WO2010067334A2

WO2010067334A2 - Building components and method of manufacturing the same

Info

Publication number: WO2010067334A2
Application number: PCT/IB2009/055692
Authority: WO
Inventors: Michael Windson Symons
Original assignee: Anglo Operations Limited
Priority date: 2008-12-11
Filing date: 2009-12-11
Publication date: 2010-06-17
Also published as: AP3731A; WO2010067334A3; AP2011005797A0; ZA201105090B

Abstract

This invention relates to a building component and more particularly, but not exclusively, to a building component suitable for use in an energy efficient building system. The invention furthermore extends to a method of manufacturing the building component(s). The method includes the steps of providing a peripheral frame comprising a plurality of frame members defining a cavity therebetween, and thereafter introducing a cementitious foam into the cavity. The foam is then allowed to cure in order to form a solid core that engages the peripheral frame members so as to form a unitary building component.

Description

BUILDING COMPONENTS AND METHOD OF MANUFACTURING THE

SAME

BACKGROUND OF THE INVENTION

THIS invention relates to a building component and more particularly, but not exclusively, to a building component suitable for use in an energy efficient building system. In addition, this invention also relates to a building structure comprising a plurality of novel building components. The invention furthermore extends to a method of manufacturing the building component(s).

The need to conserve energy has resulted in dramatic changes in emphasis in building construction. The timber frame construction typical of the United States, Australia, New Zealand and certain other countries is much more energy efficient than the brick and mortar or cast concrete approach more typical of Western Europe, and there is therefore a continuous demand for improved building components derived from the panel type design methodology.

Brick and mortar construction has a high specific heat and is therefore generally not regarded as energy efficient. It absorbs heat energy from the environment and re-emits it into the interior during hot weather conditions, whilst also absorbing heat during winter. In addition, it requires the use of a large volume of cement which is also energy inefficient. Modem demands increasingly require housing to be logistically efficient i.e. must have lightweight components, must be energy efficient, must preferably not rely on conventional building skills, must be quick to assemble, must have a good appearance, and must be cost effective, but at the same time must still meet the necessary standards in terms of fire resistance, water resistance, impact resistance, good thermal insulation, appropriate acoustic properties, and it must also preferably lend itself to modularisation and thus to flexible planning.

Various configurations of panel type designs are already known in the art. A first type of panel structure comprises siding applied over sheathing to form an outer wall, an internal liner of gypsum wall board forming an inner wall, with a core of fibre glass or rock wool insulation provided between the inner and outer wall. This configuration is particularly popular in North America. In Australia the use of a brick veneer as siding or facing is common, wherein a single layer of brick defines the external face of the wall. Due to increasing pressure on the supply of wood of appropriate quality, steel frame designs are rapidly developing as a substitute to wooden frame designs. The steel frame designs generally include galvanised steel sections of a gauge typically of 0.6mm to 0.8mm.

In existing panel type designs, thermal insulation is traditionally chosen from reflective foils, plastic bubble wraps, organic fibre blankets chosen from PET, polypropylene or acrylic fibres, inorganic loose fill, inorganic fibres chosen from rock wool or fibre glass, or organic foams chosen from polyurethane, expanded polystyrene or phenolic foams.

Aluminum powder blown and other inorganic foams are also popular in Australasia and Western Europe. However, inorganic foams do not have sufficient compressive strengths to be load bearing and must be used in combination with a structural frame system. In these types of frame systems, the frame is typically secured to the panel after the panel has been formed, and therefore reinforces the panel, but is not integrally formed with the panel. Also, additional cross-bracing is often required to provide sufficient stability and flexural strength. It is accordingly an object of the invention to provide a building component, and a method of manufacturing such building component, that will, at least partially, alleviate the above disadvantages.

It is also an object of the invention to provide a building component that will be a useful alternative to existing building components.

It is a still further object of the invention to provide a structure comprising a plurality of assembled building components, as well as a kit for constructing such a structure, which will at least partially alleviate the disadvantages associated with the existing technology, whilst at the same time also providing a useful alternative to the existing technology.

SUMMARY OF THE INVENTION

According to the invention there is provided a method of manufacturing a building component, the method including the steps of: providing a peripheral frame comprising a plurality of frame members defining a cavity therebetween; introducing a cementitious foam into the cavity; and allowing the foam to cure to form a solid core that engages the peripheral frame members so as to form a unitary building component.

The step of providing a peripheral frame may include joining the frame members in end-to-end configuration so as to form a continuous frame, and positioning the assembled frame on a horizontal surface over a release sheet so as to define a receptacle for receiving the cementitious foam between the inner surfaces of the frames and the release sheet. The release sheet may be selected form the group including close cell polyethylene foam, a Teflon coated fabric, or thin sheets of 1 to 2mm thickness selected from PVC, acrylic, ABS, polypropylene or polyethylene.

