😬 👨🏽‍🔬 🤛🏼 Air lime: types, properties, application 👨🏾‍🔧 🍉 🖖🏼

In the construction of buildings and structures, a large number of materials and components are used. One such substance is air lime. What is it, what are the properties of the material and methods of application?

Description

Building air lime is a product that is obtained by calcining calcareous and calcareous- calcareous rocks at a temperature of 900-1250 degrees. As a result, carbon dioxide is completely removed from them, mainly calcium and magnesium oxide remain in the composition.

A small content of clay, quartz sand is also allowed. However, their number should not exceed 6–8%, otherwise the product may partially lose its properties and turn into hydraulic lime.

Varieties

There are several main types of material:

Lumpy quicklime is a product of calcining calcareous rocks and has the appearance of formed pieces of different sizes. It consists of calcium oxide and magnesium; it may contain impurities of calcium carbonate, silicate, aluminate, calcium ferrite and magnesium, which did not decompose during heat treatment.

Quicklime, ground lime is clod lime crushed to a powder state. Their chemical composition is identical.

Air hydrated lime is a highly dispersed powder, which is obtained by extinguishing lump or ground quicklime. The procedure is performed by spraying liquid or vaporous water. The purpose of the technique is the conversion of calcium and magnesium oxides to their hydrates. The moisture content of the finished product should not exceed 5%.
Lime dough is a product of quenching with lump or ground lime with a large amount of water. The result is a plastic mass, which contains up to 50% of the liquid.

Depending on the concentration of magnesium oxide, these types of lime are distinguished:

magnesia;
calcium;
dolomite.

The activity of lime is determined by the amount of active calcium and magnesium oxides in it. Accordingly, the higher their number, the better the material.

Also, according to the norms, lime differs in the rate of quenching:

quick-extinguishing has a quenching rate of about 8 minutes;
medium quenching - not more than 25 minutes;
slow extinguishing - more than 25 minutes.

The rate of quenching is determined from the moment the liquid is added until the temperature of the mass begins to decline.

Raw materials

In order to obtain building air lime, it is necessary to heat-treat the following raw materials:

fine-grained crystalline limestone-marble;
dense limestones;
lime tuff;
dolomitic limestone;

pure limestones.

Among all the presented varieties of raw materials for air lime, fine-grained crystalline limestone-marble is used less often, since it has enhanced decorative properties that adversely affect practical application.

The properties

Different types of building material have different features. Properties of air lime may be as follows:

The true density of the quicklime varies from 3.1 to 3.3 g / cm ³ and depends on the temperature at which the firing was carried out.
The average density of lump lime can be from 1.6 to 2.9 g / cm ³ . Such significant differences are also explained by the temperature and duration of the heat treatment.
The bulk density for ground quicklime is 900-1100 kg / m ³ in a loose state, for hydrated lime - 400-500 kg / m ³ , for lime dough - 1300-1400 kg / m ³ .
Air lime has the property of ductility. It is necessary for the viscosity of the building material. Lime mortars are easy to apply and distribute on the surface, provide good adhesion to brick or concrete and are water-retaining.
Water demand and water holding capacity depend on the variety of the product. The highest characteristics are slaked powder or paste-like lime, the lowest - ground quicklime.
The timing of hardening of air lime also depends on the type of material. So, for example, the quicklime hardens very slowly, while the quicklime sets in 15-20 minutes after application. Also, this indicator may vary depending on the material layer and the conditions of location.
Design changes. Solutions, which are based on airborne lime, may be subject to changes such as shrinkage during drying, swelling, and uneven volume changes.
Strength directly depends on the solidification conditions of the solutions. For example, slowly hardening solutions have low strength, in contrast to quick-setting ones.

The durability of the materials depends on both their initial quality characteristics and the conditions of solidification and operation. Thus, dry conditions are most favorable for long-term operation of buildings.

Material benefits

Air lime has the following advantages:

hygroscopicity - the material is resistant to conditions of high humidity, while its quality characteristics do not change;
disinfection of surfaces on which the solution is applied, while all harmful bacteria and molds are destroyed;
the material has a neutral smell;
universality - an equal degree of efficiency when used both on an old coating and on a cleaned one.

In addition, the production of air lime is not too costly, and therefore the cost of the final material is very affordable for consumers.

disadvantages

Like all building materials, aerial lime may have disadvantages:

the possibility of bubbles or cracks when hardening the mixture if the solution was made with errors;
when working with lime, you must adhere to some safety precautions - use gloves, a protective mask and a respirator, since the material is too caustic.

