IL206814A - Facade element and method for securing the same to a wall - Google Patents

Description

27143/10 TP"? ππΐϊπ^ nunui JTTTI νη χ FACADE ELEMENT AND METHOD FOR SECURING THE SAME TO A WALL FACADE ELEMENT AND METHOD FOR SECURING THE SAME TO A WALL Field of the Invention The present invention relates to the field of wall construction methods. More particularly, the invention relates to a method for securing a facade element to a wall.

Background of the Invention Facade elements, generally made of stone and attached to a concrete wall, provide the wall with a decorative and esthetically pleasing appearance suggestive of a wall that is made entirely of stone.

One prior art method for securing a stone facade element to a concrete wall is by attaching metal wire to the facade element and to a metallic lug projecting outwardly from the wall. Over the course of time, the wire and lugs are subject to corrosion, causing some facade elements to become disengaged from the wall and to injure passers by.

GB 2075568 discloses a construction element such as a tile which is to be secured to a substrate using a layer of adhesive such as cement. The construction element is formed with a re-entrant formation such as a dovetail groove to allow the adhesive to penetrate into the re-entrant formation and to improve the bonding and retention of the element. This method is time consuming as the construction elements have to be held in place until the adhesive sets. Also, the thermal expansion coefficient of the tiles and the adhesive is different, producing a force that is liable to cause the tile to become disengaged from the substrate.

US 1,041,389 discloses a concrete wall construction having an inner and outer facing formed by bricks that constitute a form, into which concrete is poured. The bricks of both facings are provided on their rear sides with dovetail shaped recesses into which the poured concrete flows to form integrals keys, securing the core and facings together. This construction method by which a plurality of brick courses have to be laid for each facing is also time consuming, and is not suitable for the construction of prefabricated walls to be transported to a construction site.

It is an object of the present invention to provide a speedy method for securing facade elements to a concrete prefabricated wall.

It is an additional object of the present invention to provide a facade element that is assured of remaining secured to the wall despite large changes in temperature.

It is an additional object of the present invention to provide a facade element that provides a decorative appearance.

Other objects and advantages of the invention will become apparent as the description proceeds.

Summary of the Invention Some prior art stone facade elements have a tendency over time to become disengaged from a wall and injure passers by. In this invention, the facade elements are formed integrally with a prefabricated load bearing concrete wall. Each facade element is formed with a dovetail shaped groove and placed in abutting relation with adjacent elements within a form. After being poured, the concrete enters the dovetail shaped grooves to provide excellent bonding with the facade elements. Even if the concrete ceases to bond with the facade elements, the latter are prevented from falling by virtue of the dovetail formation, by which a mechanical engagement is retained between the concrete wall and the facade elements.

The present invention provides a method for securing a plurality of facade elements to a concrete wall, comprising the steps of positioning a plurality of dovetail -grooved facade elements having an inner surface and an outer surface within a wide-opening, horizontally disposed form such that each of said dovetail grooves faces the interior of said form and the form element outer surface is substantially in contact with a form surface, and pouring concrete within said form to a predetermined height above the facade elements so that the poured concrete enters each of said dovetail grooves to bond with said plurality of facade elements.

In one aspect, the method further comprises the steps of providing a block in which are formed one or more pairs of opposing and symmetrical dovetail grooves to define a corresponding number of common cavities, applying a water repelling agent to outer surfaces of said block, cutting said block along a line coinciding with a common interface of said one or more pairs of symmetrical grooves whereby to divide said block into two portions, and positioning said two portions within the form such that the dovetail grooves face the interior of the form. The two portions may be further cut to form facade elements of desired dimensions.

The present invention is also directed to a facade element integrable with a concrete wall, comprising an inner surface, an outer surface, and one or more dovetail grooves arranged such that the width of a groove opening is less than the width of a key forming region by which a groove surface recessed from said inner surface is bondable with concrete poured into a form, wherein said facade element is artificial and is made of concrete substantially resembling natural stone.

