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Is lime green?

Is lime green?


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We hear many times about lime off, alive, white, etc., these adjectives indicate a pasty and slow-setting binder, without further specifications. But what is lime and above all, is it as green as many portals lead us to believe?

That of lime is an industry with high energy consumption, in which energy costs represent up to 50% of the total production costs. The first environmental impact occurs with production, which sees high CO2 emissions linked to energy consumption.

What is the lime?
According to the public imagination, it is used exclusively as a binder for construction and for the stabilization of land in road and railway construction, instead it is a material used in numerous industrial processes such as the production of steel, paper, but also of sugar! It is used for environmental applications such as wastewater and industrial water purification and for the water purification process. According to the trade association, the Italian production of quicklime, in 2002 alone it reached 2.6 million tons.

Types of binder of lime
We can identify two types of binder:
There aerial lime and the hydraulic lime.
There aerial lime it is obtained by cooking pure limestone at temperatures of about 800 °. The resulting clod becomes quicklime. But it can be turned off: in abundance of water obtaining putty of lime, or in water shortage (stoichiometric system) obtaining hydrated lime. This binder hardens by carbonation: the evaporation of the water in the dough follows a process of "reappropriation" of the carbon dioxide dispersed during cooking. This process takes place in relatively long times.

There hydraulic lime, on the other hand, it is obtained by cooking marly limestone, that is, containing clays at slightly higher temperatures (900 °). The silicates and aluminates present in them trigger, in the presence of water, a reaction hydraulics which leads to a fast setting, called hydraulic grip, which makes the binder much more reactive. This second type of lime allows you to work even in damp situations (especially in restorations) or with significant thicknesses such as screeds, fillings, plasters of abundant thickness.

However, it guarantees setting in acceptable times and hardening even at the deepest levels. With the same marly limestone, if fired at 1500 ° C, the cements are obtained. At these temperatures, however, the "sintering" of the limestone is produced, and an extremely reactive klinker is obtained, which to be worked is then cut with plaster.

The most interesting aspect of the production cycle: the original limestone, CaCO3, releases water (H2O) and carbon dioxide (CO2) during cooking, resulting in Calcium Oxide CaO (together with small parts of other components).
By adding water in the preparation of the mixture, CaO + H2O = Ca (OH) 2 is obtained, i.e. CALCIUM HYDROXIDE; but once the mixture is applied to the surface, we have the transfer of water (H2O) and acquisition of carbon dioxide (CO2).
The result? Exactly CaCO3, the formula from which we started.

With the term lime they call themselves the quicklime and the slaked lime. Quicklime, or cooked, is calcium oxide (CaO) or calcium and magnesium oxide (CaO + MgO). There slaked lime is mainly composed of calcium hydroxide 6 (Ca (OH) 2) and includes hydrated lime (dried powder of calcium hydroxide), milk of lime and putty which involves the addition of water to the calcium hydroxide particles.

The lime industry has over 900 employees, although the estimate is falling due to the automation of production processes. The environmental impact of the industry lime it is mainly dictated by high energy consumption and harmful emissions into the air. The harmful emissions derives from lime include dust and carbon dioxide and, to a lesser extent, also carbon monoxide, nitrogen oxides and sulfur dioxide. Therefore, although its use can be considered, in certain senses, more "eco-friendly“, Its production involves large environmental costs. An excellent study on lime is offered by the pdf document released by the forumcalce.it portal

You might also be interested in Biocalce intonachino


Video: new lime green hair (July 2022).


Comments:

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  7. Adem

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