Apparatus and method for forming concrete panels

Abstract

The invention provides a form member for use in forming concrete panels comprising a pair of upright walls connected by a plurality of ribs. Each of the ribs includes an aperture for allowing a fastener through. The fastener passes through each of the ribs into a casting floor to fix the form member to the floor. A plurality of form members can be arranged to define enclosures, concrete is then poured into the enclosures to the level of the upright walls, smoothed and allowed to cure to form concrete panels. The form members of the present invention allow a number of panels to be formed at the same time, with some form members common to more than one concrete panel. The invention provides easy of use and savings in space, time and labour.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus and method for forming concrete panels. In particular, the invention relates to forming tilt-up concrete panels which are poured on a flat surface and subsequently tilted up to form walls for buildings.

2. Background of the Invention

Tilt-up construction is a method of forming concrete buildings. It provides a low cost and high speed way to construct buildings which are low maintenance and have good durability.

Typically, in a tilt-up concrete construction, panels are formed as near to their final position in the building as possible. The most convenient casting base is often the concrete floor of the building. Wood or steel edge forms are prepared and positioned on a casting base. The base is sprayed with a release agent that prevents wet concrete sticking to the base. Reinforcing steel and any desired door and window frames, electric conduits and outlet boxes are then positioned within the form. Concrete is then poured into the form on the horizontal base, the poured concrete is screed, allowed to cure and subsequently tilted into a vertical position and moved into place.

Placing and fixing the forms for the panels, and subsequently removing those forms presents a number of problems. Typically, each form is made from plywood and is fastened to the forming surface by nails or self-tapping screws. The forms are often damaged when the nails or screws are removed so that they cannot be reused. The casting surface is often damaged as well.

A chamfer is often desired on the edge of the concrete panels. This is achieved by placing a chamfer strip or fillet adjacent to the form members. However, these strips can often be displaced when the concrete is poured leading to irregular panels being formed.

The plywood forms are of a height that is equal to the thickness of the panel to be cast. Practically, this means that the panels are limited in thickness to standard plywood widths.

The forms have to be sufficiently strong to withstand the considerable pressure exerted by the poured concrete. In order to support the form members, supporting brackets are placed outside of the form members. This means that each panel requires a separate form and takes up considerable space on the casting floor. It is possible to cast a number of panels side by side with a single form section forming a common wall between two panels. However, with existing systems, in order to do this, both panels must be poured at the same time in order to balance the pressure exerted on the form by the poured concrete. It is not possible to stick brackets on either side of the form in this scheme as they would interfere with the shape of the concrete panels. However, existing forms cannot be anchored strongly enough to the casting floor to withstand the pressure from the concrete without external brackets.

U.S. Pat. No. 6,322,045 discloses a system for forming tilt-up concrete panels in which each form member is comprised of an extruded base member into which a plywood panel is inserted to form the wall of the form member. FIG. 1 shows a side view of a form of the type disclosed in U.S. Pat. No. 6,322,045. The form 1 comprises an elongate support into which a plywood board 2 is inserted. The support comprises a pair of upright walls 3, 4 and a base member 5 defining a U-shaped trough into which the plywood is inserted. The support also includes a pair of chamfered surfaces 6, 7 on either side of the U-shaped trough. The support is formed from a rigid material such as extruded aluminium and is anchored to a casting surface using a self-tapping screw 8 in the base of the trough.

There are a number of problems with the system of U.S. Pat. No. 6,322,045. Firstly, concrete can enter the gap between the plywood and the extruded form member. This will make it almost impossible to remove the plywood from the form member without significant damage to the plywood, making it unusable again. The plywood used to make the forms is a considerable expense in the process and as far as possible it is desirable to be able to reuse the plywood form members.

Secondly, in order to minimise the above problem, the plywood must fit into the support as tightly as possible. Plywood that has been sitting in the form member whilst concrete is curing will absorb moisture and will expand. Not only will this make it difficult to remove the plywood from the support but makes it almost impossible to refit it into a support member for subsequent reuse. Furthermore, if a chip of the plywood breaks off during reinsertion and jams into the bottom of the extrusion, then this will create a misalignment in the height of the form as compared with adjacent form walls. The height of all the form walls must be the same in order to create concrete panels of uniform thickness during the screeding process.