The frame members may be made from wood or metal.

Preferably, each frame member is in the form of a metal channel having inwardly protruding flanges or lips extending from upper edges of the channel, the lips encapsulating the cementitious foam at the peripheral contact zone around the periphery of the frame, as well as on both sides of the cross bracing, so as to secure the core and the frame member relative to one another.

There is provided for the cementitious foam to include at least a hydraulic binder material and a foaming agent.

The hydraulic binder material may be selected from the group including Portland cement, mortar, plaster, gypsum or a combination thereof.

The foaming agent is preferably in the form of a pre-generated polyvinyl alcohol aqueous foam generated from partially hydrolysed grades in the molecular weight range 100 000 to 160 000 with a degree of hydrolysis in the range 87% to 92% % used at a concentration in water of from 2% to 10% by mass, the foam added to the slurry by total wet mass in the range 5 to 15%.

There is also provided for the foam to be selected from the group including proteinous foams generated and blended with a slurry such as those from hydrolysed ox blood; foams generated from a dilute alkali silicate solution with surfactants; foams generated internally by the generation of hydrogen bubbles in the slurry by a reaction between aluminum powder of small particle size with added lime or alternatively with lime present in the Portland cement; and foams generated by carbon dioxide released by reaction of an acid with a carbonate or bicarbonate.

There is still further provided for the cementitious foam to be in the form of syntactic foam in which lightweight particles have been blended with the hydraulic binder. The lightweight particles may be in the form of expanded polystyrene beads, expanded and surface hydrophobised seeds,. such as corn or rice, milled rigid polyurethane, exfoliated vermiculite or expanded perlite.

The method may also include the step of applying a surface liner on either or both side surfaces of the cured core.

The surface liner may be in the form of a layer of gypsum based plaster, and/or a layer of a Portland cement composition.

The method may optionally also include the step of applying a reinforcement layer onto either or both the side surfaces of the cured core prior to applying the surface liner.

The reinforcement layer is preferably in the form of a mesh. The mesh may be steel wire mesh, or may be a fibre glass mesh.

The method may include the further step of providing an insulating strip on one side of each frame member.

The insulating strip is preferably in the form of a polystyrene, or other polymer foam, strip that is bonded to a side surface of the frame member.

More preferably the polystyrene is closed cell extruded polystyrene foam. According to a further aspect of the invention there is provided a building component including: a peripheral frame comprising a plurality of frame members defining a cavity therebetween; and a core made of cured cementitious foam; the core engaging the peripheral frame members so as to form a unitary building component.

There is also provided for the building component to include any or all of a reinforcement layer, surface liner and insulating strip as described above.

According to a still further aspect of the invention there is provided a building component manufactured in accordance with the method described above.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention is described by way of a non- limiting example, and with reference to the accompanying drawings in which:

Figure 1 is a perspective view of a peripheral frame with cross- bracing for use in the method in accordance with the invention;

Figure 2 is a perspective view of a reinforcement mesh for use in the method in accordance with the invention;

Figure 3 is a perspective view of a number of building components of different configurations secured to another so as to form part of a structure; Figure 4 is a further perspective view of a number of building components in accordance with the invention secured to another so as to form part of a structure, the components being shown in different phases of completion;

Figure 5 is a partially cut-away perspective view of a building component in accordance with the invention utilizing a wooden frame;

Figure 6 is a schematic representation of the heat transfer characteristics a building component without an insulating strip; and

Figure 7 is a cross-sectional view of part of two adjacent building components including insulating strips.

DETAILED DESCRIPTION OF INVENTION

Referring to the drawings, in which like numerals indicate like features, a non-limiting example of building component in accordance with the invention is generally indicated by reference numeral 10. Each building component 10 includes a peripheral frame 20 comprising a plurality of frame members 22 that are secured to one another in end to end configuration so as to define a cavity therebetween. The cavity is then filled with cementitious foam 30, which engages the frame 20 so as to the render the building component rigid and structurally sound. A reinforcement layer 40, in the form of a metal of fibre glass mesh, may be provided on a surface of the cementitious foam core 30, and a surface liner or liner 50 of a suitable material is applied to the reinforcement layer 40, alternatively directly onto a surface of the core 30. The frame member 20 shown in Figure 1 and 7 are in the form of metal channels 22 having inwardly protruding flanges or lips 23 extending from upper edges of the channel 22, the lips being encapsulated by the cementitious foam 30 during the manufacturing process so as to secure the core and the frame member relative to one another, as is best seen in Figure 7. Alternatively, as is shown in Figure 5, the frame 20 may be made of wood, but the metal frame is the preferred option.

