Construction Materials. GOST 125-79 - Gypsum binders. Specifications. OKS: Building materials and construction, Construction materials. GOST standards. Gypsum binders. Technical conditions. class=text>

GOST 125-79

Gypsum binders. Specifications

GOST 125-79
Group Zh12

INTERSTATE STANDARD

GYPSUM BINDERS
Specifications
Gypsum binders. Specifications

OKP 57 4431

Date of introduction 1980-07-01

INFORMATION DATA

1. DEVELOPED AND INTRODUCED by the Ministry of Industry building materials USSR

2. APPROVED AND ENTERED INTO EFFECT by Resolution of the USSR State Committee for Construction Affairs dated July 19, 1979 N 123.

3. INSTEAD GOST 125-70, GOST 5.1845-73

4. REFERENCE REGULATIVE AND TECHNICAL DOCUMENTS

5. REPUBLICATION. October 2002

This standard applies to gypsum binders obtained by heat treatment of gypsum raw materials to calcium sulfate hemihydrate and used for the manufacture of construction products of all types and in the production construction work, as well as for the manufacture of forms and models in porcelain-faience, ceramic and other industries.
The standard complies with the requirements of ST SEV 826-77 in the part specified in Appendix 2.
Requirements for medical plaster must be established by the relevant regulatory and technical document developed on the basis of ST SEV 826-77.

1. TECHNICAL REQUIREMENTS

1. TECHNICAL REQUIREMENTS

1.1. Binders must be manufactured in accordance with the requirements of this standard for technological regulations, approved in the manner established by the manufacturer's ministry.

1.2. For the production of binders, gypsum stone is used in accordance with GOST 4013 or phosphogypsum in accordance with the current regulatory and technical documentation.

1.3. Depending on the compressive strength, the following grades of gypsum binders are distinguished: G-2, G-3, G-4, G-5, G-6, G-7, G-10, G-13, G-16, G -19, G-22, G-25.
The minimum tensile strength of each brand of binder must correspond to the values ​​given in Table 1.

Table 1

1.4. Depending on the setting time, the types of binders listed in Table 2 are distinguished.

table 2

1.5. For the porcelain-faience and ceramic industries, binders are produced with the setting times established for normal-hardening gypsum.

1.6. Depending on the degree of grinding, the types of binders listed in Table 3 are distinguished.

Table 3

1.7. For the porcelain, earthenware and ceramics industries, finely ground binders are produced with a maximum residue on a sieve with cells with a clear mesh size of 0.2 mm of no more than 1%.

1.8. The manufacturer must determine the specific surface area of ​​the finely ground binder at least once a month and indicate its value in a document of the established form.

1.9. Binders used in porcelain, earthenware, ceramics and other industries must meet the additional requirements specified in Table 4.

Table 4

1.10. Binders of the highest quality category must meet the additional requirements specified in Table 5.

Table 5

Example symbol gypsum binder with a strength of 5.2 MPa (52 kgf/cm) with setting times: beginning - 5 minutes, end - 9 minutes and the residue on the sieve with a clear cell size of 0.2 mm is 9%, i.e. binder grade G-5, fast-hardening, medium grinding:

G-5 A II

Note. Possible areas of application of binders are indicated in Appendix 1.

2. ACCEPTANCE RULES AND TEST METHODS

________________
* Acceptance rules - according to GOST 26871.

2.1. Delivery and acceptance of binders is carried out in batches. A batch is considered to be binder of one type and one brand.
The batch size is determined depending on the annual capacity of the enterprise in the following quantities:

Up to 200 tons - with an annual capacity of St. 150 thousand tons;
- up to 65 tons - with an annual capacity of up to 150 thousand tons.
When exporting binder to the courts, the size of the batch is determined by agreement of the parties.

2.2. The manufacturer must guarantee and confirm with a document of the established form that the properties of the binder comply with the requirements of this standard based on the results of current tests.

