Cement ProductionCement Production

Portland CementPortland Cement

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

Source: PCA, 2003

Raw Materials Necessary for Raw Materials Necessary for Portland Cement Manufacture Portland Cement Manufacture

Must Provide the FollowingMust Provide the FollowingCalciumCalcium

SilicaSilica

AluminaAlumina

IronIron

Calcium Calcium IronIron Silica Silica AluminaAlumina SulfatSulfatee

Alkali wasteAlkali waste

AragoniteAragonite

CalciteCalcite

Cement-kiln Cement-kiln dustdust

Cement rockCement rock

ChalkChalk

ClayClay

Fuller’s earthFuller’s earth

LimestoneLimestone

MarbleMarble

MarlMarl

SeashellsSeashells

ShaleShale

SlagSlag

Blast-furnace Blast-furnace flue dustflue dust

ClayClay

Iron oreIron ore

Mill scaleMill scale

Ore washingsOre washings

Pyrite cindersPyrite cinders

ShaleShale

Calcium silicateCalcium silicate

Cement rockCement rock

ClayClay

Fly ashFly ash

Fuller’s earthFuller’s earth

LimestoneLimestone

LoessLoess

MarlMarl

Ore washingsOre washings

QuartziteQuartzite

Rice-hull ashRice-hull ash

SandSand

SandstoneSandstone

ShaleShale

SlagSlag

TraprockTraprock

Aluminum-ore Aluminum-ore refuserefuse

BauxiteBauxite

Cement rockCement rock

ClayClay

Copper slagCopper slag

FlyFly ashash

Fuller’s earthFuller’s earth

GranodioriteGranodiorite

LimestoneLimestone

LoessLoess

Ore washingsOre washings

ShaleShale

SlagSlag

StauroliteStaurolite

AnhydriteAnhydrite

Calcium Calcium sulfatesulfate

GypsumGypsum

Source: PCA, 2003

Traditional Manufacture of Traditional Manufacture of Portland CementPortland Cement

1. Stone is first reduced to 125 mm (5 in.) size, then to 20 mm (3/4 in.), and stored.

Source: PCA, 2003

2. 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

3. Burning changes raw mix chemically into cement clinker.

Source: PCA, 2003

Source: Mindess, Young, and Darwin, 2004

Source: Mindess, Young, & Darwin, 2004

3. Burning changes raw mix chemically into clinker. Note four stage preheater, flash furnaces, and shorter kiln.

Source: PCA, 2003

Pyro- Pyro- ProcessingProcessing

Source: PCA, 2003

4. Clinker is ground with gypsum into portland cement and shipped.

Source: PCA, 2003

ClinkerClinker Gypsum

Source: PCA, 2003

GrindingGrindingClinker is ground with Clinker is ground with gypsum (calcium sulfate) to gypsum (calcium sulfate) to produce portland cementproduce portland cement

Fine grinding is necessary Fine grinding is necessary for high early strengthfor high early strength– 85-95% -325 mesh (45 85-95% -325 mesh (45

microns)microns)

– ~ 7 trillion particles per ~ 7 trillion particles per poundpound

Gypsum absorbs water and Gypsum absorbs water and prevents setting of Cprevents setting of C33A A

during shipmentduring shipment

Source: van Oss and Padovani, 2002

Process of Clinker ProductionProcess of Clinker Production

Source: PCA, 2003

Source: PCA, 2003

Source: PCA, 2003

Source: Taylor, 1997

Source: MacLaren and White, 2003

Source: MacLaren and White, 2003

Clinker PhasesClinker Phases

Alite Alite oror 3CaO•SiO 3CaO•SiO22 oror C C33SS– Hydrates & hardens quicklyHydrates & hardens quickly– High early strengthHigh early strength– Higher heat of hydration (setting)Higher heat of hydration (setting)

Belite Belite oror 2CaO• SiO 2CaO• SiO22 oror C C22SS– Hydrates & hardens slower than Hydrates & hardens slower than

alitealite– Gives off less heatGives off less heat– High late strength (> 7 days)High late strength (> 7 days)

Modern cements are Modern cements are manufactured to be higher in manufactured to be higher in alite for early strengthalite for early strength

Clinker PhasesClinker PhasesAluminate Aluminate oror 3CaO• Al 3CaO• Al22OO33

oror C C33AA– Very high heat of hydrationVery high heat of hydration– Some contribution to early Some contribution to early

strengthstrength

– Low CLow C33A for sulfate A for sulfate

resistanceresistance

FerriteFerrite oror 4CaO4CaO• • AlAl22OO3 3 • •

FeFe22OO33 oror CC44AFAF– Little contribution to strengthLittle contribution to strength– Lowers clinkering Lowers clinkering

temperaturetemperature– Controls the color of cementControls the color of cement

Microscopic Images of ClinkerMicroscopic Images of Clinker

Microscopic Images of ClinkerMicroscopic Images of Clinker

Alite

Microscopic Images of ClinkerMicroscopic Images of Clinker

Belite

Microscopic Images of ClinkerMicroscopic Images of Clinker

Aluminate

Microscopic Images of ClinkerMicroscopic Images of Clinker

Ferrite

Types of Portland CementTypes of Portland Cement

II NormalNormalIIII Moderate sulfate resistanceModerate sulfate resistanceIIIIII High early strengthHigh early strengthIVIV Low heat of hydrationLow heat of hydrationVV High sulfate resistanceHigh sulfate resistance

ASTM C 150 (AASHTO M 85)

Source: Mindess, Young, and Darwin, 2004

Source: Mindess, Young, and Darwin, 2004

Source: Mindess, Young, and Darwin, 2004

Source: Mindess, Young, and Darwin, 2004