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Cementing material in great pyramid giza
Lime mortar or gypsum
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Roman Mortar
- 2 parts pozzolan (volcanic ash)
- 1 part lime
- +animal fat
- +milk
- +blood
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Smeatons lighthouse uses
Granite stone held together with natural cement (calcined impure limestone containing clay) blended with pozzolan from italy
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Joseph aspdin in 1824 named portland cement becuase
it produced a concrete that was the colour of limestone
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Aspdins first major production was fired in beehive kilns
Near limestone source
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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
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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)
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Clinker compounds
- Tricalcium silicate
- 3 CaO.siO2
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Hydration products
- Tobermorite gel
- Calcium Silicate Hydrate
- Calcium hydroxide
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Hydration of tricalcium aluminate without gypsum
C3H + H +CH -->C4AH13
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In the absence of gypsum this reaction would occur very rapidly and lead to flash set
Hydration of tricalcium aluminate without gypsum
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Hyrdration of tricalcium aluminate in the presence of gypsum
C3A + H + C3H2 -->C6HS3H32
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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
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Tricalcium Silicate (alite) What does it do, forumula
- C3S
- Hydrates and hardens rapidly
- Responsible for initial set and early strength
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Dicalcium Silicate
- Hydrates and hardens slowly
- Contributes to later age strength (beyond 7 days)
- C2S
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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
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Tetracalcium Alimnoferrite (ferrite)
- C4AF
- Reduces clinkering temperature
- Hydrates rapidly but contributes little to strength
- Colour of hydrated cement (greyness) dure to ferrite hydrates
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Hydration products
- C-S-H
- Calcium hydroxide
- AFt/AFm
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Consumed products in hydration
- Calcium sulfate
- C4AF
- C3A
- C2S
- C3S
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Original Water filled spaces:
' capillary porosity'
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Low W/CM
- Low capillary porosity
- Small pores, poorly connected
- High Strength
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High W/CM
- High Capillary porosity
- Large well connected pres
- High Permeability
- Low strength
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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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