Hollow body, method for its manufacture, concrete component, method for its manufacture and use of recycled fibers

Abstract

Hollow body (1) for use as a recess body in the production of concrete components (10), comprising a base surface (2), four wall surfaces (4), and an opening (6), and a method for its production. According to the invention, the base surface (2) and the wall surfaces (4) consist of mineral-bound recycled fibers. Concrete component (10) comprising hollow chambers internally, and a method for its production. According to the invention, the hollow chambers are formed by hollow bodies (1) according to any one of claims 1 to 6. Use of recycled fibers for the production of a hollow body (1).

Description

[0001] The invention relates to a hollow body for use as a recess body in the production of concrete components, comprising a base, four wall surfaces, and an open side. The invention also relates to a method for producing a hollow body. Furthermore, the invention relates to a concrete component having internal hollow chambers and a method for producing a concrete component. The invention also relates to the use of recycled fibers.

[0002] It is known that during the dismantling of various objects, such as wind turbine rotor blades (where glass fibers are generated) or textile-reinforced concrete components (where carbon fibers are generated), fiber remnants remain. These recycled fibers, as they will be referred to hereafter, are typically 3 to 4 cm long and are no longer suitable for use in the original product if it is to be remanufactured. The recycled fibers contain no or only minimal traces of the original matrix material in which they were embedded. The disposal of these large quantities of fibers poses a problem.

[0003] Concrete components with hollow chambers, primarily for weight reduction, are known from the prior art. These hollow chambers are created (among other methods) by inserting hollow bodies. Methods are also known for separating fibers from concrete to produce recycled fibers.

[0004] It is therefore the object of the present invention to offer a new utilization option for recycled fibers.

[0005] The problem is solved by a hollow body for use as a recess in the production of concrete components, comprising a base, four wall surfaces, and an open side, in particular a trough-shaped hollow body open on one side, preferably made of a mineral-bound fleece of recycled fibers. The hollow body, due to the mineral binder, for example a cement slurry, a fine concrete, or another hardenable mineral suspension, possesses sufficiently high strength to withstand the concreting process without deformation or damage.

[0006] Preferably, the side walls of the hollow bodies are aligned at an obtuse angle to the base surface to allow for easier demolding and stacked storage.

[0007] The wall thickness is preferably only 2 mm, including the coating, resulting in a maximum weight of 5 kg.

[0008] The object of the invention is further achieved by a method for producing a hollow body open at one end. The method comprises the following steps: • Forming a nonwoven fabric from recycled fibers, for example from recycled glass fiber (rotor blades from wind turbines, etc.) or carbon fiber. • Soaking the fleece with a curable mineral suspension, • Placing the soaked fleece into a mold, • Hardening of the mineral suspension of the impregnated fleece, • Demolding of the hollow body.

[0009] The invention is not limited to the production of hollow bodies used for concrete components with hollow chambers. Numerous other bowl-shaped products or, more generally, bodies open on one side can also be produced using the same process.

[0010] In a further advantageous development of the process, it is provided that, as an alternative to impregnating a prepared nonwoven fabric, a mixture of a mineral matrix material with the recycled fibers is used to create a fiber-reinforced concrete mass. This fiber-reinforced concrete mass is then placed into the desired shape instead of the impregnated nonwoven fabric. Such a process is particularly advantageous when dealing with very short fibers that are no longer suitable for nonwoven fabric formation.

[0011] In an advantageous further development of the process according to the invention, it is provided that the fibers are prepared for improved bonding with the mineral binder. This can be done with the existing recycled fibers by, for example, roughening their surface. Plasma surface treatment is one example of this. Alternatively, the fibers can be prepared during the recycling process itself, during the removal of residues of the original matrix material. Another alternative is the surface coating of the fibers, e.g., with fine sand.

[0012] The problem is further solved by a concrete component, in particular a hollow-core slab, whose hollow chambers are produced by hollow bodies as described above. The hollow chambers, created by recessed bodies, save weight and material, especially concrete, during the production of the concrete component. In contrast to the prior art, when using the hollow bodies according to the invention, no plastics are introduced into the concrete, which would complicate subsequent recycling; instead, only mineral binder and recycled fibers are used.

