PRE-STRUCTED CONCRETE COMPONENTS AND METHOD FOR THE MANUFACTURING OF PRE-STRUCTED CONCRETE COMPONENTS

Description

[0001] The present invention relates to a method for producing a prestressed concrete component. A further aspect of the invention relates to prestressed concrete components produced according to the aforementioned method for producing a prestressed concrete component. Prestressed concrete slabs are known from the prior art. For example, US 2002 / 0059768 A1 discloses a method for producing a prestressed concrete slab using tensioned wire ropes. To generate tension, the wire ropes are wound around opposing bolts and then subjected to tensile stress by moving the bolts apart. This results in a prestress of approximately 70% of the breaking stress of the wire ropes.

[0002] Further processes for the production of prestressed concrete components are known from US2010 / 132282 A1 and US5025605 A.

[0003] The object of the present invention is, among other things, to provide an improved method for producing prestressed concrete components.

[0004] This object is achieved by a method for producing a prestressed concrete component according to claim 1. Further embodiments according to the invention are specified in the dependent claims.

[0005] A further object of the present invention is to provide an improved prestressed concrete component. This object is achieved by a concrete component according to claim 15.

[0006] One aspect of the invention relates to a reinforcing element for the production of prestressed concrete components, comprising a plurality of fibers and several retaining elements connected to one another by the fibers, so that the fibers can be tensioned in their longitudinal direction by means of the retaining elements. The fibers are attached to the retaining elements in such a way that, in the tensioned state, the fibers extend largely straight into the retaining elements. This achieves both high prestressing and efficient, reliable, and thus cost-effective production of the concrete components.

[0007] The term "fiber" encompasses both a single or multiple elongated and flexible reinforcement elements for concrete components, such as a single filament—also called a monofilament—or a bundle of filaments—also called a multifilament, multifilament yarn, yarn, or—in the case of stretched filaments—a roving. Furthermore, the fibers can also be coated individually or together, and / or the fiber bundle can be stranded or twisted.

[0008] According to the invention, the net cross-sectional area of ​​the fibers (i.e., without resin impregnation) is less than approximately 5 mm 2 and, in particular, lies in a range from approximately 0.1 mm 2 to approximately 1 mm 2 . In another example, the elastic tensile elongation capacity of the fibers is greater than approximately 1%. In a further example, the tensile strength of the fibers, based on their net cross-sectional area, is greater than approximately 1000 N / mm 2 , in particular greater than approximately 1800 N / mm 2 .

[0009] In the manufacture of a prestressed concrete component, for example, the reinforcement elements are first laid in a casting mold, and then the fibers are tensioned by pulling apart the corresponding retaining elements. The concrete component is then cast, with the fiber portions located inside the casting mold being encased in concrete. After the concrete has hardened, the tension previously applied to the fibers is released. The tension in the encased fiber portions remains unchanged, as the encased fiber portions are force-locked to the concrete, and virtually no relative displacement occurs between these fiber portions and the concrete. The force-locked connection is based, among other things, on the wedging of the fibers in their concrete casing (Hoyer effect). The stress-free portions of the fibers protruding from the concrete component can be severed and removed along with the retaining elements.In the prestressed concrete component, the prestress is generated by the tension of the embedded fibers.

[0010] The connection between fibers and concrete can be reinforced by a variety of means, for example, by increasing the surface roughness of the fibers. In one example, this connection is designed such that the full dimension tensile force can be transmitted via the mechanical shear connection after 200 mm, in particular after 100 mm, and further after 70 mm, of the embedment length (i.e., the concreted length of the fibers).

[0011] According to the invention, the fibers are made of carbon. Carbon fibers have the advantage of being very durable, meaning that even over decades, no significant loss of strength is detectable. Furthermore, carbon fibers are corrosion-resistant; in particular, they do not corrode the surface of concrete components and are virtually invisible. Thus, the carbon fibers can often be left on the surface of concrete components. However, they can also be easily removed, for example, by breaking them off or simply scraping them off.

[0012] The fastening of the fibers "in" the holding elements includes a wide variety of fastening options, in particular the fastening of the fibers "at" or "on" the holding elements, for example, laminating the fibers without further covering.

