Metakaolin presentation

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Metakaolin presentation

  1. 1. Cement/Fly Ash /Metakaolin Ternary Blends: Effects on Compressive Strengths of Mortars and Economics Presented By: Billy Wiggins, P.E., Associate Member ACI Committee 232
  2. 2. Points of Discussion <ul><li>Pozzolans </li></ul><ul><li>Experiment Design </li></ul><ul><li>Experiment Results </li></ul><ul><li>Conclusion </li></ul>
  3. 3. Pozzolans <ul><li>ACI Definition </li></ul><ul><li>Pozzolanic Reactions </li></ul><ul><li>Fly Ash </li></ul><ul><li>Silica Fume </li></ul><ul><li>Metakaolin </li></ul><ul><li>Ternary Blends </li></ul>
  4. 4. ACI Definition <ul><li>A siliceous or alumino- siliceous material that, in finely divided form and in the presence of moisture, chemically reacts with calcium hydroxide released by the hydration of Portland cement to form compounds possessing cementing properties. </li></ul>
  5. 5. Pozzolanic Reactions <ul><li>2C 3 S + 6H C 3 S 2 H 3 + 3CH </li></ul><ul><li>2C 2 S + 4H C 3 S 2 H 3 + CH </li></ul><ul><li>Hydration of Calcium Silicates </li></ul><ul><li>Calcium Hydroxide (CH) is weak and porous by itself </li></ul><ul><li>Pozzolans react with CH to form C-S-H </li></ul>
  6. 6. Improved Aggregate-Cement Interface <ul><li>Pozzolan Acts as Micro-filler </li></ul><ul><li>Increases Bond </li></ul><ul><li>Leads to Higher Strength </li></ul>
  7. 7. Fly Ash <ul><li>A By-Product from the Combustion of Pulverized Coal </li></ul><ul><li>Small glassy beads </li></ul><ul><li>10  m Average Particle Diameter </li></ul><ul><li>Cheap… $30/ton Versus Cement at $85/ton </li></ul><ul><li>90% still goes to Land Fill </li></ul>
  8. 8. Fly Ash Properties in Cement <ul><li>Improved Workability </li></ul><ul><li>Improved Long-Term Strength Gains </li></ul><ul><li>Price </li></ul><ul><li>Lowers Heat of Hydration </li></ul><ul><li>Decreases Water Demand </li></ul><ul><li>Less Bleeding </li></ul><ul><li>Improved Durability to ASR, Sulfate, & Chlorides </li></ul>
  9. 9. Silica Fume <ul><li>Produced from the Production of Silicon </li></ul><ul><li>93% SiO 2 </li></ul><ul><li>.1  m Average Particle Diameter </li></ul>
  10. 10. Properties of Silica Fume <ul><li>Greatly Improves Compressive Strengths </li></ul><ul><li>Decreased Porosity </li></ul><ul><li>Increases Water Demand (HRWR Typ.) </li></ul><ul><li>“ Sticky” finish </li></ul><ul><li>Decreases Workability </li></ul><ul><li>Decreases Bleeding </li></ul><ul><li>Improved Durability to ASR, Sulfate, & Chlorides </li></ul>
  11. 11. Metakaolin <ul><li>Produced from Kaolin Crude Clays </li></ul><ul><li>An Engineered Product </li></ul><ul><li>1  m in diameter </li></ul><ul><li>Plate-Like in Shape </li></ul><ul><li>Kaolin Mined in Middle Georgia </li></ul><ul><li>SiO 2 + Al 2 O 3 + TiO 2 +Fe 2 O 3 </li></ul>
