The most ancient knitting material, which is widely used in both the construction industry and industrial, is air lime. What it is? This is a material that is extracted by calcining calcium and calcium-magnesium rocks until carbon dioxide is removed from them. The final result of these processes is a white powder, which is called quicklime lime or kipelka.
And what do you know about this material? How is it produced? What kinds exist? What are the positive properties of air lime? All this and much more you can learn by reading this material.
Production of material
Let's start from the very beginning - how does airy lime get? Produce a product from mountain sedimentary rocks:
- dolomitized limestone, which contains no more than 8% clay.
The main material prevailing in all these rocks is calcium carbonate, which has the formula CaCO3. In addition, there is a bit of magnesium carbonate (MgCO3) and other additives. All these rocks are fired in a rotating or shaft furnace, operating at a temperature of 900 to 1200 ° C. The formula for air lime is as follows:
CaCO3 = CaO + CO2;
MgSO3 = MgO + CO2.
After this treatment, lime is obtained (fine-porous parts 5-10 cm in size). Immediately in production, it can be extinguished with water. As a result - slaked lime, with its formula:
CaO + H2O = Ca (OH)2
If you moisten lime with water, you get a violent reaction, at which heat is released, at which water can be heated to the boiling point. This is the process of quenching lime. That's why initially, lime is called a boiling water. At the same time, if water is added little, a fine powder is formed, and if the liquid is excessive, the final result is a dough with increased plasticity. When quenched, the lime becomes larger in size and breaks up into very small particles.
As for the costs for the time of cancellation, it is different. Focusing on it, there are 3 varieties of lime:
- Quick-extinguishing (for 8 minutes).
- Medigested (for 25 minutes).
- Slow-acting (for 25 minutes or more).
In addition, if you take into account the number of added liquid used for repayment, then air hydrate lime leaves, or, as it is also called - pussy. In it, the presence of liquid is 50-65% of the weight of lime. This number of fluids is needed for the proper hydration reaction. When the liquids are three or four times higher than the raw materials, a limestone dough is obtained. And to get limestone milk, the liquid will need 8-10 times more than the lime itself.
What are the types of material
If we take into account the number of magnesium oxide and calcium, which are part of the air lime, we can determine several of its varieties:
- Dolomite, with an MgO impurity index of 21 to 40%.
- Magnesian, with an MgO impurity index of 6 to 20%.
- Calcium, with an MgO impurity index is not more than 5%.
Lime building air can be delivered to the facility in different ways:
- komovaya kipelka not quickened;
- in the form of powder, quicklime ground;
- hydrated lime pusher;
- limestone dough and milk.
Komovoe kipelka - product obtained as a result of roasting, consisting of parts of different sizes. From it you can get: ground lime, hydrated lime, limestone dough and milk. Deliver material in bulk in closed wagons and trucks. As for storage, this should be done in a warehouse that is completely dry and has a wooden floor.
Why is that? Because if it comes in contact with water, it will automatically warm up to a temperature of 300 ° C. And given that there can be flammable materials in the warehouse, everything can turn into a fire.
Powdered ground lime is obtained as a result of grinding the comic material in special ball mills. The composition is added ash and slag. Without additives, this species is divided into 3 varieties, and with additives to 2. The advantage of the powder is that when adding a liquid it is similar to a gypsum: first, a plastic dough is obtained, and after half an hour everything starts to set.
Hydrate lime or a lint is a material that has passed the extinction process at the plant. It also looks like white powder. At the same time, humidity should not be more than 5%, density - 400-4500 kg / m3. Finished material is divided into two classes. Storage takes place in a bunker, pit, or some kind of reservoir. They are transported in bulk, by means of cement carriers, containers or bags of paper.
If we talk about the limestone test, it looks like a paste, the density of which is 1300-1400 kg / m3. It is obtained by quenching the lump material, with excess fluid. Well-extinguished material, which has increased in size not less than 3 times, is called bold. The same that has increased not less than 2.5 times, is called skinny. As for transportation of dough and milk, this happens in a tanker truck.
The composition of the test - water and the smallest particles of lime, which are not dissolved. As the water evaporates from it, a solution of Ca (OH)2. As a result, the crystals that hold all the parts together in one monolithic structure are removed. That is why the dough, protected from loss of water, will unlimitedly retain its plasticity (do not grasp, do not harden).
The hardening of air lime is a very long process. It takes from 15 minutes to an hour. But, the process can be accelerated by drying the mixture or adding gypsum / cement. It is worth noting that when you re-add the liquid to the hardened lime, it becomes plastic again. In the open air, the material reacts with carbon dioxide, in which calcium carbonate is formed. It does not dissolve in water. This process is called carbonization, in which the liquid is released. In this regard, the plaster or masonry of brick on the limestone solution is dried.
When the air lime hardens, it turns out that its volume decreases, and shrinkage is formed. Therefore it is important to add sand to the mixture.
The first thing I want to note is the average density. Each species is different. The quicklime has indicators from 1.6 g / cm3 up to 2.9 g / m3. It all depends on the temperature and the duration of the firing. If it is 800 ˚C, you will get 1.6 g / cm3, and with prolonged burns from 1300 ° C, 2.9 g / cm3. If we talk about the bulk density of other species, then the indicators (kg / m3) will be:
- Grinded quicklime (loose) - 900-1100.
- Ground minced (compacted) - 100-800.
- Hydrate pushenka (loose-bulk) - 400-500.
- Hydrate pushenka, which is compacted - 600-700.
- Limestone dough - 1300-1400.
If we talk about plasticity, then this is the dignity of the material. Plasticity is a property of the binder to impart the desired consistency to the solution, for the further convenience of surface treatment. Due to the ability of the material to retain water, the plasticity of the solution is obtained at the highest level. It is easy to work with, it is simply and evenly distributed over the surface with a thin layer, creating excellent adhesion. Even if applied to a brick or other porous substrate, the liquid will be well retained in the limestone solution.
Ability to retain water and water demand
These indicators are quite high and directly depend on what kind of species it is, and what is the dispersion of the material particles. Slaked lime as a powder or dough, has very high rates. But the ground quicklime - low.
Air lime - strength
And what about the strength of the solution? It all depends on the condition of solidification. At ordinary temperatures, the solution from the quenched material hardens slowly, and after a month, has a small value of 0.5-1.5 MPa. With the hydrate hardening of the composition with quicklime, after 28 days it is possible to obtain an index of 2-3 MPa. In the case of autoclaved hardening, dense concrete is obtained, with an indicator of 30-30 MPa and more.
Resistance to frost and water
Limestone solutions - have good resistance to air. Ideal conditions for hardening the solution in an air-dry environment. All thanks to the carbonization process, which we discussed above. The more active they are, the greater the frost and water resistance of the material. A solution that has solidified at ordinary temperature will lose its strength under strong moisture. Especially with frequent freezing and thawing of liquid.
Lime is a universal material that is used in different areas of our life. She found application even in gardening. No wonder the material was used by our grandparents. Only if you work with lime, remember: this is a strong alkali! When working with it, protect the skin, face and respiratory tract. And then you do not fear its influence.