Reinforced concrete slabs gained immense popularity almost immediately after entering the market. Unlike archaic wooden floors, they are many times more reliable and have such advantages as:
- fire resistance,
- moisture resistance,
- long service life.
Reinforced concrete slabs do not rot and can retain all their properties when high temperatures and humidity. This is an ideal material for the construction of industrial and housing and communal facilities.
Reinforced concrete slabs at one time changed the canons of construction. Their low cost and high performance made a splash in the market. Because of this, many construction companies were forced to quit their business or reorient themselves.
The real shock for builders and designers was the length of one reinforced concrete slab, which reached seven and a half meters. It changed the very essence of architecture. As a result, not only new buildings appeared, but also technologies for their rapid construction.
Types of reinforced concrete slabs
Road reinforced concrete slabs
Thanks to this technology, it became possible to create complex road interchanges. Not a single autobahn or highway is complete without these structural elements.
Road reinforced concrete slabs retain their operational properties even at a temperature of -40 degrees Celsius. The use of these products in the construction of roads can significantly increase the reliability of the entire canvas.
These products are available in two versions: with prestressed and non-prestressed fittings. The average density of concrete is 2200-2500 kg/m 3 . Road reinforced concrete slabs can withstand loads of class H-30 and H-10.
The surface of the products has a special corrugation. When creating the structure, concrete is used, which, in terms of water resistance and frost resistance, meets the parameters F200 and W4.
Important ! Road reinforced concrete slabs can be of different sizes. Most often, products with parameters of 1750x3000mm are used.
Airfield reinforced concrete slabs deserve special mention. They are able to withstand high loads. When creating this design, a reinforced frame and concrete of at least grade M350 are used.
Hollow concrete slabs
PZHP are used in the construction of interfloor ceilings. The thickness of one product is 220 mm, the length is from one and a half to sixteen meters. The standard width can be 1, 1.2 1.5 meters. It is also possible to select individual parameters.
Voids in reinforced concrete slabs provide heat and sound insulation. Holes can be either round or oval. The presence of voids in the structure significantly lightens the weight, which affects the speed of installation and the overall structure of the building.
Modern technologies allow to produce large batches in a short time. The load on reinforced concrete slabs can reach 1250 kgf/m 2 . In the production process, concrete of different grades is used.
Important ! Installation is carried out by means of hinges, which allow you to deliver the structure to the right place with minimal labor costs (special equipment is used).
Flat reinforced concrete slabs
PZHP are the bearing part of floors in panel buildings. In this case, the calculated load should not exceed 6 kPa. Reinforced concrete flat slabs can withstand a seismic shock of up to 7 balls. They are installed on load-bearing structures with two, three and four support points.
The main material from which the products are made is heavy, medium and light density concrete. In this case, prestressed and non-stressed reinforcement is used. It is also allowed to use wire class Vr-1. All structural elements must comply with GOSTs.
The edges of flat reinforced concrete slabs may have bevels. They serve to connect products to each other. Also, this design feature prevents shifts. The seams between the PZHP are poured with concrete mortar.
PZHP are transported in stacks. To ensure that the products are not damaged during transportation, special gaskets are used to provide a gap between reinforced concrete slabs.
In the car body, flat reinforced concrete slabs are laid longitudinally to the axis in the direction of movement. Unloading and loading is carried out using a truck crane. Special mounting loops greatly speed up this process.
Reinforced concrete floor slabs
These products are used when you need to complete the construction. Most often, such a need arises in industrial buildings, where builders do not want to spend extra money on installing a full-fledged attic.
In the future, such a roof is covered with a special finishing material. Most often it is bitumen or liquid rubber. These substances provide excellent waterproofing, and their cost is low.
Reinforced concrete floor slabs are perfectly combined with heat-insulating materials. In addition, the installation of gutters and other engineering systems does not take much time and effort. Products are divided into two types depending on the installation methods: standard and ribbed.
Structures with ribbed surface make the roof more durable. Also, this form greatly simplifies the finishing process. In production, stressed reinforcement is most often involved. It provides durability.
Reinforced metal mesh plays an important role in the design. It is covered with a layer of concrete up to 2 cm. This protects the reinforcement from the hostile action of the external environment.
Reinforced concrete floor slabs have a high level of fire safety. Some modifications can withstand loads up to 1500 kg / m 2. Such products are used in places with high rainfall. Moreover, such strength makes it possible, if necessary, to build several more floors.
