Medical plaster chemical composition no different from regular plaster. This is calcium sulfate dihydrate, which is formed after adding calcium sulfate hydrate ordinary water. Hydrate is the original loose material in the form of a white or slightly yellowish powder, which hardens for a certain time after mixing it with water. The setting time of medical gypsum and the permissible consistency of dilution are crucial in medicine, since medical gypsum is used for the manufacture of rigid bandages, splints, plaster beds, as well as in dentistry for obtaining dental impressions and modeling prostheses.
Medical plaster is usually divided into the following types: regular burnt medical plaster, model plaster and super plaster. They all have different technology receipt and certain places of application in medicine.
Burnt medical plaster
obtained by calcination of calcium sulfate dihydrate in an open container. When heated to temperatures above 130 degrees, the dihydrate turns into hemihydrate, which is ordinary medical gypsum. An important difference between this material and other types of gypsum is that it has very large porous particles of uneven shape that strongly absorb water. Therefore, to mix medical calcined plaster, it is necessary to take water in a ratio of 2:1 (one part of water to two parts of gypsum). The setting time for this type of medical plaster is 6 minutes after dilution, and the end time for setting is about 12 minutes after dilution. The main application is plaster casts.
Model plaster obtained by heating calcium sulfate dihydrate in an autoclave under pressure. This produces hemihydrate particles correct form practically without pores. This type of medical gypsum is otherwise called alpha hemihydrate. More uniform particles make it possible to obtain denser structures with less water for mixing the powder. At the same time, the prints obtained using model plaster are more accurate. What is especially important when taking impressions of teeth in dentistry. To dilute model plaster, you need twenty milliliters of water per 100 grams of powder.
Super gypsum obtained in two stages. The dihydrate is first boiled in the presence of calcium and magnesium chlorides and then heated in an autoclave. Chlorides in this process are deflocculants that prevent floc formation and agglomeration fine particles gypsum into larger granules. Thus, the structure of supergypsum is even thinner and denser than that of model gypsum. Therefore, it is used for taking impressions of individual teeth and obtaining impressions for making root inlays for prosthetics.
Plaster casts are widely used in traumatology and orthopedics and are used to hold fragments of bones and joints in their given position.
Medical gypsum is a semi-aqueous calcium sulfate salt, available in powder form. When combined with water, the hardening process of the gypsum begins after 5–7 minutes and ends after 10–15 minutes. The plaster gains full strength after the entire bandage has dried.
Using various additives you can speed up or, conversely, slow down the hardening process of gypsum. If the plaster does not harden well, it must be soaked in warm water (35–40 °C). You can add aluminum alum to the water at the rate of 5–10 g per 1 liter or table salt(1 tablespoon per 1 liter). A 3% starch solution and glycerin delay the setting of gypsum.
Since gypsum is very hygroscopic, it is stored in a dry, warm place.
Plaster bandages are made from ordinary gauze. To do this, the bandage is gradually unwound and a thin layer of gypsum powder is applied to it, after which the bandage is again loosely rolled into a roll.
Ready-made non-shedding plaster bandages are very convenient for use. The plaster cast is intended to perform the following manipulations: pain relief for fractures, manual reposition of bone fragments and reposition using traction devices, application of adhesive traction, plaster and adhesive dressings. In some cases, it is permissible to apply skeletal traction.
Plaster bandages are immersed in cold or slightly warmed water, and air bubbles that are released when the bandages get wet are clearly visible. At this point, you should not press on the bandages, as part of the bandage may not be saturated with water. After 2–3 minutes, the bandages are ready for use. They are taken out, lightly wrung out and rolled out on a plaster table, or the damaged part of the patient’s body is directly bandaged. To make the bandage strong enough, you need at least 5 layers of bandage. When applying large plaster casts, you should not soak all the bandages at once, otherwise the nurse will not have time to use some of the bandages within 10 minutes, they will harden and will be unsuitable for further use.
