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For other uses, see Asphalt (disambiguation). Note: The terms bitumen and asphalt are mostly interchangeable, How To Pave A Driveway With Asphalt in Rosebank except where asphalt is used as a shorthand for asphalt concrete. Natural bitumen from the Dead Sea Refined asphalt The University of Queensland pitch drop experiment, demonstrating the viscosity of asphalt
Asphalt (/ˈæsˌfɔːlt, -ˌfɑːlt/), also known as bitumen (UK English: /ˈbɪtʃəmən, ˈbɪtjʊmən/,[1] US English: /bɪˈt(j)uːmən, baɪˈt(j)uːmən/)[2] is a sticky, black, and highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term asphaltum was also used.
The primary use (70%) of asphalt Asphalt Companies Hiring is in road construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete. Its other main uses are for bituminous waterproofing products, including production of roofing felt and for sealing flat roofs.
The terms "asphalt" and "bitumen" are often used interchangeably to mean both natural and manufactured forms of the substance. In American English, "asphalt" (or "asphalt cement") is commonly used for a refined residue from the distillation process of selected crude oils. Outside the United States, the product is often called "bitumen", and geologists worldwide often prefer the term for the naturally occurring variety. Common colloquial usage often refers to various forms of asphalt as "tar", as in the name of the La Brea Tar Pits.
Crocodile cracking
Naturally occurring asphalt is sometimes specified by the term "crude bitumen". How To Pave A Driveway With Asphalt Its viscosity is similar to that of cold molasses[6][7] while the material obtained from the fractional distillation of crude oil boiling at 525 °C (977 °F) is sometimes referred to as "refined bitumen". The Canadian province of Alberta has most of the world's reserves of natural asphalt in the Athabasca oil sands, which cover 142,000 square kilometres (55,000 sq mi), an area larger than England.
The word "asphalt" is derived from the late Middle English, in turn from French asphalte, based on Late Latin asphalton, asphaltum, which is the latinisation of the Greek ἄσφαλτος (ásphaltos, ásphalton), a word meaning "asphalt/bitumen/pitch" which perhaps derives from ἀ-, "without" and σφάλλω (sfallō), "make fall". Top Asphalt Companies the first use of asphalt by the ancients was in the nature of a cement for securing or joining together various objects, and it thus seems likely that the name itself was expressive of this application. Specifically, Herodotus mentioned that bitumen was brought to Babylon to build its gigantic fortification wall.[11] From the Greek, the word passed into late Latin, and thence into French (asphalte) and English ("asphaltum" and "asphalt"). In French, the term asphalte is used for naturally occurring asphalt-soaked limestone deposits, and for specialised manufactured products with fewer voids or greater bitumen content than the "asphaltic concrete" used to pave roads.
The expression "bitumen" originated in the Sanskrit words jatu, meaning "pitch", and jatu-krit, meaning "pitch creating" or "pitch producing" (referring to coniferous or resinous trees). The Latin equivalent is claimed by some to be originally gwitu-men (pertaining to pitch), and by others, pixtumens (exuding or bubbling pitch), which was subsequently shortened to bitumen, thence passing via French into English. From the same root is derived the Anglo-Saxon word cwidu (mastix), the German word Kitt (cement or mastic) and the old Norse word kvada.
In British English, "bitumen" is used instead of "asphalt". The word "asphalt" is instead used to refer to asphalt concrete, a mixture of construction aggregate and asphalt itself (also called "tarmac" in common parlance). Bitumen mixed with clay was usually called "asphaltum",[13] but the term is less commonly used today.[citation needed]
Road surface
In Australian English, "bitumen" is often used as the generic term for road surfaces.
In American English, "asphalt" is equivalent to the British "bitumen". However, "asphalt" is also commonly used as a shortened form of "asphalt concrete" (therefore equivalent to the British "asphalt" or "tarmac").
In Canadian English, the word "bitumen" is used to refer to the vast Canadian deposits of extremely heavy crude oil,[14] while "asphalt" is used for the oil refinery product. Diluted bitumen (diluted with naphtha to make it flow in pipelines) is known as "dilbit" in the Canadian petroleum industry, while bitumen "upgraded" to synthetic crude oil is known as "syncrude", and syncrude blended with bitumen is called "synbit".[15]
"Bitumen" is still the preferred geological term for naturally occurring deposits of the solid or semi-solid form of petroleum. "Bituminous rock" is a form of sandstone impregnated with bitumen. The tar sands of Alberta, Canada are a similar material.
Neither of the terms "asphalt" or "bitumen" should be confused with tar or coal tars.[further explanation needed]
See also: Asphaltene
The components of asphalt include four main classes of compounds:
The naphthene aromatics and polar aromatics are typically the majority components. Most natural bitumens also contain organosulfur compounds, resulting in an overall sulfur content of up to 4%. Nickel and vanadium are found at <10 parts per million, as is typical of some petroleum.
The substance is soluble in carbon disulfide. It is commonly modelled as a colloid, with asphaltenes as the dispersed phase and maltenes as the continuous phase.[16] "It is almost impossible to separate and identify all the different molecules of asphalt, because the number of molecules with different chemical structure is extremely large".
Asphalt may be confused with coal tar, which is a visually similar black, thermoplastic material produced by the destructive distillation of coal. During the early and mid-20th century, when town gas was produced, coal tar was a readily available byproduct and extensively used as the binder for road aggregates. The addition of coal tar to macadam roads led to the word "tarmac", which is now used in common parlance to refer to road-making materials. However, since the 1970s, when natural gas succeeded town gas, asphalt has completely overtaken the use of coal tar in these applications. Other examples of this confusion include the La Brea Tar Pits and the Canadian oil sands, both of which actually contain natural bitumen rather than tar. "Pitch" is another term sometimes informally used at times to refer to asphalt, as in Pitch Lake.
Bituminous outcrop of the Puy de la Poix, Clermont-Ferrand, France
The majority of asphalt used commercially is obtained from petroleum.[18] Nonetheless, large amounts of asphalt occur in concentrated form in nature. Naturally occurring deposits of bitumen are formed from the remains of ancient, microscopic algae (diatoms) and other once-living things. These remains were deposited in the mud on the bottom of the ocean or lake where the organisms lived. Under the heat (above 50 °C) and pressure of burial deep in the earth, the remains were transformed into materials such as bitumen, kerogen, or petroleum.
Natural deposits of bitumen include lakes such as the Pitch Lake in Trinidad and Tobago and Lake Bermudez in Venezuela. Natural seeps occur in the La Brea Tar Pits and in the Dead Sea.
Bitumen also occurs in unconsolidated sandstones known as "oil sands" in Alberta, Canada, and the similar "tar sands" in Utah, US. The Canadian province of Alberta has most of the world's reserves, in three huge deposits covering 142,000 square kilometres (55,000 sq mi), an area larger than England or New York state. These bituminous sands contain 166 billion barrels (26.4×10^9 m3) of commercially established oil reserves, giving Canada the third largest oil reserves in the world. Although historically it was used without refining to pave roads, nearly all of the output is now used as raw material for oil refineries in Canada and the United States.
The world's largest deposit of natural bitumen, known as the Athabasca oil sands, is located in the McMurray Formation of Northern Alberta. This formation is from the early Cretaceous, and is composed of numerous lenses of oil-bearing sand with up to 20% oil.[19] Isotopic studies show the oil deposits to be about 110 million years old.[20] Two smaller but still very large formations occur in the Peace River oil sands and the Cold Lake oil sands, to the west and southeast of the Athabasca oil sands, respectively. Of the Alberta deposits, only parts of the Athabasca oil sands are shallow enough to be suitable for surface mining. The other 80% has to be produced by oil wells using enhanced oil recovery techniques like steam-assisted gravity drainage.
Much smaller heavy oil or bitumen deposits also occur in the Uinta Basin in Utah, US. The Tar Sand Triangle deposit, for example, is roughly 6% bitumen.
Bitumen may occur in hydrothermal veins. An example of this is within the Uinta Basin of Utah, in the US, where there is a swarm of laterally and vertically extensive veins composed of a solid hydrocarbon termed Gilsonite. These veins formed by the polymerization and solidification of hydrocarbons that were mobilized from the deeper oil shales of the Green River Formation during burial and diagenesis.
Bitumen is similar to the organic matter in carbonaceous meteorites.[23] However, detailed studies have shown these materials to be distinct.[24] The vast Alberta bitumen resources are considered to have started out as living material from marine plants and animals, mainly algae, that died millions of years ago when an ancient ocean covered Alberta. They were covered by mud, buried deeply over time, and gently cooked into oil by geothermal heat at a temperature of 50 to 150 °C (120 to 300 °F). Due to pressure from the rising of the Rocky Mountains in southwestern Alberta, 80 to 55 million years ago, the oil was driven northeast hundreds of kilometres and trapped into underground sand deposits left behind by ancient river beds and ocean beaches, thus forming the oil sands.
The use of natural bitumen for waterproofing, and as an adhesive dates at least to the fifth millennium BC, with a crop storage basket discovered in Mehrgarh, of the Indus Valley Civilization, lined with it.[25] By the 3rd millennia BC refined rock asphalt was in use, in the region, and was used to waterproof the Great Bath, Mohenjo-daro.
In the ancient Middle East, the Sumerians used natural bitumen deposits for mortar between bricks and stones, to cement parts of carvings, such as eyes, into place, for ship caulking, and for waterproofing.[3] The Greek historian Herodotus said hot bitumen was used as mortar in the walls of Babylon.
The 1 kilometre (0.62 mi) long Euphrates Tunnel beneath the river Euphrates at Babylon in the time of Queen Semiramis (ca. 800 BC) was reportedly constructed of burnt bricks covered with bitumen as a waterproofing agent.
Bitumen was used by ancient Egyptians to embalm mummies.[3][28] The Persian word for asphalt is moom, which is related to the English word mummy. The Egyptians' primary source of bitumen was the Dead Sea, which the Romans knew as Palus Asphaltites (Asphalt Lake).