In one aspect, the facade element comprises a composition of 30-40% pure calcium carbonate sand, 5-50% basalt stone, 30-60% granite stone, 10-25% cement, 0.25-3% additives for preventing the formation of spherical bodies, and 0.2-10% paint.

Brief Description of the Drawings In the drawings: - Fig. 1 is a perspective view of an exemplary facade element, according to one embodiment of the invention; - Fig. 2 are other perspective views of the facade element of Fig. 1; - Fig. 3 is a plan view of the facade element of Fig. 1; - Figs. 4-6 are a plan view of three other dovetail formations, respectively; - Fig. 7 is a perspective view of an empty and separable horizontally disposed wide-opening form in which a plurality of dovetail-grooved facade elements and concrete to be bonded with the facade elements are introducible; - Fig. 8 is a perspective view of a horizontally disposed wide-opening form in which are positioned a plurality of facade elements; - Fig. 9 is a perspective view of a mesh of reinforcement elements to be inserted within the form of Fig. 8 and above the plurality of facade elements; - Fig. 10 is a vertical cross sectional view of a portion of a wall being set in a horizontally disposed wide-opening form; - Fig. 11 is a flow chart illustrating a method for forming a concrete facade element; - Fig. 12 is a perspective view of a block in which are formed two pairs of opposing and symmetrical dovetail grooves; and ■ Fig. 13 is a perspective view of vertically disposed exterior and interior forms in which a plurality of dovetail-grooved facade elements and concrete to be bonded with the facade elements are introducible.

Detailed Description of Preferred Embodiments The present invention is a novel method for integrally forming facade elements with a concrete prefabricated load bearing wall by placing in substantially abutting relation a plurality of grooved facade elements within a horizontally disposed form and pouring concrete into the form. After being quickly and easily poured, the concrete enters the grooves to bond with the facade elements.

Fig. 1 illustrates a perspective view of an exemplary facade element 10 made of stone or a material resembling stone, according to one embodiment of the invention. Facade element 10 is of rectilinear shape, with mutually parallel outer 3 and inner 5 surfaces, which are perpendicular to side surfaces 7, to upper surface 8, and to bottom surface 9, the directions referring to the relative position of the facade element walls when the fully constructed wall is vertically disposed. Two identical grooves 11 and 12 longitudinally extending from upper surface 8 to bottom surface 9 are formed in facade element 10. The bonding force between the concrete and facade element 10 is dependent on the quality of the poured concrete and on the spacing between adjacent grooves. Other perspective views of facade element 10 are shown in Fig. 2. Alternatively, outer surface 3 may be configured in other desired fashions, to provide a personally selected decorative appearance.

As further shown in Fig. 3, each of grooves 11 and 12 of facade element 10 is formed with a dovetail formation. As referred to herein, a "dovetail formation" means that the width of the groove opening, through which poured concrete flows before bonding with the facade element, is less than the maximum width of the groove to define a key forming region. Thus the maximum width W of grooves 11 and 12 is greater than the width 0 of the groove opening at inner surface 5. This dovetail formation is defined by two concave surfaces 16 extending from the two lateral ends, respectively, of recessed wall 14 of the groove to a corresponding pointed interface 17 at facade element inner surface 5. Concave surfaces 16 are configured such that maximum groove width W is greater than both the width of recessed wall 14 and width 0 of the groove opening. The width of recessed wall 14 may be 0. The thickness T of facade element 10 from outer surface 3 to recessed wall 14 is greater than, e.g. approximately 1.75 times as thick as, depth D of grooves 11 and 12.

Other dovetail formations are illustrated in Figs. 4-6. By virtue of the dovetail arrangement, and particularly the key forming region thereof by which a mechanical engagement is retained between the concrete wall and the facade elements, a facade element is prevented from falling even if the concrete ceases to bond with the facade elements.

In the dovetail formation of facade element 20 shown in Fig, 4, the width of recessed wall 14 is substantially equal to the maximum groove width W. A neck region 24 leading to a thin key forming region 22 has opposed convex surfaces 26 which extend from a corresponding inner wall interface 17 to a corresponding arcuate surface 25 of key forming region 22.