  12. 12. Properties of Metakaolin <ul><li>Increased Water Demand (125%) </li></ul><ul><li>Product “Creamy” </li></ul><ul><li>Greatly Improves Compressive Strengths. Comparible or Better than SF </li></ul><ul><li>Improved Durability (ASR and Sulfate) </li></ul><ul><li>Increases Heat of Hydration </li></ul><ul><li>Decreases Bleeding </li></ul><ul><li>Improved Durability to ASR, Sulfate, & Chlorides </li></ul>
  13. 13. Ternary Blends <ul><li>Flyash+Cement+Metakaolin or Silica Fume </li></ul><ul><li>Less HRWR </li></ul><ul><li>Less Sticky </li></ul><ul><li>Good Early Age and Increased Later-Age Strength </li></ul><ul><li>Lower Heat Rise </li></ul><ul><li>Improved Durability to ASR, Sulfate, & Chlorides – Better than Single Blends? </li></ul>
  14. 14. Improved Particle Packing
  15. 15. Improved Workability
  16. 16. Experiment Design <ul><li>Data on SF + FA; Not much on MK+FA </li></ul><ul><li>Synergy Between MK and FA ? </li></ul><ul><li>Economics ? </li></ul><ul><li>Standard ASTM Tests </li></ul><ul><li>Maintained Flowability </li></ul>
  17. 17. Mix Matrix % Repalcement of Cement 10/30 5/30 30/0 30 10/15 5/15 15/0 15 0/10 0/5 0/0 0 Flyash 10 5 0 Metakaolin
  18. 18. Recipes 0.41 0.45 0.44 0.48 0.53 0.52 0.54 0.50 0.52 Flow % Increase 0.46 0.45 0.48 0.47 0.50 0.49 0.45 0.47 0.49 W/(C+Pozz) Ratio 74 37 74 37 74 37 0 0 0 Metakaolin (g) 222 222 111 111 0 0 222 111 0 Flyash (g) 341.0 336.5 354.4 350.0 368.0 363.4 332.1 345.6 359 Water (g) 444 481 555 592 666 703 518 629 740 Cement (g) 2035 2035 2035 2035 2035 2035 2035 2035 2035 Sand (g) 0.3 0.3 0.15 0.15 0 0 0.3 0.15 0 %FA 0.1 0.05 0.1 0.05 0.1 0.05 0 0 0 %MK Mix #9 Mix #8 Mix #7 Mix #6 Mix #5 Mix #4 Mix #3 Mix #2 Mix #1 Recipes for Cement Mortars
  19. 20. Cost Analysis I
  20. 21. Cost Analysis II 10.12 8.06 7.27 6.92 7.06 6.55 8.10 6.71 6.92 cost of a ton of mortar/psi 3839 4135 5648 5131 6128 5759 3433 4467 4,652 28d Fc 38.86 33.33 41.06 35.53 43.26 37.73 27.80 30.00 32.19 cost for 1 ton of mortar 74 37 74 37 74 37 0 0 0 Metakaolin 222 222 111 111 0 0 222 111 0 Fly ash 444 481 555 592 666 703 518 629 740 Cement 2035 2035 2035 2035 2035 2035 2035 2035 2035 Sand 0.3 0.3 0.15 0.15 0 0 0.3 0.15 0 %FA 0.1 0.05 0.1 0.05 0.1 0.05 0 0 0 %MK Mix #9 Mix #8 Mix #7 Mix #6 Mix #5 Mix #4 Mix #3 Mix #2 Mix #1(CM) Cost Comparison of Blends @ 28 Day Compressive Break Strengths
  21. 22. Cost Analysis III
  22. 23. Cost Analysis IV
  23. 24. Cost Analysis V
  24. 25. Conclusion <ul><li>Fly Ash Lowers Water Demand in Ternary Blends. </li></ul><ul><li>Metakaolin Has Better Compressive Strength Properties Alone than in Ternary Blends in Mortar (24% Stronger at 28d than CM). </li></ul><ul><li>Metakaolin has Improved “Finishability” over control mixes. </li></ul><ul><li>The use of 5% Metakaolin lessens the cost of a mortar mixture 5.35% per psi. </li></ul>
  25. 26. Questions?

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