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Encyclopedia > Portland cement
Sampling fast set Portland cement
Sampling fast set Portland cement

Portland cement is the most common type of cement in general usage, as it is a basic ingredient of concrete, mortar and plaster. It consists of a mixture of oxides of calcium, silicon and aluminium. Portland cement and similar materials are made by heating limestone (a source of calcium) with clay or sand (a source of silicon) and grinding the product (clinker), with a source of sulfate (most commonly gypsum). The resulting powder, when mixed with water, will become a hydrated solid over time. Tom Pyle and John Beede sampling fast set Portland cement. ... Tom Pyle and John Beede sampling fast set Portland cement. ... Cement is a material for bonding stone or brick. ... The examples and perspective in this article or section may not represent a worldwide view. ... Mortar holding bricks. ... // Gypsum plaster Plaster of Paris, or simply plaster, is a type of building material based on calcium sulfate hemihydrate, nominally (CaSO₄)₂*H₂O. It is created by heating gypsum to about 150 ℃, 2(CaSO₄ · 2H₂O) → (CaSO₄)₂ · H₂O + 3 H₂O (released as steam). ... Calcium oxide (CaO), commonly known as lime, quicklime or burnt lime, is a widely used chemical compound. ... R-phrases R42 R43 R49 S-phrases S22 S36 S37 S45 S53 Flash point non-flammable Supplementary data page Structure and properties n, εr, etc. ... Aluminium oxide (or aluminum oxide) (Al2O3) is a chemical compound of aluminium and oxygen. ... Limey shale overlaid by limestone. ... Clinker has several meanings: In boat building, clinker is a method of constructing wooden boats by fixing planks to a frame so that the planks overlap each other gaining support from the frame and from adjacent planks. ... In inorganic chemistry, a sulfate (IUPAC-recommended spelling; also sulphate in British English) is a salt of sulfuric acid. ... Gypsum is a very soft mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. // Chemical structure Heating gypsum to between 100°C and 150°C (302°F) partially dehydrates the mineral by driving off exactly 75% of the water contained in its chemical structure. ... Hydrates are compounds formed by the union of water with some other substance, generally forming a neutral body, as certain crystallized salts. ...

Contents


History

Portland cement was developed from cements (or correctly hydraulic limes) made in Britain in the early part of the 19th century, and its name is derived from its similarity to Portland stone, a type of building stone that was quarried on the Isle of Portland in Dorset, England. Joseph Aspdin, a British bricklayer, in 1824 was granted a patent for a process of making a cement which he called Portland cement. However, his cement was not Portland cement but an artificial hydraulic lime similar to the material known as "Roman Cement" which was Patented in 1796 by James Parker. Aspdin's process was similar to that patented in 1822 and used since 1811 by James Frost who called his cement "British Cement". The name "Portland Cement" is recorded in a directory published in 1823 being associated with a William Lockwood and possibly others. Aspdin's son William in 1843 made an improved version of the "Roman Cement" and he initially called it "Patent Portland Cement" but he had no patent and his cement still was not Portland Cement. In 1848 William Aspdin further improved his cement and in 1853 moved to Germany where he was involved in cement making. (See "The Cement Industry 1796-1914: A History" by A J Francis 1977) The first true Portland cement was probably made by the factory of "Portlandzementfabrik Stern" in Germany about 1867. This works is mentioned by Henry Reid in his 1868 book on Cement Manufacture wherein his states that the cement is superior to any other by a large margin. The German Government issued a Standard on Portland Cement in 1878 (possibly the first standard of any kind). The Stern cement would have complied with that standard. Alternative meaning: Nineteenth Century (periodical) (18th century — 19th century — 20th century — more centuries) As a means of recording the passage of time, the 19th century was that century which lasted from 1801-1900 in the sense of the Gregorian calendar. ... The Cenotaph, in Whitehall, London, England, is made from Portland stone Portland stone is limestone from the Jurassic period quarried on the Isle of Portland, Dorset. ... Chesil Beach from the hill above Fortuneswell, Portland Harbour is on the right. ... Dorset (pronounced Dorsit, sometimes in the past called Dorsetshire) is a county in the southwest of England, on the English Channel coast. ... Royal motto (French): Dieu et mon droit (Translated: God and my right) Englands location (dark green) within the United Kingdom (light green), with the Republic of Ireland (blue) to its west Languages None official English de facto Capital None official London de facto Largest city London Area – Total Ranked... Joseph Aspdin (1788 – 20 March 1855) was an English mason, bricklayer and inventor who patented Portland cement on 21 October 1824. ...


