Cement

1. 2. 3. 4.

Of or relating relating to an actual, actual, specific specific thing thing or instance; instance; particul particular: ar: had the concrete evidence needed to convict. Existing Existing in reality reality or in real real experience; experience; percepti perceptible ble by the the senses; real: concrete objects such as trees. Formed by the coalescenc coalescencee of separate separate particles particles or or parts into into one mass; mass; solid. solid. Made of hard, hard, strong, strong, conglomerate conglomerate construction construction material. material.

n. (kŏn'krēt', kŏng'-, kŏn-krēt', kŏng-) kŏng-)

1. A hard, strong construct construction ion material material consisting consisting of sand, conglome conglomerate rate gravel, gravel, pebbles, broken broken stone, or slag in a mortar or cement matrix. 2. A mass mass formed formed by the the coales coalescen cence ce of parti particle cles. s. v., -cret·ed, -cret·ing, -cretes. (kŏn (kŏn'krēt', kŏng'-, kŏn-krēt', kŏng-) kŏng-) v.tr.

1. To build, build, treat, treat, or cover cover with hard, hard, strong strong conglomerat conglomeratee construction construction materia material.l. 2. To form into a mass by coalescence coalescence or cohesion cohesion of particl particles es or parts. parts. Artificial stone made of a mixture of cement of cement,, aggregate (hard material), and water. In addition to its potential for  immense compressive strength and its ability, when poured, to adapt to virtually any form, concrete is fire-resistant and has become one of the most common building materials in the world. The binder usually used today is portland is portland cement.. The aggregate is usually sand and gravel. Additives called admixtures may be used to accelerate the curing cement (hardening) process in low temperature conditions. Other admixtures trap air in the concrete or slow shrinkage and increase strength. See also precast concrete, concrete, prestressed concrete, concrete, reinforced concrete. concrete. Background

Concrete is a hardened building material created by combining a chemically inert mineral aggregate (usually sand, gravel,, or crushed stone), a binder  gravel a binder (natural (natural or synthetic cement), chemical additives, and water. Although people commonly use the word "cement" as a synonym for concrete, the terms in fact denote different substances: cement, which encompasses a wide variety of fine-ground powders that harden when mixed with water, represents only one of several components in modern concrete. As concrete dries, it acquires a stone-like consistency that renders it ideal for constructing roads, bridges, water supply and sewage systems, factories, airports, railroads, waterways, mass transit systems, and other structures that comprise a substantial portion of the U.S. wealth. According to the National Institute of Standards and Technology (NIST), building such facilities is in itself one of the nation's largest industries and represents about 10 percent of the gross national product. Over $4 billion $4 billion worth of hydraulic cement, a variety which hardens under water, is produced annually in the United States for use in $20 billion worth of  concrete construction. The value of all cement-based structures in the United States is in the trillions of dollars—  roughly commensurate with the anticipated cost of repairing those structures over the next twenty years. The words cement and concrete are both of Latin origin, reflecting the likelihood that the ancient Romans were the first to use the substances. Many examples of Roman concrete construction remain in the countries that encircle the Mediterranean, where Roman builders had access to numerous natural cement deposits. Natural cement consists mainly of lime, derived from limestone and often combined with volcanic ash. It formed the basis of most civil engineering until the eighteenth century, when the first synthetic cements were developed. The earliest manmade cement, called hydraulic lime, was developed in 1756, when an English engineer named John Smeaton needed a strong material to rebuild the Eddystone lighthouse off the coast of Devon. Although the Romans had used hydraulic cement, the formula was lost from the collapse of their empire in the fifth century A.D. until Smeaton reinvented it. During the early nineteenth century several other Englishmen other Englishmen contributed to the refinement of synthetic cement, most notably Joseph Aspdin and Isaac Charles Johnson. In 1824 Aspdin took out a patent on a synthetic blend of limestone and clay which he called Portland cement because it resembled limestone quarried on the English Isle of Portland. However, Aspdin's product was not as strong as that produced in 1850 by Johnson, whose formula served as the basis of the Portland cement that is still widely used today. Concrete made with

Portland cement is considered superior to that made with natural cement because it is stronger, more durable durable,, and of  more consistent quality. According to the American Society of Testing of Materials (ASTM), Portland cement is made by mixing calcareous (consisting mostly of calcium carbonate) material such as limestone with silica-, alumina-, and iron oxide-containing materials. These substances are then burned until they fuse together, and the resulting admixture admixture,, or clinker  or clinker , is ground to form Portland cement. Although Portland cement quickly displaced natural cement in Europe, concrete technology in the United States lagged considerably behind. In America, natural cement rock was first discovered during the early 1800s, when it was used to build the Erie Canal. The construction of such inland waterways led to the establishment of a number of  American companies producing natural cement. However, because of Portland cement's greater strength, many construction engineers preferred to order it from Europe, despite the additional time and expense involved. Thomas Edison was very interested in Portland cement and even cast phonograph cast phonograph cabinets of the material. When United States industry figured out how to make Portland cement during the early 1870s, the production of natural cement in America began to decline. After the refinement of Portland cement, the next major innovation in concrete technology occurred during the late nineteenth century, when reinforced concrete was invented. While concrete easily resists compression, it does not tolerate tension well, and this weakness meant that it could not be used to build structures—like bridges or buildings with arches—that would be subject to bending action. French and English engineers first rectified this deficiency during the 1850s by embedding steel bars in those portions of a concrete structure subject to tensile stress. stress. Although the concrete itself is not strengthened, structures built of reinforced concrete can better withstand better withstand bending, and the technique was used internationally by the early twentieth century. Another form of strengthened concrete, prestressed concrete, prestressed concrete, concrete, was issued a U.S. patent in 1888. However, it was not widely used until World War II, when several large docks and bridges that utilized it were constructed. Rather than reinforcing a highly stressed portion of a concrete structure with steel, engineers could now compress a section of  concrete before they subjected it to stress, thereby increasing its ability to withstand tension. Today, different types of concrete are categorized according to their method of installation. Ready- or pre-mixed concrete is batched and mixed at a central plant before it is delivered to a site. Because this type of concrete is sometimes transported in an agitator  agitator truck, truck, it is also known as transit-mixed concrete. Shrink-mixed concrete is  partially mixed at the central plant, and its mixing is then completed en route to the site. Raw Materials

Structural concrete normally contains one part cement to two parts fine mineral aggregate to four parts coarse mineral aggregate, though these proportions are often varied to achieve the strength and flexibility required in a  particular setting. In addition, concrete contains a wide range of chemicals that imbue it with the characteristics desired for specific applications. Portland cement, the kind most often used in concrete, is made from a combination of a calcareous material (usually limestone) and of silica of silica and alumina found as clay or shale or shale.. In lesser amounts, it can also contain iron oxide and magnesia magnesia.. Aggregates, which comprise 75 percent of concrete by volume, improve the formation and flow of cement paste and enhance the structural performance of concrete. Fine grade comprises  particles up to. 20 of an inch (five millimeters millimeters)) in size, while coarse grade includes particles from. 20 to. 79 of an inch (20 millimeters). For massive construction, aggregate particle size can exceed 1.50 inches (38 millimeters). Aggregates can also be classified according to the type of rock they consist of: basalt of: basalt,, flint, and granite, among others. Another type of aggregate is pozzolana, a siliceous and aluminous material often derived from volcanic ash. Reacting chemically with limestone and moisture moisture,, it forms the calcium silicate hydrates that are the basis of cement. Pozzolana is commonly added to Portland cement paste to enhance its densification densification.. One type of volcanic mineral, an aluminum silicate, silicate, has been combined with siliceous minerals to form a composite that reduces weight and improves bonding between concrete and steel surfaces. Its applications have included precast included precast concrete shapes and asphalt/concrete pavement asphalt/concrete pavement for highways. Fly ash, a coal-burning power plant byproduct that contains an aluminosilicate and small amounts of lime, is also being tested as a possible pozzolanic material for cement. Combining fly ash with lime (CaO) in a hydrothermal hydrothermal process  process (one that uses hot water under pressure) also produces cement.

