If you wondered what gypsum is, you should know that it is a mineral belonging to the class of sulfates. Two varieties of this material are known, one of which is called fibrous, and the other is granular. The latter is alabaster.
general information
Gypsum has a silky or glass luster, the first of which is peculiar to the fibrous variety. Cleavage perfect in one direction. The material is split into thin plates. Color can be:
- reddish;
- gray
- white
- brown;
- yellowish.
Fibrous species give a splintery fracture. The density of the material is 2.3 g / cm 3 . The gypsum formula is as follows: CaSO4 · 2H2O. The texture of the material is massive.
Properties and varieties
The specific gravity of the material can reach 2.4 g / cm
3 . Gypsum is quite dense, can be granular and leafy, as well as fibrous. Some of his doubles resemble a
dovetail. Sometimes it is confused with anhydride, which has medium hardness.
When you study the question of what gypsum is, you will find out that when heated, the material goes into CaSO4 • 1/2 • H2O. The temperature limit is 107 ° C. When wetted with water, it hardens and sets, and dissolves in hydrochloric acid.
To date, 3 varieties are known, among them:
- selenite;
- marino glass;
- alabaster.
The first is parallel to the needle and has a silky sheen. Transparent plate - this is marino glass. Painted fine-grained may be alabaster.
Application
Selenite, which is fibrous, is used for inexpensive jewelry. But large alabaster, which has been used since ancient times, forms the basis of large ones. Raw materials are turned. As a result, it is possible to obtain also interior items, among which:
- ink tanks
- countertops;
- vases.
If you are interested in the question of what gypsum is, then you should know: the material is used in its raw form as a fertilizer, as well as for the production of glaze, enamel and paint in the industry and the pulp and paper industry.
Calcined material is used for casts and castings. It can be eaves and bas-reliefs. In medicine and construction, the material acts as a binder. More dense varieties serve as ornamental material.
More about application
Gypsum is a valuable stone and is widely used in construction. Millennia ago, it was noticed that, when ground, it helps to combat soil salinization. This mineral was mined in karst caves. From ancient times to this day, to increase the yield of agricultural crops, gypsum is applied to the soil.
For many nations he was the breadwinner. Entire cities were built from plaster. Crystal blocks were cut from it, which went to the erection of walls. The white stone shines dazzlingly in the sun. This can be seen even today, when only ruins remained from the ancient cities.
All over the world, sculptors cannot do without this mineral. It is inexpensive, lightweight and easy to handle. Appreciated by plasterers, traumatologists and paper manufacturers.
Origin
If you are trying to understand what gypsum is, then you should also familiarize yourself with its origin. This mineral has several types, the formation method of which is different. In some deposits, a mineral is mined, which was concentrated there during the accumulation of marine sediment. In other cases, gypsum was formed when different lakes dried out. A mineral could occur during the deposition of native sulfur and during the weathering of its compounds. Deposits in this case may be contaminated with rock fragments and clays.
Place of Birth
Having familiarized yourself with the description of gypsum, you should also learn about the main deposits that are found on all continents. Russian development is carried out mainly in the Caucasus and the Urals. The mineral is mined in the mountainous regions of America and Asia. The United States is the champion of gypsum production. There are deposits also in the foothills of the Alps.
Specifications
The described mineral has a fairly dense fine-grained structure. In loose bulk form, the density can vary from 850 to 1150 kg / cm 3 . In a compacted form, this parameter reaches 1455 kg / cm 3 . Getting acquainted with the description of gypsum, you will pay attention to one of its advantages, which is expressed in quick hardening and setting. In the fourth minute after mixing the solution, the first stage of drying begins, and within half an hour the material solidifies.
Ready gypsum mortar requires immediate consumption. To slow down the setting, water-soluble animal glue is added to the ingredients . Among the properties of gypsum, the melting point should be highlighted. The material can be heated to 700 ° C without destruction. Plaster products are quite fireproof. They begin to collapse only 6 hours after exposure to high temperature.
The strength of gypsum is also often taken into account. When compressed, this parameter can vary from 4 to 6 MPa. If we are talking about high-strength material, then it reaches 40 MPa and can even exceed this value. In well-dried samples, the strength is 3 times higher. The mineral complies with state standards 125-79. It has a thermal conductivity of 0.259 kcal / m * deg / hour. The temperature range is equal to the limit of 15 to 45 ° C.
White gypsum is soluble in water in small quantities:
- At 0 ° C, 2.256 g can dissolve in one liter.
- If the temperature rises to 15 ° C, solubility increases to 2.534 g.
- This value increases to 2.684 g at 35 ° C.
If further heating occurs, then the solubility decreases.
Description, scope and properties of gypsum
If we compare gypsum with other binders, the first has a wider area of use. With it, you can save on other components. The construction variety is used in the manufacture of gypsum parts, during plastering and the formation of partition walls.
It is necessary to work with gypsum mortar very quickly. The start time of the polymerization can be from 8 to 25 minutes after mixing the solution. The final value depends on the variety. At the beginning of hardening, the mineral gains about 40% final strength. In this process, white gypsum is not covered by cracks; therefore, various aggregates can be dispensed with when mixing a solution with a lime composition. The construction variety reduces the complexity and costs of the work.
Scope and properties of high-strength and polymer gypsum
In terms of chemical composition, the high-strength variety is similar to the construction one. However, the latter has smaller crystals. High strength has coarse particles, therefore, has less porosity and high strength. This material is obtained by heat treatment of gypsum stone in a tight environment.
The scope is the manufacture of building mixtures and the construction of fireproof partitions. Molds for the production of faience and porcelain are made from high-strength mineral. The polymer species is also called synthetic and is more familiar to orthopedic traumatologists. On its basis gypsum bandages are made for applying bandages for fractures. But the scope of gypsum is not the only advantage, among others it should be highlighted:
- easy overlay;
- moisture resistance;
- less weight than conventional plaster casts.
Finally
The gypsum formula should be known to you if you are interested in this mineral. It is important to take an interest in other properties as well as varieties. Among others, it is worth highlighting molding, sculpture and cellacast.
The latter is used to make bandages, and the structure allows you to stretch the material in all directions. The most durable is sculptural gypsum, which does not contain impurities. Among the properties of white gypsum, one can distinguish its impeccable whiteness.