WO2016081989A1

WO2016081989A1 - Method of constructing a concrete wall in a multi-storey building

Info

Publication number: WO2016081989A1
Application number: PCT/AU2015/000726
Authority: WO
Inventors: George Argyrou
Original assignee: Hickory Design Pty Ltd
Priority date: 2014-11-28
Filing date: 2015-11-27
Publication date: 2016-06-02
Also published as: AU2014268276A1; CN105986675A

Abstract

A method of constructing a concrete wall in a multi-storey building constructed of modular units, including: arranging and connecting modular building units so that a framed wall of one of the building units defines a framed wall of the concrete wall to be constructed; attaching formwork on at least one side of the framed wall; and applying wet concrete to the framed wall to form a solid concrete wall when the concrete dries.

Description

METHOD OF CONSTRUCTING A CONCRETE WALL IN A MULTI-STOREY BUILDING

FIELD

The present invention relates to a method of constructing a concrete wall in a multi-storey building, particularly in a building constructed of modular building units.

BACKGROUND

Standard construction methods for building high rise structures, namely structures having more than two or three stories, include first constructing a concrete shear core and/or concrete shear exterior walls that act as primary structural elements for the building and against which the columns and transverse beams of each floor level are tied or otherwise connected for support. The concrete core is usually located centrally of the building plan and is used to carry and protect many building services including lifts, electricity, gas and water conduits, etc. Concrete shear walls generally flank the building perimeter on one or more exterior sides of the building, depending on the building design. A disadvantage in the construction of conventional concrete cores in building is that the concrete core takes a longer time to construct than each floor. For example, it typically takes one week to erect a concrete core per floor, while the remaining construction of one floor, including forming or erecting reinforced concrete surfaces to make the floors and walls only takes about one to two days. The concrete core is therefore erected first up to a certain height before the construction of each floor begins, and the floor construction will soon catch up to the level of the core.

Typically construction techniques of a concrete core include erecting a "jump form" that provides a moveable formwork containing a hollow space that is reinforced using reinforcing members and filled with concrete. One floor of concrete is usually poured at a time and will take a number of days to set before the climbing form is moved one floor up to start the process again for the core on the next floor above.

Similar timing drawbacks are experienced with constructing external shear walls, which take longer to construct and dry than a complete floor takes to erect. New construction methods aim at reducing the construction time and costs associated with building cores. The present invention aims to similarly improve on known construction techniques for constructing concrete walls in multi-storey buildings, including shear walls and cores.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided a method of constructing a concrete wall in a multi-storey building constructed of modular units, including:

arranging and connecting modular building units so that a framed wall of one of the building units defines a framed wall of the concrete wall to be constructed;

attaching formwork on at least one side of the framed wall; and applying wet concrete to the framed wall to form a solid concrete wall when the concrete dries. In one embodiment the framed walls form core perimeter walls that when applied with wet concrete and dried form a solid concrete core wall, that may be a multi-storey core wall.

In another embodiment the framed walls are arranged to form a shear framed wall that when applied with wet concrete and dried form an external solid shear wall, that may be a multi- storey shear wall.

In one embodiment the method includes pneumatically propelling wet concrete through the framed wall and against the formwork. This method can be used when the modular units are only partly finished, and internal walls such as plasterboard have not yet been erected so that a person can propel the wet concrete from inside a modular unit and through the framed wall against the formwork.

In an alternative embodiment, the method includes pouring wet concrete into the framed wall from a point above the framed wall. In this embodiment additional formwork will be required on the other side of the framed wall to the first formwork in order to confine poured wet concrete in the space of the framed wall between the first formwork and the additional formwork. This method is suitable for use where the modular units are finished before transporting to a construction site, and the internal wall surface at the framed wall of the modular unit can act as the additional formwork. The internal wall surface in this case may comprise a sheet of plasterboard, which will face the inside of the modular unit, against another more rigid sheet (timber, composite or metal) that will act as formwork to hold the wet concrete as it dries in a cavity of the framed wall. In yet another embodiment the method could include a combination of pneumatic propulsion of wet concrete and pouring. In particular, where pneumatic propulsion of wet concrete in high areas becomes difficult, the higher parts of the framed walls can be finished by pouring. In these high areas, additional formwork is erected opposite the first formwork to form a framed wall cavity at only an upper end of the perimeter wall.

