The present invention first of all relates to a formwork for manufacturing a concrete structure.

The invention also relates to a method for manufacturing such a concrete structure.

Without restricting the invention thereto, the invention may be of great practical use for manufacturing concrete foundations, rainwater buffer basins, rain water infiltration basins, basements, crawl spaces and so on.

However, the invention may just as well be applied in other domains than construction and architecture, for example for manufacturing any support structure whatsoever, such as for example vertical columns, walls, partitions, floor slabs, arches and vaults.

Naturally, many types of formworks and methods for manufacturing concrete structures are already known, but they represent a number of disadvantages.

In a conventional formwork, a mould is made of plates which need to be anchored in a surrounding structure or which need to be propped up by means of beams, struts and the like. In what are called modular formworks, use is made of standard formwork elements that are connected to one another and are supported on the building site. Many other techniques are known as well, but they all require a certain degree of anchorage or support of the formwork with respect to an existing surface or already built-up structure. A first major disadvantage of these known formworks and methods for manufacturing a concrete structure consists in that putting the formwork in place and supporting it requires a lot of operations, and thus a lot of working hours, as well as an adequate knowledge of the workmen.

All of the above is also disadvantageous to the cost price of the works.

Another disadvantage of the aforesaid known formworks and methods is that they require a lot of material, a large part of which is often not re-usable.

This has for a result that, after the concrete has cured, a large amount of waste remains, and large quantities of material such as wood are consumed.

This is not only detrimental to the environment but also, again, to the cost of these techniques. An additional disadvantage of these known formworks and methods is that the material which is used for the formwork and its support is very heavy, whereby great physical effort is often required from the workers and/or use must be made of large machines such as lorries, cranes, forklifts and all sorts of other lifting equipment for the transport and positioning of the components required for the formwork.

Yet another disadvantage of the known formworks and methods for manufacturing a concrete structure consists in that it is difficult to absorb any unevennesses in the substrate or alignment errors in the existing structure, resulting in that a highly accurate preparation and precision are required during the execution of the works, for example the digging of a building pit, and/or in that the positioning and support of the formwork is associated with all sorts of time-consuming custom work.

Also, the present invention aims to remedy one or several of the preceding disadvantages and possibly other disadvantages as well.

The invention aims in particular to provide a formwork and method with which a concrete structure can be manufactured in an extremely fast and efficient manner, whereby the number of steps during its production are restricted to a minimum.

Another aim of the invention is to achieve a formwork for manufacturing a concrete structure requiring little skill for its use.

Yet another aim of the invention is to obtain a formwork which stands on its own and which is self-supporting and with which a concrete structure may be formed, such as for example typically a water infiltration basin or a basement, wherein no or hardly any additional elements must be provided for the anchoring and support of the formwork in relation to the substrate or existing structure during the works .

Yet another object of the invention is to obtain a formwork which is very light and which can be easily placed on a substrate.

Additionally, it is an object of the invention to provide a formwork with which unevennesses , oblique positions and/or inaccuracies in the adjacent structures are automatically absorbed.

To this end, the present invention concerns a formwork for manufacturing a structure which is composed of one or several flexible folding portions in the shape of a fabric, membrane or fleece, whereby the formwork is foldable and is provided with one or several hollow and/or bag-like portions in which a filler may be applied and which, in an unfolded and stretched condition have the shape of the contours of portions of the structure to be formed, and whereby the formwork can be placed on a bottom in an initial condition, which is a folded condition or an either or not entirely unfolded condition of the formwork, and whereby by pouring or pumping filler in the hollow and/or bag-like portions of the formwork, the formwork is gradually taken from the initial condition to the stretched condition so as to form the respective portions of the structure. A first major advantage of a formwork according to the invention is that it is mainly composed of flexible, foldable material, excluding any reinforcement such as bars or other materials which may be pre-assembled as well in the foldable formwork.

Thus, such a formwork according to the invention is relatively light in weight compared to the weight of the known formworks, and such a formwork according to the invention can be easily transported as a whole to a building site, whereby it can be installed on the building site without too much difficulty and, depending on the application, may possibly be unfolded.

Another advantage of such a formwork according to the invention is that it can be placed as such on a bottom, in an initial condition, whereby no or hardly any additional support or anchoring in the bottom or other surrounding structures is required, possibly with the exception of smaller devices such as pins, pegs, hooks or the like for holding the formwork in a specific position on the bottom and/or for keeping the flexible formwork in an entirely unfolded or partially unfolded condition.

Thus, a formwork according to the invention is an essentially self-contained and self-supporting whole.

This saves a lot of time during the works, since no complex supporting structures must be erected, nor any heavy materials must be supplied. Another advantage of a formwork according to the invention consists in that is provided with hollow portions which optionally form bag-like portions and which, in an unfolded and stretched condition, adopt the contours of the concrete structure to be formed.

By a bag-like portion is meant a hollow portion with at least one open end and a closed end, such that when pouring or pumping concrete slurry through the open end in the bag-like portion, the concrete slurry will remain in the bag-like portion.

