EP1573133B1 - Frame sleeper and method for the production thereof - Google Patents

Abstract

The invention relates to a single-piece prestressed concrete frame sleeper comprising two cross-ties and two longitudinal supports which extend underneath the rails. Each of the four intersecting zones of the cross-ties (1) and longitudinal supports (2) is provided with at least one flat area which supports at least one elastic rail-bearing element (5). Said frame sleeper is sized regarding the geometry, material properties, and prestress such that at least two rail fasteners comprising two elastic spring elements (4) can be mounted onto each intersecting zone. The inventive frame sleeper can be produced by using prestress with a direct bond and clamping frames (9) for biaxial reinforcement such that the newly concreted sleeper is stripped upwards without turning the formwork shell (8) only once the concrete has reached a first degree of hardness, is stored upside down until being completely hard, and is turned into the normal position thereof only once the clamping power has been transmitted to the concrete and the sleeper has been separated from the clamping frame (9).

Description

The invention relates to a frame threshold made of prestressed concrete with an increased number of rail fasteners for a railway ballast track and a method for producing this threshold.

Grid-like railway sleepers consisting of sleepers and under the rails extending longitudinal beams, hereinafter referred to as frame sleepers, are known as monolithic prestressed concrete precast elements in various embodiments. Their advantages over the classic ballast track with sleepers are due to the positional stability of the track on the increased bearing surface in the ballast, the greater lateral displacement resistance of the single sleepers and in particular on the horizontal frame bearing effect of the track grid.

The frame support depends significantly on the size of the clamping forces in the elastic spring elements of the rail fasteners, which connect via friction rails and sleepers together. The rails act as tension and compression straps of the underlying beam formed by the track grid, while the sleepers transmit the thrust forces occurring between the belts. If the existing frictional forces in the rail fasteners are exceeded, the rails slide on the sleepers and the individual frame sleepers can rotate in the horizontal plane against each other. That is, as soon as a slipping of the rails in the rail fasteners takes place, the frame bearing effect can no longer be increased.

In mountain routes with tight bends, the demands on the positional stability of the superstructure are highest. They decrease significantly on flatland routes with large curve radii. Therefore, a close distance of the rail fortifications in mountain ranges and a long distance on flat land routes should be strived for.

It is also important that a closer spacing of the rail fasteners and thus an increased push-through resistance of the rails with respect to the sleepers is also favorable with regard to braking forces and breakages in rail breaks.

A known embodiment of the frame threshold according to DE 198 42 312 C1 with a composite of two cross sleeper and two long-beam carrier grid shows all the features of the preamble of Ansprüchs 1 and has at each intersection of the support elements a rail fastening with two spring elements and a Schienenauflagerelement on. An increase of the clamping forces on additional rail fasteners is only possible by a closer arrangement of the sleepers. Depending on the intended use, several types of thresholds are required. However, the different threshold dimensions lead to considerable additional costs in threshold production.

Another embodiment according to the DE 100 23 389 A1 with a cross sleeper and two short, projecting on both sides longitudinal beams has the disadvantage that a narrower threshold arrangement and thus more rail fasteners per running meter track is not possible because of the necessary spaces for plugging the thresholds. Also, a reduction in the number of rail fasteners by larger threshold distance is only partially executable, because thus the ballast pressure and rail stress adversely increase.

An additional problem with the arrangement of multiple rail fasteners and rail supports under a rail is that more than two rail supports on the side rail under the rolling load generate rail-to-rail constraints which can lead to rail lifting of individual rail supports. This disadvantageous effect, which results from the statically indeterminate mounting of the rail on the longitudinal member, is further enhanced by the unavoidable height tolerances of the individual components rail, intermediate layer and sleeper. The associated overuse of all parts and the consequent increased wear must be avoided at all costs.

Such a plate-like threshold frame with multiple rail supports and correspondingly long length in track longitudinal direction is the AT 377 806 refer to. In practice, such a threshold frame is used with a length of 2.4 m, ie, the rail fasteners are made in the usual distance of 60 cm. In order to master the restraint forces described above, which continue to increase with increasing threshold length in the track direction, the installation of very soft rail support elements with a spring rate of approximately 20 KN / mm in each support point is unavoidable. Such soft rail supports, however, increase noise and are also very expensive. The arrangement of several rail fasteners in the usual distance of about 60 cm in the region of the longitudinal member also leads to further technical problems. On the one hand, the sill frame lengthened in the longitudinal direction of the track so much that it can no longer be installed in tight bends because of the rectilinear rail supports. On the other hand, distributed over the longitudinal beam Schienenauflagerelemente lead to an undesirably large side member width, which complicates the Unterstopfen these components.

