The device of expansion joints in a concrete floor

Seam Types

Floors consist of topcoat and screed - almost always of concrete, not the strongest material that does not tolerate deformation force.

Because of its impact on concrete, it will start to crack, since it does not have space to report deformation further.

And if so, then in order to prevent cracking, strobing of concrete seams is required.

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Concrete stitches are of 3 kinds.

Insulation:

• The floor will be independent of load-bearing walls;
• Eliminates the deformation message from the walls of a concrete screed;
• It is created by laying insulation before pouring concrete along the walls;
• The thickness is on average 10 mm;
• Can be in the form of a square, a circle, a straight line;
• The yoke is thickened by a quarter if the seam is subject to constant pressure loads;
• You can cut around columns in hardened concrete in the form of a diamond.

Shrinkage:

• Cautions the appearance of tension inside the screed, which arises because the surface dries and shrinks faster than the lower layer;
• Creates a flat plane at the weakest point;
• It is carried out by means of forming rails, until the concrete has dried completely;
• It is desirable to make a suture map rectangular, without elongated sides;
• The shrinkage type is created and in outer corners, so that the cracks do not go from the corners.

Constructional:

• It is arranged in 1.5 meters from other seams, it is located in parallel;
• If cut in a section where an shrinkage or insulation seam is undesirable, put sleepers across it;
• It is carried out strictly in places of connection of couplers laid at different times( usually yesterday / today).
• The form of the screed is carried out by attaching the "spike into the groove".
• The construction type works by analogy with the insulation type.

Cutting rules

To ensure that the finished screed and the finished floor are strong and not cracked, you need to cut correctly.

There are a number of rules that guarantee the correct seam creation( see also SniP recommendations):

1. Sutures are cut after pouring the screed / after screed set( 8-10 hours after the pouring);
2. In dry concrete, the seams are cut in a short time - until the edge of the pouring begins to pour;
3. Perform a test shtrobu 2-3 hours after the concrete began to solidify: if the aggregate constantly leaves the concrete - cut early;
4. If the blade cuts concrete together with aggregate grains, it's time to cut;
5. Mark the strobes in the floors with a chalk on the rope;
6. In fresh concrete the cutting is performed by the carver, in dry - it is sawed out;
7. The cutting takes place in the order in which the screed was laid;
8. Cutting is carried out to a depth of 1/3 of the thickness of the screed;
9. The cutting interval is as follows: the thickness of the screed is multiplied by 24-36.With a 12-centimeter screed, you need to cut it at a distance of 288 to 432 cm. Concrete with strong shrinkage is better cut at an interval closer to 288 cm;
10. You can not allow a T-shaped intersection of the joints, otherwise cracks will appear.

Following these rules ensures the correct cutting and completion of a reliable concrete floor.

The modern approach of

Today you can buy ready-made designs, which need only at the right time to mount directly in the screed, instead of cutting yourself.

In shops it is possible to purchase separately:

• Shrink and compensation bars are strictly for tile: movable 11 mm, technical deformation 5, 8, 10 mm made of synthetic resin with soft PVC insert, deformation profile of aluminum 10, 11, 17, 22, 27mm with rubber insert - replaceable / non-replaceable;
• Movable structures: 5, 8, 9, 10 mm, made of aluminum, brass, with PVC, synthetic rubber, foam rubber;
• Surface profiles separately from brass, aluminum.

In the market there is a huge variety of finished structures, as well as separate accessories for a specific type of cutting.

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Thus, it is possible to quickly and qualitatively sew the seam from scratch by simply inserting the required kit into the coupler, or to supplement the hand-made by hand, putting a suitable profile - even the sealant does not have to be sealed.

Sealing

Sealing is a prerequisite for the functioning of the seam, it is performed using the following materials:

1. Sealing cord: a cord made of expanded polyester is placed in the slot, which retains its elasticity at constant temperature changes;
2. Sealant: the most popular method, a special case of which is pouring mastics( we will tell about it separately).After drying, the sealant completely closes the barrel and at the same time prevents the penetration of water;
3. Hydrostick: special material made of polyethylene, rubber or PVC in the form of profiled tape, laid when pouring screed;
4. Deformation profile: a special rubber profile is used on the metal guides. Rubber will not let water and dirt into the strobes, distribute the load to the screed and will not allow the concrete to crack. The profile can be invoice or embedded.

Mastic sealing

Mastic is the most popular way of sealing. It can be acrylic, latex, polyurethane.

Now we will consider in detail the sealing process using mastic:

• We prepare the tool and materials: mastic, brush, small triangular spatula, deep primer, gun for sealant;
• We prepare the substrate: it must be dry, free of fungus and dust, free from any oil, grease, rust, old paint - anything that can affect the setting of the mastic. Before embedding the sealant, it must be purged with compressed air, treated with a brush and a sandblasting unit, after treatment with a primer;
• We break the sealant: mix paste and hardener until a uniform composition is obtained. Do not break the recommended ratio! You can slightly improve the fluidity, adding to 1 kg of the finished composition, about 10-12 tablespoons of gasoline( about 50 grams);
• Apply the sealant: fill the composition in the gun, then apply evenly along the entire length, leveling the spatula level with the floor. After 40 minutes, apply a thin layer of cement to the fin and after 1 week, the maximum sealant will seize.

Technical requirements of SNiP

The requirements of SNiP regarding the deformation joint design are as follows:

• Deformation seams are created in the underlying layer, perpendicular to each other in steps of 6-12 meters;
• The depth of the joint can not be less than 4 cm and less than 1/3 of the thickness of the underlying layer;
• Seams in the field, coinciding with the seams of the building, are executed in the entire thickness of the underlying layer;
• If the room is subject to sudden temperature fluctuations, a strain joint is arranged in the screed, which coincides with the axis of the columns, the seams of the overlapping plates and the seams in the underlying layer;
• The shtroba device is made through a saw cut by a milling cutter 2 days after curing;
• At the seam device it is possible to put before laying concrete the slats with anti-adhesive compound that will be removed afterwards;
• In the thickness of 5 cm, longitudinal and transversal seams are provided, with a step of 3 to 6 meters;
• After the concrete is dried, the seams are stitched with styling in the milled slot of the special cord, and the sealant is poured.

The requirements of the SNiP partially overlap with the general rules for the creation of concrete seams, which indicates the narrow specialization of the work on suture cutting, which does not tolerate technological "liberties".

Conclusion

Seams in concrete floors are a necessity, dictated by the realities and rules of SNiP for the construction of concrete structures.

In concrete floors, there is a constant movement - an expansion and constriction, which in the absence of space in concrete coatings is fraught with their slow but sure destruction.

If you think that this practice occurs only in the floor, then pay attention to the mass of jumpers that you feel when crossing the bridge.

The seam in the construction is a guarantee of its safety, and sometimes your safety.