Slaked lime properties. Hydrated lime, milk of lime
The name "lime" comes from Greece, it means "inextinguishable". This word is applied to such materials that have been in the use of mankind for a long time. The properties of this substance were discovered randomly, it found application in various fields, its behavior was tested in different situations, tried, made mistakes, tested again, and as a result, properties were derived that are still used by mankind in many fields of activity.
Nowadays, there is a substance called slaked lime, this article will talk about the properties of this material, how it is obtained, where it is used.
Arriving at a building materials store, among the assortment of goods, you can see a substance in a bucket that has the inscription "Silicate concrete", it will indicate in its composition that it contains slaked lime. Undoubtedly, many people are interested in information about this material. Hydrated lime has the following formula: Ca (OH) 2, this is a strong base substance, it can be found under other names, for example:
- calcium hydroxide.
Fluffy lime is white, a powdery substance, almost insoluble in water. It has been found that the colder the water, the less soluble the lime. When the reaction with acid occurs, certain calcium salts are released, if mixed with sulfuric acid, water and calcium sulfate will be released. When the solution is in the air, there will be an interaction with carbon dioxide, and the solution will become cloudy. The result of this reaction is due to the interaction of water and calcium carbonate. With continued bubbling carbon dioxide, due to the reaction, calcium bicarbonate will be released, it will be destroyed if the temperature of this solution is increased.
Interaction carbon monoxide and lime at a temperature closer to 400 C will give hydrogen, carbonate. Such a substance has reaction properties with respect to salts, this occurs when the result of the process is the appearance of a precipitate, also in the case of mixing fluff with sodium sulfite, in this case the result of the reaction will be the appearance of sodium hydroxide, calcium sulfite.
The material from which lime is made
There are two types of substance: slaked and quicksanded. To get slaked, you need to extinguish a certain substance. Any connection is usually extinguished with water. It has such a name as quicklime. By adding water to such a substance, slaked lime is obtained.
The use of slaked lime
Slaked lime is used in the following cases:
In addition to all of the above, it is used in many other industries, needed almost everywhere.
Lime slaked and quicklime are different. Quicklime is calcium oxide and hydrated is calcium hydroxide, which is another substance that is formed as a result of slaking.
Lime in slaked form
It is a white powder that does not dissolve easily in water., the base is quite strong, capable of reacting with acids, in this case a neutralization reaction occurs, calcium salts are formed. The density is 2.211 g / cm, melting occurs at a temperature of 5120C, its formula is Ca (OH) 2. The material is obtained when the interaction of quicklime, calcium oxide, which is quicklime, with water occurs, this process is called quenching. During quenching, a strong heating occurs, 65 kJ per mole, equal to 1160 kJ per 1 kilogram of calcium oxide. The temperature at which the extinguishing occurs can even ignite the wood.
lime classes
Fluff, which called construction, has the form of air, ensuring the hardening of mortar or concrete, retains strength in dry conditions, the other type is hydraulic, which ensures the hardening of mortars or concrete, provides strength in water and in air. Fluff of quick air type has three types: dolomite, magnesian, as well as calcium. The type depends on how much magnesium and calcium metal oxides are contained. The air type has two types: quicklime, slaked, slaked also has the name hydrated. It is obtained by extinguishing dolomitic, magnesian, calcium.
The hydraulic type is divided into two types: strongly hydraulic as well as weakly hydraulic. The fractional composition is divided into types: powdered, lumpy, crushed. Powdered lime is obtained by breaking, slaking, and also by hydrating the type of lump lime, it can be of two types: one that has additives, and one that does not have them. Lime is divided into classes according to the time during which slaking occurs. This is a fast-extinguishing, which is extinguished for no more than eight minutes, medium-extinguishing, it is extinguished up to 25 minutes, and slow-extinguishing, its extinguishing time is more than 25 minutes.
The use of slaked lime
This material has found quite a lot of use:
Also fluff lime has found application in many other industries and situations: it is used to obtain various calcium compounds, to neutralize various solutions, this applies, for example, to wastewater; in the production of various organic acids, and many other applications. Used in the food industry as food supplement E526. A solution of calcium hydroxide is also called lime water. This water is used to determine the presence of carbon dioxide.
Milk of lime is a suspension, in other words, a suspension of calcium hydroxide. This liquid is white and opaque. Such a substance is used to produce sugar, to prepare certain mixtures that are made to treat various diseases in plants, and also to whitewash trees and trunks. In addition, there is a positive experience in the use of lime in dentistry for the disinfection of tooth canals. The chemical and physical indicators correspond to GOST 9179–77.
Water emulsion is good, but fluff is cheaper and better for disinfection . This is due to the fact that lime, in addition to its coloring ability, has an antiseptic property, therefore it prevents the formation of fungus and mold on any surface. The article will focus on the preparation of lime.
