What are foam blocks and how do they differ from aerated concrete blocks?

What is a foam block and what does it look like?

A foam block is a cellular concrete, the production technology of which involves adding a foaming agent to a mixture of cement mortar, sand and water. Foaming agents can be synthetic (simpler, cheaper), natural (more environmentally friendly, more expensive). Despite the fact that a synthetic additive in its pure form is dangerous, the finished foam block is absolutely harmless.

The appearance of foam blocks can be seen in the photo below:

The purpose of using foam blocks depends on the density: the smaller the “bubbles” in the structure, the higher the strength of the material. The larger – the higher the thermal insulation performance. In this regard, the following are distinguished:

• structural (strong, but “cold” – require insulation);
• thermal insulation (warm, but fragile);
• 2 in 1 – warm, but often still not strong enough, requires reinforcement.

The marking on the material itself will help determine the density and compressive strength: D300, D400, D500 and so on up to D1200. The number means the density in kilograms per m3 – the higher, the stronger the bricks. In accordance with this number, the weight of one foam block also differs. For example, 1 cube of D400 foam blocks will weigh about 436 kg, and the weight of the same volume of D900 foam blocks is twice as much: 996 kg. This fact must be taken into account when preparing the foundation.

Important! In addition to the D marking, the letter F can be seen on the packaging. This is an indicator of frost resistance, most often there are numbers from 15 to 75. Materials marked 15-25 are usually thin, used in interior construction. From 25 and above – suitable for the construction of private houses, other residential or commercial premises.

Standard sizes of foam concrete blocks (length, width) – 600 by 300 millimeters. Thickness may vary, and the number of individual foam blocks in the package changes along with it:

• 100 – 55 pieces per 1 sq.m (in masonry, consumption per 1 sq.m is 16.7 pieces).
• 120 – 46 (13.8).
• 150 – 37 (11.2).
• 200 – 27 (8.4).
• 250 – 22 (6.7).

Important! Foam blocks of 200 and 250 are considered wall blocks — they are suitable for the construction of external load-bearing walls of a house. 100-150 are used in the construction of partitions.

The main requirements for the dimensions, transportation, and storage of foam concrete blocks are specified in the state standard (GOST 21520-89).

The average service life of foam blocks, or rather their structures, is 100-150 years. At the same time, one should take into account the high water absorption coefficient: due to which 30-40-year-old buildings will be stronger than newly built ones.

What is the difference from aerated concrete block?

Many novice builders or those who are far from the subject of construction and finishing confuse foam block and aerated concrete block. On the one hand, it is true: both materials are made on the basis of cement, have a porous cellular structure, are suitable for the construction of internal and external partitions of buildings.

But there are many more differences between foam blocks and aerated concrete blocks than it seems at first glance.

Composition

Both options meet all the necessary environmental requirements and consist mostly of natural components.

• Foam block: cement, sand, water, foaming agent.
• Gas block: cement, sand, water, lime, quartz sand, aluminum paste.

Important! If necessary, additives such as ash and gypsum are mixed into both materials.

Production method

Both forms are classified as so-called cellular concrete, but while the pores in foam concrete blocks are the result of adding a foaming agent, the bubbles in aerated concrete are the result of a chemical reaction between aluminum and lime.

External features

Aerated concrete has a rough surface of light gray, almost white color. Foam block is gray (the more cement, the darker), smooth, and its pores are larger than those of its analogue.

Thermal conductivity

Due to their higher density, aerated concrete blocks retain heat better inside living spaces; houses made of this material are warmer and, accordingly, more economical in terms of heating costs.

Application

The technical parameters of foam blocks allow them to be used for the construction of utility (barn, granary, garage) and residential buildings. The maximum height is 2-3 floors. Aerated concrete is used for the same purposes, but is best suited for tall residential buildings.

Important! Foam blocks are lighter than gas blocks, so the foundation underneath them may be less durable and simple.

Cost

A cube of foam concrete blocks will cost 1,400-1,600 rubles. The same volume of gas blocks is 30-40% more expensive (2,000-2,600). The difference is due not only to quality, but also to production technology: foam blocks are made quite simply.

If desired, you can even produce foam blocks yourself, you will only need ingredients and suitable forms. The production of aerated concrete requires expensive equipment.

What to look for when choosing?