[0013] Surprisingly, the inventive solution achieves both high prestressing of the concrete components and efficient, reliable, and easy handling of the reinforcing elements. This allows the concrete components to be manufactured particularly cost-effectively. In particular, the following is achieved: Due to the largely straight entry of the fibers with respect to their longitudinal direction, i.e., the uniform continuation of the fibers, into the retaining elements, transverse stresses in the fibers are largely avoided. Such transverse stresses often lead to fiber breakage and occur, for example, at kinks, congestion, or tight curve radii, typically at deflection webs, pulleys, or guide pins. Thanks to the inventive fastening of the fibers with the effective introduction of the acting forces into the retaining element, a high tensile force and thus a high prestressing of the concrete components can be achieved without increasing the risk of breakage.This is particularly advantageous for carbon fibers, especially impregnated carbon fibers, as these are particularly susceptible to breakage due to transverse stresses.

[0014] In one example, the carbon fibers can be tensioned at a tension of approximately 50% to approximately 95% of the fibers' ultimate stress. In another example, the fibers can be tensioned at at least approximately 80%, and in particular at least approximately 90%, of the fibers' ultimate stress. This allows for the cost-effective production of very stable, large, and thin concrete components. High prestressing of the concrete component is particularly advantageous for carbon fibers, as carbon fibers exhibit different expansion behavior than concrete.

[0015] Thanks to the reinforcement elements, large and thin concrete components can be produced that practically do not bend under load. In one example, the thickness of the concrete component to be produced is in the range of approximately 10 mm to 60 mm, in particular approximately 15 mm to 40 mm. In another example, the area of ​​the concrete component is at least approximately 10 m x 5 m, in particular at least approximately 10 m x 10 m, and more particularly at least approximately 15 m x 15 m. In another example, the length of the concrete component is at least approximately 6 m, more particularly at least approximately 12 m.

[0016] Furthermore, the reinforcement elements can be manufactured as intermediate products at a first location, possibly packaged in appropriate transport containers, and transported to another location for the production of the concrete components. At the other location, for example, a concrete production plant, the delivered reinforcement elements are then directly available as prefabricated components.

[0017] Furthermore, the connection of the fibers with the holding elements results in a robust and space-saving unit that is therefore easy to transport.

[0018] In one embodiment, the fibers are individual fibers and / or comprise one or more rovings, particularly carbon rovings. This allows for the production of particularly stable and lightweight concrete components. Individual fibers are understood to be individual, not directly connected fibers. In contrast, a continuous fiber arrangement is considered, in which the reciprocating parts of the fiber arrangement are connected via loops.

[0019] The term "roving" refers to a bundle of drawn filaments. Such a roving, also known as drawn yarn, typically comprises several thousand filaments, in particular approximately 2,000 to approximately 16,000 filaments. The roving distributes the tensile forces acting on the fibers largely evenly across a large number of filaments, thus largely avoiding local peak loads.

[0020] Furthermore, the filaments of the roving have a small fiber diameter, resulting in a correspondingly high surface-to-diameter ratio and thus a good bond between the concrete and the filaments. Furthermore, good shear transfer and a good distribution of the tensile load on the concrete are achieved.

[0021] In one example, the fibers are made from an arrangement of multiple rovings, comprising 2 to 10, in particular 2 to 5, individual rovings. Thus, these fibers have approximately 4,000 to approximately 160,000 filaments.

[0022] In one embodiment, the holding elements comprise guide elements for the fibers, in particular a clamping device and / or a carrier for laminating the fibers in the end region, in particular a fiber-reinforced polymer matrix, more particularly a polyester matrix. These guide elements ensure good force transmission. Furthermore, the lamination results in a particularly space-saving and robust unit. The holding elements can also be designed as double-sided adhesive tape.

[0023] In one embodiment, the fibers in the retaining elements form a substantially flat layer and are arranged, in particular, largely parallel and / or largely evenly spaced from one another. As a result, the reinforcing element has the shape of a sheet or harp. This shape is easy to stack or roll up, optionally using interleaves to keep the individual fibers separate. This makes reinforcing elements easy to transport.

[0024] Such a harp-shaped reinforcement element has the advantage over a grid in that it eliminates knots and can therefore withstand very high tensile loads. Furthermore, complicated manufacturing steps such as weaving or braiding are eliminated, and there is high flexibility regarding the width of the panels, as no machines are required to produce a grid. Therefore, so-called "endless products" can be easily manufactured in both length and width.

