EP2912239B1 - Reinforcing element for producing prestressed concrete components, concrete component and production methods - Google Patents

Description

The present invention relates to a reinforcement element for the production of prestressed concrete components. Furthermore, the invention relates to a prestressed concrete component and manufacturing method for the reinforcement element and the prestressed concrete component.

Prestressed concrete slabs are known from the prior art. For example disclosed US 2002/0059768 A1 a method for producing a prestressed concrete slab using tensioned wire ropes. To generate the tension, the wire ropes are wound around opposite bolts and then tensioned by moving the bolts apart. This results in a pre-tension of approx. 70% of the breaking strength of the wire rope.

Another reinforcement element is from the U.S. 2010/132282 A1 and the U.S. 2007/175583 A1 known.

The object of the present invention is to specify an improved reinforcement element for the production of prestressed concrete components, an improved concrete component and improved production methods for the reinforcement element and the prestressed concrete component.

This object is achieved by a reinforcement element with the features of claim 1 and a concrete component and manufacturing method according to the associated claims.

Further embodiments according to the invention are specified in the further claims.

Furthermore, the present invention relates to a reinforcement element for the production of prestressed concrete components, with a large number of fibers and several holding elements which are connected to one another by the fibers so that the fibers can be tensioned in their longitudinal direction by means of the holding elements. The fibers, which have a net cross-sectional area of less than 5 mm ² and are coated with a granular material, in particular sand, and form an essentially flat layer in the holding elements (14), are attached to the holding elements by lamination or laminating and clamps fastened in such a way that the fibers in the tensioned state open out largely in a straight line into the holding elements. This achieves both high prestressing and efficient, reliable and therefore cost-effective production of the concrete components.

The term "fiber" includes both a single or several elongated and flexible reinforcement elements for concrete components, for example a single filament - also called single filament or monofilament - or a bundle of filaments - also called multifilament, multifilament yarn, yarn or - in the case of stretched filaments - roving. In particular, the term fiber also includes a single wire or multiple wires. Furthermore, the fibers can also be used individually or coated together and/or the fiber bundle may be stranded or twisted.

The net cross-sectional area of the fibers (ie, without resin impregnation) is less than about 5 mm ² , and specifically ranges from about 0.1 mm ² to about 1 mm ² . In one example, the tensile elongation of the fibers is greater than about 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 .

When producing a prestressed concrete component, for example, the reinforcement elements according to the invention are first laid in a mold and then the fibers are stretched by pulling the corresponding holding elements apart. The concrete component is then cast, with the parts of the fibers lying inside the mold being embedded in concrete. After the concrete has hardened, the tension previously applied to the fibers is released, with the tension in the cast-in parts of the fibers being maintained, since the cast-in fiber parts are frictionally connected to the concrete and there is practically no relative displacement between these fiber parts and the concrete. The non-positive connection is based - among other things - on the wedging of the fibers in their concrete coating (Hoyer effect). The projecting from the concrete component stress-free parts of the fibers can be separated and together with the Holding elements are removed. In the case of the prestressed concrete component, the prestress is therefore generated by the tension of the fibers embedded in concrete.

The connection between fibers and concrete can be strengthened by a variety of means, for example by increasing the surface roughness of the fibres. In one example, this connection is designed in such a way that the full dimensioning tensile force can be transmitted via the mechanical shear connection after 200 mm, in particular after 100 mm, further after in particular 70 mm, binding length (i.e. length of the fibers embedded in concrete).

The fibers of the reinforcing element according to the invention can be made from a large number of different materials, in particular from non-corrosive material and more particularly from alkali-resistant material. For example, this material is a polymer like carbon, but also glass, steel or natural fibers.

For example, the fibers are made of carbon. Carbon fibers have the advantage that they are very durable, which means that there is no noticeable loss of strength even over decades. In addition, carbon fibers are corrosion-resistant, in particular they do not corrode on the surface of the concrete components, and are practically invisible. This means that the carbon fibers can often be left on the surface of the concrete components. However, they can also be removed with ease, for example by breaking them off or simply stripping them off.

Fastening the fibers “in” the holding elements includes a wide variety of fastening options, in particular also fastening the fibers “to” or “on” the holding elements, for example laminating the fibers without further covering.

