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Moisture absorption of bricks. Water absorption of bricks. Special varieties of ceramic bricks

This is a building material made on the basis of mineral raw materials. By its structure, brick is fake diamond. The use of this material goes back to ancient times. IN Ancient Egypt more often, unbaked raw brick was used, which was made from clay with the addition of straw. modern bricks have a rectangular shape and undergo serious heat treatment. Brick structures are durable, reliable, frost-resistant and retain heat well indoors.

In this article we will talk about the main varieties, technical characteristics and other points that you should pay attention to when choosing a brick.

Brick sizes

Depending on the size, bricks are divided into single, one and a half and double

The photo clearly shows the difference in size between single, one and a half and double bricks.

• (250x120x65 mm)- the most common type of molding is a single rectangular bar. When working with this brick, it is convenient for a bricklayer to work with one hand.
• (250x120x88 mm)bricks have a lower consumption in area and in the amount of mortar - the masonry moves faster.
• (250x120x138 mm)- according to GOST, the stone is called ceramic. In height, it is equal to two single. When used, ceramic stone reduces material costs and increases the speed of masonry.

may differ in format from . The narrow front brick has dimensions of 250x60x65 mm, the front brick of the European format has dimensions of 250x85x65 mm.

The three surfaces of a brick have specific names.

To understand masonry, it is useful to know the names of brick surfaces.

• Bed- this is the upper working part on which the solution is placed.
• Spoon part (spoons)- this is a lateral long surface, one of which goes out.
• Poke- this is the side surface with which one brick closes with another.

To improve the adhesion of surfaces (adhesion) with finishing materials one of the surfaces may have a corrugated coating.

Brick strength

One of the most important parameters when choosing a brick is its strength. The brick should not collapse under the influence of internal stresses and deformations. Strength depends on the brand of the product. The brand is denoted by the letter "M". The number indicates the load (in kilograms) that the material can withstand per 1 square centimeter (M100, M125, M150, M175, etc.). M100 - M150 is suitable for building houses with two or three floors. M200 is used in high-rise buildings, M300 - in the socles of high-rise buildings.

Frost resistance - low temperature test

In the northern and central regions of Russia, the climate is not mild. Rains can be replaced by unexpected frosts. Frost resistance is a characteristic that allows you to choose a brick according to climatic features. The cold resistance grade is indicated by the letter combination “Mrz” or F. Frost resistance is determined using laboratory tests. The brick is immersed in water and frozen, this cycle is repeated until the material begins to collapse, change weight and strength. After tests, the brick is assigned the brand F15, F25, F35 or F50. The number indicates the number of cycles. For the northern and central regions of Russia, it is recommended to use a grade of at least F35.

Water absorption

The water absorption parameter is associated with frost resistance. This characteristic is understood as the percentage of water to the total volume that a brick can absorb when completely immersed. When temperatures drop, moisture freezes and expands, which leads to the destruction of the internal structure of the material, so frost resistance also depends on water absorption. The complete absence of water absorption is also not allowed, the minimum value according to GOST is 6%. The maximum moisture absorption for a brick is 14%, for - 10%, for a brick of internal masonry - 16%.

Thermal conductivity - how to keep warm

Thermal conductivity is the ability of materials to transfer thermal energy (heat transfer). Due to the presence of the word "heat" in the term, some attribute this property of materials only to the rate of cooling. At the same time, thermal conductivity also affects the heating of cold objects. talking plain language, if it is hot outside, then in a house with walls made of a material with low thermal conductivity, coolness will remain longer, and in winter it will be warm.

Heat transfer is carried out due to the chaotic movement of particles in a substance - convection. There is no matter in a vacuum, and therefore thermal energy not transmitted by convection. When calculating the thermal conductivity of various substances, the vacuum medium is taken as 0.

An indicator that reflects the ability of a substance to conduct heat is the coefficient of thermal conductivity (W / (m * K)). The thermal conductivity of bricks depends on the manufacturing technology and material (from 0.3 to 1). The more air inside the body of a brick, the longer it will retain heat.

Hollow or full bodied

Brick differs depending on the amount of air inside the block

• - a monolithic bar without cavities, according to the standard, porosity cannot exceed 13%. The use of solid bricks allows you to increase the strength of the structure, so they are used for laying the basement, foundation and bearing walls. At the same time, full-bodied products are considered "cold": their thermal conductivity is 0.5 - 1 W / m * K.

Solid single ordinary brick for the construction of load-bearing walls. The spoon has a corrugated coating for improved adhesion

• has cavities that are made in the form of holes in the body of a brick. Holes can be in the form of slots (slotted, seven-slotted), squares and cylinders. The voids are from 45 to 55% of the volume of the briquette. The air trapped in the cavities is a heat-insulating substance, due to which hollow bricks have low thermal conductivity (0.3 - 0.9). At the same time, such a brick is not used for the construction of capital load-bearing structures, hollow bricks are also not used for structures where high refractory properties are required (for ovens, brick barbecue grills, etc.).

