In modern capital construction multi-storey buildings the most common are reinforced concrete floors, which are distinguished by valuable qualities - high strength, durability, fire resistance and water resistance. According to the method of execution, reinforced concrete floors are prefabricated and monolithic.
The main type of prefabricated interfloor iron concrete floors- ceilings made of slabs or panels. The structural basis of such ceilings are slabs or panels - large reinforced concrete elements (solid, ribbed, with voids) produced by reinforced concrete factories. Plates are produced 6 m long, 0.8-1.6 m wide.
The most effective panels are "per room" size, the use of which allows to reduce the number of assembly units in the building, i.e., to increase the prefabrication of construction.
Panels and slabs are laid on walls and girders along a layer of cement mortar, and the depth of the ends of the panels resting on the walls must be at least 100 mm. Longitudinal seams between the panels must be filled with mortar grade "100".
To connect the ceilings to the walls and increase the overall rigidity of the building, the ends of the panels resting on the outer walls are fastened to the wall with anchors. When relying on internal walls panels are also interconnected with anchors.
When installing interfloor ceilings, a layer of sound insulation 20-50 mm thick is laid on the panels, consisting of slag, mineral wool or sand. Soundproofing can also be a 40-60 mm layer of lightweight concrete (slag concrete,). The floor in the interfloor ceilings is laid on a sound-proof layer (if it is hard enough) or on sound-proof pads from chipboard scraps or sheet rubber.
When installing attic floors on reinforced concrete panels or slabs, a layer of vapor barrier is laid, and then insulation. Vapor barrier protects the insulation from moistening with water vapor rising from the premises and condensate. As a vapor barrier, a layer of glassine is used, laid on the panels, or bituminous lubricant on the surface of the panels in contact with the insulation. As a heater in attic floors use a layer of expanded clay, granulated slag or mineral wool. In order to reduce labor costs at the construction site, mineral wool insulation is best used in the form of prefabricated prefabricated slabs. The thickness of the insulation layer in all cases is determined thermotechnical calculation. It depends on the calculated internal and external air temperature and on the insulation material.
The layer of insulation from the side of the attic is covered with clay-lime lubricant 20 mm thick to protect the insulation from destruction and weathering. In order for the lubricant and insulation not to collapse when walking in the attic, it is necessary to lay running boards at a certain distance from each other.
Prefabricated reinforced concrete floors can also be arranged in beam type. Such floors have to be used in cases where the construction site cannot be provided with reinforced concrete panels or if the load capacity of the mechanism installed at the construction site is insufficient to lift the panels. Reinforced concrete floor of the beam type consists of beams, inter-beam filling and floor. Beams (their length is from 2400 to 6000 mm) are laid on walls or girders parallel to each other at a distance of 600, 800, 1000 mm along the axes.
The depth of support of the ends of the beams on the walls or girders must be at least 150 mm, and the ends of the beams are connected to the wall using anchors. Inter-beam filling consists of rolling and soundproofing layer. Small-sized lightweight concrete (gypsum concrete, slag concrete, expanded clay concrete) solid or hollow slabs can be used as rolling.
Sound insulation laid on the reel is usually made of a layer of mineral wool. Logs (70 mm) are laid along the upper edges of the reinforced concrete beams and a wooden floor (30 mm) is laid so that a ventilation air gap is formed between the floor boards and the sound insulation.
When installing beamed attic floors, it is necessary to protect the beams from hypothermia with a layer of mineral wool or felt.
Due to the high labor intensity, reinforced concrete beam ceilings are used only in low-rise construction.
Monolithic reinforced concrete floors are beamed or beamless.
Beam monolithic floors consist of a slab resting on beams in such a way that a system of intersecting mutually perpendicular monolithic ribs is formed on the lower surface of the ceiling. Such an overlap is called ribbed. If necessary, you can arrange the ribs so that rectangular recesses of the same size - caissons - are formed on the ceiling. Compared to ribbed coffered floors, they have a more attractive appearance and their arrangement is justified from architectural considerations.
Beamless monolithic ceilings are a solid smooth slab 120-250 mm thick, based on walls and reinforced concrete columns, the distance between which is 5-6 m. The columns have widenings in the upper part - capitals that increase the supporting area of the slab. Due to the significant consumption of timber for, high labor intensity, and also in connection with long periods hardening of concrete, delaying the production of related works in construction, monolithic floors in the mass construction of typical civil and industrial buildings rarely applied. Such floors are more expedient in non-standard buildings built according to individual projects.
