WO2014007648A1

WO2014007648A1 - Improvements in, or relating to, aggregate materials

Info

Publication number: WO2014007648A1
Application number: PCT/NZ2012/000241
Authority: WO
Inventors: Peter Hamish Barrow
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-12-23
Filing date: 2012-12-19
Publication date: 2014-01-09
Anticipated expiration: 2014-06-23

Description

IMPROVEMENTS IN, OR RELATING TO, AGGREGATE MATERIALS TECHNICAL FIELD OF THE INVENTION

The present invention relates to aggregate materials.

In particular, though not solely, the present invention is directed to light-weight aggregate materials for use in building and other cementitious compositions.

BACKGROUND OF THE INVENTION

Aggregate materials have varying dimensions and are used in building and other cementitious products to provide the mechanical lock and engagement in the composition. Aggregates are typically granular in shape and are of a consistent grade meaning size, or sizes between set ranges. The aggregate provides localised reinforcement in the composition to hold the material in compression and tension and to arrest propagation of cracks. Reinforcing, for example steel rod and bar, is further added to concrete materials and other compositions to provide increased tensile strength.

Aggregates fall into two broad categories, natural and artificial. Natural aggregates are those derived from stone, rock or sand even if some form of post productions such as crushing is required. Artificial or synthetic aggregates are those derived as a by-product, or direct product from, an industrial process.

Natural aggregates for construction materials, are one of, if not the, most mined material in the world. Typically they are mined from mineral deposits and post-processed as needed to provide the necessary grade. Typically they are then transported by road, rail and ship to the desired location for storage or use. As such though dispersed the aggregate source can often be at large distances from the storage or end use point. There is therefore a transport cost and other impacts, including environmental, associated with their mining and transport.

Typically there is little re-use of such virgin materials, whether natural or artificial, and thus there is a constant demand for virgin material.

It is to artificial or synthetic aggregates the present invention is directed.

Manufactured lightweight aggregates for use in concretes are well known and may include such materials as sintered fly-ash, expanded clay, expanded shale, foamed slag and manufactured plastic aggregates. Manufactured plastic aggregates composed largely of waste steam plastics are a relatively new addition to this group of lightweight aggregates and due to their impervious nature and ductility, their inclusion has helped overcome some problems associated with the currently available lightweight aggregates. In particular, use of manufactured plastic aggregate is likely to eliminate the following problems that currently limit the usefulness of lightweight aggregates when used in concrete;

• rapid carbonation of lightweight concretes because of their high permeability by carbon and water

• difficulty in regulating water to cement ratio because of the capacity of lightweight

aggregates to absorb mixing water

• the low ductility (extreme brittleness and tendency to shatter) of lightweight aggregate concrete

• aggregate reactivity and associated expansion problems.

Presently, manufactured plastic aggregates are only able to attain low to medium compressive strength, which limits their use in concrete.

Compressive strengths in concretes rely on three main factors;

1. the strength of the aggregate

2. the strength of the cement paste

3. the strength of the bond between aggregate and cement paste. The bond between manufactured plastic aggregate and the cement paste may contribute to the lower compressive strength.

Presently most modern plastics are hydrophobic by nature and their surfaces inert. This may contribute to the lack of bond between the plastic aggregate surface and the cement paste.

Manufactured lightweight plastic aggregates are preferably manufactured from waste stream polymers.

Light weight synthetic aggregates have been proposed before. These in part have been proposed to provide lighter weight building products, and/or improved insulation properties.

Typically however such lighter weight solutions have been fillers more than aggregates, and whilst they provide improved insulation or reduced weight, they generally tend to weaken or compromise the strength of the building material. IN some situations where the synthetic aggregate is a fine or flake like particle it may rise to the surface of the concrete during vibration for any significant period of time. This can lead to difficulties in finishing the concrete.

One known synthetic aggregate goes by the name of POLYAGG™ and is manufactured from recycled Expanded Polystyrene Aggregate (EPS). However there are problems with using polystyrene in concrete as it may break down to produce toxic products.

The inventors own previous patent applications detail a comminuted commingled waste stream of plastics that is machine processed as a fine aggregate for cementitious building materials. Such aggregate was a loose particulate separate mixture of plastics of various types. Such fine aggregate (slightly courser than sand) of separate plastics still required a course aggregate. Other than cleaning and separating the only post processing of the plastics material prior to incorporation in the cementitious building material was machining it into fine pieces.

US 5,422,051 to Sawyers discloses a similar method for incorporating disparate plastics whereby the feed of different plastic types is incorporated into the feed for making building materials.

US 6,488,766 discloses a method of adding grit or other type of grip and reinforcing to individual plastic pieces of the same type by heating the plastic pieces and adding a grit (heated or not) and mixing the two so the grit imbeds into the individual pieces of plastic. Care is taken in this process to not fuse individual plastic particles together.

Other solutions to date have relied on waste plastic products of the same plastic. However the cost to separate and prepare such single streams from the commingled waste stream may not be cost-effective of at least tips the balance in favour of using virgin materials. The result being virgin materials are used (with drawbacks of weight and other impacts) and the waste stream of plastics material goes straight to land fill.

