Precast concrete floor panels. Precast concrete slabs

Looking at the stacks reinforced concrete slabs, an ordinary citizen does not suspect how much important information they can give to a specialist - a builder. This is not surprising, because in Everyday life we rarely see such constructions.

If it comes about a new building, then to the customer installation works it will be useful to know what types and sizes of floor slabs exist, as well as what is their maximum bearing capacity in accordance with GOST.

At first glance, the differences between hollow core slabs are only in their length, thickness and width. But, specifications these constructs 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 slabs depending on their thickness, the diameter of the holes and the number of sides with which they rest on the walls.

except different thickness and the geometric dimensions of the hollow floor slabs are classified according to the method of reinforcement. GOST indicates that panels that rest on walls with 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 Communication, violating the integrity of the working fittings. Otherwise, the slab may lose its bearing capacity (crack under load or collapse).

Clause 1.2.7 of GOST 9561-91 makes important exceptions, allowing for the manufacture of certain types of plates not to install prestressing reinforcement in them.

They refer to the following panels:

220 mm thick with a length of 4780 mm (voids with a diameter of 140 and 159 mm);
260mm thick, less than 5680mm long;
Thickness 220 mm, any length (voids with a diameter of 127 mm).

If such iron was brought to your facility concrete plates overlapping, and in their passport non-tensioned fittings are indicated, do not rush to send the car back to the factory. These structures comply with building codes.

Features of manufacturing technology

Floor slabs are made in different ways, which affects the quality of their front surface. Plates of the PK and PG brands 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 production, so the surface of PB slabs is smoother and smoother than that of panels of the PK and PG brands.

In addition, the conveyor production allows making 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" plates.

The fact is that when the slabs are laid out on the building plan, several sections are always formed, where standard panels do not fit. Builders find a way out by filling in such "white spots" monolithic concrete right at the facility. The quality is homemade construction noticeably inferior to that which is achieved in the factory (vibration compaction and concrete steaming).

The advantage of PC and SG plates over PB panels is that holes can be punched in them for communications without fear of structural destruction. The reason is that the diameter of their voids is at least 114 mm, which allows the sewer riser (80 or 100 mm in diameter) to pass freely.

For PB slabs, the holes are narrower (60 mm). Therefore, here, to pass the riser, you have 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 the PB slabs is allowed.

Benefits of Hollow Reinforced Concrete Slabs

There are a lot of them and they are all quite weighty:

Reducing the weight of building structures;
The voids in the slabs dampen vibrations, so such an overlap has good sound insulation;
Possibility of laying communications inside voids;
Fire resistance and moisture resistance;
High speed of installation work;
The durability of the structure.

Dimensions of hollow core slabs

Everything here is unified to the maximum so that it is possible to manufacture a structure of any assembly size. The gradation of the width and length of the slabs is in increments from 100 to 500 mm.

Marking - passport of the floor slab

The developer does not need to know the intricacies of the technology used to manufacture a hollow-core floor slab. It is enough to learn how to correctly decipher the marking.

It is performed in accordance with GOST 23009... The plate brand includes three alphanumeric groups separated by hyphens.

The first group contains data on the type of panel, its length and width in decimetres (rounded to the nearest whole number).

The second group indicates:

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;
Concrete type (L - light, C - silicate, heavy concrete is not indicated in the marking).

The third group in the marking contains additional characteristics reflecting the special conditions of use of structures (resistance to aggressive gases, seismic effects, etc.). In addition, here sometimes they indicate the design features of the plates (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 of class At-V).

Its marking will look like this: 1PK63.15-6AtVL. Here we see only two groups of symbols.

If the slab is made of heavy concrete and is intended for use in a seismic zone (seismicity up to 7 points), then a third group of symbols appears in its designation: 1PK 63.15-6AtV-C7.

The considered technical characteristics of floor slabs determine the area of their application.

All types of hollow-core panels are calculated based on a standard floor load of 150 kg / m2 (weight of people, equipment and furniture).

The load-bearing capacity of a standard board ranges from 600 to 1000 kg / m2. Comparing the norm of 150 kg / m2 with actual strength panels, it is easy to see that their safety margin is very high. Therefore, they can be installed in all types of residential, industrial and public buildings.

Plate type	Reduced plate thickness, meters	Average density of concrete slab, kg / m3	Slab length, meters	Characteristics of the building
1PC, 1PCT, 1PCK			up to 7.2 inclusive	Residential buildings (soundproofing of premises is provided by the device of floating, hollow, hollow or laminated floors, as well as single-layer floors on a screed
1pc
2PC, 2PCT, 2PCK				Residential buildings in which soundproofing of residential premises is provided by the installation of single-layer floors
3PK, 3PKT, 3PKK
4pcs				Public and industrial buildings
5pcs
6pcs
PG
7pcs				Residential buildings (low-rise and manor-type)

This table contains the given thickness of the slab - an incomprehensible term for beginners. This is not the geometric thickness of the panel, but a special parameter created to assess the efficiency of the panels. It is obtained by dividing the volume of concrete placed in a 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 "popular" panels (pickup):

PC 30.12-8 - from 4,800 rubles / unit;
PC 30.15-8 - from 5,500 rubles / unit;
PC 40.15-8 - from 7 600 rubles / unit;
PC 48.12-8 - from 7,000 rubles / unit;
PC 51.15-8 - from 9,500 rubles / unit;
PC 54.15-8 - from 9,900 rubles / unit;
PC 60.12-8 - from 8,200 rubles / unit;
PC 60.15-8 - from 10 600 rubles / unit;

Installation of hollow core slabs

The main condition quality installation panels, is strict adherence to the design parameters of support on the walls. An insufficient support area leads to the destruction of the wall material, and an excessive one leads to increased heat loss through cold concrete.

The installation of floor slabs must be carried out taking into account the minimum permissible bearing depth:

on a brick - 90 mm;
for foam concrete and aerated concrete blocks- 150 mm;
on steel structures - 70 mm;
on reinforced concrete - 75 mm;

The maximum depth of embedding slabs into walls should not be more than 160 mm (bricks and lightweight blocks) and 120 mm (concrete and reinforced concrete).