[0025] In one embodiment, the reinforcing element has additional spacers that connect the fibers to one another, for example, in the form of transverse threads and / or a woven fabric, so that even when the reinforcing element is not or only partially tensioned, a gap remains between the individual fibers. This largely or completely prevents the unstretched fibers from becoming tangled. These spacers thus serve as assembly and / or transport aids. When encased in concrete, the spacers absorb virtually no tensile loads.

[0026] In one embodiment, the reinforcement spacing is approximately 5 mm to approximately 40 mm, in particular approximately 8 mm to approximately 25 mm, and / or at least 10, in particular at least 40, fibers are secured in each of the retaining elements. For example, the reinforcement spacing, i.e., the distance between two adjacent fibers, is less than or equal to twice the thickness of the concrete component.

[0027] In one embodiment, the fibers are impregnated with an alkali-resistant polymer, in particular with a resin, more particularly with a vinyl ester resin. This results in higher tensile strength of the fibers.

[0028] In one embodiment, the fibers are coated with a granular material, particularly sand. This improves the bond between the fibers and the concrete and thus increases the resistance of the prestressing in the concrete component.

[0029] In one embodiment, the fibers are attached to the holding elements in such a way that, when tensioned, the fibers continue largely straight into the holding elements, in particular over a distance of at least approximately 5 mm, and more particularly at least approximately 10 mm. This ensures good force transmission between the fibers and the holding elements.

[0030] In one embodiment, the holding elements have a force distribution means, particularly a curvature and / or a profile, extending transversely to the fiber direction. This ensures good distribution of the acting forces and thus high tensile stress and / or low stress on the fibers during tensioning. Furthermore, this shortens the embedment length, i.e., the length required for reliable attachment of the fibers to the holding elements.

[0031] In one example, the curvature of the retaining element is designed such that the curved fibers each define planes that are arranged largely parallel, in particular perpendicular to the fiber orientation. When the fibers are arranged in a horizontal orientation, for example, their fiber ends are curved vertically downward or upward.

[0032] In particular, the profiling achieves a good force-locking connection between the holding element and the clamping device. This allows the pressure on the holding element and / or on the fibers to be reduced. In one example, the profiling is arranged on at least one of the surfaces of the holding element intended for fastening the holding element in a clamping device. In another example, the profiling is wave-shaped or serrated, in particular sawtooth-shaped.

[0033] In one embodiment of the reinforcement element, its width is greater than 0.4 m, in particular greater than 0.8 m, and / or its length is greater than 4 m, in particular greater than 12 m. This enables efficient production of large concrete components. For example, a 20 m x 20 m concrete slab can be produced in one work cycle.

[0034] A further aspect of the invention relates to a method for producing a reinforcing element for prestressed concrete components, the method comprising the steps: Providing tensioned fibers by jointly drawing out a plurality of spaced-apart fibers; and attaching a holding element to the tensioned fibers, in particular by clamping and / or laminating, in order to fix the fibers in their mutual arrangement, in particular with regard to spacing and / or orientation.

[0035] This results in a largely parallel processing of the fibers and thus in a very efficient production of the reinforcement element and an advantageous arrangement of the fibers, in particular with regard to the further use of the reinforcement element, namely for tensioning the fibers before and during concreting.

[0036] In one example, the retaining element is severed after being connected to the fibers, particularly in the middle, so that the two resulting sections in turn form two retaining elements for two successively produced reinforcing elements. The first section forms the end of a first reinforcing element, and the second section forms the beginning of the subsequent reinforcing element.

[0037] In another example, the holding element is designed as a double holding element, with an open intermediate region between the two parts of the double holding element, in which the fibers are exposed. The aforementioned severing of the holding element can be achieved by simply separating the fibers in this intermediate region, for example, by breaking them. This achieves efficient separation during production, especially during series production, of the reinforcing elements.

[0038] In one embodiment of the method for producing the reinforcing element, the holding element is secured during the simultaneous drawing out of the fibers, in particular by moving the holding element synchronously with the movement of the fibers. This achieves very efficient production, especially in series production of the reinforcing elements.

