What vapor permeability is better for a heater. How to determine which insulation is better? Chips and cracks

There is a legend about the "breathing wall", and legends about the "healthy breathing of the cinder block, which creates a unique atmosphere in the house." In fact, the vapor permeability of the wall is not large, the amount of steam passing through it is insignificant, and much less than the amount of steam carried by air when it is exchanged in the room.

Vapor permeability is one of the most important parameters used in the calculation of insulation. We can say that the vapor permeability of materials determines the entire design of insulation.

What is vapor permeability

The movement of steam through the wall occurs with a difference in partial pressure on the sides of the wall (different humidity). In this case, there may not be a difference in atmospheric pressure.

Vapor permeability - the ability of a material to pass steam through itself. According to the domestic classification, it is determined by the vapor permeability coefficient m, mg / (m * h * Pa).

The resistance of a layer of material will depend on its thickness.
It is determined by dividing the thickness by the vapor permeability coefficient. It is measured in (m sq. * hour * Pa) / mg.

For example, the vapor permeability coefficient of brickwork is taken as 0.11 mg / (m * h * Pa). With a brick wall thickness of 0.36 m, its resistance to steam movement will be 0.36 / 0.11 = 3.3 (m sq. * h * Pa) / mg.

What is the vapor permeability of building materials

Below are the values ​​​​of the coefficient of vapor permeability for several building materials (according to the regulatory document), which are most widely used, mg / (m * h * Pa).
Bitumen 0.008
Heavy concrete 0.03
Autoclaved aerated concrete 0.12
Expanded clay concrete 0.075 - 0.09
Slag concrete 0.075 - 0.14
Burnt clay (brick) 0.11 - 0.15 (in the form of masonry on cement mortar)
Lime mortar 0.12
Drywall, gypsum 0.075
Cement-sand plaster 0.09
Limestone (depending on density) 0.06 - 0.11
Metals 0
Chipboard 0.12 0.24
Linoleum 0.002
Polyfoam 0.05-0.23
Polyurethane hard, polyurethane foam
0,05
Mineral wool 0.3-0.6
Foam glass 0.02 -0.03
Vermiculite 0.23 - 0.3
Expanded clay 0.21-0.26
Wood across the fibers 0.06
Wood along the fibers 0.32
Brickwork from silicate bricks on cement mortar 0.11

Data on the vapor permeability of the layers must be taken into account when designing any insulation.

How to design insulation - according to vapor barrier qualities

The basic rule of insulation is that the vapor transparency of the layers should increase outward. Then in the cold season, with a greater probability, there will be no accumulation of water in the layers, when condensation occurs at the dew point.

The basic principle helps to decide in any cases. Even when everything is "turned upside down" - they insulate from the inside, despite the insistent recommendations to make insulation only from the outside.

In order to avoid a catastrophe with wetting the walls, it is enough to remember that the inner layer should most stubbornly resist steam, and based on this, for internal insulation, use extruded polystyrene foam with a thick layer - a material with very low vapor permeability.

Or do not forget to use even more “airy” mineral wool for a very “breathing” aerated concrete from the outside.

Separation of layers with a vapor barrier

Another option for applying the principle of vapor transparency of materials in a multilayer structure is the separation of the most significant layers by a vapor barrier. Or the use of a significant layer, which is an absolute vapor barrier.

For example, - insulation of a brick wall with foam glass. It would seem that this contradicts the above principle, because it is possible to accumulate moisture in a brick?

But this does not happen, due to the fact that the directional movement of steam is completely interrupted (at sub-zero temperatures from the room to the outside). After all, foam glass is a complete vapor barrier or close to it.

Therefore, in this case, the brick will enter into an equilibrium state with the internal atmosphere of the house, and will serve as an accumulator of humidity during its sharp jumps inside the room, making the internal climate more pleasant.

The principle of separation of layers is also used when using mineral wool - a heater that is especially dangerous for moisture accumulation. For example, in a three-layer construction, when mineral wool is inside a wall without ventilation, it is recommended to put a vapor barrier under the wool, and thus leave it in the outside atmosphere.

International classification of vapor barrier qualities of materials

The international classification of materials for vapor barrier properties differs from the domestic one.

According to the international standard ISO/FDIS 10456:2007(E), materials are characterized by a coefficient of resistance to steam movement. This coefficient indicates how many times more the material resists the movement of steam compared to air. Those. for air, the coefficient of resistance to steam movement is 1, and for extruded polystyrene foam it is already 150, i.e. Styrofoam is 150 times less vapor permeable than air.

Also in international standards it is customary to determine the vapor permeability for dry and moist materials. The boundary between the concepts of “dry” and “moistened” is the internal moisture content of the material of 70%.
Below are the values ​​of the coefficient of resistance to steam movement for various materials according to international standards.

Steam resistance factor

First, data are given for dry material, and separated by commas for moist (more than 70% moisture).
Air 1, 1
Bitumen 50,000, 50,000
Plastics, rubber, silicone — >5,000, >5,000
Heavy concrete 130, 80
Medium density concrete 100, 60
Polystyrene concrete 120, 60
Autoclaved aerated concrete 10, 6
Lightweight concrete 15, 10
Artificial stone 150, 120
Expanded clay concrete 6-8, 4
Slag concrete 30, 20
Burnt clay (brick) 16, 10
Lime mortar 20, 10
Drywall, plaster 10, 4
Gypsum plaster 10, 6
Cement-sand plaster 10, 6
Clay, sand, gravel 50, 50
Sandstone 40, 30
Limestone (depending on density) 30-250, 20-200
Ceramic tile?, ?
Metals?
OSB-2 (DIN 52612) 50, 30
OSB-3 (DIN 52612) 107, 64
OSB-4 (DIN 52612) 300, 135
Chipboard 50, 10-20
Linoleum 1000, 800
Substrate for plastic laminate 10 000, 10 000
Substrate for laminate cork 20, 10
Polyfoam 60, 60
EPPS 150, 150
Polyurethane hard, polyurethane foam 50, 50
Mineral wool 1, 1
Foam glass?, ?
Perlite panels 5, 5
Perlite 2, 2
Vermiculite 3, 2
Ecowool 2, 2
Expanded clay 2, 2
Wood across grain 50-200, 20-50

It should be noted that the data on the resistance to the movement of steam here and "there" are very different. For example, foam glass is standardized in our country, and the international standard says that it is an absolute vapor barrier.

