AU732186B2

AU732186B2 - Lightweight settable compositions

Info

Publication number: AU732186B2
Application number: AU83133/98A
Authority: AU
Inventors: Paul Donahue; Michael Morrison
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-09-15
Filing date: 1998-09-07
Publication date: 2001-04-12
Anticipated expiration: 2018-09-07
Also published as: AU8313398A

Description

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This invention relates generally to lightweight, settable compositions and products and methods for their manufacure and also provides methods for recycling and utilizing waste materials and by use of fine colloid clay enables products to be manufactured in which otherwise incompatible, heterogeneous S_ materials are bound together in a more closely-packed conglomerate.

When attempts have been made to recycle waste materials such as expanded polystyrene foam by chopping them up into aprticles for incorporation into such products as lightweight concrete by mixing with cement many problems arise such as structural weakness due to cavitiation caused by improper binding due to replusion and non-cohesion, separation and air-entrapment such problems are aggravated when foam particles are contaminated by waste.

An object of the present invention is to provide lightweight products of cement and/or plaster incorporating particles of preformed polymeric V1 materials such as chopped waste thermoplastic or expanded foam polystyrene in a matrix wherein heterogeneous otherwise incompatible particles are more closely bound together.

According to one aspect of the invention there is provided lightweight settable compositions formed of heterogeneous materials comprising cement and/or plaster and at least one primary additive selected from a material capable of forming a colloid-like suspension in water and selected from a finely powered clay obtained from washed builders sand waste material or fine brick kiln dust and which, when added to a powdered pre-mix or to a water slurry of the mix reduces repulsion between a water slurry of the cement, and/or plaster and at least one secondary additive in the form of pre-formed particulate polymeric material in the form of chopped moulded thermoplastic waste -n material and/or crushed, chopped expanded foam polystyrene recycled waste material, said at least one primary additive enabling binding of the said heterogeneous materials.

The invention also includes a method of manufacturing pre-foamed polystyrene chips from waste material which comprises the following steps: 1) crushing waste or discarded fruit and vegetable boxes of rigid foam polystyrene to form chips, 2) compressing the crushed chips to compact the polystyrene and reduce the entrained air content, 3) flailing the crushed compressed chips to produce a chip (o structure having a plurality of interlinkable fibrous tufts extending from external surfaces thereof, Throughout this specification, unless otherwise stated, all percentages are percentages by weight.

Some non-limiting examples of the compositions and final products of S this invention and methods of preparation of same will now be described.

In one example of the method of manufacture of the compositions of this invention, a primary additive capable of forming a colloid-like suspension in water is added to a dry powder premix of cement or plaster or a blend of these two the primary additive can be a dry, finely powdered clay such as that extracted from waste builders' sand or brick kiln dust by a standard process of belt press sand washing and has particle size which is preferably between 1 to 100 microns. To improve the performance of the fine clay, a standard or conventional flocculent may be added and the amount of fine clay and flocculent added to cement or plaster (or blend of both) can be in Z the ratio of 1 to 50% with an optimum ratio of Slurries of cement/water, plaster/water or cement/plaster/water in combination with the fine clay of this 3 invention have an increased tendency to thicken or gel so that if any of these mixtures were placed side by side on a vertical surface such as sheet of glass, the one with the special colloidal clay would not sag or run down the glass whereas the other would run freely. This thickening or gelling of the slurry S means that cement or plaster incorporating these additives can be used as building fillers for repairing dry rot in timber or mortar gaps in brickwork instead of using expensive two-part fibreglass products.

Secondary additives to the mix or composition of the invention are small-sized particles of waste "plastic" chip and/or expanded foam polystyrene in the form of chips of recycled, crushed, chopped waste of 1 to particle size, preferably 1 mm. However, conventional cells of foamed polystyrene structures such as discarded fruit or vegetable boxes or packing form symmetrical particles, namely spheres of very low density and minimal external surface area and which are weak because they comprise S 98% entrained air. The relatively smooth spherical surface of these expanded foam polystyrene beads makes interlinking bonding with settable cement and/or plaster mixes difficult therefor the present invention includes a method of manufacturing pre-formed, expanded foam polystyrene chips from waste material which comprises the following steps: o 1) crushing waste or discarded fruit and vegetable boxes and packing of rigid expanded foam polystyrene to form chips, 2) compressing the crushed chips to compact the crushed expanded foam polystyrene and reduce entrained air content, 3) flailing the crushed compressed chips (for example in a swing-hammer mill) to produce a chip of deformed structure having a plurality of interlinkable fibrous tufts extending from external surfaces thereof.