2.3. The consumer has the right to carry out a control check of compliance of the properties of the binder with the requirements of this standard, using the sampling procedure and test methods in accordance with GOST 23789.
If a discrepancy is detected between the bending or compressive strength of the binder and the grade specified in the relevant document, it must be changed in accordance with the actual strength.

2.4. Sampling and testing methods for binders are carried out in accordance with GOST 23789.

3. PACKAGING, LABELING, TRANSPORTATION AND STORAGE

________________
* Packaging, labeling, transportation and storage - in accordance with GOST 26871.

3.1. Binders are shipped unpacked or packed in bags in accordance with GOST 2226 and other containers.

3.2. Binders used for the porcelain-faience and ceramic industries, as well as for special purposes, must be shipped only packed in bags in accordance with GOST 2226.

3.3 The manufacturer must accompany each shipped batch with a document in the prescribed form, which indicates:
- name of the organization subordinate to which the manufacturer is located;
- name and address of the manufacturer;
- batch number and date of issue of the document;

Batch weight and dispatch date;
- name and address of the recipient;
- designation of the binder according to clause 1.10 and the results of physical and mechanical tests;
- specific surface area for finely ground astringent;
- designation of this standard.

3.4. During transportation and storage, binders must be protected from moisture and contamination.

4. MANUFACTURER WARRANTY

4.1. The manufacturer must ensure that the properties of gypsum binders comply with the requirements of this standard, subject to the conditions of transportation and storage.
The guaranteed shelf life of binders is 2 months from the date of manufacture.

APPENDIX 1 (for reference). AREA OF APPLICATION OF GYPSUM BINDERS

ANNEX 1
Information

APPENDIX 2 (for reference). INFORMATION DATA ABOUT COMPLIANCE WITH GOST 125-79 ST SEV 826-77

APPENDIX 2
Information

INFORMATION DATA ABOUT COMPLIANCE WITH THIS STANDARD ST SEV 826-77

Table 5

An example of a symbol for a gypsum binder with a strength of 5.2 MPa (52 kgf/cm2) with setting times: beginning - 5 minutes, end - 9 minutes and the residue on a sieve with a clear cell size of 0.2 mm is 9%, i.e. binder grade G-5, fast-hardening, medium grinding:

G-5 A II

Note. Possible areas of application of gypsum binders are indicated in Appendix 1.

2. Acceptance rules and test methods

2.1. Delivery and acceptance of binders is carried out in batches. A batch is considered to be binder of one type and one brand.

The batch size is determined depending on the annual capacity of the enterprise in the following quantities:

up to 200 tons - with an annual capacity of over 150 thousand tons;

up to 65 tons - with an annual capacity of up to 150 thousand tons.

When shipping binders in courts, the size of the batch is determined by agreement of the parties.

2.2. The manufacturer must guarantee and confirm with a document of the established form that the properties of the binder comply with the requirements of this standard based on the results of current tests.

2.3. The consumer has the right to carry out a control check of compliance of the properties of the binder with the requirements of this standard, using the sampling procedure and test methods in accordance with GOST 23789-79.

If a discrepancy is detected between the bending or compressive strength of the binder and the grade specified in the relevant document, it must be changed in accordance with the actual strength.

2.4. Sampling and testing methods for binders are carried out in accordance with GOST 23789-79.

3. Packaging, labeling, transportation and storage

3.1. Binders are shipped unpacked or packed in bags in accordance with GOST 2226-75 and other containers.

3.2. Binders used for the porcelain-faience and ceramic industries, as well as for special purposes, must be shipped only packed in bags in accordance with GOST 2226-75.

3.3. The manufacturer must accompany each shipment with a document in the prescribed form, which indicates:

name of the organization subordinate to which the manufacturer is located;

name and address of the manufacturer;

batch number and date of issue of the document;

batch weight and dispatch date;

name and address of the recipient;

designation of the binder according to clause 1.11 and the results of physical and mechanical tests;

specific surface area for finely ground astringent;

designation of this standard;

image of the state Quality Mark according to GOST 1.9-67 for binders of the highest quality category.

