When arranging floors in brick and concrete buildings, prefabricated reinforced concrete slabs are usually used. The weight of such structures are quite large. And therefore they are stacked in place in most cases using 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 fill in a reinforced concrete slab right on the spot. To carry out such work, of course, follows with the strict observance of all the required standards and technologies.
Design calculation
The device of monolithic ceilings is a very responsible procedure. Before embarking on the pouring of such a structure, it is imperative to make its most thorough calculation. If the stove is made with a violation of technology, living in a house in the future will simply be unsafe.
It is believed that a monolithic ceiling can only be of high quality if it can easily withstand a load of 150 kg / m 2 . In addition, when constructing such structures, according to the norms of SNiP, the safety factor of 1.3 should also be taken into account. That is, in the end, the plate must withstand a load of 195 kg / m 2 .
When calculating the monolithic overlap, the weight of the plate itself should also be added to this figure. This indicator is determined by multiplying the average density of reinforced concrete (2500 kg / m 3 ) by the thickness of the floor. In the end, an indicator of the maximum load on the walls will be obtained.
SNiP standards
Filling of monolithic reinforced concrete floors, including in country houses, must be carried out in compliance with the following rules:
- slabs are allowed to be filled only on load-bearing walls;
- if the overlap thickness does not exceed 15 cm, it is allowed to install a single-tier reinforcing cage, otherwise a two-tier should be used;
- the brand of 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 with a thickness of 10 mm should be used, a single-tier - 12 mm;
- technological holes for ventilation ducts, sewer riser, etc. should be prepared at the stage of filling the slab;
- the 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.
Pouring monolithic slabs is allowed in openings of a length of not more than 900 cm. Before installing the ceiling, check the walls for differences in height and, if necessary, eliminate defects.
Material selection
Cement for the device of a monolithic overlap, as already mentioned, should be used only the highest quality, expensive. Sand for mixing the solution is taken large river. Before use, it is mandatory to carefully sift it. Crushed stone for filling slabs use gravel or granite medium fraction. Mix the mortar for the slab usually 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, for the manufacture of the bottom of the mold under the plate, you can use corrugated board. In the future, such formwork will also play the role of external reinforcement of the structure. Professional flooring for filling the slab should be purchased the thickest - class N.
If desired, for the arrangement of a monolithic overlap, you can use a ready-made factory formwork. Such a construction will be easy to take, for example, for rent in some construction organization. Fill the plate in this case will cost more. But it will, of course, be more convenient to use a ready-made factory formwork with strong, easy-to-install telescopic supports.
The main stages of filling the slab
Work is underway on the construction of monolithic floors in houses as follows:
- mounted formwork;
- the reinforcing cage is made and installed;
- concrete mixture is being poured.
In order to ensure that the slab subsequently turns out to be safe in operation and durable, the required technologies must be strictly observed at all stages of the process of pouring it.
Formwork installation
The form for casting the floor slab is made as follows:
- install racks;
- between the supports they fill the crossbars from the timber;
- mount the cross beams;
- boards, plywood or profiled sheets are mounted on top of the beams.
Racks for self-assembly of formwork are made of logs. Install supports in increments of 1 m under the entire area of the future floor. The extreme supports are mounted from the walls at a distance of no more than 20 cm.
Sheathing on the beams is done in such a way that the board, plywood or profiled sheet rests on the walls around the entire perimeter without the formation of cracks. The side walls of the formwork are installed using supports made of timber. They are positioned in such a way that the finished plate comes into the walls of the building, subsequently no less than 120 mm.
When assembling the formwork for a monolithic slab, it is mandatory to use the building level. The bottom of the mold should be strictly horizontal, and the walls should be vertical.
If edged boards are used to assemble the formwork, the gaps between them are pre-blown with foam. In this case, the formwork itself should be covered with a film from the inside. This will prevent wood from drawing water out of the solution. In addition, to remove the formwork in the presence of a film in the future will be much easier.