Interfloor ceilings separating rooms from high humidity(sanitary facilities, washrooms, etc.) must be waterproof. To do this, waterproofing layers are introduced into the composition of the ceiling: in panel ceilings - along the upper plane of the panels, and in beam ceilings - along the concrete layer (hot bitumen coating). In addition, a waterproofing layer of two layers of roofing material on mastic is added to the floor structure over a 30-mm asphalt layer. This is laid on a concrete layer, directly under the cement screed. To protect adjacent premises from soaking in sanitary facilities, washrooms and similar premises, it is necessary to arrange 20-30 mm below the floors of adjacent premises.
When erecting brick, stone, concrete and cinder-concrete structures, reinforced concrete floors are used. This is due to their durability, strength, relative ease of installation, as well as short construction time (if prefabricated reinforced concrete floors are used). Next, we will take a closer look at what their types are, and how you can perform the overlap yourself.
Types of structures
All existing reinforced concrete floors can be divided into two types:
- prefabricated;
- Monolithic.
Now let's take a closer look at each type of structure.
Monolithic
Reinforced concrete monolithic floors, unlike prefabricated ones, are poured at the facility, directly at their location.
They are of several types:
- Ribbed- represent a system of interconnected intersecting monolithic beams and plates.
These floors consist of the following elements:- Purlins (main beams)
- Ribs (beams located perpendicular to the girders).
- coffered- are intersecting beams of the same section, which are monolithically connected to the slab. The recesses between these beams are called caissons.
- Beamless- are solid monolithic slabs laid on columns. In the upper part of the plates there is a thickening (capitals). Reinforcing bars are located at the bottom of the slab.
The frame of the slab is placed at a distance of several centimeters from the formwork so that this space is filled with concrete. Such structures are used only in cases where the span does not exceed three meters.
- Beam reinforced concrete floor- used if the span is more than three meters. In this case, reinforced concrete beams are laid on the wall in increments of about 150 centimeters. The beams are connected to the reinforcement of the slab.
I must say that there are 16 types of reinforced concrete floor beams according to GOST 20372-90. Their largest standard length is 18 meters. - Ribbed- can be used if the span does not exceed 6 m. If the length is longer, then reinforcement is performed transverse beam. As a rule, this type of structure is used in cases where it is necessary to obtain a flat ceiling. The distance between the beams should be no more than a meter.
When installing this design, embedded elements are attached to the reinforcing cage, which allows you to hem the ceiling with boards. The disadvantages of this system include the complexity of its design.
prefabricated
Reinforced concrete prefabricated floors are knitted and welded. The welded frame is made of straight reinforcement, which is connected by electric or gas welding. Making a knitted frame is more difficult. For these purposes, a special knitting wire with a thickness of not more than 2 mm is used.
Prefabricated structures are divided into the following groups:
- Made of decking, weighing up to 0.5 tons.
- Ceilings on reinforced concrete beams with small-sized filling.
- Wide floor elements weighing 1.5-2 tons.
- Large-panel structures, which consist of elements made according to the size of one room.
Prefabricated structures include reinforced concrete multi-hollow floor panels, which are very popular. They are monolithic reinforced concrete slabs reinforced with a reinforcing cage.
There are voids inside the panels cylindrical shape that run along the entire length of the plates. They can significantly reduce the weight of products, as well as increase the resistance to deformation of the plates for fracture. These panels come in different lengths and widths.
Production of reinforced concrete slab
Now let's look at how to perform a beamless overlap. I must say that do-it-yourself reinforced concrete floor beams are very rarely made.
Materials and tools
So, for the construction of the structure, you need to prepare the following materials and inventory:
- steel fittings;
- Cement brand not lower than M400;
- Sand;
- Crushed stone or gravel;
- Welding machine;
- Boards, timber;
- Concrete mixer;
- Various power tools.
Formwork and frame manufacturing
First of all, you need to do the formwork with your own hands. For the bottom of the slab, you can use plywood boards with a thickness of at least 2 cm, reinforced with bars, or plank boards with a thickness of 4-5 cm.
Suitable for side walls ordinary boards 2-3 cm thick, you can, of course, use plywood, but its price is higher.
Formwork is assembled in the following order:
- First of all, the bottom shields are laid. For their installation, supports and cross beams should be used.
- Then the sides are installed.
- The inner part of the formwork is covered with roofing material. For these purposes, you can also use a synthetic film.
