Field of the invention

The invention relates to methods of manufacturing formwork from waste materials, and the formwork manufactured by such methods.

Background to the invention

Formwork, structural formwork or forms are temporary or permanent moulds into which concrete or similar materials are poured. The formwork which is the most cost effective is timber formwork. Timber formwork is built on site, usually manually by skilled carpenters, and is easier to produce, but it is time-consuming to use for multiple larger structures.

Stay-In-Place formwork or forms are also well known in the building industry. These are assembled on site, usually out of prefabricated plastic forms. The formwork stays in place after the concrete has dried. This type of formwork confines the concrete and limits it being damaged by environmental effects. Conform™ and Octaform™ are two examples of stay in place formwork or concrete forming systems. Octaform™ comprises a forming system that stays in place, and the concrete wall is finished when formed, which eliminates the need for plastering, coatings or cladding. The plastic panels slide together vertically and interlock with each other. Conform™ also comprises panels which slide together. The panels are erected on site and the concrete is poured. No plaster, stucco, cladding or painting needs to be added. These formwork systems are designed to be lightweight.

There are enormous amounts of scrap plastic, waste and litter collected every day. There are considerable efforts being made to recycle, up-cycle and reuse the waste where possible, however the rate of wastage remains higher than the rate of recycling, up-cycling and reuse.

The concentrations of wastes continues to increase, and the results are seen in everyday litter and pollution of our oceans, rivers, streets and landscapes. The pollution has detrimental effects on industry and agriculture, sea life and human digestion.

Billions of tons of waste plastics litter the world already. The waste is accumulated in vast piles of mixtures which have varying properties. T o reuse these, they need to be cleaned and sorted into similar types. This is difficult and requires time-costly manual dextrous processes, which are usually not viable. Paper, labels, contaminants like metal closures and cans are usually present together. Drying and granulating the wastes into fine sizes are required usually. The quality of separated products are not always suitable for reuse. Typically, the waste is collected, sorted, and compressed to limit the space it occupies. Thereafter it can be processed for recycling.

To overcome the above problems, various products are being manufactured using the recycled waste. The concept of manufacturing building elements from waste materials is also known. Waste plastics can be converted into building materials using a plastic extruder and/or stamping equipment. This ultimately reduces plastic waste and recycles it into something useful. ( Noel Deepak Shiri et al.,“Processing of Waste Plastics into Building Materials Using a Plastic Extruder and Compression Testing of Plastic Bricks”, Journal of Mechanical Engineering and Automation 2015; 5(3B): 39-42).

Mixing sand with plastic waste to manufacture building bricks is also known. The bricks are produced by mixing waste plastic and sand after heating at 200°C. The heated materials are then mixed into a homogenous mix and poured into cube moulds ( Lairenlakpam Billygraham Singh et al., “Manufacturing Bricks from Sand and Waste Plastics”, International Journal of Engineering Technology, Management and Applied Sciences, March 2017, Volume 5 Issue 3). This process uses moulding which is a slower process.

Furthermore, interlocking building elements are known. Stumbelbloc™ produces plastic moulds which are used to make concrete building blocks or bricks. The blocks have a hollow core for reducing heat transmission, and they have male/female indentations on top and bottom which ensure that they interlock vertically with complete uniformity. These are also configured so that special or other blocks are needed for corners. These blocks are made with concrete and do not use waste. Furthermore moulding is a slower intermittent process.

Recycled mixed plastic has also been used to make interlocking solid palisades which are used for both small applications such as edging or raised beds as well for landscaping and terracing. These palisades are not designed for building structures such as housing, and are aesthetic in nature.

The inventor is of the opinion that the invention provides a novel and inventive method of manufacturing formwork from waste materials, the use of the formwork may help to alleviate the enormous lack of suitable housing, reduce the cost of building while providing an alternative method of recycling waste materials industrially.

Summary of the invention

According to an aspect of the invention, there is provided a method of manufacturing formwork from waste material, the method including the steps of:

granulating the waste material;

mixing the granulated waste material with sand;

heating the mixture between 250 °C and 350 °C; and

extruding the heated mixture to form elongate and interlockable building elements useable as permanent formwork for building, such that the formwork is assembled and remains in situ after building, and wherein the extruded elements include a rough surface as a result of the heated mixture being extruded through an extrusion die which includes a serrated exit profile, the rough surface facilitating plaster adherence and bonding to surfaces.