3.4. During transportation and storage, gypsum binders must be protected from moisture and contamination.

4. Manufacturer's warranty

4.1. The manufacturer must ensure that the properties of gypsum binders comply with the requirements of this standard, subject to the conditions of transportation and storage.

The guaranteed shelf life of gypsum binders is two months from the date of manufacture.

ANNEX 1

You can get acquainted with the technologies and equipment for the production of hyposum binder in the report of the Academy of Conjuncture Industrial Markets"Analysis of equipment for the production of gypsum and anhydrite binders"

By Decree of the USSR State Committee for Construction Affairs dated July 19, 1979 No. 123, the implementation period was established

from 01.07.80

This standard applies to gypsum binders obtained by heat treatment of gypsum raw materials to calcium sulfate hemihydrate and used for the manufacture of building products of all types and during construction work, as well as for the manufacture of forms and models in porcelain, earthenware, ceramics and other industries.

This standard complies with the requirements of the CMEA standard 826-77 in the part specified in the appendix.

Requirements for medical plaster must be established by the relevant regulatory and technical document developed on the basis of ST SEV 826-77.

1. TECHNICAL REQUIREMENTS

1.1. Gypsum binders must be manufactured in accordance with the requirements of this standard according to technological regulations approved in the manner established by the manufacturer's ministry.

1.2. For the production of binders, gypsum stone is used in accordance with GOST 4013-82 or phosphogypsum in accordance with the current regulatory and technical documentation.

1.3. Depending on the compressive strength, the following grades of gypsum binders are distinguished: G-2, G-3, G-4, G-5, G-6, G-7, G-10, G-13, G-16, G -19, G-22, G-25.

The minimum tensile strength of each brand of binder must correspond to the values ​​given in table. 1.

Table 1

MPa (kgf/cm 2)

1.4. Depending on the setting time, the types of binders listed in table differ. 2.

table 2

1.5. For the porcelain-faience and ceramic industries, binders are produced with the setting times established for normal-hardening gypsum.

1.6. Depending on the degree of grinding, the types of binders listed in table are distinguished. 3.

Table 3

1.7. For the porcelain, earthenware and ceramics industries, finely ground binders are produced with a maximum residue on a sieve with cells with a clear mesh size of 0.2 mm of no more than 1%.

1.8. The manufacturer must determine the specific surface area of ​​the finely ground gypsum binder at least once a month and indicate its value in a document of the established form.

1.9. Binders used in porcelain, earthenware, ceramics and other industries must meet the additional requirements specified in Table. 4.

Table 4

1.10. Binders of the highest quality category must meet the additional requirements specified in table. 5.

Table 5

An example of a symbol for gypsum binder with a strength of 5.2 MPa (52 kgf/cm 2) with setting times: beginning - 5 minutes, end - 9 minutes and residue on a sieve with a clear cell size of 0.2 mm 9%, i.e. . binder grade G-5, fast-hardening, medium grinding:

G-5 A II

Note. Possible areas of application of gypsum binders are indicated in Appendix 1.

2. ACCEPTANCE RULES AND TEST METHODS

2.1. Delivery and acceptance of binders is carried out in batches. A batch is considered to be binder of one type and one brand.

The batch size is determined depending on the annual capacity of the enterprise in the following quantities:

up to 200 tons - with an annual capacity of over 150 thousand tons;

up to 65 tons - with an annual capacity of up to 150 thousand tons.

When shipping binders in courts, the size of the batch is determined by agreement of the parties.

2.2. The manufacturer must guarantee and confirm with a document of the established form that the properties of the binder comply with the requirements of this standard based on the results of current tests.

2.3. The consumer has the right to carry out a control check of compliance of the properties of the binder with the requirements of this standard, using the sampling procedure and test methods in accordance with GOST 23789-79.

