The present invention relates to a rectangular construction panel having an upper edge, a lower edge which is situated opposite to the upper edge, and two side edges which are opposite to one another, where the construction panel comprises a sandwich structure having a first layer, a second layer and a third layer, wherein the first and third layer comprise set mortar and the second layer comprises hard foam.

Such a rectangular construction panel is known in the art, for instance for partition walls. As hard foam, for instance polystyrene is applied. For applications where the construction panel is loaded more heavily, construction panels are known wherein the first and third layer are connected by reinforcement.

The present invention aims to provide an improved construction panel.

To this end the present invention provides a rectangular construction panel having an upper edge, a lower edge which is situated opposite to the upper edge and two side edges which are opposite to one another, where the construction panel comprises a sandwich structure having a first layer, a second layer and a third layer, wherein the first and third layer comprise set mortar and the second layer comprises hard foam, wherein

• the first layer has a thickness of 5 mm to 50 mm, the second layer has a thickness of 80 mm to 400 mm and the third layer has a thickness of 5 mm to 50 mm, with the provisio that the ratio R of the second layer to the total thickness of the first and the third layer is at least 2, and
• the connection of the first layer with the second layer and the connection of the third layer with the second layer are stronger than the second layer,

Such ducts offer two important possible uses, in particular the drainage of moisture (such as rain water, condensation and the like), and the possibility to lead through utility conduits. The presence of the ducts weakens the construction panels somewhat, but the strength of the construction panels according to the invention is such that this is nevertheless made possible. For the drainage of moisture the ducts will generally have a diameter of 10 - 30 mm, and for pipes generally a diameter of 15 - 25 mm, but for both applies that a wider, and optionally a smaller diameter is also possible. The shape of the cross section of the duct is selected depending on the intended application. Because of the reduced weight of the first and the third layer in combination with the relatively great thickness of the polystyrene layer at the specified adherence between the mortar of the first and third layer with the second layer, surprisingly, such a construction panel, despite the presence of one or more ducts, appears to be so strong that it can be loaded relatively heavily but is nevertheless cheap in that reinforcement, which connects the first and the third layer, can largely, and in most cases even entirely, be omitted. The required adherence of the first layer and the third layer to the second layer can be achieved in a manner known per se. This will be pursued later in this application when a method for manufacturing the rectangular panels according to the invention is discussed.

Hereinafter some embodiments will be described which are preferred since construction panels which comply with one or more of these conditions may be loaded even more heavily.

Preferably, the ratio R is at least 2.5 and more preferably at least 4.

Preferably, the first layer has a thickness in the range of 10 mm to 25 mm, and the third layer has a thickness in the range of 10 to 25 mm.

Preferably, the second layer has a thickness of at least 125 mm, more preferably a thickness of at least 180 mm.

Preferably, at least 1 of the first and the third layer has reinforcement included in the layer in question and enclosed by the layer in question.

This reinforcement is, for instance, in the form of wire mesh, fibre mats, such as a mat of glass fibres or plastic fibres, or loose fibres mixed with the mortar. In the scope of the present application, the term "enclosed reinforcement" means that this is essentially situated in the layer in question and does not extend from the first layer to the third layer, or the other way around. The term does not exclude that no single part of the reinforcement can be visible at the surface of the layer in question.

The hard foam is preferably a thermoplastic polymer having a softening point above 70°C.

Such thermoplastic polymers are generally cheap but nevertheless afford favourable construction properties. According to an advantageous embodiment the thermoplastic polymer is expanded polystyrene.

Preferably, the at least one duct extends from the upper side in the direction of the lower edge.

Thus, particularly for applications involving a lowered ceiling, where utility conduits are fitted in the lowered ceiling, a utility conduit can readily be introduced into the duct in order to achieve that it can be made accessible at a lower location in the space that is defined at at least one location by a construction panel according to the invention, by making a hole in the construction panel. For applications with moisture drainage, the at least one duct will extend as far as the lower edge, where the moisture can be discharged in a manner known per se.

Particularly, for wall panels and outer wall panels it applies that preferably within a distance of 1 m from a side edge at least 2 ducts are provided.

Especially at this location, in practice there is a demand for utility conduits such as electricity and data conduits (such as for Internet).

Especially for moisture drainage, it is preferred that ducts are present distributed over the entire construction panel, said ducts being situated a) at the interface between the first layer and the second layer; and/or b) between the centre of the second layer and the interface between the first layer and the second layer.

After placement these run from the top down.

According to an important embodiment the construction panel is an outer wall panel having a width of at least 4 m.

Outer wall panels will more usually have a width of at least 5 m, more in particular at least 6 m.

The invention also relates to a method for manufacturing a rectangular construction panel according to the invention, wherein a first mortar is applied on a mould, a plate of hard foam is applied on the first mortar before the first mortar is set, and a second mortar is applied on the hard foam, producing the rectangular construction panel after setting of the first and the second mortar, wherein the composition of the first and the second mortar is such that they are low-shrinkage mortars and present a shrinking or swelling of no more than 1% when setting, and wherein the first layer has a thickness of 5 mm to 50 mm after the setting, the second layer has a thickness of 80 mm to 400 mm and the third layer has a thickness of 5 mm to 50 mm after setting, provided that the ratio R of the second layer to the total thickness of the first and the third layer is at least 2.5, and the composition of the first mortar and the second mortar is selected such that in the set state of the first and the second mortar, the connection of the first layer with the second layer and the connection of the third layer with the second layer are stronger than the second layer.

