Do-it-yourself monolithic concrete floor. What is a monolithic floor? Frame device for monolithic floors

In this article, we will talk about what are the methods of erecting a monolithic floor, and you will also learn about the advantages and disadvantages of these methods. The article will tell you about the basic requirements for the thickness and reinforcement of reinforced concrete floor elements.

Reinforced concrete is an almost eternal material. Many structural elements are created from it - beams, walls, lintels. One of the most difficult, at first glance, products is the overlap. However, the complexity of the construction is fully compensated by the operational properties of the finished product.

Advantages of a monolithic floor:

1. Highest load-bearing capacity of known materials.
2. The most durable material available.
3. Relatively cheap raw materials (for concrete).
4. High qualifications of the entire team are not required to perform the work (1-2 leading specialists are enough).
5. Combined functions: the base of the second floor floor, armopoyas, the connection of all walls to each other.
6. Correctly arranged monolithic construction excludes the appearance of deformation defects ("steps", distortions, cracks).

Disadvantages of concrete floors:

1. Labor intensity of construction. The work is connected with the device of horizontal formwork of high strength and rigidity.
2. The accompanying material was used, which after concreting may become unusable - plywood, flanging board, racks (wooden).
3. Heavy construction weight - strong walls and foundation are required.
4. High thermal conductivity of concrete - all areas open to the outside must be insulated.
5. Concrete flooring is only possible on stone walls.

Reinforced concrete floors are suitable for permanent structures designed for a long service life, as well as for premises in which significant static and dynamic loads are provided - workshops, hotels, hostels (with partitions made of stone material).

In private construction, monolithic floor slabs are usually arranged along brick walls, since concrete walls are much more difficult to build than brick ones.

Monolithic slab thickness

Due to the high specific gravity of concrete (2400 kg / m 3), products from it are heavy. The weight of the product can be reduced by reducing the amount of concrete in the structure, that is, simply making it thinner. In this case, the stiffness is compensated for by the reinforcement. Sufficient thickness of reinforced concrete elements:

• load-bearing walls - 160 mm
• floors - 200 mm
• partitions - 100 mm

The thickness of these elements will be considered sufficient only if the rules of reinforcement are observed. Calculations and long-term practice have shown that there is an optimal balance of mass, volume, section and bearing capacity of reinforced concrete elements. Read about it below in the section "Floor reinforcement". The sufficient thickness of the brick wall is 380 mm (1.5 bricks).

Slab formwork

Like any reinforced concrete element, the floor requires the installation of a form for concrete - formwork. Since the overlap has significant dimensions in area and is at a height, the formwork for it looks like a table: a solid plane that fills the space between the load-bearing walls (and columns) on a spatially rigid frame of racks and slopes. There are three types of formwork, but one requirement is invariable for any of them - a reliable foundation.

Inventory formwork

A set of factory products, which includes:

1. Racks - sliding screw jacks, up to 4 m long.
2. Stand hardware - "tripods" at the bottom for the stability of the freestanding jack and "crown" at the top for seating the table beams.
3. Wooden beams - factory-made glued I-profile products with a height of 200 mm and a length of up to 4.2 m.
4. Film faced plywood - sheets of plywood 18-24 mm thick, 1220x2440 mm in size, covered with a resistant film, designed to create a floor plane. The coating can withstand up to 40 concreting cycles.

Such a set is professional - high-rise residential buildings are built with inventory formwork. It is reliable, convenient and designed for constant use. The purchase of a set for the device of one floor will not justify itself - all products are steel and are not cheap. The solution is to rent a formwork. The company's specialists themselves will calculate the required amount of each of the elements for your object.

The undoubted advantages of this approach are the speed of formwork installation and ease of use, as well as the quality of the plane. The disadvantages include the risk of a delay in the lease term.

Homemade formwork

All elements of the "table" for the ceiling can be made independently from wood and some metal parts.

This method is used when the main elements - posts, beam and plane material (plywood or board) are available. This is the main advantage of the method - the use of improvised material. Obvious disadvantages:

1. Time consuming construction requiring advanced carpenter skills.
2. Large waste of material - up to 20% will become unusable.
3. Problematic height adjustment (horizontal installation).

Combined method

Provides for the partial use of elements of inventory formwork and lumber.

In this case, you can use factory racks with tripods and crowns, and make the beams and formwork flooring from a plank. Or rent a laminated plywood, and assemble the "table" frame from a scaffold at hand. There can be many combinations.

Floor reinforcement

For the device of the reinforcing cage of the hanging reinforced concrete floor with a thickness of 200 mm, a mirror mesh made of reinforcement A3 Ø 16 mm with a cell of 150-180 mm is used. When using concrete prepared on site, we recommend strengthening the frame by using a smaller rod pitch - 150 mm. If the concrete is factory-made, a step of up to 200 mm is allowed. In places of support and abutment of elements (support on a wall, column, capital), we recommend making reinforcements - add rods.

