The reinforcement method is often used in construction. This is due to the fact that a frequently used material in construction - concrete, having high strength, also has an unfavorable property - brittleness, that is, it does not have elasticity. With uneven loads, vibrations, temperature changes, in large structures it would be impossible to use concrete without reinforcement. It would just crack and crumble and crumble.
What's going on?
What forces act on the structure? Let's figure it out without delving into the diagrams of the strength of materials. Under load or vibration, each part of the structure accepts and resists as far as strength is sufficient. For example, let's take the ceiling of the first floor, which is also the floor of the second floor. When loaded from above, the beam resists downward bending.
In this case, the upper part of the beam experiences a compressive force, and the lower part - a tensile force. Since concrete canwithstand more compressive force than tensile force, then in our case, if the beam is not reinforced, then the concrete will collapse faster along the bottom of the structure. First, cracks will appear in the lower part, and then the structure will crumble. To prevent this from happening, the reinforcement of the beam is made. The point is to extinguish the forces of tension and compression due to steel reinforcement or wire. The first has a high degree of resistance to stretching and compression. Therefore, before pouring concrete, a double mesh of reinforcement is made. The first mesh layer is placed at the bottom (10-50 mm from the bottom surface of the beam), the second at the top (10-50 mm from the top surface of the beam). The distance between the upper and lower mesh will depend on the thickness of the structure.
Pour concrete with reinforcement
The work is not particularly difficult. Everything is extremely simple and comes down to four steps:
- Formwork, assembly and installation.
- Reinforcement.
- Preparation of concrete.
- Filling.
First you need to prepare a site where concrete will be poured with reinforcement and formwork. The area of the site should be as even as possible. Next, you need to prepare materials, calculate the amount of sand, cement, crushed stone, reinforcement and ready-made concrete. The pouring starts from the foundation and is made from the lower sections to the upper ones.
Formwork
Reviews say that the most important part is the assembly and installation of formwork. In fact, this is a fence made of boards, plywood or metal sheets. Such a structure is easy to buildwith your own hands. Its task is to give concrete a certain shape. The formwork must have a flat, smooth surface, all parts must fit snugly against each other so that there are no gaps, gaps, protrusions. The smoother and better the formwork is assembled, the less work and materials will be used for plastering and finishing. The most popular material for the manufacture of formwork is laminated plywood sheets with a thickness of 16 to 24 mm. The thickness is selected depending on the area of \u200b\u200bthe structure. Plywood is easy to cut, with a jigsaw you can give the most complex configuration. Plywood has a fairly flat and even surface, and due to lamination, it can be easily removed or moved from the cured concrete. After removing the formwork from one section, the same sheets can be used to make other concrete structures. All cracks after assembly are filled with mounting foam. After the foam has hardened, it is necessary to cut off all excess flows inside the formwork. Otherwise, there will be voids in the concrete structure that will have to be sealed during finishing. The internal dimensions of the formwork, its shape at all levels must comply with the project. When everything is assembled, foamed and cleaned, you can proceed to the next stage - reinforcement.
Formwork for columns, "deck"
When pouring columns, mobile formwork is used. That is, they make it according to the thickness of the column, say, a meter high. After pouring and hardening of concrete, with the help of 4 jacks, the formwork is shifted up without dismantling, and the next layer is poured. This method is good if there are a lot of columns in the structure. This saves assembly time anddismantling.
The manufacture of formwork in a horizontal plane is called "deck decking" by builders. The peculiarity is that vertically adjustable racks are first installed, at a distance of 1.5-2 m. Boards 50-60 mm thick are placed on the racks, plywood sheets are placed on them (laminated side up). It is also important to ensure that there are no gaps, and that the sheets fit snugly against each other.
Reinforcement of horizontal structures
Reinforcement is performed in two ways. The first is a ready-made iron mesh for concrete reinforcement. Suitable for not very large loads. The mesh is stretched onto the formwork and fixed with wire through holes drilled in plywood. Adjusting shims are installed at the attachment points. This is necessary so that the mesh does not touch the formwork. Otherwise, after its removal from concrete, parts of the grid will be visible, which will then rust, collapse and spoil the appearance of the structure.
The second way is wired fittings. Judging by the reviews, this design will withstand heavy loads. All work is carried out without welding. Metal rods are laid out parallel to each other, through the same distance, and then, right on them, the rods are laid out perpendicularly so that they intersect at right angles. The pitch varies. All crossings of the rods are connected with a knitting (soft) wire. Just like for the grid, shims are used. After linking the lower part of the grid, the upper part is made in the same way. Adjusting supports are also installed between the upper and lower plane of the grids. Usually they are made from reinforcement bars, which are welded between the first and second layers at certain intervals. The latter are calculated so that the rods do not sag under their own weight, and the flatness of the structure is ensured.
Reinforcement of concrete wall, columns
For walls, the rebar mesh can be tied horizontally and then lifted and fixed vertically. But with large volumes, it is more convenient to knit the mesh in a vertical position. When concreting walls, the mesh is first knitted, then spacers are installed (to adjust the thickness of the wall).
Usually plastic or plastic spacers are used. Because after the formwork is removed, they will remain in the concrete, and plastic or plastic bushings will neither rust nor decompose. After their installation, formwork elements are placed. Opposite parts are connected with metal screw studs, which are passed through spacers. This is done so that the studs do not come into contact with concrete. Then the nuts of the studs are tightened, thus pressing the opposite parts of the formwork against the spacer sleeves. The sides of the wall are attached to the fronts with clamps or clips.
Reviews note that when reinforcing vertical structures (be it walls or columns), the reinforcement bars should be above the surface of the area to be poured. Do soin order to be able to associate this section with a horizontal section of the fill. As a rule, the last (the highest section of the fill) has a horizontal plane.
Preparation of concrete
The main guarantee of the quality of the prepared concrete mixture is the exact observance of the proportions of all components. It is important to pay attention to the brand of cement used. Different grades of material correspond to different volumes of sand. You should also consider the hardness of the water. If it is fundamentally important to achieve maximum concrete strength, then it is better to check this indicator in the laboratory before preparing the mixture. In practice, water hardness is reduced using the most common detergents (the most budget option is dishwashing gel).
It's very important to follow the sequence. First, water is poured into the container, then cement, crushed stone and finally sand. For small volumes, manual tools or small automated ones are used. For large volumes, special machines are used.
Filling
An equally important part of the work is filling. Before it, you should once again check the tightness of the formwork, the presence of foreign holes. The formwork should be smeared with used machine oil or any other greasy mixture in order to make it easier to dismantle it. It is necessary to lay out the concrete mixture so as not to displace the reinforcing mesh. After pouring, it is required to carefully walk with a vibrator to compact the concrete over the entire plane of the area to be poured. This is necessary so that voids do not form, especially for complex configurations, where inthere might be air left in your pockets.
Conclusion
The key to the success of construction is the exact execution of all operations, compliance with dimensions, calculations. All work at any stage requires attention, knowledge and skills. If everything is calculated correctly, and the work is done with high quality, then the design will be strong and durable. As an alternative to classical reinforcement, there are fiber-reinforced concrete. The essence of reinforcing concrete with fibers lies in the fact that the latter, by their nature, are able to perceive greater stresses than the concrete matrix.