From the DE 198 42 312 C1 It is known to avoid the adverse effect of more than two Schienenauflagern on a side member by a combination of two outer, hard Schienenauflagerelement and a very soft, preloaded Zwischenauflagerelement. However, experience shows that this embodiment leads to an increased airborne noise emission because the very soft intermediate layer fails as a vibration damping element. However, the replacement of the soft intermediate layer by a harder is not possible experience, since it is not yet possible with reasonable effort to produce frame thresholds with sufficient accuracy. In particular, the necessary smaller concrete tolerances can not be met in the usual production of frame prestressed concrete with the immediate demoulding process.

The object of the present invention is therefore to provide a frame threshold for a track structure which is suitable for use under high stress, in particular for mountain ranges with tight curve radii, while being so inexpensive to produce that they are also suitable for use with distances low load can be used in an economical manner. Furthermore, the invention has for its object to provide a method for producing such a frame threshold.

This object is solved by the features of claims 1 and 13, respectively.

The invention is based on the recognition that high clamping forces can be generated even by the use of at least two rail fasteners in each crossing region of each two sleepers and longitudinal beams, if conventional rail fasteners and conventional Schienenauflagerelemente be used, as they are also used in pure sleepers , By providing the rail fasteners in the intersection areas they are so closely spaced that it is still possible to speak of a quasi-static bearing, even if at least two rail fasteners are provided in each intersection area. As a result, a lifting of the rail is avoided by individual rail supports under load even with more than two bearing surfaces over the length of a longitudinal member.

According to one embodiment, the at least one bearing surface, on which the respective rail is mounted with the interposition of at least one elastic rail support element, extend over substantially the entire extent of the crossing region in the rail direction. Of course, the support surface in the rail direction, however, may also be divided into a plurality of separate bearing surfaces. For example, each crossing region may have a number of bearing surfaces corresponding to the number of mountable rail fastenings, wherein Preferably, each position for a rail fastening, seen in the rail direction, is in the region of a support surface

According to the preferred embodiment, the bias of the frame threshold may be formed so that the crossing regions are biased in two axes, namely both in the direction of the respective longitudinal member and in the direction of the respective cross sleeper.

The points of each bearing surface assigned to a respective rail preferably have a maximum distance of 0.5 mm from a reference plane, which results from the fact that a rail with imaginary ideally flat underside is placed on the support surfaces, wherein the underside forms the reference plane. This makes it possible to use Schienenauflagerelemente having a relatively high spring rate.

In the preferred embodiment, the frame threshold according to the invention has a distance between the axes of the sleepers of 55 cm to 70 cm. This results in dimensions for the entire threshold, which make it possible on the one hand, that the threshold can still be used in tight bends and the required deflections of the rails at a load by the wheels of rail vehicles can still follow sufficiently flexible. On the other hand, as a result of the at least two rail fastenings per intersection region, even at this conventional rail spacing, such a large clamping force results that extremely high loads can be reliably absorbed without a fault in the rails or the track structure.

The frame sleepers according to the invention can be preassembled to prefabricated frame threshold unit, each consisting of a frame threshold and at least one rail attachment preassembled per intersection region and at least one rail support element preassembled per intersection region. This results in a simplified assembly of a track structure using such pre-assembled frame threshold units.

In a track structure according to the invention either a single Schienenauflagerelement (5 ') is provided with a spring in the range of 100 to 160 KN / mm in each intersection or more rail support elements (5) are provided in each crossing region, wherein the whole, by the Parallel connection of the spring numbers of the plurality of Schienenauflagerelemente (5) resulting total spring number is in the range of 100 to 160 KN / mm, wherein the plurality of Schienenauflagerelemente (5) preferably have the same size spring numbers.