In another embodiment the method includes arranging and connecting modular building units vertically one on top of another to define at least two storeys. The formwork is placed on one side of the vertically aligned framed walls of the vertically connected building units and wet concrete is applied to the framed wall that dries as a multi-storey concrete wall.

In an embodiment of the invention the formwork may be erected and attached to one side of the framed wall before the modular building units are arranged and connected on site. In other words the formwork may be erected on certain walls that will form the framed walls, and therefore ultimately the solid concrete wall, off site and in a factory setting where the modular units will be largely constructed and finished.

Alternatively, the formwork could be erected after arranging and connecting modular building units on site.

The formwork erected on one side of the framed walls may be sacrificial formwork, for example in the form of a plywood or other planar material that will remain a part of the core construction. Alternatively, the formwork may comprise pre-cast concrete panels or walls erected on one side of the framed walls.

In the case of forming pre-cast concrete panels or walls, wall anchors may be cast into the wall to protrude from the pre-cast wall to anchor the solid concrete wall when the wet concrete applied to the pre-cast concrete wall dries. Preferably, the method includes arranging the units so that the framed walls partially or fully form an enclosed perimeter of a core. In this manner a hollow concrete column, typically rectangular in cross section, can be constructed to extend along the height of the building. A partial perimeter may be formed with the framed walls if an access opening is required to be formed along one side of the perimeter, for example, to accommodate a doorway. Preferably the method includes providing the modular unit having reinforcement pre-fixed to the framed walls. Alternatively, the method could include inserting reinforcement, such as in the form of rebar, at the framed walls to reinforce the concrete wall. Arranging and connecting the modular building units could include arranging the units to form framed walls in a single storey arrangement before pneumatically propelling the wet concrete, or alternatively or additionally could include arranging the units to form framed walls in a multi-storey arrangement. Accordingly, the wet concrete may be propelled towards a single storey arrangement of modular building units or towards a framed wall spanning more than one storey.

In order to ensure modular connection of the building units vertically, the method may include leaving exposed from the concrete wall an upper connector of the framed wall that will allow connection of a lower modular unit having a framed wall that has formed a concrete wall to be connected to an upper modular unit, which will be vertically connected above the lower modular unit before it too may form a part of an upper framed wall of the core.

After pneumatically propelling the wet concrete at the formwork on the framed wall the method can also include finishing off the solid concrete wall surface. The wall surface may be finished by hanging plasterboard and/or the concrete wall while still wet may be troweled to vertically level off the core perimeter wall. The excess concrete trowelled off the core perimeter wall may be recycled and used as building ballast. Gaps and spaces between adjoining building units may also be formed with solid concrete walls according to the abovedescribed method. This may include placing reinforcement across gaps between framed walls of adjoining building units, attaching formwork across the gap and applying wet concrete to the framed walls and the gap inbetween to form a solid concrete wall spanning two adjacent modules.

One embodiment would include using mesh reinforcement across the gaps and applying wet concrete to form a solid concrete wall spanning adjacent modules in a horizontal and/or vertical arrangement. Another embodiment would include forming a solid concrete wall on top of and/or adjacent to an already formed solid concrete wall. BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be more clearly ascertained, embodiments will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a schematic representation of a multi-storey building having concrete walls constructed according to the method of the present invention;

Figure 2 is an isometric view of a single level in the representation of figure 1 .

