Floor slabs for a large-panel house. Precast concrete slabs

Construction characteristics

Ceilings consist of a load-bearing part, which transfers the load to individual supports or walls, and a fencing, which includes ceilings and floors. By the material of the bearing part, reinforced concrete (reinforced concrete) floors can be distinguished, by steel and wooden beams, ceramic and reinforced silicate. The cost of floors and ceilings will reach 20% of the total value of the house. The consumption of reinforced concrete for the ceiling will be up to 60% of the total consumption.

It should be understood that the overlap consumption should be minimal.

V modern construction the main material for the construction of floors is reinforced concrete. made of reinforced concrete (reinforced concrete) can be divided into monolithic and prefabricated, concreted in the formwork. Recently, only monolithic reinforced concrete floors and prefabricated ones have been used for the first floor. Prefabs allow you to block a span of up to 12 m. Speaking about which one is needed, you should know that the flow rate of this mortar per 1 m² will be 0.223 m³, and steel - 6.5 kg. This consumption is approximate and may vary slightly.

It is worth knowing that the ceilings must necessarily meet the requirements of rigidity, strength, fire resistance, durability, sound and heat insulation, if they separate the heated rooms from the outside environment or from unheated rooms. Ceilings in rooms in which wet processes will take place must be waterproof, and in rooms in which gases are emitted - gas-tight.

V country houses with brick walls, people most often give preference to precast reinforced concrete floors with round voids. Their length is from 4800 to 6980 mm, width - from 1000 to 2400 mm, and height - 220 mm. Structures with flat voids 2700-4200 mm long with a gradation of 300 mm, 1200-1500 mm wide, 120 and 160 mm thick are also used.

Panels for the first floor should be laid on a 10 mm thick layer of freshly laid masonry mortar, with at least 120 mm embedded on the support. With a pitch of 2400-3000 mm through one panel, they are connected with anchors with a diameter of 8-10 mm. Anchors are attached to the hinges and inserted into the masonry 250 mm from the end of the panel. It is necessary to finish with a bend at an angle of 90 degrees horizontally by 380 mm.

The joints between the panels are filled cement mortar... Speaking about what composition should be, it is worth knowing that it is 1: 4 in volume. Installation of panels is carried out using truck cranes.

Installation of reinforced concrete floors

Such structures for the first floor have some valuable qualities. The main ones are durability, great strength and fire resistance. To reduce the number of butt mates and assembly operations when designing the structures of prefabricated floor elements made of reinforced concrete (reinforced concrete), it will be necessary to strive to enlarge them.

Further it will be about precast concrete floors. It is divided into 3 main groups: girder, large-panel and in the form of decking (slabs). Structures in the form of decking will consist of flat or ribbed elements of the same type, which are stacked closely. Speaking about which connection method you need to use here, it is worth knowing that you need to fill the gaps with cement mortar.

Similar structures for the first floor consist of a load-bearing part made of reinforced concrete, a thermal and sound insulation layer and a floor structure. The walls and purlins will support the decking. The most common are hollow decks with a height of 160 mm if there is a span of up to 4 m, and 220 mm if there is a span of more than 4 m.

In the process of manufacturing decks with vertical voids, the consumption of concrete will be 15% less than with hollow-core decks. Round vertical voids are formed with pipe liners (the liners are welded to the channels). Floors that can be used to cover entire rooms are called large panels. V in this case consumption will be less. The absence of joints in the panels within the rooms will increase their sound insulation and provide a higher quality ceiling finish.

In order to ensure the normative soundproofing properties against airborne noise, single-layer structures of the panel floors of the first floor, which are made of heavy concrete, must necessarily have a mass that exceeds 300 kgf per 1 m².

In the process of installing split-type floors, in which the sound-insulating capacity of the air gap between the lower and upper panels of the prefabricated reinforced concrete floor is used, and when installing layered floors, it will be possible to ensure the sound-insulating standard capacity with a floor mass of less than 300 kgf per 1 m2.