If a discrepancy is detected between the bending or compressive strength of the binder and the grade specified in the relevant document, it must be changed in accordance with the actual strength.

2.4. Sampling and testing methods for binders are carried out in accordance with GOST 23789-79.

3. PACKAGING, LABELING, TRANSPORTATION AND STORAGE

3.1. The binder is shipped unpacked or packed in bags in accordance with GOST 2226-88 and other containers.

3.2. Binders used for the porcelain-faience and ceramic industries, as well as for special purposes, must be shipped only packed in bags in accordance with GOST 2226-88.

3.3. The manufacturer must accompany each shipment with a document in the prescribed form, which indicates:

Name of the organization subordinate to which the manufacturer is located;

Name and address of the manufacturer;

Batch number and date of issue of the document;

Batch weight and dispatch date;

Recipient's name and address;

Designation of binder according to clause 1.11 and results of physical and mechanical tests;

Specific surface area for finely ground astringent;

Designation of this standard.

3.4. During transportation and storage, gypsum binders must be protected from moisture and contamination.

4. MANUFACTURER WARRANTY

4.1. The manufacturer must ensure that the properties of gypsum binders comply with the requirements of this standard, subject to the conditions of transportation and storage.

The guaranteed shelf life of gypsum binders is 2 months from the date of manufacture.

ANNEX 1

Group Zh12

INTERSTATE STANDARD

GYPSUM BINDERS

Specifications

Gypsum binders. Specifications

Text Comparison of GOST 125-79 with GOST 125-2018, see the link.
- .
____________________________________________________________________

OKP 57 4431

Date of introduction 1980-07-01

INFORMATION DATA

1. DEVELOPED AND INTRODUCED by the Ministry of Construction Materials Industry of the USSR

2. APPROVED AND ENTERED INTO EFFECT by Resolution of the USSR State Committee for Construction Affairs dated July 19, 1979 N 123.

3. INSTEAD GOST 125-70, GOST 5.1845-73

4. REFERENCE REGULATIVE AND TECHNICAL DOCUMENTS

5. REPUBLICATION. October 2002

This standard applies to gypsum binders obtained by heat treatment of gypsum raw materials to calcium sulfate hemihydrate and used for the manufacture of building products of all types and during construction work, as well as for the manufacture of forms and models in porcelain, earthenware, ceramics and other industries.

The standard complies with the requirements of ST SEV 826-77 in the part specified in Appendix 2.

Requirements for medical plaster must be established by the relevant regulatory and technical document developed on the basis of ST SEV 826-77.

1. TECHNICAL REQUIREMENTS

1. TECHNICAL REQUIREMENTS

1.1. Binders must be manufactured in accordance with the requirements of this standard according to technological regulations approved in the manner established by the manufacturer's ministry.

1.2. For the production of binders, gypsum stone is used in accordance with GOST 4013 or phosphogypsum in accordance with the current regulatory and technical documentation.

1.3. Depending on the compressive strength, the following grades of gypsum binders are distinguished: G-2, G-3, G-4, G-5, G-6, G-7, G-10, G-13, G-16, G -19, G-22, G-25.

The minimum tensile strength of each brand of binder must correspond to the values ​​given in Table 1.

Table 1

1.4. Depending on the setting time, the types of binders listed in Table 2 are distinguished.

table 2

1.5. For the porcelain-faience and ceramic industries, binders are produced with the setting times established for normal-hardening gypsum.

1.6. Depending on the degree of grinding, the types of binders listed in Table 3 are distinguished.

Table 3

1.7. For the porcelain, earthenware and ceramics industries, finely ground binders are produced with a maximum residue on a sieve with cells with a clear mesh size of 0.2 mm of no more than 1%.

1.8. The manufacturer must determine the specific surface area of ​​the finely ground binder at least once a month and indicate its value in a document of the established form.