To choose the most suitable for your task from all the types of foam concrete blocks, you should pay attention to 5 main properties.

Size

In the first section, we already talked about the standard dimensions of foam blocks, but 60 * 30 is not the only option for foam blocks. Based on the length, width and thickness, choose a material for a specific task:

• For reliable external walls along the contour of the building – 60 * 30 * 20 or 60 * 40 * 20. In the second case, construction will go a little faster.
• For durable internal floors bearing the main load – 60 * 30 * 20.
• For ordinary interior partitions – 60 * 30 * 10.

Advice! When making a purchase, choose material made by one manufacturer, preferably in one batch. This is a guarantee of the same geometry, the same raw materials used, standard technical characteristics.

Structure

The appearance of each individual foam block should be uniform, the structure should also be uniform, with round, not oval air bubbles. Cracks, chips, and other damage are unacceptable.

To check whether the supplier is saving on materials and whether the manufacturing and processing process is followed, rub a small piece of foam block in your hand. Did the pebble crumble into sand? The product is not suitable for construction work.

Density

Thermal insulation goes hand in hand with the density of foam blocks. The relationship between the characteristics is inverse: the higher the density (kg/m2), the lower the thermal insulation index. And vice versa. By the way, sound insulation increases with density.

• “Soft” foam blocks with the number D500 or less and relatively low thermal conductivity are suitable for insulating walls. They are cheaper than their analogues and perfectly maintain stable temperature and moisture indicators.
• Bricks with the marking from D1000 and higher are used for load-bearing partitions. High costs are offset by a number of advantages in the form of strength and durability.
• Foam blocks D500-D1000 are average, used for the construction of low-rise buildings, interior ceilings. Unlike structural ones, they have a lower cost, and in comparison with thermal insulation ones, they have a high density.

Frost resistance

Measured in cycles, main marks: F15, F35, F50, F75. Cyclicity shows the ability to maintain the structure with temperature fluctuations. The higher – the more frost-resistant the foam block in front of you. The choice depends on the regional conditions:

• southern regions with a mild climate, warm winters – up to 35;
• middle zone of Russia – 35-50;
• northern regions, Siberia – 50-75.

Manufacturer

As we have already mentioned, working with foam blocks is relatively easy – you can even produce the building material yourself. Therefore, a huge number of companies, both Russian and foreign, are engaged in the production of foam blocks. To choose the best supplier, pay attention to how long it has been operating on the market and what reputation it has – you can find lists of the best and most popular manufacturers on the Internet.

It is best to work with large factories, but to be sure of the quality of the products for sure, be sure to ask sellers of foam blocks for quality certificates.

From year to year, the following participate in the ratings:

• XELLA;
• Aerostone;
• LSR;
• UDK;
• Aeroc;
• Stonelight;
• Bonolit.

Conclusion: buy foam blocks from one trusted manufacturer, choosing goods from the same batch. Inspect the building material before purchasing for uniformity of color and structure. Choose the type that suits your technical properties.

What types are there?

Different foam blocks differ from each other in quality, appearance, and area of use.

By manufacturing technology, there are:

• Molded foam blocks. The cement composition is poured into separate small molds or one large one with partitions.
• Cut foam blocks. A huge layer of foam concrete is poured and dried, which is cut with a special machine into foam blocks of the required size. Cut foam blocks have better natural geometry, but are more expensive.

By composition:

• Natural. Mixtures based on silicate glue, caustic soda, and natural pine rosin act as foaming agents. Bricks with a natural composition are denser and more reliable.
• Synthetic. Chemical substances, such as PB-Lux, Rospen, PB-2000, are cheaper than natural analogues, but they produce more voluminous foam, so the foam block turns out to be “loose”.

By structure:

• Standard. Brick made of solid foam concrete.
• Reinforced. Foam block is reinforced with fiber, consisting of polypropylene – the second name is fiber foam block. It is distinguished by increased strength.

By properties:

We have already talked about them earlier.

• Structural. Dense, cold.
• Thermal insulation. Less dense, warm due to large air cavities.
• Structural and thermal insulation. Medium density, with an average level of thermal conductivity.

By area of application:

• External walls. Large, thick.
• Internal load-bearing. Smaller, thinner than the previous ones.
• Internal non-load-bearing. Thin (10-15 cm).

