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Encyclopedia > Concrete
The interior of the Pantheon in the 18th century, painted by Giovanni Paolo Panini
The interior of the Pantheon in the 18th century, painted by Giovanni Paolo Panini
The Baths of Caracalla, in 2003
The Baths of Caracalla, in 2003
Concrete being poured, raked and vibrated into place in residential construction in Toronto, Ontario, Canada.
Concrete being poured, raked and vibrated into place in residential construction in Toronto, Ontario, Canada.
1930s vibrated concrete, manufactured in Croydon and installed by the LMS railway after an art deco refurbishment in Meols.
1930s vibrated concrete, manufactured in Croydon and installed by the LMS railway after an art deco refurbishment in Meols.

Concrete 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 and water) and chemical admixtures. The word concrete comes from the Latin word "concretus", which means "hardened" or "hard". Look up concrete in Wiktionary, the free dictionary. ... Download high resolution version (1193x1535, 457 KB)The interior of the Pantheon, Rome, by Giovanni Paolo Panini. ... Download high resolution version (1193x1535, 457 KB)The interior of the Pantheon, Rome, by Giovanni Paolo Panini. ... Categories: Stub | 1691 births | 1765 deaths | Italian painters ... Wikipedia does not have an article with this exact name. ... Wikipedia does not have an article with this exact name. ... Image File history File links Download high-resolution version (3477x4634, 1554 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Concrete ... Image File history File links Download high-resolution version (3477x4634, 1554 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Concrete ... For other uses, see Construction (disambiguation). ... Motto: Ut Incepit Fidelis Sic Permanet (Latin: Loyal she began, loyal she remains) Capital Toronto Largest city Toronto Official languages English (de facto) Government Lieutenant-Governor David C. Onley Premier Dalton McGuinty (Liberal) Federal representation in Canadian Parliament House seats 107 Senate seats 24 Confederation July 1, 1867 (1st) Area... Image File history File links Size of this preview: 337 × 599 pixelsFull resolution (576 × 1024 pixel, file size: 308 KB, MIME type: image/jpeg) File historyClick on a date/time to view the file as it appeared at that time. ... Image File history File links Size of this preview: 337 × 599 pixelsFull resolution (576 × 1024 pixel, file size: 308 KB, MIME type: image/jpeg) File historyClick on a date/time to view the file as it appeared at that time. ... For other uses, see Croydon (disambiguation). ... LMS is an acronym with a few different meanings: London Mathematical Society Learning Management System Least mean squares an algorithm for adaptive filtering in digital signal processing London, Midland and Scottish Railway London Missionary Society LMS Color Space Library Management System LMS is also a user name used by Larry... Asheville City Hall. ... British Railways London Midland Region totem sign for Meols railway station. ... For other uses, see Cement (disambiguation). ... 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. ... Fly ash (one of several coal combustion products, or CCPs) is the finely divided mineral residue resulting from the combustion of coal in electric generating plants. ... Limestone Quarry Construction aggregate, or simply, aggregate, is a broad category of coarse particulate material used in construction, including sand, gravel, crushed stone, slag, and recycled concrete. ... Gravel (largest fragment in this photo is about 4 cm) Gravel is rock that is of a certain particle size range. ... For other uses, see Limestone (disambiguation). ... For other uses, see granite (disambiguation). ... For other uses, see Sand (disambiguation). ... H2O and HOH redirect here. ... For other uses, see Chemistry (disambiguation). ...


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. The reactions are highly exothermic and care must be taken that the build-up in heat does not affect the integrity of the structure. Concrete is used to make pavements, architectural structures, foundations, motorways/roads, bridges/overpasses, parking structures, brick/block walls and footings for gates, fences and poles. For other uses, see Chemical reaction (disambiguation). ... Mineral hydration is an inorganic chemical reaction where water is added to the crystal structure of a mineral, usually creating a new mineral. ... In thermodynamics, the word exothermic outside heating describes a process or reaction that releases energy usually in the form of heat, but it can also release energy in form of light (e. ... This article or section does not cite its references or sources. ... An architectural structure is a free-standing or guy anchored manmade outdoor construction for permanent use. ... A foundation is a structure that transmits loads from a building or road to the underlying ground. ... Motorway symbol in UK, France and Ireland. ... For other uses, see Road (disambiguation). ... This article is about the edifice (including an index to articles on specific bridge types). ... Overpass in East Potomac Park, Washington, D.C. Flyover in Miami Beach, Florida An overpass (In UK, most Commonwealth countries flyover) is a bridge, road or similar structure that crosses over another road. ... For other uses, see Parking (disambiguation). ... For other uses, see Brick (disambiguation). ... Look up block in Wiktionary, the free dictionary. ... A foundation is a structure that transmits loads from a building or road to the underlying ground. ... A fence in Westtown Township, Pennsylvania. ...


More concrete is used than any other man-made material in the world.[1] As of 2006, about seven billion cubic meters of concrete are made each year—more than one cubic meter 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. More than 55,000 miles of highways in America are paved with this material. The People's Republic of China currently consumes 40% of the world's cement [concrete] production. Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... One thousand million (1,000,000,000) is the natural number following 999,999,999 and preceding 1,000,000,001. ... The cubic meter (symbol m³) is the SI derived unit of volume. ... The United States dollar is the official currency of the United States. ... “Miles” redirects here. ... For other uses, see Highway (disambiguation). ...

Contents

History

In Serbia, remains of a hut dating from 5600 BC have been found, with a floor made of red lime, sand, and gravel. The pyramids of Shaanxi in China, built thousands of years ago, contain a mixture of lime and volcanic ash or clay [3]. The Assyrians and Babylonians used clay as cement in their concrete. The Egyptians used lime and gypsum cement. Not to be confused with Republika Srpska. ... This article or section does not adequately cite its references or sources. ... For other meanings, see pyramid (disambiguation). ...   (Simplified Chinese: ; Traditional Chinese: ; pinyin: ShÇŽnxÄ«; Wade-Giles: Shan-hsi; Postal map spelling: Shensi) is a north-central province of the Peoples Republic of China, and includes portions of the Loess Plateau on the middle reaches of the Yellow River as well as the Qinling Mountains across the... Ash plume from Mt Cleveland, a stratovolcano Diamond Head, a well-known backdrop to Waikiki in Hawaii, is an ash cone that solidified into tuff Volcanic ash consists of very fine rock and mineral particles less than 2 mm in diameter that are ejected from a volcanic vent. ... Language(s) Aramaic Religion(s) Syriac Christianity Related ethnic groups Other Semitic peoples, and other ethnic groups from the Fertile Crescent. ... Babylonia was an ancient state in Iraq), combining the territories of Sumer and Akkad. ... For other uses, see Clay (disambiguation). ... Map of Ancient Egypt Ancient Egypt was the civilization of the Nile Valley between about 3000 BC and the conquest of Egypt by Alexander the Great in 332 BC. As a civilization based on irrigation it is the quintessential example of an hydraulic empire. ... This article or section does not adequately cite its references or sources. ... For other uses, see Gypsum (disambiguation). ...


Roman invention

During the Roman Empire, Roman concrete was made from quicklime, pozzolanic ash/pozzolana, and an aggregate of pumice; it was very similar to modern Portland cement concrete. The widespread use of concrete in many Roman structures has ensured that many survive almost intact 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 have masonry cladding to a concrete core, a technique they used in structures such as the Pantheon, Rome, the interior dome of which is unclad concrete. For other uses, see Roman Empire (disambiguation). ... Calcium oxide (CaO), commonly known as lime or quicklime, is a widely used chemical compound. ... 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. ... Specimen of highly porous pumice from Teide volcano on Tenerife, Canary Islands. ... The Baths of Caracalla, in 2003 The Baths of Caracalla were Roman public baths, or thermae, built in Rome between 212 and 216 AD, during the reign of the Emperor Caracalla. ... For other uses, see Rome (disambiguation). ... For other uses, see Roman Empire (disambiguation). ... Pont du Gard, France, a Roman era aqueduct circa 19 BC. It is one of Frances top tourist attractions at over 1. ... Facade of the Pantheon The Pantheon (Latin Pantheon[1], from Greek Πάνθεον Pantheon, meaning Temple of all the gods) is a building in Rome which was originally built as a temple to the seven deities of the seven planets in the state religion of Ancient Rome. ...