Rules for applying bandages:
– before rolling out the plaster, measure the length of the applied bandage along the healthy limb;
– in most cases, the bandage is applied with the patient lying down. The part of the body on which the bandage is applied is raised above the table level using various devices;
– the plaster cast should prevent the formation of stiffness in the joints in a functionally unfavorable (vicious) position. To do this, the foot is placed at a right angle to the axis of the shin, the shin is in a position of slight flexion (165°) at the knee joint, the thigh is in a position of extension in the hip joint. Even with the formation of contracture in the joints lower limb in this case it will be supportive and the patient will be able to walk. On the upper limb, the fingers are placed in a position of slight palmar flexion with the first finger opposed, the hand is in a position of dorsal extension at an angle of 45° in the wrist joint, the flexor forearm is at an angle of 90-100° in the elbow joint, the shoulder is abducted from the body at an angle of 15– 20° using a cotton-gauze roll placed in armpit. For some diseases and injuries, as directed by a traumatologist, a bandage may be applied in the so-called vicious position for a period of no more than one and a half to two months. After 3–4 weeks, when initial consolidation of the fragments appears, the bandage is removed, the limb is placed in the correct position and fixed with a plaster;
– plaster bandages should lie evenly, without folds or kinks. Anyone who does not know desmurgy techniques should not apply plaster casts;
– areas subject to the greatest load are additionally strengthened (joint area, sole of the foot, etc.);
– the peripheral part of the limb (toes, hands) is left open and accessible for observation in order to notice the symptoms of compression of the limb in time and cut the bandage;
– before the plaster hardens, the bandage must be well modeled. By stroking the bandage, the body part is shaped. The bandage must be an exact cast of this part of the body with all its protrusions and depressions;
– after applying the bandage, it is marked, i.e., the diagram of the fracture, the date of the fracture, the date of application of the bandage, the date of removal of the bandage, and the name of the doctor are applied to it.
Methods of applying plaster casts. According to the method of application, plaster casts are divided into lined and unlined. With padding, a limb or other part of the body is first wrapped in a thin layer of cotton wool, then plaster bandages are placed on top of the cotton wool. Unlined dressings are applied directly to the skin. Pre-bone protrusions (area of the ankles, femoral condyles, iliac spines, etc.) are isolated with a thin layer of cotton wool. The first bandages do not compress the limb and do not cause bedsores from the plaster, but they do not fix bone fragments firmly enough, so when they are applied, secondary displacement of the fragments often occurs. Unlined bandages, if not carefully observed, can cause compression of the limb to the point of necrosis and pressure sores on the skin.
According to their structure, plaster casts are divided into longitudinal and circular. A circular plaster cast covers the damaged part of the body on all sides, while a splint cast covers only one part. A variety of circular dressings are fenestrated and bridge-like dressings. A windowed bandage is a circular bandage in which a window is cut out over a wound, fistula, drainage, etc. Care must be taken that the edges of the plaster in the area of the window do not cut into the skin, otherwise when walking soft fabrics will swell, which will worsen the wound healing conditions. Protrusion of soft tissues can be prevented by covering the window with a plaster flap each time after dressing.
A bridge bandage is indicated in cases where the wound is located throughout the entire circumference of the limb. First, circular bandages are applied proximally and distally to the wound, then both bandages are connected to each other with U-shaped curved metal stirrups. When connected only with plaster bandages, the bridge is fragile and breaks due to the weight of the peripheral part of the bandage.
Bandages applied to various parts of the body have their own names, for example, corset-coxite bandage, “boot”, etc. A bandage that fixes only one joint is called a splint. All other bandages must ensure immobility of at least 2 adjacent joints, and the hip bandage – three.
A plaster cast on the forearm is most often applied to fractures of the radius in a typical location. The bandages are laid out evenly along the entire length of the forearm from the elbow joint to the base of the fingers. A plaster splint for the ankle joint is indicated for fractures of the lateral malleolus without displacement of the fragment and ruptures of the ankle ligaments. Plaster bandages are rolled out with gradual expansion at the top of the bandage. The length of the patient’s foot is measured and, accordingly, 2 cuts are made on the splint in the transverse direction at the bend of the bandage. The splint is modeled and strengthened with a soft bandage. Splints are very easy to turn into circular bandages. To do this, it is enough to strengthen them on the limb not with gauze, but with 4–5 layers of plaster bandage.
A lining circular plaster cast is applied after orthopedic operations and in cases where bone fragments are welded together by callus and cannot move. First, the limb is wrapped in a thin layer of cotton wool, for which they take gray cotton wool rolled into a roll. It is impossible to cover it with separate pieces of cotton wool of different thicknesses, since the cotton wool will become matted and the bandage will cause a lot of inconvenience to the patient when wearing it. After this, a circular bandage in 5–6 layers is applied over the cotton wool with plaster bandages.
