What reinforcement is suitable for reinforcing walls made of aerated concrete. Features of reinforcement of aerated concrete masonry

A series of articles on our website continues. We discussed:

• • • in the article there is a dispute between manufacturers of aerated concrete blocks and designers of buildings from this building material: is it necessary, in general, to reinforce the masonry of the wall from these blocks ?;
    • in the article the choice of mesh material for each specific case of masonry;
    • in the article full information about this building material.

So, having read the above articles, you have decided on the need to reinforce walls from aerated concrete blocks (in certain cases, walls are not reinforced from this material). And you know that all types of structural reinforcement of the masonry walls of gas-block buildings do not increase its bearing capacity, but only lead to a significant reduction in the risk of thermal shrinkage cracks.

Now you need to select the reinforcement material. Today we will give an answer to the question: what is the best way to reinforce aerated concrete blocks in different cases - with mesh or reinforcement?

Choosing the reinforcement material

Metal fittings have high mechanical strength and withstand heavy loads compared to non-metal. The total cross-sectional area of ​​the reinforcing steel bar should be only ≥ 0.02% of the same parameter of the reinforced aerated concrete masonry. Therefore, this material is widely used, but not everywhere.

The fact is that steel has several drawbacks, forcing, at the first opportunity (i.e., while ensuring the necessary mechanical strength of the masonry), to replace it with non-metallic reinforcement. Here is an incomplete list of these annoying "cons":

• • • susceptibility to corrosion. In an aggressive environment, which is mortar or glue, a metal rod or mesh can rust and lose its original strength;
    • the process of reinforcing with steel reinforcement has a high cost (transportation and handling costs, the cost of material and installation with strobing and fitting of rods in place, etc.);
    • steel reinforcement creates "cold bridges", which significantly increase the thermal conductivity of walls made of gas blocks.

Non-metallic meshes serve as a replacement for metal: propylene, composite and fiberglass. They have less mechanical strength compared to metal structures. But, they include a large number of polymer additives that are not subject to corrosion and the effects of an aggressive alkaline environment. In addition, these grids exclude the formation of "cold bridges", which significantly reduces the thermal conductivity of the wall (this is especially true if the wall is external).

Metal fittings

Rods and welded meshes are used as metal reinforcement. Rods are necessarily used when installing the entire vertical reinforcement circuit (lower and upper armored belt, vertical ties, etc.).

They are used to strengthen masonry under window and door frames, technological hatches, etc. Strobs are made for laying rods. To reduce the corrosion process, the metal rod must be recessed in the mortar (inside the gate) by at least 2 mm on each side.

The most complex, time-consuming and expensive reinforcement process is the process using welded meshes. If, to increase strength, a mesh made of large diameter reinforcement is used, this will lead to an increase in the thickness of the seam and, accordingly, a decrease in its strength. This is due to the fact that between the rows of blocks there will be a large amount of mortar. Therefore, nets with a rod diameter of Ø 3 ... 5 mm are used.

Technical characteristics of the grid are regulated by the GOST 23279-2012 standard “Reinforcing welded grids for reinforced concrete structures and products. General technical conditions". In accordance with it, the mesh is made of reinforcing wire of class Vr-1 and V-1 Ø 3 ... 5 mm. The dimensions are shown in the picture.

Non-metallic fittings

This type of reinforcement includes propylene, composite and fiberglass meshes. They are discussed in detail in the article. We will not repeat ourselves, but here we only note that the most widespread, due to its properties, is a composite mesh consisting of basalt rods.

Composite meshes are produced in accordance with the enterprise standard STO 5952-022-98214589-2013* “Basalt fiber meshes of the SBNPs “GRIDEX” brand. Specifications". This document prescribes the following cell sizes, mm: 25 x 25, 25 x 8, 50 x 50, 100 x 100, 150 x 150, 200 x 200. The width of the grid should be within, mm: 105 ... 5400.

Recommendations for reinforcing aerated concrete using masonry mesh

Often during the repair process it is required to install partitions, and more and more often aerated concrete (gas silicate) is used for this. It is lightweight - it weighs several times less than a brick, the walls fold quickly. Therefore, aerated concrete partitions are installed in apartments and houses, regardless of what the load-bearing walls are made of.