Portland cement is considered superior to that made with natural cement because it is stronger, more durable durable,, and of  more consistent quality. According to the American Society of Testing of Materials (ASTM), Portland cement is made by mixing calcareous (consisting mostly of calcium carbonate) material such as limestone with silica-, alumina-, and iron oxide-containing materials. These substances are then burned until they fuse together, and the resulting admixture admixture,, or clinker  or clinker , is ground to form Portland cement. Although Portland cement quickly displaced natural cement in Europe, concrete technology in the United States lagged considerably behind. In America, natural cement rock was first discovered during the early 1800s, when it was used to build the Erie Canal. The construction of such inland waterways led to the establishment of a number of  American companies producing natural cement. However, because of Portland cement's greater strength, many construction engineers preferred to order it from Europe, despite the additional time and expense involved. Thomas Edison was very interested in Portland cement and even cast phonograph cast phonograph cabinets of the material. When United States industry figured out how to make Portland cement during the early 1870s, the production of natural cement in America began to decline. After the refinement of Portland cement, the next major innovation in concrete technology occurred during the late nineteenth century, when reinforced concrete was invented. While concrete easily resists compression, it does not tolerate tension well, and this weakness meant that it could not be used to build structures—like bridges or buildings with arches—that would be subject to bending action. French and English engineers first rectified this deficiency during the 1850s by embedding steel bars in those portions of a concrete structure subject to tensile stress. stress. Although the concrete itself is not strengthened, structures built of reinforced concrete can better withstand better withstand bending, and the technique was used internationally by the early twentieth century. Another form of strengthened concrete, prestressed concrete, prestressed concrete, concrete, was issued a U.S. patent in 1888. However, it was not widely used until World War II, when several large docks and bridges that utilized it were constructed. Rather than reinforcing a highly stressed portion of a concrete structure with steel, engineers could now compress a section of  concrete before they subjected it to stress, thereby increasing its ability to withstand tension. Today, different types of concrete are categorized according to their method of installation. Ready- or pre-mixed concrete is batched and mixed at a central plant before it is delivered to a site. Because this type of concrete is sometimes transported in an agitator  agitator truck, truck, it is also known as transit-mixed concrete. Shrink-mixed concrete is  partially mixed at the central plant, and its mixing is then completed en route to the site. Raw Materials

Structural concrete normally contains one part cement to two parts fine mineral aggregate to four parts coarse mineral aggregate, though these proportions are often varied to achieve the strength and flexibility required in a  particular setting. In addition, concrete contains a wide range of chemicals that imbue it with the characteristics desired for specific applications. Portland cement, the kind most often used in concrete, is made from a combination of a calcareous material (usually limestone) and of silica of silica and alumina found as clay or shale or shale.. In lesser amounts, it can also contain iron oxide and magnesia magnesia.. Aggregates, which comprise 75 percent of concrete by volume, improve the formation and flow of cement paste and enhance the structural performance of concrete. Fine grade comprises  particles up to. 20 of an inch (five millimeters millimeters)) in size, while coarse grade includes particles from. 20 to. 79 of an inch (20 millimeters). For massive construction, aggregate particle size can exceed 1.50 inches (38 millimeters). Aggregates can also be classified according to the type of rock they consist of: basalt of: basalt,, flint, and granite, among others. Another type of aggregate is pozzolana, a siliceous and aluminous material often derived from volcanic ash. Reacting chemically with limestone and moisture moisture,, it forms the calcium silicate hydrates that are the basis of cement. Pozzolana is commonly added to Portland cement paste to enhance its densification densification.. One type of volcanic mineral, an aluminum silicate, silicate, has been combined with siliceous minerals to form a composite that reduces weight and improves bonding between concrete and steel surfaces. Its applications have included precast included precast concrete shapes and asphalt/concrete pavement asphalt/concrete pavement for highways. Fly ash, a coal-burning power plant byproduct that contains an aluminosilicate and small amounts of lime, is also being tested as a possible pozzolanic material for cement. Combining fly ash with lime (CaO) in a hydrothermal hydrothermal process  process (one that uses hot water under pressure) also produces cement.

A wide range of chemicals are added to cement to act as plasticizers, superplasticizers, accelerators, dispersants, and water-reducing agents. Called admixtures, these additives can be used to increase the workability of a cement mixture still in the nonset state, the strength of cement after application, and the material's water tightness. Further, they can decrease the amount of water necessary to obtain workability and the amount of cement needed to create strong concrete. Accelerators, which reduce setting time, include calcium chloride or aluminum or aluminum sulfate and other  acidic materials. Plasticizing or superplasticizing agents increase the fluidity of the fresh cement mix with the same water/cement ratio, thereby improving the workability of the mix as well as its ease of placement. Typical  plasticizers include polycarboxylic include polycarboxylic acid materials; superplasticizers are sulphanated melamine formaldehyde or  sulphanated naphthalene formaldehyde condensates. Setretarders, another type of admixture, are used to delay the setting of concrete. These include soluble zinc salts, soluble borates, and carbohydrate-based materials. Gas forming admixtures, powdered zinc or aluminum in combination with calcium hydroxide or hydrogen or hydrogen peroxide, peroxide, are used to form aerated concrete by generating hydrogen or oxygen bubbles that become entrapped in the cement mix. Cement is considered a brittle a brittle material; in other words, it fractures easily. Thus, many additives have been developed to increase the tensile strength of concrete. One way is to combine polymeric combine polymeric materials such as polyvinyl as polyvinyl alcohol,, polyacrylamide alcohol  polyacrylamide,, or hydroxypropyl methyl cellulose with the cement, producing what is sometimes known as macro-defect-free cement. Another method entails adding fibers made of stainless of stainless steel, steel, glass, or carbon. These fibers can be short, in a strand, sheet, non-woven fabric or woven fabric form. Typically, such fiber represents only about one percent of the volume of fiber-reinforced concrete. The Manufacturing Process

The manufacture of concrete is fairly simple. First, the cement (usually Portland cement) is prepared. Next, the other  ingredients—aggregates (such as sand or gravel), admixtures (chemical additives), any necessary fibers, and water   —are mixed together with the cement to form concrete. The concrete is then shipped to the work site and placed, compacted, and cured.  Preparing Portland cement  •

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The limestone, silica, and alumina that make up Portland cement are dry ground into a very fine powder, mixed together in predetermined in predetermined proportions, preheated, and calcined (heated to a high temperature that will  burn off impurities without fusing the ingredients). Next the material is burned in a large rotary kiln at 2,550 degrees Fahrenheit (1,400 degrees Celsius). At this temperature, the material partially fuses into a substance known as clinker. A modern kiln can produce as much as 6,200 tons of clinker a day. The clinker is then cooled and ground to a fine powder in a tube or ball mill. A ball mill is a rotating drum filled with steel balls of different sizes (depending on the desired fineness of the cement) that crush and grind the clinker. Gypsum is added during the grinding process. The final composition consists of several compounds: tricalcium silicate silicate,, dicalcium silicate, tricalcium aluminate aluminate,, and tetracalcium aluminoferrite.

Mixing  •

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The cement is then mixed with the other ingredients: aggregates (sand, gravel, or crushed stone), admixtures, fibers, and water. Aggregates are pre-blended or added at the ready-mix concrete plant under normal operating conditions. The mixing operation uses rotation or stirring to coat the surface of the aggregate with cement paste and to blend the other ingredients uniformly. A variety of batch or continuous mixers are used. Fibers, if desired, can be added by a variety of methods including direct spraying spraying,, premixing, impregnating impregnating,, or hand laying-up. Silica fume is often used as a dispersing or densifying agent.

Transport to work site •

Once the concrete mixture is ready, it is transported to the work site. There are many methods of transporting concrete, including wheelbarrows, buckets, belt conveyors, special trucks, and pumping. Pumping transports large quantities of concrete over large distances through pipelines using a system consisting of a hopper , a  pump, and the pipes. Pumps come in several types—the horizontal piston horizontal piston pump with semi-rotary valves and

small portable pumps called squeeze pumps. A vacuum provides a continuous flow of concrete, with two rotating rollers squeezing a flexible pipe to move the concrete into the delivery pipe.  Placing and compacting  •

Once at the site, the concrete must be placed and compacted. These two operations are performed almost simultaneously. Placing must be done so that segregation of the various ingredients is avoided and full compaction—with all air bubbles eliminated—can be achieved. Whether chutes or buggies are used, position is important in achieving these goals. The rates of placing and of compaction should be equal; the latter is usually accomplished using internal or external vibrators. An internal vibrator uses a poker housing a motordriven shaft. When the poker is inserted into the concrete, controlled vibration occurs to compact the concrete. External vibrators are used for precast or thin in situ sections having a shape or thickness unsuitable for internal vibrators. These type of vibrators are rigidly clamped to the formwork , which rests on an elastic support. Both the form and the concrete are vibrated. Vibrating tables are also used, where a table  produces vertical vibration by using two shafts rotating in opposite directions.

Curing  •

Once it is placed and compacted, the concrete must cured before it is finished to make sure that it doesn't dry too quickly. Concrete's strength is influenced by its moisture level during the hardening process: as the cement solidifies, the concrete shrinks. If site constraints prevent the concrete from contracting, tensile stresses will develop, weakening the concrete. To minimize this problem, concrete must be kept damp during the several days it requires to set and harden.

