AU2008100775A4 - Method of building construction - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION INNOVATION

PATENT

Invention Title: Method of building construction The following statement is a full description of this invention, including the best method of performing it known to me/us: 00 0 FIELD OF THE INVENTION 0This invention relates to a method of constructing buildings. In particular, the

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tbinvention is directed to improved methods of constructing walls and ceilings using Z autoclaved aerated concrete to achieve higher fire ratings and other advantages.

5 t The invention also relates to buildings constructed by such methods.

tfl BACKGROUND ART [Mere reference to background art herein should not be construed as an admission that such art constitutes common general knowledge in relation to the invention.] 00 10 A commonly used method of constructing a wall of a building is to use masonry blocks. However, there are several disadvantages of using concrete blocks, namely the standard concrete blocks are heavy; the masonry block walls require skilled labour to construct; and the fire rating of the resultant wall is not particularly high.

The heavy weight of the concrete blocks imposes significant load requirements for the transport of the blocks to the worksite and the storage of the blocks in work areas within the building. Once on site, the laying of the blocks can only be done by strong and fit block layers. Block layers rarely lay blocks for their whole working life because of the problems of back strain.

Lightweight AAC blocks are known, with the most common type being sold under the trade mark Hebel®. The lighter blocks reduce the physical strain imposed on block layers, and assist in reducing the risk of injuries of laying blockwork. However, AAC blocks are structurally weak. For this reason, AAC blocks are normally used only for non load bearing walls.

Moreover, AAC blocks are formed as solid blocks during the autoclaving process.

If such walls are to carry services, a trades person is required to drill or cut out rebates in the wall to carry required services (electrical wires, plumbing pipes etc). Thereafter, the holes or groves are required to be filled with render or other cementitious material. This adds cost to the finished wall.

If AAC blocks are to used for load bearing walls, steel reinforcing must be added.

This requires that vertical through holes to be post formed in the blocks, which is typically achieved by drilling narrow bores. This is very tedious and time consuming, particularly if there is a large number of blocks to be drilled. To provide the requisite tensile strength to AAC blockwork, steel bars are threaded through the aligned bores in 00 0 the AAC blockwork after the blocks have been laid. This can be difficult and time 0 I consuming, as the drilled narrow bores are difficult to align and/or feed reinforcing bars tor services through.

Another problem with inserting steel reinforcing bars into bored out AAC s blockwork is that the steel bars cannot be satisfactorily covered by concrete.

Consequently, parts of the bars are liable to rust after exposure to moisture. If the bars rust, the structural strength of the wall would be affected and the walls could fail. This is a difficult problem to control on site and requires close supervision of the laying of the blockwork.

00 O 10 There are also some known 'forming' blockwork systems which are currently available in Australia. These systems generally use various rigid foams to create a form into which concrete slurry is poured. One such system which creates a form out of foam is known as the 'Zego' system. This system uses various forms which are not the standard concrete or AAC block size. The majority of these 'forming' blockwork systems use expanded polystyrene as the rigid foam. Some have fire retardants in the foam.

These systems suffer from the common problem that the foams are flammable, and/or generate noxious fumes when burnt, and therefore fail to meet rigid fire rating requirements. These systems can be permitted for use in construction if the forming material is covered or contains a fire retardant. Regardless of how the forming material is covered or 'retarded' however, the foams generally used are not inert and could be considered a potential hazard under fire conditions.

Roofs, eaves and ceilings are particularly vulnerable to fires as they are usually made largely of wood, plaster or other material with a low fire rating. Although there are fire rated ceiling systems available, these are generally designed to prevent fires from penetrating the roof space from the inside of the building. The known systems are not particularly effective in preventing fire penetration from the outside the building.

It is an aim of this invention to provide a method of building construction which overcomes or ameliorates one or more of the disadvantages or problems described above, or which at least provides a useful alternative.

SUMMARY OF THE INVENTION In one broad form, the present invention provides an aerated concrete block, preferably formed in an autoclave, having at least one large bore extending transversely 00 0 through it. The direction of the bore is such that when the block is placed in its normal working orientation, the bore extends generally vertically.

SThe term "large" is intended to mean that the cross-sectional dimensions of the bore are large relative to the width of the block, and typically at least 25% of the width, and more preferably approximately half the width of the block.

Preferably, the block has a similar shape to a standard concrete block.