- The next step is to assemble the frame, which should be located at a distance of 2-3 cm from the bottom of the formwork. To do this, you can use special liners, or use bars. The diameter of the reinforcement should be at least 10-12 mm, and the size of the mesh cell should be 150x150 or 200x200 mm.
The thickness of the frame is calculated in such a way that the protective layer of the solution is at least 2 cm from the bottom and top. Those. its thickness should be thinner than the thickness of the plate by 4 cm.
fill
To fill the slab, you should perform the solution in the following proportion:
- One part of M400 cement;
- Two parts of sand;
- Four parts with a diameter of fractions not more than 20 mm;
- Water until desired consistency is obtained.
Filling is performed without interruption, starting from one corner and ending with the opposite. In this case, the solution is tamped with a deep vibrator.
After pouring, the concrete is protected from rapid drying. To do this, it is covered with wet burlap and sawdust. The first 8-10 days the surface is periodically moistened.
After 2-3 weeks, after the solution has gained about 80 percent of its own, it is removed. However, the plates can only be used after 28 days.
Advice!
After the slab has been completed, it may need to be machined.
It is most effective to perform procedures with a diamond tool.
In particular, cutting of reinforced concrete with diamond wheels, grinding with diamond cups or diamond drilling holes in concrete.
I must say that in some cases it may be necessary not to build a slab from scratch, but to repair reinforced concrete floors. It consists in strengthening the structure additional elements in the form of plates, beams, shells, etc. The procedure is quite complicated, so it should be handled by specialists.
Conclusion
As we found out, there are many types of concrete floors that are designed to different cases. Therefore, in each individual case, you need to choose the right type of construction. In private construction, you can make reinforced concrete floors with your own hands, using the technology indicated above.
See the video in this article for more information on this topic.
Overlappings consist of a bearing part, which transfers the load to the walls or individual supports, and an enclosing part, which includes floors and ceilings. According to the material of the bearing part, they distinguish reinforced concrete ceilings, on wooden and iron supports, also armosilicate and clay. The price of ceilings and floors in the total price of the house achieves 20% of its total price.
The main material for floor devices in modern construction is reinforced concrete. Reinforced concrete floors divide by prefabricated And whole, concreted in formwork. IN last years used in the main prefabricated And solid ceilings.
Overlappings must meet the requirements of strength, rigidity, fire resistance, durability, sound and thermal insulation, if they separate heated rooms from unheated rooms or from the external environment. Overlappings in rooms with wet processes they must be waterproof, and in rooms with the release of gases - gas-tight.
In suburban houses with brick walls, they use reinforced concrete floor panels with round voids, the length of which is from 4800 mm to 6980 mm, the width is from 1000 to 2400 mm, the height is 220 mm, also with flat ones - 2700-4200 mm long with a gradation of 300 mm, 1200, 1500 mm wide, 120 and 160 mm wide . Panels they are laid (Fig. 1) on a layer of freshly laid masonry mortar 10 mm wide with embedding on supports more than 120 mm. Through one panel(pitch 2400-3000 mm) are connected to the walls with anchors with a diameter of 8-10 mm, which are strengthened to the hinges and led into the masonry 250 mm from the end of the panel, ending with a bend at an angle of 90 ° horizontally by 380 mm.
Seams between panels fill with cement substance composition 1: 4 (by volume). Panel installation produced using cranes. Reinforced concrete floors
Such floors possess a number of valuable properties, the main of which are great strength, durability and fire resistance. When designing parts prefabricated concrete floors it is necessary to strive to enlarge them to reduce the number of assembly operations and butt mates.
Precast concrete floors
Precast concrete floors subdivided into three main groups: in the form of flooring (slabs), large-panel and beam. Overlappings in the form of floorings consist of flat or ribbed parts of the same type, laid tightly; connect them by filling the gaps with cement. Such floors consist of a bearing reinforced concrete part (usually textured from below), a sound or thermal insulation layer and a floor structure. The supports for the flooring are walls and girders. More common hollow flooring 160 mm high with gaps up to 4 m and 220 mm - with gaps over 4 m. The decks have longitudinal voids of circular cross section (Fig. 2, a).
In the manufacture of floorings with vertical voids, the consumption of concrete is reduced by up to 15% compared to round-hollow ones. Vertical round voids are formed using pipe liners (the liners are welded to the channels). decking, which can cover entire rooms, are called large panels. No connections in floor panels within the boundaries of the room increases their sound insulation and provides a higher quality ceiling finish.
