Construction guide "Megastroy.biz"

What is gypsum made from?

At construction sites, in the composition of cements and building mixtures, it is often necessary to have a quickly setting binder so that the solutions do not have time to “float”. For the preparation of such a bindermainly natural gypsum and gypsum-containing rocks are used. But now the waste of many industrial production also contains calcium sulfate - the main component of gypsum. There are already about 50 types of such waste, therefore it is advisable to use many of them to produce gypsum.

Natural gypsum (CaSO 4 2H 2 0) is a crystalline sedimentary rock. If the formations of natural gypsum are large and dense, they are called gypsum stone. Coarse-layered gypsum stone is called gypsum spar, fine-fibered - selenite (moonstone), granular white color(and gypsum can have different shades due to impurities) - alabaster, which is translated from Greek as "white".

Gypsum-containing rocks include anhydrite, gypsum-containing clays and loess.

Anhydrite― it is the calcium sulfate which is not containing the bound water. Usually it underlies gypsum from below, it is a small crystals.

drywall- marsh clay containing calcium carbonate, calcium sulfate and directly clay substance. In principle, all its components are binders. And since drywall contains 15-90% CaSO4 , then it is advisable to use it to obtain gypsum.

Ganch, arzyk- gypsum-containing loess rocks. Along with carbonates and sulfates, they contain loess, that is, a substance consisting of particles much smaller than clay particles. These breeds are Central Asia found in very large deposits.

Gypsum-rich wastes of chemical and Food Industry, waste from other industries. Why are they not being used to their full potential? Some of them must be freed from harmful impurities by washing, drying, neutralization, which is often not cost-effective. The other part requires removal of excess moisture or high processing costs. But in any case, this direction is promising, since the annual amount of such waste amounts to hundreds of millions of tons, and the earth's interior is not unlimited.

For the production of binders from recycled materials, chemical industry waste is most often used:

• - borogypsum remaining after the production of boric acid and borax;
• - phosphogypsum remaining after receiving phosphate fertilizers (after the production of 1 ton of fertilizers, 4.5 tons of phosphogypsum remains);
• - fluorogypsum, derived from the production of hydrofluoric acid and its salts;
• - titanogypsum obtained by decomposition of titanium-containing ores.

More about lime and gypsum and products from them:

For many people who are inexperienced in repair and construction matters, the question often arises: what is the difference between such building materials as gypsum and alabaster? And why is it written on the top of the bags “gypsum plaster”, and below - “alabaster”?

In order not to get lost in terms, you need to figure out what gypsum and alabaster really are, whether there are differences between them and, if so, which ones.

Gypsum - origin, application

Gypsum is a dry composition made on the basis of a natural mineral - gypsum stone. The mineral is calcium sulfate dihydrate - CaSO4 2H2O with impurities in the form of oxides of silicon, aluminum and iron.

Gypsum is a mineral of sedimentary origin. In nature, it is most often found in the form of elongated prism-shaped crystals, although it sometimes forms in the form of dense tablet or scaly aggregations. The mineral is quite soft, easy to grind.

Large deposits of gypsum stone are located in countries such as Iran, USA, Canada, Turkey, Spain. In Russia, deposits of this rock are located in the Kama and Volga regions, Tatarstan, on the western slopes Ural mountains and in the Krasnodar Territory.

An astringent is obtained from a natural mineral - in fact, the gypsum that we all know. It is a powder of white, cream or grayish color (depending on the impurities present), which, when mixed with water, turns into a plastic mass that hardens quite quickly in air.

The method of using ground gypsum depends on what exactly it is planned to be used for:

• "raw" gypsum is used in medicine for fixing fractures, as well as in agriculture- scatter in the fields to normalize the acidity of the soil;
• in the form of "building gypsum" it is used during repair and finishing works, for the production of wall slabs and blocks, cornices, stucco moldings.

Also, the mineral is widely used in paper and chemical industry: in the production of cement, sulfuric acid, glazes and paints.