Floor concreting

There are concreting rules that should be followed unquestioningly so as not to subject the structure to destruction in the future:

1. Placing concrete in the floor must be done in one go. With prolonged downtime during concreting, the laid concrete can set, and the new one cannot mix with it. As a result, you get a border along which a crack can go.
2. When concreting in a cool period (0 ... + 5 ° C), use special antifreeze additives. Read more about winter concreting in this article.
3. Be sure to use vibrators - deep or surface vibrators. Concrete without vibration has 40-50% of design strength. You will find more information about concreting in our article.
4. The slab formwork is dismantled no earlier than 28 days after the concrete is placed.

In this article, we will consider the main types of floors and the materials from which these floors are constructed. So what is overlap? Overlapping is a structure that divides adjacent rooms in height, that is, forms floors and separates them from attic and basement rooms.

Basic requirements for floors

• The slabs must be strong enough to withstand both their own weight and useful loads (furniture, equipment, people in the room, etc.).The value of the payload per 1 m2 of overlap is set depending on the purpose of the room and the nature of its equipment. For attic floors, the payload should not exceed 105 kg / m2, and for basement and interfloor floors, 210 kg / m2.
• The overlap should be rigid, that is, under the action of loads, it should not bend (the permissible value is from 1/200 for attic floors to 1/250 span for interfloor floors).
• During the installation of the floor, a sufficient degree of sound insulation must be provided, the value of which is established by the norms or special recommendations for the design of buildings for one purpose or another. To do this, it is necessary to carefully close the slots at the joints of the material, in order to avoid the transfer of sound from neighboring rooms located above or below.
• Ceilings separating rooms with a temperature difference of 10 Gd (for example, separating a cold basement from the first floor or an attic from the first floor) must meet the requirements of thermal protection, that is, it is necessary to increase the layer of thermal insulation.
• Not a single structure of floors, especially wooden ones, can withstand prolonged exposure to fire, but each material has its own value for the fire resistance limit. The limit of fire resistance of reinforced concrete floors - 60 minutes; wooden floors with backfill and lower plastered surface - 45 minutes; wooden floors protected with plaster, about 15 minutes; there are even fewer wooden floors not protected by fireproof materials.

Types of house floors

• interfloor (dividing residential floors, including the attic),
• basements (separating the basement from the residential floor),
• basement (separating the residential floor from the cold underground),
• attic (separating the residential floor from the unheated attic).

According to its constructive solution, the load-bearing part of the floors can be divided into:

• beam, standing from the bearing part (beams) and filling;
• bezel-less, made of homogeneous elements (floor slabs or floor panels).

Types of floors for the house

Beam floors

In beamed ceilings, the supporting base is made up of beams located at the same distance from each other, on which filling elements are laid that perform enclosing functions. Beams can be wood, reinforced concrete or metal.

Overlapping from wooden beams

In private housing construction, the most popular are timber beams, usually used in timber and frame houses.

For wooden beams there is a limitation on the width of the span (room). They can be used to:

• intermediate floors - with a span of 5 meters;
• for attic floors (with an unexploited attic) with a span of up to 6 meters. Metal beams can be used for any span width.

The timber floor is made of coniferous and hardwood beams. On the upper side of the beams, a flooring is made, which is at the same time a floor. The structure of the beam floor consists of the beams themselves, the roll-over, the floor and the insulation.

With a rectangular house plan, it is advisable to block the span along the short wall.

Layout of floor slabs along a short wall

So that the beams do not bend under the weight of the floor, they must be laid at a certain distance (see table). The cross-section of the beam is determined based on the load on it.

For example: You need to build a ceiling with a size of 3.0 * 4.0 m. We lay wooden beams (with a section of 6x20) on a wall equal to 3.0 meters. If the overlap is interfloor, the beams are laid at a distance of 1.25 m from each other, if the attic is 1.85 m.That is, the greater the width of the span of the future overlap, the less distance between the beams, since more overlap area is required loads.

The distance between the beams is also influenced by the thickness of the floor boards. If they are 28 mm or less thick, the distance between the beams should not exceed 50 cm.

The advantages of a wooden floor:

• The main advantage is that a wooden floor is quickly and easily mounted in any (even difficult) place, without the use of any special means, that is, you can do without a crane and other equipment. Wooden floors are lightweight and relatively inexpensive.

Disadvantages of wood flooring:

• The main disadvantage of wooden floors is increased flammability, sometimes the possibility of decay and infection with a bark beetle.

Wood floor installation technology:

Installation of beams: Before installing the beam, it must be treated with an antiseptic solution. If the beams rest on a stone or concrete wall, then its ends must be wrapped with two layers of roofing material. The beam is led into a nest prepared during the construction of the wall. When inserted into the nest, the beam should not reach the rear wall by 2–3 cm. The end of the beam is made beveled.

