ZA200701221B - Lightweight cementitious elements, manufacture thereof, and prefabricated structure constructed using same - Google Patents

Description

t M 4 0 7 o . 07/012, g

LIGHTWEIGHT CEMENTITIOUS ELEMENTS, MANUFACTURE THEREOF, AND

PREFABRICATED STRUCTURE CONSTRUCTED USING SAME

TH | *

BACKGROUND OF THE INVENTION l JO 5 .

NE © —

This invention relates to prefabricated building structure elements, the manufacture thereof and to a structure comprising a plurality of these elements.

The use of concrete to construct buildings and other structures is well known. The use of prefabricated concrete components to construct buildings and other structures, both small and large is known to be a preferred way of achieving this. The reasons for this are numerous, but amongst other things it can be said that: - the components can be made under more controlled factory conditions thereby cutting costs and enhancing quality control; - the potential to incorporate patterns and specific finishes are enhanced; and - it lends itself to faster cycle times when repeat products are made, thereby saving time and money, etc.

Conventional concrete sections/panels of any significant size tend to be so heavy that humans cannot effectively handle them. To circumvent this problem, alternatives are applied of which four common types are here described as: - using machines to handle components of up to several tons, such as whole wall g sections. - breaking up the components into small sections (that can still be handled by men). Typically such sections will be fairly thin concrete panels so as to achieve more surface area, such as pre-cast garden walls;

- breaking up the components in to very small sections (that can easily be handled by a man) such as bricks; 20 07/01 271 - the other alternative is to create a lightweight panel of substantial size but limit the weight to that, which can still be handled by men. This objective can be attained by: a) using alternative materials, such as having a polystyrene core with only a cementitious material as a skin; b) by aerating the concrete so that itis less dense;

C) by designing the panel in such a way that it forms recesses or cavities and thereby limiting the volume of concrete used.

It is further to be noted that concrete, is brittle by nature when cured and shrinks during the curing process. Thus sections/panels of any notable size tend to crack due to shrinkage inherent to cement based products and have a high compressive strength but relatively low tensile strength (x 10 x less than compressive). Therefore, steel is often used to 1) control the shrinkage (‘crack control steel’) and 2) to compensate for the low tensile strength properties of the product thereby to ensure that it does not deform under load, crack and ultimately fail (‘tensile steel’). Such steel is commonly referred to as reinforcing steel and it is to be noted that, depending on the conditions where the product is to be used and the type of steel used, such steel usually requires to be embedded reasonably deeply into the concrete, ie. 10 mm to 40 mm (alternatively the steel needs to be stainless or coated, which comes at a high premium in terms of cost), to prevent it from rusting and potentially spalling the concrete and losing its strength. Therefore the use of steel as reinforcing usually influences the minimum thickness of the concrete panel that can be made. In thicker slabs and especially ones with recesses, the careful placing of reinforcing steel can be very effectively used to compensate for the tensile weakness of concrete or alternatively for the cavities in the slab, such as in coffer slabs. When steel is used to counter the “tensile shortcomings’ of concrete, the steel can be divided in 3

Co 07/701, categories: a) Mild steel/ hard drawn steel b) Pre-stressed steel ¢) Post-stressed steel (usually cables in sleeves). Depending on the application, all of the above can be very effectively applied.

The use of fibres, both natural and synthetic has also proven very effective to control the appearance of cracks caused by shrinkage in concrete. However, as reinforcing, to compensate for concrete’s inherent low tensile strength, they cannot be compared with steel as an effective solution. Glass fibre has reasonable results but is attacked by the high alkalinity of the cement in concrete and therefore degenerates with time.

Even when treated or manufactured to be alkaline resistant, which again comes at a high premium in terms of cost, this will merely retard the inevitable degeneration process. Natural fibres also decompose with time as well as swell/shrink when in . contact with varying moisture conditions, rendering concrete products filled with them unsuited to outdoor use, whilst asbestos has become known to be a health hazard and therefore unacceptable for use. Certain synthetic fibres such as polypropylene fibre have proven to be completely alkaline resistant and suited to exposure to varying moisture levels if used for the control of crack forming in concrete caused by shrinkage.