[0039] In one embodiment of the method for producing the reinforcing element, the fastening of the holding element is carried out by fastening an upper part and a lower part of the holding element from opposite sides of the fibers, in particular by joining glass fiber mats.

[0040] In a further embodiment of the method for producing the reinforcing element, the fibers are arranged by placing them on a first part of the retaining element and are secured by adding a second part of the retaining element and pressing these two parts together. This tightly encloses the fibers in the retaining elements, resulting in a particularly strong and robust fastening.

[0041] Furthermore, the present invention relates to a prestressed concrete component, in particular a concrete slab, which was produced using at least one reinforcing element, wherein preferably the prestress of the concrete component is at least 80%, in particular at least 90%, of the breaking stress of the fibers.

[0042] In one example, this concrete component is manufactured using a plurality of reinforcing elements according to the invention, particularly arranged in groups. The grouped arrangement achieves improved adaptation to the specific conditions of the concrete component. Grouping can be achieved by one or more horizontal and / or vertical spacings or by an angular, particularly rectangular, arrangement.

[0043] In one example, the fibers are prestressed by section-by-section tensioning, specifically individually for each of the reinforcement elements used. This allows the prestressing to be flexibly adjusted to specific requirements.

[0044] In one example, the reinforcement spacing, i.e. the distance between two adjacent fibers, is less than or equal to twice the thickness of the concrete member, in particular less than or equal to twice the slab thickness.

[0045] As mentioned at the outset, the present invention relates, inter alia, to a method for producing a prestressed concrete component, the method being carried out according to claim 1.

[0046] This allows for highly efficient and easy-to-manage preparatory work, thus enabling cost-effective production of the concrete component. In particular, the time-consuming and complicated installation of individual fibers, especially delicate braiding, is eliminated. Thus, the method according to the invention is highly suitable for the manufacturing processes in a concrete component production plant.

[0047] The method according to the invention is particularly suitable for the production of large prestressed concrete components, for example, concrete slabs approximately 20 m wide and approximately 20 m long. In a subsequent work step, these large prestressed concrete components can then be divided into smaller prestressed concrete components, since the prestress of the concrete components is always maintained during division. The smaller concrete components can then be individually cut to size, for example by sawing, CNC milling, or waterjet cutting, to produce, for example, specially shaped floor slabs, stair treads, or table tennis table tops. Such subdivision can be achieved – as described in more detail below – by using separating elements, in particular a foam.

[0048] In a further embodiment of the method according to the invention for producing the prestressed concrete component, the provision of the at least one reinforcement element is achieved by arranging several of the reinforcement elements in a single layer, in particular by placing them largely parallel and / or adjacent to one another. This allows for efficient installation of large surfaces.

[0049] The inventive method for producing the prestressed concrete component is designed by providing the at least one reinforcement element by arranging the reinforcement elements in at least two layers, with the reinforcement elements in adjacent layers being aligned at an angle, in particular largely at right angles. This allows for efficient and flexible installation of a complex reinforcement. For example, the at least one reinforcement element is provided by stacking several of the reinforcement elements on top of one another.

[0050] In a further embodiment of the inventive method for producing the prestressed concrete component, this additionally comprises the step of introducing a separating element, in particular a foam, before concreting the concrete component. This achieves an effective subdivision of the concrete component. In particular, a foam offers a very flexible, easily applicable, and cost-effective subdivision. As a further function, the foam provides an aid for positioning the fibers and / or fixes the fibers during concreting. A solid material, for example, rubber or Styrofoam, can also be used as the separating element.

[0051] In a further embodiment of the above method for producing the prestressed concrete component, this additionally comprises the step of separating the concrete component after concreting, in particular by breaking and / or sawing. Since the foam does not make a significant contribution to the strength, the individual subdivisions of the concrete component are held together practically only by the fibers. Thus, the concrete components can be easily separated, in particular by simply breaking them. This achieves a convenient and very efficient division into easily manageable parts. For example, these parts can be distributed from a concrete component production plant to other production locations and brought into their final shape there. It is expressly pointed out that any combination of the aforementioned examples and embodiments or combinations of combinations can be the subject of a further combination.Only those combinations that would lead to a contradiction are excluded.

[0052] In the following, a selection of further conceivable embodiments of the invention and of further conceivable embodiments of partial aspects of the invention are described in more detail by way of example.

