Elimination of cracks in aerated concrete walls. Cracks in aerated concrete walls How to repair cracks in aerated concrete

Aerated concrete is an excellent building material, the main advantage of which is the preservation of heat. But at the same time, aerated concrete is quite fragile, which makes it less versatile.

Aerated concrete house should be built exactly according to the technology, and then it will be warm, comfortable and will last 100 years. But if some stages of construction technology are violated, cracks will appear in aerated concrete.

And it is about cracks in aerated concrete that we will talk about in this article. So, cracks can be small shrinkage, which in principle is not scary, but can be solid.

Causes of cracks in aerated concrete:

1. Laying blocks for mortar.
2. Do not level the plane of aerated concrete with a grater.
3. Absence or incorrect masonry reinforcement.
4. Incorrect or missing jumpers.
5. The absence of an armored belt.
6. Poor quality aerated concrete.
7. Savings on foundation, pillow, drainage.
8. The use of low density aerated concrete.

Laying the gas block on the mortar is not allowed, since the mortar joint will not be able to fasten the gas blocks with high quality. The thing is that aerated concrete very quickly draws water from a conventional solution, and as a result, the cement does not have time to react with water. That is, the cement mortar holds the gas blocks together very poorly, therefore glue is needed.

The only place where gas blocks need to be laid on the mortar is the first row for waterproofing.

Between themselves, the blocks must be laid on a special glue, which provides a thin seam, and excellent bonding of the blocks.

You can read more about the composition of the adhesive for aerated concrete in our previous article - the composition of the adhesive for aerated concrete.

Also recently, a special mounting foam for masonry has appeared, which is also an excellent material.

Although aerated concrete blocks are geometrically accurate, there is still an error of 1-2 mm. And during laying, this error must be removed with a grater. The plane of the gas blocks must be perfectly flat.

The thing is that the adhesive for aerated concrete has a very strong shrinkage, about 1.5 times. It follows from this that if the difference between the blocks is a few millimeters, a void will form under one of the blocks, and with the growth of the walls, tension will be created in this place, which will create a crack along the entire wall.

It is necessary to level the plane of the blocks with a grater. It is absolutely impossible to align the blocks with the thickness of the glue.

Reinforcement of aerated concrete masonry is also an important part of the technology, without which a crack in the wall is provided. The reinforcement works in tension, and provides the rigidity of the walls and resistance to cracking.

Reinforce the first and every fourth row. Two rebars with a diameter of 8 mm are used per row, although 10 mm can also be used. Reinforcement overlap must be at least 200 mm, with obligatory bends at the corners. The distance from the edges of the block to the reinforcement must be at least 690 mm. You need to reinforce places under window openings, under lintels.

We described in more detail about reinforcement in the article at the link, be sure to read it, there is very important information!

Lintels over windows and doorways should be rigid, they should not sag. For such rigidity, there are two solutions: buy ready-made aerated concrete jumpers, or pour the jumper yourself. In order for a home-made jumper to turn out to be of high quality, four bars of reinforcement with a diameter of 8-10 mm must be used for reinforcement, and concrete grade 300 should also be used.

The lintels must be supported by blocks of at least 300 mm on each side. Also, do not forget about the insulation of the jumpers with polystyrene foam to avoid cold bridges.

The armored belt is a necessary reinforced concrete structure that creates a monolithic ring around the perimeter of the walls. The armored belt significantly strengthens the walls of the house, and also evenly distributes the load from the ceilings and the truss system.

Poor-quality (garage) aerated concrete has different densities and sizes, which affects the overall quality of the masonry. Moreover, the garage gas block gives different shrinkage, which can crack.

Other causes of cracks

Aerated concrete house requires a reliable and rigid foundation. We also note that the lower the density of gas blocks, the greater the likelihood of cracks in the walls.

It is also desirable to protect aerated concrete from getting wet, because if frost hits, microcracks in the blocks are possible, although in most cases, aerated concrete does not collapse in the cold.