Prefabricated concrete panels can be joined together in a plurality of ways such as: a) By making chemical bonding which includes gluing with epoxy and bonding via cementitious grouting, as used in bricklaying, etc.

Db) Mechanical bonding which includes having protruding objects (such as re-bar) cast in that can again be cast into something else or anchored via bolts, lugs, etc.

Cc) By making use of gravity such as interlocking bricks, etc.

The alternatives of prefabricated concrete sections/panels mentioned above all have certain distinct disadvantages such as: :

In many instances it is difficult for a machine or machinery to have access to the area where the construction is intended, such as the backyard of a residential stand and therefore large panels are not feasible. Large panels also tend to be less dynamic in that only large structures of fixed design can be constructed with them.

Smaller sections that can be man-handled are often thin and therefore pose a problem in being joined together and then often require a multitude of concrete/steel posts or frames with grouting to hold them together, such as garden walls. This poses a particular problem in larger structures where stability or aesthetics of the structure is paramount. They also tend to easily crack or break.

Brick-like sections overcome most of the other alternatives’ problems and can be easily multi-layered for added strength and have therefore always been very popular.

However, when used, it requires a substantial amount of time, plurality of materials, skill and expertise to produce an acceptable result.

Lightweight concrete sections on the other hand mostly offer a negative compromise between loss of weight and loss of strength and durability. Typically, half the weight per displacement may only offer one third or less of the strength, purely as an example of the negative trade off.

Other important objectives of relevance when selecting a suitable composition include that when UV sensitive materials are combined with concrete they need to be protected from direct UV exposure.

A need has been identified for an alternative, lightweight concrete panel that can be used to construct buildings of multiple structures whilst overcoming the negatives as noted above.

SUMMARY OF THE INVENTION

According to the invention there is provided a lightweight construction element, said element including a set settable composition, said element being in the form a panel less than 25 mm average thickness, the panel including:

- stone particles in the settable composition; : - one or more ribs; - steel rods located in the ribs to counter tensile-stress on the ribs; and - a textile mesh bonded into the two faces of the settable composition thereby to protect it from sunlight.

The textile mesh may be made from multistrand and/or dreft wrapped flat strand type synthetic material.

The textile mesh may be made of polypropylene.

As is the case with glass fibre, polypropylene and other synthetic fibres are available as loose “cut strands” and in a “textile mesh” form.

When blended into concrete, polypropylene loose fiores break up and dissipate through the concrete but do tend to enhance the impact resistance of the concrete (much more so than for instance glass fibre) and assists in preventing shrinkage cracks from forming.

When blending polypropylene textile mesh into the surfaces of especially a thin concrete panel these characteristic are dramatically enhanced by having the fibre concentrated at the surface, as it tends to localize damage on impact and resists cracks from forming from the impact point. Even to the extent that a hole can be punched right through such a thin concrete panel without obvious cracks radiating from the impact point, as would be expected from a brittle product such as concrete.

Synthetic fibre used to make the described polypropylene textile mesh can be divided into 3 differentiable variations: a) Flat strand type that has little water absorption / capillary capabilities and is therefore difficult to bond to cementitious products. Although treatment with

Fluorine gas may enhance binding abilities somewhat. This product is fairly stiff.

b) Multifilament type that is made up of several fine strands and therefore has good water absorption / capillary capabilities and therefore good binding abilities to cementitious products. This product is very floppy. c) Flat strand type, wrapped in very fine strands (sometimes called “Dreft’) that gives the stiffness of the flat strands and yet good water absorption / capillary capabilities and therefore good binding abilities to cementitious products. This combination also offers better impact resistance than the flat strand type.

To maximize effectiveness of bonding to cementitious products and hence having the maximum benefits of the textile mesh in terms of impact resistance, crack control etc, only textile mesh made of items “b" and “c’ or a combination of ‘b” & “c’ are recommended.