Before installation, each slab must be filled with voids (light concrete to a depth of at least 12 cm). Laying the panel "dry" is prohibited. To evenly transfer the load 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 bearing depths, when installing floor slabs on fragile blocks of their gas or foam concrete, a monolithic concrete should be laid under them. reinforced belt... It excludes the pushing 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. This must be done at the seams. Do not listen to builders who put panels in "steps" and tell you that it is impossible to lay them more 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.

When building a house, any developer faces the question of choosing an interfloor overlap. The most common are three types of floors - wood, monolithic reinforced concrete and precast reinforced concrete, mounted from flat hollow core slabs. It is about this type of overlap, as the most popular and practical for low-rise construction, that will be discussed in this material. From this about interfloor floors in a private house, you will learn:

What is the difference between hollow-core floor slabs (PC) and floor slabs made by formless molding (PB).
How to properly lay floors.
How to avoid mistakes during installation.
How to store floor slabs.

How to choose a hollow core slab

At first glance at hollow ceilings, it may seem that they differ from each other only in length, thickness and width. But the technical characteristics of hollow floor slabs are much broader and are detailed in GOST 9561-91.

Hollow floor slab, private house.

Hollow interfloor slabs differ in the way of reinforcement. Moreover, reinforcement (depending on the type of slabs) can be performed using prestressed reinforcement or without prestressed reinforcement. Overlappings with prestressed working reinforcement are more often used.

When choosing floor slabs, you should pay attention to the following important point, as the permissible number of sides on which they can be supported. ... Usually only two short sides can be supported, but some types of slabs can be supported on three and four sides.

PB. Provides support on both sides;
1pc. Thickness - 220 mm. The diameter of the round voids is 159 mm. Supports only two sides;
1PCT. Having the same dimensions, it can be supported on three sides;
1PCK. Can be supported on four sides.

Also, floor slabs differ in the manufacturing method. Often there is a dispute about which to prefer - PC or PB.

Andrey164 FORUMHOUSE user

It's time to cover the basement floor of the building with floor slabs, but I just can't determine what to choose - PC or PB, PB has a better surface finish than PC, but I heard that PB are used only in monolithic frame houses and country houses, and the end of such a slab cannot be loaded with a wall.

Sasha1983 FORUMHOUSE user

The main difference between the plates lies in the technology of their manufacture.

PC (with a thickness of 160 to 260 mm and a typical bearing capacity of 800 kg / sq. M.) Is cast in formwork. Panels of the PB brand (with a thickness of 160 mm to 330 mm and a typical bearing capacity of 800 kg / sq.m) are manufactured by the method of non-formwork continuous casting (this allows obtaining a smoother and more even surface than that of PC panels). PB is also called extruder.

PB, due to the prestressing of the compressed and stretched zones (prestressing of the reinforcement is done at any length of the slab), are less susceptible to cracking than PCs. PCs with a length of up to 4.2 meters can be produced without prestressed reinforcement and have a greater free deflection than PB.

At the request of the customer, PB can be cut to individual specified dimensions (from 1.8 to 9 meters, etc.). They can also be cut lengthwise and into separate longitudinal elements, as well as bevel cut at an angle of 30-90 degrees, without losing its bearing capacity. This greatly simplifies the layout of such floor slabs at the construction site and provides a great deal of freedom for the designer, because the dimensions of the building box and load-bearing walls are not tied to standard PC dimensions.

When choosing interfloor PC slabs (more than 4.2 meters long), it is important to remember this feature - they are prestressed with special stops at the ends of the slab. If you cut off the end of the PC, then the stop (cut off together with the end of the PC and vertical reinforcement) will not work. Accordingly, the working reinforcement will cling to concrete only with its lateral surface. This will significantly reduce the load-bearing capacity of the slab.

Despite the higher quality smooth surface, good geometry, lower weight and high load-bearing capacity, such a moment should be taken into account when choosing a PB. Hollow holes in the PC (depending on the width of the slab, with a diameter of 114 to 203 mm) allow you to easily punch a hole in it for a sewer riser with a diameter of 100 mm. While the size of the hollow hole in the PB is 60 mm. Therefore, in order to punch a through hole in a PB brand panel (so as not to damage the reinforcement), you should check with the manufacturer in advance how this is best done.

Floor slabs for a private house: installation features

PB (unlike PC) do not have mounting loops (or you have to pay extra for their installation), which can complicate their loading, unloading and installation.

It is not recommended to use the "popular" method of installing the PB, when the fastening hooks cling to the end of the hollow hole. In this case, there is a high probability that the hook will tear out of the hole due to the destruction of the end of the plate, or the hook will simply slip off. This will cause the slab to fall. Also, at your own peril and risk, you can apply a method in which scrap is inserted into the hollow holes of the PB (two scrap on one side of the slab) and hooks cling to them.

Installation of PB plates is allowed only with the use of soft rods or a special traverse.

ProgC FORUMHOUSE user

To pull the pull out from under the slab, while laying it, leave a 2 cm gap to the adjacent slab. Then we move the already laid slab with a crowbar to the neighboring one.

Max_im FORUMHOUSE user

Personal experience: I laid the slabs at my construction site using this method. The gap left at 3 cm. The slabs lay on a cement-sand mixture 2 cm thick. The mixture served as a lubricant, and the slabs were easily moved with a crowbar to the distance I needed.

Also, when installing floor slabs, it is necessary to observe the calculated values of the minimum support depth of the slab. The following numbers can be used as a guideline:

brick wall, the minimum bearing depth is 8 cm, the maximum bearing depth is 16 cm;
reinforced concrete - 7 cm, maximum bearing depth - 12 cm;
gas and foam concrete blocks- at least 10-12 cm, optimal bearing depth - 15 cm;
steel structures - 7 cm.

