EP1923185B1 - Method and installation for forming a single-piece prefabricated element made of concrete - Google Patents

Description

The present invention relates to a method and an apparatus for producing a one-piece precast concrete element.

When concreting prefabricated parts, formwork is usually filled with concrete from above. The concrete falls from a certain height from above into the open formwork, possibly also on a reinforcement arranged in the formwork. To fill all cavities of the formwork, the concrete must be mechanically compacted, for example vibrated.

Also known is the use of flowable self-compacting concrete (SVB), which can cover a longer flow path, without demixing it. On its flow path, the concrete rolls around and vents itself automatically without the use of mechanical energy. Self-compacting concrete can be conveyed by means of a pump in the formwork. Again, the filling of the concrete is done from above into the open formwork, for example by a hose or pipe, the lower end is always held in the already filled concrete and is pulled up with increasing filling height, in this way as little air in to introduce the concrete.

It is also already known, flowable self-compacting concrete via a provided on the bottom or in the lower part of the side mold gate valve in formwork, mainly Ortbetonschalungen filled. The concrete rises from the bottom up. Its surface is affected only by atmospheric pressure. The filling of especially long formwork up to a defined upper edge is hardly possible, since the concrete reaches the filling height first at the point of the smallest resistance and then overflows over the upper edge of the open formwork. Parts with complex geometries, such as hollow room modules with a bottom and side walls, can be very difficult to produce with the known methods and with thin liquid special concretes in one piece.

Shuttering smooth surfaces in visual quality or profilings on all sides can not be produced with the known concreting methods or at least not in sufficient quality. Another major disadvantage of the conventional method is that, for example, room modules with bottom and thin side walls can only be concreted upside down, ie, with the floor upwards, and thus turned into the transport or installation position only after complete hardening of the concrete have to. Accordingly, the whole formwork is blocked.

US Pat. No. 6,395,213 B1 discloses a method of making a precast concrete element comprising the steps of: providing an empty formwork comprising bottom formwork, side formwork, a displacer, and a flameproof cap terminating the formwork at the top; Pressing in flowable concrete in the area of the floor formwork; continuous filling of the formwork with concrete, which rises under pressure from bottom to top, until the cavities of the formwork are completely filled; Solidification of the concrete in the formwork; Remove the cover, the displacement body and the side formwork so that at the end the freshly concreted prefabricated part only stands with the bottom on the bottom formwork.

US Pat. No. 6,395,213 B1 also discloses a device and a method for producing a precast concrete element, according to the preamble of claims 1 and 7, comprising a cap which closes pressure-resistant upwards formwork, and at least one closable inlet for flowable concrete arranged in the region of the bottom formwork. In the cover openings are provided, can escape from the inflowing concrete displaced air from the interior of the formwork in the environment. These holes are flush with the horizontal top of the cap.

EP 0 382 536 A1 describes a method and apparatus for making articles from a liquid, solidifying material. The device comprises a mold composed of two halves enclosing a cavity, a gasket for pressure-tight sealing of the mold to the atmosphere and an inlet for the liquid material. A vacuum port is also provided to create a negative pressure in the mold before the liquid material is filled.

FR 2 619 047 discloses an apparatus for injecting concrete into a mold consisting of two halves. The concrete is filled from a arranged above the mold funnel under pressure. Top-mounted on the form of control (témoins) allow to control the completion of the filling of the mold with concrete.

In view of the described disadvantages in the prior art, it is an object of the present invention to provide a method and an apparatus with which a precast concrete part with higher quality of the visible surfaces can be produced as one-piece precast concrete, wherein the finished part hardens immediately in the final position in the formwork , so after hardening no longer needs to be rotated or turned.

The stated object is initially achieved by the method having the features of patent claim 1 and the device having the features of patent claim 7.

In the method according to the invention, an empty formwork is first provided, which consists of bottom formwork, side formwork, displacement body and a cap. The formwork is thus sealed off at the top. It is also provided at least one open riser, which projects beyond the formwork.