All reference to “Textile mesh” hereinafter refers to textile mesh made only of items “b” and “c” or a combination of ‘b” & “c" and as such preferably of polypropylene material.

Generally the combination is preferred, being more practical to manufacture and use and hereinafter all “Textile mesh” referred to will refer to the combination product described.

The polypropylene textile mesh may be 50 g/m? to 150 g/m?.

Typically the polypropylene textile mesh is 75 g/m?.

The settable composition may be a cementitious composition such as concrete.

The concrete may be prepared as a wet mix but with acceptably low water: cement ratio, resulting in a strong yet economical concrete mix.

The concrete may include additives, which reduce water by decreasing the friction / viscosity in the concrete when mixing and also creating a faster chemical reaction for higher early strength.

The reduction in water may also enable the use of less cement whilst maintaining the desired water: cement ratio. By using less water in the initial mix, the cured concrete may also tends to shrink less.

The textile mesh may be pre-dipped in water or a cement/water solution. Slurry of sand/cement/water may then be used to bind it to the mould before the concrete is cast and again to work it in smoothly onto the cast concrete.

Thin concrete very easily dries out and this interrupts the chemical (hydration) process of the cement, resulting in very weak concrete. Curing is therefore critical. Merely adding water to the concrete mix to counter this effect may increase the water: cement ratio, which may weaken the concrete and cause tremendous shrinkage that may results in shrinkage cracks.

The textile mesh has a tendency to draw out water by capillary action and may therefore not be effectively bound to the concrete in its dry form.

Placing wet (water or water/cement) drenched textile mesh on high quality thin skin concrete, may allow the textile mesh to inhibit the concrete drying from the surface, thereby maintaining its chemical (hydration) process whilst also maintaining a proper water: cement ratio in the concrete.

If the concrete is a bit rich in water, it is believed that the textile mesh draws water out.

When the concrete hydrates and requires damp to ensure ideal curing, the textile mesh may release some moisture into the concrete.

The panel ribs may allow water to be poured into the cavities formed for extended curing, when the initial curing has taken place and the product has been removed from its mould.

The ribs may include steel suited to counter the tensile shortcomings of the settable composition.

The panel may include one or more pre-formed apertures, which may be reinforced or flange-style, thereby to permit easy access for pipes, cables, and the like through the panel.

The invention extends to a prefabricated structure, such as a dwelling or a latrine (toilet structure), which is constructed using the panels of the invention.

One or more of the wall, roof, and floor elements may include concrete, and may be formed by casting it in a mould.

The structure typically includes a base shaped to receive a lowermost element of the structure.

The base may be a cast or moulded concrete section, soil that is excavated and trimmed or brickwork.

Accordingly, the structure may be a latrine (toilet structure) or a larger structure such as a house, and the base may be formed with suitable drainage or plumbing apertures.

Each wall element may be formed with a plurality of transversely extending apertures sized to receive bolts, plumbing, electrical wiring or similar items to aid in bolting together elements or bolting to a frame or frame sections to form a structure or : servicing the end structure.

Apertures are made or cast into the flat surface of the elements, where it may be needed to run services through.

Lugs or mounting points are cast into the elements where needed to facilitate bolting together or attaching items, so as not to require bolts running through the elements for attaching purposes. Thickening of the concrete panel at these points may be required.

Each wall element may be formed with a plurality of ribs on the surface of the element with transversely extending apertures being formed in the ribs, where they may be required for bolting together or to run services there through.

Insulating / isolating material such as non-combustible Poly-urethane may be placed in the cavity formed by the ribs (or placed in the mould before the textile mesh / casting of the concrete and therefore cast into position between the ribs). The services / bolts and insulating / isolating material may be concealed by cladding the cavity side of the panel with a suitable material such as ‘gypsum board”. The edges of the apertures may be reinforced, for example, flange-style.

The wall elements may be finished in a variety of finishes to suit the structure to be erected.

Further, according to the invention there is provided a structure comprising a plurality of elements as defined above, bolted together to form a structure.

The panel may have a mass of less than 160 kg per panel.