As a result of this article, let's say that aerated concrete is a good building material, but requiring full compliance with the technology. Build wisely and don't skimp on quality.

Hello everyone, Happy New Year and Merry Christmas.
The story is this:
In 2013, the foundation was poured - a slab of 25 cm.
In 2014, a box of aerated concrete house 600X400X250 (D600) was delivered. + roof, each 3rd row is reinforced + reinforcement under the windows. + 2 armored belts above each floor. The plinth is made of concrete blocks, the lintels above the openings are made as follows - on the outside there are two corners on which there is an aerated concrete block, about 15 cm thick, the rest of the space is filled with concrete with reinforcement.
Windows installed in 2015
Partial heating was launched in 2016
In 2017, the walls inside were plastered (mainly with a rotband) and plastered, full-fledged heating was launched.

Recently noticed two types of cracks:
1) Above window openings, in the area of ​​lintels
2) Cracks of unknown origin in the bay window of the house.

More information on cracks from point 1. (cracks are very thin, less than a millimeter), the lintels before the plaster were treated with concrete contact. My assumption is that cracks could appear as a result of uneven shrinkage of the plaster (however, then they would have appeared at the stage of plastering, it seems to me, and not at the stage of putty) or they appeared due to the fact that concrete and aerated concrete have different thermal expansion.
According to item 2. (cracks are very thin, less than a millimeter) They are divided into 2 groups, under the windows - vertical. It can be seen that they go along the seam in the block, but not in full length - that is, the crack hides a little behind the battery and stops there. The second group - horizontal - go from the opening to the perpendicular wall. They don't seem to go deep into the block. My guess is that these cracks may be the result of the same sandwich of different materials that have different expansions. There is metal (bay window poles) and concrete in the bay window lintel and aerated concrete, in general, a whole set. In addition, it seemed to me that the cracks appeared after I abruptly cooled the room from 21 degrees to 2, with the help of ventilation. (the last plastering work was carried out a long time ago, the plaster should have completely dried by now)
Outside, the house is not finished and not insulated, and on the day when I decided to air it, there was a very cold and strong wind.
Below is a series of photos with comments to better understand the situation.

I would like some comments from experts, why these cracks could appear, how they can be repaired, and solutions for interior decoration, with different scenarios (initially I wanted to paint most of the walls)

1) Blocks used in construction

2) An example of a jumper device (an external gas block is set to 2 corners, the rest of the space will be filled with concrete with reinforcement)

3) Bay window design. In the gas block, the hole is filled with concrete, in which there is an embedded part made of metal, to which the pillars are welded.

4) Lintel above the window before pouring concrete

5) Formwork on top of the bay window, outside and inside 50mm EPS, the middle will be filled with concrete. This is all part of the armored belt.

6) Filled ereker of the 1st floor. On the second floor, a similar design

7) View of the lintel inside - concrete treated with concrete contact before plastering

I'm sorry to you, the problem is the high moisture absorption of gas silicate. When you started to heat the house, the gas silicate began to dry and shrink, a consequence of a crack in the masonry. And on the corner cracks there is a complex of reasons, the first has already been voiced, the second you yourself have voiced (different materials with different coefficients of linear expansion, well, apparently, when plastering at the corners, they did not make additional reinforcement of the plaster (as it should be done in the upper and lower corners of windows). I sympathize , but until the load-bearing wall is covered with cladding and completely dry (and this is after facade work of 2-3 autumn-winter seasons with strong heating in order to squeeze moisture out of the wall by the difference in partial pressure), all your efforts will be in vain. !

Cracks of different sizes occur in aerated concrete for two reasons: due to ground or foundation movements, due to temperature changes and excessive moisture or mixing defects made during production. In this article, we will discuss ways to seal cracks in aerated concrete cottage walls that can be used for cosmetic repairs.