Low-shrinkage mortars are generally known in the art and need no further explanation. As a result of setting of the mortar such mortars preferably shrink or swell no more than 0,5%, more preferably no more than 0,2%. In order to ensure that a mortar presents the adherence to the second layer as required according to the invention, the person skilled in the art has a wide range of options at his disposal. Firstly, the person skilled in the art can provide the plate applied with an enlarged surface, for instance by coarsening it or by providing it with a profile. Secondly, as a low-shrinkage mortar, a mortar of low viscosity can be selected, which penetrates further into the surface cavities of the hard foam. Finally, it is also possible to adjust the composition of the mortar by using additives. For instance, a glue is contemplated, such as Beamix Primer 780 (Beamix, Eindhoven, The Netherlands).

Most advantageously, the hard foam is a thermoplastic polymer, and the at least one duct is provided in the hard foam by means of a hot heating element.

It has been found that particularly with polystyrene, it is possible to provide ducts very easily.

According to a preferred embodiment a connecting split that is formed by the hot heating element between the duct and a surface of the hard foam is filled using a kit or foam.

Thus, an optional loss in strength of the construction panel formed therewith can be limited. Advantageously, in particular if the hard foam is polystyrene, polyurethane foam can be used as a foam, which presents a proper adherence and has in addition filling properties.

In an alternative embodiment, the at least one duct is formed by gluing together two hard foam parts of which at least 1 has a groove, and the groove is formed into a duct which is defined by both hard foam parts.

Finally, the invention relates to a method for laying utility conduits, which is characterized in that in a dwelling provided with a rectangular construction panel producible according to the invention, a place is selected at a location along the at least one duct where a utility connection has to be fitted, at that location a through-hole is formed, through the second layer of mortar, which connects to the duct, and from an end of the duct selected from the through-hole and an edge of the rectangular duct a utility conduit is introduced into the duct, wherein the hard foam prior to or after the application is provided with at least 1 duct.

Thus, it can be achieved that the utility conduits, such as a water conduit, are out of sight, without slotting of the first or third layer or the like. When more ducts are present, it is also very well possible, should there be a need to change, to provide a utility conduit of the same or a different type at another location.

Preferably, the utility conduit is selected from a flexible water conduit, an optical fiber cable, an electric cord and a cable for transision of electronic data.

Generally, these can readily be bent and fed through the ducts.

The present invention will now be illustrated by the following working examples with reference to the drawing, in which

• fig. 1 shows a front view of a construction panel;
• fig. 2 shows a cross-section according to line II-II through the construction panel of fig. 1;
• fig. 3 corresponds with fig. 2, but here the construction panel, according to the invention, has ducts for the drainage of moisture;
• fig. 4 corresponds with fig. 3, but here the construction panel according to the invention has ducts for a utility conduit;
• fig. 5 shows a longitudinal cross section through the construction panel via line V-V of fig. 4;
• fig. 6a and 6b show, respectively, a front view and a perspective front view of a wire loop suitable for forming ducts in a thermoplastic polymer; and
• fig. 7 shows a detail of a plate of thermoplastic polymer provided with a duct.

The figures are schematic and not to scale, wherein particularly the thickness of the construction panel is shown exaggeratedly.

A construction panel was manufactured for testing purposes having a width of 50 cm and having a length, representative of a construction panel, of 3 m. To this end, a boundary casing having the aforesaid dimensions was placed on a mould. A low-shrinkage mortar composition was prepared using casting mortar TM5203 (Tillman, Megchelen, The Netherlands) prepared according to the instructions of the manufacturer. A layer of this mortar composition having a thickness of 2 cm (first layer) was cast and spread on the mould. The layer of mortar was then immediately covered with a polystyrene plate having a thickness of 20 cm (second layer; EPS foam, Firma Unidek B.V., Gemert, The Netherlands). When doing so, the plate was put into the mortar with one edge first and was subsequently positioned horizontally in order to prevent air from getting trapped under the plate. The plate was pressed down by walking over it. Subsequently, a finishing mortar was made using the fibre reinforced casting mortar ABS340 of Beamix prepared according to the instructions of the manufacturer. The finishing mortar was applied onto the plate of polystyrene (in a thickness of 2 cm). This layer of finishing mortar (third layer) was levelled using a spatula. After 16 hours of setting at 20°C the construction panel 1 thus formed could be taken from the mould, and was allowed an additional setting of 7 days.