The panel may have a mass of from 40 kg to 160 kg, typically from 70 kg to 130 kg.

The ribs may be shaped to fit the hands of a worker.

The panel may have a surface area in excess of 1 m2

The panel may have a surface area of about 2 m?.

The panel may have a mass of above 30 kg/m?.

Typical panels have a mass of from 50 kg/m? to 90 kg/m?.

All UV sensitive components of the panel may be covered by non-sensitive materials.

The panel may be made without any alkaline sensitive or organic materials except for plastics.

Itis believed to be an advantage of the invention that the cost of a panel, and thus of a structure made there from, is low due to small quantities of material used, even though the process is more complicated and the pro-rata of materials may be more than conventional concrete. It is further believed that due to the large panels at low weight with cast in mounting points and convenient ribs / cavities, erection cost of a structure may be reduced due to the ease and simplicity with which it may be erected, services builtin / insulation inserted and cladding added, if needed.

Mounting points, service openings, and the like may be accommodated by making thickenings where these are required.

BRIEF DESCRIPTION OF EXAMPLE CHARACTERISITICS AND

MANUFACTURING PROCESS THEREFOR

. A manufacturing process for manufacturing a panel of the invention and the characteristics of such a panel are described below by way of a non-limiting example only.

Panel

A panel of the invention is typically a flat surface panel of about 16 mm thickness. 16 mm thickness is desirable because small sized (9,5 mm) stone chips can still be used and without stone chips in the mix, the concrete is very weak. Further, 16 mm is light enough but still thick enough to mount items and is still thick enough not to dry out quickly and thereby negatively affect the curing process.

The panel may be provided with ribs of about 54 mm on one side that act as handles and move the axis of bending from the center of the 16 mm panel to approximately the center of the 70 mm panel with ribs (16 mm + 54 mm = 70 mm). Steel rods of around

5.6 mm diameter may be placed in the ribs to counter-tensile stress on the ribs. The ribs themselves have adequate compressive properties, whilst the panel (flat sheet section), being much larger in surface has adequate tensile properties and excessive compressive properties.

A textile mesh, typically 75-g/m? polypropylene, is placed on the outer faces of the 16 mm section of the panel. This has the effect of keeping the panel from forming cracks when setting/curing and keeping it from drying out, thereby providing a quality thin panel. Further to this the textile mesh will also give this thin skin concrete panel dramatic added impact resistance and ensure that impact damage is localized and does not cause cracks through the panel when handled or in use as part of a structure.

The textile mesh is protected and bonded with a slurry mix that binds it to the concrete and protects it from the sun.

The panel is made from a concrete, which is a “wet mix”, but with additives and thus has a fairly low water: cement ratio, resulting in a strong yet economical concrete mix : (the additives reduce water by decreasing viscosity and also create faster chemical reaction for early strength).

The textile mesh is pre-dipped in a water or cement/water solution. A slurry of sand/cement/water is then used to bind it to the mould before the concrete is cast and again to work it in smoothly onto the cast concrete.

Thin concrete very easily dries out and this interrupts the chemical (hydration) process of the cement, causing very weak concrete. Curing is therefore critical. Adding water to the concrete increases the water: cement ratio, which also weakens the concrete and causes tremendous shrinkage that may result in cracks.

The textile mesh has a tendency to draw water by capillary action and can therefore not be effectively bound in its dry form. Placing wet (water or water/cement) drenched textile mesh on high quality thin skin concrete, allows the textile mesh to ensure the concrete does not dry from the surface, thereby maintaining its chemical (hydration)

process. It allows proper water: cement ratio in the concrete. If the concrete is a bit rich in water, the textile mesh draws water out. When the concrete hydrates (cures) and requires damp to ensure ideal curing, the textile mesh free's its moisture.

The panel with its ribs allows water to be poured into the cavities formed for extended curing, when the product has been removed from the mould (placing it ribs up).

The ribs also allow for easy bolting together of components (or to a frame or frame sections) and the cavity formed between the ribs can accommodate services / insulation and may be clad to conceal these and offer an acceptable finish.