Ceramic brick for facing works, voids are made in the form of squares

Voidness affects the consumption of the solution during the work. Part of the solution falls into the holes. With proper masonry, this should be avoided, because of this, thermal insulation is violated.

• (warm ceramics)- a kind of hollow ceramic brick. The material used is fusible clay, to which sawdust and peat are added. Burning out, these inclusions leave cavities in the block. The grades of strength and frost resistance of porous bricks reach M-200 and F-200. Thermal conductivity is 0.1 - 0.261 W/m*K.

Some manufacturers mold porous bricks for a joint system where grooves and lugs alternate.

Wealth of colors - color choice

Traditionally brick house appears in orange-red tones (brick color). This color is typical for ceramic bricks. Shades in this case depend on various factors. The region of origin of the clay influences. Some varieties become yellowish or Orange color. Pigment additives can also change colors.

Initially it has a white color, but after making certain additives, its color can also be changed. When using one and a half masonry with facing bricks, the color of the inner masonry does not actually play a role. The front masonry can be given any color by glazing or engobing.

Glazed brick has a glossy color finish

An unusual color can have a radiated brick; outwardly, the surface of the brick is filled with overflows and gradients. This effect is achieved using a special firing technology. At the end of firing, the access of oxygen is limited, as a result, oxygen begins to be released from the clay, forming an uneven color on the surface of the material.

brick material

Brick is divided into types depending on the material.

• - the most common and oldest type of brick. The raw material for it is red clay. After molding the bars rectangular shape are fired in kilns. Such bricks can be used in a wide variety of areas. Initially, the material has a high moisture absorption, so it is treated with water-repellent substances.

Ceramic brick has a characteristic red color. The shape of a rectangular bar first began to be widely used in England in the 16th century.

In terms of strength, ceramic bricks correspond to grades from M-50 to M-300. The material can be either . Ceramic hollow bricks have one of the best performance in terms of thermal insulation.

Roasting is an important technological procedure in the production of bricks. Burnt brick will have black spots. Unburned is distinguished by light pink. Both technological marriages affect the characteristics of the material

• consists of a mixture of lime and sand. Temperature treatment does not take place in an oven, but in an autoclave - a heating apparatus that creates a pressure above atmospheric pressure. The mass fraction of lime and moisture does not exceed 10%. It is applied in summer cottage urban construction. The material is used for internal partitions because it has good sound insulation. Due to its fragility, it is not used for load-bearing structures and plinth. Silicate brick does not retain heat well, therefore, it needs additional thermal insulation. Silicate face brick is more suitable for hot and dry climates, ceramic - for areas with high humidity.

Silicate brick for facade cladding European standard

• Made from high quality clay. The material should not contain impurities of chalk and alkali metals. The material is used for street construction: paving paths, curbs, retaining walls and plinth cladding. Clinker brick has a high density (up to 2100 kg/m3) and low porosity (up to 5%), respectively, it practically does not absorb moisture.

Clinker brick in chocolate color is suitable for decorative facade masonry

• made of refractory clay - chamotte. The main property is low thermal conductivity, high cyclicity and resistance to high temperatures. It has the ability to accumulate and slowly release heat. Refractory material is used in the construction of stoves, chimneys, barbecue grills and other structures that require resistance to high temperatures.

outdoor oven from fireclay bricks for barbecue

• Hyper pressed brick- bricks of this type are used for facing works, to give the facade a final appearance. Various limestone rocks are used in production. These rocks include shell rock, marble chips, etc. The role of the binder is played by cement. Forming takes place using high pressure(20 MPa). The disadvantages of hyper-pressed bricks include significant weight, therefore, during the construction of it, a reinforced monolithic foundation will be required.

Different by purpose

Depending on the method of application, bricks are also divided into types.

• applied to carriers internal walls and partitions, erection of foundations, plinth and external walls. At the same time, the appearance of the brick is poorly suited for finishing works. The surface sometimes contains chips, which is allowed by the standards.

In inserts: Due to the unpresentable appearance, the outer walls of ordinary brick are faced, and the inner ones are finished off.

• - the face of any building. It has minimal deviations in size. By standards facing brick should not contain chips. Brick for facades can be silicate, ceramic or hyper-pressed. Depending on the climate, you can give preference to one of the species.

Facing hollow brick has a wood-like texture

Facing bricks can be of two types: textured and shaped. The surface of the textured brick is finished to look like stone, wood or velvet, the edges are sometimes rolled to give more decorative effect. Shaped bricks are designed for structures of complex shapes; shaped bricks include angular, rounded, and other varieties.

After molding, the facing brick can be applied various coatings: engobing and glazing. For engobed brick, a composition of liquid clay (engobe), crushed glass and mineral dyes is used. The clay mixture is applied in a thin layer, after which the brick is fired. After firing, the material acquires a matte even color. Glazed brick has glossy finish. After firing, a layer of glaze is applied to the briquette, a colored emulsion of crushed glass, then repeated firing is carried out at a lower temperature.

Brick molding

The types of molding bars can vary depending on the technological features.