It is not recommended to support the floor slab more than 20 cm, because with an increase in the depth of support, it begins to "work" like a restrained beam. When laying floor panels on walls built from gas and foam concrete blocks, it is necessary to install a reinforced reinforced concrete armored belt, which is described in detail in the article:. Read also our article, which tells in detail,. We wish you to successfully apply the acquired knowledge on your construction sites!

It is recommended to seal the ends of the hollow holes before starting the installation of the slabs. The voids are sealed to prevent water from getting inside the panel. It also increases the strength at the ends of the plates (this is to a greater extent refers to a PC than to a PB) in the case of bearing partitions on them. The voids can be repaired by inserting half a brick into them and covering the gap with a layer of concrete. Typically, voids are sealed to a depth of at least 12-15 cm.

If water does get inside the slabs, it must be removed. To do this, a hole is drilled in the panel, in the "void", from below, through which water can flow out. This is especially important if the ceilings have already been laid, and the house went into the winter without a roof. Water in frost can freeze inside the hollow hole (since it has nowhere to flow out) and break the slab.

Sergey Perm FORUMHOUSE user

The slabs laid on the ceiling lay for a whole year. I specially drilled holes in the "voids" with a perforator, a lot of water leaked out. Each channel must be drilled.

Before laying floor slabs, it is necessary to select a crane with the required lifting capacity. It is important to take into account the accessibility of access roads, the maximum possible boom reach at the truck crane and the permissible load weight. And also calculate the ability to lay floor panels not from one point, but from two sides of the house.

zumpf FORUMHOUSE user

The surface on which the floor slab is laid must be flat, free of debris. Before laying the panel "spreads out" cement mix, the so-called mortar "bed", 2 cm thick. This will ensure its reliable adhesion to the walls or armored belt. Also, before installing the panels and before applying the mortar to the wall, you can lay a reinforcing bar with a diameter of 10-12 mm.

This method will allow you to strictly control the verticality of mixing of all slabs during their laying (since the panel will not go down below the bar). The rod will not allow it to completely squeeze out the cement mortar from under itself and lie down "dry". It is not allowed to place the slabs "steps". Depending on the length of the slabs, the divergence of the ends should not exceed 8-12 mm.

A serious mistake during laying is the overlap of two spans with one slab at once, i.e. it rests on three walls. Because of this, loads that are not provided for by the reinforcement scheme appear in it, and under certain, unfavorable circumstances, it can crack.

If such a layout cannot be avoided, to relieve stress, a cut is made with a grinder on the upper surface of the panels, just above the middle partition (wall).

Another point to focus on is how to block the flight of stairs between the floor slabs, if there is nothing to support them. In this case, two channels can be run parallel to the slabs, and one can be placed across, along the edge of the opening, the reinforcement cage can be connected in the form of a mesh with a cell of 20 cm and a bar diameter of 8 mm, etc. Place the formwork and pour monolithic area... It is not necessary to tie the channel to the floor slabs. In this case, they rest on two short sides and are not subjected to loads from the support unit of the staircase.

How to properly store floor slabs on the site

Ideally, if the panels were brought to the site, they must be installed immediately. If for some reason this cannot be done, the question arises: how to store them correctly.

For storage of slabs, it is necessary to prepare a firm and level platform in advance. You can't just put them on the ground. In this case, the lower slab can lean on the ground, and, due to uneven loading, under the weight of the upper slabs, it will break.

Products should be stacked no more than 8-10 pcs. Moreover, spacers are placed under the bottom row (from a bar of 200x200 mm, etc.), and all subsequent rows are placed through spacers - an inch board 25 mm thick. The gaskets should be located no further than 30-45 cm from the ends of the plates, and they should be placed strictly vertically above each other. This will ensure an even redistribution of the load.

, and read about e. The video reveals everything

The simplest type of monolithic reinforced concrete floor is a smooth single-span slab, the span of which is taken in the range from 1.5 to 3 mm; the thickness of the slab can be from 60 to 100 mm, depending on the load and the span.

For spans of more than 3 m, a smooth slab is uneconomical due to its large thickness and significant dead weight. In these cases, floors are used in the form of a system of beams and slabs interconnected in one piece (ribbed and coffered floors).

Ribbed overlap

A ribbed floor (Fig. 107, a) is a structure consisting of an interconnected slab and beams. In fig. 107, b shows a diagram of a ribbed ceiling over a room 24 l long and 16 m wide.

Three powerful girders, called main beams, are laid across the room, resting on the outer walls and a column. The so-called secondary beams, or ribs, resting on walls and girders are located along the premises. The span of the slab (the distance between the axes of the ribs) is 2 m. In general, the span of the slabs is taken from 1.5 to 3.0 m, their thickness is from 60 to 100 mm.

The normal span of a secondary beam, at which its height is acceptable in terms of the total floor height, is a span of 4 to 6 m. In this case, the height of the beams (including the thickness of the slab) can be approximately taken equal to 1/12 to 1/16 of their span, and the width is within 1 / 8-1 / 12 of the distance between their axes. Since a larger cross-section is usually taken for the main beam than for the secondary one, its span can be increased to 6-9 m. Thus, the ribbed floor has a rectangular grid of columns with rather large distances between them.

In ribbed floors, up to 50-70% of the total amount of concrete is consumed per slab. By reducing the distance between the ribs and at the same time their thickness, you can get a thinner plate. The desire to reduce the thickness of the slab in order to save concrete has led to the creation of often ribbed floors(fig. 108).

For the construction of such ceilings, instead of formwork, a sparse flooring of boards resting on girders supported by temporary wooden racks of supporting scaffolds is laid. Ceramic or cinder-concrete hollow stones are laid on the boards, the transverse seams between which are filled with mortar.

The rows of stones are laid so that a space is formed between them for the construction of reinforced concrete ribs. Reinforcement is laid on top of the ribs and stones and the ribs and slab are concreted. To protect the stones from possible falling out, it is recommended to make the side edges of them grooved or beveled.