Removing the plaster cast. The bandage is removed using plaster scissors, a file, plaster forceps and a metal spatula. If the bandage is loose, you can immediately use plaster scissors to remove it. In other cases, you must first insert a spatula under the bandage in order to protect the skin from cuts from the scissors. The bandages are cut on the side where there is more soft tissue. For example, a circular bandage up to the middle third of the thigh - along the posterior outer surface, a corset - on the back, etc. To remove the splint, it is enough to cut the soft bandage.
Many people who are inexperienced in repair and construction often have a question: what is the difference between building materials such as gypsum and alabaster? And why do the bags say “construction gypsum” on the top and “alabaster” on the bottom?
In order not to get lost in the terms, you need to figure out what gypsum and alabaster actually are, whether there are differences between them and, if so, what they are.
Gypsum - origin, application
Gypsum is a dry composition made from a natural mineral - gypsum stone. The mineral is calcium sulfate dihydrate – CaSO4 2H2O with impurities in the form of silicon, aluminum and iron oxides.
Gypsum is a mineral of sedimentary origin. In nature, it most often occurs in the form of elongated prismatic crystals, although sometimes it forms in the form of dense tablet-like or scaly aggregates. The mineral is quite soft and easy to grind.
Large deposits of gypsum stone are located in countries such as Iran, the USA, Canada, Turkey, and Spain. In Russia, deposits of this rock are located in the Kama and Volga regions, Tatarstan, on the western slopes of the Ural Mountains and in the Krasnodar Territory.
A binder is obtained from a natural mineral - in fact, the gypsum that we all know. This is a white, cream or grayish powder (depending on the existing impurities), 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 to fix fractures, as well as in agriculture– scattered on fields to normalize soil acidity;
- in the form " building gypsum» it is used when carrying out repairs and finishing works, for the production of wall slabs and blocks, cornices, stucco moldings.
The mineral is also widely used in the paper and chemical industries: in the production of cement, sulfuric acid, glazes and paints.
Natural gypsum is fibrous and granular. To produce alabaster, fine-grained gypsum is used - alabaster. Construction alabaster has a finer grind and is the same calcium sulfate, but not dihydrate, but hemihydrate - CaSO4 0.5H2O. It is obtained by firing crushed natural alabaster at temperatures up to 180 degrees.
Thus, the alabaster that we purchase in hardware store, in a broad sense, is gypsum, but not all gypsum can be called alabaster.
Construction gypsum has the following characteristics:
- Density (true) is 2.6 – 2.76 g/cu. cm. In this case, in loose form, the density is 0.85 - 1.15 g/cu. cm, and in compacted - 1, 245 - 1,455 g / cubic meter. cm.
- Products made from gypsum have high fire resistance - they are destroyed only after 6-8 hours of exposure high temperature. The structures can withstand heating up to 600-700 degrees without destruction.
- The compressive strength of building gypsum is 4-6 MPa, high-strength gypsum is 15-40 MPa.
- Gypsum and products made from it conduct heat poorly; its heat transfer coefficient in the temperature range from 15 to 45 degrees is only 0.259 kcal/m deg/hour.
- Drying speed. After mixing with water, the gypsum solution begins to set within 4 minutes and over the next half hour it completely hardens. Therefore, you need to work with this solution very quickly.
Brands and properties of building gypsum
The regulatory document regulating the properties and quality of construction gypsum binders is GOST 125-79. The industry produces 12 grades of alabaster, differing in compressive strength.
The indicators are shown in the table:
| Gypsum brand | Tensile strength of beam samples measuring 40×40×160 mm 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 (start no earlier than 2 minutes, end no later than 15 minutes).
- B - normal hardening (start of setting no earlier than 6 minutes, end - no later than 30 minutes).
- B – slowly hardening (start of setting no earlier than 20 minutes, end – not standardized).
The degree of grinding is also standardized:
Thus, by the brand of binder, all its main characteristics can be determined.
For example, the bag says: G-6 B II.
This means that we have before us a material with the following characteristics:
- strength not less than 6 and not more than 7 MPa;
- slow hardening;
- medium grind.