Production

Schematic explanation of Portland cement production
Schematic explanation of Portland cement production

There are three fundamental stages in the production of Portland cement: Image File history File links Download high resolution version (240x607, 5 KB) Skildring Schematic overview on Portland Cement Production. ... Image File history File links Download high resolution version (240x607, 5 KB) Skildring Schematic overview on Portland Cement Production. ...

  1. Preparation of the raw mixture
  2. Production of the clinker
  3. Preparation of the cement

The chemistry of cement is very complex, so cement chemist notation was invented to simplify the formula of common molecules found in cement. Clinker has several meanings: In boat building, clinker is a method of constructing wooden boats by fixing planks to a frame so that the planks overlap each other gaining support from the frame and from adjacent planks. ... Cement chemist notation (CCN) was developed to simplify the formulas cement chemists use on a daily basis. ...



The raw materials for Portland cement production are a mixture (as fine dust in the 'Dry process' or in the form of a slurry in the 'Wet process') of calcium oxide, silicon oxide, aluminium oxide, ferric oxide, and magnesium oxide. The raw materials are usually quarried from local rock, which in some places is already practically the desired composition and in other places requires the addition of clay and limestone, as well as iron ore, bauxite or recycled materials. A slurry is a sloppy mixture, which comes in different varieties: Metal Slurry can be used in pipe fitting and other welding tasks, as well as slurry based bombs like the BLU-82. ... Calcium oxide (CaO), commonly known as lime, quicklime or burnt lime, is a widely used chemical compound. ... The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ... Flash point Non-flammable. ... Iron(III) oxide - also known as ferric oxide, red iron oxide, synthetic maghemite, rouge,or rust - is one of several oxide compounds of iron, and is most notable for its ferromagnetic properties. ... Magnesium oxide is a white solid mineral that occurs naturally as periclase and is a source of magnesium. ... The Gay Head cliffs in Marthas Vineyard are made almost entirely of natural clays. ... Limey shale overlaid by limestone. ... This heap of iron ore pellets will be used in steel production. ... Bauxite with penny Bauxite (pebbly) Bauxite is a naturally occurring, heterogeneous material composed primarily of one or more aluminium hydroxide minerals, plus various mixtures of silica, iron oxide, titania, aluminium silicates, and other impurities in minor or trace amounts. ...


The raw mixture is heated in a kiln, a gigantic slowly rotating and sloped cylinder, with temperatures increasing over the length of the cylinder up to ~1480°C. The temperature is regulated so that the product contains sintered but not fused lumps. Too low a temperature causes insufficient sintering, but too high a temperature results in a molten mass or glass. In the lower-temperature part of the kiln, calcium carbonate (limestone) turns into calcium oxide (lime) and carbon dioxide. In the high-temperature part, calcium oxides and silicates react to form dicalcium and tricalcium silicates (C2S C3S). Small amounts of tricalcium aluminate (C3A) and tetracalcium aluminoferrite (C4AF)are also formed. The resulting material is clinker, and can be stored for a number of years before use. Prolonged exposure to water decreases the reactivity of cement produced from weathered clinker. Charcoal Kilns, California Gold Kiln, Victoria, Australia Hop kiln. ... A degree Celsius (°C) is a unit of temperature named after the Swedish astronomer Anders Celsius (1701-1744), who first proposed a similar system in 1742. ... Sintering is a method for making objects from powder, by heating the material (below its melting point) until its particles adhere to each other. ... Calcium carbonate is a chemical compound, with chemical formula CaCO3. ... Calcium oxide (CaO), commonly known as lime, quicklime or burnt lime, is a widely used chemical compound. ... Carbon dioxide is an atmospheric gas comprised of one carbon and two oxygen atoms. ... Clinker has several meanings: In boat building, clinker is a method of constructing wooden boats by fixing planks to a frame so that the planks overlap each other gaining support from the frame and from adjacent planks. ... Reactivity refers to the rate at which a chemical substance tends to undergo a chemical reaction in time. ...