In other cases, the hollow portions may have an entirely closed wall which needs to be pierced to insert concrete slurry, or a hollow portion may be provided with a wall with one or several openings, whereby the hollow portion does not form a bag-like portion in the sense that when applying concrete slurry in the hollow portion, the concrete slurry would normally flow away, but whereby the concrete slurry can be prevented from flowing away, for example by applying one or several pressure installations, such as a pump or the like, in the opening or openings concerned . In any case, it is a major advantage of the invention that the aforesaid hollow or bag-like portions, in a stretched condition, form the contours of the structure to be manufactured, such that the required shape can be immediately obtained.

Since the formwork is composed of flexible and folding portions, such flexible formworks for structures with very different and rather complex shapes can be designed and manufactured beforehand in a relatively simple manner, for example in a factory building, whereby foldable and flexible portions may be custom-cut and connected to one another, and so on.

Of course, all modern design and manufacturing tools can be used to that end, such as custom design software, CAD- CAM systems and the like.

The aim of a formwork according to the invention is to be placed on a bottom in an initial condition.

This initial condition may be a folded, partially unfolded or entirely unfolded condition, whereby by pouring and/or pumping filler in the cavities of the bag-like portions of the formwork, the formwork can be further unfolded as of the initial condition if need be, and put in a stretched condition which assumes the shape of the concrete structure to be manufactured, as it were like a bouncing castle which is inflated with air.

Naturally, with such a formwork according to the invention it is possible to erect structures in a very efficient manner and in no time, which would require an enormous amount of work and material with the known means.

Another advantage of a formwork according to the invention consists in that, thanks to its flexible character, unevennesses in a surface can be easily absorbed, and in that a special design of the formwork makes it possible for certain portions of the formwork to be automatically vertically aligned, irrespective of any inclination of the bottom, at least within certain limits.

In a possible application, the formwork according to the invention is used for manufacturing a concrete structure, but structures made of other materials are not excluded either .

Also, the filler may merely consist of concrete slurry, but the filler may just as well consist of filling material such as sand, Argex grains, air, PU foam, PS granules, water or a combination thereof.

Filling the formwork with filler can be done in one or several steps.

According to a preferred embodiment of a formwork according to the invention, one or several hollow and/or bag-like portions of the formwork, in an unfolded and stretched condition, have the shape of a vertical column of the structure to be manufactured.

Such a hollow and/or bag-like portion of the formwork which is designed as a portion to form a vertical column of a concrete structure may for example be entirely or partially folded when the formwork is placed on a bottom in its initial condition, whereby by pumping concrete slurry in said hollow or bag-like portion, the formwork will gradually unfold, raise itself and stretch, so that the shape of a vertical column is obtained. Usually, the concrete slurry will be supplied from below at the height of the aforesaid bottom in this case.

In other cases, concrete slurry can be inserted in said hollow and/or bag-like portion at a certain height above the bottom in question on which the structure is to be erected, for example by pouring the concrete slurry from a lorry or concrete mixer through an opening and by gradually filling the column as of the bottom.

In this case, such a hollow and/or bag-like portion of the formwork which is designed as a portion for forming a vertical column of a concrete structure is preferably largely or entirely unfolded in the initial condition, for example by suspending it on a surrounding structure or with the help of other supporting means, whereby by pumping or pouring the concrete slurry, the relevant portion is further stretched so as to form a vertical column .

It is clear that, in both cases, a formwork according to the invention offers many advantages compared to the known formworks, since its positioning takes little time and since no or only a limited number of additional means are required.

In other preferred embodiments of a formwork according to the invention, the formwork additionally or alternatively contains, in a similar manner, one or several hollow or bag-like portions which, in an unfolded and stretched condition, have the shape of other elements of the concrete structure to be manufactured, such as for example :

- hollow or bag-like portions forming adjacent columns so as to form a vertical wall of the structure;

- one or several flexible folding portions in the shape of a fabric, membrane or fleece which, in an unfolded condition of the formwork, form a flat portion of the formwork for manufacturing a concrete slab of the structure ;

- tubular hollow portions for forming arc-shaped spans of the structure to be manufactured;

- hollow or bag-like portions of the formwork which, in an unfolded and stretched condition, have the shape of a base of the concrete structure, for example the shape of a foot, a base plate or a beam.

Naturally, the list is not limitative, and flexible formworks according to the invention with portions which in a stretched condition assume other shapes for manufacturing an element of a concrete structure may be applied while still remaining within the scope of the invention .

The invention also relates to a formwork system for forming a formwork according to the invention as explained above in order to make it possible to manufacture a concrete structure according to a pattern with repeatedly recurring structure portions or with symmetrically provided structure portions.

In particular, such a formwork system according to the invention contains one or several types of flexible and foldable system portions whereby each system portion of a certain type of system portions always has the same shape corresponding to a specific structure portion to be obtained, and whereby different system portions can be connected to each other in accordance with the structure pattern to be achieved.

In this way, a kind of standardisation can be obtained, whereby very large structures can be realised with merely a few types of system portions by connecting them according to different patterns.

According to a preferred embodiment of a formwork system according to the invention, the concrete structure to be manufactured represents a regular pattern of columns which are mutually connected by means of connecting portions, and an above-mentioned type of flexible and foldable system portion corresponds to a vertical section through such column and one or several associated connecting portions.

