Reinforced monolithic structures were first used in Russia in 1802 during the construction of the Tsarskoye Selo palace. The material was metal rods. Monolithic reinforced concrete structures allow the construction of buildings with different levels of complexity and configuration. Often this technology is used in the construction of tanks, foundations, ceilings, walls.
Advantages and disadvantages of monolithic frame technology
Monolithic reinforced walls have the following advantages:
- the seamless construction without joints is strong and reliable, it does not blow, it does not form temperature bridges;
- smooth smooth surface allows you to start finishing work without preliminary preparation;
- building construction in a short time;
- monolithic houses have a free layout;
- increased service life of reinforced concrete structures;
- complex architectural curved elements and arches are easy enough.
Disadvantages of monolithic walls:
- low sound insulation;
- obligatory wall insulation;
- the ability of concrete to vibrate.
What is the need for reinforcement?
In order to increase the strength of concrete and reduce its quantity, reinforcement is used. In theory, any material can act as reinforcement. But in practice, steel and composite are most often used.
Composite is a complex of materials. The basis can be basalt or carbon fibers, which are filled with polymer. Such fittings are lightweight and not subject to corrosion.
Steel, in comparison with composite, has much greater strength and relatively low cost. In the process of reinforcing monolithic walls, channels, corners, I-beams, corrugated and smooth rods are used. In the case of creating complex building structures, metal meshes are used for reinforcement.
The fittings are of various shapes. But most often on sale you can find the rod. In the construction of low-rise buildings, corrugated rods are usually used. They have a low price and excellent adhesion to concrete, which makes them very popular among buyers. Steel rods that are used in the construction of monolithic structures usually have a diameter in the range of 12-16 mm.
Reinforcement Nuances
With independent reinforcement of monolithic walls, the following factors should be taken into account:
- When creating a reinforcing mesh, it is best to use new steel bars because they can withstand heavy loads.
- If rust is found on new rods, do not remove it. This can lead to poor adhesion of concrete and rods.
- To cut the rods, it is best to use a grinder. If the rod needs to be bent, then the place of the bend is preheated immediately before the manipulation itself. But this is highly discouraged. As in the case of welding, the material loses strength.
- If concrete has already been poured into the formwork, then reinforcement cannot be installed. If the order of work is not followed, then the whole process must be started again.
- It is also not recommended to increase the reinforcing mesh in length or height, as under heavy loads in the places of building breaks can form. If such loads are not expected, then you need to perform these works as efficiently as possible.
On the walls of rooms located below ground level, there will be a heavy load. Therefore, for mounting the mesh, you need to choose high-quality reinforcement of standard sizes, and the nodes of reinforcing monolithic walls should be made of special wire.
Formwork and its installation
The construction of monolithic walls occurs with the help of formwork. At its core, it is a mold for pouring concrete. The design is divided into two types:
- removable - is removed after the concrete mixture hardens;
- fixed - is part of the wall, giving it additional qualities.
Most often, formwork made of expanded polystyrene is used. It comes in the form of blocks that are connected by locks. Expanded polystyrene insulates a layer of concrete and increases sound insulation.
Installation of fixed formwork is quite simple:
- Formwork blocks are laid on the waterproofing layer of the foundation. This must be done in such a way that reinforcement fastened to the foundation passes through them. In the process of laying the first row of blocks, slopes for doors and bends of internal walls are formed.
- The second row of blocks should dig through all the vertical seams of the first row. That is, the laying method is very similar to bricklaying. Locks located at the bottom and top of the edges should be connected without gaps.
- The third row is the most important. It is on it that all layers of blocks are aligned.
The amount of material required is affected by the area that will be poured with the concrete mixture and the wall thickness. The more concrete there is, the more support walls are needed.
In fact, the process of calculating the formwork system is not complicated. The size of the structure is calculated by dividing by the height and width of the board. For example, the average number of boards for the installation of 1 m 3 formwork is 40-43 pcs.
Typical polystyrene block sizes:
- length - 1.2 m;
- width - 25 or 30 cm;
- height - 25, 30 or 40 cm;
- the thickness of the inner wall is 5 cm;
- outer wall thickness - 5 or 10 cm.
Reinforcement of monolithic walls and piers
The percentage of reinforcement from the wall section is about 10%. For this process, reinforcing mesh made of steel or frame is used (for increased strength).
Reinforcing reinforcement is most often performed horizontally and vertically. To do this, use rods with a diameter of 6-8 mm. They are placed symmetrically at the side walls. Horizontal rods with vertical at opposite side walls are connected by transverse ties. Such joints are needed in order to prevent buckling of vertical reinforcement. Reinforcement of corners of a monolithic wall is mandatory. For this, it is advisable to use U-shaped clamps. They provide the necessary fastening of the ends of the horizontal rods and protect the vertical ones from buckling.
