In residential and industrial construction, concrete foundation is currently one of the most popular. It is suitable for almost any decorative coatings, and it can be operated in its original form, if appropriate processing is carried out. Subject to the pouring technology, the main advantages of such a coating are preserved, among which are:
- resistance to destruction;
- high strength;
- durability.
What solution to use for pouring
Pouring a concrete screed may include the use of one of several solutions known today. The mixture must be selected taking into account further cladding and minimum strength. The coating of the composition of the M-150 will be able to withstand a force of 150 kg / cm 2 . If you plan to use a self-leveling compound, then the requirements here are even higher - from the M-200.
A classic mortar, which is used for a conventional concrete screed, is a cement-sand mixture, which shuts in a ratio of 1 to 3. This recipe is time-tested, but you should not use washed river sand that has not been previously processed to prepare concrete. The frozen surface in this case will not be strong, but will crack and crumble over time. This is due to the fact that sand grains are smoothed under the influence of water, which eliminates proper adhesion.
Career sand is much better in this matter. When choosing, you should make sure that there are no clay inclusions in it that reduce the strength of the screed. An important condition for durability and strength is a properly selected amount of water. Some masters try to facilitate the work by using excess fluid to produce a semi-liquid solution. At the exit, the screed does not have the required quality.
An excessively liquid mixture will shrink, but you should not expect a smooth surface in this case. In case of violation of the cement-water balance, the surface is unbound, and the floors during operation form an increased amount of dust.
Concrete screed technology may involve the use of a finished dry composition. It has outstanding performance and strength characteristics. There is no need to use heavy manual labor or powerful equipment for mixing. A mixer or a powerful electric drill will be enough. Problems with the dosage of dry components should not arise, because everything is already provided by the manufacturer. Many solutions are lighter, which reduces the load on the floor and facilitates the lifting of the material to the floor.
Surface preparation
Before making a concrete screed, you must prepare the surface. If the floor is laid on the ground, then the work is carried out in a certain sequence. The soil is selected to a depth of 500 mm. A sand cushion 100 mm thick is filled up at the bottom.
The preparation is tamped, and a gravel layer is poured on top. Next, you can pour concrete with the addition of expanded clay. The thickness of this layer is 200 mm. It is necessary for surface insulation.
After the base has hardened, it is waterproofed with polyethylene or roofing material to prevent the penetration of soil moisture. The waterproofing material is laid on the bottom of the wall, and the height should slightly exceed the thickness of the planned screed. If necessary, another layer of insulation is poured on top, after which you can proceed with pouring the reinforced finish screed.
If the work is carried out in the apartment, then the old screed is removed. It does not guarantee integrity, with time it may begin to crack and peel off, and deformations will be transferred to the filled layer. This stage is also important for the reason that there are permissible loads on floor slabs. In serial high-rise buildings, the permissible load is 400 kg per square meter.
Another factor that favors the need to remove the material of the old screed is the height of the ceilings in the apartments, which is not always significant. Concrete can be removed with a perforator, but destruction or damage to the floor slab cannot be allowed. The remains of construction waste are taken out, and after that the surface is removed and dust removed.
Repairing a rough surface
The device concrete screed at the stage after removal of the concrete layer provides for repair work. If the screed is bonded, then the existing recesses are cleaned, and cracks and cracks are separated by a width of 5 mm so that concrete mortar can penetrate there.
When the plans are floating screed, then all the flaws are repaired. There should not be voids under the waterproofing layer, because condensate will accumulate there. These areas will become areas of high humidity. Damage can be repaired with a repair compound, concrete mortar or epoxy putty. Foam is suitable for large defects.
The corners between the floor and the walls should be repaired. Water from the mortar when pouring the screed can be in the ceiling or leak to the neighbors from below. Before the concrete screed is poured, the floor surface is primed with a penetrating compound. This measure allows you to dust the surface and improve adhesion to the poured concrete. Overlapping will not so actively absorb moisture from the solution.
The soil is spread over the surface and evenly distributed by a roller. In hard to reach places it is better to use a brush. An elastic damper tape must be glued around the perimeter of the walls, which will act as a compensator for the expansion in the screed and prevent the material from deforming or cracking. If the screed will be located on the separation layer, then the overlap should be covered with plastic wrap. The strip is laid with an overlap of 100 mm. Joints should be glued with waterproof tape.
The film is especially neatly placed in the corners so that wrinkles and jams do not form. There may remain air pockets. The edges of the film should be 10 mm above the screed.
Installation of beacons, reinforcement and determination of zero level
In order for the screed to be horizontal, it is necessary to create a system of beacons. If the farm has a laser level, then you can determine the zero floor level. On the walls, horizontal stripes beat off. For this, it is most convenient to use a rail. The step between the guide and the wall should be 300 mm. If this distance is made larger, a poorly aligned area or failure forms along the wall.
Between adjacent guides the distance is not regulated. Not so long ago, improvised materials such as pipes or wooden blocks were used as guides. Today, metal profiles are the beacons. You can use screws as fasteners.
Grouting
At the next stage, you can begin to form a concrete screed. To do this, a solution above the zero level is laid out between the guides. When it begins to set, you can begin to form a plane. In the process, a rule is used with which the base is smoothed to the hats.
Using a reinforcement system can be a useful measure, especially for screeds of large thickness. For this, a metal mesh made of galvanized steel wire is purchased. The mesh size can vary from 50 to 100 mm. However, many people make mistakes when laying reinforcement by placing rods on the waterproofing layer.
In order for the reinforcing cage to fulfill its function, it must be placed in the thickness of the solution. To do this, polymer stands are purchased. You can make supports from the wire or lift the net by laying it on a lining from the battle of tiles or fragments in a concrete screed. The use of wooden linings should be discarded.
Screed insulation
Warming concrete floor screed can be carried out with plate materials. Before installing thermal insulation, communications are laid. In the insulation, it is necessary to cut out the grooves for pipes and wires. The insulation must adhere to the damper tape glued around the perimeter. Plates are mounted in a checkerboard pattern, this will eliminate the temperature corridors.
Waterproofing
The next layer will be waterproofing, which is laid with an overlap. Sheets are fastened together with a construction tape. If you plan to use mineral wool as a heater, then another layer of waterproofing is laid on the bottom to prevent moisture from entering from below. An additional layer of film is not required if the insulation is carried out with foam or foam.
Reinforcement and filling
Concrete floor screed will consist of several layers. An reinforcing mesh is located on top of the waterproofing, it is laid with an overlap and the elements are connected with wire. Further beacons from aluminum corners are exposed, and the slats will serve as the formwork. The next step will be the preparation of the mortar for the screed, the components of which are:
Screed Thickness Selection
The thickness of the concrete screed may vary depending on the composition. When reinforced concrete is the basis, the thickness can be equal to 2 cm. If there is no reinforcing element, then the minimum thickness is 4 cm. The maximum parameters are not regulated. But pouring to a height of more than 17 cm does not make sense. Structures of this type are created only when necessary, because the cost of materials and time will be quite large.
Finally
A concrete screed can be thicker if large loads are placed on it during operation. The simplest example of such a room is a garage, where the weight of the car and the impact on the floor when moving are large. The 15 cm floor is justified. Concrete screed can be part of the supporting structure, and it should also be high enough.