Figure 3 is a plan drawing illustrating a concrete core and concrete walls formed from connected modular building units in accordance with the invention;

Figure 4 is a first upper isometric view of a modular building unit having a concrete wall made in accordance with the method of the present invention;

Figure 5 is a second upper isometric view of a modular building unit having a concrete wall made in accordance with the method of the present invention; Figure 6 is a top sectional view of a first embodiment of a concrete wall formed in accordance with the invention and suitable for forming an internal shear wall or core wall;

Figure 7 is a top sectional view of a second embodiment of a concrete wall formed in accordance with the invention and suitable for forming an internal shear wall or core wall;

Figure 8 is a top sectional view of a third embodiment of a concrete wall formed in accordance with the invention and suitable for forming an internal shear wall or core wall; and Figure 9 is a top sectional view of an embodiment of an external concrete shear wall formed in accordance with the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT A solid concrete wall 10 in a multi-story building 20 is illustrated in the drawings either as partially formed within the framed walls 12 of a modular building unit 15 (figures 3 to 5) or formed in its entirety as part of the multi-storey building 20 constructed by connecting modular building units 15 side-by-side and one on top of the other to form a greater building.

The concrete wall 10 formed according to the method described herein can take the form of various load bearing or non-load bearing walls within the building 20. In many cases the concrete wall is a shear wall. For example, the concrete wall can form an internal shear wall within the building and/or the internal shear wall can be a part of a perimeter wall 23 of a concrete core 13 in the building. Additionally, the concrete wall may form an external shear wall 14 in the building.

The concrete core in a building constructed of the modular units is intended to be used to provide services including amenities (gas, electricity and water, plumbing) and/or to be used as a lift well or a stairwell. The external shear walls are structural fagade walls designed to take lateral loads in a building, but will also withstand vertical loads.

The internal/external shear walls, including core walls, are important structural walls in a building but the concrete wall formed by the described method may also be an internal non- load bearing wall or non-structural fagade wall. The method for constructing a concrete wall described herein is particularly suited for constructing concrete walls in a multi-storey building made of modular units. Modular construction as described herein relates to the mode of constructing a residential or commercial building using modularised units that are partly or wholly constructed offsite in a factory controlled environment. The modular units usually have steel framed internal and external walls and may alternatively or additionally comprise pre-cast concrete walls, that are usually external of the unit. A floor or base is usually provided although the modular unit may entirely comprise the floor, walls and ceiling just in framed form as it leaves the factory. The modular unit may be entirely fitted out with all surface furnishings and bathroom/kitchen hardware and fittings, or the wet areas and furnishings may only be partly completed.

In the embodiment illustrated in the drawings the modular units 15 are provided with a steel frame, a concrete floor and an open ceiling that, when assembled on site, will be closed off by the modular unit above. On site, the modular units can be assembled in any desired configuration, as designed for the project.

The currently described method for constructing a multi-storey concrete wall in a building constructed of modular building units provide significant advantages in the construction of a multi-storey building. Firstly, the current method does not require a "climbing form" used in known construction techniques for concrete cores.

Furthermore, the concrete walls when forming a core or external shear walls can be formed at the same time as constructing the floors and non-cocnrete walls of the same level. The concrete wall is built at the same time as each level or multiple stories of the concrete wall can be built at the same time as building multiple stories of the building. This provides significant time savings in the construction time of a multi-storey building. Another advantage is that much of the construction of the concrete wall can be carried out off-site which provides for, not only further time savings, but also greater quality control of the interconnecting components forming the framework of the concrete wall, which in turn lead to less room for error in the construction of the concrete wall. Figure 1 illustrates a multi-storey building 20 formed by interconnecting modular building units 15. To show greater clarity, Figure 2 illustrates a single storey of the multi-storey building illustrated in Figure 1.

