EP3109021B1 - Method for making prestressed concrete products, in particular prestressed concrete sleepers or prestressed concrete points - Google Patents

Description

The invention relates to a process for the production of prestressed precast concrete parts, in particular prestressed concrete sleepers or prestressed concrete sleepers, wherein in at least one mold bed several moldings are produced by casting and the mold bed receives a variety of prestressing steels, between the moldings and in the end regions of the mold bed Abstellkästen are used, on the one hand to fix the position of the prestressing steels and the geometry of the molding determining mold sheets during casting, and on the other hand to scarf the respective molding end and to create a space between adjacent moldings for later cutting the prestressing steels, according to the preamble of claim 1.

For example, from the DE 101 63 138 A1 It is known to produce concrete components by casting. These casting methods consist essentially of filling a reusable mold with a concrete mass, drying or hardening the mass and stripping the solid object after drying from the mold.

In such methods reusable molds must be cleaned after each casting and optionally polished and provided with release agents, since when stripping residues of concrete mass or other impurities remain in the mold.

In the advanced manufacturing process for components after the DE 101 63 138 A1 For example, a mold is lined with a release film, and then a composition containing a binder is applied to the release film. After drying the mass is then stripping the mass from the mold. By this method and the lining of the mold with a release film direct contact between the mass and the mold is prevented. Remaining dried residual mass on the mold when stripping the object is avoided. This eliminates post-cleaning of the mold after the manufacturing process. It is achieved by the film that the component after removal of the film has a smooth surface. In order to adapt the release film to the contour of the mold, it is necessary to pull the film under vacuum, for example by means of a vacuum in the mold. In this regard, the film is placed over the mold and then a vacuum is created between the film and the mold so that the film comes to rest completely on the surface of the mold without wrinkles. A simplification of the lining of the mold with foil is possible by heating the foil for lining the mold.

In addition, methods are known for producing concrete sleepers with an insert molding, for example after DE 10 2006 042 910 A1 ,

In order to produce sleepers with steep walls of the recesses for the rail fasteners in the shell over head, a formwork with the usual sloping walls or with flat bottom is provided with a shaped part with steep walls, which dissolves when stripping the formwork and up to sufficient hardening remains in the threshold, while at the same time the threshold formwork, using another similar shaped part, can be used again for the production of a new threshold.

In the known production of sleepers on a so-called Longline plant is assumed, for example, two parallel mold beds in which are inserted for the respective geometry of the respective thresholds shaped sheets.

The end of each threshold is achieved by so-called storage boxes and / or similar equipment parts for separating and shelling of individual precast concrete parts. The storage boxes have several functions. On the one hand, they serve to fix the location of the inserted molded sheets. Furthermore, the storage boxes fix the prestressing steels in the tension track during concreting. Finally, the storage boxes are used to shutter the emerging ends.

Through the respective Abstellkasten a space between two longitudinally adjacent sleepers is still created in the mold bed to be able to remove after hardening of the concrete on the one hand the prestressing steel and thus to isolate the thresholds, and on the other hand to create a crane crane for lifting the threshold sufficient operating space.

In the known method, the storage boxes must be pulled out at a time from the mold bed up when the concrete has a strength that allows him to no longer plastically deform alone. However, the concrete must not be so strong that the cement paste already adheres to the storage box. It is therefore necessary from the prior art to pull the storage boxes at such a time when the so-called green strength of the concrete is present and there is a sufficient connection between concrete and prestressing steel.

Since the use of release agents, in particular formwork oil, on the storage boxes is extremely critical, it is necessary to avoid such release agents. Release agents on or near the storage boxes lead due to the direct contact of the respective Abstellkastens with the prestressing steel to a wetting of the profiled Spannstahloberfläche with the release agent, which in turn draws composite problems related to the concrete material by itself.

For this reason, the decoating process and the pulling of the storage boxes are preferred upon reaching the green strength of the concrete.