Lime composition
- It is customary to call lime materials after firing and a special technology for processing such natural materials, like chalk, shell rock, limestone and other carbonate rocks. Thermally processed in furnaces of various types at +1000 - 1200 degrees, blocks of rocks turn into pieces of various shapes.
- For further use, they are subjected to special processing without any chemical components and catalysts. Therefore, a 100% natural material is obtained, in the composition of which a small content of mineral additives and clay impurities is allowed.
- Lime is most often used in construction. And not only. Special grades of lime are widely used in ferrous metallurgy, food, pulp and paper, leather, chemical, textile and sugar industries. Workers also use lime Agriculture and environmentalists for the neutralization of flue gases or water effluents.
Popularity of lime
History has not preserved the name of the one who first thought of using the unique possibilities of lime. It is quite possible that it was one of the first finishing materials for decorating the dwellings of our ancestors. Obtaining patents and copyrights for innovations appeared already at the time recent history. Now he would be among the richest oligarchs in the world.
After all, according to experts, about 300 million tons of lime are produced annually in the world. Of these, 120 million tons are sold on the market. Russia is among the leading manufacturers of this finishing material. About 10 million tons of lime are produced annually in the country. Of these, 4 million tons are for construction.
- Longer than all decorative materials and more often lime is used for whitewashing. Using it does not require special skills and physical effort. It is reliable and not too burdensome for the family wallet.
- Whitewashing wooden structures or house walls with a lime solution is a tool that has been used and proven for centuries. It was made not only for decorative purposes, but also to prevent wood decay, fire protection.
- Today, in megacities, almost no one covers the walls of rooms with lime. However, in the rural outback, they still prefer to use it to cover hidden beams, invisible rafters or internal girders.
Varieties of lime
Silicates give lime hydraulic properties. Depending on the degree of their content, lime is considered air or hydraulic. Hydraulic lime has the ability to enhance the process of hardening and maintain the strength of solutions both in air and in aquatic environment. Depending on the content of clinker minerals, it can be weakly hydraulic or strongly hydraulic.
Air lime is designed to ensure the hardening of mortars used in construction and to maintain their strength at a normal level of humidity.
- calcium;
- magnesian;
- dolomite.
By type of processing lime is:
- lumpy, so-called boiling water;
- ground in the form of a powder obtained by grinding burnt lumps;
- fluff, which is a slaked material obtained after quenching lumps with water;
- lime dough - a product of quenching lumpy raw materials;
- milk of lime - white suspension.
In addition, lime is divided into:
- quickly extinguished within no more than 8 minutes;
- medium quenching - no more than 25 minutes;
- slowly quenched for at least 25 minutes.
Powdered lime is available with or without additives. The most famous type is quicklime. It is widely used in the manufacture of concrete, building, finishing, bonding and antiseptic solutions. With its help, an artificial stone is produced.
When using different technological parameters for burning rocks, lumps of lime are obtained with varying degrees strength:
- hard fired;
- softly burnt;
- intermediate option.
as material for construction works soft burnt lime is more often used, in which:
- the smallest grain size;
- lower density;
- minimum extinguishing time.
During the extinguishing process, heat is released. If you do not follow the safety precautions, there is a risk of severe burns.
From the certificate of conformity of lime quality, you can learn about the grade and condition of lime, the percentage of impurities. This document is issued only to organizations that comply with GOST in the manufacture of the material.
What is lime made from?
The type and brand of lime determines the main scope of its use.
- Lime for building works It is made from rocks containing a large percentage of calcium and magnesium. It is used as a plasticizer in concrete mixtures and binding solutions. This brand is sold with lime dough or in lumps and fluff.
- For the manufacture of hydraulic lime by firing, limestones with 6-20% content of clay impurities are used. This brand is used for the production of low-grade concrete, because it has low ductility, unlike high level strength. Hydraulic lime is more often used in the construction of structures that will be operated in conditions of high humidity.
- Lump lime used as a semi-finished product for the preparation of powders or solutions. Store it in closed warehouses to protect it from moisture. It is most often used for the preparation of whitewash solutions.
- garden lime used to enrich acidic soil with calcium. Without enough of it, plants grow and develop poorly. Slaked and quicklime are added to the soil in a rainy spring or autumn weather. Precipitation contributes to a better dissolution of limestone.
- Porous white mass soda lime is caustic soda mixed with slaked lime. Another area of application is the production of gas masks and pressure chambers, equipment for divers.
- As part of bleach free chlorine and calcium hydroxide. It has powerful disinfectant power and whitening property.
Lime properties
- Low cost. In the ranking of materials, lime in lumps is rated quite high. It is almost impossible to find a material for finishing work with the same combination of price and quality.
