Foam blocks allow you to build a warm, strong house as soon as possible. This material conquered domestic builders with its operational qualities, therefore its range and the number of manufacturers is constantly growing. Unfortunately, the percentage of foam blocks produced by handicraft without taking into account any standards is also increasing, so it becomes more and more difficult to choose high-quality material. What foam blocks are suitable in each specific case and what to look for when buying in order to purchase a really high-quality, strong and durable material?
# 1. Features of the production of foam blocks
The basis of the foam block is cement, sand and water. A special foam is added to the thoroughly mixed mixture, which is usually obtained on the basis of a surfactant or foam concentrate. The homogeneous mass is cut or laid out in molds, leaving to freeze in the open air or in an autoclave.
Not the most complicated production process allows dubious companies to manufacture foam blocks, which led to the flooding of the market with products that do not comply with GOST. Factory packaging in plastic wrap, the presence of pallets and markings indicating the density, purpose and permissible errors in dimensions indirectly testifies to the manufacturer’s conscientiousness.
There are some differences in the general scheme for the production of foam blocks, which mostly relate to the formation of individual blocks, which determines the quality and geometry of the product. According to the manufacturing technology, foam blocks are divided into the following types:
molded block. The raw mass is poured into prepared cell molds of specified sizes. Hardening takes about 10 hours. This is the most economical method, but the accuracy is not the highest. Now more and more often they use a more modernized version, when the blocks undergo automatic demoulding. In this case, a special machine with partitions is used, where the mass is poured, and after it has solidified, the finished blocks are squeezed out, which makes it possible to obtain products with better geometry;
rifled block. Such products are obtained by cutting the raw mass with a steel string or by cutting one large frozen foam block into elements with the desired parameters. Thus, it is possible to achieve more accurate dimensions of the product;
reinforced block. For its manufacture, polypropylene fiber is added to the mixture, which increases the strength of the finished product.
Often, foam blocks are confused with aerated concrete. What are the differences? The main one is hiding in the composition. For the manufacture of foam block and aerated concrete, a mixture of cement, sand and water is used, and the gas generators are different. Instead of special foam, lime and aluminum dust are added to aerated concrete, as a result of the interaction of which hydrogen is released, foaming the mass. The internal structure is also different: aerated concrete has continuous pores. In addition, it necessarily undergoes heat treatment, and therefore costs more.
# 2. Advantages and disadvantages of foam blocks
If the foam block is made with high quality and in compliance with all requirements, then it gets a lot of excellent performance, for which it has gained such significant popularity.
The main advantages of foam blocks:
high compressive strength. This figure reaches 3-5 MPa and grows over time. Comparison of a new recently made foam block and a foam block that has been in operation for 50 years has shown that the density of the latter is 3 times higher;
low density. For blocks of different brands, this figure is 400-1200 kg / m3;
light weight, which makes it possible to simplify the transportation of material, construction work and reduce the load on the foundation;
ease of use. Large and lightweight blocks make it easy and quick to build a house. Processing the material is simple, so it can be given any shape;
thermal insulation properties. Due to the porous structure and a large amount of air inside the material (up to 40-80%), the thermal insulation qualities of the material increase. Compared to brick, the thermal conductivity of the D700 foam block is 3.5 times lower. In practice, this means that it is possible to make the masonry of a smaller thickness, reducing the load on the foundation, and in areas with a warm climate, subject to high-quality masonry, and do without additional thermal insulation at all;
soundproofing qualities. The porous structure of the foam block allows you to significantly dampen external noise, especially low frequencies. Wall 30 cm thick absorbs noise 60 dB;
environmental friendliness. Foam blocks are absolutely harmless to human health, are made from environmentally friendly materials, and the foaming agent used during production does not form harmful gases. Foam blocks do not rot and do not decompose;
high fire resistance, moisture resistance and frost resistance. The material almost does not absorb moisture, and thanks to this and the closed pore structure, the foam blocks easily withstand tens of freezing and thawing cycles without losing strength and integrity;
acceptable cost. 1 m3 of foam block is several times cheaper than solid wood, timber and much cheaper than brick, so building a house from a foam block will be more economical.
The main disadvantages of the foam block:
low bending strength. According to this indicator, the material is significantly inferior to concrete and reinforced concrete, however, with an increase in density, the strength of products also increases, but at the same time the thermal insulation properties decrease. Remember that foam concrete increases its strength over time and reaches the values necessary for the construction of buildings as early as 28 days. It is not recommended to use a newly made foam block, namely, such a material is often present on the market at the height of construction work, so it does not interfere with letting it settle for 3-4 weeks after purchase before construction;
- often the geometry of the blocks is far from ideal, which complicates the installation. It is better to buy a foam block from trusted manufacturers who offer high-quality products with the most accurate dimensions;
natural shrinkage. Within two months after the completion of construction, the foam block shrinks, which is associated with a set of strength. Shrinkage reaches 2-4 mm per linear meter. Since it is uniform, the building is not in danger, but the finishing work will be delayed for several months;
- not the best appearance, therefore houses built from a foam block are additionally finished, for example, with decorative or ordinary bricks, ventilated facades are equipped, etc.