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. 1756 was a leap year starting on Thursday (see link for calendar). ... Portrait of John Smeaton, with the Eddystone Lighthouse in the background John Smeaton, FRS, (June 8, 1724 – October 28, 1792) was a civil engineer – often regarded as the father of civil engineering – responsible for the design of bridges, canals, harbours and lighthouses. ... Hydraulic lime is a variety of slaked lime used to make mortar. ... 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. ...


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 byproduct 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. As cement production creates massive quantities of carbon dioxide, cement-replacement technology such as this will play an important role in future attempts to cut carbon dioxide. Fly ash (one of several coal combustion products, or CCPs) is the finely divided mineral residue resulting from the combustion of coal in electric generating plants. ... Coal Example chemical structure of coal Coal is a fossil fuel formed in ecosystems where plant remains were saved by water and mud from oxidization and biodegradation. ... Carbon dioxide (chemical formula: ) is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ...


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. Horsehair refers to hair taken from the mane or tail of horses. ...


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

There are many types of concrete available, created by varying the proportions of the main ingredients below. This article is about the construction material. ...


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). 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. ... Mortar holding weathered bricks. ... This article is about the building material. ... Joseph Aspdin (1788 – 20 March 1855) was an English mason, bricklayer and inventor who patented Portland cement on 21 October 1824. ... 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. ... The Isle of Portland is a long by wide limestone island in the English Channel. ... This article is about the capital of England and the United Kingdom. ... 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. ... For other uses, see Limestone (disambiguation). ... Cement clinker, in the manufacture of Portland cement, is the product of the kiln. ... The sulfate anion, SO42− The structure and bonding of the sulfate ion In inorganic chemistry, a sulfate (IUPAC-recommended spelling; also sulphate in British English) is a salt of sulfuric acid. ... For other uses, see Gypsum (disambiguation). ...


High-temperature applications, such as masonry ovens and the like, generally require the use of a refractory cement; concretes based on Portland cement can be damaged or destroyed by elevated temperatures, but refractory concretes are better able to withstand such conditions. A wood-burning brick oven. ... In metallurgy, refraction is a property of metals that indicates their ability to withstand heat. ...


Water

Combining water with a cementitious material forms a cement paste. The cement paste glues the aggregate together, fills voids within it, and allows it to flow more easily.


Less water in the cement paste will yield a stronger, more durable concrete; more water will give an easier-flowing concrete with a higher slump.[4] This article is about the construction material. ...


Impure water used to make concrete can cause problems, either when setting, or later on.


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. For other uses, see Sand (disambiguation). ... 20 millimetre crushed stone construction aggregate Crushed stone or angular rock is a form of construction aggregate, typically produced by mining a suitable rock deposit and breaking the removed rock down to the desired size using crushers. ... Blast furnace in Sestao, Spain. ... Bottom ash refers to the non combustible constituents of coal with traces of combustibles embedded in forming clinkers and sticking to hot side walls of furnace during the furnace working. ...


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. Quartzite Quartzite (from German Quarzit[1]) is a hard, metamorphic rock which was originally sandstone. ...


Reinforcement

Installing rebar in a floor slab during a concrete pour
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 metal reinforcing bars, glassfiber, or plastic fiber to carry tensile loads. Download high resolution version (1200x764, 875 KB)Installing rebar in a concrete floor during a pour Image copyleft: Image taken by me, released under GFDL, Pollinator 04:07, Dec 24, 2004 (UTC) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this... Download high resolution version (1200x764, 875 KB)Installing rebar in a concrete floor during a pour Image copyleft: Image taken by me, released under GFDL, Pollinator 04:07, Dec 24, 2004 (UTC) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this... A tied rebar beam cage. ... Reinforced concrete at Sainte Jeanne dArc Church (Nice, France): architect Jacques Dror, 1926–1933 Reinforced concrete, also called ferroconcrete in some countries, is concrete in which reinforcement bars (rebars) or fibers have been incorporated to strengthen a material that would otherwise be brittle. ... A tied rebar beam cage. ...


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.[5] The most common types of admixtures [6] are: For other uses, see Chemistry (disambiguation). ...

  • Accelerators speed up the hydration (hardening) of the concrete.
  • Retarders slow the hydration of concrete, and are used in large or difficult pours where partial setting before the pour is complete is undesirable.
  • Air-entrainers add and distribute tiny air bubbles in the concrete, which will reduce damage during freeze-thaw 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.

An accelerator is an agent used to speed the chemical hardening of plastic materials such as concrete. ... Th term retarder can refer either to a chemical agent or to a type of optical material, as described below. ... Air entrainment is the intentional creation of tiny air bubbles in concrete. ... Weathering is the decomposition of rocks, soils and their minerals through direct contact with the Earths atmosphere. ... Plasticizers are additives that soften the materials (usually a plastic or a concrete mix) they are added to. ... Natural Ultramarine pigment in powdered form. ... Corrosion inhibitor - Wikipedia /**/ @import /w/skins-1. ...

Mineral admixtures and blended cements

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),[5] or as a replacement for Portland cement (blended cements).[7] A pozzolan is a material which, when combined with calcium hydroxide, exhibits cementitious properties. ... Granularity is a measure of the size of the components, or descriptions of components, that make up a system. ...

  • 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.[8]
  • 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.[9]
  • Silica fume: A byproduct 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.[10]
  • 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.

Fly ash (one of several coal combustion products, or CCPs) is the finely divided mineral residue resulting from the combustion of coal in electric generating plants. ... For other uses, see Power station (disambiguation). ... A pozzolan is a material which, when combined with calcium hydroxide, exhibits cementitious properties. ... Calcareous formed from or containing a high proportion of Calcium carbonate. ... Ground granulated blastfurnace slag (GGBS or GGBFS) is obtained by quenching molten iron blast furnace slag (a by-product of iron and steel making) in water or stream, to produce a glassy granular product that is then dried and ground into a fine powder. ... For other uses, see Steel (disambiguation). ... Silica fume, also known as microsilica, is a byproduct of the reduction of high-purity quartz with coal in electric furnaces in the production of silicon and ferrosilicon alloys. ... Ferrosilicon, or ferrosilicium, is a ferroalloy an alloy of iron and silicon with between 15 and 90% silicon. ... A pozzolan is a material which, when combined with calcium hydroxide, exhibits cementitious properties. ... Metakaolin is a dehyroxylated form of kaolinite. ...

Mixing concrete

Pouring a concrete floor for a commercial building, (slab-on-grade)
Pouring a concrete floor for a commercial building, (slab-on-grade)

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.[11] 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 premixed paste is then blended with aggregates and any remaining batch water, and final mixing is completed in conventional concrete mixing equipment.[12] Download high resolution version (1400x1050, 1380 KB)Pouring a concrete floor for a comercial building Image copyleft: Image taken by me, released under GFDL, Pollinator 04:04, Dec 24, 2004 (UTC) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old... Download high resolution version (1400x1050, 1380 KB)Pouring a concrete floor for a comercial building Image copyleft: Image taken by me, released under GFDL, Pollinator 04:04, Dec 24, 2004 (UTC) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old... For other uses, see Cement (disambiguation). ... Limestone Quarry Construction aggregate, or simply, aggregate, is a broad category of coarse particulate material used in construction, including sand, gravel, crushed stone, slag, and recycled concrete. ... Compressive strength is the capacity of a material to withstand axially directed pushing forces. ... Water-cement ratio is the ratio of weight of water to the weight of cement used in a concrete mix. ... Limestone Quarry Construction aggregate, or simply, aggregate, is a broad category of coarse particulate material used in construction, including sand, gravel, crushed stone, slag, and recycled concrete. ...


