By purchasing gas silicate blocks, you can hear that they are light, warm, environmentally friendly, but not always everything is as good as it looks at first glance.
Now let's try to consider not only the positive qualities of this material, but also the disadvantages, which, in some cases, are much more important to know about.
What are gas silicate blocks
Let's start with the fact that gas silicate, as a material for building walls, began to appear on the construction markets relatively recently, but has already gained popularity among developers, primarily because of its low cost and practicality.
Gas silicate itself is aerated concrete with improved characteristics, belonging to cellular concrete. Unlike other types of blocks, inside gas silicate blocks there are a huge number of small voids - bubbles, due to which significant thermal insulation is achieved.
Gas silicate blocks are made from water, cement, lime, sand and aluminum chips (powder), which contributes to the formation of those same bubbles. But despite the availability of the constituent components, it is impossible to make gas silicate blocks yourself. Their production includes expensive equipment and not a simple technological process, the strict observance of which is required condition during their manufacture.
Walls made from gas silicate blocks are laid using special glue. The use of mortar is usually allowed for blocks with poor geometric characteristics, due to which the thickness of the glue seam will not be sufficient to level them.
How critical are the disadvantages of gas silicate blocks?
If there was a material for the walls of a house that had only advantages and no disadvantages, then all private houses would be built from it. But unfortunately, these are just dreams and such building material has not yet been invented. Some are too fragile, others are not suitable for all homes, and others are very expensive.
It is also not without its shortcomings, which we will now consider:
- Low tensile strength. Due to their porosity, gas silicate blocks are very fragile in tensile strength. This means that using them without additional reinforcement, both the walls themselves and the armored belt on top of them, is not recommended. Otherwise, cracks cannot be avoided.
- Low compressive strength. It manifests itself in shrinkage of the entire wall during the operation of the house, which is fraught with the appearance of cracks. This occurs due to the low density of gas silicate blocks. In order to reduce this effect, it is necessary to use blocks of higher density, but this is no longer economical, and the thermal insulation properties will be worse.
- Due to the low density and external smoothness, problems may arise with wall finishing, both with plaster and siding, for example.
- Large block size. On the one hand, this is most likely an advantage that will speed up the laying, but on the other hand, these blocks have significant weight, which is not always convenient.
- Gas silicate blocks absorb moisture very well, which winter period, without insulating the blocks from precipitation, will be destructive.
- It is not recommended to use gas silicate blocks in bathrooms and other rooms with high humidity.
Exaggerated and dubious qualities of gas silicate
As I already said, every manufacturer praises its product as best it can, but not always, all the advantages it describes correspond to reality. Now we will look at the dubious qualities of aerated concrete blocks, which manufacturers exaggerate a little:
- The main quality of gas silicate blocks is high thermal insulation. This is true, a wall made of such blocks will retain heat well in the house, but the characteristics specified by the manufacturer, as a rule, are suitable for low-density gas silicate blocks, which are suitable for load-bearing walls, in most cases, are not suitable.
- There is an opinion that under a house made of gas silicate blocks you can use an insufficiently reliable foundation, taking into account the low weight of gas silicate, saving a lot of money on this, but this is just fiction. The walls of a gas silicate house need very durable and solid foundation, and you can learn more about this from my article about the foundation for a house made of aerated concrete.
- The low cost of walls made of this material is also one of the main dubious advantages. If we consider bare walls made of gas silicate blocks, then the low cost may be confirmed. But if you take everything into account additional expenses: reinforced foundation for the house, due to the low strength of the walls, good reinforcement, increased wall thickness, then it doesn’t come out very cheap.
- Increased service life of a gas silicate house. The most questionable quality, because gas silicate blocks began to be widely used in construction not long ago to judge their durability.
- And finally, very often you come across unscrupulous manufacturers who do not adhere to the technology for manufacturing gas silicate blocks, which worsens the quality of an already fragile material.
I tried to describe all the possible disadvantages of gas silicate blocks, which you should pay attention to when choosing Special attention. But this in no way means that this material is not suitable for building walls, since it has enough and positive qualities, which also need to be taken into account when choosing a material.
Aerated concrete in last years has become one of the most popular materials for masonry walls. The blocks are used both in private construction and on an industrial scale. Individual developers use them to build houses, garages, bathhouses, and utility rooms for various household needs. In the second case, gas blocks are used to construct partition walls between rooms (premises) inside multi-storey buildings.