Such methods also have at least the problem of ensuring superior meshing of the plastics with the concrete, and also present random colour variations in the finished product due to the individual colours of the plastics unless the plastics are sorted to select only one colour type, or are pre- coloured to the desired hue.

In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art. It is an object of the present invention to provide an improved aggregate material, or to overcome the above shortcomings or address the above desiderata, or to at least provide the public with a useful choice.

BRIEF DESCRIPTION OF THE INVENTION In a first aspect the present invention consists in a method of manufacture of an aggregate material comprising or including the steps of;

obtaining a source of plastics material, whether of the same or different plastics types, heating said plastics material and mixing into a substantially homogenous melt or bound melt of heterogeneous plastics,

extruding said melt via at least one extrusion head, and

interrupting said melt leaving said at least one extrusion head to form individual pieces of aggregate,

wherein the result is an aggregate with a textured surface.

Preferably a volatile liquid is added prior to extruding said melt. Preferably said volatile liquid is water or substantially water based.

Preferably said volatile liquid is sprayed onto said plastics material or melt.

Preferably said heating produces at least partial out-gassing of said melt including any said volatile liquid added, which in turn produces surface texturing on said aggregate.

Preferably said source of plastics material is at least in part derived from a waste stream of plastics.

Preferably said source of plastics material is substantially derived from a waste stream of plastics.

Preferably at least part of said extrusion is into an atmosphere at a lower temperature than said melt.

Preferably said melt is extruded and interrupted within or into a liquid bath. Preferably said liquid is water.

Preferably there is a plurality of extrusion heads said melt is extruded from.

Preferably said plurality of extrusion heads are all of the same size to produce substantially similar size aggregates. Preferably said plurality of extrusion heads are of at least two or more differing sizes to produce different size aggregates.

Preferably said source is clean and consists substantially only of plastics materials devoid of contaminants. Preferably said source is dried prior to said heating and melting.

Preferably one or more additives is/are introduced to said plastics material before, during or after said heating into a melt.

Preferably said additives include any one or more of the following:

• stearates,

· sand,

• silica,

• fly ash, and

• air entrainer.

Preferably said source is predominantly comprised of thermoplastics. Preferably said heterogeneous mixture of granulated plastics comprises at least one of high density polyethylene, polypropylene, polyvinyl chloride (PVC), acrylonitrile butadiene styrene (ABS), polyurethane, polyamide, PET and other rigid plastics materials or the like.

Preferably said heterogeneous mixture of plastics comprises polypropylene and polyethylene.

Preferably said plastics material is heated to a point where the majority of said plastics material is in a plastic flow state, such that a sufficient portion of the plastics material, or any additive thereto, is/are in a state to as to bind the remainder of the plastics materials, or any additives thereto, as a whole.

Preferably said heating and extruding is achieved in an extrusion machine.

Preferably said extrusion machine is a planetary extrusion machine. Preferably said melt is in a plastic state (rather than elastic or melted state) at least prior to said interruption.

Preferably said plastics material prior to heating is in the region of 1 mm to 10 mm in overall diameter. Preferably said plastics material is heated to a temperature which for the majority of said plastics material is in its plastic flow range, and some material is still in the elastic flow region, and yet still further material has started to degrade and outgas.

Preferably said aggregate material is in the range of 5 mm to 30 mm in length with a diameter of between 5 mm to 30 mm.

In another aspect the present invention consists in an apparatus to form an artificial aggregate, said apparatus comprising or including:

means to receive a source of plastics material and heat said material,

a mixer to mix said plastics material to produce a substantially homogeneous melt or bound melt of heterogenous plastics,

a head to extrude at least one extrusion of said melt, and

an interruption mechanism to interrupt said at least one extrusion,

wherein said apparatus produces an artificial aggregate with a textured surface from said melt.

Preferably said heating produces at least partial out-gassing of said melt which in turn produces surface texturing on said aggregate.

In another aspect still the present invention consists in a building product including an artificial aggregate, wherein said aggregate is manufactured from a plastics material which is:

heated and mixed into a substantially homogenous melt or bound melt of heterogeneous plastics,

extruded via at least one extrusion head, and

interrupted such that said melt leaving said at least one extrusion head forms individual pieces of aggregate,

wherein the result is an aggregate with a textured surface.

Preferably the building product comprises said aggregate in the range of 30% to 95% (by volume) of the composition.

Preferably said building product comprises 40% to 60% (by volume) said aggregate.

Preferably said building product comprises 50% (by volume) of said aggregate.

Preferably said plastics materials and/or said aggregate comprise at least one or more of

high density polyethylene,

polypropylene,

polyvinyl chloride (PVC), acrinyl butadene styrene,

polyurethene,

polyamide,

Polyethylene terephthalate, and

other rigid plastics materials or the like.

Preferably said plastics material and said aggregate comprises substantially thermoplastic materials.

Preferably said plastics material is a heterogeneous mix of plastics.

