Reinforcing element for producing prestressed concrete components, concrete component and production methods

Abstract

The present invention concerns a reinforcing element for producing concrete components, a concrete component and corresponding production methods. The reinforcing element comprises a plurality of fibers and a plurality of holding elements which are connected to each other by the fibers so that the fibers can be stressed in their longitudinal direction by means of the holding elements. The fibers are fixed to the holding elements such that the fibers in the stressed state enter the holding elements in a substantially linear manner. This enables both a high degree of pretension and an efficient, reliable and thus cost-effective production of the concrete components.

Claims

1. A reinforcing element for producing prestressed concrete components, the reinforcing element comprising: a plurality of fibers and several holding elements, which are connected to each other by the plurality of fibers so that the plurality of fibers is capable of being stressed in longitudinal direction of the plurality of fibers by means of the holding elements, wherein the fibers form one essentially flat layer and the net cross-sectional area of the fibers is smaller 5 mm.sup.2, wherein the fibers are coated with a granular material, wherein the holding elements comprise guiding elements for the plurality of fibers, and wherein the guiding elements comprise at least one polymer matrix for laminating the plurality of fibers.

2. The reinforcing element according to claim 1, wherein the reinforcing element comprises the shape of a harp such that no knots appear.

3. The reinforcing element according to claim 1, wherein the tensile strength of the fibers related to the net cross-sectional area of the fibers is greater than about 1000 N/mm.sup.2.

4. The reinforcing element according to claim 1, wherein the plurality of fibers is fixed to the holding elements by laminating or clamping and laminating.

5. The reinforcing element according to claim 1, wherein the plurality of fibers is made from at least a material selected from the group consisting of carbon, glass, steel and natural fiber.

6. The reinforcing element according to claim 1, wherein the reinforcing distance is about 5 mm to about 40 mm.

7. The reinforcing element according to claim 1, wherein the plurality of the fibers is fixed to the holding elements such that the plurality of the fibers in a stressed state at least enter or continue in a substantially linear manner into the holding elements.

8. The reinforcing element according to claim 1, wherein the width of the reinforcing element is larger than 0.4 m and the length of the reinforcing element is larger than 4 m.

9. The reinforcing element according to claim 1, wherein the reinforcing element is harp-shaped.

10. The reinforcing element according to claim 1, wherein the fibers are impregnated with an alkali-resistant polymer.

11. The reinforcing element according to claim 1, wherein the fibers are coated with sand.

12. A method for producing a prestressed concrete component, comprising in the following order the steps of: providing at least one reinforcing element according to claim 1; stressing the plurality of fibers of the reinforcing element by pulling apart the holding elements to create a stressed state; and concreting of the concrete component by, at least partially, pouring in concrete the plurality of fibers.

13. A method according to claim 12, wherein the step of stressing the plurality of fibers of the reinforcing element by pulling apart the holding elements to create a stressed state is accomplished by applying a tension of at least about 30 kN/m.

14. A method according to claim 12, wherein the step of providing at least one reinforcing element is accomplished by arranging several of the reinforcing elements in a layer.

15. A method according to claim 12, wherein the step of providing at least one reinforcing element is accomplished by arranging the reinforcing elements in at least two layers, wherein the orientation of the reinforcing elements in neighboring layers is arranged at an angle.

16. The method according to claim 12, wherein the method comprises additionally the step of: inserting a separation element before concreting the concrete component.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further embodiment examples of the present invention are illustrated hereafter by means of figures. It is shown in:

(2) FIG. 1 a simplified schematic illustration of an embodiment example of the reinforcing element 10 according to the invention with carbon fibers 12, which can be prestressed using two holders 14;

(3) FIG. 2 a simplified schematic detail view of a holder 14 according to FIG. 1;

(4) FIG. 3 a simplified schematic illustration of an intermediate state during the production of a prestressed concrete slab 20 using a plurality of reinforcing elements 10 according to FIG. 1;

(5) FIG. 4 a simplified schematic side view of the holder 14 according to FIG. 2;

(6) FIG. 5 a simplified schematic illustration according to FIG. 3, however, additionally with a building foam 40 for partition of the concrete slab 20 and fixation of the carbon fibers 12; and

(7) FIG. 6 a simplified schematic said view of the holder 14 according to FIG. 2, wherein the said holder, however, comprises a curvature.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(8) The following embodiments are examples and are meant to limit the invention in no way.

(9) FIG. 1 shows a simplified schematic illustration of an embodiment example of the reinforcing element 10 according to the invention in stretched state. Such a reinforcing element 10 serves for the production of prestressed concrete components.

(10) The reinforcing element 10 comprises ten individual fibers, which are formed as carbon fibers 12 (only partially labeled) in this example and two holding elements in shape of two holders 14. The holders 14 are arranged in distance to each other and connected to each other by the ten carbon fibers 12. The carbon fibers 12 can be stressed by pulling apart the holders 14 in their longitudinal direction T.