The modular building units 15 are interconnected at structural columns 16 in each building unit 15. Specifically, the structural columns 16 are provided with end flange plates 17 that are aligned and abut corresponding end flange plates on a upper or lower level and then fastening means, for example in the form of bolts, are used to fasten the end plates together in order to connect one building unit 15 above another building unit 15. Similar techniques are used to interconnect building units adjacent each other in a side-by- side arrangement, and namely tie plates (not shown) bridge and bolt together adjoining units 15.

It is practical to complete as much of the building unit off site as possible. For example, the wall and floor finishes may be completed in a warehouse offsite so that the modular unit is partially completed before shipping the entire modular unit on site and connecting it to other modular units which are all then fitted out with the conveniences and finishings of the multistorey building, whether it be residential, commercial, or otherwise. Alternatively, each modular building unit may be finished in its entirety in the warehouse and offsite before transporting to the building site where the units are connected to each other in their finished state so that only the services need to be connected to each unit. In the presently described construction method of building a multi-storey concrete wall in a building constructed of modular units, as described above the modular units may be provided in a basic framed state or a semi-completed state before the framed walls forming the concrete walls are completed. In this unfinished state the method can include

pneumatically propelling wet concrete through the framed wall and against the formwork from a position standing inside a modular unit facing the formwork.

The present method also provides for modular units transported and erected at a

construction site in an entirely finished state with finished internal walls. In this state wet concrete is poured into the perimeter wall from a point above the perimeter wall.

The method of constructing the multi-storey concrete wall 10 includes arranging and connecting modular building units 15 so that framed walls 12 of the building units 15 form framed walls of the concrete wall that is to be constructed. For example, for constructing a core, a core perimeter wall 23 is formed of framed walls 12. The core is essentially formed by arranging internal shear walls into a perimeter around a core space 25.

Figure 3 illustrates a plan of modular building units 15 that have been arranged and connected across one level. Using the construction of a core as an example, surrounding the space 25 where the core is to be provided are framed walls 12 belonging to the building units immediately surrounding the core space 25. Accordingly, the framed walls 12 surrounding the core space 25 have a double purpose to both form walls of the building unit but to also form the core perimeter walls 23 of the concrete core. Accordingly, there is no need to erect additional framework to form the concrete core because the core perimeter walls 23 defined by the framed walls 12 of the building units 15 immediately surrounding the core space 25 act as both a wall for the concrete core and a wall for the immediately adjoining building units 15.

It is understood that the modular building units may define a variety of internal building spaces, from entire residential apartments, to hallways and common areas, to commercial offices, and to amenity blocks such as bathroom facilities. The framed walls of each modular building unit may double up to form shared walls with adjoining units, passages, cores, etc, and attaching formwork to at least one side of the framed wall will allow that wall to form a framed wall for a concrete wall when wet concrete is applied to that wall pneumatically or by pouring. Once the building units 15 have been arranged and connected together across one level formwork 28 is erected on an inside of the core perimeter walls 23. Alternatively, the formwork 28 may be erected off site and during fabrication of the modular units. The formwork defines an inner wall of the core. The formwork may be formwork that is removed after the application of concrete or, and more typically, the formwork may be sacrificial formwork that remains as part of the concrete walls.

In a first embodiment, and using the concrete core construction as an example, after the formwork is in place the concrete core is constructed by pneumatically propelling wet concrete against the formwork 28 on the core perimeter wall and in a direction towards the core which, when dry will form a solid concrete core wall 1 1 .

The pneumatic propulsion of wet concrete is also known as "shotcreting" where fluid concrete is "shotcreted" particularly in applications where a vertical surface is to be applied with concrete. The consistency and density of the concrete is such that makes it suitable for pneumatic propulsion against a surface. Additionally, the concrete may be provided with additives, chemicals or particulate material, that can be added to enhance or improve the characteristics of the concrete core or to provide a particularly desired finished surface on the core. Such additives are known in the field of concrete.