Experts have mixed opinions about the pros and cons. The difference in assessment is due to the relatively short period of its mass use. Therefore, it is too early to make generalizations. No basic research behavior of aerated concrete blocks over several decades. Observations and measurements are carried out relatively recently. The overall picture is formed by reviews of private developers who do not always comply construction technologies and blaming “poor quality material” rather than their own unprofessionalism and negligence.
At the same time, the quality of gas blocks that were produced 5-8 years ago and modern ones is radically different. Now there are dozens of companies on the market offering truly reliable building materials. One thing is certain: modern blocks is an affordable and reliable wall stone, quite suitable for the construction of objects with a service life of about 50-80 years.
General overview and features
First, you should study the composition of aerated concrete. Blocks are produced based on the following components:
- cement (from 50 to 70%);
- sand (20-40%);
- lime (5%);
- water (less than 1%);
- special additives (0.05-0.1%).
The mixture is poured into molds heated to 40 °C and sent to the autoclave. Aerated blocks suitable for masonry are manufactured only at large enterprises where there are chambers in which a pressure of up to 12 bar is created and a temperature of about 2000 ° C. The mixture contains aluminum powder, which activates rapid gas formation. It is this additive that makes autoclaved aerated concrete a cellular (porous) material. Air bubbles in the structure of the stone determine thermal insulation characteristics and allow it to “breathe”.
After the aerated concrete mass has completely hardened, it is cut into blocks using strings certain sizes and configurations. High-quality stone, produced in compliance with technology, is characterized by ideal precision of lines. Regular parallelepipeds stacked on top of each other provide thin seams between the rows of the wall being built. Cold bridges can be avoided, thereby significantly reducing the heat loss of the building.
Blocks that have not been autoclaved are also sold. They are dried in hydration boxes under conditions of elevated temperature and humidity. Accordingly, the strength of concrete is 3 times less than that obtained using the autoclave method. This type aerated concrete is suitable for insulation, but not for masonry.
And the quality of blocks made by hand is very low. Reviews about them are a continuous stream of negative statements. But, given the fact that in each of the three production options ready material is called “gas block”, consumers make a generalization. Accordingly, an opinion is formed that there are much more minuses than pluses. In fact, high-quality aerated concrete has very few disadvantages. Experts in their reviews indicate that when proper arrangement foundation and adherence to technology, the operational parameters of the blocks are not much inferior to brick or cinder block.
Technical characteristics of blocks
1. Dimensions.
Standard linear dimensions parallelepiped blocks:
- length – from 500 to 600 mm;
- height – 200 mm;
- thickness - from 75 mm to 500 mm.
2. Configurations.
Produced in the form of parallelepipeds with 6 smooth surfaces or with grooves and ridges on 2 end faces. U-blocks are also produced for arranging armored belts.
3. Strength of aerated concrete.
The material is lightweight, but at the same time has good strength. Depending on the brand, the compressive strength coefficient ranges from 1.5 to 3.5 kgf/cm².
4. Classification of grades depending on the density of aerated concrete:
- D300-D500 – thermal insulation;
- D500-D900 - an intermediate option used for structural and thermal insulation work;
- D1000-D1200 – structural aerated concrete.
Advantages and disadvantages
All of the above properties of aerated concrete blocks should be taken into account during construction. Depending on the type of future building (house, bathhouse, garage), you can use wall stone of various sizes and densities.
Of course, aerated concrete blocks, produced both by autoclave and obtained by drying in hydration chambers, have pros and cons. But in the first case, the declared properties practically coincide with the operational ones, and in the second, the material may behave “inappropriately”. After all, the parameters are designed for the same climatic conditions, and developers make their own adjustments without taking into account expert reviews on construction from aerated blocks.
1. Advantages of aerated concrete:
- Ease of processing.
Using a tool, gas blocks can be easily processed manually. You can saw, make recesses, grind surfaces.
- Thermal insulation properties.
Using D500 and D600 brand blocks, the developer achieves two goals at once: constructing the frame of a house or bathhouse, as well as thermal insulation of these buildings.
- Soundproofing.
The ability to soundproof directly depends on the brand of aerated concrete blocks and the thickness of the walls.
- Fire resistance.
Aerated concrete blocks- This is a non-flammable material. They have the highest fire resistance class.
- Environmental friendliness.