Quality Control

Concrete manufacturers expect their raw material suppliers to supply a consistent, uniform product. At the cement  production factory, the proportions of the various raw materials that go into cement must be checked to achieve a consistent kiln feed, and samples of the mix are frequently examined using X-ray fluorescence analysis. The strength of concrete is probably the most important property that must be tested to comply with specifications. To achieve the desired strength, workers must carefully control the manufacturing process, which they normally do  by using statistical process control. The American Standard of Testing Materials and other organizations have developed a variety of methods for testing strength. Quality control charts are widely used by the suppliers of readymixed concrete and by the engineer on site to continually assess the strength of concrete. Other properties important for compliance include cement content, water/cement ratio, and workability, and standard test methods have been developed for these as well. The Future

Though the United States led the world in improving cement technology from the 1930s to the 1960s, Europe and Japan have since moved ahead with new products, research, and development. In an effort to restore American leadership, The National Science Foundation has established a Center for Science and Technology of Advanced Cement-Based Materials at Northwestern University. The ACBM center will develop the science necessary to create new cement-based materials with improved properties. These will be used in new construction as well as in restoration and repair of highways, bridges, power plants, and waste-disposal systems. The deterioration of the U.S. infrastructure has shifted the highway industry's emphasis from building new roads and  bridges to maintaining and replacing existing structures. Because better techniques and materials are needed to reduce costs, the Strategic Highway Research Program (SHRP), a 5-year $150 million research program, was established in 1987. The targeted areas were asphalt, pavement performance, concrete structures, and highway operations. The Center for Building Technology at NIST is also conducting research to improve concrete performance. The  projects include several that are developing new methods of field testing concrete. Other projects involve computer 

modeling of properties and models for predicting service life. In addition, several expert systems have been developed for designing concrete mixtures and for diagnosing causes of concrete deterioration. Another cement industry trend is the concentration of manufacturing in a smaller number of larger-capacity  production systems. This has been achieved either by replacing several older production lines with a single, highcapacity line or by upgrading and modernizing an existing line for a higher production yield. Automation will continue to play an important role in achieving these increased yields. The use of waste byproducts as raw materials will continue as well. Where To Learn More  Books

American Concrete Institute. Cement and Concrete Terminology. 1967. Mindess, S. Advances in Cementitious Materials. The American Ceramic Society, 1991. Vol. 16: Ceramic Transactions.

 Neville, A. M. and J. J. Brooks. Concrete Technology. John Wiley & Sons, Inc., 1987. Skalny, Jan P. Materials Science of Concrete I. The American Ceramic Society, 1989. Skalny, J. and S. Mindess. Materials Science of Concrete II. The American Ceramic Society, 1991.  Periodicals

Holterhoff, A. "Implementing SPC in the Manufacture of Calcium Aluminate Cements." Ceramic Bulletin, 1991. Jiang, W. and D. Roy. "Hydrothermal Processing of New Fly Ash Cement." Ceramic Bulletin, 1992. Sheppard, L. "Cement Renovations Improve Concrete Durability." Ceramic Bulletin,1991. [Article by: L. S. Millberg]

Sponsored Links Swanag Constructions Bringing world class construction to India for over two decades www.swanag.com Manufactured Sand - V7 Innovative Sand Manufacturing Plant 100% Replacement for Natural Sand www.kayasand.com Sci-Tech Encyclopedia: Concrete Top Home > Library > Science > Sci-Tech Encyclopedia Any of several manufactured, stonelike materials composed of particles, called aggregates, that are selected and graded into specified sizes for construction purposes and that are bonded together by one or more cementitious materials into a solid mass. The term concrete, when used without a modifying adjective, ordinarily is intended to indicate the product formed from a mix of portland cement, sand, gravel or crushed stone, and water. There are, however, many different types of concrete. The names of some are distinguished by the types, sizes, and densities of aggregates—for example,

wood-fiber, lightweight, normal-weight, or heavyweight concrete. The names of others may indicate the type of   binder used—for example, blended-hydraulic cement, natural-cement, polymer , or  bituminous (asphaltic) concrete. Concretes are similar in composition to mortars, which are used to bond unit masonry. Mortars, however, are normally made with sand as the sole aggregate, whereas concretes contain much larger aggregates and thus usually have greater strength. As a result, concretes have a much wider range of structural applications, including  pavements, footings, pipes, unit masonry, floor slabs, beams, columns, walls, dams, and tanks. See also Concrete  beam; Concrete column; Concrete slab. Because ordinary concrete is much weaker in tension than in compression, it is usually reinforced or prestressed with a much stronger material, such as steel, to resist tension. Use of plain, or unreinforced, concrete is restricted to structures in which tensile stresses will be small, such as massive dams, heavy foundations, and unit-masonry walls. For reinforcement of other types of structures, steel bars or structural-steel shapes may be incorporated in the concrete. Prestress to offset tensile stresses may be applied at specific locations by permanently installed compressing jacks, high-strength steel bars, or steel strands. Alternatively, prestress may be distributed throughout a concrete component by embedded pretensioned steel elements. Another option is use of a cement that tends to expand concrete while enclosures prevent that action, thus imposing compression on the concrete. See also Prestressed concrete; Reinforced concrete. There are various methods employed for casting ordinary concrete. For very small projects, sacks of prepared mixes may be purchased and mixed on the site with water, usually in a drum-type, portable, mechanical mixer. For large  projects, mix ingredients are weighed separately and deposited in a stationary batch mixer , a truck mixer, or a continuous mixer . Concrete mixed or agitated in a truck is called ready-mixed concrete. In general, concrete is  placed and consolidated in forms by hand tamping or puddling around reinforcing steel or by spading at or near  vertical surfaces. Another technique, vibration or mechanical puddling, is the most satisfactory one for achieving  proper consolidation. Finishes for exposed concrete surfaces are obtained in a number of ways. Surfaces cast against forms can be given textures by using patterned form liners or by treating the surface after forms are removed, for instance, by brushing, scrubbing, floating, rubbing, or  plastering. After the surface is thoroughly hardened, other textures can be achieved  by grinding, chipping, bush-hammering, or sandblasting. Unformed surfaces, such as the top of  pavement slabs or  floor slabs, may be either broomed or smoothed with a trowel. Brooming or dragging burlap over the surface  produces scoring, which reduces skidding when the pavement is wet. Adequate curing is essential to bring the concrete to required strength and quality. The aim of curing is to promote the hydration of the cementing material. This is accomplished by preventing moisture loss and, when necessary, by controlling temperature. Moisture is a necessary ingredient in the curing process, since hydration is a chemical reaction between the water and the cementing material. Unformed surfaces are protected against moisture loss immediately after final finishing by means of wet burlap, soaked cotton mats, wet earth or sand, sprayed-on sealing compounds, waterproof paper, or waterproof plastic sheets. Formed surfaces, particularly vertical surfaces, may be  protected against moisture loss by leaving the forms on as long as possible, covering with wet canvas or burlap, spraying a small stream of water over the surface, or applying sprayed-on sealing compounds. The length of the curing period depends upon the properties desired and upon atmospheric conditions, such as temperature,humidity, and wind velocity, during this period. Short curing periods are used in fabricating concrete products such as block or   precast structural elements. Curing time is shortened by the use of elevated temperatures. Sponsored Links Silica Sand - Natural Washed,Cleaned,Screened,Packed For, Flooring,Glass,Moulds,Building www.micaindia.com Les Champs Mélisey Maison d'Hôtes en Bourgogne Chambre Table d'Hôtes/Ac. de stages www.champsmelisey.Com Thesaurus: concrete

Top Home > Library > Literature & Language > Thesaurus adjective

1. Having verifiable existence: objective, real, substantial, substantive, tangible. See real/imaginary. 2. Composed of or relating to things that occupy space and can be perceived by the senses:corporeal, material, objective, phenomenal, physical, sensible, substantial, tangible. See body/spirit, matter . verb

1. To bring or come together into a united whole: coalesce, combine, compound, conjoin, conjugate, connect, consolidate, couple, join, link , marry, meld, unify, unite, wed, yoke. See assemble/disassemble. 2. To make or become physically hard: cake, congeal, dry, harden, indurate, petrify, set, solidify. See solid/liquid/consistency.

Sponsored Links Mumbai Apartment Give Us Your Requirement and Buy Apartments of Your Choice!Visit Now Classifieds.Sulekha.Com Waterstop – Joints Waterproofing products. Additives for concrete . www.mibosrl.it Antonyms: concrete Top Home > Library > Literature & Language > Antonyms adj Definition : actual, factual Antonyms: abstract, ideal, immaterial, intangible

adj Definition : hardened Antonyms: bending, flexible, pliable

Sponsored Links Mármol Crema Marfil Hnos. Jimenez posee cantera propia. Exportamos mármol al mundo entero. www.HnosJimenez.es Construction Fibre & Chem Mfg. of PP/Ca reinforced PP fibers Mfg. of Admixture, Surface hardener  www.xetexcorp.com Architecture: concrete Top Home > Library > Home & Garden > Architecture and Construction A composite stonelike material formed by mixing an aggregate (such as stones of irregular shape or crushed rock) with cement (which acts as the binding material) and water, then allowing the mixture to dry and harden; portland cement, now used in making concrete, was not developed until the 19th century. Also see average concrete,

cyclopean concrete, poured concrete, reinforced concrete .