Thickness of aerated concrete partitions

For the construction of partitions inside the premises, special gas silicate blocks are produced, which have a smaller thickness. The standard thickness of partition blocks is 100-150 mm. You can find non-standard in 75 mm and 175 mm. The width and height remain the same:

• width 600 mm and 625 mm;
• height 200 mm, 250 mm, 300 mm.

The brand of aerated concrete blocks must be at least D 400. This is the minimum density that can be used to build partitions up to 3 meters high. Optimal - D500. You can also take denser ones - grades D 600, but their cost will be higher, but they have a better bearing capacity: it will be possible to hang objects on the wall using special anchors.

Without experience, it is almost impossible to determine the brand of aerated concrete. You can "by eye" see the difference between the heat-insulating blocks density. D300 and wall D600, but between 500 and 600 it is difficult to catch.

The lower the density, the larger the "bubbles"

The only available control method is weighing. Data on the size, volume and weight of aerated concrete partition blocks are given in the table.

The thickness of aerated concrete partitions is selected according to several factors. The first is whether it is a load-bearing wall or not. If the wall is bearing, in a good way, a calculation of the bearing capacity is required. In real life, they are made the same width as the outer load-bearing walls. Basically - from wall blocks 200 mm wide with reinforcement through 3-4 rows, like for external walls. If the partition is not load-bearing, use the second parameter: height.

• With a height of up to 3 meters, blocks of 100 mm wide are used;
• from 3 m to 5 m - the thickness of the block is already taken 200 mm.

More precisely, you can choose the thickness of the block according to the table. It takes into account factors such as the presence of an interface with the upper floor and the length of the partition.

Device and features

If aerated concrete partitions are installed in the process of repairing and or houses, you must first apply markings. The line is upholstered around the entire perimeter: on the floor, ceiling, walls. The easiest way to do this is with a laser plane builder. If it doesn't exist, it's better to start with a stream:

• A line is marked on the ceiling (two points on opposite walls). Between them, a masking cord is pulled, dyed with blue or some other coloring dry substance. With his help beat off the line.
• The lines on the ceiling are transferred to the floor with a plumb line.
• Then the lines on the floor and ceiling are connected, drawing verticals along the walls. If everything is done correctly, they should be strictly vertical.

The next step in the construction of aerated concrete partitions is the waterproofing of the base. The floor is cleaned of debris and dust, waterproofing roll material is laid (any: film, roofing material, waterproofing, etc.) or coated with bituminous mastics.

Vibration damping strips

To reduce the possibility of crack formation and improve soundproofing characteristics, a vibration damping strip is spread on top. These are materials with many small air bubbles:

• hard mineral wool - mineral wool cardboard;
• polystyrene foam of high density, but small thickness;
• soft fiberboard.

On short spans - up to 3 meters - reinforcement is not done at all. On longer ones, a reinforcing polymer mesh, a perforated metal strip, as in the photo, etc. are laid.

Wall connection

To ensure connection with adjacent walls at the stage of laying, flexible connections are laid in the seams - these are thin metal perforated plates or T-shaped anchors. They are installed in every 3rd row.

If a gas silicate partition is placed in a building where such connections are not provided, they can be fixed on the wall by bending in the form of the letter “G”, leading one part into the seam.

When using anchors, the connection with the wall is rigid, which in this case is not very good: a rigid rod from vibrations (wind, for example) can destroy the adjacent adhesive and the body of the block. As a result, the junction strength will be zero. When using flexible links, all these phenomena will not affect the blocks so much. As a result, the bond strength will be higher.

To prevent the formation of cracks in the corners, between the wall and the partition, a damper seam is made. It can be thin foam, mineral wool, special damper tape, which is used when laying underfloor heating and other materials. To exclude the "suction" of moisture through these seams, they are treated with steam after laying. not permeable sealant.