Surprisingly, with the solution according to the invention, both a high prestressing of the concrete components and an efficient, reliable and simple handling of the reinforcing elements are achieved. As a result, the concrete components can be produced particularly inexpensively. In particular, the following is achieved:
Due to the fact that the fibers flow in a largely straight line with respect to their longitudinal direction, ie the fibers continue to flow evenly into the holding elements, transverse stresses in the fibers are largely avoided. Such transverse stresses often lead to fiber breaks and occur, for example, at kinks, jams or tight curve radii, i.e. typically with deflection webs, deflection rollers or guide bolts. Thanks to the fastening of the fibers according to the invention with the good introduction of the forces acting into the holding 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 in the case of carbon fibers, in particular in the case of impregnated carbon fibers, since these are particularly at risk of breaking with regard to transverse stresses.

In one example, the fibers, particularly the carbon fibers, can be stressed at a stress of from about 50% to about 95% of the breaking stress of the fibers. In another example, the fibers can be stressed with at least about 80%, more preferably at least about 90%, of the breaking stress of the fibers. As a result, a cost-effective production of very stable, large and thin concrete components is achieved. A high prestressing of the concrete component is particularly advantageous with carbon fibers, since carbon fibers have a different expansion behavior than concrete.

Thanks to the reinforcement elements according to the invention, large and thin concrete components can be produced which practically do not sag under load. In one example, the thickness of the concrete component to be produced is in the range from approx. 10 mm to 60 mm, in particular approx. 15 mm to 40 mm. In another example, the surface area of the concrete component is at least approx. 10 m x 5 m, in particular at least approx. 10 m x 10 m, more particularly at least approx. 15 m x 15 m. In another example, the length of the concrete component is at least approx m, further in particular at least approx. 12 m.

Furthermore, the reinforcing elements can be produced as intermediate products at a first location, possibly packed in appropriate transport containers and transported to another location for the production of the concrete parts become. At the other location, for example in a concrete production plant, the reinforcement elements that have been delivered are then directly available as prefabricated components.

Furthermore, the connection of the fibers to the holding elements according to the invention results in a robust and space-saving unit, which is therefore easy to transport.

In one embodiment of the present invention, the fibers are individual fibers and/or comprise one or more rovings, in particular carbon rovings. As a result, the production of particularly stable and light concrete components is achieved. Individual fibers are to be understood as meaning individual fibers that are not directly connected. In contrast, a continuous fiber assembly is seen where the reciprocating portions of the fiber assembly are connected via loops.

The term "roving" means a bundle of stretched filaments. Such a roving, also referred to as a stretched yarn, typically comprises a few thousand filaments, in particular approximately 2,000 to approximately 16,000 filaments. Due to the roving, the tensile forces acting on the fibers are distributed largely evenly over a large number of filaments, so that local peak loads are largely avoided.

Furthermore, the filaments of the roving have a small fiber diameter, so that a correspondingly large surface-to-diameter ratio and thus a good bond between the concrete and the filaments is achieved. Furthermore, a good shear transmission and a good distribution of the tensile load on the concrete are achieved.

In one example, the fibers are produced from an arrangement of several rovings, which comprises 2 to 10, in particular 2 to 5, individual rovings. Thus, these fibers have about 4,000 to about 160,000 filaments.

In one embodiment of the present invention, the holding elements have 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. Good power transmission is achieved by these guide elements. In addition, a particularly space-saving and robust unit is achieved through the lamination. The holding elements can also be designed as double-sided adhesive tape.

According to the present invention, the fibers in the holding elements form an essentially planar layer and, in one embodiment, are arranged in particular largely parallel and/or largely evenly spaced from one another.

As a result, the reinforcement element has the shape of a track or a harp. This form is easily stacked or rolled up, optionally using interleaving sheets to keep the respective fibers separate. This means that reinforcement elements are easy to transport.

Such a harp-shaped reinforcement element has the advantage over a lattice (grid) that no knotting occurs and thus very high tensile loads can be achieved. In addition, there are no complicated production steps such as weaving or braiding and there is a high degree of flexibility with regard to the width of the webs, since no machines are required to produce a grid. Therefore, so-called "endless products" can be produced in a simple manner, both in terms of length and width.