Process of casting a Panel

Clean mould

Wipe with release oil

Place steel in ribs using spacers

Add cast in items / insulating (isolating) material and aperture formers if required (this process may take place prior to the placing of the steel)

Cast ribs (and cavities below thin panel section) in concrete and vibrate

Brush on cement/sand/water slurry on the surface now level with cast ribs. (However, with fairly wet concrete this process may be excluded if a guaranteed aesthetic finish is not required on the inner face, that may be clad. This could make the process simpler but requires “wetter concrete”. The same could apply to the outer skin, should this be clad or covered, although with the outer skin it tends to make the process more difficult.)

Dip textile mesh in water/cement or water only and place over entire surface (cutting where required)

Place concrete on entire surface and vibrate

Screed off excess concrete using mould edge as guide and quick vibrate to level and compact (only if a flat and even surface is required)

Place second textile mesh, after also dipping in water/cement or water

Pour slurry (water/cement/sand) mix in correct quantity onto the product, wood floatin and finish with a nosing tool on the edges (nosing only if the finish requires this)

Apply or add any desired texture or finish to the upper face, if required (this may also be done at a later stage)

Allow to cure under roof or cover until the panel has adequate strength to be removed from the mould (usually 12 hours +)

Flip over, loosen all that restrains it from stripping and lift off mould

Place product on suited platform and pour water into voids formed by ribs (if required for added curing)

Repeat process

DESCRIPTION OF AN EMBODIMENT

The invention will now be described, by way of non-limiting example only, with reference to an embodiment of the invention.

Figure 1 shows, a three dimensional view of a latrine (toilet structure) of the invention;

Figure 2 shows, an exploded view of the latrine (toilet structure) of Figure 1;

Figure 3 shows, in cross section, a latrine (toilet structure) of Figures 1 and 2,

Figure 4 shows the back panel of a latrine (toilet structure) of Figures 1 to 3 and a section there through.

Figure 5 shows, in three dimensional view, a house of the invention;

Figure 6 shows, in partially exploded view, a house of Figure 5; and

Figure 7 shows, in exploded view, a house of Figure 5.

In Figures 1 to 3, a latrine (toilet structure) 20 was made from light concrete panels of the type as shown and broadly in accordance with the invention.

In Figures 1 to 4, the back panel 10 has a mass of 108.6 kg and is light enough to be carried by 4 persons.

In Figures 1 and 2 reference numeral 12 indicates sidewall panels 12 having ribs 14, which panels are described in greater detail here below.

In Figure 4 on the cross-section, it can be seen that the panel 10 is 16 mm thick and has ribs 15 which are 54 mm thick giving a thickest dimension of 70mm.

The panel 10 has an opening 16 through which a pipe (not shown), may pass. The edges of which aperture are re-inforced 18.

The structure 20 consists of: 1. Concrete roof panel 22: one x lightweight interlocking concrete roof panel with a built-in socket to accept the internal vent stack and therefore providing a neat finish without the need of unsightly brackets. All overhangs are drip-edged and the roof shape allows very generous head height in the structure and has overlapping air-flow openings all round that ensures proper ventilation whilst keeping excess light from the structure as is required for a well-functioning fly-free VIP structure. The roof is completely rustproof and being concrete remains cool in summer. Visually the product is in a class of its own. The roof bolts internally onto the walls with four galvanized bolts and requires no wires whatsoever. The roof panel is professionally finished on all surfaces of the product. 2. Sidewall panels 12: two x lightweight interlocking concrete sidewall panels with built-in recesses and protrusions at anchoring points and to accept the door latch and hand washing apparatus. The sidewall panels bolt internally on to the rear wall panel with two galvanized bolts each and require no grouting etc. These sidewall panels are professional finished on all surfaces of the product. Ribs 14 are provided on sidewall panels 12. 3. Rear wall panel 10: one x lightweight interlocking concrete rear wall panel with built-in recesses and protrusions at anchoring points. The sidewall panel bolts internally on to the rear wall panel with two galvanized bolts each and requires no grouting. The rear wall panels are professionally finished on all surfaces of the product. A knockout for a waterborne sewer connection upgrade is provided. 4. Floor slab 24: one x lightweight interlocking concrete floor siab with a non-slip finish. The floor incorporates a “plug-in” built-in plumbing socket to accept the internal vent stack and a cast-in opening to suit any toilet pan required by the client. The floor edge overlaps and overhangs the sub-structure as a drip edge, whilst also providing convenient finger grips for placing. A proper seal is provided between the floor and the pit cover slab to keep all and any run-off water out of the pit below the structure.