Sponsored Links Teknokon Engineering, Manufacturing and Construction Company www.teknokon.com DGA (UK) Ltd Commercial and Programming Services Across All Sectors of Construction www.dga.eu.com Columbia Encyclopedia: concrete Top Home > Library > Miscellaneous > Columbia Encyclopedia concrete, structural masonry material made by mixing broken stone or gravel with sand, cement, and water and allowing the mixture to harden into a solid mass. The cement is the chemically active element, or matrix; the sand and stone are the inert elements, or aggregate. Concrete is adaptable to widely varied structural needs, is available  practically anywhere, is fire resistant, and can be used by semiskilled workers. The use of artificial masonry similar to modern concrete dates from a remote period but did not become a standard technique of construction until the Romans adopted it (after the 2d cent. B.C.) for roads, immense buildings, and engineering works. The concrete of the Romans, formed by combining pozzuolana (a volcanic earth) with lime,  broken stones, bricks, and tuff, was easily produced and had great durability (the Pantheon of Rome and the Baths of  Caracalla were built with it). Enormous spaces could be roofed without lateral thrusts by vaults cast in the rigid homogeneous material. Scientifically proportioned concrete formed with cement is an invention of modern times; the name did not appear  until c.1830. Modern portland cement has revolutionized the production and potentialities of concrete and has superseded the natural cements, to which it is vastly superior. The component materials of concrete are mixed in varying proportions, according to the strength required and the function to be fulfilled; the proportions were first worked out by Duff Abrams in 1918. The ideal mixture is that which solidifies with the minimum of voids, the mortar and small particles of aggregate filling all interstices. A typical proportioning is 1:2:5, i.e., one part of  cement, two parts of sand, and five parts of broken stone or gravel, with the proper amount of water for a pouring consistency. A simple test called a "slump test" is used to confirm the proportions and consistency of the mixture, and it is then poured into wood or steel molds, called forms. Concrete usually takes about five days to cure, or reach acceptable hardness, but a technique called steam saturation can shorten that curing time to less than 18 hours. A wide variety of additives allow the concrete to harden faster or slower, resist scaling, have increased strength, or  adopt the final shape more easily. Concrete used without strengthening is termed mass, or plain, concrete and has the structural properties of stonegreat strength under compressive forces and almost none under tensile ones. F. Joseph Monier, a French inventor, found that the tensile weakness could be overcome if steel rods were embedded in a concrete member. The new composite material was called reinforced concrete, or ferroconcrete. It was patented in 1857, and a private house in Port Chester, N.Y., first demonstrated (1857) its use in the United States. It is now rivaled in popularity as a structural material only by steel. Concrete reinforced with polypropylene fibers instead of steel yields equivalent strength with a fraction of the thickness. Reinforced concrete was improved by the development of prestressed concrete-that is, concrete containing cables that are placed under tension opposite to the expected compression load  before or after the concrete hardens. Another improvement, thin-shell construction, takes advantage of the inherent structural strength of certain geometric shapes, such as hemispherical and elliptical domes; in thin-shell construction great distances are spanned with very little material. The perfecting of reinforced concrete has profoundly influenced structural building techniques and architectural forms. Bibliography

See A. A. Raafat, Reinforced Concrete in Architecture (1958); J. J. Waddell, Concrete Construction Handbook  (1968); D. F. Orchard, Concrete Technology (1976). Sponsored Links Jobs in Cement Immediate Requirement in Companies. Submit Your Resume Free. Now! MonsterIndia.com Concrete Tools Trowels, Fresnos, Floats and More! Simply the Finest Tools You Can Buy woodinvilleconcrete.com Veterinary Dictionary: concrete Top Home > Library > Animal Life > Veterinary Dictionary Mixture of cement and reinforcing gravel or stones used in the surfacing of yards, passageways, milking parlors and the like; critical to the good condition of feet and hooves of farm livestock. Excessive wear due to a too-abrasive surface causes footrot of pigs and epidemic lameness in dairy herds. Sponsored Links Total Panel System S.A. ® stone panels, wall coverings bricks, wood, concrete , marble www.totalstone.com Construction Jobs Middle East Job Opportunities. Upload your Resume now: Free! www.Bayt.com Literary Glossary: Concrete Top Home > Library > Literature & Language > Literary Glossary Concrete is the opposite of abstract, and refers to a thing that actually exists or a description that allows the reader to experience an object or concept with the senses. Henry David Thoreau's Walden contains much concrete description of nature and wildlife. Sponsored Links Ceprocim Engineering SRL Engineering for the Industry Design & Equipment - Cement Plants www.ceprocimeng.ro Wikipedia: Concrete Top Home > Library > Miscellaneous > Wikipedia This article is about the construction material. For other uses, see Concrete (disambiguation).

1930s vibrated concrete, manufactured in Croydon and installed by the LMS railway after an Art Deco refurbishment in Meols, United Kingdom.

Concrete plant facility (background) with concrete delivery trucks. is a construction material composed of cement (commonly Portland cement) as well as other cementitious materials such as fly ash and slag cement, aggregate (generally a coarse aggregate such as gravel, limestone, or  granite, plus a fine aggregate such as sand), water , and chemical admixtures. The word concrete comes from the Latin word "concretus" (meaning compact or condensed), the past participle of "concresco", from "com-" (together) and "cresco" (to grow). Concrete

Concrete solidifies and hardens after mixing with water and placement due to a chemical process known as hydration. The water reacts with the cement, which bonds the other components together, eventually creating a stone-like material. Concrete is used to make pavements, pipe, architectural structures, foundations, motorways/roads, bridges/overpasses, parking structures, brick / block walls and footings for gates, fences and poles. Concrete is used more than any other man-made material in the world.[1] As of 2006, about 7.5 cubic kilometres of  concrete are made each year—more than one cubic metre for every person on Earth.[2] Concrete powers a US $35 billion industry which employs more than two million workers in the United States alone.[citation needed ] More than

55,000 miles (89,000 km) of highways in the United States are paved with this material. Reinforced concrete and  prestressed concrete are the most widely used modern kinds of concrete functional extensions.

Contents [hide] • •

1 History 2 Composition 2.1 Cement 2.2 Water  2.3 Aggregates 2.4 Reinforcement 2.5 Chemical admixtures 2.6 Mineral admixtures and blended cements 3 Concrete production 3.1 Mixing concrete 3.2 Workability 3.3 Curing 4 Properties 5 Environmental concerns 5.1 Worldwide CO2 emissions and global change 5.2 CO2 uptake by concrete in the Biosphere 2 project building 5.3 Surface runoff  5.4 Urban heat 5.5 Concrete dust 6 Health concerns 6.1 Concrete handling / Safety precautions 7 Damage modes 8 Types of concrete 9 Concrete recycling 10 World records 10.1 Continuous pours 11 Use of concrete in infrastructure 11.1 Mass concrete structures 11.2 Concrete textures 11.3 Reinforced concrete structures 11.4 Prestressed concrete structures 12 See also 13 References 14 External links o o o o o o

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History

Outer view of the Roman Pantheon, still the largest unreinforced solid concrete dome to this day[3]

Opus caementicium laying bare on a tomb near Rome. In contrast to modern concrete structures, the concrete walls

of Roman buildings were covered, usually with brick or stone. During the Roman Empire, Roman concrete (or Opus caementicium) was made from quicklime, pozzolanic ash/ pozzolana, and an aggregate of  pumice. Its widespread use in many Roman structures, a key event in the history of architecture termed the Concrete Revolution, freed Roman construction from the restrictions of stone and brick  material and allowed for revolutionarily new designs both in terms of structural complexity and dimension.[4] Concrete, as the Romans knew it, was in effect a new and revolutionary material. Laid in the shape of arches, vaults and domes, it quickly hardened into a rigid mass, free from many of the internal thrusts and strains which trouble the  builders of similar structures in stone or brick.[5] Modern tests show Opus caementicium to be as strong as modern Portland cement concrete in its compressive strength (ca. 200 kg/cm2).[6] However, due to the absence of reinforced steel, its tensile strength was far lower and its mode of application was also different: Modern structural concrete differs from Roman concrete in two important details. First, its mix consistency is fluid and homogeneous, allowing it to be poured into forms rather than requiring hand-layering together with the  placement of aggregate, which, in Roman practice, often consisted of rubble. Second, integral reinforcing steel gives modern concrete assemblies great strength in tension, whereas Roman concrete could depend only upon the strength of the concrete bonding to resist tension.[7] The widespread use of concrete in many Roman structures has ensured that many survive to the present day. The Baths of Caracalla in Rome are just one example of the longevity of concrete, which allowed the Romans to build this and similar structures across the Roman Empire. Many Roman aqueducts and Roman bridges have masonry cladding to a concrete core, a technique they used in structures such as the Pantheon, the dome of which is concrete. The secret of concrete was lost for 13 centuries until 1756, when the British engineer John Smeaton pioneered the use of hydraulic lime in concrete, using pebbles and powdered brick as aggregate. Portland cement was first used in concrete in the early 1840s. This version of history has been challenged however, as the Canal du Midi was constructed using concrete in 1670.[8] Recently, the use of recycled materials as concrete ingredients is gaining popularity because of increasingly stringent environmental legislation. The most conspicuous of these is fly ash, a by-product of coal-fired power   plants. This has a significant impact by reducing the amount of quarrying and landfill space required, and, as it acts as a cement replacement, reduces the amount of cement required to produce a solid concrete.[citation needed ] Concrete additives have been used since Roman and Egyptian times, when it was discovered that adding volcanic ash to the mix allowed it to set under water. Similarly, the Romans knew that adding horse hair made concrete less liable to crack while it hardened, and adding blood made it more frost-resistant.[9] In modern times, researchers have experimented with the addition of other materials to create concrete with improved properties, such as higher strength or electrical conductivity.