To ensure standard soundproofing parameters from airborne noise, single-layer structures interfloor panel ceilings, made of heavy concrete, must have a mass exceeding 300 kgf / sq.m.
At flooring device separate type, in which the soundproofing ability of the air gap between the upper and lower floor panels of the connection is used, also when installing layered floors, it is possible to ensure the normative soundproofing ability with a floor mass of at least 300 kgf / sq.m.
By design interfloor large-panel reinforced concrete floors can be with a layered floor, separate type (with a separate floor, ceiling or from 2 separate load-bearing panels) and with a layered floor and a separate ceiling (Fig. 3). All these floor structures have a relatively small mass (less than 300 kgf / sq.m.); normative noise insulation is provided by a layered floor structure or the presence of a continuous air gap in the thickness floors.
floor panels produce solid, hollow (with round voids) and tented. The bearing single-layer panel (Fig. 4, a) is reinforced concrete slab unchanged section with a bottom surface ready for coloring, and a flat top.
solid single layer reinforced concrete panels 140 mm wide cover gaps up to 3.6 m. To cover huge spans (6-6.6 m), they mainly use solid single-layer for previously stressful reinforced concrete panels 14-16 cm wide or expanded clay-reinforced concrete 18 cm wide.
hipped panel(Fig. 4, b) has the form of a slab framed along the contour with ribs facing downwards in the form of a cornice. satisfied interfloor floors and from flat reinforced concrete panels 14-16 cm wide.
Ceilings on reinforced concrete supports
Prefabricated reinforced concrete floors(Fig. 5) beam type consist of T-beams and filling between them. The filler here is a roll of gypsum concrete or lightweight concrete slabs 80 wide and 395 mm long, reinforced with wooden slatted or bar frames, and in attic floors - lightweight concrete slabs 90 wide and 395 mm long, reinforced with welded iron meshes. The seams between the supports and slabs are filled with cement and rubbed. Attic and basement floors certainly insulate, interfloor soundproof. To do this, use expanded clay or sand bedding, layered coatings with elastic gaskets. With all this, it is better that heat and sound insulation be carried out not due to an increase in the weight of the building structures.
Because the elements beam floors have a relatively small weight, they are used on buildings equipped with low-capacity cranes (up to 1 ton).
At installation of reinforced concrete floors and in sanitary facilities, a waterproofing layer is included in the floor structure. To do this, over decking or panels are usually glued to bituminous mastic 1-2 layers of roofing material.
Solid ceilings
Solid ceilings make according to the established formwork. Transferring loads from the floor to load-bearing walls, solid ceilings serve as an additional rigid frame of the structure. Their device requires a certain professional skill and should be done according to the project under the guidance of a specialist builder. fabrication floors locally has its own merits. With all this, special transport and lifting equipment are not required. Small-scale mechanization is sufficient for lifting and moving concrete. To base solid floors laid down Monier plate, in which the reinforcement is located in places of tension, in other words, at the bottom of the slab. This is justified by the fact that steel has 15 times greater tensile strength than concrete. The reinforcing frame of the slab should be placed at a distance of more than 3-5 cm from the formwork walls so that concrete can fill this place. The length of the gap covered solid slabs, should not exceed 3 m. For plumbing pipelines, special iron 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.
To the shortcomings solid floors we can attribute the need to install wood formwork virtually throughout the entire area of the house. But, this does not mean that the formwork must be exposed all at once. overlap can be made in separate gaps, transferring the formwork as the concrete sets.
Load bearing capacity solid floors provided with reinforcement, the diameter of which must be at least 8-12 mm. With all this, intermediate connections of the rods along the entire length of the floor are undesirable. A small layer of concrete on the outer side of the ceiling should be more than 2 cm. It is necessary to concrete the gap in one working cycle.
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Design characteristics
Ceilings consist of a bearing part, which transfers the load to individual supports or walls, and an enclosing part, which includes ceilings and floors. According to the material of the bearing part, it is possible to distinguish reinforced concrete (reinforced concrete) floors, for steel and wooden beams, ceramic and armosilicate. The cost of floors and ceilings will reach 20% of the total cost 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 cost of overlapping should be minimal.
