GB2525032A

GB2525032A - Prefabricated building element

Info

Publication number: GB2525032A
Application number: GB1406503.1A
Authority: GB
Inventors: Daniel Callaghan; Richard Benson; Paul O'neill; Andrew Corkery
Original assignee: UNDER PARDCO SYSTEMS Ltd
Current assignee: UNDER PARDCO SYSTEMS Ltd
Priority date: 2014-04-10
Filing date: 2014-04-10
Publication date: 2015-10-14
Also published as: GB201406503D0

Abstract

A prefabricated building element such as a panel, sill, lintel or quoin, comprises a shell 12 formed from a composite of plastics resin mixed with a poly-aramid fibre, such as Kevlar, and crushed marble. The shell is filled with an expanded foam insulation 14. The resin may be unsaturated polyester and may include a catalyst which causes the resin to set. The resin may also include a fire retardant such as alumina trihydrate. The foam may be polyurethane and may be injected into the shell via an aperture. The foam may be reinforced by steel, carbon fibre or engineered plastics. The crushed marble provides the building element with the appearance of stone and the para-aramid fibre provides increased strength, which would allow the panel to be substantially bullet proof.

Description

PREFABRICATED BUILDING ELEMENT

The invention relates to a prefabricated building element and particularly but not exclusively to a prefabricated building element having a high thermal insulation value and high strength for use in properties with an external insulation system applied.

BACKGROUND TO THE INVENTION

Solid wall buildings with no insulation are estimated to lose around 38% of their heat through the walls in winter. In the UK and other European states, governments are introducing targets to reduce the thermal loss from property, in order to try and reduce energy consumption and greenhouse gases created in energy generation.

It is now common practice to apply insulation materials, such as Expanded Polystyrene (EPS) provided in panels, to the exterior of a building in order to reduce thermal loss from the building. It is common to fix the panels to the building, sometimes with reinforcing, and then to apply render or brick/stone effect slip panels over the insulation to weatherproof it.

Typically, render is applied in layers, with the base layer being reinforced with a plastics mesh.

The problems in applying these systems arise at openings, such as windows and doors, where cold bridges can occur between the inner walls of the building and exterior, i.e. where there is no insulation. In this respect, the invention is directed to sills, but also has application in lintels, quoins, band-strips and cladding. Currently, the practice with sills, where there is an external insulation system, is to apply an oversill to an existing stone or concrete sill, to try and improve the thermal value of the sill. Such oversills are well known and an example is disclosed, for example, in GB 2500924 Al.

Oversills typically have very little strength, either in bending or compression. They are often manufactured using expanded polystyrene (EPS) and coated on one or two sides with a resin.

Examples currently on the market have styrene in the resin, which is acidic and tends to attack the EPS, leading to long term degradation of the EPS and a reduction in the thermal insulation provided by the oversill.

Sometimes oversills are manufactured with EPS insulation covered with a metal skin. This overcomes any problems of acid degradation of the insulation material, but reduces the insulation value of the oversill, because the metal skin is an effective heat conductor and goes some way to mitigating the thermal benefit of the oversill, i.e. the metal is a thermal bridge.

The metal skins are typically painted steel or aluminium extrusions, which are sharp to handle during installation. A complete sill may be manufactured from an open metal extrusion filled with foam insulation, as disclosed in US 2008282626 Al, but again the metal forms a thermal bridge. Also, metal is not an attractive material for most domestic buildings and tends to be used more in commercial and industrial applications.

On new build projects, sills also cause handling problems. In the UK, for example, a site worker is only allowed to lift up to 58kg without assistance. Cast stone, stone or concrete sills are often purchased to fit a particular aperture and may be long. This being the case, they often weigh well in excess of the 58kg limit and require two people or more to carry them to the position where they need to be built in. They also have little or no thermal insulation qualities and form cold bridges when installed, which must be covered with oversills to match the insulation values of external insulation systems. A 25mm strip of EPS may be bedded onto the bottom and inner faces of stone sills to provide some insulation, but it is generally inadequate for purpose. Similar problems apply to both lintels and quoins.

Another problem of stone, cast stone and concrete sills is that they can easily be damaged in storage or transit, on or off site, and repairs are often inadequate and unsightly. Stone is porous and is prone to water damage, particularly in frost conditions, overtime. There is also a significant turnaround time from order to delivery, which can delay a build, with consequent penalty costs.

There are also instances when a building, such as a public building, barracks, embassy or political building, may be vulnerable to attack from hostile forces or terrorists. Buildings constructed from conventional materials are not particularly resistant to ballistics and, as a consequence, there may be a need for any cladding to serve as a first defence against attack from guns and/or explosives. It is known, for example, that bullet-resistant fibreglass panels can be provided on the exterior of a building. These panels delaminate when hit by a bullet, causing the bullet to be "captured" without ricocheting or spalling. A disadvantage of such panels is that they need to be replaced once hit to maintain their effectiveness and this may not be possible in some hostile environments. Also, fibreglass panels fitted to a wall do not typically offer a significant increase in the insulation value of the wall.