The waste materials may be washed before or after granulating. The unsorted waste material is preferably washed in large stirred tanks. The waste material may be washed using heated or unheated water, and chemicals to assist in cleaning the waste material.

The waste materials are preferably washed before granulating. The washing of the waste material results in the wetting thereof, and the wet waste materials are then granulated into small pieces. The small pieces may be around 25 mm ² in size.

Granulating the waste material includes granulating plastic, paper, and metal, amongst other wastes into relatively small pieces. The waste material is chopped by hammer mills or granulators.

The waste material may be partially or completely sorted into different types of waste before being granulated. For example, the waste material may be sorted into plastics, tin, paper and other types of waste.

The granulated waste material is transported into one or more large hoppers with stirrers. Scale vibrating conveyors are preferably used to transport the granulated and washed waste material to the large hoppers with stirrers. The scale vibrating conveyors constantly transport reasonably consistent amounts of materials which assists in producing uniform mixtures. The wet waste material may be mixed with sand, sand and rubble, sand and paper waste, or sand, rubble and sorted waste materials. The addition of sand to the mixture increases mass and acts as a fire-retardant. The sorted waste material may include paper waste material. Sand is preferably added together with paper waste material in reasonably constant proportions. For example, for each part of sand mixed in, a substantially equal part of paper is added. However, other suitable proportions or ratios may be used.

The one or more hoppers may funnel the mixtures into one or more large extrusion machines which are heated and heat the mixture. The extrusion machines are preferably heated by band heaters. The mixture is preferably heated to between 250 and 350°C which results in the meltable waste material melting and this temperature range converts the plastic waste material into adhesives which bind the waste materials together under pressure when extruding. Different plastics have different melting points. Temperatures between 250 and 350 °C cause low viscosity fluids to be used as adhesives for the waste material.

The wet mixture is preferably fed into the extrusion machine heated by band heaters, which heats the mixture. The heating of the mixture generates steam which produces random cavities or recesses in the interstices of the extruded elements. These cavities or recesses may also reduce heat transfer and increase heat retention.

The serrated exit profile of the extrusion machine die preferably permits the escape of steam at irregular intervals, so that a rough surface to the walls is produced as the heated mixture is extruded and the steam eliminates bacteria and sterilizes the extruded profile.

The heated mixture is preferably extruded through dies which produce building elements which include a lug configured at one end of the element and a recess at the other end, such that the elements are interlockable side by side. The lug of a first element is shaped and dimensioned to engage and friction fit with the recess of a second building element. In this way, two or more elements are interlocked. One or both side surfaces of the element may allow perpendicular or angled elements to be connected. As a result, one or more walls or surfaces may be built using the interlocked elements. Corner sections may be extruded, the corner sections being generally L-shaped.

The heated mixture is preferably extruded through dies which produce building elements which have hollow profiles. The extruded building elements may be about 6 metres (m) in length, which may be cut to desired lengths and the elements interlocked and then used as formwork for building. The width of the extruded elements may be between 40 - 1 10 cm. in other words the width of an upright formwork is between 40 - 1 10 cm.

In use, the hollow profiles of elements form vertical cavities which may be filled with concrete, which enable vertical concrete columns to be formed inside the cavities. The vertical concrete columns may be formed quickly and sequentially if concrete is pumped into the cavities. The cavities may be filled with concrete, or the cavities may be left unfilled, depending on the compressive strength required to support higher floors or roofs. The formwork remains in situ, and is not removed. As a result, the formwork becomes an integrated part of the walls of the building that is eventually built.

Plaster, stucco, render, cladding or the likes thereof may be applied to the filled or unfilled formwork.

Reinforcing bars may be secured in base plinths, strip foundations, or other suitable foundations. The reinforcing bars may engage with concrete poured into the formwork.

A lower ring beam may be installed on the foundation, below the formwork. An upper ring beams may be installed above the formwork, such that it provides support for a roof structure. The ring bean may be a complete reinforced ring beam. The ring beam may engage with concrete poured into the formwork, the concrete surrounding the ring beam and filling the cavities in the formwork.

Concrete lintels or ring beams may be fitted at required heights to provide horizontal connections and stability.

