Download as PDF, PPTX
Uploaded byCALTRA BV
Metakaolin ecs final
The document discusses the production and properties of metakaolin, which is produced by calcining kaolin clay. Kaolin clay consists of the aluminum silicate mineral kaolinite. Metakaolin is produced through either flash calcination at temperatures around 670°C for a few seconds, or rotary kiln calcination at 750°C for 2-5 hours, which results in amorphous metakaolin with different particle morphologies depending on the production method. Metakaolin has pozzolanic properties and reacts with calcium hydroxide in cement to form additional calcium silicate hydrates, improving the strength and durability of concrete.
More Related Content
Metakaolin ecs final
- 1. RAW KAOLINITE KAOLIN CALCINED amorphous aluminium silicate
- 2. content 1. introduc7on 2. produc7on 3. rheology 4. Chapelle test 5. advantages 6. Calcium-‐sulpho aluminate cement 7. geo polymer 8. conclusion
- 3. 1. introduc+on 2. produc7on 3. rheology 4. Chapelle test 5. Advantages 6. Calcium-‐sulpho aluminate cement 7. geo polymer 8. conclusion
- 4. KAOLINITE aluminium silicate Al2O3 (SiO2)2 (H2O)2 amorphous aluminum silicate 600° - 800° C. dehydroxyla7on breaks the crystaline laQce (temperature depends on purity of kaolinite) Al2O3(SiO2)2(H2O)x+(2-‐x)H2O high reac7ve pozzolan (temperatures >900° C. recrystalliza7on forming mullite with no pozzolanic effect)
- 5. Al O SiO OH de hydroxyla7on breaks the crystaline laQce dehydroxyla7on
- 6. Al2O3 × 2SiO2 + Ca(OH) 2 + H2O a chemical reac7on of calcium hydroxide with amorphous siliceous material forming calcium silicate hydrates pozzolanic reac7on ac7ve alumina is soluble in basic environment , pH> 11 (cemen77ous matrix ) forms stable hydrates; • C4AH13 • C3AH6 (hydrogarnet) • C2ASH8 (strätlingite) • C-‐S-‐H (calcium silicate hydrate)
- 7. metakaolin reac7on in cement Pozzolanic reac7on in a cement mix depends on: • rate of addi7on • dissolu7on of alite and belite phases • temperature • water ra7o Two main stages of reac7on; • 0-‐14 days 80% of pozzolanic reac7on takes place dissolu7on alite (C3S) • 14-‐28 days comple7on of reac7on dissolu7on belite (C2S)
- 8. Portlandcement blend When Portlandcement hydrates it forms Portlandite (Ca(OH)2) (phase 3 and 4) and Ca2+ released by alite (C3S) and belite (C2S) (phase 2 and 3) Amorphous Metakaolin reacts with OH-‐and Ca2+ ions forming C-‐S-‐H calcium silicate hydrates-‐reducing the amount of free lime. main effects: • binds calcium • accelerate hydra7on of silicates • addi7onal calcium silicate hydrates • reduced pH • dense matrix
- 9. 1. cement minerals 2. metakaoline fills pores d50 = 10 μ 3. Forma7on of new hydrates AL2O3 × 2SiO2 + Ca(OH) 2 + H2O → CSH, C4AH13, C3AH6, C2ASH8 4. closed structure improving physical, mechanical and chemical performance
- 10. 1. introduc7on 2. produc+on 3. rheology 4. Chapelle test 5. advantages 6. Calcium-‐sulpho aluminate cement 7. geo polymer 8. conclusion
- 11. rotary kiln calcina7on flash calcina7on raw kaolinite finely ground + flash calcina7on (few seconds ~670°C) core grinding / pelle7zing rotary kiln calcina7on (2/5h ~750°C) + ground plate structure round shaped different morphology different way of calcina7on
- 12. CYCLONE GRINDING PRE-‐HEATING BURNING ZONE COOLING ZONE CYCLONE GRINDING RAW FEED STORAGE FLASH CALCINATION
- 13. average composi7on Al203 40~45 % SiO2 30~55 % small amount of quarz , feldspath oxides:-‐ iron ,7tanium ,potassium ,phosphore ,sodium ,calcium ,magnesia LOI < 2 % Par7cle size < 45 μm average par7cle size 5 μm Blaine > 12,000 gm2/g large surface area allows density 2,6 shelf live indefini7ve colour pink -‐ white
- 14. FLASH CALCINED metakaoline turns to round beats , versus a plate structure in tradi7onal produc7on giving beser workability at lower water ra7o. 1 μm 0,5 μm 0,5 μm 0,5 μm kaolinite metakaolin flash calcina+on rotary kiln
- 15. 1. introduc7on 2. produc7on 3. rheology 4. Chapelle test 5. advantages 6. Calcium-‐sulpho aluminate cement 7. geo polymer 8. conclusion
- 16. 90 100 110 120 130 140 150 160 0 10 20 30 flow mm metakaolin % Flow table test : cement/sand = 1: 3 w/c = 0,5 Up to 10% subs7tu7on of Portland cement by regular metakaolin rheology was slightly effected. Addi7on of flash calcined metakaoline allows a higher addi7on tradi7onal calcina7on flash calcina7on
- 17. 0,0 5,0 10,0 15,0 20,0 25,0 30,0 0 5 10 20 30 compressive strength MPa metakaolin % 1 day 7 days 28 days op7mum is reached at 10% subs7tu7on of Portlandcement by tradi7onal calcined metakaolin