[0013] The problem is also solved by a method for producing a slab-shaped concrete component with hollow chambers, in particular a hollow-core slab. The method comprises the following steps: • Concreting of a first side, the reinforced top slab of the concrete component, whereby the concrete and a reinforcing mat are placed into a mold. • Place the hollow bodies according to the above description, placing them with their open side onto the fresh concrete and allowing them to sink in up to the reinforcement, so that the open side is in the concrete and a completely closed hollow body is formed. • Curing of the top plate, • Concreting of a second side, the reinforced base plate of the concrete component, whereby the concrete and a reinforcing mat are placed into a mold. • Demolding, rotating the first side by 180° and placing it on the fresh concrete of the base plate, so that the protruding hollow bodies sink into the concrete up to the reinforcement of the base plate, • Curing of the second side and demolding of the finished concrete component.

[0014] Preferably, the upper and lower slabs are concreted automatically, with a thickness of preferably 5 cm.

[0015] The invention is also achieved by using recycled fibers for a hollow body, as described above. This indirectly allows for its use in a concrete component or a hollow-core slab.

[0016] The invention embodies advantages compared to known recess bodies, in particular in that • No material mixing occurs (recycled concrete and plastics do not need to be separated later), • Use of existing waste material (fibrous materials, especially from rotor blades of wind turbines or concrete components), • Do not use plastic recess bodies, • Larger cavities can be formed than with other constructions, since the fiber-reinforced, mineral-bonded hollow bodies have a greater load-bearing capacity than conventional plastic-based hollow bodies.

[0017] The invention is explained in more detail below with reference to the description of exemplary embodiments and their illustration in the accompanying drawings. The drawings show: Fig. 1: schematically a perspective view of an embodiment of a hollow body according to the invention; Fig. 2: schematically a cutaway view of an embodiment of a top plate of a hollow body ceiling according to the invention; Fig. 3: schematically a cutaway view of an embodiment of a hollow body ceiling according to the invention.

[0018] Fig. Figure 1 schematically shows a perspective view of an embodiment of a hollow body 1 according to the invention, which has a base surface 2 and four wall surfaces adjoining the base surface 2 and projecting from it at an obtuse angle. A fourth side, shown here as the underside opposite the base surface 2, remains open and forms the opening 6. This design results in a trough-shaped element corresponding to a hollow body shape (not shown). The hollow body 1 is thus stackable for storage and transport (before installation). It preferably has dimensions of 35 cm in width at the bottom, at the opening 6, and 30 cm in width at the top, at the base surface 2.

[0019] Ultimately, the shape of the hollow body 1 results from the hollow body mold used, into which the pre-product is placed and where it solidifies. The pre-product is either a nonwoven fabric impregnated with a mineral binder, in particular cement slurry, which was previously formed from the recycled fibers.

[0020] Alternatively, short fibers are used to produce a fiber-reinforced concrete mass, which is then also introduced into the hollow body mold.

[0021] The fleece is cut to dimensions of 70x70, 90x90, and 100x100 cm, corresponding to the three heights of the hollow body 1 (30 cm + 2 x height). The wall thickness is only 2 mm, including the coating, resulting in a low weight of a maximum of 5 kg.

[0022] Fig. Figure 2 schematically shows a cutaway view of an embodiment of a top slab of a hollow-core slab 10 according to the invention. To produce the top slab 12, a form (not shown) with embedded reinforcement 16 is cast in concrete, and the hollow cores 1 with their downward-facing opening 6 are pressed into the still-soft concrete. This also closes the opening 6 and forms a completely enclosed cavity. The hollow cores 1 sink into the concrete up to the reinforcement 16.

[0023] Fig.Figure 3 schematically shows a cutaway view of an embodiment of a hollow-core slab 10 according to the invention. To produce it, the base slab 14 with embedded reinforcement 16 was first cast in concrete. Then, the already hardened, inverted top slab 12, with the top surfaces 2 of the hollow cores 1 facing forward, was pressed into the still-soft concrete of the base slab 14. The hollow cores 1, preferably assisted by vibration, sank with their bottom surface 2 down to the reinforcement 16, into the inner concrete cover of the reinforcement.