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 mixer. This paste can be used itself or foamed (expanded) for lightweight concrete.[13] 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 concrete roof and siding tiles, paving stones and lightweight concrete block production. The fuel value or relative energy density is the quantity of potential energy in fuel, food or other substance. ... Plasticizers are additives that soften the materials (usually a plastic or a concrete mix) they are added to. ... In telecommunications a mixer is a frequency mixer. ... It has been suggested that this article or section be merged into Capillary action. ...


Characteristics

During hydration and hardening, concrete needs to develop certain physical and chemical properties. Among other qualities, mechanical strength, low moisture permeability, and chemical and volumetric stability are necessary. The phrase chemical property is context-dependent, but generally refers to a materials quality which becomes evident during a chemical reaction; this is, which can only be established by changing a substances chemical identity. ... Strength of materials is materials science applied to the study of engineering materials and their mechanical behavior in general (such as stress, deformation, strain and stress-strain relations). ...


Workability

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. For the Talib Kweli album Quality (album) Quality can refer to a. ... Limestone Quarry Construction aggregate, or simply, aggregate, is a broad category of coarse particulate material used in construction, including sand, gravel, crushed stone, slag, and recycled concrete. ... In chemistry, hydration is the condition of being combined with water. ... Surface water is water on the ground or in a stream, river, lake, sea or ocean; as opposed to groundwater. ...


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). ASTM International is an international voluntary standards organization that develops and produces technical standards for materials, products, systems and services. ...


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. The midrange of a set of statistical data values is the arithmetic mean of the smallest and largest values in the set. ... A reducing agent (also called a reductant or reducer) is the element or a compound in a redox (reduction-oxidation) reaction (see electrochemistry) that reduces another species. ... Water-cement ratio is a term usually associated with concrete. ...


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. This article is about the construction material. ...


Curing

A concrete slab ponded while curing
A concrete slab ponded while curing
Concrete columns curing while wrapped in plastic
Concrete columns curing while wrapped in plastic

In all but the least critical applications, care needs to be taken to properly cure (hydrate) concrete, and achieve best strength and hardness. This happens after the concrete has been placed. Cement requires a moist, controlled environment to cure 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. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ...


It does not set by drying out, but by the cementitious material chemically reacting with the water, hydrating. 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. Mineral hydration is an inorganic chemical reaction where water is added to the crystal structure of a mineral, usually creating a new mineral. ...


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. Improper curing can cause scaling, reduced strength and abrasion resistance and cracking. In thermodynamics, the word exothermic outside heating describes a process or reaction that releases energy usually in the form of heat, but it can also release energy in form of light (e. ...


Strength

Concrete has relatively high compressive strength, but significantly lower tensile strength (about 10% of the compressive strength). As a result, without compensating, concrete would almost always fail from tensile stresses – even when loaded in compression. The practical implication of this is that concrete elements subjected to tensile stresses must be reinforced with materials that are strong in tension. Concrete is most often constructed with the addition of steel or fiber reinforcement. The reinforcement can be by bars (rebar), mesh, or fibres, which provide the required tensile strength to concrete producing reinforced concrete. Concrete can also be prestressed (reducing tensile stress) using internal steel cables (tendons), allowing for beams or slabs with a longer span than is practical with reinforced concrete alone. Inspection of concrete structures can be non-destructive if carried out with equipment such as a Schmidt hammer, which is used to estimate concrete strength. Compressive strength is the capacity of a material to withstand axially directed pushing forces. ... Tensile strength isthe measures the force required to pull something such as rope, wire, or a structural beam to the point where it breaks. ... Stress is a measure of force per unit area within a body. ... Fiber or fibre[1] is a class o f materials that are continuous filaments or are in discrete elongated pieces, similar to lengths of thread. ... A tied rebar beam cage. ... Reinforced concrete at Sainte Jeanne dArc Church (Nice, France): architect Jacques Dror, 1926–1933 Reinforced concrete, also called ferroconcrete in some countries, is concrete in which reinforcement bars (rebars) or fibers have been incorporated to strengthen a material that would otherwise be brittle. ... Traditional reinforced concrete is based on the use of steel reinforcement bars, rebar, inside poured concrete. ... Tensile stress (or tension) is the stress state leading to expansion; that is, the length of a material tends to increase in the tensile direction. ... A statically determinate beam, bending under an evenly distributed load. ... Span is a section between two intermediate supports of a bridge. ... This article is considered orphaned, since there are few or no other articles linked to this one. ...


The ultimate strength of concrete is influenced by the water-cementitious ratio (w/cm), the design constituents, and the mixing, placement and curing methods employed. All things being equal, concrete with a lower water-cement (cementitious) ratio makes a stronger concrete than that with a higher ratio. The total quantity of cementitious materials (Portland cement, slag cement, pozzolans) can affect strength, water demand, shrinkage, abrasion resistance and density. All concrete will crack independent of whether or not it has sufficient compressive strength. In fact, high Portland cement content mixtures actually crack earlier due to increased hydration rate. As concrete transforms from its plastic state, hydrating to a solid, the material undergoes shrinkage. Plastic shrinkage cracks can occur soon after placement but if the evaporation rate is high they often can actually occur during finishing operations, for example in hot weather or a breezy day. In very high strength concrete mixtures (greater than 10,000 psi) the crushing strength of the aggregate can be a limiting factor to the ultimate compressive strength. In lean concretes (with a high water-cement ratio) the crushing strength of the aggregates is not so significant. In biology, agricultural science, physiology, and ecology, a limiting factor is one that controls a process, such as organism growth or species population size or distribution. ...


Experimentation with various mix designs begins by specifying desired "workability" as defined by a given slump, "durability" requirements taking into consideration the weather exposure conditions (freeze-thaw) to which the concrete will be exposed in service, and the required "28 day compressive strength" as determined by properly molded standard-cured cylinder samples. The characteristics of the cementitious content, coarse and fine aggregates, and chemical admixtures determine the water demand of the mix in order to achieve the desired workability. The 28 day compressive strength is obtained by determination of the correct amount of cementitious (and often chemical admixtures) to achieve the target water-cementitious ratio.


The internal forces in common shapes of structure, such as arches, vaults, columns and walls are predominantly compressive forces, with floors and pavements subjected to tensile forces. Compressive strength is widely used for specification requirement and quality control of concrete. The engineer knows his target tensile (flexural) requirements and will express these in terms of compressive strength. For other uses, see Arch (disambiguation). ... The Lierne vault of the Liebfrauenkirche, Mühlacker 1482. ...


Wired.com reported on April 13, 2007 that a team from the University of Tehran, competing in a contest sponsored by the American Concrete Institute, demonstrated several blocks of concretes with abnormally high compressive strengths between 50,000 and 60,000 PSI at 28 days.[14] The blocks appeared to use an aggregate of steel fibres and quartz – a mineral with a compressive strength of 160,000 PSI, much higher than typical high-strength aggregates such as granite (15,000-20,000 PSI). is the 103rd day of the year (104th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... Tehran University is the largest university in Iran, with 32,000 students. ... For other uses, see Steel (disambiguation). ... For other uses, see Quartz (disambiguation). ... For other uses, see granite (disambiguation). ...


Elasticity

The modulus of elasticity of concrete is a function of the modulus of elasticity of the aggregates and the cement matrix and their relative proportions. The modulus of elasticity of concrete is relatively linear at low stress levels but becomes increasingly non-linear as matrix cracking develops. The elastic modulus of the hardened paste may be in the order of 10-30 GPa and aggregates about 45 to 85 GPa. The concrete composite is then in the range of 30 to 50 GPa. In mathematics, a nonlinear system is one whose behavior cant be expressed as a sum of the behaviors of its parts (or of their multiples. ...