The energy required to produce clinker is ~1700 J/g. However, because of heat loss during production, actual values can be much higher. The high energy requirements and the release of significant amounts of carbon dioxide makes cement production a concern for global warming. Global mean surface temperatures 1856 to 2005; this map shows mean surface temperature anomalies during the period 1995 to 2004 with respect to the average temperatures from 1940 to 1980 Global warming refers to the increases in the average temperature of the Earths atmosphere and oceans that have been...


In order to achieve the desired setting qualities in the finished product, about 2% gypsum is added to the clinker and the mixture is finely pulverized. The powder is now ready for use, and will react with the addition of water. Gypsum is a very soft mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. // Chemical structure Heating gypsum to between 100°C and 150°C (302°F) partially dehydrates the mineral by driving off exactly 75% of the water contained in its chemical structure. ...

Typical constitutents for portland clinker and portland cement:
Clinker Weight% Cement Weight%
Tricalcium silicate C3S 45-65% C - Calcium oxide, CaO 62-67%
Dicalcium silicate C2S 15-30% S - Silicon oxide, SiO2 20-25%
Tricalcium aluminate C3A 1-8% A - Aluminium oxide, Al2O3 3-7%
Tetracalcium aluminoferrite C4AF 8-15% F - Ferro oxide, Fe2O3 2-5%
Gypsum 1-3% Sulfate



Use

The most common use for portland cement is the production of concrete. Concrete is a composite material consisting of aggregate (gravel), cement, and water. As a construction material, concrete can be cast in almost any shape desired, and once hardened, can become a structural (load bearing) element. The examples and perspective in this article or section may not represent a worldwide view. ...


When water is mixed with Portland cement, the product sets in a few hours and hardens over a period of weeks. The initial setting is caused by a reaction between the water, gypsum, and tricalcium aluminate (C3A), forming the crystalline hydration products calcium-alumino-hydrate (CAH), ettringite (Aft), and monosulfate (Afm). The later hardening and the development of cohesive strength is due to the reaction of water and tricalcium silicate (C3S), forming an amorphous hydrated product called calcium-silicate-hydrate(CSH gel). In each case the hydration products surround and cement together the individual grains. The hydration of dicalcium silicate (C2S) proceeds more slowly than that of the above compounds slowly increasing later-age strength. The ultimate cementing agent is probably gelatinous silica (SiO2). All three reactions mentioned above release heat. Gypsum is a very soft mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. // Chemical structure Heating gypsum to between 100°C and 150°C (302°F) partially dehydrates the mineral by driving off exactly 75% of the water contained in its chemical structure. ... Calcium silicate, otherwise known as slag, has a low bulk density and high physical water absorption. ... Some examples of silica gel sachets Silica gel is a granular, porous form of silica made synthetically from sodium silicate. ...


