Hyper-pressed bricks: features and recommendations for use

Hyper-pressed brick is a versatile building and finishing material and is widely used for the construction of buildings, facade cladding and decoration of small architectural forms. The material appeared on the market at the end of the last century and almost immediately became very popular and in demand.

Hyper-pressed brick is an artificial stone, for the manufacture of which granite screenings, shell rock, water and cement are used. Cement in such compositions acts as a binder, and its share in relation to the total mass is usually at least 15%. Mining waste and blast furnace slag can also be used as raw materials. The color of the products depends on which of these components will be used. So, screening out granite gives a gray tint, and the presence of shell rock paints the brick in yellowish-brown tones.

In terms of its performance characteristics, the material is quite similar to concrete and is distinguished by its high strength and resistance to aggressive environmental influences. In terms of its reliability and durability, pressed brick is in no way inferior to clinker models and can be used as the main building material for the construction of capital walls. Visually, it is somewhat reminiscent of natural stone, due to which it has become widespread in the design of building facades and fences. In addition, the cement mortar is able to mix well with various pigments and dyes, which makes it possible to produce bricks in a wide range of colors and use them as decorative cladding.

The main characteristics of hyper-pressed bricks, which determine its working qualities, are density, thermal conductivity, water absorption and frost resistance.

• The strength of hyper-pressed bricks is largely determined by the density of the material, which averages 1600 kg / m3. Each series of artificial stone corresponds to a certain strength index, which is denoted M (n), where n denotes the strength of the material, which for concrete products ranges from 100 to 400 kg / cm2. So, the models with the M-350 and M-400 index have the best strength indicators. Such a brick can be used for the construction of masonry bearing walls of the structure, while the products of the M-100 brand belong to the front models and are used only for decoration.

• An equally important characteristic of a stone is its thermal conductivity. The heat-saving ability of the material and the possibility of its use for the construction of residential buildings depend on this indicator. Full-bodied hyper-pressed models have a lower thermal conductivity index equal to 0.43 conventional units. When using such a material, it should be borne in mind that it is not able to trap heat inside the room and will freely remove it outside. This must be taken into account when choosing a material for the construction of capital walls and, if necessary, take an additional set of measures to insulate them. Hollow porous models have the highest thermal conductivity, equal to 1.09 conventional units. In such bricks, there is an inner layer of air that does not allow heat to escape outside the room.

• The frost resistance of hyper-pressed products is indicated by the index F (n), where n is the number of freeze-thaw cycles that the material can transfer without losing the main working qualities. This indicator is greatly influenced by the porosity of the brick, which in most modifications ranges from 7 to 8%. Frost resistance of some models can reach 300 cycles, which makes it possible to use the material for the construction of structures in any climatic zones, including the regions of the Far North.

• The water absorption of a brick means how much moisture a stone can absorb in a given amount of time. For pressed bricks, this indicator varies within 3-7% of the total volume of the product, which makes it possible to safely use the material for exterior decoration of facades in areas with a humid and maritime climate.

Hyper pressing is a non-firing method of production in which limestone and cement are mixed, diluted with water and mixed well after adding the dye. The semi-dry pressing method involves the use of a very small amount of water, the share of which does not exceed 10% of the total volume of raw materials. Then, from the resulting mass, bricks of a hollow or full-bodied design are formed and sent under a 300-ton hyperpress. In this case, the pressure indicators reach 25 MPa.

Next, the pallet with the blanks is placed in the steaming chamber, where the products are kept at a temperature of 70 degrees for 8-10 hours. At the stage of steaming, the cement manages to gain the moisture it needs and the brick acquires up to 70% of its branded strength. The remaining 30% of the product is collected within a month after production, after which they become completely ready for use. However, it is possible to transport and store bricks immediately, without waiting for the products to gain the necessary strength.

After production, dry-pressed brick does not have a cement film, due to which it has much higher adhesion properties than concrete. The absence of a film increases the self-ventilation ability of the material and allows the walls to breathe. In addition, the products are distinguished by a flat surface and regular geometric shapes. This greatly facilitates the work of bricklayers and allows them to make the masonry more accurate. At the moment, a unified standard for hyper-pressed bricks has not been developed. The material is produced according to the standards specified in GOST 6133-99 and 53-2007, which only regulate the size and shape of the products.

High consumer demand for dry-pressed concrete bricks due to a number of indisputable advantages of this material.

• The increased resistance of the stone to extreme temperatures and high humidity allows the use of stone in construction and cladding in any climatic zone without restriction.
• The ease of installation is due to the correct geometric shapes and smooth edges of the products, which significantly saves mortar and facilitates the work of bricklayers.
• High bending and tear strength distinguishes hyper-pressed models from other types of bricks. The material is not prone to cracks, chips and dents and has a long service life. Products are able to maintain their operational properties for two hundred years.

• Due to the absence of a concrete film on the brick surface, the material has high adhesion to cement mortar and can be used at any time of the year.
• The absolute safety for human health and the ecological purity of the stone are due to the absence of harmful impurities in its composition.
• The surface of the brick is dirt-repellent, so dust and soot are not absorbed and washed away by rain.
• A wide assortment and a wide variety of shades greatly facilitates the choice and allows you to purchase material for every taste.