Usually, reinforced concrete slabs 3X6 and 2X12 are used in the construction process. But of course, exceptions are possible. Sometimes factories create special modifications for specific tasks.
The thickness of products varies from 250 to 455 mm. But there are also thicker options. An increase in thickness gives a decrease in weight, respectively, the load on the supporting structures is minimized.
In the structure of reinforced concrete slabs, it is impossible to do without embedded elements. They are made of steel and can be welded to the fittings of neighboring products. This provides a strong connection.
Products are transported on special trucks and used at the very end of construction work. They are suitable for almost any type of construction and have high strength and reliability.
Production of reinforced concrete slabs
The main element of reinforced concrete slabs is concrete. This material is made by mixing cement with sand and gravel. It has a high resistance to compression, but is easily stretchable. Reinforcement is used to increase the strength of this material. It is made from composite and steel.
Important ! Concrete protects reinforcement from corrosion.
Crushed stone acts as an inert material. There is no reaction between it and the cement. It is also called a placeholder. It significantly affects the structure of the reinforced concrete slab.
In the production of reinforced concrete slabs, crushed stone of different fractions is used, from small to large. The choice largely depends on the purpose of the structure, as well as the requirements that the designer faces.
There are two types of fittings: working and mounting. The first view is the lower part of the reinforced concrete slab. He works on bend. The second is the skeleton of the structure.
Important ! Wire can be used as an alternative to steel bars.
In the process of manufacturing reinforced concrete slabs, stressed reinforced concrete is used. Special technologies allow pouring rebar into the monolith when it is partially tense. This is due to the fact that reinforced concrete floor slabs must effectively resist bending and compensate for the load created by the floor structure and the weight of additional objects on it.
Technological process
It all starts with the creation of a preliminary drawing. Based on it, future products are created. Usually the whole process consists of the following steps:
- A frame made of reinforcement is installed in a specially prepared form. Usually ribbed rods are used for this. They are pre-tensioned using electric heating or a jack.
- The rods are fixed on the side equipment of the form.
- The further production process is carried out on the basis of a conveyor line, special stands, roller molding or rolled products.
- After the formation of the main structure, the reinforced concrete slab is sent for heat treatment. For this, special cameras are used. Heat treatment can significantly increase the rate of hardening of the concrete mass. For 10 hours in the chamber, the product gains about 60 percent strength. This usually takes at least 25 days under normal conditions.
- After the product has acquired the necessary strength, the fasteners on the walls of the mold, which fixed the reinforcing bars, are removed.
- The rods are compressed in length. As a result, the necessary state of the entire structure is formed.
This is the canonical production process of a reinforced concrete slab. But many companies are trying to bring something of their own to it in order to achieve greater productivity and reduce costs.
Rules for the installation of reinforced concrete slabs
During the laying of floors, builders are primarily guided by SNiPs. Compliance with all norms and standards guarantees the safety and long life of the structure.
Reinforced concrete slabs are laid on the walls of the building. At the same time, they must rest on a load-bearing wall by at least 12 centimeters. Products can be installed with or without mortar. The size of a technological seam lies in the range from 5 to 20 cm. The ideal parameter is 7-8 centimeters. If the seam is too wide, then in the future you will have to spend a lot of time and mortar on sealing it.
Naturally, the rules for laying, for example, road reinforced concrete slabs are strikingly different from the rules for installing hollow ones. But the initial stage is the same in both cases. Before installation, the plates are carefully inspected. In this case, the presence of markings on each design is mandatory. If there are cracks with a width of more than 1 mm along the entire length, the reinforced concrete slab is replaced.
Results
Depending on the type of structure and its purpose, builders use one or another type of reinforced concrete slabs. At the same time, there are a huge number of modifications and types designed for a specific construction.
Ceilings are called in the construction industry the supporting structures of buildings that are located horizontally and perform the task of separating adjacent floors. They also separate the residential floor from the basement or attic, so the floors are divided according to their purpose:
- on interfloor;
- basement;
- attic.
Overlappings serve as stiffening elements of the entire structure, ensuring its stability, take on the load from the parts of the structure located above them and distribute them to other elements with which they are associated in the structure of the house. The main characteristics of floors include:
- strength indicators (bearing capacity);
- fire resistance:
- rigidity that can prevent kinks due to significant loads;
- high parameters of sound insulation and thermal protection;
- moisture and frost resistance.