Such an embodiment of a formwork system according to the invention is ideal for realising water infiltration basins, reservoir basins, rainwater buffer systems or basements and the like, as will be further illustrated.

The invention also relates to a method for manufacturing a structure which consists in:

- composing a formwork containing one or several flexible folding portions in the shape of a fabric, membrane or fleece, whereby the formwork is foldable and is provided with one or several hollow and/or bag-like portions in which a filler can be provided and which, in an unfolded and stretched condition, have the shape of the contours of portions of the structure to be formed;

positioning the formwork on a bottom in an initial condition, which is a folded condition or an either or not partially unfolded or entirely unfolded condition;

- pouring or pumping filler in the cavities of bag-like portions of the formwork, whereby the formwork is gradually taken from the initial condition to the stretched condition so as to form the relevant portions of the structure to be formed; and,

- making the concrete slurry cure.

The advantages of this method speak for themselves, and further details will be further explained by means of the figures .

In order to better explain the characteristics of the invention, the following preferred embodiments of a formwork for manufacturing a concrete structure, a formwork system for composing such a formwork, as well as a method for manufacturing a concrete structure according to the invention are described with reference to the accompanying figures, in which: figure 1 is a view in perspective of a first possible embodiment of a formwork according to the invention for manufacturing a rainwater buffer system, whereby the portions for pouring a top plate have been omitted;

figure 2 is a top view according to arrow F2 in figure 1; figures 3 and 4 illustrate in perspective how, in an additional step, a flat portion can be provided on the formwork from figures 1 and 2 for pouring a top plate ;

figure 5 schematically shows a side view of a rainwater buffer system;

figure 6 is a view in perspective of an alternative embodiment of a formwork according to the invention for manufacturing a regular pattern of columns that are mutually connected;

figures 7 and 8 represent a variant of the embodiment from figure 6, seen in perspective, before the pouring and after the pouring respectively of a top plate on top of the columns;

figure 9 shows another embodiment of a formwork according to the invention, seen in perspective;

figure 10 shows a variant of the embodiment of the formwork from figure 9, seen in perspective;

figure 11 illustrates a possible method according to the invention for manufacturing a vertical column, seen in perspective;

figures 12 to 14 schematically represent another method according to the invention for manufacturing a rainwater buffer basin;

figure 15 illustrates system portions of a formwork system according to the invention for manufacturing a rainwater buffer basin according to a square or rectangular pattern, seen in perspective;

figure 16 illustrates in perspective how several types of system portions of a type represented in figure 15 can be connected to one another and to other types of system portions so as to form the rainwater buffer basin;

figures 17 and 18 represent, in a similar manner, another possible embodiment of a formwork system according to the invention;

figure 19 schematically and in perspective shows a type of system portions of yet another formwork system according to the invention;

figure 20 shows a section through a concrete structure in perspective so as to illustrate a number of types of system portions of a more realistic embodiment of a formwork system according to the invention;

figures 21 and 22 illustrate the use of such an embodiment of a formwork system according to figure

20, seen in perspective;

figure 23 schematically represents, as in figure 19, a type of system portions of yet another formwork system according to the invention, this time for realising a rainwater buffer basin according to a hexagonal pattern;

figures 24 to 28 illustrate a possibly more realistic embodiment of such a formwork system according to the invention, seen in perspective, designed for realising a concrete structure according to a hexagonal pattern;

figure 29 illustrates a formwork system according to the invention, schematically and in perspective, for realising a rainwater buffer basin according to a triangular pattern; figure 30 shows a formwork according to the invention, seen in perspective, with which an arched vault can be obtained;

figures 31 and 32 are a front view and a top view respectively of the formwork from figure 30, according to arrows F31 and F32 respectively;

figure 33 shows a model in perspective of an application of the formwork from figures 30 to 32; figure 34 shows a model in perspective of a formwork according to the invention with which a rather linear structure can be obtained;

figure 35 is a perspective view of an application of the formwork from figure 34;

figure 36 shows a top portion of a formwork according to the invention, seen in perspective, for manufacturing a vertical column; and,

figure 37 is a top view according to arrow F37 from figure 36. The first embodiment of a formwork 1 according to the invention, represented in figures 1 to 4, is designed for manufacturing a rainwater buffer basin 2 or a similar structure such as a crawl space and the like. The different elements out of which such a rainwater buffer basin 2 is typically built are schematically represented in figure 5.

The rainwater buffer basin 2 hereby forms an underground structure, for example under a large parking lot or the like, whereby a top plate 3 is supported by a support structure 4 which in this case consists of concrete vertical columns 5 which are distributed over the surface of the building pit 6 according to a regular pattern, as well as of a pair of opposite side walls 7 which each define an edge of the building pit 6.