Types of gypsum
Gypsum binders are used not only in their pure form, but also with various additives that allow them to change their properties.
Currently, the following varieties of gypsum can be found on sale:
- Construction – for the production of gypsum building materials and for carrying out plastering works. This material is good because it does not form cracks when drying. 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 is used to construct fireproof partitions and molds for the production of earthenware 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 plaster are much lighter than conventional plaster, allow the skin to breathe, are not afraid of moisture, and are permeable to x-rays (allowing you to control the process of bone fusion).
- Sculptural gypsum is the highest strength gypsum, practically free of impurities. The material has high degree white and is used to make figurines. Sculptures, souvenirs, as well as in the automotive and aviation industries. This astringent 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 plaster, but much lighter. Due to this, it is often used for ceiling stucco. The material is frost-resistant and has low water absorption, so 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 less wide application.
Gypsum has been known since ancient times and is still popular both in construction and in other industries, as well as in medicine. The formula of natural (dihydrate) gypsum is CaSO4 x2H2O. Even many modern materials do not surpass it in some technical characteristics. If we talk about construction, gypsum is most often used in the form of a powder, which is obtained by firing and grinding gypsum stone. Used as a binder for preparing various mortars, and also various decorative elements. To work with gypsum, it must be diluted in a certain proportion with water, filler must be added if necessary, after which it will turn into a plastic composition, and you can begin working with it directly.
Properties and application of building gypsum.
A distinctive feature of building gypsum from others binding materials(cement, lime paste) is its ability to expand during hardening. The setting process occurs quite quickly - from 5 to 30 minutes, which, in some cases, is not entirely convenient. The setting time of gypsum depends on various components: properties of raw materials, manufacturing technology, storage duration, amount of water introduced, temperature of the binder and water, mixing conditions, presence of additives, etc. To regulate the setting time, various additives are added to the gypsum when mixing with water. . For example, to slow down setting, SDB, lime-adhesive and keratin retarders are added to the gypsum solution in an amount not exceeding 0.1-0.5% (in terms of dry matter) by weight of gypsum. For small volumes of work, for example during repairs, hide glue or gelatin is also used as a retarder. These additives are known as gypsum plasticizers and retarders.
To speed up the setting (which is necessary, for example, for faster removal of a cast product from a mold) of gypsum, gypsum dihydrate, table salt and sodium sulfate are most often used, introducing them in an amount of 0.2 to 3% by weight.
Based on strength, gypsum is divided into 12 grades. In construction and repairs, grades from G2 to G7 are mainly used. The letter stands for the word “gypsum”, and the number indicates the compressive strength of this material. For example, the G7 gypsum grade has a compressive strength of 7 MPa or 70 kg/cm2. This is quite high strength with a density of 1200 ÷ 1500 kg/m 3.
Among the disadvantages, one can highlight its rather low hygroscopicity, so its use is only applicable in rooms with low humidity.
Working with plaster.
In practice, when working with gypsum, a solution of pure gypsum is mainly used, less often with filler. Depending on the type of work, the gypsum solution can have varying degrees of density: liquid, medium or normal or thick. To prepare a liquid solution for 1 kg of gypsum you will need approximately 0.7 liters of water, a medium or normal solution - for 1.5 kg of gypsum 1 liter of water and for a thick solution - for 2 kg of gypsum 1 liter of water.
The solution is prepared as follows: first pour into the prepared container required quantity water and gypsum is gradually poured into it with constant thorough mixing. With this method of preparation, a homogeneous mass is obtained without any admixtures of lumps of unmixed gypsum. You should not stir a gypsum solution that has already begun to set, since in this case the gypsum begins to rejuvenate and practically loses its strength qualities.
When working with gypsum, you should take into account the rapid setting of the gypsum solution and prepare in small portions. To slow down the setting time of the gypsum mortar, set retarders are used, which have already been discussed above. When using an adhesive solution as a retarder, it is poured into the water prepared for mixing, mixed thoroughly and the plaster is mixed in this water. Prepare glue solution should be based on one day of work.
Gypsum-based building materials.
Probably the most famous and widely used construction products made of gypsum is plasterboard sheets
. They are usually used for finishing walls, ceilings and installing partitions in rooms and buildings with dry, normal and even wet conditions. Drywall sheets are available in various sizes and are divided into two types rectangular shape: with straight longitudinal edges or with thinned edges on the front side.