Where did the legend of the breathing wall come from?

A lot of companies produce mineral wool. This is the most vapor-permeable insulation. According to international standards, its vapor permeability resistance coefficient (not to be confused with the domestic vapor permeability coefficient) is 1.0. Those. in fact, mineral wool does not differ in this respect from air.

Indeed, it is a "breathing" insulation. To sell mineral wool as much as possible, you need a beautiful fairy tale. For example, that if you insulate a brick wall from the outside with mineral wool, then it will not lose anything in terms of vapor permeability. And this is absolutely true!

The insidious lie is hidden in the fact that through brick walls 36 centimeters thick, with a humidity difference of 20% (outside 50%, in the house - 70%), about a liter of water will come out of the house per day. While with air exchange, about 10 times more should come out so that the humidity in the house does not increase.

And if the wall is insulated from the outside or from the inside, for example, with a layer of paint, vinyl wallpaper, dense cement plaster (which, in general, is “the most common thing”), then the vapor permeability of the wall will decrease several times, and with complete insulation - tens and hundreds of times .

Therefore, it will always be absolutely the same for a brick wall and for households - whether the house is covered with mineral wool with “raging breath”, or “dull-sniffing” foam plastic.

When making decisions on the insulation of houses and apartments, it is worth proceeding from the basic principle - the outer layer should be more vapor-permeable, preferably at times.

If for some reason it is not possible to withstand this, then it is possible to separate the layers with a continuous vapor barrier (use a completely vapor-tight layer) and stop the movement of steam in the structure, which will lead to a state of dynamic equilibrium of the layers with the environment in which they will be located.

The concept of "breathing walls" is considered a positive characteristic of the materials from which they are made. But few people think about the reasons that allow this breathing. Materials capable of passing both air and steam are vapor-permeable.

A good example of building materials with high vapor permeability:

• wood;
• expanded clay slabs;
• foam concrete.

Concrete or brick walls are less permeable to steam than wood or expanded clay.

Sources of steam indoors

Human breathing, cooking, water vapor from the bathroom and many other sources of steam in the absence of an exhaust device create a high level of humidity indoors. You can often observe the formation of perspiration on window panes in winter, or on cold water pipes. These are examples of the formation of water vapor inside the house.

What is vapor permeability

The design and construction rules give the following definition of the term: the vapor permeability of materials is the ability to pass through moisture droplets contained in the air due to different partial vapor pressures from opposite sides at the same air pressure values. It is also defined as the density of the steam flow passing through a certain thickness of the material.

The table, which has a vapor permeability coefficient, compiled for building materials, is conditional, since the specified calculated values ​​\u200b\u200bof humidity and atmospheric conditions do not always correspond to real conditions. The dew point can be calculated based on approximate data.

Wall construction taking into account vapor permeability

Even if the walls are built from a material with high vapor permeability, this cannot be a guarantee that it will not turn into water in the thickness of the wall. To prevent this from happening, it is necessary to protect the material from the difference in partial vapor pressure from inside and outside. Protection against the formation of steam condensate is carried out using OSB boards, insulating materials such as foam and vapor-tight films or membranes that prevent steam from penetrating into the insulation.

The walls are insulated in such a way that a layer of insulation is located closer to the outer edge, incapable of forming moisture condensation, pushing the dew point (water formation) away. In parallel with the protective layers in the roofing cake, it is necessary to ensure the correct ventilation gap.

The destructive action of steam

If the wall cake has a weak ability to absorb steam, it is not in danger of destruction due to the expansion of moisture from frost. The main condition is to prevent the accumulation of moisture in the thickness of the wall, but to ensure its free passage and weathering. It is equally important to arrange a forced extraction of excess moisture and steam from the room, to connect a powerful ventilation system. By observing the above conditions, you can protect the walls from cracking, and increase the life of the whole house. The constant passage of moisture through building materials accelerates their destruction.

Use of conductive qualities

Taking into account the peculiarities of the operation of buildings, the following principle of insulation is applied: the most steam-conducting insulation materials are located outside. Due to this arrangement of layers, the likelihood of water accumulation when the temperature drops outside is reduced. To prevent the walls from getting wet from the inside, the inner layer is insulated with a material having low vapor permeability, for example, a thick layer of extruded polystyrene foam.

The opposite method of using the steam-conducting effects of building materials is successfully applied. It consists in the fact that a brick wall is covered with a vapor barrier layer of foam glass, which interrupts the moving flow of steam from the house to the street during low temperatures. The brick begins to accumulate humidity in the rooms, creating a pleasant indoor climate thanks to a reliable vapor barrier.

Compliance with the basic principle when building walls

Walls should be characterized by a minimum ability to conduct steam and heat, but at the same time be heat-retaining and heat-resistant. When using one type of material, the desired effects cannot be achieved. The external wall part is obliged to retain cold masses and prevent their impact on internal heat-intensive materials that maintain a comfortable thermal regime inside the room.

Reinforced concrete is ideal for the inner layer, its heat capacity, density and strength have maximum performance. Concrete successfully smooths out the difference between night and day temperature changes.

When carrying out construction work, wall cakes are made taking into account the basic principle: the vapor permeability of each layer should increase in the direction from the inner layers to the outer ones.

Rules for the location of vapor barrier layers

To ensure the best performance of multilayer structures of buildings, the rule is applied: on the side with a higher temperature, materials with increased resistance to steam penetration with increased thermal conductivity are placed. The layers located outside must have a high vapor conductivity. For the normal functioning of the building envelope, it is necessary that the coefficient of the outer layer is five times higher than the indicator of the layer located inside.

When this rule is followed, it will not be difficult for water vapor that has entered the warm layer of the wall to quickly escape through more porous materials.

If this condition is not observed, the inner layers of building materials lock up and become more heat-conducting.