- Disinfection. Bacteria that get on the film formed by lime die.
- moisture resistance.
- No unpleasant odor.
- Versatility. Possibility of use both on old whitewash and on new surfaces.
- UV resistant.
- Friendly attitude towards dyes.
Two main disadvantages of lime:
- Risk of occurrencestreaks and stripes, bubbles if the rules for the percentage of preparation of a solution for whitewashing or concrete are not followed. A very liquid consistency will not color the surface to the required saturation, and a thick solution of whitewash, when dried, will turn into bubbles and crumble.
- Because of the causticity, extreme care is required when working with lime..
DIY lime
Lime for whitewashing is used on facades after plastering, wall and ceiling surfaces in basements and rooms with high humidity or dry, kitchens, toilets. The lime composition is steadfastly indifferent to the influence of water and temperature changes. For example, ceilings are whitewashed with lime milk, and even walls after plastering are painted with lime-based paints.
- Lime is used for primers and water-based paints for interior and exterior surfaces, not only as a paint, but also as a binder. However, only alkali-resistant pigments are used for tinting lime mixtures with an alkaline character. For example, for 1 kg of lime, no more than 100 g of soot or chromium oxide, mummy or umber are added. These dyes are diluted with water to a thick porridge. After 5 hours of exposure, stirring vigorously, add color to the fluff, which is diluted to the consistency of milk.
- It is more rational to buy dry lime. It keeps for quite a long time. Preparation for use will not take much time.
- Before lime is spread, large lumps must be crushed and quenched. Depending on how the solution will be used, fluff (powder solution) or dough is prepared. For this it is necessary to take different amount liquids.
- To prepare fluff for whitewashing a surface with an area of 2.5 squares, you need to take a sufficiently deep container without rust. This is necessary because during the quenching of lime with water, the volume increases by 2-3 times.
- Put 1 kg of lime lumps in a bowl. Pour 0.75 - 1 l of cool water. Cover loosely with a lid to allow steam to escape. If you take little water to slake lime, it can “burn out”. If there is too much water, lime lumps can "suffocate".
- The procedure should be carried out with extreme caution, because the solution heats up to about 140-150 degrees. The boiling mixture hisses and splashes, so it is better to play it safe and put on goggles and gloves before extinguishing the lime.
- During the 8-30 minute boil, the bubbling mass should be thoroughly mixed with a wooden stick.
- When the extinguishing process is completed, it is necessary to close the container with a lid and put it in the cellar for 15-30 days. Only after such exposure the material acquires the most effective, disinfecting and reliable properties.
- On the day of whitewashing, you need to dilute the fluff with water. Whitewashing walls or ceilings is done with milk of lime, obtained by thoroughly mixing 3 parts of water with 1 part of freshly slaked lime. The liquid should be added so much that on the stick with which the solution is stirred, ideally white lime remains in the form of a dense and even film.
- For the preparation of lime dough, the algorithm of work will be the same. In addition to the amount of liquid, which will require much less.
- To increase the strength of the coating and prevent swelling of the plaster layer, 10-15% paint with a latex base or wallpaper glue is added to lime milk.
- For a more dense sticking of the lime milk solution, green soap (1 tablespoon) is added to ½ bucket of whitewash solution.
- To give decorative whitewash additional durability, drying oil (1/3 of a full tablespoon) and table salt (about 5 g) are added to this volume. Everything is thoroughly mixed, and then filtered through a fine sieve to remove undissolved lumps and grains.
- A light bluish tint that favorably sets off the surface of the ceiling in daylight can be obtained by adding blue (20 g).
- Painting with lime coloring compositions should be carried out on cold or damp days.
Lime consumption
- Whitewashing the surface of walls, ceilings or other building structures is considered the most inexpensive finish. Consumption depends on the selected application technology and the smoothness of the surface. When using a brush, more whitewash is required. Perfectly aligned walls require less milk of lime than painting brick surfaces. Approximate consumption per 1 m² of smooth walls is 0.5 liters of ready-made whitewash solution.
- Usually, professional masters of whitewashing 1 m2 of walls in one layer are estimated at 50 rubles and more. The price depends on the need for cleaning from dirt or paint, surface structure, number of layers.
Lime consumption for whitewashing
At a cost, using lime is more profitable than painting walls with water-based paints or decorating with other materials. And in terms of quality characteristics and antiseptic properties, it surpasses many of them.
If there is no ready-made caustic soda or potassium, you can cook:
- the first of soda ash or crystalline soda and slaked lime,
- and the second - from potash and slaked lime.
Sodium hydroxide. For 1 kg of soda ash, or 2.85 kg of crystalline soda, take 900 g of slaked lime. A soda solution is prepared with a strength at 30 ° C at 23 ° B, for which 1 kg of soda is dissolved in 4.5-4.6 liters of water.