Beam installation diagram

(1 - beam, 2 - roofing material, 3 - insulation, 4 - solution).

The free space remaining in the nest is filled with insulation, you can fill it with polyurethane foam.

Roll-up setting: Bars (section 4x4 or 5x5), which are called cranial, are nailed to the side faces of the beams.

Scheme of rolling wooden boards

(1 - wooden beam, 2 - cranial bar, 3 - roll-up shield, 4 - vapor barrier, 5 - insulation, 6 - finished floor finish, 7 - ceiling finish).

A roll of wooden boards is attached to these bars. The roll is made from shields from longitudinal boards or shields from transverse boards. The reel plates must be tightly pressed against each other. They are attached to the cranial bar with self-tapping screws. The roll-off serves as a preparation for fixing a "clean" ceiling.

Insulation strip: An integral part of a timber joist floor is insulation, which in the interfloor ceiling performs primarily the role of sound insulation, and in the attic floor also the function of thermal insulation. First of all, it is necessary to determine what material to use. Insulation material can be mineral wool, polystyrene, slag, perlite, expanded clay, as well as dry sand, sawdust, shavings, straw, woody foliage. Mineral wool is a lightweight, easy-to-use material, unlike foam it "breathes", has sufficient heat and sound insulation, in general, in most cases, cotton wool is suitable for insulating interfloor and attic floors. Expanded clay (fraction 5-10 mm) is a material heavier than mineral wool, which makes the structure heavier (weight of 1 m2 of expanded clay - from 270-360 kg).

After the roll is fixed, a layer of thermal insulation is placed on top of it. First, a layer of roofing tar, glassine or a vapor barrier film is laid between the beams, bending it about 5 cm onto the beams and proceed to thermal insulation. The thickness of any insulation, for the interfloor overlap, should be at least 100 mm, and for the attic overlap, that is, between the cold and heated room - 200-250 mm.

Cost and consumption of materials: The consumption of timber for traditional wooden floors is approximately 0.1 m3 per 1 m2 of floor at a depth of 400 cm. The average cost per cubic meter of a timber beam is from $ 145 (or $ 14 / rm). And the cost of the boards will cost you about $ 200 per cubic meter. Costs for 1 square meter of flooring on wooden beams from $ 70 and more.

Overlapping on metal beams

Compared to wooden ones, they are quite reliable and more durable, and also have a smaller thickness (save space), but such floors are rarely erected. To fill the openings between the beams, you can use lightweight concrete inserts, lightweight reinforced concrete slabs, wooden shields or a wooden roll. The mass of 1 m2 of such an overlap often exceeds 400 kg.

Advantages:

• Large spans (4-6 meters or more) can be covered with a metal beam.

• The metal beam is non-combustible and resistant to biological influences (rot, etc.).

But overlappings on metal beams are not without drawbacks:

• in places of high humidity, corrosion forms on the metal.

• In addition, such ceilings have reduced heat and sound insulation qualities. To mitigate this disadvantage, the ends of the metal beams are wrapped in felt. In such ceilings, the bearing element is a rolling profile: I-beam, channel, corners.

Rolled profile

Between the beams, prefabricated reinforced concrete hollow slabs with a thickness of 9 cm are laid. A layer of slag and reinforced concrete screed with a thickness of 8-10 cm is applied over the reinforced concrete slabs. Steel consumption is high - 25-30 kg / m2, depending on the steel grade from which the beams are made.

Structural diagram of a prefabricated reinforced concrete floor slab on metal beams

1 - "clean" floor; 2 - boardwalk; 3 - beam; 4 - precast reinforced concrete plate; 5 - waterproofing; 6 - plaster mesh; 7 - plaster.

Material cost: The price of a steel profile is from 7 to 18 USD / rm. The cost of lightweight reinforced concrete slabs - from $ 110 per piece. For 1 square meter of flooring on metal beams, you will spend from $ 100 and more.

Reinforced concrete beams

Arranged on spans from 3 m to 7.5 meters. The work is complicated by the fact that it is necessary to use lifting equipment. The weight of such beams is 175 - 400 kg.

Advantages:

• With the help of reinforced concrete beams, it is possible to bridge larger spans than using wooden beams.

Disadvantages:

• For the installation of floors on reinforced concrete beams, it is necessary to use lifting equipment.

Mounting: Reinforced concrete beams are laid at a distance of 600-1000 mm. The filling of the interbeam space is arranged in the form of lightweight concrete slabs or hollow lightweight concrete blocks (with plank floors or parquet floors, slabs are used, and with linoleum or parquet floors on a concrete base - hollow blocks).

Scheme of the structure of a floor slab from a lightweight concrete slab on reinforced concrete beams

(1 - reinforced concrete beam, 2 - lightweight concrete slab, 3 - cement screed and substrate, 4 - parquet, laminate)

Scheme of the construction of a floor slab from hollow blocks on reinforced concrete beams

(1 - reinforced concrete beam, 2 - hollow blocks, 3 - cement screed, 4 - linoleum)

The seams between the beams and slabs are filled with cement mortar and rubbed over. Attic floors must be insulated, interfloor floors are soundproofed, basement ceilings are also insulated.