Then flowable concrete is pressed into the area of the bottom formwork. The formwork is then filled continuously with nachfließendem concrete, wherein the displacement body displaces the infiltrated concrete so that it rises in the formwork under pressure from bottom to top until all the cavities are completely filled with concrete.

Since the formwork is capped at the top in a pressure-resistant manner, a locally increased pressure builds up at the points where the concrete builds up, which leads to The concrete is evenly distributed in the formwork and also the last corners and angles are gradually filled. Of course, the pressure with which the concrete is pressed into the formwork, must be chosen so that the formwork withstands this.

During the filling of the formwork, concrete is pushed up out of the formwork into the open riser towering above the formwork. This allows the concrete column to rise above the upper edge of the formwork, thereby exerting additional defined pressure on the concrete in the formwork. At the same time, pressure peaks that could damage the formwork are avoided. How high this additional pressure is depends on the height of the upper edge of the riser above the ground or above the concrete filling holes.

When the formwork is completely filled, the concrete in the formwork is allowed to solidify. Subsequently, the cap and the side mold are removed and the displacer pulled out. At the end, the freshly concreted finished part stays with the floor, ie in the installed position, on the lower formwork.

The method according to the invention is very well suited for the production of a room module which comprises at least one floor and side parts integrally formed thereon and can be used to create a simple building, for example a garage or a small house. But it can also be any other components, for example, flat, rod-shaped or spatial components are manufactured with and without openings or recesses.

If a room module is to be produced by the method according to the invention, the formwork comprises a displacement body in the form of a removable inner core whose distance from the bottom formwork and the side formwork determines the thickness of the floor or side walls of the room module to be concreted.

The concreting of a room module in installation position under pressure in the rising current from bottom to top causes the bottom of the room module is first concreted, in which the corresponding cavity is filled at the bottom first with concrete. Only then does the concrete rise into the cavities that form the side walls of the room module. The higher the concrete rises, the greater the pressure in the floor area, since there the weight of the rising concrete column acts.

The pressure with which the concrete is introduced into the formwork thus serves not only to convey the concrete but also to distribute it within the formwork. For this purpose, as stated, the formwork must be sufficiently pressure-stable and, in particular, also have a sufficiently pressure-resistant cover to the top. The pressure prevailing in the formwork when filled with concrete is composed of the geodetic concrete pressure, the friction and adhesion resistance as well as an additional operating pressure, which is necessary for the inflowing concrete to flow through narrow passages and into all angles and the reached the highest cavities in the formwork sufficiently fast.

The fact that the finished part does not have to be turned over after concreting, but immediately stands with the bottom on the lower formwork, has the great advantage that the freshly concreted part can be quickly turned off and transported away. Side formwork, displacement body and cover can be reused immediately for concreting the next finished part; only the lower formwork remains on the finished part until the concrete has completely hardened or the part has been transported to the installation site.

Another great advantage of the concreting process according to the invention is the high quality of the exposed concrete surfaces that can be achieved therewith. The use of flowable concrete and its air-poor distribution within the formwork under pressure results in smooth walls in fair-quality concrete and can be any profiles, for example, at the bottom of the soil, if necessary.

The following method has proved to be particularly useful: The flowable concrete is pressed from below into the formwork until the formwork is completely filled and beyond a projecting concrete column has formed in the riser. Subsequently, the supply of concrete is turned off. The concrete column in the riser begins to sink to the extent that the concrete in the formwork settles due to its own weight. As soon as the concrete column in the riser pipe no longer sinks, the connection to the formwork is sealed off. This procedure ensures that all cavities within the formwork are filled with concrete. The riser thus works as a pressure equalizing vessel with memory function.

Since the flowability of the concrete is limited, care must be taken that the flow path of the concrete in the formwork is not too long. This can be avoided by simultaneously pressing the concrete into the formwork at several points. It is of course expedient to distribute the inlets so that the concrete column in the formwork everywhere rises about the same speed. The provision of several, well-distributed risers has proved to be highly advantageous, since then a fast and uniform filling of the whole formwork can be achieved.