• plastic molding involves the use of plastic clay masses with a water content of up to 21%. Used in production screw presses. The settings differ depending on the availability of air. The vacuum forming method is used for hollow bricks.
• Semi-dry molding is based on the use of high pressure and bringing the raw material to a certain moisture level (10 - 14%). Roasting takes place in special tunnel kilns.

How to protect yourself from buying low-quality bricks

To insure yourself against the purchase of a low-quality product, it is recommended to purchase a brick made in accordance with GOST. A brick made according to specifications can seriously differ in its properties. In this case, it is impossible to do without a visual assessment of quality.

Examine the brick. It is desirable that there are no cracks and chips on the body (according to GOST, no more than two corners (up to 15 mm) can be chipped), chipping (10 mm) is also allowed in an amount of no more than two, only one crack is allowed, while it should be no more 300 mm). Cracks and chips are not allowed on the front brick. Inspect the spoons; they should not have limestone deposits in the form of white spots or lumps. If black spots appear on the bed - this is a burnt brick. The amount of slabs (broken in half bars) should be less than 5%.

The geometry must not be broken. Check the strength and loudness indicators. When struck, a hollow brick should make a ringing sound, a full-bodied one sounds more muffled. To test the strength, drop the brick from a meter height onto a hard surface. The brick must either not break, or break into large pieces, if the material shattered into small crumbs, then the strength of the product leaves much to be desired. Before buying, it is recommended to inspect structures built from specific types of bricks.

brick consumption

When buying a brick, it is very important to correctly calculate the consumption. This will determine the main construction costs. The calculation is made by area (1 sq.m.) and by masonry volume (1 sq.m.). For a correct calculation, it is desirable to have on hand finished project structures or sketch. The number of floors, ceiling height, presence of gables, openings for windows and doors, wall thickness, as well as the thickness of the masonry seam affect the number of bricks. First you need to decide on the thickness of the walls.

visual view various ways masonry for different thickness walls

• In half a brick (12 cm)- the wall is not a carrier, but plays the role of a partition for delimiting zones inside the house. Such masonry can be reinforced with reinforcement.
• One brick (25cm)- load-bearing wall inside the room.
• One and a half bricks (38 cm)- bricks are stacked in two rows. The outer row is laid out along (poking to each other), and in the inner row the bricks are in contact with spoon parts. Masonry is allowed in small one-story houses.
• Two bricks and two and a half (51 cm and 64 cm)- used for load-bearing walls of houses in areas with temperate climate. In multi-storey buildings, a decrease in wall thickness is allowed depending on the height (first floor - 64 cm, second floor - 51 cm).

When calculating the consumption of bricks, the volume and area window openings are excluded. At the same time, it is recommended to take a margin of 10%, since during construction some of the bricks may go into marriage.

Conclusion

All types of bricks have their own advantages and disadvantages. For capital buildings, a full-bodied ceramic brick is suitable, the front one will help to give the building a unique look. Silicate brick is suitable for the construction of walls and partitions. Refractory brick will find application when laying a stove or fireplace.

Building yard

Choosing a brick: an overview

/articles/vybiraem-kirpich-obzor/

Water absorption of a brick is one of the most important indicators for hygroscopicity as a percentage.

The higher the hygroscopicity of a brick, the lower its strength.

This indicator shows the porosity of the product, which depends on its composition.

After all, the hygroscopicity of bricks has a rather impressive effect on the frost resistance of the material. For this reason, when the material is saturated with moisture, its strength will significantly decrease in comparison with dry material. To do this, it is necessary to take into account this important indicator when choosing a brick for the construction of a country estate.

In order to find out the hygroscopicity of a brick, the material is placed in an oven for several hours at a temperature of 110-120 ºС. After heating, the brick is cooled at natural temperature, then weighed. Then it is immersed in water for 2 days and weighed again. The difference in weight determines how much is absorbed into the material as a percentage. For building bricks the increase in mass must not be exceeded by more than 5%, and for finishing block no more than 14%.

Building bricks are divided into 3 main types

Building bricks are divided into three types: concrete block, silicate and ceramic bricks.

• concrete block;
• silicate;
• ceramic brick.

Concrete bricks are made by pouring them into specially prepared molds. cement mortar. At the same time, it is not in great demand in construction due to heavy weight, poor sound insulation, high thermal conductivity and high cost. From positive traits Concrete bricks can be noted for low water absorption of about 5%, in some types 3%, excellent strength for laying load-bearing walls and resistance to rapidly changing atmospheric conditions.

Sand-lime brick is 89.2% sand, the rest is lime and binder additives.

The composition of the silicate block includes 89.2% sand, the rest is lime and binder additives. In some cases, a coloring pigment is added to the composition of the workpiece to give the block the desired shade. Water absorption in silicates sometimes reaches 15%. For this reason, it is not recommended to use it in places with high humidity. Such as basements, laying foundations, baths, etc. The silicate block has good sound insulation, an acceptable price and is strong enough for laying load-bearing walls. The disadvantage is the high thermal conductivity in comparison with ceramic bricks.

The dull mustard color of ceramic bricks indicates under-firing, and in some places black, on the contrary, indicates over-firing.