The height of frequently ribbed floors with spans up to 6.0 m is taken from 200 to 300 mm with a slab thickness of 30 to 50 mm. The width of the ribs is 60-120 mm, the distance between them in the clear is from 250 to 600 mm. Often ribbed floors have the following advantages in comparison with ribbed ones: they are more profitable in terms of concrete consumption, less wood is consumed for formwork, and the formwork design is simple. In addition, these slabs have a slightly lower construction height and form a smooth ceiling.

Coffered ceilings

Coffered ceilings (Fig. 109) are ribbed structures in which the main and secondary beams have the same height. In this case, rectangular or square recesses are formed on the ceiling, in French - caissons. Economically, coffered ceilings are less profitable than conventional ribbed ones, and their use is justified mainly by architectural considerations.

Beamless ceilings

In bezel-less ceilings (Fig. 110), a reinforced concrete slab (150-200 mm thick) rests directly on columns, in the upper part of which there are broadenings called capitals. The grid of columns with a non-girder overlap is taken to be square or close to square with a side size of 5-6 m.

Beamless ceilings are advisable to use under heavy loads, as well as, if necessary, have a smooth ceiling (for example, in refrigerators, slaughterhouses, garages, etc.).

Precast concrete slabs

Precast concrete floors have great advantages over monolithic ones. They fully meet the requirements of complex mechanization of building construction, make it possible to reduce the labor intensity of work, exclude work on the arrangement of scaffolds and formwork, and also sharply reduce the construction time.

When designing the structures of elements of precast concrete floors, it is necessary to strive to enlarge them, since this reduces the number of assembly operations for lifting and laying elements, and the number of butt joints. The best option would be a slab for the room to keep the ceiling smooth.

In prefabricated floor structures, it is also necessary to provide for all kinds of holes, grooves and channels for heating, water supply and sewerage and electrical networks.

Prefabricated reinforced concrete floors are divided into three main groups: beam, in the form of decking (slabs) and large-panel.

Beam floors(Fig. 111) is made of T-profile beams and filling between them. As a filling, a roll is used from gypsum concrete or lightweight concrete slabs 80 mm thick and 395 mm long, reinforced with wooden lath or bar frames (for interfloor floors), or lightweight concrete slabs 90 mm thick and 385 mm long, reinforced with welded steel mesh(for attic floors) (Fig. 111, a). In order to isolate from airborne sound transmission, the gaps between the beams and the roll-up are sealed with a solution, and slag is poured over the pa-kat.

Instead of rolling, lightweight concrete double-hollow insert stones with a height of 250 and a length of 195 mm are also used (Fig. 111, b). The gaps between stones and beams are carefully filled cement mortar... This creates some solidity of the floor and increases its rigidity. It is also necessary to fill the joints to improve sound insulation.

For the possibility of using in ceilings with various payloads of the same types of beams, they are installed different distances between their axes - 600, 800 and 1000 mm with slab rolls and 600 mm when filled with insert stones. In this case, the width of the rolling slabs is, respectively, 510, 710 and 910 mm, and of the liners - 510 mm.

The elements of girder floors are relatively lightweight and therefore are used in buildings equipped with low-capacity cranes (up to 1 ton).

Floor slabs consist of flat or ribbed elements of the same type, laid close and connected to each other by filling the gaps between them with cement mortar. The elements laid close to one another form a continuous floor structure. For this kind of floor, no beams are required, and they consist of a load-bearing reinforced concrete part (usually textured underneath), a sound or thermal insulation layer and a floor structure. Deckings are supported by walls or purlins.

The most common decks used in the practice of modern construction are hollow decks (Fig. 112) with a height of 160 mm with spans up to 4 m and 220 mm with spans of more than 4 m. The decks have longitudinal voids of a round (Fig. 112, a), oval vaulted (Fig. 112, b) or oval section (Fig. 112, c). The diameter of the round holes is 160 mm in 220 mm decks and 120 mm when the decking heights are 160 mm.

The oval-vaulted holes are 350 mm long and 110 mm high in 160 mm high decks and 165 mm in 220 mm high decks.

Decks with oval voids have not been used in recent years due to the complexity of their production by a conveyor method.

The reduced concrete thickness in floorings with a length of 5.6-6.0 m with round voids is about 120 mm, with oval-vaulted - about 100 mm and with oval - about 80 mm. Thus, decks with oval-vaulted and oval voids are more advantageous than round ones.

Recently, instead of floorings with round voids, floorings with so-called vertical voids have been used (Fig. 112, d), which reduce concrete consumption by up to 15% compared to round-hollow ones. Vertical voids are formed during concreting if channels are welded to the pipe liners used to form round voids. When the ends of the floorings with oval-vaulted and oval voids are embedded in the walls, it is possible for the upper floor plate to be pushed through by the overlying wall. Therefore, these floorings provide for the sealing of holes from one end during the molding process (Fig. 112, 8), and from the other, after molding, by placing concrete inserts on the mortar into specially provided cutouts in the upper deck plate.

Decking large area, which can cover entire rooms, are called floor panels... The absence of joints in such ceilings within the room increases their sound insulation from airborne noise, provides simplicity and more high quality ceiling finishes. In addition, floor panels can be manufactured in the factory with a clean floor.

To ensure the normative soundproofing ability from airborne noise, single-layer structures of interfloor panel floors, made of heavy concrete, must have a weight of 1 m 2 of about 300 kg.

When arranging slabs of separate slimes, in which the sound-insulating capacity of the air gap between the upper and lower floor panels, which do not have a rigid connection with each other, is used, as well as when constructing layered ceilings, the standard sound-insulating capacity can be achieved with a slab weight of 200 kg / m 2.

According to the constructive scheme (Fig. 113), the following types of interfloor large-panel slabs are distinguished; with laminated floor, split type and with laminated floor and split ceiling.

Slab with laminated floor(Fig. 113, a) consists of a carrier, the lower surface of which serves as a ceiling, and a laminated floor, including a layer of soft and elastic material that improves sound insulation from airborne and impact noise, as well as a hard base for floors and a clean floor.

