EP2155455A2

EP2155455A2 - Amorphous formwork

Info

Publication number: EP2155455A2
Application number: EP08734537A
Authority: EP
Inventors: Karl Christiansen; Anders Gammelgaard Nielsen
Original assignee: Newton Concrete ApS
Current assignee: Newton Concrete ApS
Priority date: 2007-05-18
Filing date: 2008-05-16
Publication date: 2010-02-24
Also published as: AU2008253382A1; WO2008141644A2; WO2008141644A3; US20100117248A1

Abstract

The invention disclose a method and formwork for casting concrete or concrete like elements where said elements may have an amorphous shape, wherein the method comprises the following steps: - in a block (51) of formable material having a size larger than the element to be cast, a model of the element is cut out, thereby creating an inner formwork; - an outer load bearing support structure (21) having an inner size corresponding to the outer dimensions of the block is created; - the parts of the block not representing the model are arranged in the interior of the load bearing support structure, thereby creating a cavity corresponding to the model; - optionally reinforcement is arranged in the cavity; fresh concrete or other concrete like material is poured into the cavity and al- lowed to cure; - the outer load bearing support structure (21) and the inner formwork (51) are removed.

Description

Amorphous formwork

Field of the Invention

The present invention relates to formwork for casting concrete or concrete like elements where these elements may have an amorphous shape.

Background of the Invention

In the art of casting concrete or concrete like elements it is well-known to cast elements which are round, circular, square, rectangular or any other well-defined linear or symmetrical shape. This fact has given, in particular concrete a relatively anonymous (boring) image, in that the constructions made from this material usually both by people skilled in the art such as architects, engineers, etc. and the general public are conceived as being useful for only walls, floor slabs, pillars, tiles and a few other constructional elements which all have the part in common, that they are designed with a relatively simple geometry in order to provide for a relatively inexpensive construction material.

Fresh concrete, however, has the ability to flow and thereby fill out spaces which would otherwise, with other materials be very difficult to fill out, which in turn makes it possible to create shapes and forms having an internal strength and integrity which could not be addressed by very many other materials. Until now the cost of formwork has made it prohibitive to contemplate such shapes for ordinary constructions.

From US-A-4,887,789 is a form system as well as a method known where a plastic core is used as an inner formwork in combination with a load bearing outer formwork. By appropriate shaping means, such as a hot wire, laser, water jet or the like a cavity is formed in the inner formwork. After the formation the inner formwork is placed inside the outer formwork, where after a hardenable material, such as concrete is poured into the cavity. The method and formwork disclosed expressly states that no intervening layer or material should be placed between the inner formwork and the hardenable material to be placed inside the cavity in the inner formwork. This aspect has, by the inventors of the present invention been found involve problems in some of the areas where it is desirable to cast elements, and has therefore necessitated improvements involving substantial creativity. Particularly when casting elements which are not cylindrical, i.e. where the cross section is not formed by an infi- nite number of parallel lines, it was fairly impossible to utilise the method, even when applying conventional release agents used extensively in the construction industry. The problems were further aggravated when the inner formwork was made from expanded polystyrene foam materials. The use of expanded polystyrene foam products is especially advantageous due to low prices, very low weight pr volume unit and high/easy formability.

Object of the Invention

The present invention therefore provides both a method for casting and a form work for casting concrete or concrete like elements where said elements may have an amor- phous shape. In this connection amorphous shape covers a wide variety of shapes (symmetrical as well as asymmetrical) as will be evident from the description with reference to the detailed embodiments, see below. Furthermore the invention is directed at providing a method which is easy to carry out, at low cost, and where the finish on the manufactured elements is greatly improved compared to the state of the art.