Familiarity with the table of vapor permeability of materials

When designing a house, the characteristics of building materials are taken into account. The Code of Practice contains a table with information on what vapor permeability coefficient building materials have under conditions of normal atmospheric pressure and average air temperature.

Material	Vapor permeability coefficient mg/(m h Pa)
extruded polystyrene foam
polyurethane foam
mineral wool
reinforced concrete, concrete
pine or spruce
expanded clay
foam concrete, aerated concrete
granite, marble
drywall
chipboard, OSB, fiberboard
foam glass
ruberoid
polyethylene
linoleum

The table refutes erroneous ideas about breathing walls. The amount of steam escaping through the walls is negligible. The main steam is removed with air currents during ventilation or with the help of ventilation.

The importance of the material vapor permeability table

The vapor permeability coefficient is an important parameter that is used to calculate the thickness of the layer of insulation materials. The quality of the insulation of the entire structure depends on the correctness of the results obtained.

Sergey Novozhilov is an expert in roofing materials with 9 years of practical experience in the field of engineering solutions in construction.

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General information

Movement of water vapor

• foam concrete;
• aerated concrete;
• perlite concrete;
• expanded clay concrete.

aerated concrete

The right finish

Expanded clay concrete

The structure of expanded clay concrete

Polystyrene concrete

rusbetonplus.ru

Vapor permeability of concrete: features of the properties of aerated concrete, expanded clay concrete, polystyrene concrete

Often in construction articles there is an expression - the vapor permeability of concrete walls. It means the ability of the material to pass water vapor, in a popular way - "breathe". This parameter is of great importance, since waste products are constantly formed in the living room, which must be constantly brought out.

In the photo - moisture condensation on building materials

General information

If you do not create normal ventilation in the room, dampness will be created in it, which will lead to the appearance of fungus and mold. Their secretions can be harmful to our health.

Movement of water vapor

On the other hand, vapor permeability affects the ability of the material to accumulate moisture in itself. This is also a bad indicator, since the more it can hold in itself, the higher the likelihood of fungus, putrefactive manifestations, and destruction during freezing.

Improper removal of moisture from the room

Vapor permeability is denoted by the Latin letter μ and is measured in mg / (m * h * Pa). The value shows the amount of water vapor that can pass through the wall material on an area of ​​1 m2 and with a thickness of 1 m in 1 hour, as well as a difference in external and internal pressure of 1 Pa.

High capacity for conducting water vapor in:

• foam concrete;
• aerated concrete;
• perlite concrete;
• expanded clay concrete.

Closes the table - heavy concrete.

Tip: if you need to make a technological channel in the foundation, diamond drilling in concrete will help you.

aerated concrete

1. The use of the material as a building envelope makes it possible to avoid the accumulation of unnecessary moisture inside the walls and preserve its heat-saving properties, which will prevent possible destruction.
2. Any aerated concrete and foam concrete block contains ≈ 60% of air, due to which the vapor permeability of aerated concrete is recognized as good, the walls in this case can "breathe".
3. Water vapor freely seeps through the material, but does not condense in it.

The vapor permeability of aerated concrete, as well as foam concrete, significantly exceeds heavy concrete - for the first 0.18-0.23, for the second - (0.11-0.26), for the third - 0.03 mg / m * h * Pa.

The right finish

I would especially like to emphasize that the structure of the material provides it with effective removal of moisture into the environment, so that even when the material freezes, it does not collapse - it is forced out through open pores. Therefore, when preparing the finishing of aerated concrete walls, this feature should be taken into account and appropriate plasters, putties and paints should be selected.

The instruction strictly regulates that their vapor permeability parameters are not lower than aerated concrete blocks used for construction.

Textured facade vapor-permeable paint for aerated concrete

Tip: do not forget that the vapor permeability parameters depend on the density of aerated concrete and may differ by half.

For example, if you use concrete blocks with a density of D400, their coefficient is 0.23 mg / m h Pa, while for D500 it is already lower - 0.20 mg / m h Pa. In the first case, the numbers indicate that the walls will have a higher "breathing" ability. So when choosing finishing materials for D400 aerated concrete walls, make sure that their vapor permeability coefficient is the same or higher.

Otherwise, this will lead to a deterioration in the removal of moisture from the walls, which will affect the decrease in the comfort level of living in the house. It should also be noted that if you used vapor-permeable paint for aerated concrete for the exterior, and non-vapor-permeable materials for the interior, the steam will simply accumulate inside the room, making it wet.

Expanded clay concrete

The vapor permeability of expanded clay concrete blocks depends on the amount of filler in its composition, namely expanded clay - foamed baked clay. In Europe, such products are called eco- or bioblocks.

Tip: if you can’t cut the expanded clay block with a regular circle and a grinder, use a diamond one. For example, cutting reinforced concrete with diamond wheels makes it possible to quickly solve the problem.

The structure of expanded clay concrete

Polystyrene concrete

The material is another representative of cellular concrete. The vapor permeability of polystyrene concrete is usually equal to that of wood. You can make it with your own hands.

What does the structure of polystyrene concrete look like?

Today, more attention is being paid not only to the thermal properties of wall structures, but also to the comfort of living in the building. In terms of thermal inertness and vapor permeability, polystyrene concrete resembles wooden materials, and heat transfer resistance can be achieved by changing its thickness. Therefore, poured monolithic polystyrene concrete is usually used, which is cheaper than finished slabs.

Conclusion

From the article you learned that building materials have such a parameter as vapor permeability. It makes it possible to remove moisture outside the walls of the building, improving their strength and characteristics. The vapor permeability of foam concrete and aerated concrete, as well as heavy concrete, differs in its performance, which must be taken into account when choosing finishing materials. The video in this article will help you find more information on this topic.

Page 2

During operation, a variety of defects in reinforced concrete structures can occur. At the same time, it is very important to identify problem areas in time, localize and eliminate damage, since a significant part of them tend to expand and aggravate the situation.

Below we will consider the classification of the main defects in the concrete pavement, as well as give a number of tips for its repair.

During the operation of reinforced concrete products, various damages appear on them.

Factors that affect strength

Before analyzing common defects in concrete structures, it is necessary to understand what can be their cause.