Another type of gypsum-based building material is gypsum fiber extruded decorative boards. This material is widely used for interior decoration, as it has a noble and attractive appearance. In addition, the use of decorative boards reduces the labor intensity of finishing work, since putty and plastering work is eliminated. The front side of the slabs has low water absorption and a denser structure.
In addition to gypsum-based products, they are widely used bulk materials. It's a different kind dry mixes(plasters, putties, etc.). The use of dry plaster mixtures allows you to mechanize the application of the plaster layer and significantly reduce the drying time of the surfaces being finished.
Along with gypsum-based finishing materials, building materials such as gypsum concrete. And, although, due to the rather long drying period of structures, gypsum concrete is rarely used for the construction of walls, it has found quite wide application in the construction of partitions.
The undoubted advantage of gypsum concrete is its low thermal conductivity compared to traditional concrete, as well as its heat and sound insulation properties, which significantly reduces the cost of construction and provides sound insulation for each individual residential area.
Gypsum has been known since ancient times, but has not yet lost its popularity; even many modern materials cannot compete with it. It is used in construction, porcelain, ceramic, oil industry and in medicine.
Description of building material
Gypsum is produced from gypsum stone. To obtain gypsum powder, the stone is fired in rotary kilns and then ground to form a powder. Gypsum is most common in construction.
Walls, plastered gypsum mortar, capable of absorbing excess moisture and give it away when the air is too dry.
Gypsum formula
The name gypsum comes from Greek word gypsos. This material belongs to the class of sulfates. His chemical formula CaSO4?2H2O.
There are two types of gypsum:
- Fibrous - selenite;
- Grainy - alabaster.
Photos of gypsum varieties
Selenite Alabaster
Technical characteristics and properties
Everyone has gypsum mixtures technical specifications have great similarities, let us dwell on the properties and features of building gypsum.
These include:
- Density. Gypsum has a dense, fine-grained structure. The true density is 2.60-2.76 g/cm?. When loosely poured, it has a density of 850-1150 kg/m2, and when compacted, the density is 1245-1455 kg/m2.
- How long does it take to dry? The advantages of gypsum include rapid setting and hardening. The gypsum sets in the fourth minute after mixing the solution, and after half an hour it completely hardens. Therefore, the finished gypsum solution must be used immediately. To slow down the setting, water-soluble animal glue is added to the plaster.
- Specific gravity. Is the specific gravity of gypsum measured in kg/m? in the MKGSS system. Since the ratio of mass is equal to the volume it occupies, the specific, volumetric and bulk weight of gypsum is approximately the same.
- What temperature can it withstand? t melting). Gypsum can be heated to 600-700°C without destruction. The fire resistance of gypsum products is high. Their destruction occurs only six to eight hours after exposure to high temperature.
- Strength. Construction gypsum has a compressive strength of 4-6 MPa, high-strength - from 15 to 40 MPa or more. Well-dried samples have two to three times higher strength.
- GOST State standard of gypsum 125-79 (ST SEV 826-77).
- Thermal conductivity. Gypsum is a poor conductor of heat. Its thermal conductivity is 0.259 kcal/m deg/hour in the range from 15 to 45°C.
- Solubility in water. R dissolves in small quantities: 2.256 g dissolves in 1 liter of water at 0°, 2.534 g at 15°, 2.684 g at 35°; with further heating, the solubility decreases again.
The video talks about building gypsum and how you can improve its properties by giving additional strength:
Types of gypsum
Gypsum has the greatest variety of applications among other binding materials. It allows you to save on other materials. There are many varieties of gypsum.
Building
It is used for the production of gypsum parts, partition slabs for plastering work. Work with gypsum mortar must be carried out very quickly short time– from 8 to 25 minutes, it depends on the type of plaster. During this time it must be completely used up. When hardening begins, gypsum already gains about 40% of its final strength.
Since cracks do not form on the gypsum during hardening, when mixing the solution with lime mortar, which gives it plasticity, you don’t have to add various fillers. Due to short terms setting retarders are added to gypsum. Construction gypsum reduces labor intensity and construction costs.
In deposits by blasting gypsum-containing rock. The ore is then transported to factories in the form of gypsum stones.