The application of concrete by pneumatic propulsion provides the advantage that formwork need only be provided on one side of the perimeter wall defining a perimeter wall forming the concrete core. Furthermore, it allows the concrete core to be formed at the same time or after the frame floors and walls of a level are erected. The concrete propulsion application process is easier than pouring concrete down into movable formwork because an operator can stand on the same level as the level at which the core is to be constructed and direct a hose substantially horizontally towards the formwork 28 at the core. Standard shotcrete equipment is envisaged to be used where wet concrete is pumped under pressure from a source of wet concrete (typically from a rotating drum in a concrete truck) and the wet concrete under pneumatic pressure is forced through a hose to an end nozzle from which it is sprayed under a sufficient force to be propelled against a surface located 200 to 500mm away from the nozzle for optimum controlled results. The wet concrete is propelled through the framed wall 12, which may include nonstructural framework, to impact the formwork on the other side of the framed wall.

In a second embodiment, the wet concrete can be poured into a perimeter wall cavity 38 from a point above the perimeter wall. In this embodiment additional formwork 39, shown in Figure 2, will be required to be erected on the other side of the perimeter wall 23 to the first formwork 28 in order to confine poured wet concrete in the perimeter wall cavity 38. This method is suitable for use where the modular units are substantially entirely finished off site and then transported to a construction site.

The internal wall surface 35 at the perimeter wall of the modular unit can act as the additional formwork 39. The internal wall surface in this case may comprise a sheet of plasterboard, which will face the inside of the modular unit, against another more rigid sheet acting as the structural formwork to hold the wet concrete as it dries in a cavity of the perimeter wall. The more rigid sheet can comprise a range of materials known for use as formwork, which are described in more detail further below.

Figures 1 and 2 illustrates multi storey concrete cores (as lift well 55 and stair well 56)in the building formed by modular building units 15 where the cores are prepared to be constructed by a hybrid of the pneumatic propulsion and pouring techniques for wet concrete. This hybrid technique is suitable where pneumatic propulsion of wet concrete is difficult to control and apply in high areas such as near ceilings. Figure 1 illustrates the higher part of the core perimeter walls, extending approximately 300mm downwards from the ceiling, can be finished by pouring concrete on top of the shotcreted concrete. In this higher area, additional formwork 39 in the form of a formwork skirt depending from the ceiling, is erected opposite the first formwork 28 to form a perimeter wall cavity 38 at only an upper end of the perimeter wall. Concrete is then poured from above perimeter wall into the cavity 38.

Figure 2 also illustrates the framed walls 26 that will form the external concrete shear walls 24 that are constructed using the same technique as described above in relation to forming internal shear walls of the concrete core.

Figures 4 and 5 illustrate different isometric views of a building unit 15. The building unit 15 includes structural columns 16 and beams 18, as well as non-structural framework 19 that together form the framed walls 12 of the building unit. Connections plates 17 are used to connect columns to columns and columns to beams and to connect columns of one building unit 15 to another building unit. Also illustrated are flooring bearers 21 and flooring 22. An external shear wall 24 of the building unit is formed from a pre-cast concrete panel 27 which is erected on the building unit on site and acts as the formwork against which wet concrete is poured or shotcreted to form an external shear wall 24. Figures 4 and 5 show framed walls 12 defining some of the perimeter walls 23 of core 10 and the shear framed walls 26 that will form the external shear wall 24. If the core is intended to be a square or rectangular form, the perimeter walls 23 form one side of the core 10 and two opposite partial side walls of the core 10. The building units 15 can be arranged so that the framed walls 12 partially or fully form an enclosed perimeter of the core. The core is in this manner formed on a level by level basis, or could even be formed two levels at a time, and creates the hollow concrete core column that extends the height of the building. The perimeter may be formed partially in some sections if an access opening is required on one side of the perimeter, for example to form a lift opening or a utilities door.