Approximately 40 AD, Dioscorides described the Dead Sea material as Judaicum bitumen, and noted other places in the region where it could be found.[29] The Sidon bitumen is thought to refer to material found at Hasbeya.[30] Pliny refers also to bitumen being found in Epirus. It was a valuable strategic resource, the object of the first known battle for a hydrocarbon deposit—between the Seleucids and the Nabateans in 312 BC.
In the ancient Far East, natural bitumen was slowly boiled to get rid of the higher fractions, leaving a thermoplastic material of higher molecular weight that when layered on objects became quite hard upon cooling. This was used to cover objects that needed waterproofing,[3] such as scabbards and other items. Statuettes of household deities were also cast with this type of material in Japan, and probably also in China.
In North America, archaeological recovery has indicated bitumen was sometimes used to adhere stone projectile points to wooden shafts.[32] In Canada, aboriginal people used bitumen seeping out of the banks of the Athabasca and other rivers to waterproof birch bark canoes, and also heated it in smudge pots to ward off mosquitoes in the summer.
In 1553, Pierre Belon described in his work Observations that pissasphalto, a mixture of pitch and bitumen, was used in the Republic of Ragusa (now Dubrovnik, Croatia) for tarring of ships.
An 1838 edition of Mechanics Magazine cites an early use of asphalt in France. A pamphlet dated 1621, by "a certain Monsieur d'Eyrinys, states that he had discovered the existence (of asphaltum) in large quantities in the vicinity of Neufchatel", and that he proposed to use it in a variety of ways – "principally in the construction of air-proof granaries, and in protecting, by means of the arches, the water-courses in the city of Paris from the intrusion of dirt and filth", which at that time made the water unusable. "He expatiates also on the excellence of this material for forming level and durable terraces" in palaces, "the notion of forming such terraces in the streets not one likely to cross the brain of a Parisian of that generation".
But the substance was generally neglected in France until the revolution of 1830. In the 1830s there was a surge of interest, and asphalt became widely used "for pavements, flat roofs, and the lining of cisterns, and in England, some use of it had been made of it for similar purposes". Its rise in Europe was "a sudden phenomenon", after natural deposits were found "in France at Osbann (Bas-Rhin), the Parc (Ain) and the Puy-de-la-Poix (Puy-de-Dôme)", although it could also be made artificially.[35] One of the earliest uses in France was the laying of about 24,000 square yards of Seyssel asphalt at the Place de la Concorde in 1835.
Among the earlier uses of bitumen in the United Kingdom was for etching. William Salmon's Polygraphice (1673) provides a recipe for varnish used in etching, consisting of three ounces of virgin wax, two ounces of mastic, and one ounce of asphaltum.[37] By the fifth edition in 1685, he had included more asphaltum recipes from other sources.
The first British patent for the use of asphalt was "Cassell's patent asphalte or bitumen" in 1834.[35] Then on 25 November 1837, Richard Tappin Claridge patented the use of Seyssel asphalt (patent #7849), for use in asphalte pavement,[39][40] having seen it employed in France and Belgium when visiting with Frederick Walter Simms, who worked with him on the introduction of asphalt to Britain.[41][42] Dr T. Lamb Phipson writes that his father, Samuel Ryland Phipson, a friend of Claridge, was also "instrumental in introducing the asphalte pavement (in 1836)".[43] Indeed, mastic pavements had been previously employed at Vauxhall by a competitor of Claridge, but without success.
Claridge obtained a patent in Scotland on 27 March 1838, and obtained a patent in Ireland on 23 April 1838. In 1851, extensions for the 1837 patent and for both 1838 patents were sought by the trustees of a company previously formed by Claridge. Claridge's Patent Asphalte Company—formed in 1838 for the purpose of introducing to Britain "Asphalte in its natural state from the mine at Pyrimont Seysell in France",—"laid one of the first asphalt pavements in Whitehall". Trials were made of the pavement in 1838 on the footway in Whitehall, the stable at Knightsbridge Barracks,"and subsequently on the space at the bottom of the steps leading from Waterloo Place to St. James Park". "The formation in 1838 of Claridge's Patent Asphalte Company (with a distinguished list of aristocratic patrons, and Marc and Isambard Brunel as, respectively, a trustee and consulting engineer), gave an enormous impetus to the development of a British asphalt industry".[45] "By the end of 1838, at least two other companies, Robinson's and the Bastenne company, were in production",[50] with asphalt being laid as paving at Brighton, Herne Bay, Canterbury, Kensington, the Strand, and a large floor area in Bunhill-row, while meantime Claridge's Whitehall paving "continue(d) in good order".
How To Pave A Driveway With Asphalt in Rosebank ?Not to be confused with cement or mortar (masonry). Exterior of the Roman Pantheon, finished 128 AD, the largest unreinforced concrete dome in the world.[1] Interior of the Pantheon dome, seen from beneath. The concrete for the coffered dome was laid on moulds, probably mounted on temporary scaffolding. Opus caementicium exposed in a characteristic Roman arch. In contrast to modern concrete structures, the concrete used in Roman buildings was usually covered with brick or stone.
Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens over time. Most concretes used are lime-based concretes such as Portland cement concrete or concretes made with other hydraulic cements, such as calcium aluminate cements. However, asphalt concrete, which is frequently used for road surfaces, is also a type of concrete, where the cement material is bitumen, and polymer concretes are sometimes used where the cementing material is a polymer.
When aggregate is mixed together with dry Portland cement and water, the mixture forms a fluid slurry that is easily poured and molded into shape. The cement reacts chemically with the water and other ingredients to form a hard matrix that binds the materials together into a durable stone-like material that has many uses.[2] Often, additives (such as pozzolans or superplasticizers) are included in the mixture to improve the physical properties of the wet mix or the finished material. Most concrete is poured with reinforcing materials (such as rebar) embedded to provide tensile strength, yielding reinforced concrete.
Famous concrete structures include the Hoover Dam, the Panama Canal, and the Roman Pantheon. The earliest large-scale users of concrete technology were the ancient Romans, and concrete was widely used in the Roman Empire. The Colosseum in Rome was built largely of concrete, and the concrete dome of the Pantheon is the world's largest unreinforced concrete dome.[3] Today, large concrete structures (for example, dams and multi-storey car parks) are usually made with reinforced concrete.
After the Roman Empire collapsed, use of concrete became rare until the technology was redeveloped in the mid-18th century. Today, concrete is the most widely used human-made material (measured by tonnage).[citation needed]
The word concrete comes from the Latin word "concretus" (meaning compact or condensed),[4] the perfect passive participle of "concrescere", from "con-" (together) and "crescere" (to grow).
Small-scale usage of concrete has been documented to be thousands of years old. Concrete-like materials were used since 6500 BC by the Nabataea traders or Bedouins, who occupied and controlled a series of oases and developed a small empire in the regions of southern Syria and northern Jordan. They discovered the advantages of hydraulic lime, with some self-cementing properties, by 700 BC. They built kilns to supply mortar for the construction of rubble-wall houses, concrete floors, and underground waterproof cisterns. They kept the cisterns secret as these enabled the Nabataea to thrive in the desert.[5] Some of these structures survive to this day.[5]
In the Ancient Egyptian and later Roman eras, builders re-discovered that adding volcanic ash to the mix allowed it to set underwater.
German archaeologist Heinrich Schliemann found concrete floors, which were made of lime and pebbles, in the royal palace of Tiryns, Greece, which dates roughly to 1400–1200 BC.[6][7] Lime mortars were used in Greece, Crete, and Cyprus in 800 BC. The Assyrian Jerwan Aqueduct (688 BC) made use of waterproof concrete.[8] Concrete was used for construction in many ancient structures.[9]
The Romans used concrete extensively from 300 BC to 476 AD, a span of more than seven hundred years.[10] During the Roman Empire, Roman concrete (or opus caementicium) was made from quicklime, pozzolana and an aggregate of pumice. Its widespread use in many Roman structures, a key event in the history of architecture termed the Roman Architectural Revolution, freed Roman construction from the restrictions of stone and brick materials. It enabled revolutionary new designs in terms of both structural complexity and dimension.[11]
Concrete, as the Romans knew it, was a new and revolutionary material. Laid in the shape of arches, vaults and domes, it quickly hardened into a rigid mass, free from many of the internal thrusts and strains that troubled the builders of similar structures in stone or brick.[12]
Modern tests show that opus caementicium had as much compressive strength as modern Portland-cement concrete (ca. 200 kg/cm2 [20 MPa; 2,800 psi]).[13] However, due to the absence of reinforcement, its tensile strength was far lower than modern reinforced concrete, and its mode of application was also different:[14]
Modern structural concrete differs from Roman concrete in two important details. First, its mix consistency is fluid and homogeneous, allowing it to be poured into forms rather than requiring hand-layering together with the placement of aggregate, which, in Roman practice, often consisted of rubble. Second, integral reinforcing steel gives modern concrete assemblies great strength in tension, whereas Roman concrete could depend only upon the strength of the concrete bonding to resist tension.[15]
The long-term durability of Roman concrete structures has been found to be due to its use of pyroclastic (volcanic) rock and ash, whereby crystallization of strätlingite and the coalescence of calcium–aluminum-silicate–hydrate cementing binder helped give the concrete a greater degree of fracture resistance even in seismically active environments.[16] Roman concrete is significantly more resistant to erosion by seawater than modern concrete; it used pyroclastic materials which react with seawater to form Al-tobermorite crystals over time.[17][18]Smeaton's Tower
The widespread use of concrete in many Roman structures ensured that many survive to the present day. The Baths of Caracalla in Rome are just one example. Many Roman aqueducts and bridges, such as the magnificent Pont du Gard in southern France, have masonry cladding on a concrete core, as does the dome of the Pantheon.
