GB2197005A - Building element and method of manufacture - Google Patents

Abstract

A composite moulded or cast building element 30 comprises a precast core 26 and a stone or marble finish surface layer 28 which is cast or moulded thereto. The premoulded and precured core promotes rapid curing of the external surface layer. The moulding operation may be performed with the external material sandwiched between two core elements, followed by the step of cutting the assembly into two parts symmetrically through the band of surface finish material so as to produce two symmetrical building blocks. The blocks may be formed with a lip or shoulder portion 214 to enable the conventional narrow mortar gap 208 to be provided. The surface layer may be of insulating material and be attached to the precast core by adhesive rather than by being moulded thereto. <IMAGE>

Description

SPECIFICATION Building element and method of making same This invention relates to building elements and a method of making such elements. An example of the application of the invention is to the manufacture of building blocks for use in the construction of building walls. The invention is however applicable to other building elements including copings and the like.

More particularly, the invention concerns composite building elements comprising a core material forming an internal portion of the element, and a surface finish material providing the exterior of the element.

To the best of the Applicants' knowledge, previous techniques for manufacturing composite building elements have involved moulding the core material and the surface finish material in a substantially continuous or stepwise process, the surface finish material being moulded first, and the core material immediately thereafter.

This process is subject to important disadvantages. Firstly, there is the fact that it is slow and laborious. Especially in the case of non-rectangular building elements there is often a need to form the exterior or surface finish material into a shape suitable to receive the liquid core material for the subsequent core-moulding step. Such a process is labour intensive and therefore costly. Moreover, such a composite moulded element is relatively slow to cure. This in itself leads to prolonged occupation of moulding equipment with attendant cost implications. In an effort to reduce these problems it has been proposed to mould the exterior material in a relatively stiff and relatively dry condition. This in itself is inconvenient and laborious and overall the process tends to lead to inconsistent results.

In view of the foregoing it will be appreciated that there is a need for improvements in the methods of constructing composite building elements, and indeed in such elements themselves and it is an aim of the present invention to provide a method of making composite building elements, together with such building elements themselves offering improvements in relation to one or more of the matters discussed above, or generally.

According to the invention there is provided a method of making a composite building element comprising the steps of forming as a moulded or cast assembly a core material and an external material, characterised in that said core material is premoulded and said external material is moulded or cast thereto.

Preferably, the building element is in the form of a building block and said core material occupies the entire lower portion of the building element during moulding of said external material, and said external material occupies the remainder thereof.

The core material is preferably fully cured in its said pre-moulded condition, i.e. at least 28 days have elapsed since it itself was moulded, or if not, then 7 to 28 days have elapsed.

The building element may be formed in a mould defined by steel shuttering.

Said external material, or surface finish material may comprise a simulated natural or marble or stone composition.

Said external material may be surface finished by a cutting or grinding operation. Preferably, said external material comprises marble or stone as part of the mix used for moulding. The stone or marble may be in fine particulate form such as dust.

In a preferred embodiment, the building element is formed as a moulded assembly comprising said external material sandwiched between two pieces of said core material. After setting of the assembly, and preferably after curing for a period of up to 5 or 7 days, the sandwich assembly is cut into two portions, the cut being made through the external material so as to leave a layer of the latter adhering to both pieces of core material. Preferably, the moulded assembly is formed as a symmetrical sandwich and the severing operation is preformed exactly centrally so as to produce two substantially identical building elements.

The invention also provides a composite building element made by a method according to any of the steps defined above.

Another aspect of the invention also relates to building elements and to a method of making such elements. An example of the application of this aspect of the invention is to manufacture building blocks for use in the construction of building walls. The invention is particularly, but not exclusively, applicable to building blocks and building elements as described in detail below.

More particularly, the present invention is concerned with providing improved methods and improved products for the thermal insulation of buildings and like structures.

Presently available methods of thermally insulating buildings and the like suffer from the problems of being labour intensive and expensive. Such methods include techniques of cavity wall infilling and treatment of walls after building.

There is a need for an improved and simplified and less expensive method of providing buildings and the like with improved thermal insulation which can use presently available techniques and materials while achieving results which have hitherto not been achieved with such materials. An object of the present invention is to provide improvements in one or more of these respects, or generally.