The disadvantages of hyper-pressed bricks include the large weight of the material. This obliges us to measure the maximum permissible load on the foundation with the mass of the brickwork. In addition, the stone is prone to moderate deformation due to thermal expansion of the material, and over time it can begin to swell and crack. At the same time, the masonry looses and it becomes possible to pull out the brick from it. As for cracks, they can reach a width of 5 mm and change it during the day. So, when the facade cools down, the cracks noticeably increase, and when it heats up, they decrease. Such mobility of brickwork can cause many problems with walls, as well as with gates and gates built of solid bricks. Among the minuses, they also note the tendency of the material to fade, as well as the high cost of products, reaching 33 rubles per brick.

The classification of hyper-pressed bricks occurs according to several criteria, the main of which is the functional purpose of the material. According to this criterion, three categories of stone are distinguished: ordinary, facing and figured (shaped).

Among ordinary models, solid and hollow products are distinguished. The former are distinguished by the absence of internal cavities, high weight and high thermal conductivity. Such material is not suitable for the construction of housing, but it is used very often in the construction of arches, columns and other small architectural forms. Hollow models weigh on average 30% less than their solid counterparts and are characterized by low thermal conductivity and more moderate temperature deformation. Such models can be used for the construction of load-bearing walls of houses, however, due to their high cost, they are not used so often for these purposes.

An interesting version of the hyper-pressed hollow brick is the Lego model, which has 2 through holes with a diameter of 75 mm each. The brick got its name from its visual resemblance to a children's construction set, in which vertical holes are used to connect elements. When laying such a stone, in principle, it is impossible to get lost and disrupt the order. This allows even inexperienced craftsmen to perform perfectly even masonry.

Facing bricks are produced in a very wide range. In addition to smooth models, there are interesting options that imitate natural or wild stone. And if everything is more or less clear with the former, the latter are called torn or chipped stone and look very unusual. The surface of such products has numerous chips and is dotted with a network of small cracks and potholes. This makes the material very similar to ancient building stones, and the houses built from it, almost indistinguishable from old medieval castles.

Another criterion for classifying a brick is its size. The hyper-pressed models are available in three traditional sizes. The length and height of the products are 250 and 65 mm, respectively, and their width can vary. For standard bricks, it is 120 mm, for spoon bricks - 85, and for narrow ones - 60 mm.

Hyper-pressed models are an ideal material option for creating complex embossed surfaces and can be subjected to any type of machining. The stone is considered a real find for designers and allows them to implement the most daring decisions. However, when using it, you should follow a number of recommendations. So, during the construction of fences and facades, it is necessary to reinforce the masonry using a galvanized mesh with small cells.In addition, it is desirable to form gaps for thermal expansion, placing them every 2 cm. In general, it is not recommended to use solid hyper-pressed bricks for the construction of load-bearing walls of residential buildings. For these purposes, only hollow ordinary models are allowed.

When a building has already been built, whitish spots and stains, which are called efflorescence, are often formed during its operation. The reason for their appearance is the passage of water contained in the cement slurry through the pores of the stone, during which the precipitation of salts occurs on the inside of the brick. Further, they come to the surface of the salt and crystallize. This, in turn, greatly spoils the appearance of the masonry and the general appearance of the structure.

To prevent or minimize the appearance of efflorescence, it is recommended to use cement of the M400 brand, the percentage of soluble salts in which is very low. The solution should be mixed as thick as possible and try not to smear it on the face of the stone. In addition, it is undesirable to engage in construction during the rain, and after the end of each stage of work, you need to cover the masonry with a tarpaulin. Covering the facade with water-repellent solutions and equipping the constructed building with a drainage system as soon as possible will also help prevent the appearance of efflorescence.

If efflorescence does appear, then it is necessary to mix 2 tbsp. tablespoons of 9% vinegar with a liter of water and process whitish stains. Vinegar can be replaced with a solution of ammonia or 5% hydrochloric acid. Good results are obtained by treating the walls with the means "Facade-2" and "Tiprom OF". The consumption of the first drug will be half a liter per m2 of surface, and the second - 250 ml. If it is not possible to process the facade, then you should be patient and wait a couple of years: during this time, the rain will wash away all the whiteness and return the building to its original appearance.

Relying on the professional opinion of builders, hyper-pressed bricks show excellent adhesion strength with cement mortar, exceeding those of ceramic bricks by 50-70%. In addition, the index of the intra-layer density of the masonry of concrete products is 1.7 times higher than the same values ​​of ceramic products. The situation is the same with layer-by-layer strength, it is also higher for hyper-pressed bricks. There is also a high decorative component of the material. Houses faced with hyper-pressed stone look very dignified and rich. Attention is also drawn to the increased resistance of the material to the effects of low temperatures and high humidity, which is explained by the low water absorption of products and excellent frost resistance.

For information on how to lay hyper-pressed bricks, see the next video.