ZA200907085B

ZA200907085B - Building construction system

Info

Publication number: ZA200907085B
Application number: ZA200907085A
Authority: ZA
Inventors: Richard John Payne
Original assignee: Village Construction Ltd
Priority date: 2009-08-21
Filing date: 2009-10-12
Publication date: 2010-08-25
Also published as: GB0914649D0

Description

oo BUILDING CONSTRUCTION SYSTEM

Field of the Invention

The invention relates to a building construction system and to a building constructed using the system.

Background to the Invention

The inventor is aware of a need for housing which is quick to construct, of high quality, and durable for a period of several tens of years at the minimum. In particular, the inventor is aware of a need for so called low cost housing which does not have the look and feel of inferior accommodation which can be erected in remote locations without the need for complex construction methods, highly skilled labour, and a plurality of building materials and methods.

Currently, one type of low cost housing is erected using cement blocks, wooden trusses, wooden window frames, steel doors, plaster , and corrugated steel roofing.

However, experience has shown that these houses are typically not well constructed, suffer from cracking walls, leaky roofs and drafty windows leading to poor acceptance by the community which perceives them as being inferior.

Other construction methods have been proposed, including concrete panel construction : i.e. prefabricated housing, steel element construction systems resulting in steel houses.

: ® “2009/0709 5 which have an appearance not dissimilar to a shanty town and which are perceived as being inferior.

Another construction system which has been proposed and used to some extent, is a mould system in which a number of plastic formwork or mould elements are secured to each other to form a plastic formwork having an inner and an outer wall tied together by connecting rods which are distributed over the entire extent of the formwork, said formwork providing a cavity into which aerated concrete is cast to form the walls of the building being erected. Reinforcing steel bars are positioned within the cavity in a predetermined pattern as is conduiting for electrical wiring and/or water piping before the concrete is cast into the cavity. These monolithic walls stand on and are secured to a previously prepared floor and roof trusses are required to support the roof of the building. Once the walls have been cast and the concrete has set the connecting rods are removed one by one and the plastic formwork is removed for re-use. The concrete walss have an off-the-formwork finish which does not require plastering. Such a system is available from Moladi™ and which can be seen at www.moladi.net (as at 1 August 2009). This system requires a floor to be cast and ready prior to the erection of the walls and, during the erection of the walls, for correct placement of re-inforcing steel bars within the cavity to ensure that walls of sufficient strength are erected.

The above systems each have drawbacks, whether of perceived inferiority, cost and complexity, and durability.

Thus, the inventor proposes the following building construction system.

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Summary of the Invention

According to a first aspect of the invention, there is provided a building construction system in which the walls and at least a portion of the foundations are monolithically cast from a cementitious composition without the use of reinforcing steel bars or rods.

According to a second aspect of the invention, there is provided a building construction system in which the walls, the foundations, and the floor are monolithically cast from a cementitious composition without the use of reinforcing steel bars or rods.

The foundations may be in the form of piles extending into the ground and forming an integral part of the walls.

The floor may be integrally cast with the walls and the piles so that there is no need to prepare a floor or slab of any kind prior to the walls being erected.

The cementitious composition may include synthetic fibres which reinforce the composition, when set, thereby obviating the need for steel reinforcing bars or rods.

The cementitious composition may include one or more slump modification agents so that the slump of the composition is in the range 120 mm to 170 mm thereby facilitating the casting of the composition in a single pour and for removal of any air therefrom thereby to result in a monolithic strong structure when the composition sets.

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The slump may be from 120 mm to 150 mm after 2 minutes, typically 135 mm.

The slump may be from 140mm to 160 mm after 50 minutes, typically 150 mm.

The synthetic fibres may be from 25mm to 50 mm in length, typically 40 mm in length.

The synthetic fibres may be used in a quantity of from 0.05 mass% to 1.0 mass% of the cementitious composition, typically around 0.1 mass%, which mass% is calculated on a dry materials basis i.e. excluding the water address to the dry materials during preparation of the cementitious composition.

According to a third aspect of the invention, there is provided a steel formwork kit for monolithically casting the walls and foundation of a building to be constructed, said kit including: - a plurality of steel formwork elements which are assembled to form an outer wall of the formwork with openings in the outer wall for windows and doors; - a plurality of steel formwork elements which are assembled to form an inner wall of the formwork with openings in the inner wall for windows and doors; - a plurality of struts which are configured at one end of each strut to be secured to a steel formwork element of the inner wall and at the other end to be anchored to or against a rigid surface or an opposite steel formwork element of the inner wall; - a plurality wale members, each of which is secured to at least one other wale member to brace the outer walls against the forces exerted by the weight of the cast composition retained between the inner and outer walls of the formwork;

let ' . 5200970704 5 - a plurality of spacers which do not attach the inner wall to the outer wall but which maintain a predetermined gap between them thereby to ensure that the wall which is cast from the cementitious composition is of substantially equal thickness throughout; and - one or more funnel means locatable at an open upper portion of the steel formwork thereby to facilitate the casting of the cementitious composition into the gap between the inner and outer walls.

