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Calcium Aluminate Cements
Calcium aluminate cements are cements consisting predominantly of hydraulic calcium aluminates. Alternative names are "aluminous cement", "high-alumina cement" and "Ciment fondu" in French. They are used in a number of small-scale, specialized applications. History The method of making cement from limestone and low-silica bauxite was patented in France in 1908 by Bied of the Pavin de Lafarge Company. The initial development was as a result of the search for a cement offering sulfate resistance. The cement was known as "Ciment fondu" in French. Subsequently, its other special properties were discovered, and these led to its future in niche applications. By the 2010s, the product was found in the US market under the name FONDAG cement (FOND Aluminous Aggregate), sometimes referred to as ALAG (ALuminous AGgregate). FONDAG cement is a mix of up to 40 percent alumina, stable at high temperatures and thermal cycling from Composition The main active constituent of calcium alum ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dodecacalcium Hepta-aluminate
Dodecacalcium hepta-aluminate (12CaO·7Al2O3, Ca12Al14O33 or ) is an inorganic solid that occurs rarely in nature as the mineral mayenite. It is an important phase in calcium aluminate cements and is an intermediate in the manufacture of Portland cement. Its composition and properties have been the subject of much debate, because of variations in composition that can arise during its high-temperature formation.Taylor, H F W (1990) ''Cement Chemistry'', Academic Press, , pp. 36–38 Synthesis Polycrystalline can be prepared via a conventional solid-state reaction, i.e., heating a mixture of calcium carbonate and aluminium oxide or aluminium hydroxide powders, in air. It is not formed in oxygen or in moisture-free atmosphere. It can be regrown into single crystals using the Czochralski or zone melting techniques. In Portland cement kilns, is an early reaction product of aluminium and calcium oxides in the temperature range 900–1200 °C. With the onset of melt-phases at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pulverized Coal
Coal dust is a fine powdered form of which is created by the crushing, grinding, or pulverizing of coal. Because of the brittle nature of coal, coal dust can be created during mining, transportation, or by mechanically handling coal. It is a form of fugitive dust. Grinding coal to dust before combusting it improves the speed and efficiency of burning and makes the coal easier to handle. However, coal dust is hazardous to workers if it is suspended in air outside the controlled environment of grinding and combustion equipment. It poses the acute hazard of forming an explosive mixture in air and the chronic hazard of causing pulmonary illness in people who inhale excessive quantities of it. The distribution of the particle-size of coal dust is frequently measured in mesh. The British slang term for cheap fuel consisting of coal dust (slack) containing small lumps of coal (nuts) is nutty slack. Risks The Occupational Safety and Health Administration (OSHA) has set the legal limit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reverberatory Furnace
A reverberatory furnace is a metallurgical or process furnace that isolates the material being processed from contact with the fuel, but not from contact with combustion gases. The term ''reverberation'' is used here in a generic sense of ''rebounding'' or '' reflecting'', not in the acoustic sense of ''echoing''. Operation Chemistry determines the optimum relationship between the fuel and the material, among other variables. The reverberatory furnace can be contrasted on the one hand with the blast furnace, in which fuel and material are mixed in a single chamber, and, on the other hand, with crucible, muffling, or retort furnaces, in which the subject material is isolated from the fuel and all of the products of combustion including gases and flying ash. There are, however, a great many furnace designs, and the terminology of metallurgy has not been very consistently defined, so it is difficult to categorically contradict other views. Applications and comparison with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kiln
A kiln is a thermally insulated chamber, a type of oven, that produces temperatures sufficient to complete some process, such as hardening, drying, or chemical changes. Kilns have been used for millennia to turn objects made from clay into pottery, tiles and bricks. Various industries use rotary kilns for pyroprocessing—to calcinate ores, to calcinate limestone to lime for cement, and to transform many other materials. Pronunciation and etymology According to the Oxford English Dictionary, kiln was derived from the words cyline, cylene, cyln(e) in Old English, in turn derived from Latin ''culina'' ("kitchen"). In Middle English the word is attested as kulne, kyllne, kilne, kiln, kylle, kyll, kil, kill, keele, kiele. For over 600 years, the final "n" in kiln was silent. It wasn't until the late 20th century where the "n" began to be pronounced. This is due to a phenomenon known as spelling pronunciation, where the pronunciation of a word is surmised from its spelling ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clinker (cement)