Interfloor large-panel reinforced concrete (reinforced concrete) ceilings by design can be with a layered floor, with a layered floor and a split ceiling, of a separate type (from two separate load-bearing panels, with a split ceiling or with a split floor). All of the above floor structures have a relatively low weight (less than 300 kgf per 1 m²). Standard sound insulation can be provided by a layered floor structure or by the presence of a continuous air layer in the thickness.

Floor panels for the first floor are made of solid, hollow (with round hollows) and hipped roof. A single-layer load-bearing panel is a reinforced concrete slab with a bottom surface of a constant cross-section, which is ready for painting, and a flat top surface.

Single-layer solid reinforced concrete (reinforced concrete) panels, which have a thickness of 140 mm, can cover a span of up to 3.6 m. 16 cm, or expanded clay-reinforced concrete, which are 18 cm thick.

The hip panel has the form of a slab, which is framed along the contour by ribs facing in the form of a cornice. they are also arranged from flat reinforced concrete panels with a thickness of 14-16 cm. The type of overlap will depend on which span should be covered. The maximum span is 12 m.

Installation of the beam structure

Interfloor prefabricated reinforced concrete structures beam type consists of T-profile beams and infill between the beams. The filler in this case will be a roll of lightweight concrete and gypsum concrete slabs with a thickness of 80 mm and a length of 395 mm, reinforced with lath wooden or bar frames. In the attic floors - lightweight concrete slabs, which are 90 mm thick and 95 mm long, reinforced with welded steel mesh.

Seams in slabs and beams are filled with cement mortar and trowelled. Basement and attic floors it is imperative to insulate, and the interfloor ones - to soundproof. To do this, use sand or expanded clay filling in the slabs, a layered coating with an elastic pad.

It is recommended that sound and heat insulation in the slabs is not carried out by increasing the weight building structures... Due to the fact that the elements of girder structures are relatively lightweight, they are often used in buildings that are equipped with low-capacity cranes (about 1 ton).

In the process of installing reinforced concrete beams in sanitary facilities, a waterproofing layer should be included in the slabs. For this purpose, 1-2 layers of roofing material are most often glued on top of the flooring or panels on bituminous mastic. Beam floors are used if you need to block a span of 3-7.5 m.

Installation of monolithic buildings

Monolithic structures are made according to pre-installed formwork. Such slabs will serve as an additional rigid frame of the building in the process of transferring the load to the load-bearing walls from the floor. Their device requires a certain professional skill. It is imperative to carry out the project under the guidance of a construction specialist.

On-site fabrication of such structures has several advantages. To do this, you do not need to have a special transport or any kind of lifting equipment. To move and raise concrete, it is enough to have a means of small mechanization.

The foundation monolithic structures embedded in the Monier slabs. In it, the reinforcement is placed in places of tension, meaning the lower part of the slab. This is due to the fact that steel has a tensile strength 15 times greater than concrete. The reinforcing frame of the slab should be located at a distance from the walls of the formwork on minimum distance 3-5 cm. This is necessary in order for the concrete to be able to fill this space.

The span, which is covered with a monolithic slab, should have a maximum length of 3 m. For plumbing pipelines, care should be taken to install metal or vinyl sleeves that have an inner diameter larger than the pipeline to be laid. The clearance of the pipeline and metal sleeves must be minted with tarred tow.

The disadvantage of such monolithic structures is installation wooden formwork almost over the entire area of ​​the house. However, this does not mean at all that you need to expose the formwork all at once. Overlapping can be performed in separate spans, while transferring the formwork as the concrete sets.

The load-bearing capacity will be provided with reinforcement. In this case, intermediate joints of the rods along the entire length are undesirable. On the outside of the slab, the minimum layer of concrete must be at least 2 cm. The span must be concreted in one working cycle.

Formwork installation

For the device of monolithic reinforced concrete floors, you will need to install a horizontal removable formwork.

Such formwork can be made from wooden boards(from cut boards, which have a thickness of 25-35 mm) or waterproof plywood, which has a thickness of at least 20 mm. If the formwork panels, which are made of planks, have gaps, a layer is needed on top of the formwork waterproofing film... It will be needed so that the liquid solution cannot flow out.

The removable formwork should be laid on the girders, which will be supported by the supporting vertical posts... Racks can be telescopic, made independently from round timber with a diameter of 8-15 mm and beams, or factory-made.