Here, the key factor will be the strength of the hardened concrete solution, which is determined by the following parameters:

The closer the composition of the solution to the optimal, the less problems there will be in the operation of the structure.

• Composition of concrete. The higher the brand of cement included in the solution, and the stronger the gravel that was used as a filler, the more resistant the coating or monolithic structure will be. Naturally, when using high-quality concrete, the price of the material increases, therefore, in any case, we need to find a compromise between economy and reliability.

Note! Excessively strong compositions are very difficult to process: for example, to perform the simplest operations, expensive cutting of reinforced concrete with diamond wheels may be required.

That is why you should not overdo it with the selection of materials!

• reinforcement quality. Along with high mechanical strength, concrete is characterized by low elasticity, therefore, when exposed to certain loads (bending, compression), it can crack. To avoid this, steel reinforcement is placed inside the structure. It depends on its configuration and diameter how stable the entire system will be.

For sufficiently strong compositions, diamond drilling of holes in concrete is necessarily used: an ordinary drill “will not take”!

• surface permeability. If the material is characterized by a large number of pores, then sooner or later moisture will penetrate into them, which is one of the most destructive factors. Particularly detrimental to the state of the concrete pavement are temperature drops, at which the liquid freezes, destroying the pores due to an increase in volume.

In principle, it is these factors that are decisive for ensuring the strength of cement. However, even in an ideal situation, sooner or later the coating is damaged, and we have to restore it. What can happen in this case, and how we need to act - we will tell below.

Mechanical damage

Chips and cracks

Identification of deep damages with a flaw detector

The most common defects are mechanical damage. They can arise due to various factors, and are conventionally divided into external and internal. And if a special device is used to determine the internal ones - a concrete flaw detector, then problems on the surface can be seen independently.

The main thing here is to determine the cause of the malfunction and eliminate it promptly. For the convenience of analysis, we structured examples of the most common damage in the form of a table:

Defect
Bumps on the surface	Most often they occur due to shock loads. It is also possible to form potholes in places of prolonged exposure to a significant mass.
chipped	They are formed under mechanical influence on the areas under which there are zones of low density. The configuration is almost identical to potholes, but usually have a shallower depth.
Delamination	Represents the separation of the surface layer of the material from the main mass. Most often it occurs due to poor-quality drying of the material and finishing until the solution is completely hydrated.
mechanical cracks	Occur with prolonged and intense exposure to a large area. Over time, they expand and connect with each other, which can lead to the formation of large potholes.
Bloating	They are formed if the surface layer is compacted until air is completely removed from the mass of the solution. Also, the surface swells when treated with paint or impregnations (silings) of uncured cement.

Photo of a deep crack

As can be seen from the analysis of the causes, the appearance of some of the listed defects could have been avoided. But mechanical cracks, chips and potholes are formed due to the operation of the coating, so they just need to be repaired periodically. Instructions for prevention and repair are given in the next section.

Prevention and repair of defects

To minimize the risk of mechanical damage, first of all, it is necessary to follow the technology for arranging concrete structures.

Of course, this question has many nuances, so we will give only the most important rules:

• Firstly, the class of concrete must correspond to the design loads. Otherwise, saving on materials will lead to the fact that the service life will be reduced significantly, and repairs will have to be spent much more often.
• Secondly, you need to follow the technology of pouring and drying. The solution requires high-quality concrete compaction, and when hydrated, the cement should not lack moisture.
• It is also worth paying attention to the timing: without the use of special modifiers, it is impossible to finish surfaces earlier than 28-30 days after pouring.
• Thirdly, the coating should be protected from excessively intense impacts. Of course, the loads will affect the condition of the concrete, but it is in our power to reduce the harm from them.

Vibrocompaction significantly increases strength

Note! Even a simple restriction of the speed of traffic in problem areas leads to the fact that defects in the asphalt concrete pavement occur much less frequently.

Another important factor is the timeliness of the repair and compliance with its methodology.

Here you need to act according to a single algorithm:

• We clean the damaged area from fragments of the solution that have broken off from the main mass. For small defects, brushes can be used, but large-scale chips and cracks are usually cleaned with compressed air or a sandblaster.
• Using a concrete saw or a perforator, we embroider the damage, deepening it to a durable layer. If we are talking about a crack, then it must not only be deepened, but also expanded in order to facilitate filling with a repair compound.
• We prepare a mixture for restoration using either a polyurethane-based polymer complex or non-shrink cement. When eliminating large defects, so-called thixotropic compounds are used, and small cracks are best sealed with a casting agent.

Filling embroidered cracks with thixotropic sealants

• We apply the repair mixture to the damage, after which we level the surface and protect it from loads until the agent is completely polymerized.

In principle, these works are easily done by hand, so we can save on the involvement of craftsmen.

Operational damage

Drawdowns, dusting and other malfunctions

Cracks in the sagging screed

In a separate group, experts distinguish the so-called operational defects. These include the following:

Defect	Characteristics and possible cause
Screed deformation	It is expressed in a change in the level of the poured concrete floor (most often the coating sags in the center and rises at the edges). Can be caused by several factors: · Uneven density of the base due to insufficient tamping · Defects in the compaction of the mortar. · Difference in humidity of the top and bottom layer of cement. Insufficient reinforcement thickness.
Cracking	In most cases, cracks do not occur due to mechanical action, but due to deformation of the structure as a whole. It can be provoked both by excessive loads exceeding the calculated ones and by thermal expansion.
Peeling	Peeling of small scales on the surface usually begins with the appearance of a network of microscopic cracks. In this case, the cause of peeling is most often the accelerated evaporation of moisture from the outer layer of the solution, which leads to insufficient hydration of the cement.
Surface dusting	It is expressed in the constant formation of fine cement dust on the concrete. May be caused by: Lack of cement in the mortar. Excess moisture during pouring. · Ingress of water to the surface during grouting. · Insufficient quality cleaning of gravel from dusty fraction. Excessive abrasive effect on concrete.

Surface peeling

All of the above disadvantages arise either due to a violation of technology, or due to improper operation of the concrete structure. However, they are somewhat more difficult to eliminate than mechanical defects.