Expansion and shrinkage

Concrete has a very low coefficient of thermal expansion. However if no provision is made for expansion very large forces can be created, causing cracks in parts of the structure not capable of withstanding the force or the repeated cycles of expansion and contraction. During heat transfer, the energy that is stored in the intermolecular bonds between atoms changes. ... Expansion can have several meanings, including: In physics: Expansion of space In computer hardware: an Expansion card In computer programming: In-line expansion In computer gaming: an expansion pack See also: Wikipedia:Requests for expansion This is a disambiguation page — a navigational aid which lists other pages that might otherwise... Look up Contraction in Wiktionary, the free dictionary. ...


As concrete matures it continues to shrink, due to the ongoing reaction taking place in the material, although the rate of shrinkage falls relatively quickly and keeps reducing over time (for all practical purposes concrete is usually considered to not shrink any further after 30 years). The relative shrinkage and expansion of concrete and brickwork require careful accommodation when the two forms of construction interface.


Because concrete is continuously shrinking for years after it is initially placed, it is generally accepted that under thermal loading it will never expand to its originally placed volume.


Cracking

All concrete structures will crack to some extent. One of the early designers of reinforced concrete, Robert Maillart, employed reinforced concrete in a number of arched bridges. His first bridge was simple, using a large volume of concrete. He then realized that much of the concrete was very cracked, and could not be a part of the structure under compressive loads, yet the structure clearly worked. His later designs simply removed the cracked areas, leaving slender, beautiful concrete arches. The Salginatobel Bridge is an example of this. Image File history File links Size of this preview: 800 × 533 pixelsFull resolution‎ (3,521 × 2,347 pixels, file size: 4. ... Image File history File links Size of this preview: 800 × 533 pixelsFull resolution‎ (3,521 × 2,347 pixels, file size: 4. ... Salginatobel Bridge is a concrete arch bridge designed by renowned Swiss civil engineer Robert Maillart. ... // Robert Maillart Robert Maillart (February 6, 1872 - April 5, 1940) was a Swiss civil engineer who revelutionized reinforced concrete with such designs as the three-hinged arch, the deck-stiffened arch, and the mushroom slab. ... Salginatobel Bridge is a concrete arch bridge designed by renowned Swiss civil engineer Robert Maillart. ...


Concrete cracks due to tensile stress induced by shrinkage or stresses occurring during setting or use. Various means are used to overcome this. Fiber reinforced concrete uses fine fibers distributed throughout the mix or larger metal or other reinforcement elements to limit the size and extent of cracks. In many large structures joints or concealed saw-cuts are placed in the concrete as it sets to make the inevitable cracks occur where they can be managed and out of sight. Water tanks and highways are examples of structures requiring crack control. The concept of using fibers in concrete as reinforcement is not new. ... A tied rebar beam cage. ...


Shrinkage cracking

Shrinkage cracks occur when concrete members undergo restrained volumetric changes (shrinkage) as a result of either drying, autogenous shrinkage or thermal effects. Restraint is provided either externally (i.e. supports, walls, and other boundary conditions) or internally (differential drying shrinkage, reinforcement). Once the tensile strength of the concrete is exceeded, a crack will develop. The number and width of shrinkage cracks that develop are influenced by the amount of shrinkage that occurs, the amount of restraint present and the amount and spacing of reinforcement provided.


Concrete is placed while in a wet (or plastic) state, and therefore can be manipulated and moulded as needed. 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.


Plastic-shrinkage cracks are immediately apparent, visible within 0 to 2 days of placement, while drying-shrinkage cracks develop over time.


Tension cracking

Concrete members may be put into tension by applied loads. This is most common in concrete beams where a transversely applied load will put one surface into compression and the opposite surface into tension due to induced bending. The portion of the beam that is in tension may crack. The size and length of cracks is dependent on the magnitude of the bending moment and the design of the reinforcing in the beam at the point under consideration. Reinforced concrete beams are designed to crack in tension rather than in compression. This is achieved by providing reinforcing steel which yields before failure of the concrete in compression occurs and allowing remediation, repair, or if necessary, evacuation of an unsafe area. A statically determinate beam, bending under an evenly distributed load. ... Figure 1. ...


Creep

Because it is a fluid, concrete can be pumped to where it is needed. Here a concrete transport truck is feeding concrete to a concrete pumper, which is pumping it to where a slab is being poured.
Because it is a fluid, concrete can be pumped to where it is needed. Here a concrete transport truck is feeding concrete to a concrete pumper, which is pumping it to where a slab is being poured.

Creep is the term used to describe the permanent movement or deformation of a material in order to relieve stresses within the material. Concrete which is subjected to forces is prone to creep. Creep can sometimes reduce the amount of cracking that occurs in a concrete structure or element, but it also must be controlled. The amount of primary and secondary reinforcing in concrete structures contributes to a reduction in the amount of shrinkage, creep and cracking. Download high resolution version (5621x1579, 2114 KB)A concrete pumping truck taking concrete from a concrete truck and pumping it over to where a concrete slab is being poured. ... Download high resolution version (5621x1579, 2114 KB)A concrete pumping truck taking concrete from a concrete truck and pumping it over to where a concrete slab is being poured. ... Creep is the term used to describe the tendency of a material to move or to deform permanently to relieve stresses. ...


Physical properties

The coefficient of thermal expansion of Portland cement concrete is 0.000008 to 0.000012 (per degree Celsius) (8-12 1/MK) [15]. The density varies, but is around 150 pounds per cubic foot (2400 kg/m³).[16]


Damage modes

Fire

Due to its low thermal conductivity, a layer of concrete is frequently used for fireproofing of steel structures. However, concrete itself may be damaged by fire. K value redirects here. ... Fireproofing, a passive fire protection measure, subject to bounding, refers to the act of making materials or structures more resistant to fire, or to those materials themselves. ...


Up to about 300 °C, the concrete undergoes normal thermal expansion. Above that temperature, shrinkage occurs due to water loss; however, the aggregate continues expanding, which causes internal stresses. Up to about 500 °C, the major structural changes are carbonation and coarsening of pores. At 573 °C, quartz undergoes rapid expansion due to Phase transition, and at 900 °C calcite starts shrinking due to decomposition. At 450-550 °C the cement hydrate decomposes, yielding calcium oxide. Calcium carbonate decomposes at about 600 °C. Rehydration of the calcium oxide on cooling of the structure causes expansion, which can cause damage to material which withstood fire without falling apart. Concrete in buildings that experienced a fire and were left standing for several years shows extensive degree of carbonation. In physics, thermal expansion is the tendency of matter to change in volume in response to a change in temperature. ... For other uses, see Quartz (disambiguation). ... This diagram shows the nomenclature for the different phase transitions. ... Doubly refracting Calcite from Iceberg claim, Dixon, New Mexico. ... Calcium carbonate is a chemical compound, with the chemical formula CaCO3. ...


Concrete exposed to up to 100 °C is normally considered as healthy. The parts of a concrete structure that is exposed to temperatures above approximately 300 °C (dependent of water/cement ratio) will most likely get a pink color. Over approximately 600 °C the concrete will turn light grey, and over approximately 1000 °C it turns yellow-brown.[17] One rule of thumb is to consider all pink colored concrete as damaged, and to be removed.


Fire will expose the concrete to gasses and liquids that can be harmful to the concrete, among other salts and acids that occur when fire-gasses get in contact with water.