Thirdly, if the plywood does get jammed in the support and cannot be removed then it is impossible to remove the support from the floor as the screw is covered by the plywood. The entire section then remains locked to the floor until the panel is lifted out. Not only will the plywood be damaged on removal from the support, but the form member can also then be damaged by the panel lifting equipment during the lifting of the panel.

Fourthly, difficulties can arise when trying to unscrew the form member from the floor. The screws used to attach the form member to the floor are necessarily very small. This is because the form members are restricted to the thickness of standard plywood making the trough in which the screw sits quite narrow. If the screw head gets rounded the only way to remove the form member is to stick a bar underneath the screw head and prise it out. This damages both the form member and the underlying concrete surface.

Fifthly, as with previous systems, if using a form wall as a common wall for two panels, it is necessary to pour both panels simultaneously in order to balance the pressure exerted by the concrete on the form member. The top of the plywood will typically bend over and out of alignment if concrete is poured on one side, creating an irregular shaped panel. Further damage can be caused to the plywood during pouring if the pump hose is dragged across the top surface or by the screeding machine during screeding, preventing reuse.

Accordingly, it is an objection of this invention to provide a solution to the abovementioned problems or to at least provide the public with a useful choice.

SUMMARY OF THE INVENTION

In a first aspect, this invention provides an apparatus for use in forming a concrete panel comprising a rigid form member, the form member comprising:

a pair of upright walls, having internal surfaces facing one another and external surfaces facing away from one another; and

a plurality of ribs connecting the internal surfaces of the walls, wherein the ribs each include an aperture to allow a fastener shaft therethrough.

Preferably, the form member further includes a base portion including at least one chamfered surface extending outwardly from the exterior surface of one of the walls. More preferably, the base portion includes two chamfered surfaces, one extending outwardly from each of the exterior surfaces of the walls. Preferably, each chamfered surface is substantially non-perpendicular to the ribs.

Preferably, the apparatus further includes a bolt having a shaft and a head, wherein, in use, the bolt shaft passes through the apertures and into a floor. Preferably, the rib furthest from the floor provides a seat on which the bolt head rests. Preferably, in use, the upright walls extend above the extent of the bolt head.

Preferably, the apparatus further includes a cap, adapted to cover the bolt head. Preferably, in use, the cap does not extend above the upright walls

The apparatus may further include an extension piece, adapted to fit on the rigid form member at the opposite end to the base portion, the extension member comprising a pair of walls connected by a plurality of rib members, the extension member adapted to provide additional height to the rigid form member. Preferably, the ribs of the extension piece each include an aperture to allow a fastener therethrough.

Preferably, the form member is formed from an aluminium alloy. Alternatively, the form member may be made of any other rigid material. Preferably, the extension piece is formed from an aluminium alloy. Alternatively, the extension piece may be made of any other rigid material.

Preferably the end of the form member is sealed between the upright walls.

According to a second aspect of the invention, a kit for forming concrete panels comprises a plurality of form members in accordance with the first aspect of the invention and a plurality of exterior form members, wherein each exterior form member comprises a first wall, and a second wall, wherein the second wall is substantially perpendicular to the first wall and connected to the first wall to form a corner, wherein the second wall is substantially shorter than the first wall and wherein each of the first and second walls include apertures therethrough.

Preferably, the exterior form members are formed from aluminium alloy. Preferably, the exterior form members are formed in two parts.

According to a third aspect of the invention, there is provided a method of forming a concrete panel, comprising the steps of:

arranging a plurality of form members in accordance with the first or second aspect of the invention on a casting floor to define an enclosure;

fastening the form members to the floor using fasteners passed through the apertures; and

pouring concrete into the enclosure.

Preferably, the form members form a plurality of enclosures, with at least one form member being common to two enclosures.

Preferably, the method further includes the steps of:

allowing the concrete to set to form a panel; and,

lifting the panel into a desired position.

Preferably, the method further includes the step of unfastening at least one of the form members defining the enclosure from the floor and removing those form members prior to the step of lifting the panel.

Preferably, the step of arranging further comprises placing exterior form members in two parallel lines and placing form members extending between the parallel lines to define enclosures.

Preferably, the step of arranging comprises placing form members in a grid pattern to define enclosures.

Preferably, the step of pouring concrete into the enclosure comprises pouring concrete up to the level of the upright walls.