What are floor slabs
The existing classification divides floor slabs into monolithic, prefabricated and precast-monolithic. The most common option in the construction of houses and cottages with brick and block walls are reinforced concrete slab floors, consisting of three parts:
- A structural carrier that transfers the load and its mass to the supports.
- The lower part serving as the ceiling. To create it, plastering, tiled materials and other types of cladding are used.
- Top component forming leveling screeds and floors.
The lower and upper parts of the structure provide heat and sound insulation of the premises.
According to the shape of the cross section, the ceilings are solid, ribbed and with voids of various shapes.
For the construction of floors, beams of reinforced concrete material are often used, tightly fitting one to the other. When laying them between adjacent elements, it is recommended to insert special ceramic liners and concrete the gaps formed between the joints.
Floor slabs PB: how are they different from PC
Both types of concrete slabs (formless and channeled) are widely used for flooring in the construction of multi-storey buildings, in low-rise individual construction of brick houses, various blocks and monolithic-frame technology. These are affordable economical panels that have both similarities and a number of differences. If we talk about the analogy of structures, then this is the multi-hollowness and identical thickness of products, which is usually 220 mm. To understand the differences, you should understand what each type of plate is.
PK slabs are round-hollow concrete products, which are produced by the formwork molding method. The process consists of pouring the finished mixture into metal molds, where unstressed reinforcing bars and steel mesh are pre-laid. The next step is vibration and heat treatment of the material. The length parameters of formwork slabs depend on the dimensions of the formwork, which are regulated by the standards. Maximum size the length of hollow core floor slabs according to GOST is 9 meters. Standard PC sizes are formed according to the step length equal to 300 mm. The presence of elements such as reinforced ribs and voids provide high bending strength of the product with a relatively small weight of products.
PB slabs are also hollow. They are produced by loading the initial concrete mass onto a formless conveyor vibration line. After the formation of concrete, it is cut with machines designed for this purpose in accordance with the required dimensions (in increments of 100 mm). Concrete floor slabs are formed from concrete with a class of at least B15, prestressed reinforcement or high-strength steel ropes are used.
One of the differences between PC and PB panels is the quality of their surface. In PC floor slabs, the sizes of technological cracks are present and regulated by GOST, and slight deviations in the parameters of geometric values are allowed: length, width, thickness. As for PB boards, thanks to improved technology (special smoothing equipment is involved in the production process), exemplary shape accuracy and a straight, even surface are achieved.
The difference between these types of floor slabs is also the presence of sling loops in standard PC versions, the holes for which are made in finished panels. PB plates imply loopless mounting at the construction site.
Since there is no transverse reinforcement in PB products, and they are beam-type structures, they can be sawn across or at an angle of 45 degrees to create jumpers, overlapping bay windows and other architectural elements.
The use of PC boards ensures the convenience of conducting intra-house communications. The cross section and shape of the voids makes it easy to install pipelines. In PB slabs, when laying engineering, it is necessary to break stiffeners between voids that have an elongated configuration.
Both types of floors are united by the presence of voids that dampen unnecessary vibrations and provide a high level of sound insulation and thermal protection of the building. In addition, the air chambers make the structure relatively light. For example, the weight of a hollow core slab measuring 6x1.5 m weighs about 3 thousand kg.
Hollow slab structures are made from heavy and structural concrete. In low-rise private construction, both versions of floor panels are used. Each developer chooses one or another option, based on their subjective views on this product.
Marking of floor slabs and its interpretation
Markings are applied to the side faces of the plate or to its upper surface. They consist of an alphanumeric group of symbols separated by a hyphen. This standard covers all types of manufactured reinforced concrete floors, regardless of the manufacturer. Thanks to the marking, you can easily determine which group the product belongs to, its dimensions.
The first two letters indicate the type of building structure (PC, PB), the following numeric characters through a hyphen tell about the dimensions of the product, its length and width. All numerical values are indicated in decimeters. Another indicator present in the marking is the permitted design load, which allows you to navigate and accurately determine the scope of this type of product.