Openings in gas silicate partitions

Since the partitions are not load-bearing, the load will not be transferred to them. Therefore, there is no need to lay standard reinforced concrete beams above the doors or make a full-fledged jumper, as in load-bearing walls. For a standard doorway of 60-80 cm, two corners can be laid, which will serve as a support for the overlying blocks. Another thing is that the corner should protrude beyond the opening by 30-50 cm. If the opening is wider, a channel may be required.

In the photo, to reinforce the opening of a standard door, two metal corners were used (on the right), in the opening on the left, a channel was walled up, under which grooves in the blocks were selected.

If the opening is not wide, and there are only two blocks in it, it is advisable to pick them up so that the seam is almost in the middle of the opening. So you get a more stable opening. Although, when laying on corners or a channel, this is not a table that matters: the bearing capacity is more than enough.

So that the metal does not bend while the glue dries, the openings are reinforced. In narrow openings, it is enough to nail boards; in wide openings, a supporting structure resting on the floor may be required (fold a column of blocks under the middle of the opening).

Another option on how to reinforce a doorway into aerated concrete partitions is to make a reinforced tape from reinforcement and glue / mortar. A flat board is stuffed strictly horizontally into the opening, nailing it to the walls with nails. Sidewalls are nailed / screwed on the sides, which will hold the solution.

A mortar is laid on top of the board, three bars of class A-III reinforcement with a diameter of 12 mm are placed in it. Partition blocks are placed on top, as usual, following the displacement of the seams. The formwork is removed after 3-4 days, when the cement "grabs".

Last row - adjoining the ceiling

Since the floor slabs can sag under loads, the height of the partition is calculated so that it does not reach the ceiling by 20 mm. If necessary, the blocks of the upper row are sawn. The resulting expansion gap can be sealed with damping material: the same mineral wool cardboard, for example. With this option, sounds from the upper floor will be less heard. An easier option is to moisten the seam with water and fill it with mounting foam.

Sound insulation of aerated concrete

Although the sellers of gas silicate blocks talk about high rates of sound insulation, they greatly exaggerate. Even a standard block with a thickness of 200 mm conducts sounds and noises well, and even thinner partition blocks even more so.

According to the norms, the sound resistance of partitions should not be lower than 43 dB, but it is better if it is higher than 50 dB. This will give you silence.

To have an idea of ​​how "noisy" the gas silicate blocks are, we present a table with standard indicators of the sound resistance of blocks of different density and different thicknesses.

As you can see at the block, 100 mm thick, it falls short of the lowest requirement. Therefore, at , it is possible to increase the thickness of the finishing layer in order to “hold out” to the standard. If normal sound insulation is required, the walls are additionally sheathed with mineral wool. This material is not soundproofing, but reduces noise by about 50%. As a result, sounds are almost inaudible. The best indicators have specialized soundproof materials, but when choosing them, you need to look at the vapor permeability characteristics so as not to lock moisture inside the gas silicate.

If you need absolutely "quiet" walls, experts advise installing two thin partitions with a distance of 60-90 mm, which is filled with sound-absorbing material.

Reinforcement of aerated concrete masonry is a necessary step that prevents the occurrence of temperature-shrinkage cracks. To reinforce the rows, metal or fiberglass reinforcement with a diameter of 8 mm or more is usually used.

It should be noted that the reinforcement of the masonry does not increase the bearing capacity of the aerated concrete itself, because the reinforcement works in tension, and for the bearing capacity, compressive work is needed.

Now consider what exactly needs to be reinforced in aerated concrete house.

1. first row of masonry;
2. every fourth row on walls longer than 6 m;
3. jumper support points, 90 cm from the edges of the openings;
4. areas under window openings;
5. armored belt for ceilings and for the rafter system;
6. other sections of the wall with increased load.

For more clarity, see the aerated concrete reinforcement scheme.

To lay the reinforcement in a row of a gas block, it is necessary to make two strobes, 20-30 mm deep and wide. The distance from the gate to the edge of the blocks must be at least 60 mm. For a smoother strobe, you can nail a wooden block, which will act as a guide.

For chasing, special hand-held chasing cutters are used.

1. Clean the grooves from dust with a brush;
2. fill them with glue for aerated concrete;
3. drown the reinforcement in the middle of the strobe;
4. align the plane of the blocks with a spatula.