A solution of soda is placed in a cauldron or soda is immediately dissolved in a cauldron for boiling, the liquid is heated to 60 C in small portions, slaked lime mixed with water is poured - “milk of lime”. In this case, the solution is very foamy and can go over the edge. Therefore, the boiler must be loaded only to 2/3 of its capacity and the liquid must be vigorously stirred during cooking.
The more thoroughly the liquid is mixed, the better the process of converting ordinary soda into caustic soda (caustic soda) will occur.
The mixture must be heated for 40-60 minutes, then it is allowed to settle and the clear solution is drained from the sediment. * The transparent liquid is a solution of caustic soda with an approximate strength of 20 ° -21 ° B, and part of the undissolved lime, remnants of caustic soda, chalk and other impurities. After removing the clear solution, water can be added to the precipitate, boiled several times, allowed to stand and drained again of the clear liquid, which will also be a solution of caustic soda, but of a much lower strength.
With this preparation of caustic soda, a solution is obtained at 20 ° -21 ° B. If a stronger alkali is needed to saponify the fat from which soap is supposed to be made, the resulting solution can be evaporated; As the water evaporates, the solution will become stronger. If you need an alkali of a lower strength, the solution is diluted with water.
With this home-made production of caustic soda (caustic soda) from 1 kg of soda ash, 780-820 g of caustic soda is obtained.
It was indicated above that soda ash should be taken 1 kg, and crystalline - 2.85 kg. The difference between soda ash and crystalline soda is that the latter contains water of crystallization.
If crystalline soda is calcined, it crumbles with a crash and turns into a white powder, already completely devoid of water (calcined).
Caustic potassium. Caustic potash is prepared in the same way as caustic soda. For 1 kg of calcined potash, 6.8-7 kg of slaked lime and 10-11 liters of water are taken. A solution of potash in water is heated without boiling, and slaked lime mixed with water (milk of lime) is added in small portions to the boiler. The liquid is constantly stirred vigorously and heating is continued for 40-60 minutes. Then the mixture is allowed to settle, a clear liquid is drained, which is a solution of caustic potassium with an approximate strength of 16-17 ° B, and the precipitate is again poured over with water, heated to a boil, allowed to settle, and a clear liquid, which is a much lower strength solution, is drained.
Potash can be made at home- extracting it (leaching) from the ashes of plants, from the ashes obtained by burning firewood, and in general from any wood or vegetable ash. The ash is placed in a vessel with a hole in the bottom, lightly tamped and water is poured over the ash. Water will seep through the ash and flow out of the hole in the bottom in the form of a cloudy liquid, which is collected in a separate vessel. Then the wet ash is removed, fresh ash is poured, which is poured over with the resulting cloudy liquid from the wetted first ash.
This operation is repeated until the same water, passed through several portions of ash, becomes thick. The thick liquid is passed through a sparse cloth to remove solid particles and heated in a deep iron pan until the water evaporates.
As the water evaporates, gray scale will remain on the bottom and walls of the pan, which is collected in another vessel. The collected scale is calcined at high heat in a frying pan and a white powder is obtained - potash.
Potassium lye can also be prepared from vegetable or wood ash as follows: the ashes sifted through a sieve are piled in heaps on a compacted earthen or stone floor and doused with a small amount of water to make it wet. Then, recesses are made in the heaps, approximately 8-10% of quicklime is poured, poured, everything is mixed well, and when the lime is all extinguished, it is sprinkled with ash on top. The cooled and well-mixed mass is placed in a vat with two bottoms, of which the top one has many small holes. A piece of coarse canvas is placed on the upper bottom and a mixture of ash and lime is poured. A hole is made between both bottoms on one side, into which a tube is inserted to remove air, and on the opposite side a tap is attached to drain the liquor. Warm water is poured onto the ash with lime, mixed well and allowed to stand for 6-8 hours. After that, liquor is released through the tap, having approximately a strength of 20-25 ° B.
The second dousing with water will give lye with a strength of 8-10 ° B, the third - 4-2 ° B.
Hydrated lime is the main component of various coatings, mixtures and mortars, giving them high performance characteristics. The most unique material, known since ancient times, is available in preparation, is stored for a long time, has disinfectant properties, is widely used in industry, households, and is valuable for the garden.
The wide range of applications of lime is due to its low cost.
What it is?
Lime is an industrial product used in metallurgy, the construction industry, the pulp and paper and chemical industries, and for agricultural needs. In considerable volumes and with significant benefits, it is used in solving environmental problems (processing Wastewater and harmful gases).
In European countries, its consumption reaches 80 kg per person per year. The total production of the product in the world reaches 300 million tons per year. In Russia, up to 10 million tons of lime are produced every year, of which 4 million tons are for construction. It is obtained by firing to the maximum release of carbon dioxide of calcium and magnesium rocks. Carbonates are used as raw materials: limestone rocks, chalk, shell rock and other materials.