• Firstly, the solution must be poured and processed in accordance with all the rules, preventing it from delamination and peeling during drying.
• Secondly, the base must be prepared no less qualitatively. The denser we compact the soil under the concrete structure, the less likely it will be to subside, deform and crack.
• So that the poured concrete does not crack, a damper tape is usually mounted around the perimeter of the room to compensate for deformations. For the same purpose, polymer-filled seams are arranged on large-area screeds.
• It is also possible to avoid the appearance of surface damage by applying polymer-based reinforcing impregnations to the surface of the material or by “ironizing” the concrete with a fluid solution.

Protective treated surface

Chemical and climate impact

A separate group of damages is made up of defects that have arisen as a result of climatic effects or reactions to chemicals.

This may include:

• The appearance on the surface of stains and light spots - the so-called efflorescence. Usually the reason for the formation of salt deposits is a violation of the humidity regime, as well as the ingress of alkalis and calcium chlorides into the composition of the solution.

Efflorescence formed due to excess moisture and calcium

Note! It is for this reason that in areas with highly carbonate soils, experts recommend using imported water to prepare the solution.

Otherwise, a whitish coating will appear within a few months after pouring.

• Destruction of the surface under the influence of low temperatures. When moisture enters porous concrete, microscopic channels in the immediate vicinity of the surface gradually expand, since when freezing, water increases in volume by about 10-15%. The more often freezing / thawing occurs, the more intensively the solution will break down.
• To combat this, special anti-frost impregnations are used, and the surface is also coated with compounds that reduce porosity.

Before repair, the fittings must be cleaned and processed

• Finally, reinforcement corrosion can also be attributed to this group of defects. Metal mortgages begin to rust in places where they are exposed, which leads to a decrease in the strength of the material. To stop this process, before filling the damage with a repair compound, we must clean the reinforcing bars from oxides, and then treat them with an anti-corrosion compound.

Conclusion

The defects of concrete and reinforced concrete structures described above can manifest themselves in a variety of forms. Despite the fact that many of them look quite harmless, when the first signs of damage are found, it is worth taking appropriate measures, otherwise the situation may worsen over time.

Well, the best way to avoid such situations is to strictly adhere to the technology of arranging concrete structures. The information presented in the video in this article is another confirmation of this thesis.

masterabeton.ru

Vapor permeability of materials table

To create a favorable microclimate in the room, it is necessary to take into account the properties of building materials. Today we will analyze one property - the vapor permeability of materials.

Vapor permeability is the ability of a material to pass vapors contained in the air. Water vapor penetrates the material due to pressure.

They will help to understand the issue of the table, which cover almost all the materials used for construction. After studying this material, you will know how to build a warm and reliable home.

Equipment

When it comes to Prof. construction, then it uses specially equipped equipment to determine vapor permeability. Thus, the table that is in this article appeared.

Today the following equipment is used:

• Scales with a minimum error - an analytical type model.
• Vessels or bowls for experiments.
• Instruments with a high level of accuracy for determining the thickness of layers of building materials.

Dealing with property

There is an opinion that "breathing walls" are useful for the house and its inhabitants. But all builders think about this concept. “Breathable” is the material that, in addition to air, also allows steam to pass through - this is the water permeability of building materials. Foam concrete, expanded clay wood have a high rate of vapor permeability. Walls made of brick or concrete also have this property, but the indicator is much less than that of expanded clay or wood materials.

This graph shows the permeability resistance. The brick wall practically does not let in and does not let in moisture.

Steam is released when taking a hot shower or cooking. Because of this, increased humidity is created in the house - an extractor hood can correct the situation. You can find out that the vapors do not go anywhere by the condensate on the pipes, and sometimes on the windows. Some builders believe that if the house is built of brick or concrete, then the house is "hard" to breathe.

In fact, the situation is better - in a modern home, about 95% of the steam leaves through the window and the hood. And if the walls are made of breathable building materials, then 5% of the steam escapes through them. So residents of houses made of concrete or brick do not particularly suffer from this parameter. Also, the walls, regardless of the material, will not let moisture through due to vinyl wallpaper. The "breathing" walls also have a significant drawback - in windy weather, heat leaves the dwelling.

The table will help you compare materials and find out their vapor permeability index:

The higher the vapor permeability index, the more moisture the wall can contain, which means that the material has low frost resistance. If you are going to build walls from foam concrete or aerated concrete, then you should know that manufacturers are often cunning in the description where vapor permeability is indicated. The property is indicated for dry material - in this state it really has a high thermal conductivity, but if the gas block gets wet, the indicator will increase by 5 times. But we are interested in another parameter: the liquid tends to expand when it freezes, as a result, the walls collapse.

Vapor permeability in a multi-layer construction

The sequence of layers and the type of insulation - this is what primarily affects the vapor permeability. In the diagram below, you can see that if the insulation material is located on the front side, then the pressure on moisture saturation is lower.

The figure shows in detail the action of pressure and the penetration of steam into the material.

If the insulation is located on the inside of the house, then condensation will appear between the supporting structure and this building. It negatively affects the entire microclimate in the house, while the destruction of building materials occurs much faster.

Dealing with the ratio

The table becomes clear if you understand the coefficient.

The coefficient in this indicator determines the amount of vapor, measured in grams, that pass through materials with a thickness of 1 meter and a layer of 1 m² in one hour. The ability to pass or retain moisture characterizes the resistance to vapor permeability, which is indicated in the table by the symbol "µ".

In simple words, the coefficient is the resistance of building materials, comparable to the permeability of air. Let's analyze a simple example, mineral wool has the following vapor permeability coefficient: µ=1. This means that the material passes moisture as well as air. And if we take aerated concrete, then its µ will be equal to 10, that is, its vapor conductivity is ten times worse than that of air.

Peculiarities

On the one hand, vapor permeability has a good effect on the microclimate, and on the other hand, it destroys the materials from which houses are built. For example, “cotton wool” perfectly passes moisture, but in the end, due to excess steam, condensation can form on windows and pipes with cold water, as the table also says. Because of this, the insulation loses its qualities. Professionals recommend installing a vapor barrier layer on the outside of the house. After that, the insulation will not let steam through.