Important: the overlap of the reinforcement must be at least 200 mm, and there must be a bend in the reinforcement at the corners.

Aerated concrete reinforcement technology (video)

For partitions, special aerated concrete blocks of smaller thickness are produced. The standard thickness of such blocks is 100-150 mm, but there are also 75 mm. To reinforce the rows, reinforcing bars with a diameter of 8 mm, or a flat punched strip, are used.

Usually, every fourth row of masonry is reinforced, but in areas with increased seismic activity, every second row is reinforced.

The gap between the partition and the ceiling should be 15-20 mm, and it should be filled with damping materials, for example, foam or expanded polystyrene.

To connect the partition with the adjacent walls, flexible metal ties or T-shaped anchors are used, which are fixed in every 3rd row of masonry.

Jumpers are also an integral part of the technology. The task of the jumpers is to withstand the loads that are transmitted from the higher elements of the wall.

Usually, to create a jumper, U-shaped blocks are used, in which reinforcement is installed and filled with durable concrete of the M300 grade. Fittings in lintels are used with a diameter of 8-12 mm. And the frame itself consists of four to six bars connected in the form of a square.

The U-blocks must be supported by a strong formwork which must not buckle under the weight of the lintel concrete. The lintel must rest on the wall at least 300 mm on each side. A week later, after pouring concrete, the formwork can be dismantled.

Blocks should be installed with the thickened side facing out. And it is even better to insulate the jumper with 30 mm thick polystyrene foam.

The gas blocks on which the jumpers will rest also need to be reinforced by 900 millimeters on both sides.

Note that ready-made aerated concrete lintels can be found on sale, such products are provided by Aeroc.

The condition of the armored belt is obligatory - it must be inseparable, because its task is to significantly increase the resistance of the walls to loads and prevent cracks.

There are two types of armopoyas, the first of which is interfloor, the second is underroof. The interfloor strengthens the walls and distributes the load from the ceilings.

The under-roof belt distributes the load from the entire roof over the box of the house, and also allows you to level the plane and fix the Mauerlat.

The reinforcement scheme of the armored belt consists of four working rods of metal reinforcement with a diameter of 10-12 mm. Working reinforcement is fixed by a square of structural reinforcement. The installation step of the square should be 300 mm.

Do not forget that the reinforcing cage must have a concrete protective layer of at least 40 mm. The overlap of the reinforcement rods must be at least 50 cm. The bending of the reinforcement at the corners is obligatory. Also remember about the insulation of the armored belt with polystyrene foam. For the armored belt, it is recommended to use concrete grade M300, which must be poured at a time.

We described the detailed process of reinforcing the armored belt with all the pictures and diagrams in our previous article - armored belt for aerated concrete.

Tools for reinforcing aerated concrete

1. Estimating brush;
2. brush;
3. wall chaser;
4. carriage or bucket;
5. hammer;
6. Bulgarian;
7. lace;
8. formwork;
9. yardstick;
10. building level.

Before building an object, you should carefully familiarize yourself with all building materials and their characteristics. Building a house or a garage from gas silicate blocks, for example, is cost-effective. But in order not to crack, it is necessary not only to correctly select the density of aerated concrete and its strength class, but also to reinforce the masonry.

Aerated concrete masonry reinforcement scheme: 1 - Wall masonry, 2 - Floor slabs, 3 - Strapping belt, 4 - Mauerlat, 5 - Roof truss elements.

It should be borne in mind that even if you build a house with the correct preliminary calculation of the foundation, there is a risk of getting cracks on the facade of the building.

Often this is due to the process of building shrinkage, drying of cellular concrete and subsequently reducing its release moisture.

Reinforcement of masonry has been used for a very long time in Finland. Using this technology and choosing the right characteristics of aerated concrete, you can even build buildings up to 6 floors. After conducting an analytical analysis, it turned out that during operation for 20 years, such houses made of aerated concrete have practically no cracks on the facade. This strength of the walls is achieved by reinforcing the walls and corners. According to Finnish regulations, it is necessary to reinforce the first, and then every fourth row of aerated concrete masonry. To do this, strobes are made in the gas silicate block, into which reinforcement is laid and pressed with an adhesive solution.