The ceramic block is made from a mixture of clays and fired in a tunnel kiln at a temperature of 1000ºС. Fired according to the required standards, the ceramic billet has a reddish-brown color and, with a slight impact, makes a sonorous sound. Also, marriage can be distinguished by the color of the ceramic blank. A dull mustard color indicates underfiring, and in some places black indicates overfiring. According to the red standard ceramic block the minimum water absorption should be 6%, but can reach 14%. The optimum water absorption is 8%. The ceramic block has a layered structure. Water absorption is on average. Due to the moisture absorbed by ceramic bricks between the layers and the impossibility of rapid release of water during periods of significant temperature fluctuations and unfavorable weather conditions ceramic brick begins to collapse. At the beginning, small cracks appear, which later develop into through cracks. As a result, ceramic brick loses its properties.

GOST 7025-91

Group G19

STATE STANDARD OF THE UNION OF THE SSR

BRICK AND STONES CERAMIC AND SILICATE

Methods for determining water absorption,

density and frost resistance control

Ceramic and calcium silicate bricks and stones.

Methods for water absorption and density

determination and frost resistance control

OKSTU 5709

Introduction date 1991-07-01

Information data

1. DEVELOPED AND INTRODUCED by the Research Institute of Building Physics of the Gosstroy of the USSR

DEVELOPERS

Yu.D.Yasin, Ph.D. tech. sciences (topic leader); R.V. Maciulaitis, Ph.D. tech. sciences; A.N. Goncharov, Ph.D. tech. sciences; A.S.Bychkov, Ph.D. tech. sciences; N.A. Lisovsky; M.I. Shimanskaya; A.B.Morozov

2. APPROVED AND INTRODUCED BY Decree of the State Construction Committee of the USSR dated February 12, 1991 N 5

3. Author's certificate N 622007 with priority dated 04/28/77, author's certificate N 1013827 with priority dated 12/11/81, decision to issue an author's certificate for an industrial design on application N 50185/49/06127 dated 09/19/89

4. REPLACE GOST 7025-78, GOST 6427-75

5. REFERENCE REGULATIONS AND TECHNICAL DOCUMENTS

This standard applies to ceramic (including for chimneys) and silicate ordinary and facing bricks and stones (hereinafter referred to as products) and establishes methods for determining water absorption, density and control of frost resistance.

The application of methods is established in the regulatory and technical documentation (NTD) for products of specific types.

1. General requirements

1.1. Tests should be carried out in rooms with an air temperature of (20 ± 5) ° C on samples of whole products or their halves.

1.2. Drying of specimens and samples to constant weight is considered completed if the difference between two successive weighings during the drying process does not exceed the established weighing error. The interval between two weighings must be at least 4 hours for the sample and 2 hours for the sample.

Drying is carried out in an electrical cabinet at a temperature of (1055) °C.

1.3. Weighing samples and samples, depending on their mass, is performed with an error, g, not more than:

up to 20 g incl. .................................0.002

St. 20 "1000 g" ....................1

"1000" 10000 g "............................5

" 10000 .................................... 50

1.4. Silicate products are tested not earlier than one day after their autoclaving.

2. Determination of water absorption at atmospheric

pressure in water temperature (20±5) °C

2.1. Means of testing

Vessel with a lattice.

Scales according to GOST 24104.

2.2. Preparing for the test

Water absorption is determined on at least three samples.

Samples ceramic products pre-dried to constant weight. The water absorption of silicate products is determined without preliminary drying of the samples.

2.3. Conducting a test

2.3.1. The samples are placed in one row in height with gaps between them of at least 2 cm on the grate in a vessel with water at a temperature of (20 ± 5) ° C so that the water level is 2-10 cm higher than the top of the samples.

2.3.2. Samples are kept in water

2.3.3. The samples saturated with water are removed from the water, wiped with a damp cloth and weighed. The mass of water flowing out of the sample per weighing pan is included in the mass of the sample saturated with water. Weighing of each sample must be completed no later than 2 minutes after its removal from the water.

2.3.4. After weighing, the samples of silicate products are dried to constant weight.

2.4. Results processing

2.4.1. Water absorption () of samples by weight in percent is calculated by the formula

(1)

For the value of water absorption of products, the arithmetic mean of the results of determining the water absorption of all samples, calculated with an accuracy of 1%, is taken.

2.4.2. The initial data and results of determinations of water absorption are recorded in the test log.

3. Determination of water absorption under vacuum

in water temperature (20±5) °C

Methods for determining water absorption in water at a temperature of (20 ± 5) ° C at atmospheric pressure and under vacuum are interchangeable.

3.1. Means of testing

Installation for determining water absorption under vacuum, the scheme of which is shown in Fig.1.

Scheme of installation for determining water absorption

under vacuum

1 - vacuum pump according to GOST 26099; 2 - product samples;

3 - vacuum desiccator version 1 according to GOST 25336 or any other detachable

container with vacuum seal; 4 - vacuum hose; 5 - vacuum valve;

6 - exemplary pressure gauge according to GOST 2405; 7 - trap

Damn.1

Electric drying cabinet according to TU 16-681.032 or any other design with automatic temperature control within 100-110 °C.