According to this aspect of the present invention there is provided a method of making a building element comprising the steps of providing a preformed building element, applying adhesive to one face of the element, then applying a sheet of thermal insulation to the face carrying adhesive, and subsequently applying pressure to the sheet of thermal insulation material to cause same to be held by the adhesive.

Preferably, a plurality of building elements are arranged in a continuous sequence or series, such as a line, for the application of adhesive and the subsequent steps. The adhesive may be applied to said building elements successively in said series followed by application of said thermal insulation material in sheet form. The thermal insulation material may be in the form of aluminium foil or sheet.

The width of said sheet may be the same as the width of the building elements. The length of the sheet may be greater than the length of two of said elements and the sheet may be formed with perforations at intervals of the length of one element whereby successive portions of the sheet may be readily severed.

According to another aspect of the invention there is provided a building element made by a method according to any one or more of the steps defined above.

The invention also provides a method of building a thermally insulated wall or the like comprising fabricating the wall employing building elements as defined above. The method may comprise the steps of forming the wall with a cavity. Preferably, the thermal insulation material is provided on an inner surface of said wall, said inner surface forming one face defining the cavity. A further preferred feature comprises providing the thermal insulation material on both inner faces of the cavity wall, said inner faces defining the lateral width of the cavity between the wall portions.

The invention also provides a method of making a building element, a building element produced by such method, and structures built therewith offering any technical feature or advantage disclosed herein and comprising any novel structural feature or method step, or combination of such features or method steps disclosed in this application.

In a preferred embodiment of the invention, a building element is in the form of a composite rectangular building block. The core material is entirely separately moulded from the external surface finish material and forms a base or raw material for the manufacture of the building block, in a fully cured and dry condition.

The rectangular block of core material is assembled on a work table with flat plates of steel shuttering material to form a mould in which the core block forms the lower portion and the steel shuttering defines a rectangular upward continuation of the core block whereby when a liquid or semi-liquid composition of exterior surface finish material is poured into the mould formed by the steel shuttering, the composition sets and cures in a form such as to correspond in size exactly with the core block and thus to form a uniform and rectangular and composite block.

The external composition of the block sets and cures relatively rapidly. This is due in large measure to the presence of the solid, pre-set and fully cured block of core material.

This latter tends to extract water from the external material composition as the latter sets. Indeed, this self-drying action of the core material may require to be inhibited somewhat and it is preferred to thoroughly wet the block of core material with water prior to commencing the step of moulding the external material. The time taken for a block to set, as described above, is approximately one day and the block is fully cured in approximately one week. This is to be compared' with the period of approximately three to four weeks for a conventional concrete block.

A waterproofing composition may be incorporated in the mix of the external surface material. Such waterproofing compositions are commercially available and their selection and use will be known to those skilled in the art.

The external surface finish material may be formed with a moulded external surface, or the latter may be allowed to set generally flat and may then be manually finished by a semiskilled operative with a suitable chisel or the like to effect a simulated stone surface finish.

Such an operation can be performed relatively rapidly. For a conventionally-sized building block a time of only one minute per block would be needed.

In examples of the invention, it has been possible to mould 25 building blocks each of a size 18 inches by 9 inches by 4 inches on a work table of size 8 foot by 4 foot. (Metric equivalents of these dimensions are: block 45.72 centimetres by 22.86 centimetres by 10.16 centimetres; and table: 244 centimetres by 122 centimetres).

In one example, the composition of the external finish material comprises two portions of clipsham stone dust having a very fine particle size and one part of ancaster sand (fine particle size) and one part of "Snowcrete" cement obtainable from Messrs. Blue Circle. This composition provided a good sample of a clipsham type stone. For a portland stone effect, the above composition is varied by the addition of a quantity of portland cement to provide the more grey colouration of portland stone. Thus in these examples, the cement itself is employed as a colouring agent. In addition, oxidisers may be employed to provide particular colours. For example green, red, buff, or any other desired colour.

Many modifications may be made in the technique of the invention as described above and in the following example, these including wide variations in the constituents of the core material and the external composition and in the form of the building elements produced therefrom, whether building blocks or other building elements, whether rectangular, nonrectangular, curved, or any other shape. The nature of the mould employed for forming the building elements may be varied considerably.