- 18. Lower viscosity allows higher dosage of metakaoline , improving further strength development Addi7on of a plas7cizing agent will improve the workability and further increase the strength 0 5 10 15 20 25 30 35 compressive strength MPa metakaoline % 1 day 7 days 28 days
- 19. plas7cizing agent Because of its fineness (10 7mes finer than Portlandcement!) and its sponge type character, the addi7on of metakaoline influences the rheology of the blend This increase in viscosity can be overcome by adding a plas7cizing-‐ / super plas7cizing agent SeQng 7me can off course be adjusted by addi7on of retarder
- 20. 0 10 20 30 40 50 60 1 day 7 days 28 days compressive strength MPa 7me reference W/C 0,5 poly carboxylate ether 0,2% W/C 0,375 Addi7on of right super plas7cizing agent strength can be further increased (20-‐50%)
- 21. 1. introduc7on 2. produc7on 3. rheology 4. Chapelle test 5. advantages 6. Calcium-‐sulpho aluminate cement 7. geo polymer 8. conclusion
- 22. puzzolanic ac7vity (Chapelle test) • pozzolanic reac7vity is measured by mixing 1 g metakaolin with 2 g CaO in 250 ml of water • s7rred and heated for 16 hours • aver cooling amount of lev non reacted lime is established • result is expressed in mg Ca(OH)2 bound • values lies between 1000 and 1400 mg
- 23. comparision of puzzolanic reac7vity (Chapelle) materials average puzzolanic ac7vity mg Ca(OH)2/g blast furnace slag 40 silica fume 430 calcined bauxite 535 paper sludge 600 fly ash 875 metakaoline 1300
- 24. 1. introduc7on 2. produc7on 3. rheology 4. Chapelle test 5. advantages 6. Calcium-‐sulpho aluminate cement 7. geo polymer 8. conclusion
- 25. advantages METAKAOLIN in combina7on with Portlandcement forms a dense-‐knit structure improving, physical, mechanical and chemical proper7es. • accelera7on of ses – lime gel is bounds allowing C3A , C3S to dissolute quickly • pH is reduced giving more protec7on to glass fibers (GRC) • reduced thermal stress slower hardening which limits shrinkage and cracking • increase of elas7c modulus (EMR) • new hydrates formed; calcium silicate, strätlingite, and hydrogarnet • fewer pores and smaller pore size-‐reduc7on of efflorescence,
- 26. • lower water uptake • less energy needed versus tradi7onal method • tight control on calcina7on • consistency of product • grinding raw kaolinite first contributes to round structure of par7cles • contribu7ng to an improved workability • higher amount cement subs7tu7on • higher abrasive resistance • improved opacity flash calcina7on
- 27. 1. introduc7on 2. produc7on 3. rheology 4. Chapelle test 5. advantages 6. Calcium-‐Sulpho Aluminate cement 7. geo polymer 8. conclusion
- 28. CSA-‐cement • calcium sulpho aluminate cement relies on forma7on of ye’elimite (C4A3Š) it takes calcium out of the solu7on, lowering the pH • low pH slows down the dissolu7on of aluminium silicates • belite (C2S) goes into solu7on at a later stage of hydra7on at this stage the pozzolan effect is reduced • an excess of calcium hydrates form a gel /layer on the pozzolan grain "isola7ng” it to go solu7on and blocking the reac7on kine7cs when CSA cement is blended with Portlandcements it is recommended to first make extensive tests to establish the possible pozzolan effect
- 29. 1. introduc7on 2. produc7on 3. rheology 4. Chapelle test 5. advantages 6. Calcium-‐sulpho aluminate cement 7. geo polymer 8. conclusion
- 30. alumino silicate alkaline reagent water geo-‐polymer Metakaoline combined with “waterglass” is currently under research to produce so called “geo-‐polymers” sodium or potassium geo-‐polymer World-‐wide there is an increased interest in alterna7ve binders, “geo-‐polymers” are a good example of this.
- 31. 1. introduc7on 2. produc7on 3. rheology 4. Chapelle test 5. advantages 6. Calcium-‐sulpho aluminate cement 7. geo polymer 8. conclusion
- 32. Decora+ve , durable and detailed Mortar and concrete containing metakaoline proof to have a beser durability. The consump7on of calcium hydroxide and cement alkalis in combina7on with the increased density give beser sulphate resistance. It further reduces the risk of alkali-‐silica reac7on and so called “lime-‐bloom”. In decora7ve mortars and concrete colours are more durable. Increased density and reduced alkali prevent water to migrate lime and alkali preven7ng primary and secondary efflorescence. Addi7on of metakaoline increases the fineness of the binder. Fine details are followed beser and the surface quality is improved. White metakaoline can easily be integrated in a white Portlandcement matrix. Combining metakaoline with calcium hydroxide allows a simple produc7on of a type of hydraulic lime oven used as replacement of Portlandcement in restoring natural stone. conclusion
- 34.