History of application of lime.

 

 
         The first evidence of the use of lime as a building material dates back to 4000 BC Egyptians, who used lime, gypsum in the building of the pyramids. Data from eastern Turkey indicate the use of lime is 14 000 years ago. Wide distribution the use of lime in almost industrial purpose was the Roman Empire. The Roman architect Vitruvius discovers the first known “recipe” for the mortar. During the Roman Empire, about 2000 years ago, another great feature of lime was opened. If you add to it some kind of chopped materials obtained mixture acquires the ability to freeze not only in dry conditions, but also in water.

Quicklime obtained by calcination (burning) limestone or chalk at 1000-1200 ° C. The process of "burning" exercise in vertical shaft kilns lined inside refractory bricks. Blend, namely a mixture of limestone and coke load in the furnace through the top hole. Pieces of limestone and coke made such that their diameter was about 10 sm. Then air and topochni gases easily pass through the charge, and limestone decomposes uniformly throughout the mass. Hot gases arising from combustion and decomposition of limestone, rising up, slowly cooled to warm the batch. Scorched lime falls to the bottom of the furnace, where cool by air, which supplied from below.

Lime is widely used in the construction industry, as well as in the chemical industry to get bleaching powder. Annual universal production of lime is hundreds of millions of tons. In the construction slaked lime is used. For this purpose quicklime treated water. At that porous lumps of quicklime greedily absorb water and react with it, emitting a large amount of heat. As a result water evaporated, and quicklime turns into thick paste of slaked lime. In case of excess of water slaked lime produced in a doughy mass. In the construction slaked lime mix of 3-4 parts of sand and add that amount of water that formed pappy mass. This mass is called mortar and used for binding bricks in building brick walls as a plaster. To the mortar, which is used for binding   bricks and external plaster sometimes add cement and to the inside plaster – gypsum. Binding properties of slaked lime are based on the fact that slaked lime gradually crystallizes and reacting with carbon dioxide of air change into a solid mass.  

Nevertheless, the ecological significance of lime was found in the recent past when the public realized the need of environmental protection. We can say that lime is the material that comes from nature; it is very useful for conservation and return to nature. Nowadays, more than 20% of lime is used for environmental protection.
Lime is produced from raw materials, which are almost everywhere on our planet (huge reserves of limestone), or raw materials imported for the minimum distance.
Production costs are not expensive - fuel for burning and waste, mainly CO2. Features lime: cleaning properties - the neutralization of acid environment, the creation of insoluble compounds with most chemicals, the stabilization of the sediment by absorption water from different layers,
distraction of bacteria, it is suitable for water purification, to reduce the hardness of water.

Lime – is a powerful building material, so a great future. 

 

 

 

History of cement.

 

At all times people looked for a material that could stick stones, to strengthen the wall. For this purpose people used clay, the solution of limestone and gypsum. As time goes by, the Romans invented the mixture, which gave the opportunity to build strong and durable construction. Extraction technologies were known in ancient Egypt. It is believed also that the Egyptian pyramids were built with concrete blocks, based on the hypothesis that among the pyramids of stone blocks were found hair. Famous Roman baths, Coliseum - examples of structures which were used mortars based on cement, which received by mixing slaked lime with volcanic tufom (putcolan - on behalf of Putsuolli in Italy, where were large deposits of pozzolana - volcanic ash). Then recipe for cement production was lost and restored only in the 18 century. Cement produced by burning natural compounds, which are included in the limestone and clay, its properties varied as dependent on raw materials from which it was made. When roasting a mixture of lime and clay to a "white hot" (t ° over 1100-1200 ° C) received a product that in the crushed form became solid in water.

In the early 19 century the British decorator D. Aspdin on your own kitchen heated a mixture of well-crushed limestone and clay in the kitchen stove, then powdered it and got hydraulic cement that became solid by adding water. Aspdin named this product - portland cement, because during cement production, he used stones from the quarry, located on the island of Portland. Since that time began development of cement industry.

In cement production mainly used fusible clay, agrility, and clay shale, which forms part of the cement batch. The second main component of it is carbonate rock. The raw material for cement production are limestone and clay which are mixed in certain proportion (75-80% limestone and 20 - 25% clay) and roasted about 1450 ° C. Roast carried out in special cylindrical furnaces, refractory material contained within. Modern cement kiln reaches 185 m in length and have an internal diameter of 5 metre to set them slightly bent. Batch load at the upper end of the furnace. Furnace slowly rotates and downloaded material, strews, moves to the lower end, towards the glowing gases - products of burning fuel (coal or sprayed flammable gases).

Cement is usually used in mixtures with sand. In one part of cement weight use 3-5 parts of sand. From this mixture with water produced semisolid dough mass, which is called cement. After a time grout become hard and looks like a stone. Under normal temperature this process continued for almost a month.  This phenomenon occurs owing to a complex chemical reaction. Mixing cement with gravel and detritus makes concrete. If concrete filled iron skeleton (iron rod, wire, etc.), then it is called reinforced concrete. Cement (concrete) is very tightly connected with iron and it has the similar coefficient of thermal expansion, at the same time concrete has a high resistance to compression, and metal structures - to bending. Concrete and reinforced concrete have very high hardness and mechanical strength; they are widely used in the construction of hydroelectric power stations, bridges, canals, factory buildings and house building.

 

 

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