Preferably, the bore is formed during the autoclave manufacturing process by using a mould. Alternatively, the bore may be post formed by cutting.

In the preferred embodiment, the aerated concrete block has two large bores 00 to through it, as in a standard concrete block. Reinforcing can be inserted easily through aligned or overlapping bores in several courses of the aerated concrete blocks, and the bores then filled, to enable a strong wall with high fire rating to be achieved with lightweight blocks. Services can also be run easily through other bores in the blocks.

In another broad form, the present invention provides a method of constructing a wall comprising the steps of: providing a plurality of aerated concrete blocks as described above, placing the blocks in a plurality of vertically stacked courses, placing reinforcing elements through aligned bores in the blocks in a plurality of courses; and inserting cementitous material into the aligned bores containing the reinforcing elements.

The masonry wall system of this invention is lighter and stronger than standard AAC blockwork, can be constructed easily, and has improved fire rating when compared to normal concrete blockwork masonry.

The present invention also provides a method of constructing a roof structure comprising the steps of: providing a plurality of aerated concrete ceiling panels; and supporting the aerated concrete ceiling panels in an elevated position, with the panels being juxtaposed to form a substantially contiguous layer.

In another form, the invention resides in a roof structure comprising: an elevated support structure, and a plurality of aerated concrete ceiling panels mounted on the support structure, the panels being juxtaposed to form a substantially contiguous layer.

00 O Preferably, the panels are rectangular with their opposite edges being of I complementary cross-section. In use, the complementary edges of adjacent panels are tarranged in an abutting interlocking arrangement so that the panels form a substantially continuous layer. The roof structure is therefore comprised essentially of a layer of s lightweight aerated concrete which provides both high fire resistance and structural reinforcement.

Preferably, the layer of aerated concrete panels spans between the aerated Sconcrete block walls described above, so that it forms a solid fireproof barrier which prevents fires penetrating the inside of a building from the outside. It also prevent fires 00 10 from spreading to the outside of a building from the inside.

The invention provides a practical and economical method of achieving a high fire rating for a roof. This is particularly useful where the building is a bushfire prone area.

The aerated concrete layer also provides high thermal insulation.

Typically, roofing material is fixed to the upper side of the layer of aerated concrete ceiling panels, e.g. metal sheeting may be screwed to battens fixed directly onto the aerated concrete ceiling panels.

In order that the invention may be more readily understood and put into practice, one or more embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is sectional perspective view of part of a building constructed in accordance with one embodiment of the invention.

Fig. 2 is perspective view of an AAC block suitable for use in the construction of Fig. 1.

Fig. 3 is perspective view of another embodiment of an AAC block suitable for use in the construction of Fig. 1.

Fig. 4 is sectional end elevation of part of the building of Fig. 1.

Fig. 5 is an enlarged view of part of the building of Fig. 4.

Fig. 6 is a sectional perspective view of the building of Fig. 1.

Fig. 7 is sectional perspective view of part of the building of Fig. 6.

00 6 0 DESCRIPTION OF PREFERRED EMBODIMENT(S) N Figs I to 7 illustrate part of a building comprising a roof structure 10 supported 1 on walls 20. The walls 20 are formed from blocks 21, 22 as shown in Figs 2 and 3, respectively.

The blocks 21, 22 are aerated concrete blocks, preferably formed in an autoclave.

They may be formed using a process similar to that used to manufacture Hebel blocks.

The blocks 21, 22 are provided with hollow cores or bores 23, 24, respectively. The bores 23, 24 are preferably of a large size, and the blocks 21, 22 have similar shapes to standard concrete blocks. Typically, two or three bores are provided in each block.

00 1to The bores 23, 24 may be formed in the blocks during the manufacturing process N by using a mould to create the bores in the block (similar to the standard concrete blockwork) Alternatively, the bores 23, 24 can be post formed by cutting into the blocks 21, 22 after the blocks have been cured The former avoids the wastage associated with the 'off cuts' of the latter, but the 'off cuts' could be reused.

Various core patterns can be used, but preferably the blocks 21,22 have shapes similar to those of conventional concrete block.

In use, the blocks 21,22 are laid in vertically stacked courses in a conventional manner. Reinforcing rods 25 are inserted vertically through aligned bores in blocks in the multiple courses. If horizontal reinforcing rods are to be used, blocks 22 are used for the courses in which such horizontal reinforcing rods 26 are to be inserted. The blocks 22 have cut-outs forming a channel profile to accommodate the horizontal reinforcing rods 26, as shown in Fig. 3.