Aggregate expansion

Various types of aggregate undergo chemical reactions in concrete, leading to damaging expansive phenomena. The most common are those containing reactive silica, that can react (in the presence of water) with the alkalis in concrete (K2O and Na2O, coming principally from cement). Among the more reactive mineral components of some aggregates are opal, chalcedony, flint and strained quartz. Following the reaction (Alkali Silica Reaction or ASR), an expansive gel forms, that creates extensive cracks and damage on structural members. On the surface of concrete pavements the ASR can cause pop-outs, i.e. the expulsion of small cones (up to 3 cm about in diameter) in correspondence of aggregate particles. When some aggregates containing dolomite are used, a dedolomitization reaction occurs where the magnesium carbonate compound reacts with hydroxyl ions and yields magnesium hydroxide and a carbonate ion. The resulting expansion may cause destruction of the material. Far less common are pop-outs caused by the presence of pyrite, an iron sulfide that generates expansion by forming iron oxide and ettringite. Other reactions and recrystallizations, e.g. hydration of clay minerals in some aggregates, may lead to destructive expansion as well. For other uses, see Opal (disambiguation). ... Chalcedony knife, AD 1000-1200 Bloodstone redirects here. ... This article is about the sedimentary rock. ... For other uses, see Quartz (disambiguation). ... Alkali-Silica Reaction (ASR) is a reaction between reactive silica (in the concrete aggregates) and an alkali (usually present in the cement), which results in the formation of a gel. ... For other uses, see Dolomite (disambiguation). ... Magnesium carbonate, MgCO3, is a white solid that occurs in nature as a mineral. ... It has been suggested that this article or section be merged with Milk of Magnesia. ... Ball-and-stick model of the carbonate ion, CO32− For other meanings, see Carbonate (disambiguation) In chemistry, a carbonate is a salt or ester of carbonic acid. ... The mineral pyrite, or iron pyrite, is iron sulfide, FeS2. ... Ettringite is Hexacalcium Aluminate Trisulfate, (CaO)6(Al2O3)(SO3)3. ... Clay minerals are hydrous aluminium silicates, sometimes with minor amounts of iron, magnesium and other cations. ...


Sea water effects

Concrete exposed to sea water is susceptible to its corrosive effects. The effects are more pronounced above the tidal zone than where the concrete is permanently submerged. In the submerged zone, magnesium and hydrogen carbonate ions precipitate about 30 micrometers thick layer of brucite on which a slower deposition of calcium carbonate as aragonite occurs. These layers somewhat protect the concrete from other processes, which include attack by magnesium, chloride and sulfate ions and carbonation. Above the water surface, mechanical damage may occur by erosion by waves themselves or sand and gravel they carry, and by crystallization of salts from water soaking into the concrete pores and then drying up. Pozzolanic cements and cements using more than 60% of slag as aggregate are more resistant to sea water than pure Portland cement. Sea water is water from a sea or ocean. ... For baking soda, see Sodium bicarbonate In inorganic chemistry, a bicarbonate (IUPAC-recommended nomenclature: hydrogencarbonate) is an intermediate form in the deprotonation of carbonic acid. ... Brucite is the mineral form of magnesium hydroxide, with the chemical formula Mg(OH)2. ... Aragonite Aragonite is a polymorph of the mineral calcite, both having the chemical composition CaCO3. ... For morphological image processing operations, see Erosion (morphology). ...


Bacterial corrosion

Bacteria themselves do not have noticeable effect on concrete. However, anaerobic bacteria (Thiobacillus) in untreated sewage tend to produce hydrogen sulfide, which is then oxidized by aerobic bacteria present in biofilm on the concrete surface above the water level to sulfuric acid which dissolves the carbonates in the cured cement and causes strength loss. Concrete floors lying on ground that contains pyrite are also at risk. Using limestone as the aggregate makes the concrete more resistant to acids, and the sewage may be pretreated by ways increasing pH or oxidizing or precipitating the sulfides in order to inhibit the activity of sulfide utilizing bacteria. Aerobic and anaerobic bacteria can be identified by growning them in liquid culture: 1: Obligate aerobic bacteria gather at the top of the test tube in order to absorb maximal amount of oxygen. ... Genera Hydrogenophilus Thiobacillus The Hydrogenophilaceae are a small family of Proteobacteria, with two genera. ... Hydrogen sulfide (hydrogen sulphide in British English) is the chemical compound with the formula H2S. This colorless, toxic and flammable gas is responsible for the foul odor of rotten eggs and flatulence. ... Aerobic and anaerobic bacteria can be identified by growning them in liquid culture: 1: Obligate aerobic bacteria gather at the top of the test tube in order to absorb maximal amount of oxygen. ... Staphylococcus aureus biofilm on an indwelling catheter. ... Sulfuric acid, (also known as sulphuric acid) H2SO4, is a strong mineral acid. ... The mineral pyrite, or iron pyrite, is iron sulfide, FeS2. ... For other uses, see Limestone (disambiguation). ...


Chemical damage

Carbonation

Carbonation-iniated detoriation of concrete (at Hippodrome Wellington)
Carbonation-iniated detoriation of concrete (at Hippodrome Wellington)

Carbon dioxide from air can react with the calcium hydroxide in concrete to form calcium carbonate. This process is called carbonation, which is essentially the reversal of the chemical process of calcination of lime taking place in a cement kiln. Carbonation of concrete is a slow and continuous process progressing from the outer surface inward, but slows down with increasing diffusion depth. Carbonation has two effects: it increases mechanical strength of concrete, but it also decreases alkalinity, which is essential for corrosion prevention of the reinforcement steel. Below a pH of 10, the steel's thin layer of surface passivation disolves and corrosion is promoted. For the latter reason, carbonation is an unwanted process in concrete chemistry. Carbonation can be tested by applying Phenolphtalein solution, a pH indicator, over a fresh fracture surface, which indicates non-carbonated and thus alkaline areas with a violet color. Carbon dioxide (chemical formula: ) is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ... It has been suggested that Portlandite be merged into this article or section. ... Calcium carbonate is a chemical compound, with the chemical formula CaCO3. ... Calcination is the process of heating a substance to a high temperature, but below its melting or fusing point, to bring about thermal decomposition or a phase transition in its physical or chemical constitution. ... Calcium carbonate is a chemical compound, with the chemical formula CaCO3. ... This article, image, template or category belongs in one or more categories. ... Sea surface alkalinity (from the GLODAP climatology) Alkalinity or AT is a measure of the ability of a solution to neutralize acids to the equivalence point of carbonate or bicarbonate. ... For the hazard, see corrosive. ... For other uses, see PH (disambiguation). ... Acids and bases: Acid-base extraction Acid-base reaction Acid dissociation constant Acidity function Buffer solutions pH Proton affinity Self-ionization of water Acids: Lewis acids Mineral acids Organic acids Strong acids Superacids Weak acids Bases: Lewis bases Organic bases Strong bases Superbases Non-nucleophilic bases Weak bases edit A...


Chlorides

Chlorides, particularly calcium chloride, have been used to shorten the setting time of concrete.[18] However, calcium chloride and (to a lesser extent) sodium chloride have been shown to leach calcium hydroxide and cause chemical changes in Portland cement, leading to loss of strength,[19] as well as attacking the steel reinforcement present in most concrete. R-phrases S-phrases , , Related Compounds Other anions calcium fluoride calcium bromide calcium iodide Other cations magnesium chloride strontium chloride Supplementary data page Structure and properties n, εr, etc. ... R-phrases 36 S-phrases none Flash point Non-flammable Related Compounds Other anions NaF, NaBr, NaI Other cations LiCl, KCl, RbCl, CsCl, MgCl2, CaCl2 Related salts Sodium acetate Supplementary data page Structure and properties n, εr, etc. ... It has been suggested that Portlandite be merged into this article or section. ...


Sulphates

Sulphates in solution in contact with concrete can cause chemical changes to the cement, which can cause significant microstructural effects leading to the weakening of the cement binder.


Leaching

Physical damage

Damage can occur during the casting and de-shuttering processes. The corners of beams for instance, can be damaged during the removal of shuttering because they are less effectively compacted by means of vibration (improved by using form-vibrators). Other physical damage can be caused by the use of steel shuttering without base plates. The steel shuttering pinches the top surface of a concrete slab due to weight of the next slab being constructed.