To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are now described, by way of example only, with reference to the drawings in which:

FIG. 1 shows a form member in accordance with the prior art;

FIG. 2 a is a cross-section of a form member in accordance with the present invention;

FIG. 2 b is a partial perspective view of the form member shown in FIG. 2a;

FIG. 2 c is a partial plan view of the form member shown in FIG. 2a;

FIG. 3 a is a cross-section of an extension piece for a form member in accordance with the present invention;

FIG. 3 b is a partial perspective view of the extension piece shown in FIG. 3a;

FIG. 3 c is a cross-section of an alternative extension piece in accordance with the present invention;

FIG. 4 a is a cross-section of a second type of form member in accordance with the present invention;

FIG. 4 b is a partial perspective view of the form member shown in FIG. 4a;

FIG. 5 is a plan view of a first arrangement of form members in accordance with the present invention used for forming concrete panels;

FIG. 6 is a plan view of a second arrangement of form members in accordance with the present invention used for forming concrete panels;

FIG. 7 is a front view of an end cap member in accordance with the present invention; and,

FIG. 7 b is a side view of the end cap member shown in FIG. 7a.

DETAILED DESCRIPTION

FIG. 2 a is a cross-section of a form member 24 in accordance with the present invention. The form member comprises a pair of upright walls 10, 11 which are connected at their inner surfaces 14, 15 by a plurality of ribs 16, 17 and a base member 18. The form member includes a pair of chamfered surfaces 19, 20 extending between the upright walls 10, 11 and the base member 18. In this example, the external surfaces of the upright walls 12, 13 are parallel to one another and substantially perpendicular to the base member. However, it should be appreciated that the external surfaces can have any desired profile. It should also be appreciated that the chamfered surfaces 19, 20 are optional as is base member 18. The form member 24 also includes a flat top surface 25. This flat top surface is also optional.

The form member is of substantially uniform cross-section, except for a series of apertures for receiving fasteners positioned along its length. This is clearly seen in FIG. 2b and in FIG. 2c. FIG. 2b is a perspective view of the form member shown in FIG. 2a, but of only a portion of its length. FIG. 2c is a plan view of a portion of the form member shown in FIG. 2a. The apertures are formed at corresponding positions in each of the ribs, the base member and the top surface. A larger aperture is formed in the top surface than in the uppermost rib 16 for reasons that are explained below.

In this example, the form member is 6.5 metres in length and is 120 mm in height. However, form members in accordance with the invention may be of any desired length and height. The form member can be formed of any rigid material, but in this example an aluminium alloy is used. The aluminium alloy can be extruded to produce the desired form. The form member is preferably painted with a suitable paint to prevent concrete from sticking to it.

In use, the form member is fastened to a casting floor using a bolt 21. The bolt is inserted into the form member from the top (the opposite end to the base member) with the shaft of the bolt passing through apertures in the top surface 25, the ribs 16, 17 and the base member 18. The head 22 of the bolt rests on a seat provided by one of the rib members. In the example shown in FIG. 2a, a washer is interposed between the bolt head and the rib member 16. The aperture on the top surface is larger than the aperture formed in the rib member on which the bolt head rests to allow the bolt head to pass below the level of the top surface 25. A hole is drilled into the floor to receive the bolt. The drill bit may be located using the apertures of the form member to ensure a correct position and angle. A plurality of bolts may be used, along the length of the form member to fasten it to the floor. Typically, 3 bolts per 6.5 metre section are sufficient. This is considerably fewer fasteners than are required in prior systems. Furthermore, bolts can be used on greener concrete than the self-tapping screws of the prior art, reducing construction time. The apertures in the rib members may be elongate to accommodate a plurality of bolts or a series of discrete apertures may be formed in the ribs as shown in FIG. 2b. A plastic cap 23 can be placed over the top of the bolt head 22 to protect it from wet concrete during the screeding process, as will be explained below. Each bolt may have an individual cap or a single cap may be shaped to cover a plurality of bolt heads.

The bolt head is positioned close to the top of the upright walls but crucially does not extend above them. The bolt head can be covered with a cap which similarly does not extend above the upright walls when in use. This is shown in FIG. 2a and ensures that nothing extends above the level of the concrete during the screeding process. It is desirable to have the bolt head close to the top of the upright walls to allow for simple installation and removal of the bolt. The cap is preferably formed from a plastics material. The cap covers the bolt head and rests on the same rib as the bolt head in this example. The cap fits into the aperture in the top surface snugly and is flush with the top surface. The cap prevents concrete from setting around the bolt head, which would make removal of the bolt head difficult.