It will be appreciated that the chips produced by the steps 1 to 3 above are greatly deformed compared to spherical cells and are substantially asymmetrical and of much greater relative external surface area compared both to the spherical cells incorporated within structures or alternatively as free beads. The air content of the chips produced by the process set forth in the above-described steps 1) to 2) is also inverted or O O reduced to within 2 to 20% and possibly reduced down to 2% and the fibrous tufts produced by the process of step 3) promote physical bonding or mechanical interlinking between adjacent chips when coated with slurry of the invention and after setting of the mix in the slurry. In one example, a .;.*.reduction in particle size of polystyrene chips from 7-10mm down to about 300 I- to 500 micron can be achieved during flailing and heat is generated by friction when a hammer mill is used which activates elastic memory of cells to partially re-inflate them to restore and entrained air content of for example 20% to When combining moulded preformed (thermoplastic) waste products with expanded foam polystyrene chips an optimum ratio is between 20% and 27 100% of polystyrene the optimum quantity being 50% by volume When the clay is incorporated in the correct ratio with cement or plaster or cement/ plaster/blend and water is added and mixed in to form a slurry, for convenience in this example the slurry mix will be referred to hereinafter as "the flow material" which flows around expanded foam polystyrene particles and adheres to them and moves like a soft foam. Unexpectedly, the flow material will not sag and is not repelled by or does not flow away from the polystyrene as would normally be the case if the fine colloid-like forming clay was not present the clay promotes surface cohesion and binding between normally incompatible materials in a heterogeneous mixture. The anti-sag properties of the slurry mix according to the invention enables its use for patching holes in plaster.

A wide variety of fibres ranging from cellulosic material such as S paper fibre and sisal to glass fibres may optionally be added to the slurry mix of the invention or may be used in conjunction therewith to strengthen the flow material. The fibres used may vary in length from 5mm to The dry powder mixes of the invention are placed into a dry, clean vessel and a wet mix is made mixing 15% to 35% by weight of water into the dry powder mix. The wet mix is suitable for pouring into moulds or for mixing with fillers. A dry mix is made by mixing 5% to 15% by weight of water to the dry powder mix. The dry mix is suitable for sculpting.

Additionally, for applications where the product of the invention ,:*.will be exposed to wet conditions for exterior use or otherwise exposed to or 1 5 come into contact with water it is desirable that the product be water-resistant and to this end a conventional or "off-the-shelf' waterproofing agent which is preferably in the form of a dry powder is preferably added to the initial powder pre-mix of the-flow material.

9S** An example of a preferred waterproofing material for use in this 2'o invention is a stearate selected from calcium stearate, zinc stearate and magnesium stearate or mixtures thereof. The amount of the selected stearate or stearates to be added to the dry powdered pre-mix can be between 1% and 30% while the preferred amount is When the final product sets it is highly water-resistant. The resultant water-resistance contributes many "2 unique properties to the flow material. Slurries of settable flow material with water incorporating the waterproofing agent or agents absorb water slowly and once a slurry has been prepared, dry powdered concrete colouring agents can be sprinkled onto the mixture and are slow to mix which creates a marbled 6 effect controllable by the degree of stirring. Afterwards this product may be further coated with a second layer of waterproofing stearate which will still bond to the surface but bonding is enhanced by the use of heat applied with a heat gun, blow torch or oven or kiln. If an extra layer of stearate is dusted onto the surface it increases water resistance and can be fused onto the surface as the heating melts the stearate crystals and fuses the stearate to form an extremely water-resisitant glaze. The resultant surface takes painting. Heretofore air bubbles entrained or trapped in slurry have caused a major problem of destroying reproduction features during moulding particularly in undercut to areas. The addition of stearates serves another very important function namely escape of air from the slurry is facilitated. Entrained air tends to form large single bubbles which slip easily out of the slurry.