To remove air bubbles captured under the polystyrene, an underpressure can be applied. This is, for instance, possible by covering the totality of the mould and panel with a PVC foil, and subjecting the space under the foil to an underpressure. For that matter, it is noted that, although the presence of bubbles may not be desirable, especially the large bubbles are disadvantageous, and especially the large bubbles, should they even occur, can be removed properly with the underpressure technique described above. The air can escape between adjacent polystyrene plates or via holes that have been provided in the polystyrene plates for this purpose. These holes can be made, for instance, by using, optionally hot, needles. Another advantageous method to prevent air from getting trapped under the hard foam in the method according to the invention, is using strips of hard foam having a width of 50 cm or less, such as 40 cm or less. Advantageously, plates are cut to strips and the strips are placed with a cut face (thus, transverse to the original surface of the plate) on the first mortar.

Once it is taken out of the mould and placed upright, the construction panel 1 as obtained above has an upper edge 2, a lower edge 3 and side edges 4 and 5 (fig. 1). Fig. 2 shows a cross section along line II-II of fig. 1. Here, the first layer of set mortar 6, the second layer 7 consisting of polystyrene, and the third layer of set finishing mortar 8 can be seen.

The construction panel 1 as manufactured hereinabove was subjected to loading tests. Here, the construction panel 1 was supported at the long ends 2, 3, and across the length of the construction panel 1, weights in the form of bags of cement (25 kg each) were put onto the construction panel 1. Starting from the middle, the bags were put on the construction panel 1 in pairs, flat (and longitudinally transverse to the longitudinal direction of the construction panel 1). When the ends 2, 3 of the construction panel 1 were reached, a new layer was begun starting from the middle again. After every pair of bags, the deflection was measured and was checked for formation of cracks. Once the construction panel 1 was loaded with 550 kg, during which no formation of cracks was observed, an endurance test of 28 days was performed. Regular checks were made to find whether the degree of deflection had altered and whether formation of cracks had occurred. This appeared not to be the case. Thus, it can be concluded that with using the method an extremely strong and light (90 kg/m²) construction panel 1 can be obtained.

Fig. 3 corresponds with fig. 2, except that as a second layer 7 a polystyrene plate is used which is provided with ducts 9. The ducts 9 serve for draining moisture, particularly moisture accumulated near the first layer 6 (which, when used as an outer wall panel, functions as the side that is exposed to the atmosphere) as a result of cold (condensation), rain etc. According to the invention these ducts 9 in the second layer 7 will preferably be situated between the centre of the second layer 7 and the first layer 6 (fig. 5). Usually the distances between the ducts 9 will be smaller than the thickness of the second layer 7. It has been found that despite the presence of ducts, the strength of such a construction panel is more than sufficient.

According to the invention, the second layer 7 can be used for laying a utility conduit in a duct 10 (fig. 4, 5). In practice, such a utility conduit will most often be an electric cord or power cable, but may also be, for instance, glass fiber for an optical data network. After placement of the construction panel 1 and particularly when there is more than 1 duct 10, this allows the laying of a connecting socket or a connection for telephone, Internet etc. in a desired location. According to the invention, these ducts 10 in the second layer 7 will preferably be situated between the centre of the second layer 7 and the third layer 8.

Using this method according to the invention and using a panel according to the invention, a bendable utility conduit can be laid in a concealed fashion, without a great deal of work. For instance, when using a lowered ceiling, the utility conduit (not shown) can be hidden in the lowered ceiling, and can be introduced into the duct 10 by means of a hole 11, to be made in the third layer 8 at the location of a duct 10. At the location in the room where the connection for the utility conduit has to be provided, also a hole 12 is made in the third layer 8. As shown in fig. 5, at the location of a hole 11, 12, excess material of the second layer 7 can be removed to facilitate connecting.

For laying the ducts 9, 10 in the second layer 7, in particular for thermoplastic polymers such as polystyrene advantageously a copper wire loop 13 can be used (fig. 6). The wire loop has two ends 14, 15 which connect a loop part 16. The two ends 14, 15 may be connected to a low-voltage supply (eg. 20 V). The current that runs through the loop part 16 is such that it reaches a temperature at which polystyrene melts. For manufacturing a duct 9 or 10 situated in the second layer 7, the ends 14, 15 are designed flat (fig. 6b) and are placed in line with each other, substantially transverse to the intended direction of movement of the wire loop 13, which defines the cross section of the duct to be made using the wire loop 13. A hot wire loop 13 is passed through the polystyrene plate from the upper edge 2 or lower edge 3 of a plate polystyrene. Although for forming a duct 10, this may take place after the plate polystyrene has been applied onto the first layer 6, forming ducts 9, 10 will usually take place prior to applying the second layer 7 onto the first layer 6. Usually the hot wire loop will be passed along the entire distance between the upper edge 2 and the lower edge 3. A residual core of polystyrene formed in the duct 9, 10 during this process can be readily pushed or blown out of the duct 9, 10.

By forming the wire ends 14, 15 as described above, a duct 9 or 10 can be formed, which along its length is connected with the surface of the plate polystyrene 7 only by means of a narrow gap 17 (fig. 7). Particularly, in case of duct 10, and when using a relatively thin or little thixotropic mortar, but also more generally in order not to unnecessarily affect the properties of strength of the second layer 7, it may be recommended to fill the gap 17, for instance using polyurethane foam.