The method according to the invention is characterized in that the filling process can be carried out at high speed. Tests have shown that filling speeds of up to 40 l / min with a delivery line with a cross section of 50 mm pose no problem and also have no negative effects on the quality of the exposed concrete surface, even with very narrow formwork geometry. However, the prerequisite for such high filling speeds is the use of a suitable fresh concrete. Particularly good results have been achieved with self-compacting concrete (SCC), in particular with good-flowable SCC of the flour-type, which is characterized by an excess proportion of flour meal.

A device which serves to carry out the method according to the invention comprises a sufficiently pressure and deformation-resistant formwork, which consists at least of bottom formwork, side formwork and a displacement body. According to the invention, a pressure-resistant cover is provided, which closes the formwork at the top. In the area of the floor formwork at least one lockable inlet for flowable concrete is provided. The device according to the invention also comprises an open riser pipe, which projects beyond the formwork and is connected to the latter via a closable opening. The device designed in this way allows the introduction of flowable concrete in the area of the bottom formwork and the continuous filling of the formwork with concrete, which rises under pressure from bottom to top in the riser until the cavities of the formwork are completely filled with concrete and a supernatant Concrete pillar has formed in the riser.

Preferably, several closable inlets for concrete along the side mold are distributed so that the concrete column rises as evenly as possible in the formwork. This is supported by the fact that preferably also several pressure equalization vessels are provided, which are also distributed along the edge of the side mold.

To promote the flowable concrete, a high-pressure concrete pump is preferably used, which is in fluid communication with the closable inlets. The pressure generated by the pump not only serves to transport the concrete, but is also responsible for the uniform distribution of the concrete within the formwork. Preferably, the concrete is pumped via a branched system of hoses and pipes to the inlets of the formwork.

Preferably, the riser pipes are made of transparent material, in particular plastic, so that the height of the concrete column can be observed. As obturator is for example a horizontal disc with an eccentrically arranged recess which can be rotated by hand via a corresponding opening in the cap. Conveniently, the riser is detachably connected to the top of the cap and decoupled. This makes it possible for the riser pipe to be quickly separated from the formwork cover and for the residual concrete contained therein to be dumped before it cures.

Figuren 1 bis 7

das Ein- und Ausschalen eines Raummoduls im Verlauf seiner Herstellung als einstückiges Fertigteil aus Beton, in sieben perspektivischen Zeichnungen;

Figur 8

eine obere Ecke der Schalung gemäß Fig. 5 mit Deckelung und aufgesetztem Steigrohr, in etwas größerem Maßstab;

Figuren 9a, 9b, 9c

das Steigrohr von Fig. 8, in nochmals vergrößertem Maßstab;

Figuren 10 bis 13

das Betonieren eines Raummoduls mit Boden und Seitenwänden, schematisch;

Figur 14

das Betonieren eines anderen Raummoduls mit Boden, Seitenwänden und Decke, schematisch.

The concreting method according to the invention and the shuttering apparatus used therefor are explained in more detail below by way of example with reference to the accompanying drawings. Show it:

FIGS. 1 to 7

the fitting and stripping of a room module in the course of its manufacture as a one-piece prefabricated concrete, in seven perspective drawings;

FIG. 8

an upper corner of the formwork according to Fig. 5 with lid and raised riser, on a slightly larger scale;

FIGS. 9a, 9b, 9c

the riser of Fig. 8 in an even larger scale;

FIGS. 10 to 13

concreting a room module with floor and side walls, schematic;

FIG. 14

the concreting of another room module with floor, side walls and ceiling, schematic.

The method according to the invention and the associated apparatus will be explained below with reference to the example of the production of a room module with side walls and monolithic floor.

In Fig. 1 is a bottom form 1 to see. This is also designed as a transport pallet and has on its upper side a contouring 2, the negative is to impress in the bottom of the space module to be produced.