When manufacturing a building component 10, the peripheral frame 20 is formed by joining a plurality of frame members 22 in end-to-end configuration so as to form a continuous frame, and positioning the assembled frame on a horizontal surface over a release sheet (not shown) so as to define a receptacle or cavity 30 for receiving the cementitious foam between the inner surfaces of the frame sections 22 and the release sheet (not shown). The release sheet is typically selected from the group including close cell polyethylene foam, a Teflon coated fabric, or thin sheets of 1 to 2mm thickness selected from PVC, acrylic, ABS, polypropylene or polyethylene. The cementitious foam is now pumped into the cavity, and allowed to cure so as to form a solid core 30 that engages the peripheral frame members, and more particularly the lip formations 23 extending therefrom, so as to form a unitary building component 10. A reinforcement layer 40 in the form of a metal or fibre glass mesh is, if required, now applied to the surface of the core 30, followed by a suitable surface liner 50, which is preferably in the form of gypsum based plaster, and/or a layer of a Portland cement composition.

Even though the required structural strength is provided by the peripheral frame of the building component, the use of a reinforcement layer in the form of a mesh sheet will still be beneficial. The reinforcement layer will, inter alia, prevent surface cracking, strengthen the plaster due to the plaster bonding to the foam core via the mesh apertures or adhesively, and will furthermore distribute the impact of an external force so as to improve the impact resistance of the building component. The philosophy behind the design configuration of building components 10 is that they are produced in a factory in a module preferably of 600mm with or multiples of 600mm, each component being the full height of a wall i.e. 2.4m to 2.7m or whatever length is required for roofing members. Alternatively, complete wall, roof, or slab sections can be manufactured and completed and shipped as such.

In the case of steel framing, the frame sections 22 are between 0.4mm to 0.8mm gauge, and are configured in a lip or open channel section which is typically 90 mm to 120 mm in width. The frame sections 22 are galvanized and joined to each other by riveting or screwing with similar section cross bracing at suitable centres for walls and a channel section typically 30 mm to 50 mm of 0.25 to 0.50 gauge with similar cross bracing, for ceiling panels.

The cementitious foam comprises at least a hydraulic binder material and a foaming agent. The hydraulic binder material is selected from the group including Portland cement, mortar, plaster, gypsum or a combination thereof.

The foaming agent is chosen from those generated by a polyvinyl alcohol of a partially hydrolyzed specification with a molecular weight between 100 000 and 160 000 and a degree of hydrolysis in the range 85% to 92.5% and generated in a sparge unit with compressed air as claimed in patent application number PCT/ZA2005/00111 ; alternatively the foam may be in the form of cement foams that are generated by aluminum powder reacting with calcium hydroxide to blow the cementitious matrix by the release of hydrogen within the slurry.

Hydraulic gypsum and cement, once set, have very little tensile strength and are usually reinforced with suitable facing materials which improve the resistance to tensile and flexural loads. However, in this case the frame members contribute the necessary compressive support, beam strength and flexural strength to the building component or panel. In return, the cementitious foam and the frame in essence form a monolithic structure, and the cementitious foam acts as bracing for the frame. It is important to note that the frame members are not secured to the cementitious foam panel after the panel has been manufactured, but that the frame members are actually secured to the cementitious core during the manufacturing process.

The choice of a cementitious foam core, as opposed to a polymeric foam core, is important in order to achieve the objectives of this invention, and is not merely an arbitrarily chosen design variation. Some of the advantages of selecting a cementitious core over a polymeric foam core include: Improved fire resistance;

- Superior acoustic qualities due to higher density;

- Better thermal properties;

- Higher structural strength - especially taking into the account the monolithic, unitary nature of the building component;

- Less prone to thermal expansion; and

- Smaller carbon footprint.

The hydraulic binder slurry is mixed in a paddle or pan (or any other appropriate mixer) and discharged into a hopper that feeds a rotor stator pump. The slurry is pumped into a dynamic mixer which is sealed and is effectively a high shear pin mixer. The foam is generated in a sparge unit by pumping the polyvinyl alcohol solution into the sparge unit comprising a cylinder filled with thin strands or micro perforated steel discs. Compressed air is pumped into the sparge unit, the pressure being exactly balanced with that of the polymer solution. A micro bubble foam is produced in this way which continues under pressure into the dynamic mixer. The foam and the slurry are now thoroughly blended in the dynamic mixer, and the foamed hydraulic binder is pumped into the cavity of the panels as described. Where aluminum blown foams are used, the aluminum is dispersed in water or a polymer solution and pumped directly into the dynamic mixer. The slurry likewise is pumped into the dynamic mixer and the foaming hydraulic binder is then pumped into the cavity of the panels. Polyvinyl alcohol is a useful constituent in this composition as well, because foam stability and bubble size are both improved.