After the Roman Empire, the use of burned lime and pozzolana was greatly reduced until the technique was all but forgotten between 500 and the 14th century. From the 14th century to the mid-18th century, the use of cement gradually returned. The Canal du Midi was built using concrete in 1670.[19]
Perhaps the greatest driver behind the modern use of concrete was Smeaton's Tower, the third Eddystone Lighthouse in Devon, England. To create this structure, between 1756 and 1759, British engineer John Smeaton pioneered the use of hydraulic lime in concrete, using pebbles and powdered brick as aggregate.[20]
Developed in England in the 19th century, a method for producing Portland cement was patented by Joseph Aspdin in 1824.[21] Aspdin named it due to its similarity to Portland stone which was quarried on the Isle of Portland in Dorset, England. His son William Aspdin is regarded as the inventor of "modern" Portland cement due to his developments in the 1840s.[22]
Reinforced concrete was invented in 1849 by Joseph Monier.[23] In 1889 the first concrete reinforced bridge was built, and the first large concrete dams were built in 1936, Hoover Dam and Grand Coulee Dam.[24]
Many types of concrete are available, distinguished by the proportions of the main ingredients below. In this way or by substitution for the cementitious and aggregate phases, the finished product can be tailored to its application. Strength, density, as well chemical and thermal resistance are variables.
Aggregate consists of large chunks of material in a concrete mix, generally a coarse gravel or crushed rocks such as limestone, or granite, along with finer materials such as sand.
Cement, most commonly Portland cement, is associated with the general term "concrete." A range of other materials can be used as the cement in concrete too. One of the most familiar of these alternative cements is asphalt concrete. Other cementitious materials such as fly ash and slag cement, are sometimes added as mineral admixtures (see below) - either pre-blended with the cement or directly as a concrete component - and become a part of the binder for the aggregate.
To produce concrete from most cements (excluding asphalt), water is mixed with the dry powder and aggregate, which produces a semi-liquid slurry that can be shaped, typically by pouring it into a form. The concrete solidifies and hardens through a chemical process called hydration. The water reacts with the cement, which bonds the other components together, creating a robust stone-like material.
Chemical admixtures are added to achieve varied properties. These ingredients may accelerate or slow down the rate at which the concrete hardens, and impart many other useful properties including increased tensile strength, entrainment of air and water resistance.
Reinforcement is often included in concrete. Concrete can be formulated with high compressive strength, but always has lower tensile strength. For this reason it is usually reinforced with materials that are strong in tension, typically steel rebar.
Mineral admixtures have become more popular over recent decades. The use of recycled materials as concrete ingredients has been gaining popularity because of increasingly stringent environmental legislation, and the discovery that such materials often have complementary and valuable properties. The most conspicuous of these are fly ash, a by-product of coal-fired power plants, ground granulated blast furnace slag, a byproduct of steelmaking, and silica fume, a byproduct of industrial electric arc furnaces. The use of these materials in concrete reduces the amount of resources required, as the mineral admixtures act as a partial cement replacement. This displaces some cement production, an energetically expensive and environmentally problematic process, while reducing the amount of industrial waste that must be disposed of. Mineral admixtures can be pre-blended with the cement during its production for sale and use as a blended cement, or mixed directly with other components when the concrete is produced.
The mix design depends on the type of structure being built, how the concrete is mixed and delivered, and how it is placed to form the structure.Main article: Cement A few tons of bagged cement. This amount represents about two minutes of output from a 10,000 ton per day cement kiln.
Portland cement is the most common type of cement in general usage. It is a basic ingredient of concrete, mortar and many plasters. British masonry worker Joseph Aspdin patented Portland cement in 1824. It was named because of the similarity of its colour to Portland limestone, quarried from the English Isle of Portland and used extensively in London architecture. It consists of a mixture of calcium silicates (alite, belite), aluminates and ferrites - compounds which combine calcium, silicon, aluminium and iron in forms which will react with water. Portland cement and similar materials are made by heating limestone (a source of calcium) with clay or shale (a source of silicon, aluminium and iron) and grinding this product (called clinker) with a source of sulfate (most commonly gypsum).
In modern cement kilns many advanced features are used to lower the fuel consumption per ton of clinker produced. Cement kilns are extremely large, complex, and inherently dusty industrial installations, and have emissions which must be controlled. Of the various ingredients used to produce a given quantity of concrete, the cement is the most energetically expensive. Even complex and efficient kilns require 3.3 to 3.6 gigajoules of energy to produce a ton of clinker and then grind it into cement. Many kilns can be fueled with difficult-to-dispose-of wastes, the most common being used tires. The extremely high temperatures and long periods of time at those temperatures allows cement kilns to efficiently and completely burn even difficult-to-use fuels.[25]
Combining water with a cementitious material forms a cement paste by the process of hydration. The cement paste glues the aggregate together, fills voids within it, and makes it flow more freely.[26]
As stated by Abrams' law, a lower water-to-cement ratio yields a stronger, more durable concrete, whereas more water gives a freer-flowing concrete with a higher slump.[27] Impure water used to make concrete can cause problems when setting or in causing premature failure of the structure.[28]
Hydration involves many different reactions, often occurring at the same time. As the reactions proceed, the products of the cement hydration process gradually bond together the individual sand and gravel particles and other components of the concrete to form a solid mass.[29]
Reaction:[29]Cement chemist notation: C3S + H → C-S-H + CH Standard notation: Ca3SiO5 + H2O → (CaO)·(SiO2)·(H2O)(gel) + Ca(OH)2 Balanced: 2Ca3SiO5 + 7H2O → 3(CaO)·2(SiO2)·4(H2O)(gel) + 3Ca(OH)2 (approximately; the exact ratios of the CaO, SiO2 and H2O in C-S-H can vary) Crushed stone aggregate Main article: Construction aggregate
Fine and coarse aggregates make up the bulk of a concrete mixture. Sand, natural gravel, and crushed stone are used mainly for this purpose. Recycled aggregates (from construction, demolition, and excavation waste) are increasingly used as partial replacements for natural aggregates, while a number of manufactured aggregates, including air-cooled blast furnace slag and bottom ash are also permitted.
The size distribution of the aggregate determines how much binder is required. Aggregate with a very even size distribution has the biggest gaps whereas adding aggregate with smaller particles tends to fill these gaps. The binder must fill the gaps between the aggregate as well as pasting the surfaces of the aggregate together, and is typically the most expensive component. Thus variation in sizes of the aggregate reduces the cost of concrete.[30] The aggregate is nearly always stronger than the binder, so its use does not negatively affect the strength of the concrete.
Redistribution of aggregates after compaction often creates inhomogeneity due to the influence of vibration. This can lead to strength gradients.[31]
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.
In addition to being decorative, exposed aggregate may add robustness to a concrete.[32]Constructing a rebar cage. This cage will be permanently embedded in poured concrete to create a reinforced concrete structure. Main article: Reinforced concrete
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 adds either steel reinforcing bars, steel fibers, glass fibers, or plastic fibers to carry tensile loads.
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.[33] (See the section on Concrete Production, below.)The common types of admixtures[34] are as follows:
Inorganic materials that 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),[33] or as a replacement for Portland cement (blended cements).[39] Products which incorporate limestone, fly ash, blast furnace slag, and other useful materials with pozzolanic properties into the mix, are being tested and used. This development is due to cement production being one of the largest producers (at about 5 to 10%) of global greenhouse gas emissions,[40] as well as lowering costs, improving concrete properties, and recycling wastes.Concrete plant facility showing a Concrete mixer being filled from the ingredient silos.
Concrete production is the process of mixing together the various ingredients—water, aggregate, cement, and any additives—to produce concrete. Concrete production is time-sensitive. Once the ingredients are mixed, workers must put the concrete in place before it hardens. In modern usage, most concrete production takes place in a large type of industrial facility called a concrete plant, or often a batch plant.
In general usage, concrete plants come in two main types, ready mix plants and central mix plants. A ready mix plant mixes all the ingredients except water, while a central mix plant mixes all the ingredients including water. A central mix plant offers more accurate control of the concrete quality through better measurements of the amount of water added, but must be placed closer to the work site where the concrete will be used, since hydration begins at the plant.
A concrete plant consists of large storage hoppers for various reactive ingredients like cement, storage for bulk ingredients like aggregate and water, mechanisms for the addition of various additives and amendments, machinery to accurately weigh, move, and mix some or all of those ingredients, and facilities to dispense the mixed concrete, often to a concrete mixer truck.
Modern concrete is usually prepared as a viscous fluid, so that it may be poured into forms, which are containers erected in the field to give the concrete its desired shape. Concrete formwork can be prepared in several ways, such as Slip forming and Steel plate construction. Alternatively, concrete can be mixed into dryer, non-fluid forms and used in factory settings to manufacture Precast concrete products.
A wide variety of equipment is used for processing concrete, from hand tools to heavy industrial machinery. Whichever equipment builders use, however, the objective is to produce the desired building material; ingredients must be properly mixed, placed, shaped, and retained within time constraints. Any interruption in pouring the concrete can cause the initially placed material to begin to set before the next batch is added on top. This creates a horizontal plane of weakness called a cold joint between the two batches.[46] Once the mix is where it should be, the curing process must be controlled to ensure that the concrete attains the desired attributes. During concrete preparation, various technical details may affect the quality and nature of the product.