Plastic cement is a type of Portland cement with the addition of a plasticizing material (limestone or hydrated lime), as well as other materials to reduce setting time and facilitate workability (see superplasticizer). Plastic cement is used primarily for spreading onto walls to make exterior stucco, as Portland cement (used primarily for concrete) would have poor spreadability. In this usage, the term "plastic" does not refer to the addition of an organic polymer. Rather, it refers to the addition of a substance to increase the workability of the mixture. Limey shale overlaid by limestone. ... Calcium hydroxide Calcium hydroxide is a chemical compound with the chemical formula Ca(OH)2. ... It has been suggested that this article or section be merged with Plasticizer. ... To meet Wikipedias quality standards, this article or section may require cleanup. ...


Portland cement business

In 2002 the world production of hydraulic cement was 1,800 million metric tons. The top three producers were China with 704, India with 100, and the United States with 91 million metric tons for a combined total of about half the world total by the world's three most populous states. [1] For album titles with the same name, see 2002 (album). ...


"For the past 18 years, China consistently has produced more cement than any other country in the world. [...] China's cement export peaked in 1994 with 11 million tons shipped out and has been in steady decline ever since. Only 5.18 million tons were exported out of China in 2002. Offered at $34 a ton, Chinese cement is pricing itself out of the market as Thailand is asking as little as $20 for the same quality." Jan 7, 2004


"Demand for cement in China is expected to advance 5.4% annually and exceed 1 billion metric tons in 2008, driven by slowing but healthy growth in construction expenditures. Cement consumed in China will amount to 44% of global demand, and China will remain the world's largest national consumer of cement by a large margin." Nov 1, 2004


Types of Portland cement

General

There are different standards for classification of portland cement. The two major standards are the American ASTM C150 and European EN-197. EN 197 cement Types CEM I, II, III, IV, and V do not correspond to the cement types in ASTM C 150, nor can ASTM cements be substituted for EN specified cement, without the designer’s approval.


ASTM C150

There are five types of Portland cements with variations of the first three according to ASTM C150. ASTM stands for the American Society of Testing Materials and is basically a manual for all materials and their properties and proper uses. In addition, pozzolanic ash or other pozzolans are often added to cement to improve its properties and lower its cost. ASTM International is an international voluntary standards organization that develops and produces technical standards for materials, products, systems and services. ... Pozzolanic ash is an alumino-siliceous material which reacts with calcium hydroxide in the presence of water to form compounds possessing cementitious properties at room temperature, producing C-S-H. This allowed it to be used in the Roman Empire to make cement by combining with lime and water. ... Pozzolana is a fine sandy volcanic ash, originally discovered and dug at Pozzuoli in the region around Vesuvius, but later at a number of other sites. ...


Type I Portland cement is known as common cement. It is generally assumed unless another type is specified. It is commonly used for general construction especially when making precast and precast-prestressed concrete that is not to be in contact with soils or ground water. The typical compound compositions of this type are: Cement is a material for bonding stone or brick. ... The examples and perspective in this article or section may not represent a worldwide view. ...


55% (C3S), 19% (C2S), 10% (C3A), 7% (C4AF), 2.8% MgO, 2.9% (SO3), 1.0% Ignition loss, and 1.0% free CaO.


A limitation on the composition is that the (C3A) shall not exceed fifteen percent. This type is the most basic and common type of Portland cement.


Type II is known to have moderate sulfate resistance with or without moderate heat of hydration. This type of cement costs about the same as Type I. Its typical compound composition is: In inorganic chemistry, a sulfate (IUPAC-recommended spelling; also sulphate in British English) is a salt of sulfuric acid. ...


51% (C3S), 24% (C2S), 6% (C3A), 11% (C4AF), 2.9% MgO, 2.5% (SO3), 0.8% Ignition loss, and 1.0% free CaO.


A limitation on the composition is that the (C3A) shall not exceed eight percent which reduces its vulnerability to sulfates. This type is for general construction that is exposed to moderate sulfate attack. This is meant for use when concrete is in contact with soils and ground water especially in the western United States due to the high sulfur content of the soil. Another limitation is the percentage of (C3S) + (C3A) shall not exceed 58. The two limitations are meant to minimize cracking caused by temperature gradients.