Gas blocks are safe. Aerated concrete can be harmful to health in one case - if there are radioactive elements in the base mixture. But this is practically impossible on an industrial scale when the components undergo laboratory testing. During operation, the blocks do not react to form toxic substances. According to their own environmental characteristics aerated concrete is comparable to natural materials and is not much inferior to wood.
- Light weight.
It is very light, so it is easy to work with. You can do the laying yourself.
- Large product size.
This option should also be considered a plus. The construction of houses made of aerated concrete is carried out much faster than similar ones made of brick.
- Resistance to biological effects.
Aerated blocks are an environment unfavorable for the formation of mold, fungal colonies and bacterial growth. The material does not need to be treated with antiseptics.
2. Disadvantages and negative parameters:
- Fragility.
This disadvantage of the block manifests itself during transportation, during the laying process. But the main point is the predisposition to cracking of the walls in the event of improper foundation arrangement. Small irregularities in the strip base - and after 2-3 years the blocks will begin to crack. The problem can be solved by using mesh reinforcement at intervals of 3-4 rows.
- High water absorption coefficient.
It can be reduced with special impregnations, which are applied before plastering. It is strictly not recommended to leave aerated concrete walls “open”.
- Problem with fasteners on aerated concrete surfaces.
Massive shelves, cabinets and other objects are very difficult to mount on the wall. The best solution– self-tapping screws. But they have their own nuance - oxidation, and as a result, loss of aesthetic appearance.
- The frost resistance parameter is overestimated by sellers.
Some experts claim that the real frost resistance of D500 blocks is only 25 cycles. Although sellers declare at least 50 (this is the indicator that is suitable for exterior finishing). Frost resistance at the F50 level is observed in gas blocks of grades D600 and higher.
- Presence of free lime.
This deficiency leads to active corrosion processes occurring inside aerated concrete. Lime corrodes sections of pipes, fittings, jumpers and other metal elements.
To build or not to build with aerated concrete?
This question very often arises among individual developers. On the one hand, the material has many advantages, and on the other, no fewer disadvantages. The relative cheapness of the blocks is compensated by the “lottery” in terms of the durability of the building. It is unknown how long a house made of aerated concrete will last if deficiencies in the foundation or masonry are suddenly discovered.
Developers are actively discussing the disadvantages of aerated concrete baths. These include the properties of the material to actively absorb moisture. But the use of impregnations and primers, as well as waterproofing finishing is good decision in this case.
Savings on foundations also speak in favor of houses, garages or bathhouses made from aerated blocks. Future construction does not require massive monolithic slab, enough strip base. Accordingly, it can be built on any type of soil.
You need to start constructing a building from aerated concrete by first weighing the pros and cons. In this case, it is important to take into account all factors (location, soil type and freezing depth, relief, number of storeys). Even in the case of a light structure (garage, bathhouse), you need to adhere to technology so that in a few years you do not witness the destruction of an almost new building.
The main costs in the construction of a low-rise building are the material used for the construction of external load-bearing walls and partitions inside the building. To save money, builders often recommend using gas silicate blocks for this. They are environmentally friendly and light in weight. Their housing is warm and energy efficient. However, in addition to a lot of advantages, these blocks also have negative sides.
What is a gas silicate block?
Gas silicate blocks are artificial stone, made from one of the varieties cellular concrete. This building material can be made even in artisanal conditions. It is enough to mix the solution and leave it to harden in the air for several days near the foundation of the future house. But oh high quality there is no need to talk about such a stone.
Grinding the mixture to produce blocks
Much more often, the production of gas silicate blocks occurs using an autoclave. Heat with pressure in the latter accelerate the hardening process concrete mixture and make the product more durable. Now the autoclave method is the main one for all factories where this building material for walls is produced on an industrial scale in sizes corresponding to GOSTs.
To make a gas silicate block, mix:
Quicklime;
Portland cement;
Sand (fine or ground);
Water with aluminum powder;
Additives to accelerate hardening.
Autoclaves in which they dry at a temperature of 120 degrees and a pressure of 12 atmospheres
During the process of mixing the solution, aluminum powder, lime and water react, resulting in the formation of hydrogen. Because of this, after hardening in concrete, it forms a large number of small sealed cavities. On the one hand, these voids make the block light, and on the other hand, they reduce its thermal conductivity.
Types and sizes of gas silicate blocks
The weight, dimensions of gas silicate blocks and their other parameters are determined by GOSTs 21520-89 and 31360-2007. These standards provide general tables for all similar products from cellular concrete. Moreover, the standardized sizes of foam blocks and gas silicate building materials with similar properties differ greatly in numbers.