Types of concrete

A highway paved with concrete.
A highway paved with concrete.
Regular concrete paving blocks
Regular concrete paving blocks

Various types of concrete have been developed for specialist application and have become known by these names. Image File history File linksMetadata Size of this preview: 800 × 599 pixelsFull resolution (2288 × 1712 pixel, file size: 741 KB, MIME type: image/jpeg) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Interstate Highway System Interstate 355 Metadata... Image File history File linksMetadata Size of this preview: 800 × 599 pixelsFull resolution (2288 × 1712 pixel, file size: 741 KB, MIME type: image/jpeg) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Interstate Highway System Interstate 355 Metadata... For other uses, see Highway (disambiguation). ... Image File history File linksMetadata Size of this preview: 800 × 532 pixelsFull resolution (3008 × 2000 pixel, file size: 4. ... Image File history File linksMetadata Size of this preview: 800 × 532 pixelsFull resolution (3008 × 2000 pixel, file size: 4. ...


Regular concrete

Regular concrete is the lay term describing concrete that is produced by following the mixing instructions that are commonly published on packets of cement, typically using sand or other common material as the aggregate, and often mixed in improvised containers. This concrete can be produced to yield a varying strength from about 10 MPa to about 40 MPa, depending on the purpose, ranging from blinding to structural concrete respectively. Many types of pre-mixed concrete are available which include powdered cement mixed with an aggregate, needing only water.


Typically, a batch of concrete can be made by using 1 part Portland cement, 2 parts dry sand, 3 parts dry stone, 1/2 part water. The parts are in terms of weight – not volume. For example, 1 cubic foot of concrete would be made using 22 lbs cement, 10 lbs water, 41 lbs dry sand, 70 lbs dry stone (1/2" to 3/4" stone). This would make 1 cubic foot of concrete and would weigh about 143 lbs. The sand should be mortar or brick sand (washed and filtered if possible) and the stone should be washed if possible. Organic materials (leaves, twigs, etc) should be removed from the sand and stone to ensure the highest strength.


High-strength concrete

High-strength concrete has a compressive strength generally greater than 6,000 pounds per square inch (40 MPa). High-strength concrete is made by lowering the water-cement (W/C) ratio to 0.35 or lower. Often silica fume is added to prevent the formation of free calcium hydroxide crystals in the cement matrix, which might reduce the strength at the cement-aggregate bond.


Low W/C ratios and the use of silica fume make concrete mixes significantly less workable, which is particularly likely to be a problem in high-strength concrete applications where dense rebar cages are likely to be used. To compensate for the reduced workability, superplasticizers are commonly added to high-strength mixtures. Aggregate must be selected carefully for high-strength mixes, as weaker aggregates may not be strong enough to resist the loads imposed on the concrete and cause failure to start in the aggregate rather than in the matrix or at a void, as normally occurs in regular concrete.


In some applications of high-strength concrete the design criterion is the elastic modulus rather than the ultimate compressive strength. An elastic modulus, or modulus of elasticity, is the mathematical description of an object or substances tendency to be deformed when a force is applied to it. ...


High-performance concrete

High-performance concrete (HPC) is a relatively new term used to describe concrete that conforms to a set of standards above those of the most common applications, but not limited to strength. While all high-strength concrete is also high-performance, not all high-performance concrete is high-strength. Some examples of such standards currently used in relation to HPC are:

  • Ease of placement
  • Compaction without segregation
  • Early age strength
  • Long-term mechanical properties
  • Permeability
  • Density
  • Heat of hydration
  • Toughness
  • Volume stability
  • Long life in severe environments

Self-consolidating concretes

During the 1980s a number of countries including Japan, Sweden and France developed concretes that are self-compacting, known as self-consolidating concrete in the United States. This self-consolidating concrete (SCCs) is characterized by:

  • extreme fluidity as measured by flow, typically between 650-750 mm on a flow table, rather than slump(height)
  • no need for vibrators to compact the concrete
  • placement being easier.
  • no bleed water, or aggregate segregation
  • Increased Liquid Head Pressure, Can be detrimental to Safety and workmanship

SCC can save up to 50% in labor costs due to 80% faster pouring and reduced wear and tear on formwork. This article or section does not cite its references or sources. ... Wear and tear is a term for damage that naturally and inevitably occurs due to normal use or aging. ... Modular steel frame formwork for a foundation. ...


As of 2005, self-consolidating concretes account for 10-15% of concrete sales in some European countries. In the US precast concrete industry, SCC represents over 75% of concrete production. 38 departments of transportation in the US accept the use of SCC for road and bridge projects. 2005 is a common year starting on Saturday of the Gregorian calendar. ... It has been suggested that Transportation in Alaska be merged into this article or section. ...


This emerging technology is made possible by the use of polycarboxylates plasticizer instead of older naphthalene based polymers, and viscosity modifiers to address aggregate segregation. Plasticizers are additives that soften the materials (usually a plastic or a concrete mix) they are added to. ...


Shotcrete

Main article: Shotcrete

Shotcrete (also known by the trade name Gunite) uses compressed air to shoot concrete onto (or into) a frame or structure. Shotcrete is frequently used against vertical soil or rock surfaces, as it eliminates the need for formwork. It is sometimes used for rock support, especially in tunnelling. Shotcrete and gunite are two commonly used terms for sprayed concrete. ... Modular steel frame formwork for a foundation. ... The word tunneling (also spelled tunnelling) has more than one meaning. ...


There are two application methods for shotcrete.

  • dry-mix – the dry mixture of cement and aggregates is filled into the machine and conveyed with compressed air through the hoses. The water needed for the hydration is added at the nozzle.
  • wet-mix – the mixes are prepared with all necessary water for hydration. The mixes are pumped through the hoses. At the nozzle compressed air is added for spraying.

For both methods additives such as accelerators and fiber reinforcement may be used.[20] Compressed air is used to refer to: Pneumatics, the use of pressurized gases to do work, as used in the Air car Breathing gas, often used in scuba diving, also to inflate buoyancy devices Compressed air can also be used for cooling using a vortex tube. ... An accelerator is an agent used to speed the chemical hardening of plastic materials such as concrete. ...


Pervious concrete

Pervious concrete contains a network of holes or voids, to allow air or water to move through the concrete. Permeable paving, also called pervious paving or porous pavement, is a term used to describe paving methods for roads, parking lots and walkways that allow the movement of water and air through the paving material. ...


It is formed by leaving out some or all of the fine aggregate (fines), the remaining large aggregate then is bound by a relatively small amount of cement paste. When set, typically between 15 and 25% of the concrete volume are voids, allowing water to drain at around 5 gal/ft²/ min or 200 L/m²/min) through the concrete.


Pervious concrete allows water to drain naturally through roadway or other structures, reducing the amount of artificial drainage needed, and allowing the water to naturally replenish groundwater Drainage is the natural or artificial removal of surface and sub-surface water from a given area. ... Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of lithologic formations. ...


It can significantly reduce noise, by allowing air squeezed between vehicle tyres and the roadway to escape.


Cellular concrete

Aerated concrete produced by the addition of an air entraining agent to the concrete (or a lightweight aggregate like expanded clay pellets or cork granules and vermiculite) is sometimes called Cellular concrete. Expanded clay pellets, most commonly known under the brand name LECA (acronym of light expanded clay aggregate), also known as Hydroton and under the non-proprietary terms fired clay pebble, grow rocks, expanded clay (pellets) or hydrocorns, are small globes of burnt and puffed clay, used in construction and farming... Lightweight Expanded Clay Aggregate, also known as fired clay pebble and grow rocks or Hydrocorns, has a low thermal conductivity coefficient. ... For other uses, see Cork. ... Vermiculite is a natural, non toxic mineral that expands with the application of heat. ...

See also: Aerated autoclaved concrete

Stacked blocks of AAC. Autoclaved Aerated concrete (AAC), or otherwise known as Autoclave Cellular Concrete (ACC), is a lightweight, precast building material. ...