When initially mixed, Portland cement and water rapidly form a gel of tangled chains of interlocking crystals, and components of the gel continue to react over time. Initially the gel is fluid, which improves workability and aids in placement of the material, but as the concrete sets, the chains of crystals join into a rigid structure, counteracting the fluidity of the gel and fixing the particles of aggregate in place. During curing, the cement continues to react with the residual water in a process of hydration. In properly formulated concrete, once this curing process has terminated the product has the desired physical and chemical properties. Among the qualities typically desired, are mechanical strength, low moisture permeability, and chemical and volumetric stability.See also: Volumetric concrete mixer and Concrete mixer
Thorough mixing is essential for the production of uniform, high-quality concrete. For this reason 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.[47] The paste is generally mixed in a high-speed, shear-type mixer at a w/cm (water to cement ratio) of 0.30 to 0.45 by mass. The cement paste premix may include admixtures such as accelerators or retarders, superplasticizers, pigments, or silica fume. The premixed paste is then blended with aggregates and any remaining batch water and final mixing is completed in conventional concrete mixing equipment.[48]Decorative plate made of Nano concrete with High-Energy Mixing (HEM) Pouring and smoothing out concrete at Palisades Park in Washington DC. Main article: Concrete slump test
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, like superplasticizer. Raising the water content or adding chemical admixtures increases concrete workability. Excessive water leads to increased bleeding or segregation of aggregates (when the cement and aggregates start to separate), with the resulting concrete having reduced quality. The use of an aggregate blend with an undesirable gradation[49] can result in a very harsh mix design with a very low slump, which cannot readily be made more workable by addition of reasonable amounts of water. An undesirable gradation can mean using a large aggregate that is too large for the size of the formwork, or which has too few smaller aggregate grades to serve to fill the gaps between the larger grades, or using too little or too much sand for the same reason, or using too little water, or too much cement, or even using jagged crushed stone instead of smoother round aggregate such as pebbles. Any combination of these factors and others may result in a mix which is too harsh, i.e., which does not flow or spread out smoothly, is difficult to get into the formwork, and which is difficult to surface finish.[50]
Workability can be measured by the concrete slump test, a simple 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 to consolidate the layer. When the cone is carefully lifted off, the enclosed material slumps a certain amount, owing to gravity. A relatively dry sample slumps very little, having a slump value of one or two inches (25 or 50 mm) out of one foot (305 mm). A relatively wet concrete sample may slump as much as eight inches. Workability can also be measured by the flow table test.
Slump can be increased by addition of chemical admixtures such as plasticizer or superplasticizer without changing the water-cement ratio.[51] Some other admixtures, especially air-entraining admixture, can increase the slump of a mix.
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.
After mixing, concrete is a fluid and can be pumped to the location where needed.A concrete slab ponded while curing.
A common misconception is that concrete dries as it sets, but the opposite is true - damp concrete sets better than dry concrete. In other words, "hydraulic cement" needs water to become strong. Too much water is counterproductive, but too little water is deleterious. Curing allows concrete to achieve optimal strength and hardness.[52] Curing is the hydration process that occurs after the concrete has been placed. In chemical terms, curing allows calcium-silicate hydrate (C-S-H) to form. To gain strength and harden fully, concrete curing requires time. In around 4 weeks, typically over 90% of the final strength is reached, although strengthening may continue for decades.[53] The conversion of calcium hydroxide in the concrete into calcium carbonate from absorption of CO2 over several decades further strengthens the concrete and makes it more resistant to damage. This carbonation reaction, however, lowers the pH of the cement pore solution and can corrode the reinforcement bars.
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 sufficient strength, resulting in greater shrinkage cracking. The early strength of the concrete can be increased if it is kept damp 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 that increases shrinkage and cracking. The strength of concrete changes (increases) for up to three years. It depends on cross-section dimension of elements and conditions of structure exploitation.[54] Addition of short-cut polymer fibers can improve (reduce) shrinkage-induced stresses during curing and increase early and ultimate compression strength.[55]
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, poor abrasion resistance and cracking.
During the curing period, concrete is ideally maintained at controlled temperature and humidity. To ensure full hydration during curing, concrete slabs are often sprayed with "curing compounds" that create a water-retaining film over the concrete. Typical films are made of wax or related hydrophobic compounds. After the concrete is sufficiently cured, the film is allowed to abrade from the concrete through normal use.[56]
Traditional conditions for curing involve by spraying or ponding the concrete surface with water. The picture to the right shows one of many ways to achieve this, ponding – submerging setting concrete in water and wrapping in plastic to prevent dehydration. Additional common curing methods include wet burlap and plastic sheeting covering the fresh concrete.
For higher-strength applications, accelerated curing techniques may be applied to the concrete. One common technique involves heating the poured concrete with steam, which serves to both keep it damp and raise the temperature, so that the hydration process proceeds more quickly and more thoroughly.Main article: Pervious concrete
Pervious concrete is a mix of specially graded coarse aggregate, cement, water and little-to-no fine aggregates. This concrete is also known as "no-fines" or porous concrete. Mixing the ingredients in a carefully controlled process creates a paste that coats and bonds the aggregate particles. The hardened concrete contains interconnected air voids totalling approximately 15 to 25 percent. Water runs through the voids in the pavement to the soil underneath. Air entrainment admixtures are often used in freeze–thaw climates to minimize the possibility of frost damage.Two-layered pavers, top layer made of pigmented HEM Nanoconcrete.
Nanoconcrete is created by high-energy mixing (HEM) of cement, sand and water. To ensure the mixing is thorough enough to create nano-concrete, the mixer must apply a total mixing power to the mixture of 30 - 600 watts per kilogram of the mix. This mixing must continue long enough to yield a net specific energy expended upon the mix of at least 5000 joules per kilogram of the mix.[57] A plasticizer or a superplasticizer is then added to the activated mixture which can later be mixed with aggregates in a conventional concrete mixer. In the HEM process, the intense mixing of cement and water with sand provides dissipation of energy and increases shear stresses on the surface of cement particles. This intense mixing serves to divide the cement particles into extremely fine nanometer scale sizes, which provides for extremely thorough mixing. This results in the increased volume of water interacting with cement and acceleration of Calcium Silicate Hydrate (C-S-H) colloid creation.
The initial natural process of cement hydration with formation of colloidal globules about 5 nm in diameter[58] spreads into the entire volume of cement – water matrix as the energy expended upon the mix approaches and exceeds 5000 joules per kilogram.
The liquid activated high-energy mixture can be used by itself for casting small architectural details and decorative items, or foamed (expanded) for lightweight concrete. HEM Nanoconcrete hardens in low and subzero temperature conditions and possesses an increased volume of gel, which reduces capillarity in solid and porous materials.
Bacteria such as Bacillus pasteurii, Bacillus pseudofirmus, Bacillus cohnii, Sporosarcina pasteuri, and Arthrobacter crystallopoietes increase the compression strength of concrete through their biomass. Not all bacteria increase the strength of concrete significantly with their biomass.[59]:143 Bacillus sp. CT-5. can reduce corrosion of reinforcement in reinforced concrete by up to four times. Sporosarcina pasteurii reduces water and chloride permeability. B. pasteurii increases resistance to acid.[59]:146 Bacillus pasteurii and B. sphaericuscan induce calcium carbonate precipitation in the surface of cracks, adding compression strength.[59]:147Main article: Polymer concrete
Polymer concretes are mixtures of aggregate and any of various polymers and may be reinforced. The cement is more costly than lime-based cements, but polymer concretes nevertheless have advantages, they have significant tensile strength even without reinforcement, and they are largely impervious to water. They are frequently used for repair and construction of other applications such as drains.
Concrete, when ground, can result in the creation of hazardous dust. The National Institute for Occupational Safety and Health in the United States recommends attaching local exhaust ventilation shrouds to electric concrete grinders to control the spread of this dust.[60]Main article: Properties of concrete
Concrete has relatively high compressive strength, but much lower tensile strength. For this reason it is usually reinforced with materials that are strong in tension (often steel). The elasticity of concrete is relatively constant at low stress levels but starts decreasing at higher stress levels as matrix cracking develops. Concrete has a very low coefficient of thermal expansion and shrinks as it matures. All concrete structures crack to some extent, due to shrinkage and tension. Concrete that is subjected to long-duration forces is prone to creep.
Tests can be performed to ensure that the properties of concrete correspond to specifications for the application.Compression testing of a concrete cylinder
Different mixes of concrete ingredients produce different strengths. Concrete strength values are usually specified as the lower-bound compressive strength of either a cylindrical or cubic specimen as determined by standard test procedures.
Different strengths of concrete are used for different purposes. Very low-strength - 14 MPa (2,000 psi) or less - concrete may be used when the concrete must be lightweight.[61] Lightweight concrete is often achieved by adding air, foams, or lightweight aggregates, with the side effect that the strength is reduced. For most routine uses, 20 MPa (2,900 psi) to 32 MPa (4,600 psi) concrete is often used. 40 MPa (5,800 psi) concrete is readily commercially available as a more durable, although more expensive, option. Higher-strength concrete is often used for larger civil projects.[62] Strengths above 40 MPa (5,800 psi) are often used for specific building elements. For example, the lower floor columns of high-rise concrete buildings may use concrete of 80 MPa (11,600 psi) or more, to keep the size of the columns small. Bridges may use long beams of high-strength concrete to lower the number of spans required.[63][64] Occasionally, other structural needs may require high-strength concrete. If a structure must be very rigid, concrete of very high strength may be specified, even much stronger than is required to bear the service loads. Strengths as high as 130 MPa (18,900 psi) have been used commercially for these reasons.[63]The Buffalo City Court Building in Buffalo, NY.
Concrete is one of the most durable building materials. It provides superior fire resistance compared with wooden construction and gains strength over time. Structures made of concrete can have a long service life. Concrete is used more than any other human-made material in the world.[65] As of 2006, about 7.5 billion cubic meters of concrete are made each year, more than one cubic meter for every person on Earth.[66]Main article: Mass concrete Aerial photo of reconstruction at Taum Sauk (Missouri) pumped storage facility in late November, 2009. After the original reservoir failed, the new reservoir was made of roller-compacted concrete.