The floor slab is professionally finished on all surfaces of the product. 5. Pit cover slab 26: one x lightweight interlocking concrete pit cover slab with a non-slip finish. The pit cover slab spans 1.8 min diameter and can be leveled with the soil as the floor rises 65 mm above the pit cover slab’s final level ensuring a watertight seal to the pit. The floor slab is professionally finished on all surfaces of the product. 6. Non-concrete items.

One x galvanized mild steel door with a lockable spring-loaded latch, complete with a fail-safe pipe hinge and a recessed escutcheon plate that ensures the door latches the way a proper door should when swung closed. The latch mechanism is designed in such a manner that the door can always be opened from the inside, even when locked from the outside.

One 110 mm vent stack consisting of:

An internal jointless section and a black external end section with an approved fly screen at the end (no brackets required and a guaranteed straight and neat internal system); :

One toilet pan; and

One plastic toilet seat.

Should the engineer so require, the following below ground options are available and recommended: a) The pit, although circular, can be layered with a textile mesh mat and plaster in layers to provide extra strength and resistance to sidewall collapse. Polypropylene textile mesh can be supplied by Rocla (Pty) Ltd (SA) in the form of 75 gram/m?. b) A brick built collar as per engineer design that will allow a much larger diameter, as the pit cover can be supported on the edge only. This enables very shallow or above ground pits to have adequate volume.

General

This unit is designed in specific components to be easily manhandled even in difficult terrain and yet offers a very attractive and durable, aesthetically pleasing house-like structure than any person will be proud of. Only the latest technology is incorporated and the structure is very large and spacious inside (1 100 mm deep x 900 mm wide x head height of 2000 mm). The weight of the structure is evenly distributed amongst the panels (taking into consideration that an item such as the roof has to be lifted to head height) so that only two persons are required to carry a panel.

Approximate panel weights are: pit cover — 113 kg. floor — 89 kg. walls — 105 to 109 kg, roof — 74 kg, all with easy hand hugging grip area, allowing easy handling even in difficult terrain. All 12 mounting bolts are situated internally and are not accessible when the door is locked, whilst the door cannot be removed when the bolts are in place. Thus, when locked, the structure cannot be tampered with, without removing the lock. Only a 10 mm spanner is required for assembly and all bolts (galvanized coach screws) self tap into plastic lugs that are cast into the opposing panel and therefore unbolting for easy later relocation of the structure to a new pit is guaranteed.

In Figures 5 to 7, a house 30 is shown which is built using elements 32 made in accordance with the invention and as described above for Figures 1 to 4, but includes wooden frame members 34 between the elements, that the elements 32 bolt on to.

Claims (35)

Claims I I il ee

1. A lightweight construction element, said element including a set settable composition, said element being in the form a panel less than 25 mm average thickness, the panel including: - stone particles in the settable composition; - one or more ribs; - steel rods located in the ribs to counter-tensile stress on the ribs; and - a textile mesh bonded into the two faces of the settable composition, thereby to protect it from sunlight.

2. An element as claimed in claim 1, wherein the textile mesh is made from multistrand and/or dreft wrapped flat strand type synthetic material.

3. An element as claimed in claim 2, wherein the textile mesh is 50 g/m? to 150 g/m>.

4. An element as claimed in claim 3, wherein the textile mesh is 75 g/m?.

5. An element as claimed in any of claims 2 to 4, wherein the textile mesh is made from polypropylene material.

6. An element as claimed in any one of the preceding claims, where the textile mesh is close to the upper and lower surface of the panel with the set settable composition sandwiched in between.