What is important to know
Under the pressure of the poured plate, the ends of the racks installed under the bottom of the formwork can sometimes move. To prevent this from happening, the supports during the assembly of the form must necessarily be further strengthened. To do this, you just need to make a two-level tying racks.
The boards during the assembly of the reinforcing structure should be fastened to the posts both along and across. In this case, the first harness is supposed to be done at a height of 10 cm from ground level, and the second - approximately in the middle of the posts in height.
Frame mounting
The tiers of the reinforcing cage of a monolithic slab are collected as follows:
- Stack the longitudinal rods, and then the transverse ones so that the dimensions of the resulting cells are 120-150 mm.
- Joints of bars are tied with wire.
- If necessary, a second tier of the frame is made with a mesh size of 120-150 mm as well.
- Raise the second tier above the first to the required height and install it on supports made of a bent rod.
- Tiers are connected using staples.
The reinforcement of the monolithic floor should be made so that the frame is raised above the bottom of the formwork by 3 cm. For this, special plastic clips are placed under the intersection of the rods.
Grouting
The mixture for a monolithic floor slab should be made exclusively in a concrete mixer. When using such equipment, the highest quality homogeneous solution is obtained. Fill the slab relies in one step. In this case, it will turn out to be as durable as possible.
Actually, the process of filling the floor includes two main stages:
Pouring should be done as carefully and accurately as possible. At this stage, shifts in the formwork structures are possible. Too thick layer in the mold when pouring concrete is not poured. The purpose of this operation is to fill all joints and existing cavities.
As soon as the pouring is ready, its surface should be smoothed out with a shovel. This will remove all excess air from the thickness of the concrete and completely fill all the cavities.
The final casting of a monolithic overlap 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 the plate with such a thickness that 2.5-3 cm remain to its design top;
- level the shovel fill, as in the previous step;
- leave the concrete to dry for about 2 days.
Next, prepare the solution in the ratio of cement / sand as 1/3. Crushed stone is not put in the mixture. So much water is added to the solution to make it of medium density. With this mixture, fill the plate to the end and level its surface with the rule.
Tip
If the opening is wide and it is impossible to fill the slab in one step, several wooden lintels should be pre-installed in the formwork for monolithic overlapping. In this case, each compartment is filled with concrete subsequently separately.
The reinforcing cage in all the slabs so filled should be common. To do this, in each jumper board, cuts are made on both sides to a depth of 3 cm before installation. Through these cuts, the rods of the first and second tiers of the reinforcing frame are subsequently passed through.
To connect two adjacent floor slabs, a recess is made in the first of them. To do this, use an ordinary thick board. This element is fixed between the tiers of the reinforcement so that it does not rest on the rods below.
When pouring slabs with concrete, in any case, you should definitely use a vibrator. In no case should bubbles remain in the thickness of the overlap. This can greatly weaken the slabs. At the same time, the concrete itself should, of course, be sufficiently dense.
Caring for the first time
Strengthening the monolithic overlap, just like pouring it, must be carried out in compliance with all the required technologies. But it is equally important and to properly care for the finished stove at first. Errors made during this period can affect the quality of the overlap in the most negative way.
The concrete hardening process is always accompanied by the release of a certain amount of heat. It is precisely because of this that moisture begins to evaporate intensively from the thickness of the flooded structures. Lack of water, unfortunately, can lead to cracking of concrete. To prevent this from happening, in the first time after pouring, the overlap must be periodically moistened.
Surface cracks can be avoided 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 dousing the stove with water, you need to cover it with some unnecessary rags or burlap.
What more needs to be done
In the heat, the wetted floor should also be laid with a thick plastic film. If cracks form on the surface of the plate, during operation it will begin to crumble from above and below. And this, in turn, of course, will negatively affect its strength characteristics.
The last wetting of the floor filled with your own hands should be done just before the removal of the formwork. Remove the form from the finished plate about 10 days after pouring. In the future, the overlap will gain strength for another 3-5 weeks. After this time, you can proceed with the further implementation of the planned construction work. Different kinds of loads from construction equipment, constructions of the building of the second floor, etc. A properly poured matured monolithic slab can withstand absolutely no problems.