Vapor permeability of materials table is building code domestic and, of course, international standards. In general, vapor permeability is a certain ability of fabric layers to actively pass water vapor due to different pressure results with a uniform atmospheric index on both sides of the element.
The considered ability to pass, as well as retain water vapor, is characterized by special values \u200b\u200bcalled the coefficient of resistance and vapor permeability.
At the moment, it is better to focus your own attention on the internationally established ISO standards. They determine the qualitative vapor permeability of dry and wet elements.
A large number of people are adherents of the fact that breathing is good sign. However, it is not. Breathable elements are those structures that allow both air and vapor to pass through. Expanded clay, foam concrete and trees have increased vapor permeability. In some cases, bricks also have these indicators.
If the wall is endowed with high vapor permeability, this does not mean that it becomes easy to breathe. Indoors recruited a large number of moisture, respectively, there is a low resistance to frost. Leaving through the walls, the vapors turn into ordinary water.
When calculating this indicator, most manufacturers do not take into account important factors, that is, they are cunning. According to them, each material is thoroughly dried. Damp ones increase thermal conductivity by five times, therefore, it will be quite cold in an apartment or other room.
The most terrible moment is the fall of night temperature regimes, leading to a shift in the dew point in wall openings and further freezing of condensate. Subsequently, the resulting frozen waters begin to actively destroy the surface.
Indicators
The vapor permeability of materials table indicates the existing indicators:
- , which is an energy type of heat transfer from highly heated particles to less heated ones. Thus, equilibrium is realized and appears in temperature conditions. With a high apartment thermal conductivity, you can live as comfortably as possible;
- Thermal capacity calculates the amount of supplied and stored heat. It must necessarily be brought to a real volume. This is how temperature change is considered;
- Thermal absorption is an enclosing structural alignment in temperature fluctuations, that is, the degree of absorption of moisture by wall surfaces;
- Thermal stability is a property that protects structures from sharp thermal oscillatory flows. Absolutely all full-fledged comfort in the room depends on the general thermal conditions. Thermal stability and capacity can be active in cases where the layers are made of materials with increased thermal absorption. Stability ensures the normalized state of structures.
Vapor permeability mechanisms
Moisture in the atmosphere at a reduced level relative humidity is actively transported through existing pores in building components. They acquire appearance, similar to individual water vapor molecules.
In those cases when the humidity begins to rise, the pores in the materials are filled with liquids, directing the working mechanisms for downloading into capillary suction. Vapor permeability begins to increase, lowering the resistance coefficients, with an increase in humidity in the building material.
For internal structures in already heated buildings, dry-type vapor permeability indicators are used. In places where heating is variable or temporary, wet types are used. building materials designed for outdoor construction.
Vapor permeability of materials, the table helps to effectively compare the various types of vapor permeability.
Equipment
In order to correctly determine the vapor permeability indicators, experts use specialized research equipment:
- Glass cups or vessels for research;
- Unique tools required for thickness measurement processes with high level accuracy;
- Scales analytical type with weighing error.
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 exhaust device create a high level of indoor humidity. You can often observe the formation of perspiration on window panes in winter time, 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 various sizes partial vapor pressures opposite sides at the same air pressure. 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 that has 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 the penetration of steam 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. Parallel to protective layers in 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. Equally important is to arrange forced exhaust excess moisture and steam from the room, 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 conducting construction works make up wall cakes, taking into account the basic principle: the vapor permeability of each layer should increase in the direction from the inner layers to the outer.
Rules for the location of vapor barrier layers
To provide the best performance characteristics multilayer structures of structures, the rule applies: from the side with more high temperature, have materials with increased resistance to steam penetration with increased thermal conductivity. The layers located outside must have a high vapor conductivity. For normal functioning The enclosing structure requires that the coefficient of the outer layer is five times higher than the coefficient of the layer located inside. 
When this rule is followed, water vapor that has fallen into warm layer walls, it will not be difficult to get out with acceleration 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 |
extruded polystyrene foam | |
polyurethane foam | |
reinforced concrete, concrete | |
pine or spruce | |
expanded clay | |
foam concrete, aerated concrete | |
granite, marble | |
drywall | |
chipboard, OSB, fiberboard | |
foam glass | |
ruberoid | |
polyethylene | |
linoleum |
The importance of the material vapor permeability table
The vapor permeability coefficient is important parameter, which is used to calculate the layer thickness insulation materials. The quality of the insulation of the entire structure depends on the correctness of the results obtained.
Sergey Novozhilov - expert in roofing materials with 9 years of experience practical work in the field of engineering solutions in construction.