Preferably said plastic material and/or said aggregate comprises substantially the following materials in the following ranges:

60% to 80% ww polyolefin type plastics

40% to 20% ww styrenic type plastics.

1% to 20% ww filler materials.

Preferably said fillers are any one or more of the following:

· gypsum,

• fly ash,

• fine mineral sand, and

• zinc stearate.

In a further aspect the present invention consists in an extrusion head for forming discrete pieces from an extrusion flow, comprising or including:

a first aperture to receive at least one extrusion flow of material,

a second aperture in fluid communication with said first aperture, whereby said extrusion flow of material can move from said first aperture and exit from said second aperture,

at least one interruption mechanism to interrupt said extrusion flow of material from said second aperture such that said extrusion flow of material is interrupted and forms discrete pieces of extrusion.

Preferably said extrusion head has more than one said second aperture as a die to extrude said extrusion flow.

Preferably said more than one second apertures are all the same shape or diameter. Preferably said more than one second apertures are of different shape or diameter, such that for example the discrete pieces of extruded material are of different shapes and sizes to reflect a range of aggregates they may replace.

Preferably there are between 1 to 30 said second apertures.

Preferably there are between 3 to 20 said second apertures.

Preferably said at least one interruption mechanism is a blade that cuts off said material as it is extruded.

Preferably said interruption mechanism is a rotating blade.

Preferably said rotating blade is at least coated with Teflon or other low adhesive quality material.

Preferably said rotating blade is driven by a prime mover.

Preferably said prime mover is an electric or hydraulic motor. Preferably said extrusion head extrudes into a bath of cooling liquid.

Preferably said cooling liquid helps the extrusion flow, or discrete pieces of extrusion to form a skin or non-adhering external surface and start the cooling process.

Preferably said cooling liquid is water.

Preferably said discrete pieces form aggregate of between 0.25gm to 5gms in weight. Preferably said discrete pieces form aggregate of between 0.5gm to 2gms in weight. Preferably said interruption mechanism runs at a rate to deliver said weight range.

In still yet a further aspect the present invention consists in a composite construction material including an aggregate formed from a commingled comminuted plastics material, wherein said aggregate is manufactured by

heating and mixing said commingled comminuted plastics material into a substantially homogenous melt or bound melt of heterogeneous plastics,

extruding said melt via at least one extrusion head, and

interrupting said melt or extrusion such that said melt or extrusion leaving said at least one extrusion head forms individual pieces of aggregate,

wherein the result is an aggregate with a textured surface.

In yet a further aspect the present invention consists in a method of manufacture of an aggregate material as herein described with reference to any one or more of the accompanying Figures 3 through 13.

In yet a further aspect the present invention consists in an apparatus as herein described with reference to any one or more of the accompanying Figures 3 through 13.

In yet a further aspect the present invention consists in a building product as herein described with reference to any one or more of the accompanying Figures 3 through 13.

In yet a further aspect the present invention consists in an extrusion head as herein described with reference to any one or more of the accompanying Figures 3 through 13.

In yet a further aspect the present invention consists in composite construction material as herein described with reference to any one or more of the accompanying Figures 3 through 13. As used herein the term "and/or" means "and" or "or", or both.

As used herein "(s)" following a noun means the plural and/or singular forms of the noun.

The term "comprising" as used in this specification means "consisting at least in part of". When interpreting statements in this specification which include that term, the features, prefaced by that term in each statement, all need to be present, but other features can also be present. Related terms such as "comprise" and "comprised" are to be interpreted in the same manner.

It is intended that reference to a range of numbers disclosed herein (for example, 1 to 10) also incorporates reference to all rational numbers within that range (for example, 1 , 1.1 , 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9 and 10) and also any range of rational numbers within that range (for example, 2 to 8, 1.5 to 5.5 and 3.1 to 4.7). The entire disclosures of all applications, patents and publications, cited above and below, if any, are hereby incorporated by reference.

To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and application of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting.

Other aspects of the invention may become apparent from the following description which is given by way of example only and with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred forms of the present invention will now be described with reference to the accompanying drawings in which;

Figure 1 : shows a cross-section through a concrete cylinder using aggregate of the prior art and clearly can be shown the matrix of the fine particles and course part or aggregate,

Figure 2: shows a further prior art product known as POLY AG 10 which is an expanded polystyrene aggregate that can be used for fill,

Figure 3: shows the plastics material that can be taken by the present invention to form an aggregate and is comprised of communited commingled plastics materials, in the preferred embodiment from a waste stream of plastics material,

Figure 4: is a further view of an amount of the plastics material shown in Figure 3,

Figure 5: shows closeups of typical plastics materials from the plastic materials the present invention can use showing the size ranging from 3mm up to 10mm in length, Figure 6: shows an extrusion head of the present invention to take an extrusion flow of melted plastics material and extrude it and interrupt it to form an aggregate material,

Figure 7: shows the extrusion header Figure 6 attached to an extrusion machine to receive a flow of extrusion material,

Figure 8: shows aggregate material formed from the extrusion head of Figure 7 falling into a setting fluid, in this case the setting fluid is water at a lower temperature to solidify the extrusion material as it falls from the head,

Figure 9: shows the continuance of the liquid bath of Figure 8 showing a conveyor system to remove cooled aggregate material,

Figure 10: shows the resultant aggregate material in closeup form,

Figure 11 : shows a cross section through a concrete material including the aggregate

material of the present invention,

Figure 12: shows a flow chart for a method of manufacture of the aggregate material of the present invention, and

Figure 13: is a close up of one form of the extrusion head.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments and methods will now be described with reference to Figures 1 through 13.