In the dovetail formation of facade element 30 shown in Fig, 5, the width of planar recessed wall 14 is also substantially equal to the maximum groove width W. Neck region 34 leading to key forming region 32 has substantially parallel side walls 36 that are substantially perpendicular to the planar facade element inner wall 5. Key forming region 32 has two substantially parallel side walls 38 and two inner surfaces 39, each of the latter being substantially perpendicular to corresponding side walls 36 and 38.

The dovetail formation of facade element 40 shown in Fig, 6 is triangular such that two oblique walls 44 extend from recessed wall 14 having maximum groove width W to a corresponding inner wall interface 17 to define groove 46.

Fig. 7 illustrates a horizontally disposed form 50 having a wide-area opening 51, through which concrete and a plurality of facade elements 10 are introducible. Form 50 comprises a bottom surface 56 on top of which a plurality of facade elements can be placed, end walls 52 and side walls 54. The length of bottom surface 56 is preferably substantially equal to the height of one floor of a building to be constructed, and the width of walls 52 and 54 is substantially equal to the thickness of the wall to be constructed. Adjacent end walls 52 and side walls 54 are separable from each other by means of one or more detachable elements 53 to enable a completely fabricated wall to be removed from form 50 and to be transported to a construction site. Even though end walls 52 and side walls 54 are separable from each other, form 50 is sufficiently sturdy to resist bending when the facade elements are mounted thereto and when concrete is poured within its interior.

Fig. 8 illustrates the placement of a plurality of facade elements 10 in a horizontally disposed wide-opening form 50. The plurality of facade elements 10 are placed in abutting relation with each other, whether in mutual alignment or in an offset formation, while that the grooves face upwardly so as to be exposed to the poured cement. A water repelling agent may be applied to each facade element 10 before being placed within form 50. Alternatively or in addition, a sealing element may be applied along the gaps between adjacent facade elements.

A mesh 55 of metallic reinforcement elements 49 and 57 shown in Fig. 9, which is preferably prefabricated such that each pair of reinforcement elements 49 and 57 is arranged in a mutually perpendicular disposition, may be placed within the form and on top of the plurality of facade elements before the concrete is poured. A plurality of concrete or polymeric spacers 59 may be interposed between the reinforcement elements and the facade elements, in order to prevent damage to the facade elements and to separate the reinforcement elements from the inner surface of the facade elements, thereby reducing the risk of reinforcement element corrosion when wall 60 is attached to a building.

After concrete is quickly and effortlessly poured throughout the wide-opening form and above the plurality of facade elements, without having to carefully pour the concrete into the narrow interspace between two vertically disposed forms as has been practiced heretofore in prior art methods, the concrete enters the grooves to bond with the facade elements. Since the form is horizontally disposed, the height of mesh 55 is less than height of the form sidewalls. Due to the relatively small change in height of the discharged concrete, from slightly above the form to the form bottom surface, the reinforcement elements will therefore not become damaged when impacted by the poured concrete The concrete is poured to a predetermined height above the facade elements, which may correspond to the thickness of the wall to be constructed. The facade elements are therefore integrated with a reinforced concrete wall without having to be attached to metallic lugs, which have a tendency of corroding and causing disengagement of the facade elements.

If so desired, the wall may be integrated with a ceiling section.

Fig. 10 illustrates a vertical cross sectional view of a portion of a wall 60 being set in the form.