Cork-cement composites

Cork granules are obtained during production of bottle stoppers from the treated bark of Cork oak or Quercus suber trees.[21] These trees are mainly found in Portugal, Spain and North Africa.[22] Portugal is the largest cork producing country, followed by Spain. The waste cork granules have a density of about 300 kg/m³, which is lower than that of most of the lightweight aggregates used for making lightweight concrete. It has been found that cork granules do not significantly influence cement hydration. However, cork dust can influence hydration.[23] Cork cement composites have several advantages over standard concrete, such as lower thermal conductivities, lower densities and good energy absorption characteristics. These composites can be made of density from 400 to 1500 kg/m³, compressive strength from 1 to 26 MPa, and flexural strength from 0.5 to 4.0 MPa. For other uses, see Cork. ... Binomial name L. The Cork Oak (Quercus suber) is a medium-sized, evergreen oak tree in the section Quercus sect. ...


Roller-compacted concrete

Roller-compacted concrete, sometimes called rollcrete, is a low-cement-content stiff concrete placed using techniques borrowed from earthmoving and paving work. The concrete is placed on the surface to be covered, and is compacted in place using large heavy rollers typically used in earthwork. The concrete mix achieves a high density and cures over time into a strong monolithic block.[24] Roller-compacted concrete is typically used for concrete pavement, but has also been used to build concrete dams, as the low cement content causes less heat to be generated while curing than typical for conventionally placed massive concrete pours.


Glass concrete

The use of recycled glass as aggregate in concrete has become popular in modern times, with large scale research being carried out at Columbia University in New York. This greatly enhances the aesthetic appeal of the concrete. Recent research findings have shown that concrete made with recycled glass aggregates have shown better long term strength and better thermal insulation due to its better thermal properties of the glass aggregates. [1]


Asphalt concrete

Strictly speaking, asphalt is a form of concrete as well, with bituminous materials replacing cement as the binder. Asphalt As shown in this cross-section, many older roadways are smoothed by applying a thin layer of asphalt concrete to the existing portland cement concrete. ... Ewer from Iran, dated 1180-1210CE. Composed of brass worked in repoussé and inlaid with silver and bitumen. ...


Rapid strength concrete

This type of concrete is able to develop high resistance within few hours after been manufactured. This feature has advantages such as removing the formwork early and to move forward in the building process at record time, repair road surfaces that become fully operational in just few hours.


Rubberized concrete

While "rubberized asphalt concrete" is common, rubberized Portland cement concrete ("rubberized PCC") is still undergoing experimental tests, as of 2007 [2] [3] [4] [5]. Rubberized asphalt is pavement material that consists of regular asphalt concrete mixed with crumb rubber -- ground, used tires that would otherwise be discarded or take up space in landfills. ...


Polymer concrete

Polymer concrete is concrete which uses polymers to bind the aggregate. Polymer concrete can gain a lot of strength in a short amount of time. For example, a polymer mix may reach 5000 psi in only four hours. Polymer concrete is generally more expensive than conventional concretes. Polymer concrete is an engineering material, composed by a thermosetting resin binder (initially liquid) and carefully graded minerals such as quartz, granite and bassalt particles. ...


Limecrete

Limecrete or lime concrete is concrete where cement is replaced by lime.[25] This article or section does not adequately cite its references or sources. ...


Concrete testing

Compression testing of a concrete cylinder
Compression testing of a concrete cylinder
Same cylinder after failure
Same cylinder after failure

Engineers usually specify the required compressive strength of concrete, which is normally given as the 28 day compressive strength in megapascals (MPa) or pounds per square inch (psi). Twenty eight days is a long wait to determine if desired strengths are going to be obtained, so three-day and seven-day strengths can be useful to predict the ultimate 28-day compressive strength of the concrete. A 25% strength gain between 7 and 28 days is often observed with 100% OPC (ordinary Portland cement) mixtures, and up to 40% strength gain can be realized with the inclusion of pozzolans and supplementary cementitious materials (SCM's) such as fly ash and/or slag cement. As strength gain depends on the type of mixture, its constituents, the use of standard curing, proper testing and care of cylinders in transport, etc. it becomes imperative to proactively rely on testing the fundamental properties of concrete in its fresh, plastic state. Image File history File linksMetadata Download high-resolution version (1680x2036, 837 KB) A lightweight/low-strength (~80 pounds per cubic foot) concrete test cylinder under compression testing. ... Image File history File linksMetadata Download high-resolution version (1680x2036, 837 KB) A lightweight/low-strength (~80 pounds per cubic foot) concrete test cylinder under compression testing. ... Image File history File linksMetadata Download high-resolution version (2604x1509, 1291 KB) A lightweight/low-strength (~80 pounds per cubic foot) concrete cylinder after failing under load in a compression test. ... Image File history File linksMetadata Download high-resolution version (2604x1509, 1291 KB) A lightweight/low-strength (~80 pounds per cubic foot) concrete cylinder after failing under load in a compression test. ... A square inch is by definition the area enclosed by a square with sides each 1 inch long. ...


Concrete is typically sampled while being placed, with testing protocols requiring that test samples be cured under laboratory conditions (standard cured). Additional samples may be field cured (non-standard) for the purpose of early 'stripping' strengths, that is, form removal, evaluation of curing, etc. but the standard cured cylinders comprise acceptance criteria. Concrete tests can measure the "plastic" (unhydrated) properties of concrete prior to, and during placement. As these properties affect the hardened compressive strength and durability of concrete (resistance to freeze-thaw), the properties of slump (workability), temperature, density and age are monitored to ensure the production and placement of 'quality' concrete. Tests are performed per ASTM International or CSA (Canadian Standards Association) and European methods and practices. Technicians performing concrete tests MUST be certified. Structural design, material design and properties are often specified in accordance with ACI American Concrete Institute) code (www.concrete.org); with test methods, production and delivery under the "prescription" or "performance" purchasing options per ASTM C94 (www.astm.org). ASTM International (ASTM) is an international standards developing organization that develops and publishes voluntary technical standards for a wide range of materials, products, systems, and services. ... CSA Logo with C and US Established in 1919, the Canadian Standards Association (CSA) is a world leader in safety standards testings. ... I NEED TO FUCK SOMEONE! I AM TIRED OF PORN! SOMEONE HELP ME! ...


Compressive-strength tests are conducted using an instrumented hydraulic ram to compress a cylindrical or cubic sample to failure. Tensile strength tests are conducted either by three-point bending of a prismatic beam specimen or by compression along the sides of a cylindrical specimen. A hydraulic ram that drives a fountain at the Centre for Alternative Technology A hydraulic ram is a water-powered cyclic pump. ...


Concrete recycling

Main article: Concrete recycling

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. When structures made of concrete are to be demolished, concrete recycling is an increasingly common method of disposing of the rubble. ... Look up landfill in Wiktionary, the free dictionary. ...


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. A crusher is a machine designed to reduce large solid chunks of raw material into smaller chunks. ...


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 byproducts of concrete based waste. A tied rebar beam cage. ... For other uses, see Magnet (disambiguation). ... Aggregate base is typically composed of crushed rock comprised of material capable of passing through a 3/4 inch rock screen. ... is the 62nd day of the year (63rd in leap years) in the Gregorian calendar. ... For the Jimi Hendrix song, see 1983. ...


Recycling concrete provides environmental benefits, conserving landfill space and use as aggregate reduces the need for gravel mining. Limestone Quarry Construction aggregate, or simply, aggregate, is a broad category of coarse particulate material used in construction, including sand, gravel, crushed stone, slag, and recycled concrete. ... El Chino, located near Silver City, New Mexico, is an open-pit copper mine Open-pit mining, or opencast mining, refers to a method of extracting rock or minerals from the earth by their removal from an open pit or borrow. ...


Use of concrete in structures

Mass concrete structures

These include gravity dams such as the 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. dam stands for dekametre. ... For the dam near Westerville, Ohio, see Hoover Dam (Ohio). ... The Three Gorges Dam (simplified Chinese: ; traditional Chinese: ; pinyin: ) is a Chinese hydroelectric river dam that spans the Yangtze River in Sandouping, Yichang, Hubei, China. ... Breakwaters create safe harbors, but can also trap sediment moving along the coast. ...