1. Minimize Selection inner space only a heater with the lowest coefficient of thermal conductivity can
2. Unfortunately, the storage heat capacity of the array outer wall we lose forever. But there is a win here:
A) there is no need to spend energy on heating these walls
B) when you turn on even the smallest heater in the room, it will almost immediately become warm.
3. At the junction of the wall and the ceiling, "cold bridges" can be removed if the insulation is applied partially on the floor slabs with subsequent decoration of these junctions.
4. If you still believe in the "breathing of the walls", then please read THIS article. If not, then the obvious conclusion is: thermal insulation material should be very tightly pressed against the wall. It is even better if the insulation becomes one with the wall. Those. there will be no gaps and cracks between the insulation and the wall. Thus, the moisture from the room will not be able to get into the dew point zone. The wall will always remain dry. Seasonal temperature fluctuations without moisture access will not adversely affect the walls, which will increase their durability.
All these tasks can be solved only by sprayed polyurethane foam.
Possessing the lowest coefficient of thermal conductivity of all existing thermal insulation materials, polyurethane foam will take up a minimum of internal space.
The ability of polyurethane foam to adhere reliably to any surface makes it easy to apply it to the ceiling to reduce "cold bridges".
When applied to walls, polyurethane foam, being in a liquid state for some time, fills all the cracks and microcavities. Foaming and polymerizing directly at the point of application, polyurethane foam becomes one with the wall, blocking access to destructive moisture.
VAPOR PERMEABILITY OF WALLS
Supporters of the false concept of “healthy breathing of walls”, in addition to sinning against the truth of physical laws and deliberately misleading designers, builders and consumers, based on a mercantile urge to sell their goods by any means, slander and slander thermal insulation materials with low vapor permeability (polyurethane foam) or heat-insulating material and completely vapor-tight (foam glass).
The essence of this malicious insinuation boils down to the following. It seems like if there is no notorious “healthy breathing of the walls”, then in this case the interior will definitely become damp, and the walls will ooze moisture. In order to debunk this fiction, let's take a closer look at the physical processes that will occur in the case of lining under the plaster layer or using inside the masonry, for example, a material such as foam glass, the vapor permeability of which is zero.
So, due to the heat-insulating and sealing properties inherent in foam glass, the outer layer of plaster or masonry will come into an equilibrium temperature and humidity state with the outside atmosphere. Also, the inner layer of masonry will enter into a certain balance with the microclimate. interior spaces. Water diffusion processes, both in the outer layer of the wall and in the inner one; will have the character of a harmonic function. This function will be determined, for the outer layer, by diurnal changes in temperature and humidity, as well as seasonal changes.
Particularly interesting in this respect is the behavior of the inner layer of the wall. Actually, inner part walls will act as an inertial buffer, the role of which is to smooth out sudden changes in humidity in the room. In the event of a sharp humidification of the room, the inner part of the wall will adsorb the excess moisture contained in the air, preventing the air humidity from reaching the limit value. At the same time, in the absence of moisture release into the air in the room, the inner part of the wall begins to dry out, preventing the air from “drying out” and becoming like a desert one.
As a favorable result of such an insulation system using polyurethane foam, the harmonics of fluctuations in air humidity in the room are smoothed out and thus guarantee a stable value (with minor fluctuations) of humidity acceptable for a healthy microclimate. The physics of this process has been studied quite well by the developed construction and architectural schools of the world, and to achieve a similar effect when using inorganic fiber materials as a heater in closed systems insulation, it is highly recommended to have a reliable vapor-permeable layer on the inside of the insulation system. So much for "healthy breathing walls"!
In order to destroy it
Calculations of units of vapor permeability and resistance to vapor permeability. Technical characteristics of membranes.
Often, instead of the Q value, the vapor permeability resistance value is used, in our opinion it is Rp (Pa * m2 * h / mg), foreign Sd (m). Vapor permeability is the reciprocal of Q. At the same time, imported Sd is the same Rp, only expressed as an equivalent diffusion resistance to vapor permeability of an air layer (equivalent diffusion thickness of air).
Instead of further reasoning in words, we correlate Sd and Rn numerically.
What does Sd=0.01m=1cm mean?
This means that the diffusion flux density with a difference dP is:
J=(1/Rp)*dP=Dv*dRo/Sd
Here Dv=2.1e-5m2/s diffusion coefficient of water vapor in air (taken at 0°C)/
Sd is our very Sd, and
(1/Rp)=Q
Let's transform the right equality using the ideal gas law (P*V=(m/M)*R*T => P*M=Ro*R*T => Ro=(M/R/T)*P) and see.
1/Rp=(Dv/Sd)*(M/R/T)
Hence Sd=Rp*(Dv*M)/(RT) which is not clear to us yet
To get the correct result, you need to represent everything in units of Rp,
more precisely Dv=0.076 m2/h
M=18000 mg/mol - molar mass water
R=8.31 J/mol/K - universal gas constant
T=273K - temperature on the Kelvin scale, corresponding to 0 degrees C, where we will carry out calculations.