In one embodiment of the present invention, the reinforcement element has additional spacers which connect the fibers to one another, for example in the form of transverse threads and/or a fabric, so that there is a distance between the individual fibers even when the reinforcement element is not tensioned or is only partially tensioned. This largely or completely prevents the slack fibers from becoming tangled. These spacers thus serve as an assembly aid and/or transport aid. When concreted in, the spacers absorb practically no tensile loads.

In one embodiment of the present invention, the distance between the reinforcements is about 5 mm to about 40 mm, in particular about 8 mm to about 25 mm, and/or at least 10, in particular at least 40 fibers are fixed in each of the holding elements. For example, the reinforcement distance, ie the distance between two adjacent fibers, is less than or equal to twice the thickness of the concrete component.

In one embodiment of the present invention, the fibers are impregnated with an alkali-resistant polymer, in particular with a resin, more particularly with a vinyl ester resin. This increases the tensile strength of the fibers.

According to the present invention, the fibers are coated with a granular material, in particular with sand. This improves the bond between the fibers and the concrete and thus increases the resistance of the prestressing in the concrete component.

According to the present invention, the fibers are fastened to the holding elements in such a way that, in the tensioned state, the fibers continue largely in a straight line in the holding elements, in particular over a distance of at least approx. 5 mm, more particularly at least approx. 10 mm. This achieves good power transmission between the fibers and the holding elements.

In one embodiment of the present invention, the holding elements have means for force distribution, in particular running transversely to the direction of the fibers, in particular a curvature and/or a profile. This achieves good distribution of the acting forces and thus high tensile stress and/or low stress on the fibers during tensioning. In addition, this shortens the binding length, that is, shortens the length required for reliable attachment of the fibers to the holding elements.

In one example, the curvature of the holding element is designed in such a way that the curved fibers each define planes that are arranged largely parallel, in particular perpendicular to the position of the fibers. If the fibers are arranged in a horizontal position, their fiber ends are curved vertically downwards or upwards, for example.

In particular, the profiling achieves a good non-positive connection between the holding element and the clamping device. The pressure on the holding element and/or on the fibers can thus be reduced. In one example, the profiling is arranged on at least one of those surfaces of the holding element which is provided for fastening the holding element in a clamping device. In another example, the Profiling wavy or jagged, especially saw-toothed.

In one embodiment of the reinforcing element according to the invention, 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. Efficient production of large concrete components is thereby achieved. For example, a 20 m x 20 m concrete slab can be produced in one work cycle.

• Bereitstellen von gespannten Fasern durch gemeinsames Ausziehen einer Vielzahl von untereinander beabstandeten Fasern, wobei die Fasern (12) eine Netto-Querschnittsfläche von kleiner 5 mm² aufweisen und mit einem körnigen Material, insbesondere mit Sand, beschichtet sind; und
• Befestigen eines Halteelements an den gespannten Fasern, insbesondere durch Klemmen und/oder Laminieren, um die Fasern in ihrer gegenseitigen Anordnung, insbesondere bezüglich Abstand und/oder Ausrichtung, zu fixieren, wobei die Fasern (12) in dem Halteelement (14) eine im Wesentlichen ebene Lage bilden.

Furthermore, the present invention relates to a method for producing a reinforcing element for prestressed concrete components, the method comprising the steps:

• providing tensioned fibers by drawing a plurality of spaced fibers together, said fibers (12) having a net cross-sectional area of less than 5 mm ² and being coated with a granular material, particularly sand; and
• Fastening a holding element to the taut fibers, in particular by clamping and/or laminating, in order to fix the fibers in their mutual arrangement, in particular with regard to distance and/or orientation, the fibers (12) in the holding element (14) having a substantially form an even layer.

This results in a largely parallel processing of the fibers and thus 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.

In one example, the holding element is severed after being connected to the fibers, in particular in the middle, so that the two sections produced in turn form two holding elements for two reinforcing elements produced in succession. The first section forms the end of a first reinforcement element and the second section forms the beginning of the subsequent reinforcement element.

In another example, the holding element is designed as a double holding element, with an open intermediate area between the two parts of the double holding element in which the fibers are exposed. The previously mentioned severing of the holding element can be done by simply severing the fibers in this intermediate area, for example by breaking. As a result, efficient separation is achieved during production, in particular in series production, of the reinforcement elements.