A split-type overlap consists of floor and ceiling elements, separated by a closed air gap that isolates the room from airborne and impact noise, while the floor element must be separated by sound-insulating gaskets from the ceiling and walls.

Separate slabs are divided into three groups:

1) separate overlap of two bearing panels (Fig. 113, b);
2) from one bearing panel and a separate floor structure resting on it (Fig. 113, c);
3) an overlap with one load-bearing panel and a separate suspended or self-supporting ceiling (Fig. 113, d, e.).

Ceilings with a laminated floor and a split ceiling (Fig. 113, e) consist of a load-bearing panel rigidly connected to the walls, a laminated floor and a suspended or self-supporting ceiling structure.

According to their structural form, floor panels are divided into solid (single-layer and layered), ribbed (with ribs up or down), hollow (with round or vertical voids) and hipped roof.

Load-bearing single-layer solid panel(Fig. 114, a) is a reinforced concrete slab of constant cross-section with a bottom surface, ready for painting, and a flat top, prepared for flooring.

Solid single-layer reinforced concrete panels have a thickness of 100-120 mm with a multi-layer floor structure and 140 mm with a sticker on a linoleum slab on an elastic basis.

To cover large spans (6-6.6 liters), continuous single-layer prestressed reinforced concrete panels 140 mm thick have recently been used, in which sound insulation from airborne noise is provided by the weight of the slab itself.

Load-bearing laminated solid panel(Fig. 114, b) is a reinforced concrete slab of constant cross-section, the lower layer of which is made of more durable concrete in which the stretched reinforcement is located; the second layer is made of lightweight, less durable concrete. In three-layer panels, the third, top, layer also consists of more durable concrete (unreinforced or weakly reinforced).

Ribbed panels can be with ribs facing up or down. Load-bearing floor panels with upward ribs (Fig. 114, c) should be completed with the floor structure at the factory, which is ensured high degree factory readiness and safety of panels during storage in a warehouse and installation.

Load-bearing slabs with downward ribs are recommended for use in slabs with split ceilings and in slabs with laminated soundproofing floors and split ceilings.

Economical often ribbed panels, consisting of two vibro-rolling shells (Fig. 114, d), one of which forms the base for a clean floor, and the other serves as a ceiling. A continuous air gap and soundproofing spacers between the shells provide the necessary soundproofing of the floor.

The bottom panel with upward ribs (ceiling panel), which has a bottom surface ready for painting, rests rigidly on the load-bearing walls and serves as a horizontal stiffening diaphragm. A top panel with downward ribs (floor panel), having a top surface ready for flooring, rests on the bottom panel through soundproofing pads.

In the floor panel in the operating position, according to the sound insulation conditions, there must be no rigid connections with the bottom panel and with the walls. Such panels are assembled at the factory; each of them has 4 mounting loops that hold the upper and lower shells together. After installing the panel, the hinges are removed and the rigid connection between the shells is removed.

The disadvantage of a separate floor structure of two often-ribbed vibro-rolled shells, as shown by field studies, is their unsatisfactory soundproofing qualities. Sound insulation deteriorates due to the appearance of shrinkage cracks in the shells, which arise as a result of the use of sandy concrete with a high consumption of cement, as well as due to the forced steaming of products. In addition, the small width of the support part of the upper shell (60 mm) causes crushing of the fiberboard gaskets and their loss of elastic properties. Finally, the gap between the top shell and the wall, instead of filling it with insulating fibreboard, is often mortarized.

In this regard, recently more rational decision Consider the structure of the floor slab in the form of a flat reinforced concrete slab 140 mm thick, the weight of which provides reliable sound insulation from airborne sound transmission.

Hollow-core panels along with hollow flooring have become widespread in construction. However, the cost of these panels is comparatively high. It should also be noted that these panels do not perform well in bending in a direction perpendicular to the direction of the voids.

Hip panel(Fig. 114, d) has the form of a slab, framed along the contour with ribs facing downward in the form of a cornice. The use of such panels, manufactured in the size of a room, makes it possible to exclude girders and other beam elements from the structural scheme of the building, and, due to their small thickness, reduce the height of the floor without reducing the height of the room.

When installing reinforced concrete floors in sanitary facilities, a waterproofing layer is introduced into the floor structure. To do this, 1-2 layers of roofing material are usually glued on top of the flooring or panels on the bitumen mastic. In places of abutment to walls or partitions, the waterproofing is raised upwards by 100 mm.

In recent years, the glued waterproofing of ceilings in sanitary facilities has been replaced with a 30 mm thick cement-sand screed (from a 1: 3 cement mortar), sealed with a 3% sodium aluminate solution. Such a screed is a completely reliable and simpler protection against water penetration through the ceiling than pasting with roll material. Also used are waterproofing screeds made of cement-sand mortars with the addition of ferric chloride to the latter, which also reduce water permeability.

IN attic floors(Fig. 115, a) on top of reinforced concrete flooring or panels, first a vapor barrier is laid (from one or two layers of glassine or tar-leather on the appropriate mastic), and then a layer of insulation. Boiler slag and expanded clay are usually used as insulation. To reduce weight and labor intensity, they also use plate heaters(mineral wool slabs, fiberboard, cellular concrete slabs).

In beamed ceilings, thermal insulation is placed between the beams, and reinforced concrete beams are insulated, for example, with mineral wool mats (Fig. 115, b).

The use of slag as a heater in attic ceilings does not meet modern construction requirements. Delivery of slag and filling the attic floor with it manually is a very laborious and expensive operation. In addition, the weight of 1 m 2 of the attic floor, insulated with slag, is very large - 520-550 kg / m 2. If you use reinforced foam concrete flooring, in which the bearing and heat-insulating functions are combined, you can 2 times lighten the weight of the attic floor and reduce the labor intensity of its device.