200px, Typical clinker nodules 200px, Hot clinker Cement clinker is a solid material produced in the manufacture of Portland cement as an intermediary product. Clinker occurs as lumps or nodules, usually to in diameter. It is produced by sintering (fusing together without melting to the point of liquefaction) limestone and aluminosilicate materials such as clay during the cement kiln stage. Composition and preparation The Portland clinker essentially consists of four mineral phases: two calcium silicates, alite (Ca3Si) and belite (Ca2Si), along with tricalcium aluminate (Ca3Al) and calcium aluminoferrite (Ca4AlFe). These main mineral phases are produced by heating at high temperature clays and limestone. Portland cement clinker is made by heating a homogeneous mixture of raw materials in a rotary kiln at high temperature. The products of the chemical reaction aggregate together at their sintering temperature, about . Aluminium oxide and iron oxide are present only as a f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Basalt
Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% of all volcanic rock on Earth is basalt. Rapid-cooling, fine-grained basalt is chemically equivalent to slow-cooling, coarse-grained gabbro. The eruption of basalt lava is observed by geologists at about 20 volcanoes per year. Basalt is also an important rock type on other planetary bodies in the Solar System. For example, the bulk of the plains of Venus, which cover ~80% of the surface, are basaltic; the lunar maria are plains of flood-basaltic lava flows; and basalt is a common rock on the surface of Mars. Molten basalt lava has a low viscosity due to its relatively low silica content (between 45% and 52%), resulting in rapidly moving lava flows that can spread over great areas before cooling and solidifying. Flood basalts are t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vesicular Texture
Vesicular texture is a volcanic rock texture characterized by a rock being pitted with many cavities (known as vesicles) at its surface and inside. This texture is common in aphanitic, or glassy, igneous rocks that have come to the surface of the earth, a process known as extrusion. As magma rises to the surface the pressure on it decreases. When this happens gasses dissolved in the magma are able to come out of solution, forming gas bubbles (the cavities) inside it. When the magma finally reaches the surface as lava and cools, the rock solidifies around the gas bubbles and traps them inside, preserving them as holes filled with gas called vesicles. A related texture is amygdaloidal in which the volcanic rock, usually basalt or andesite, has cavities, or vesicles, that are filled with secondary minerals, such as zeolites, calcite, quartz, or chalcedony. Individual cavity fillings are termed amygdules (American usage) or amygdales (British usage). Sometimes these can be sou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Corundum
Corundum is a crystalline form of aluminium oxide () typically containing traces of iron, titanium, vanadium and chromium. It is a rock-forming mineral. It is a naturally transparent material, but can have different colors depending on the presence of transition metal impurities in its crystalline structure. Corundum has two primary gem varieties: ruby and sapphire. Rubies are red due to the presence of chromium, and sapphires exhibit a range of colors depending on what transition metal is present. A rare type of sapphire, padparadscha sapphire, is pink-orange. The name "corundum" is derived from the Tamil- Dravidian word ''kurundam'' (ruby-sapphire) (appearing in Sanskrit as ''kuruvinda''). Because of corundum's hardness (pure corundum is defined to have 9.0 on the Mohs scale), it can scratch almost all other minerals. It is commonly used as an abrasive on sandpaper and on large tools used in machining metals, plastics, and wood. Emery, a variety of corundum with no val ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wüstite
Wüstite ( Fe O) is a mineral form of iron(II) oxide found with meteorites and native iron. It has a grey colour with a greenish tint in reflected light. Wüstite crystallizes in the isometric-hexoctahedral crystal system in opaque to translucent metallic grains. It has a Mohs hardness of 5 to 5.5 and a specific gravity of 5.88. Wüstite is a typical example of a non-stoichiometric compound. Wüstite was named after Fritz Wüst (1860–1938), a German metallurgist and founding director of the ''Kaiser-Wilhelm-Institut für Eisenforschung'' (presently Max Planck Institute for Iron Research GmbH). In addition to its type locality in Germany, it has been reported from Disko Island, Greenland; the Jharia coalfield, Jharkhand, India; and as inclusions in diamonds in a number of kimberlite pipes. It also is reported from deep sea manganese nodules. Its presence indicates a highly reducing environment. Wüstite redox buffer Iron minerals on the earth's surface are typicall ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
