2 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
3 Source: PCA, 2003Fig Aerial view of a cement plant. (70000)
4 Raw Materials Necessary for Portland Cement Manufacture Must Provide the Following CalciumSilicaAluminaIron
5 Calcium Iron Silica Alumina Sulfate Alkali waste Aragonite Calcite Cement-kiln dustCement rockChalkClayFuller’s earthLimestoneMarbleMarlSeashellsShaleSlagBlast-furnace flue dustIron oreMill scaleOre washingsPyrite cindersCalcium silicateFly ashLoessQuartziteRice-hull ashSandSandstoneTraprockAluminum-ore refuseBauxiteCopper slagGranodioriteStauroliteAnhydriteCalcium sulfateGypsumSource: PCA, 2003Table 2-1. Sources of Raw Materials Used in Manufacture of Portland CementSulfate, 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.
6 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, 2003Fig Steps in the traditional manufacture of portland cement
8 Raw materials are ground to powder and blended. or2. Raw materials are ground, mixed with water to form slurry, and blended.Source: PCA, 2003Fig Steps in the traditional manufacture of portland cement
9 3. Burning changes raw mix chemically into cement clinker. Source: PCA, 2003Fig Steps in the traditional manufacture of portland cement
12 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, 2003Fig Steps in the modern dry-process manufacture of portland cement.
13 Pyro- Processing Modernized in 1999 by HBZ and Fuller 1500 tpd to 2000 tpdFuel Consumption decreased by 15%Modern – State of the Art Preheater / Precalciner System with down draft calciner/ & DeSox
15 Source: PCA, 2003Fig Rotary kiln (furnace) for manufacturing portland cement clinker. Inset view inside the kiln. (58927, 25139)
16 4. Clinker is ground with gypsum into portland cement and shipped. Source: PCA, 2003Fig Steps in the traditional manufacture of portland cement
17 Clinker Gypsum Source: PCA, 2003 Fig 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 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)
18 GrindingClinker is ground with gypsum (calcium sulfate) to produce portland cementFine grinding is necessary for high early strength85-95% -325 mesh (45 microns)~ 7 trillion particles per poundGypsum absorbs water and prevents setting of C3A during shipment
26 Clinker Phases Alite or 3CaO•SiO2 or C3S Belite or 2CaO• SiO2 or C2S Hydrates & hardens quicklyHigh early strengthHigher heat of hydration (setting)Belite or 2CaO• SiO2 or C2SHydrates & hardens slower than aliteGives off less heatHigh late strength (> 7 days)Modern cements are manufactured to be higher in alite for early strength
27 Clinker Phases Aluminate or 3CaO• Al2O3 or C3A Very high heat of hydrationSome contribution to early strengthLow C3A for sulfate resistanceFerrite or 4CaO• Al2O3 • Fe2O3 or C4AFLittle contribution to strengthLowers clinkering temperatureControls the color of cement