Vapor resistance

If the material has a low vapor permeability, then this is only a plus, because the owners do not have to spend money on insulating layers. And to get rid of the steam generated from cooking and hot water, the hood and the window will help - this is enough to maintain a normal microclimate in the house. In the case when the house is built of wood, it is impossible to do without additional insulation, while wood materials require a special varnish.

The table, graph and diagram will help you understand the principle of this property, after which you can already decide on the choice of a suitable material. Also, do not forget about the climatic conditions outside the window, because if you live in a zone with high humidity, then you should forget about materials with a high vapor permeability.

Table of vapor permeability of building materials

I collected information on vapor permeability by linking several sources. The same plate with the same materials walks around the sites, but I expanded it, added modern vapor permeability values ​​from the sites of building materials manufacturers. I also checked the values ​​with the data from the document "Code of Rules SP 50.13330.2012" (Appendix T), added those that were not there. So at the moment this is the most complete table.

Material	Vapor permeability coefficient, mg/(m*h*Pa)
Reinforced concrete	0,03
Concrete	0,03
Cement-sand mortar (or plaster)	0,09
Cement-sand-lime mortar (or plaster)	0,098
Lime-sand mortar with lime (or plaster)	0,12
Expanded clay concrete, density 1800 kg/m3	0,09
Expanded clay concrete, density 1000 kg/m3	0,14
Expanded clay concrete, density 800 kg/m3	0,19
Expanded clay concrete, density 500 kg/m3	0,30
Clay brick, masonry	0,11
Brick, silicate, masonry	0,11
Hollow ceramic brick (1400 kg/m3 gross)	0,14
Hollow ceramic brick (1000 kg/m3 gross)	0,17
Large format ceramic block (warm ceramic)	0,14
Foam concrete and aerated concrete, density 1000 kg/m3	0,11
Foam concrete and aerated concrete, density 800 kg/m3	0,14
Foam concrete and aerated concrete, density 600 kg/m3	0,17
Foam concrete and aerated concrete, density 400 kg/m3	0,23
Fiberboard and wood concrete slabs, 500-450 kg/m3	0.11 (SP)
Fiberboard and wood concrete slabs, 400 kg/m3	0.26 (SP)
Arbolit, 800 kg/m3	0,11
Arbolit, 600 kg/m3	0,18
Arbolit, 300 kg/m3	0,30
Granite, gneiss, basalt	0,008
Marble	0,008
Limestone, 2000 kg/m3	0,06
Limestone, 1800 kg/m3	0,075
Limestone, 1600 kg/m3	0,09
Limestone, 1400 kg/m3	0,11
Pine, spruce across the grain	0,06
Pine, spruce along the grain	0,32
Oak across the grain	0,05
Oak along the grain	0,30
Plywood	0,02
Chipboard and fiberboard, 1000-800 kg/m3	0,12
Chipboard and fiberboard, 600 kg/m3	0,13
Chipboard and fiberboard, 400 kg/m3	0,19
Chipboard and fiberboard, 200 kg/m3	0,24
Tow	0,49
Drywall	0,075
Gypsum slabs (gypsum boards), 1350 kg/m3	0,098
Gypsum slabs (gypsum boards), 1100 kg/m3	0,11
Mineral wool, stone, 180 kg/m3	0,3
Mineral wool, stone, 140-175 kg/m3	0,32
Mineral wool, stone, 40-60 kg/m3	0,35
Mineral wool, stone, 25-50 kg/m3	0,37
Mineral wool, glass, 85-75 kg/m3	0,5
Mineral wool, glass, 60-45 kg/m3	0,51
Mineral wool, glass, 35-30 kg/m3	0,52
Mineral wool, glass, 20 kg/m3	0,53
Mineral wool, glass, 17-15 kg/m3	0,54
Expanded polystyrene extruded (EPPS, XPS)	0.005 (SP); 0.013; 0.004 (???)
Expanded polystyrene (foam plastic), plate, density from 10 to 38 kg/m3	0.05 (SP)
Styrofoam, plate	0,023 (???)
Ecowool cellulose	0,30; 0,67
Polyurethane foam, density 80 kg/m3	0,05
Polyurethane foam, density 60 kg/m3	0,05
Polyurethane foam, density 40 kg/m3	0,05
Polyurethane foam, density 32 kg/m3	0,05
Expanded clay (bulk, i.e. gravel), 800 kg/m3	0,21
Expanded clay (bulk, i.e. gravel), 600 kg/m3	0,23
Expanded clay (bulk, i.e. gravel), 500 kg/m3	0,23
Expanded clay (bulk, i.e. gravel), 450 kg/m3	0,235
Expanded clay (bulk, i.e. gravel), 400 kg/m3	0,24
Expanded clay (bulk, i.e. gravel), 350 kg/m3	0,245
Expanded clay (bulk, i.e. gravel), 300 kg/m3	0,25
Expanded clay (bulk, i.e. gravel), 250 kg/m3	0,26
Expanded clay (bulk, i.e. gravel), 200 kg/m3	0.26; 0.27 (SP)
Sand	0,17
Bitumen	0,008
Polyurethane mastic	0,00023
Polyurea	0,00023
Foamed synthetic rubber	0,003
Ruberoid, glassine	0 - 0,001
Polyethylene	0,00002
asphalt concrete	0,008
Linoleum (PVC, i.e. not natural)	0,002
Steel	0
Aluminum	0
Copper	0
Glass	0
Block foam glass	0 (rarely 0.02)
Bulk foam glass, density 400 kg/m3	0,02
Bulk foam glass, density 200 kg/m3	0,03
Glazed ceramic tile (tile)	≈ 0 (???)
Clinker tiles	low (???); 0.018 (???)
Porcelain stoneware	low (???)
OSB (OSB-3, OSB-4)	0,0033-0,0040 (???)

It is difficult to find out and indicate in this table the vapor permeability of all types of materials; manufacturers have created a huge variety of plasters and finishing materials. And, unfortunately, many manufacturers do not indicate such an important characteristic as vapor permeability on their products.

For example, when determining the value for warm ceramics (position “Large-format ceramic block”), I studied almost all the websites of manufacturers of this type of brick, and only some of them had vapor permeability indicated in the characteristics of the stone.

