- Monolithic slab thickness
- Slab formwork
- Inventory formwork
- Homemade formwork
- Combined method
- Floor reinforcement
- Floor concreting
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 elements of reinforced concrete floors..
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:
- Highest load bearing capacity of known materials.
- The most durable material available.
- Relatively cheap raw materials (for concrete).
- High qualifications of the entire team are not required to carry out the work (1-2 leading specialists are enough).
- Combined functions: base of the second floor floor, armopoyas, connection of all walls to each other.
- Correctly arranged monolithic construction excludes the appearance of deformation defects (“steps”, distortions, cracks).
Disadvantages of concrete floors:
- Labor intensity of construction. The work is connected with the device of horizontal formwork of high strength and rigidity.
- An accompanying material is involved, which after concreting may become unusable – plywood, flanging board, racks (wooden).
- Heavy construction weight – strong walls and foundation are required.
- High thermal conductivity of concrete – all areas open to the outside must be insulated.
- 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, dormitories (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.
Monolithic slab thickness
Due to the high specific gravity of concrete (2400 kg / m3) 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 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 many years of 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”. Adequate brick wall thickness – 380 mm (1.5 bricks).
Like any reinforced concrete element, the floor requires the installation of a form for concrete – formwork. Since the ceiling has significant dimensions in area and is at a height, the formwork for it looks like a table: a solid plane filling 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.
A set of factory products, which includes:
- Racks – screw sliding jacks, up to 4 m long.
- Equipment for racks – “tripods” at the bottom for the stability of the freestanding jack and “crown” at the top for seating the table beams.
- Wooden beams – factory-made glued I-profile products with a height of 200 mm and a length of up to 4.2 m.
- Film faced plywood – sheets of plywood 18–24 mm thick, 1220×2440 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 being 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 work, as well as the quality of the plane. The disadvantages include the risk of a delay in the lease term.
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:
- Time-consuming construction requiring advanced carpenter skills.
- Large waste of material – up to 20% will become unusable.
- Problematic height adjustment (horizontal installation).
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 the board. Or rent a laminated plywood, and assemble the “table” frame from an improvised forest. There can be many combinations.
For the device of the reinforcing cage of the hanging reinforced concrete floor 200 mm thick, a mirror mesh made of reinforcement A3 O 16 mm with a cell of 150-180 mm is used. When using on-site concrete, we recommend strengthening the frame by using a smaller bar spacing of 150 mm. If the concrete is factory made, a pitch of up to 200 mm is allowed In the places of support and abutment of elements (support on a wall, column, capital), we recommend making reinforcements – add rods.
There are concreting rules that should be followed unquestioningly so as not to subject the structure to destruction in the future:
- 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..
- When concreting in a cool period (0 … + 5 ° С), use special antifreeze additives. Read more about winter concreting in this article..
- Be sure to use vibrators – deep or surface vibrators. Vibration-free concrete has 40-50% of its design strength. You will find more information about concreting in our article..
- The slab formwork is dismantled no earlier than 28 days after the concrete is placed.