Shuttering may be provided to close off the steel formwork around door and window frame portions of the formwork.

The shuttering may be an integral part of the steel formwork and may be made of the same steel as the formwork.

Thus, the kit does not include any connector rods for connecting the inner wall to the outer wall as is used in the prior art and which requires a lot of time and effort to put in place and then later remove.

The kit may include corner inner wall elements which provide an arcuate rather than a right angle finish at the intersection of perpendicular or angled walls.

According to a fourth aspect of the invention, there is provided a method of construction of a building using a kit as described above, said method including: - excavating a cavity for a foundation for a building; } p Lo Ce 3 ]

. le! : . %2009/070g 5 - erecting a steel formwork as described above over the foundation:so that the cavity of the foundation and the gap between the inner and outer walls of the formwork are contiguous; - positioning spacers at window and door openings of the formwork to ensure that the gap between the inner and outer formwork walls is substantially constant; - securing the struts to the inner wall of the steel formwork to inhibit expansion or displacement of the inner wall towards the interior of the building being constructed; - setting the wale members to brace the outer walls against outward displacement or expansion at ground level, near roof level, and one or more levels in between the ground and roof levels; - positioning the funnel means at open upper portions of the gap between the inner and outer formwork walls so that a cementitious composition may be poured into the gap; and - pouring the cementitious composition into the gap and foundation cavity in a single pour and allowing it to set thereby forming a monolithic wall and foundation for a building in which the door and window frame receiving openings are provided.

The cementitious composition may include synthetic fibres which reinforce the composition, when set, thereby obviating the need for steel reinforcing bars or rods, which composition is prepared by mixing the synthetic fibres, together with slump modifying additives just prior to the pouring thereof into the gap.

The cementitious composition may include one or more slump modification agents so that the slump of the composition is in the range 120 mm to 170 mm thereby facilitating lew 2009/0794 the casting of the composition in a single pour and for removal of any air therefrom thereby to result in a monolithic strong structure when the composition sets.

The slump may be from 120 mm to 150 mm after 2 minutes, typically 135 mm.

The slump may be from 140mm to 160 mm after 50 minutes, typically 150 mm.

The synthetic fibres may be from 26mm to 50 mm in length, typically 40 mm in length.

The cavity for the foundations may include piles which are made monolithically with the rest of the foundation and the walls of the building.

Casting the floor of the building either separate from the monolithic wall and foundation or integrally therewith.

Positioning one or more roof beams at desired positions in the formwork so that, when the walls are cast, the beams are cast integrally therewith.

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The invention extends to a cementitious composition as described above and elsewhere in this specification.

Description of Embodiments of the Invention

In the figures that follow, embodiments of the invention are shown, which embodiments are not to be interpreted as limiting of the invention and are provided only as examples of how the principles of the invention may be applied. Any descriptions of the figures are intended to be by way of explanation and all principles which are explained therein are intended as disclosure of the general principles of which the embodiments are examples.

In the figures,

Figure 1 shows, in plan view, a layout of a building which may be erected using the invention;

Figure 2 shows, in sectional view, a monolithic wall and foundation of the building of

Figure 1;

Figure 3 shows, in plan view, a steel formwork kit of the invention through the use of which the building of Figure 1 can be erected; Ce

Figure 4 shows, in orthographic projection, the building of figure 3;

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Figure 5, shows in side view, a section through the building of Figure 4; and

Figure 6 shows, again in orthographic projection, another house which may be erected in accordance with the invention.

Thus, in Figures 1 to 6 is shown a house 10 in which the walls and foundations are monolithic having been poured in a single pour from a cementitious composition which, in addition to the usual cement, concrete stone dolomite, filler sand, crusher sand dolomite, includes synthetic fibres of about 40mm ion length, sold under the trademark

Strux 40/90 ™ from Grace Construction Products in South Africa and slump modifying additive Darecet CF ™ and Adva XR 3301 ™ all from Grace.