With the frame thresholds or frame threshold units according to the invention, a track structure can be realized in such a way that frame sleepers are involved in the track structure which is exposed to high loads, in particular in sections which have a large pitch and / or narrow curve radii and / or which are exposed to large temperature fluctuations at least two rail fasteners per intersection are provided. On the other hand, in sections of the track structure which are subjected to low loads, particularly in sections which have little or no slope and / or large or no radii of curvature and / or which are subject to small temperature variations, the same frame ties can be used with only a single rail attachment per intersection be provided. In this case, the frame thresholds may be formed so that the rail fasteners are mountable or preassembled so that the position at which, if necessary, the only rail fastening per intersection is mounted between the positions where, if necessary, two or more rail fasteners are mounted per crossing area.

1. 1. für alle Einsatzbereiche der Rahmenschwelle sowohl in Gebirgsstrecken wie in Flachlandstrecken nur ein einziger Schwellentyp verwendet werden kann. Die Elemente der Schienenbefestigungen und Schienenauflager sind dank der beschränkten Schwellenlänge in Gleisrichtung die gleichen wie im bekannten Querschwellengleis. Die damit verbundenen Vereinfachungen in Produktion, Lagerhaltung und Verlegung führen zu erheblichen Kosteneinsparungen.
2. 2. die Schwelle hauptsächlich im Werk, aber auch auf der Baustelle mit der notwendigen Anzahl von Schienenbefestigungen ausgerüstet werden kann. Damit verbessert sich die Anpassung an unvorhergesehene Planungsänderungen.
3. 3. alle Einbauteile der Schienenbefestigungen sich innerhalb der Kreuzungsbereiche der vorgespannten Querschwellen und Längsträger befinden, d.h., sie liegen in einer zweiachsig gedrückten Betonzone. Eine mögliche Rissbildung im Beton rings um die Einbauteile wird dadurch verhindert. Wegen der Konzentration der Schienenbefestigungen auf den Kreuzungsbereich kann außerdem die Breite von Querschwellen und Längsträgern unabhängig vom Platzbedarf der Schienenbefestigungen frei gewählt werden.
4. 4. nur mit dem erfindungsgemäßen Herstellungsverfahren der "Frühentschalung" die erfindungsgemäße Rahmenschwelle in einem Arbeitsgang hergestellt werden kann. Das Verfahren führt durch die Teilerhärtung des Betons in der Schalungsform zu einer hohen Maßgenauigkeit der insgesamt acht Schienenauflagerflächen einer Schwelle in Bezug auf Höhenlage und Ebenheit.

The particular advantages of the frame threshold according to the invention are to be seen in the fact that:

1. 1. only one type of threshold can be used for all uses of the frame threshold, both in mountain ranges and in low-level lines. The elements of the rail fasteners and rail supports are thanks to the limited threshold length in the track direction the same as in the known crossbar track. The associated simplifications in production, warehousing and installation lead to significant cost savings.
2. 2. The threshold can be equipped mainly in the factory, but also on the construction site with the necessary number of rail fasteners. This improves the adaptation to unforeseen planning changes.
3. 3. all fittings of the rail fasteners are located within the intersection of the prestressed sleepers and side members, ie, they are in a biaxially depressed concrete zone. A possible cracking in the concrete around the built-in parts is prevented. Because of the concentration of rail fasteners on the crossing area, the width of sleepers and side rails can be chosen freely, regardless of the space requirements of the rail fasteners.
4. 4. Only with the inventive manufacturing process of the "Frühentschalung" the frame threshold according to the invention can be produced in one operation. The method results in a high dimensional accuracy of the total of eight rail support surfaces of a threshold in terms of altitude and flatness by the Teilerhärtung of the concrete in the formwork.

The method according to the invention for producing such a frame threshold is characterized in that the freshly concreted in a corresponding formwork frame threshold is not immediately disengaged, but only after reaching a first hardening stage of the concrete, which excludes deformation of the concrete body. As a result, the required tight tolerances between the support surfaces of the frame threshold per rail can be achieved without reworking the threshold.

A further advantage of the method according to the invention is that the backing sheets or pallets usually used in the hitherto customary immediate demoulding of the sleepers for supporting the fresh concrete under the tensioning frames can be dispensed with. In addition, since the molds and clamping frames are no longer rotated when Entschalen the thresholds, the later turning back of these manufacturing facilities by appropriate Drehvornchtungen is no longer required.

Further embodiments of the frame threshold or frame threshold unit or the method for producing such frame thresholds according to the invention will become apparent from the dependent claims.