Increasing the security of such buildings as described above to mitigate the risks posed by ballistics with a maintenance-free device is of particular importance to the military (amongst others), maintaining an ordinary outward appearance whilst significantly improving the protective capability of a building for personnel inside. Ideally, such a device would be able to effectively withstand multiple impacts, and significantly reduce the energies of any fragments produced from initial impacts. In order to easily retrofit existing structures with improved protection, it needs to be easy to install these shells to the exterior of any building without being prohibitively expensive to produce.

It is an object of the invention to provide an improved building element which substantially mitigates the aforementioned problems and which is for general use in the construction of new build structures, the renovation of existing structures and the protection of buildings.

STATEMENT OF INVENTION

According to the present invention, there is provided a prefabricated building element for use in cladding a building comprising a shell, the shell being made from a composite of plastics resin mixed with a polymerised para-aramid fibre and crushed marble; the shell being filled with an expanded plastics foam.

The building element of the invention is highly advantageous because it can take the appearance of stone due to the addition of crushed stone or marble with the resin. The building element is extremely strong, and is substantially bullet proof, due to the use of polymerised para-aramid fibre. It also has an extremely high U-value, since the whole body of the building element is filled with an insulation material.

The polymerised para-aramid fibre may comprise polymerised paraphenylene terephthalamide monomers. Polymerised para-aramid fibre, particularly polymerised paraphenylene terephthalamide monomers, is a reinforcing material exemplified, for example, by the trade material Kevlar (RTM), particularly Kevlar KM2, which may be provided as a yarn or woven fabric.

Different grades of, for example, Kevlar are available for use, with variations in fibre-weaving and chain length altering the properties of each type. In this regard, Kevlar KMZ has been designed to have improved ballistic fragmentation resistance and kinetic energy absorption capacity compared to other known forms of Kevlar, whilst still having very high strength and toughness.

The integral outer shell is formed in a silicone mould and has a very high strength to weight ratio, both in compression and bending. A 2m length weighs well under the 58kg lifting limit for a single site worker, and so is easy to handle.

The composite of plastics resin is preferably a polyester resin, more preferably composed of at least one orthophthalic polyester resin. Using a composite plastics resin is advantageous as it provides more flexibility to include a component with desirable structural properties alongside one with fire retardant properties, which may be possible but more difficult to achieve using a single polyester resin.

The orthophthalic polyester resin preferably includes a catalyst, causing the resin to set. The catalyst may be, for example, a methyl ethyl ketone peroxide, such as the commercially known Butanox M50. Unlike other resin composites, the resin described can withstand thermal shock, for example in ambient weather extremes. It is also impervious to water.

The orthophthalic polyester resin may contain a fire retardant component such as, for example, alumina trihydrate. This improves the fire resistance of polyester resins, suppressing smoke production and impeding burning, which are both advantageous features for materials used to construct buildings, particularly buildings under attack.

The outer shell may be at least 6mm in thickness. For example, the thickness of the outer shell could be 25mm in thickness or greater, depending on the degree of protection required. It has been found that a shell of at least 6mm thickness will resist a hammer blow with little or no marking and so is less vulnerable to damage on site and in transit. The shell is also substantially impervious to small arms gunfire.

At least one aperture may be provided in the shell for injecting the expanded plastics foam.

Ideally two apertures are provided and more apertures may be provided if the sill is very long, for example several metres. The foam is injected in metered shots or batches to minimise waste and to guarantee a perfect fill of the shell each time.

The aperture(s) may be provided through the upper surface of the building element.

Alternatively, the apertures may be positioned on a lower or rear surface, but should be in a position not exposed to weather, or to detract from the appearance of the building element.

The expanded plastics foam may be expanded polyurethane and may be composed of a liquid polyisocyanate (such as a diisocyanato diphenyl methane -for example: Cellanate M) and a polyol which is mixed in a nozzle on injection, generally known as a Rio Foam.

Advantageously, the expanded polyurethane has no VOC5, CFC5, HFC5 or urea. The density of the foam can be controlled to produce a required insulation value, as required.

Alternatively, the expanded plastics foam may be formed of one of the types known commercially as Envirofoam 16.381 or Enviromould MP7160.

Reinforcing may be disposed inside the shell, which may be of steel, carbon fibre or engineered plastics. Reinforcing may be advantageous where the building element is to be used as a lintel and significant loads are to be applied, as well as instances where the building element may be subject to highly energetic impacts.