Experiments have shown that even a slightly conical design of the storage boxes does not improve the pulling. When pulling the storage boxes from the still relatively fresh concrete, the young concrete structure is disturbed in many cases, especially in the forehead of the switch sleepers, resulting in cracks and thus Quality loss leads. Such cracks immediately make the manufactured concrete sleeper a scrap product or, if the cracks are extremely small and can not be detected at the manufacturing plant, a product with hidden defects resulting in damage after installation in the rail network. From the NL-A-9 100 251 From the above, it is therefore an object of the invention to provide a further developed method and an associated device for the production of prestressed precast concrete parts, in particular prestressed concrete sleepers or prestressed concrete sleepers, which are suitable for use on longlines Plants is suitable and whereby damage to the precast concrete part, due to the pulling of known storage boxes can be avoided. In accordance with the object, the aim is to extract the storage boxes for shelling from the mold bed only after the concrete has hardened to the condition of the Umspannfestigkeit.

The object of the invention is achieved by a method according to the teaching of claim 1, wherein the dependent claims comprise at least expedient refinements and developments.

The method is based on a known manufacturing process for prestressed precast concrete parts, in particular prestressed concrete sleepers or prestressed concrete sleepers, wherein in at least one mold bed, a plurality of moldings is produced by casting. The mold bed has a plurality of prestressing steels with a structured surface, wherein between the mold parts and in the end regions of the mold bed so-called storage boxes are used to fix the one hand, the position of the prestressing steels and the geometry of the molding determining mold sheets during casting, and on the other hand the respective Peel off molding end and to create a space between adjacent moldings for later cutting the prestressing steels.

According to the invention, at least the surfaces coming into contact with the concrete of the respective separating agent-free storage box are provided with a detachable, temporary, elastic properties-containing cover. The cover has openings or openings for sealingly encompassing the prestressing steels. This means that the cover is not just the lighter Pulling the Abstellkästen serves, but also effectively prevented by the sealing effect of the penetration of concrete or cement slurry into the interior of Abstellkastens.

This results in a little more expensive cleaning of the storage boxes and thus a faster reusability at a reduced overall cost and higher quality of manufactured precast concrete.

After complete curing of the concrete, the respective separating agent-free storage box is pulled in a known manner. Following this, the cover adhering to the finished part can then be removed.

For attaching the cover to the storage box no special measures or manual skills are necessary. After inserting the storage boxes in the respective form, arranging the prestressing steels and other preparatory measures prefabricated covers, preferably as stamped surface pieces of a plastic foam material to the storage box designed so that the coming into contact with the fresh concrete surfaces are covered and the aforementioned seal results in the area penetrated by the prestressing steel surfaces.

As mentioned, the cover consists of a foamed material, in particular a plastic material, which has a water absorption capacity of ≦ 5 vol .-%, in particular substantially at most 1 vol .-%.

The cover can also consist of a foamed material based on natural substances.

The cover preferably consists of a polyethylene foam material (PE).

The preferably used polyethylene foam is closed-cell and fine-pored and has, for example, a thickness of 5 mm.

In the apparatus for producing prestressed precast concrete according to the above-outlined method, this is formed as a plate-shaped, elastic properties having cover. This cover is used to separate the concrete from the actual storage box and surround it Storage box on the outside. Furthermore, the cover slits and in the slots provided, have adapted to the cross section of the prestressing steel recesses, in such a way that the cover is clamped and held relative to the prestressing steels form fit to the storage box and the Abstellkasten and the prestressing steel against the concrete during the Casting processes and seals during the curing process.

The elastic properties of the cover surprisingly secure the absorption of forces due to the changes in length during the curing process of the concrete. This too leads to a significantly improved quality of the manufactured precast concrete parts.

At least the surface facing away from the Abstellkasten surface of the cover has a predominantly smooth, fine-pored structure.

In one embodiment of the invention, it is possible to provide the concrete facing surface side of the cover with a structuring or embossing to identify the respective end face of the respective finished part in the form of a name, a type, a logo or the like.

Preferably, the cover is formed as a flat blank or stamped part, wherein the blank or the stamped part corresponds in shape to the settlement of the respective storage box. The cover has predetermined bending points or predetermined bending points in order to be able to easily envelop the storage box with the same.

In the form of a storage box with a substantially U-shape with two lateral legs and a connecting leg, the cover at least the lateral or even the lateral and the connecting leg can be arranged overlapping.