Fig. 1

eine Draufsicht der Rahmenschwelle mit zwei Schienenbefestigungen bzw. vier elastischen Federelementen und zwei Schienenauflagerelementen in jedem Kreuzungsbereich von Querschwellen und Längsträgern;

Fig. 2

eine Draufsicht der Rahmenschwelle mit zwei Schienenbefestigungen und zwei, zu einem einstückigen Element zusammengefassten Schienenauflagern in jedem Kreuzungsbereich von Querschwellen und Längsträgern;

Fig. 3

eine Draufsicht der Rahmenschwelle mit einer mittigen Schienbefestigung und zwei Schienenauflagern in jedem Kreuzungsbereich;

Fig. 4

einen Schnitt längs der Achse eines Längsträgers gemäß Fig. 1;

Fig. 5

verschiedene Phasen des erfindungsgemäßen Verfahrens zur Herstellung einer Rahmenschwelle nach den Fig. 1 bis 4.

The invention will be explained in more detail with reference to embodiments illustrated in the drawing. In the drawing show:

Fig. 1

a plan view of the frame threshold with two rail fasteners or four elastic spring elements and two Schienenauflagerelementen in each crossing region of sleepers and side rails;

Fig. 2

a plan view of the frame threshold with two rail fasteners and two, combined into a one-piece element rail supports in each crossing region of sleepers and side rails;

Fig. 3

a top view of the frame threshold with a central rail attachment and two Schienenauflagern in each crossing region;

Fig. 4

a section along the axis of a longitudinal member according to Fig. 1 ;

Fig. 5

various stages of the inventive method for producing a frame threshold according to the Fig. 1 to 4 ,

In Fig. 1 a frame threshold known type with two sleepers 1 and two longitudinal beams 2 is shown, the crossing areas have been increased so that according to the invention at least two, preferably also used in previously known track structures rail fasteners can be juxtaposed and still the voltage flow in the sleepers 1 and 2 side rails only slightly disturbed. In the illustrated embodiment, exactly 2 rail fasteners and two Schienenauflagerelemente 5 are shown. Of course, however, more than two rail fasteners or even, regardless of the number of rail fasteners, any number of Schienenauflagerelementen be provided. In practice, however, it may be appropriate for economic reasons, for example, for reasons of reduced storage, to use two Schienenauflagerelemente, as they are already used in known track structures. In particular, a rail support element can be provided per rail fastening such that the respective rail support element lies in the region between rail and sleeper frame in which the clamping forces generated by the rail fastenings also act.

Compared to known embodiments of the frame threshold with only a rail fastening and a rail support in each crossing area so here is the number of rail fasteners and Schienenauflager doubled. This means that the transferable between rails and sleepers forces and thus the carrier rust effect also double.

This embodiment is intended for the highest requirements. Thus, even elevated temperatures in the rail due to the eddy current brake used in modern trains can be easily absorbed. Narrow arch up to 200 m radius can be run without the risk of track warping with continuously welded rails.

In Fig. 2 a further embodiment of Auflagerrabbildung is shown, in which the two Schienenauflagerelemente 5 are summarized in an intersection region to a one-piece Schienenauflagerelement 5 '. This embodiment can contribute to a simplification in the manufacture and assembly of the elastic intermediate layers.

Fig. 3 shows a cost-effective embodiment of the frame threshold after the Fig. 1 or 2 for routes with only low load, for example low-level lines. In such cases, it is sufficient to provide only one rail attachment per intersection area instead of two or more rail fasteners. However, it is still possible to arrange two rail supports 5 between rail and sleeper frame. This embodiment leads to reduced costs for rail fastening. However, one and the same threshold frame can be used for high and low load routes.

The arrangements for mounting the rail fasteners, for example holes or dowels provided in the sleeper shape in each intersection area, can already be made in the factory during the production of the sleeper molds. Like from the Fig. 1 to 4 As can be seen, for example, a single threshold frame type can be produced, which has three positions for each one rail fastening on each side of the rail to be mounted in each crossing region, seen in the longitudinal direction of the rail to be mounted. This can be all in the Fig. 1 to 4 realize the mounting methods shown. In Fig. 3 the vacant points represent the positions for rail fasteners that are not occupied in this case.

Fig._4 shows a vertical section along the axis of a longitudinal member 2 according to Fig. 1 with the arrangement of two rail fasteners in the widened bearing surface a crossing area. In the middle of the longitudinal member 2 is located between rail 3 and threshold a mounting recess 6 in on the top of the longitudinal member 2 for installation of molds for rail welds in case of breakage of the rail during operation.