Applications

Foam concrete blocks cover a lot of construction tasks, including:

• Construction of load-bearing walls. In simple terms – construction of low-rise (up to 3 floors) buildings.
• Redevelopment of premises. Thin foam blocks are an ideal material for partitions: lightweight, cheap, easy to work with.
• Thermal insulation. The least durable foam concrete is an excellent heat insulator. It is laid as a second layer on a wall or floor. Foam blocks are also used to insulate floors between floors, roof openings, and load-bearing walls (for example, in corner rooms).

Foam blocks are used to build:

• residential buildings in any climatic (and even seismic!) zones: foam blocks do not burn, have high resistance values;
• outbuildings: a garage or a barn can be built in a matter of days;
• commercial buildings: warehouses, offices, small shops.

Pros and cons of houses made of foam blocks

Since block construction is becoming increasingly popular in the residential sector, let’s consider the advantages and disadvantages of this option.

Pros:

1. Low thermal conductivity. And, as a result, excellent thermal insulation. According to some data, foam block is as much as 2 times warmer than brick!
2. High level of sound insulation. Walls made of foam blocks protect not only from heat loss, but also provide almost complete blocking of extraneous sounds. This applies to walls both outside and inside the house – between rooms.
3. Frost resistance. Cellular concrete does not change its structure due to freezing and thawing, and therefore retains its basic functions and characteristics.
4. Fire safety. Concrete, unlike wood, does not burn: it is suitable for building baths and summer kitchens.
5. Ease of pouring the foundation. Its light weight allows you to save time and effort at the preparatory stages: the foundation may be less durable than, for example, for brick.
6. Speed of laying. Standard brick sizes are 250*120*65 mm, there are 65 pieces per 1 square meter of masonry. Foam block dimensions are 600*300*200 mm. To lay 1 square meter, 9 foam blocks are enough. Accordingly, building a wall is 7 times faster!
7. Durability. If you choose the right grade of foam concrete blocks and lay them correctly, the lifespan of the house is practically unlimited: the building is guaranteed to stand for 100-150 years.
8. Budget-friendly. A cube of brick will cost about 3,000-4,000 rubles, aerated concrete – 2,000-2,500, and foam blocks ~1,500 rubles. Work on laying foam blocks also costs less – at least due to the fact that they are larger than bricks, so 9-10 times less glue and effort is spent.
9. Hygroscopicity. A dubious advantage, but foam blocks really do not absorb moisture, unlike the same aerated concrete.
10. Environmentally friendly. Even taking into account the use of synthetic foaming agents, concrete bricks are considered safe, to say nothing of models with natural components. An excellent choice for a residential building.
11. Ease of processing. Foamed blocks are easy to cut, sand, groove for laying communications and much more.

Cons:

1. A small shrinkage is possible within 50-65 days after the completion of the work. It is only 0.1-0.4% of each meter of height (1-4 millimeters). This fact affects only one aspect: it is better to postpone finishing work for a couple of months.
2. Fragile foam blocks can break not only during transportation or processing, but also during operation of the house. The latter occurs exclusively in cases of incorrect choice of material – to avoid a mistake, seek advice from a specialist. Builders know which types are best to use in which cases.
3. Due to the porous texture, problems with wall fastenings may arise. The problem is solved simply: instead of regular dowels, choose special ones designed for cellular concrete.
4. Since the production technology is very simple, there is a high risk of stumbling upon counterfeit products, fakes or unscrupulous manufacturers. Always check certificates, carefully inspect the packaging.
5. The need to choose between strength and heat capacity complicates the purchase. In each individual case, it is recommended to make a mandatory preliminary load calculation in order to understand how dense the concrete should be.
6. Low aesthetic indicators. Foam block is still a rough building material. Masonry made from it can hardly be called beautiful or attractive, rather the opposite. To level this point, you will have to spend money on high-quality finishing inside and outside. Brick (provided that the foundation is strong), wood or vinyl, acrylic siding, as well as standard facade plaster are suitable for the facade decoration of buildings made of foam blocks. The base can be decorated with natural or artificial stone, base siding.

As you can see, foam blocks have a huge number of advantages and a few solvable disadvantages. You can even build houses from them yourself, which, coupled with the budget price, makes the material even more popular among land owners.