Concrete Manufacture and Hydration (2)

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Author:
Marciaho
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269734
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Concrete Manufacture and Hydration (2)
Updated:
2014-04-08 18:52:10
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Concrete Manufacture Hydration
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Concrete Manufacture and Hydration
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Concrete Manufacture and Hydration
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  1. Cementing material in great pyramid giza
    Lime mortar or gypsum
  2. Roman Mortar
    • 2 parts pozzolan (volcanic ash)
    • 1 part lime
    • +animal fat
    • +milk
    • +blood
  3. Smeatons lighthouse uses
    Granite stone held together with natural cement (calcined impure limestone containing clay) blended with pozzolan from italy
  4. Joseph aspdin in 1824 named portland cement becuase
    it produced a concrete that was the colour of limestone
  5. Aspdins first major production was fired in beehive kilns
    Near limestone source
  6. Sources of major components of portland cement
    Lime: Calcite, limestone, marl, shale, aragonite

    Iron: Clay, Iron ore, mill scale

    Silica: Clay, marl, sand, shale

    Alumina : aluminium ore refuse, clay, fly ash, shale

    Also used Anhydrite, gypsum
  7. Portland cement production
    • Quarrying (crusher) 
    • Drying and grinding (storage hall, raw mill, raw meal silos) 
    • Kiln burning and cooling (suspension preheaters, rotary kiln, clinker cooler, clinker silos) 
    • Finish Grinding (gypsum, cement mill cement silos) 
    • Packing (packer, bagged cement, culk cement)
  8. Clinker compounds
    • Tricalcium silicate 
    • 3 CaO.siO2
  9. Hydration products
    • Tobermorite gel
    • Calcium Silicate Hydrate
    • Calcium hydroxide
  10. Hydration of tricalcium aluminate without gypsum
    C3H + H +CH -->C4AH13
  11. In the absence of gypsum this reaction would occur very rapidly and lead to flash set
    Hydration of tricalcium aluminate without gypsum
  12. Hyrdration of tricalcium aluminate in the presence of gypsum
    C3A + H + C3H2 -->C6HS3H32
  13. IN the presence of gypsum C3A reacts to form ettringite, which coats the c3A grans and prevents rapid hydration and flast set
    Hyrdation of tricalcium aluminate in the presence of gypsum
  14. Tricalcium Silicate (alite) What does it do, forumula
    • C3S 
    • Hydrates and hardens rapidly
    • Responsible for initial set and early strength
  15. Dicalcium Silicate
    • Hydrates and hardens slowly
    • Contributes to later age strength (beyond 7 days)
    • C2S
  16. Tricalcium Aluminate
    • Liberates a large amount of heat during first few days
    • Contributes slight to early strength
    • Cements with low % ages are more resistant to sulgates
    • C3A
  17. Tetracalcium Alimnoferrite (ferrite)
    • C4AF
    • Reduces clinkering temperature
    • Hydrates rapidly but contributes little to strength
    • Colour of hydrated cement (greyness) dure to ferrite hydrates
  18. Hydration products
    • C-S-H
    • Calcium hydroxide
    • AFt/AFm
  19. Consumed products in hydration
    • Calcium sulfate
    • C4AF
    • C3A
    • C2S
    • C3S
  20. Original Water filled spaces:
    ' capillary porosity'
  21. Low W/CM
    • Low capillary porosity
    • Small pores, poorly connected
    • High Strength
  22. High W/CM
    • High Capillary porosity
    • Large well connected pres
    • High Permeability
    • Low strength
  23. Types of Portland Cement (60
    • GP - General purpose containing up to 10% mineral additions (include fly ash, slag and limestone) 
    • GB - General purpose blended cement contains portland cement plus greater than 10% fly ash or slag and up to 10% silica fume
    • HE - High early strength, rapid strength development
    • LH - Low heat, intended to limit the heat of hydration (dams- large amount of concrete)
    • SR - Sulphate resisting, C3A Content limited to 5%
    • SL - Shrinkage limiting

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