Similarly, some of the building units will be arranged to have a framed wall 26 that will face an exterior of the building and that will form a shear wall 24 (some exterior facing framed walls 12 will form external fagade walls instead). These externally facing framed walls 26 will be provided with formwork, usually in the form of a solid pre-cast concrete panel 27, against which wet concrete can be propelled to form a two layered concrete structure forming the external shear wall 24. If wet concrete is to be poured, another panel of formwork will need to be secured spaced from the pre-cast concrete panel formwork.

Before propelling wet concrete against the formwork reinforcement is usually inserted in the form of rebar, mesh reinforcement and other types of reinforcing steel rods or sheets, in the framed walls to reinforce the concrete material forming the core. Reinforcement with steel rods is usually applied in accordance with engineering specifications horizontally and vertically within the framed wall to be embedded within the concrete wall 10. In the preferred embodiment, reinforcing bars are tied in position to the framed walls off site. The modular units are therefore delivered to site and assembled with reinforcement already in place.

It may be desired to fill gaps and spaces (not shown) between adjoining building units 15 with solid concrete walls. Using the method described herein of forming a concrete wall, reinforcement is placed across gaps between framed walls of adjoining building units, and formwork is attached across the gap behind the reinforcement(ie. to define an outer side of the concrete wall 10). Wet concrete is then applied (practically by pneumatic means) to the framed walls of the adjoining modular units and the gap inbetween to form a solid concrete wall spanning across two adjacent modules. As discussed earlier, the modular building units 15 can be arranged in a single storey arrangement where the concrete wall is constructed by pneumatically propelling wet concrete for every storey, or the building units could alternatively be arranged in a multi- storey arrangement where wet concrete may be propelled against framed walls defining the multi-storey core walls or external shear walls or other internal shear concrete walls to be formed. Generally, the concrete walls are constructed on building units already connected in a multistorey arrangement so that the inter-connections between upper and lower units are embedded in the concrete walls. Alternatively, and at some stage in a multi-storey development, a concrete wall can be formed using the method described herein on top of, or adjacent to, an already formed solid concrete wall. Anchoring and fastening devices, often embedded in the walls, are used to tie the walls together.

The method could also further include trowelling the wet concrete as, or soon after, it is pneumatically propelled against the formwork on the perimeter wall 23 or shear framed wall 26. Not only will troweling the wet concrete level off the vertical framed wall, but the excess concrete trowelled off the framed wall could be recycled and used for other purposes in the building, for example used as building ballast.

Figures 6 and 7 show two different embodiments of a cross section of a concrete wall 10 forming an internal shear wall, also used for the core, and specifically illustrate different combinations of materials that could constitute the concrete wall 10.

Figure 6 illustrates the concrete wall 10 for forming a core 13 having an inner surface 30, where the inner surface faces into the core 13, and an outer surface 32, which surface faces the opposite side of concrete wall 10 of the core 13 and namely faces the inside of the building unit 15. Figure 6 illustrates the structural framework of the perimeter walls 23 and namely two hollow steel structural columns 16 and horizontal and vertical structural reinforcement 34.

Steel sheeting (about 1 mm thick) on the inner surface 30 forms the formwork 28 against which wet concrete is shotcreted. The steel sheeting is fixed against the framework of core perimeter walls 23 using standard techniques including formwork framing whereby steel sheeting is fixed to square hollow sections 36 forming the formwork framing that are vertically fixed to various points on the perimeter walls 23. Shotcreted concrete 40 is illustrated in Figures 6 as forming the infill 40 of wall 10. The concrete infill 40 is applied by propelling wet concrete from the outer surface 32 side of the concrete wall 10 towards the formwork 28 in order to build up the mass of concrete 40 in the concrete wall 10. As the wet concrete is propelled against the formwork the build-up of wet concrete is trowelled to form the vertical outside surface 42 of the concrete 40. A plaster support frame 44 forms part of the modular unit and after application of the concrete protrudes out of the concrete wall 10 and into the building unit 15. Frame 44 is used to support plasterboard 46 in a manner so as to be spaced from the outside surface 42 of the concrete wall 10. Space 50 between the concrete wall 10 and plasterboard 46 is to allow for insulation infill, electrical wiring and the like.