Due to cement's exothermic chemical reaction while setting up, large concrete structures such as dams, navigation locks, large mat foundations, and large breakwaters generate excessive heat during hydration and associated expansion. To mitigate these effects post-cooling[67] is commonly applied during construction. An early example at Hoover Dam, installed a network of pipes between vertical concrete placements to circulate cooling water during the curing process to avoid damaging overheating. Similar systems are still used; depending on volume of the pour, the concrete mix used, and ambient air temperature, the cooling process may last for many months after the concrete is placed. Various methods also are used to pre-cool the concrete mix in mass concrete structures.[67]
Another approach to mass concrete structures that minimizes cement's thermal byproduct is the use of roller-compacted concrete, which uses a dry mix which has a much lower cooling requirement than conventional wet placement. It is deposited in thick layers as a semi-dry material then roller compacted into a dense, strong mass.Main article: Decorative concrete Black basalt polished concrete floor
Raw concrete surfaces tend to be porous, and have a relatively uninteresting appearance. Many different finishes can be applied to improve the appearance and preserve the surface against staining, water penetration, and freezing.
Examples of improved appearance include stamped concrete where the wet concrete has a pattern impressed on the surface, to give a paved, cobbled or brick-like effect, and may be accompanied with coloration. Another popular effect for flooring and table tops is polished concrete where the concrete is polished optically flat with diamond abrasives and sealed with polymers or other sealants.
Other finishes can be achieved with chiselling, or more conventional techniques such as painting or covering it with other materials.
The proper treatment of the surface of concrete, and therefore its characteristics, is an important stage in the construction and renovation of architectural structures.[68]40-foot cacti decorate a sound/retaining wall in Scottsdale, Arizona Main article: Prestressed concrete
Prestressed concrete is a form of reinforced concrete that builds in compressive stresses during construction to oppose those experienced 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. For example, a horizontal beam tends to sag. Prestressed reinforcement along the bottom of the beam counteracts 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.
More than 55,000 miles (89,000 km) of highways in the United States are paved with this material. Reinforced concrete, prestressed concrete and precast concrete are the most widely used types of concrete functional extensions in modern days. See Brutalism.
Extreme weather conditions (extreme heat or cold; windy condition, and humidity variations) can significantly alter the quality of concrete. In cold weather concreting, many precautions are observed.[69] Low temperatures significantly slow the chemical reactions involved in hydration of cement, thus affecting the strength development. Preventing freezing is the most important precaution, as formation of ice crystals can cause damage to the crystalline structure of the hydrated cement paste. If the surface of the concrete pour is insulated from the outside temperatures, the heat of hydration will prevent freezing.
The American Concrete Institute (ACI) definition of cold weather concreting, ACI 306,[70] is:
In Canada, where temperatures tend to be much lower during the cold season, the following criteria is used by CSA A23.1:
The minimum strength before exposing concrete to extreme cold is 500 psi (3.5 MPa). CSA A 23.1 specified a compressive strength of 7.0 MPa to be considered safe for exposure to freezing.
Concrete roads are more fuel efficient to drive on,[71] more reflective and last significantly longer than other paving surfaces, yet have a much smaller market share than other paving solutions. Modern-paving methods and design practices have changed the economics of concrete paving, so that a well-designed and placed concrete pavement will be less expensive on initial costs and significantly less expensive over the life cycle. Another major benefit is that pervious concrete can be used, which eliminates the need to place storm drains near the road, and reducing the need for slightly sloped roadway to help rainwater to run off. No longer requiring discarding rainwater through use of drains also means that less electricity is needed (more pumping is otherwise needed in the water-distribution system), and no rainwater gets polluted as it no longer mixes with polluted water. Rather, it is immediately absorbed by the ground.
Energy requirements for transportation of concrete are low because it is produced locally from local resources, typically manufactured within 100 kilometers of the job site. Similarly, relatively little energy is used in producing and combining the raw materials (although large amounts of CO2 are produced by the chemical reactions in cement manufacture).[72] The overall embodied energy of concrete at roughly 1 to 1.5 megajoules per kilogram is therefore lower than for most structural and construction materials.[73]
Once in place, concrete offers great energy efficiency over the lifetime of a building.[74] Concrete walls leak air far less than those made of wood frames.[75] Air leakage accounts for a large percentage of energy loss from a home. The thermal mass properties of concrete increase the efficiency of both residential and commercial buildings. By storing and releasing the energy needed for heating or cooling, concrete's thermal mass delivers year-round benefits by reducing temperature swings inside and minimizing heating and cooling costs.[76] While insulation reduces energy loss through the building envelope, thermal mass uses walls to store and release energy. Modern concrete wall systems use both external insulation and thermal mass to create an energy-efficient building. Insulating concrete forms (ICFs) are hollow blocks or panels made of either insulating foam or rastra that are stacked to form the shape of the walls of a building and then filled with reinforced concrete to create the structure.A modern building: Boston City Hall (completed 1968) is constructed largely of concrete, both precast and poured in place. Of Brutalist architecture, it was voted "The World's Ugliest Building" in 2008.
Concrete buildings are more resistant to fire than those constructed using steel frames, since concrete has lower heat conductivity than steel and can thus last longer under the same fire conditions. Concrete is sometimes used as a fire protection for steel frames, for the same effect as above. Concrete as a fire shield, for example Fondu fyre, can also be used in extreme environments like a missile launch pad.
Options for non-combustible construction include floors, ceilings and roofs made of cast-in-place and hollow-core precast concrete. For walls, concrete masonry technology and Insulating Concrete Forms (ICFs) are additional options. ICFs are hollow blocks or panels made of fireproof insulating foam that are stacked to form the shape of the walls of a building and then filled with reinforced concrete to create the structure.
Concrete also provides good resistance against externally applied forces such as high winds, hurricanes, and tornadoes owing to its lateral stiffness, which results in minimal horizontal movement. However this stiffness can work against certain types of concrete structures, particularly where a relatively higher flexing structure is required to resist more extreme forces.
As discussed above, concrete is very strong in compression, but weak in tension. Larger earthquakes can generate very large shear loads on structures. These shear loads subject the structure to both tensile and compressional loads. Concrete structures without reinforcement, like other unreinforced masonry structures, can fail during severe earthquake shaking. Unreinforced masonry structures constitute one of the largest earthquake risks globally.[77] These risks can be reduced through seismic retrofitting of at-risk buildings, (e.g. school buildings in Istanbul, Turkey[78]).Concrete spalling caused by the corrosion of rebar Main article: Concrete degradation
Concrete can be damaged by many processes, such as the expansion of corrosion products of the steel reinforcement bars, freezing of trapped water, fire or radiant heat, aggregate expansion, sea water effects, bacterial corrosion, leaching, erosion by fast-flowing water, physical damage and chemical damage (from carbonatation, chlorides, sulfates and distillate water).[citation needed] The micro fungi Aspergillus Alternaria and Cladosporium were able to grow on samples of concrete used as a radioactive waste barrier in the Chernobyl reactor; leaching aluminium, iron, calcium and silicon.[79]The Tunkhannock Viaduct began service in 1912 and is still in regular use more than 100 years later.
Concrete can be viewed as a form of artificial sedimentary rock. As a type of mineral, the compounds of which it is composed are extremely stable.[80] Many concrete structures are built with an expected lifetime of approximately 100 years,[81] but researchers have suggested that adding silica fume could extend the useful life of bridges and other concrete uses to as long as 16,000 years.[82] Coatings are also available to protect concrete from damage, and extend the useful life. Epoxy coatings may be applied only to interior surfaces, though, as they would otherwise trap moisture in the concrete.[83]
A self-healing concrete has been developed that can also last longer than conventional concrete.[84] Another option is to use hydrophobic concrete.Concrete mixing plant in Birmingham, Alabama in 1936
Concrete is widely used for making architectural structures, foundations, brick/block walls, pavements, bridges/overpasses, highways, runways, parking structures, dams, pools/reservoirs, pipes, footings for gates, fences and poles and even boats. Concrete is used in large quantities almost everywhere mankind has a need for infrastructure. Concrete is one of the most frequently used building materials in animal houses and for manure and silage storage structures in agriculture.[85]
The amount of concrete used worldwide, ton for ton, is twice that of steel, wood, plastics, and aluminum combined. Concrete's use in the modern world is exceeded only by that of naturally occurring water.[86]
Concrete is also the basis of a large commercial industry. Globally, the ready-mix concrete industry, the largest segment of the concrete market, is projected to exceed $100 billion in revenue by 2015.[87] In the United States alone, concrete production is a $30-billion-per-year industry, considering only the value of the ready-mixed concrete sold each year.[88] Given the size of the concrete industry, and the fundamental way concrete is used to shape the infrastructure of the modern world, it is difficult to overstate the role this material plays today.Main article: Environmental impact of concrete
The manufacture and use of concrete produce a wide range of environmental and social consequences. Some are harmful, some welcome, and some both, depending on circumstances.
A major component of concrete is cement, which similarly exerts environmental and social effects.[59]:142 The cement industry is one of the three primary producers of carbon dioxide, a major greenhouse gas (the other two being the energy production and transportation industries). As of 2001, the production of Portland cement contributed 7% to global anthropogenic CO2 emissions, largely due to the sintering of limestone and clay at 1,500 °C (2,730 °F).[89]
Concrete is used to create hard surfaces that contribute to surface runoff, which can cause heavy soil erosion, water pollution, and flooding, but conversely can be used to divert, dam, and control flooding.
Concrete is a contributor to the urban heat island effect, though less so than asphalt.[90]
Workers who cut, grind or polish concrete are at risk of inhaling airborne silica, which can lead to silicosis.[91] Concrete dust released by building demolition and natural disasters can be a major source of dangerous air pollution.
The presence of some substances in concrete, including useful and unwanted additives, can cause health concerns due to toxicity and radioactivity. Fresh concrete (before curing is complete) is highly alkaline and must be handled with proper protective equipment.Recycled crushed concrete, to be reused as granular fill, is loaded into a semi-dump truck. Main article: Concrete recycling
Concrete recycling is an increasingly common method for disposing of concrete structures. Concrete debris was once routinely shipped to landfills for disposal, but recycling is increasing due to improved environmental awareness, governmental laws and economic benefits.
Concrete, which must be free of trash, wood, paper and other such materials, is collected from demolition sites and put through a crushing machine, often along with asphalt, bricks and rocks.