Peculiarities
Hydrated lime (fluff) or calcium hydroxide (Ca (OH) 2) is a chemical compound with a whitish powder structure, slightly soluble in water, with characteristic astringent and plastic qualities. As a result of hydroquenching, it actively interacts with acids in neutralization reactions.
Calcium particles in the composition of the substance retain water well, so these mixtures do not harden as quickly as cement ones. This is precisely the main advantage of lime mortars - the solidification time makes it possible to qualitatively level the surface with a smooth and thin layer. In addition, the product perfectly adheres to brick and concrete textures, which provides the necessary strength after hardening.
If hydroxide is not used for a long period of time, then reverse process, which occurs with the absorption of CO2, brings the composition into a solid state. On sale, fluff or lump lime is most often found.
Pros and cons
The main advantage of the product, perhaps, can be attributed to the vast scope of its use and low cost of manufacture. In addition, during the production of many works with it, there is practically no waste, which brings undoubted economic benefits.
The product perfectly absorbs moisture, which allows it to be effectively used as a full-fledged component in the preparation of solutions and mixtures with enhanced strength characteristics. The hydration process occurs rapidly, with abundant heat release (exothermic reaction), which ensures uniform hardening of the composition and additional hardening of its surface.
We will consider the advantages and disadvantages more widely using the example of the widely used lime plaster with slaked lime in the composition:
- undoubted thermal insulation qualities - plaster allows you to keep warm in the premises, which means saving on heating;
- fire safety - does not burn and does not support combustion;
- easy to use, because it is plastic and does not quickly harden, that is, it simplifies the workflow;
- hygiene - the alkaline base counteracts the appearance of mold and fungi;
- vapor permeability - prevents the accumulation of moisture;
- mechanical strength - the surface of the plaster does not crack even when nails are driven into it.
Flaws:
- Freeze duration. When layer-by-layer applied to the wall (it is necessary to wait until the previous layer dries), the repair time is significantly increased.
- The time for self-extinguishing lime is about two weeks or more.
- Lime plaster is not recommended for use in places with high humidity. For example, in the bathroom it is better to use a cement-lime mortar.
Specifications
The preparation of lime is regulated in detail state standards. Structurally, the product consists of carbonate substances, mineralized additives (blast-furnace or electrothermophosphorus slags, quartz sands and other inclusions). Each additive has its own regulations. Any component of the composition known way affects physical qualities product, respectively, and its consumption per 1 sq. m.
Air quicklime is produced in three grades (1, 2, 3); quicklime powdered - two varieties; hydrated, without additives and with them, is divided into the first and second grades.
The dispersion of the first and third types must satisfy special conditions - during the sifting of material samples through a sieve (nets No. 02, No. 008, GOST 6613), at least 98 and 85% of the entire sample taken, respectively, must pass.
The speed and complete completion of the quenching reaction, the amount of waste and the level of the final quality of the material depend on numerous factors, among which are the quality of the grade, the level of ability to chemical reactions, the fractional parameters of the raw materials, the speed and quality of mixing the mixture components, the volumes of water used, the temperature state of the reagents, methods quenching, processing elements and exposure time of the product. The product conformity certificate includes information about its grade, amount of impurities and condition.
From the point of view of ecology, lime is an environmentally friendly material that disinfects rooms well, resists the development of fungi and negatively affects harmful bacteria. Whitewashing the premises contributes to the penetration of air into them (the surface “breathes”). Lime is not dangerous for allergy sufferers.
Kinds
The firing results largely depend on the technologies used, which allows you to select a number of types of lime:
- Quick lump - "boiling".
- Quicklime ground (flour) - a dry powdery consistency obtained during the grinding of the first.
- Hydrated lime (hydroxide), or fluff, is a finely dispersed powdered product produced during the quenching of lump lime (“boilers”) with a fixed volume of water. The main composition is Ca (OH) 2. Against quick-burning material, the percentage of moisture in the hydroxide should be from 60 to 70%. Usually fluff is sold in packaged form.
- Lime dough (paste) is derived from the quenching of raw materials (“boilers”) with large volumes of water. The consistency is similar to the test. The water consumption is about 3.5 times more than for the preparation of fluff.
- Lime milk is a thickish consistency of light shades, obtained by mixing with water in a ratio of 1: 10. It is used in the treatment of premises, facades, outbuildings, and gardening.
The higher the quality level of the feedstock, the higher the percentage of CaO in the product, and hence the yield of Ca (OH) 2 during the quenching process. The low quality of raw materials is associated with an increase in the amount of CO2 in it, which occurs due to its underburning and the formation of calcium carbonate (CaCO3), pieces of which are easy to detect by weight - they are heavier than completely burned pieces. As calcium carbonate rises, waste increases. The smallest volumes of waste have a product of the first grade and moderate - of the second.