The columns 5 rest on one or several feet or, as in figure 5, on a bottom plate 8 provided on the bottom 9 of the building pit 6. In the top plate 3 is further usually provided a reinforcement 10, and the top plate 3 is poured by means of a clamping formwork or hanging formwork 11 on top of the columns 5. Such rainwater buffer basins 2 are important in that, when it's rainy weather, the large amount of rainwater which ends up for example on a parking lot can be led to the underground rainwater buffer basin 2, for example by means of drain pipes, to temporarily store the rainwater there in the space 12 between the columns 5 so as to further discharge it to rivers and/or other drains later on, when they have sufficient capacity to further discharge the rainwater . According to the known techniques, when building such a rainwater buffer basin 2, one typically starts with the excavation of a building pit 6 whereby, before the actual excavation works begin, the side walls 7 are often manufactured by means of several ground drillings performed adjacent to one another and which are filled with a concrete slurry and possibly a reinforcement to form the side walls 7. The base plate 8 is then poured on the bottom 9 of the building pit 6. After the base plate 8 has cured, formworks are installed on the spot of the vertical columns 5 to be poured and the reinforcement of these columns 5 is further developed, which usually involves the use of many, often heavy materials and supports of all types.

Finally, after the columns 5 have been poured and cured, a formwork is provided adjacent to the columns 5, and the top plate 3 is poured. With the known techniques, the latter formwork usually has to be supported again by numerous beams and struts.

It is clear that such a known method requires a huge amount of work and material and is associated with many separate successive steps whereby a waiting period has to be respected each time to allow the poured concrete slurry to cure .

With a formwork 1 according to the invention it is possible to apply a method according to the invention which is much simpler and faster and requires less separate steps.

Characteristic of such a formwork 1 according to the invention is that it is composed of one or several flexible folding portions 13 in the shape of a fabric, membrane or fleece, such that a foldable formwork 1 is obtained .

These folding portions 13 may for example be woven from fibre materials with a relatively high tenacity such as fibreglass, jute, Kevlar, polypropylene, nylons and the like, whether or not provided in a matrix of another flexible material, for example by means of melting. However, it is not excluded according to the invention to manufacture the folding portions 13 without applying a weaving technique.

The foldable formwork 1 is hereby provided with one or several hollow and/or bag-like portions 14 in which concrete slurry 15 can be provided.

In an unfolded and stretched condition, these hollow and/or bag-like portions 14 have the shape of the contours of portions of the concrete structure 16 to be obtained, i.e. in this case of portions of the rainwater buffer basin 2.

More specifically, the formwork contains several hollow portions 17 which, in an unfolded and stretched condition, have the shape of the contours of a vertical column 5 of the concrete structure 16 to be formed.

These hollow portions 17 are somewhat conical, whereby the section of the vertical column 5 to be obtained narrows somewhat towards its top 18. At their tops 18, the hollow portions 17 communicate with a narrowed hollow portion 19 having a cylindrical surface, at least in the unfolded and stretched condition, and which, after the concrete slurry 15 has been poured and cured, serves as an anchoring element for anchoring each vertical column 5 to a top plate 3.

For the formation of the side walls 7 of the concrete structure 16, the formwork 1 is further provided with several hollow portions 20 which, in an unfolded and stretched condition, have the shape of a vertical, cylindrical or slightly conical column and whereby the relevant hollow portions 20 are adjacent to one another so as to form such a vertical side wall 7 of the structure 16.

These hollow portions 20 have cylindrical or slightly conical contours in the unfolded and stretched condition. The foldable formwork 1 further contains several hollow portions 21 which, in an unfolded and stretched condition, together have the shape of a base 22 of the concrete structure 16. The hollow portions 17 are erected according to a regular pattern on the bottom 9 of the building pit 6 so as to form vertical columns 5 in a square pattern, and with a fixed mutual spacing T between two successive columns 5. In the given example, the hollow portions 21 forming the base 22 each time connect two successive hollow portions 17 at their bottom side 23. In the unfolded and stretched condition, the hollow portions 21 have a concave gradient, such that on each vertical column 5, on its bottom side 23, is formed a widened foot 24.

In the given example, in between four vertical columns 5 standing in a square, a circular opening 25 is each time formed by the connecting hollow portions 21.

At the position of the vertical columns 5 adjacent to the side walls 7, the hollow portions 21 for the base 22 connect the corresponding hollow portions 17 and 20. The formwork 1 is further also provided with portions 26 which each time connect the tops 18 of successive hollow portions 17 for the vertical columns 5 and which serve as connecting pieces 26 for supporting the top plate 3 to be formed .

These portions 26 may be either or not hollow and they also serve as drawing elements to position the vertical shapes and distribute them well. The formwork 1 according to the invention illustrated in figures 1 and 2 has a rather complex shape which corresponds to the complex shape of the contours of a support structure 4 of a rainwater buffer basin 2. The different hollow portions 14 may hereby be all mutually connected, or separate compartments may be formed . Depending on the case, the concrete structure 16 may thus be formed by filling the entire formwork 1 with concrete slurry 15 all at once, or by pouring or pumping concrete slurry 15 in the separate compartments one by one.

Furthermore, in an initial condition, the formwork 1 can be placed on the bottom 9, which according to the invention generally does not correspond to what is represented in figures 1 and 2.

For, in the initial condition, the formwork 1 may be entirely folded or either or not partially or entirely unfolded, for example for applying a reinforcement.