The plastic material 3 shown in Figures 3 through 5 used in the present invention is, in the preferred embodiment, sourced from precursor plastics materials intended for recycling (such as drink bottles, house hold cleaner bottles and the like). These precursors are not sorted by type of plastic. The plastics are simply collected and granulated in an appropriate granulating machine (not shown).

The plastics materials may be constructed from a variety of different plastic materials such as, but not limited to high density polyethylene, polypropylene, polyvinyl chloride (PVC), acrylonitrile butadiene styrene, polyurethane, polyamide, PET and other rigid plastics materials and the like. These are largely thermoplastic plastics, but to an extent thermoset plastics may also form part of the mix, since if they do not melt or otherwise decompose during the process they will add body to the resulting aggregate material 8.

Granulation will produce a heterogeneous mix of plastics material 3 which will vary in size, shape and composition. The exact grading of plastics material will depend on the requirements of the melt and heating system chosen, for example an extruder 5. In the preferred embodiment and experiments to date the preferred granule size of the plastics material 3 is between 3mm to 10mm.

It is not necessary for the plastics materials 3 to be sorted from small amounts of other waste materials such as glass and wood; this may help reduce the potential cost of the present invention and the time spent processing the plastics materials. Such additional material may help bulk out the aggregate material as needed.

The plastics materials 3 are preferably then dried to ensure there is minimal or a desired volatile content, such as for example water and chemicals. Again the extent to which this is required, if at all, will depend on the melt flow process chosen. Where an extruder 5 is chosen for this then the drying can be to the levels required for that extruder 5.

Additives for example but not limited to fly ash, Gypsum and refined sand can be added at this point prior to heating and processing.

Prior to the heating process an amount of volatile liquid may be added to the plastics materials 3. This may be achieved in a number of ways, but in the most preferred form is done by spraying such as for example to form a mist which then settles on the material. In other forms there may be an atmosphere of volatile liquid, for example in gaseous form, the plastics material 3 is subjected to. The concentration, volume, rate, and time can all be varied to result in a plastics material with the desired amount of volatile liquid or material applied.

The volatile material or liquid may be introduced before, as part or, or intermediate of the heating or extruding process, for example partway through a multiple extrusion process. The result of introducing a volatile liquid or material onto the plastics material or melt is that volatile liquid will that evaporate off during the heating or forming stage and further texture the surface of the aggregate to roughen its exterior and improve its traction and grip when used as an aggregate. In one preferred form the volatile material is water, or a substantially water based material.

The plastics materials are then heated and melted such that a majority of the plastics material is in a plastic flow state. At the very least the plastic materials are heated such that a sufficient portion of them, or any additive thereto, is/are in a state to as to bind the remainder of the plastics materials 3, or any additives thereto, as a whole.

In a preferred form the equipment to achieve this melting and heating is an extruder. One such example extruder is a planetary extruder made by Beier Machinery Co Ltd And marketed under the name of WE250 Two-step Planetary Extruder. Such an extruder is also a two stage one that allows further materials to be added partway through the extrusion process.

As the plastics materials 3 (described further below) or any additives thereto melt and form a whole, or melt, then further additives can be added as needed. These additives may be such as a lubricant zinc styrate. A planetary extruder provides an intermediate point as part of the two stage configuration for addition of these additives. The equipment, for example the extruder 5 mixes the plastics materials and any additives into a melt which can then be, for example, extruded. In the preferred embodiment the melt is extruded to, or by an extrusion head 4.

In the preferred embodiment the plastics materials 3 and additives (if present) are heated to temperature where the majority, or sufficient, of the plastics materials / additives are in their plastic flow zone, that is have melted and can flow. Due to the presence of several different plastics some materials may be heated past their plastic flow zone and may start to degrade or outgas. Other materials (non plastic) and additives may also do this, for example as described above as a volatile material or liquid. This aspect is desired as it will cause surface eruptions and texturing of the melt flow and the resulting aggregate material 8. Such texturing is vital in providing a secure keying of the aggregate material with the product it is mixed into, for example as an aggregate in concrete. One of the key aspects of the aggregate 8 formed is that it has a high surface area, such texturing, explosion and similar create this surface texturing. In other forms for manufacture the aggregate may be formed into geometric shapes, again with high surface area to increase its keying when incorporated into a building material, such as, but not limited to, concrete. Other additives by the texture (such as fly ash, sand etc) may also add this texture.