Earlier on the portal site, we have already discussed the technology of building walls of cottages from aerated concrete. This technology has its advantages and disadvantages. The main disadvantages of aerated concrete include, as a rule, the fragility and inelasticity of the material, its loose structure, even under ideally correct installation conditions, tends to “scatter” with small cracks that risk “breaking through” the plaster layer. Larger cracks occur due to ground movements. Smart people advise to deal with this by draining the land around the house, diverting water from the foundation, and prevent the shortcomings of the appearance of cracks by pasting aerated concrete with the cheapest glass wallpaper.

But if cracks in aerated concrete have formed, how to repair them correctly?
At the first stage, it is necessary to clean the walls from the collapsed layer of aerated concrete. After cleaning, the surface is dedusted, you can use water or an aqueous solution, you can do dry dedusting with a hairdryer or vacuum cleaner.

At the second stage, the surface should be primed. For these purposes, experts recommend using an aqueous 50% PVA dispersion or a mixture of SKS-65GP latex in a 1:3 volume ratio with water.

At the third stage, the actual sealing of cracks is performed, depending on the size of the damage.
Single cracks in aerated concrete with a width of a little more than 0.4 mm are usually expanded to 5-15 mm and sealed with any mortar. You can take a cement mortar, you can use glue for aerated concrete. The solution acquires additional qualities if small crumbs of aerated concrete are added to it.

Cracks in aerated concrete of a larger size up to 10 mm are sealed using a porous adhesive composition, having previously expanded them to 15-20 mm.

For larger cracks up to 20 mm, glue or cement is applied to the cleaned surface with the addition of large crushed stone from aerated concrete.
To improve the setting of the material, it is recommended to apply notches or grooves to the cleaned surface. When repairing large cracks in aerated concrete, it is recommended to use a large flat spatula, grout or a conventional plywood shield. The shield is used in such a way as to prevent the adhesive mass from slipping and gradually, as the seams are closed, the shield is lifted up.
After filling the recess with mortar, the seam should be stabilized for 3-5 hours. This is done using a sheet of plywood, which is fixed with self-tapping screws on the wall opposite the seam.

The situation looks different when aerated concrete not only cracked, but collapsed 20-30 centimeters deep. In such a situation, it is customary to “reinforce” concrete with nails and iron mesh. For these purposes, the damaged aerated concrete is cleaned, and then the wall is metallized with galvanized nails 150-200 mm long, placing them at a distance of 10-15 cm from each other. Pieces of metal mesh can be put on nails. Then, by analogy with the previous method of restoring aerated concrete, the cavity is filled with a solution of glue with pieces of aerated concrete. The cavity should be filled in 2 steps, laying layers with a metal mesh.

When carrying out restoration work on aerated concrete walls with a high degree of damage, it should be borne in mind that the restored pieces of the wall of a cottage or country house should have, on average, the same density as the unrestored aerated concrete. This is one of the reasons why large damages are repaired using fragments of aerated concrete and fragments of new aerated concrete so that they fit into the general masonry.

Especially for the portal site - Dmitry Levy

Permanent address of the article:

About the article "How to restore cracks in aerated concrete"

How to restore an aerated concrete wall?
How to restore aerated concrete?
How to remove cracks in aerated concrete?

Overview of programs for Horticulture and cottage settlements
In this article, we will talk about the evolution of horticultural services and cottage settlements, about the new expectations and requirements that urban residents place on the service, as well as the problems that horticulture managers and chairmen face when organizing payment collection.

Townhouses or wishful thinking
In the presented article, we will analyze the structure of demand and the specifics of supply, resulting from requests from the "consumer" of suburban and urban real estate. It will be about what type of housing is most attractive to buyers at a given time in the real estate market. We will try not only to conduct a study, but also to compare the results with a similar survey conducted in December 2011. In this way, we will be able to identify the dynamics of the wishes of customers.