In one embodiment of the method according to the invention for producing the reinforcement element, the retaining element is fastened while the fibers are being pulled out together, in particular by moving the retaining element in synchronism with the movement of the fibers. As a result, a very efficient production is achieved, in particular in the series production of the reinforcement elements.

In one embodiment of the method according to the invention for producing the reinforcement element, the retaining element is fastened by fastening an upper part and a lower part of the retaining element from opposite sides of the fibers, in particular by assembling glass fiber mats.

In a further embodiment of the method according to the invention for producing the reinforcement element, the fibers are arranged by placing the fibers on a first part of the holding element and fixing the fibers by adding a second part of the holding element and by pressing these two parts together. As a result, the fibers are firmly enclosed by the holding elements, so that a particularly strong and robust attachment is achieved.

Furthermore, the present invention relates to a prestressed concrete component, in particular a concrete slab, which was produced using at least one reinforcing element according to the invention, the prestressing of the concrete component being at least 50%, in particular at least 80%, more in particular at least 90%, of the breaking stress of the fibers.

The present invention further relates to a concrete component, in particular a concrete slab, comprising a large number of fibers which are tensioned in their longitudinal direction. The Fibers have a net cross-sectional area of less than 5 mm ² , are coated with a granular material, in particular sand, and form at least one essentially planar layer, with the prestressing of the concrete component being at least 50%, in particular at least 80%, more particularly at least 90%, the breaking stress of the fibers.

In one example, this concrete component is produced using a large number of reinforcing elements according to the invention, in particular arranged in groups. Due to the arrangement in groups, an improved adaptation to the conditions of the concrete component is achieved. A grouping can be achieved by one or more horizontal and/or vertical distances or by an angular, in particular right-angled, arrangement.

In one example, the fibers are pretensioned by tensioning in sections, in particular individually for each of the reinforcement elements used. As a result, the preload can be flexibly adjusted to specific requirements.

In one example, the reinforcement distance, ie the distance between two adjacent fibers, is less than or equal to twice the thickness of the concrete component, in particular less than or equal to twice the plate thickness.

• Bereitstellen mindestens eines erfindungsgemässen Armierungselements;
• Spannen der Fasern des Armierungselements durch Auseinanderziehen der zugehörigen Halteelemente; und
• Betonieren des Betonbauteils unter zumindest teilweisem Einbetonieren der gespannten Fasern.

Furthermore, the present invention relates to a method for producing a prestressed concrete component, the method comprising the steps:

• providing at least one reinforcement element according to the invention;
• Tensioning of the fibers of the reinforcement element by pulling apart the associated holding elements; and
• Concreting of the concrete component with at least partial concreting of the tensioned fibers.

This results in very efficient and easy-to-handle preparatory work and therefore a cost-effective one Production of the concrete component achieved. In particular, there is no need for time-consuming and complicated laying work for individual fibers, in particular filigree braiding work. The method according to the invention is therefore very well suited for the production processes in a production plant for concrete components.

The method according to the invention is particularly suitable for the production of large prestressed concrete components, for example for concrete slabs approximately 20 m wide and approximately 20 m long. In a subsequent work step, these large prestressed concrete components can then be subdivided into smaller prestressed concrete components, since the prestressing 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 water jet cutting, in order to produce, for example, specially shaped floor panels, stair treads or panels for table tennis tables. As described in more detail below, such a subdivision can be achieved by using separating elements, in particular a foam.

In a further embodiment of the method according to the invention for producing the prestressed concrete component, the at least one reinforcement element is provided by arranging several of the reinforcement elements in one layer, in particular by largely parallel and/or adjacent ones To lay next to each other. This means that large areas can be set up efficiently.

In a further embodiment of the method according to the invention for producing the prestressed concrete component, the at least one reinforcement element is provided 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 achieves an efficient and flexible set-up 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.

In a further embodiment of the method according to the invention for producing the prestressed concrete component, this additionally includes the step of introducing a separating element, in particular a foam, before the concrete component is cast in concrete. This achieves an effective subdivision of the concrete component. In particular, a foam offers a very flexible, easy to use and inexpensive partition. As a further function, the foam offers an aid for positioning the fibers and/or fixing the fibers during concreting. A solid material can also be used as a separating element, for example rubber or styrofoam.