If desired, it may be arranged that the external composition extends down the sides of the core material as well as covering the top thereof.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows a perspective view of a work table; Figure 2 shows a plan view of moulding apparatus set up on the table of Fig. 1; Figure 3 shows a section through the assembly of Fig. 2; Figure 4 shows a perspective view of a portion of a cast product from the apparatus of Figs. 1 to 3; Figure 5 shows a section through a building block incorporating an alternative surface finish comprising embedded flint material; and Figure 6 shows a plan view of the surface finish of Fig. 5.

As shown in Figs. 1, 2 and 3 a working table 10 has a table top 12 on which may be assembled moulding apparatus 14 provided with edge supports 16 in the form of angleiron sections. The moulding apparatus comprises steel shuttering 18 including lengthwise shuttering 20 and transverse shuttering 22 which together define rectangular oblong moulds 24.

Into the moulds 24 are inserted core blocks 26 which fit exactly therein. The steel shuttering is 100 millimetres deep and each mould is of length 215 millimetres. Naturally, these dimensions may be varied as necessary. In this embodiment, the core block is a Leca or concerete block obtainable from Messrs. ARC Concrete Limited and manufactured to British standard 6073 Parts 1 and 2 1981. The depth of the block is 75 millimetres. Its other dimensions are 215 millimetres and 440 millimetres. This leaves a depth of 25 millimetres for the surface finish material 28 which comprises two parts clipsham stone dust, one part ancaster sand and one part Snowcrete to which is added Cementone integral waterproofing liquid No. 2 and water sufficient to provide a workable mix. This composition is poured into the moulds up to the level indicated in Fig. 3.

Fig. 4 shows the resulting cast building block 30 with core 26 and surface finish layer 28. The latter is extremely strongly bonded and keyed to the core by the moulding operation described above and the assembly is resistent to extremes of weather conditions including sequential rain and freezing.

Figs. 5 and 6 show a further embodiment, otherwise constructed as described above, but in which the core 32 is surmounted by an exterior layer 34 in which are embedded knapped Norfolk flints 36. The latter are manually placed in the exterior composition after pouring same. Fig. 6 shows a typical surface finish which may be achieved in this way.

Other materials may be embedded in the exterior layer to achieve alternative visual results.

The stone finish of exterior layer 28 in Fig. 4 may be manually finished by use of a stone mason's drag or other cutting or abrasive means.

The advantage of using a pre-moulded and cured core material in the above embodiment lies in the fact that this greatly speeds up the process of setting and curing the composite building element. As a result, the product is in a condition for use only 7 days after casting whereas 28 days are required with conven- tional techniques of simultaneous casting of both materials.

Amongst other modifications which may be made in the embodiments described above is the following. It may be possible to achieve acceptable results by a technique in which the exterior material is placed in the mould first and the premoulded and cured core is then inserted into the mould on top of it. Possibly a degree of pressure may be needed to provide full keying engagement between the two constituents of the resulting composite block.

In this way, the exterior layer could be conveniently provided with a moulded surface finish at the bottom of the mould. Alternatively, a similar moulded finish for the exterior layer may be achievable by means of an mould member inserted into the top of the mould in the apparatus of Figs. 2 and 3.

Fig. 7 shows an isometric view of a composite building element forming an intermediate product in the manufacture of a finished building element in accordance with the invention.

As shown in the drawing, a composite building element 100 is formed by placing two blocks 102, 104 of core material in a rectangular assembly of steel shuttering on a production table as described in the preceding embodiments. The core elements are placed against.the side walls of the shuttering leaving a space therebetween. Into the space is poured a mix of the external material 106 containing marble dust.

The mix is brought up to the level of the top surfaces of the core elements and the assembly is allowed to set, after which the steel shuttering is removed and the sandwich block 100 thus produced is allowed to cure for up to 5 to 7 days. After that, the block is severed longitudinally in a plane lying within the central band 106 of cast material, preferably symmetrically, by a rotary diamond-tipped saw to produce two identical building elements each having a surface or external layer of the marble mix, securely adhered to its block of core material.