In order to prevent the passage of the poured concrete 61 via one or more gaps 64 between adjacent facade elements 10A and 10B to a void area 67 unintentionally formed between the facade elements and form bottom surface 56, metal wires 69 are used to bring outer surface 3 of the facade elements in abutting relation with form bottom surface 56. A plurality of metal wires 69 are wrapped about a reinforcement element 57 and passed through a corresponding gap 64 between adjacent facade elements, which is aligned with an aperture 58 bored in form bottom surface 56. Alternatively, a metal wire 69 is passed through an aperture formed in the facade element, which is to be suitably occluded before the concrete is poured. After a downwardly directed force is applied to reinforcement element 57, such as by means of the plurality of metal wires 69, and the force is transmitted to reinforcement element 49, underlying spacer 59, and facade element 10A, outer surface 3 of the facade elements is brought in abutting relation with form bottom surface 56 so as essentially eliminate void area 67. The ends 71 of metal wire 69 are then wrapped about metal bar 73 attached to, or integral with, the form and tied or intertwined together, in order to retain the facade elements in abutting relation with form bottom surface 56. Thus outer surface 3 of the facade elements will remain essentially free of concrete. A sealing element 79 may be applied along each gap 64 between adjacent facade elements. Ends 71 are cut after the concrete has been poured and has set.

The load bearing and facade retention performance of a prefabricated wall 60 employing a plurality of integrated dovetail-grooved facade elements is greatly dependent on the quality of the concrete poured into the form. The use of high quality concrete will reduce the formation of cracks in the wall and will be better sealed, as well as improving its flowability into the dovetail grooves 11 and its adhesiveness with the facade elements.

The main factors that influence the quality of the concrete for the purposes of the present invention are its density and compressive strength. High density concrete to be poured into the wide-area form may be achieved when its sedimentation is at least 6". A superplasticizer may be used to ensure such a sedimentation level. A high compressive strength may be achieved when the concrete has a low cement content as the compressive strength is dependent on the cement content and porosity. In order to reduce shrinkage and the resulting strain and crack formation, the concrete to be poured has a low water content and a low water/cement ratio.

After the constituents of the concrete are selected and mixed in order to achieve high quality concrete, the concrete is guided, e.g. by a chute, to the interior of the wide-opening form. As the form is horizontally disposed and of a wide opening, the concrete need not be introduced into a localized region of the form by means of a hose, but rather may be advantageously uniformly and quickly discharged over the large area of the wide-opening form. Thus the concrete may be evenly spread into the wide-opening form by being sprayed or by other means such as a screw spreader well known to those skilled in the art for discharging the concrete to a uniform height.

The high quality concrete needs to be vibrated after being discharged into the form not only to remove the entrapped air while increasing its compressive strength, but also to maximize influx of the concrete into the entire volume of the dovetail grooves. Good concrete particle consolidation for increasing concrete flowability within the dovetail grooves and for sealing purposes occurs at a vibration frequency of approximately 12,000 vibrations per minute. Vibrator 82 for generating such high frequency vibrations may be attached externally to form bottom surface 56 as shown or to any other selected surface of the form, or alternatively, may be an internal vibrator such that a plurality of spaced vibrating heads, each of which having a diameter of at least 35 mm and spaced e.g. at a spacing of approximately 30 cm.

Before concrete 61 is fully set, a panel comprising a thermal insulation layer 76, e.g. made of polyurethane or expanded polystyrene, and a plaster layer 77 may be combined with the upper surface of the concrete. The panel may be combined with the upper surface of the concrete by inserting metallic elements within thermal insulation layer 76. A completely fabricated wall may be removed from the form and transported, e.g. by means of a crane, to a construction site and connected to a building by means well known to those skilled in the art.

In one embodiment, the facade element of the present invention is artificial and made of concrete which resembles natural stone. As the facade element is made from concrete, the concrete may be poured in a selected mold so as to produce a desired shape, size, or surface characteristics Although the facade element resembles natural stone, its concrete composition is significantly less permeable than natural stone.

Natural stone has high water permeability, resulting in a relatively high level of water that is absorbed in the stone, so that the oxygen partially dissolved in the absorbed water is in constant contact with the ferrous reinforcement elements and with the ferrous lugs connecting stone facade elements and the concrete wall. The reinforcement element and lugs therefore corrode due to oxidation reduction, so that over the course of time the prior art facade elements made of natural stone are liable to become disengaged from the wall and injure passers by.