When installing reinforced concrete floors over cold basements and undergrounds, it is necessary, as in the attic floors, to provide for the installation of insulation. However, in this case, the vapor barrier should be placed not below, but on top of the insulation.

The most promising types of floors are prefabricated reinforced silicate and ceramic floors. Compared to reinforced concrete, they are more economical in terms of cement consumption and total cost.

The peculiarity of reinforced silicate floor structures (beams and slabs) is that instead of cement, local materials are used for their manufacture - lime and sand. Reinforced silicate products are processed in autoclaves at high blood pressure and high temperature.

Ceramic floors are laid from thin-walled hollow ceramic stones, from which individual floor elements are made in the form of beams and panels. The stones are fastened together with cement mortar and steel reinforcement.

Ceilings consist of a load-bearing part that transfers the load to the walls or individual supports, and a fencing, which includes floors and ceilings. According to the material of the bearing part, there are reinforced concrete floors, wooden and steel beams, as well as reinforced silicate and ceramic. The cost of floors and floors in the total cost of the house reaches 20% of its total cost.

The main material for the device of floors in modern construction is reinforced concrete. Reinforced concrete floors are divided into prefabricated and monolithic, concreted in the formwork. In recent years, prefabricated and monolithic floors have been used mainly.
Ceilings must meet the requirements of strength, rigidity, fire resistance, durability, sound and heat insulation, if they separate heated rooms from unheated ones or from the outside environment. Ceilings in rooms with wet processes must be waterproof, and in rooms with the release of gases - gas-tight.

IN country houses with brick walls overlappings made of reinforced concrete panels with round voids are used, the length of which ranges from 4800 mm to 6980 mm, width from 1000 to 2400 mm, height 220 mm, as well as with flat - length 2700-4200 mm with a gradation of 300 mm, width 1200, 1500 mm , 120 and 160 mm thick. The panels are laid (fig. 1) on a layer of freshly laid masonry mortar with a thickness of 10 mm with an embedment on supports not less than 120 mm. Through one panel (step 2400-3000 mm), anchors with a diameter of 8-10 mm are connected to the walls, which are attached to the hinges and inserted into the masonry 250 mm from the end of the panel, ending with a bend at an angle of 90 ° horizontally by 380 mm.

The seams between the panels are filled with cement mortar of the composition 1: 4 (by volume). Installation of panels is carried out using truck cranes.

Reinforced concrete floors

Such ceilings have a number of valuable qualities, the main of which are great strength, durability and fire resistance. When designing the structures of elements of precast concrete floors, it is necessary to strive to enlarge them in order to reduce the number of assembly operations and butt joints.

Precast concrete slabs

Precast reinforced concrete floors are divided into three main groups: in the form of decking (slabs), large-panel and beam. Floors in the form of decking consist of flat or ribbed elements of the same type, stacked close; connect them by filling the gaps with cement mortar. Such ceilings consist of a load-bearing reinforced concrete part (usually textured from below), a sound or thermal insulation layer and a floor structure. Walls and purlins serve as supports for decking. The most common are hollow floorings with a height of 160 mm with spans up to 4 m and 220 mm with spans of more than 4 m. The floorings have longitudinal voids of a circular cross-section (Fig. 2, a).

In the manufacture of floorings with vertical voids, the consumption of concrete is reduced by up to 15% in comparison with hollow core. Vertical round voids are formed using pipe liners (the liners are welded to the channels). Floors that can cover entire rooms are called large panels. The absence of joints in the floor panels within the room increases their sound insulation and provides a higher quality ceiling finish.
To ensure the normative soundproofing properties against airborne noise, single-layer structures of interfloor slabs made of heavy concrete, must have a mass exceeding 300 kgf / sq.m.

When constructing separate ceilings, in which the sound-insulating capacity of the air gap between the upper and lower panels of the connection overlap is used, as well as when constructing layered ceilings, it is possible to ensure the normative sound-insulating capacity with the weight of the overlap less than 300 kgf / sq.m.
By design, interfloor large-panel reinforced concrete ceilings can be with a layered floor, of a separate type (with a split floor, a ceiling or two separate load-bearing panels) and with a layered floor and a split ceiling (Fig. 3). All these floor structures have a relatively small mass (less than 300 kgf / sq. M.); standard sound insulation is provided by a layered floor structure or by the presence of a continuous air gap in the thickness of the floor.
Floor panels are made of solid, hollow (with round voids) and hipped roof. The load-bearing single-layer panel (Fig. 4, a) is a reinforced concrete slab of constant cross-section with a bottom surface ready for painting and a flat top surface.

Solid single-layer reinforced concrete panels 140 mm thick cover spans up to 3.6 m.

The hipped-roof panel (Fig. 4, b) has the form of a slab framed along the contour with ribs facing downwards in the form of a cornice. Interfloor ceilings are also arranged from flat reinforced concrete panels with a thickness of 14-16 cm.

Prefabricated reinforced concrete interfloor floors (Fig. 5) of beam type consist of T-profile beams and filling between them... The filler here is a roll of gypsum concrete or lightweight concrete slabs 80 mm thick and 395 mm long, reinforced with wooden lath or bar frames, and in the attic floors - light concrete slabs 90 mm thick and 395 mm long, reinforced with welded steel mesh. The seams between the beams and slabs are filled with cement mortar and rubbed over. Attic and basement floors must be insulated, interfloor soundproofed. To do this, use expanded clay or sand bedding, layered coatings with elastic gaskets. At the same time, it is desirable that heat and sound insulation is not carried out due to an increase in the weight of building structures.
Since the elements of girder floors are relatively lightweight, they are used in buildings equipped with low-capacity cranes (up to 1 ton).
When installing reinforced concrete floors in sanitary facilities, a waterproofing layer is included in the floor structure. To do this, 1-2 layers of roofing material are usually glued on top of the flooring or panels on the bitumen mastic.