It is only by pouring or pumping concrete slurry 15 in the hollow and/or bag-like portions 14 of the formwork 1 that the formwork 1 is gradually taken from the initial condition to a stretched condition, as is represented in figures 1 and 2, so as to form the relative portions of the concrete structure 16 after the concrete slurry 15 has cured, more specifically in this case the support structure 4 of the rainwater buffer basin 2. In order to erect and as it were inflate the formwork 1 as of an initially folded or partially folded condition, concrete slurry 15 can be pumped in the hollow portions 14 at the level of the bottom 9 of the building pit 6, for example in openings provided in the hollow portions 21 for the base 22 or at the bottom side 13 of the hollow portions 17 for the vertical columns 5. The conical shape of the hollow portions 17 creates a counter-pressure as they are being filled up, such that a well stretched whole is obtained. The aim is to provide an additional portion 27 of the formwork 1, after the concrete slurry 15 has cured, on top of the obtained support structure 4, more specifically on the portions 17 forming the vertical columns 5, the portions 20 forming the side walls 7 and the portions 26 forming the connecting pieces.

This additional portion 27 of the formwork 1 is formed, just as the other portions of the formwork 1, by one or several flexible folding portions 13 in the shape of a fabric, membrane or fleece.

In the given embodiment of figures 1 to 4, this flexible foldable portion 27 is a separate portion which, in an unfolded condition of the formwork 1, forms a flat portion 27 of the formwork 1.

After this additional flat portion 27 has been applied on the support structure 4, it will extend between the portions 17 and 19 of the formwork 1 forming the columns 5 of the structure 5, and a hanging or clamping formwork 11 is formed so to say for realising a top plate 3.

This is represented in figures 3 and 4. Reinforcement and possibly additional tensioning means may possibly be provided before pouring a concrete slurry 15 on the flat portions 27 so as to form the top plate 3 of the structure 4.

It is clear that with such a foldable formwork 1 according to the invention a very efficient method according to the invention can be applied, requiring only two sessions during which concrete slurry 15 is being poured to obtain a structure 4 such as a rainwater buffer basin 2. This results in a huge reduction of the required waiting times .

Also the preparation of the formwork 1 itself in the building pit 6 takes far less time than with the conventional formworks 1.

Figure 6 represents another embodiment of a formwork 1 according to the invention for realising a grid of vertical columns 5 in a square pattern whereby successive columns 5 are connected at their bottom sides 23.

The formwork 1 is again composed of flexible folding portions 13 which all form hollow portions 14, more specifically hollow portions 17 and 19 for forming the vertical columns 5 with a narrowed protrusion at the tops 18, as well as hollow portions 21 for the connection between successive columns 5, which are not concave this time but cylindrical. Neither hollow portions 20 are provided for forming side walls 7, nor hollow portions 26 for the supporting connecting pieces at the tops 18 of the columns 5. The hollow portions 17, 19 and 20 may together form one large cavity or several compartments thereof. With this formwork 1 may be erected a support structure 4 for pouring a top plate 3 in a minimum of time, essentially in the same manner as described above with reference to the preceding embodiment. After the concrete slurry 15 has cured, a box-shaped formwork can be provided on the columns 5 for pouring the top plate 3, for example according to the known techniques or by applying a flat, flexible portion 27 analogous to what is illustrated in figures 3 and 4 and which is additionally lined with a border preventing the concrete slurry 15 from flowing away.

Figure 7 shows a variant of the formwork 1 in figure 6, whereby the formwork 1 is this time additionally provided with several flexible folding portions 27 in the shape of a fabric, membrane or fleece, which are an integral part of the formwork 1 and which, in an unfolded condition of the formwork 1, form a flat portion 27 of the formwork 1 extending between the hollow portions 17 and 19 of the formwork 1 forming the columns 5 of the structure 4, more specifically at the tops 18 of these columns 5.

The aim hereby is that, in a first step of a method according to the invention, concrete slurry 15 is pumped or poured in the hollow portions 17, 19 and 21 so as to form a support structure 4 consisting of a grid of mutually connected vertical columns 5, whereby during the filling, erecting and tightening of said hollow portions 17, 19 and 21, the flat portions 27 simultaneously stretch between the columns 5 while the latter are being formed. According to the invention, it is not excluded to unfold the entire formwork 1 as a whole or partially and to stretch it more or less with additional means, for example for providing a reinforcement, before providing concrete slurry 15.

After the support structure 4 has cured, a top plate 3 of the structure 16 may be formed by pouring concrete slurry 15 on the flat portions 27, which is illustrated in figure 8, albeit with the top plate 3 raised somewhat above the flat portions 27 of the formwork 1.

It is clear that such an embodiment of a formwork 1 according to the invention makes the construction of for example a rainwater buffer basin 2 or any other basement even easier, since while the support structure is being formed, a flat formwork for the top plate 3 is automatically and simultaneously unfolded.

Figure 9 represents another embodiment of a formwork 1 according to the invention for manufacturing a vertical column 5.

This formwork 1 comprises a bag-shaped flexible portion 17 which, in the unfolded and stretched condition, adopts the shape of the column 5 and which is connected to a hollow portion 19 so as to form a narrowed protrusion on the top 18 of the column 5. What makes this embodiment of a formwork 1 according to the invention special, is that it also comprises three hollow foldable and flexible portions 28 which are adjacent to one another and which, in the unfolded and stretched condition, are at right angles to the vertical column 5, and which thus extend horizontally.