[0053] Further embodiments of the present invention or (partial) aspects of the present invention are explained in more detail below with reference to figures. They show: Fig. 1 is a simplified schematic representation of an embodiment of the reinforcing element 10 according to the invention with carbon fibers 12, which can be tensioned by means of two supports 14; Fig. 2 is a simplified schematic detailed view of a support 14 according to Fig. 1 ; Fig. 3 a simplified schematic representation of an intermediate state in the production of a prestressed concrete slab 20 by means of a plurality of reinforcing elements 10 according to Fig. 1 ; Fig. 4 a simplified schematic side view of the carrier 14 according to Fig. 2 ; Fig. 5 a simplified schematic representation according to Fig. 3 , but additionally with a construction foam 40 for subdividing the concrete slab 20 and fixing the carbon fibers 12; and Fig. 6 a simplified schematic side view of the support 14 according to Fig. 2 , although this one has a curvature.

[0054] The following statements are examples and are not intended to limit the invention in any way.

[0055] Fig. 1 shows a simplified schematic representation of an embodiment of a reinforcement element 10 in the stretched state. Such a reinforcement element 10 is used for the production of prestressed concrete components.

[0056] The reinforcing element 10 comprises ten individual fibers, which in this example are formed as carbon fibers 12 (only partially designated), and two holding elements in the form of two supports 14. The supports 14 are arranged at a distance from one another and are connected to one another by the ten carbon fibers 12. The carbon fibers 12 can be tensioned in their longitudinal direction T by pulling the supports 14 apart.

[0057] The carbon fibers 12 are secured to the supports 14 in such a way that the stretched carbon fibers 12 extend straight into the supports 14. Furthermore, the carbon fibers 12 form a substantially flat layer in which the carbon fibers 12 are arranged largely parallel and largely evenly spaced from one another. As a result, the reinforcing element 10 has the shape of a harp. In this example, the reinforcement spacing, i.e., the distance between the parallel carbon fibers 12, is approximately 10 mm, and thus the width of the reinforcing element 10 is approximately 10 cm.

[0058] Each of the carbon fibers 12 comprises a carbon roving, i.e., a bundle of several thousand stretched, juxtaposed, and essentially uniformly aligned filaments (approximately 2,000 to approximately 16,000 filaments). These filaments, and thus also the carbon fibers 12, are impregnated with an alkali-resistant resin in the form of vinyl ester resin, so that the carbon fibers 12 form a compact unit, similar to a metal wire. Impregnation can be achieved, for example, by means of an immersion bath through which the roving is drawn to produce the carbon fibers 12.

[0059] In addition, the carbon fibers 12 are coated with sand, resulting in an improved bond between the fibers and the concrete. In this example, with an embedment length of 100 mm, the full dimension tensile force can be transmitted via the mechanical shear connection.

[0060] Furthermore, the supports 14 each have two openings 16 (shown in dashed lines) by means of which the supports 14 can be positioned on a clamping device (not shown). The clamping device allows the carbon fibers 12 to be precisely aligned during the manufacture of the concrete components, in particular without horizontal and / or vertical tilting. In another example, the support 14 has one hole or a plurality of holes, in particular more than two holes, for positioning the support 14.

[0061] In one example, inexpensive materials are used to manufacture the carrier 14. An exemplary material composition and the corresponding manufacture of the carrier 14 is described with reference to Fig. 2 Other materials may also be used, since the support 14 is not part of the concrete component to be manufactured and is usually separated and removed after concreting.

[0062] Fig. 2 shows a simplified schematic detailed view of a carrier 14 according to Fig. 1 .

[0063] The carrier 14, also referred to as a patch, comprises a fiber-reinforced polymer matrix in the form of a polyester matrix with fibers enclosed therein in the form of two glass fiber mats. This polyester matrix encloses the stretched carbon fibers 12 in their end regions. For example, the size of this polyester matrix is ​​approximately 10 cm x 10 cm and the total thickness is approximately 2 mm. In another example, the length of the polyester matrix in the direction of the carbon fibers 12 is between approximately 10 cm and approximately 20 cm. The fiber mats form a lower and an upper layer, with the stretched carbon fibers 12 arranged between these layers and secured therein by lamination with polyester. The polyester matrix therefore forms a straight guide element for the carbon fibers 12 (indicated by dashed lines), with the carbon fibers 12 continuing largely in a straight line within the polyester matrix, ie within the carrier 14.By means of the carrier 14, the carbon fibers 12 are fixed in their mutual arrangement, namely in a flat position, largely parallel and evenly spaced from one another.