Natural gypsum is fibrous and granular. For the production of alabaster, fine-grained gypsum is used - alabaster. Construction alabaster has a finer grinding and is the same calcium sulfate, but not dihydrate, but semi-hydrous - CaSO4 0.5H2O. It is obtained by roasting crushed natural alabaster at temperatures up to 180 degrees.

Thus, the alabaster that we purchase at the hardware store is broad sense is gypsum, but not every gypsum can be called alabaster.

Building gypsum has the following characteristics:

• Density (true) is 2.6 - 2.76 g / cu. cm. At the same time, in a loose-filled form, the density is 0.85 - 1.15 g / cu. cm, and in compacted - 1, 245 - 1.455 g / cu. cm.
• Gypsum products have high fire resistance - they are destroyed only after 6-8 hours of exposure high temperature. Designs withstand heating up to 600-700 degrees without destruction.
• The compressive strength of building gypsum is 4-6 MPa, high-strength gypsum - 15-40 MPa.
• Gypsum and products made from it do not conduct heat well, its heat transfer coefficient in the temperature range from 15 to 45 degrees is only 0.259 kcal/m deg/h.
• Drying speed. After mixing with water, the gypsum mortar begins to set after 4 minutes and within the next half hour it completely hardens. Therefore, you need to work with such a solution very quickly.

Grades and properties of building gypsum

The normative document regulating the properties and quality of building gypsum binders is GOST 125-79. The industry produces 12 brands of alabaster, differing in compressive fracture strength.

The indicators are shown in the table:

Gypsum brand	Tensile strength of beam specimens 40 × 40 × 160 mm in size at the age of 2 hours,MPa, not less
	compression	bend
G-2	2	1,2
G-3	3	1,8
G-4	4	2,0
G-5	5	2,5
G-6	6	3,0
G-7	7	3,5
G-10	10	4,5
G-13	13	5,5
G-16	16	6,0
G-19	19	6,5
G-22	22	7,0
G-25	25	8,0

An important indicator is the setting time of the binder.

Depending on it, the following types of building gypsum are distinguished:

• A - fast-hardening (beginning no earlier than 2 minutes, end - no later than 15 minutes).
• B - normally hardening (setting begins no earlier than 6 minutes, end - no later than 30 minutes).
• B - slowly hardening (the beginning of setting is not earlier than 20 minutes, the end is not standardized).

The degree of grinding is also normalized:

Thus, according to the brand of binder, all its main characteristics can be determined.

For example, the bag says: Г-6 В II.

This means that we have a material with the following characteristics:

• strength not less than 6 and not more than 7 MPa;
• slowly hardening;
• medium grind.

Varieties of gypsum

Gypsum binders are used not only pure form, but also with various additives that allow you to change their properties.

Currently on sale you can find gypsum of the following varieties:

• Construction - for the production of gypsum building materials and for carrying out plastering works. Such material is good because it does not form cracks when dried. Lime is often added to it, which gives the mixture plasticity. The material is mainly used for interior decoration dry rooms.
• High-strength - a binder with large crystals, providing the final product with less porosity and, accordingly, greater strength. This material used for the construction of fireproof partitions, molds for the production of faience and porcelain sanitary ware. It is also used in traumatology and dentistry.
• Polymer gypsum is a binder with the addition of polymers. Often used in traumatology. Dressings with such gypsum are much lighter than ordinary gypsum ones, allow the skin to breathe, are not afraid of moisture, are permeable to X-rays (they allow you to control the process of bone fusion).

• Sculptural - the most high-strength gypsum, practically free of impurities. The material has a high degree whiteness and is used to make figurines. Sculptures, souvenirs, as well as in the automotive and aviation industry. This binder is the basis of dry putty mixtures.
• Acrylic gypsum - obtained by adding water-soluble acrylic resin to the binder. Externally, it is practically indistinguishable from ordinary gypsum, but much lighter. Because of this, it is often used for ceiling moldings. The material is frost-resistant and has low water absorption, therefore it can be used for work on building facades.

Thus, alabaster is one of the varieties of gypsum, which is mainly used in construction. It has greater hardness than natural gypsum, but is less widely used.