1.9. Binders used in porcelain, earthenware, ceramics and other industries must meet the additional requirements specified in Table 4.

Table 4

1.10. Binders of the highest quality category must meet the additional requirements specified in Table 5.

Table 5

An example of a symbol for a gypsum binder with a strength of 5.2 MPa (52 kgf/cm) with setting times: beginning - 5 minutes, end - 9 minutes and residue on a sieve with a clear cell size of 0.2 mm 9%, i.e. binder grade G-5, fast-hardening, medium grinding:

G-5 A II

Note. Possible areas of application of binders are indicated in Appendix 1.

2. ACCEPTANCE RULES AND TEST METHODS

________________
* Acceptance rules - according to GOST 26871.

2.1. Delivery and acceptance of binders is carried out in batches. A batch is considered to be binder of one type and one brand.

The batch size is determined depending on the annual capacity of the enterprise in the following quantities:

Up to 200 tons - with an annual capacity of St. 150 thousand tons;

Up to 65 tons - with an annual capacity of up to 150 thousand tons.

When shipping binders in courts, the size of the batch is determined by agreement of the parties.

2.2. The manufacturer must guarantee and confirm with a document of the established form that the properties of the binder comply with the requirements of this standard based on the results of current tests.

2.3. The consumer has the right to carry out a control check of compliance of the properties of the binder with the requirements of this standard, using the sampling procedure and test methods in accordance with GOST 23789.

If a discrepancy is detected between the bending or compressive strength of the binder and the grade specified in the relevant document, it must be changed in accordance with the actual strength.

2.4. Sampling and testing methods for binders are carried out in accordance with GOST 23789.

3. PACKAGING, LABELING, TRANSPORTATION AND STORAGE

________________
* Packaging, labeling, transportation and storage - in accordance with GOST 26871.

3.1. Binders are shipped unpacked or packed in bags in accordance with GOST 2226 and other containers.

3.2. Binders used for the porcelain-faience and ceramic industries, as well as for special purposes, must be shipped only packed in bags in accordance with GOST 2226.

3.3 The manufacturer must accompany each shipped batch with a document in the prescribed form, which indicates:

Name of the organization subordinate to which the manufacturer is located;

Name and address of the manufacturer;

Batch number and date of issue of the document;

Batch weight and dispatch date;

Recipient's name and address;

Designation of the binder according to clause 1.10 and the results of physical and mechanical tests;

Specific surface area for finely ground astringent;

Designation of this standard.

3.4. During transportation and storage, binders must be protected from moisture and contamination.

4. MANUFACTURER WARRANTY

4.1. The manufacturer must ensure that the properties of gypsum binders comply with the requirements of this standard, subject to the conditions of transportation and storage.

The guaranteed shelf life of binders is 2 months from the date of manufacture.

APPENDIX 1 (for reference). AREA OF APPLICATION OF GYPSUM BINDERS

ANNEX 1
Information

APPENDIX 2 (for reference). INFORMATION DATA ABOUT COMPLIANCE WITH GOST 125-79 ST SEV 826-77

APPENDIX 2
Information

INFORMATION DATA ABOUT COMPLIANCE WITH THIS STANDARD ST SEV 826-77

Electronic document text
and verified by:
official publication
M.: IPK Standards Publishing House, 2002

Construction and other gypsum materials are used in various industries National economy. They won't surprise anyone for a long time. But few people think about what gypsum binder actually is, what its raw materials are and how it is obtained. But for the production of all building materials (plasters, masonry mortars, plaster sheets) and other parts, you must first prepare the raw materials. After all, the characteristics of the finished material largely depend on the quality of the raw materials used.

Concept and composition

Gypsum binder is an airy material that consists primarily of gypsum dihydrate. The composition of gypsum is also supplemented by natural anhydride and certain industrial wastes, which include calcium sulfide.

This group also includes combined substances. They contain semi-hydrous gypsum, lime, cement.

