Cement Production

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Cement Production
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Portland Cement

• By definition
• a hydraulic cement produced by pulverizing
  clinker consisting essentially of hydraulic
  calcium silicates, usually containing one or more
  of the forms of calcium sulfate as an interground
  addition

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Source PCA, 2003
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Raw Materials Necessary for Portland Cement
Manufacture Must Provide the Following

• Calcium
• Silica
• Alumina
• Iron

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Calcium Iron Silica Alumina Sulfate
Alkali waste Aragonite Calcite Cement-kiln dust Cement rock Chalk Clay Fullers earth Limestone Marble Marl Seashells Shale Slag Blast-furnace flue dust Clay Iron ore Mill scale Ore washings Pyrite cinders Shale Calcium silicate Cement rock Clay Fly ash Fullers earth Limestone Loess Marl Ore washings Quartzite Rice-hull ash Sand Sandstone Shale Slag Traprock Aluminum-ore refuse Bauxite Cement rock Clay Copper slag Fly ash Fullers earth Granodiorite Limestone Loess Ore washings Shale Slag Staurolite Anhydrite Calcium sulfate Gypsum
Blast-furnace flue dust Clay Iron ore Mill scale Ore washings Pyrite cinders Shale Calcium silicate Cement rock Clay Fly ash Fullers earth Limestone Loess Marl Ore washings Quartzite Rice-hull ash Sand Sandstone Shale Slag Traprock Aluminum-ore refuse Bauxite Cement rock Clay Copper slag Fly ash Fullers earth Granodiorite Limestone Loess Ore washings Shale Slag Staurolite Anhydrite Calcium sulfate Gypsum
Source PCA, 2003
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Traditional Manufacture of Portland Cement
1. Stone is first reduced to 125 mm (5 in.) size,
then to 20 mm (3/4 in.), and stored.
Source PCA, 2003
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• Raw materials are ground to powder and blended.

or 2. Raw materials are ground, mixed with water
to form slurry, and blended.
Source PCA, 2003
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3. Burning changes raw mix chemically into cement
clinker.
Source PCA, 2003
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Source Mindess, Young, and Darwin, 2004
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Source Mindess, Young, Darwin, 2004
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3. Burning changes raw mix chemically into
clinker. Note four stage preheater, flash
furnaces, and shorter kiln.
Source PCA, 2003
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Pyro- Processing
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Source PCA, 2003
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4. Clinker is ground with gypsum into portland
cement and shipped.
Source PCA, 2003
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Clinker
Gypsum
Source PCA, 2003
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Grinding

• Clinker is ground with gypsum (calcium sulfate)
  to produce portland cement
• Fine grinding is necessary for high early
  strength
• 85-95 -325 mesh (45 microns)
• 7 trillion particles per pound
• Gypsum absorbs water and prevents setting of C3A
  during shipment

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Source van Oss and Padovani, 2002
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Process of Clinker Production
Source PCA, 2003
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Source PCA, 2003
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Source PCA, 2003
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Source Taylor, 1997
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Source MacLaren and White, 2003
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Source MacLaren and White, 2003
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Clinker Phases

• Alite or 3CaOSiO2 or C3S
• Hydrates hardens quickly
• High early strength
• Higher heat of hydration (setting)
• Belite or 2CaO SiO2 or C2S
• Hydrates hardens slower than alite
• Gives off less heat
• High late strength (gt 7 days)
• Modern cements are manufactured to be higher in
  alite for early strength

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Clinker Phases

• Aluminate or 3CaO Al2O3 or C3A
• Very high heat of hydration
• Some contribution to early strength
• Low C3A for sulfate resistance
• Ferrite or 4CaO Al2O3 Fe2O3 or C4AF
• Little contribution to strength
• Lowers clinkering temperature
• Controls the color of cement

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Microscopic Images of Clinker
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Microscopic Images of Clinker
Alite
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Microscopic Images of Clinker
Belite
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Microscopic Images of Clinker
Aluminate
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Microscopic Images of Clinker
Ferrite
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Types of Portland Cement
ASTM C 150 (AASHTO M 85)

• I Normal
• II Moderate sulfate resistance
• III High early strength
• IV Low heat of hydration
• V High sulfate resistance

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Source Mindess, Young, and Darwin, 2004
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Source Mindess, Young, and Darwin, 2004
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Source Mindess, Young, and Darwin, 2004
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Source Mindess, Young, and Darwin, 2004