Monolithic floors

Monolithic ceilings are performed according to the installed formwork... Transferring loads from the floor to the load-bearing walls, monolithic ceilings serve as an additional rigid frame of the building. Their device requires a certain professional skill and should be carried out according to the project under the guidance of a specialist - builder. On-site production of slabs has its advantages. This does not require special transport and lifting equipment. Small-scale mechanization is sufficient for lifting and moving concrete. The monolithic floors are based on the Monier slab, in which the reinforcement is placed in places of tension, that is, in the lower part of the slab. This is because steel has 15 times the tensile strength of concrete. Reinforcement cage the slabs should be located at a distance of at least 3-5 cm from the walls of the formwork so that concrete can fill this space. The length of the span covered by monolithic slabs should not exceed 3 m. For pipelines of sanitary communications, special metal or vinyl sleeves with an inner diameter larger than the pipeline being laid are installed in the ceiling. The gap between the sleeve and the pipeline is minted with tarred tow.

The disadvantages of monolithic floors include the need to install wooden formwork over almost the entire area of the house. However, this does not mean that the formwork must be exposed all at once. Overlapping can be performed in separate spans, transferring the formwork as the concrete sets.
The bearing capacity of monolithic floors is provided by reinforcement, the diameter of which must be at least 8 -12 mm. In this case, intermediate joints of the rods along the entire length of the overlap are undesirable. Minimum concrete layer with outside the overlap must be at least 2 cm. The span must be concreted in one working cycle.

Floor structures must meet the requirements for strength, fire resistance, sound insulation and thermal insulation. All these characteristics are possessed by slab-type concrete products. They are used in the construction of industrial, multi-apartment and individual buildings.

They serve as floor slabs, where their lower surface is the ceiling, and the upper one is the floor of the upper room. Also, the slabs are laid on garages, sheds and other household buildings, thus forming a roof. They are often used as a foundation.

Types of floor slabs

Two types can be distinguished: monolithic floor slabs and hollow ones. The first ones are distinguished by a large margin of safety and bearing capacity. Among the serious disadvantages are their weight, high thermal conductivity and low sound insulation properties. Such products are often used for the construction of public and industrial structures.

Floor slabs photo

Hollow concrete products are used in the construction of private houses due to their cheaper cost and light weight compared to monolithic counterparts. This factor, of course, does not allow you to do without special equipment for delivering PCs to the site and installation, but, nevertheless, it makes it possible to significantly reduce the load on the load-bearing walls and foundation. And as a result, to reduce the cost of their arrangement, using less building material.
The voids running along the entire length of the concrete product can be round, oval and polygonal. They can be used when laying communications using cable channels, plastic boxes or corrugated pipes.

Hollow-core floor slabs guarantee:

good heat and sound insulation qualities;
fire resistance;
load distribution on load-bearing walls;
high mechanical strength;
durability.

Thanks to the smooth surfaces of the slabs, all further Finishing work will take place with not only a minimum investment in leveling the ceiling (floor), but also with less labor costs.

Floor slabs dimensions

Floor slabs are produced in lengths from 1880 to 6280 mm in increments of 100 mm.
Floor slab thickness is 220 mm. Standard width products are equal to 990, 1190 or 1490 mm, although you can find plates with other standard sizes.
The weight of the floor slab determines its dimensions, approximately this indicator varies from 500 to 1500 kg. As for the bearing capacity of a product unit, on average it is 800 kg per 1 sq. M.

What you need to know before purchasing a PC

The presence of traces of rust and grease on the surfaces of the product is not allowed.

The maximum allowable cracks are 0.1 mm, but better is their complete absence.
All edges of the slabs should have the most even surfaces, without bulges and depressions.
The permissible deviation from the nominal value is 10 mm in length, 5 mm in thickness, and 5 mm in width.
The product must have appropriate quality certificates.

Before you start laying floor slabs, you need to know that:

the rough side of the plate should be facing up, and the smooth side should be down;
fitting of products is carried out on their lower sides;
Reinforced concrete products should rest on 2 short sides; it is not recommended to put the long side on the wall;
you will need components for a sand-cement mortar;
the plates are laid close to each other without gaps;
crane services are hourly, so everything necessary is prepared for his arrival so that the work goes without a hitch;
slabs should only rest on load-bearing walls, the rest of the internal partitions (walls) are erected after the installation of the ceiling;
for a well-coordinated installation, at least 2, and preferably 3 people will be needed to help the crane;

before rough finishing, the hollows of the slabs are filled with crushed stone or expanded clay.

Preparing walls before installing floor slabs

Bearing walls are leveled. They must be as flat as possible in height, the allowable discrepancy is a maximum of 10 mm. You can identify the difference in height using a long beam that is placed on two opposite walls. Placed on top of the timber building level, and the longer it is, the more accurate the result is.
In this way, all the supports for the floor slabs are checked. At the same time, it is important to take measurements as often as possible. For this, a beam or timber is installed in the corners of the building, then moves every 1-1.5 m. The corresponding data can be written on the walls with chalk or a marker.
Next, the highest and lowest point is found and the concrete mix is laid out using a cellular metal mesh. Supports erected from foam concrete, slag, gas silicate blocks are reinforced without fail. This can be done by means of a reinforcing belt with a height of at least 15 cm.
Armopoyas evenly distributes the load, prevents wall deformation and protects floor slabs from breaking.

The formwork is assembled from the most even boards in accordance with the obtained values, that is, the edges may have different meanings in height. You can use a special U-shaped profile. The structure is arranged around the entire perimeter of the house box, including curtain walls, especially if the building is made of light block materials.
For mixing the sand-cement mortar, 1 bucket of cement (M500) and 3 buckets of sand are taken, so much water is needed so that the mixture is not liquid, but also not thick. The sand must be sifted to remove pebbles, which will contribute to the destruction of the layer under the weight of the slab.
After pouring, the mortar is pierced with a trowel or a piece of reinforcement to prevent the formation of air gaps. The rammer should be given special attention.