Foam blocks have more advantages than disadvantages, and if you choose the right material, then the building will be durable and reliable. From foam blocks, you can build houses up to three stories high. Reinforcement of the walls is recommended to increase the strength.
No. 3. The size of the foam blocks
The first thing that is taken into account when buying a foam block is its size. Today, almost all manufacturers make foam blocks of the following sizes:
20 * 40 * 60 cm (height / depth / length) for load-bearing external walls;
- 30 * 20 * 60 cm for load-bearing internal walls;
- 10 * 30 * 60 cm for curtain walls and partitions.
All foam blocks in a batch must be strictly the same size – this is a guarantee that they will fit exactly to each other. The pre-purchase check can be carried out by measuring the parameters of the blocks and comparing them, or by placing the blocks on a flat surface, so that you can compare the sizes of the products and see how tightly they fit together. The presence of gaps and steps on the surface of the blocks is not allowed – this will not only increase construction costs, but can also lead to the formation of cold bridges.
No. 4. Density and frost resistance of foam blocks
Density is a key characteristic of foam blocks. According to this parameter, a particular brand is assigned to the material. Density is indicated by the letter D, foam blocks of grades from D400 to D1200 are on the market. Foam blocks with different densities are used for different purposes:
heat-insulating foam blocks of grades D400 and D500 have a thermal conductivity coefficient of about 0.12 W / m ºС, weigh 11-19 kg, highly porous, used for wall insulation;
structural and heat-insulating blocks of grades D600-D900 have a thermal conductivity coefficient in the range of 0.14-0.29 W / mºС and a weight of 23-35 kg. Can be used for the construction of load-bearing walls in low-rise buildings;
structural blocks of grades D1000-D1200 with a thermal conductivity coefficient of 0.36 W / m ºС and weighing 39-47 kg are used for the construction of load-bearing walls and floors.
With an increase in density, the thermal insulation characteristics of the blocks decrease, since the amount of air trapped in its structure decreases.
Another characteristic of foam blocks is frost resistance, i.e. the number of cycles of freezing and defrosting that the material can withstand without changing its properties. This indicator is indicated by the letter F, followed by a figure showing the number of allowable freezing and defrosting cycles. This indicator ranges from 15 to 75. The highest level of frost resistance is suitable for areas with an extremely harsh climate.
No. 5. Foam block structure
Foam blocks must be durable. If you managed to grind a piece of material between your fingers, it means that the manufacturer is saving on cement or violating the technology. In any case, such material cannot be used for the construction of load-bearing walls. Only heat-insulating foam blocks with a density of up to 15 kg / cm2 can be rubbed between the fingers.
The block should not contain cracks – their presence indicates the existing internal stress as a result of an incorrect drying process. The structure of the block should be uniform throughout the mass, and the bubbles should be small (no more than 1 mm) and spherical – oval-shaped bubbles indicate the fragility of the product. The uneven color of the block and the presence of streaks should also alert.
No. 6. What else to consider when examining the foam block?
Since the production of foam blocks does not require special equipment, today the number of unscrupulous entrepreneurs offering products that do not meet GOSTs is growing, so it becomes more and more difficult to choose a really durable and high-quality material. When examining the foam block, you should focus on the following signs of quality material:
the color should be light gray to dark gray. The whitish color indicates that lime was used in the production, which negatively affects the strength characteristics and environmental friendliness;
no traces of black grease, since their presence will not allow normal plastering of the wall surface. The fact is that responsible manufacturers use a high-quality self-decomposing mold release agent that does not leave marks on the block. To save money, waste machine oil can be used, which creates a film on the product, and in this place the plaster will simply flake off;
- a good foam block does not sink in water;
- high-quality products must necessarily be packed in film, otherwise excessive drying of the block will lead to the formation of a mesh of microcracks;
- foam blocks must have quality certificates, and a normal manufacturer is ready to provide full information about their products, therefore, hiding some data should alert;
- too low a price is also an indirect sign that the manufacturer saved and violated the production technology.
And, finally, it is better to trust trusted large manufacturers that have been on the market for a long time – this is how the guarantee is higher that the constructed structure will be durable, and the foam block will meet your expectations.