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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.
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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
Raw Materials Necessary for Portland Cement Manufacture Must Provide the Following • Calcium • Silica • Alumina • Iron
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
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
3. Burning changes raw mix chemically into clinker. Note four stage preheater, flash furnaces, and shorter kiln. 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 C3A during shipment
Process of Clinker Production Source: PCA, 2003
Clinker Phases • Alite or 3CaO•SiO2or C3S • Hydrates & hardens quickly • High early strength • Higher heat of hydration (setting) • Belite or 2CaO• SiO2or C2S • 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• Al2O3or C3A • Very high heat of hydration • Some contribution to early strength • Low C3A for sulfate resistance • Ferriteor4CaO• Al2O3 • Fe2O3orC4AF • Little contribution to strength • Lowers clinkering temperature • Controls the color of cement
Microscopic Images of Clinker Aluminate
Microscopic Images of Clinker Ferrite
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