The present as a flat blank cover can be placed from the top of the storage box and by folding or kinking lateral surfaces using the mentioned slots with the recesses between the Tensioning steels are spent and transferred to such a position that the corresponding exposed legs of the respective storage box are covered. The mentioned predetermined bending or predetermined bending points, which are adapted in their position to the dimensions of the storage box, facilitate the introduction of the cover in the region of the prestressing steels or prestressing steel penetrations.

In one alternative, working with a multi-part, in particular two-part cover, which covers one of the lateral legs of the storage box. To prevent ingress of fresh concrete from the top, i. As viewed from the connecting leg, a U-shaped or clip-like protective cover can be applied over the connecting leg, which is reusable.

The invention will be explained below with reference to an embodiment and with the aid of figures.

• Fig. 1 eine prinzipielle Ausbildung eines Abstellkastens mit Spannstählen und Distanzblechen, wobei aus Gründen der Übersichtlichkeit das Formenbett nicht dargestellt ist;
• Fig. 2 eine Darstellung ähnlich derjenigen nach Fig. 1, jedoch mit dem beginnenden Anordnen der Abdeckung bezogen auf den Abstellkasten, wobei die in den Seitenflächen der Abdeckung ersichtlichen Schlitze dem Einfädeln bezogen auf den Raum zwischen den Spannstählen dienen und wobei letztendlich die gewünschte Lageposition und Abdichtung der Abdeckung bezogen auf den Abstellkasten dann erreicht ist, wenn alle dem Querschnitt der Spannstähle entsprechenden Öffnungen oder Ausnehmungen in den Seitenflächen der Abdeckung ihre endgültige Lage erreicht haben;
• Fig. 3 eine Darstellung der gewünschten Position und Endlage der Abdeckung vor dem Vergussprozess und
• Fig. 4 eine Seitenansicht einer einfachen Abdeckung mit Sollbiege- oder Sollknickstelle und Schlitzen sowie lochartigen Ausnehmungen für das Hindurchführen der Spannstähle.

Hereby show:

• Fig. 1 a basic design of a Abstellkastens with prestressing steels and spacer plates, for reasons of clarity, the mold bed is not shown;
• Fig. 2 a representation similar to that after Fig. 1 However, with the beginning of arranging the cover with respect to the storage box, wherein the slots shown in the side surfaces of the cover are used for threading with respect to the space between the prestressing steels and ultimately the desired position position and sealing of the cover is then achieved with respect to the storage box, when all of the cross section of the prestressing steel corresponding openings or recesses in the side surfaces of the cover have reached their final position;
• Fig. 3 a representation of the desired position and end position of the cover before the potting process and
• Fig. 4 a side view of a simple cover with predetermined bending or predetermined bending point and slots and hole-like recesses for passing the prestressing steels.

According to the representations after the Fig. 1 to 3 is used in the manufacture of prestressed concrete sleepers, in particular prestressed concrete sleepers in Longline method on storage boxes 1, which have a substantially U-shape with lateral legs 2 and a connecting leg 3.

In the storage boxes 1 spacers or spacers 4 are still used. Furthermore, the lateral legs 2 slot-like recesses 5, which serve the horizontal fixation of the prestressing steels 6.

In the area of the connecting leg 3, the storage box 1 still has a projection 7 to attach there a stop means for pulling the Abstellkastens 1 and to fix the Abstellkasten in the tension track.

The storage box 1 thus serves to fix the position of mold plates, which are not shown in the figures, the fixation of the stressing during concreting in the tension track prestressing steels and ultimately the shuttering of the sleeper ends and the creation of a free space between two closely adjacent sleepers or precast concrete in the mold bed in order to be able to separate out the prestressing steel after hardening of the concrete and thus to separate the sleepers and to create space for a crane cross-beam for lifting the sleepers.

As in the FIGS. 2 and 3 Shown, the respective storage boxes 1 according to the invention are surrounded with a cover made of a foamed plastic or natural material. The cover 8 is formed in a preferred embodiment as a flat blank or stamped part and corresponds to the extent of the Abstellkastens.

Also, the cover 8 has corresponding slots 9 to facilitate the threading and attachment to the storage box 1.

In addition, the cover 8 has in its side surfaces in the region of the slots 9 still formations 10, which are adapted in their contour or shape to the cross section of the respective prestressing steels 6.