The prefabricated building element may be formed as a window sill, for example, with an elongate recess provided along the lower surface of the shell for serving as a drip bead. A portion of the upper surface may be sloped downwardly towards one side of the sill in conventional manner to take water away from a building, when in situ.

Alternatively, the prefabricated building element may be a lintel, and may have a decorative element integrally formed in resin on a side surface of the lintel. Other alternatives are that the prefabricated building element may be a quoin or a panel. For building protection purposes, the building elements may take the form of panels, which interconnect or are intended to overlap one another, to provide a complete protective covering for the building.

BRIEF DFSCRIPTION OF THF DRAWINGS

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 shows a perspective view of a first embodiment of building element in the form of a sill; Figure 1A shows a cross section through the sill of Figure 1; Figure 2 shows a perspective view of an alternative embodiment of sill; Figure 2A shows a cross section through the sill of Figure 2; Figure 3 shows a perspective view of a third embodiment of building element in the form of a lintel; Figure 3A shows a cross section through the lintel of Figure 3; Figure 4 shows a perspective view of an alternative embodiment of lintel; and Figure 4A shows a cross section through the lintel of Figure 4.

DESCRIPTION OF PREFERRED EMBODIMENT(S)

Referring firstly to Figures 1 and 1A, a first embodiment of building element in the form of a sill is indicated generally at 10. The sill has an outer shell 12 and an expanded foam inner 14.

In the embodiment shown, the sill is a stooled sill, which is a well-known design shape of sill.

The outer shell 12 has an upper surface 16, a lower surface 18, a front surface 20, a rear surface 22 and first and second end surfaces 24, 26. A front area of the upper surface 16 is effectively cut away and slopes downwardly to allow water to run off in conventional manner.

A longitudinally extending groove or recess 28 is provided in the upper surface 16 of the sill to provide a key for mortar. Also, a longitudinally extending groove or recess 29 is provided on the lower surface 18 of the shell 12, providing a drip bead. Grooves of this nature are

conventional in the field.

The outer shell 12 is made from polyester resin in a silicone mould. The mould itself is made from catalysed liquid silicone with silicone thickener. Glass fibre and burlap is used to strengthen the mould as the layers of silicone are laid down, which add both elasticity and strength. The layers of silicone are brushed on evenly by hand and allowed to dry between coats.

The outer shell 12 is cast as a closed casting in a rotational casting machine. Resin, preferably a composite plastics resin and more preferably composed of at least one orthophthalic unsaturated polyester resin (such as the commercially known CRYSTIC 196 LV and CRYSTIC 302 resins), is mixed with a quantity of crushed marble, a polymerised para-aramid fibre for reinforcement and a catalyst of methyl ethyl ketone peroxide, where the polymerised para-aramid fibre reinforcement may be laid into the resin in mat form. The crushed marble may take the consistency of a powder, although crushed glass may also be added. The resin of the outer shell 12 is allowed to cure, initially at room temperature for around 24 hours, and is then heated to 60 degrees Celsius for around four hours. The heating accelerates the curing process, which at 15 degrees Celsius would take twenty eight days for an equivalent cure hardness. On removal from the silicone mould, the outer shell 12 has the appearance of a solid casting, but in fact is hollow. The curing and post-curing processes may differ somewhat from the above temperatures and timescales, depending on the proportion of Kevlar added.

The ideal wall thickness of the outer shell 12 has been found to be around 6mm. However, wall thicknesses of 6mm or greater are contemplated for different applications and subject to controlled testing.

Two small holes (not shown) are provided in the top of the outer shell 12, towards respective ends, on the upper surface 16 towards the rear surface 22. The expanded foam insulation 14 is injected through these holes simultaneouslyto fill the outer shell 12. The expanded plastics foam is expanded polyurethane and is prepared from a liquid polyisocyanate and a polyol which is mixed in the injection nozzle(s) on injection. It falls within the class of substances, generally known as a Bio Foams. Advantageously, the expanded polyurethane has no VOCs, CFCs, HFCs or urea. The density of the foam can be controlled to produce a required insulation value, as required. The foam has an r-value of 0.021. If the density of the foam is increased, the strength of the building element in both compression and bending can be improved. The foam has no food value for rodents or insects and is self-bonding. It is also envisaged that expanded plastics foam commercially known as Envirofoam 16.381 or Enviromould MP7160 A key factor in the choice of the resin and foam is that they must not react together and degenerate in any way, for example, the resin must not break down bonds in the foam causing it to effectively dissolve.

