6505-3 - Hydraulic and Nonhydraulic Cements Hydraulic...

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1 Hydraulic and Nonhydraulic Cements Hydraulic cement - hardens by reacting with water to form a water-resistant product. The presence of air is not required for the hardening process. Example : Portland cement . Nonhydraulic cement - reacts with water to form a product which is not stable in water. The hydration product may then react with air to form a water-resistant product. Example : Quick Lime . CaO + H 2 O Ca(OH) 2 hydrated lime Ca(OH) 2 + CO 2 CaCO 3 + H 2 O Invention of Portland Cement • Greeks and Romans had used a blend of lime and pozzolanic materials to produce a hydraulic cement. • Modern Portland cement was invented by Joseph Aspdin, an English mason who obtained a patent for his product in 1824. • It was name Portland cement because the concrete it produced resembled the color of the natural limestone quarried on the Isle of Portland, a peninsula in the English Channel.
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2 Location of Isle of Portland Isle of Portland Scotland England Northern Island Wales Modern Cement Plant
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3 2. Proportioning & Grinding of Raw Materials • Dry Process - Dry raw materials are proportioned, ground to a powder, blended together and fed to the kiln in a dry state . • Wet Process - A slurry is formed by adding water to the properly proportioned raw materials. The grinding and blending operations are then completed with the materials in slurry form.
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4 3. Heating in a Kiln • After blending, the mixture of raw materials is fed into the upper end of a tilted rotating, cylindrical kiln. • Inside the kiln, raw materials reach temperatures of 2600 ° F to 3000 ° F (1430 ° C to 1650 ° C). At 2700 ° F (1480 ° C), a series of chemical reactions cause the materials to fuse and form cement clinkers, often the size of marbles. Proper amount of gypsum is added to the clinkers and the mixture is ground in a grinding mill to form Portland cement.
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5 Bags of Portland cement Portland cement transport in bulk Portland cement
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6 Physical Properties of Portland Cement • Particle Size: Finer than No. 200 sieve (75 μ m) Typical particle size distribution of a normal Portland cement: Size %Passing 75 μ m1 0 0 45 μ m8 8 30 μ m7 4 15 μ m4 6 7.5 μ m2 2 • Typical Specific Gravity : 3.15 • Typical Unit Weight: 94 pcf • A commercial bag of Portland cement in the U.S. weighs 94 lbs. Chemical Composition of Portland Cement • Portland cement consists essentially of various compounds of calcium. • Results of chemical analysis are usually reported in terms of oxides of the elements present. The main oxides in Portland cement are: Oxides Abbreviation (1) CaO Calcium Oxide C (2) SiO 2 Silicon Oxide S (3) Al 2 O 3 Aluminum Oxide A (4) Fe 2 O 3 Iron Oxide F (5) MgO Magnesium Oxide M (6) SO 3 Sulfur Oxide Ŝ (7) H 2 O Water H Chemical Composition of Portland Cement (Cont’d) • The 4 main compounds, which make up over 90% by weight of the Portland cement are: Compound Abbreviation 3CaO·SiO 2 Tricalcium Silicate C 3 S 2CaO·SiO 2 Dicalcium Silicate C 2 S 3CaO·Al 2 O 3 Tricalcium Aluminate C 3 A 4CaO·Al 2 O 3 ·Fe 2 O 3 Tetracalcium Aluminoferrite C 4 AF
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6505-3 - Hydraulic and Nonhydraulic Cements Hydraulic...

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