Description of the Invention

The invention accordingly provides a method which is new and inventive in that the method for casting concrete or concrete like elements where said elements may have an amorphous shape, comprises the following steps:

in a block of formable material having a size larger than the element to be cast, a model of the element is cut out, thereby creating an inner formwork; - an outer load bearing support structure having an inner size corresponding to the outer dimensions of the block is created; - the parts of the block not representing the model are arranged in the interior of the load bearing support structure, thereby creating a cavity corresponding to the model; - a release agent either in liquid form or as a foil or membrane is arranged covering the cavity in the inner formwork;

- optionally reinforcement is arranged in the cavity;

- fresh concrete or other concrete like material is poured into the cavity and al- lowed to cure;

- the outer load bearing support structure and the inner formwork are removed.

hi order to be able to cut a model out of the formable block, the block must be of a size larger than the element to be cast. When the model is cut out of the block, care should be taken not to damage the formable material, in that the model as such is not interesting, but the cavity that it leaves in the fortnable material is the part which will give the shape for the finished cast construction.

The inner formwork is therefore made up of the cavity created in the block when the model of the element to be cast has been removed, hi some instances it may be necessary to partition the block of formable material in order to remove the model depending on the shape of the model. The inner formwork will therefore consist of a number of parts which will thereafter be assembled inside an outer load bearing support structure, where the size of the support structure corresponds to the size of the block so that an efficient support for the block of formable material is created.

When the inventive method according to the invention is used for casting elements of a certain size or elements which are not entirely ornamental, it will be desirable to arrange a reinforcement inside the concrete in order to be able to give the concrete the physical characteristics which are normally associated with reinforced concrete strac- tures.

Depending on the material from which the block of formable material is made, the removal of the inner formwork from the cured concrete element will usually be carried out by firstly removing the concrete and the inner formwork from the load bearing support structure and thereafter removing the inner formwork from the concrete element, hi some instances depending on the material from which the formable material is selected it may be difficult to remove the inner formwork from the cast element and in these instances a suitable release agent should be applied to the inner formwork prior to casting the concrete. These techniques are very well-known in the art of casting concrete in order to be able to release the formwork from the hardened concrete.

5 Although traditional substances may be used with some success, tests have shown that exceptionally good results are achieved with the following substances, in particular when the inner form-work is made from a foam material or an expanded polystyrene material.

10. A traditional retarder was applied to the inner formwork before casting the concrete. This substance, for example a simple sugar solution, made it very easy to part the cast element from the formwork, and at the same time had no effect on the formwork, such that the formwork was suitable to be reused. The micro-surface of the concrete element, however, was relatively large/open, and it is contemplated that elements manu-

15 factured in this manner, should be used indoors or be treated, for example by a coat of paint, before exposed to an outside environment.

An oil based on vegetables, such as for example oils derived from sunflowers, sesame, grapes, flax and the like is also usable. When a crisp white result is desired, care shall 20 be exercised when selecting the oil, in that the oil may cause mis-colouring of the white concrete surfaces.

A suitable wax also showed remarkable results. A wax from X-Coating, a Danish corporation, sold under the tradename X-1 1000 proved very usefull. A mixture of oil and 25 wax was used where the oil was pure oil used for medical purposes containing 3 % to 15 % wax. The surfaces of the cast elements showed no signs of the release agent.

Also Vaseline, wood glue (PE glue), silicone, Latex and other substances were tested, but the wax solution was selected as the best, both with respect to application, release 30 and discolouring.

In addition to release agents in liquid form, also membranes and in particular flexible membranes proved to provide very satisfactory results. The method as well as the form work is equally suitable for one-off constructions and for the manufacture of elements on an industrial scale.

In a further advantageous embodiment of the invention the block is made from a polystyrene based product and a hot wire is used for cutting the model.

By selecting a polystyrene material it becomes very easy to shape the model simply by pulling a hot wire through the polystyrene material which will thereby melt and pro- vide for an easy and very smooth cut. Furthermore, polystyrene based products are usually very cheap and very light and as such easy to handle, and furthermore by selecting an appropriate, high quality polystyrene, a very smooth form surface may.be achieved by this method.

The invention is also directed at a formwork for use in the inventive method where said formwork comprises:

an outer load bearing support structure, which support structure has means allowing the structure to be disassembled, thereby freeing - an inner formable structure, which inner structure defines the outer shape of the element to be cast.