7. An element as claimed in any one of the preceding claims, wherein the settable composition is a cementitious composition.

8. An element as claimed in claim 7, wherein the cemetitious composition is concrete.

9. An element as claimed in claim 8, wherein the concrete is prepared as a wet mix but with a low water; cement ratio, resulting in a strong yet economical concrete mix.

10. An element as claimed in any one of claims 8 and 9, wherein the concrete includes additives, which reduce water by decreasing viscosity / friction when mixing the concrete and also create faster chemical reaction for early strength.

11. An element as claimed in any one of the preceding claims, wherein the textile mesh is pre-dipped in water.

12. An element as claimed in any one of claims 1 to 10, wherein the textile mesh is pre-dipped in a cement / water solution.

13. An element as claimed in any one of the preceding claims, wherein a slurry of sand and cement and water is used to bind the textile mesh to the mould before the concrete is cast and again to work it in smoothly onto the cast concrete.

14. An element as claimed in any one of the preceding claims, wherein the ribs are configured to allow water to be poured into the cavities formed for added curing, - when the product has been removed from its mould.

15. An element as claimed in any one of the preceding claims, which includes one or more pre-formed apertures which are reinforced thereby to permit easy access for pipes, cables, and the like.

16. A prefabricated structure, such as a dwelling or a latrine (toilet structure), which is constructed using a plurality of elements as claimed in any one of claims 1 to

15.

17. A structure as claimed in claim 16, wherein one or more of the wall, roof, and floor elements may include concrete, and may be formed by casting it in a mould.

18. A structure as claimed in any one of claims 16 and 17, which includes a base shaped to receive a lowermost element of the structure.

19. A structure as claimed in claim 18, wherein the base is a cast or moulded concrete section.

20. A structure as claimed in any one of claims 16 to 19, which structure is a latrine (toilet structure) or a larger structure, and includes a base formed with suitable drainage or plumbing apertures.

21. A structure as claimed in any one of claims 16 to 20, wherein each wall element is formed with a plurality of transversely extending apertures sized to receive bolts, plumbing, electrical wiring or similar items to aid in bolting together elements to form a structure or servicing the end structure.

22. A structure as claimed in claim 21, wherein apertures are made or cast into a flat surface of the elements, where it may be needed to run services through.

23. A structure as claimed in any one of claims 16 or 22. wherein lugs or mounting points are cast into the elements where needed to facilitate bolting together or attaching items, so as not to require bolts running through the elements for attaching purposes.

24 A structure as claimed in any one of claims 16 to 23, wherein each wall element is formed with a plurality of ribs on the surface of the element with transversely extending apertures being formed in the ribs, where they are required for bolting together or to run services there through.

25 A structure as claimed in any one of claims 20 to 24, wherein edges of the apertures are reinforced, flange-style.

26. A structure as claimed in any one of claims 16 to 25, wherein each element has a mass of less than 160 kg.

27. A structure as claimed in any one of claims 16 to 26, wherein each element has a surface area in excess of 1 m?.

28. A structure as claimed in claim 27, wherein each element has a surface area of about 2 m2.

29. A structure as claimed in any one of claims 16 to 28, which includes insulating / isolating materials cast in or placed in between the ribs of the element as claimed in claim 1.

30. A structure as claimed in any one of claims 16 to 29, which is clad on the inside surface (ribbed surface) so as to provide varying aesthetic or visual effect to the end product and conceal services, insulating / isolating materials and fasteners.

31. A structure as claimed in any one of claims 16 to 30, which is clad or finished on the outer surface (non ribbed surface) so as to provide varying aesthetic or visual effect to the end product.

32. An element as claimed in claim 1, substantially as herein described and illustrated. :

33. A structure as claimed in claim 16, substantially as herein described and illustrated.

34. Anew element or a new structure substantially as herein described.

35. A method of manufacture of a new element or a new structure substantially as herein described. DATED THIS 12™ DAY OF FEBRUARY, 2007. N & HAHN INC. Agents for Applicant