In contrast, high quality concrete has low permeability and resists water ingress. The high quality concrete from which the facade elements are made may be identical to the concrete poured in the form. The low-permeable and alkaline facade elements of the present invention therefore prevent the formation of corrosion, particularly by virtue of the dovetail-grooves which are integrated with a concrete wall without use of ferrous lugs. As added safeguards, a water repelling agent is applied to the facade elements, and the facade elements are sufficiently thick, e.g. 4 cm, to isolate precipitation that may impinge their outer surface from the reinforcement elements.

An added advantage of the use of a concrete facade element is that the thermal expansion coefficient of the facade element is substantially equal to that of the concrete wall with which it is integrated, to prevent the generation of a resulting force which would cause the separation of the facade element from the wall. By virtue of the substantially equal thermal expansion coefficient of the facade element and of the concrete wall with which it is integrated, there is no need to form a gap between the facade elements and the concrete wall as has been practiced heretofore in prior art methods to reduce stress, thereby saving valuable construction costs and time. Tests conducted by the applicant have demonstrated that the bonding force between the high quality poured concrete and each concrete based, dovetail-grooved facade element of the present invention is approximately 10 tons, a value much greater than the bonding force with respect to a natural stone facade element.

The following is an exemplary composition of a concrete facade element to be imparted with the appearance of natural stone, as well as with alkaline, low permeability, and concrete wall thermal expansion coefficient matching characteristics: 1. pure calcium carbonate sand: 30-40%; 2. basalt stone: 5-50%; 3. granite stone: 30-60%; 4. white/grey cement: 10-25%; . additives, e.g. for preventing the formation of spherical bodies: 0.25-3%; and 6. paint: 0.2-10%.

The size distribution of the stone particles ranges from 0.8-1.2 mm. The compressive strength of the facade element is dependent on the type of aggregate used, hardness of the aggregate, and the cement content. The appearance of the facade element is influenced by the average aggregate particle size and the amount of paint used.

The various steps for forming a concrete facade element are illustrated in Fig. 11. Firstly, each of the various constituents of the concrete including water, cement, aggregate, additives, and paint, is weighed and separately stored in a corresponding compartment. The various constituents are then mixed together in step 91, e.g. by means of a concrete mixer housed on a truck or in. any other desired configuration, to form a paste. The paste is then poured in step 93 into a mold defining a facade element having one or more dovetail groove formations which are spaced from each other by a selected dimension, after which the mold is vibrated in step 95, e.g. at a vibration of approximately 12,000 VPM, and transferred to a curing station in step 97, whereat the cementitious mixture hardens within a relatively short period of time and is imparted with a relative high compressive strength. The hardened mixture is removed from the curing station and is subjected in step 99 to an evaporating station so that any water remaining in the mixture will be removed. The various surfaces of the product are smoothened in step 101 at a polishing station, which may comprise a plurality of polishing heads, for one or more cycles until achieving a desired reflectivity. In step 103, a water repelling agent is applied to the product. The product is then cut in step 105 to produce a facade element of desired dimensions. Each facade element is then packaged in step 107 if not placed in a form in step 109 as shown in Fig. 8.

Concrete is preferably bonded with a facade element only after the facade element has sufficiently hardened and 14 days have elapsed after the concrete was poured in step 93. Nevertheless, the facade elements to be bonded with the concrete within the horizontally disposed form are preferably not overly hardened, i.e. less than 30 days have elapsed after the concrete was poured in step 93, to provide good thermal expansion coefficient matching with the concrete wall so that separation of the facade elements from the wall will be avoided.

Fig. 12 illustrates another embodiment of the invention wherein a block 110 is used for the construction of two facade elements. In order to prevent damage to an interface at a facade element inner surface during storage or handling of a facade element, e.g. to pointed interface 17 shown in Fig. 3, two opposing dovetail grooves 11A and 11B that face in opposite directions to define a common cavity 112 are formed in block 110. Likewise other common cavities such as common cavity 113 defined by opposing dovetail grooves 12A and 12B may be formed in block 110. Each interface 117 is protected by the external surfaces of block 110, e.g. surfaces 118-123, and will therefore not be damaged during storage and handling of the block. When block 110 is made of stone, cavities 112 and 113 may be formed by any means well known to those skilled in the art such as by drilling, laser radiation, sandblasting, chemical reactions, and manual means. When block 110 is molded, the mold will* be suitably formed to define cavities 112 and 113.