Gypsum properties

Gypsum(hydrous calcium sulfate) - the most common mineral belonging to the group of sulfates. Its name comes from Greek word gypsos. Gypsum scratches with a fingernail and is easily cut with a knife. Several varieties of gypsum used as collection stones, in particular fine-grained alabaster. silky spar, fibrous gypsum and white plaster They have a silky sheen and are often cut into cabochons and polished to produce a cat's-eye effect.

Soft selenite, which is colorless and transparent, is also sometimes cut. Popular among collectors are the beautiful "desert roses", dovetail twin crystals and star shapes.

The use of gypsum

Gypsum is used in the manufacture of plaster, fertilizer, Portland cement, paper, paints and pencils. It is the most common evaporite - the sediment remaining after the evaporation of water. Gypsum occurs as massive deposits in sedimentary rocks along with limestone and shale. It is formed as a result of hydration of the anhydrite mineral.

Gypsum is accompanied by calcite, sulfur, quartz, dolomite, halite, and clay. Sometimes gypsum is deposited as a result of evaporation of salt water or forms soft translucent crystals in place of dried-up lakes. It also occurs as crystals in clay, as shells of salt domes, and in volcanic zones. Alabaster, both dense and fine-grained, is used to create statues and moldings.

However, due to the extreme softness of alabaster, products made from it break easily and quickly collapse. As a rule, alabaster is translucent and colored white, pinkish or brownish. Main gypsum deposits and alabaster are found in Italy and in England. Pink alabaster is mined in Wales.

Origin of gypsum

There are deposits of alabaster in Spain, Iran and Pakistan. "Alabaster", from which Ancient Egypt and Ancient Rome they allegedly made vases, tombstones, etc., in fact, marble (calcium carbonate). There are rich deposits of gypsum in the USA (Arizona, California, Utah, Colorado, Oklahoma, New Mexico, Ohio, Michigan, Virginia and New York), Canada and France.

Gypsum, or calcium hydrogen sulfate, is a mineral widely used in construction, medicine, and sculptural casting. AT ready-made it is a powder that is mixed with water, after which it gradually dries, acquiring high rigidity. Its color can be white, gray or with shades of brown, pink, yellow or red. The hardness of the mineral on the Mohs scale is 2 points.

Gypsum mining

The mineral occurs as inclusions in sedimentary rocks. Its particles are presented in the form of scaly or fine-grained masses. Its deposits are usually found in clayey sedimentary rocks. Outwardly, they resemble marble. The mineral is mined by mining. Underground deposits break away from total weight point explosions. The extracted gypsum stone is brought to the surface, after which it is ground into powder. Initially, it has a high humidity, so it is initially dried, and then baked for several hours. The gypsum leaving the kiln is already completely ready for use.

The technological process may include additional ways purification of the composition from impurities, which depends on the raw materials used. If the production of gypsum for medical purposes is required, then it is refined to a higher quality to increase its binding properties.

Advantages of gypsum as a material

Gypsum has a number of advantages that allow it to significantly outperform the vast majority of other materials used in construction, as well as other areas. Its undeniable advantages include:

• Light weight.
• Easy mixing when preparing solutions.
• Fast freezing.
• Short drying time.
• Moderate hardness.

The undoubted advantages of gypsum include the possibility of its easy grinding. Thanks to this, you can correct the shape of the product made from it. Depending on the object or surface, this can be done, or special.

Listed Properties, which are the advantages of the material, may differ depending on the degree of grinding, cleaning and the presence of plasticizers. It is usually classified according to the degree of compression. By this criterion There are 12 types of gypsum. This indicator measures the number of kilograms per square centimeter that must be applied in order to carry out the destruction of the material. The number in the nomenclature name means given quantity kilogram. For example, gypsum marked 5 has top point compression 5 kg/cm2.

Where is gypsum used?

There are 3 main areas of application of this material:

• The medicine.
• Sculpture.
• Construction.

Medical use

Refined gypsum powder is used to create a bandage to block the limbs, which is necessary for the healing of broken bones. To do this, it is diluted in water, preparing a liquid solution. Bandages are soaked in it, with which the dressing is done. After hardening, the solution reinforced with bandages acquires rigidity, completely protecting the plastered limb from undesirable effects.