In order to lift the rail of individual rail supports 5 in Fig. 2 To avoid the elasticity of the Schienenauflagerelemente 5 and the height tolerances between the four bearing surfaces along a rail 3 must be coordinated. The embodiment of the invention provides spring numbers of 50 to 80 KN / mm for each rail support element 5 and height tolerances of no more than 0.5 mm between the supports of a threshold per rail. The tolerances are defined in such a way that, given an imaginary placement of a rail with a completely flat underside on the support surfaces of the threshold frame (without rail support elements), a maximum distance of 0.5 mm from each point of the support surfaces to the plane defined by the underside of the rail consists.

The rails are fastened using standard rail fasteners with compressive forces of approx. 17 to 25 KN, so that there is a force of approx. 8.5 KN per rail fastening assuming a coefficient of friction of 0.5, which can be absorbed in the direction of the rail before the rail starts slipping against over the sill frame.

According to the state of the art, the production of a frame threshold requires the use of immediate shuttering in order to reduce the number of molds and to limit the constantly necessary dimensional control of the molds, because of the high cost of the expensive formwork molds. In immediate shuttering, the manufactured thresholds are deactivated immediately after concreting out of the mold.

As a result, however, the required height tolerances of not more than 0.5 mm in the four bearing surfaces of a longitudinal member with the instantaneous shuttering method are not to comply because small deformations of the freshly diverted concrete during in-house transport can hardly be avoided.

In addition to the above-mentioned economic considerations, the process of instant peeling was selected for the production of frame thresholds also for the technical reason that a late shells with reasonable effort is hardly possible. In the case of late shelling, the prestressed concrete sleeper is removed from the mold only after a hardening time of approx. 24 hours. However, during this long curing time, the shrinkage of the concrete already occurs in all three spatial directions, in particular in the longitudinal direction of the longitudinal members and the transverse tie. This would require a mold that allows such a shrinkage stress-free. However, this is hardly feasible in practice.

With the inventive production method of Frühentschalung as a new part of the known tenter frame method, the threshold is raised only after reaching a concrete strength of about 5-10 N / mm ² from the mold, so that subsequent concrete deformations are excluded. This concrete strength is reached after about three to four hours curing time. The existing in the formwork and continuously controlled support heights are transmitted in this way without change to the threshold.

Since the first hardening phase of the concrete takes several hours, although an increased number of forms is necessary in order to continue concreting further thresholds during the hardening phase can. However, the dimensional accuracy of the thresholds achieved in this respect is more advantageous in economic terms than the associated increase in the molding costs.

Fig. 5 shows the concreting to explain the individual stages of the process. First, as in Fig. 5a shown, the clamping frame 9 with the therein, preferably made of steel tension rods 10 from above into the formwork 8 inserted, the tension rods 10 are guided by vertical slots in the formwork 8 down. The sleepers are then concreted by the introduction of a suitable concrete mix in the formwork 8 in overhead position.

How out Fig. 5b shows, the threshold after the first hardening phase of the concrete, ie after a few hours, together with the clamping frame 9 up "early-breaking". Because of the existing concrete strength eliminates the known from the immediate shuttering turning threshold and shape and settling the fresh thresholds on special documents called pallets. The further hardening of the concrete takes place in such a way that several sleepers are superimposed with their associated tenter frame 9 to box-like stacks of FIG. 6c.

After completion of hardening the tension rods 10 are released in a special decompression system of the clamping frame 9 and the thresholds; the sleepers will then, as in Fig. 5d shown, lifted upwards and only in this phase turned over to the normal position.

