When arranging floors in brick and concrete buildings, ready-made reinforced concrete slabs are usually used. The weight of such structures are quite large. And therefore they are stacked in place in most cases with the help of a truck crane. But sometimes it happens that the organization of the entrance of special equipment to the place of work becomes impossible. In this situation, it is usually necessary to pour a reinforced concrete slab right on the spot. To perform such work, of course, should be in strict compliance with all applicable standards and technologies.
Design calculation
The installation of monolithic ceilings is a very responsible procedure. Before proceeding with the pouring of such a structure, it is necessary to make its most careful calculation. If the stove is made in violation of technology, it will simply be unsafe to live in the house in the future.
It is believed that a high-quality monolithic ceiling can only be if it can easily withstand the load in150 kg/m2. In addition, when erecting such structures, in accordance with the SNiP standards, the safety factor in 1.3 should also be taken into account. That is, in the end, the slab must withstand a load of 195 kg/m2.
When calculating a monolithic floor, the weight of the slab itself should be added to this figure. This indicator is determined by multiplying the average density of reinforced concrete (2500 kg/m3) by the floor thickness. In the end, you will get an indicator of the maximum load on the walls.
SNiP standards
Pouring of monolithic reinforced concrete floors, including in country houses, must be carried out in compliance with the following rules:
- pouring slabs is allowed only on load-bearing walls;
- if the thickness of the ceiling does not exceed 15 cm, it is allowed to install a single-tier reinforcement cage, otherwise a two-tier one should be used;
- grade cement for pouring the slab should use M400-M600;
- the ratio of the thickness of the plate and its area should be 1:30;
- for the manufacture of a two-tier frame, a rod 10 mm thick should be used, a single-tier one - 12 mm;
- technological holes for ventilation ducts, sewer riser, etc. should be prepared at the stage of pouring the slab;
- reinforcement must be immersed in concrete so that the distance from the extreme rods to the outer planes of the slab is at least 3 cm.
It is allowed to pour monolithic slabs in openings no longer than 900 cm.check the walls for height differences and correct if necessary.
Selection of materials
Cement for monolithic flooring, as already mentioned, should be used only the highest quality, expensive. Sand for mixing the solution is taken large river. Before use, it must be carefully sieved. Crushed stone for pouring the slab is used gravel or granite of the middle fraction. The mortar for the slab is usually kneaded in the proportion of cement / crushed stone / sand as 1/1/2.
Formwork for overlapping, if desired, can be made from a thick edged board. However, it is better to fill the bottom with laminated plywood. In this case, the ceiling on the lower floor will subsequently turn out to be perfectly flat. Also, corrugated board can be used to make the bottom of the mold for the slab. In the future, such formwork will also play the role of external reinforcement of the structure. The corrugated board for pouring the slab should be purchased the thickest - class H.
If desired, ready-made factory formwork can also be used to arrange a monolithic ceiling. It will not be difficult to take such a design, for example, for rent in some construction organization. Filling the plate in this case will cost more. But it will, of course, be more convenient to use ready-made formwork with durable, easy-to-install telescopic supports.
The main stages of pouring the slab
Work is in progress on the construction of monolithic floors in houses as follows:
- mountedformwork;
- manufactured and installed reinforcing cage;
- concrete is being poured.
In order for the plate to subsequently turn out to be safe in operation and durable, the prescribed technologies must be strictly observed at all stages of work on its pouring.
Formwork installation
The mold for pouring the floor slab is made as follows:
- install racks;
- crossbars are stuffed between the supports;
- mount crossbeams;
- Boards, plywood or corrugated board are fixed on top of the beams.
Racks for self-assembly of formwork are made of logs. Install supports in 1 m increments under the entire area of \u200b\u200bthe future floor. From the walls, the extreme supports are mounted at a distance of no more than 20 cm.
Sheathing along the beams is done in such a way that the board, plywood or profiled sheet abut against the walls around the entire perimeter without the formation of cracks. The side walls of the formwork are installed using props made of timber. They are positioned in such a way that the finished slab comes on the walls of the building subsequently by at least 120 mm.
When assembling the formwork for a monolithic floor slab, it is imperative to use the building level. The bottom of the form should be strictly horizontal, and the walls - vertically.
If edged boards are used to assemble the formwork, the gaps between them are pre-blown with mounting foam. In this case, the formwork itself from the inside should be covered with a film. This will preventpulling wood out of a solution of water. In addition, it will be much easier to remove the formwork in the future with the presence of a film.