The popularity of townhouses can push urban real estate
According to experts, today the market of townhouses in St. Petersburg and the Leningrad region is able to compete with the volume of sales and popularity of urban real estate. According to the study, the supply of economy class townhouses, located near the city limits, is growing day by day and gaining momentum.

City and region - a digest of new buildings, or what projects have entered the sales market?
It has been noted that recently more and more interesting projects of new buildings appear in the economy class segment. The apartment "mass - market" occupies not only the regional territories already known for their price democracy, but penetrates into the inhabited St. Petersburg. In this review, we will consider the dynamics of the development of the real estate market of the city and region. We will consider in detail both projects within the boundaries of St. Petersburg and in a suburban area.

The main styles in the interior of country houses
Often we can come across the names of cottage settlements or residential complexes that reflect the peculiarity of architecture. For example, the "Italian Quarter" or "Vita Verde" are reminiscent of sunny Italy. And often, houses in such villages are designed in a single, in this case, Italian style. As for the interior decoration of the premises, buyers can show their imagination and equip their home according to their desires and possibilities.

ElenaRudenkaya (Expert Builderclub)

Good day, Sergey.

You see, it makes no sense for us to tell you not what it really is or somehow hide something that we can help eliminate. On the contrary, we want you to find the causes of your cracks, eliminate them and live in your beautiful home for many, many more years.

I will try to explain and answer all your questions.

1. Yes, your monolithic slab is a whole mechanism (structure), which has its own loads, deformations, and it has its own “work”. It works both in deflection and in compression. This is a design that does not have a rigidly fixed frame and adapts to work depending on various influences. According to the project, you had to calculate and take into account all these deflections. In your case, it also works on vertical forces (“plays” like a raft rises and falls up and down in small waves). The level of hot water rises in the spring, the slab together with the grillage and piles rises up in the garage area, since the piles do not work as a support for the walls at the entrance to the garage. There is no elementary drainage from the rains that wash away the same part. After spring, the water went into the reservoir, the stove sat down like a raft in its place. But, for example, if we talk about walls, then they just have a rigid frame and it is enough to raise the plate by only 2 - 3 mm from the design level, then the wall breaks and a crack occurs. Where does the direction of the crack come from? You described everything correctly about the directions of the cracks yourself. The slab rose, the crack opened up to the roof, the slab sank back into place, the crack moved in equilibrium along the second wall, only to open up to the ground. It is strange that the builders cannot explain this to you.

2. It can be said for sure that if during construction you did not pour piles on a solid foundation, and they “hang” or float in water, then 2 m is very small. They are simply linked with a grillage, loaded with a slab of variable cross section and in one part the weight of the house, in the other - the garage, and, accordingly, there are vertical shifts from the GV. They build houses in swamps, but at the same time they deepen the piles by at least 5-6 m. A specialist cannot be ignorant of this.

3. It is very bad that the floor slab has a variable section of 25 mm and 45 mm, although the house and garage have different loads, so a monolithic slab cannot work as a whole. And just the stress was initially in the foundation, and then went along the walls (what your specialist is talking about), but since the monolithic slab has a certain margin for deformation, therefore, no cracks have formed in it yet. But you know, it's temporary. With such advances, anything can happen very quickly.

Start the sooner the better to follow our recommendations described above. This is the first and main thing we can advise you. It is necessary to observe the house after the installation of the blind area for several years, so that there is no more opening and the formation of new cracks. If this does not help, then we have another very difficult way for builders to strengthen your piles in the garage area. It is possible that it will be easier to dismantle the garage than to do what I am writing about, but more on that later. And we are almost sure that the blind area and removal of GW will be enough in your situation.

Ask.

to answer

During construction work, various unpleasant situations can arise from which no one is immune. One of them is a crack in .

There are several reasons why cracks may appear, this is usually due to subsidence of the foundation or due to a violation of block production technology.

There is another reason that arises when creating a ventilated facade, when wind load through the frame is transferred to the walls of the house.

