Concrete floors: prefabricated and monolithic structures in

Concrete floor beams, as well as slab and other structures are used to form horizontal surfaces of a building under construction. They must be strong enough to efficiently transfer loads to vertical supporting structures, and therefore they are almost always reinforced either with steel reinforcement or other elements.

Below we describe the features of these architectural details, as well as a number of tips on their independent arrangement.

Overview of building floors

Design requirements

The overlap is a horizontal structure, which divides the various rooms - the basement, the floors, the attic, etc. Besides the fact that they perceive and transmit static loads, these parts also act as horizontal screeds of the entire building.

The requirements for overlapping are rather serious:

• First, they must be strong enough and durable.
• Secondly, their rigidity and the absence of deformations are extremely important.
• Also for these elements desirable high fire resistance, water and air tightness.
• Additional wishes include sound and thermal insulation characteristics, but usually they are realized only in low-rise construction. In other cases, additional warming of concrete floors is required.

From this point of view, designs made of reinforced concrete using monolithic or prefabricated technology look preferable. Wooden beam floors also have the right to exist, but their carrying capacity is insufficient for use in conditions of high weight and operational loads.

Monolithic varieties

By arrangement, basement, attic and interfloor floors are divided into two groups:

• Monolithic, which are poured directly on the object.
• Prefabricated, which are mounted from individual elements.

Below we consider the features of the construction of both types.

Instructions for casting monolithic construction is as follows:

• Reinforcing rods with a diameter of 10 to 20 mm (depending on the design load) are welded to metal plates in the so-called reinforcing belt around the perimeter of the building.
• We tie the rods with wire or weld the honey with ourselves, forming a reinforcing mesh.. For most buildings, the optimal cell size will be 200x200 mm.

Note! When forming the frame, spaces for laying communications are foreseen in advance, for example, the passage of a chimney through a concrete ceiling, etc.

• Next, from OSB shields or thick boards we assemble formwork. Wooden parts in order to avoid swelling is to wrap a dense polyethylene. All parts of the formwork are fastened together, stuffing wooden bars on the outside.
• Assembled shields fastened to the fixture with a sufficiently thick wire. When installing, make sure that the formwork is located below the metal parts by 30-50 mm. To facilitate the positioning of today are actively used special remote liners.
• In order to avoid formwork sag, we support the parts with wooden beams or telescopic rods, after which we proceed to pouring.
• It is advisable to fill the slab in one go - so voltage zones will not form in concrete. To do this, you need to prepare a large amount of the solution, which is problematic in the home.
• The solution is simple: you need to buy ready-made concrete in the required amount. Of course, the price will be higher, but you will not have to bother with combining several sites by installing mortgages.

Since the concrete in this case will be held solely on the reinforcement, the formwork can be removed only after the cement has completely hardened. The optimal exposure time is about 28 days.

As a result, we get a monolith with excellent mechanical characteristics. It perfectly resists loads, and to remove even a small part of it (for example, when building a hatch), cutting of reinforced concrete with diamond circles should be used.

Prefabricated varieties

If the dimensions of the opening allow, then you can equip the prefabricated structure of reinforced concrete slabs:

• We select the dimensions of concrete floors in such a way that the plate or module covers all free space.
• With the help of a truck crane we lay the parts on the reinforced belt, connecting them together with cement mortar.

Note! The edges of the slab should come on a support not less than 12 cm along the entire length.

• To increase the strength of the joint, we weld the metal parts of the plates to the mortgages in the walls of the building.

This method has several advantages:

• First, the speed of installation works increases significantly.
• Secondly, the dimensions of the plates and their bearing capacity are unified, which greatly simplifies the calculation of the concrete floor.
• Thirdly, hollow products provide better thermal insulation than reinforced monolith.

At the same time, this technique can be implemented only for small spans. In addition, when laying the plates, it is difficult to equip the necessary openings and communication paths in advance, so it may take a very time-consuming cutting of concrete floors using expensive tools.

Mounting issues

Tips for calculating

If you are doing all the work yourself, then you should definitely take into account such a parameter as the thickness of the concrete floor between floors.

Here you need to focus on these numbers:

• In the case of slab floors, everything is simple: for spans up to 4 m we take parts with a thickness of 16 cm, for spans of more than 4 m - 22 cm. Deviations from this rule are met, but in housing construction they are quite rare.
• When erecting a monolithic structure, one must take into account the own weight of the floor and capital base, the mass of the load with a safety margin, etc. Knowing this data, as well as the opening area, we will be able to calculate the specific load on the monolith in kg / m².

Note! According to SNiP, the standard value of this indicator is 150 kg. However, the safety factor (1.3) must be taken into account, so ideally we should work with values ​​of the order of 195 - 200 kg / m².

• Based on these numbers, we select the thickness of the slab, as well as the section and configuration of the reinforcement.

Without appropriate skills, it is quite difficult to perform such calculations at the required quality level. That is why we strongly recommend either using special calculator programs (Lira, SCAD, STAAD and its analogues), or to contact professional designers.

Independent production of plates

A description of the technology for arranging such structures would be incomplete if we did not tell us how to make a concrete floor with our own hands. In fact, if you have certain skills, you can pour a few fairly solid plates.

This is done like this:

• From boards up to 50 mm thick or plywood reinforced with wooden fins, we assemble the bottom for future shape. The side walls are made of boards 25-30 mm.

Tip! We select the formwork dimensions in accordance with the dimensions of the span.

• Bottom we cover with roofing material or plastic wrap: so we will avoid leakage, and the process of excavation will be facilitated many times.
• Then we assemble the reinforcement cage. Since the welding machine is quite expensive, with independent production, the most often, knitting is done with thin wires.

Tip! To facilitate the design and improve its operational properties, it is possible to lay longitudinal polypropylene pipes with a diameter of about 60 mm in the reinforcement.

• The frame is lowered into the formwork, installing at a distance of 30-50 mm from the bottom. To do this, you can use both special gaskets and the available material - pebbles, fragments of dense bricks, etc.
• Fill the formwork with reinforcement with a cement-based solution with a grade not lower than M350 with the addition of sand and gravel. Carefully seal the concrete material with splicing or vibration treatment.

During drying, we support the surface of the slab in a wet state, covering it with sacking or polyethylene. We carry out the stripping for at least two weeks, after which we dry the product in the open form. The total time for a concrete product to build up strength should be at least 28 days.

Conclusion

Steel concrete floors, despite the relatively high cost and complexity in the construction, today have virtually no alternatives. Moreover, in most cases it is desirable to involve professionals for their design of the arrangement, since the cost of an error in this matter is very high. In more detail the nuances of the raised topic are covered in the video in this article.