Floor slabs from hollow blocks on reinforced concrete beams

Cost: For one running meter, the beam will have to pay from $ 25. The price for one lightweight concrete block is from $ 1.5. As a result, spend from $ 65 for 1 square meter of flooring on reinforced concrete beams.

Beamless ceilings

They are homogeneous elements (slabs or panels) laid close to each other or a solid monolithic slab, which serve both as supporting and enclosing structures. Depending on the technology of execution, non-girder floors can be prefabricated, monolithic or precast-monolithic.

Precast concrete slabs

Most popular, especially in brick houses. For the installation of reinforced concrete floors, two types of panels are used: solid (they are made mainly of lightweight concrete) and hollow-core ones. The latter have round holes, a kind of "stiffening ribs". The panels are selected depending on the width of the span to be covered and the bearing capacity.

Advantages:

• Reinforced concrete slabs have high strength and are designed for a payload of over 200 kg / m2.

• Unlike wood, concrete is not afraid of dampness and does not require any maintenance.

Disadvantages:

• When installing floors made of reinforced concrete slabs, lifting equipment is required.

• It is not always possible to purchase ready-made slabs of the required size, since they are made at the factory in standard sizes.

Beamless floor plan for home

Mounting: Floor slabs are laid on a layer of grade 100 cement mortar. The support of the slabs on walls (wall thicker than 250 mm) must be at least 100 mm. The joints between the slabs must be cleaned of debris and thoroughly filled with cement mortar.

Approximate material cost: The cost of one floor slab is from $ 110. For 1 square meter of reinforced concrete slabs, you will spend at least $ 35-40.

Monolithic reinforced concrete floors

They can be of various shapes. Monolithic reinforced concrete floors are a solid monolithic slab 8-12 cm thick made of concrete grade 200, resting on the load-bearing walls. The weight of a square meter of a monolithic floor with a thickness of 200 mm is 480-500 kg.

Photo of reinforcement of a monolithic reinforced concrete floor

Installation of monolithic floors is carried out in four stages:

• Mounting of steel load-bearing beams to prepared places;
• Installation of suspended wooden formwork from unedged boards (suspended from steel beams);

The device of suspended wooden formwork from unedged boards

• Have reinforcement laying (with a diameter of 6-12 mm);
• Concreting the floor slab with M200 concrete.

Advantages of the monolith:

• Lack of expensive handling operations and a higher quality of the concrete surface that does not require grouting, as well as the possibility of implementing complex architectural and planning solutions.

The disadvantages of monolithic floors include the need to install wooden formwork over almost the entire area of ​​the future floor. 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.

Mounting: Before proceeding with the installation of the floor, it is necessary to build a formwork (it is bought ready-made or rented), which consists of telescopic racks, tripods, uniloks, beams, flooring and plywood. Formwork made of wooden and aluminum beams allows the formwork of slabs of any configuration - rectangular, cantilever and even round. Plywood sheets are applied to the upper wooden part of the beam, forming a formwork for pouring concrete. Next, the reinforcement cage is installed and secured. The ends of steel rods 60-80 cm long are bent and tied with wire with reinforcement. Then, over the entire area of ​​the overlap, concreting is carried out to a height of 10-30 cm. Full adhesion of the concrete occurs after 28 days.

Formwork for a monolithic slab made of wood flooring and plywood

Installation of the reinforcement cage in the formwork for the installation of a monolithic reinforced concrete slab

Approximate material cost: The cost of floor formwork, with timber and aluminum beams, from $ 40. The approximate consumption of reinforcement for the ceiling is 75-100 kg / m3 of concrete. The cost of 1 ton of reinforcement is $ 650. The cost of 1 cubic meter of ready-mixed concrete is from $ 130. As a result, the price for 1 square meter of monolithic flooring will cost you $ 45 and more (excluding the cost of formwork).

Precast-monolithic floor

A more modern flooring solution. The bottom line is that the space between the floor beams is filled with hollow blocks, after which the entire structure is poured on top with a layer of concrete.

Prefabricated monolithic floor slab for home

Advantages:

• Installation without the use of lifting mechanisms, improvement of thermal insulation properties, the possibility of overlapping complex shapes, reduction of construction time.

Disadvantages:

• The disadvantages include that the prefabricated monolithic structure has a laborious (manual) installation process, which is not advisable when building a house with 2-3 floors.

Mounting: During installation, precast-monolithic floor beams are laid on the walls with a step of 600 mm. The weight of a running meter of a beam does not exceed 19 kg. This allows, in most cases, the installation of beams without the use of a crane. Hollow blocks are manually placed on the beams. Weight of expanded clay concrete block - 14 kg, polystyrene concrete block - 5.5 kg. As a result, the dead weight of one square meter of the original floor structures is 140 kg for expanded clay concrete blocks and 80 kg for polystyrene concrete blocks.

