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Concrete


Concrete
Concrete invention preceded the opening of cement - a special binder that can harden after adding water to it. In 1796, Englishman Parker by firing a mixture of clay and lime was romantsement - the first in the history of the brand of cement. In subsequent years, new recipes produce cement were opened. Mixed in certain proportions with gravel, sand, cement and water formed concrete. Due to its plastic properties (wet weight of it can be given any shape, which is then retained after curing) concrete in the first half of the XIX century is widely came into use in construction work. Concrete construction has high compressive strength, fire resistance, water resistance, hardness and durability. But they, like any stone, badly maintained tensile load, so their use has been rather limited. Concrete was used mainly for the construction of thin walls and beams span up to 4 m. The basic material for load-bearing structures served as the iron in the form of various kinds of forged rods and strips. In contrast to concrete, iron structures perfectly maintained compressive load, tensile and flexural strength, but in the open air, they rapidly lose these characteristics due to corrosion. Moreover, it was observed that when heated over five hundred degrees iron becomes flowable and loses its strength. As a result, severe fires high-rise buildings where the bearing load is imposed on the iron parts were destroyed. By the end of the XIX century began to be felt a strong need for a new building material, which combines the advantages of concrete and iron, but would not have their drawbacks. It is a material and become concrete. Applying separate concrete and iron, builders long thought about the fact that they can be joined together. By empirically arrived. Meanwhile, the situation in the formwork fittings easily enveloping concrete, and is now operating in its mass. Due to the high strength of adhesion to concrete, iron both materials started to work as a whole (it is very important that the concrete and iron, have the same coefficient of thermal expansion).

The first patent for the use of reinforced concrete in 1854 took the English plasterer William Wilkinson. In the future, it is widely applied in the construction of reinforced concrete slabs, and in 1865 erected in Newcastle-upon-Tyne small house entirely of reinforced concrete structures made of reinforced concrete were carried out here is not only the walls and ceilings, but also stairs, steps and chimney. Apparently, it was the first reinforced concrete building in history. However, the discovery Wilkinson is not widespread and remains unnoticed. Along with Wilkinson his experiments with reinforced concrete began in France, a building contractor Kuan. He built using this material a few buildings, and in 1861 published a small booklet "Use of concrete in the construction art", in which, inter alia, wrote that the iron rods that are included in concrete and increase the carrying capacity of the concrete. But the discovery of Quan also had to continue. His company went bankrupt.

The honor of opening the concrete communicates therefore with the name of another Frenchman - Joseph Monier. There is a strange irony in the fact that the two professional builder, despite all efforts, could not introduce in the practice of concrete construction, but it was possible to make a person very far from the building, which made its invention by chance. Monier worked as a gardener in a horticultural company "Brothers Fleur" at Versailles. From 1861, he began to conduct experiments for the production of sand and cement garden tubs. Soon he was able to make a concrete tub, which was planted an orange tree. After some time, Monier discovered cracks in the walls of the tub. Then he strengthened its iron hoops of wire. Iron was soon rust, forming a dirty-brown spots and stains on the surface of the tub. In order to improve its appearance, Monier smeared it on top of cement mortar. Thus obtaining zhelezotsementnaya tub was so good that Monier came to the idea to continue to use the tub in a similar way.

It is believed that Monier acted not only empirically, but was familiar with the work of Kwan and borrowed his idea. But be that as it may, he was more fortunate. Monier has not only earned fame official reinforced the creator, but also managed to extract from his invention some material benefits. In 1867 he took his first patent for a portable garden tubs made of iron and cement mortar. Will not rest on this, he began to produce this material new experiments. In 1868 Monier built-in Maysons Alforte zhelezotsementny a small swimming pool and in the same year took out a patent on zhelezotsementny tank and pipes. In 1869 he made a patent application for zhelezotsementnye slabs and walls and built zhelezotsementnoe overlap over his workshop. Strictly speaking, from a modern point of view, all these inventions were not yet concrete. Monier, not being a professional builder, had a very vague idea about how to interact with each concrete and iron. It is, for example, wire mesh laid recommended plate strictly in its middle section, while all were rationally arrange it on the bottom of the structure. However, this does not in any way diminish his fame as the discoverer of one of the most remarkable and widely used building materials of the XX century. Indeed - to Monier concrete work on the creation of several inventors, but that he is credited with its versatile practical application. Once having achieved success in the future Monnier always thinking to expand the scope of their invention. In 1873 he received a patent for reinforced concrete bridge and presented his model of the expert committee in 1875, has withstood the test load. In the same year, an inventor has built on this model, a pedestrian bridge with a span of 16 m and a width of 4 m In 1878, he was granted a patent for reinforced concrete beams and ties, and in 1880 -. A joint patent on all declared his earlier designs. Then he made an application for their inventions in Germany and Russia.

You can not, however, say that the new material is immediately received widespread recognition. Large-scale use of reinforced concrete began only in the next century, when Monier concrete structures were improved and other engineers when we developed the fundamental doctrine of reinforced concrete, to reveal its remarkable properties. In the XIX century, this is only the first step was taken. In 1879, German engineer Weiss, who had a construction company, interested in reinforced concrete and bought Monier patent law on the use of its system in Germany. After that he bought the rest of its patents. It is thanks to the new material Weiss became widely known. In 1886, at the direction of Weiss scientific experiments on the properties of concrete were carried out, which gave the most brilliant results. However, the really independent and new building material was only reinforced after Weiss in 1887 suffered a reinforcement of the middle section, where she was putting Monnier, in the lower zone of the beam or slab, experiencing in this part of the greatest load in tension. It is known that Monier saw manufacturing plate on one of Berlin's buildings, protested against the new technology, asking angrily: "Tell me, who is the inventor of this design - you or me?" To this, Weiss said calmly: "You are the first combined iron and concrete, and therefore I call this design Monier system, but I was the first properly positioned iron and concrete, although, unfortunately, I could not get a patent on it. " Through innovation Weiss span reinforced concrete slab has been increased to 5 m. Since that time, concrete slabs began to get more and more versatile use in construction.

Concrete, for example, has made a real revolution in bridge construction, allowing to solve a lot of difficulties, this seemed to be insurmountable. Previously, for the construction of bridges used ashlar exact sizes and special grades of iron. To lay down the heavy stones and elements of metal structures needed powerful lifting mechanisms and special transport devices. Meanwhile, the use of reinforced concrete structures do not require large funds, since most of their components were widely distributed in nature, sand and gravel, which could produce at the construction site. Shelters in concrete and rusted iron is not maintained its strength for much longer. However, the concrete showed high flame retardancy. While iron beams quickly destroyed under strong fire, concrete structures maintained a strong effect fire for 4-5 hours. Huge interest in reinforced concrete appeared after the great fire in Baltimore in 1904, when burned and destroyed about 300 large buildings constructed with the use of public railway construction. Since that time, all load-bearing structures made of reinforced concrete only. The widest application was reinforced and fortification, as shown four times more durable than conventional concrete.

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