The aim is to first fill these horizontally directed, hollow portions 28 with a filler such as sand mortar 29 or the like, so that a stabilisation wall or sand buffer 30 is obtained and the hollow portions 17 and 19 for the column 5 are also simultaneously unfolded and erected. The sand mortar 29 requires no curing time, so that the concrete works can start immediately.

Such a formwork 1 is very practical for example for trench-shaped infiltration basins, which must usually be provided with a sand buffer 30 on both sides.

Figure 10 shows a variant whereby the foldable formwork 1 is this time provided with several vertically directed, hollow portions 17 and 19 which are successively provided along the horizontally extending hollow portions 28 so as to form a concrete side wall 7 or a series of columns 5 leaning against the stabilisation wall or sand buffer 30.

Naturally, the configurations of figures 9 and 10 can be combined with those of figures 6 to 8, whereby by making use of said sand buffers 30, a top plate 3 and the support structure 4 can be even poured simultaneously, since in this case the top plate 3 immediately finds support on the sand buffers 30 which are already filled with sand mortar 29 without the concrete support structure 4 needing to cure first.

Figure 11 represents a method according to the invention for manufacturing a concrete structure 16, more specifically a vertical column 5, by means of a formwork 1 according to the invention.

The formwork 1 is in this case composed of one or several flexible folding portions 31 in the shape of a fabric, membrane or fleece, whereby the foldable formwork 1 comprises a bag-like portion 32 with a closed bottom 33 and wherein concrete slurry 15 can be provided via an open end 34.

In an unfolded and stretched condition of the formwork 1, the bag-like portion 32 has the shape of the concrete column 5 to be manufactured, more specifically of a vertical column 5 with a pentagonal cross section and with a widened foot 24 and head 18, each in the shape of a frustum 35. The formwork 1 is first put in an initial condition (represented in the left portion of figure 11) by placing it on a bottom 9 and unfolding it and possibly suspending or supporting it with additional means. A reinforcement may be provided in the cavity of the bag ^¬ like portion 32. Via the open end 34 is subsequently poured concrete slurry 15 in the bag-like portion 32 (which is represented in the centre of figure 11) . The bag-like portion 32 is hereby gradually filled as of the bottom 9 and thus also stretched, so that it adopts the required shape.

Once the concrete slurry 15 has cured, the vertical column 5 is ready, whereby the folding portions 31 can be further removed from the concrete column 5, for example by cutting them off.

This situation is represented in the right portion of figure 11.

Further, it is not excluded according to the invention for portions of the formwork 1 to be part of the concrete structure 16 to be manufactured, such as in the case of a lost formwork .

Figures 12 to 14 illustrate another method according to the invention for manufacturing an infiltration basin or rainwater buffer basin 2 or other applications by means of a formwork 1 according to the invention.

The formwork 1 has in this case a shape similar to that in figures 7 and 8, save for the fact that one or several hollow portions 17 (or all hollow portions 17 as is the case in the figures) are provided with an open end 34 on their top side, so that concrete slurry 15 can be poured in the hollow portions 17 and 21 of the formwork 1 via this open end, for example from a lorry or concrete mixer 36.

In a first step I of the method, the formwork 1 is unfolded and placed in an initial condition on the bottom 9 of a building pit 6.

In a subsequent step II, the hollow portions 21 and 17 are filled with concrete slurry 15 whereby, thanks to the conical shape of the hollow portions 20, as the concrete slurry 15 rises as of the bottom 9, an upward force F is exerted on the walls of the formwork 1.

This force F contributes to the unfolding and/or erecting and raising of the foldable formwork 1, as well as its stretching into the desired shape in accordance with the contours of the rainwater buffer basin 2 to be formed.

Simultaneously, thanks to the forces exerted by the concrete slurry 15, the flat portions 27 of the formwork 1 will be stretched, upon which the top plate 3 is to be poured later on.

The third step III of the method consists of a waiting period for the curing of the concrete 15 to form the support structure 4 of the rainwater buffer basin 2 with columns 5 and a base 22.

In the fourth step IV of the method is then poured concrete slurry 15 on the flat, flexible portions 27 of the formwork 1 so as to form the top plate 3 which rests on the columns 5 and which cures in step V of the method. Figures 15 and 16 illustrate a first embodiment of a formwork system 37 according to the invention. The formwork system 37 is designed for composing a formwork 1 according to the invention, whereby the aim is more specifically to erect a concrete structure 16 forming a pattern with repeatedly recurring structure portions or with symmetrically provided structure portions.

To this end, the formwork system 37 comprises a first type of flexible and foldable system portions 38, which each have the same shape corresponding to a particular structure portion to be achieved.

In this case, such a system portion 38 consists of a flexible, foldable portion 40 which, in its unfolded and stretched condition, forms the contours of a vertical section through a central axis AA' of a vertical column 5, for example in this case a section through an angle B of 90° .

In the unfolded and stretched condition, the foldable portion 40 has a radially flared portion 41 designed to form a portion of a vault 42 extending as of the respective vertical column 5 up to nearby vertical columns 5.

