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HISTORY OF TECHNOLOGY, TECHNOLOGY, OBJECTS AROUND US
Reinforced concrete. History of invention and production
Directory / The history of technology, technology, objects around us Reinforced concrete is a building composite material consisting of concrete and steel.
The invention of reinforced concrete was preceded by the discovery of cement - a special binder that can harden after adding water to it. In 1796, the Englishman Parker, by firing a mixture of clay and lime, obtained romancement - the first brand of cement in history. In subsequent years, new recipes for producing cement were discovered. Mixed in certain proportions with gravel, sand and water, cement formed concrete. Due to its plastic properties (its raw mass can be given any shape, which was then preserved after solidification), concrete in the first half of the XNUMXth century was widely used in construction work. Concrete structures had high compressive strength, fire resistance, water resistance, rigidity and durability. But they, like any stone, did not withstand the tensile load well, so their use was rather limited. Concrete was used mainly for the construction of thin partitions and beams with a span of up to 4 m. The main material for the supporting structures was iron in the form of various kinds of forged rods and strips. Unlike concrete, iron structures perfectly withstood the load of compression, tension and bending, but in the open air they quickly lost these qualities due to corrosion. In addition, it was noticed that when heated above five hundred degrees, iron becomes fluid and loses its strength. As a result, during strong fires, high-rise buildings, where the bearing load was placed on the iron parts, were destroyed. By the end of the XNUMXth century, a strong need began to be felt for a new building material that would combine the advantages of iron and concrete, but would not have their disadvantages. Reinforced concrete became such a material. Using concrete and iron separately, the builders did not think for a long time that they could be connected together. This came about through experience. Meanwhile, the reinforcement placed in the formwork was easily enveloped in concrete and turned out to be included in its mass. Due to the strong adhesion of iron to concrete, both materials began to work as a whole (it is very important that concrete and iron have the same coefficient of thermal expansion). The first patent for the use of reinforced concrete was taken in 1854 by the English plasterer William Wilkinson. Later, he widely used reinforced concrete in the construction of floors, and in 1865 he erected a small house in Newcastle-on-Tyne, entirely of reinforced concrete structures. Not only walls and ceilings were made of reinforced concrete, but also stairs, steps and a chimney. Apparently, it was the first reinforced concrete house in history. However, Wilkinson's discovery was not widely disseminated and went unnoticed. Simultaneously with Wilkinson, the construction contractor Coignet began his experiments with reinforced concrete in France. He built several buildings using this material, and in 1861 published a small pamphlet "The Use of Concrete in the Art of Building", in which, in particular, he wrote that iron rods included in concrete increase the bearing capacity of concrete. But Coignet's discovery also had no continuation. His firm went bankrupt. The honor of the discovery of reinforced concrete is therefore associated with the name of another Frenchman - Joseph Monnier. There is some strange irony in the fact that two professional builders, despite all their efforts, could not introduce reinforced concrete into construction practice, but this was done by a person who was very far from construction, who made his invention quite by accident. Monier worked as a gardener at the Fleur Brothers horticultural firm in Versailles. Since 1861, he began to conduct experiments on the manufacture of garden tubs from sand and cement. Soon he managed to make a concrete tub in which an orange tree was planted. Some time later, Monnier discovered cracks in the walls of this tub. Then he reinforced it with iron wire hoops. The iron soon began to rust, forming dirty brown spots and smudges on the surface of the tub. To improve its appearance, Monier smeared it on top with cement mortar. The resulting iron-cement tub turned out to be so good that Monier came up with the idea to continue making tubs in this way. There is an opinion that Monier acted not only by experience, but was familiar with the work of Coignet and borrowed his idea. But be that as it may, he was more fortunate. Monier not only earned the official fame of the creator of reinforced concrete, but also managed to extract some material benefits from his invention. In 1867, he took out his first patent for portable garden pots made from iron and cement mortar. Not satisfied with this, he began to make new experiments with this material. In 1868, Monnier built a small iron-cement basin at Mysons Alfort, and in the same year he took out a patent for an iron-cement tank and pipes. In 1869 he made a patent application for iron-cement slabs and partitions and built an iron-cement ceiling over his workshop. Strictly speaking, from a modern point of view, all these inventions were not yet reinforced concrete.
Monier, not being a professional builder, had very vague ideas about how concrete and iron interacted with each other. For example, he recommended laying wire mesh in a slab strictly in the middle of its section, while it was most rational to place it in the lower part of the structure. However, this in no way diminishes his fame as the discoverer of one of the most remarkable and widely used building materials of the XNUMXth century. Indeed, several inventors worked on the creation of reinforced concrete before Monnier, but it is he who has the merit of its versatile practical application. Once having achieved success, Monier in the future constantly thought about expanding the scope of his invention. In 1873, he received a patent for a reinforced concrete bridge, and in 1875 presented his model to an expert committee, which passed the load test. In the same year, the inventor built a footbridge with a span of 16 m and a width of 4 m according to this model. In 1878, he was granted a patent for reinforced concrete beams and sleepers, and in 1880, a combined patent for all previously declared designs. Then he made applications for his inventions in Germany and Russia. It cannot, however, be said that the new material immediately received universal recognition. The large-scale use of reinforced concrete did not begin until the next century, when Monier's reinforced concrete structures were improved by other engineers and when the fundamental doctrine of reinforced concrete was developed, revealing its remarkable properties. In the XNUMXth century, only the first step was taken towards this. In 1879, the German engineer Weiss, who had his own construction company, became interested in reinforced concrete and bought the patent right from Monier to use his system in Germany. After that, he bought up all the rest of his patents. It was thanks to Weiss that the new material became widely known. In 1886, at the direction of Weiss, scientific experiments were carried out to study the properties of reinforced concrete, which gave the most brilliant results. However, reinforced concrete became a truly independent and new building material only after Weiss in 1887 transferred the reinforcement from the middle of the section, where Monier laid it, to the lower zone of the beam or slab, which experienced the greatest tensile load in this part. It is known that Monnier, having seen the production of a plate at one of the Berlin construction sites, protested against the new technology, angrily asking: "Tell me, who is the inventor of this design - you or me?" To this, Weiss calmly replied: "You were the first to connect iron to concrete, and therefore I call this design the Monier system, but I was the first to correctly arrange iron and concrete, although, unfortunately, I could not get a patent for this." Thanks to Weiss's innovation, the span of the reinforced concrete slab was increased to 5 m. Since that time, reinforced concrete slabs have been used more and more in construction. Reinforced concrete, for example, made a real revolution in bridge construction, allowing to solve many difficulties that had previously seemed insurmountable. Previously, hewn stones of precise dimensions and iron of special grades were used to build bridges. To put heavy stones and metal elements in place, powerful lifting mechanisms and special transport devices were required. Meanwhile, the use of reinforced concrete structures did not require large funds, since most of their components were sand and gravel, widespread in nature, which could be mined at the construction site. Iron covered in concrete did not rust and retained its strength much longer. At the same time, reinforced concrete showed high fire resistance. While iron beams quickly collapsed in a strong fire, reinforced concrete structures withstood the action of a strong fire for 4-5 hours. A huge interest in reinforced concrete came after the great fire in Baltimore in 1904, when about 300 large buildings built using open iron structures burned down and collapsed. Since that time, all load-bearing structures were made only of reinforced concrete. Reinforced concrete was also widely used in fortification, since it showed four times the strength compared to ordinary concrete. Author: Ryzhov K.V.
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