The raw materials for production are rocks containing sulfates. GOST determines that for the production of gypsum binder only gypsum stone (meeting all the requirements imposed on it by GOST 4013) or phosphogypsum, which also meets the requirements of regulatory documents, can be used.

Characteristics of gypsum binders

The gypsum solution must be used until it has completely hardened. You cannot stir it after the crystallization process has already begun. Stirring causes the destruction of the formed bonds between the crystals of the framework. Because of this, the solution loses its astringent abilities.

Products made from gypsum are not waterproof. But material manufacturers have found a way out of this situation. Scientists have determined that various additions of gypsum binders can increase this figure. Therefore, various substances are added to the material: lime, crushed blast furnace slag, organic liquids that contain silicon.

The use of gypsum materials does not require the use of additional fillers. They do not shrink and cracks will not appear on the treated surface. Gypsum binders, on the contrary, increase in volume after complete hardening. In some situations, sawdust, firewood, pumice, expanded clay and other materials are added.

Another feature is that gypsum materials accelerate the corrosion process of ferrous metals (nails, fittings, wire, etc.). This process occurs even faster in humid conditions.

Gypsum binders quickly absorb moisture and lose their activity. Therefore, during storage and transportation it is necessary to follow some rules. The material can only be stored in a dry place. Even if this rule is followed, after three months of storage the material will lose approximately thirty percent of its activity. The material is transported in bulk or packed in containers. It is important to protect it from debris and moisture.

Production

For this process The following processes need to be performed:

• crushing natural gypsum substance;
• drying of raw materials;
• influence of temperature.

It is fed into a hopper, from where it enters the crusher. There it is crushed into pieces whose size does not exceed four centimeters. After crushing, the material is sent through the elevator to the supply hopper. From there it goes into the mill in equal parts. There it is dried and crushed to a smaller fraction. Drying at this stage is necessary to speed up and facilitate the process of crushing the material.

In the mill the powder is heated to ninety degrees. In this state, it is transported to the gypsum boiler. This is where water is released from the substance during the firing process. This process begins with low temperatures (about eighty degrees). But water leaves the material best at a temperature range from one hundred ten to one hundred eighty degrees.

The entire temperature treatment process is divided into two stages. First, the material is kept in a digester for three hours. There the water is removed and the dihydrous gypsum turns into semi-hydrous. All this time, the gypsum is stirred to ensure uniform heating. At the end of the specified time, the substance in a heated state is sent to the so-called simmering bunker. It no longer heats up. But due to the high temperature of the substance itself, the dehydration process continues there. This takes about another forty minutes. After this, the binding materials are considered ready. And they are sent to the finished goods warehouse.

Hardening of the material

Hardening of gypsum binders occurs when the powder is mixed with water. In this case, a plastic mass is formed, which hardens within a few minutes. From a chemical point of view, the opposite process occurs to what occurred during the production process. It just happens much faster. That is, semi-aqueous gypsum adds water, resulting in the formation of a dihydrate gypsum substance. This whole process can be divided into three stages.

In the first stage, the semi-aqueous gypsum substance is dissolved in water to form a saturated solution of gypsum dihydrate. The dihydrate has a high solubility. Due to this, the process of supersaturation of the solution occurs very quickly. As a result, a precipitate forms, which is a dihydrate. These fallen particles stick together, thereby starting the setting process.

The next stage is crystallization. As individual crystals of the substance grow, they begin to connect and form a strong frame. As it dries (moisture is removed), the bonds between the crystals become stronger.

Changing the setting speed

The setting process can be accelerated or, conversely, slowed down as necessary. This is done using additives that are added to gypsum binders.

Types of additives that speed up the setting process:

• substances that increase the solubility of the hemihydrate: sodium or potassium sulfate, table salt and others;

• substances that will be the center of crystallization in the reaction: salts of phosphoric acid, crushed natural gypsum, and so on.