Figure 7 illustrates a different embodiment of a concrete wall 10 forming an internal shear wall for a concrete core 13 where only one steel hollow support column 16 is provided, which may occur on a straight section of the perimeter wall. In this embodiment rather than the formwork being formed by steel sheeting the formwork is sacrificial formwork in the form of a board product 28. The formwork board 28 is similarly mounted on square hollow sections 36 that are fastened onto the steel framework of the core perimeter walls 23.

Reinforcement 34 is added to the framework and embedded into the wet concrete that is propelled against formwork 28 under pneumatic pressure. In this example the outer surface 32 of the concrete wall 10 is lined with a packing material, that is packing board 48 and may have a channel or air gap between the packing board 48 and the plaster board 46, which is for reducing noise transmission across the concrete wall 10.

Figures 8 illustrates a third embodiment of an internal shear concrete wall 10 that may form a core wall or may simply form an internal shear wall in the building. The wall of this embodiment has steel sheeting as the formwork 28, similar to the Figure 6 embodiment, and packing board 48 between the steel sheeting 28 and plaster board 46 to improve noise insulation. This embodiment also has a frame 44 that is used to support further plasterboard 46 on an opposite side of the concrete wall to the plasterboard 46 against the packing board.

Figure 9 illustrate an embodiments of a concrete wall 10 forming an external shear wall 24. The concrete wall comprises the pre-cast concrete panel 27 that forms the permanent formwork for the concrete wall 10. Structural reinforcement 34 (in the form of reinforcement mesh) is fixed to be spaced from pre-cast panel 27. Hollow support columns 16 forming part of the modular unit's steel frame are also illustrated.

Wet concrete is shotcreted against pre-cast panel 27 and the dried concrete 40 embedded with reinforcement 34 together with the panel 27 in the framed wall, forms the shear concrete wall 24. In one embodiment the surface of the dried concrete 40 may have a cut wall finish. In Figure 9 a frame 44 is embedded in the concrete wall 10 and supports plasterboard 46.

Not shown but contemplated are wall anchors that are cast into the pre-cast panel 27 to protrude into the space where concrete 40 is applied. The anchors assist in strengthening the bond, or engagement, between the concrete 40 and pre-cast panel 27 to form the shear wall 24. The inner facing surface of the pre-cast panel 27 may additionally be roughened to assist in adhesion/bonding with concrete 40. To reiterate, the present method of constructing a concrete wall in a building constructed of modular units minimises as much as possible the time spent in building a concrete wall or walls, such as an internal shear wall in a core or a for an external shear wall, which in conventional construction techniques is where construction time is often delayed. This is achieved by de-coupling the forming of concrete shear walls, such as core walls and external shear walls, from the construction process of building each storey in a multi-storey building. Construction of each storey can continue at a faster pace because it is not being held up by construction of the core or structural concrete walls. Furthermore, using concrete rather than steel for load bearing walls provides a much stronger and stiffer construction that will allow a building to withstand a greater load, and therefore a taller building.

The method also allows as much as possible of the modular units and core/shear wall construction to be prepared offsite before the final application of wet concrete to form the concrete wall is carried out on site. As discussed, the formwork may be attached to the framed walls onsite but may also be attached offsite if more convenient.

As already shown the formwork may take the form of any planar surface suitable for use as formwork including board, whether it be a timber plywood, timber sheeting, metal sheeting or pre-fabricated concrete panel. The concrete walls formed by the method described herein are very strong walls capable of supporting and anchoring columns and beams tied to the wall and spanning multiple stories and reaching the height of high rise buildings. It is understood that the method of constructing concrete walls described herein apply equally to concrete walls that may be shear walls, such as boundary walls as well as walls defining building cores. Furthermore, the savings in materials are recognised in that the core perimeter walls are also the framed walls of the modular building units so that material is saved compared to providing a framework for the core walls alone.