Prior to use of a facade element, block 110 is cut along line 115, which coincides with each interface 117 and divides block upper surface 119 into two portions, and in a plane parallel to outer surface 118. Thus two identical facade elements 126 and 127 will be produced from block 110. A water repelling agent applied to external surfaces 118-123 of block 110 will provide sufficient water repellent protection to facade elements 126 and 127 even though their inner surface, which is formed only after cutting of the block, has not been applied with the water repelling agent since the inner surface contacts the concrete wall and will not be exposed to precipitation impinging the facade element.

In another embodiment of the invention as shown in Fig. 13, a wall may be constructed by mounting a plurality of dovetail-grooved facade elements 10 on a vertically disposed exterior form 130 by means of corresponding releasable anchor elements 132. Form 130, which comprises a plurality of wall sections 133-135 arranged such that two adjacent wall sections are perpendicular to each other, extends and is connected to a prefabricated ceiling section 131 An interior form 138 of similar configuration as exterior form 130 is spaced therefrom and also connected to ceiling section 131. A plurality of telescopingly expandable support members 142 are attached to the exterior form 130 or to the interior form 138. After concrete in poured within the interspace between exterior form 130 and interior form 138, the resulting wall structure will become integrated with the plurality of facade elements 10 and with ceiling section 131. Reinforcement elements may be positioned between exterior form 130 and interior form 138, and a conduit of rectangular cross section through which mixed concrete is discharged may be placed between adjacent reinforcement elements so as not to be damaged when the concrete is introduced.

While some embodiments of the invention have been described by way of illustration, it will be apparent that the invention can be carried out with many modifications, variations and adaptations, and with the use of numerous equivalents or alternative solutions that are within the scope of persons skilled in the art, without departing from the spirit of the invention or exceeding the scope of the claims. 27143/10 206814/2

Claims (31)

1. A method for securing a plurality of facade elements to a concrete wall, comprising the steps of: a) providing a plurality of dovetail-grooved, artificial facade elements made of concrete resembling natural stone, each of said facade elements having an inner surface, an outer surface, an upper surface and a bottom surface, wherein each of the dovetail grooves extends from said upper surface to said bottom surface; b) positioning each of said facade elements within a wide-opening, horizontally disposed form such that each of said dovetail grooves faces the interior of said form and the facade element outer surface is substantially in contact with a form surface; and c) pouring concrete within said form to a predetermined height above the facade elements so that the poured concrete enters each of said dovetail grooves to bond with said plurality of facade elements.

2. The method according to claim 1, wherein the facade element outer surface is substantially in contact with the form bottom surface.

3. The method according to claim 1, wherein each of the dovetail grooves has a formation arranged such that the width of a groove opening is less than the width of a key forming region by which a wall of the groove recessed from the inner surface is bonded with the poured concrete.

4. The method according to claim 3, wherein the poured concrete enters substantially the entire volume of the key forming region. 27143/10 206814/2 - 17 -

5. The method according to claim 1, wherein the plurality of facade elements are positioned within the form such that adjacent facade elements are in abutting relation with each other.

6. The method according to claim 2, wherein a mesh of metallic reinforcement elements is placed within the form and on top of the plurality of facade elements before the concrete is poured.

7. The method according to claim 6, wherein a plurality of spacers are interposed between the reinforcement elements and the facade elements, in order to separate the reinforcement elements from the inner surface of the facade elements.