Before laying the floor slabs, it is necessary to seal up the voids in order to avoid freezing. If the concrete products were stored at the construction site long time, it is recommended to drill one or two holes in the areas where the voids pass through which excess moisture will escape. It should be noted that the holes are sealed with concrete mortar, and during installation, the slab must face them down.
Factory voids are filled with expanded clay or large pieces of one-and-a-half bricks are simply inserted, and the remaining cracks are closed with cement mortar. Although recently factories have been producing slabs with closed voids.
The mixture in the formwork should dry well, gain strength, this will take at least 3 weeks.

Crane platform

The ground where the lifting equipment will stand must be caked. Do not install a crane near a house under construction if there is a basement. The support "leg" of the special equipment creates a very significant load on the ground, which can lead to the collapse of the basement wall.
For loose or loose soil, it is recommended to order a crane with a longer boom. If the work is carried out in spring or autumn, when the soil is saturated with moisture, the area under the truck crane is laid out with road slabs (you can use used products). Because technology can get bogged down in slush under its own weight.

Ruling of slabs

It is not recommended to cover two spans with one slab. Such loading under certain circumstances can lead to its cracking. If just such a laying scheme was chosen, then in this case it is recommended to make an incision with a grinder with diamond disc(to its depth) exactly in the center of the middle wall.
If a crack does arise, then it will go exactly in the direction of the notch, which is quite acceptable.
Unfortunately, it is not always possible to overlap with whole slabs. Sometimes they have to be lined both in width and length. Here you need a sledgehammer, a grinder with a diamond disc, a crowbar and muscle strength.

To facilitate the process, a timber or board of an appropriate length is used. The lumber is placed under the slab strictly along the line of the future cut. At some point, the concrete product will break under its own weight.
First, a grinder is cut on the upper surface of the slab along the marked line. Further, by means of a sledgehammer, blows are applied along the entire length of the concrete goods. The blows should be applied as often as possible. If the cut falls on a hollow hole, then the plate will break quite quickly.
When cutting the slab in width, you will have to make a lot of effort. Reinforcement that comes across is cut off welding machine or with a cutter. It is not recommended to use a grinder, as the disc can "bite". But if only this tool is available, then do not cut the metal rod to the end - leave 2-3 mm. Perform the final break with a crowbar or a sledgehammer.

When cutting the slab, everyone possible consequences fall on your shoulders! No manufacturer will give official permission to carry out these works.

If there are not enough whole slabs for a complete overlap, and the remaining space is small, then you can avoid the laborious cutting process using the following two methods:
The last or the first slab does not adjoin the wall in length. The formed void between the slab and the retaining wall is filled with bricks or blocks. Cement strainer, carried out at the completion of construction, will reliably join and fasten the masonry to the slab.
This method is good if the existing concrete panels are laid end-to-end, and the remaining distance is distributed between the two retaining walls and filled with the described method.

It should be remembered that if the empty opening is more than 30 cm, then when pouring the screed, reinforcement is performed in this area.
The slabs are mounted flush with the walls, leaving an empty gap between the slabs themselves. Thick moisture-resistant plywood is attached to the lower surfaces of reinforced concrete products, reinforcement must be laid with an approach to the upper surfaces of the slabs.
Thus, you get something in the form of formwork, which is poured with concrete. After complete drying, the plywood is dismantled, and a general screed is made on top of the boards.

Installation of floor slabs

For work, you will need a crane and at least 4 people (crane operator, slinger and 2 assistants). On the bearing supports with a reinforcing belt, the prepared concrete mortar no more than 20 mm thick. The plate is lifted horizontally by the right height... All actions, namely the movement and direction of the load, are carried out under the guidance of the slinger.

The installers accept the floor slab, adjust the optimal location. Before removing the slings by means of crowbars, the concrete panel is directed to the installation site with maximum accuracy:

from the slab to the wall along the long side, a minimum distance of 50 mm is left;
there must be no gap between the plates;
the width of the support on each short side of the slabs must be at least 150 mm.

Checking concrete floor slabs

After the installation of the ceiling, the evenness of the surfaces of the adjacent slabs is checked according to the level. If the height difference is more than 4 mm, then the plates are re-installed. Reinforced concrete elements are raised again with a crane, and in accordance with the position, the solution is removed or added.
It is impossible to dilute the set concrete layer with water, the hardened mixture is completely removed, and a freshly closed mixture is applied in its place. As soon as the leveling is completed, they proceed to fixing the plates to each other and to the load-bearing walls.

Anchoring reinforced concrete floor slabs

Upon completion of the installation work and after the leveling of the slabs has been carried out, they are anchored. If there is a project, then a special scheme must be present in the documents. Otherwise, anchoring is done as follows:

anchor loops are mounted to the load-bearing walls and extend onto the floor slabs by about 40-50 cm. As a rule, two fasteners are sufficient for the entire length of the panel (they are located one meter from the edge of the slabs). In the same way, one anchor is set in width;

if the joining of the slabs occurs along their short side, then these sections are fixed diagonally using the working holes, with the reinforcement located in them. In their absence, you can use special mounts with L- and U-shaped shapes;
concrete slabs are fastened to each other at the points of the mounting holes. Metal rods must be tightened as much as possible and fixed by welding, at least at three points.
After that, the lugs and seams between the slabs are filled with fine crushed stone, and then sealed with sand-cement mortar. It is not worth delaying with these works, as construction debris can get into the holes.

Features of the technology of installation of floor slabs

Hollow core slabs are widely used in the construction of low-rise and individual buildings. Although they are smaller and lighter in weight than their monolithic counterparts, they nevertheless require thickened walls and a reinforced foundation. In addition, they will not be able to block structures that are complex in architecture.
But, despite these disadvantages, the slabs provide a reliable overlap, characterized by a long service life. Their use is justified in cases where the slabs become the basis for flooring. roofing material, that is, they act as a flat roof.

Floor slabs video

When preparing and installing floor slabs, it is important to take into account many technical points, which means that it is necessary to have certain knowledge and skills. If you are not sure of the calculations, contact a specialized organization, which will draw up a project in accordance with all the requirements of SNiP.