The building element may also be provided as a standard non-stooled sill, indicated at 30 in Figures 2 and 2A; a lintel as indicated at 40 in Figures 3 and 3A (also usable as a quoin) and a decorated lintel as indicated at 50 in Figures 4 and 4A. The decorated lintel 50 includes an integral keystone member 52 disposed on the front surface of the lintel. It will be appreciated that in view of the manufacturing process of the building element, decorative features can be added as desired, as long as they can be moulded effectively. It is also to be noted in Figures 3A and 4A, that reinforcing 44, 54 is set into the foam 14. The shell can be moulded around the reinforcing, which may be steel, carbon fibre or engineered plastics and the foam then injected around the reinforcing. High density polyurethane foam can also be reinforced with strands of fibreglass to make structurally reinforced foam. The reinforcement is generally required when the building element is used as a lintel. Alternatively, the foam may be reinforced with Kevlar, providing a structurally reinforced foam which has ballistics resistance properties suited for use in panels.

It will be appreciated that the building elements described are extremely strong, light to handle, do not have sharp edges, can withstand all weather conditions, have the appearance of stone and most importantly, can be used with or without external insulation systems to meet required insulation standards. By the use of plastics, cold bridges are entirely avoided.

Temperatures inside the structure are therefore less dependent on exterior conditions, remaining warmer in winter and cooler in summer than they might otherwise be, potentially contributing to a reduction of heating costs.

Importantly, incorporating Kevlar in either strand or mat form (particularly Kevlar KM2) into the shells provides added security to all personnel stationed in buildings at risk of attack, as the panels have increased resistance to ballistics over conventional structures. Panels, for example, could be bolted or bonded onto existing structures, making it easy to significantly improve the defensive properties of a building.

The embodiments described above are provided by way of example only, and various changes and modifications will be apparent to persons skilled in the art without departing from the scope of the present invention as defined by the appended claims.

Claims

CLAIMS1. A prefabricated building element for use in cladding a building comprising a shell, the shell being made from a composite of plastics resin mixed with a polymerised para-aramid fibre and crushed marble; the shell being filled with an expanded plastics foam.
2. A prefabricated building element as claimed in claim 1, in which the polymerised para-aramid fibre comprises polymerised paraphenylene terephthalamide monomers.
3. A prefabricated building element as claimed in claim 1 or claim 2, in which the composite of plastics resin comprises at least one orthophthalic unsaturated polyester resin.
4. A prefabricated building element as claimed in claim 3, in which the orthophthalic polyester resins include a catalyst, causing the resin to set.
5. A prefabricated building element as claimed in claim 3 or claim 4, in which the at least one orthophthalic polyester resin contains a fire retardant component.
6. A prefabricated building element as claimed in claim 5, in which the fire retardant is alumina trihydrate.
7. A prefabricated building element as claimed in claim 4, in which the catalyst is a methyl ethyl ketone peroxide.
8. A prefabricated building element as claimed in any preceding claim, in which the outer shell is at least 6mm in thickness.
9. A prefabricated building element as claimed in any one of claims 1 to 5, in which the outer shell is substantially 6mm in thickness. :ii
10. A prefabricated building element as claimed in any preceding claim, in which at least one aperture provided in the shell for injecting an expanded plastics foam.
11. A prefabricated building element as claimed in claim 8, in which two apertures are provided in the sill for injecting an expanded plastics foam.
12. A prefabricated building element as claimed in claim 9, in which the apertures are provided through the upper surface of the building element.
13. A prefabricated building element as claimed in any preceding claim, in which the expanded plastics foam is polyurethane.
14. A prefabricated building element as claimed in claim 13, in which the polyurethane is composed of a polyisocyanate and a polyol which is mixed in a nozzle on injection.
15. A prefabricated building element as claimed in claim 14, in which the polyisocyanate is a diisocyanato diphenyl methane.
16. A prefabricated building element as claimed in any preceding claim, in which reinforcing is disposed inside the shell.
17. A prefabricated building element as claimed in claim 16, in which the reinforcing is of steel, carbon fibre or engineered plastics.
18. A prefabricated building element as claimed in any preceding claim, in which the prefabricated building element is a window sill.
19. A prefabricated window sill as claimed in claim 16, in which an elongate recess is provided along the lower surface of the shell for serving as a drip bead.
20. A prefabricated window sill as claimed in claim 16 or claim 17, in which a portion of the upper surface is sloped downwardly towards one side thereof.
21. A prefabricated building element as claimed in any one of claims ito 15, in which the prefabricated building element is a lintel.
22. A prefabricated lintel as claimed in claim 19, in which a decorative element is integrally formed in resin on a side surface of the lintel.
23. A prefabricated building element as claimed in any one of claims ito 15, in which the prefabricated building element is a quoin.
24. A prefabricated building element as claimed in any one of claims ito 15, in which the prefabricated building element is a panel.
25. A cladding for a building comprising a plurality of prefabricated building elements as claimed in any preceding claim, the prefabricated building elements being directly connected together and overlapping.
26. A prefabricated building element substantially as described herein with reference to and as illustrated in Figures ito 4a of the accompanying drawings.