Further advantageous embodiments of the invention are set out in the dependent patent claims.

Below examples illustrating the inventive principle are described. The examples shall not however be construed or interpreted as having a limiting effect on the scope of protection sought, but merely serve to illustrate how the inventive principle may be exploited.

Description of the Drawing

Fig. 1 illustrates prior art formwork;

Fig. 2 illustrates a wall created using the invention; Fig. 3 illustrates form elements used for the wall in fig. 2; Fig. 4 illustrates a block before being shaped; Fig. 5 illustrates a template; Fig. 6 illustrates a template arranged on a block; Fig. 7 illustrates the assembly of the formwork; Fig. 8 illustrates how the inner form is cut;

Fig. 9 illustrates how separate forms fit together for longer constructions; Fig. 10 and 11 illustrate a further embodiment where the formwork is used in a very complex shaped construction. Fig. 11 a- 16 illustrate various methods of carrying out the invention.

Detailed Description of the Invention

In figure 1 is illustrated a traditional formwork used to cast the underside of a staircase. Due to the flowing shape of the staircase it is necessary to build a rather complicated formwork in order to achieve this shape for the actual staircase. The traditional formwork as illustrated in figure 1 comprises a large number of latches 1 which are arranged side by side in order to create the form face. The bottom shape is created by the latches 1 being shaped by plate members 2 arranged along the sides of the formwork. The plates 2 are bolted 3 to an under structure 4 in order to create a construction stiff enough to maintain the shape of the formwork during the casting process of the concrete. It is evident that this type of construction requires a substantial amount of labour and thereby becomes very costly.

The invention, however, provides a relatively cheap alternative to this, which furthermore may be able to provide much smoother transitions between curved sections and therefore also achieve a far more pleasing result with less effort and less cost.

Turning to figure 2 an example of a wall element 5 is illustrated. The wall element has a substantial homogenous thickness which is created by having substantially parallel lines from the bottom of the wall to the top of the wall, but apart from that the wall may be given any suitable shape. From figure 2 it is evident that both curves in the vertical as well as the horizontal plane are possible, and also double curvature may be achieved. The wall may furthermore be equipped with support sections 6 which will

RMRRTlTl JTE SHEET help this particular shape to keep its balance on its own, but for practical purposes the wall element 5 will be placed on a foundation and fastened in a traditional way, e.g. with bolts, to the underlying foundation structure. The wall as depicted in figure 2 may be achieved with a formwork as illustrated in figure 3.

In order to understand how the inventive formwork is made, the attention is directed to figure 4. In figure 4 a block of a formable material 10, in this example polystyrene is depicted. The block has a size, i.e. a width, height and length larger than the object which is to be cast. By means of a heated wire 11 in this instance connected by handle 12 to a source of electrical energy the heated wire may easily cut through the block of polystyrene. -The "cutting" is achieved by melting the polystyrene as the wire is pulled

,.<Λ through the material. fc

In order to ensure that the desired shape is achieved a template as illustrated in figure 5 and 6 may be used. The template 13 is fastened in either end of the block 10. The template 13 is decisive for the shape of the end of the element to be cast. Turning to figure 6 it is clear that the template 14 will provide for a different shape of the element to be cast. By pulling the hot wire 11 as illustrated in figure 6 through the block material 10 and arranging the hot wire through the material it becomes possible to cut away part of the block material 10 as illustrated in figure 6. From the exposed surfaces of the material 16 it is evident that the exposed surface has a curved shape both with respect to the longitudinal direction of the element to be cast and in a crosswise direction. This is achieved by the curvature 17 of an edge of the template 14 and by not tightening the hot wire completely, so that the friction/resistance created by the polystyrene block material 10 on the wire, will create the longitudinal curvature of the exposed surface 16. Should such shape have been created by traditional means it would have been a very expensive and cumbersome process to create such a shape, and in this connection reference is made to the rather simple shape illustrated in figure 1 which in spite of being a relatively simple curved surface requires a substantial amount of work and craftsmanship in order to create an acceptable shape.