FIG. 3 shows a cross-section of an extension piece, which can be mounted on top of the form member shown in FIG. 2 to provide the form member with additional height. The extension piece comprises a pair of upright walls 30, 31 connected by ribs 32, 33. The ribs include apertures for receiving a bolt shaft. The lower rib 33 provides a seat for a bolt head to rest against. In use, the extension piece 30 is placed on the form member with the extension piece walls 31 lining up with form member walls 10, 11. A bolt is passed through the extension piece and the form member into the floor. In this way, the external walls of the form member are effectively increased in height allowing for the formation of thicker concrete panels. In this example the extension piece adds 30 mm allowing for panels 150 mm thick to be formed. It should be appreciated that the walls 31 of the extension piece can have any desired exterior profile. For example, as shown in FIG. 3c, the extension piece could have chamfered surfaces 35 that mirror chamfered surfaces 19, 20. It is also possible to use a plurality of extension pieces, stacked on top of one another. The plastic cap is fitted to the extension piece instead of to the underlying form member in the same manner as it is to the form member 24 when an extension piece is not used. If necessary a different height plastic cap can be used for the extension piece.

FIG. 4 is a cross-section of a second type of form member 40 in accordance with the present invention. In use, form member 40 is used as an exterior element in a concrete panel forming arrangement and so will be referred to as an exterior form member throughout the specification. Exterior form member 40 is a two piece aluminium alloy extrusion. However, any rigid material may be used and the form member may be formed using any suitable process. In this example, the two pieces of the exterior form member 40 are welded together. The two pieces are formed with an interlocking section 48, which ensures that they are properly aligned and firmly joined. Form member 40 comprises a long wall 41 and a short wall 42. The long wall and the short wall meet at a corner and extend substantially perpendicular to one another. The exterior form member is strengthened by a back wall 43 connected to the long wall and the short wall by ribs or solid portions 44. The back wall 43 includes a portion substantially parallel to the long wall 41, a portion substantially parallel to the short wall 42 and an angled portion connecting the two. The exterior form member has substantially uniform cross-section and extends as shown in FIG. 4b. In this example, the long wall is 150 mm long, the short wall is 120 mm long and the form member extends 6 metres. FIG. 4b is a perspective view of one end of the exterior form member 40. However, the form member 40 may be of any desired dimensions.

In use the exterior form member 40 may be in one of two orientations. Depending on the thickness of the concrete panels that are to be formed, the long wall may either form an upright wall in contact with the poured concrete or may form a base member in contact with the casting floor. If it is desired to form panels of 150 mm thickness then the long wall 41 is in an upright position and the short wall is in contact with the floor. The exterior form member is fastened to the casting floor using bolts at intervals along its length, typically a couple of metres apart. Bolt holes 45 are drilled through the exterior form members in the long wall 41 and bolt holes 46 are drilled through short wall 42. The exterior form member is preferably solid in the regions around the bolt holes 45, 46 to provide sufficient strength and rigidity. In a fastened position, the bolt heads rest against the back wall 43.

Exterior form member 40 does not include a chamfered surface which in use is in contact with the poured concrete as it is not necessary or desirable to have chamfers on the top or bottom edges of the concrete panels. The use of specific exterior form members as described means that when laid out the form members can abut each other without any gaps though which concrete could escape. It also means that extension pieces are not necessary for the exterior form members as they can be arranged for two different thicknesses of panel. The exterior form members can also be designed to be strong enough to resist the pressure exerted by the poured concrete from one side.

FIG. 5 shows a plan view of a plurality of form members in accordance with the present invention, laid out on a casting floor to define moulds for concrete panels. The form members are laid out to define a series of adjacent enclosures 50 into which wet concrete is poured. In this example, exterior form members 40 form opposite sides of the enclosures. Form members 24 are placed between the exterior form members at substantially right angles to the exterior form members to form rectangular enclosures. Extension pieces are placed on form members 24 if necessary to align with the top of exterior form members 40. The arrangement is such that a number of form members 24 are common to two enclosures. This arrangement of common form members has the advantage that adjacent panels will always fit together in the lifted position, regardless of whether the sides are not accurately square with the base due to errors made during the laying of the forms. This reduces the amount of sealant needed between the panels.