Still other materials will be heated but to a point below their plastic flow zone but above their elastic zone and so can deform easier. Others will be heated only but not to an elastic flow zone. Such materials (whether plastic or otherwise) will combine with the melt and add further toughening and reinforcement and texturing. Effectively they will form an aggregate within the aggregate material 8, and the melted materials will be the matrix holding the resulting mixture all together.

The extrusion head 4 will now be described with reference to Figures 6 and 7. The extrusion head 4 can have one or many extrusion dies (second apertures) 10 in it to extrude the melt. The dies 10 may be of the same shape and diameter, or may be a mixture of diameters and shapes as needed. Thus if only one form of aggregate material 8 is required then a multi-die extruder will speed the process up. Conversely if a specific mix ration of aggregate material 8 sizes is required then the dies can be shaped accordingly to produce this mixed size. For example if an aggregate material is required that runs the grade sizes from fine sand to course stone then the one head can make all these size at the same time.

In one preferred form the extrusion head 4 shown in Figure 6 has a back plate 13 which bolts down onto the extrusion head body 15. Inside the extrusion head body 15 there is an extrusion three or more stage port 16. This divides the flow into the extrusion head 4 and diverts it the extrusion die or dies 10. The extrusion head 4 also has a mount 17 to mount it so the extruder 5. The extrusion dies 10 can also be seen, in this case there are three shown. A drive shaft 18 is also shown that drives a cutter mount 19 for the interrupter 9, as a blade 11 (not shown). An external plate 20 is also shown which also helps in the initial cooling of the extruded material.

In some forms the extrusion head 4 or parts thereof may be cooled, such as for example, but not limited to, water cooling or similar fluids. There may also be initial cooling liquid spraying on to the material as it first extrudes.

In other less preferred forms the extruded material rather that passing through an extrusion head 4 may be extruded from the extruder 5 onto a roll form or similar with pockets or cavities therein to form the extruded material. In one preferred form of the extrusion head 4 there are between 1 and 30 dies 10, and preferably between 3 and 20. The flow 14 can be seen in Figure 13.

The extrusion head 4 just past the die opening from which the melt flows has an interrupter 9. In one form of the present invention the interrupter can be a rotating knife, blade or bar 1 1 which breaks the melt as it flows from the die 10. In the preferred embodiment the blade 1 1 is made from a low adherent material, to prevent the extruded product from sticking, such as Teflon or similar. The blade may be driven by a prime mover 12, such as an electric or hydraulic motor. In one form, where the extruder die 10 exits downwardly, the blade is driven from above as shown in Figure 13. The flow conditions from the equipment are adjusted to the melt as it exits the die 10 so it is close to elastic flow, or is only just on the cusp of plastic flow, such that it is brittle and will break, even though it is flowing from the die 10.

The extruder 5 is preferably run at close to maximum speed and the dies size and number and interrupter speed are sized to match. In one preferred form the resulting extruded material 8 from the head 4 is between 0.25 gms to 5 gms in weight, and preferably 0.5 gms to 2 gms in weight.

The "broken" melt flow, in one embodiment, then falls into a cooling medium, such as, but not limited to a water bath 6, as shown in Figures 7 through 9, whether at room temperature, or elevated or reduced temperature. This cools and finally solidifies the melt flow and is the final step in forming the aggregate 8. In some embodiments, it may not be necessary to have the bath 6, but experiments to date have shown it to be beneficial in speeding up the cooling and solidifying process and thus the manufacturing process.

In other embodiments the extrusion head 4, may be all or partly submerged in a cooling medium, such as, but again not limited to, a water (or other fluid) bath 6. Where the formed aggregate material drops into a collector, such as a trough, or a bath 6 then a conveyor 7 collects the aggregate material 8 and transports it as needed, for example to a drying and/or packaging line. The conveyor 7 is configured in methods known in the art to allow as much fluid as possible (if the aggregate is being removed from a fluid) to drain off. There may be agitation as needed to encourage such drain off. If there is a high proportion of material or aggregate 8 that is predominantly comprises of a polyolefin or a styrenic material, then this can be detected in the bath, due to a high styrenic content aggregate 8 sinking and a high polyolefin content aggregate 8 floating on the surface. In this way screening due to the float sink separation can be done to remove high contents of either material. Example Aggregate Recipes

Example of recipes for the plastics materials and additives will now be described. The plastic raw material for the heating and melting process is preferably a heterogeneous mix of all plastic types, preferably substantially thermoplastic materials. Typically for waste streams that can be used the mix is predominantly, however the plastics raw material that can be used can be any one or more of

• high density polyethylene,

• polypropylene, • polyvinyl chloride (PVC),

• acrinyl butadene styrene,

• polyurethene,

• polyamide,

· polyethylene terephthalate, and

• other rigid plastics materials or the like.

In one preferred mix the raw plastics material or resulting aggregate comprises substantially the following materials in the following ranges:

60% to 80% ww polyolefin type plastics

40% to 20% ww styrenic type plastics.

1 % to 20% ww filler materials.