In a further embodiment of the above method for producing the prestressed concrete component, this additionally includes 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 practically only held together by the fibers. The concrete components can thus be easily separated, in particular by simply breaking them. This achieves a breakdown into manageable parts in a convenient and very efficient way. For example, these parts can be distributed from a production plant for concrete components to other work stations and brought into the final form 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 which would result in a contradiction or are outside the scope of the claims are excluded.

Fig. 1

eine vereinfachte schematische Darstellung eines Ausführungsbeispiels des erfindungsgemässen Armierungselements 10 mit Carbon-Fasern 12, die mittels zweier Träger 14 gespannt werden können;

Fig. 2

eine vereinfachte schematische Detailansicht eines Trägers 14 gemäss Fig. 1;

Fig. 3

eine vereinfachte schematische Darstellung eines Zwischenzustands bei der Herstellung einer vorgespannten Betonplatte 20 mittels einer Vielzahl von Armierungselementen 10 gemäss Fig. 1;

Fig. 4

eine vereinfachte schematische Seitenansicht des Trägers 14 gemäss Fig. 2;

Fig. 5

eine vereinfachte schematische Darstellung gemäss Fig. 3, jedoch zusätzlich mit einem Bauschaum 40 zur Unterteilung der Betonplatte 20 und Fixierung der Carbon-Fasern 12; und

Fig. 6

eine vereinfachte schematische Seitenansicht des Trägers 14 gemäss Fig. 2, wobei dieser jedoch eine Krümmung aufweist.

Further exemplary embodiments of the present invention are explained in more detail below with reference to figures. Show it:

1

a simplified schematic representation of an embodiment of the inventive reinforcement element 10 with carbon fibers 12, which can be stretched by means of two carriers 14;

2

a simplified schematic detailed view of a carrier 14 according to 1 ;

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 1 ;

4

a simplified schematic side view of the carrier 14 according to 2 ;

figure 5

a simplified schematic representation according to 3 , but additionally with a construction foam 40 for subdividing the concrete slab 20 and fixing the carbon fibers 12; and

6

a simplified schematic side view of the carrier 14 according to 2 , but this has a curvature.

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

1 shows a simplified schematic representation of an embodiment of the inventive reinforcement element 10 in the stretched state. Such a reinforcement element 10 is used to produce prestressed concrete components.

The reinforcement element 10 comprises ten individual fibers, which in this example are carbon fibers 12 (only partially designated) are formed, and two holding elements in the form of two carriers 14. The carriers 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 carriers 14 apart.

The carbon fibers 12 are preferably fastened in the supports 14 in such a way that the stretched carbon fibers 12 open into the supports 14 in a straight line. Furthermore, the carbon fibers 12 form an essentially planar layer, in which the carbon fibers 12 are arranged largely parallel and at a largely even distance from one another. As a result, the reinforcement element 10 has the shape of a harp. In this example, the distance between the reinforcements, i.e. the distance between the carbon fibers 12 arranged in parallel, is approximately 10 mm and the width of the reinforcement element 10 is therefore approximately 10 cm.

Each of the carbon fibers 12 comprises a carbon roving, ie a bundle of a few thousand stretched filaments arranged next to one another and essentially aligned in the same way (approx. 2,000 to approx. 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. The impregnation can, for example, by means of a Take place immersion bath through which the roving for the production of the carbon fibers 12 is pulled.

In addition, the carbon fibers 12 are coated with sand, so that an improved connection between fibers and concrete is achieved. In this example, with an anchoring length of 100 mm, the full dimensioning tensile force can be transmitted via the mechanical shear connection.

Furthermore, the carriers 14 each have two openings 16 (shown in dashed lines) by means of which the carriers 14 can be positioned on a clamping device (not shown). With the clamping device, the carbon fibers 12 can be aligned precisely during the production of the concrete components, in particular without horizontal and/or vertical tilting. In another example, the carrier 14 has a hole or a multiplicity of holes, in particular more than two holes, for positioning the carrier 14 .

In one example, carrier 14 is manufactured using inexpensive materials. An exemplary material composition and the corresponding production of the carrier 14 is based on 2 described. Other materials can also be used since the carrier 14 is not part of the concrete component to be produced and is usually separated and removed after concreting.

2 shows a simplified schematic detail view of a carrier 14 according to FIG 1 .

