Reinforced concrete floors - prefabricated and monolithic

21-08-2018

Building

During the construction of brick, stone, concrete and cinder-concrete buildings using floors of reinforced concrete. 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 take a closer look at what their types are, and how you can perform the overlap yourself.

Types of designs

All existing reinforced concrete floors can be divided into two types:

Prefabricated;
Monolithic.

Now take a closer look at each type of structures.

Monolithic

Reinforced concrete monolithic floors, as opposed to prefabricated ones, are poured on the object, directly at its location.

They are of several types:

Ribbed - represent a system of interconnected intersecting monolithic beams and slabs. These floors consist of the following elements:

Runs (main beams)
Ribs (beams located perpendicular to the girders).

Caisson - are intersecting beams of the same section, which are monolithically connected with the slab. The grooves between these beams are called caissons.

Non-beamed - represent the continuous monolithic plates laid on columns. At the top of the plates there is a thickening (capitals). The reinforcement rods are located at the bottom of the plate. The frame of the slab is placed at a distance of several centimeters from the formwork in order to fill this space with concrete. Such structures are used only in cases where the span does not exceed three meters.

Girder reinforced concrete floor - used if the length of the span is more than three meters. In this case, reinforced concrete beams with a pitch of about 150 centimeters are laid on the wall. The beams are connected to the reinforcement slab overlap. I must say that reinforced concrete beams of overlap in accordance with GOST 20372-90, there are 16 types. Their largest standard length is 18 meters.
Ribbed - can be used if the length of the span does not exceed 6 m. If the length is longer, then reinforcement is performed with a transverse beam. As a rule, this type of construction is used in cases when it is necessary to obtain a flat ceiling. The distance between the beams should be no more than a meter. When mounting this design, the fixing elements are attached to the reinforcement cage, which makes it possible to hem the ceiling with boards. The disadvantages of this system include the complexity of its device.

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. Make knitted frame more difficult. For these purposes, use a special knitting wire with a thickness of not more than 2 mm.

Prefabricated конструкции делятся на следующие группы:

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

Prefabricated structures include reinforced concrete hollow core floor panels, which are very popular. They are monolithic reinforced concrete slabs, reinforced reinforcing cage.

Inside the panels are hollow cylindrical shapes 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 at the fracture. Such panels are of different lengths and widths.

Production of reinforced concrete slabs

Now consider how to perform beamless overlap. I must say that reinforced concrete beams do very rarely with their own hands.

Materials and tools

So, for the construction of the structure you need to prepare the following materials and equipment:

Steel reinforcement;
Brand cement not lower than M400;
Sand;
Rubble or gravel;
Welding machine;
Boards, timber;
Concrete mixer;
Various power tools.

Manufacturing formwork and frame

First of all, you need to do your own formwork. For the bottom of the slab, you can use plywood boards not less than 2 cm thick, reinforced with bars, or board boards 4-5 cm thick.

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

The formwork is assembled in the following order:

First of all, bottom shields are laid. For their installation, use supports and cross beams.
Then install the sidewall.
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 build 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 mesh size of the grid 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 below and above. Those. its thickness should be 4 cm thinner than the plate thickness.

Tip! When performing the frame, it is not recommended to fit the reinforcement along the length, as this will affect its strength.

Fill

To fill the slab, the solution should be made in the following proportion:

One piece of cement M400;
Two pieces of sand;
Four parts of gravel or crushed stone for concrete with a diameter of not more than 20 mm;
Water to obtain the necessary consistency.

Fill perform without interruption, starting from one corner and ending with the opposite. When this is done, the tamping solution of the deep vibrator.

After pouring, the concrete is protected from quick drying. For this, it is covered with wet sacking and sawdust. The first 8-10 days periodically moisten the surface.

After 2-3 weeks, after the solution has reached about 80 percent of its strength, the formwork is removed from the concrete. However, it is possible to operate the plates only after 28 days.

Tip! After the slab has been machined, it may need to be machined. The most effective way to perform procedures with a diamond tool. In particular, reinforced concrete can be cut with diamond circles, grinding with diamond cups or diamond drilling holes in concrete.

It must be said 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 slabs, beams, shells, etc. The procedure is quite complicated, so experts must deal with it.

Conclusion

As we found out, there are many types of concrete floors, which are designed for 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, according to the technology indicated above.

From the video in this article, you can get more information on this topic.