8. The method according to claim 7, wherein the spacers are concrete or polymeric spacers.

9. The method according to claim 8, wherein each of a plurality of metal wires is wrapped about a reinforcement element and passed through a corresponding occludable aperture bored in the form bottom surface, a force is applied to the mesh of reinforcement elements whereby the outer surface of the facade elements is brought in abutting relation with the form bottom surface so as to essentially eliminate a void area between a facade element and the form bottom surface, ends of the metal wire are wrapped about a metal bar attached to, or integral with, the form, and the metal wire ends are tied or intertwined together before the concrete is poured.

10. The method according to claim 9, wherein the metal wire ends are detached from the metal bar after the concrete is poured and sets. 27143/10 206814/2 18

11. The method according to claim 9, wherein each of the metal wires is passed through a corresponding gap between adjacent facade elements which is aligned with the occludable aperture bored in the form bottom surface.

12. The method according to claim 9, wherein each of the metal wires is passed through an occludable aperture formed in the facade element which is aligned with the occludable aperture bored in the form bottom surface.

13. The method according to claim 1, wherein a sealing element is applied along gaps between adjacent facade elements.

14. The method according to claim 1, wherein a water repelling agent is applied to each facade element before being positioned within the form.

15. The method according to claim 1, wherein high quality concrete is poured within the form.

16. The method according to claim 15, wherein the concrete is vibrated at a vibration frequency of approximately 12,000 vibrations per minute after being poured within the form.

17. The method according to claim 15, wherein a panel comprising a thermal insulation layer and a plaster layer is combined with an upper surface of the concrete after being cured.

18. The method according to claim 1, wherein the thermal expansion coefficient of the facade element is substantially equal to the thermal expansion coefficient of the concrete poured into the form. 27143/10 206814/2 19

19. The method according to claim 18, wherein the bonding force between the concrete poured into the form and each artificial facade element is approximately 10 tons.

20. The method according to claim 1, wherein the facade element comprises a composition of 30-40% pure calcium carbonate sand, 5-50% basalt stone, 30-60% granite stone, 10-25% cement, 0.25-3% additives for preventing the formation of spherical bodies, and 0.2- 10% paint.

21. The method according to claim 20, wherein the facade element is molded and is positioned with the form between 14 and 30 days after having been molded.

22. The method according to claim 14, further comprising the steps of providing a block in which are formed one or more pairs of opposing and symmetrical dovetail grooves to define a corresponding number of common cavities, applying the water repelling agent to outer surfaces of said block, cutting said block along a line coinciding with a common interface of said one or more pairs of symmetrical grooves whereby to divide said block into two portions, and positioning said two portions within the form such that the dovetail grooves face the interior of the form.

23. The method according to claim 22, wherein the two portions are further cut to form facade elements of desired dimensions.

24. The method according to claim 1, wherein the concrete is substantially uniformly discharged throughout the area of the wide-opening form.

25. The method according to claim 1, further comprising the steps of separating adjacent end walls and side walls of the form from each other by 27143/10 206814/2 20 means of one or more detachable elements, removing a completely fabricated wall from the form, and transporting said fabricated wall to a construction site to be connected to a building mesh of metallic reinforcement elements.

26. A facade element integrable with a concrete wall, comprising inner, outer, upper, and bottom surfaces, and is configured with one or more dovetail grooves arranged such that they extend from said upper surface to said bottom surface and that the width of a groove opening is less than the width of a key forming region by which a groove surface recessed from said inner surface is bondable with concrete poured into a form, wherein said facade element is artificial and is made of concrete substantially resembling natural stone.

27. The facade element according to claim 26, which comprises a composition of 30-40% pure calcium carbonate sand, 5-50% basalt stone, 30-60% granite stone, 10-25% cement, 0.25-3% additives for preventing the formation of spherical bodies, and 0.2- 10% paint.

28. The facade element according to claim 26, wherein the one or more dovetail grooves are substantially vertically oriented.

29. The facade element according to claim 26, which is of a rectilinear configuration having a thickness of greater than 3.5 cm.

30. The facade element according to claim 29, which has a thickness ranging from 4 to 5 cm.

31. The facade element according to claim 26, which is applied with a water repelling agent.