Violation of manufacturing technology

Some manufacturers, during the creation of blocks, may experiment with the composition of the mixture and violate the technology for their manufacture.

This may be the use of inappropriate additives, when they begin to set earlier and the gas-forming processes do not have time to complete, there may be no hardening accelerators, additives that ensure the uniformity of the structure.

Violations of the technology for the production of foam blocks lead to the deterioration of the performance of the material.

In this case, cracks usually appear almost immediately or 1-2 weeks after.
It will not be possible to correct the specified defect., since the structure of the building material has been changed, so the way out of the situation is to dismantle the walls and use normal foam blocks.

Be sure to carry out high-quality waterproofing, since foam concrete absorbs moisture well and this can cause cracks.

If you plan to install a ventilated facade with additional insulation, then it is necessary to use blocks of brand D600 and higher, otherwise they may not withstand the wind load, which is transmitted from the cladding to the walls.

With the wrong creation of the truss system, the load is unevenly distributed, which can cause damage to the walls of the foam blocks.

To compensate for the forces created by the rafter system, it is necessary to install puffs (a beam connecting the rafters at the Mauerlat level) and use an installation scheme with inclined legs.

Errors during construction

Often, the cause of cracks is associated with a violation of the technology for creating both the foundation and the walls of the building:

• during the installation of the foundation, the characteristics of the soil were not taken into account and as a result of the action of heaving forces, the soil layers are displaced, which destroy the concrete foundation of the house;
• not performed, this should be done every 3-4 rows, due to which the rigidity of the wall decreases, and cracks may appear on it;
• homemade solution is used, in which the recommended proportions are not observed or there are impurities that reduce the strength of the seams.

Unlike brick walls, foam blocks must be protected from precipitation, wind, sunlight with high quality and reliability, it is best to do this by creating a wet facade.

What to do if the block burst

Care must be taken to ensure that the cracks that occur on the foam blocks are not transferred to the finish, this can be achieved in several ways:

1. cracks are sealed with putty, while the facade is leveled, and only then the finishing coating is mounted;
2. at , it is recommended to use fiberglass mesh, due to which the surface is reinforced, this prevents the appearance of cracks on the finishing material;
3. use of decorative plaster, which has wear-resistant fillers, such as basalt or granite chips.

These methods do not eliminate the formation of cracks, they allow you to hide them and prevent them from appearing on the facade cladding.

strengthening

In order to prevent further formation of cracks on the walls of foam blocks, it is necessary:

• to strengthen the foundation;
• install an additional armored belt;
• change the scheme of the truss system in order to reduce the horizontal loads on the walls.

For additional protection of the foam concrete house, experts recommend making a drainage system and a blind area around its perimeter.

Storm sewers or will allow ground, flood and melt water to be diverted from the walls, which will not increase soil moisture, so the foundation and walls will not absorb it.

How to fix a crack

To repair a crack, you will need:

1. a vacuum cleaner;
2. glue;
3. water;
4. cement;
5. grout;
6. putty knife;
7. primer;
8. iron mesh.

First, the place where the crack appears is well cleaned and the destroyed material is removed, then it is washed with water or cleaned with a vacuum cleaner.

A primer is applied to a dry and clean surface and the crack is sealed.. Depending on the size of the crack, it can be repaired with a mortar with crushed stone or glue.

The selected composition fills the crack, do this with a spatula and grout, after which it is closed with a sheet of plywood, which is attached to the wall with self-tapping screws.

If a large crack or hole has formed, then it is reinforced with an iron mesh, which is fastened with screws, after which it is filled with a solution.

Output

To avoid the occurrence of cracks in the walls of foam concrete, it is necessary to buy high-quality building material, make the foundation correctly, prevent violations and create a truss system.
If everything is done correctly, then you can independently build a reliable, durable and comfortable home.

Useful video

How to fix a wall crack in an apartment with your own hands, video:

In contact with