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 areas. For example, the size of this polyester matrix is about 10 cm x 10 cm and the total thickness is about 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, the stretched carbon fibers 12 being arranged between these layers and fixed therein by lamination with polyester. The polyester matrix therefore forms a rectilinear guide element for the carbon fibers 12 (indicated by dashed lines), with the carbon fibers 12 continuing largely rectilinearly within the polyester matrix, ie within the carrier 14 . The carbon fibers 12 are fixed in their mutual arrangement by means of the carrier 14, namely in a flat position, largely parallel and spaced evenly apart from one another.

The ends of the carbon fibers 12 protrude a little beyond the supports 14 on the exit side of the supports 14 . However, the fibers 12 can also end in the carrier 14 or flush on its surface, for example if the carrier 14 has been separated from a larger unit.

• Bereitstellen einer Vielzahl von nebeneinanderliegenden und untereinander beabstandeten Carbon-Rovings durch weitgehend gleichzeitiges Abziehen der Carbon-Rovings von einer entsprechenden Anzahl von Vorratsrollen;
• Imprägnieren der Carbon-Rovings mittels Durchleiten der Carbon-Rovings durch ein Vinylesterharz-Tauchbad, so dass die Carbon-Rovings kompakte Carbon-Fasern 12 bilden;
• Gemeinsames Ausziehen der Carbon-Fasern 12, gegebenenfalls mittels eines bereits zuvor angebrachten Trägers 14, so dass die Carbon-Fasern 12 gespannt werden;
• Anlegen zweier mit Polyester getränkter Glasfasermatten an die gespannten Carbon-Fasern 12, eine von unten und die andere von oben;
• Zusammenfügen der beiden Glasfasermatten, gegebenenfalls unter Hinzufügen einer zusätzlichen Menge des Polyesters, so dass die getränkten Glasfasermatten und der Polyester die gespannten Carbon-Fasern 12 umschliessen; und
• Erhärtenlassen des Polyesters, so dass die Carbon-Fasern 12 kraftschlüssig im Träger 14 befestigt sind.

For example, such a carrier 14 is produced by the following steps:

• providing a multiplicity of carbon rovings lying next to one another and spaced apart from one another by largely simultaneously drawing off the carbon rovings from a corresponding number of supply rolls;
• impregnating the carbon rovings by passing the carbon rovings through a vinyl ester resin immersion bath so that the carbon rovings form compact carbon fibers 12;
• Pulling out the carbon fibers 12 together, if necessary by means of a carrier 14 that has already been attached beforehand, so that the carbon fibers 12 are tensioned;
• applying two fiberglass mats impregnated with polyester to the tensioned carbon fibers 12, one from below and the other from above;
• Joining the two glass fiber mats, optionally with the addition of 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 fixed in the carrier 14 in a non-positive manner.

As a result of this lamination, the carrier 14 forms a compact and robust unit together with the carbon fibers 12 .

3 FIG. 12 shows a simplified schematic representation of an intermediate stage in the manufacture of a prestressed concrete slab 20, for example in a prefabricated concrete slab plant. The intermediate state corresponds to an arrangement after the preparatory work has been completed, but before the concrete slab 20 is poured.

The arrangement comprises a concreting table (not shown), a hollow frame 30 arranged thereon and a multiplicity of identical reinforcing elements 10 according to the invention (in some cases only indicated schematically). Together with the surface of the concreting table, the hollow frame 30 forms a mold for the concrete, also called a prestressing bed.

The reinforcement elements 10 each have a large number of carbon fibers 12 (for the sake of clarity, only the outer fibers are shown in some cases) and two carriers 14 and largely correspond in their structure 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 carrier 14 is approximately 1 m. The distance between the reinforcements corresponds to the previous example, ie as in FIG 1 approx. 10 mm, so that approx. 100 carbon fibers 12 are fastened to the carriers 14 in each case.

When arranging the reinforcement elements 10, the carriers 14 are each pulled apart, so that the carbon fibers 12 are in the hollow frame 30 in the 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 outside of the hollow frame 30, for example at a distance of 30 cm from the hollow frame 30. In the case of a two-part hollow frame 30, the passage channels are also formed by corresponding gaps between the lower part and the upper part of the hollow frame 30 . In this case, the hollow frame 30 is constructed from a plurality of slats lying one above the other, so that the carbon fibers 12 can be guided through the interstices of the individual slats. The gaps can also be sealed with foam rubber and/or brush hairs. In one example, the height of the superimposed bars is 3mm, 12mm and 3mm.