Composition

Cement and sand ready to be mixed. There are many types of concrete available, created by varying the proportions of the main ingredients below. The mix design depends on the type of structure being built, how the concrete will be mixed and delivered, and how it will be placed to form this structure. Cement

Portland cement is the most common type of cement in general usage. It is a basic ingredient of concrete, mortar , and plaster . English engineer Joseph Aspdin patented Portland cement in 1824; it was named because of its similarity in colour to Portland limestone, quarried from the English Isle of Portland and used extensively in London architecture. 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, and grinding this product (called clinker ) with a source of sulfate (most commonly gypsum). The manufacture of Portland cement creates about 5 percent of  human CO2 emissions.[10] Water

Combining water with a cementitious material forms a cement paste by the process of hydration. The cement paste glues the aggregate together, fills voids within it, and allows it to flow more freely. Less water in the cement paste will yield a stronger, more durable concrete; more water will give an freer-flowing concrete with a higher slump.[11] Impure water used to make concrete can cause problems when setting or in causing premature failure of the structure. Hydration involves many different reactions, often occurring at the same time. As the reactions proceed, the  products of the cement hydration process gradually bond together the individual sand and gravel particles, and other  components of the concrete, to form a solid mass. Reaction: Cement chemist notation: C3S + H → C-S-H + CH Standard notation: Ca3SiO5 + H2O → (CaO)•(SiO2)•(H2O)(gel) + Ca(OH)2 Balanced: 2Ca3SiO5 + 7H2O → 3(CaO)•2(SiO2)•4(H2O)(gel) + 3Ca(OH)2 Aggregates

Fine and coarse aggregates make up the bulk of a concrete mixture. Sand, natural gravel and crushed stone are mainly used for this purpose. Recycled aggregates (from construction, demolition and excavation waste) are increasingly used as partial replacements of natural aggregates, while a number of manufactured aggregates, including air-cooled blast furnace slag and bottom ash are also permitted.

Decorative stones such as quartzite, small river stones or crushed glass are sometimes added to the surface of  concrete for a decorative "exposed aggregate" finish, popular among landscape designers. Reinforcement

Installing rebar in a floor slab during a concrete pour  Concrete is strong in compression, as the aggregate efficiently carries the compression load. However, it is weak in tension as the cement holding the aggregate in place can crack, allowing the structure to fail. Reinforced concrete solves these problems by adding either metal reinforcing bars, steel fibers, glass fiber, or plastic fiber to carry tensile loads. Chemical admixtures Chemical admixtures are materials in the form of powder or fluids that are added to the concrete to give it certain

characteristics not obtainable with plain concrete mixes. In normal use, admixture dosages are less than 5% by mass of cement, and are added to the concrete at the time of batching/mixing.[12] The most common types of admixtures[13] are: •

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Accelerators speed up the hydration (hardening) of the concrete. Typical materials used are CaCl2 and  NaCl.However use of Chlorides may cause corrosion in steel reinforcing and is prohibited in some countries. Acrylic retarders slow the hydration of concrete, and are used in large or difficult pours where partial setting  before the pour is complete is undesirable. A typical retarder is table sugar , or sucrose (C12H22O11). Air entrainments add and distribute tiny air bubbles in the concrete, which will reduce damage during freezethaw cycles thereby increasing the concrete's durability. However, entrained air is a trade-off with strength, as each 1% of air may result in 5% decrease in compressive strength. Plasticizers (water-reducing admixtures) increase the workability of plastic or "fresh" concrete, allowing it  be placed more easily, with less consolidating effort. Superplasticizers (high-range water-reducing admixtures) are a class of plasticizers which have fewer deleterious effects when used to significantly increase workability. Alternatively, plasticizers can be used to reduce the water content of a concrete (and have been called water reducers due to this application) while maintaining workability. This improves its strength and durability characteristics. Pigments can be used to change the color of concrete, for aesthetics. Corrosion inhibitors are used to minimize the corrosion of steel and steel bars in concrete. Bonding agents are used to create a bond between old and new concrete. Pumping aids improve pumpability, thicken the paste, and reduce dewatering – the tendency for the water to separate out of the paste.

Mineral admixtures and blended cements

Blocks of concrete in Belo Horizonte, Brazil. There are inorganic materials that also have pozzolanic or latent hydraulic properties. These very fine-grained materials are added to the concrete mix to improve the properties of concrete (mineral admixtures),[12] or as a replacement for Portland cement (blended cements).[14] •

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Fly ash: A by product of coal fired electric generating plants, it is used to partially replace Portland cement (by up to 60% by mass). The properties of fly ash depend on the type of coal burnt. In general, silicious fly ash is pozzolanic, while calcareous fly ash has latent hydraulic properties.[15] Ground granulated blast furnace slag (GGBFS or GGBS): A by product of steel production, is used to  partially replace Portland cement (by up to 80% by mass). It has latent hydraulic properties.[16] Silica fume: A by-product of the production of silicon and ferrosilicon alloys. Silica fume is similar to fly ash, but has a particle size 100 times smaller. This results in a higher surface to volume ratio and a much faster  pozzolanic reaction. Silica fume is used to increase strength and durability of concrete, but generally requires the use of superplasticizers for workability.[17] High Reactivity Metakaolin (HRM): Metakaolin produces concrete with strength and durability similar to concrete made with silica fume. While silica fume is usually dark gray or black in color, high reactivity metakaolin is usually bright white in color, making it the preferred choice for architectural concrete where appearance is important.

Concrete production The processes used vary dramatically, from hand tools to heavy industry, but result in the concrete being placed where it cures into a final form. When initially mixed together, Portland cement and water rapidly form a gel, formed of tangled chains of  interlocking crystals. These continue to react over time, with the initially fluid gel often aiding in placement by improving workability. As the concrete sets, the chains of crystals join up, and form a rigid structure, gluing the aggregate particles in place. During curing, more of the cement reacts with the residual water (Hydration). This curing process develops physical and chemical properties. Among other qualities, mechanical strength, low moisture permeability, and chemical and volumetric stability. Mixing concrete

Cement being mixed with sand and water to form concrete. Thorough mixing is essential for the production of uniform, high quality concrete. Therefore, equipment and methods should be capable of effectively mixing concrete materials containing the largest specified aggregate to  produce uniform mixtures of the lowest slump practical for the work. Separate paste mixing has shown that the mixing of cement and water into a paste before combining these materials with aggregates can increase the compressive strength of the resulting concrete.[18] The paste is generally mixed in a high-speed , shear-type mixer at a w/cm (water to cement ratio) of 0.30 to 0.45 by mass. The cement paste premix may include admixtures, e.g. accelerators or retarders, plasticizers, pigments, or silica fume. The latter is added to fill the gaps between the cement particles. This reduces the particle distance and leads to a higher final compressive strength and a higher  water impermeability.[19] The premixed paste is then blended with aggregates and any remaining batch water, and final mixing is completed in conventional concrete mixing equipment.[20] High-Energy Mixed Concrete (HEM concrete) is produced by means of high-speed mixing of cement, water and sand with net specific energy consumption at least 5 kilojoules per kilogram of the mix. It is then added to a  plasticizer admixture and mixed after that with aggregates in conventional concrete mixer . This paste can be used itself or foamed (expanded) for lightweight concrete.[21] Sand effectively dissipates energy in this mixing process. HEM concrete fast hardens in ordinary and low temperature conditions, and possesses increased volume of gel, drastically reducing capillarity in solid and porous materials. It is recommended for precast concrete in order to reduce quantity of cement, as well as for concrete roof and siding tiles, paving stones and lightweight concrete block   production. Workability

Pouring a concrete floor for a commercial building, ( slab-on-grade) Workability is the ability of a fresh (plastic) concrete mix to fill the form/mold properly with the desired work 

(vibration) and without reducing the concrete's quality. Workability depends on water content, aggregate (shape and size distribution), cementitious content and age (level of hydration), and can be modified by adding chemical

admixtures. Raising the water content or adding chemical admixtures will increase concrete workability. Excessive water will lead to increased bleeding (surface water ) and/or segregation of aggregates (when the cement and aggregates start to separate), with the resulting concrete having reduced quality. The use of an aggregate with an undesirable gradation can result in a very harsh mix design with a very low slump, which cannot be readily made more workable by addition of reasonable amounts of water. Workability can be measured by the Concrete Slump Test, a simplistic measure of the plasticity of a fresh batch of  concrete following the ASTM C 143 or EN 12350-2 test standards. Slump is normally measured by filling an "Abrams cone" with a sample from a fresh batch of concrete. The cone is placed with the wide end down onto a level, non-absorptive surface. It is then filled in three layers of equal volume, with each layer being tamped with a steel rod in order to consolidate the layer. When the cone is carefully lifted off, the enclosed material will slump a certain amount due to gravity. A relatively dry sample will slump very little, having a slump value of one or two inches (25 or 50 mm). A relatively wet concrete sample may slump as much as six or seven inches (150 to 175 mm). Slump can be increased by adding chemical admixtures such as mid-range or high-range water reducing agents (super-plasticizers) without changing the water-cement ratio. It is bad practice to add excessive water upon delivery to the jobsite, however in a properly designed mixture it is important to reasonably achieve the specified slump prior  to placement as design factors such as air content, internal water for hydration/strength gain, etc. are dependent on  placement at design slump values. High-flow concrete, like self-consolidating concrete, is tested by other flow-measuring methods. One of these methods includes placing the cone on the narrow end and observing how the mix flows through the cone while it is gradually lifted.

