Deformation seam in concrete floors: technology, norms and rules

A common option for floors of buildings, structures and coatings in industrial premises with intensive mechanical influences is the concrete floor. The material from which these structural elements are created is subject to shrinkage and has a low strength to deformation, resulting in cracks. To avoid repeated repairs, artificial cuts are created in monolithic structures. For example, a deformation seam in concrete floors, in the walls of a building, roofs, bridges.

What are they needed for?

The concrete floor seems to be a solid and durable base. However, under the influence of temperature fluctuations, shrinkage processes, air humidity, operational loads, soil sediment, its integrity is lost - it begins to crack.

To betray some degree of elasticity of this building structure, deformation seams are created in concrete floors. SNiP2.03.13-88 and the Handbook contain information on the requirements for designing and constructing floors, indicating the need for a tearing device in the screed, underlying layer or coating that provides relative displacement of the disparate sections.

Main functions:

• Minimization of sudden deformations, by dividing a monolithic plate into a certain number of cards.
• Ability to avoid expensive repairs with the replacement of rough and core coverage.
• Increased resistance to dynamic loads.
• Ensuring the durability of the constructive basis.

Main types: insulation seam

The deformation seam in concrete floors, depending on its purpose, is divided into three types: insulating, structural and shrinkage.

Insulating sections are made in the places of abutment of structural elements of the room. That is, they are an intermediate seam between walls, foundations for equipment, columns and floor. This makes it possible to avoid cracks in the shrinkage of concrete in the places where horizontal and vertical elements of the room adjoin. If you neglect their arrangement, then the screed when drying and reducing the volume with a rigid adherence to the wall, for example, is likely to give a crack.

Along the walls, columns and in places where the concrete floor borders on other types of grounds, an insulation seam is created. And near the columns a seam is cut not parallel to the faces of the pillar-shaped element, but in such a way that a straight cut occurs at the corner of the column.

The seam is considered to be filled with insulation materials capable of allowing horizontal and vertical movement of the screed relative to the foundation, columns and walls. The thickness of the seam depends on the linear expansion of the screed and is about 13 mm.

Main types: shrinkage seam

If insulation seams prevent deformation of a monolithic concrete floor in places where it is in contact with walls, then shrink cuts are necessary to prevent chaotic cracking of concrete over the entire surface. That is, preventing damage caused by shrinkage of the material. As the concrete dries from the top down, a voltage appears inside it, created by hardening the top layer.

The device of expansion joints in concrete floors of this type occurs along the axes of the columns, where the cuts are joined with the joint angles along the perimeter. Cards, that is, parts of a monolithic floor, bounded from all sides by shrinkage seams, should be square, L-shaped and elongated rectangular shapes should be avoided. The work is carried out both during the laying of concrete with the help of forming racks, and by cutting the joints after the screed has dried.

The probability of cracking is directly proportional to the size of the cards. The smaller the floor area, limited by shrinkage seams, so the likelihood of cracking is minimal. Deformations and sharp corners of the screed are subject to deformation, therefore, in order to avoid rupture of concrete in such places, it is also necessary to cut the shrinkage joints.

Main types: structural seam

Such protection of monolithic floors is created when technological breaks occur. The only exception is a room with a small pouring area and a continuous supply of concrete. The deformation seam in concrete structural type floors is cut at the joints of the screed made at different times. The shape of the end of such a connection is created by the type of "spike-groove". Features of structural protection:

• The seam is arranged at a distance of 1.5 m parallel to other types of deformation delineation.
• It is created only if the concrete is laid at different times of the day.
• The shape of the ends should be of the "spike-groove" type.
• For the thickness of the screed up to 20 cm, on the wooden side protrusions a cone of 30 degrees is made. It is allowed to use metal cones.
• Conical seams protect the monolithic floor from minor horizontal movements.

Deformation seams in concrete floors of industrial buildings

Increased to wear resistance requirements are imposed on the floors laid in factories, warehouses and other industrial facilities. This is due to the appearance of the influence of different intensity of the mechanical impact (traffic of vehicles, pedestrians, impacts when falling solid objects) and possible liquid on the floor.

Typically, the structural feature of the floor is a screed and a covering. But under the screed there is an underlying layer, which in rigid execution is laid from concrete. It is cut in mutually perpendicular directions of the seam through 6-12 m, depth of 40 mm with at least 1/3 of the thickness of the underlying layer (SNiP 2.03.13-88). A prerequisite is the coincidence of the expansion joint of the floor with similar protective tearing of the building.

A distinctive feature of the structure of floors in industrial buildings is the creation of a top layer of concrete. Depending on the intensity of the mechanical effect, coatings of different thicknesses are projected. At a thickness of 50 mm or more, the deformation seam in concrete floors (SNiP "Polya" p.8.2.7) is created in the transverse and longitudinal direction with the repetition of the elements after 3-6 m. The cutting is cut by a width of 3-5 mm, its depth is not Less than 40 mm or a third of the thickness of the coating.

Requirements for the creation of deformation protection of the floors

The propyl of concrete must be milled after two days hardening. The depth of cuts according to the norms is 1/3 of the thickness of the concrete. In the underlying layer, it is allowed in the places of the supposed breaks before casting of concrete to use rails treated with compositions against adhesion, which, after hardening of the material, are removed and, as a result, protective seams are obtained.

The lower parts of columns and walls to the height of the future thickness of the coating should be glued with roll-on waterproofing materials or foamed polyethylene. In those places where the project provides for expansion joints in concrete floors. The cutting technology begins with a chalk marking and a ruler of places of artificial ruptures.

Indicator of timely cutting is the trial joint: if the filler grains do not fall out of the concrete, but are cut by the cutter blade, then the time of creating the expansion joints is chosen correctly.

Seam processing

The normal functioning of the seam is achieved by its sealing. The sealing of expansion joints in concrete floors is realized with the help of the following materials:

• The waterstop is a profiled strip of rubber, polyethylene or PVC, laid when pouring concrete screed;
• Sealing cord made of foamed polyester is laid in the slot and with temperature drops retains its elasticity, ensuring safe movement of the concrete coating;
• Acrylic, polyurethane, latex mastic;
• Deformation profile consisting of rubber and metal guides. It is built-in or invoiced.

Before sealing, the working surface of the gaps must be cleaned and purged with compressed air (compressor). Also, to increase the service life of concrete floors, it is desirable to harden the top layer with topping or polyurethane material.

Terms of creation

The deformation seam in concrete floors (monolithic) becomes mandatory under the following conditions:

1. Screed with a total area of more than 40 m2.
2. Complex configuration of the floor.
3. Use of floor covering at elevated temperatures.
4. The length of the rib (enough one) of the floor structure is more than 8 m.

Deformation seams in concrete floors: standards

In conclusion, the requirements for the installation of protective gaps in concrete floors according to the norms are given.

The underlying layer must have deformation cuts perpendicular to each other in increments of 6 to 12 meters. The seam is made at a depth of 4 cm and constitutes the third part of the thickness of the concrete cover or underlying layer.

With a concrete coating thickness of 50 mm or more, the deformation joint is created in the transverse and longitudinal directions with repetition every 3-6 m. These cuts must coincide with the seams of the floor slabs, the axes of the columns, the deformation gaps in the underlying layer. The width of the cut is 3-5 mm.

Propyl is carried out two days after the installation of concrete. The sealing of protective cuts is carried out by special cords and sealants.