In the construction industry, there has always been an acute question of whether the material has sufficient bearing capacity, while possessing good heat and sound insulating properties. That is why this article will consider polystyrene concrete as a material that best meets these requirements..
The use of lightweight concrete in construction allows solving a number of problems and significantly reducing labor intensity in the production of work. So, structures built on the basis of these materials have a lower mass, which reduces the load on the foundations and greatly facilitates the construction process. The thermal insulation parameters of the buildings being erected are much higher than those of those using classical materials (brick, heavy concrete), which ultimately leads to a significant reduction in the cost of work. Despite the variety of lightweight concrete (foam concrete, aerated concrete, slag concrete, etc.), special attention should still be paid to the original material – polystyrene concrete.
Pros and cons
Polystyrene concrete is a lightweight concrete based on cement filled with expanded polystyrene granules. The filler is obtained by foaming polystyrene chips, which, in turn, is a product of recycling polymer waste. From this it follows that in terms of its environmental properties, polystyrene concrete is not inferior to similar building materials, and even surpasses some. The production of the same expanded clay is notorious for the active pollution of the adjacent territories. In technical terms, polystyrene has a qualitatively lower hygroscopicity (water absorption) and thermal conductivity than traditional aggregates (expanded clay, vermiculite, etc.). As a result, the structural indicators of the final product are defined as D 450-600 (wall density is up to 500 kg / m3, which is 2 times less than that of foam blocks), thermal insulation – D 150-350 (low density of the material contributes to high energy-saving properties, and the lower this indicator, the better), structural and thermal insulation – D 350-450.
The advantages of polystyrene concrete include the following characteristics:
- the lowest thermal conductivity coefficient among all known wall materials (0.55–0.12 W / m);
- low hygroscopicity with normal vapor permeability;
- high degree of sound insulation;
- frost resistance class F100 and higher;
- sufficiently high strength (class B 0.5–2.5);
- wide density range: 150–600 kg / m3;
- hardly combustible – if the structure is plastered or clad with brick, then it can be used for the construction of buildings and structures up to 25 floors high (class G1);
- low cost compared to other materials.
In addition, it should be borne in mind that polystyrene concrete does not rot and is not affected by fungi, microorganisms and rodents. It is environmentally friendly and has a material life of over 100 years. Additional heat-insulating properties of structures made of polystyrene concrete blocks are given by the fact that the thickness of the joints does not exceed 4 mm. Due to the low weight at the stage of erection of the enclosing structures, lifting equipment is not used, and labor costs are reduced by three times, since with a block weight of only 22 kg, it replaces 17 pieces. bricks. If the structures are made in a monolithic version, then the use of a polystyrene concrete mixture can significantly reduce the time required for demoulding, since this concrete hardens rather quickly, without giving practically any shrinkage. In the event of a fire, polystyrene concrete does not lose its properties, since the granules in the outer layer melt and prevent the destruction of the filler inside the material.
However, such a wonderful material is not without drawbacks, the main of which must be listed:
- polystyrene concrete has a rather low index of compressive, tensile and bending strength;
- the concrete mix tends to exfoliate during transportation, laying, as well as during pressure delivery;
- the production process of polystyrene concrete is rather complicated;
- it is rather difficult to obtain a material with stable characteristics;
- the production uses highly specialized technological equipment;
- a very high quality of block masonry is required (with an increase in the thickness of the joints, all characteristics will sharply decrease).
As a matter of fact, the bulk of the disadvantages of polystyrene concrete lies either in the field of production (which does not concern the consumer in any way), or in the field of application (which directly depends on the consumer himself). The opinion about the low strength characteristics of this material is often based on the use of polystyrene concrete from an unscrupulous manufacturer. In addition, do not forget that it belongs to the class of lightweight concrete, not heavy one. Accordingly, in its niche, polystyrene concrete has fairly good strength characteristics..
The polystyrene concrete production process begins with the production of the filler using granule pre-foaming agents. These units can operate both from centralized steam supply lines and from steam generators. After that, in the activator-mixing plants (based on gerotor pumps) a ready-made mixture is formed.
