Concrete blocks: dimensions, pros and cons, scope

The last century brought us many new building materials. One of them is aerated concrete. This is a porous type of concrete, which is also called cellular concrete. The presence of air-filled pores made the material light and warm. As a result, it is used both for the construction of walls and partitions, and for insulation. Light weight allows you to vary the size of aerated concrete blocks from small in width, more like slabs – for interior partitions, to wide – for exterior walls.

What are aerated concrete blocks

Aerated concrete is a material that is obtained from a mixture of cement and sand, to which reagents are added, which, when interacting with cement, form foam. Powdered aluminum or paste from it is used as reagents for aerated concrete. As a result of the reaction of aluminum powder and cement (or lime), pores are formed in concrete – air bubbles, evenly distributed throughout the volume. The bubbles are enclosed in a binder – cement or lime. Such concrete is called cellular or lightweight.

General principles of production

A feature of aerated concrete is that the pores are closed, which reduces the water absorption of the material. It is, of course, more than that of ordinary concrete, but not so critical. The standard defines the area of ​​operation – external and internal walls and partitions in conditions of normal humidity or at a humidity not higher than 60% according to one GOST and 70% in another way.

In production, the dry ingredients are first mixed, to which water is then added. As a result of the reaction, the composition “rises”. The reaction goes up to the primary hardening of the binder. Then the cellular concrete is removed from the molds, cut into blocks or slabs of the desired size. Finished products are sent to ripen – to gain sales strength. There are two types of aerated concrete ripening:

• Autoclave. The blocks are sent to special chambers where they are treated with steam. The chambers are pressurized. This treatment speeds up the process of curing. In terms of quality, autoclave blocks are better: uniform moistening throughout the entire depth gives the material greater strength. But autoclaved aerated concrete costs more: additional equipment, additional energy costs for processing. But for building a house, it is better to buy an autoclave.
• Non-autoclave. The blocks are simply placed outdoors and wait for the concrete to gain strength. This is the easiest option, but no one guarantees quality. According to the technology, the blocks are dried in drying chambers.

Depending on the amount of reagent, aerated concrete can have a different density and strength. In more durable, there are fewer pores, the walls of the bubbles are thicker. Such marks are used for the construction of walls.

There are brands of aerated concrete in which there are a lot of air bubbles, their walls are thin. Such blocks and plates are used for insulation. In general, the material itself has very good thermal insulation characteristics, and it is also easy to process. The presence of a large number of bubbles leads to the fact that the mass of porous concrete is very small. This allows you to make large-format blocks, which greatly speeds up the process of building walls. And even with large blocks you can work alone.

Types and types of aerated concrete

In the production of cellular concrete, a binder of various types can be used. Also, various mineral components can be introduced into the composition of the material. Depending on the binder and additives, the name should change. This is written in GOST.

• Aerated concrete. The binder is cement, and Portland cement is at least 50%. The best gas blocks are obtained from this material.
• Silica concrete. A mixture of cement and lime. Boiler lime is at least 50%, cement – 15% by weight, the rest can be additives – slag or gypsum. Silicate gas blocks can be distinguished by their white color. On a cement binder, they are gray.
  

• Slag-gas concrete. If it contains slag in an amount of more than 50% by weight. The second component of the binder can be cement, lime.
• Zologazobeton. If the high basic ash is 50% of the binder by weight or more.

It is these names that should be present in the labeling and the name of the material. They can also use as a filler not only quartz sand, but also ash (TPP waste), waste generated during the manufacture of ferroalloys, ore dressing and other technological processes.

Pros and cons of gas blocks

Gas blocks are an excellent building material. They are easily processed. You can cut them with an ordinary manual hacksaw for metal, they are drilled without problems. When using blocks of sufficient density, fasteners are normally twisted into them. The material does not burn and does not support combustion. Lightweight, warm, durable, breathable.

Advantages of gas blocks:

• High strength with low weight. Autoclaved aerated concrete has sufficient strength so that it can be used to build a two-three-story mansion. At the same time, the weight is small. And this means that there will be less load on the foundation, which reduces the cost of its arrangement.
• Lightweight block of aerated concrete. For the construction of walls, blocks with a width of 200 mm are usually used, strength grade D500 or D600. Even gas blocks of this size – of considerable width – weigh from 12 to 16 kilograms.
  

• Excellent thermal insulation properties. According to thermotechnical calculations, a wall of 200 mm thick gas blocks has the same thermal resistance as a brick wall 60-70 cm thick. Despite the fact that it has many times less weight, the cost of building a house is much lower. There are also such names for this material as a heat block, a heat block, etc.
• High geometry accuracy. If the blocks do not differ in size, laying is easy. But this parameter is very dependent on the manufacturer.
• Moisture resistance and frost resistance. Autoclaved gas blocks have good moisture resistance. These figures are much lower than those of bricks, but they are more than enough to build a house.

For all its merits, the gas block is not ideal. Leaving the walls unfinished is not worth it. But the decoration of the house from aerated concrete must be correct. The material is breathable and hygroscopic. To prevent moisture from being locked inside, it is necessary to choose the right vapor permeability of finishing materials.