(11) According to the invention, the carbon fibers 12 are fixed in the holders 14 such that the stretched carbon fibers 12 enter the holders 14 in a linear manner. Further, the carbon fibers 12 form an essentially flat layer, wherein that layer the carbon fibers 12 are arranged substantially parallel and substantially uniformly spaced to each other. The reinforcing element 10 has the shape of a harp. According to this example, the reinforcing distance, i.e. the distance between the parallelly arranged carbon fibers 12, is ca. 10 mm and thus the width of the reinforcing element 10 is ca. 10 cm.

(12) Each of the carbon fibers 12 comprises a carbon roving each, i.e. a bundle of a few thousand stretched, arranged side by side and essentially equally oriented filaments (ca. 2,000 to ca. 16,000 filaments). The said filaments and thus the carbon fibers as well, 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 impregnating can be carried out, for instance, by means of a dipping bath, through which the roving is pulled for producing the carbon fibers 12.

(13) Moreover, the carbon fibers 12 are coated with sand so that an improved connection of the fibers with the concrete is achieved. According to this example, with an embedment of 100 mm, the full dimensional tensile force can be transmitted by the mechanical shear connection.

(14) Further, the holders 14 comprise two openings 16 each (drawn as dashed line) by means of which the holders 14 can be sited on a clamping device (not shown). With the clamping device, the carbon fibers 12 can precisely be adjusted during the production of the concrete components and can be stressed, in particular without horizontal and/or vertical tilting. According to another example, the holder 14 comprises a hole or a plurality of holes, in particular more than two holes, for positioning the holder 14.

(15) According to an example, for producing the holder 14 cost-effective materials are used. An exemplary material composition and the appropriate production of the holder 14 is illustrated by means of FIG. 2. Other materials can be used as well, since the holder 14 is not a part of the concrete component to be produced and is normally separated and removed after concreting.

(16) FIG. 2 shows a simplified schematic detail view of a holder 14 according to FIG. 1.

(17) The holder 14, also referred to as patch, comprises a fiber-reinforced polymer matrix in form of a polyester matrix with therein enclosed fibers in form of two glass fiber mats. The said polyester matrix encloses the stretched carbon fibers 12 at their end zones. For instance, the size of the said polyester matrix is ca. 10 cm×10 cm and the total thickness is ca. 2 mm. According to another example, the length expansion of the polymer matrix in direction of the carbon fibers 12 is between ca. 10 cm and ca. 20 cm. The fiber mats form an upper and lower layer, wherein the stretched carbon fibers 12 are located between these layers and fixed therein by lamination with polyester. Therefore, the polyester matrix forms a straight-lined guiding element (indicated by dashed lines) for the carbon fibers 12, wherein the carbon fibers 12 inside the polyester matrix, i.e. inside the holder 14, substantially continue in a linear manner. By means of the holder 14, the carbon fibers 12 are fixed in their mutual position, namely in a flat layer, substantially parallel and uniformly spaced to each other.

(18) The ends of the carbon fibers 12 protrude at the outlet side of the holder 14 beyond the holder 14 at some extend. But also, the fibers 12 can end within the holder 14 or be flush with the ends on the surface of the holder 14, for instance, when the holder 14 is separated from a larger unit.

(19) For instance, such a holder 14 is produced by the following steps: providing a plurality of adjacent and mutually spaced carbon rovings by substantially simultaneously stripping of the carbon rovings from an appropriate number of supply rolls; impregnating of the carbon rovings by means of passing the carbon rovings through a vinyl ester resin dipping bath so that the carbon rovings form compact carbon fibers 12; collective pulling out the carbon fibers 12, where required by means of a previously placed holder 14 so that the carbon fibers 12 are stressed; applying two glass fiber mats saturated with polyester to the stressed carbon fibers 12, one from below and the other from above; joining the two glass fiber mats, where required by adding an additional quantity of the polyester so that the saturated glass fiber mats and the polyester enclose the stressed carbon fibers 12; and hardening of the polyester so that the carbon fibers 12 are fixed frictionally in the holder 14.

(20) By means of this laminating, the holder 14 forms together with the carbon fibers 12 a compact and robust unit.

(21) FIG. 3 shows a simplified and schematic illustration of an intermediate state for the production of a prestressed concrete slab 20, for instance, at a precast concrete plant for concrete slabs. The intermediate state means an arrangement after conclusion of the preparatory work, however, even before the concreting of the concrete slab 20.

(22) The arrangement comprises a shuttering table (not shown), a hollow frame 30 arranged thereon and a plurality of identical reinforcing elements 10 according to the invention (partially only indicated schematically). The hollow frame 30 forms together with the surface of the shuttering table a mold for the concrete, also called pretension bed.

(23) The reinforcing elements 10 comprise a plurality of carbon fibers 12 each (due to clarity partially only the outer fibers are shown) and two holders 14 and correspond in their set-up substantially to the reinforcing elements 10 according to FIG. 1. According to this example, the length of the carbon fibers is, however, ca. 20 m and the width of the holders 14 is ca. 1 m. The reinforcing distance is equal to the preceding example, i.e. as in FIG. 1 ca. 10 mm, so that ca. 100 carbon fibers 12 are fixed on the holders 14 each.