[0064] The ends of the carbon fibers 12 extend slightly beyond the supports 14 at the exit side of the supports 14. However, the fibers 12 can also end in the support 14 or flush with its surface, for example, if the support 14 has been separated from a larger unit.

[0065] For example, such a carrier 14 is produced by the following steps: Providing a plurality of adjacent and spaced-apart carbon rovings by largely simultaneously pulling the carbon rovings from a corresponding number of supply rolls; Impregnating the carbon rovings by passing the carbon rovings through a vinyl ester resin dip bath, so that the carbon rovings form compact carbon fibers 12; Jointly pulling out the carbon fibers 12, optionally by means of a previously attached carrier 14, so that the carbon fibers 12 are tensioned; Applying two polyester-impregnated glass fiber mats to the tensioned carbon fibers 12, one from below and the other from above; Joining the two glass fiber mats together, optionally adding an additional amount of polyester, so that the impregnated glass fiber mats and the polyester enclose the tensioned carbon fibers 12; and allowing the polyester to harden so that the carbon fibers 12 are firmly fixed in the carrier 14.

[0066] Through this lamination, the carrier 14 together with the carbon fibers 12 forms a compact and robust unit.

[0067] Fig. 3 shows a simplified schematic representation of an intermediate state during the production of a prestressed concrete slab 20, for example, in a precast concrete slab plant. The intermediate state corresponds to an arrangement after completion of the preparatory work, but before the concrete slab 20 is poured.

[0068] The assembly comprises a concreting table (not shown), a hollow frame 30 arranged thereon, and a plurality of identical reinforcing elements 10 according to the invention (some of which are only schematically indicated). The hollow frame 30, together with the surface of the concreting table, forms a casting mold for the concrete, also called a prestressing bed.

[0069] The reinforcement elements 10 each comprise a plurality of carbon fibers 12 (for the sake of clarity, only the outer fibers are shown) and two supports 14 and their structure largely corresponds to the reinforcement elements 10 according to Fig. 1 In this example, however, the length of the carbon fibers 12 is approximately 20 m and the width of the beams 14 is approximately 1 m. The reinforcement spacing corresponds to the previous example, ie as in Fig. 1 approx. 10 mm, so that approx. 100 carbon fibers 12 are attached to each of the supports 14.

[0070] When arranging the reinforcing elements 10, the supports 14 are each pulled apart so that the carbon fibers 12 in the hollow frame 30 are in a stretched state. The carbon fibers 12 are guided outwards through the hollow frame 30 so that the ends of the carbon fibers 12 and the supports 14 are located outside the hollow frame 30, for example, at a distance of 30 cm from the hollow frame 30. In a two-part hollow frame 30, the passage channels can also be formed by corresponding gaps between the lower and upper parts of the hollow frame 30. The hollow frame 30 is constructed from several superimposed strips so that the carbon fibers 12 can be guided through the spaces between the individual strips. The spaces can additionally be sealed with foam rubber and / or brush bristles. In one example, the height of the superimposed strips is 3 mm, 12 mm, and 3 mm.

[0071] In the illustrated arrangement, the first half of the reinforcement elements 10 are arranged in a first layer, parallel and adjacent to one another, and the second half of the reinforcement elements 10 are arranged in a second layer, also parallel and adjacent to one another, but perpendicular to the reinforcement elements 10 of the first layer. The reinforcement elements 10 are thus stacked in separate layers and aligned at right angles to one another in the two adjacent layers. The reinforcement elements 10 therefore form both longitudinal and transverse reinforcement, but without individual interweaving of the individual carbon fibers 12.

[0072] After the reinforcement elements 10 are arranged, the beams 14 are pulled apart, for example, using a tensioning device, also called a prestressing system, or manually with a torque wrench (not shown). For example, a tension of at least approximately 30 kN / m or at least approximately 300 kN / m is generated, depending on the load requirements of the concrete slab (sizing force).