So, substituting everything, we have:
sd= Rp*(0.076*18000)/(8.31*273) \u003d 0.6 Rp or vice versa:
Rp=1.7Sd.
Here Sd is the same imported Sd [m], and Rp [Pa * m2 * h / mg] is our resistance to vapor permeation.
Also Sd can be associated with Q - vapor permeability.
We have that Q=0.56/Sd, here Sd [m] and Q [mg/(Pa*m2*h)].
Let us check the obtained relations. For this, take specifications different membranes and substitute.
To begin with, I will take the data on Tyvek from here
As a result, the data is interesting, but not very suitable for formula testing.
In particular, for the Soft membrane we obtain Sd=0.09*0.6=0.05m. Those. Sd in the table is underestimated by 2.5 times or, accordingly, Rp is overestimated.
I take further data from the Internet. By Fibrotek membrane
I will use the last pair of permeability data, in this case Q*dP=1200 g/m2/day, Rp=0.029 m2*h*Pa/mg
1/Rp=34.5 mg/m2/h/Pa=0.83 g/m2/day/Pa
From here we will extract the difference in absolute humidity dP=1200/0.83=1450Pa. This humidity corresponds to a dew point of 12.5 degrees or a humidity of 50% at 23 degrees.
On the Internet, I also found on another forum the phrase:
Those. 1740 ng/Pa/s/m2=6.3 mg/Pa/h/m2 corresponds to vapor permeability ~250 g/m2/day.
I'll try to get that ratio myself. It is mentioned that the value in g/m2/day is also measured at 23 deg. We take the previously obtained value dP=1450Pa and we have an acceptable convergence of the results:
6.3*1450*24/100=219 g/m2/day Hurrah Hurrah.
So, now we are able to correlate the vapor permeability that you can find in the tables and the resistance to vapor permeability.
It remains to make sure that the relation between Rp and Sd obtained above is correct. I had to dig and found a membrane for which both values are given (Q * dP and Sd), while Sd is a specific value, and not "no more". Perforated membrane based on PE film
And here is the data:
40.98 g/m2/day => Rp=0.85 =>Sd=0.6/0.85=0.51m
Again it doesn't fit. But in principle, the result is not far off, which, given the fact that it is not known at what parameters, the vapor permeability is determined is quite normal.
Interestingly, according to Tyvek they got misalignment in one direction, according to IZOROL in the other. Which suggests that you can’t trust some values everywhere.
PS I would be grateful for the search for errors and comparisons with other data and standards.
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 entering 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 better 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 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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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 - vapor permeability concrete walls. It means the ability of the material to pass water vapor, in a popular way - "breathe". This setting has 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 indicates the amount of water vapor that can pass through wall material on an area of 1 m2 and with a thickness of 1 m for 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
- 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.
- Any aerated concrete foam concrete block has in its composition ≈ 60% of air, due to which the vapor permeability of aerated concrete is recognized at a good level, the walls in this case can "breathe".
- 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 moisture in environment, so that even when the material freezes, it does not collapse - it is forced out through open pores. Therefore, preparing the finish aerated concrete walls, should be considered this feature and select the appropriate plasters, putties and paints.
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, and 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 have been applied for exterior finish vapor-permeable paint for aerated concrete, and for interior - non-vapor-permeable materials, 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 Additional 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 consider the classification of the main defects concrete pavement, and also 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 frozen concrete mortar, which is defined by the following parameters:
The closer the composition of the solution to the optimum, the less problems will be in operation
- 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, inside the structure is placed steel reinforcement. 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 observe the technology of arranging structures made of concrete.
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 you will have to spend more effort and money on repairs.
- 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 speed limit for vehicles problem areas leads to defects 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 reason occurrence |
| 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 when mechanical action, and during 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, it is usually mounted around the perimeter of the room. damper tape compensating for deformations. For the same purpose on screeds large area seams with polymer filling are equipped.
- 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 cause of the formation of salt deposits is a violation 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.
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Vapor permeability of materials table
To create favorable microclimate indoors, 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. Having studied given material, you will know how to build a warm and secure 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. Brick wall practically does not pass 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 modern dwelling 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. There are "breathing" walls and significant disadvantage- 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, the more wall can contain moisture, 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 heater will be inside at home, between load-bearing structure and this building will appear condensate. 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 within 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 air permeability. 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 with outside at home. 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 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.
A table, graph and diagram will help you understand the principle of this property, after which you can already make a choice suitable material. Also, do not forget about climatic conditions outside the window, because if you live in an area with high humidity, then you should forget about materials with a high vapor permeability.
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