Disadvantages of aerated concrete blocks

The disadvantages of aerated concrete are a consequence of its advantages. For example, ease of processing. When building, it’s good. But it is also easy to cut a passage in aerated concrete wall with a chainsaw. Some attackers take advantage of this. The way out is to make a “burglary-resistant” finish, for example, to overlay a house with bricks. There are other disadvantages of the gas block:

• Aerated concrete is brittle, does not hold bending loads well. The problem is solved by the device of reinforcing belts. But it is important that there are no subsidence of the foundation.
• When laying gas blocks, special glue is used, which costs a lot. The advantage is that with good geometry of the blocks, its consumption is very small – the seams are made in 3 mm.
  

• If you build from blocks containing lime, it quickly corrodes the reinforcement. The problem is solved by using polymer rather than metal fittings.
• When using gas blocks of low density, special fasteners are needed.

The material is not bad, but you need to really evaluate the pros and cons of gas blocks. You can build a house of permanent residence from them without much concern. Aerated concrete blocks are not suitable for the construction of a bath, as they are too hygroscopic. It is better not to use them for the construction of a house in the country – the low frost resistance of the material will lead to the fact that it will begin to quickly collapse. Is that the positive temperature will be constantly maintained in the house, and the walls will be well insulated.

Features

The main characteristics of any building material are density and compressive strength. It is they that are established by GOST 31359-2007, which describes the requirements for autoclaved cellular concrete.

The compressive strength of an aerated concrete block can be as follows: B0,35; B0,5; B0,75; B1,0; B1,5; B2,0; B2,5; B3,5; AT 5; B7,5; AT 10 O’CLOCK; B12,5; B15; B17,5; IN 20. This indicator characterizes the load that the material can withstand without destruction. The higher the number, the more durable the material.

The second important parameter is the average density. They are related to compressive strength. The higher the density of the material, the greater the load it can bear. So, in essence, both characteristics describe the strength or load-bearing capacity of materials. Just from different angles. For a gas block, the average density can be from D200 to D1200.

Depending on these characteristics, aerated concrete blocks are divided into:

• Structural. For the construction of load-bearing walls and partitions. Specifications B3,5 and above, D700 and above.
• Thermal insulation and construction. For load-bearing and unloaded walls and partitions with a simultaneous improvement in thermal performance. The required bearing capacity of the walls is gained due to the greater thickness. This category includes blocks and slabs with a compressive strength of at least B1,5, a density of not more than D700.
  

• Thermal insulation. To reduce heat loss through walls. The strength grade is not higher than D400, the density is not lower than B0,35. The lower the density, the better the thermal insulation characteristics.

The frost resistance grade is also determined – the number of defrosting / freezing cycles that the material can withstand without changing its properties. This parameter is indicated by the Latin letter F and numbers, which indicate the number of cycles. For autoclaved aerated concrete, the following frost resistance grades are defined: F15, F25, F35, F50, F75, F100. The minimum value of frost resistance for aerated concrete blocks of external walls is F25, internal – F15.

Dimensions of aerated concrete blocks according to GOST 31360-2007 and 21520-89

As often happens, several regulatory documents are in force at once, which creates some confusion in labeling. In addition, the dimensions of aerated concrete blocks are also determined by these standards in different ways. An older standard prescribes exact values ​​in millimeters for the length, width and height of the block. It also introduces differences for masonry with mortar or with glue. On the solution, the seam is larger, the block sizes are smaller. For laying on glue, the thickness of the seam is less, the blocks are larger.

The block size itself is encoded with a Roman numeral. This, of course, is inconvenient. You must remember the correspondence or have a correspondence table with you. In addition, increased requirements for the energy efficiency of houses have led to the fact that cellular concrete is placed only on glue. Cement mortar is not used, as it is a cold bridge in the masonry, thereby worsening the overall performance of the wall. An example of marking according to the old standard: I-В2,5D500F35-2. This means that the block of the first size (188 * 300 * 588 mm), compressive strength B2,5, average density D500 and frost resistance F35, accuracy category 2.

The new GOST simply introduces two concepts: an aerated concrete block and a slab. For each of them, the maximum dimensions are determined. The exact dimensions are not determined.

Marking according to the new standard is easier. The block dimensions must be specified in millimeters. For example, Block I / 600×300×200 / D500 / B2,5 / F25. Here the category (permissible error in size is indicated by the Roman numeral I or II) is moved to the beginning, the order of the characteristics is changed, but their list remains the same.

Category of limit deviations

Both standards prescribe possible deviations in size and defects in the form of violation of squareness, curvature of edges and faces, and chips. These defects affect the category of the block. Previously, there were three of them: one for laying with glue, two for laying with mortar. The new standard describes only two categories.

In general, the marginal deviations are small by both standards. But foam blocks of the first category have greater accuracy. Precise geometry – less consumption of expensive glue. But even with second-class material, low consumption can be achieved. True, this will require additional effort and time. The secret is simple – too large blocks are hemmed with a conventional planer, adjusting the dimensions.

Types of gas blocks

Construction – wall and partition blocks – made of aerated concrete can be in the form of a parallelepiped with even edges or with a tongue-and-groove system formed on the sides. The second option is done if the dimensions of aerated concrete blocks are closer to large ones: with a width of 200 mm or more. In large blocks, additional holes are often made – for ease of carrying. It really makes the job easier.

There are also U-shaped blocks for the construction of reinforcing belts. Reinforcement is placed in the recesses formed by the walls of the block, everything is poured with concrete.