In the arrangement shown, the first half of the reinforcing elements 10 are in a first layer, parallel and adjacent to each other and the second half of the reinforcing elements 10 are in a second layer, also parallel and adjacent to but perpendicular to the reinforcing elements 10 of the first layer. The reinforcing elements 10 are thus superimposed in separate layers and in the two adjacent ones Layers aligned at right angles to each other. The reinforcement elements 10 therefore form both a longitudinal reinforcement and a transverse reinforcement, but without individual interweaving of the individual carbon fibers 12.

After the reinforcement elements 10 have been arranged, the carriers 14 are pulled apart, for example with a clamping device, also called a prestressing system, or manually with a torque wrench (not shown). For example, a stress of at least approx. 30 kN/m or at least approx. 300 kN/m is generated, depending on the load requirements on the concrete slab (dimensioning force).

Subsequent to 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. The parts of the tensioned carbon fibers 12 which are located in the hollow frame 30 are enclosed by the concrete and thus embedded in concrete. SCC fine concrete (at least C30/37 according to the SIA SN505 262 standard) which can easily flow through the spaces between the carbon fibers 12 is particularly suitable. However, the concrete can also be introduced into the hollow frame 30 by spraying or spatula and evenly distributed by vibration.

After the concrete has hardened, the concrete slab 20 can be removed from the hollow frame 30 . The concreted carbon fibers 12 the static reinforcement of the concrete slab 20. The parts 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 concrete slab produced is approximately 6 mx 2.5 m in size and the reinforcement content of this concrete slab 20 is more than 20 mm ² /m width. In another example, the concrete slab produced is about 7 mx about 2.3 m.

4 14 shows a simplified schematic side view of a carrier 14 according to FIG 2 . The carbon fibers 12 flow straight 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.

The carrier 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 carrier 14 . These surfaces are provided for mounting the carrier 14 in a fixture (not shown), for example by clamping. The jagged profiling 16 achieves a non-positive connection between the carrier 14 and the clamping device in the form of teeth.

figure 5 shows a representation according to 3 However, in the case of the reinforcement elements 10, a subdivision is also made in that a construction foam 40 (shown as a wavy line) is foamed as a separating element both on the bottom of the hollow mold and under and over the carbon fibers 12. This subdivision means that no or only a negligible amount of the poured concrete can penetrate into the space occupied by the subdivision. Thus, only the partial spaces of the hollow frame with the fiber parts located therein are concreted. In addition, the construction foam 40 offers a fixation of the fibers during concreting.

After the concrete has hardened, the concrete slab 20 can be broken into individual raw slabs along the construction foam subdivisions. These raw panels can then be processed further, for example by cutting the raw panels into the desired shape using a circular saw.

In this example, the concrete slab produced is approx. 20 mx approx. 20 m and its thickness is approx. 20 mm. By separating the concrete slab 20 according to the subdivision with the construction foam 40, 24 smaller slabs with a size of approx. 5 mx approx. 3 m result. For example, 3 table tennis tables can then be sawn from these smaller slabs.

6 14 shows a simplified schematic side view of a carrier 14 according to FIG 2 , but this has a means for force distribution in the form of a bend 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 fastened in the entry area of the carrier 14 in such a way that the carbon fibers 12 continue largely in a straight line into the carrier 14 over a distance d of 10 mm. This shape achieves both good introduction of the fibers into the carrier 14 and an even distribution of the forces to be absorbed.

Claims (17)