Syntactic foams are those that contain lightweight particles to assist in reaching lower dry densities, to maintain foam stability during pouring or pumping and which, at a given density, concentrate the hydraulic binder foam around the syntactic particles improving cohesive strength. Examples of syntactic particles are expanded polystyrene beads - virgin or recycled, expanded perlite, exfoliated vermiculite expanded seeds such as surface hydrophobised expanded corn or rice or lightweight plant cores such as those from the Kenaf plant or particles of closed cell phenolic or polyurethane foam. The preferred syntactic particle is expanded polystyrene regrind, which is added to the slurry at a rate of between 0.5 and 2.5% by dry mass on the mass of the hydraulic binder, more preferably between 0.75 and 1.5%. It is foreseen that syntactic foam may be utilized in this invention, although it is not necessarily a preferred embodiment.

The surface liners 50 applied onto the reinforcement layer 40, alternatively directly onto the cementitious foam core 30, is preferably in the form of hydraulic binder plasters. For exterior surfaces Portland cement, preferably of 42.5 mPa specification or higher, is used. Interior surfaces are preferably plastered with a gypsum hemihydrate, such as Alfamould or Escayola by BPB. Alternatively, one can also use gypsum produced from water desalination plants or flue gas desulphurization, reinforced with an acrylic fibre such as Dolanit, of lengths 6mm to 12mm or surface modified polypropylene or fluorinated polypropylene used at a level of between 0.1% and 0.4% by mass on the cement or gypsum of 6 d-tex diameter and having as many as 500 000 fibres per gram. During assembly of various building components 10, as seen in Figures 3 and 4, a floor runner 12 and top wall plate 14 engage with bottom 22.1 and top 22.2 cross rails of the peripheral frames 20, while vertical sides 22.3 of each component 10 engage with opposing sides 22.3 of juxtaposed components, ensuring perfect assembly alignment in both directions.

As mentioned above, each component 10 will include a steel (Figure 1 or 7) or wood (Figure 5) peripheral frame 20. Adjacent frames are preferably joined to one another with a solventless waterproof adhesive, preferably a diphenylmethane, diisocyanate (MDI) terminated pre-polymer. This is packed in pressure pots and subjected to compressed air to extrude the adhesive for rapid application in the form of a bead of between 6mm and 15mm diameter. The adhesive is applied to the outer face of the frame and the adjacent component is then pushed against it, so that the adhesive spreads between the two faces forming a very strong flexible waterproof seal by which method the components are joined together more reliably and with greater strength than would be the case with mechanical fixing. An example of such an adhesive is Duthane 623 from Industrial Urethanes, South Africa. The adhesive can withstand temperatures up to 120⁰C without loss of property, has a viscosity of between 9 000 and 11 00OmPa has a free NCO content percentage of 15 - 17, contains no volatiles, has a specific gravity in the range 1.1 to 1.2 and the setting time is between 45 minutes and 120 minutes. An alternative is a two pack epoxy that can be mechanically applied. Alternatively panels are joined by sheet metal cleats or secure to floor runners and wall plates by screws.

In the case of demountable buildings, a steel runner 12 is mechanically secured to the concrete base, or alternatively support posts 16 are secured in the ground with concrete and the steel runner secured thereto. The panels are now assembled in the runner 12 in or on the floor and are secured to an appropriate channel section. In this case a compressible closed cell polymeric foam seal is used between the panels instead of adhesive securing, and panels are mechanically secured. Decorative fibre reinforced resin tiles or sheets may be applied onto the cementitious foam core 30, or onto the surface liner 50 on the core 30, so as to provide an aesthetically pleasing surface finish. The decorative tiles or sheets are manufactured in silicone rubber moulds. In particular, polyester resin is suitably filled and accelerated, catalysed and applied preferably by a spray followed by a fibre such as glass from a chopper gun, which is rapidly polymerised by the use of infrared emitters. Dimensional stability is achieved by an appropriate back-fill.