The most commonly used is crushed gypsum stone. Its particles serve as crystallization centers around which the crystal will grow in the future. “Recycled” gypsum is characterized by greater efficiency. It is understood as gypsum, which has already gone through the stage of setting and hardening of calcium sulfide. This type includes broken and crushed products.

The following substances slow down the setting process:

• increasing the plasticity of the dough: a solution of wood glue in water, pine infusion, lime-glue emulsion, LST, and so on;

• The growth of crystals is prevented by a film that forms on grains of semi-aqueous gypsum under the influence of substances such as borax, ammonia, keratin retarder, alkali metal phosphates and borates, lilac alcohol and others.

It is worth noting that the introduction of additives accelerating the process negatively affects the strength of gypsum. Therefore, they must be used with caution and added in small quantities.

The setting (hardening) time largely depends on the quality of the starting material, time and storage conditions, the temperature at which the process of combining the material with water occurs, and even the time of mixing the solution.

Too much a short time Setting is usually associated with the presence of dihydrate particles in the material that remained there after firing. The setting time will also increase if the gypsum substance is heated to approximately forty-five degrees. If the temperature of the material is increased even more, the process, on the contrary, will slow down. Prolonged stirring of the gypsum mixture will speed up the setting process.

Differences between theory and practice

A feature of the hardening process is that gypsum, unlike other binders, increases in volume when hardening (up to one percent). Due to this, for the hydration of a semi-aqueous substance, approximately four times more water is needed than should be in theory. In theory, water requires approximately 18.6% of the mass of the material. In practice, water is taken to obtain a solution of normal thickness in an amount of up to seventy percent. To determine the water requirement of a material, determine the volume of water as a percentage of the mass of the material itself, which must be added to obtain a solution of normal thickness (cake diameter 180 + 5 millimeters).

Another difference in practice is that when excess water is removed during drying, pores form in the material. Due to this, the gypsum stone loses its strength. This issue can be eliminated by additional drying. Gypsum products are dried at a temperature not exceeding seventy degrees. If the temperature is increased even more, the dehydration reaction of the substance will begin.

The influence of temperature on the resulting substance

To obtain gypsum binder, gypsum stone is subjected to high temperatures. Depending on the value of this temperature, the gypsum substance can be of two types:

• Low-firing, for the production of which the processing of raw materials occurs under the influence of temperatures from one hundred twenty to one hundred eighty degrees. The raw material in this case is most often semi-aqueous gypsum. The main difference of this material is the high speed of hardening.

• High-firing (anhydrite), which are formed as a result of high temperature (over two hundred degrees). This material takes longer to harden. It also takes longer to set.

Each of these groups, in turn, has several various materials included in it.

Types of low-burning binders

Gypsum binder of this category includes the following materials:

• Construction gypsum. To manufacture it, it is necessary to select the right raw materials. The production of gypsum for construction work is permissible using as a raw material a binder grade of grade five and above, the remainder of which on the sieve is no more than twelve percent. For the manufacture of construction products, binders of grades two to seven are suitable, regardless of setting time and degree of grinding. Decorative elements are made from the same types of materials. With the exception of coarse and slow-setting substances. Gypsum plaster mixtures are made from substances of grade 2-25, except for coarse and quick-hardening binders.

• High-strength gypsum can be characterized by one of several grades (with indices from 200 to 500). The strength of this material is about 15-25 MPa, which is significantly higher than that of other types.

• Molding gypsum has a high water requirement and high strength in the hardened state. It is used to produce gypsum products: ceramic forms, porcelain and earthenware elements, and so on.

Anhydrite materials

This species, in turn, forms two substances:

• anhydrite cement, obtained by processing at temperatures up to seven hundred degrees;

• Estrich-gypsum, formed under the influence of temperatures above 900 degrees on calcium sulfate.

The composition of anhydrite gypsum includes: from two to five percent lime, a mixture of sulfate with vitriol (copper or iron) up to one percent, from three to eight percent dolomite, from ten to fifteen percent blast furnace slag.