For clarity, we give a specific example. The plate is labeled as follows:
1PB 63-15-6At-VL. This encoding will mean:
The first three characters: the number 1 in combination with the letter designation PB indicate that the slab belongs to the formless type, has a thickness of 220 mm with round voids with a diameter of 159 mm (according to the GOST standard). The value 63 indicates the length of the product rounded to the nearest integer in decimeters, and 15 indicates the width of the structure. The number 6 in the marking indicates the permissible load in kilopascals, the letter L indicates that the slab is made of lightweight concrete using prestressing reinforcement of the At-VL class.
Thus, the marking makes it possible to accurately determine the type of structure, load level and dimensions of the floor panel.
In addition to the main marking in accordance with the requirements of GOST, the products contain information marks containing the following information:
- date of manufacture;
- weight of the structure
as well as mounting signs depicting:
- plate top;
- place of support;
- installation risks;
- slinging place (in PC ceilings).
Beams are also used in private individual construction. wooden floors, they are most often used in the construction of log cabins and timber houses.
Prefabricated floor slabs are categorized as precast concrete products. Widely used in construction multi-storey buildings, road construction. In different types of work, structures of certain dimensions and shapes are used. To facilitate the design and construction processes, the dimensions were brought to a single standard.
Characteristics
Reinforced concrete floor slabs are made from the so-called structural (using coarse filler) heavy and light concrete mixtures. The main function is carrier.
Their popularity among builders is due to the ease of installation, speed of installation and reasonable price. However, they are heavy, so the support must be much stronger than concrete products. In addition, the concrete structure is not water resistant, so it cannot be stored outdoors for a long time without waterproofing protection.
Available in 3 types:
1. Solid. Differ high level compressive strength, large mass and low sound and heat insulation properties.
2. Tent in the form of a tray with smoothed ribs. When using them, crossbars and similar beam elements are excluded from the project. They make it possible to simplify soundproofing and finishing of surfaces inside the room, to raise the level of the ceiling without building up the walls. The dimensions of the tent-type reinforced concrete floor slab are dictated by the length and width of the room, the standard height is 14-16 cm.
3. Hollow. This is the most demanded type of concrete goods. They are a parallelepiped with longitudinal tubular voids. Due to their design, they are considered more durable in bending, withstand significant loads - up to 1250 kg / m 2, the dimensions are convenient for spanning spans up to 12 m long, and the shape is for laying communications.
Hollow core slabs are marked:
- 1P - single layer reinforced concrete product- no more than 12 cm.
- 2P - similar to the previous one, but the thickness is already 16.
- 1pc - multi-hollow reinforced concrete products with internal cavities up to 16 cm in diameter. Height - up to 22 cm.
- 2PC - the same with a cross section of voids up to 14.
- PB - hollow structure with a thickness of 22.
Standard overall dimensions of multi-hollow floor panels according to GOST 26434-85 are shown in the table below.
The weight of the finished product reaches 2500 kg.
Floor slab marking contains complete information: type, dimensions, compressive strength. For example, PC 51.15-8 is:
- PC - multi-hollow panel with tubular longitudinal cavities with a diameter of 15.9 cm, height - 22 cm.
- 51 - length in dm, that is, 5.1 m.
- 15 - width in dm - 1.5 m.
- 8 - the load that it will withstand. In this case - 800 kgf / m 2.
In addition to the standard, solid floor slabs made of cellular concrete (aerated concrete and others) are produced. They are quite light, withstand minor loads - up to 600 kg, and are used in low-rise construction. To create a strong connection, manufacturers produce grooved products (thorn groove).
Assembly of prefabricated slabs
Before laying, all bases are leveled, if necessary, reinforced with an annular reinforced belt made of monolithic reinforced concrete with a width of at least 25 cm, a thickness of 12 cm or more. The differences between opposite main walls should not be more than 1 cm.
Prefabricated reinforced concrete products are stacked closely with the help of lifting equipment, the gaps are filled with mortar. For connection to a rigid monolith, the anchoring method is used.
When installing the slabs, they must rest on the main wall or foundation with a section of the panel at least 15-20 cm wide. The gaps between the concrete goods and the interior partition are laid with bricks or blocks of lightweight concrete.