In another embodiment of the invention, the extruded building elements may be extruded as solid panels. The solid panels may have a thinner width than the hollow profiled elements, and may be used to form formwork for internal walls. The solid panels may be configured to interlock with the side of the hollow profiled element. The solid panel may include lugs and recesses of the same shapes and dimensions as the lugs and recesses configured on the hollow profiled element, such that the lug of a solid panel is interlocked with the side recess of a hollow profiled element. The solid panels may also be configured with a recess on at least one side, similar to the recess configured on the side of the hollow profiled element.

The profile length of the solid panels may be between 40 - 1 10 cm, in other words the width of an upright solid is between 40 - 1 10 cm. In another form, the solid panels may be extruded through a die which configures the solid panel with lugs at both ends thereof, which allows for the completion and joining of the end of the formwork of an internal wall to the formwork of an outer or perimeter wall.

The formwork may be conveniently stored and transported in desired lengths.

The formwork may have a minimal coefficient of expansion under fixed in-situ positions which reduces plaster cracking. The invention uses waste materials, such as paper, plastic and metal, as well as rubble, which is easily available everywhere, in desired imperfectly mixed compositions. The invention produces useful housing formwork by recycling waste. The use of recycled waste material to manufacture the formwork may reduce the cost of the formwork and as a result make building using the formwork more affordable and accessible to all. Drying of pieces of plastic waste together with metallic waste pieces is not required using the method of the invention.

In another aspect of the invention, the method may extend to the manufacture of smaller solid panels having a width of between 45 - 55 mm for use in the construction of model buildings, such as toy houses.

According to another aspect of the invention, there is provided formwork and extruded profiles manufactured by the method described above.

Brief description of the drawings

The invention shall be described with reference to the following non-limiting drawings, in which:

Figure 1 is an end view of a hollow formwork element;

Figure 2 is an end view of a further embodiment of a hollow formwork element;

Figure 3 is an end view of a further embodiment of a hollow formwork element;

Figure 4 is an end view of a further embodiment of a hollow formwork element;

Figures 5a-d are various views of the formwork element of figure 3;

Figures 6 and 7 are perspective views of the formwork elements of figures 3 and 4 respectively;

Figures 8 and 9 are end views of two embodiments of solid formwork elements;

Figures 10a-d are various views of the solid formwork element of figure 9;

Figure 11 is a perspective view of the solid formwork element of figure 9;

Figures 12a-d are various views of a corner formwork element; Figures 13 a-d are various views of hollow door or window frame formwork elements;

Figures 14 a-c are various views of solid door or window frame formwork element;

Figure 15 is a plan view of formwork of the walls a building comprising interlocked hollow and solid formwork elements;

Figure 16 is a plan view the completed walls of the building comprising the formwork of figure 15;

Figure 17 is a perspective view the completed building with a portion of the roof cutaway; and Figure 18 is a perspective view of the completed building with the roof.

Detailed description of the invention

It should be appreciated by those skilled in the art that, without derogating from the scope of the invention as described, there are various alternative embodiments or configurations or adaptions of the invention and its features.

The method of manufacturing formwork from waste material includes the steps of:

Firstly, unsorted waste material which includes granulating plastic, paper, and metal, amongst other wastes is washed in large stirred tanks. The washing of the waste material results in the wetting thereof. The wet waste material is then granulated into small pieces of around 25 mm ² in size using a granulator or a hammer mill. Scale vibrating conveyors are used to transport the granulated and washed waste material to the large hoppers with stirrers. The scale vibrating conveyors constantly transport relatively consistent materials which assists in producing uniform mixtures;

Secondly, the washed and granulated waste materials are mixed with sand, rubble and paper waste materials. For each part of sand mixed in, a substantially equal part of paper waste is added in. Other suitable proportions or ratios can be used.

Thirdly, the one or more hoppers funnel the wet mixture into one or more large extrusion machines which are heated by band heaters. The mixture is preferably heated to between 250°C and 350°C which results in the meltable waste material melting and this temperature range converts the plastic waste material into an adhesive material which bind the waste materials together under pressure when extruding. Different plastics have different melting points. Temperatures between 250 °C and 350 °C cause low viscosity fluids intended to be used as adhesives for the waste material, to be infused into the mixture. The heating of the mixture generates steam which produces random cavities or recesses in the interstices of the extruded elements. These cavities or recesses may also reduce heat transfer and increase heat retention. The heated mixture is extruded from the extrusion machine to form elongate and interlockable building elements which are useable as permanent formwork for building.