The formwork should be installed without gaps, strictly horizontally. On a horizontal structure, steel reinforcement in the form of a mesh with cells measuring 200x200 mm is laid and tied using a soft knitting wire.

Rebar frame

The reinforcement on the formwork is laid in such a way that a gap of at least 25 mm remains between it and the formwork. To do this, use standard special plastic stands or make them yourself from wood, plywood or other material. What material to choose is up to everyone. Any of the above will be needed.

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 lay floors correctly.
• 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 specifications hollow floor slabs are much wider 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, you can only support on two short sides, 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 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 on construction site and provides a great deal of freedom to the designer, since the dimensions of the building box and load-bearing walls not attached to standard sizes PC.

When choosing interfloor slabs PCs (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 only cling to the concrete 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, this 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 sewer riser, with a diameter of 100 mm. While the size of the hollow hole in the PB is 60 mm. Therefore, to punch a through hole in the 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 slabs 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 ​​for the minimum depth of support 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 entering the inside of the panel. It also increases the strength at the ends of the slabs (this is more related to the PC than to the 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 consider 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 solution 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 arise in it, and under certain, unfavorable circumstances, it can crack.

If such a layout cannot be avoided, to relieve stress, a grinder is cut along 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, tied reinforcement cage in the form of a grid with a cell of 20 cm and a rod diameter of 8 mm, etc. Place the formwork and fill the 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 bottom plate can lean on the ground, and, due to uneven loading, under the weight of the top plates, 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

Floors made of monolithic reinforced concrete floor slabs have long been known and have proven themselves well in the construction of private and multi-storey buildings... To this day, they are in demand and popular, especially in the construction of cottages. large area... Reinforced concrete hollow floor slabs have a lot of advantages, the design of these slabs is such that, in addition to evenly distributing the load over the entire surface, they also additionally add rigidity and stability to the building.

General information and advantages of reinforced concrete slabs

The slabs are made of concrete, in which iron reinforcement is installed during pouring. Slabs have longitudinal voids along their length round shape, which in combination with fittings gives the design a huge advantage. Reinforced concrete slab is able to withstand bends, not break when high loads, it is very durable when used correctly during construction. Prefabricated monolithic slabs meet all the requirements for floors, they are strong and resistant at high temperatures. It is very important that a reinforced concrete slab is a good sound insulator and, in addition, retains heat.

Equally important is the fact that the use of slabs in construction greatly speeds up and simplifies the process, they can be installed where no other method of flooring is suitable. For example, laying the floors of a private house with an area of ​​over 100 m² using casting will take a lot of time, in addition, labor costs, and financial expenses will be much higher than when laying the floor with reinforced concrete slabs.

Correct selection of plates and calculation

When laying the floor of the first floor, you need to understand that a large load will be placed on it, therefore it is important to correctly calculate the weight of the structure and take everything into account, up to total weight home and furniture or equipment to be installed in the premises. The thickness of reinforced concrete slabs is standard and equal to 220 mm, but slabs can be designed for different weight loads depending on their brand. Here the reinforcement of the slab plays a role and what grade of concrete it is made of.

Reinforced concrete slabs are produced in lengths of 2.4-6.8 meters, the width of such slabs, depending on the length, is equal to 1.2-1.5 meters, weight 0.9-2.5 tons. This allows the use of small equipment during construction, cranes up to 3 tons of load lifting. It is not difficult to understand which plate you need, markings are put on the surface, for example, the PK 8-42-12 plate will be 4.2 meters long, 1.2 m wide, with a weight load of 800 kg / m².

Installation rules for slabs depending on the floor

When laying floor slabs, it is important to consider where they will be laid, since installation rules basement floor differ from the laying of floors between floors.

In the case of laying a basement floor, it is necessary first to carry out work to level the foundation, namely its upper edge. To do this, the upper edge of the foundation is made of a low formwork made of boards; here it is necessary to pour a small layer of concrete in order to bring out a perfectly flat surface horizontally. Now a reinforced concrete slab can be laid on such a site.