Reinforced concrete products cost
Due to the fact that the composition of the floor and the dimensions are standardized, the policy of the enterprises is aimed at maintaining a stable price. The average cost of hollow core panels is shown in the table below.
| Name | Parameters, cm | Price, rubles |
| PC 21.10-8 | 210x100x22 | 2 800 |
| PC 21.12-8 | 210x120x22 | 3 100 |
| PC 25.10-8 | 250x100x22 | 3 300 |
| PC 25.12-8 | 250x100x22 | 3 700 |
| PC 30.10-8 | 300x100x22 | 3 600 |
| PC 30.12-8 | 300x120x22 | 4 000 |
Reinforced concrete floor slabs are a material that is actively used in the construction of multi-storey buildings. Their main role is to cover the floors of the house. Due to the wide variety of sizes and designs of reinforced concrete slabs, slabs have proven themselves with positive side in any construction industry. As a rule, the presented products are used when covering trays of heating mains, when laying communication tunnels.
At present, reinforced concrete slabs have slightly lost their former positions in the field of multi-storey construction. The reason is that builders began to actively use monolithic-frame construction, the essence of which is the formation of one solid slab over the entire area of the house.
What are floor slabs Assortment and how they are used can be found in this
Of course, this method has its drawbacks: time and labor costs. Therefore, reinforced concrete slabs are still being introduced when performing certain tasks.
The main advantage of such products over a monolithic design is the low price. In addition, the reinforced concrete slab does not need to be tied in time, but the monolith needs a non-stop process.
Table 1 - Collector plates of the bottom of the KD
| Name | Length, mm. | Width, mm | Height, mm. |
| KD-21 | 700 | 2080 | 140 |
| KD-25 | 700 | 2080 | 140 |
| KD-30 | 1600 | 2080 | 160 |
| KD-36 | 2200 | 2080 | 160 |
| KD-42 | 2800 | 2080 | 160 |
Standard
All reinforced concrete floor slabs are used in accordance with the instructions in the working drawings of the panels, which are determined by GOST 21924.2-84. Taking into account the project of a particular house, the presented panels can be equipped with the following elements:
If continuous reinforcement was used in the manufacturing process of the plate, as well as multi-temperature electrothermal stress, then it is necessary to use high-strength wire reinforcement. To lift and mount these products, you must use special equipment. The location and dimensions of the hole in the GOST 21924.2-84 slabs can be determined from the drawings that are included in the design documentation of the gripping device used.
How to use reinforced concrete multi-hollow floor slabs is described
The voids present in the tiles serve to support on 2 or 3 sides, they are located parallel to the direction in which the length of the floor panels is led.
If you use floor slabs to support on 4 sides, then the location of the voids will be parallel to each of any sides of the product contour. Floor slabs, which serve to support on 2 or 3 sides, are prestressed.
In an aerated concrete house, it is possible to use wooden floor slabs, and how this is done is described
There are products that, during production, are obtained with non-stressed reinforcement. They are characterized by the following dimensions:
- thickness - 220 and 260 mm;
- length - 4780 and 5680 mm;
- void diameter - 159 mm, 140 mm, 127 mm.
According to GOST 21924.2-84, the dimensions of reinforced concrete floor slabs are divided into 5 types, each of which has its own dimensions.
About what should be bearing wall from aerated concrete, so that it would be possible to lay a floor slab on it is described in this
Table 2 - Types and standard sizes reinforced concrete panels
| Brand | Structure | void diameter | Thickness, m | Length, m | Width, m |
| 1P | Solid single layer | _ | 1,2 | 3-3,6 | 4 |
| 2P | Solid single layer | _ | 1,6 | 2,4-6 | 1,2-6 |
| 1pc | Round voids | 1,6 | 2,2 | 7,2 | 3,6 |
| 2pcs | Round voids | 1,4 | 2,2 | 1,7-6 | 1,2-6 |
| PB | multi-hollow | _ | 2,2 | 2,5 | 1 |
Price
The price of the presented products also depends on such a parameter as size.
Table 3 - The cost of reinforced concrete floors
| Brand | Length, m | Width, m | Height, m | Price, rubles |
| PC 17-10.8 | 1,68 | 9,9 | 0,22 | 2 580 |
| PC 39-12.8 | 3,88 | 1,2 | 0,22 | 7 150 |
| PK 458-15.8 | 5,78 | 1,6 | 0,22 | 13 280 |
| PC 66-15.8 | 6,58 | 1,6 | 0,22 | 18 760 |
| PC 79-15.8 | 7,88 | 3,6 | 0,22 | 26 950 |
| PK 89-12.8 | 8,88 | 6 | 0,22 | 39 330 |
Reinforced concrete floor slabs are products that are characterized by high strength and durability. This is achieved due to the presence of reinforcement, which can be performed in various ways. When choosing a reinforced concrete structure, it is necessary to pay attention not only to its advantages and disadvantages, but also to such a parameter as size.