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. Reinforced concrete at Sainte Jeanne dArc Church (Nice, France): architect Jacques Dror, 1926–1933 Reinforced concrete, also called ferroconcrete in some countries, is concrete in which reinforcement bars (rebars) or fibers have been incorporated to strengthen a material that would otherwise be brittle. ...


Prestressed concrete structures

Main article: Prestressed concrete

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. Traditional reinforced concrete is based on the use of steel reinforcement bars, rebar, inside poured concrete. ... Compressive stress is the stress applied to materials resulting in their compaction (decrease of volume). ...


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.


See also

There are very few or no other articles that link to this one. ... Brutalism is an architectural style that spawned from the modernist architectural movement and which flourished from the 1950s to the 1970s. ... Construction on the North Bytown Bridge in Ottawa, Canada. ... For other uses, see Cement (disambiguation). ... Papercrete is a fairly new construction material that consists of re-pulped paper fiber with portland cement or clay and/or other dirt added. ... 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. ... A concrete canoe is a canoe made of concrete, typically created for an engineering competition. ... This portable concrete/mortar mixer has wheels so it can be moved around by hand, and its rotation is powered by mains electricity. ... A stack of rectangular concrete blocks A Concrete masonry unit (CMU) [US], concrete block, or breeze block [UK], cinder block or foundation block [US], clinker block (if bottom ash or clinker is used as an aggregate) is a large rectangular brick used in construction. ... When structures made of concrete are to be demolished, concrete recycling is an increasingly common method of disposing of the rubble. ... Fireproofing, a passive fire protection measure, subject to bounding, refers to the act of making materials or structures more resistant to fire, or to those materials themselves. ... Modular steel frame formwork for a foundation. ... Controlled Permeability Formwork (CPF) CPF is the only system proven to significantly enhances the durability of surface concrete during the casting process. ... LiTraCon (light transmitting concrete) is a translucent concrete product. ... HPFRCCs, commonly referred to as bendable concretes, are a fairly new variety of cement based composites composed of fine aggregates, cement, water, a super plasticizer, and a number of polymeric or metallic fibers that possess the unique ability to, as the name implies, bend. ... Metakaolin is a dehyroxylated form of kaolinite. ... Mortar holding weathered bricks. ... Plasticizers are additives that soften the materials (usually a plastic or a concrete mix) they are added to. ... Prefabrication is the practice of manufacturing the parts of an assembly in one location, ready for them to be assembled in another place. ... Pykrete is a composite material made of approximately 14% sawdust (or, less frequently, wood pulp) and 86% water by weight then frozen, invented by Max Perutz and proposed during World War II by Geoffrey Pyke to the Royal Navy of the United Kingdom as a candidate material for making a... Slab-on-grade foundations are a building practice whereby the concrete slab that is to serve as the foundation for the structure is formed from a mold set into the ground. ... Asphalt As shown in this cross-section, many older roadways are smoothed by applying a thin layer of asphalt concrete to the existing portland cement concrete. ... Stacked blocks of AAC. Autoclaved Aerated concrete (AAC), or otherwise known as Autoclave Cellular Concrete (ACC), is a lightweight, precast building material. ... Decorative concrete involves utilizing concrete in roles that are not strictly related to its functional elements. ... There are very few or no other articles that link to this one. ... Traditional reinforced concrete is based on the use of steel reinforcement bars, rebar, inside poured concrete. ... A precast concrete walled house in construction Precast concrete is an ancient type of construction material made with concrete cast in a reusable mold or form and cured in a controlled environment, then transported to the construction site and lifted into place. ... Ready-mix concrete is a type of concrete that is manufactured in a factory according to a set recipe, and then delivered to a worksite, often by truck. ... Reinforced concrete at Sainte Jeanne dArc Church (Nice, France): architect Jacques Dror, 1926–1933 Reinforced concrete, also called ferroconcrete in some countries, is concrete in which reinforcement bars (rebars) or fibers have been incorporated to strengthen a material that would otherwise be brittle. ... Seacrete, also known as Seament and Sea Cement, is a substance formed by electro-accumulation of minerals dissolved in seawater. ...

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). Retrieved on 2008-01-16.
  3. ^ Wild, Stan (27 Jan. 2007). "Concrete evidence". New Scientist (2588): 21. 
  4. ^ Missing File
  5. ^ a b U.S. Federal Highway Administration. Admixtures. Retrieved on 2007-01-25.
  6. ^ Cement Admixture Association. CAA. www.admixtures.org.uk. Retrieved on 2008-04-02.
  7. ^ 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. 
  8. ^ U.S. Federal Highway Administration. Fly Ash. Retrieved on 2007-01-24.
  9. ^ U.S. Federal Highway Administration. Ground Granulated Blast-Furnace Slag. Retrieved on 2007-01-24.
  10. ^ U.S. Federal Highway Administration. Silica Fume. Retrieved on 2007-01-24.
  11. ^ Premixed Cement Paste
  12. ^ Measuring, Mixing, Transporting, and Placing Concrete
  13. ^ U.S. Patent 5,443,313  - Method for producing construction mixture for concrete
  14. ^ David Hambling (April 13, 2007). Iran's Invulnerable Bunkers?. Wired. Retrieved on 2008-01-29.
  15. ^ Thermal Coefficient of Portland Cement Concrete. Portland Cement Concrete Pavements Research. Federal Highway Administration. Retrieved on 2008-01-29.
  16. ^ Jones, Katrina (1999). Density of Concrete. The Physics Factbook.
  17. ^ Norwegian Building Research Institute, publication 24. Fire-damage to buildings.
  18. ^ Accelerating Concrete Set Time (1999-06-01). Retrieved on 2007-01-16.
  19. ^ ;Kejin Wanga, Daniel E. Nelsena and Wilfrid A. Nixon, "Damaging effects of deicing chemicals on concrete materials", Cement and Concrete Composites Vol. 28(2), pp 173-188. doi:10.1016/j.cemconcomp.2005.07.006
  20. ^ American Shotcrete Association Homepage
  21. ^ Gibson, L.J. & Ashby, M.F. 1999. Cellular Solids: Structure and Properties; 2nd Edition (Paperback), Cambridge Uni. Press. pp.453-467.
  22. ^ Olley, P. 1992. Cork. In: Doran, D.K.(Ed.). Construction Materials Reference Book, Chapter 26. Butterworth, Oxford. pp. 26/1-5.
  23. ^ Karade S.R., Irle M.A., Maher K. 2006. Influence of granule properties and concentration on cork-cement compatibility. Holz als Roh- und Werkstoff. 64: 281–286 (DOI 10.1007/s00107-006-0103-2).
  24. ^ Roller-Compacted Concrete (RCC) Pavements | Portland Cement Association (PCA)
  25. ^ An Investigation Into The Feasibility Of Timber And Limecrete Composite Flooring

Bjørn Lomborg (born January 6, 1965) is an Adjunct Professor at the Copenhagen Business School and a former director of the Environmental Assessment Institute in Copenhagen. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 152nd day of the year (153rd in leap years) in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 16th day of the year in the Gregorian calendar. ... The Federal Highway Administration (FHWA) is a division of the United States Department of Transportation that specializes in highway transportation. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 25th day of the year in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 92nd day of the year (93rd in leap years) in the Gregorian calendar. ... The Federal Highway Administration (FHWA) is a division of the United States Department of Transportation that specializes in highway transportation. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 24th day of the year in the Gregorian calendar. ... The Federal Highway Administration (FHWA) is a division of the United States Department of Transportation that specializes in highway transportation. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 24th day of the year in the Gregorian calendar. ... The Federal Highway Administration (FHWA) is a division of the United States Department of Transportation that specializes in highway transportation. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 24th day of the year in the Gregorian calendar. ... is the 103rd day of the year (104th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 29th day of the year in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 29th day of the year in the Gregorian calendar. ... Events of 2008: (EMILY) Me Lesley and MIley are going to China! This article is about the year. ... is the 152nd day of the year (153rd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 16th day of the year in the Gregorian calendar. ...

External links

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