It should be appreciated that form members in accordance with the present invention can be used to form individual concrete panels but that there are clear advantages in space, material and labour to forming a plurality of panels together, with form members which are common to more than one panel.

A method of forming concrete using form members of the type shown in FIGS. 2-4 will now be described. Firstly, the exterior form members are laid out on the casting floor parallel to one another. If more than one form exterior member is required on each side, lugs connecting adjacent exterior form members 40 can be placed in conduit 47 formed between the front wall 42 and the back wall 43 of the exterior form members. The lugs will ensure that the form members are correctly aligned. The interior form members 24 are then positioned extending between the exterior form members 40 to define enclosures, as shown in FIG. 5. The form members are fastened to the floor using bolts and plastic caps placed over the bolt heads of the interior form members 24. Adhesive tape is used to cover unused bolt holes 45, 46 in the exterior form members. Concrete is then poured into the enclosures defined by the form members up to the level of the top of the form members. The top surface of the concrete is smoothed over and any excess concrete can be pushed into the adjacent enclosure before filling and smoothing the adjacent enclosure. This reduces wastage of concrete.

The concrete is then left to cure. During curing the concrete is screed using a power float machine which passes across the top surface of the enclosures. By placing the panels side by side with common form members, the power float can pass directly from one panel to the next without the need for lifting the machine off and on different panels. Furthermore, the panels can be poured consecutively and then screed consecutively. In prior systems in which each panel had separate form members, the power float had to be continuously moved from one panel to the next to keep up with the different stages of curing that the panels had reached.

Once the concrete is set, the form members from one side of the panel are unfastened and removed the crane used for tilting the panel then approaches the panel from the side from which the forms have been removed and tilts the panel up into position. The remaining forms from that panel are then removed and the crane moves forward to lift the next panel in the same manner. This method provides for quick and efficient lifting and positioning of the panels, reducing the time required for crane usage, another significant expense in tilt-up construction. Once all the panels have been lifted into position the remaining form members are removed and the floor cleaned.

FIG. 6 shows a plan view of an alternative layout of form members in accordance with the present invention. FIG. 6 shows a plurality of form members of the type shown in FIGS. 2a-2c laid out in a grid. There are no exterior form members used, although they could replace the outermost form members.

The form members are laid out to form a grid of enclosures, with form members abutting each other at right angles. Owing to the chamfered surfaces 19, 20, a gap is present between two form members abutting at right angles. This gap can be plugged with an appropriately shaped piece of ply wood or using a custom made plug formed from aluminium alloy, plastic or any other suitable material.

In order to prevent a form member 24 from becoming clogged with concrete, concrete dust and dirt the cavities between the upright walls at the ends of the form member 24 can be filled with expanding foam prior to use. Extension pieces can be sealed in the same way.

As an alternative, FIG. 7 shows an end cap 70 that can be used to seal the end of a form member 24 to prevent it becoming filled with concrete and concrete dust. FIG. 7a is a front view of the end cap, which has the same shape as the end of a form member 24. Raised portions 71 are shaped to fit in the cavities defined by the form member 24 to retain the end cap in place. FIG. 7b shows the end cap from the side. The end cap of FIG. 7 is preferably formed from a plastics material but may be formed from any suitable material.

The end cap may be shaped to fill the gap between two form members 24 abutting each other at right angles in a grid, as described above.

End cap members may also be provided to fit the ends of the extension pieces shown in FIG. 3.

The system of the present invention has a number of advantages over the prior art. The forms are strong, robust and easily and quickly cleaned for reuse as compared with prior plywood forms. They will not be damaged during removal or screeding and retain substantially the same dimensions regardless of the conditions, e.g. they do not expand by absorbing moisture and they will not be affected by sunlight. The forms can be made of uniform height and extension pieces can be used to adjust their height. The forms are easily fastened to and unfastened from the floor as the bolt heads are easily accessed. Separate chamfer strips are not required as the forms can be made to include any desired exterior profile in a one piece extrusion or moulding.