The floor structure prepared in this way performs the function of a permanent formwork, on which a layer of monolithic concrete of class B15 (M200) is laid.

Before pouring concrete, it is necessary to reinforce the structure with a reinforcing mesh with cells measuring 100x100 mm made of wire with a diameter of 5-6 mm.

The weight of one square meter of the finished floor is 370-390 kg for expanded clay concrete blocks and 290-300 kg for polystyrene concrete blocks.

Expanded clay concrete block for precast-monolithic floors

Approximate cost: The cost of precast-monolithic floor structures (beams and blocks) will cost you 40-50 dollars / m2. The cost of finished floor structures (beams + blocks + mesh + concrete) is 70-75 dollars / m2.

Heat and sound insulation of floors:

The thermal protection of the floor must be such that the temperature on the floor surface is close to the temperature of the internal air and does not drop below it by more than 2 ° C. To avoid dampness between heated and unheated rooms, to protect the insulation layer from moisture, the glassine layer should be placed above the thermal insulation.

Layout of heat and sound insulation materials in the floor

(1 - a wooden bar, 2 - a cranial bar, 3 - a roll, 4 - a layer of insulation, 5 - a vapor barrier film or glassine, 6 - boards)

In addition to good thermal protection, the ceilings must also provide sufficient sound insulation of the premises. In accordance with the current regulations (data for the Russian Federation), the insulation index Rw must be equal to or greater than 49 dB.

For hollow-core reinforced concrete slabs with a thickness of 220 mm, the insulation index is Rw = 52 dB.

For wooden floors (insulation layer 280 mm + one layer of drywall 12 mm), the sound insulation index is 47 dB.

Now a little about heaters. Ready-made mineral wool slabs have proven themselves well as thermal insulation. In addition to the well-known insulation with ready-made mineral wool slabs, there are alternative options that are carried out on site, for example: You can fill in slag or ordinary sawdust on a roll lined with roofing material or covered with a solution of clay with the addition of sand (the solution must dry well). By the way, they are 4 times lighter than slag and at the same time provide 3 times better thermal insulation with the same layer thickness. So, at a winter temperature of -20 ° C, the slag backfill should be 16 cm thick, shavings - 7, and from sawdust - only 5 cm.

Sawdust concrete slabs for the same purpose can be made independently. To do this, you can take 1 volumetric part of sawdust, 1.5 parts of lime mortar or 4 parts of clay, 0.3 parts of cement and from 2 to 2.5 parts of water. The finished slabs are dried in the shade, laid on a roofing felt pad, the seams are sealed with clay or lime mortar. A square meter of such a slab weighs about 5-6 kg with a thickness of 10 cm.

What kind of overlap to choose for your home. It all depends on the type of house, as well as on the installation technology and the price of this floor. As a conclusion to this article, I will give a table in which you can compare different types of floors and choose the most suitable one for yourself.

Note: In this article, prices are for the period 2008. Be careful!

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 times (if prefabricated reinforced concrete floors are used). Next, we will take a closer look at what types of them are, and how you can overlap yourself.

Types of structures

All existing reinforced concrete floors can be conditionally 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- are a system of interconnected criss-crossing monolithic beams and slabs.
  These slabs consist of the following elements:
  • Purlins (main beams)
  • Ribs (beams perpendicular to the purlins).
• Caisson- are intersecting beams of the same cross-section, which are monolithically connected to the slab. The recesses between these beams are called caissons.
• Bezel-less- are solid monolithic slabs laid on columns. There is a thickening (capitals) in the upper part of the slabs. The reinforcing bars are located at the bottom of the slab.
  The slab frame 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 with a step of about 150 centimeters. The beams are connected to the slab reinforcement.
  I must say that there are 16 types of reinforced concrete floor beams according to GOST 20372-90. Their longest standard length is 18 meters.
• Ribbed- can be used if the span length does not exceed 6 m. If the length is greater, then reinforcement with a transverse beam is performed. As a rule, this type of structure is used in cases where it is necessary to obtain an even ceiling. The distance between the beams should be no more than a meter.
  When installing such a structure, embedded elements are attached to the reinforcing cage, which allows the ceiling to be hemmed 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 fittings, which are connected by electric or gas welding. It is more difficult to make a knitted frame. For these purposes, use a special knitting wire with a thickness of not more than 2 mm.

Prefabricated structures are divided into the following groups:

• Made of flooring, weighing up to 0.5 tons.
• Overlappings on reinforced concrete beams with small-sized filling.
• Wide slab elements weighing 1.5-2 tons.
• Large-panel structures, which consist of elements made to the size of one room.