Note: Cement is increasingly sold as a blend of Type I/II on the world market.


Type III is known for its high early strength. Its typical compound composition is:


57% (C3S), 19% (C2S), 10% (C3A), 7% (C4AF), 3.0% MgO, 3.1% (SO3), 0.9% Ignition loss, and 1.3% free CaO.


This cement is produced grinding clinker, bonded cement chunks, with a high percentage of (C3A) and (C3S) into a finer texture. The gypsum level is also increased a small amount. This gives the concrete using this type of cement a three day compressive strength equal to the seven day compressive strength of types I and II. Its seven day compressive strength is almost equal to types I and II 28 day compressive strengths. The only downside is that the six month strength of type III is the same or slightly less than that of types I and II. Therefore the long-term strength is sacrificed a little. The highly early strength is gained by increasing the tricalcium silicate, (C3S), in the mix. This increased amount of tricalcium silicate brings the danger of free lime in the cement and high volume changes after setting. Type III can also be used in concrete that comes in contact with soil and ground water. It is usually used for emergency construction and repairs and construction of machine bases and gate installations. Cement is a material for bonding stone or brick. ... Gypsum is a very soft mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. // Chemical structure Heating gypsum to between 100°C and 150°C (302°F) partially dehydrates the mineral by driving off exactly 75% of the water contained in its chemical structure. ... The examples and perspective in this article or section may not represent a worldwide view. ... Cement is a material for bonding stone or brick. ...


Type IV Portland cement is generally known for its low heat of hydration. Its typical compound composition is:


28% (C3S), 49% (C2S), 4% (C3A), 12% (C4AF), 1.8% MgO, 1.9% (SO3), 0.9% Ignition loss, and 0.8% free CaO.


The percentages of (C2S) and (C4AF) are relatively high and (C3S) and (C3A) are relatively low. This causes the heat given off by the hydration reaction to develop at a slower rate. However, as a consequence the strength of the concrete develops slowly. After one or two years the strength is higher than the other types after full curing. This cement is used for very large concrete structures, such as dams, which have a low surface to volume ratio. This type of cement is generally not in stock and has to be special ordered in large quantities. A limitation on this type is that the maximum percentage of (C3A) is seven, and the maximum percentage of (C3S) is thirty-five. Another negative about this type of cement is its higher cost. Recently mix designs using pozzolans and water-reducing admixtures have been developed to decrease the cement content which has allowed for Type II Portland cement to be substituted in for Type IV in the production of dams. This helps lower the cost of the dam. In organic chemistry, a hydration reaction is a chemical reaction in which a hydroxyl group (OH-) and a hydrogen cation (an acidic proton) are added to the two carbon atoms bonded together in the carbon-carbon double bond which makes up an alkene functional group. ... The examples and perspective in this article or section may not represent a worldwide view. ... Cement is a material for bonding stone or brick. ... Cement is a material for bonding stone or brick. ...


Note: Type IV cement is not really used any in industry.


Type V is known for its sulfate resistance. Its typical compound composition is:


38% (C3S), 43% (C2S), 4% (C3A), 9% (C4AF), 1.9% MgO, 1.8% (SO3), 0.9% Ignition loss, and 0.8% free CaO.