Once the hot wire 11 has been pulled along the entire circumference of the template 14, the pieces 18, 19, 20 will be the inner formwork against which the fresh concrete will be cast. The part of the block material 10 between the template 14 in either end of the block is a model of the concrete structure to be cast, but will not be used for the casting process.

The inner mould sections are hereafter arranged in an outer load bearing support structure, where this load bearing support structure has an inner size corresponding to the outer size of the block material 10.

This is illustrated in figure 7 wherein the cut-away sections 18, 19, 20 being the inner formwork are in the process of being arranged inside the outer load bearing support structure 21. Before the concrete is poured into the mould all the inner moulds are arranged and the outer load bearing structure is closed in order to enclose the inner moulds completely except naturally for the upper opening through which the concrete is poured. A very rigid and strong formwork is hereby created.

Turning to figure 3 the inner formwork for the wall as illustrated in figure 2 is illustrated. The inner formwork consists of a front and back part 30, 31 and for illustrative purposes the templates 32, 33, 34, 35 are also illustrated. The inner moulds have been shaped by pulling the hot wire along the template 32 as illustrated in figure 8.

In figure 3 the corresponding inner moulds 30, 31, do not have end sections which correspond to the next consecutive element. This, however, may be solved as illustrated with reference to figure 9, wherein the same template used in the first set of elements is also used for the second set. The first set of inner moulds 41, 42 is created as explained above by using templates and cutting with a hot wire through the block material. The template used on the face 43 of the inner mould 41 is also used for the next set of inner moulds 44, 45 so that the inner mould 45 on one end surface is cut along the same template 43 as the first set of inner moulds '4I, 42. In this manner it is ensured that the inner mould elements 41, 45 will create a smooth transition such that a continuous element e.g. as illustrated in figure 2 may be created. The following end face of the inner mould 45 is created by the template 46 which again is used for the adjoining set of inner moulds as already explained, and so on. In figure 10 is illustrated an inner mould created according to the principles described above which inner mould 50 may be fitted inside an outer load bearing support structure 51. The elements cast in the inner mould 50 are depicted in figure 11 and are mentioned here in order to illustrate the versatility and the wide variety of possibilities which are possible with the inventive formwork according to the invention. With traditional formwork the structures as illustrated with reference to figures 2, 6 and 11 would have been so expensive that in fact it is very likely that they would have been taken out of the projects had it not been possible to manufacture them by using the versatile and relatively cheap formwork system according to the present invention.

With reference to fig. 1 Ia to 16 various embodiments of performing the invention are illustrated.

In fig. 11a a membrane 47 made from latex or synthetic rubber, typically having a thickness of from a few tenths of a millimetre to a few millimetres is fastened to a frame 48. The membrane 47 is not pre-shaped, but is a straight flat membrane section. The size of the frame 48 is such that it may be supported on the upper ledge 49 of the load bearing outer formwork 50. The block of formable material 51, made from polystyrene, is provided with a cavity 52 corresponding to the desired shape of the finished cast element.

By placing the block 51 inside the formwork 50, and superposing the frame 48 with the membrane 47 over the ledge 49, the formwork is ready to receive the concrete. The concrete is poured on the membrane 47, which thereby deforms to the shape of the cavity 52.

Once the concrete has set, it is relatively easy to remove and reuse the membrane 47. Additionally the surface finish of the concrete element is very smooth, due to the surface characteristics of the membrane, in particular when made from Latex.

The embodiment illustrated in fig. 12 corresponds to the embodiment described with reference to fig. 11a. Only in this embodiment the membrane 53 is pre-shaped. When pouring the concrete the membrane does not need to stretch as much, and with this

Rl IRCTITI ITC QMPPT embodiment it is therefore possible to make larger constructions compared to the previous embodiment. This embodiment also corresponds to the embodiment illustrated in fig. 15, where an element having a limited cross section, but a relatively long shape is illustrated.