For medical purposes, only fine grinding of gypsum is used, which ensures high solidity after setting. In addition to its use in the treatment of fractures, it is also used in dentistry. With its help, casts of teeth are made for the further manufacture of implants. With the advent of more modern non-staining materials this method recedes into the past.

Gypsum in sculpture

The use of gypsum has found its application in artistic creativity especially the creation of sculptures. For this purpose, high-quality grinding without impurities is used, similar to that in medicine. There are two ways to apply it. The first involves carving works from large gypsum stones, and the second is ordinary casting. Plaster carving is practically no longer used, since the resulting works have external defects, which is due to heterogeneity natural material. In addition, this method of production requires great skill and significant time costs. It is much easier to pour gypsum mortar into molds. It hardens quite quickly, so that having an injection mold, such production can be put on stream.

Gypsum products are far from eternal, because their hardness on the Mohs scale is only 2 points, which is of course less than concrete, gaining 4-5 points. Under mechanical action, it is destroyed. Nevertheless, maintainability can be attributed to the advantages of gypsum, because products from it can be glued together, and the resulting seams are easily rubbed with emery cloth. After grinding, defects can be completely hidden with sufficient skill.

Construction use

Most often, gypsum is used to create plasters. Unlike cement or lime compounds, they have a more convenient consistency for work. At an average temperature of +20 degrees, the duration of drying of such plasters is only 7 days. During this time, they fully gain their strength, which is 4 times faster than in the case of concrete.

Putties are also made from gypsum. They use a finer grinding fraction than plasters, due to which the resulting surface has a high smoothness. This is especially important if wallpapering is required, and even more so when painting.

Decorative products for decoration are poured from gypsum. It is made from:

• Wall 3D panels.
• Wall tiles.
• Stucco.
• Baguettes.
• Columns.
• Pilasters.
• Moldings.
• Ornaments.
• Designer outlets.

The vast majority of gypsum produced for construction purposes is used to make drywall. It is used as a level ground for fast erection interior partitions and suspended ceilings. Also, with the help of drywall, the large curvature of the walls is leveled.

Using plaster to create decorative elements

Gypsum powder is an excellent material for the production of interior decorations. Most often, 3D wall panels are made from it, as well as various products for imitation ancient architecture. With the advent of polyurethane, such interior items began to be made from it, but gypsum is still an affordable material that is used if you wish to make such decorations with your own hands. To do this, 3D molds made of plastic or silicone for casting are offered for sale at quite reasonable prices. When using them, pure gypsum compositions are used. Ideally, the sculptural variety is suitable, but its cost is too high, which is not economically viable. A better choice would be to use granular gypsum, sold in stores under the name alabaster.

For production, alabaster is diluted with water in equal proportions. The resulting liquid composition is poured into the mold, after which it is shaken to ensure the release of air bubbles. It is best to install it on a vibrating machine. Its presence allows you to prepare a solution with less addition of water, which in the future will positively affect the strength. The form is left until the alabaster sets. Usually in summer time 25-30 minutes is enough for this. After removing the product from it, it is set to dry, and the form can be reused required amount once.

Since the mold depth is usually about 20-25 mm, at an air temperature of +20 degrees, the complete drying of the casting takes about 3 days. After that, the product can be used for its intended purpose.

When using molds, they must be lubricated to ensure normal casting output. This can be done with technical petroleum jelly, but the easiest and cheapest way is to use ordinary refined sunflower oil.

Features of working with gypsum plasters

Plasters based on gypsum can be applied to mineral surfaces. First of all, they are suitable for covering walls made of brick, concrete, aerated concrete, expanded clay concrete, etc. They are also used for leveling ceilings.

Although gypsum-based plasters and putties have good adhesion, surface preparation with a deep penetration primer is essential. This allows you to create an impermeable film between the base and the gypsum, preventing the return of moisture to the wall or ceiling. This ensures that during the drying period the plaster will have enough water for normal flow. chemical reaction crystallization between mixed grinding of gypsum. In the future, this will provide a higher hardness of the material and resistance to mechanical damage.