Prefabricated structures include hollow-core reinforced concrete slabs, which are very popular. They are monolithic reinforced concrete slabs reinforced with a reinforcing cage.

Cylindrical voids are made inside the panels, which run along the entire length of the panels. They can significantly reduce the weight of products, and also increase the resistance to deformation of the plates to fracture. These panels come in different lengths and widths.

Reinforced concrete slab manufacturing

Now let's look at how to perform a non-girder slab. 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 reinforcement;
• Cement grade 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 yourself. For the bottom of the slab, you can use plywood boards with a thickness of at least 2 cm, reinforced with bars, or board boards with a thickness of 4-5 cm.

For side walls, ordinary boards 2-3 cm thick are suitable, you can, of course, use plywood, but its price is higher.

The assembly of the formwork is carried out in the following order:

• First of all, the bottom shields are laid. Supports and cross-beams should be used for their installation.
• Then the sidewalls are installed.
• The inner part of the formwork is covered with roofing felt. 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 inserts, or use bars. The diameter of the reinforcement should be at least 10-12 mm, and the mesh size of the mesh should be 150X150 or 200x200 mm.
  The thickness of the frame is calculated in such a way that the protective layer of the mortar is at least 2 cm from the top and bottom. Those. its thickness should be 4 cm thinner than the thickness of the slab.

Fill

To fill the slab, you should perform the mortar in the following proportion:

• One part of M400 cement;
• Two pieces of sand;
• Four parts with a diameter of fractions not exceeding 20 mm;
• Water until the required consistency is obtained.

Fill 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 picks up about 80 percent of its is removed. However, the plates can be used only after 28 days.

Advice!
After the slab is finished, 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 of holes in concrete can be carried out.

I must say that in some cases it may be necessary not to erect a slab from scratch, but to repair reinforced concrete floors. It consists in strengthening the structure with additional elements in the form of plates, beams, shells, etc. The procedure is quite complicated, so specialists should deal with it.

Output

As we found out, there are many types of concrete slabs that are designed for different situations. Therefore, in each individual case, you need to choose the right type of structure. In private construction, you can make reinforced concrete floors with your own hands, according to the technology indicated above.

You can get more information on this topic from the video in this article.

For the device of the columns, wooden formwork boxes are used. The formwork box is sewn, as a rule, from three sides. Installation begins with the installation of a frame, which is pressed against the corks laid in advance in fresh concrete.

The frame is installed in such a way that the axes printed on it during manufacture coincide with the axes drawn in the concrete of the structure, and the surface into which the box is installed is at the same level with the risks on the reinforcement outlets.

The assembled formwork boxes are installed in frames and secured with braces or inclined braces, which are nailed to the plugs previously laid in concrete, or to the logs laid in a spar between adjacent columns. ’The verticality of the boxes is made using a frame plumb bob. The fourth shield of the box and the clamps that are missing in the box of the column formwork are installed after the installation of the reinforcing cages. There are openings in the formwork for supplying the concrete mixture inside the structures.

The columns are reinforced with a crane. The installed frames are calibrated and temporarily fixed with clamps. Clamps are used for alignment and axial alignment of the column frames. Removal of temporary fasteners is carried out after tacking the frames to the reinforcement outlets of the lower columns by electric welding.

Dismantling of the formwork is carried out in the reverse order after the concrete has reached its stripping strength. The formwork is dismantled with panels, which are then transferred to the workplace for cleaning and lubrication.

The device of formwork and reinforcement according to SKM No. 1 is produced by a gantry crane, according to SKM No. 2 by a tower crane, that is, by the same lifting means that are used for laying the concrete mixture. According to SKM No. 3, the installation of formwork and fittings is carried out with a tower crane, which is used only for these works. Concrete mix is ​​supplied using portable bunkers. Hoppers are served by gantry cranes according to SKM No. 1 (Fig. 95) or tower cranes according to SKM No. 2 (Fig. 96). Concrete mixture supply according to SKM No. 3 is carried out by a concrete pump (fig. 97, tables 68, 69).

For the device of the beams, the panel formwork is adopted. First, the bottom of the formwork of the beams is laid in the cut of the formwork of the columns and fastened with nails. Then they substitute inventory racks under the bottom of the formwork and knock them out from below with wedges. After verifying the position and construction lifting of the bottom of the beams, the side shields of the formwork of the beams are installed in the frames of the cutouts of the columns and attached to the lower ribs of the bottom.

Dismantling of the formwork is carried out in the reverse order after the concrete reaches its stripping strength. The formwork is dismantled with boards. First, the inventory racks are removed, then the side and bottom shields are torn off.

Reinforcement of beams begins with the laying of the reinforcing cage in the beam formwork. Before laying the frame, clamps are installed on its lower part to create a protective layer. Installation of clamps is carried out in a staggered manner with a step of 1 m. Installation of reinforcement and formwork of beams is carried out with a KB-100 crane from mobile platforms.

