Experts unanimously classify aerated concrete as artificial stones, although in general it is one of the varieties of aerated concrete. The composition of this building material includes quartz sand, cement, lime and a gas-forming agent, which is usually a paste or powder of aluminum. Aerated concrete is obtained as a porous material, micropores are from 1 to 3 millimeters in size and are evenly distributed throughout the block. There are GOST 31359-2007 and GOST 31260-2007, which relate to products from aerated concrete, produced by the method of autoclave hardening.
Important! All the advantages that we will try to tell you about will relate to aerated concrete, which is produced by autoclaving. This is a process that occurs when heated and under pressure exceeding atmospheric.
Autoclaved aerated concrete is produced on high-precision equipment, the whole process is automated. Only in this case can you achieve high quality and geometric accuracy up to 2 millimeters..
Note one more thing: aerated concrete is usually produced in three modifications – D400 B2.5, D500 B3.5 and D600 B3.5-5.
Important! Aerated concrete D400 B2.5 has a lower thermal conductivity, that is, it retains heat well and can serve as a heater. But the strength is lower. Only low-rise buildings can be built. For buildings up to five floors, the more durable D600 B3.5–5 is used, but its thermal conductivity is higher and the house will have to be insulated. So there is no need to say that all aerated concrete perfectly retain heat or are suitable for load-bearing walls!
Thermal conductivity data from GOST:
- D400 – 0.096 W / (m • ° С)
- D500 – 0.12 W / (m • ° C)
- D600 – 0.14 W / (m • ° C)
However, these figures are for dry blocks. If we take an indicator of equilibrium moisture content of 5%, then the data on thermal conductivity will be completely different:
- D400 – 0.117 W / (m • ° C)
- D500 – 0.147 W / (m • ° C)
- D600 – 0.183 W / (m • ° C)
Manufacturers point to the following advantages of aerated concrete:
- Low construction cost. Indeed, we carried out calculations of what is more profitable to build from – foam concrete or aerated concrete. So the cheapness of the construction process is actually an advantage of this material, although it itself costs a lot..
- Aerated concrete has a minimal radiation background, as a result of a chemical reaction, metallic aluminum in its composition turns into harmless aluminum oxide, therefore the material is safe and considered environmentally friendly.
- A house made of D400 B2.5 aerated concrete will not need insulation, as it perfectly retains heat. As a result, heating costs can be significantly reduced. However, as we wrote above, the material of this brand is not suitable for load-bearing walls, but it is better to insulate aerated concrete D600 B3.5-5.
- It is easy to build from aerated concrete, the material is light, cut, drilled. The speed of building a house is higher than in the case of using bricks. Moreover, blocks with a clear geometry are attached to a thin layer of glue, so there will be a minimum of gaps, the wall should be perfectly flat. However, this advantage will continue if construction technologies are followed. If the workers applied glue at random, then gaps will remain.
- From aerated concrete, you can build houses of any configuration, even complex shapes, build arches, kinks, various structures.
- The material does not burn, it contains only mineral components.
Aerated concrete has enough disadvantages:
- Let’s go back to the question of choosing a material grade. For the masonry of load-bearing walls, D600 gas blocks are required, but they have less thermal insulation properties. Experts advise to build walls in two rows with bandaging. That is, the outer part should be built from strong load-bearing gas blocks, and inside for insulation, a more porous, but fragile material should be used. But such a construction process turns out to be more costly and time-consuming, although the house in the end will definitely turn out to be warm..
- Manufacturers claim that the thickness of the wall made of gas blocks of 37.5 centimeters will be sufficient for the Moscow region. Moreover, the brand D400 is indicated. However, judging by user reviews, the wall thickness must be at least 45 centimeters in order to really get a warm house in the central, and even more so in the northern region. So when building a house from aerated concrete, you will definitely have to carry out careful calculations and clearly choose the technology.
- Cracks. This is the main disadvantage of aerated concrete, which users complain about. In practice, even if all construction technologies were followed, approximately 20% of all gas blocks will crack. A reliable monolithic foundation will help to minimize the deformation loads that appear when the house shrinks. Yes, in this case there should be fewer cracks, but there will be costs for a powerful monolithic base.
- A house made of gas blocks must be plastering, finishing! Manufacturers claim that the house will stand for several years without finishing. But aerated concrete absorbs moisture, then gives it away, absorbs it again … The house will look terrible, dampness will form inside.
It is the plaster that is the optimal finish for gas blocks, and users are advised to choose silicone as the most reliable and modern. In this case, you should use a reinforcing facade mesh so that the plaster is held securely.
Here are some more negative reviews we found:
- The walls of gas blocks should be primed twice, since the mixtures do not adhere well to the surface. All you need is a deep penetration primer.
- Ordinary plaster does not hold, a special adhesive mixture is required, it is expensive.
- Fasteners do not hold well, special ones are needed to hang a water heater or shelf on a wall of aerated concrete.
Let’s try to draw conclusions: houses made of aerated concrete are really built quickly and are inexpensive compared to other building materials. Does the house keep warm? If the foundation is reliable, the wall thickness and the brand of gas blocks are chosen correctly – of course, yes. There are cracks left, there is no high-quality exterior decoration – no.
Small cracks in aerated concrete can be dealt with by external finishing, for example, using fiberglass canvas instead of the usual reinforcing mesh. The cracks will simply hide under the finish and the house will retain its attractive appearance..
If you did not have time to finish building a house of aerated concrete before autumn, we strongly advise you to reliably preserve the structure. In the spring, it may turn out that the gas blocks, like a sponge, have absorbed a lot of moisture, have become dark gray and you should wait until they dry completely to continue construction. Therefore, it is best to hurry up and rent out the house before the rains and cold weather. In the case of gas blocks, this is real, because construction is proceeding quickly.