The method of the present invention also has a number of inherent advantages. The forms can be used for two panels simultaneously, saving time and labour and allowing more panels to be formed per square metre of floor. The forms can be laid out in a grid to provide for optimal use of space and labour. The screeding process is made simple as the power float can move across all the panels freely without the need for lifting the power float on and off. There is less overflow of concrete on to the casting floor; this reduces the clean up time required and saves cost. The time required for cranage is also reduced as the crane can move swiftly from one panel to the next.

It is to be understood that the scope of the invention is not limited to the described embodiments and therefore that numerous variations and modifications may be made to these embodiments without departing from the scope of the invention as set out in this specification. For example, whilst the use of exterior form members has been described, it is possible to form enclosures for forming concrete panels using only form members of the type shown in FIG. 2.

Claims

1. An apparatus for use in forming a concrete panel comprising a rigid form member, the form member comprising: a pair of upright walls, having internal surfaces facing one another and external surfaces facing away from one another; and a plurality of ribs connecting the internal surfaces of the walls, wherein the ribs each include an aperture to allow a fastener shaft therethrough.

2. The apparatus according to claim 1, wherein the form member further includes a base portion including at least one chamfered surface extending outwardly from the exterior surface of one of the walls.

3. The apparatus according to claim 2, wherein the base portion includes two chamfered surfaces, one extending outwardly from each of the exterior surfaces of the walls.

4. The apparatus according to claim 2, wherein each chamfered surface is substantially non-perpendicular to the ribs.

5. The apparatus according to claim 1, wherein the form member is formed in one piece.

6. The apparatus according claim 1, further comprising a bolt having a shaft and a head, wherein, in use, the bolt shaft passes through the apertures and into a floor on which the form member sits.

7. The apparatus according to claim 6, wherein the rib furthest from the floor provides a seat on which the bolt head rests.

8. The apparatus according to claim 6, wherein in use, the upright walls extend above the extent of the bolt head.

9. The apparatus according to claim 6, further including a cap, adapted to cover the bolt head.

10. The apparatus according to claim 9, wherein in use, the cap does not extend above the upright walls.

11. The apparatus according to claim 9, wherein the cap rests on the rib furthest from the floor.

12. The apparatus according to claim 1, further including an extension piece, adapted to fit on the rigid form member at the opposite end to a base portion, the extension member comprising a pair of walls connected by a plurality of rib members.

13. The apparatus according to claim 12, wherein the rib members of the extension piece each include an aperture to allow a fastener shaft therethrough.

14. The apparatus according to claim 1, wherein the form member is formed from an aluminium alloy.

15. The apparatus according to claim 12, wherein the extension piece is formed from an aluminium alloy.

16. The apparatus according to claim 1, wherein an end of the form member is sealed between the upright walls.

17. The apparatus according to claim 1, further comprising an end cap, wherein the end cap covers an end of the form member to prevent concrete entering a space between the upright walls.

18. A kit for forming concrete panels comprising a plurality of form members in accordance with any one of the preceding claims and a plurality of exterior form members, wherein each exterior form member comprises a first wall, and a second wall, wherein the second wall is substantially perpendicular to the first wall and connected to the first wall to form a corner, wherein the second wall is substantially shorter than the first wall and wherein each of the first and second walls include apertures therethrough.

19. The kit according to claim 18, wherein the exterior form members are formed from aluminium alloy.

20. The kit according to claim 18, wherein the exterior form members are each formed in two parts.

21. A method of forming a concrete panel, comprising the steps of: arranging a plurality of form members or a kit of form members in accordance with any one of the preceding claims on a casting floor to define an enclosure; fastening the form members to the floor using fasteners passed through the apertures; and pouring concrete into the enclosure.

22. The method according to claim 21, wherein the form members form a plurality of enclosures, with at least one form member being common to two enclosures.

23. The method according to claim 21, further including the steps of: allowing the concrete to set to form a panel; and lifting the panel into a desired position.

24. The method according to claim 23, further including the step of unfastening at least one of the form members defining the enclosure from the floor and removing those form members prior to the step of lifting the panel.

25. The method according to claim 21, wherein the step of arranging further comprises placing exterior form members in two parallel lines and placing form members extending between the parallel lines to define enclosures.

26. The method according to claim 21, wherein the step of arranging comprises placing form members in a grid pattern to define enclosures.

27. The method according to claim 21, wherein the step of pouring concrete into the enclosure comprises pouring concrete up to the level of the upright walls.