Further, if blocks are being produced, standard molding of products is performed, and if the mixture is intended for monolithic construction, transportation to the facility. Often, polystyrene concrete mix is made directly at the construction site – for this, so-called mobile complexes are used.
Comparison of materials
Comparing the technical and operational characteristics of polystyrene concrete with other lightweight concrete, it is easiest to rely on its main competitor – foam concrete.
Products made of foam concrete have increased water permeability, which leads to their rapid destruction. At the same time, precisely because of the characteristics of the filler, polystyrene concrete actively resists the penetration of moisture into the material. The strength characteristics of foam concrete are an order of magnitude lower than that of polystyrene concrete – at the slightest dynamic load, it collapses, since it is very fragile. The costs of production of works using foam concrete are much higher, since its weight is 1.5–2 times higher than that of polystyrene concrete. The setting and hardening of polystyrene concrete is much faster than that of foam concrete, and the requirements for raw materials are much lower. So, when the grade of cement or the properties of sand changes, there are no critical changes in the parameters of the final product..
If we compare polystyrene concrete with expanded clay concrete, then it is favorably distinguished by its lower weight and lower (2 times) thermal conductivity, and gas silicate loses much with its high hygroscopicity and rather limited variations in the finish of external surfaces.
In practical application, it is quite convenient to use polystyrene concrete blocks as a wall material, although the method of monolithic casting into formwork is often used. The high speed and manufacturability of masonry from such blocks is ensured by the fact that they are easily sawn with a hacksaw, drilled, milled, nailed and do not create obstacles to giving them any shape. The large size of the blocks greatly simplifies the laying, and the small thickness of the seams saves mortar (glue-based mixture). The blocks are available in various sizes and configurations, which allows you to speed up the construction of enclosing structures by 10 times in relation to the use of classical materials. At the same time, the cost savings for the production of work is in the range of 12-12.5%.
The laying of polystyrene blocks does not differ significantly from the laying of any other blocks: the optimum temperature for the production of work is +5 … + 25 ° С, it is necessary to level and level the foundation, etc. Also, do not forget that before installing the structures overlap, it is imperative to perform a monolithic reinforcing belt made of reinforced concrete. The consumption of dry mixes is usually 17–20 kg / m3 blocks (with a joint thickness of 2–4 mm).
Directly laying blocks includes the following operations:
- Cleaning the surface of blocks from possible sagging or debris.
- Thorough mixing of the adhesive mixture.
- Laying blocks on a layer of glue.
- Control of rows for horizontal and vertical.
We get the highest productivity when carrying out work by the “four” link: a highly qualified bricklayer makes masonry rows of milestones, controls the dressing of seams, horizontal and vertical masonry; two handy bricklayers prepare and bring the blocks, spread the glue and help in installing the blocks in accordance with the design position; the remaining assistant worker kneads the glue solution. It is recommended to lay the masonry on one grip, and to do preparatory work on the other (procurement of materials, installation of scaffolds).
The applied seam dressing scheme is chain. Both horizontal and vertical seams must not have cavities or breaks. Laying is done in tiers from 0.8 to 1.2 m in height. The distance between the beacon blocks (along which the mooring is stretched) should not exceed 15 m. The bed of the glue mixture should be laid out evenly and not brought to the edge of the block by 15–20 mm. Its leveling should be done with a notched trowel (comb). It is better to tap the blocks with a rubber hammer to avoid mechanical damage. The block to be glued should be verified no later than 10 minutes after the start of its laying..
Choice and purchase
When choosing blocks from polystyrene concrete, it should be borne in mind that their cost directly depends on the brand of the product. Thus, for one-storey construction, blocks with a density grade D400 or D600 are sufficient, but one should not forget that the cost of 1 m3 polystyrene concrete cannot be lower than 80–90 cu. e. The underestimated price indicates that the grade of used cement is lower than PC-500, and polystyrene is handicraft.
In addition, quality control affects the cost – the tests performed make a significant contribution to the price of the final product. It follows from this that a cheap product will not meet the declared characteristics.
Also, when choosing a manufacturer, one should be interested in the availability of the necessary certificates: sanitary and epidemiological, for compliance with standards for radionuclides and according to the results of fire tests. At the same time, reference to GOST R 51263-99 is not an excuse for the absence of such documents.