Where a timber frame is adopted, as shown in Figure 5, the sections would be of a grade 5 or better, plain or round and impregnated with a boron wax solution, giving resistance to termite and microbial attack as well as preventing water ingress from the foam. Typical sizes would be 38 x 114mm in cross section and 2550mm long or alternatively 38 x 76mm in cross section. A major application for a light easily handled frame of this kind is for interior walling of conventional building to replace brick work. Gypsum has outstanding behaviour in fire and wood is easily and conveniently joined panel to panel with metal cleats and then over skimmed with a resin modified gypsum or cement plaster. In the case of wooden frames the reinforcing mesh 40 will be secured to the frame 20 by way of screws 45 or staples.

It will be appreciated that each building component 10 forming part of an erected building structure 15 will, in use, have a first outer surface that is exposed to the environment, and a second inner surface that is exposed to an internal volume of the building structure. Referring now to Figure 6, it will be appreciated that if there is a temperature differential between the outside and the inside, heat will be conducted through the building component, generally in the direction indicated by arrow A. However, due to the vastly different heat transfer coefficients, the rate of heat transfer through the cementitious core material (indicated by arrow B) will be substantially lower than the rate of heat transfer through the steel frame member 22 (indicated by arrow C). This will result in a temperature gradient (T2 - T1) along the inner surface, which may result in cracking of the inner surface liner due to thermal stresses developed therein.

This problem is alleviated by introducing the configuration shown in Figure 7. The configuration is similar to that which has been described before, but in this case an insulation element 60 is secured to the outer face of each frame member 22, and serves to thermally insulate the metal frame form the environment, this preventing the conductive heat transfer indicated by arrow C in Figure 6. The insulating element is in the form of an elongate strip made from closed cell extruded polystyrene, and is glued to the side of the frame member 22.

It will be appreciated that the above are only some embodiments of the invention, and that there may be many variations without departing from the spirit and/or the scope of the invention.

Claims

CLAIMS:

1. A method of manufacturing a building component, the method including the steps of: providing a peripheral frame that comprises a plurality of frame members defining a cavity therebetween; introducing a cementitious foam into the cavity; and allowing the foam to cure to form a solid core that engages the peripheral frame members so as to form a unitary building component.

2. The method of claim 1 wherein the step of providing the peripheral frame may include joining the frame members in end-to-end configuration so as to form a continuous frame, and positioning the assembled frame on a horizontal surface over a release sheet so as to define a receptacle for receiving the cementitious foam between the inner surfaces of the frames and the release sheet.

3. The method of claim 1 or claim 2 wherein the frame member is in the form of a metal channel having inwardly protruding flanges or lips extending from upper edges of the channel, the lips being encapsulated by the cementitious foam during the manufacturing process so as to secure the core and the frame member relative to one another.

4. The method of any one of the preceding claims wherein the cementitious foam to include at least a hydraulic binder material and a foaming agent.

5. The method of claim 4 wherein the cementitious foam is selected from the group including Portland cement, mortar, plaster, gypsum or a combination thereof.

6. The method of claim 4 wherein the foaming agent is in the form of a pre-generated polyvinyl alcohol aqueous foam.

7. The method of any one of the preceding claims including the step of applying a reinforcement layer onto either or both the side surfaces of the cured core.

8. The method of claim 7 wherein the reinforcement layer is in the form of a mesh that may be made of steel, fiberglass or fabric.

9. The method of any one of the preceding claims including the step of applying a surface liner on either or both side surfaces of the cured core.

10. The method of claim 9 wherein the surface liner is in the form of a layer of gypsum based plaster, and/or a layer of a Portland cement composition.

11. The method of any one of the preceding claims including the step of applying an insulating strip on at least one side of each frame member.

12. The method of claim 11 wherein the insulating strip is in the form of a polymeric foam strip that is bonded to a side surface of the frame member.

13. The method of claim 12 wherein the polymeric foam is closed cell extruded polystyrene foam.

14. A building component including: a solid core made of a cured cementitious material; and a peripheral frame comprising a plurality of frame members surrounding the core; the core encapsulating at least part of the peripheral frame members so as to form a unitary building component.

15. The building component of claim 14 in which the frame is in the form of a metal channel having inwardly protruding flanges or lips extending from upper edges of the channel, and wherein the core encapsulates at least part of the lip formations.

16. The building component of claim 14 or claim 15 including a reinforcement layer in the form of a mesh.

17. The building component of any one of claims 14 to 16 including a surface liner provided on an inner, outer, or inner and outer surfaces of the core.

18. The building component of claim 17 in which the surface liner is in the form of a layer of gypsum based plaster, and/or a layer of a Portland cement composition.

19. The building component of any one of claims 14 to 18 including an insulating strip on at least one side of each frame member.

20. The building component of claim 19 wherein the insulating strip is in the form of a polymeric foam strip that is bonded to a side surface of the frame member.