Scheme of reinforcement of aerated concrete masonry along the height of the walls: 1 - Strapping belt, 2 - Reinforcement of the masonry of the window sill zone, 3 - Reinforcement of the masonry within the height of the pier, 4 - Reinforcement of the masonry at a distance of no more than 3 m, 5 - At a distance of more than 3 m.

At the corners of the walls, the turns of the strobe in aerated concrete blocks are cut with or using a special power tool. Before you start laying reinforcement in aerated concrete and building walls, the strobe must be cleaned of dust and filled with glue. Steel bars with a diameter of 8-10 mm can be used as reinforcement. In order to be able to bend it in various places, manual devices are used.

The reinforcement should be pressed into the strobe of walls and corners of aerated concrete so that it is completely covered with glue. From the front (external) surface of the gas silicate block, the reinforcement should be located at a distance of 6 cm. It is customary for us to lay 2 reinforcing rods in the wall for reinsurance at once. At the corners of a house under construction, strobes must be made with rounding.

It is imperative to reinforce the masonry of gas silicate blocks under the window openings. An important condition must be observed: under the doors and windows, the fittings must extend beyond the opening by at least 90-100 cm, and in the best case, if possible, then by 150 cm.

If they have a thickness of more than 250 mm, then two rods must be laid. If more than 500 mm, then it is advisable to lay three. If the thickness of the blocks is less than 250 mm, then it will be enough to do the reinforcement using one reinforcement bar. Before starting to build a house, it is necessary to calculate not only the consumption of the main material, but also to calculate the necessary reinforcing material.

Tools and materials

• fittings;
• adhesive mortar or cement composition;
• wall chaser;
• building level, tape measure and other measuring tool;
• grater, planer, sweeping brush;
• bucket, water.

Stages of work

1. After laying the first row of aerated concrete blocks, you need to wipe the seams and check the horizontal position using the building level. With the help of a chasing cutter, a groove is sawn - a strobe. If it is necessary to make two gates, then each of them should be located at a distance of not less than 60 cm from the outer edge of the gas silicate block. To make a strobe, you can also use an electric tool, but there is no particular need to buy it, since it will be very easy to strobe a fresh gas block.
2. After that, it is necessary to use a sweeping brush and sweep out aerated concrete crumbs and dust from all grooves. Next, water is poured into the bucket, and all the resulting grooves of the aerated concrete masonry are poured. Gas silicate building blocks must be saturated with moisture.
3. The next step will be partial filling (about half) of the resulting grooves with adhesive. For these purposes, you can use ordinary sand with cement to save glue. If the masonry grooves are not cleaned and not sufficiently moistened, then the cement mortar will not be able to soak into the walls of aerated concrete and you will not succeed in good reinforcement, as the mortar will mix with dust and the block will absorb all the moisture from it. It makes no sense to build insufficiently reliable walls.
4. If everything is done correctly, then you can take the reinforcement and drown it in the strobes, which are half filled with a solution. Individual rods are laid with an overlap of at least 35 cm (even better 40-45 cm for strength). The ends of the reinforcing bars are bent and gently flooded into the strobes specially prepared for them. Reinforcement of a house or garage from gas silicate blocks must be done in such a way that, under force, the ends of the reinforcement firmly hold the masonry in a monolithic array. It is necessary to build a house, taking into account the fact that the glue after solidification has high strength.
5. After that, you can fill the strobes with reinforcement with a solution to the end. After drying, with the help of a grater, a planer and a sweeping brush, the masonry surface is leveled and prepared for laying the next row. In the future, it is recommended to make reinforcement every 4th row of aerated concrete masonry.

Reinforcement of aerated concrete is an obligatory stage of construction when using this material, thanks to which it is possible to level the impact on the strength and reliability of the building of the shortcomings of the blocks. demonstrate excellent performance, are inexpensive, do not require additional thermal insulation, are convenient and easy to use, and allow you to speed up the process of building a building.