Reinforced concrete contains rebar and other metallic reinforcements, which are removed with magnets and recycled elsewhere. The remaining aggregate chunks are sorted by size. Larger chunks may go through the crusher again. Smaller pieces of concrete are used as gravel for new construction projects. Aggregate base gravel is laid down as the lowest layer in a road, with fresh concrete or asphalt placed over it. Crushed recycled concrete can sometimes be used as the dry aggregate for brand new concrete if it is free of contaminants, though the use of recycled concrete limits strength and is not allowed in many jurisdictions. On 3 March 1983, a government-funded research team (the VIRL research.codep) estimated that almost 17% of worldwide landfill was by-products of concrete based waste.[citation needed]
The world record for the largest concrete pour in a single project is the Three Gorges Dam in Hubei Province, China by the Three Gorges Corporation. The amount of concrete used in the construction of the dam is estimated at 16 million cubic meters over 17 years. The previous record was 12.3 million cubic meters held by Itaipu hydropower station in Brazil.[92][93][93][94]
The world record for concrete pumping was set on 7 August 2009 during the construction of the Parbati Hydroelectric Project, near the village of Suind, Himachal Pradesh, India, when the concrete mix was pumped through a vertical height of 715 m (2,346 ft).[95][96]
The world record for the largest continuously poured concrete raft was achieved in August 2007 in Abu Dhabi by contracting firm Al Habtoor-CCC Joint Venture and the concrete supplier is Unibeton Ready Mix.[97][98] The pour (a part of the foundation for the Abu Dhabi's Landmark Tower) was 16,000 cubic meters of concrete poured within a two-day period.[99] The previous record, 13,200 cubic meters poured in 54 hours despite a severe tropical storm requiring the site to be covered with tarpaulins to allow work to continue, was achieved in 1992 by joint Japanese and South Korean consortiums Hazama Corporation and the Samsung C&T Corporation for the construction of the Petronas Towers in Kuala Lumpur, Malaysia.[100]
The world record for largest continuously poured concrete floor was completed 8 November 1997, in Louisville, Kentucky by design-build firm EXXCEL Project Management. The monolithic placement consisted of 225,000 square feet (20,900 m2) of concrete placed within a 30-hour period, finished to a flatness tolerance of FF 54.60 and a levelness tolerance of FL 43.83. This surpassed the previous record by 50% in total volume and 7.5% in total area.[101][102]
The record for the largest continuously placed underwater concrete pour was completed 18 October 2010, in New Orleans, Louisiana by contractor C. J. Mahan Construction Company, LLC of Grove City, Ohio. The placement consisted of 10,251 cubic yards of concrete placed in a 58.5 hour period using two concrete pumps and two dedicated concrete batch plants. Upon curing, this placement allows the 50,180-square-foot (4,662 m2) cofferdam to be dewatered approximately 26 feet (7.9 m) below sea level to allow the construction of the Inner Harbor Navigation Canal Sill & Monolith Project to be completed in the dry.[103]
Diverging diamond interchangeBoulevard Haussmann in Paris, France. The Straße des 17. Juni in Berlin, Germany.
A boulevard (French, from Dutch: Bolwerk – bulwark, meaning bastion), often abbreviated Blvd, is a type of large road, usually running through a city.
In modern American usage it often means a wide, multi-lane arterial thoroughfare, often divided with a median down the centre, and perhaps with roadways along each side designed as slow travel and parking lanes and for bicycle and pedestrian usage, often with an above-average quality of landscaping and scenery.
Phnom Penh has numerous boulevards scattered throughout the city. Norodom Boulevard, Sisowath Boulevard, Monivong Boulevard, and Sothearos Boulevard are the most famous.Marine Drive, Mumbai View of Rajpath from Raisina Hill with India Gate at its terminal Keshavarz Boulevard of Tehran, Iran in mid 1970s
In Iran, "Boulevard" is generally defined as a wide road surrounded by trees in sides and divided by a green space line including grass, trees or buxuses in the middle. There are many boulevards in Iran. One of the most famous one is Keshavarz Boulevard in Tehran which is usually referred to as "The Boulevard". Isfahan has also a historical boulevard which is called Chaharbagh Boulevard.
Tel Aviv, was originally designed along the guidelines set out by architect Sir Patrick Geddes. Geddes designed a green or garden ring of boulevards surrounding the central city, which still exists today and continues to characterize Tel Aviv. One of the most famous and busy streets in the city is Rothschild Boulevard.Roxas Boulevard in Manila, Philippines.
Roxas Boulevard is a major boulevard in Metro Manila, Philippines. The boulevard, which runs along the shores of Manila Bay, is popular for its view of Manila's famous sunsets and stretch of coconut trees. The boulevard is an eight-lane major arterial road designated as Radial Road 1 that connects the center of Manila with Pasay and Parañaque.
Other boulevards in Metro Manila include the Shaw Boulevard, España Boulevard, Pedro Tuazon Boulevard and Quezon Boulevard. Not all boulevards in the Philippines have ornamentation, or slow lanes, like the Aurora Boulevard and E. Rodriguez Sr. Boulevard, which have no ornamentation at all.
Osmeña Boulevard is a boulevard in Cebu City, the Philippines' second city. It is Cebu's most important street and is its primary ceremonial avenue,[1] the conventional route of the city's civic and cultural parades. Measuring six to ten lanes wide with 3-5 meter-wide sidewalks on both sides and a landscaped central median, the boulevard is lined with narra trees. Midway is the park and roundabout of Fuente Osmeña.See also: Vienna Ring Road
The Ring Road (German: Ringstraße) is a circular ring road surrounding the Innere Stadt district of Vienna, Austria and is one of its main sights. Constructed in the mid-19th century after the dismantling of the city fortification walls, its architecture is typical of the eclectic, historicist style called Ringstraßenstil (Ring Road Style) of the 1860s to 1890s.
Known for its unique architectural beauty and history, it has also been called the "Lord of the ring roads", and is inscribed by UNESCO as part of Vienna's World Heritage Site.
The Ringstraße is 5.2 kilometers (3.2 miles) long and has several sections. It surrounds the central area of Vienna on all sides, except for the northeast, where its place is taken by the Franz-Josephs-Kai, the street going along the Donaukanal (a branch of the Danube). Starting from the Ringturm at the northern end of the Franz-Josephs-Kai, the sections are:See also: Boulevards of Paris
Baron Haussmann made such roads well known in his re-shaping of Second Empire Paris between 1853 and 1870. The French word boulevard originally referred to the flat summit of a rampart (the etymology of the word distantly parallels that of bulwark which is a Dutch loanword [bolwerk]). Several Parisian boulevards replaced old city walls; more generally, boulevards encircle a city center, in contrast to avenues that radiate from the center.
Boulevard is sometimes used to describe an elegantly wide road, such as those in Paris, approaching the Champs-Élysées. Famous French boulevards: Avenue Montaigne, Montmartre, Invalides, Boulevard Haussmann. Frequenters of boulevards were sometimes called boulevardiersUnter den Linden, Berlin, Germany.
The historically most famous boulevard in Berlin and arguably in all of Germany is Unter den Linden: location of the Berlin State Opera, Berlin Cathedral, the former royal palace, Humboldt University, the Neue Wache state memorial, the Germany Historical Museum housed in the old arsenal and Brandenburg Gate being the boulevard's focal point. Most famed for its classy shopping facilities is Berlin's Kurfürstendamm.
In the 1920s it was considered one of the most cosmopolitan places in Europe, being not only an elegant residential area but also a major centre of nightlife and leisure. Ku'damm retained this air throughout the Cold War becoming the hub of free West-Berlin. Still today it is the city's most frequented shopping district.
A notable boulevard in Berlin's East is Karl-Marx-Allee, which was built primarily in the 1950s in Stalinist Classicism architecture with decorative buildings. One section of the boulevard is more decorative while the other is more modern. In the center of the boulevard is the Strausberger Platz, which has buildings in wedding-cake style. The boulevard is divided into various blocks. Between 1949 and 1989, it was the main center of East Berlin. The Königsallee in Düsseldorf is known for its many famous fashion stores and showrooms.
Munich is well known for its four royal avenues constructed by the Bavarian monarchs of the 19th century, which can also be classified as boulevards: Brienner Straße, Leopoldstrasse, Maximilianstraße, and Prinzregentenstraße.Combino Supra at the Grand Boulevard, Budapest, Hungary
The Hungarian capital Budapest is also known for its well planned street system with wide avenues and boulevards, running through the city. There are three main boulevards, named Little Boulevard, Grand Boulevard and Hungária Boulevard. Little Boulevard was built on the demolished medieval city walls of Pest in the late 19th century. Grand Boulevard, the most prominent, was built for the 1000th anniversary of the Hungarian conquest in 1896. It has a uniform facade, and the busiest tram line in Europe.[2]
Hungária Boulevard was built from 1980 to 2000 and it is the widest (70 meters, like Champs-Élysées) and longest (13 kilometers) boulevard in Budapest with six to ten traffic lanes and a rapid tram line. Although the construction of the boulevard was finished in 2000, the facade is still incomplete, as there are many empty parcels due to demolition of old apartments and factories.
As in the UK, Ireland also has a lack of boulevards, but O'Connell Street in Dublin is one of Europe's widest streets and is very like a Victorian boulevard. In recent housing developments in Dublin, the boulevard is becoming more and more common in addresses (e.g. Tyrellstown Blvd, Park Blvd, Bayside Blvd), and a boulevard was opened in Gorey, County Wexford in early 2015.Boulevard in Florence, Italy
Florence's historic centre, for example, is surrounded by the Viali di Circonvallazione, a series of 6-lane wide streets; the boulevards follow the outline of the ancient walls of Florence, that were demolished since 1865 to make Florence, then the capital of Italy (for 5 years, 1865–1870), a modern and big city like the other European capitals. The Viali were inspired by the similar Parisian boulevards.Oder in Szczecin
Boulevards are representative places in cities situated near big rivers and usually parts of their centres, for example in Cracow, Warsaw, Toruń, Bydgoszcz, Gdańsk, Gorzów Wielkopolski, Wrocław and Świnoujście.