In modern construction, the main material for the construction of floors is reinforced concrete. from reinforced concrete (reinforced concrete) can be divided into monolithic and prefabricated, concreted in the formwork. IN Lately for the first floor, only monolithic reinforced concrete floors and prefabricated ones are used. Prefabricated allow you to block the span up to 12 m. Speaking about which one is needed, you should know that the consumption of this mortar per 1 m² will be 0.223 m³, and steel - 6.5 kg. This cost is approximate and may vary slightly.
It is worth knowing that floors must necessarily meet the requirements of rigidity, strength, fire resistance, durability, sound and heat insulation, if they separate 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 released, gas-tight.
In country houses with brick walls, most often people prefer precast 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 ground floor should be laid on a layer of freshly laid masonry mortar 10 mm thick, embedded on the support at least 120 mm. With a step of 2400-3000 mm, they are connected through one panel with anchors with a diameter of 8-10 mm. The anchors are attached to the hinges and driven 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.
Seams between panels are filled cement mortar. Speaking about what composition should be, it is worth knowing that it is 1: 4 by volume. Installation of panels is carried out with the help of truck cranes.
Reinforced concrete floor installation
Similar designs for the first floor have some valuable qualities. The main ones are durability, high strength and fire resistance. In order to reduce the number of butt joints and assembly operations, when designing the structures of elements of prefabricated reinforced concrete floors (reinforced concrete), it will be necessary to strive to enlarge them.
Next, we will talk about precast concrete floors. It is divided into 3 main groups: beam, large-panel and in the form of flooring (slabs). The structures in the form of decks will consist of flat or ribbed elements of the same type, which are stacked closely. Speaking about which connection method to use here, it is worth knowing that you need to fill the gaps with cement mortar.
Similar structures for the ground floor consist of a reinforced concrete bearing part, a thermal and sound insulation layer and a floor structure. The walls and girders will serve as supports for the decks. The most common are hollow flooring, having 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 floorings with vertical voids, the consumption of concrete will be 15% less than with round-hollow floorings. Round vertical voids are formed using pipe liners (the liners are welded to the channels). Floorings that can cover entire rooms are called large panels. In this case, the cost 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 provide standard soundproofing properties from airborne noise, single-layer structures of panel ceilings on the first floor, which are made of heavy concrete, must necessarily have a mass that exceeds 300 kgf per 1 m².
During the installation of separate type ceilings, in which the soundproofing capacity of the air gap between the lower and upper panels of the precast concrete floor is used, and when installing layered ceilings, it will be possible to ensure the soundproofing normative ability with a floor weight 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 separate ceiling, of a separate type (from two separate load-bearing panels, with a separate ceiling or with a separate floor). All of the above floor structures have a relatively small mass (less than 300 kgf per 1 m²). Normative 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 solid, hollow (having round voids) and tented. A single-layer load-bearing panel is a reinforced concrete slab with a lower surface of constant cross-section, which is ready for painting, and a flat upper 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 have a thickness of 18 cm.
The hipped panel has the form of a slab, which is framed along the contour with ribs facing in the form of a cornice. they are also arranged from flat reinforced concrete panels having a thickness of 14-16 cm. The type of overlap will depend on which span should be blocked. The maximum span is 12 m.
Installation of a beam structure
Interfloor prefabricated reinforced concrete structures beam type consist of T-beams and filling between the beams. The filler in this case will be a roll of lightweight concrete and gypsum concrete slabs, having a thickness of 80 mm and a length of 395 mm, reinforced with slatted wooden or bar frames. In the attic floors - lightweight concrete slabs, which have a thickness of 90 mm and a length of 95 mm, reinforced with welded steel mesh.
Seams in slabs and beams are filled with cement mortar and rubbed. Basement and attic floors must be insulated, and interfloor floors must be soundproofed. To do this, sand or expanded clay bedding, a layered coating with an elastic gasket should be used in the slabs.
It is recommended that sound and heat insulation in slabs be carried out not by means of weight gain. building structures. Due to the fact that the elements of beam structures have a relatively small weight, they are often used in buildings that are equipped with low-capacity cranes (about 1 ton).
In the process of installing reinforced concrete beam floors in sanitary facilities, a waterproofing layer should be included in the slabs. For this, 1-2 layers of roofing material on bituminous mastic are most often glued over the flooring or panels for this. Beam ceilings are used if it is necessary to cover a span of 3-7.5 m.
Installation of monolithic buildings
Monolithic structures are made according to pre-installed formwork. Such ceilings on 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 must be carried out according to the project under the guidance of a specialist builder.