Of the limestone hydrates, the so-called freshly slaked lime is often used, applied no later than six hours from the moment of slaking. It is used for the preparation of lime milk.
As a viscous inorganic in combination with asbestos fibers, lime acquires specific qualities, forming a number of valuable derivative materials (asbestos cardboard, asbestos paper). Based on its intended use, various components are added to the composition.
Lime is classified according to several criteria (features).
According to the time period spent on extinguishing:
- quick-extinguishing - within 8-10 minutes;
- medium extinguishing - about 25 minutes;
- slow extinguishing - more than 30 minutes.
The first and second have become widespread in the metallurgical and construction sectors, in the chemical industry (fiber production), in agricultural activities (soil liming), and in medicine.
By type of hardening:
- air hardening, used to ensure the hardness of building mortars in an open environment;
- hydraulic hardening - used to form high-strength mixtures, often for work in water (bridges, port foundations, etc.).
Fraction size:
- lumpy - sold in bulk;
- crushed;
- powdery.
In addition, lime is divided into:
- air, which breaks up into 3 subgroups: dolomite, calcium, magnesia;
- hydraulic, containing about 20% of alite and belite, used both in air and under water;
- chlorine (bleach);
- sodium - compounds of sodium and hydrate used to absorb harmful gases (respiratory and diving equipment).
Cement, gypsum and clay are used as binder components for the formation of mixtures of various purposes.
For safety reasons, lime is transported closed.
Scope of application
The scope of hydroxides is truly enormous.
For the preparation of special mixtures and masonry, they have been used since ancient times. The traditional recipe: three to four shares of sand are mixed with one share of the mixture of fluff with water. In the process, water is released, which is a negative aspect, since high humidity is maintained in rooms built using such material for a long time. Therefore, cement as a binding element and pressed lime at construction sites.
Lime is also used for the manufacture of silicate materials, the hardening process of which is accelerated, since the mixture of calcium oxides and quartzites is not affected by water, but by steam heated to 190 ° C with a pressure of 15 atm. For this, special devices called autoclaves are used.
Lime is also used:
- in the process of water softening;
- in the production of bleach;
- when receiving fertilizers and neutralizing acidified soils;
- in the process of caustification of carbonates;
- in leather tanning;
- in order to obtain other chemical compounds, in the reactions of neutralization of acidic compounds (industrial, waste water);
- as a food additive (E526);
- to detect CO2, interacting with which it becomes cloudy;
- as a means of disinfecting dental tissues in medicine;
- for grounding equipment in soils with an excessive level of resistance (reduces the degree of soil resistivity);
- milk of lime is used to make fungicides;
- to repel rodents by introducing into the soil;
- in brickwork, especially stove, because it provides excellent adhesion to brick or cinder-concrete texture;
- for finishing on wood with the use of plaster mesh (shingles);
- for high-quality wall insulation in the chicken coop.
A separate topic is the use of fluff for tillage.
It is mainly used in order to correct the soil condition.
The dosage of the agent depends on 2 aspects:
- soil composition and degree of its acidity;
- type and depth of placement of funds on the site.
The level of an overestimated degree of soil acidity is revealed by the following features:
- the presence of a whitish, ashy layer on the soil;
- unsatisfactory growth of clover on the soil;
- overgrown mosses, sorrel, rosemary, belus and other plants that love an acidic environment.
To more accurately determine the level of soil acidity, its samples are taken to a special chemical laboratory or pH meters and well-known indicative means are used.
Soils are distinguished by pH level:
- strongly acidic - pH 4;
- medium acid - pH 4-5;
- slightly acidic - pH 5-6.5;
- neutral - pH 6.5-7;
- slightly alkaline - pH 7-8;
- medium alkaline - pH 8-8.5;
- strongly alkaline - pH 8.6 or more.
Neutral soils and below are not subject to processing.
It is important to take into account that for each particular crop and soil type, the volumes and parameters of the applied fertilizer are different.
How to breed?
It is not difficult to prepare exactly the target composition of the substance.
To do this, you need to know that a number of lime mortars are distinguished:
- Gypsum-lime. Seizes within 5-10 minutes. Therefore, it is made in small volumes and immediately applied to the surface. The final hardening time is from one to two days. The coating is durable and easy to process. Cornices and other wooden elements are finished with this solution.
- Cement-lime. The solution is highly durable and resistant to moisture. Used in basements and bathrooms. Apply cement M400 (for strength) or M200. The mixture is prepared at the rate of 1 share of cement and lime for 3 shares of sand.