Anhydrite cement has a slow setting (from thirty minutes to a day). Depending on the strength, it is divided into the following grades: M50, M100, M 150, M200. This type of cement is widely used in construction. It is used for:

• production of adhesive, plaster or masonry mortar;

• concrete production;

• production of decorative elements;

• production of thermal insulation materials.

Estrich gypsum has the following characteristics:

1. Slow setting.
2. Durability up to twenty megapascals.
3. Low thermal conductivity.
4. Good sound insulation.
5. Resistant to moisture.
6. Frost resistance.
7. Slight degree of deformation.

These are the main, but not all, advantages that estrich gypsum has. Its application is based on these indicators. It is used for plastering walls, producing artificial marble, constructing mosaic floors, and so on.

Division of binder into types

The properties of gypsum binders make it possible to divide them into several different groups. Several classifications are used for this.

Based on setting time, the following groups are distinguished:

• Group "A". It contains binders that set quickly. This takes from two to fifteen minutes.

• Group "B". Binding materials of this group set in a time of six to thirty minutes. They are called normally setting substances.

• Group “B”, which includes slow-setting binders. It takes more than twenty minutes to set. The upper limit is not standardized.

The grinding fineness is determined by the particles remaining on the sieve. This is due to the fact that gypsum binders always remain on a sieve with a mesh size of 0.2 millimeters. GOST indicates the following groups:

• A coarse grind or first group indicates that up to twenty-three percent of the material remains on the sieve.

• Medium grinding (second group), if no more than fourteen percent of the binder remains on the sieve.

• Fine grinding (third group) means that the remaining substance on the sieve does not exceed two percent.

The material is tested for strength in bending and compression. To do this, bars with dimensions of 40 x 40 x 160 millimeters are prepared from gypsum mortar. Two hours after manufacture, when the crystallization and hydration processes are completed, testing begins. Gypsum binders (GOST 125-79) are divided into twelve grades based on strength. They have indexes from two to twenty-five. The tensile strength values ​​depending on the brand are collected in special tables. It can be seen even in GOST itself.

The main parameters and types of material can be recognized by its markings. It looks something like this: G-6-A-11. This inscription will mean the following:

• G-gypsum binder.
• 6 - grade of material (means that the strength is more than six megapascals).
• A - determines the type based on the setting time (that is, quick-hardening).
• 11 - indicates the degree of grinding (in this case, medium).

Scope of application of gypsum substances

The technology of gypsum binders makes it possible to obtain materials suitable for use in various fields. Gypsum is most widely used in construction. The scale of its use can be compared with the use of cement. Gypsum binder has some advantages over cement. For example, its production requires almost four times less fuel. It is hygienic, resistant to fire, has a porosity ranging from thirty to sixty percent, and low density (up to one and a half thousand kilograms per cubic meter). These characteristics determined the scope of the material.

Gypsum is widely used. Its use does not depend on the grade of material. A binder with fine and medium grinding of particles is used, which sets normally and slowly. Gypsum is added to limestone and sand plaster. This improves the strength of the solution after drying. And the layer of plaster on the surface becomes smooth and light, suitable for further finishing.

Gypsum substances belonging to grades G-2 to G-7 are used for the manufacture of partition panels, sheets of so-called dry plaster and other gypsum concrete products. They are added to solutions to obtain compositions for interior work.

Ceramic, porcelain and earthenware products and parts are made with the addition of gypsum binder, belonging to grades from G-5 to G-25. The binder must belong to the category of normally setting and finely ground substances.

Gypsum binder is used to prepare a solution that is used for caulking windows, doors, and partitions. Lower grades of material are suitable for this purpose.

As you can see, the characteristics of gypsum binder allow the material to be used for various purposes and in various fields of activity. It is durable, frost-resistant, hygienic, environmentally friendly. Its quality characteristics are determined by belonging to a certain group of materials on one or another basis.