5 The present method and product achieved provides advantages in cost savings, time

savings and improved quality over current techniques used in core construction. This is achieved by de-coupling the forming of concrete cores and shear walls, and other structural concrete walls, from the construction process of building each storey in a multi-storey building. Construction of each storey can continue at a faster pace because it is not being l o held up by construction of the core or structural concrete walls. Furthermore, using concrete rather than steel for load bearing walls provides a much stronger and stiffer construction that will allow a building to withstand a greater load, and therefore a taller building.

It will be understood to persons skilled in the art of the invention that many modifications 15 may be made without departing from the spirit and scope of the invention.

Claims

CLAIMS:

1. A method of constructing a concrete wall in a multi-storey building constructed of modular units, including:

attaching formwork on at least one side of the framed wall; and applying wet concrete to the framed wall to form a solid concrete wall when the concrete dries.

2. The method claimed in claim 1 , including applying wet concrete by pneumatically propelling wet concrete through the framed wall and against the formwork.

3. The method claimed in claim 1 , including applying wet concrete by pouring wet concrete into the framed wall from a point above the framed wall.

4. The method claimed in any one of the preceding claims, including arranging and connecting modular building units vertically one on top of another to define at least two storeys; placing formwork on one side of the vertically aligned framed walls of the vertically connected building units and applying wet concrete to the framed wall that dries as a multi- storey concrete wall.

5. The method claimed in any one of the preceding claims, including attaching the formwork to one side of the framed wall of the building unit before the modular building units are arranged and connected on site.

6. The method claimed in any one of the preceding claims, including using sacrificial formwork.

7. The method claimed in any one of the preceding claims, including attaching additional formwork to an opposite side of the framed wall to the first formwork, to form a framed wall cavity into which concrete can be poured.

8. The method claimed in any one of the preceding claims, including using a pre-cast concrete wall as formwork.

9. The method claimed in claim 8, including forming in the pre-cast concrete wall anchors that protrude from the pre-cast wall to anchor the solid concrete wall when the wet concrete applied to the pre-cast concrete wall dries.

10. The method claimed in any one of the preceding claims, including horizontally arranging the modular building units so that framed walls of the building units partially or fully form an enclosed perimeter defining a core perimeter wall.

5

1 1. The method claimed in claim 10, including arranging the modular building units to form core perimeter walls in a multi-storey arrangement before applying wet concrete.

12. The method claimed in any one of the preceding claims, including placing i o reinforcement in the framed walls to reinforce the concrete core.

13. The method claimed in any one of the preceding claims, including providing the modular building units having reinforcement pre-fixed to the framed walls.

15 14. The method claimed in any one of the preceding claims, including placing

reinforcement across gaps between framed walls of adjoining building units, attaching formwork across the gap and applying wet concrete to the framed walls and the gap inbetween to form a solid concrete wall spanning two adjacent modules.

20 15. The method of claim 14, including using mesh reinforcement across the gaps and applying wet concrete to form a solid concrete wall spanning adjacent modules in a horizontal and/or vertical arrangement.

16. The method claimed in any one of the preceding claims, including forming a solid 25 concrete wall on top of and/or adjacent to an already formed solid concrete wall.

17. The method claimed in any one of the preceding claims, including mounting plasterboard in front of the concrete wall to finish the concrete wall on an inside of a building unit.

30

18. The method claimed in any one of the preceding claims, including troweling wet concrete to level off the concrete wall before drying, and recycling excess concrete trowelled off the core perimeter wall as building ballast.

35

19. The method claimed in any one of the preceding claims, including constructing a multi-storey external shear wall or a multi-storey core wall.

20. A concrete wall in a multi-storey building constructed of modular units, constructed according to the method of any one of claims 1 to 13.