- Clay lime. It is used less frequently, but has excellent strength properties. It is important to consider that clay is an inexpensive and environmentally friendly material. It is mainly used for working with objects made of clay.
To convert lime raw materials into plaster, it must be extinguished. The entire process takes an average of 36 hours to complete. However, slaked lime must be aged for up to 15 days. During the extinguishing process, it is recommended to adhere to safety regulations, since the reaction is pronounced exothermic.
Protective goggles, gloves, boots and rough clothing should be worn.
The container is usually used metal. During the reaction, the mixture grows in volume by about 3 times, which is important to consider when choosing a suitable container.
Ratio:
- for fluff - 1 kg per 1 liter of water;
- for the test - for 1 kg 0.5 l.
During the process, the raw material is poured with cold water. At the end of the procedure, the resulting mixture is mixed and aged. Next, the product is passed through a sieve.
Then proceed to the production of plaster, for example, based on cement. Mixing proportions vary depending on the type of solution and the purpose of its use.
Cement-lime mortar for plastering satisfies many types of work. For its manufacture, cement M400-500 is usually used, as well as sifted sand of medium fractions. It is easy to make a plastic consistency for finishing work: 25 kg of cement, 14 kg of lime, 230 kg of sand, 60 liters of water. For a more durable mortar, the proportions are somewhat different: 25 kg of cement, 7 kg of lime, 175 kg of sand, 55 liters of water.
For elasticity, productive adhesion and increased moisture resistance, solutions are improved by adding liquid soap (0.2 l per 20 l of the mixture) or PVA glue (0.5 l per 20 l of the mixture).
Thus, the whole procedure looks like this: cement and lime are placed in a certain volume of water, mixed, sand is added.
After the formation of a homogeneous consistency, the remaining liquid is drained, and the solution is mixed again.
Subtleties of use
The product is also effective for repairs, for example, for whitewashing walls. In these cases, a hydrator is often used for slaking - a device for automated slaking of lime and obtaining hydrated lime (fluff). The desired composition is prepared in advance, a day or two before the main operations. In order to obtain saturated and light tones of the diluted fluff, a 1: 1 ratio is observed. A thoroughly mixed solution is applied to the material with a brush or using a sprayer in 2-3 layers.
Fluffy is often added to various formulations. So, added to cement, it forms a viscous consistency that does not crack even after drying.
Hydrated lime with its inherent fire resistance is used to cover the wooden elements of houses in 1-3 layers. This eliminates the processes of decay and improves the quality of wood.
Lime is a corrosive substance, therefore, when working with it, it is important to adhere to safety measures:
- work in special glasses and gloves;
- in the process of extinguishing, you should stay away from the container where the reaction is taking place, since the latter is so active that you can get burned from flying spray;
- protect the respiratory system with a cotton-gauze mask;
- in case of contact with the skin, it is necessary to remove the drops with a cotton swab soaked in vegetable oil, and place a compress of gauze pre-treated with 5% vinegar on the injured area;
- if the mixture gets into the eyes, rinse immediately with water and, if necessary, go to the doctor.
Trees need to be whitewashed in autumn and spring periods, this procedure saves them from freezing and pests.
- 10 liters of water;
- 2.5 kg fluff;
- 0.1 kg of wood glue;
- 0.5 kg of copper sulfate;
- a handful of dried hellebore (repels hares).
The components should be mixed until a homogeneous consistency. Then hold for 4-5 hours. The composition is applied to the trees with a brush or sponge. It is better to apply several layers.
Fluffy lime is the very material whose application we will consider in the article, that is, we will tell you how to extinguish and apply it correctly. For the initial intermediate, quenching is mandatory. This is necessary so that during contact with moisture, the finished structure does not fall apart. Let's try to understand the manufacturing process and the features of this material.
Pushonka lime (slaked lime)
Fluffy lime is an extremely fine white powder, the production of which is associated with lime slaking.
In its original form, lime is disordered clods; lime is quenched most often in the factory by mixing with a small amount of water.
Upon receipt of slaked lime (fluff), its volumes increase significantly (about 100% increase). The resulting material has a bulk density of about 400 kg / m³, and a moisture content of not more than 5%.
The work of damping can be performed during construction, or it can be centralized. During centralized quenching, a combination is made with the unquenched wet ground particles, in this process quality is improved and yield is increased.
During construction, lime slaking is carried out using special installations, which are called well-known hydrators. Approximately one third of the lump lime is loaded into these apparatuses (the value of the average thickness of the lime layer should be approximately 10 cm), since when the lime is slaked, the volumes of the substance will approximately double.
In addition, quicklime (fluff) is poured with relatively large volumes of water, since slaking occurs within a short period of time. This is done to avoid overheating of the source material, and the boiling of water. However, if the slaking of the mixture is carried out gradually, water is added in small doses and constantly monitored so that the lime does not cool.