(24) For the arrangement of the reinforcing elements 10, the holders 14 are pulled apart each so that the carbon fibers 12 are located inside of the hollow frame 30 in stretched state. The carbon fibers 12 are lead through the hollow frame 30 to the outside so that the ends of the carbon fibers 12 and the holders 14 are located outside of the hollow frame 30, for instance, with a distance to the hollow frame 30 of 30 cm. For a two-part hollow frame 30, the passages can also be formed by appropriate interspaces between upper part and lower part of the hollow frame 30. The hollow frame 30 is built of several strips lying upon another so that the carbon fibers 12 can be led through the interspaces of the individual strips. The interspaces can additionally be sealed with sponge rubber and/or brush hair. According to an example, the height of the strips lying upon another is 3 mm, 12 mm and 3 mm.

(25) In the shown arrangement, the first half of the reinforcing elements 10 lays in a first layer, parallel and neighboring side by side and the second half of the reinforcing elements 10 lays in a second layer, also parallel and neighboring side by side, however, perpendicular to the reinforcing elements 10 of the first layer. The reinforcing elements 10 are thus arranged in separated layers, put one on top of another and are oriented in the two neighboring layers perpendicular to each other. The reinforcing elements 10 form thus both a longitudinal armor and a transverse armor, however, without individual braiding of the individual carbon fibers 12.

(26) After arranging the reinforcing elements 10, the holders 14 are pulled apart, for instance, by means of a clamping device, also called pretension facility, or manually by means of a torque wrench (not shown). For instance, a tension of at least ca. 30 kN/m to at least 300 kN/m is created, depending on the load requirements for the concrete slab (dimensioning force).

(27) Subsequent to the described situation, concrete can be poured in the, in such a manner prepared, hollow frame 30 to concrete the concrete slab 20 in a single working step. The parts of the stressed carbon fibers 12, which are located in the hollow frame 30, are enclosed by the concrete and thus encased in concrete. Especially suitable is SCC fine concrete (at least C30/37 according to NORM SIA SN505 262), which can easily flow through the interspaces of the carbon fibers 12. The concrete can also be inserted into the hollow frame 30 by extruding or filling and be uniformly distributed by vibration.

(28) After the hardening of the concrete, the concrete slab 20 can be removed from the hollow frame 30. The carbon fibers 12 encased in concrete form 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 holders 14. According to this example, the produced concrete slab is ca. 6 m×2.5 m large and the reinforcing share of this concrete slab 20 is more than 20 mm.sup.2/m width. According to another example, the concrete slab is ca. 7 m×2.3 m large.

(29) FIG. 4 shows a simplified and schematic side view of a holder 14 according to FIG. 2. The carbon fibers 12 enter the holder 14 in a linear manner. Further, the carbon fibers 12 continue in a linear manner in the inside of the holder 14 so that the holder 14 forms a straight-lined guidance for the carbon fibers 12. According to this example, the longitudinal extension of the holder 14 in direction of the carbon fibers 12 is ca. 3 cm.

(30) The holder 14 can additionally comprise a profile 16 (drawn as dashed line). According to this example, a teeth-shaped profile 16 is located on a first (upper) area and on the thereto oppositely located (lower) area of the holder 14. The said areas are intended for the fixing of the holder 14 in a clamping device (not shown), for instance, by clamping. By means of the teeth-shaped profile 16, a frictional connection between the holder 14 and the clamping device in form of a toothing is achieved.

(31) FIG. 5 shows an illustration according to FIG. 3, for the reinforcing elements 10, however, a partition is additionally carried out by foaming a building foam 40 (indicated as wavy line) as separative element both on the bottom of the hollow mold and underneath and above the carbon fibers 12. By means of the said partition no or only a negligible quantity of the poured concrete can enter into that space that is filled up by the partition. Thus, only the partial spaces of the hollow frame with the fiber parts located therein are concreted. In addition, the building foam 40 provides a fixation of the fibers during concreting.

(32) After the hardening of the concrete, the concrete slab 20 can be broken into individual raw slabs along the building foam partitions. The said raw slabs can be further processed, for instance, by bringing the raw slabs into the desired shape by means of a buzz saw.

(33) According to this example, the produced concrete slab is ca. 20 m×20 m large and its thickness is ca. 20 mm. From separating the concrete slab 20 according to the partition by the building foam 40, 24 smaller slabs having a size of ca. 5 m×ca. 3 m do result. Out of the said smaller slabs, for instance, 3 table tennis tables can be sawed.

(34) FIG. 6 shows a simplified schematic side view of a holder 14 according to FIG. 2, wherein the said holder 14, however, comprises a means for the force distribution in form of a curvature 18. The carbon fibers 12 enter the holder 14 in a linear manner and continue inside the holder, according to the curvature 18 of the holder 14, with a curvature as well. The carbon fibers 12 are fixed in the entry zone of the holder 14 such that the carbon fibers 12 continue in a substantially linear manner for a distance d of 10 mm in the holder 14. By means of the said shape, both a good introduction of the fibers into the holder 14 and a uniform distribution of the forces to be absorbed is achieved.