Concrete pump

A concrete transport truck is feeding concrete to a concrete pumper, which is pumping it to where a slab is being  poured. After mixing, concrete is a fluid and can be pumped to where it is needed. Curing

Main article: Concrete curing

A concrete slab ponded while curing.

Concrete columns curing while wrapped in plastic. In all but the least critical applications, care needs to be taken to properly cure concrete, and achieve best strength and hardness. This happens after the concrete has been placed. Cement requires a moist, controlled environment to gain strength and harden fully. The cement paste hardens over time, initially setting and becoming rigid though very weak, and gaining in strength in the days and weeks following. In around 3 weeks, over 90% of the final strength is typically reached though it may continue to strengthen for decades.[22] Hydration and hardening of concrete during the first three days is critical. Abnormally fast drying and shrinkage due to factors such as evaporation from wind during placement may lead to increased tensile stresses at a time when it has not yet gained significant strength, resulting in greater shrinkage cracking. The early strength of the concrete can  be increased by keeping it damp for a longer period during the curing process. Minimizing stress prior to curing minimizes cracking. High early-strength concrete is designed to hydrate faster, often by increased use of cement which increases shrinkage and cracking. During this period concrete needs to be in conditions with a controlled temperature and humid atmosphere. In  practice, this is achieved by spraying or ponding the concrete surface with water, thereby protecting concrete mass from ill effects of ambient conditions. The pictures to the right show two of many ways to achieve this, ponding –  submerging setting concrete in water, and wrapping in plastic to contain the water in the mix. Properly curing concrete leads to increased strength and lower permeability, and avoids cracking where the surface dries out prematurely. Care must also be taken to avoid freezing, or overheating due to the exothermic setting of  cement (the Hoover Dam used pipes carrying coolant during setting to avoid damaging overheating). Improper  curing can cause scaling, reduced strength, poor abrasion resistance and cracking.

Properties Main article: Properties of concrete

Concrete has relatively high compressive strength, but significantly lower tensile strength, and as such is usually reinforced with materials that are strong in tension (often steel). The elasticity of concrete is relatively constant at low stress levels but starts decreasing at higher stress levels as matrix cracking develops. Concrete has a very low coefficient of thermal expansion, and as it matures concrete shrinks. All concrete structures will crack to some extent, due to shrinkage and tension. Concrete which is subjected to long-duration forces is prone to creep. Tests can be made to ensure the properties of concrete correspond to specifications for the application.

Environmental concerns  For the environmental impact of cement production see Cement 

Worldwide CO2 emissions and global change

The cement industry is one of two primary producers of carbon dioxide (CO2), creating up to 5 percent of  worldwide emissions of this gas. The embodied carbon dioxide (ECO2) of a tonne of concrete varies with mix design and is in the range of: 75–176 kg CO2/tonne 0.075 - 0.176 tonne CO2/tonne[23] Cement manufacture contributes greenhouse gases both directly through the production of carbon dioxide when calcium carbonate is heated, producing lime and carbon dioxide[24], and also indirectly through the use of energy, particularly if the energy is sourced from fossil fuels. The cement industry produces 5% of global man-made CO2 emissions, of which 50 % is from the chemical process, and 40 % from burning fuel.[25] CO2 uptake by concrete in the Biosphere 2 project building

A deficit of CO2 was observed in the mass balance of the gases in the closed atmosphere environments of the Biosphere 2 project. It was found that the respiration rate was faster than the photosynthesis resulting in a slow decrease of oxygen. An unresolved question accompanied the oxygen decline: the corresponding increase in carbon dioxide did not appear in the mass balance calculations. This concealed the underlying process until an investigation  by Severinghaus et al. (1994) of Columbia University’s Lamont-Doherty Earth Observatory using isotopic analysis showed that carbon dioxide was reacting with exposed concrete inside Biosphere 2 to form calcium carbonate, thereby sequestering the carbon dioxide.[26][27] After being poured, concrete can absorb CO2 for up to 5 years until fully cured. Surface runoff 

Surface runoff , when water runs off impervious surfaces, such as non-porous concrete, can cause heavy soil erosion. Urban runoff tends to pick up gasoline, motor oil, heavy metals, trash and other pollutants from sidewalks, roadways and parking lots.[28][29] The impervious cover in a typical city sewer system prevents groundwater percolation five times than that of a typical woodland of the same size.[30] A 2008 report by the United States National Research Council identified urban runoff as a leading source of water quality problems.[31] Urban heat

Both concrete and asphalt are the primary contributors to what is known as the urban heat island effect. Using light-colored concrete has proven effective in reflecting up to 50% more light than asphalt and reducing ambient temperature.[32] A low albedo value, characteristic of black asphalt, absorbs a large percentage of solar heat and contributes to the warming of cities. By paving with light colored concrete, in addition to replacing asphalt with light-colored concrete, communities can lower their average temperature.[33] Many U.S. cities show that pavement comprise approximately 30-40% of their surface area.[32] This directly impacts the temperature of the city, as demonstrated by the urban heat island effect. In addition to decreasing the overall temperature of parking lots and large paved areas by paving with light-colored concrete, there are supplemental

 benefits. One example is 10-30% improved nighttime visibility. [32] The potential of energy saving within an area is also high. With lower temperatures, the demand for air conditioning decreases, saving vast amounts of energy. Atlanta has tried to mitigate the heat-island effect. City officials noted that when using heat-reflecting concrete, their  average city temperature decreased by 6 °F.[34] New York City offers another example. The Design Trust for Public Space in New York City found that by slightly raising the albedo value in their city, beneficial effects such as energy savings could be achieved. It was concluded that this could be accomplished by the replacement of black asphalt with light-colored concrete.[33] Concrete dust

Building demolition, and natural disasters such as earthquakes often release a large amount of concrete dust into the local atmosphere. Concrete dust was concluded to be the major source of dangerous air pollution following the Great Hanshin earthquake.[35]

Health concerns The presence of some substances in concrete, including useful and unwanted additives, can cause health concerns.  Natural radioactive elements (K, U and Th) can be present in various concentration in concrete dwellings, depending on the source of the raw materials used.[36] Toxic substances may also be added to the mixture for making concrete  by unscrupulous makers. Dust from rubble or broken concrete upon demolition or crumbling may cause serious health concerns depending also on what had been incorporated in the concrete. Concrete handling / Safety precautions

Handling of wet concrete must always be done with proper protective equipment. Contact with wet concrete can cause skin burns due to the caustic nature of the mix with cement and water.

Damage modes Main article: Concrete degradation Concrete can be damaged by fire, aggregate expansion, sea water effects, bacterial corrosion, leaching, physical damage and chemical damage (from carbonation, chlorides, sulfates and distillate water).

Types of concrete Main article: Types of concrete There are many different types of concrete including Mix design, Regular concrete, High-strength concrete, Stamped concrete, High-performance concrete, Self-consolidating concretes, Vacuum concretes, Shotcrete, Pervious concrete, Cellular concrete, Cork-cement composites, Roller-compacted concrete, Glass concrete, Asphalt concrete, Rapid strength concrete, Rubberized concrete, Polymer concrete, Geopolymer or green concrete, Limecrete, Refractory Cement, Concrete cloth, Innovative mixtures and Gypsum concrete.

Concrete recycling Main article: Concrete recycling is an increasingly common method of disposing of concrete structures. Concrete debris was once routinely shipped to landfills for disposal, but recycling is increasing due to improved environmental awareness, governmental laws, and economic benefits. Concrete recycling

Concrete, which must be free of trash, wood, paper and other such materials, is collected from demolition sites and  put through a crushing machine, often along with asphalt, bricks, and rocks. Reinforced concrete contains rebar and other metallic reinforcements, which are removed with magnets and recycled elsewhere. The remaining aggregate chunks are sorted by size. Larger chunks may go through the crusher again. Smaller pieces of concrete are used as gravel for new construction projects. Aggregate base gravel is laid down as the lowest layer in a road, with fresh concrete or asphalt placed over it. Crushed recycled concrete can sometimes be used as the dry aggregate for brand new concrete if it is free of contaminants, though the use of recycled concrete limits strength and is not allowed in many jurisdictions. On March 3, 1983, a government funded research team (the VIRL research.codep) approximated that almost 17% of worldwide landfill was by-products of concrete based waste. Recycling concrete provides environmental benefits, conserving landfill space and use as aggregate reduces the need for gravel mining.