[0024] After curing, the base plate 14 can also be demolded, and the hollow core ceiling 10 with thickness D is complete. Preferred properties of the hollow core ceiling 10 are: • Ceiling thicknesses 30-50 cm, especially 30-39 cm, 40-44 cm and 45-50 cm • Spacing of lattice girders according to structural analysis approx. 50 cm • Three preferred recess body heights: 20, 30 and 35 cm • Transverse reinforcement can be added on the construction site for the two-axis design. • The upper layer of reinforcement lies on the lattice girder, as with a conventional precast concrete slab. Reference symbol list 1 hollow body 2 Floor area 4 wall surface 6 Opening 10 Concrete component, hollow core ceiling 12 Top plate 14 Base plate 16 Reinforcement, reinforcing mat D ceiling thickness

Claims

[1] Hollow body (1) for use as a recess body in the manufacture of concrete components (10), comprising a bottom surface (2), four wall surfaces (4) and an opening (6), characterized by , that the floor surface (2) and the wall surfaces (4) consist of mineral-bound recycled fibers. [2] Hollow body according to claim 1, wherein the recycled fibers are present as a recycled fiber fleece. [3] Hollow body according to claim 1 or 2, wherein the mineral binder is cement. [4] Hollow body according to one of the preceding claims, wherein the wall surfaces (4) are arranged at obtuse angles to the bottom surface (2) and result in a trough shape. [5] Hollow bodies according to claim 4, wherein the hollow bodies (1) are stackable. [6] Hollow body according to any of the preceding claims, wherein the wall thickness is 2 mm, with a maximum weight of 5 kg. [7] Method for producing a hollow body (1) according to any one of claims 1 to 6, characterized by the steps a. Formation of a pre-product from recycled fibers and a curable mineral suspension as a binder, b. Inserting the pre-product into a hollow body mold, c. Hardening of the mineral suspension in the precursor, d. Remove the hollow body (1) from the mold. [8] Method according to claim 7, wherein the pre-product is produced by forming a nonwoven fabric from recycled fibers and subsequently impregnating the nonwoven fabric with a curable mineral suspension. [9] Method according to claim 7, wherein the pre-product is produced by mixing a mineral matrix material with the recycled fibers to form a fiber-reinforced concrete mass. [10] Method according to any one of claims 7 to 9, wherein the mineral suspension is cement slurry or fine concrete. [11] Method according to any one of claims 7 to 10, wherein the recycled fibers are roughened by surface treatment or surface coating to improve the bond with the mineral binder. [12] Method according to claim 11, wherein the surface treatment is carried out with plasma. [13] Method according to claim 11 or 12, wherein the surface treatment is already carried out during recycling and in the course of removing residues of a previous matrix material. [14] Concrete component (10) which has hollow chambers inside, characterized by , that the hollow chambers are formed by hollow bodies (1) according to one of claims 1 to 6. [15] Concrete component according to claim 14, designed as a slab-shaped concrete component (10). [16] Concrete component according to claim 14 or 15, designed as a hollow core slab (10). [17] Method for producing a concrete component (10) according to any one of claims 14 to 16, characterized by the steps a. Concreting of a first side, a reinforced top slab (12) of a concrete component (10), wherein the concrete and a reinforcing mat (16) are placed in a mold b. Inserting the hollow bodies (1) according to one of claims 1 to 6, wherein these are placed with their opening (6) on the fresh concrete and sink in up to the reinforcement (16), so that the opening (6) lies in the concrete and a completely enclosed hollow body (1) is formed. c. Curing of the top plate (12) d. Concreting of a second side, the reinforced base plate (14) of the concrete component (10), wherein the concrete and a reinforcing mat (16) are placed in a mold e. Demolding, rotating the top plate (12) by 180° and placing it on the fresh concrete of the bottom plate (14), so that the hollow bodies (1) protruding from the top plate (12) sink into the concrete up to the reinforcement (16) of the bottom plate (14). f. Curing of the base plate (14) and demolding of the concrete component (10). [18] Method according to claim 17, wherein the upper and lower slabs (12, 14) are automatically concreted and each has a thickness of 5 cm. [19] Use of recycled fibers for the production of a hollow body (1) according to any one of claims 1 to 6.

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