The slabs are laid taking into account their taper; it turns out that the lower part of the slab will be exactly joined with the adjacent one. A small seam forms at the top, which must be sealed with cement mortar. Thus, a practically flat floor surface is obtained in the shortest possible time. Depending on what kind of floor you will be installing, you may need to make a thin screed, but for most materials that cover the floor, a slab will work without additional finishing.

In the case when a reinforced concrete slab is laid as an overlap between floors, then an additional reinforced concrete belt must be made on the walls of bricks or blocks. This is something like a seismic belt, which is performed in the following way. When the height of the walls is laid out to the desired height, another row is laid, but one layer must be laid in order to leave the inner end around the entire perimeter, into which the slab will lie, and from the outside this place will be closed with bricks. Before laying the slab, as in the first case, it is necessary to formwork and pour a thin layer of concrete with reinforcement laying. As a result, a niche is formed with a small gap for laying insulation materials, where the slab is placed. A thin layer of reinforced concrete increases the strength of the surface and evenly distributes the load from the slab along the walls.

Warming

Floor slabs themselves serve good insulation, since they are located inside the premises of the house, there is no need to insulate them, however, it is necessary to insulate the ends. The slab has a high thermal conductivity, which is undoubtedly good, since the slab of the upper floor conducts heat from below and thus the floor becomes warm. But the plate will receive cold from the ends, so you need to protect it with a layer of insulation. In the niche that was formed during the reinforcement process, in the places where the slab adjoins the wall, it is necessary to lay insulation. Then this space, like the rest of the cracks, is poured with concrete.

It is imperative to make insulation, otherwise condensation will form in these voids, which the plate will absorb and gradually collapse. In addition to the destruction of the slab, moisture will appear in the room, and in places where there are fittings, rust will appear, which will not be covered with any putty.

Actually, this is the process of creating floors and floor slabs finished, now you can start finishing the floor with materials. As already mentioned, it may be necessary to perform a thin leveling layer of the screed.

With these types of work, construction equipment can significantly help you, for example

Floor slabs are load-bearing structures that separate floors or different-temperature zones. Products are made of concrete and reinforced concrete, the second type is considered universal and is suitable for both horizontal and vertical placement. The main criteria for their selection include the type of slab, dimensions and weight, bearing capacity, void diameter, additional conditions application. This information must be indicated by the manufacturer in the marking, the order of arrangement of the symbols is regulated by GOST 23009-2016.

Depending on the design, solid (corpulent) and hollow varieties are distinguished. By the way of arrangement, they can be monolithic, prefabricated-monolithic or prefabricated. The maximum demand is for hollow-core reinforced concrete floor slabs, which combine light weight and reliability. Their technical conditions and the marking is regulated by GOST 9561-91, based on the thickness, number of sides, shape and diameter of voids, 15 main types are distinguished.

Full-bodied products depending on the shape and functional purpose are divided into:

1. Solid bezel-less panels with smooth surface optimal for bookmark ceiling slabs... They are in demand in private construction, they are valued for the simplicity of decoration, their use implies the rejection of suspension systems... A significant part is made of cellular concrete.

2. Ribbed - with vertical stiffeners acting as supports. The reliability of such floor slabs is due to the removal of concrete from areas subject to tensile loads and an increase in its volume at the points of compression. The characteristics and designations of this variety are regulated by GOST 28042-89. The main area of ​​application is civil and residential construction, in private houses it is economically inexpedient.

3. Caesonic (often ribbed or frequently girded) groups. Represent monolithic slab laid on top of square cells from floor beams. Thus, on the one hand, they have a flat surface, on the other, they resemble waffles.

These structures are intended for operation under heavy loads, in private construction they are practically not used (according to SP 52-103-2007, they are recommended when the span of one room is exceeded by more than 12-15 m).

The standard marking of floor slabs, regardless of their type, sequentially includes:

• Designation of the type of construction and product.
• Dimensions in numbers: length and width, height refers to standard values ​​and is not indicated.
• Bearing capacity of floor slabs (1 unit in numerical value corresponds to the sustained 100 kg / m 2).
• The class of the tested reinforcement.
• Additional characteristics and properties, such as: resistance to aggressive environments, seismic effects, low temperatures, designation of embedded elements or holes (if any).