Claims (16)

1. A single-unit frame sleeper made of prestressed concrete

   a) consisting of two cross-ties and two longitudinal supports,

   b) with each of the four areas at which the cross-ties (1) cross the longitudinal supports (2) exhibiting at least one level bearing surface to bear at least one elastic rail-bearing element (5),
   characterised by

   c) a frame sleeper, which in its geometry, material make-up and the prestressing is dimensioned such that at least two rail fasteners can be mounted on each crossing area at specified mounting positions along the rail to be fastened, each of which has two elastic spring elements (4),

   d) wherein provisions for mounting one rail fastener each have been taken in each crossing area at three different mounting positions along the rail to be fastened, arranged such that the two outer positions in the longitudinal direction of the rail can be engaged by one rail fastener each at one and the same time.
2. A frame sleeper according to claim 1, characterised by at least one bearing surface essentially extending over the entire length of the crossing area in the direction of the rail.
3. A frame sleeper according to claim 1, characterised by each crossing area exhibiting a number of bearing surfaces that equals the number of mountable rail fasteners, wherein each position for fastening a rail preferably lies in the area of the bearing surface when looking in the direction of the rail.
4. A frame sleeper according to one of the preceding claims, characterised by the prestressing of the frame sleeper being designed such that the crossing areas are prestressed biaxially, i.e. both in the direction of the respective longitudinal support and in the direction of the respective cross-tie.
5. A frame sleeper according to one of the preceding claims, characterised by the points of all bearing surfaces being assigned to one rail having a maximum clearance of 0.5 mm from the reference level, which results by placing one rail with a theoretically ideal underside on the bearing surface with the underside forming the reference level.
6. A frame sleeper according to one of the preceding claims, characterised by a preferentially central recess (6) being provided in each case between the crossing areas that serves as mounting aperture for rail welding work.
7. A frame sleeper according to one of the preceding claims, characterised by the clearance of the axes of the cross-ties measuring between 55 cm and 70 cm.
8. A frame sleeper unit, consisting of one frame sleeper according to one of the preceding claims and at least one rail fastener pre-mounted for each crossing area and at least one rail-bearing element (5) pre-mounted for each crossing area.
9. A track structure, consisting of several frame sleepers according to one of claims 1 through 7 and two rails mounted thereon, characterised by each frame sleeper holding each rail at each crossing area with at least one rail fastener, with at least one elastic rail-bearing element being provided at each crossing area between the underside of the rail concerned and at least one level bearing area.
10. A frame sleeper unit according to claim 8 or a track structure according to claim 9, characterised by either one single rail-bearing element (5') with a stiffness of between 100 and 160 KN/mm being provided at each crossing area or several rail-bearing elements (5) being provided at each crossing area, wherein the overall stiffness resulting from the parallel arrangement of the stiffness values of the several rail-bearing elements (5) ranges between 100 and 160 KN/mm, with the several rail-bearing elements (5) exhibiting equal stiffness values.
11. A frame sleeper unit according to claim 8 or 10 or a track structure according to claim 9 or 10, characterised by each rail-bearing element exhibiting a stiffness ranging from 50 to 80 KN/mm.
12. A track structure according to claim 9 or 10, characterised by frame sleepers with at least two rail fasteners per crossing area being provided in the sections of the track structure exposed to high stress, particularly in the sections exhibiting a high gradient and/or narrow curve radii and/or exposed to large temperature fluctuations, and frame sleepers with only one single rail fastener per crossing area being provided in sections of the track structure exposed to low stress, particularly in sections exhibiting a low gradient and/or large or no curve radii and/or exposed to small temperature fluctuations.
13. A method of manufacturing a frame sleeper according to claims 1 through 8, with the following procedural steps:

    a) concrete casting of the frame sleeper in a mould (8) in upside-down position, into which tension rods (10) have been introduced in order to produce pretension with direct bonding in a clamping frame (9);

    b) curing of the concrete cast sleeper in the mould (8) until a first curing stage of the concrete is reached that excludes any distortion of the concrete structure;

    c) stripping of the sleeper in upside-down position by pulling the sleeper and
    the clamping frame upward;

    d) positioning of the stripped sleeper in the clamping frame (9) until the concrete has cured completely;

    e) transmission of the tensile forces onto the cured sleeper in upside-down position;

    f) turning of sleeper into normal position after complete separation from the clamping frame (9).
14. A method according to claim 13, characterised by the installation of tension rods (10) in the mould (8), at least in the appropriate areas of the mould, in order to ensure biaxial reinforcement in transverse and longitudinal direction and fixation in the clamping frame (9).
15. A method according to claim 13 or 14, characterised by placing several sleepers - once they have been stripped - with their corresponding clamping frames (9) on top of each other to form box-like stacks for the purpose of further curing.
16. A method according to claims 13 through 15, characterised by reaching the first curing stage of the concrete when the concrete of the sleeper exhibits a strength of approx. 5 to 10 N/mm².

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