Manufacturing such structures in situ has some advantages. To do this, you do not need to have special transport or any lifting equipment. To move and raise concrete, it is enough to have small-scale mechanization.
The basis of monolithic structures is laid in 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 formwork walls at a minimum distance of 3-5 cm. This is necessary so that the concrete can fill this space.
A span that is covered with 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 being laid. The gap of the pipeline and metal sleeves must be minted with tarred tow.
The disadvantage of such monolithic structures is the installation of wooden formwork over almost the entire area of \u200b\u200bthe house. However, this does not mean at all that it is necessary to expose the formwork all at once. Overlapping can be performed in separate spans, while transferring the formwork as the concrete sets.
The bearing capacity will be provided with the help of reinforcement. Intermediate joints of the rods along the entire length are undesirable. On the outer side of the ceiling, the minimum layer of concrete must be at least 2 cm. The span must be concreted in one working cycle.
Formwork installation
For the installation of a monolithic reinforced concrete floor, it will be necessary to install a horizontal removable formwork.
Such formwork can be made from wooden shields(from cut boards that have a thickness of 25-35 mm) or waterproof plywood that has a thickness of at least 20 mm. If the formwork panels, which are made of boards, have gaps, a layer of waterproofing film is needed over the formwork. It will be needed so that the liquid solution cannot flow out.
Removable formwork should be laid on beams-transoms, which will be supported by supporting uprights. Racks can be telescopic, made independently from round timber with a diameter of 8-15 mm and beams, or factory-made.
The formwork must be installed without gaps, strictly horizontally. Steel reinforcement in the form of a mesh with cells measuring 200x200 mm is laid and tied using a soft knitting wire along a horizontal structure.
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 coasters 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.
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.
With 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 into one whole (ribbed and coffered floors).
Ribbed cover
Ribbed ceiling (Fig. 107, a) is a structure consisting of a mutually connected slab and beams. On fig. 107, b shows a diagram of a ribbed ceiling over a room 24 liters long and 16 meters wide.Across the room are laid 3 powerful runs, called the main beams, based on the outer walls and the column. Along the room are the so-called secondary beams, or ribs, based on walls and girders. 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 height of the floor, 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 from 1/12 to 1/16 of their span, and the width - within 1/8-1/12 of the distance between their axes. Since a larger 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 ceilings, up to 50-70% of the total amount of concrete is spent on the slab. By reducing the distance between the ribs and at the same time their thickness, a thinner plate can be obtained. The desire to reduce the thickness of the slab in order to save concrete led to the creation often ribbed floors(Fig. 108).
For the installation of such floors, instead of formwork, a sparse flooring is laid from boards supported by girders supported by temporary wooden racks supporting forests. Ceramic or cinder-concrete hollow stones are laid along the boards, the transverse seams between which are filled with mortar.
Rows of stones are laid so that between them a space is formed for the construction of reinforced concrete ribs. Reinforcement is laid on top of the ribs and stones and the ribs and the slab are concreted. To protect stones from possible falling out, it is recommended to make their side faces corrugated or beveled.
The height of often-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 with a clear distance between them of 250 to 600 mm. Often-ribbed ceilings have the following advantages compared to ribbed ones: they are more profitable in terms of concrete consumption, less wood is spent on the formwork, and the formwork design is simple. In addition, these floors have a slightly lower structural height and form a smooth ceiling.
Caisson floors
Caisson floors (Fig. 109) are ribbed structures in which the main and secondary beams are of the same height. In this case, rectangular or square recesses are formed on the ceiling, in French - caissons. Economically, coffered floors are less profitable than conventional ribbed ones, and their use is justified mainly by architectural considerations.Beamless floors
In beamless ceilings (Fig. 110), a reinforced concrete slab (150-200 mm thick) rests directly on columns, in the upper part of which there are extensions called capitals. The grid of columns with a beamless ceiling is taken square or close to a square with a side size of 5-6 m.It is advisable to use beamless ceilings for heavy loads, and also, if necessary, to have a smooth ceiling (for example, in refrigerators, slaughterhouses, garages, etc.).
Precast concrete floors
Prefabricated reinforced 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, eliminate work on the installation of scaffolds and formwork, and also drastically reduce construction time.When designing the structures of elements of prefabricated reinforced concrete floors, it is necessary to strive to enlarge them, since this reduces the number of assembly operations for lifting and laying elements, and reduces the number of butt joints. The best option there would be a floor slab on the room so that the ceiling was 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 flooring (slabs) and large-panel.