For the first foam concrete option, the standards indicate ten standard sizes from 88x200x398 to 188x300x588 mm. Wall blocks as such do not have standard GOST dimensions.
For them there are only maximum values:
Height no more than 500 mm.
Width (thickness) up to 500 mm.
Length no more than 625 mm.
However, manufacturers often produce gas silicate according to specifications. The size in this case can be anything. For example, products for partitions in a house are most often made in the form of thin slabs with parameters 100x250x600. And analogues for external walls usually have dimensions of 300x250x625.
Much in terms of size depends on the manufacturer and the equipment he has for cutting aerated concrete into individual blocks. The comparative table below shows some options for such products, indicating density, frost resistance and other characteristics.
Table of sizes and characteristics of wall gas silicate
Table of sizes and characteristics of gas silicate partition blocks
According to their purpose and density, gas silicate products are:
Thermal insulation D300–D500;
Structural and insulating D600–D900;
Structural D1000–D1200.
Their weight depends not only on size, but also on medium density aerated concrete. For comparison, one cubic meter of D400 weighs about 520 kg, and D600 is already 770 kg. Accordingly, the walls are made of different types gas silicate blocks have different loads on the foundation of a house. All this must be taken into account when choosing the building material in question.
Pros and cons of blocks
The advantages are the following:
Light weight - you can load/unload aerated concrete products, as well as build a house from them, alone;
Excellent sound insulation - the presence of many voids guarantees excellent insulation of all street noise;
Ease of processing – for cutting aerated concrete blocks with self-construction a hacksaw is enough for a cottage;
Low thermal conductivity - a house made of gas silicate is warm and energy efficient;
High speed of wall construction - the blocks are larger than standard bricks 1NF, which greatly speeds up the masonry process;
Non-flammability – gas silicate belongs to the group of low-flammable materials “G1”.
Construction of block walls
Houses made from gas silicate blocks are famous for their comfort and environmental friendliness. Thanks to good vapor permeability, their walls are “breathable”. However, such a cottage can be built with a maximum of two floors. Otherwise, if the load is too heavy, the lower rows will begin to collapse under the weight of those laid on top.
Gas silicate blocks also have disadvantages, including
High water absorption;
Relatively low heat resistance.
Aerated concrete does not burn. However, at temperatures above 700 C it begins to collapse. After strong fire a house made of gas silicate blocks will most likely become unsuitable not only for habitation, but also for reconstruction.
The second problem is moisture absorption. When water gets on aerated concrete, almost all of it ends up inside the block. And when it freezes, such a “sponge” simply breaks into pieces.
In this regard, ceramic blocks have much more advantages. Of course, photos of brick houses sometimes disappoint aesthetes with efflorescence stains, which are also associated with exposure to moisture. But this does not have much effect on the strength of the masonry. But gas silicate blocks quickly begin to lose their high heat from exposure to water specifications and gradually collapse.
This is what a damp block looks like
Photos of houses
Aerated concrete blocks retain heat well in the cottage, but only as long as they remain dry. If gas silicate walls from the facade are not reliably protected from precipitation, they will not last long. At the cost of this construction material outperforms many analogues. However, in the general estimate for the construction of such a building, it is necessary to take into account the obligation to complete its façade finishing.
For houses that are planned to be built from gas silicate blocks, there is no need to make an expensive and powerful foundation. This building material does not weigh that much. However, the foundation for masonry from it must have a grillage or be strip. The slightest distortion will inevitably lead to the appearance of cracks in the enclosing structures of their aerated concrete.
Gas silicate is inferior to brick in strength, but benefits in terms of thermal efficiency and less load on the foundation. Foam concrete analogue with equal density it will also win in terms of heat retention. However, aerated concrete is much inferior to both of them in terms of moisture absorption. You need to choose this material thoughtfully, having first weighed all the pros and cons. It will take more money to finish and waterproof a home than for a brick or wooden building.
View of a block house
Unusual house geometry
House "under the roof" made of blocks
It is better not to leave the blocks open during the winter.
House with a turret
Partition gas silicate blocks were used above the window spaces
Most often, such walls are faced with brick.
The construction estimate, required for the construction of private housing, shows that 50% of the cost of building materials is load-bearing walls and partitions. Therefore, developers try to choose a material that is cheaper, but with high performance characteristics. And gas silicate blocks with their low thermal conductivity coefficient and low production costs make building a house attractive and in demand. Having an idea of the advantages and disadvantages of this building material, you can largely avoid negative aspects, affecting the durability of operation and the quality of housing.