In Fig. 2 is a side formwork 3 placed on the bottom formwork 1. The side mold 3 is composed of a number of side panels. Floor formwork 1 and side formwork 3 define a rectangular parallelepiped. The height of the side formwork 3 corresponds to the height of the side walls of the room module to be concreted.

According to Fig. 3 Now, an inner core 4 is introduced from above between the walls of the side mold 3. The inner core 4 also has the shape of a rectangular parallelepiped whose dimensions are somewhat smaller than the clearances between the respective opposite walls of the side mold 3. On its upper side, the inner core 4 carries a number of parallel cross member 5, which survive right and left. The inner core 4 is lowered gently close to the bottom formwork 1, so that it fills most of the space formed by the bottom formwork 1 and the side formwork 3.

In Fig. 4 is the inner core 4 completely inserted into the side mold 3. The lateral projections of the cross member 5 sit on top of the side mold 3 and keep the inner core 4 characterized in a defined small distance from the bottom formwork 1 (cf. Fig. 1 . Fig. 2 ). So that the inner core 4 does not float during concreting, the cross member 5 are firmly connected by means of fastening screws 6 with the side panel 3. As a result, the side formwork 3 is stiffened at the same time. Between the inner core 4 and the side wall 3 remains a running around vertical side gap 7, which determines the thickness of the side walls of the space module to be produced. So that the inner core 4 can be easily lifted out of the side formwork 3 again after concreting, it is designed as a shrink core, that is, its outer dimensions can be reduced with respect to the finished part to be concreted.

In Fig. 4 the formwork consisting of floor formwork 1, side formwork 3 and inner core 4 is still open at the top, namely in the area of the side gap 7. According to FIG Fig. 5 This side gap 7 is now closed by means of a hinged cap 8. Thus, a completely closed formwork is provided.

In the lower part of the side mold 3, a number of inlets 9 is provided. Each inlet 9 is connected by a short tube 10 to a conduit 11 leading to a high pressure concrete pump (not shown). The inlets 9 are distributed at regular intervals along the outside of the side mold 3. Each inlet 9 has its own obturator, so that the inlets 9 each open and close independently.

On the closed cap 8 risers 12 are placed. At the top, these risers 12 are open, below they are connected via a small closable opening with the otherwise pressure-tight closed interior of the formwork in combination.

The formwork is now ready for concreting.

In Fig. 5 is indicated by arrows that flowable self-compacting concrete (SVB) is introduced in a split-flow through the conduit 11 via the hoses 10 and the inlets 9 in the formwork. By selective opening and Closing the inlets 9, the cavities are filled in the interior of the formwork. The concrete rises steadily under pressure from bottom to top until it reaches the upper edge of the side mold 3 and overflows into the riser pipes 12.

By selective opening and closing of the inlets 9 and the risers 12, the concreting can be controlled so that first the space between the bottom mold 1 and bottom of the inner core 4 is rinsed with concrete and then nachgefießender concrete as evenly as possible in the side gap 7 between the side mold 3 and inner core 4 (cf. Fig. 4 ) goes up. Only when all cavities in the formwork are completely filled with concrete and the concrete is also raised in the risers 12, the concrete pump is turned off and all the inlets 9 are shut off. Inlets 9 and risers 12 are uncoupled and the corresponding openings closed form smooth as long as the concrete is liquid.

After the concrete in the formwork has become sufficiently strong, the cap 8 is removed. After loosening the mounting screws 6, the inner core 4 can be lifted upwards, wherein the cross member 5 stand out from the top of the side mold 3. Previously, the inner core 4 was shrunk to disengage from the adjacent concrete wall. In Fig. 6 the inner core 4 is already pulled a piece upwards. There, where was at the empty formwork of the side gap 7 (see. Fig. 4 ), the side walls 13 of the freshly concreted space module have now formed.