Further, the foldable portion 40 is provided with a hollow portion 43 to form a section of a foot 24 on a vertical column 5, as well as a hollow portion 44 to form a rib 45 extending as of the foot 24 of the vertical column 5 to be formed up to the top 46 of the vault 42 to be formed.

The first type of system portions 38 is hereby also provided with a hollow portion 47 for achieving a base 22 for a grid of vertical columns 5.

This hollow portion 47 has the shape of a tubular piece 48 designed to form a kind of beam or a connecting portion 49 extending between the feet 24 of two successive columns 5 of the grid to be obtained.

The formwork system 37 comprises a second type of system portions 39 similar to the first type of system portions 38, but whereby the system portions 39 of the second type are not provided with a hollow portion 47.

The different system portions 38 and 39 can be connected to one another in accordance with the pattern of the structure 16 to be achieved.

More specifically, four system portions 38 and/or 39 together form a single hollow vertical column 5, whereby depending on whether more or less connections are required than with other columns 5, more system portions 38 are used to form the respective column 5.

After the assembly of the formwork 1, which can be done in advance or at the site itself, the formwork 1 can be unfolded. By filling the hollow portions 43, 44 and 47 of the formwork 1 with a filler such as concrete slurry or other fillers such as sand, air, PU, Argex grains, water, polystyrene or a combination thereof, a first supporting structure 4 can be achieved with annular feet 24 and standing ribs 45, whereby the feet 24 are mutually connected by beams 49.

The remaining flexible portions 40 of the formwork 1 are hereby put in a stretched condition which is appropriate for filling the cavities 50 in the vertical columns 5 and for forming the vaults 42 which are supported by the radially flared portions 41 of the system portions 38 and 39.

In this manner is obtained a very efficient formwork system 37 with which numerous configurations can be achieved in a very fast way. Naturally, many variants of the foregoing are possible, with system portions provided with several tubular pieces 48 or which enclose a vertical section over a larger or smaller angle B of a column 5. Figures 17 and 18 show an alternative embodiment of a formwork system 37 according to the invention.

Use is hereby made of a single type of system portions 51 which is composed of foldable, flexible portions 52.

In an unfolded and stretched condition, such a system portion 51 assumes the shape of a hollow column 5, halved according to a vertical intersecting plane CC which is somewhat pointed, with a wider foot 24 and a narrower top 18. To this end, the system portion 51 comprises a first hollow portion 53 designed to be vertically erected, which is done by filling the hollow formwork 1 with a filler such as for example concrete slurry 15. At the top 18 of the column 5 to be formed is also provided a narrowed hollow portion 19 to anchor the top of the column 5 in a top plate 3, as was for example also the case in the embodiment of figure 4. Crosswise to the foot 24 of this half-column 5 and crosswise to the intersecting plane CC is further provided a hollow portion 54 designed to be connected to a hollow portion 54 of an adjacent column 5 to be formed. Thus is obtained a base 22 in the shape of a connecting portion 55 which connects the feet 24 of two adjacent columns 5 to be formed.

A column 5 is composed of two system portions 51 which are connected to one another at their intersecting plane CC .

Several such columns 5 may be connected to one another via the hollow portions 54 which form connecting portions 55. After pouring a concrete slurry 15 in the respective hollow portions 53 and 54, a row 56 of successive columns 5 is thus obtained which are connected at the feet 24. In figure 18, two such rows of columns 5 are placed parallel to each another, after which a flat, flexible and foldable portion 27 is provided over the tops 18 of the columns 5 for pouring a concrete top plate 3.

In a variant, according to the invention, such a flat portion 27 for a top plate 3 may also be part of the system portion 51, and more or less rows 56 of columns 5 may be realized, as well as a variety of other configurations .

Instead of composing formworks 1 from several system portions 51, according to the invention, a uniform formwork 1 may of course also be manufactured at once, out of one piece, without having to connect several system portions 51 to that end.

Figure 19 depicts yet another possible embodiment of a type of system portions 57 of a formwork system 37 according to the invention.

In this case, such a system portion 57 is composed of foldable and flexible portions 58 which also form a number of hollow portions 19, 59, as well as a bag-like portion 60.

In the unfolded and stretched condition of such a system portion 57, the hollow portion 59 forms a vertical column 5 which is slightly conical with a pointed top 18, whereby a narrowed hollow portion 19 is provided to form a protrusion for anchoring the column 5 to be formed on the top 18.

In the unfolded and stretched condition, the bag-like portion 60 forms a foot 24 with a square perimeter and with a pyramidal gradient towards the column 5.

The system portion 57 is further provided with a flat portion 27 provided at the top 18 of the column 5 and which forms an integral part of the system portion 57.

In the unfolded condition, the flat portion 27 of the system portion 57 has a square perimeter 61 whose dimensions correspond to the perimeter 62 of the foot 24.

Thus, system portions 57 can be coupled to each other as desired on the four sides of the feet 24 and the corresponding four sides of the flat portion 27 to form a larger whole.

This is illustrated in figures 20 to 22 for an embodiment of a formwork system 37 which is similar to that of figure 19, but which has been developed more realistically. Figure 20 is a vertical section through a structure 16 formed with a formwork 1 which is composed on the basis of the aforesaid formwork system 37 according to the invention, whereby a first type of system portions 57 corresponds to those of figure 19.