This embodiment provides a modification of the preceding embodiments by providing for surface finishing of the external material by means of a saw. Instead of removing a thin layer of the external material by means of the saw, a sandwich assembly is formed and the single sawing operation serves to surface-prepare two building elements without any waste.

The above embodiment has the advantage that it produces two identical building elements which are identicaly surface finished.

The surface finish is of a precision nature and is already effectively polished and may be further polished by suitable surface treatments.

In other embodiments, not described in detail, individually shaped blocks of core material and external material may be produced in any suitable shape with individual surface finishes produced by moulding or cutting or hand finishing.

In a further embodiment (not illustrated), a building element in the form of a building block as disclosed in the above embodiments provides the starting material for the manufacture of a thermally insulated block.

A series of such blocks is provided, for example at the end of the production line for the manufacture of such blocks. Each of these blocks, arranged in a line, is in sequence treated on one of its main two side faces with a uniform layer of an adhesive such as the adhesive currently available in the U.K. under the trade mark "Unibond" This adhesive is intended for securing porous materials to non-porous materials, and is suitable for the present application. It is believed that other adhesives may be equally suitable.

The adhesive is applied by means of a roller. Preferably the roller is provided with automatic dispensing means for the adhesive.

After application of adhesive to one face of each block, a sheet of thermal insulation material in the form of aluminium foil is applied to the adhesive-coated face. The width of the sheet is exactly that of the block. The length of the sheet is a multiple of the block lengths.

Perforations extend across the width of the sheet at intervals of one block length whereby the sheet can be readily severed at the end of each block. The aluminium sheet may be applied from a dispensing roller arranged directly above a production line carrying the blocks in sequence past the dispensing station. Equally, a travelling carriage carrying a roll of aluminium foil may travel lengthwise of a sequence of blocks for dispensing purposes.

After each block has received its sheet of thermal insulation foil and the latter has been severed, pressure is applied to the sheet to press it firmly into place and cause it to adhere to the block in a uniform manner. After the adhesive has set, the block is ready for use.

Blocks manufactured by the technique described above can be employed for building purposes in the conventional manner. Where the block to be thermally insulated is a block as produced in our prior G.B. patent applications, having one side face intended for external exposure, such as with a simulated stone finish, then obviously the thermal insulation material is applied to the opposite side face which will be on the inner side when a wall has been constructed. In this manner, a cavity wall may be constructed with the thermal insulation material on the inner side of the outer wall. Likewise, the inner wall of the pair defining a cavity, may likewise be constructed from building blocks thermally insulated in the manner described above.Such blocks may not necessarily be constructed in accordance with the principles of our prior G.B. patent application, but may be conventional building blocks.

Where both sides of a cavity in a cavity wall are treated in the above manner, the thermal insulation effect is substantial. It is not ruled out however that for certain applications it may be desirable to fill the cavity with suitable materials if an even higher level of thermal insulation is required.

As will now be apparent, the advantages provided by the above embodiments include the simplicity with which a thermally insulated wall can be constructed. By providing building elements which are already thermally insulated, a wall can be constructed in the conventional manner without any additional time or labour, nor indeed any additional materials.

So far as manufacturing cost of the original building blocks is concerned, the above-described technique of applying the thermal insulation material in the form of aluminium sheet is extremely cost effective. Previous proposals for the use of conventional thermal insulation materials have involved either cavity wall filling or application of sheets of material to prefabricated walls, or indeed treatment of such walls with suitable liquid compositions. None of these techniques have the simplicity and cost effectiveness of the above-described method in which aluminium sheet is applied to the building blocks during their original manufacture.

Modifications envisaged with respect to the above embodiment, include the use of alternative adhesive materials, alternative or slightly modified thermal insulation materials and automation of the process of application of the thermal insulation material to the building blocks.

In the embodiment of Fig. 8, a building element 200 is otherwise constructed as in the embodiment of Fig. 4, but is provided with a modified relationship for the surface finish material 202 relative to the core material 204 so that the mortar 206 between successive blocks in a wall provides the required conventional appearance, with only a 5 millimetre (approximately) visible band of mortar 208 on the front side 210 of the wall 212.

