Cracks in aerated concrete masonry. The cause of cracks in the walls of gas silicate blocks and ways to eliminate the cause and the cracks themselves. Block Production Violations

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 cement mortar very poorly fastens gas blocks, 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 in recent times a special polyurethane foam for masonry, 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. Need to reinforce places under window openings, under the jumpers.

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 bend. 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.

Armor belt required reinforced concrete structure, which 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.

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 own way. beautiful house for many, many more years.

I will try to explain and answer all your questions.

1. Yes, yours monolithic slab- this is a whole mechanism (construction), 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 different direction cracks. 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.

Popular today building material- aerated concrete, there are several disadvantages. One of them is the appearance of cracks. Let's talk about possible reasons the occurrence of this problem, preventive measures and ways to deal with cracks that have already appeared in the walls and partitions of aerated concrete.

We described in detail the properties, pros and cons of aerated concrete, mentioning separately that approximately 20% of all blocks used in building a house are cracking. Of course, most often the cracks are very small, not critical, and nothing special needs to be done with them.

External small cracks perfectly hidden, for example, under plaster or siding, without violating the thermal insulation of the house and the load-bearing capabilities of the walls. From the inside, such small flaws in aerated concrete blocks are also usually hidden. finishing and do not lead to serious problems.

And if the crack goes through several blocks and is noticeable even from afar? If it was formed on important area walls, for example, at a corner and threatening to expand over time?

Cracks are of two types: caused by shrinkage of the house, exposure to moisture and temperature, as well as mechanical, associated with the applied load.

The reasons for the appearance of cracks in the laying of aerated concrete can be:

• Poor quality aerated concrete. Simply defective material, which has no chance to calmly "survive" the coming winter. We strongly advise you to purchase aerated concrete blocks exclusively from trusted suppliers, from manufacturers already known on the market, and not from “shrubs”;
• Wrong choice of block class. Recall that for bearing walls you should choose aerated concrete modification D500, and preferably D600 and with a density of B2.5, B3.5-5. Otherwise, the material will simply not be adapted to high loads and will start to crack.
• Foundation problems. Yes, aerated concrete is relatively light material, especially when compared to hyper-pressed bricks or good old cinder blocks. However, you can not save on the foundation! It needs to be reinforced, hydro- and thermally insulated, otherwise frost heaving and uneven subsidence will lead to the appearance of very serious cracks;
• Laying of aerated concrete low-quality mortar or adhesive mixture. It is better to purchase a special adhesive recommended by manufacturers of aerated concrete blocks to prevent problems.

So, in order to prevent the appearance of cracks in aerated concrete as much as possible, it is necessary:

1. Choose quality material.
2. Use the material of the desired grade and density.
3. Get a quality adhesive.
4. take care of solid foundation, its thermal and waterproofing.

That is, in fact, to comply with the technology of building houses from aerated concrete blocks, paying attention to all the details. There is no guarantee that even in this case there will be no cracks at all, but serious problems will definitely not appear.

Based on the causes of cracks in aerated concrete blocks there are several ways to fix them. For example, in case of problems with the foundation, most often it is required to first strengthen it, insulate it, waterproof it, and only then deal with the cracks themselves.

The crack itself should be dealt with like this:

• clean this place from dust, wet with water;
• primed;
• cover the cracks with putty;
• use reinforcing material on top, for example, fiberglass, which will then hide under the finish.

Important! Most of the cracks in aerated concrete are formed during the cold season. High risk of occurrence large cracks if the house has already been built, but not finished and no one lives in it, that is, there is no heating.

One of the most efficient and cheapest wall materials, which are used in private construction, gas blocks are considered. The advantages of such products are obvious - it is sufficient strength, good performance heat and sound insulation, resistance to high temperatures, fungus and mold, and the price of such materials is quite affordable.

Some builders who used aerated concrete to build walls could notice the appearance of various defects on the walls, and especially after wintering. Many are looking for an answer to the question: why do cracks appear in aerated concrete? Some attribute this phenomenon to wall shrinkage, but in fact this is not the only reason. Let's look at the answer in more detail.

Causes of cracks in aerated concrete

• use of defective products. Cracks on the walls can occur as a result of improper product manufacturing technology. In the manufacture of blocks, an insufficient amount of binder may be included in the raw mix, or the proportions of the main components may be violated. Experienced craftsmen recommend buying autoclaved aerated concrete;
• the possibility of subsidence of the foundation. This phenomenon usually leads to the formation of long transverse cracks. It is known that up to 25% of the cost of the cost of the entire house falls on the arrangement of the foundation. It should be noted that the structure under consideration perceives loads from all sides, therefore, when designing the foundation, it is necessary to take into account not only the applied efforts, but also the characteristics of the soil;
• wrong choice of finishing material. For example, for the device of a ventilated facade, a crate is needed, which will be mounted on outer wall. The frame itself experiences various loads (wind pressure, etc.), which can lead to cracks on the wall surface. For this reason, installation load-bearing structures performed using gas blocks of the D600 brand and above;
• the next reason for the appearance of cracks on aerated concrete walls is considered to be the wrong masonry technology, poor waterproofing or lack of insulation.

How to fix cracks in aerated concrete walls

We figured out the reasons for the appearance of cracks, and now we will get acquainted with the technology of their masking and ensuring the solidity of the wall.

The affected area must be cleaned of dirt, dust removed with a vacuum cleaner or spilled with water. Next, the crack is primed, and when the liquid is completely dry, it is sealed with cement mortar. With a significant width of damage, dirt is removed, the crack is cleaned and primed, and then it is filled with a solution with aerated concrete particles.

cracks different sizes occur in aerated concrete for two reasons: due to movements of the soil or foundation, due to temperature changes and excess moisture or mixing defects made during manufacture. 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 when ideally right conditions installation tends to “run up” with small cracks that risk “breaking through” the layer of plaster. Larger cracks occur due to ground movements. Smart people it is advised 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 water solution, you can do dry dusting 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, after expanding 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 can be put on nails metal mesh. 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 conducting restoration work above aerated concrete walls with a high degree of damage, it should be borne in mind that the restored pieces of the cottage wall or country house should have, on average, the same density as 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

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

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