Looking at the piles of reinforced concrete slabs, an ordinary citizen does not suspect how much important information they can inform a specialist builder. This is not surprising, because in Everyday life we rarely see such structures.
If we are talking about the new building, then the customer installation work it will be useful to know what types and sizes of floor slabs exist, as well as what is their maximum bearing capacity according to GOST.
At first glance, the differences between hollow core slabs are only in their length, thickness and width. However, specifications These structures are much more extensive, so we will consider them in more detail.
State standard - a set of laws of strength
All basic requirements for hollow core slabs, including their purpose and strength characteristics, describes GOST 9561-91.
First of all, it indicates the gradation of the plates depending on their thickness, the diameter of the holes and the number of sides with which they rest on the walls.
In addition to different thicknesses and geometric dimensions, hollow core slabs are classified according to the method of reinforcement. GOST specifies that panels that rest on walls on 2 or 3 sides must be made using prestressed reinforcement.
The practical conclusion that follows from this for the developer is that it is impossible to punch holes for engineering communications, violating the integrity of the working fittings. Otherwise, the slab may lose its bearing capacity (crack under load or collapse).
Paragraph 1.2.7 of GOST 9561-91 makes important exceptions, allowing the manufacture of certain types of plates not to put prestressing reinforcement in them.
They belong to the following panels:
- 220 mm thick with a length of 4780 mm (voids with a diameter of 140 and 159 mm);
- Thickness 260mm, length less than 5680mm;
- Thickness 220 mm, any length (voids with a diameter of 127 mm).
If such reinforced concrete floor slabs were brought to your facility, and non-tensioned reinforcement is indicated in their passport, do not rush to send the car back to the factory. These designs comply with building codes.
Features of manufacturing technology
Floor slabs are made different ways, which affects the quality of their front surface. Plates of PK and PG grades are cast in formwork, and PB panels are made in a continuous way on a conveyor line. The latest technology is more perfect than formwork manufacturing, so the surface of PB boards is more even and smooth than that of PK and PG boards.
In addition, conveyor production allows you to make PB slabs of any length (from 1.8 to 9 meters). This is very convenient for the customer when it comes to the so-called "additional" slabs.
The fact is that when laying out plates on a building plan, several sections are always formed where standard panels do not fit. Builders get out of the situation by filling such "white spots" with monolithic concrete right on the site. The quality of such a home-made design is noticeably inferior to that achieved in the factory (vibration compaction and steaming of concrete).
The advantage of PK and PG boards over PB panels is that it is possible to punch holes in them for communications without fear of destruction of the structure. The reason is that the diameter of their voids is at least 114 mm, which allows you to freely pass the sewer riser (80 or 100 mm in diameter).
For PB plates, the holes are narrower (60 mm). Therefore, here, in order to skip the riser, it is necessary to cut the rib, weakening the structure. Experts say that such a procedure is unacceptable only for high-rise construction. When erecting low-rise housing, punching holes in PB slabs is allowed.
Advantages of hollow reinforced concrete slabs
There are many of them and they are all quite significant:
- Reducing the weight of building structures;
- The voids in the slabs dampen vibrations, therefore, such an overlap has good sound insulation;
- The possibility of laying communications inside the voids;
- Fire resistance and moisture resistance;
- High speed of installation work;
- Durability of the building.
Dimensions of hollow core slabs
Here, everything is unified to the maximum so that it is possible to manufacture a structure of any mounting size. The gradation of the width and length of the plates comes in increments of 100 to 500 mm.
Marking - floor slab passport
The developer does not need to know the intricacies of the technology used to manufacture a multi-hollow slab. It is enough to learn how to correctly decipher the marking.
It is performed in accordance with GOST 23009. The slab brand includes three alphanumeric groups separated by hyphens.
The first group contains data on the panel type, its length and width in decimeters (rounded to the nearest whole number).
The second group says:
- The bearing capacity of the slab or the design load (kilopascals or kilogram-force per 1 m2);
- For prestressed slabs, the class of reinforcing steel is indicated;
- Type of concrete (L - light, C - silicate, heavy concrete is not indicated in the marking).