Figure 2 shows detail of the monolithic wall 11 and foundation 12 which was made by ~ © 15 .excavating a cavity 14 for the foundation and erecting formwork (not shown in Figure 2) and pouring said composition into the formwork and cavity 14 in a single pour. The composition is then allowed to set for 16 hours upto a strength of almost 6 MPa, and over 11 MPa at 24 hours, which allows for the formwork to be removed while the composition cures further to an eventual strength of over 30 MPa in days.

In Figures 3, 4, 5, and 6 the steel formwork 16 is shown as erected with a gap 18 of about 100 mm width defined between an inner wall 20 and outer 22 of the formwork 16.

As can be seen, where walls 24, 26 would have intersected, rounded corner units 28 are provided which lead to arcuate corner portions of the erected house 10 rather than sharp corners as is usual in normal house construction. 10 : Co 3

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The formwork 14 defines window apertures 30 and door apertures 32 into which conventional or novel door and window frames may be fitted.

As can be seen, the upper lip 34 of the formwork 14 slopes upwardly towards a roof apex 36 which would be expected to cause difficulties for the single pour method of casting the walls 11 as a fluid would usually want to slump to a horizontal level rather than maintaining the angle of the upper lip 34. It is due to the cementitious composition used that this is possible, especially, the use of the slump modifying additive and the synthetic reinforcing fibres rather than the usual water and reinforcing steel rods or bars, often referred to as rebars.

A typical cementitious composition for use with the system, kit and method of the invention is:

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In another embodiment of the cementitious composition, conveniently termed the “Denholm Concrete Mix”, the following materials are used in the ratio’s as provided:

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Product Application

Strux™ 90/40 Structural Fibre

Ragic™ Accelerator

ADVA™ Plastisiser 19 mm Concrete stone (Dolomite)

Crusher sand (Dolomite)

Admixture (ADVA) (0.8%) "Admixture (Ragic) (0.2%) hi I Li

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The strut and wale bracing system is as described above under the summary of the invention and is used in the conventional manner for such a system.

Figure 6 shows a larger house 46 constructed using the system, kit and method of the invention. = : 13 SE Le

The invention has a number of advantages of convention construction methods, which include but are not limited to, speed of construction and the strength of the thus constructed structure.

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Claims

Claims INA CL pe

1. A building construction system in which the walls and at least a portion of the foundations are monolithically cast from a cementitious composition without the use of reinforcing steel bars or rods.

2. A building construction system as claimed in claim 1, in which the walls, the foundations, and the floor are monolithically cast from the cementitious composition without the use of reinforcing steel bars or rods.

3. A building construction system as claimed in claim 1 or claim 2, wherein the foundations are in the form of piles extending into the ground and forming an integral part of the walls.

4. A building construction system as claimed in claim 3, wherein the floor is integrally cast with the walls and the piles so that there is no need to prepare a floor or slab of any kind prior to the walls being erected.

5. A building construction system as claimed in any one of the preceding claims, wherein the cementitious composition includes synthetic fibres which reinforce the composition, when set, thereby obviating the need for steel reinforcing bars or rods.

6. A building construction system as claimed in any one of the preceding claims, wherein the cementitious composition includes one or more slump modification agents so that the slump of the composition is in the range 120 mm to 170 mm thereby Le : . : 15 ) ot . “oo : /

facilitating the casting of the composition in a single pour and for removal of any air therefrom thereby to result in a monolithic strong structure when the composition sets.

7. A building construction system as claimed in claim 6, wherein the slump is from 120 mm to 150 mm after 2 minutes.

8. A building construction system as claimed in claim 7, wherein the slump is 135 mm after 2 minutes.

9. A building construction system as claimed in claim 6, wherein the slump is from 140mm to 160 mm after 50 minutes.

10. A building construction system as claimed in claim 6, wherein the slump is from 150 mm after 50 minutes.

11. A building construction system as claimed in any one of claims 5 to 10, wherein the synthetic fibres are from 25mm to 50 mm in length.

12. A building construction system as claimed in claim 11, wherein the synthetic fibres are typically 40 mm in length.

13. A building construction system as claimed in any one of claims 5 to 12, wherein the synthetic fibres are used in a quantity of from 0.05 mass% to 1.0 mass% of the cementitious composition which mass% is calculated on a dry materials basis.

14. A building construction system as claimed in claim 13, wherein the synthetic fibres are used in a quantity of about 0.1 mass% of the cementitious composition which mass% is calculated on a dry materials basis.