1. Reinforcing element (10) for producing prestressed concrete components (20), having a plurality of fibers (12) and a plurality of holding elements (14) which are connected to one another by the fibers (12), so that the fibers (12) can be stressed in their longitudinal direction (T) by means of the holding elements (14), characterized in that the fibers (12) have a net cross-sectional area of less than 5 mm² and are coated with a granular material, in particular with sand, and form a substantially planar layer in the holding elements (14) and are fixed to the holding elements (14) by lamination or by lamination and clamping in such a way that, in stressed state, the fibers (12) open into the holding elements (14) in a substantially straight line.
2. Reinforcing element (10) according to claim 1, wherein the fibers (12) are individual fibers and/or comprise one or more rovings, in particular carbon rovings.
3. Reinforcing element (10) according to claim 1 or 2, wherein the holding elements (14) comprise guiding elements for the fibers (12), in particular a clamping device and/or a support for laminating the fibers (12) in the end region, in particular a fiber-reinforced polymer matrix, further in particular a polyester matrix.
4. Reinforcing element (10) according to one of the preceding claims, wherein the fibers (12) are arranged in the holding elements (14) substantially parallel and/or substantially uniformly spaced apart from one another.
5. Reinforcing element (10) according to one of the preceding claims, wherein the reinforcement spacing is approx. 5 mm to approx. 40 mm, in particular approx. 8 mm to approx. 25 mm, and/or wherein at least 10, in particular at least 40, fibers (12) are fixed to? each of the holding elements (14).
6. Reinforcing element (10) according to one of the preceding claims, wherein the fibers (12) are fastened to the holding elements (14) in such a way that, in the stressed state, the fibers (12) continue substantially in a straight line in the holding elements (14), in particular over a distance (d) of at least about 5 mm, further in particular of at least about 10 mm.
7. Reinforcing element (10) according to one of the preceding claims, wherein the holding elements (14) have a means for force distribution, in particular a curvature (18) and/or a profiling (16), extending in particular transversely to the direction of the fibers (12).
8. Reinforcing element (10) according to one of the preceding claims, wherein the width of which is greater than 0.4 m, in particular greater than 0.8 m, and/or the length of which is greater than 4 m, in particular greater than 12 m.
9. Method for producing a reinforcing element for prestressed concrete components (20), comprising the steps of:

   - providing stressed fibers (12) by drawing a plurality of spaced-apart fibers (12) together, wherein the fibers (12) have a net cross-sectional area of less than 5 mm² and are coated with a granular material, in particular with sand; and

   - fixing a holding element (14) to the stressed fibers (12) by lamination or clamping and lamination to fix the fibers (12) in their mutual arrangement, in particular with respect to spacing and/or orientation, wherein the fibers (12) form a substantially planar layer in the holding element (14).
10. Method for producing a reinforcing element for prestressed concrete components (20), comprising the steps of:

    - coating the fibers with a granular material, in particular with sand; providing stressed fibers (12) by drawing a plurality of spaced-apart fibers (12) together, wherein the fibers (12) have a net cross-sectional area of less than 5 mm²; and

    - fixing a holding element (14) to the stressed fibers (12) by lamination or clamping and lamination to fix the fibers (12) in their mutual arrangement, in particular with respect to spacing and/or orientation, wherein the fibers (12) form a substantially planar layer in the holding element (14).
11. Method according to claim 9 or 10, wherein the fixing of the holding element (14) takes place during the drawing of the fibers (12) together, in particular by moving the holding element (14) in synchronism with the movement of the fibers (12).
12. Concrete component (20), in particular concrete slab, having at least one reinforcing element (10) according to one of claims 1 to 8, wherein the prestressing of the concrete component (20) is at least 50%, in particular at least 80%, further in particular at least 90%, of the breaking stress of the fibers (12).
13. Concrete component (20), in particular concrete slab, comprising a plurality of fibers (12) which are stressed in their longitudinal direction (T), characterized in that the fibers (12) have a net cross-sectional area of less than 5 mm² and are coated with a granular material, in particular with sand, and form at least one substantially planar layer, wherein the prestressing of the concrete component (20) is at least 50%, in particular at least 80%, further in particular at least 90%, of the breaking stress of the fibers (12).
14. Method for producing a prestressed concrete component (20), comprising the steps of:

    - providing at least one reinforcing element (10) according to one of claims 1 to 8;

    - stressing the fibers (12) of the reinforcing element (10) by pulling apart the associated holding elements (14); and

    - concreting the concrete element (20) while at least partially embedding the stressed fibers (12) in concrete.
15. Method according to claim 14, wherein the providing of the at least one reinforcing element is accomplished by arranging a plurality of the reinforcing elements (10) in a layer, in particular by laying them substantially parallel and/or adjacent to one another.
16. Method according to claim 14, wherein the providing of the at least one reinforcing element (10) is accomplished 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.
17. Method according to one of claims 14 to 16, wherein this additionally comprises the step of:
    inserting a separating element, in particular a foam (40), before concreting the concrete component (20).

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