Reinforcement of the floor slab: step by step instructions, features and drawings

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

The most popular flooring in the construction of low-rise individual buildings are reinforced concrete hollow core slabs. But for their installation, lifting equipment is required, which negatively affects the final cost of the work. Among other things, ready-made platforms are used for buildings with simple shapes.

A number of developers prefer to perform floors on their own, using reinforced concrete. This method is most suitable for objects that must have irregular geometry. All this makes it possible to abandon standards and build architecturally complex buildings.

Why is it necessary to reinforce the slab

Reinforcement of the floor slab is carried out taking into account technological subtleties. This allows the product to be used for several decades. When pouring, thin ceilings are obtained that do not have seams, and the floors in this case do not require laborious and expensive repairs when interior finishing.

Reinforcement of the floor slab allows to reduce the weight of the structure compared to prefabricated reinforced concrete slabs, but this does not negatively affect the strength. The load on the foundation is reduced, because lighter building materials are used. Not to mention strength. Concrete and iron create a solid foundation. The platform is used to cover large-span and loaded structures.

Additional benefits of reinforcement

Reinforcement of the floor slab is also carried out to ensure reliability. Structures acquire high resistance to loads due to the use of reinforcement. They acquire the ability to endure loads up to 800 kg/m2. In this way, products can also be given fire resistance, because the materials used are not combustible.

The stove does not support combustion, withstands exposure to an open flame for a long time. Overlapping costs do not exceed the cost of the factory product. The area to be built will determine the price.

Features of the work

Carrying out work on the reinforcement of the floor slab involves the use of technology that provides ample opportunities in the matter of space planning. The platform at the same time turns out to be quite durable, it withstands high loads, does not contribute to the development of fungus and insects, as well as harmful bacteria. Work is carried out according to the rules. You should not save on building materials, because the ceiling can be deformed, which will lead to the destruction of the slab and the entire building.

Susing a removable formwork, the ceiling is poured, while there must be reinforcement inside. Steel rods are tied with wire. But you can also use welding equipment. The frame is positioned so that it is completely recessed into the concrete solution. The fittings take on the load, and the solution excludes the flow of oxygen, which negatively affects the metal.

About additional items

When drawing up a reinforcement scheme, auxiliary reinforcement should be taken into account. It should be located in the center of the platform, where the loads are concentrated, as well as at the point of contact between the ceiling and the holes. Auxiliary reinforcement should also be at the point of contact of the monolith with internal walls, columns and arches.

As for the concentration of loads, in this case we are talking about heavy equipment or a fireplace. Additional elements are also installed at the exit point of the stairs to the upper floor, as well as at the point of passage of chimney pipes or ventilation elements.

Step by step instructions

Reinforcement of the prefabricated floor slab is carried out after calculating the thickness of the reinforcement, which will depend on the length of the floor. If the pitch between the bearing supports is 5 m, the thickness of the platform should be 170 mm. When calculating, a ratio of 1 to 30 should be used. But with a structure thickness of less than 150 mm, it cannot be allowed to operate. If the thickness of the overlap has a minimum thickness, then the remaining elements must be laid in onelayer. As this parameter increases, the number of layers also increases to two.

For mortar, you should purchase concrete grade M-200 or higher. This brand combines affordable price and excellent performance. The compressive strength class should be 150 kgf/cm2. The diameter of the steel bars used can reach 14 mm, the minimum parameter is 8 mm. If the metal rods are arranged in 2 layers, then the diameter of the rolled metal of the first row should be larger than that located on top.

Working on the fence

Having considered the drawings of the reinforcement of the monolithic floor slab, which are offered in the article, you can start work. At the next stage, the technology provides for the installation of formwork from moisture-resistant plywood or boards. These materials can be combined. The supports must be well fixed, because the weight of the structure to be poured is 300 kg per square meter. The support elements can be telescopic jack stands. They allow you to set the desired height with high accuracy. Supports withstand loads up to 2.5 kg.

Formwork work

The floor slab reinforcement scheme is proposed in the article, but its observance is not a guarantee of success. You must follow the rules at every stage of the work. For example, with regard to the formwork, it is a removable structure, which consists of boards 150 x 25 mm. They will not be able to provide a perfectly flat ceiling surface, because the thickness of the lumber is allowederror. Irregularities can be hidden under the plaster. This is true if you plan to work on suspended ceilings. If the presence of a flat surface is fundamentally important, laminated 22 mm plywood can be used instead of boards. However, such formwork will cost more.

It is more economical to use edged boards as a base, on top of which 8 mm plywood is laid. Before reinforcing a monolithic floor slab, you can prepare boards 150 x 50 mm, which are installed around the perimeter of the room and will be formwork. The distance between the transverse bars is 800 mm or less. Under them, telescopic racks or props are installed strictly according to the level.