15. A steel formwork kit for monolithically casting the walls and foundation of a building to be constructed, said kit including: - a plurality of steel formwork elements which are assembled to form an outer wall of the formwork with openings in the outer wall for windows and doors; : - a plurality of steel formwork elements which are assembled to form an inner wall of the formwork with openings in the inner wall for windows and doors; - a plurality of struts which are configured at one end of each strut to be secured to a steel formwork element of the inner wall and at the other end to be anchored to or against a rigid surface or an opposite steel formwork element of the inner wall; - a plurality wale members, each of which is secured to at least one other wale member to brace the outer walls against the forces exerted by the weight of the cast composition retained between the inner and outer walls of the formwork; - a plurality of spacers which do not attach the inner wall to the outer wall but which maintain a predetermined gap between them thereby to ensure that the wall which is cast from the cementitious composition is of substantially equal thickness throughout; and - one or more funnel means locatable at an open upper portion of the steel formwork thereby to facilitate the casting of the cementitious composition into the gap between the inner and outer walls. 17 : x : -

16.A steel formwork kit as claimed in claim 15, in which shuttering is provided to close off the steel formwork around door and window frame portions of the formwork.

17. A steel formwork kit as claimed in claim 16, wherein the shuttering is an integral part of the steel formwork and is made of the same steel as the formwork.

18. A steel formwork kit as claimed in any one of claims 15 to 17, which kit does not include any connector rods for connecting the inner wall to the outer wall.

19.A steel formwork kit as claimed in any one of claims 15 to 18, which kit includes corner inner wall elements which provide an arcuate rather than a right angle finish at the intersection of perpendicular or angled walls.

20.A method of construction of a building using a kit as claimed in any one of claims 15 to 19, said method including: - excavating a cavity for a foundation for a building; - erecting a steel formwork as described above over the foundation so that the cavity of the foundation and the gap between the inner and outer walls of the formwork are contiguous; - positioning spacers at window and door openings of the formwork to ensure that the gap between the inner and outer formwork walls is substantially constant; - securing the struts to the inner wall of the steel formwork to inhibit expansion or displacement of the inner wall towards the interior of the building being constructed; Di BE . 18 : . EEN

- setting the wale members to brace the outer walls against outward displacement or expansion at ground level, near roof level, and one or more levels in between the ground and roof levels; - positioning the funnel means at open upper portions of the gap between the inner and outer formwork walls so that a cementitious composition may be poured into the gap; and - pouring the cementitious composition into the gap and foundation cavity in a single pour and allowing it to set thereby forming a monolithic wall and foundation for a building in which the door and window frame receiving openings are provided.

21. A method as claimed in claim 20, wherein the cementitious composition includes synthetic fibres which reinforce the composition, when set, thereby obviating the need for steel reinforcing bars or rods, which composition is prepared by mixing the synthetic fibres, together with slump modifying additives just prior to the pouring thereof into the gap.

22. A method as claimed in claim 21, which includes adding one or more slump modification agents so that the slump of the composition is in the range 120 mm to 170 mm thereby facilitating the casting of the composition in a single pour and for removal of any air therefrom thereby to result in a monolithic strong structure when the composition sets.

23. A method as claimed in any one of claims 20 to 22, wherein piles are positioned in the cavity which are then cast monolithically with the rest of the foundation and the walls of the building. ve 19 ‘ co

24. A method as claimed in any one of claims 20 to 23, which includes the step of casting the floor of the building either separate from the monolithic wall and foundation or integrally therewith.

25. A method as claimed in any one of claims 20 to 24, which includes the step of positioning one or more roof beams at desired positions in the formwork so that, when the walls are cast, the beams are cast integrally therewith.

26. A cementitious composition which includes: - from 0.05 mass% to 1.0 mass% synthetic fibres which reinforce the composition, when set; and - one or more slump modification agents so that the slump of the composition is in ‘the range 120 mm to 170 mm.

27. A cementitious composition as claimed in claim 26, which includes 0.1 mass% synthetic fibres of 40 mm in length.

28. A cementitious composition as claimed in claim 26 or claim 27, wherein the slump modification agents is selected to allow for 150 mm slump in 50 minutes.

29. A building construction system as claimed in claim 1, substantially as herein described and illustrated.

30. A steel formwork kit as claimed in claim 15, substantially as herein described and iflustrated. :

31. A method of construction of a building as claimed in claim 20, substantially as herein described and illustrated.

32. A cementitious composition as claimed in claim 26, substantially as herein described and illustrated.

33. A new building construction system, a new steel formwork kit, a new method of construction of a building, or a new cementitious composition substantially as herein described. DATED AT PRETORIA. THIS 12TH DAY OF OCTOBER 2009 2) Z 4 77 / vA \ (Z EVERSHEDS : PATENT ATTORNEY FOR APPLICANT . . 21 fia : Rn