The formwork is assembled and remains in situ after building. The extruded elements (10, 10A) include a rough surface (not shown) as a result of the heated mixture being extruded through an extrusion die which includes a serrated exit profile, the rough surface facilitating plaster adherence and bonding to surfaces. The serrated exit profile of the die preferably permits the escape of steam at irregular intervals, so that a rough surface to the walls is produced as the heated mixture is extruded and the steam eliminates bacteria and sterilizes the extruded profile. For that purpose the infed materials to the extruder may be wet after washing.

The extruded building elements (10, 10A) are about 6 m in length, and may then be cut into different lengths as required. The elements (10, 10A) are interlocked and used as formwork for building.

Referring to Figures 1 to 7, the heated mixture is preferably extruded through dies which produce building elements (10) which are hollow and include one or more lugs (12) and one or more recesses (14) configured such that the elements (10) are interlockable side by side. As shown in Figures 1 -3, 5a-d and 6, there is a lug (12) configured at one end of the element (10) as well as a recess (14) at the other opposing end thereof. The lug (12) of a first element (10) is shaped and dimensioned to engage and friction fit with the recess (14) of a second building element (10). In this way, two or more elements (10) are interlocked.

Referring to Figures 2 to 7, a side surface (16) of the element (10) is configured with one or more side recesses (18) which allows another element (10) to be joined to the element (10) at a right angle and as a result a corner formwork (24C) of two elements (10 can be assembled or an intersecting formwork (30) between a hollow element (10) and a solid panel (10A) can be assembled.

The hollow profiles of elements (10) form vertical cavities (20) which are filled with concrete or similar material as shown in Figure 16. This enables vertical concrete columns (22) to be formed inside the cavities (20). The vertical concrete columns are formed quickly and sequentially if concrete is pumped into the cavities (20). Some or all of the cavities (20) can be left unfilled, depending on the compressive strength required to support higher floors or roofs. The formwork remains in situ, and is not removed. As a result, the formwork becomes an integrated part of the walls (24) of the building (26) that is eventually built, as shown in Figures 16 and 17.

Referring to Figures 4 and 7, the hollow elements (10) include lugs (12) at both ends thereof, which allows for the completion and joining of the end of the formwork of a wall (24A) to the side of the formwork of an perpendicular wall (24B), to create a neat corner formwork (24C), as shown in Figure 15.

Alternatively, and referring to figure 12a-d, a corner element (40) may be extruded, which can be used to provide a joint at the corners of the building.

Referring to figures 13a-d, and 14a-c, frame elements (42) and (44) may be extruded by the method, for constructing door or window frames.

Plaster (24D) is applied to the formwork, as has shown in Figures 16 to 18.

Reinforcing bars can be secured in base plinths, strip foundations, or other suitable foundations. The reinforcing bars engage with concrete poured into the formwork. Alternatively, a lower ring beam can installed on the foundation, below the formwork. In addition to this, upper ring beams can be installed above the formwork, such that it provides support for a roof structure. The ring beam can be in the form of a complete reinforced ring beam. The ring beam engages with concrete poured into the formwork, the concrete surrounding the ring beam and filling the cavities in the formwork.

Concrete lintels or ring beams can also be fitted at required heights to provide horizontal connections and stability.

Referring to Figures 8 to 1 1 , the extruded building elements (10) can also be extruded as solid panels (10A). The solid panels (10A) have a thinner width than the hollow profiled elements (10), and are used to form formwork for internal walls (28). The solid panels (10A) are configured to interlock with and connect to the side of the hollow profiled element (10). Referring to Figures 8, 10 and 1 1 , the solid panels (10A) also includes lugs (12A) and recesses (14A) of the same shapes and dimensions as the lugs (12) and recesses (14) configured on the hollow profiled element (10). The profile length of the solid panels (10A) is preferably 6m, which can be cut into desired lengths, in the same way as the hollow element (10). The width of the upright solid panel (10A) is between 88 - 1 10 cm. In another form shown in Figure 9, the solid panels (10A) are extruded through a die which configures the solid panel (10A) with lugs (12A) at both ends thereof, which allows for the completion and joining of the end of the solid panel (10A) of an internal wall (28) to the hollow element (10) formwork of an outer or perimeter wall (24), as shown in Figure 15.

The size of the extruded building elements may be scaled down to provide building elements for use in the construction of model buildings such as toy houses or architectural models.