World records The world record for the largest concrete pour in a single project is the Three Gorges Dam in Hubei Province, China  by the Three Gorges Corporation. The amount of concrete used in the construction of the dam is estimated at 21 million cubic yards over 17 years. Surpassing the previous record of 3.2 million cubic meters which was held by Itaipu hydropower station in Brazil. [37] [38] Continuous pours

The world record for largest continuously poured concrete raft was achieved March 23, 2007 in Al Durrah, Dubai by contracting firm, Dubai Contracting Company. The pour was close to 10,500 cubic meters of concrete poured within a two day period. This surpassed the previous record which was also held by Dubai Contracting Company.[39][40] The  pour was part of the foundation for the Dubai's Sama Tower . The world record for largest continuously poured concrete floor was completed November 8, 1997 in Louisville, Kentucky by Design-build firm, EXXCEL Project Management. The pour consisted of 225,000 sq. ft of concrete within a 30 hour period with a flatness of FF 54.60 and levelness of FL 43.83. This surpassed the previous record by 50% in total volume and 7.5% in total area.[41][42]

Use of concrete in infrastructure

The interior of the Pantheon in the 18th century, painted by Giovanni Paolo Pannini.

The Baths of Caracalla, Italy, in 2003. Mass concrete structures

These include gravity dams such as the Itaipu, Hoover Dam and the Three Gorges Dam and large breakwaters. Concrete that is poured all at once in one block (so that there are no weak points where the concrete is "welded" together) is used for tornado shelters. Concrete textures

When one thinks of concrete, oftentimes the image of a dull, gray concrete wall comes to mind. With the use of  form liner , concrete can be cast and molded into different textures and used for decorative concrete applications. Sound/retaining walls, bridges, office buildings and more serve as the optimal canvases for concrete art. For example, the Pima Freeway/Loop 101 retaining and sound walls in Scottsdale, Arizona, feature desert flora and fauna, a 67-foot lizard and 40-foot cacti along the 8-mile stretch. The project, titled "The Path Most Traveled," is one example of how concrete can be shaped using elastomeric form liner .

A 67-foot concrete lizard basks in the sun, Three textures of concrete featured featured on a sound/retaining wall in in Scottsdale, AZ, created with Scottsdale, AZ. [formliner]. (Scott System) (Scott System)

40-foot cacti decorate a sound/retaining wall in Scottsdale, AZ. (Scott System)

Reinforced concrete structures

Main article: Reinforced concrete Reinforced concrete contains steel reinforcing that is designed and placed in structural members at specific positions to cater for all the stress conditions that the member is required to accommodate. Prestressed concrete structures

Main article: Prestressed concrete

is a form of reinforced concrete which builds in compressive stresses during construction to oppose those found when in use. This can greatly reduce the weight of beams or slabs, by better distributing the stresses in the structure to make optimal use of the reinforcement. Prestressed concrete

For example a horizontal beam will tend to sag down. If the reinforcement along the bottom of the beam is  prestressed, it can counteract this. In pre-tensioned concrete, the prestressing is achieved by using steel or polymer tendons or bars that are subjected to a tensile force prior to casting, or for post-tensioned concrete, after casting.

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Anthropic rock  Biorock  Construction Bunding Brutalist architecture, encouraging visible concrete surfaces Cement Geopolymers, a class of synthetic aluminosilicate materials Hempcrete, a mixture with hemp hurds Mudcrete, a soil-cement mixture Papercrete, a paper-cement mixture Portland cement, the classical concrete cement Cement accelerator  Concrete moisture meter  Concrete canoe Concrete curing Concrete leveling Concrete mixer  Concrete masonry unit Concrete recycling Concrete step barrier  Efflorescence Fireproofing Foam Index Form liner  Formwork  o

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KU Mix LiTraCon High performance fiber reinforced cementitious composites High Reactivity Metakaolin Mortar  Plasticizer  Prefabrication Pykrete, a composite material of ice and cellulose Silica fume Shallow foundation Types of concrete Asphalt concrete Aerated autoclaved concrete Decorative concrete Fiber reinforced concrete Lunarcrete Prestressed concrete Precast concrete Ready-mix concrete Reinforced concrete Salt-concrete Seacrete Terrazzo Whitetopping

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Controlled permeability formwork 

References 1. ^ The Skeptical Environmentalist: Measuring the Real State of the World, by Bjorn Lomborg, p 138. 2. ^ "Minerals commodity summary - cement - 2007". 2007-06-01. http://minerals.usgs.gov/minerals/pubs/commodity/cement/index.html. Retrieved 2008-01-16. 3. ^ The Roman Pantheon: The Triumph of Concrete 4. ^ Lancaster, Lynne (2005), Concrete Vaulted Construction in Imperial Rome. Innovations in Context , Cambridge University Press, ISBN 978-0-511-16068-4 5. ^ D.S. Robertson: Greek and Roman Architecture, Cambridge, 1969, p. 233 6. ^ Henry Cowan: The Masterbuilders, New York 1977, p. 56, ISBN 978-0471027409

7. ^ Robert Mark, Paul Hutchinson: "On the Structure of the Roman Pantheon", Art Bulletin , Vol. 68, No. 1 (1986), p. 26, fn. 5 8. ^ http://www.allacademic.com/meta/p_mla_apa_research_citation/0/2/0/1/2/p20122_index.html 9. ^ http://www.djc.com/special/concrete/10003364.htm 10. ^ Fountain, Henry (March 30, 2009). "Concrete Is Remixed With Environment in Mind". The New York  Times. http://www.nytimes.com/2009/03/31/science/earth/31conc.html. Retrieved 2009-03-30. 11. ^ olemiss.edu - Missing File 12. ^ U.S. Federal Highway Administration. "Admixtures". http://www.fhwa.dot.gov/infrastructure/materialsgrp/admixture.html. Retrieved 2007-01-25. 13. ^ Cement Admixture Association. "CAA". www.admixtures.org.uk. http://www.admixtures.org.uk/publications.asp. Retrieved 2008-04-02. 14. ^ Kosmatka, S.H.; Panarese, W.C. (1988). Design and Control of Concrete Mixtures. Skokie, IL, USA: Portland Cement Association. pp. 17, 42, 70, 184. ISBN 0-89312-087-1. 15. ^ U.S. Federal Highway Administration. "Fly Ash". http://www.fhwa.dot.gov/infrastructure/materialsgrp/flyash.htm. Retrieved 2007-01-24. 16. ^ U.S. Federal Highway Administration. "Ground Granulated Blast-Furnace Slag". http://www.fhwa.dot.gov/infrastructure/materialsgrp/ggbfs.htm. Retrieved 2007-01-24. 17. ^ U.S. Federal Highway Administration. "Silica Fume". http://www.fhwa.dot.gov/infrastructure/materialsgrp/silica.htm. Retrieved 2007-01-24. 18. ^ Premixed Cement Paste 19. ^ The use of micro- and nanosilica in concrete 20. ^ Measuring, Mixing, Transporting, and Placing Concrete 21. ^ U.S. Patent 5,443,313 - Method for producing construction mixture for concrete 22. ^ "Concrete Testing". http://technology.calumet.purdue.edu/cnt/rbennet/concrete%20lab.htm. Retrieved 2008-11-10. 23. ^ http://www.sustainableconcrete.org.uk/main.asp?page=0 24. ^ EIA - Emissions of Greenhouse Gases in the U.S. 2006-Carbon Dioxide Emissions 25. ^ The Cement Sustainability Initiative: Progress report, World Business Council for Sustainable  Development , published 2002-06-01 26. ^ Severinghaus, J.P. , W. Broecker, W. Dempster, T. MacCallum, and M. Wahlen (1994) Oxygen loss in Biosphere 2. EOS, Transactions of the American Geophysical Union, vol. 75, N°. 3, pp. 33, 35-37 27. ^ http://adsabs.harvard.edu/abs/1994EOSTr..75...33S Oxygen loss in Biosphere 2 28. ^ Water Environment Federation, Alexandria, VA; and American Society of Civil Engineers, Reston, VA. "Urban Runoff Quality Management." WEF Manual of Practice No. 23; ASCE Manual and Report on Engineering Practice No. 87. 1998. ISBN 1-57278-039-8. Chapter 1. 29. ^ G. Allen Burton, Jr., Robert Pitt (2001). Stormwater Effects Handbook: A Toolbox for Watershed  Managers, Scientists, and Engineers. New York: CRC/Lewis Publishers. ISBN 0-87371-924-7. http://unix.eng.ua.edu/~rpitt/Publications/BooksandReports/Stormwater%20Effects%20Handbook%20by %20%20Burton%20and%20Pitt%20book/MainEDFS_Book.html. Chapter 2. 30. ^ U.S. Environmental Protection Agency (EPA). Washington, DC. "Protecting Water Quality from Urban Runoff." Document No. EPA 841-F-03-003. February 2003. 31. ^ United States. National Research Council. Washington, DC. "Urban Stormwater Management in the United States." October 15, 2008. pp. 18-20. 32. ^ "Cool Pavement Report" (PDF). Environmental Protection Agency. June 2005. http://www.epa.gov/heatisland/resources/pdf/CoolPavementReport_Former%20Guide_complete.pdf . Retrieved 2009-02-06. 33. ^ Gore, A; Steffen, A (2008). World Changing: A User's Giode for the 21st Century. New York: Abrams.  pp. 258. 34. ^ "Concrete facts". Pacific Southwest Concrete Alliance. http://www.concreteresources.net/categories/4F26A962-D021-233F-FCC5EF707CBD860A/fun_facts.html. Retrieved 2009-02-06. 35. ^ http://jeq.scijournals.org/cgi/reprint/31/3/718.pdf  36. ^ Radionuclide content of concrete building blocks and radiation dose rates in some dwellings in Ibadan,  Nigeria a b