Alternatives to the embodiments described with reference to fig. 12 and 15 are illustrated in fig. 13 and 16. Here the release agent is in the shape of a liquid 54. Preferably a mixture of oil and wax is used as a coating on the inside of the cavity 52.

In fig. 14 is illustrated an embodiment of the invention suitable to manufacture surface elements. The formable material is sand 55, which is placed inside the outer formwork 50. The upper surface of the sand 55 will determine the surface shape of the element to.¹.. be cast. The. membrane 47 will due to its stretchability and flexibility conform to the shape of the sand 55, when the concrete is poured on top of the membrane 47.

Above the invention has been explained with reference to a few detailed embodiments, but the scope of the invention shall not be construed as being limited by these examples, but should rather be limited only by the scope of the appended claims.

Although the invention has been explained above with reference to specific embodiments, the inventive principle may be achieved by other, not illustrated means and method steps. For example instead of manual labour cutting the block material this may be carried out by industrial robots. Industrial robots are great for repetitive processes and for processes which may be designed by for example an architect on a com- puter and transferred to the robot which thereafter exactly creates the design on the block. In such instances the templates may be superfluous, in that the robot may work without such aids.

The inner formwork may also be preformed. For applications where a large number of identical amorphous elements are to be manufactured, it may be advantageous to pre- manufacture the polystyrene foam elements, or use other suitable materials for this purpose, as the requirement to being able to shape the inner formwork by means of a hot wire has been dispensed with. A computer based design aid may be contemplated, where the software automatically reserves a central zone for reinforcement, tension cables etc, and sufficient concrete cover over the reinforcement, such that the designer is free to use the rest of a given cross section in order to create the desired shape.

Claims

1. Method for casting concrete or concrete like elements where said elements may have an amorphous shape, wherein the method comprises the following steps:

- in a formable material having a size larger than the element to be cast, a model of the element is cut out, thereby creating an inner formwork; an outer load bearing support structure having an inner size corresponding to the outer dimensions of the formable materialis created;

- • the parts of the formable material not representing the model are arranged in: the interior of the load bearing support structure, thereby creating. a cavity corresponding to the model; a release agent either in liquid form or as a foil or membrane is arranged cover- ing the cavity in the inner formwork; optionally reinforcement is arranged in the cavity; fresh concrete or other concrete like material is poured into the cavity and allowed to cure; the outer load bearing support structure and the inner formwork are removed.

2. Method according to claim 1 wherein the formable material is a block made from a polystyrene based product, and that a hot wire is used for cutting the model.

3. Method according to claim 1 or 2 wherein the elements are sections of a larger structure, and where templates defining end surfaces of the elements to be joined are used, such that surfaces of two adjacent elements to be joined, use the same template when the model is being cut out of the formable material.

4. Method according to any of claims 1 to 3 wherein the inner formwork is pre- manufactured, and optionally allowed to remain in contact with the concrete during the hardening process, whilst another set of inner formwork is arranged inside the outer load bearing support structure.

5. Method according to any of claims 1 to 4 wherein a suitable release agent is applied to the formwork before casting, where the release agent is a liquid which is selected among one or more of the following: retarder, vegetable oil, oilbased wax, Vaseline, PE glue, latex, synthetic rubber, silicone.

6. Method according to any of claims 1 to 4 wherein a suitable release agent is applied to the formwork before casting, where the release agent is a membrane or foil, where the foil is flexible and made from latex, or synthetic rubber, where said membrane or foil optionally is preformed.

7. Formwork for casting concrete or. concrete like elements, where said elements may have an amorphous shape, cfer-sracterised in that the formwork comprises:

an outer load bearing support structure, which support structure has means al- lowing the structure to be disassembled, thereby freeing an inner formable structure, which inner structure defines the outer shape of the element to be cast a liquid, foil or membrane release agent, covering the inner structure.

8. Formwork according to claim 1 wherein the inner formable structure is made from a polymer-based lightweight foam material.

9. Formwork according to claim 7 wherein the inner formable structure is made from a castable material, and that the inner formwork is created by casting the castable mate- rial around a model of the element to be cast.