The concrete mixture is laid with the help of portable bunkers installed in the area of ​​the crane, which are fed to the place of concreting by a tower crane (Fig. 98). As the formwork is filled, the concrete mix is ​​compacted with deep vibrators.

The installation of the slab formwork is carried out in the following sequence. Before the attack of the formwork installation, support scaffolds are mounted with a flooring device 1.8 m below the bottom of the ceiling formwork. The installation of the formwork of the floor slabs is carried out simultaneously with the installation of the formwork of the beams and is carried out in accordance with the project for the production of works.

When dismantling the formwork, first remove the supporting posts, then tear off the shields. Reinforcement of slabs begins with the laying of reinforcing meshes in the slab formwork. Before laying the nets, clamps are installed on them to create a protective layer. The clamps are installed in a checkerboard pattern with a step of 1 m.

Installation of formwork and reinforcement is carried out with the same lifting mechanisms as for laying the concrete mixture.

The concrete mixture is supplied to the place of laying in the ceiling formwork with portable bunkers using a gantry crane according to SKM No. 1 (Fig. 99) or a tower crane according to SKM No. 2 (Fig. 100, Table 70-73).

For the construction of the walls, panel formwork is used. The wall formwork is installed in two steps: first, the formwork of one side of the wall is installed to its entire height between the floors, and after the wall is reinforced, the formwork of the other side is mounted. At the same time, holes are provided in the formwork for supplying the concrete mixture through them into the structure.

The formwork on the outside of the wall is fixed to the inside with tie bolts or wire ties.

To comply with the design wall thickness, wooden or concrete spacers are installed inside them, placing them in the places where tie bolts or wire ties pass. Wooden spacers are removed during the concreting process. Reinforcement of the walls begins with the installation of the frames with a crane and the rods are manually installed. The ratio of frames and rods is 85 and 15%. The installed frame is verified and temporarily secured with clamps. For alignment and axial alignment of the wall frame, a clamp is used. Removal of temporary fasteners is carried out after tacking by electric welding of the frames to the outlets of the reinforcement of the lower tier of the wall.

Dismantling of the formwork is carried out in the reverse order. The formwork is dismantled with shields: the screeds are removed, first the shields of one side of the wall are torn off, then the other. All shields are moved to the workplace for cleaning and lubrication. The stripping of the walls is carried out after the concrete has reached stripping strength.

Laying the concrete mixture into the wall formwork is carried out according to SKM No. 1 using a gantry crane (Fig. 101), according to GRM No. 2 - a tower crane (Fig. 102), according to OKM No. 3 - a concrete pump (Fig. 103, Table 74 , 75).

In the practice of construction, prefabricated monolithic frame structures of multi-storey buildings with spatial stiffness cores, performed in monolithic reinforced concrete, are widely used.

Structurally, the creation of a solid box-shaped stiffening core instead of flat stiffening walls increases the stiffness of the entire building, thus significantly reducing the consumption of reinforced concrete. Thus, the consumption of reinforcement in a monolithic core of a house is 3-4 times lower than in a similar house with prefabricated reinforced concrete walls. In addition to the core of stiffness, the weight of the bearing and enclosing elements of the building is usually carried out in prefabricated products.

Monolithic stiffening cores are also combined with prefabricated panel structures for internal and external walls. It is recommended to erect stiffening cores with a height of more than 15 m in sliding formwork or in formwork with a tear-off device (Fig. 104). The stiffening cores being erected at present are made of M300 heavy monolithic concrete. In plan, they can be rectangular, cylindrical, cruciform or of a more complex configuration. The thickness of the walls ranges from 20 to 80 cm.

The walls are reinforced with both rigid and flexible reinforcement. The working one is the longitudinal reinforcement. Flexible reinforcement is installed both from the outside and from the inside of the barrel made of steel of classes A-II and A-III. The diameter of the reinforcement is set by calculation and decreases with the height of the core (for example, from 28 to 16 mm).

Horizontal reinforcement is not calculated and is installed constructively.

Monolithic tank structures are made of concrete of the M200 brand, rectangular in plan with a height of up to 2 m and round - up to 6 m.The thickness of the bottom is 25-70 cm.Reinforcement is carried out with nets or frames made of steel of class A-II or A-III with a diameter of 10-16 mm.

The walls are made of in-situ concrete by conventional methods or by gunning. With generally accepted methods of concreting, the thickness of the walls is 25-30 cm.

Shotcrete is applied to the outer wall formwork under a pressure of 0.45-0.5 MPa, with a thickness of 4-5 cm in three passes. The formwork and fittings are set immediately to their full height. Steel fittings of grades A-II and A-III.

Prefabricated monolithic structures can be rectangular or round in plan with a height of up to 5 m. The bottom is made of monolithic reinforced concrete with the same structural characteristics as for the monolithic version.

Monolithic beam floors, ribbed floors.