Fig. 8 shows a section through a portion of the wall 212 with the blocks 200, one above the other, and with the band of mortar 206 therebetween. As can be seen, the surface finish material 202 is provided with a portion 214 standing proud of the remainder of the block so that it can be assembly with a band of mortar 208 having a width of only approximately 5 millimetres, whereas the remainder of the band of mortar 206 can have the width of approximately 10 millimetres which is required, or at least is preferable, from purely structural considerations. By providing a portion of the block including at last the front portion of the surface finish material, which stands proud of the remainder, this embodiment enables the mortar to be provided with a narrower width at the visible front of the assembled wall, then rearwardly thereof.

For manufacturing purposes, the difference in width of the two prtions of the block can be achieved by means of suitable packing members inserted into the steel shuttering.

Conveniently, just the external material 202 stands proud of the remainder, but the shoulder portions 214 could include part of the core material, or less than the full depth of the surface material.

A further advantage of the embodiments described above is that the surface finish material can be constructed so as to have a longer life than conventional stone due to its mode of manufacture, and the materials thereof.

Claims (22)

1. A method of making a composite building element comprising the steps of forming as a moulded or cast assembly a core material and an external material, characterised in that said core material is pre-moulded and said external material is moulded or cast thereto.

2. A method according to claim 1 wherein the core material is fully cured prior to said moulding step.

3. A method according to claim 1 wherein said core material has been cured during a period of 7 to 28 days prior to said moulding step.

4. A method of making a composite building element comprising forming as a moulded or cast assembly a core material and an external material, characterised in that said moulded assembly comprises said external material sandwiched between two pieces or portions of said core material.

5. A method according to any one of claims 1 to 3 wherein said external material is sandwiched between two pieces or portions of said core material.

6. A method according to claim 4 or claim 5 characterised by the step of cutting said sandwiched assembly into two portions, the cut being made through said external material so as to leave a layer of the latter adhering to both pieces or portions of core material.

7. A method according to claim 6 characterised in that said moulded assembly is formed as a symmetrical sandwich and the severing operation is formed symmetrically so as to produce two substantially identical building elements.

8. A method according to any one of the preceding claims wherein at least a portion of said surface finish material is moulded or cast so as to stand proud of at least a portion of the remainder of said building element whereby, when asembled with other building elements, the layer of mortar therebetween can be of less width at the visible front portion of the wall formed thereby, than in a rearward portion thereof.

9. A method of making a building element comprising the steps of providing a preformed building element, applying adhesive to one face of the element, then applying a sheet of thermal insulation material to the face carrying adhesive, and subsequently applying pressure to the sheet of thermal insulation material to cause same to be held by the adhesive.

10. A method according to claim 9 wherein a plurality of building elements are arranged in a continuous sequence or series, such as a line, for the application of adhesive and the subsequent steps.

11. A method according to claim 10 wherein said adhesive is applied to said building elements successively in said series followed by application of said thermal insulation material in sheet form.

12. A method according to claim 11 wherein said thermal insulation material is in the form of aluminium foil or sheet.

13. A method according to any one of claims 10 to 12 wherein the width of said thermal insulation material is the same as the width of said building elements.

14. A method according to claim 13 wherein the length of said thermal insulation material is greater than the length of two of said building elements, and the sheet of thermal insulation material is formed with perforations at intervals of the length of one element, whereby successive portions of the sheet may be readily severed.

15. A building element made by a method according to any one of the preceding claims.

16. A method of building a thermally insulated wall or the like comprising fabricating the wall employing building elements according to any one of claims 9 to 14.

17. A method according to claim 16 comprising the step of forming said wall with a cavity.

18. A method according to claim 17 wherein said thermal insulation material is provided on an inner surface of said wall, said inner surface forming one face defining said cavity.

19. A method according to claim 17 or claim 1 8 comprising providing the thermal insulation material in both inner faces of said cavity wall, said inner faces defining the lateral width of the cavity between the wall portions.

20. A building element substantially as described herein with reference to the accompanying drawings.

21. A composite building element comprising a core portion and a portion of external surface material, characterised in that at least a portion of said external surface material is formed with a shoulder or lip standing proud of at least a portion of the remainder of the building element so that when assembled with an adjacent building element in a wall structure, a layer of mortar therebetween comprises a narrow portion at the front side of the wall, and a thicker portion located rearwardly thereof.

22. A building element according to claim 21 in the form of a building block or a tile.