After the side shuttering 3 has been removed, is at the end of the finished room module with the ground on the floor formwork 1, as in Fig. 7 shown. In this example, the room module made of one piece of concrete comprises, in addition to the sidewalls 13, a flat floor 14 which is monolithically connected to the sidewalls 13. In the side walls 13 openings 15 are provided for doors and windows. Even if the concrete is not fully cured, the floor formwork 1 can be transported away together with the room module resting on it. All surfaces are smooth and have fair-faced concrete quality.

The scale enlarged picture of Fig. 8 allows a look inside the formwork. For this purpose, the inner core 4 is shown vertically cut. It can be seen the side gap 7 between the inner core 4 and side mold 3 and the cap 8, which closes the formwork towards the top. The cap 8 is formed as a flat sheet of steel and is with its outer (in Fig. 9 left) edge pivotally attached to the top of the side mold 3. With its opposite edge, the cap 8 lies on the inner core 4, so that the side gap 7 is covered. The closed lid 8 is held closed by a latch 16 so that it withstands the pressure acting from below of the concrete rising in the side gap 7.

The attached to the outside of the closed cap 8 riser 12 is made of transparent plastic, so that it can be seen whether and how high the concrete column has risen in the riser 12.

In the Figures 9a, 9b and 9c are details of the riser 12 to recognize.

A flange 17 serves to quickly connect and disconnect the riser 12 to and from the cap 8 (see. Fig. 9 ). Knockable wedges 18 press the flange 17 firmly on top of the cap 8. The flange 17 has a small round opening 19. In addition, a disc 20 is horizontally rotatably mounted, which has an eccentric bore 21. By means of a radially outwardly projecting lever 22, the bore 21 can rotate over the opening 19, so that concrete can rise from below from the closed formwork in the riser 12. By turning back the disc 20, the opening 19 can be closed again to interrupt the connection between the riser 12 and the interior of the formwork. After removal of the wedges 18, the completely or partially filled with concrete riser 12 can be decoupled from the cap 8 to empty it before the concrete has set.

The running in the interior of the closed formwork operations when concreting a room module are described below with reference to FIGS. 10 to 14 described in more detail. The illustrations are greatly simplified and show the device used only schematically.

In Fig. 10 In principle, the same formwork is shown as in Fig. 5 but horizontally cut and not to scale. The hollow core 4 fills most of the interior of the formwork except for the side gap 7. Towards the top, the formwork is closed by the cover 8 in a pressure-tight manner. Separately lockable inlets 9 are arranged on the right and left in the lower region of the side mold 3. By means of individually controllable filling valves 23, the supply of fresh concrete can be controlled. On the top of the cover 8, a riser 12 are placed on the right and left, which are in fluid and pressure communication with the interior of the formwork. The connection can be opened or closed by means of shut-off valves 24. Above the risers 12 are open, so are in contact with the atmosphere. In the open state, the riser tubes 12 function as pressure equalization vessels.

Initially, the formwork is empty. The filling valves 23 at the inlets 9 are all closed, whereas the shut-off valves 24 of the risers 12 are opened.

In the first phase, the in Fig. 10 is shown, the filling valve 23 is now opened on the left side, whereupon flowable self-compacting concrete (SVB) flows at high speed on the bottom mold 1. The displaced by the inflowing air can escape through the open risers 12 upwards. Even if the concrete is pressed into the formwork with a very high pressure - up to 5 bar in the area of the inlets 9 - the viscous concrete does not distribute itself uniformly. Rather, the inflowing concrete accumulates in the area behind the left inlet 9 and begins to rise first on the left side in the side gap 7 to the top. At the same time limited by the bottom mold 1 and the inner core 4 bottom gap 25 is flushed from left to right with the liquid concrete. It should be noted that the bottom gap 25 is in truth much narrower than shown in the drawings. Therefore, it requires a fairly high pressure, so that the concrete is pushed through the bottom gap 25 therethrough.

In Fig. 11 the bottom gap 25 is already completely filled with concrete. The left part of the side gap 7 is filled to about one third with concrete, whereas almost no concrete has arrived on the left side.