Scales according to GOST 24104.

3.2. Preparation for the test - according to clause 2.2.

3.3. Conducting a test

3.3.1. The samples are placed in a vacuum desiccator on a stand and filled with water so that its level is at least 2 cm above the top of the sample. When using a split container, the samples are placed in one row in height with a gap between them of at least 2 cm.

3.3.2. The desiccator (container) is closed with a lid and vacuum pump create a rarefaction (0.05 ± 0.01) MPa [(0.5 ± 0.1) kgf / sq. cm] above the water surface, fixed by an exemplary pressure gauge.

3.3.3. Reduced pressure is maintained by noting the time until the release of air bubbles from the samples ceases, but not more than 30 minutes. After restoration of atmospheric pressure, the samples are kept in water for the same amount of time as under vacuum, so that the water fills the volume occupied by the removed air. Then proceed according to paragraphs 2.3.3 and 2.3.4.

3.4. Processing of results - according to clause 2.4.

4. Determination of water absorption of ceramic products

at atmospheric pressure in boiling water

Methods for determining water absorption at atmospheric pressure in water with a temperature of (20 ± 5) ° C and in boiling water are not interchangeable.

4.1. Means of testing - according to clause 2.1.

Electric stove in accordance with GOST 14919 or any other heating device that provides boiling water in a vessel.

4.2. Preparation for the test - according to clause 2.2.

4.3. Conducting a test

The samples are placed in a vessel with water according to p. Then proceed according to clause 2.3.3.

4.4. Processing of results - according to clause 2.4.

5. Determination of the average density

5.1. Means of testing

Electric drying cabinet according to TU 16-681.032 or any other design with automatic temperature control within 100-110 °C.

Scales according to GOST 24104.

Metal measuring ruler according to GOST 427.

5.2. Preparing for the test

The average density is determined on at least three samples.

5.3. Conducting a test

5.3.1. The volume of samples is determined by their geometric dimensions, measured with an error of not more than 1 mm. To determine each linear dimension, the sample is measured in three places - along the edges and in the middle of the face. The arithmetic mean of three measurements is taken as the final result.

5.3.2. The samples are cleaned of dust and dried to constant weight.

5.4. Results processing

5.4.1. The average density () of the sample in kg / cubic meter is calculated by the formula

(2)

where is the volume of the sample, cc

For the value of the average density of products, the arithmetic average of the results of determining the average density of all samples, calculated with an accuracy of 10 kg / m3, is taken.

5.4.2. The initial data and the results of the determinations of the average density are recorded in the test log.

6. Determination of true density

6.1. Means of testing

Electric drying cabinet according to TU 16-681.032 or any other design with automatic temperature control within 100-110 °C.

Scales according to GOST 24104.

Thermostat of any design, providing temperature maintenance (20.0±0.5) °C.

Vacuum desiccator version 1 in accordance with GOST 25336 complete with a water-jet or oil vacuum pump in accordance with GOST 25662, providing a vacuum of not more than 532 Pa (4 mm Hg).

Desiccator version 2 according to GOST 25336 with concentrated sulfuric acid according to GOST 4204 or anhydrous calcium chloride according to GOST 450.

Pycnometers with a capacity of 50-100 ml of types PZH2, PZH3 and PT according to GOST 22524 with cones according to GOST 8682.

Porcelain or agate mortar with pestle.

A glass bottle according to GOST 25336 or a porcelain cup according to GOST 9147.

Sieves with mesh N 1 and N 0.063 according to GOST 6613.

Bath water or sand.

Distilled water according to GOST 6709 or other liquid inert with respect to the material being tested.

6.2. Preparing for the test

6.2.1. The true density is determined on a sample of the material of products obtained from at least three samples.

6.2.2. To prepare a sample, two pieces weighing at least 100 g each are chipped from the outside and from the middle of each sample, which are crushed to grains about 5 mm in size. A weighing of at least 100 g is taken by quartering and crushed in a porcelain or agate mortar until it passes completely through a sieve with a mesh No. 1. Then a weighing of at least 30 g is selected by quartering and crushed until it completely passes through a sieve with a mesh of N 0.063.

The prepared powder sample of the sample material is dried to constant weight and cooled to room temperature in a desiccator over concentrated sulfuric acid or anhydrous calcium chloride.

6.3. Conducting a test

6.3.1. The determination is carried out in parallel on two portions weighing about 10 g each, taken from the sample.

6.3.2. The selected sample is poured into a clean, dried and pre-weighed pycnometer. The pycnometer is weighed together with the powder to be tested, then water (or other inert liquid) is poured into it in such an amount that it is filled to approximately half the volume.

To remove air from the sample material and liquid, the pycnometer with the contents is kept under vacuum in a desiccator until bubbles cease to form. It is allowed (when using water as a liquid) to remove air by boiling the pycnometer with the contents for 15-20 minutes in a slightly inclined state in a sand or water bath.

You should also remove air from the liquid with which the pycnometer will be supplemented.