But the material has one drawback - the gas block is poorly resistant to bending deformations, it is fragile, therefore, without additional reinforcement, the walls soon become covered with cracks and require additional finishing and repair. Reinforcement of aerated concrete blocks with reinforcement will help to avoid shrinkage cracks and increase bending strength.

Aerated concrete: the pros and cons of the material

The material is widely used today. And before abandoning it due to the unwillingness to reinforce the house from aerated concrete and spend money on additional work, it is worth considering the positive aspects of using blocks in construction.

Main advantages:

• Light weight, which saves on the foundation and greatly simplifies the process of transportation, construction of the building
• Low heat transfer coefficient - it will be much more economical to heat the house
• High strength - the ability to build multi-storey buildings without arranging a complex expensive foundation
• Possibility of abandoning the cement mixture - a special adhesive composition minimizes the negative effect of cold bridges, reducing heat loss from 25% to 7-10%
• Durability - according to laboratory tests, blocks can last at least 100 years with full preservation of the original appearance of operational properties
• Sufficient level of air and vapor permeability - corresponds to the indicators of wooden structures and guarantees natural air circulation in the room, which creates an optimal microclimate, normalizes the level of humidity
• Resistance to changes in humidity and temperature, open fire, microorganisms (fungus, mold)
• Ease and simplicity in installation, processing - even a beginner can lay walls from neat, even blocks
• Large dimensions and high precision - walls can be erected with minimal deviations, saving money on exterior finishes, avoiding gaps in the masonry thanks to the use of slotted blocks, spending less time forcing walls
• Safety - the material is environmentally friendly, not afraid of fire, resistant to damage by rodents, insects
• Frost resistance - blocks withstand frost down to -50C, survive about 50 freeze / thaw cycles

Disadvantages of aerated concrete:

• The need to make the wall of sufficient thickness (about 65 centimeters), subject to the presence of cold bridges, heat resistance, the obligatory hardening of the canvas and lintels of window and door openings
• High hygroscopicity - in the total mass, the volume of moisture reaches 35%, which destroys the material, lowers the thermal insulation properties, but is solved by treatment with water-repellent impregnations (carried out at least once every 2 years)
• Increase in the cost of interior decoration due to the need to use reinforcing mesh and certain types of plaster
• Poor work in tension and bending - under high compression and other loads, the material quickly collapses, but this problem is solved by strengthening with metal rods or mesh

How to increase the resistance of aerated concrete structures to bending

To avoid the appearance of cracks on partitions and walls due to soil subsidence or external influences, aerated concrete is reinforced with reinforcement. The question of why and whether this should be done should not arise at all, because metal rods will not take on tensile loads and protect the structure from cracks and destruction.

It is necessary to choose the type of hardening and the place for it at the design stage. Metal rods and meshes are laid along the perimeter of the walls in the most dangerous structural elements. Before starting work, it is imperative to learn how to properly reinforce, what materials are better to use and where it is necessary, and in which cases it is superfluous.

Where a reinforcing element is required:

• The first row of aerated concrete blocks laid on the foundation - create monolithic reinforced concrete belts
• In walls whose length exceeds 6 meters, where it is important to compensate for the wind load, they make a horizontal bookmark in each subsequent fourth row
• Window and door openings - reinforced with reinforcing bars with a diameter of 8-12 millimeters in the longitudinal grooves of the upper floor blocks, under the lintels, at the bottom of the window openings in width with an overlap of 90 centimeters on both sides of it

• Places of junction with wall structures of rafters and ceilings - you will need an armored belt with laying rods in U-shaped blocks
• Locations where heavy loads are likely to occur
• The zones that are loaded from the roof are reinforced with metal rods with a diameter of 10-14 millimeters, creating a single reinforcing system
• Stair elements often require strengthening and floors are required

Whether it is necessary to reinforce in every fourth row, the designer decides, taking into account such factors: design features, the length of the walls, the rose and strength of the winds, the seismic zone, soil features, the type of foundation, the strength of the aerated concrete block. Experts still advise not to save and reinforce the walls in order to definitely avoid the destruction of the building.