High strength
The chemical composition of high-strength gypsum is similar to building gypsum. But building gypsum has smaller crystals, while high-strength gypsum has large crystals, so it has less porosity and very high strength.
High-strength gypsum is produced by heat treatment in a sealed apparatus into which gypsum stone is placed.
The scope of application of high-strength gypsum is extensive. Various are prepared from it building mixtures, build fireproof partitions. It is also made from various shapes for the production of porcelain and earthenware sanitary products. High-strength gypsum is used in traumatology and dentistry.
Polymeric
Orthopedic traumatologists are more familiar with synthetic polymer plaster; plaster bandages are produced on its basis for applying bandages for fractures.
Advantages of polymer plaster casts:
- three times lighter than conventional plaster;
- easy to apply;
- allow the skin to breathe, as they have good permeability;
- resistant to moisture;
- allow you to control bone fusion, as they are permeable to x-rays.
Cellacast
Bandages are also made from this plaster; their structure allows the bandage to be stretched in all directions, so very complex bandages can be made from it. Cellacast has all the properties of a polymer bandage.
Sculpted or molded
This is the most highly durable gypsum, it does not contain any impurities, it has high natural whiteness. It is used for making molds for sculptures, plaster figurines, sculpting souvenirs, in the porcelain and earthenware, aviation and automotive industries.
This is the main component of dry putty mixtures. Molding gypsum is obtained from building gypsum, for this it is additionally sifted and ground.
Known for several centuries, it still remains relevant in our time. The most common rosettes are gypsum, they are easy to make with your own hands.
Acrylic
Acrylic plaster is made from water-soluble acrylic resin. After hardening, it looks similar to regular plaster, but is much lighter. Ceiling stucco and other decorative details are made from it.
Acrylic gypsum is frost-resistant and has little moisture absorption, so it can be used to decorate building facades, creating interesting design solutions.
Working with acrylic plaster is very simple. If you add a little marble chips or aluminum powder or other inert fillers to the solution, acrylic plaster products will closely resemble marble or metal ones.
This is what acrylic plaster looks like
Polyurethane
Gypsum stucco can also be made from polyurethane or polystyrene gypsum. It costs much less than ordinary gypsum, and its qualities are almost no different from it.
White
By using white plaster seal seams, cracks, make stucco molding and carry out other types of construction and repair work. It is compatible with various types building materials. White gypsum hardening time 10 minutes.
Fine grain
Fine-grained gypsum is also called translucent. It is used to fill seams, joints in slabs, etc.
Liquid
Liquid gypsum is prepared from gypsum powder.
It is prepared using the following technology:
- Pour water in the required quantity.
- Pour in gypsum and mix immediately.
- The density of the solution can be varied. A liquid solution is made to fill the molds
Waterproof (moisture resistant)
Waterproof gypsum is obtained by processing raw materials according to special technology. To improve the properties of gypsum, stillage is added to it - a waste product from the production of ethyl alcohol.
Refractory
Gypsum is a non-flammable material and is not flammable, but plasterboard sheets made from it are quite flammable. To give them fire resistance, tongue-and-groove gypsum is used. It is used wherever it is required to increase fire resistance.
Architectural
Architectural gypsum does not contain toxic components, it is very plastic. Its acidity is similar to that of human skin. Designers really like classic modeling from architectural plaster; there is a very high demand for it.
It requires certain knowledge, so you should first carefully study the features of such work, and only then proceed to practice.
Stamps
Plaster marking is carried out after testing standard samples of sticks for bending and compression two hours after they are molded. According to GOST 129-79, twelve grades of gypsum are established, with strength indicators from G2 to G25.
Plaster substitute
An analogue of gypsum is a fine grayish powder white- alabaster. It is also popular in construction. Alabaster is obtained from natural gypsum dihydrate by heat treatment at temperatures from 150 to 180? C. Externally, alabaster and gypsum are no different from each other.
Alabaster is used to plaster walls and ceilings with low humidity in the room. Gypsum panels are produced from it.
What is the difference between plaster and alabaster?
Gypsum and alabaster have the following differences:
- Alabaster is more limited in application, as it is used only in the construction industry. Gypsum is also used in medicine.
- Alabaster dries instantly, so it is not suitable without the addition of special substances.
- Gypsum is safer for environment and human health.
- Alabaster has greater hardness than gypsum.