The fillers as previously stated may be any one or more of the following,

• gypsum,

• fly ash,

· fine mineral sand, and

• zinc stearate.

In one recipe the zinc stearate is used as a filler of up to 10% ww to help lubricate through the extrusion process, and fine sand or fly ash or gypsum in the range of 2 to 4%.

In addition to these the following materials are added during the heating and melting process an air entraining agent in the range of 5% of the filler used.

Example building product recipes incorporating the aggregate

The aggregate material 8 once manufactured may be used in a number of different building products and processes and will be discussed in more detail below.

The aggregate material 8 in one preferred embodiment is formed into a cementitious composition containing:

- 50% (by volume) heterogeneous mix of granulated plastics materials (polypropylene and polyethylene)

- 50% (by volume) cement mix (cement (1 part), sand (4 parts), plasticiser).

Plasticiser is generally added in small amounts; the exact amount may be varied depending on the subsequent application to which the mix will be put. The above components are mixed with an amount of water sufficient to result in a cementitious mixture of a desired consistency for a particular application so as to form a substantially homogeneous mixture, moulded, poured or the like, and allowed to set.

A further example comprises 70% plastic and 30% cement mix.

Other additives may also be incorporated into the above general composition such as concrete stabilisers and other additives known in the trade.

In another embodiment of the invention the aggregate material 8 mix replaces all of the aggregate material used in known cementitious mixes; that is the aggregate material 8 replaces all of the gravel or sand utilised in prior art compositions.

In this preferred embodiment the building material 101 may be formed from a composition containing approximately:

70% plastic to 25% cement (or 3 parts plastic to 1 part cement)

66.6% plastic to 33.3% cement (or 2 parts plastic to 1 part cement)

91% plastic to 9% cement (or 10 parts plastic to 1 part cement)

In another embodiment the aggregate material 8 may be used in the following recipe of Mix 1. Mix 2 uses a foamed polystyrene prior art material as the aggregate:

Above mix designs are for 1 cubic metre (typical)

The results from this trial are as follows:

These recipes are those in common usage to form a 25 MPa concrete, with the aggregate predominately replaced in Mix 1 by the aggregate material 8 of the present invention. The result was a concrete material with a 25 MPa unconfined compressive strength. The bond between the aggregate material 8 and the cement is excellent, similar to that of a natural aggregate. The mixtures abovementioned are mixed with an amount of water and processed as described in the first preferred embodiment.

The resulting aggregate may be used in a variety of building products. For example it may be used to manufacture light weight concrete panels, such as those used in flooring and TILTSLAB™ constructions. The advantage here being light weight, strength and insulating properties. Other applications are in roofing for example roofing tiles, panels and the like.

The aggregate may also find use in roading or paving where exposure of the aggregate will provide grip. Incorporation of the aggregate in such slabs will also provide greater flexibility and thus reduce the likelihood of cracking. Other uses for materials constructed using the cementitious composition of the present invention may include: concrete, bricks, blocks, pipes, paving stones, tiles.

Testing Results

The results from various testing of aggregate material 8 when incorporated in various building materials will now be described. In normal concrete mixes using the aggregate material 8 compressive strengths of 20 MPa and higher have been achieved with cured concrete that is of lower density than standard when tested according to NZS 3112:1986 Part 2 Section 6. The resulting concrete using these near standard mixes also displayed very high flexural strength in excess of twice that of standard concretes (standard 20 MPa concrete is 2 MPa). An example concrete using the aggregate 8 of the present invention when prepared using compaction and vibration to form a paving slab had a flexural strength of 15MPa with an unconfined compressive strength of 40 MPa.

In compression test pieces concrete using the aggregate 8 develops numerous closely-spaced fractures at failure. This homogeneous strain distribution at high imposed stress is a potentially valuable property because forces are transmitted uniformly to embedded steel reinforcement, thereby preventing development of localised stress concentrations.

Concrete materials with the aggregate 8 have good sound insulation characteristics, chemical resistance, impact resistance, and can be machined easily. Porous compacted formulations for blocks and pavers have acceptable water absorption characteristics.

The aggregates 8 low density is potentially advantageous in seismic engineering. Concrete and other building products using the aggregate 8 are less permeable to fluids than currently available lightweight aggregates. The aggregate 8 is also chemically inert. Utilising the aggregate 8 in mixes will enable lower densities and higher strengths to be achieved without increasing mix cement content, and will hence confer significant technical and economic advantages.

It should be noted that recycled plastics materials of the kinds used in the present invention are believed not to breakdown and leach toxins into the environment. Other known additives to concrete, such as polystyrene, may breakdown to produce toxic by-products.

The advantage of the present invention is recycling of a waste stream that would otherwise remain in a landfill or be burnt or put to some lower economic value use.

Both methods have the effect of changing the plastic particle surface proving a bond between the plastic aggregate particle and the cement paste. This allows higher compressive strengths to be achieved in the concretes using plastic aggregate particles.