The cored blockwork acts as a form, and (at least) the bores containing the reinforcing bars are filled with mixed 'wet' (pre mixed concrete slurry) concrete.

When the concrete slurry has cured (especially when reinforced with steel reinforcement), the wall strength increases dramatically. After the cores are cured, the structural strength of the wall is basically determined by the poured and reinforced concrete cores and not the blocks which act as the form. The reinforced cores give the wall tensile strength which stacked blockwork lacks.

The above described method has several advantages over the prior art, including: S The cored aerated blocks are much lighter than conventional concrete blocks, and even lighter than standard solid AAC blocks, and therefore much easier to carry and quicker to lay.

00 The cored aerated blocks use material which is inert and does not burn, and C would not pose a potential hazard under fire conditions. The resultant tconstruction would have a better fire rating than concrete blocks 0 The cored aerated blocks can also be used in other applications for which 'Foam Formed' concrete formwork systems would likely not be permitted.

9 The cored aerated blocks permit easier installation of services than concrete blockwork, as they are easier to cut and drill.

0 The problem of rusting steel reinforcing bars is avoided as the bars can be 0covered in concrete.

00 There is also disclosed herein a method of constructing a roof or ceiling structure I formed from autoclaved aerated concrete ceiling panels.

As shown in the drawings, a plurality of panels 11 are supported on steel joists or rafters 12 in an elevated position. The panels 11 are elongate rectangular panels, which are arranged transversely to the rafters 12, with adjacent panels contiguous or abutting.

The ceiling panels 11 preferably are provided with a "tongue and groove" configuration on their edges so that they may engage or interlock with each other as shown in Figs 1, and 7. The panels 11 effectively form a continuous layer of aerated concrete. The panels can be fixed in place on the rafters 11 by screws 16.

Roofing material 14, such as metal sheeting or other suitable cladding, may be placed on the layer of ceiling panels 11 by being screwed or otherwise fixed to metal roof battens fixed to the panels 11. The battens may be easily screwed or otherwise fastened to the panels. Insulation 15 may be inserted between the panels 11 and roof cladding 14 if required.

The above described ceiling system and its method of construction have several advantages, including: The aerated concrete ceiling serves as a fire resisting barrier or building 'envelope', providing protection from fires both within and outside the building.

The aerated concrete ceiling can be formed on a incline (to suit an inclined roof) of horizontally.

The aerated concrete ceiling provides structural reinforcement.

The aerated concrete ceiling provides thermal insulation.

It is to be understood that the terminology employed above is for the purpose of description and should not be regarded as limiting.

00 8 The foregoing embodiments are intended to be illustrative of the invention, Swithout limiting the scope thereof. The invention is capable of being practised with tbvarious modifications and additions as will readily occur to those skilled in the art.

Accordingly, it is to be understood that the scope of the invention is not to be limited to the exact construction and operation described and illustrated, but only by the following claims which are intended, where the applicable law permits, to include all suitable modifications and equivalents within the spirit and concept of the invention.

Throughout this specification, including the claims, where the context permits, the term "comprise" and variants thereof such as "comprises" or "comprising" are to be oO 00 10 interpreted as including the stated integer or integers without necessarily excluding any other integers.

Claims (4)

1. An aerated concrete building block having at least one large bore extending transversely through it.

2. An aerated concrete block as claimed in claim 1, wherein the block is formed in an autoclave and the bore is mould formed in the block during its manufacture.

3. A method of constructing a wall using a plurality of aerated concrete blocks as 00 0claimed in claim 1 or 2, comprising the steps of: placing the blocks in a plurality of vertically stacked courses, placing reinforcing elements through aligned bores in the blocks in a plurality of courses; and inserting cementitous material into the aligned bores containing the reinforcing elements.

4. A method of constructing a roof structure comprising the steps of: providing a plurality of aerated concrete ceiling panels; and supporting the aerated concrete ceiling panels in an elevated position, with the panels being juxtaposed to form a substantially contiguous layer, and optionally fixing roofing material to the upper side of the layer of aerated concrete ceiling panels. A roof structure comprising: an elevated support structure, a plurality of aerated concrete ceiling panels mounted on the support structure, the panels being juxtaposed to form a substantially contiguous layer, and optionally roofing material fixed to the upper side of the layer of aerated concrete ceiling panels.