It now begins the second phase of the filling process by additionally the filling valve 23 of the inlet 9 is opened on the right side, so that now flows in concrete from both sides. The side gap 7 and possibly all other cavities of the formwork are gradually filled with concrete, the concrete under pressure in the rising current steadily rising from bottom to top. Also, the side gap 7 is much narrower in nature than shown in the drawings, so that it represents a proper resistance for the flowing from bottom to top concrete, which must be overcome by a correspondingly high pressure.

Fig. 12 shows a state in which the concrete column on the left side has almost reached the top of the side shell 3, while the side gap 7 is filled on the right side only about two-thirds.

In Fig. 13 the concrete on the left side was already pushed up into the riser 12 and thus reached its highest point. Now, the third phase is initiated by the riser pipe 12 is closed on the left side by closing the associated shut-off valve 24. By this riser 12 so now no concrete and no air can escape. As a result, the pressure in the left part of the side gap 7 increases up to the maximum permissible operating pressure. Through the left inlet 9 less and less concrete flows to. According to the principle of communicating tubes, a certain amount of the concrete flows from the left side through the bottom gap 25 to the right and thus supports the filling of the not yet completely filled part of the side gap 7 on the right side.

If the concrete now rises in the last, still open (in Fig. 13 right) riser 12 up, the formwork is completely filled. By closing the filling valves 23 at all inlets 9 then the supply of concrete is interrupted. At the same time closed at this time risers 12 are opened again, whereby a pressure equalization takes place. Locally increased or even dangerously excessive pressures within the formwork are thereby reduced; accumulated concrete can escape as rising concrete column in the nearest riser 12.

Due to the heaviness of the concrete, immediately after completion of the filling process, the still fresh concrete is set. This can be seen from the fact that the concrete column in the risers 12 drops slightly. This can be compensated by subsequent flow of the concrete contained in the nearest riser 12. The risers 12 thus not only serve the pressure equalization or the construction of a controlled backpressure, but at the same time also provide storage for the still flowable concrete and thereby ensure that even after settling of the concrete really all voids of the formwork remain completely filled. Only when the concrete column no longer sinks in the riser tubes 12, the associated shut-off valves 24 are closed and thus the connection to the interior of the formwork is interrupted. The risers 12 can then be dismantled, emptied and cleaned.

The method has hitherto been explained using the example of a room module with side walls and monolithically connected floor. The proposed method is by no means limited to this. It is equally possible to produce also room modules with floor and ceiling by means of the method according to the invention using the device according to the invention from a piece of concrete. It is also possible to introduce a plurality of inner cores at a distance in the formwork, so that monolithic center walls arise in the room module. In addition, solid bodies with very simple geometry, such as wall elements, round or square tubes, columns and blocks can be manufactured efficiently and in the best quality using the proposed method.

Fig. 14 explains the production of a room module with floor, side walls and in addition a ceiling as a one-piece concrete precast. Here again, the formwork consists of bottom formwork 1, side formwork 3 and a cover 8 ', which, however, covers the entire side formwork 3 here. The inner core 4 'is here arranged centrally in the interior of the formwork, so that apart from the bottom gap 25, a ceiling gap 26 remains between the upper side of the inner core 4' and underside of the cover 8 '. Thus, it becomes possible to inject concrete around the inner core 4 '.

From the filled formwork, the inner core 4 'can be pulled out later to the front.

Also in Fig. 14 Formwork shown is filled with well flowable self-compacting concrete, which rises under pressure from bottom to top. The filling process is assisted by an additional inlet 9, which is arranged on the left side of the side mold 3 just below the cap 8 '. In Figure 14 is to see a state in which the concrete column has risen on the left side already in the left riser 12 and thus reached its maximum, while on the right side below the right riser 12 still air, especially in the ceiling gap 26, located. In this phase, the two lower inlets 9 are already closed, while the additional upper inlet 9 'is still open. By this inlet 9 'depressed concrete flows almost only in the ceiling gap 26 to the right in the not yet filled area of the right side gap 7. The riser located there 12' is kept open until the concrete column reaches its maximum level there Has.