The amount of lime in one kilogram is converted into lime paste, with a volume of 2 liters. However, this is an average, and much depends on the quality of the lime. The result of lime slaking is called "dough yield". Therefore, fluff lime is the only binder that passes into a powdery state, not due to the grinding process, but when slaked with water.
Lime whitewash (how to cook)
More recently, chalk or lime whitewash was used for residential premises. Today, these materials are being squeezed out of living spaces with water-based paint, however, if you don't want to overpay or need to whitewash an industrial facility, then lime whitewash is a great solution.
Lime whitewash is usually used to whitewash facades or industrial premises. Surface finishing with it is a cheap and simple method.
Lime whitewash is not washed away by rain. This material is great for rooms with high humidity, however, it is better to refrain from using it in basements for storing vegetables, where humidity is maintained at 10% -20%.
Lime whitewash can be applied over concrete, brick, plaster and wood surfaces.
Before lime whitewashing, the surface should be prepared, dust, dirt, and easily resolved areas should be removed from it, if the facade has cracks, they should be repaired with cement mortar or cement putty.
In the room itself, it is better to seal large cracks with lime mortar, and small ones with putty.
Lime whitewash also has disinfectant bactericidal properties, this is the reason for the absence of fungi, bugs, bedbugs and various bacteria. For this reason, it is often applied to tree trunks.
If you purchase unslaked lime, it must be repaid. To do this, lime is poured into a metal or enameled container, poured with cold water and stirs. During the extinguishing process, the lime mortar boils and splashes, for this reason, during these works, goggles, a respirator and rubber gloves should be used.
The composition of the lime mortar
Lime whitewash is prepared in a ratio of one to three with water. To make the whitewash stronger, add table salt in a ratio of 1 g per 10 liters, drying oil (3 tbsp. L). To give the whitewash the desired color, use ultramarine, red lead or ocher. Ready lime whitewash is filtered using a sieve, gauze or nylon stocking.
Lime whitewash is applied with a brush, fur roller or with a spray gun. If a spray gun is used, the lime whitewash must be filtered again. The density of the whitewash is checked with a wooden stick, if the lime whitewash does not linger on the stick, then the whitewash is rare and requires the addition of lime. If a thick layer of whitewash remains on the stick, then it is too thick and requires the addition of water. A sign of the normal composition of the whitewash is the full coverage of the stick with a slow drain of the solution.
Before applying the lime whitewash, the substrate must be wetted with water. Whitewashing is carried out in two stages, the application of the second layer can be done on top of the first one that has not yet dried. If the whitewash is applied with a spray gun, then in the process you should perform circular movements with a fishing rod.
If a brush or roller is used to apply whitewash, then the first layer is applied with horizontal movements, and the second with vertical ones. When applying lime whitewash to the surface of the ceiling, the first layer is applied perpendicular to the light, and the second - parallel to the light.
Remember that lime can burn you. Use goggles, a respirator, rubber gloves.
Well, that's all with the tricks of lime whitewashing.
Whitewashing the ceiling with lime (use of slaked lime)
This type of finish is characterized by a long service life, and is applied to various surfaces. For this reason, when choosing a way to finish the ceiling, many people stop at the lime coating.
Be careful! Lime whitewash should not be applied to rusty or greasy surfaces.
Consider step by step how the ceiling is whitewashed with lime mortar:
- Substrate preparation for lime finish. The surface of the ceiling should be primed and puttied. Before applying lime mortar, the surface must be clean and sound.
- Lime mortar preparation. To prepare a solution for two and a half square meters of space, you need slaked lime (0.4 kg) and water (0.6 l). In order for the solution to be durable and waterproof, drying oil (0.3 tablespoons) and table salt (5 g) should be added to it. Next, the resulting mixture should be mixed well in a metal container and filtered with a sieve to get rid of lumps and impurities. To give the solution a bluish tint, add ultramarine (20 - 25 g) to it.
- Applying lime to the ceiling. The surface of the ceiling should be slightly moistened, and then apply 2 layers of whitewash. The application of the second layer is carried out on top of the first, which has not yet dried. These actions will make whitewashing more durable.
Important point! The application of lime whitewash on the ceiling at elevated temperatures is not desirable, therefore, in the heat it is better not to whitewash the ceiling with lime.
Now, a few words about the moments that affect the quality of whitewashing the ceiling.
Lime whitewash can be made stronger by carbonizing it (saturating it with carbon dioxide). To create the right conditions for this process Moisture should remain in the whitewash for some time. For this reason, a prerequisite for applying lime whitewash is the moisture content of the ceiling surface. In addition, in order to ensure the normal crystallization of whitewash, its composition must include table salt, which makes it possible for additional moisture from the environment to accumulate in the composition of the lime film.