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:
- one-piece seamless construction is strong and reliable, does not blow through, does not form thermal bridges;
- smooth, even surface allows you to start finishing work without prior preparation;
- building construction in a short time;
- monolithic houses have a free layout;
- increased service life of reinforced concrete structures;
- complex architectural curvilinear elements and arches are quite easy to do.
Disadvantages of monolithic walls:
- poor sound insulation;
- mandatory wall insulation;
- The ability of concrete to conduct vibrations.
Why is reinforcement necessary?
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 bas alt or carbon fibers, which are filled with polymer. Such fittings are lightweight and not subject to corrosion.
Steel, compared to 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.
Armature comes in different shapes. But most often on sale you can find a 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 used in the construction of monolithic structures usually have a diameter in the range of 12-16 mm.
Nuances of reinforcement
When self-reinforcing 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 largeload.
- If rust is found on new rods, do not remove it. This can lead to a deterioration in the 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 with welding, the material loses strength.
- If concrete has already been poured into the formwork, then reinforcement cannot be placed. If the order of work is not followed, then the whole process must be started from the beginning.
- It is also not recommended to increase the reinforcing mesh along the length or height, since under heavy loads, gaps may form in the places of extension. If such loads are not expected, then these works must be performed with the highest quality.
There will be a heavy load on the walls of rooms located below ground level. Therefore, for the installation of the mesh, you need to choose high-quality reinforcement of standard sizes, and the reinforcement units of monolithic walls should be made of special wire.
Formwork and its installation
The erection of monolithic walls occurs with the help of formwork. At its core, it is a form for pouring concrete mix. The design is divided into two types:
- removable - removed after the concrete mixture has set;
- non-removable - is part of the wall, giving it additional qualities.
The most commonly used formwork made of expanded polystyrene. It is produced in the form of blocks, which are connected by locks. Styrofoam insulates the concrete layer 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 made.
- The second row of blocks should dig through all the vertical seams of the first row. That is, the method of laying is very similar to laying bricks. Locks located at the bottom and top of the edges must 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 needed is affected by the area to be poured with concrete mix and the thickness of the walls. The more concrete there is, the more supporting 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 mounting 1 m3 formwork is 40-43 pieces
Typical styrofoam block sizes:
- length - 1.2 m;
- width - 25 or 30 cm;
- height - 25, 30 or 40 cm;
- thickness of the inner wall - 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 steel meshes or a frame are used (for increasedstrength).
Reinforcement with reinforcement is most often performed horizontally and vertically. For this, rods with a diameter of 6-8 mm are used. They are arranged symmetrically at the side walls. Horizontal rods with vertical ones at opposite side walls are connected by transverse ties. Such connections are needed in order to prevent buckling of vertical reinforcement. Reinforcement of the corners of a monolithic wall is mandatory. For this, it is desirable 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 a wall between two openings (windows, doors). Reinforcement of small piers in monolithic walls occurs with the help of flat meshes mounted on both sides. If the floors are prefabricated, then a prefabricated frame is used. The flat walls of the first partition must be combined with spatial frames by connecting the rods.
Typical sequence for reinforcing basement walls
Strengthening the walls of the basement is necessary in any case and regardless of their thickness. Reinforcement of monolithic basement walls is as follows:
- Purchasing wire with a diameter of 3 mm. Reinforcement mesh can be bought in rolls (the most common option). It is she who 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 the mesh. It has an electric motor that starts the broachwire.
- The necessary calculations are being made. Be sure to take into account the level of groundwater when calculating the thickness of the walls. If the reinforcement of the monolithic wall of the basement needs to be carried out below the groundwater level, then the base slab should be from 20 cm thick and extend beyond the walls by 40 cm. Provided that the groundwater is far from the base, then the requirements are as follows: the thickness of the basement walls with the placement depth 1, 5-2, 5 m can be from 20 to 40 cm, and the lower wall can be non-powerful, and a protrusion beyond the building contour by 10 cm is allowed.
- Cleaning the formwork. In fact, this is the removal of construction dust and dirt from the structure.
- Production of reinforcing mesh. 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, as voids may occur when pouring concrete.
- Laying reinforcing mesh into the formwork. The required strength of a monolithic wall will be reinforced with a mesh in two layers. It is important that the diameter of the wire is not less than 12 mm, and the pitch both horizontally and vertically is not more than 40 cm. Both layers of the mesh must be connected in a checkerboard pattern every two cells. For connection use a wire of the same diameter. In addition, the reinforcement and its elements should not come into contact with the walls of the formwork.
- Checking the correct installation of the reinforcing mesh. The fittings must be placed strictly vertically. Permissible deviation 1-2 mm. The reason for this is the pressure of the soil on the basement walls. The correct location can be checked with a building or laser level.
- Pour concrete and soil around the walls. To provide anti-corrosion protection of reinforcement, special solutions are added to concrete.
Reinforce openings
Any opening is a weak point of the structure. Therefore, the perimeters of window and door openings must be strengthened additionally. If this is done incorrectly, the structure will crack and deform.
The size and type of metal structures to strengthen the openings is selected according to accurate calculations. It is necessary to take into account all the parameters that affect the integrity of the building structure: the material of the walls, the number of storeys, the size of the opening, the type of foundation, the weight of the roof.
There are several ways to reinforce openings in a monolithic wall:
- Reinforcement in one row using channels. This is the standard method, which consists in anchoring a metal frame to the wall. The width of the channel should be slightly larger than the width of the wall.
- Two-row reinforcement. The bottom line is to lay two channels on the wall, which are then additionally attached and welded to metal plates.
- Strengthening with corners. Metal elements are attached to the edges of the opening. Their inner part is connected with a strip, which is fixed in the wall. Racks in such cases are pulled together with studs or welded.
- Box gain. The channels are welded in parallel andvertically. A power I-beam serves as the upper element.
- Reinforcement from the corner. They are used when it is necessary to strengthen non-standard openings and holes.
- Combining methods. Depends on the design features of the openings.
Reinforcing holes in a monolithic wall is a rather complicated and responsible process, especially when an opening needs to be made in a load-bearing wall. An improperly executed 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.
Short algorithm for strengthening openings:
- Marking the future hole and reinforcement.
- Installing temporary props.
- Direct reinforcement using metal profiles.
- Cut.
Reinforcement of the basement floor
The ground floor most often has a height of 1.5 to 2.5 m.
- Install fixed plastic formwork. It also serves as a wall insulation.
- When installing the formwork, openings for windows and doors are laid, as well as metal sleeves for laying communications.
- You need to reinforce in the longitudinal direction of the walls. In this case, the metal rods are connected to the already installed vertical bars. The cross section of the rod is 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 option, eachthe next layer is poured three days after the previous one. The required hardness is set within 28 days.
- After the final hardening, you can proceed to further construction work.
Useful video on the topic and conclusions
In addition, a useful video on reinforcement.
In conclusion, it should be said that the process of reinforcing monolithic walls is not very complicated. But it requires correct calculation, accuracy of work performance and high-quality material.