This cement has a very low (C3A) composition which accounts for its high sulfate resistance. The maximum content of (C3A) allowed is five percent for type V Portland cement. This type is used in concrete that has a tendency to be exposed to alkali soil and ground water sulfates. It is generally not meant for use around seawater, but it can be done as long as the (C3A) composition is above two percent. It usually requires an advance order and is generally available to the western United States and Canada. Another limitation is that the (C4AF) + 2(C3A) composition cannot exceed twenty percent. This type of cement is essential in the construction of canal linings, culverts, and siphons because of their contact with ground waters containing sulfates. This is required because sulfates cause serious deterioration and swelling to the other types of Portland cement. The serious deterioration will eventually cause the concrete to fail. Type V Portland cement is a very uncommon type used in everyday construction but is routinely used in harsh marine environments. Cement is a material for bonding stone or brick. ... The examples and perspective in this article or section may not represent a worldwide view. ... In chemistry, an alkali (from Arabic: al-qaly) is a specific type of base, formed as a carbonate, hydroxide or other ionic salt of an alkali metal or alkali earth metal element. ... Sulfate is the IUPAC name for the SO42- ion, consisting of a central sulfur atom single bonded to four tetrahedrally oriented oxygen atoms. ... Cement is a material for bonding stone or brick. ... Sulfate is the IUPAC name for the SO42- ion, consisting of a central sulfur atom single bonded to four tetrahedrally oriented oxygen atoms. ... Sulfate is the IUPAC name for the SO42- ion, consisting of a central sulfur atom single bonded to four tetrahedrally oriented oxygen atoms. ... The examples and perspective in this article or section may not represent a worldwide view. ...


In many countries this type of cement is no longer made. It has been replaced by binary blended cements containing more than 60% ground granulated blast furnace or tertiary blended cements containing slag and fly ash.


Types Ia, IIa, and IIIa have the same composition as types I, II, and III. The only difference is that in Ia, IIa, and IIIa an air-entraining agent is ground into the mix. The air-entrainment must meet and minimum and maximum optional specification found in the ASTM manual. These types are only available in the eastern United States and Canada but can only be found on a limited basis. They are a poor approach to air-entrainment which improves resistance to freezing under low temperatures. ASTM International is an international voluntary standards organization that develops and produces technical standards for materials, products, systems and services. ...


EN 197

EN 197-1 classify Portland cement in 5 classes that differ from ASTM.

I Portland cement Comprising Portland cement and up to 5% of minor additional constituents
II Portland-composite cement Portland cement and up to 35% of other single constituents
III Blastfurnace cement Portland cement and higher percentages of blastfurnace slag
IV Pozzolanic cement Comprising Portland cement and higher percentages of pozzolana
V Composite cement Comprising Portland cement and higher percentages of blastfurnace slag and pozzolana or fly ash

Safety and environmental effects

When cement is mixed with water a highly alkaline solution (pH ~13) is produced by the dissolution of calcium, sodium and potassium hydroxides. Gloves, goggles and a filter mask should be used for protection. Hands should be washed after contact. Cement can cause serious burns if contact is prolonged or if skin is not washed promptly. Once the cement hydrates, the hardened mass can be safely touched without gloves. In chemistry, an alkali (from Arabic: al-qaly) is a specific type of base, formed as a carbonate, hydroxide or other ionic salt of an alkali metal or alkali earth metal element. ... The correct title of this article is pH. The initial letter is capitalized due to technical restrictions. ... General Name, Symbol, Number calcium, Ca, 20 Chemical series alkaline earth metals Group, Period, Block 2, 4, s Appearance silvery white Atomic mass 40. ... General Name, Symbol, Number sodium, Na, 11 Chemical series alkali metals Group, Period, Block 1, 3, s Appearance silvery white Atomic mass 22. ... General Name, Symbol, Number potassium, K, 19 Chemical series alkali metals Group, Period, Block 1, 4, s Appearance silvery white Atomic mass 39. ... Hydroxide is a polyatomic ion consisting of oxygen and hydrogen: OH− It has a charge of −1. ... A glove (Middle English from Old English glof) is a type of garment which covers the hand. ... Watersport goggles Blowtorching goggles and safety helmet Goggles are a form of protective eyewear that usually enclose the eye area to prevent particulates or chemicals from striking the eyes. ... A half face particulate mask is generally worn to protect the wearer from dust and paint fumes A filter mask or particulate mask is a protective mask which usually covers the mouth and nose only. ... In chemistry, hydration is the condition of being combined with water. ...