[0073] Following the situation shown, concrete can be poured into the hollow frame 30 prepared in this way in order to concrete the concrete slab 20 in one operation.

[0074] The sections of the tensioned carbon fibers 12 located in the hollow frame 30 are enclosed in concrete and thus encased. SCC fine-grained concrete (at least C30 / 37 according to standard SIA SN505 262) is particularly suitable, as it can easily flow through the spaces between the carbon fibers 12. However, the concrete can also be injected or spread into the hollow frame 30 and evenly distributed by vibration.

[0075] After the concrete has hardened, the concrete slab 20 can be removed from the hollow frame 30. The encased carbon fibers 12 form the structural reinforcement of the concrete slab 20. The portions of the carbon fibers 12 protruding from the concrete are broken off at the edges of the concrete slab 20 and removed together with the supports 14. In this example, the manufactured concrete slab measures approximately 6 m x 2.5 m, and the reinforcement content of this concrete slab 20 is more than 20 mm² / m width. In another example, the manufactured concrete slab measures approximately 7 m x 2.3 m.

[0076] Fig. 4 shows a simplified schematic side view of a carrier 14 according to Fig. 2 The carbon fibers 12 extend in a straight line into the carrier 14. Furthermore, the carbon fibers 12 continue in a straight line inside the carrier 14, so that the carrier 14 forms a straight guide for the carbon fibers 12. In this example, the length of the carrier 14 in the direction of the carbon fibers 12 is approximately 3 cm.

[0077] The support 14 can additionally have a profile 16 (shown in dashed lines). In this example, a serrated profile 16 is arranged on a first (upper) surface and on the opposite (lower) surface of the support 14. These surfaces are intended for fastening the support 14 in a clamping device (not shown), for example by clamping. The serrated profile 16 creates a force-locking connection between the support 14 and the clamping device in the form of a toothing.

[0078] Fig. 5 shows a representation according to Fig. 3 However, in the case of the reinforcement elements 10, an additional subdivision is created by foaming a construction foam 40 (shown as a wavy line) as a separating element both onto the bottom of the hollow mold and under and over the carbon fibers 12. This subdivision prevents any or only a negligible amount of the poured concrete from penetrating the space filled by the subdivision. Thus, only the subspaces of the hollow frame with the fiber components contained therein are concreted. Furthermore, the construction foam 40 secures the fibers during concreting.

[0079] After the concrete has hardened, the concrete slab 20 can be broken into individual raw slabs along the expansion foam dividers. These raw slabs can then be further processed, for example, by cutting them into the desired shape with a circular saw.

[0080] In this example, the manufactured concrete slab measures approximately 20 m x 20 m and is approximately 20 mm thick. Dividing the concrete slab 20 according to the subdivision using the 40 mm foam creates 24 smaller slabs measuring approximately 5 m x 3 m. These smaller slabs can then be sawn into three ping-pong tables, for example.

[0081] Fig. 6 shows a simplified schematic side view of a carrier 14 according to Fig. 2, however, this has a means for force distribution in the form of a curvature 18. The carbon fibers 12 flow straight into the carrier 14 and then run inside the carrier 14, corresponding to the curvature 18 of the carrier 14, also with a curvature. The carbon fibers 12 are attached in the entry area of ​​the carrier 14 in such a way that the carbon fibers 12 continue largely straight into the carrier 14 over a distance d of 10 mm. This shape achieves both a good introduction of the fibers into the carrier 14 and an even distribution of the forces to be absorbed.

Claims

1. Method for producing a prestressed concrete component (20), comprising, preferably in the following order, the steps: - providing at least one reinforcing element (10) comprising a plurality of carbon fibers (12) and several removable holding elements (14), which are connected to each other by the carbon fibers (12), so that the carbon fibers (12) can be tensioned in their longitudinal direction (T) by means of the holding elements (14), wherein the carbon fibers (12) are attached to the holding elements (14) in such a way that the carbon fibers (12) open into the holding elements (14) in a largely straight line when tensioned, the carbon fibers (12) have a net cross-sectional area of less than 5 mm2, and the carbon fibers (12) are attached to the holding elements (14) by laminating or by laminating and clamping and are fixed in their mutual arrangement; - tensioning the carbon fibers (12) of the reinforcing element (10) by pulling apart the associated holding elements (14) in their longitudinal direction (T); and - concreting of the concrete component (20) with at least partial concreting of the tensioned carbon fibers (12) .