Further advantages are realised when it is understood that manufacture of the aggregate of the present invention can occur in localised areas of waste stream such as for example at landfill and recycling sites. Thus transport of the manufactured aggregate can be cheaper as distance to use and thus transport cost is lower than mining of traditional aggregates. A lighter aggregate such as that of the present invention also provides cost savings in transport in raw and in finished form (for example as uncured concrete en route to a pour, or cured precast items, such as TILTSLAB™ and the like).

Further advantages will be understood as the aggregate of the present invention results in a building product, for example concrete, that is easier to machine, for example drill and cut, as it cuts cooler and is more lubricating. Nailing and grinding is also easier.

The present invention also results in a product that has less impact on handling and preparation equipment

The foregoing description of the invention includes preferred forms thereof. Modifications may be made thereto without departing from the scope of the invention.

Claims

I . A method of manufacture of an aggregate material comprising or including the steps of; obtaining a source of plastics material, whether of the same or different plastics types, heating said plastics material and mixing into a substantially homogenous melt or bound melt of heterogeneous plastics,

extruding said melt via at least one extrusion head, and

wherein the result is an aggregate with a textured surface. 2. A method as claimed in claim 1 wherein a volatile liquid is added prior to extruding said melt.

3. A method as claimed in claim 2 wherein said volatile liquid is water or substantially water based.

4. A method as claimed in either of claims 2 or 3 wherein said volatile liquid is sprayed onto said plastics material or melt.

5. A method as claimed in any one of claims 2 to 4 wherein said heating produces at least partial out-gassing of said melt including any said volatile liquid added, which in turn produces surface texturing on said aggregate.

6. A method as claimed in any one of claims 1 to 5 wherein said source of plastics material is at least in part derived from a waste stream of plastics.

7. A method as claimed in any one of claims 1 to 6 wherein said source of plastics material is

substantially derived from a waste stream of plastics.

8. A method as claimed in any one of claims 1 to 7 wherein at least part of said extrusion is into an atmosphere at a lower temperature than said melt.

9. A method as claimed in any one of claims 1 to 8 wherein said melt is extruded and interrupted within or into a liquid bath. 10. A method as claimed in claim 9 wherein said liquid is water.

I I . A method as claimed in any one of claims 1 to 11 wherein there is a plurality of extrusion heads said melt is extruded from.

12. A method as claimed in claim 11 wherein said plurality of extrusion heads are all of the same size to produce substantially similar size aggregates.

13. A method as claimed in claim 1 1 wherein said plurality of extrusion heads are of at least two or more differing sizes to produce different size aggregates.

14. A method as claimed in any one of claims 1 to 13 wherein said source is clean and consists substantially only of plastics materials devoid of contaminants.

15. A method as claimed in any one of claims 1 to 14 wherein said source is dried prior to said heating and melting.

16. A method as claimed in any one of claims 1 to 15 wherein one or more additives is/are

introduced to said plastics material before, during or after said heating into a melt. 17. A method as claimed in claim 16 wherein said additives include any one or more of the

following:

• stearates,

• sand,

• silica,

· fly ash, and

• air entrainer.

18. A method as claimed in any one of claims 1 to 17 wherein said source is predominantly

comprised of thermoplastics.

19. A method as claimed in any one of claims 1 to 18 wherein said heterogeneous mixture of granulated plastics comprises at least one of high density polyethylene, polypropylene, polyvinyl chloride (PVC), acrylonitrile butadiene styrene (ABS), polyurethane, polyamide, PET and other rigid plastics materials or the like.

20. A method as claimed in any one of claims 1 to 19 wherein said heterogeneous mixture of plastics comprises polypropylene and polyethylene. 21. A method as claimed in either of claim 16 or 17 wherein said plastics material is heated to a point where the majority of said plastics material is in a plastic flow state, such that a sufficient portion of the plastics material, or any additive thereto, is/are in a state to as to bind the remainder of the plastics materials, or any additives thereto, as a whole.

22. A method as claimed in any one of claims 1 to 21 wherein said heating and extruding is

achieved in an extrusion machine.

23. A method as claimed in claim 22 wherein said extrusion machine is a planetary extrusion machine.

24. A method as claimed in any one of claims 1 to 23 wherein said melt is in a plastic state (rather than elastic or melted state) at least prior to said interruption. 25. A method as claimed in any one of claims 1 to 24 wherein said plastics material prior to heating is in the region of 1 mm to 10 mm in overall diameter.

26. A method as claimed in any one of claims 1 to 25 wherein said plastics material is heated to a temperature which for the majority of said plastics material is in its plastic flow range, and some material is still in the elastic flow region, and yet still further material has started to degrade and outgas.

27. A method as claimed in any one of claims 1 to 26 wherein said aggregate material is in the range of 5 mm to 30 mm in length with a diameter of between 5 mm to 30 mm.

28. An apparatus to form an artificial aggregate, said apparatus comprising or including:

means to receive a source of plastics material and heat said material,

a head to extrude at least one extrusion of said melt, and

an interruption mechanism to interrupt said at least one extrusion,

wherein said apparatus produces an artificial aggregate with a textured surface from said melt. 29. The apparatus as claimed in claim 28 wherein said heating produces at least partial out- gassing of said melt which in turn produces surface texturing on said aggregate.