6.3.3. After removing the air, the PZh3 type pycnometer is filled with liquid completely, and the PZh2 and PT types - up to the mark. The pycnometer is placed in a thermostat with a temperature of (20.0 ± 0.5) ° C, in which it is kept for at least 15 minutes.

6.3.4. After holding in a thermostat, the PZh3 type pycnometer is closed with a stopper with a hole so that the liquid fills the capillary and its excess is removed. Then it is carefully wiped off, a drop of liquid is removed from the capillary with filter paper.

In the pycnometer types PZH2 and PT, the liquid level is adjusted to the mark along the lower meniscus.

After reaching a constant liquid level, the pycnometer is weighed.

6.3.5. After weighing, the pycnometer is freed from the contents, washed, filled with the same liquid, air is removed from it, kept in a thermostat, the liquid is brought to a constant level and weighed again.

6.4. Results processing

6.4.1. The true density () of the sample material in g / cc is calculated by the formula

(3)

The value of the true density of products is taken as the arithmetic mean of the results of determining the true density of the material of two samples, calculated with an accuracy of 0.01 g / cc.

6.4.2. The discrepancy between the results of parallel determinations should not be more than 0.02 g/cc. With large discrepancies, the true density of the products is determined again.

6.4.3. The initial data and the results of determining the true density are recorded in the test log.

7. Control of frost resistance during bulk freezing

7.1. Means of testing

Freezer with forced ventilation and automatically controlled temperature from minus 15 to minus 20 °С. Recommended types of cameras and their main characteristics are given in Appendix 1.

Containers welded from steel rods or strips.

Vessel with a lattice.

Thermostat according to TU 64-1-3229 or any other design that maintains the water temperature in the vessel (20±5) °C.

Electric drying cabinet according to TU 16-681.032 or any other design with automatic temperature control within 100-110 °C.

Bath with a hydraulic seal, the scheme of which is shown in Fig.2.

Bathtub with hydraulic seal

1 - base vessel with water; 2 - stand for laying samples;

3 - cap; 4 - container with product samples

Damn.2

Scales according to GOST 24104.

7.2. Preparing for the test

7.2.1. To control frost resistance by the degree of damage or weight loss, at least five samples are taken.

To control frost resistance by loss of strength, at least twenty samples are taken, half of which are used as controls for comparison. Control samples are stored in a bath with a hydraulic seal.

On the samples, the existing cracks, near edges, corners and other defects allowed by the NTD for products of specific types are fixed.

7.2.2. Samples are saturated with water in accordance with Section 2 or 3. Samples of ceramic products are dried to constant weight before water saturation. Samples of silicate products after water saturation are weighed.

It is allowed to use samples immediately after determining their water absorption.

7.2.3. Freezing samples in the freezer and thawing them in water is carried out in containers.

Horizontal gaps between samples in containers should be at least 20 mm. When laying samples in containers up to three rows in height, the vertical gaps between rows formed by spacers must be at least 20 mm. At more rows in height, the gaps between rows should be at least 50 mm.

7.3. Conducting a test

7.3.1. The air temperature of the freezer before loading the samples should not exceed minus 15 °C, and after loading should not exceed minus 5 °C. The beginning of sample freezing is considered to be the moment when the temperature in the chamber reaches minus 15 °C. The air temperature in the chamber from the beginning to the end of freezing should be from minus 15 to minus 20 °C.

7.3.2. The duration of one freezing of samples should be at least 4 hours. A break in the process of one freezing is not allowed.

7.3.3. After the end of freezing, the samples in containers are completely immersed in a vessel with water at a temperature of (20 ± 5) ° C, maintained by a thermostat until the end of the thawing of the samples.

The defrosting time must be at least half the freezing time.

7.3.4. One freezing and subsequent thawing constitutes one cycle, the duration of which should not exceed 24 hours.

7.3.5. At the end of the frost resistance test or its temporary termination, the samples after thawing are stored in a bath with a hydraulic seal. When resuming the test, the samples are additionally saturated with water in accordance with Section 2 or 3 (without drying the samples of ceramic products and weighing the silicate products after water saturation).

7.3.6. When assessing frost resistance according to the degree of damage, after the required number of freeze-thaw cycles, a visual inspection of the samples is carried out and the defects that have appeared are fixed.

7.3.7. When assessing frost resistance by weight loss after the required number of freeze-thaw cycles, samples of ceramic products are dried to constant weight, and samples of silicate products are saturated with water in accordance with Section 2 or 3.

7.3.8. When assessing frost resistance in terms of loss of compressive strength after the required number of freeze-thaw cycles, the supporting surfaces of each sample separately (including control ones) are leveled with cement mortar according to Annex 2 of GOST 8462. It is allowed not to level the supporting surfaces of samples of silicate products and ceramic products made by pressing, in the absence of unevenness, swelling, peeling, etc. on them.

The samples are saturated with water in accordance with Section 2 or 3 and a compression test is carried out for each sample separately in accordance with Section 3 of GOST 8462.

7.4. Results processing

7.4.1. After a visual inspection of the samples, a conclusion is made on the compliance of their degree of damage with the requirements of the NTD for products of specific types.