The cover now seals well on the one hand at the threshold ends against cement slurry, so that it no longer runs in the storage boxes, and on the other hand ensures a separation layer between concrete and storage box. Due to the elastic properties, in particular air pockets, a slight pulling the storage boxes is possible even after complete curing of the concrete, in a way that can be dispensed with release agent.

So it is a late demoulding possible, while maintaining the desired manufacturing qualities for the precast concrete parts. The parts in the storage box and the storage boxes themselves are protected by the covers from dirt, which reduces the cleaning effort and reduces wear.

Fig. 4 shows an exemplary side view of a simple cover with a purely exemplary dimension based on the formation of a predetermined bending or predetermined bending point 11 and with respect to the slots 9 and the apertures 10 for receiving the prestressing steels (see Fig. 1 to 3 ).

A large number of experiments has shown that foamed plastics can be used in a particularly advantageous manner as the material for the cover 8. These may in particular be PE plastic materials which have a water absorption capacity of less than 5% by volume, in particular up to a maximum of 1% by volume.

Comparative tests with a cover formed as a rubber plate were unsuccessful. Such rubber plates are very difficult to obstruct and just as difficult to remove. Also, the idea of training foam storage boxes proved to be unworkable because the corresponding storage boxes were not up to the challenge and were subject to destruction. The same applies to tentatively made storage boxes made of plastic material. The desired multiple usability was therefore not given in these latter materials.

Claims (7)

1. Method for making prefabricated prestressed concrete products, in particular prestressed concrete sleepers or prestressed concrete turnout sleepers, wherein several molded parts are produced by casting in at least one molding bed, and the molding bed receiving a plurality of prestressing tendons (6), between the molded parts and in the end areas of the molding bed, stabling boxes (1) are inserted in order to fix, during the casting process, the position of the prestressing tendons and molding sheets determining the geometry of the molded part, on the one hand, and to shutter the respective molded part end and to create a free space between adjacent molded parts, on the other, for subsequently severing the prestressed tendons, wherein
   at least the surfaces of the respective stabling box (1), that is free form releasing agents, which come into contact with the concrete, are provided with a detachable, temporary cover (8) exhibiting elastic properties, wherein the cover (8) has openings or breakthroughs for sealingly encompassing the prestressing tendons (6), after complete hardening of the concrete, the respective stabling box (1), that is free from releasing agents, is drawn, and, following this, the cover (8) adhering to the prefabricated part is removed,
   characterized in that
   the cover (8) is formed as a cut part or a planar punched part which corresponds in its shape to the development of the respective stabling box (1), wherein the cover (8) has target bending points or target kink points (11), in order to enclose the stabling box (1) by the latter completely or in part, the respective stabling box (1) furthermore exhibiting a U-shape with two lateral legs (2) and one connecting leg (3), wherein the cover (8) can be arranged to cover the lateral legs (2) or the lateral legs (2) and the connecting leg (3).
2. Method according to claim 1,
   characterized in that
   the cover (8) is composed of a foamed material, in particular plastic material, which has a water absorbency of ≤ 5 vol.-%, in particular of a maximum of 1 vol.-%.
3. Method according to claim 1,
   characterized un that
   the cover is composed of a foamed material based on natural material.
4. Method according to claim 1,
   characterized in that
   the cover is composed of a foamed material of polyethylene.
5. Method according to anyone of claims 1 to 4,
   characterized in that
   the cover (8) is formed to be plate-shaped, which, for separating between concrete and stabling boxes (1), surrounds the latter on the outside, furthermore, the cover (8) has slots (9) and recesses (10) provided in the area of the slots and adapted to the diameter of the prestressing tendons (6) such that the cover (8) is held on the stabling box (1) in a clamping manner and seals the stabling box (1) as well as the prestressing tendons (6) against the concrete during the casting process and the hardening.
6. Method according to claim 5,
   characterized in that
   the upper surface side of the cover (8) facing the concrete exhibits a structuring or stamping for marking the respective front side of the respective prefabricated part.
7. Method according to claim 5 or 6,
   characterized in that
   the cover (8) exhibiting elastic properties absorbs the length changes, occurring during the hardening process of the concrete, and forces resulting therefrom.

Images