In Scandinavia and France, the level of chrome VI, which is thought to be toxic and a major skin irritant, may not exceed 2 ppm (parts per million), which corresponds to a maximum chromium level of 3.3 micrograms per gram. Scandinavia is a region in Northern Europe named after the Scandinavian Peninsula. ... General Name, Symbol, Number chromium, Cr, 24 Chemical series transition metals Group, Period, Block 6, 4, d Appearance silvery metallic Atomic mass 51. ... Parts per million (ppm) is a measure of concentration that is used where low levels of concentration are significant. ...


"Epidemiologic Notes and Reports Sulfur Dioxide Exposure in Portland Cement Plants" from the Centers for Disease Control states "Workers at Portland cement facilities, particularly those burning fuel containing sulfur, should be aware of the acute and chronic effects of exposure to SO2 [sulfur dioxide], and peak and full-shift concentrations of SO2 should be periodically measured." [2]


"The Arizona Department of Environmental Quality was informed this week that the Arizona Portland Cement Co. failed a second round of testing for emissions of hazardous air pollutants at the company's Rillito plant near Tucson. The latest round of testing, performed in January 2003 by the company, is designed to ensure that the facility complies with federal standards governing the emissions of dioxins and furans, which are byproducts of the manufacturing process." [3] Lest one feel this is an isolated case, Cement Reviews' "Environmental News" web page details case after case of environmental problems with cement manufacturing. [4]


In light of safety, environmental, and other concerns, "[t]he Cement Sustainability Initiative (CSI) was formed to help the cement industry to address the challenges of sustainable development. [Areas of concern include:]

  1. Climate protection and carbon dioxide (CO2) management,
  2. Responsible use of fuel and materials,
  3. Employee health and safety,
  4. Emission monitoring and reporting,
  5. Local impacts on land and communities, and
  6. Reporting and Communication" [5]

An independent research effort of AEA Technology to identify critical issues for the cement industry today concluded the most important environment, health and safety performance issues facing the cement industry are atmospheric releases (including greenhouse gas emissions, dioxin, NOx, SO2, and particulates), accidents and worker exposure to dust. [6]


A recent article in the Guardian newspaper discusses the environmental effects of cement production and possible solutions to the carbon dioxide emissions created by the process. [7]


Cement plants as alternatives to conventional waste disposal or processing

Due to the high temperatures inside the cement kilns, combined with the oxidizing (oxygen-rich) atmosphere and long residence times, it has proven to be an excellent processing option for various types of waste streams. The waste streams often contain combustible material which allows the substitution of part of the fossil fuel normally used in the process.


Waste materials used in cement kilns as a fuel supplement: [8]

  1. Car and truck tires; steel belts are easily tolerated in the kilns
  2. Waste solvents and lubricants.
  3. Hazardous waste; cement kilns completely destroy hazardous organic compounds
  4. Bone meal; slaughter house waste due to bovine spongiform encephalopathy contamination concerns (in Europe)
  5. Waste plastics
  6. Sewage sludge
  7. Rice shells
  8. Sugar cane waste

Waste materials used as a raw material or additive: Look up Bovine spongiform encephalopathy in Wiktionary, the free dictionary. ...

  1. Blast furnace slag (granulated, water quenched)
  2. Fly ash (from power plants)
  3. Micro silica (from steel mills)
  4. Synthetic gypsum (from desulfurization)

External links


  Results from FactBites:
 
Portland cement - definition of Portland cement in Encyclopedia (961 words)
Portland cement is the most common type of cement in general usage, as it is a basic ingredient of concrete and mortar.
Portland cement and similar materials are made by heating limestone (as source of calcium) with clay or sand (as source of silicon) and grinding the product.
Portland cement was first manufactured in Britain in the early part of the 19th century, and its name is derived from its similarity to Portland Stone, a type of building stone that was quarried on the Isle of Portland in Dorset, England.
  More results at FactBites »

 
 

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