Explanation of designations

Overlap types have letter marking, the number in front of them is indicated in hollow varieties and characterizes the diameter internal holes... Examples of possible designations and their decoding for demanded solid species are given in the table:

The marking of hollow core panels includes the letter designation of the number of support sides of the slab ("T" corresponds to three, "K" - four). The absence of the third letter implies that the structure is supported on both sides. Decoding of the main types in this case:

The main difference between PC and SG panels from PB panels is the manufacturing method: the first two are poured into formwork structures, the latter is molded in a continuous way (conveyor technology). As a result, floors with PB marking have a smoother and more protected surface from external influences. They are less limited in length and are suitable for rooms with non-standard dimensions... The disadvantages of molding plates include narrower holes (the diameter of the voids when marking PB does not exceed 60 mm), unlike PC and SG, they cannot be drilled through to lay communications, at least this rule applies to high-rise buildings.

The length and width of each type are also limited by the standard, they are indicated in decimetres and rounded up. Real size can hollow-core slabs usually 10-20 mm less. Following numerical designation characterizes the design load of the slab, this indicator depends on the quality of the concrete and the reinforcement metal used. The reinforcement class is not always indicated; its mention is mandatory only for prestressed structures. If necessary, its designations are guided by the technical specifications for reinforcing steel.

The next paragraph of the labeling refers to the grade of concrete used (not indicated for heavy groups). Other types include: cellular (I), light (L), dense silicate (C), fine-grained (M), heat-resistant (W) and sand-concrete (P) compositions. For floor slabs intended for work in conditions of exposure to aggressive media, resistance is indicated in literal terms: normal permeability (N), reduced (P) and especially low (O). Another indicator is seismic resistance: structures designed for such loads are marked with the letter "C". All additional features are indicated in the product labeling in Arabic numerals or letters.

Slab cost

The main elements of the floor are supporting structures, which can be made from beams with liners, decks and panels. In large-panel houses, as a rule, they are used floor panels of various designs the size of a room. The nomenclature of the II-03-02 catalog includes prestressed floor panels with a height of 22 cm in accordance with GOST 9561-60 with horizontal oval and vertical voids made of heavy and lightweight concrete... Vertical voids are formed by liners from pipes with a channel welded from below. Until January 1, 1963, the use of panels with round voids is allowed. Floor slabs over 5 m are allowed only prestressed. If equipment is available for manufacturing, two-layer panels and flooring made on concreting combines are allowed.

Floor panels are taken in four sizes in width - 80.100, 120, 160 cm and are designed for two standard loads - 600 and 900 kg / m 2 (PO and PTO).

The panels are reinforced with cold-drawn carbon steel wire or low-alloy hot-rolled steel of a periodic profile of grades 35 GS, 25 G2S, 30HG2S, mounting loops from Art. 3. Panels reinforced with cold drawn wire should be made of 300 grade heavy concrete; reinforced with steel 35 ГС, 25 Г2С, 30ХГ2С - from heavy concrete of grade 200.

Panels should be manufactured, as a rule, with one end, which is sealed during the molding process.

Table 1. Indicators of floor panels

For 3-5-storey buildings, the II-03-02 catalog recommends panels of the type PO, PTO, PV and PTV - 59-16; 59-12 and 59-10, other types of panels are intended for civil construction.

Permissible deviations from the design dimensions · in length ± 5 mm, in width + 5-10 mm in height ± 3 mm, in a protective layer ± 2 mm.

For 1-2-storey construction, the catalog provides for the use of:

• flat slabs 318 and 258 cm long, 79 cm wide, reinforced with nets;
• ribbed slabs 398 cm long, 39.5 cm wide, reinforced with nets and frames;
• T-beams, reinforced with frames (for filling from gypsum concrete and lightweight concrete slabs).

The catalog allows for 1-2-storey residential construction the use of products intended for 3-5-storey buildings.

In prefabricated construction, it is possible to use other rational structures of floor panels, which provide weight reduction load-bearing structures, reduction in material consumption, cost and labor intensity. The characteristics of some panels are given in table. 2.