a b c

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37. ^ "Concrete Pouring of Three Gorges Project Sets World Record". 2001-01-04. http://english.peopledaily.com.cn/200101/02/eng20010102_59432.html. Retrieved 2009-08-24. 38. ^ China’s Three Gorges Dam By The Numbers 39. ^ Record concrete pour takes place on Al Durrah 40. ^ What was the world’s Largest concrete pour? 41. ^ "Continuous cast: Exxcel Contract Management oversees record concrete pour ". 1998-03-01. http://concreteproducts.com/mag/concrete_continuous_cast_exxcel/?smte=wr . Retrieved 2009-08-25. 42. ^ Exxcel Project Management - Design Build, General Contractors •

Matthias Dupke: Textilbewehrter Beton als Korrosionsschutz . Examicus, Frankfurt am Main 2009, ISBN 978-3-86943-336-3.

External links Wikimedia Commons has media related to: Concrete Related article and publications • •

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Concrete History Oct 1 2009 Refractory Concrete Information related to heat resistant concrete; recipes, ingredients mixing ratio, work  with and applications. The effect of curing on the tensile strength of medium to high strength concrete The History of Concrete Concrete carbonation chemistry at the TU Dresden Howard Kanare - Problems With Moisture in Concrete Concrete Moisture Testing - Relative Humidity vs. Calcium Chloride Short film on the reinforced concrete buildings that Ove Arup helped design for Dudley Zoo in the 1930s Free Concrete Books : Standard Practice for Concrete Pavements Concrete Repair  High Performance Concrete Structural Roller Compacted Concrete Concrete Crack Repair  o o o o o

[hide] v•d•e

Roads and Junctions

[show] Types of road

Highspeed

Access via interchanges Other access

Autobahn · Autocesta · Autopista · Autostrada · Autostrasse · Auto-estrada · Freeway · Motorway · Semi-highway · HQDC Arterial road · Collector/distributor road · Distributor  road · Dual carriageway/divided highway · Expresscollector setup · Expressway · Farm-to-market road ·

Highway · Link road · Parkway · Super two · Twolane expressway · 2+1 road · 2+2 road Boulevard · Business route · Frontage road · Regional road · Road · Single carriageway · Street

Standard Lowspeed

Alley · Backroad · Cul-de-sac · Driveway · Lane · Primitive road · Range road

Low traffic

Other  Concurrency · Concession road · Private highway · Special route · Toll road Surfaces

Asphalt concrete · Brick · Chipseal · Cobblestone · Concrete · Corduroy · Dirt · Gravel · Ice · Macadam · Oiled (bitumen) · Plank · Tarmac

List of road types by features [show] Road junctions

Interchanges Cloverleaf · Diamond · Directional T · Diverging diamond · Parclo · Trumpet · SPUI · Stack · Three(gradelevel diamond · Raindrop · Roundabout interchange separated) IntersectionsBox junction · Continuous flow · Hook turn · Jughandle · Michigan left · Quadrant roadway · (at-grade) Roundabout · Superstreet · 3-way junction · Traffic circle · Bowtie This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by  professional editors (see full disclaimer ) Donate to Wikimedia

Translations: Concrete Top Home > Library > Literature & Language > Translations Dansk (Danish) adj. - konkret, håndgribelig n. - tingsnavn, beton v. tr. - støbe i beton, udstøbe, gøre til fast masse v. intr. - blive til fast masse, størkne idioms:

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concrete jungle betonhelvede concrete mixer betonblandemaskine

 Nederlands (Dutch)  beton(nen), concreet, (ver)harden, beton storten, concreet maken in beton gestort Français (French) adj. - (fig) concret, (Constr) de béton/en béton n. - béton v. tr. - recouvrir de béton, bétonner  v. intr. - recouvrir de béton, bétonner  idioms:

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concrete jungle univers de béton concrete mixer bétonnière

Deutsch (German) n. - Beton adj. - Beton-, konkret v. - betonieren, konkretisieren idioms:

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concrete jungle Betondschungel concrete mixer Betonmischmaschine

Ελληνική (Greek) n. - σκυρόδεμα (κν. μπετόν) adj. - συγκεκριμένος, απτός, χειροπιαστός, (οικοδ.) σκυρόδετος, μπετονένιος v. - πήζω, στερεοποιούμαι (κν. δένω), συγκολλώ/-ούμαι, (οικοδ.) σκυροδετώ (κν. ρίχνω μπετά), (μτφ.) παγιώνω, συγκεκριμενοποιώ idioms:

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concrete jungle η ζούγκλα του μπετόν, η απάνθρωπη μεγαλούπολη concrete mixer (οικοδ.) αναμικτήρας σκυροδέματος (κν. μπετονιέρα)

Italiano (Italian) costruire in calcestruzzo, solidificarsi, calcestruzzo, concreto, di calcestruzzo idioms:

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concrete jungle giungla di cemento concrete mixer betoniera set/embedded in concrete cementato

Português (Portuguese) n., adj. - concreto (m) v. - concretizar, solidificar  idioms:

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concrete jungle selva (f) de concreto concrete mixer betoneira (f) (Téc.) set/embedded in concrete chumbada (f) em concreto

Русский (Russian) бетонировать, укрепляться, конкретный, бетонный, бетон idioms:

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concrete jungle каменные джунгли, опасная часть города concrete mixer бетономешалка set/embedded in concrete забетонированный

Español (Spanish) adj. - específico, de hormigón n. - concreto, hormigón v. tr. - cubrir con hormigón v. intr. - solidificarse, coagularse, concrecionarse idioms:

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concrete jungle jungla de asfalto, metrópoli concrete mixer hormigonera, mezcladora

Svenska (Swedish) n. - konkret föremål, konkret ord, fast massa, betong adj. - konkret, materiell, påtaglig, fast, stelnad, sammanvuxen, av betong v. - smälta samman, konkretisera, belägga m betong, smältas samman, använda betong 中文（简体）(Chinese (Simplified)) 具体的, 水泥的, 实在的, 水泥, 混凝土, 使凝固, 用混凝土修筑, 使结合, 浇混凝土于, 凝结, 固结 idioms:

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concrete jungle 水泥丛林 concrete mixer  混凝土搅拌机, 混凝土搅拌车

中文（繁體）(Chinese (Traditional)) adj. - 具體的, 水泥的, 實在的 n. - 水泥, 混凝土 v. tr. - 使凝固, 用混凝土修築, 使結合, 澆混凝土於 v. intr. - 凝結, 固結 idioms:

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concrete jungle 水泥叢林 concrete mixer  混凝土攪拌機, 混凝土攪拌車

한국어 (Korean) adj. - 현실의, 특수한, 굳어진 n. - 응고물, 콘크리트, 구체적관념 v. tr. - 콘크리트로 굳히다, 실제화 하다 v. intr. - 응고하다, 콘크리트를 사용하다

日本語 (Japanese) adj. - 具体的な, 有形の, コンクリート製の n. - コンクリート, 具体物 v. - コンクリートで固める , 凝結させる

idioms:

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concrete jungle コンクリートジャングル concrete mixer  コンクリートミキサー reinforced concrete 鉄筋コンクリート set/embedded in concrete 固める, 身動きとれなくする

‫( العربيه‬Arabic) ‫سمنت‬‫بنى ب‬ (‫فع‬) ‫واقع‬ , ,‫م‬ (‫ه‬‫ص‬) ‫اسمنت‬ ,‫ط‬‫ب‬ ,‫ه‬‫( خرس‬‫س‬‫ا‬) ‫עברית‬ (Hebrew) adj. - ‫ממשי‬ ,‫מוחשי‬ n. - ‫חומר בנייה‬ ,‫בטון‬ v. tr. - ‫כיסה בבטון‬ v. intr. - ‫התגבש‬ ,‫התלכד לגוש‬ If you are unable to view some languages clearly, click here. To select your translation preferences click here.

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