The third group in the marking contains additional characteristics that reflect the special conditions for the use of structures (resistance to aggressive gases, seismic effects, etc.). In addition, the design features of the plates are sometimes indicated here (the presence of additional embedded parts).
As an example explaining the principle of marking hollow core panels, consider the following design:
Hollow panel type 1PK, length 6280 mm, width 1490 mm, designed for a load of 6 kPa (600 kg / m2) and made of lightweight concrete using prestressing reinforcement class At-V).
Its marking will look like this: 1PK63.15-6AtVL. Here we see only two groups of characters.
If the slab is made of heavy concrete and is intended for use in a seismically hazardous area (seismicity up to 7 points), then the third group of symbols appears in its designation: 1PK 63.15-6АтV-С7.
The considered technical characteristics of floor slabs determine the scope of their application.
All types of multi-hollow panels are calculated based on the normative floor load - 150 kg / m2 (weight of people, equipment and furniture).
The bearing capacity of a standard board is in the range of 600 to 1000 kg/m2. Comparing the standard of 150 kg/m2 with the actual strength of the panels, it is easy to see that their safety margin is very high. Therefore, they can be laid in all types of residential, industrial and public buildings.
|
Plate type |
Reduced plate thickness, meters |
Average density of concrete slab, kg/m3 |
Plate length, meters |
Building characteristics |
| 1PC,1PCT, 1PCC |
up to 7.2 inclusive |
Residential buildings (sound insulation of premises is provided by the installation of floating, hollow, hollow or layered floors, as well as single-layer floors on a screed | ||
| 1pc | ||||
| 2PCS, 2PCT, 2PCC | Residential buildings in which the sound insulation of residential premises is provided by the installation of single-layer floors | |||
| 3PCS, 3PCT, 3PCC | ||||
| 4pcs | Public and industrial buildings | |||
| 5pcs | ||||
| 6pcs | ||||
| PG | ||||
| 7pcs | Residential buildings (low-rise and estate type) |
This table contains the given thickness of the slab - a term not understood by beginners. This is not the geometric thickness of the panel, but a special parameter created to evaluate the cost-effectiveness of the panels. It is obtained by dividing the volume of concrete laid in the slab by its surface area.
Estimated prices
During construction, dozens of standard sizes of hollow core slabs are used, so a separate article would have to be devoted to a detailed description of their prices. We will indicate the price parameters of the most "running" panels (self-delivery):
- PK 30.12-8 - from 4,800 rubles / unit;
- PK 30.15-8 - from 5,500 rubles / unit;
- PK 40.15-8 - from 7,600 rubles / unit;
- PK 48.12-8 - from 7,000 rubles / unit;
- PK 51.15-8 - from 9,500 rubles / unit;
- PK 54.15-8 - from 9,900 rubles / unit;
- PK 60.12-8 - from 8,200 rubles / unit;
- PK 60.15-8 - from 10,600 rubles / unit;
Installation of hollow core slabs
The main condition for the high-quality installation of panels is strict observance of the calculated parameters of support on the walls. Insufficient support area leads to the destruction of the wall material, and excessive - to increased heat loss through cold concrete.
Installation of floor slabs must be carried out taking into account the minimum allowable support depth:
- on a brick - 90 mm;
- for foam concrete and aerated concrete blocks- 150 mm;
- on steel structures - 70 mm;
- for reinforced concrete - 75 mm;
The maximum depth of embedding slabs into walls should not exceed 160 mm (brick and light blocks) and 120 mm (concrete and reinforced concrete).
Before installation, each slab must be filled with voids (with lightweight concrete to a depth of at least 12 cm). Laying the panel "dry" is prohibited. For uniform load transfer on the walls, a mortar “bed” with a thickness of no more than 2 cm is spread before laying.
In addition to observing the standard support depths, when installing floor slabs on fragile blocks of their gas or foam concrete, a monolithic reinforced concrete belt should be laid under them. It eliminates the punching of blocks, but requires good external insulation to eliminate cold bridges.
During the installation process, the deviation of the difference in the marks of the front surfaces of adjacent panels should be constantly monitored. You need to do this in the seams. Don't listen to the builders who put the panels in "steps" and tell you that it's impossible to lay them evenly.
Building codes establish the following tolerances depending on the length of the slabs:
- up to 4 meters - no more than 8 mm;
- from 4 to 8 meters - no more than 10 mm;
- from 8 to 16 m - no more than 12 mm.