Typically, gypsum plaster can be applied to a surface with a layer thickness of 0.5 to 3 cm. Some manufacturers offer gypsum mixtures with the addition of special plasticizers and other impurities, making plastering with a large layer thickness quite possible.

Plaster based on gypsum is characterized by less pronounced slippage of the material. Due to this, they need less trimming of the influx. All this contributes to more high performance labor in their application.

Gypsum is a material that easily absorbs moisture, therefore plasters and putties based on it are of little use for use in bathrooms. Under conditions of high humidity, the possibility of destruction of the layer increases many times over. To solve this problem, special moisture-proof polymer compositions are produced, but even with their use, cement plasters are still more reliable.

January 19th, 2010

Gypsum(from the Greek. gypsos - chalk, lime) - a mineral, aqueous calcium sulfate. Gypsum crystals are lamellar, columnar, acicular and fibrous. They occur mainly in the form of continuous granular and fibrous masses, as well as various crystalline groups. Often associated with and. Pure gypsum is colorless and transparent, in the presence of impurities it has gray, yellowish, pink, brown and other colors. precipitated from aqueous solutions, rich in sulfate salts, during the drying of sea lagoons, salt lakes. One of physical properties gypsum - fluorescence. Glow in long-wave UV light - yellow, orange, blue or green tones. Mineral anhydrite(CaSO4) is similar in composition to gypsum, only devoid of water. Gypsum has chemical formula- CaSO4.2H2O

gypsum crystal

Gypsum crystals up to 11 meters long were found in the caves of Naica Mine, Mexico. The crystals grew in an extremely rare natural environment caves. The temperature there constantly remained around 58 ° C, and the cave was filled with water rich in minerals, as is necessary for the growth of crystals. The largest of these crystals weighing 55 tons had age about 500,000 years . The two brothers who discovered this cave dubbed it "Queen's Eyes". The length of the cave is 290 meters underground.

And this is my cast sample from the magazine.
Red selenite

There are such varieties of gypsum:
Selenite- a colorless and transparent grade of gypsum, which has a pearly sheen.

Another variety is a silky, fibrous form called "Satin Spar" - satin spar . This variety has a satiny, silky sheen that gives a play of light up and down the surface of the crystal.
Alabaster- a kind of gypsum, white or slightly tinted, which is a compressed fine-grained mass - a decorative ornamental stone used for fine carving for centuries, even eras.
In dry areas, gypsum can form into flowery forms, usually opaque with embedded grains of sand, called "desert roses". It can also have the following names: Sand rose, Stone rose, Selenite rose, Gypsum rose, Gypsum rosette.

ordite(ordite) - actually gypsum pseudomorphs. The only deposit is in Russia - Orda, Perm region, Ural.
sugar gypsum - gypsum in the form of a granular mass, crystallizes like sugar.
Gypsum is also occasionally found in some meteorites .

Even in the Neolithic era, gypsum was used as a building material. Back in 7000 BC. in the city of Chatal-Guyuk, in Asia Minor, gypsum was used to decorate the interior. Around 3000 BC in Uruk and later in Egypt, gypsum was used as a mortar mixed with lime to join stones. For example, at the Sphinx(2700-2600 BC) for certain works, gypsum plaster was limed. In addition, translucent alabaster windows were known to the Egyptians. In the Minoan civilization, gypsum was used to make floors or wall coverings and used it as building blocks. (famous Knossos palace, 2100-1800 BC, located on the Greek island of Crete and preserved to this day). The Romans used gypsum only for decorative plaster inside buildings, as they were familiar with much more durable materials.

In our time, gypsum is used for the manufacture of binders, soil gypsum, and in medicine - for prosthetics. It is also used for removing masks, modeling sculpture, creating relief decorations (stucco moldings) in rooms. Since ancient times, gypsum has been popular as an ornamental stone. Even now openwork vases, figurines, ashtrays and other decorative items are cut out of it. In Asian cuisine gypsum is added to tofu (traditional bean curd) as a coagulant, making it the ultimate source of calcium.