One of the most famous boulevards in Poland is the street named Wały Chrobrego (former German name: Hakenterrasse) in Szczecin, where the final events of The Tall Ships' Races took place in 2007 and 2013. This is a street complex, about 100 years old, at the river bank of Oder with some connections to the harbour in Szczecin and the Baltic Sea. There are many tourist attractions e.g. National Museum in Szczecin, The Contemporary Theater (Teatr Współczesny), Statue of Hercules fighting the Centaur and the waterfront for ships, including harbour cruise ships and hydrofoil to Świnoujście. In the area there are more historic buildings situated, for instance The Ducal Castle.
Some tourist towns and villages are known among others for their boulevards and esplanades. There are many localities situated by the sea, for example Sopot, Gdynia, Kołobrzeg, Misdroy and Świnoujście, or other types of big water areas as Trzebież lying on the Szczecin Lagoon. Feliks Nowowiejski Seaside Boulevard in Gdynia was the first stage of the Tour de Pologne in 2003. Boulevards are also representative places in Gryfino (dictrict town in Poland) and German village Mescherin localized by both sides of the valley of Oder river protected with Lower Odra Valley Landscape Park.
There are also many boulevards by lakes and small rivers, mainly in harbours areas, as in Giżycko, and in urban parks, for example in Łobez, Piotrków Trybunalski, Poznań and the oldest Polish urban park in Kalisz founded in 1798. Boulevards and paths in Łazienki Park in Warsaw surround Palace on the Water. The medieval port crane, called Żuraw, over Motława river, the junction of two boulevards - Długie Pobrzeże and Rybackie Pobrzeże - is the symbol of the medieval harbour of Gdańsk. The Old Town Promenade (Promenada Staromiejska) in Wrocław was built on the former on the former defensive fortifications along the City Moat and a small section along the Oder river. The boulevard in Kasprowicz Park in Szczecin leads along Rusałka Lake from the City Hall area to The Summer Theater (Teatr Letni) and then to Różanka Rose Garden and the forest of Puszcza Wkrzańska. The scenic above ground promenade in Augustów enables the observation of the Augustów Canal and national roads 8 and 16.Clean Ponds in the wide median green of Chistoprudny Boulevard, Moscow, Russia
The dictionary defines boulevard as a wide green strip in the middle of a city street or on the embankment.[3] Historical Boulevard Ring in Moscow emerged on the site of the former White City walls (demolished in the 1760s and 1770s) before the Fire of 1812, starting with Tverskoy Boulevard in 1796.[4] The whole ring was replanted and rebuilt after the fire, in the 1820s; together with the embankments of Moskva River the boulevards form the second centremost city ring.
Green boulevards of that period were terminated with corner hotel and shop buildings, most of them eventually demolished to make way for street traffic. Garden Ring, developed in the middle of the 19th century, had traditional median boulevards in its western part and side gardens in the east (streets with side strips of green, even those separating main traffic and frontage roads, are not usually considered boulevards).
Street names of Saint Petersburg evolved differently: median greens of major avenues were called boulevards, but the avenues themselves typically were and still are called prospekts (i.e. Bolshoy Prospekt of Vasilievsky Island).
Owing to city planning and physical geography, the UK has only a few boulevards. Glasgow's Mosspark Boulevard, a former segregated tram and car wide road along Bellahouston Park, and Great Western Road, colloqially known as 'The Boulevard' north of the River, is a good example, a mostly dual carriageway road running to the outer suburbs passing through the fashionable West End district, with many shops and bars dotted along the route.
After the Great Fire of London, London was supposed to be formed of straight boulevards, squares and plazas which are seen in mainland Europe, but due to land ownership issues these plans never came to fruition. Boulevards in London are rare but examples, such as Blackfriars Road, do exist. Milton Keynes, Buckinghamshire, is one of only a handful of examples where boulevards are a key feature. This is due to Milton Keynes being built as a modern new town in the 1960s.
Nottingham (and to a lesser extent, Leicester) also have extensive networks of boulevards, although some lower-capacity highways are named boulevards even when they are streets; for example Gilbert Boulevard, Arnold[5] (Asquith Way/Boulevard, West Knighton).
Furthermore, the north-west town of Warrington in Cheshire has a large number of boulevards, some more recent than others. Lining the Gemini Retail Park in Warrington is Europa Boulevard with the traditional tree lined pavements and two-lane traffic. Also, on the recent housing development, Chapelford - built on the old Burtonwood Airbase site, are a number of boulevards such as Boston and Santa Rosa Boulevard, built in reference to the American history associated from World War II on the site.Barbaros Boulevard in Istanbul, Turkey
Barbaros Boulevard is opened in 1958 due to new city planning in Istanbul. Ankara also has a lot of boulevards.View of Mexico City's Paseo de la Reforma from Castillo de Chapultepec.
In the Dominican Republic, more specifically in Greater Santo Domingo there is the Winston Churchill and 27 de Febrero Boulevard in Downtown Santo Domingo and Las Americas Boulevard in Santo Domingo Este. These boulevards are known for their wide median with plazas and trees on it.
Paseo de la Reforma (English: "Reform Promenade") is a 12 kilometer long boulevard in Mexico City, Mexico that runs in a straight line, cutting diagonally across the city. It runs from Chapultepec Park, then passes alongside the Torre Mayor (currently Latin America's tallest building), continues through the fashionable Zona Rosa and then to the Zócalo by Juárez Avenue and Francisco I. Madero Street. One of the most famous monuments of the Paseo is El Ángel de la Independencia – a tall column with a gilded statue of a Winged Victory on its top and marble statues at its base depicting the heroes of the Mexican War of Independence.
The Paseo de la Reforma was designed in the 1860s during the Second Mexican Empire by the Austrian military officer and engineer Ferdinand von Rosenzweig on the orders of Maximilian I of Mexico. He wanted to connect his imperial residence, Chapultepec Castle, to the Palacio Nacional in the city's center. When it was inaugurated, it was named the Paseo de la Emperatriz (The Empress's Promenade), after his consort, Empress Carlota of Mexico. The name now commemorates the liberal reforms of 19th-century president Benito Juárez.Queens Boulevard in New York City Road verge (or Boulevard) in Oak Park, Illinois Roosevelt Boulevard in Philadelphia, Pennsylvania
In many places in the United States of America and Canada, municipalities and developers have adapted the term to refer to arterial roads, not necessarily boulevards in the traditional sense. In California, many so-called "boulevards" extend into the mountains as narrow, winding road segments only two lanes in width. However, boulevards can be any divided highway with at-grade intersections to local streets. They are commonly abbreviated Blvd. Some celebrated examples in California include:
In Chicago, the boulevard system is a network of wide, planted-median boulevards that winds through the south, west, and north sides of the city and includes a ring of parks. Most of the boulevards and parks are 3–6 miles from The Loop. Trucks are not allowed on boulevards in Chicago. Seattle also features a network of boulevards that connect most of the city's public parks to each other, a design recommended by the Olmsted Brothers.[6]
In Philadelphia, the boulevard system includes the length of the Benjamin Franklin Parkway known as the Museum District. It also includes the arterial roadway of the Roosevelt Boulevard and the Southern Boulevard Parkway built as a connecting median of two urban parks, but now also serves as the west roadway entrance of the world class centralized Philadelphia Sports Complex and gatehouse entrance of the Philadelphia Navy Yard in South Philadelphia.
Sometimes, the word "boulevard" is used as a standalone name, as is the case in Atlanta, and Roosevelt Boulevard in the Northeast section of Philadelphia is sometimes referred to, chiefly by locals, simply as "The Boulevard." In Pittsburgh, "The Boulevard of the Allies" runs through and connects major areas of the city.
Kansas City, Missouri and St. Louis, Missouri are famous for having more boulevards and avenues in the world than any city (if the term is used lightly). In Charlotte, North Carolina, Independence Boulevard connects Uptown to the southeastern section of the city, although the westernmost segment is actually a freeway.
New York City has a lot of boulevards, many of which are not designated as such (like Ocean Parkway or Broadway). In the borough of Queens, many important thoroughfares are designated as Boulevards.
Nineteenth century parkways, such as Brooklyn's Ocean Parkway, were often built in the form of boulevards and are informally referred to as such. In some cities, however, the term "boulevard" does not specify a larger, wider, or more important road. "Boulevard" may simply be used as one of many words describing roads in communities containing multiple iterations of the same street name (such as in the Ranchlands district of Calgary, where Ranchlands Boulevard exists side-by-side with Ranchlands Road, Ranchlands Court, Ranchlands Mews, etc.) Nowadays boulevards can be found most anywhere and their original structured meaning has lost almost all meaning.
Lake Shore Boulevard, a six-lane thoroughfare runs along the lakefront in Toronto from Woodbine Avenue in the east to the city limits in the west. The section between Jameson Avenue and the Humber River (the original section), as an example of urban planning, was laid out to provide a pleasant drive with a view of Humber Bay on Lake Ontario and easy access to the park lands by automobile. It was later expanded for commuting.
A famous American example is Las Vegas Boulevard in Las Vegas, Nevada.Norodom Boulevard
Melbourne has at least four roads named "the Boulevard." These are, generally, long roads with many curves which wind alongside the Yarra River. In addition, the spelling of boulevard with an extra 'e' is common, for example the Southlands Boulevarde shopping centre in southern Perth. Australia post officially abbreviates boulevard as "BVD".[7]
Several Melbourne thoroughfares not named as a boulevard do in fact follow the boulevard configuration of multiple lanes and landscaping. These include St Kilda Road, Royal Parade, Victoria Parade, Flemington Road, and the outer section of Mount Alexander Road.
Boulevards in Sydney include:
Additionally, single-suburb boulevards are situated in Brighton-le-Sands, Cammeray, Cheltenham, Epping, Lidcombe, Lilyfield, Malabar, Newport, Sans Souci, Strathfield and Yagoona.