7.4.2. Weight loss () of samples of ceramic products as a percentage is calculated by the formula

(4)

where is the weight of the sample dried to constant weight after the required number of freeze-thaw cycles, g.

The weight loss of samples of silicate products in percent is calculated by the formula

(5)

Where mass of the sample saturated with water after the required number of freeze-thaw cycles, g.

The arithmetic mean of the results of determining the mass loss of all samples, calculated with an accuracy of 1%, is taken as the value of the mass loss of products.

7.4.3. The loss of strength () of products during compression as a percentage is calculated with an accuracy of 1% according to the formula

(6)

7.4.4. The initial data and results of frost resistance control are recorded in the test log. The log should show:

product name, strength grade, test date;

frost resistance control method (volumetric, one-sided);

dimensions of each sample;

a description of the defects found on each sample before testing;

freezing temperature and the duration of the temperature decrease in the freezer to minus 15 °C after loading it with samples;

description of the appeared defects found on each sample during inspections during the test;

the mass of each sample before and after the test and the mass loss;

compressive strength of each of the tested samples and loss of strength;

number of cycles of freezing - thawing of samples.

8. Control of frost resistance with one-sided freezing

Methods for controlling frost resistance during bulk and one-sided freezing are not interchangeable.

8.1. Means of testing

Refrigeration and sprinkling unit (CDU), the main technical characteristics of which are given in Appendix 2.

It is allowed to use the freezer according to clause 7.1 with the following devices and equipment:

apparatus for one-sided freezing of samples (ADOZO), the main technical characteristics of which are given in Appendix 2, or a locking, heat-insulating, removable through frame;

sprinkler installation.

Rubber plates OMB5 or OMB10 according to GOST 7338.

Vessel with a lattice.

Electric drying cabinet according to TU 16-681.032 or any other design with automatic temperature control within 100-110 °C.

Bath with a hydraulic seal according to clause 7.1.

Scales according to GOST 24104.

The remaining funds - according to Section 1 of GOST 8462, necessary for testing to determine the compressive strength of the samples.

8.2. Preparing for the test

8.2.1. To control frost resistance by the degree of damage or weight loss, at least eight whole samples are taken, and by loss of strength - at least sixteen whole samples.

Selected samples by appearance and dimensions must meet the requirements of the NTD for products of specific types.

Existing cracks, near edges, corners and other defects allowed by the NTD for products of specific types are fixed on the samples, and the surface of the samples intended for freezing is also marked.

8.2.2. Samples are saturated with water in accordance with Section 2 for hours. Samples of ceramic products are dried to constant weight before water saturation. Samples of silicate products after water saturation are weighed.

It is allowed to use the samples immediately after determining their water absorption, provided that they are additionally saturated with water for one hour.

8.2.3. Samples are collected in the form of a fragment of the enclosing structure with a thickness of one brick in a heat-insulating locking frame or cassettes of the ADOZO container.

In a fragment of each eight samples, two (previously sawn across in half) are installed in paired halves one after the other with a poke, and six samples - one after the other with a spoon. Horizontal and vertical transverse seams between the samples are imitated by gaskets made of rubber plates. Vertical longitudinal seams are left in the form of an air gap.

In case of incomplete filling of the frame or cassette with samples, the volume remaining in height is filled with a heat insulator (rubber plates, foam plastic, etc.).

8.2.4. When assessing frost resistance in terms of the degree of damage and weight loss, at least five (two bond and three spoon) samples are used, and when assessing frost resistance in terms of strength loss, at least ten (four bond and six spoon) samples are used from the side of the fragment intended for freezing. At the same time, samples adjacent to them from the uncooled side (opposite to the frozen side) of the fragment are used as control ones when assessing by loss of strength.

8.2.5. The duration of the assembly of the fragment should not exceed 1 hour.

After assembly, the surface of the fragment intended for freezing is subjected to preliminary sprinkling for at least 8 hours so that it is covered with a continuous water film.

In the absence of CDU, sprinkling is carried out at the installation, the scheme of which is shown in Figure 3.

The temperature of the water washing the surface of the fragment should be (15±5) °C.

8.2.6. When using a CDU or a through removable heat-insulating locking frame, a fragment with a surface intended for freezing is attached to the opening of the freezer. The test scheme is shown in Fig.4.

When using ADOZO, the heat-insulating container of the apparatus with cassettes is placed inside the freezer. The test scheme is shown in Figure 5.

8.3. Conducting a test

8.3.1. The temperature regime inside the CDU (freezer) - according to clause 7.3.1. In this case, the temperature on the uncooled side (opposite to the frozen side) of the fragment should be (20±5) °C.

8.3.2. The duration of one freezing of samples should be at least 8 hours. A break in the process of one freezing of samples is not allowed.

8.3.3. After the end of the freezing of the samples, the cooled surface of the fragment is thawed by sprinkling.

Sprinkling is carried out by disconnecting the heat-insulating locking frame from the freezing chamber, or by unloading the ADOZO heat-insulating container from the freezer and removing the cassettes from it.

The defrosting time must be equal to the freezing time.

