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 Fig. 2-5. Aerial view of a cement plant. (70000)

Raw Materials Necessary for Portland Cement Manufacture Must Provide the Following Calcium Silica Alumina Iron

Calcium Iron Silica Alumina Sulfate Alkali waste Aragonite Calcite Cement-kiln dust Cement rock Chalk Clay Fuller’s earth Limestone Marble Marl Seashells Shale Slag Blast-furnace flue dust Iron ore Mill scale Ore washings Pyrite cinders Calcium silicate Fly ash Loess Quartzite Rice-hull ash Sand Sandstone Traprock Aluminum-ore refuse Bauxite Copper slag Granodiorite Staurolite Anhydrite Calcium sulfate Gypsum Source: PCA, 2003 Table 2-1. Sources of Raw Materials Used in Manufacture of Portland Cement Sulfate, often in the form of gypsum, is added during the grinding of the clinker to regulate the setting time of the cement and to improve shrinkage and strength development properties.

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 Fig. 2-3. Steps in the traditional manufacture of portland cement

Natural Cement Rock Two Benches No Blasting only Ripping 5- 10 hour shifts Haul trucks 2 – 796C cat 1 – 35R Euclid 988 Cat Loaders

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 Fig. 2-3. Steps in the traditional manufacture of portland cement

3. Burning changes raw mix chemically into cement clinker. Source: PCA, 2003 Fig. 2-3. Steps in the traditional manufacture of portland cement

Source: Mindess, Young, and Darwin, 2004

Source: Mindess, Young, & Darwin, 2004

3. Burning changes raw mix chemically into clinker 3. Burning changes raw mix chemically into clinker. Note four stage preheater, flash furnaces, and shorter kiln. Source: PCA, 2003 Fig. 2-4. Steps in the modern dry-process manufacture of portland cement.

Pyro- Processing Modernized in 1999 by HBZ and Fuller 1500 tpd to 2000 tpd Fuel Consumption decreased by 15% Modern – State of the Art Preheater / Precalciner System with down draft calciner/ & DeSox

Kiln –2,000 stpd 12’ x 165’ 3.1 RPM

Source: PCA, 2003 Fig. 2-8. Rotary kiln (furnace) for manufacturing portland cement clinker. Inset view inside the kiln. (58927, 25139)

4. Clinker is ground with gypsum into portland cement and shipped. Source: PCA, 2003 Fig. 2-3. Steps in the traditional manufacture of portland cement

Clinker Gypsum Source: PCA, 2003 Fig. 2-9. Portland cement clinker is formed by burning calcium and siliceous raw materials in a kiln. This particular clinker is about 20 mm (3¼4 in.) in diameter. (60504) Fig. 2-11. Gypsum, a source of sulfate, is interground with portland clinker to form portland cement. It helps control setting, drying shrinkage properties, and strength development. (60505)

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

Source: van Oss and Padovani, 2002

Process of Clinker Production Source: PCA, 2003 Fig. 2-10. Process of clinker production from raw feed to the final product (Hills 2000).

Source: PCA, 2003 Fig. 2-10. Process of clinker production from raw feed to the final product (Hills 2000).

Source: PCA, 2003 Fig. 2-10. Process of clinker production from raw feed to the final product (Hills 2000).

Source: Taylor, 1997

Source: MacLaren and White, 2003

Source: MacLaren and White, 2003

Clinker Phases Alite or 3CaO•SiO2 or C3S Belite or 2CaO• SiO2 or C2S 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 (> 7 days) Modern cements are manufactured to be higher in alite for early strength

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

Microscopic Images of Clinker

Microscopic Images of Clinker Alite

Microscopic Images of Clinker Belite

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

Source: Mindess, Young, and Darwin, 2004

Source: Mindess, Young, and Darwin, 2004

Source: Mindess, Young, and Darwin, 2004

Source: Mindess, Young, and Darwin, 2004