Beam ceilings(Fig. 111) are made of T-beams and filling between them. As a filling, a roll of gypsum concrete or lightweight concrete slabs with a thickness of 80 and a length of 395 mm, reinforced with wooden rack or bar frames (for interfloor floors), or lightweight concrete slabs with a thickness of 90 and a length of 385 mm, reinforced with welded steel mesh (for attic floors) is used (Fig. 111, a). In order to isolate from the air transfer of sound, the gaps between the beams and the reel are sealed with a solution, and slag is poured over the pa-kat.
Instead of rolling, light-weight concrete double-hollow liner stones 250 mm high and 195 mm long are also used (Fig. 111, b). The gaps between the stones and beams are carefully filled with cement mortar. This creates some solidity of the overlap and increases its rigidity. It is also necessary to fill the seams to improve sound insulation.
To be able to be used in ceilings with different payloads of the same types of beams, different distances between their axes are set - 600, 800 and 1000 mm for slab rolls and 600 mm for filling from insert stones. At the same time, the width of the plate-rollers is 510, 710 and 910 mm, respectively, and the liners are 510 mm.
Elements of beam ceilings are relatively light in weight and therefore they are used in buildings equipped with low-capacity cranes (up to 1 t).
Floor coverings 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. This type of floor does not require beams and consists of a load-bearing reinforced concrete part (usually textured at the bottom), a sound or thermal insulation layer and a floor structure. Supports for flooring are walls or girders.
The most common flooring used in practice modern construction, are hollow decking (Fig. 112) 160 mm high with spans up to 4 m and 220 mm with spans over 4 m. oval section (Fig. 112, c). Diameter round holes is 160 mm in decks 220 mm high and 120 mm when decks are 160 mm high.
The oval-vaulted openings are 350 mm long and 110 mm high in 160 mm decks and 165 mm in 220 mm decks.
Floors with oval voids have not been used in recent years due to the complexity of their manufacture by a conveyor method.
The given thickness of concrete in floorings 5.6-6.0 m long 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 those with round ones.
Recently, instead of floorings with round voids, floorings with so-called vertical voids (Fig. 112, d) are used, which reduce the consumption of concrete 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 embedding the ends of floorings with oval-vaulted and oval voids into walls, it is possible for the upper flooring slab to be forced through by the overlying wall. Therefore, these floorings provide for sealing holes from one end during the molding process (Fig. 112, 8), and from the other after molding by laying concrete inserts on the mortar into specially provided cutouts in the upper floor slab.
Flooring of a large area, which can cover entire rooms, is called floor panels. The absence of joints in such ceilings within the room increases their sound insulation from airborne noise, provides simplicity and higher quality ceiling finishes. In addition, floor panels can be factory made with a clean floor.
To ensure the normative soundproofing ability from airborne noise, single-layer structures of interfloor panel ceilings made of heavy concrete should have a weight of 1 m 2 of about 300 kg.
When constructing split-type floors, which use the soundproofing capacity of the air gap between the upper and lower floor panels that do not have a rigid connection between them, as well as when installing layered floors, the normative soundproofing capacity can be achieved with a floor weight of 200 kg / m 2.
According to the design scheme (Fig. 113), the following types of interfloor large-panel floors 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 layered floor, including a layer of soft and elastic material that improves sound insulation from airborne and impact noise, as well as a hard base under the floors and a clean floor.
A separate type ceiling 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 soundproofing gaskets from the ceiling element and walls.
Overlappings of a separate type are divided into three groups:
- 1) separate floor of two load-bearing panels (Fig. 113, b);
- 2) from one bearing panel and a separate floor structure resting on it (Fig. 113, c);
- 3) ceiling with one carrier panel and a separate suspended or self-supporting ceiling (Fig. 113, d, e.).
According to the constructive form, floor panels are divided into solid (single-layer and layered), ribbed (with ribs up or down), hollow (with round or vertical voids) and tented.
Load-bearing single-layer solid panel(Fig. 114, a) is a reinforced concrete slab of constant cross-section with a lower surface ready for painting and an upper flat surface prepared for flooring.
Solid single-layer reinforced concrete panels have a thickness of 100-120 mm with a multilayer floor structure and 140 mm with a sticker on a linoleum slab on an elastic basis.