2. The method of claim 1, wherein providing at least one reinforcing element is effected by arranging several reinforcing elements (10) in at least one layer, in particular by placing them largely parallel and / or adjacent next to each other, and / or wherein the provision of at least one reinforcing element (10) is effected by arranging the reinforcing elements (10) in at least two layers, wherein the orientation of the reinforcing elements (10) in adjacent layers is at an angle, in particular, substantially at a right angle.

3. The method according to one of claims 1 or 2, wherein the tensioning of the carbon fibers (12) of the reinforcing element (10) is carried out by sectional tensioning, in particular individual tensioning for each of the used reinforcing elements.

4. The method of one of claims 1 to 3 comprising: - inserting a separating element, in particular a foam (40) or a solid material such as rubber or polystyrene, before concreting the concrete component (20).

5. The method of one of the preceding claims, wherein the carbon fibers (12): - are individual fibers; and / or - comprise one or more rovings, in particular carbon rovings; and / or - form an essentially flat layer in the holding elements (14) .

6. The method according to one of the preceding claims, wherein the holding elements (14) comprise guide elements for the fibers (12), in particular a clamping device and / or a carrier for laminating the carbon fibers (12) in the end area, further in particular a fiber-reinforced polymer matrix, further in particular a polyester matrix.

7. The method according to one of the preceding claims, wherein the tensioning of the carbon fibers (12) is carried out with a tension of approx. 50% to approx. 95% of the breaking stress of the carbon fibers, in particular with at least approx. 80% of the breaking stress of the carbon fibers, further in particular with at least approx. 90% of the breaking stress of the carbon fibers.

8. The method according to one of the preceding claims, wherein: - the carbon fibers (12) are arranged largely parallel to each other in the holding elements (14); and / or - the carbon fibers (12) in the holding elements (14) are arranged largely evenly spaced from each other; and / or - the reinforcing distance is approx. 5 mm to approx. 40 mm, in particular approx. 8 mm to approx. 25 mm; and / or - at least 10, in particular at least 40, fibers (12) are attached to each of the holding elements (14).

9. The method according to one of the preceding claims, wherein the carbon fibers (12) are attached to the holding elements (14) in such a way that the carbon fibers (12) continue in a largely straight line in the holding elements (14) in the tensioned state, in particular over a distance (d) of at least approx. 5 mm, further in particular at least approx. 10 mm.

10. The method according to one of the preceding claims, wherein the holding elements (14) have a means for force distribution, in particular transversely to the direction of the carbon fibers (12), in particular a curvature (18) and / or a profile (16).

11. The method according to one of the preceding claims, wherein the carbon fibers (12) form an essentially flat layer wherein the carbon fibers (12) are arranged largely parallel and largely evenly spaced from each other, so that the reinforcing element (10) has the shape of a harp and is not a lattice.

12. The method according to one of the preceding claims, wherein providing at least one reinforcing element (10) comprises: - providing tensioned carbon fibers (12) by jointly pulling out a plurality of carbon fibers spaced apart from each other (12); and - fastening a holding element (14) to the tensioned carbon fibers (12) by laminating or clamping and laminating in order to fix the carbon fibers (12) in their mutual arrangement, in particular with regard to distance and / or orientation, wherein the fastening of the holding element (14) is carried out in particular during the joint extraction of the carbon fibers (12), further in particular by moving the holding element (14) in parallel with the movement of the carbon fibers (12).

13. The method of claim 12, wherein after fastening the holding element (14) to the tensioned carbon fibers (12) the holding element is severed.

14. The method according to one of the preceding claims, wherein after concreting the concrete component (20), the parts of the carbon fibers (12) protruding from the concrete are broken off at the edges of the concrete component (20) and removed together with the holding elements (14).

15. Concrete component (20), in particular concrete slab, produced by the method according to one of claims 1 to 14, having a plurality of carbon fibers (12) tensioned in their longitudinal direction (T), wherein: - the carbon fibers (12) have a net cross-sectional area of less than 5 mm2; and - the carbon fibers (12) form at least two layers, wherein the orientation of the carbon fibers (12) in adjacent layers is at an angle.