Technical field

The invention belongs in the field of construction, specifically the invention relates to a temperature and shrinkage joint inducer of sheet material for use in a predetermined position in vertical concrete structures in outdoor environment, specifically concrete retaining walls.

Prior art

A problem involved in casting concrete walls, floors and ceilings is that large surfaces cannot be cast all at once due to the shrinking of concrete during the initial setting, which results in cracks caused by volume shrinking. Furthermore, temperature cracks occur in concrete walls in the outdoor environment.

Known is the WFP GmbH rupture element SFG (https://wfp- waterproofing.de/en/products/rapture-elements), which comprises a straight steel element coated or uncoated with rubber bitumen, and an element with a right angle profile attached on top of it. This solution is used for sealing triple-layer wall elements in the corners of straight joints to achieve a water-tight diagonal breaking point. The solution creates cracks in vertical surfaces, but does not transfer strength.

Known is an inducer of watertight joint (CN108442543A, China MCC17 Group Co Ltd, published 24.08.2018). These are stepwise expanded reinforced strips, which also contain water barriers and are used in continuous casting of concrete floors. A disadvantage of this solution is that it cannot be used in case of vertical surfaces (such as walls) and the profile requires two separate castings.

Known is a joint structure for concrete wall, which creates cracks in designated places in concrete wall (KR100624190B1 , Dawoo Consultants Co Ltd, published 19.09.2006). The joint structure is installed on the outer sides of the concrete wall, one against one another, and is further reinforced with metal rods. The joint structure forms a crack, as it has been smoothly inserted in the shrinkage area of the concrete wall. The joint structure with Y-shaped cross-section includes a crack inducing part and shrinkage inducing parts. Metal rods are installed into the retaining wall, a metal rod is inserted into a groove in a joint structure part and the metal rod itself also becomes a crack inducer. The crack inducer is installed on the front and rear wall of the retaining wall so that the crack inducing parts are against one another, resulting in a crack, which is formed only in the crack inducing part. The crack inducer is fixed to a metal rod and installed inside the retaining wall in order to increase the binding force. This solution creates a crack in a concrete wall, but it is not water-tight.

Description of the invention

The objective of the invention is to create a temperature and shrinkage resistant joint in a predetermined position in an external concrete retaining wall by means of a special profile (to prevent the occurrence of spontaneous shrinkage and temperature joints in random places in the concrete wall). Here it is important that the profile of this invention makes the formed joint watertight and can be used in concrete walls, where behind the wall (in outdoor environment on the other side of the wall or inside the building) is soil or any another wet environment (such as a manure storage building), where there could be water that would impose the wall to water load.

The joint inducer profile for temperature and shrinkage joint comprises a sheet of sheet material, where an expanding (water absorbing) joint strip (such as https://www.besealed.com/en/products/hydrophilic-profiles/po lybar) is attached to the edges, and borders of sheet material that are perpendicular to the sheet of sheet material and bent at various angles.

Due to the material of production, the sheet of sheet material is a water barrier element and the joint strip provides the sheet of sheet material with water-tightness (the need for water-tightness arises from the expansion and shrinkage of concrete). The joint strip is in conformity with the environmental conditions required for the use of the concrete retaining wall. The joint strips that are used have different properties, depending on the place of application, such as public buildings and production facilities (incl. agricultural buildings (e.g. manure storage), which are exposed to major load arising from special conditions (e.g. slurry, wastewater), residential buildings (neutral environment), structures used in roadworks (high content of salt). The sheet of sheet material and borders of sheet material are produced either from galvanized or stainless steel. List of figures

Figure 1 shows the profile according to the invention.

Figure 2 shows the profile in conformity with the invention, used in a concrete wall.

Embodiment of the invention

The inducer of temperature and shrinkage joints comprises sheet 1 of sheet material, where profile borders 2 of sheet material are welded perpendicularly to both sides of sheet 1 , while each border includes a section with a zigzag crosssection at various angles (in a preferred embodiment at angles of approx. 120 to 145 degrees), which give the joint 4 that is formed in the concrete wall 5 a triangular (tenon-shaped) cross-section, thereby retaining the strength properties of the concrete wall. On the edges at both ends of sheet 1 , an expanding (water absorbing) joint strip 3 in conformity with the environmental conditions at the site of use of the concrete retaining wall (either a joint strip for normal environmental conditions or a special joint strip for application in environments of e.g. wastewater, slurry or high content of salt). Depending on the properties of the material used, sheet 1 of sheet material functions as a water barrier element and joint strips 3 provide sheet 1 of sheet material and the whole profile with water tightness, which again provides the concrete wall with waterproofness.

The preferable width of sheet 1 of sheet material is 150 mm and thickness 1 mm and the length of the joint strip 3 is 20 mm.

Sheet 1 and borders 2 of sheet material are preferably produced from sheet metal, specifically from stainless or galvanized sheet steel based on the conditions of the application environment of the concrete retaining wall, but other materials may also be used, such as stainless steel, Zn, rubber, plastic or carbon material, etc.

The joint inducer for temperature and shrinkage joint is used for forming a joint in a predetermined place in reinforced concrete retaining walls used in outdoor conditions. With the use of the joint inducer it is also possible to cast very long retaining walls in one work step without the fear that unwanted shrinking cracks and later cracks on account of temperature fluctuations would form. The joint inducer profile is installed by means of a tying wire between the reinforcement rods in the cast concrete wall before the preparation of the concrete surface, while a special chamfered profile for joints is used in areas that will be later visually exposed. Then the concrete wall (e.g. retaining wall) of any size will be cast without interruption. The joint inducer profile is installed in the retaining wall preferably at approx, every 6 to 14 meters so that the sheet 1 of sheet material, which also functions as a water barrier element, is parallel with the wall, and borders 2 of the sheet material are perpendicular to the wall. At the point of installation of the joint inducer it is necessary to cut the reinforcement rods. If continuation is needed during the installation of joint inducers, approx. 10 cm overlap is required at the connection points of the joint inducer profiles. The overlap is prepared by means of adhesive and fixing clamps, applying a strip of adhesive in the centre of the overlap, pressing the elements together and fixing with clamps. A proper joint on the visible side requires the use of special triangular profiles.

Advantages of the invention:

• the joint inducer profile creates controlled temperature and shrinkage joints in concrete walls (retaining walls) in outdoor conditions, avoiding thereby spontaneous formation of these in random places;

• water-tightness (waterproofness and resistance to pressure water) of the joint is ensured;

• the created joint has no major weakening effect on the cross-section of the concrete wall, the weakening caused by the joint profile is minor and has no effect on the ultimate result of the dimensioning of the concrete wall;

• using the joint inducer profile as a joint allows casting large vertical concrete surfaces (e.g. whole retaining wall) all at once, facilitating the performance of concreting stages; substantial savings in time in concreting (concrete can be cast “from left to right”, i.e. without interruptions in casting) and later preservation of the quality of the concrete wall, also savings from the use of reinforcement in concreting.