Regardless of the geometry of the precast concrete part, it is important in the described method that the flowable concrete is not only pressed into the formwork, but that it is optimally distributed by means of locally different pressures. This is achieved by the fact that the concrete always rises from bottom to top and depending on the degree of filling local pressure peaks are constructed or compensated controlled. This is achieved by the variably controlled pumping in of the concrete in conjunction with the coordinated controlled venting of the formwork.

reference numeral

1

floor formwork

2

contouring

3

page formwork

4, 4 '

inner core

5

crossbeam

6

fixing screw

7

side gap

8, 8 '

capping

9, 9 '

inlet

10

tube

11

management

12, 12 '

risers

13

side walls

14

ground

15

openings

16

bars

17

flange

18

wedge

19

opening

20

disc

21

drilling

22

lever

23 (out of 9)

filling valve

24 (out of 12)

shut-off valve

25

ground clearance

26

cover gap

Claims (13)

1. Process for producing a one-piece prefabricated part from concrete, comprising the steps of:

   a) providing an empty formwork, comprising a base formwork (1), a lateral formwork (3), a displacement body, a pressure-resistant cover (8, 8') which closes the formwork towards the top, and at least one open riser pipe (12) which projects above the formwork;

   b) introducing flowable concrete under pressure in the region of the base formwork (1);

   c) continuously filling the formwork with concrete, which rises under pressure from bottom to top until the cavities of the formwork have been completely filled;

   d) causing concrete to rise upwards under pressure beyond the formwork into the open riser pipe (12);

   e) allowing the concrete to solidify in the formwork;

   f) removing the cover (8, 8'), the displacement body and the lateral formwork (3), so that finally the freshly made prefabricated concrete part is supported only by its base (14) on the base formwork (1).
2. Process according to claim 1, characterised by the successive steps of:

   a) introducing concrete under pressure into the formwork until a protruding column of concrete has formed in the riser pipe (12);

   b) interrupting the supply of concrete, whereupon the column of concrete begins to sink;

   c) breaking the connection between formwork and riser pipe (12) when the column of concrete in the riser pipe (12) no longer continues to sink.
3. Process according to claim 1 or 2, characterised in that the concrete is introduced under pressure into the formwork simultaneously at a plurality of locations.
4. Process according to any one of claims 1 to 3, characterised in that the concrete is introduced under pressure into the formwork at a volumetric flow rate of between 10 and 50 I/min with an inlet cross-section of 50 mm
5. Process according to any one of claims 1 to 4, characterised in that the concrete is a self-compacting concrete.
6. Process according to claim 5, characterised in that the self-compacting concrete is of the powder type.
7. Apparatus suitable for producing a one-piece prefabricated part from concrete in accordance with the process of claim 1, comprising

   a) a formwork which comprises a base formwork (1), a lateral formwork (3) and a displacement body;

   b) a cover (8, 8') which effects pressure-resistant closure of the formwork towards the top;

   c) at least one closable inlet (9, 9') for flowable concrete arranged in the region of the base formwork (1);
   characterised by

   d) at least one open riser pipe (12) which projects above the formwork and is connected thereto via a closable opening (24).
8. Apparatus according to claim 7, characterised in that the displacement body is an internal core (4, 4') which is arranged to be withdrawn from the formwork.
9. Apparatus according to claim 7 or 8, characterised in that a plurality of inlets (9, 9') are distributed along the lateral formwork (3).
10. Apparatus according to any one of claims 7 to 9, characterised in that a plurality of riser pipes (12, 12') are distributed along the lateral formwork (3).
11. Apparatus according to claim 9 or 10, characterised in that the inlets (9, 9') are connected to a concrete pump via a branched system of hoses (10) and lines (11).
12. Apparatus according to any one of claims 7 to 11, characterised in that the riser pipes (12, 12') are made of transparent material.
13. Apparatus according to any one of claims 7 to 12, characterised in that the riser pipe (12, 12') is arranged to be releasably coupled to and uncoupled from the upper side of the cover (8, 8').

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