Reinforced concrete floors. Depending on the method of construction, they are divided into monolithic and prefabricated. The advantage of such slabs is their high bearing capacity. The compressive strength of the concrete is used here, since the dimensions of these slabs can be accurately determined using static calculations. The disadvantage of reinforced concrete floors is high sound permeability.

Monolithic reinforced concrete floors are made at a construction site in the formwork. Carrying out the function of transferring the load from the floor to the load-bearing walls, they serve in buildings with a massive frame as well as stiffeners. For the manufacture of monolithic reinforced concrete floors, formwork is required, made of a scarce material - wood. Monolithic reinforced concrete floors are divided in shape into slab, beam, ribbed and liner floors (Fig. 84).

Monolithic slab floors. The simplest construction of monolithic slabs is the Monier slab, in which the reinforcement is placed in places of tension, i.e., in the lower part of the slab, since steel has 15 times higher tensile strength than concrete.

Rice. 84. Reinforced concrete floors a - monolithic reinforced concrete slab; b - reinforced concrete monolithic beam floor; 1 - transverse reinforcement of the beam; 2 - beam; 3 - longitudinal main reinforcement of the beam; c - reinforced concrete monolithic ribbed floor

The slab is usually laid on a load-bearing wall, and the length of the surface on which the slab is laid is 10 cm; when using boards with a thickness of more than 10 cm, the length of the surface on which the board is laid is equal to the thickness of the board. Such overlaps can have a maximum span of 300 cm (see Fig. 84, a) . With a larger span, a reinforced concrete slab is concreted on steel load-bearing beams that span the large span. Such slabs are called monolithic reinforced concrete slabs or combined slabs with steel load-bearing beams.

Monolithic beam floors. For large spans, the floors can have a maximum span of 300 cm. Reinforced concrete beams are laid on the wall; they are connected to a reinforced concrete slab and reinforced. Such slabs, invented by the French engineer Annabik, are called Annabik slabs. The beams are laid at a distance of 130-500 cm from one another. The length of laying beams on load-bearing brick walls should be 7.5% of the beam span, but not less than 22 cm. Usually, beams are anchored into monolithic reinforced concrete belts with brickwork.

Reinforced concrete beam ceilings are used in rooms where a flat ceiling is required (basements, warehouses, workshops, etc.), since for finishing a flat ceiling, the axial distance between the beams of this floor is too large.

The use of reinforced concrete beam floors is cost-effective in the presence of spans of 6 m (see Fig. 84, b).

Monolithic ribbed floors. If, when using reinforced concrete floors, it is necessary to make an even ceiling, the distance along the axis between the beams should be reduced by 0.5-1 m. The cross-section of the beams is smaller, therefore they are called ribs. So that the ribs do not bulge, they are reinforced with a span of 6 m with one transverse rib (see Fig. 84, c).

A flat ceiling is finished with filing and lime-gypsum plaster or plaster on reeds. Before concreting the ribbed reinforced concrete floor, pins or wire with a diameter of 10 mm are laid in the reinforcement so that after concreting and stripping they protrude from the sides of the ribs. Planks 2 cm thick are installed on these embedded parts, the lower edge of which protrudes 1 cm beyond the edge of the lower rib (Fig. 85, a).

Rice. 85.

a - side mount; b - plate - the base of the filing; c - finishing without a plate; 1 - steel rod with a diameter of 8 mm; 2 - grid

Another method consists in the fact that in the manufacture of the formwork, the ribs are placed in it before the reinforcement is laid and the plank bottom is fixed, after which both ends of the wire are monolithic. To the base made in this way, a cladding of 12-20 mm thick slabs, nailed down, is attached. The joints between the boards must not be wider than 15 mm. A simple plaster is applied to the cladding or lined with a reed mat (Fig. 85, b). Sometimes a wire is monolithic into the slab and the ribs, and after stripping, a Rabitz mesh is attached to it and lime-gypsum plaster is applied (Fig. 85, c).

Monolithic floors with inserts. A big disadvantage of ribbed floors and especially floors with a flat ceiling is the laboriousness of their arrangement and the high consumption of wood for the manufacture of formwork and filing. Therefore, overlaps with liners are more often used. In places of future gaps between the ribs, inserts are placed, which serve as the formwork of the ribs and at the same time the lower part of the slab formwork. The undersides of the inserts replace the boarding with boards and serve as the base for the plaster. Liners are made from various materials of various shapes. The most common are rigid baked clay liners, the lower part of which reaches the shelves, forming the lower formwork of the ribs. The inserts are placed in the horizontal formwork and, after preparing the reinforcement for the ribs and slabs, they are concreted (Fig. 86).

Rice. 86. 1 - plaster; 2 - ceramic insert; 3 - rib reinforcement

The disadvantage of slabs with liners is that they are more sound permeable than the slabs described above, since the liner, after adhesion to reinforced concrete, forms a solid resonant slab.