Cement Production

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

Source: PCA, 2003

Raw Materials Necessary for Portland Cement Manufacture Must Provide the Following CalciumSilicaAluminaIron

CalciumIronSilicaAluminaSulfate Alkali waste AragoniteCalcite Cement-kiln dust Cement rock ChalkClay Fuller’s earth LimestoneMarbleMarlSeashellsShaleSlag Blast-furnace flue dust Clay Iron ore Mill scale Ore washings Pyrite cinders Shale Calcium silicate Cement rock Clay Fly ash Fuller’s earth LimestoneLoessMarl Ore washings Quartzite Rice-hull ash SandSandstoneShaleSlagTraprock Aluminum-ore refuse Bauxite Cement rock Clay Copper slag Fly ash Fuller’s earth GranodioriteLimestoneLoess Ore washings ShaleSlagStauroliteAnhydrite Calcium sulfate Gypsum Source: PCA, 2003

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

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- Processing

Source: PCA, 2003

4. Clinker is ground with gypsum into portland cement and shipped. Source: PCA, 2003

Clinker Gypsum Source: PCA, 2003

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 C 3 A during shipment

Source: van Oss and Padovani, 2002

Process of Clinker Production Source: PCA, 2003

Source: Taylor, 1997

Source: MacLaren and White, 2003

Clinker Phases Alite or 3CaOSiO 2 or C 3 S –Hydrates & hardens quickly –High early strength –Higher heat of hydration (setting) Belite or 2CaO SiO 2 or C 2 S –Hydrates & hardens slower than alite –Gives off less heat –High late strength (> 7 days) Modern cements are manufactured to be higher in alite for early strength

Clinker Phases Aluminate or 3CaO Al 2 O 3 or C 3 A –Very high heat of hydration –Some contribution to early strength –Low C 3 A for sulfate resistance Ferrite or 4CaO Al 2 O 3 Fe 2 O 3 or C 4 AF –Little contribution to strength –Lowers clinkering temperature –Controls the color of cement

Microscopic Images of Clinker

Alite

Microscopic Images of Clinker Belite

Microscopic Images of Clinker Aluminate

Microscopic Images of Clinker Ferrite