The main reason why gas silicate is a leader in individual construction– its low cost. Also important role The speed and ease of laying products into a specific design plays a role. Practice has shown that 1 m2 of surface made from blocks costs half as much as the same area made from ordinary brick, even taking into account the fact that gas blocks can be produced in complex geometric shapes.
Gas silicate belongs to a subtype of cellular concrete, which is produced using an autoclave ( industrial production) or manually (at home) from the following components:
- Portland cement and quicklime;
- Siliceous aggregate;
- Aluminum powder;
- Water.
Lime serves as a catalyst in the reaction with aluminum to foam the mixture, during which the released hydrogen forms many tiny bubbles in the mass. In industrial autoclave production, this reaction is followed by steaming the mold into which the working mixture is poured, and then the solution is left to harden. This produces highly porous gas silicate concrete. Finished dimensional and molded products are obtained by cutting the plate into blocks of given dimensions: length ≤ 600 mm, thickness ≤ 250 mm, height ≤ 500 mm. Based on density, the material is divided into the following subtypes:
- Structural products having a compressive strength ≥ D700. They are used in the construction of load-bearing walls and internal partitions;
- Structural and thermal insulation products with strength grade D500-D700. Used for the construction of partitions and any walls in low-rise buildings;
- Thermal insulation blocks with strength grade D400. For the construction of new walls and insulation of the constructed facility;
Aerated blocks are most often in demand in individual housing construction, since it is recommended to use them to construct low-rise buildings. But as insulated objects, premises made of gas silicate bricks are built into multi-story buildings or combined industrial construction projects.
Calculation of the number of gas silicate blocks
The sizes of the blocks are adjusted to existing standards of building materials and, taking into account the thickness of the mortar layer, correspond to a multiple of the brick sizes. Therefore, calculating the required number of products for building a house is not difficult, quick and simple. To do this, you do not need to use special programs or order the services of an architect. Standard size – 60 x 300 x 200 mm. Based on these figures, we obtain the volume of one product - 0.036 m 3. There will be 29 gas silicate products in 1 m3.
The dimensions of load-bearing walls and partitions are indicated in the project, and how many units will be needed is easy to calculate. From the result you need to subtract the area of windows and doors, and therefore multiply this figure by the width of one product. This is how the volume of gas blocks for any walls is calculated in m3. It remains to divide the total volume by the number of products in 1 m 3, and you will get the required result. Don't forget to add 15-20% for chips, surface defects and damage during transportation and installation. Also, in order to make dressings when laying gas silicate products, you will need to saw them, and this can be done with an ordinary hacksaw or grinder. You can hammer the blocks with a chisel or a hammer drill.
It takes about 20 minutes to lay 1 m³ of a wall made of aerated silicate bricks, and up to 5 hours to lay 1 m³ of brick. This speed of work is ensured by the larger sizes of the blocks compared to bricks, precise dimensions (deviation during sawing - 0.3-0.8 mm), and laying with special glue, and not with cement-sand mortar. Also, adhesive for gas silicate has thermal insulation properties, and its use eliminates the appearance of “cold bridges”. Even taking into account the high cost of this composition, its consumption is much less than the consumption of the solution, so masonry is cheaper.
The outer surfaces of the walls of a house made of gas silicate blocks must be insulated and isolated from moisture penetration. At the same time, the wall must “breathe” so that in the house and between the layers of thermal insulation and waterproofing materials no condensation formed. Polystyrene foam, polystyrene foam or sand-cement mortar They do not allow air to pass through well, and their use for insulation is not recommended. Most suitable material for finishing and insulation is gypsum or alabaster plaster, as well as decorative Decoration Materials– siding, plastic (lining), facing brick (clinker). Mineral wool is used as insulation, and membrane materials are used for waterproofing.
The most popular siding: it can be mounted on metal carcass immediately after the construction of the walls, without waiting for the house to shrink. Usage facing bricks makes building a house a little more expensive, but increases the thermal insulation of the walls. If the walls are not covered with plaster, using the dry method, then between the wall and decorative material must remain air gap 5-10 cm.
To avoid purchasing and installing insulation, the walls must have a thickness of at least 0.5 m. That is, the developer will have to separately calculate whether it is more profitable to purchase more gas blocks or to make thermal insulation.