A wall is a part of the wall between two openings (windows, doors). Reinforcement of small piers in monolithic walls occurs with the help of flat grids mounted on both sides. If the floors are prefabricated, then use a prefabricated frame. The flat walls of the first wall must be combined with spatial frames connecting the rods.
Typical basement wall reinforcement sequence
Strengthening the walls of the basement is necessary in any case and regardless of their thickness. Reinforcement of monolithic basement walls is as follows:
- Purchase of wire with a diameter of 3 mm. Reinforcement mesh can be bought in the form of rolls (the most common option). It is it that is most often used for floor screed or wall reinforcement.
- Tool preparation. Usually enough wire and wire cutters. But the gun for knitting reinforcement will speed up the process of knitting a mesh. It has an electric motor that starts the wire drawing.
- The necessary calculations are made. The level of groundwater occurrence is necessarily taken into account when calculating the wall thickness. If the reinforcement of the monolithic basement wall needs to be carried out below the groundwater level, then the base plate should be 20 cm thick and 40 cm beyond the walls. Provided that the groundwater is far from the base, the requirements are as follows: basement wall thickness with depth 1.5-2.5 m can be from 20 to 40 cm, and the lower wall can be non-force, and a protrusion beyond the contour of the building by 10 cm is allowed.
- Formwork cleaning. In fact, this is the removal of building dust and dirt from the structure.
- Reinforcing mesh fabrication. At this point, it is important to correctly determine the size of the cell. For basement walls, it can be in the range of 25-35 cm. Accordingly, the smaller the link, the stronger and more reliable the mesh. But cells less than 5 cm are not allowed, since voids may occur when pouring concrete mixture.
- Laying reinforcing mesh in the formwork. The required strength of a monolithic wall will give reinforcement with a mesh in two layers. It is important that the diameter of the wire is not less than 12 mm, and the step both horizontally and vertically is not more than 40 cm. Both layers of the mesh must be staggered every two cells. To connect using a wire of the same diameter. In addition, the reinforcement and its elements should not be in contact with the walls of the formwork.
- Checking the correct installation of the reinforcing mesh. The fittings should be placed strictly vertically. Tolerance 1-2 mm. The reason for this is soil pressure on the basement walls. Correct location can be checked by building or laser level.
- Pouring concrete and falling asleep near the walls. To ensure corrosion protection of the reinforcement, special solutions are added to the concrete.
Reinforcement of openings
Any opening is a design weakness. Therefore, the perimeters of window and doorways necessarily strengthen additionally. If this is done incorrectly, then the structure cracks and deforms.
The sizes and type of metal structures for reinforcing the openings are selected according to accurate calculations. It is necessary to take into account all the parameters that affect the integrity of the building structure: wall material, number of storeys, opening size, type of base, roof weight.
There are several ways to reinforce openings in a monolithic wall:
- Reinforcement in a row using channel channels. This is the standard method, which consists in anchoring the metal frame to the wall. The width of the channel should be slightly larger than the width of the wall.
- Double row reinforcement. The bottom line is to put two channels on the wall, which are then additionally attached and welded to metal plates.
- Corner reinforcement. Metal elements are attached to the edges of the opening. Their inner part is connected using a strip that is fixed in the wall. Racks in such cases are pulled together with studs or welded.
- Box gain. Channel bars are welded in parallel and vertically. As the upper element is a power I-beam.
- Reinforcement from the corner. Apply when it is necessary to strengthen non-standard openings and holes.
- A combination of methods. Depends on the design features of the openings.
Reinforcing holes in a monolithic wall is a rather complicated and critical process, especially when the opening needs to be made in the supporting wall. An improperly designed opening device can lead to a significant decrease in the reliability of the building. Therefore, such processes are best done with the help of a specialist.
A brief algorithm for enhancing openings:
- Marking future holes and reinforcing.
- Setting temporary backups.
- Direct reinforcement using metal profiles.
- Cutting.
Ground floor reinforcement
The ground floor most often has a height of 1.5 to 2.5 m. The reinforcement of the monolithic wall of the basement is as follows:
- Install fixed plastic formwork. It simultaneously serves as a heater for walls.
- When installing the formwork, openings for windows and doors are laid, as well as metal sleeves for laying communications.
- Reinforce need in the longitudinal direction of the walls. In this case, the metal rods are connected with already installed vertical rods. Rod cross section not less than 10 mm.
- If you have the necessary equipment and materials, it is better to pour concrete immediately. If this is not possible, then the concrete mixture is poured in layers. In the second embodiment, each subsequent layer is poured three days after the previous one. The set of required hardness occurs within 28 days.
- After final hardening, you can proceed with further construction work.
Useful video on the topic and conclusions
In addition, a useful video on the topic of reinforcement.
In conclusion, it is worth saying that the process of reinforcing monolithic walls is not very complicated. But the correct calculation, accuracy of work and quality material are required.