Also, different manufacturers have different vapor permeability values. For example, for most foam glass blocks it is zero, but for some manufacturers the value is "0 - 0.02".

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In domestic standards, the vapor permeability resistance ( vapor permeability Rp, m2. h Pa/mg) is standardized in chapter 6 "Resistance to vapor permeability of enclosing structures" SNiP II-3-79 (1998) "Construction heat engineering".

International standards for the vapor permeability of building materials are given in ISO TC 163/SC 2 and ISO/FDIS 10456:2007(E) - 2007.

The vapor permeability coefficient indicators are determined on the basis of the international standard ISO 12572 "Thermal properties of building materials and products - Determination of vapor permeability". Vapor permeability indicators for international ISO standards were determined in a laboratory method on time-tested (not just released) samples of building materials. Vapor permeability was determined for building materials in a dry and wet state.
In the domestic SNiP, only calculated data on vapor permeability are given at a mass ratio of moisture in the material w,%, equal to zero.
Therefore, for the choice of building materials for vapor permeability in summer cottage construction it is better to focus on international ISO standards, which determine the vapor permeability of "dry" building materials at a moisture content of less than 70% and "wet" building materials at a moisture content of more than 70%. Remember that when leaving the "pies" of vapor-permeable walls, the vapor permeability of materials from the inside to the outside should not decrease, otherwise the inner layers of building materials will gradually "freeze" and their thermal conductivity will increase significantly.

The vapor permeability of materials from the inside to the outside of the heated house should decrease: SP 23-101-2004 Design of thermal protection of buildings, clause 8.8: To ensure better performance in multilayer building structures, on the warm side, layers of greater thermal conductivity and greater resistance to vapor permeation should be placed than the outer layers. According to T. Rogers (Rogers T.S. Designing thermal protection of buildings. / Lane from English - m.: si, 1966) Separate layers in multilayer fences should be arranged in such a sequence that the vapor permeability of each layer increases from the inner surface to outdoor. With such an arrangement of layers, water vapor that has entered the enclosure through the inner surface with increasing ease will pass through all the barriers of the enclosure and be removed from the enclosure from the outer surface. The enclosing structure will function normally if, subject to the formulated principle, the vapor permeability of the outer layer is at least 5 times higher than the vapor permeability of the inner layer.

Mechanism of vapor permeability of building materials:

At low relative humidity, moisture from the atmosphere is in the form of individual water vapor molecules. With an increase in relative humidity, the pores of building materials begin to fill with liquid and the mechanisms of wetting and capillary suction begin to work. With an increase in the humidity of the building material, its vapor permeability increases (the vapor permeability resistance coefficient decreases).

ISO/FDIS 10456:2007(E) vapor permeability ratings for "dry" building materials apply to internal structures of heated buildings. Vapor permeability indicators of "wet" building materials are applicable to all external structures and internal structures of unheated buildings or country houses with a variable (temporary) heating regime.

To begin with, let's refute the misconception - it is not the fabric that “breathes”, but our body. More precisely, the surface of the skin. Man is one of those animals whose body strives to maintain a constant body temperature, regardless of environmental conditions. One of the most important mechanisms of our thermoregulation is the sweat glands hidden in the skin. They are also part of the excretory system of the body. The sweat emitted by them, evaporating from the surface of the skin, takes with it part of the excess heat. Therefore, when we are hot, we sweat to avoid overheating.

However, this mechanism has one serious drawback. Moisture, quickly evaporating from the surface of the skin, can provoke hypothermia, which leads to colds. Of course, in Central Africa, where man has evolved as a species, such a situation is rather rare. But in regions with changeable and mostly cool weather, a person constantly had to supplement his natural thermoregulation mechanisms with various clothes.

The ability of clothing to "breathe" implies its minimal resistance to the removal of vapors from the surface of the skin and the "ability" to transport them to the front side of the material, where the moisture released by a person can evaporate without "stealing" an excess amount of heat. Thus, the "breathable" material from which clothing is made helps the human body maintain optimal body temperature, preventing overheating or hypothermia.

The "breathing" properties of modern fabrics are usually described in terms of two parameters - "vapor permeability" and "air permeability". What is the difference between them and how does this affect their use in sports and outdoor clothing?

What is vapor permeability?

Vapor permeability- this is the ability of the material to pass or retain water vapor. In the outdoor clothing and equipment industry, the material's high ability to water vapor transport. The higher it is, the better, because. this allows the user to avoid overheating and still stay dry.

All fabrics and insulation used today have a certain vapor permeability. However, in numerical terms, it is presented only to describe the properties of membranes used in the manufacture of clothing, and for a very small amount not waterproof textile materials. Most often, vapor permeability is measured in g / m² / 24 hours, i.e. the amount of water vapor that passes through a square meter of material per day.

This parameter is denoted by the abbreviation MVTR ("moisture vapor transmission rate" or "water vapor transmission rate").

The higher the value, the greater the vapor permeability of the material.

How is vapor permeability measured?

The MVTR numbers are obtained from laboratory tests based on various methods. Due to the large number of variables that affect the operation of the membrane - individual metabolism, air pressure and humidity, the area of ​​\u200b\u200bthe material suitable for moisture transport, wind speed, etc., there is no single standardized research method for determining vapor permeability. Therefore, in order to be able to compare samples of fabrics and membranes with each other, manufacturers of materials and ready-made garments use a number of techniques. Each of them individually describes the vapor permeability of a fabric or membrane in a certain range of conditions. The following test methods are most commonly used today:

"Japanese" test with "upright cup" (JIS L 1099 A-1)

The test sample is stretched and hermetically fixed over a cup, inside of which is placed a strong desiccant - calcium chloride (CaCl2). The cup is placed for a certain time in a thermohydrostat, which maintains an air temperature of 40 ° C and a humidity of 90%.

Depending on how the weight of the desiccant changes during the control time, the MVTR is determined. The technique is well suited for determining vapor permeability not waterproof fabrics, because the test sample is not in direct contact with water.