30. A building product including an artificial aggregate, wherein said aggregate is manufactured from a plastics material which is: heated and mixed into a substantially homogenous melt or bound melt of heterogeneous plastics,

extruded via at least one extrusion head, and

wherein the result is an aggregate with a textured surface. 31. A building product as claimed in claim 30 wherein the building product comprises said

aggregate in the range of 30% to 95% (by volume) of the composition.

32. A building product as claimed in either of claims 30 or 31 wherein said building product comprises 40% to 60% (by volume) said aggregate.

33. A building product as claimed in any one of claims 30 to 32 wherein said building product

comprises 50% (by volume) of said aggregate. 34. A building product as claimed in any one of claim 30 to 33 wherein said plastics materials

and/or said aggregate comprise at least one or more of

• high density polyethylene,

• polypropylene,

• polyvinyl chloride (PVC),

· acrinyl butadene styrene,

• polyurethene,

• polyamide,

• Polyethylene terephthalate, and

• other rigid plastics materials or the like. 35. A building product as claimed in any one of claim 30 to 34 wherein said plastics material and said aggregate comprises substantially thermoplastic materials.

36. A building product as claimed in any one of claims 30 to 35 wherein said plastics material is a heterogeneous mix of plastics.

37. A building product as claimed in any one of claims 30 to 36 wherein said plastic material and/or said aggregate comprises substantially the following materials in the following ranges:

60% to 80% ww polyolefin type plastics

40% to 20% ww styrenic type plastics.

1% to 20% ww filler materials.

38. A building product as claimed in claim 37 wherein said fillers are any one or more of the following:

· gypsum,

• fly ash,

• fine mineral sand, and

• zinc stearate.

39. An extrusion head for forming discrete pieces from an extrusion flow, comprising or including: a first aperture to receive at least one extrusion flow of material,

a second aperture in fluid communication with said first aperture, whereby said extrusion flow of material can move from said first aperture and exit from said second aperture, at least one interruption mechanism to interrupt said extrusion flow of material from said second aperture such that said extrusion flow of material is interrupted and forms discrete pieces of extrusion. 40. An extrusion head according to claim 39 wherein said extrusion head has more than one said second aperture as a die to extrude said extrusion flow.

41. An extrusion head as claim 40 wherein said more than one second apertures are all the same shape or diameter.

42. An extrusion head as claimed in either of claims 40 or 41 wherein said more than one second apertures are of different shape or diameter, such that for example the discrete pieces of extruded material are of different shapes and sizes to reflect a range of aggregates they may replace.

43. An extrusion head as claimed in claim any one of claims 40 to 42 wherein there are between 1 to 30 said second apertures. 44. An extrusion head as claimed in any one of claims 40 to 43 wherein there are between 3 to 20 said second apertures.

45. An extrusion head as claimed in any one of claims 39 to 43 wherein said at least one

interruption mechanism is a blade that cuts off said material as it is extruded.

46. An extrusion head as claimed in any one of claims 39 to 43 wherein said interruption

mechanism is a rotating blade.

47. An extrusion head as claimed in claim 46 wherein said rotating blade is at least coated with Teflon or other low adhesive quality material.

48. An extrusion head as claimed in either of claims 46 or 47 wherein said rotating blade is driven by a prime mover. 49. An extrusion head as claimed in claim 48 wherein said prime mover is an electric or hydraulic motor.

50. An extrusion head as claimed in any one of claims 39 to 49 wherein said extrusion head

extrudes into a bath of cooling liquid.

51. An extrusion head as claimed in claim 50 wherein said cooling liquid helps the extrusion flow, or discrete pieces of extrusion to form a skin or non-adhering external surface and start the cooling process.

52. An extrusion head as claimed in either of claims 50 or 51 wherein said cooling liquid is water.

53. An extrusion head as claimed in any one of claims 39 to 52 wherein said discrete pieces form aggregate of between 0.25gm to 5gms in weight.

54. An extrusion head as claimed in any one of claims 39 to 53 wherein said discrete pieces form aggregate of between 0.5gm to 2gms in weight.

55. An extrusion head as claimed in either of claims 53 or 54 wherein said interruption mechanism runs at a rate to deliver said weight range. 56. A composite construction material including an aggregate formed from a commingled

comminuted plastics material, wherein said aggregate is manufactured by

extruding said melt via at least one extrusion head, and

wherein the result is an aggregate with a textured surface.

57. A method of manufacture of an aggregate material as herein described with reference to any one or more of the accompanying Figures 3 through 13. 58. An apparatus as herein described with reference to any one or more of the accompanying Figures 3 through 13.

59. A building product as herein described with reference to any one or more of the

accompanying Figures 3 through 13.

60. An extrusion head as herein described with reference to any one or more of the

accompanying Figures 3 through 13.

61. A composite construction material as herein described with reference to any one or more of the accompanying Figures 3 through 13.