150 x 25 mm boards are laid out on top of the frame. Their fastening to the base is not required, otherwise, after completion of work, it may be difficult to dismantle the formwork. Plywood sheets should be laid on top of the boards. In order for the formwork material to be used for other purposes, the structure should be covered with plastic wrap. The sheets must be laid with an overlap of 200 mm. When working, it is important to avoid material jams.

Expert advice

If the slab will serve as a flooring under the roof, instead of side boards, you can use brick or cellular block boards. After completion of the work on the manufacture of the slab, the formwork must be dismantled, not broken. All fasteners connected to this must be on the outside.

Rebar

The example of reinforcing a monolithic floor slab described in the article involves the use of a mesh that binds itself. The rods must be laid along the length, while gaps should be excluded. If there is a need for a tie, the metal elements must be laid with an overlap of 0.5 m. In the place where the rods intersect, they must be fixed with wire or a welding machine. Spot welding is recommended when using rebar of an impressive diameter. Thin rods in the process may become thinner, which will reduce the strength of the metal and lead to a loss in the bearing capacity of the plate.

After reviewing the drawing of the reinforcement of the floor slab, you can start work. However, it is important to stock up on tools and materials, among which a special hook should be highlighted. It is used for knitting. But its application will require certain skills. As part of the construction of your house, you can get by with pliers. Metal cards will make the process easier. They are laid with an overlap in 2 cells. Fixation is carried out with a wire.

The steel frame must not rest on the bottom of the formwork. It is installed on the battle of tiles, stones or bricks. If the thickness of the reinforced concrete slab is more than 150 mm, then another layer of the lattice is knitted. The second layer should be located at some distance from the first, while the top layers are covered with concrete mortar.

Settlements

Before starting work, it is necessary to calculate the reinforcementmonolithic floor slab. In this case, you can take into account the area of \u200b\u200bthe building, which in the example will be equal to 6 x 6 m. Transverse walls are taken into account here.

The thickness of the plate will be 160 mm. The cross section of the ceiling, taking into account steel reinforcement, is 14 cm². The construction will be based on B200 grade concrete. In this case, the calculation of the reinforcement of the floor slab will look like this: Rb=117 kg/cm², Rbin=14.3 kg/cm², Eb=3.110'5kg/cm. The fittings used correspond to class A-500C. Further calculations are as follows: Rs=4500 kg/cm², E2=5.510 ‘5 kg/cm. If we use AKP-SP fiberglass reinforcement in our work, the calculations will look different: Rs=12,000 kg/cm^{2, E=5.510 '5 kg/ see}

Reinforcement example

If you do not have enough experience, you can consider a specific example of reinforcing a floor slab. The pressure on the structure will be vertically downward, and distributed over the entire area. The upper part of the reinforcement cage will take on compressive loads, while the lower part will take on tensile loads. The rods must be laid in the formwork and tied together with wire. Thick rods are used for the lower mesh.

If the plate has a thickness ranging from 180 to 200 mm, a distance of 100 to 125 mm should be maintained between the grids. To do this, you can use clamps from scraps of reinforcement. Long rods are bent in the form of the letter L and arranged in meter increments.

In those areas that require reinforcement, the distance should be reduced to 40 cm. As a rule, these are placesconnections with supports, the central part and points of maximum load. Reading the instructions for reinforcing the floor slab in dwg format, you can find out that a 25 cm layer of concrete should be poured under the bottom grid. To maintain this size, it is necessary to lay out plastic coasters under the reinforcing units, which can be found in a hardware store. They are sometimes replaced with wooden bars, fixed to the base of the formwork with self-tapping screws. The upper mesh of the frame is filled with the same layer.

Hollow core slab reinforcement

Reinforcement of a hollow core slab should not be accompanied by making additional holes for communication networks. For this, it is better to purchase plates, the reinforcement of which was carried out with prestressing reinforcement. Otherwise, the bearing capacity of the product will be reduced.

After reviewing GOST 9561-91, you will be able to learn about a number of exceptions in the manufacture of certain types of hollow core panels. They are allowed not to use reinforcement of stressed reinforcement. Such panels have a thickness of 220 mm, and their length is 4,780 mm. The hole diameter varies from 140 to 159 mm. In the calculation of the reinforcement of a ribbed floor slab, it is necessary to include data on the compressive strength of concrete (11.5 MPa), which is 117 kgf/cm2. The fittings used correspond to class AIII. The design tensile strength is 355 MPa.

If the concrete beams will be carried out separately from the floor slab, then their calculation will not differfrom what is used in the case of conventional reinforced concrete rectangular beams. If concreting is carried out simultaneously, then the beams can be considered as T-beams.