To cover large spans (6-6.6 l), recently, solid single-layer prestressed reinforced concrete panels 140 mm thick have 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 stronger concrete, in which tensile reinforcement is located; the second layer is made of light, less durable concrete. In three-layer panels, the third, upper, layer also consists of stronger concrete (unreinforced or weakly reinforced).
Ribbed panels may be with ribs facing up or down. It is advisable to complete load-bearing floor panels with ribs upwards (Fig. 114, c) with the floor structure at the factory, which ensures a high degree of factory readiness and safety of the panels during storage in a warehouse and installation.
Bearing floor panels with ribs down are recommended for use in floors with a split ceiling and in floors with a layered soundproof floor and a split ceiling.
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 soundproof gaskets between the shells provide the necessary soundproofing of the ceiling.
Bottom panel with ribs upwards (ceiling panel), having a bottom surface ready for painting, is rigidly supported by bearing walls and serves as a horizontal rigidity diaphragm. The top panel with ribs down (floor panel), having a top surface ready for flooring, rests on the bottom panel through soundproofing pads.
In the floor panel in the operational position, according to sound insulation conditions, there should not be any rigid connections with the bottom panel and with the walls. Such panels are assembled at the factory; they have 4 mounting loops that fasten the upper and lower shells. 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-rolling shells, as field studies have shown, is their unsatisfactory soundproofing qualities. Sound insulation deteriorates due to the appearance of shrinkage cracks in the shells, which occur as a result of the use of sandy concrete with a large consumption of cement, as well as due to the forced steaming of products. In addition, the small width of the supporting part of the upper shell (60 mm) causes the fibreboard gaskets to collapse and lose their elastic properties. Finally, the gap between the top shell and the wall, instead of being filled with insulating fibreboard, is often filled with mortar.
For this reason, more recently rational decision consider the construction of an interfloor ceiling in the form of a flat reinforced concrete slab 140 mm thick, the weight of which provides case sound insulation from airborne sound transfer.
Hollow core panels along with hollow decks are widely used in construction. However, the cost of these panels is relatively high. It should also be noted the poor performance of these panels in bending in a direction perpendicular to the direction of the voids.
hipped panel(Fig. 114, e) has the form of a slab framed along the contour with ribs facing downwards in the form of a cornice. The use of such panels, manufactured in the size of a room, makes it possible to exclude crossbars and other beam elements from the structural scheme of the building, and, due to their small thickness, to reduce the height of the floor without reducing the height of the room.
When constructing reinforced concrete floors in sanitary facilities, a waterproofing layer is introduced into the structure of the floor. To do this, 1-2 layers of roofing material are usually glued on bituminous mastic over decking or panels. In places of junction with walls or partitions, the waterproofing is raised up by 100 mm.
In recent years, glued waterproofing of floors in sanitary facilities has been replaced with a device cement-sand screed 30 mm thick (from a cement mortar with a composition of 1: 3), closed with a 3% solution of sodium aluminate. Such a screed is a completely reliable and simpler protection against water penetration through the ceiling than pasting with rolled material. Waterproof screeds are also used cement-sand mortars with the addition of the latest ferric chloride, which also reduce water permeability.
In attic floors (Fig. 115, a), a vapor barrier is first laid on top of reinforced concrete flooring or panels (from one or two layers of glassine or only 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 complexity, they are also used plate heaters(mineral wool slabs, fiberboard, cellular concrete slabs).
In beam 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 floors does not meet modern construction requirements. Delivery of slag and backfilling of the attic floor by hand is a very time-consuming and expensive operation. In addition, the weight of 1 m 2 of an attic floor insulated with slag is very large - 520-550 kg / m 2. If reinforced concrete floorings are used, in which load-bearing and heat-insulating functions are combined, it is possible to lighten the weight of the attic floor by 2 times and reduce the complexity of its installation.
When installing reinforced concrete floors above cold basements and undergrounds, it is necessary, as in attic floors, to provide for the laying of insulation. However, in this case, the vapor barrier should be placed not from below, but from above the insulation.
Promising types of floors are prefabricated armosilicate and ceramic floors. Compared to reinforced concrete, they are more economical in terms of cement consumption and total cost.
The peculiarity of the reinforced silicate floor structures (beams and slabs) is that instead of cement, local materials are used for their manufacture - lime and sand. Armosilicate products are processed in autoclaves at high pressure and high temperature.
Ceramic ceilings are laid from thin-walled hollow ceramic stones, from which they are made individual elements ceilings in the form of beams and panels. The stones are fastened together with cement mortar and steel reinforcement.