What is important to know
Under the pressure of the poured slab, the ends of the racks installed under the bottom of the formwork can sometimes shift. To prevent this from happening, the supports during the assembly of the form must be further strengthened. To do this, you just need to make a two-level strapping racks.
When assembling the reinforcing structure, the boards should be fastened to the racks both along and across. In this case, the first strapping is supposed to be done at a height of 10 cm from the ground level, and the second - approximately in the middle of the pillars in height.
Installing the frame
The tiers of the reinforcing cage of a monolithic floor slab are assembled as follows:
- The longitudinal rods are laid, and then the transverse ones in such a way that the dimensions of the cells formed as a result are 120-150 mm.
- The joints of the bars are tied with wire.
- If necessary, a second tier of the frame is made with a cell size of 120-150 mm.
- Raise the second tier above the first to the required height and install it on supports made of bent rod.
- Connect the tiers using staples.
Reinforcement of a monolithic ceiling should be done in such a way that the frame is raised above the bottom of the formwork by 3 cm. To do this, special plastic clamps are placed under the intersection of the rods.
Filling solution
Mix for monolithic floor slab should beproduced exclusively in a concrete mixer. When using such equipment, the highest quality homogeneous solution is obtained. It is supposed to pour the floor slab in one step. In this case, it will turn out to be as strong as possible.
Actually, the process of filling the ceiling includes two main stages:
- spill;
- finish fill.
Washing should be done as carefully and accurately as possible. At this stage, movement of the formwork structures is possible. Concrete is not poured into the mold when pouring too thick a layer. The purpose of this operation is to fill all the seams and existing cavities.
As soon as the spill is ready, its surface should be smoothed out with a shovel. This will remove all excess air from the thickness of the concrete and finally fill all the cavities.
The final pouring of a monolithic slab is made of concrete prepared in the same proportions, but with the addition of less water - that is, thicker. Perform this procedure as follows:
- fill in a slab of such thickness that 2.5-3 cm remains to its calculated top;
- level the fill with a shovel, as in the previous step;
- leave the concrete to dry for about 2 days.
Next, prepare a mortar in the proportion of cement / sand as 1/3. Crushed stone is not put in the mixture. Water is added to the solution so much that it turns out to be of medium density. The slab is poured with this mixture to the end and its surface is leveled with the rule.
Tip
If the openingwide and it is impossible to pour the slab in one go, several wooden lintels must first be installed in the formwork for a monolithic ceiling. In this case, each compartment is subsequently filled with concrete separately.
The reinforcing cage in all slabs filled in this way must be common. To do this, cuts are made on both sides to a depth of 3 cm in each jumper board before installation. The rods of the first and second tiers of the reinforcing frame are subsequently passed through these cuts.
To connect two adjacent floor slabs, a notch is made in the first of them. To do this, use the usual thick board. This element is fixed between the tiers of reinforcement so that it does not rest on the bars below.
When pouring concrete slabs, in any case, be sure to use a vibrator. In no case should bubbles remain in the thickness of the overlap. This can greatly weaken the plates. At the same time, the concrete itself should, of course, turn out to be quite dense.
First time stove care
Strengthening of a monolithic floor, just like its filling, must be carried out in compliance with all required technologies. But it is equally important and properly care for the finished stove at first. Mistakes made during this period can adversely affect the quality of the overlap.
The process of solidification of concrete is always accompanied by the release of some amount of heat. It is because of this that moisture begins to evaporate intensively from the thickness of the flooded structures. Lack of water, unfortunately, can lead to concrete cracking. To prevent this from happening, in the first time after pouring, the overlap must be periodically moistened.
It is possible to avoid the appearance of surface cracks by wetting the plate with water, for example, from buckets. But it is best to use a garden hose with a spray nozzle for this purpose. Before pouring water over the stove, you need to cover it with some unnecessary rags or burlap.
More things to do
In the heat, the moistened overlap should also be additionally laid with a thick plastic film. If cracks form on the surface of the plate, it will begin to crumble from above and below during operation. And this, in turn, of course, will negatively affect its strength characteristics.
The last wetting of the do-it-yourself overlap should be done just before the formwork is removed. The mold is removed from the finished slab approximately 10 days after pouring. In the future, the overlap will gain strength for another 3-5 weeks. After this time, you can proceed to the further implementation of the planned construction work. All kinds of loads from construction equipment, second floor building structures, etc. A properly poured, matured monolithic slab can withstand absolutely no problems.