The formwork system 37 in the embodiment of figures 20 to 22 also comprises other types of system portions 63 and 64 which largely have a similar shape as the type of system portions 57, but which can be used to form the edges 65 and the angles 66 respectively of the structure 16. To this end, the flat portion 27 of the system portions 61 and 62 is partially vertically connected to the narrowed hollow portion 19 so as to form standing edges 67, so that, after a formwork 1 has been assembled by coupling the different system portions 57, 63 and 64, as is represented for example in figure 21, a bag-shaped or rather tub-shaped whole is obtained on top of the columns 5 which can serve as a formwork for forming a top plate 3.

The use of the formworks 1 assembled with the here discussed formwork systems 37 is entirely analogous to what was discussed with reference to figures 1 to 10, apart from the fact that complex formworks 1 may be formed, either or not on the building site, on the basis of merely a few types of system portions 57, 63 and 64.

Figure 21 further illustrates how a reinforcement 68 may be provided before concrete slurry 15 is poured on the flat portions 27, whereas figure 22 shows the condition after the top plate 3 has been poured, whereby portions of the narrowed hollow portions 19 protrude from the top plate 3 to possibly serve as anchoring points for any further structure elements that are built on top of the top plate 3. Figures 23 to 28 represent in a similar manner yet another formwork system 37 according to the invention which this time comprises system portions 69 of a type with a hollow portion 70 for forming vertical columns 5, hollow portions 71 which extend radially as of the foot 24 of a column 5 in the radial directions of a hexagon 72 so as to form connecting portions 73 for connecting several system portions 69 at their feet 24.

At the top 18 of a column 5, in the case of figures 24 to 28, are provided similar radially extending, hollow portions 74 for forming connecting portions 75 to connect several system portions 69 at their tops 18.

In the case of figure 17, the top is provided with a hexagonal flat portion 27 which corresponds to the dimensions of the foot 24.

Thus, different configurations of formworks 1 may be formed according to a hexagonal pattern, as is illustrated for example in figures 26 and 27. Rather than pouring a top plate 3 afterwards on the support structure 4 formed with the system portions 69, use is made of preformed, hexagonal concrete tiles or plates 76 in the example of figure 28 which fit over the protrusions formed by the narrowed, hollow portions 19 and which rest on the connecting portions 75 to form a floor or the like.

Figure 29 represents yet another embodiment of a formwork system 37 according to the invention which is entirely analogous to the above-described cases, but which is based on system portions 77 with which triangular configurations can be assembled. Figures 30 to 33 represent yet another embodiment of a formwork 1 according to the invention comprising several hollow flexible and folding portions 78 which in an unfolded and stretched condition have the shape of an arched span 79 of the structure 16 to be formed.

The hollow portions 78 are cylindrical portions 78 with two open ends 80 and 81.

Several hollow, cylindrical portions 78 are disposed adjacent to one another and are mutually connected by means of a pair of longitudinal bag-like portions 82 and 83 which are connected to the open ends 80 and 81 respectively.

The bag-like portions 82 and 83 form the base 22 of the concrete structure 16 to be achieved. By pumping concrete slurry 15 in the bag-like portions 82 and 83, the entire formwork 1 is inflated as it were and, as soon as this concrete slurry has cured, a semi- cylindrical vault 84 is thus obtained. Such a vault 84 may for example be provided in a water gully 85, as is illustrated in figure 33, and it may serve to support an overlying structure or road or the like.

Figure 34 represents a formwork 1 according to the invention which consists of an elongated structure 86 which extends in a direction DD' and which is formed of one or several rugged, bag-like portions 87. As is represented in figure 35, such a formwork 1 may be used to form a support structure 24 by filling the bag ^¬ like portions with concrete slurry 15.

The support structure 24 may be placed in a water gully 85 to support a road or the like, while the water 88 can flow between the rugged shapes of the concrete bag-like portions 87.

Figures 36 and 37 are views on the open end 89 of a narrowed hollow portion 19 at the top 18 of a vertical column 5 to be formed. In the narrowed open end 89 are provided flaps 90 which automatically close the open end 89 whenever concrete slurry 15 exerts pressure on the flaps 90 inside the hollow portion 19. In this manner, a top plate 3 can be immediately poured on a support structure 24 without the concrete slurry 15 being already fully cured in the portion of the formwork 1 of the support structure 24, since concrete slurry 15 is prevented from flowing from this portion of the formwork 1 under the additional pressure of the top plate 3.

Finally, figures 38 to 40 further illustrate that, with a formwork 1 according to the invention which is composed of flexible and folding portions 13, it is easy to take measures to absorb unevennesses in a bottom 9 or to automatically vertically align certain portions of the formwork 1. The invention is by no means restricted to the embodiments of a formwork 1 and a formwork system 37 according to the invention, described by way of example only and illustrated by means of the figures; on the contrary, formworks 1 and formwork systems 37 may be achieved in many other ways while still remaining within the scope of the invention.

Nor is the invention restricted to the described examples of methods according to the invention for manufacturing a concrete structure 16; on the contrary, other methods may be applied while still remaining within the scope of the invention .