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última version al 18:26 29 mar 2012
Concrete is actually a composite building materials composed largely of aggregate, cement and drinking water. You will discover several formulations which have assorted qualities. The aggregate is usually a coarse gravel or crushed rocks these types of as limestone, or granite, along with a great aggregate such as sand. The cement, normally Portland cement, as well as other cementitious components such as fly ash and slag cement, serve like a binder for that aggregate. Several chemical admixtures will also be additional to accomplish diversified attributes. H2o is then combined using this type of dry composite which enables it for being formed (normally poured) then solidified and hardened into rock-hard energy by way of a chemical method often called hydration. The h2o reacts with the cement which bonds the opposite factors together, sooner or later building a robust stone-like stuff. Concrete has relatively significant compressive energy, but a lot reduce tensile power. For this reason is often strengthened with elements that happen to be solid in tension (generally steel). Concrete is usually damaged by a lot of processes, this kind of as being the freezing of trapped drinking water.
Concrete is widely utilized for earning architectural structures, foundations, brick/block walls, pavements, bridges/overpasses, motorways/roads, runways, parking structures, dams, pools/reservoirs, pipes, footings for gates, fences and poles and even boats. Famous concrete structures include things like the Burj Khalifa (world's tallest making), the Hoover Dam, the Panama Canal plus the Roman Pantheon.
Concrete technological know-how was recognized with the Historic Romans and was broadly used within the Roman Empire. After the Empire passed, use of concrete became scarce till the technologies was re-pioneered within the mid-18th century.
The environmental effects of concrete is really a intricate mixture of not fully destructive effects; whilst concrete can be a key contributor to greenhouse gas emissions, recycling of concrete is ever more common in structures which have arrived at the finish of their lifestyle. Structures designed of concrete might have a protracted service life. As concrete features a high thermal mass and really minimal permeability, it may possibly make for vitality effective housing.
History
The word concrete emanates from the Latin phrase "concretus" (this means compact or condensed), the perfect passive participle of "concrescere", from "con-" (with each other) and "crescere" (to increase).
Concrete was used for design in lots of historical structures.
Through the Roman Empire, Roman concrete (or opus caementicium) was made from quicklime, pozzolana and an aggregate of pumice. Its prevalent use in lots of Roman structures, a key occasion in the record of architecture termed the Roman Architectural Revolution, freed Roman development in the limitations of stone and brick substance and allowed for innovative new designs regarding each structural complexity and dimension. Hadrian's Pantheon in Rome can be an example of Roman concrete construction.
Concrete, because Romans knew it, was a brand new and groundbreaking material. Laid in the form of arches, vaults and domes, it quickly hardened right into a rigid mass, absolutely free from lots of from the internal thrusts and strains that troubled the
builders of comparable structures in stone or brick.
Contemporary exams show that opus caementicium had as significantly compressive energy as modern day Portland-cement concrete (ca. two hundred kg/cm2). Even so, a result of the absence of metal reinforcement, its tensile energy was considerably decrease and its mode of software was also different:
Present day structural concrete differs from Roman concrete in two essential particulars. Initially, its blend consistency is fluid and homogeneous, allowing for it to become poured into varieties alternatively than demanding hand-layering collectively using the placement
of aggregate, which, in Roman apply, normally consisted of rubble. 2nd, integral reinforcing metal provides modern-day concrete assemblies great power in pressure, whereas Roman concrete could count only on the power from the concrete bonding to resist tension.
The prevalent utilization of concrete in many Roman structures has ensured a large number of survive to the current day. The Baths of Caracalla in Rome are just one particular example. Numerous Roman aqueducts and bridges have masonry cladding on a concrete core, as does the dome from the Pantheon.
Some have said the technique of concrete was missing for 13 centuries until finally 1756, if the British engineer John Smeaton pioneered the usage of hydraulic lime in concrete, applying pebbles and powdered brick as aggregate. Nonetheless, the Canal du Midi was designed utilizing concrete in 1670. Similarly there are concrete structures in Finland that day back towards the 16th century.[citation needed] Portland cement was 1st utilised in concrete during the early 1840s.
Additives
Concrete additives happen to be utilised considering the fact that Roman and Egyptian moments, when it was uncovered that incorporating volcanic ash to the blend allowed it to set below h2o. Equally, the Romans knew that including horse hair created concrete much less liable to crack even though it hardened and including blood built it far more frost-resistant.
In fashionable instances, scientists have experimented with the addition of other elements to generate concrete with enhanced qualities, this sort of as bigger strength or electrical conductivity.
Composition
There are actually a lot of sorts of concrete available, produced by different the proportions with the most important substances down below. In this manner or by substitution to the cemetitious and aggregate phases, the finished solution could be tailor-made to its software with varying strength, density, or chemical and thermal resistance attributes.
Just lately using recycled materials as concrete substances may be attaining attractiveness as a consequence of progressively stringent environmental legislation. Probably the most conspicuous of such is fly ash, a by-product of coal- fired energy crops. This use decreases the amount of quarrying and landfill area necessary as the ash acts as a cement alternative thus minimizing the amount of cement necessary.
The mix layout is dependent about the type of structure getting crafted, how the concrete is going to be mixed and delivered and the way it'll be placed to type this composition.
Ready-mixed concrete share is consistently increasing while in the composition of concrete output and using. In European Union the share of ready-mixed concrete reached ninety three.39% in 2010.
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