Japanese Inverted Cup Test (JIS L 1099 B-1)

The test sample is stretched and hermetically fixed over a vessel of water. After it is turned over and placed over a cup with a dry desiccant - calcium chloride. After the control time, the desiccant is weighed and the MVTR is calculated.

The B-1 test is the most popular, as it shows the highest numbers among all methods that determine the rate of passage of water vapor. Most often, it is his results that are published on labels. The most "breathable" membranes have an MVTR value according to the B1 test greater than or equal to 20,000 g/m²/24h according to test B1. Fabrics with values ​​of 10-15,000 can be classified as perceptibly vapor-permeable, at least within the framework of not very intensive loads. Finally, for garments with low mobility, a vapor permeability of 5-10,000 g/m²/24h is often sufficient.

The JIS L 1099 B-1 test method quite accurately illustrates the operation of a membrane under ideal conditions (when there is condensation on its surface and moisture is transported to a drier environment with a lower temperature).

Sweat plate test or RET (ISO - 11092)

Unlike tests that determine the rate of transport of water vapor through a membrane, the RET technique examines how the test sample resists passage of water vapor.

A tissue or membrane sample is placed on top of a flat porous metal plate, under which a heating element is connected. The temperature of the plate is maintained at the surface temperature of human skin (about 35°C). The water evaporating from the heating element passes through the plate and the test sample. This leads to heat loss on the surface of the plate, the temperature of which must be maintained constant. Accordingly, the higher the level of energy consumption to maintain the temperature of the plate constant, the lower the resistance of the test material to the passage of water vapor through it. This parameter is designated as RET (Resistance of Evaporation of a Textile - "material resistance to evaporation"). The lower the RET value, the higher the "breathing" properties of the tested sample of the membrane or other material.

RET 0-6 - extremely breathable; RET 6-13 - highly breathable; RET 13-20 - breathable; RET more than 20 - not breathing.

Equipment for conducting the ISO-11092 test. On the right is a camera with a "sweating plate". A computer is required to receive and process the results and control the test procedure © thermetrics.com

In the laboratory of the Hohenstein Institute, with which Gore-Tex collaborates, this technique is complemented by testing real clothing samples by people on a treadmill. In this case, the results of the "sweating plate" tests are corrected in accordance with the comments of the testers.

Testing clothes with Gore-Tex on a treadmill © goretex.com

The RET test clearly illustrates the operation of the membrane in real conditions, but is also the most expensive and time-consuming in the list. For this reason, not all outdoor clothing companies can afford it. At the same time, RET is today the main method for assessing the vapor permeability of Gore-Tex membranes.

The RET technique usually correlates well with B-1 test results. In other words, a membrane that shows good breathability in the RET test will show good breathability in the inverted cup test.

Unfortunately, none of the test methods can replace the others. Moreover, their results do not always correlate with each other. We have seen that the process of determining the vapor permeability of materials in various methods has many differences, simulating different working conditions.

In addition, different membrane materials work in different ways. So, for example, porous laminates provide a relatively free passage of water vapor through the microscopic pores in their thickness, and pore-free membranes transport moisture to the front surface like a blotter - using hydrophilic polymer chains in their structure. It is quite natural that one test can imitate the winning conditions for the operation of a non-porous membrane film, for example, when moisture is closely adjacent to its surface, and the other for a microporous one.

Taken together, all this means that there is practically no point in comparing materials based on data obtained from different test methods. It also makes no sense to compare the vapor permeability of different membranes if the test method for at least one of them is unknown.

What is breathability?

Breathability- the ability of the material to pass air through itself under the influence of its pressure difference. When describing the properties of clothing, a synonym for this term is often used - “blowing”, i.e. how much the material is "windproof".

In contrast to the methods for assessing vapor permeability, relative monotony reigns in this area. To evaluate the breathability, the so-called Fraser test is used, which determines how much air will pass through the material during the control time. The airflow rate under test conditions is typically 30 mph, but may vary.

The unit of measurement is the cubic foot of air passing through the material in one minute. Abbreviated CFM (cubic feet per minute).

The higher the value, the higher the breathability ("blowing") of the material. Thus, pore-free membranes demonstrate an absolute "non-permeability" - 0 CFM. Test methods are most often defined by ASTM D737 or ISO 9237, which, however, give identical results.

Exact CFM figures are published relatively rarely by fabric and ready-to-wear manufacturers. Most often this parameter is used to characterize the windproof properties in the descriptions of various materials developed and used within the production of SoftShell clothing.

Recently, manufacturers have begun to “remember” much more often about breathability. The fact is that along with the air flow, much more moisture evaporates from the surface of our skin, which reduces the risk of overheating and accumulation of condensate under clothing. Thus, the Polartec Neoshell membrane has a slightly higher air permeability than traditional porous membranes (0.5 CFM versus 0.1). As a result, Polartec has been able to achieve a significantly better performance of its material in windy conditions and fast user movement. The higher the air pressure outside, the better Neoshell removes water vapor from the body due to greater air exchange. At the same time, the membrane continues to protect the user from wind chill, blocking about 99% of the air flow. This is enough to withstand even stormy winds, and therefore Neoshell has found itself even in the production of single-layer assault tents (a vivid example is the BASK Neoshell and Big Agnes Shield 2 tents).

But progress does not stand still. Today there are many offers of well-insulated middle layers with partial breathability, which can also be used as a stand-alone product. They use either brand new insulation - like Polartec Alpha - or use synthetic bulk insulation with a very low degree of fiber migration, which allows the use of less dense "breathable" fabrics. For example, Sivera Gamayun jackets use ClimaShield Apex, Patagonia NanoAir uses FullRange™ insulation, which is produced by the Japanese company Toray under the original name 3DeFX+. The same insulation is used in Mountain Force 12 way stretch ski jackets and trousers and Kjus ski clothing. The relatively high breathability of the fabrics in which these heaters are enclosed allows you to create an insulating layer of clothing that will not interfere with the removal of evaporated moisture from the skin surface, helping the user to avoid both getting wet and overheating.

SoftShell-clothing. Subsequently, other manufacturers created an impressive number of their counterparts, which led to the ubiquity of thin, relatively durable, breathable nylon in clothing and equipment for sports and outdoor activities.