In order to get the perfect mixture, it is important to follow the instructions that are indicated on the individual packaging with the material.

Application methods

This material is quite multifaceted. The most widely used such methods of application of air lime:

Disinfection of premises. To do this, lime is diluted to a liquid state and is used to treat rooms. After these procedures, mold does not form on the walls.
As a heater. When mixing lime with sawdust and gypsum, an inexpensive and environmentally friendly insulation is obtained, which is in demand in private construction.
When laying bricks, lime is necessary to increase the adhesion of surfaces.
Lime is a component of many compositions of plaster, slag concrete, coatings.

Slaked and quicklime varieties of material have different properties, so they are used for different purposes. For example, quicklime cannot be used to decorate fireplaces and other heating surfaces, as it can give off carbon dioxide, which is toxic to humans.

Slaked lime is used for the following purposes:

whitewashing of the house, borders, trees;

in industry for processing genuine leather, as it has emollient properties;
disinfection of the mouth and dental canals in dentistry;
to increase the adhesion of sand-cement compositions in construction;
E526 is a food supplement that helps to mix non-miscible components;
as a feed additive for farm animals.

In addition, the material is used to neutralize sewage and wastewater during their treatment at treatment plants.

How to extinguish lime?

Today you can buy many varieties of material, including ready-to-use slaked material. However, situations that may require you to do this yourself are not ruled out.

In order to get hydrated lime, you need to add water to it. The liquid reacts with calcium oxide, generating a large amount of heat and carbon dioxide. This process occurs due to the conversion of water into steam, which loosens the lumps of lime to a fine fraction.

To obtain a hydrated composition - fluff, it is necessary to add liquid in an amount of 70-100% of the total weight of lime. To get building lime dough, you need to add water in a ratio of 3: 1, where 3 is the amount of limestone.

Useful Tips

Depending on the application, lime is bred in different proportions:

for whitewashing walls and ceilings, you need to take 1 kg of powder and 2 liters of water;
for the treatment of tree trunks, 1 kg of material per 4 liters of fluid is taken.

When performing construction work, experts recommend sticking to the following points:

When used as a mixture for plastering, it is necessary to add a small amount of wallpaper glue. It will make the mixture more durable.
In decorative whitewash, you can add natural drying oil (1/3 teaspoon per 1 liter of the composition) for the resistance of the coating to adverse environmental conditions.

In addition, lime compositions can be painted if necessary. For these purposes, blue or latex-based paint is used.

Safety precautions

Lime is a rather caustic material, so when contacting it, you need to adhere to some rules:

mixing of compounds or quenching must be carried out exclusively in metal containers;
do not neglect the use of protective equipment - gloves, masks, respirators;
when extinguishing lime, a large amount of heat and gas is released, therefore, during the active phase, it is undesirable to bend over the vessel;
It is important to extinguish in the open air, as gas that is toxic to humans is released in the process.

Also, do not knead the compounds with your hands, even if they are in protective gloves.

Storage rules

There is a small set of recommendations regarding the storage of limestone:

storage of the quicklime product should take place in a dry room in a waterproof bag or container, since even slight humidity can trigger the blanking process;
when saving material in a paper bag, its shelf life upon opening is reduced to a month, since lime quickly loses its properties;
the room in which storage is carried out must be equipped with wooden floors, which are raised above the ground by 30 cm.

Violation of storage recommendations is fraught not only with deterioration in the quality of the material, but also with the possibility of fire if lime is near electrical appliances. It is also forbidden to use water to extinguish limestone, only powder fire extinguishers are allowed.

Burns

If safety precautions are not observed, chemical damage to the skin, mucous membranes or respiratory tract can be obtained. The alkali of which the solution consists penetrates into the deeper layers of the skin. The lesion focus is significantly larger than the area of contact of the skin with lime. Affected tissues partially lose their ability to regenerate, wound healing takes a long period. Contact with the mucous membrane of the eye can result in inflammation or partial loss of vision with a large volume of damage.

It is important to call a medical team for first aid immediately after getting a burn. After contact with hydrated lime, it is recommended to wash the skin with cool water. But with a quicklime burn, it is strictly forbidden to use water for washing. You can try to remove the residues with a soft cloth, and apply oil or any other grease to the lesion itself, and then cover it with soft cloth. To reduce pain, painkillers may be used.

Air lime: types, properties, application