Test scheme using ADOZO

1 - freezer; 2 - evaporators; 3 - fans; 4 - freezer door;

5 - heat-insulating container ADOZO; 6 - a fragment of the enclosing structure in the ADOZO cassette;

7 - control panel and temperature control of the electric heater in

heat-insulating container ADOZO; 8 - ADOZO wiring

Damn.5

8.3.4. The duration of the freeze - thaw cycle - according to clause 7.3.4.

8.3.5. At the end of the frost resistance test or its temporary termination, the samples after thawing are stored in a bath with a hydraulic seal. When the test is resumed, the samples collected in the form of a fragment are additionally saturated with water by sprinkling for at least 8 hours.

8.3.6. The frost resistance of the samples is assessed:

according to the degree of damage - according to clause 7.3.6;

for weight loss - according to clause 7.3.7. In this case, samples of silicate products are saturated with water in accordance with Section 2 for an hour;

for loss of strength - according to clause 7.3.8.

8.4. Processing of results - according to clause 7.4.

Annex 1

Reference

Specifications freezers

Table 1

Annex 2

Reference

Technical characteristics of CDU and ADOZO

table 2

Manufacturer - NPO "Thermoisolation"

The text of the document is verified by:

official publication

M.: Publishing house of standards, 1991

The water absorption of a brick is one of the most important indicators that determine the suitability of the material in a particular area of ​​construction. To understand why this characteristic so important when choosing, you should understand the basic properties building material. Water absorption is the ability to absorb and retain moisture. The water absorption index is determined as a percentage of the volume of the material.

The porosity of a brick directly affects its water absorption.

The higher the porosity of the material (the more quantity voids), the more moisture it absorbs. Porosity is directly related to strength and load bearing capacity. Water entering the cavity sub-zero temperatures freezes, increases in size and destroys the building material. The higher the water absorption rate, the lower the level of structural strength and resistance to low temperatures. This will also negatively affect the durability of the building material.

Water absorption rates

To increase the strength and durability of the material, its water absorption should be minimized, but practice shows otherwise.

The moisture absorption rate cannot be limited for several reasons:

1. If the water absorption rate is low, then the masonry will turn out to be less durable, as the adhesion to the mortar will be broken.
2. An insufficient number of pores and voids will significantly reduce its thermal performance, making the material unsuitable for use in regions with long winters. To avoid such problems, experts have developed certain standards, according to which the water absorption rate should not be lower than 6%. The maximum level is determined depending on the type of building material.

There are 3 main types of building bricks:

• silicate;
• ceramic.

Production of products from concrete mix occurs by pouring the solution into special forms. On practice this species rarely used because it is heavy, expensive, does not retain heat well. Despite these shortcomings, this product has the lowest water absorption rate of 3-5%. Masonry made of such a building material perfectly withstands sudden changes in temperature and is characterized by a long service life.

The level of water absorption of a building product is one of the the most important characteristics, which allows you to determine the scope of use of building material. For example, at silicate brick good moisture absorption, therefore its use for the construction of foundations, basement floors of surfaces located in an environment with high humidity is limited. It is quite suitable for the construction of walls and load-bearing partitions.

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When choosing a brick for construction, you should always be guided by its characteristics so that the building is strong and durable.

Water absorption refers to the tendency to absorb and store moisture. For its designation, the ratio of the volume of absorbed moisture and material is used.

This value increases as the pores or voids in the brick structure increase. It is also important to understand that the presence of internal pores negatively affects the strength of the product and its resistance to stress transfer.

When the temperature drops below zero, the water inside can cause its destruction, since when the liquid freezes, it increases in volume. This puts strength and frost resistance in direct proportion to the degree of water absorption: the higher it is, the shorter the service life of the constructed wall.

Helpful information:

A little about water absorption standards

To increase strength and durability, it is important to reduce the level of water absorption of the material to a minimum. In practice, this is not so easy to do, which is due to objective reasons:

If you reduce the amount of water absorbed, this may affect the strength brickwork, due to reduced adhesion with masonry mortar.
Internal voids give products additional insulating and soundproofing properties, which is very much appreciated in areas with harsh climatic conditions or increased noise. Accordingly, with a decrease in porosity, these qualities are lost. For this reason, special rules are established lower limit for water absorption of ceramic bricks at the level of 6%. The upper line is determined by the purpose of each particular type of material.

Types of bricks for water absorption

GOST defines for different types bricks have different limits of maximum water absorption. Also, this indicator depends on the operating conditions.

• For ordinary brick this indicator is set at the level 12-14%
• Water absorption of ceramic bricks for facing masonry - from 8 to 10%.
• For internal works (finishing, partitions) brick has a limiting rate of water absorption 16% .

Such a significant difference for different types due to the different conditions in which they are used. For example, the interior masonry is not affected by precipitation, and the temperature is usually within comfortable limits.

The material used in outdoor conditions feels all the destructive weather effects. This is especially true for regions with harsh climatic conditions, for which facing ceramic bricks with the lowest possible moisture absorption coefficient are being developed. In order not to harm him thermal insulation characteristics, special technological voids are provided inside.