolanic binding agent without use of concrete prove much higher strength in pressure and bending tensile strength than classic lime plasters. The majority of humidity and temperature properties is also comparable or better than with classic plasters. The only exception is the coefficient of length dilatability, which is with lime-pozzolanic plasters higher than with classic lime plasters. A great advantage of lime-pozzolanic plasters is their weather resistance and excellent frost resistance. Regarding the porosity of metakaolin and its ability to hold-up water it positively affects the humidity gradient at maturing of fresh plasters and it prevents their cracking.
- Geopolymer binding agent
Metakaolin can be used as a latent hydraulic substance in alkalinously activated mixtures, which prove high resistance against both acids and alkaline substances. In mixture with mineral filling agents the alkalinously activated metakaolin is a basic binding system in cements by which a high resistance to acids and resistance against high temperatures (up to 1000 oC) is required.
- Refractory materials
Metakaolin is a proper micro-filling agent in refractory materials. It finds its place in refractory cements, where it brings, apart from other properties, the acid resistance.
- Rubber industry
All around the world the metakaolin is applied as a filling agent in rubber manufacturing, where it can replace an expensive coagulated silicon dioxide. Famous are its applications at the production of incombustible cables, further it is used in production of mixtures for tyres and other products of rubber industry.
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Metakaolin GW 60 |
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| Characteristics:
metakaolin is ground, thermally processed washed kaolin. It is used as an additive to refractory materials, concretes and mortars, as a filling agent to rubber and plastics as well as for further applications. |
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| Typical and guaranteed properties: | typical | guaranteed | ||||
| contents of Al2O3 | % | 40-42 | min. 40 | |||
| contents of SiO2 | % | 51-53 | 50-55 | |||
| contents of Fe2O3 | % | 1,2-1,4 | max. 1,45 | |||
| contents of TiO2 | % | 0,7-0,75 | max. 0,8 | |||
| contents of K2O + Na2O | % | 1,35-1,45 | max. 1,5 | |||
| contents of CaO | % | 0,25-0,30 | 0,05-0,5 | |||
| contents of MgO | % | 0,35-0,40 | 0,20-0,45 | |||
| further not specified oxides | % | ca 0,5 | ||||
| loss on ignition (1100oC) | % | ca 1,5 | max. 3,5 | |||
| specific surface | m2/g | |||||
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Informative properties: |
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| particle size distribution
by Sedigraph |
20 – 40 µm ⇒ 2,5 %
10 – 20 µm ⇒ 9,6% 5 – 10 µm ⇒ 27,4 % |
2 – 5 µm ⇒ 15, 5 %
1 – 2 µm ⇒ 18,1 % < 1 µm ⇒ 26,9 % |
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| sieve residue | 63 µm
40 µm |
%
% |
ca 1,0 (max. 2)
ca 1,8 (max. 3) |
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| oil number | g/100 l | ca 63 | ||||
| whiteness (R 457) | % | ca 71 | ||||
| mass activity Ra226 | Bq/kg | 100 | ||||
| mass activity index I | – | 0,8 | ||||
| Recommendations for manipulation and storage:
the pack must be air-proof sealed due to water and water steam absorption into the material. |
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| Packing:
delivered in big-bags with PE inlay, other options upon agreement with customer. |
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| Health protection information:
the product’s dust has no dangerous properties as described in Act No. 356/2003 Coll. S 22 – do not inhale dust! |
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