Construction began on the Orewa Boulevard in March 2009, the works are expected to be complete by February 2010. This boulevard will be approximately 400 m long with Pohutukawa and palm lined footpaths, a wide cycleway will be constructed on the beach side of the road and carparks on the business side. The Orewa Boulevard is a project commissioned by the Rodney District Council with the vision of connecting the CBD to Orewa Beach.
Central Christchurch is surrounded and connected by a series of large boulevards (usually called "avenues" in New Zealand). These include four which surround the central city, Bealey Avenue, Fitzgerald Avenue, Deans Avenue, and Moorhouse Avenue, and also Riccarton Avenue, which traverses the large central city park, Hagley Park. The centre of the city is often described locally as being "within the Four Avenues".[8]
Avenida 9 de Julio in the heart of Buenos Aires, which is the capital city of Argentina, is as wide as 7 lanes in each direction, with 4 further lanes flanking the main boulevard in parallel roads on either side.View of Bogota's La Soledad Park Way Boulevard
In Bogotá, '''La Soledad Park Way Boulevard''' is an 1 kilometer important boulevard, in the Locality of Teusaquillo located in Bogotá's City Center and it crosses from the street 35 to street 45.
In the boulevard you can see several monuments and restaurants including Crepes & Waffles, Kokoriko, Subway, The Cheesecake Factory, and the historical hotel ''Hotel Park Way Boulevard''
In Montevideo, Artigas Boulevard is an important avenue (40 metres (130 ft) wide) that encloses the central area.


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Keep in mind that Liquid Roof only cures, or "sets," when temperatures are 55° F or higher. It's possible to apply the product when temperatures are below that number. However, the product will only continue to cure when temperatures reach that point or higher. Both Liquid Rubber and Liquid Roof boast a one-year shelf life as long as the catalyst isn't mixed. Roof leaks repair is a problem that every homeowner or RV owner will have to address. However, it doesn't have to be expensive or difficult.
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subset: commoncrawl


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Hawaiian Electric supports work of UH Manoa Climate Change Commission
Funds support a GHG emissions inventory that may be model for othersUniversity of Hawaiʻi at Mānoa
University of Hawaii Foundation
Darren Pai, (808) 543-7753
Hawaiian Electric Company
HONOLULU - A check for $25,000 to support the work of the University of Hawaii at Manoa Climate Change Commission was presented today to new UH Manoa Chancellor Virginia Hinshaw by Mike May, president and CEO of Hawaiian Electric Company.
"Global climate change is one of the most important issues facing our state and our world today. We have the good fortune to have some of the leading experts on climate change already on the faculty here at the University of Hawaii," May said. "We are happy as part of the UH Manoa-Hawaiian Electric energy partnership to support the work of the Manoa Climate Change Commission."
The funds will be used to inventory the electricity, natural gas, transportation fuel purchased, the airlines miles traveled and to survey commuter travel by students, faculty and staff at Manoa and its off-campus sites. Inventory results will then be registered in a new Honolulu Greenhouse Gas Registry to be established by the Manoa Climate Change Commission.
"The work of this Commission will lead the way for Hawaii to better understand the significant consequence of climate change and develop new directions in reducing our energy use," Hinshaw said. "We very much appreciate both Hawaiian Electric's financial assistance and its technical support to monitor and control energy use on our UH Manoa campus."
The University of Hawaii at Manoa and Hawaiian Electric Company Energy Partnership was formally initiated in April 2007.
The Manoa Climate Commission was created to address climate change concerns by developing and promoting research, education and outreach on issues and also by measuring the greenhouse gas emissions of the Manoa campus and taking steps to reduce them.
Two key members of the commission were also on hand for the check presentation today. Professor of Economics Denise Konan established the commission during her time as interim UH Manoa chancellor. Commission Chairman Lorenz Magaard was also present. Magaard, a professor of oceanography, also serves as director of the International Center for Climate andSociety.
About the University of Hawaii Foundation
The University of Hawaii Foundation is an independent, university-related, nonprofit organization whose purpose is to raise private funds according to priorities determined by the academic leadership of the University of Hawaii and approved by the Board of Regents. Founded in 1955, the Foundation provides a full range of fund raising and alumni relations services for all 10 UH campuses.
For more information on the Foundation, visit www.uhf.hawaii.edu.
For more information, visit: http://www.uhf.hawaii.edu


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NeedHelp necesitaba un nuevo diseño de papelería y lanzó un concurso de diseño en 99designs.
Un ganador ha sido elegido entre 30 diseños de 18 diseñadores freelance.
31 Media
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Our target audience are companies who have a website who are looking for more traffic and customers. Clients can be small companies or Fortune 500 companies.
Please incorporate logo and color scheme http://www.31media.com.
Looking for some creativity with overall look and feel to display uniqueness of the internet.
Site should have logo and then place for contact information.
31 Media, a 1ShopMall Company (need to have this in company name)
Bill Gates, Partner
1234 Main St, Suite 567
Springfield, MA 01122
p 898.555.1122
f 898.555.2233
Feel free to play around with the location of the above information. It does not necessarily need to be in a block of text.
On the back of the card we would like the following services noted:
Search Engine Marketing
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We will need all images, fonts and graphics.


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Height 6-6, Weight 190, B/T: R/R, DOB: 09/02/1991
2008 Redlegs Baseball Prospect Ranking: Not Ranked
Obviously, I was wrong when I said that Adam Rosales was the most challenging prospect to rank. Hands down, Juan Duran and Yorman Rodriguez are the winners in that department. It's almost impossible to rate or evaluate such young prospects, who are still maturing and developing physically. While they have tremendous tools for their age, they have a lot of developing to do before they reach the majors. Even so, it's great to have two more potential impact prospects in the system, as it is evidence that the Reds are really focusing on improving the farm system and building from within.
The Reds have finally gotten aggressive in their international scouting, which paid off when they reeled in two of the best international prospects in Juan Duran and Yorman Rodriguez. However, there still isn't a great deal of information available on either.
Juan Duran is a 16-year old outfielder from the Dominican Republic. He has the blend of youth, size, and athletic skills that scouts dream on. The Reds found a loophole in the rules that allowed them to sign Duran earlier than was commonly believed by the competition. The Reds signed him for $2M and assigned him to the Billings Mustangs of the Pioneer League, though they never intended to have him play there. Given his age, the Reds are likely to keep Duran in the Dominican Republic for the foreseeable future. In fact, he played in the Dominican Summer League in 2008.
Duran played in 41 games for the DSL Reds, posting a line of .215/.340/.319/.658 with 1 homerun and a 47/24 K/BB ratio. Obviously, the isolated on base percentage is nice, but he also struck out once every 2.9 at bats. Even so, little of value can be gleaned from the stats, as Duran is so young and the sample size is so small. The scouting reports are more revealing.
One AL international scouting director called him "one of those guys who don't come around very often."
"He's got all the tools," he said. "He's a pretty good player, very advanced for his age. I think it was a good investment. He's a good athlete, he has above-average power right now and he has a chance for 80 power (on the 20-80 scouting scale). He demonstrated every ability that you like to see in a kid. He's a very outgoing kid, good swing. There's no doubt about his approach, bat speed and power . . . he has all the common denominators you like to see, good balance, rhythm and a pretty good idea of what to do at the plate.
"If he has to go to a corner (outfield position), he certainly has the power to go there. But right now I'd give him every opportunity to play center field because he's light on his feet and has a good idea how to play out there. He's probably 6-foot-6, 195 pounds, somewhere in that area, so he could gain a whole 40 pounds with no problem. You look at this guy, and you hate to compare guys to major league players, especially at his age, but he could be a young Dave Winfield in the making."
It goes without saying that a Dave Winfield comparison is very, very high praise, but with it comes very high expectations. While Duran is largely a mystery man, there is a bit of video on him. Here is a clip of him from the instructional league. It's short on action, but it does give us a look at Duran at the plate.
Obviously, this video clip isn't the best, as Duran doesn't swing during the at bat. However, a few things jump out at me when watching this clip. First, Duran is a very tall kid. Second, he looks like a kid who has grown so quickly that he isn't yet accustomed to his new body. His stride looks more than a little bit awkward, as does his habit of taking his bottom hand off the bat as the pitch hits the catcher's mitt. He just looks a bit raw and uncomfortable at the plate. If you pair this video clip with his stats in the DSL (which show a lot of walks and strikeouts), it seems clear that he just doesn't swing very much. At this point, it's too early to say whether he's a purposely patient, discerning hitter or if he just isn't very aggressive at the plate. However, from this clip he doesn't look like he has a clear idea of what he wants to do at the plate, which wouldn't be surprising given his age and experience level.
Given his size and reputation, it's easy to imagine him filling out and becoming a big-time power hitter. However, his size also raises the question of whether he'll ever be able to hit for a high average, as tall hitters have longer arms, longer swings, and bigger strikezones. Even so, everything is up in the air on Duran right now. Duran seems more like the traditional slugger than Yorman Rodriguez, who seems like a more well-rounded player.
At this point, I don't feel comfortable rating Juan Duran any higher than #18. I just need to see how he fares in a full season league against established competition. He is so far from the majors that it is impossible to know what to expect, as he has a lot of development left to do. He's all projection and no track record. He could be the next Vladimir Guerrero, the next Wily Mo Pena, or the next player who never even made a name for himself. It's just too soon to tell. It's easy to get excited about such a highly regarded prospect, but it's a long road to the majors.
For now, Duran checks in at #18, but he could skyrocket once he gets a chance to prove himself.


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6:00, 7:00, 8:00am; 12:10, 5:15pm
8:00am, 12:10pm
Saturday Evening Vigil Masses:
5:15pm, 7:30pm
7:00, 8:15, 9:30, 11:00am; 12:30, 5:15pm
Confessions (Saturdays) In the Lower Level of the Cathedral
3 to 5pm & 6:15 to 7:15
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