The invention enables formation of a combination matrix which can :::vary in strength and density and the composition can be utilized in a laminating S 15 process to produce a wide variety of both ornamental and utility products. For example the inside surface of a mould may be coated with a water slurry of cement and/or plaster incorporating the colloidal clay binder with or without the waterproofing or colouring agents. When, the desired consistency has been reached this slurry can be swirled around the inside of the mould leaving a ZO coating approximately 2mm thick of the flow material mix on the inside wall surface of the mould. When this first layer has dried into a skin, a second coating may be applied which incorporates additives such as any of the above-described waterproofing agents, colouring agents or a core-forming cement/ polystyrene mix or cement/plaster mix may be packed into the mould cavity and onto the first layer or skin to produce a solid object. When the solid product so-formed is released from the mould the outer exposed surface is a hard, durable, water-resistant and or decorative finish. The inner part of the finished product is a light but firm core. The end result is a moulded product such as a statue or ornamental product such as a penguin having required strength and external durability.

The concrete or plaster setting agents used in this invention can be selected from a wide variety of these materials and blended accordingly. For example hard-setting types of plaster and cement may be added to softersetting types of plaster to increase their strength amounts added can vary from 1% to 99% but a range within 10% to 20% is ideal.

Plaster may be added to any cement used in the compositions of the invention for more rapid drying and setting.

10 Optionally, sand or granite dust may be added to increase wear strength of final products.

In another alternative techique for producing laminated foam-core products according to the invention, a soft core such as that produced by the expanded foam polystyrene-laminated or filled core process described above is t5 obtained by mixing aluminium powder or bicarbonate of soda orany other suitable foaming agent with "DONCRETE" or any other similar such material 00 0 to produce a thick foam which is then blended with plaster or cement with or without the colloidal clay and/stearate. There results a foamy, aerated lightweight plaster or cement which can be used as a core in place of expanded rigid -foamed polystyrene.

An advantage of using the waste product of fine colloidal-like clay/binder obtained from washed out builder's sand clay in the composition and method of the invention is that it functions both as binder and suspension agent. promotes cohesion between particles of normally incompatible materials 2 5 it allows pre-formed particles of synthetic polymeric material such as "plastic" waste material to be suspended in the cement and/or plaster water/slurry mix without "plastic" materials separating out or dramatically reducing the strength of the closely bound finally set, heterogeneous product.

8 Another advantage of the products obtained using the compositions of the invention is that it is possible to paint directly onto the surface of the set products without use of primer.

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Claims

1. Lightweight settable compositions formed of heterogeneous materials comprising cement and/or plaster and at least one primary additive selected from a material capable of forming a colloid-like suspension in water and selected from a finely powered clay obtained from washed builders sand waste material or fine brick kiln dust and which, when added to a powdered pre-mix or to a water slurry of the mix reduces repulsion between a water slurry of the cement, and/or plaster and at least one secondary additive in the form of pre-formed particulate polymeric material in the form of chopped moulded thermoplastic waste material and/or crushed, chopped expanded foam polystyrene recycled waste material, said at least one primary additive enabling binding of the said heterogeneous materials.

2. The compositions according to claim 1 wherein the primary additive is a finely-powered clay which is added to a dry powdered pre-mix of cement, or plaster or a blend of same.

3. The compositions according to claim 2 wherein the finely-powdered clay has a particle size between 1 to 100 microns.

4. The compositions according claim 2 or 3 wherein the finely-powered clay and flocculent are added to the dry powdered pre-mix in the ratio of 1 to by weight. The compositions according to claim 4 wherein 3% by weight of the finely powdered clay and flocculent are added to the premixes.

6. The compositions according to claim 1 wherein the at least one secondary additive is added to the pre-mixes in the form of crushed, chopped particles in the form of tufted chips of expanded foam polystyrene having a particle size range of 1 to

7. The compositions according to claim 6 wherein the chips have a iarticle size of approximately 1 mm.

8. The compositions according to any preceding claim wherein moulded pre-formed thermoplastic waste products are combined or admixed with tufted chips of waste expanded foam polystyrene in a ratio between and 80% by volume of polystyrene.

9. The compositions according to claim 8 wherein the ratio of moulded, pre-formed thermoplastic waste products is 50% by volume. The compositions according to any preceding claim wherein at least one waterproofing agent is added.

11. The compositions according to claim 10 wherein the waterproofing agent is a stearate.

12. The compositions according to claim 11 wherein the stearate is selected from calcium stearate, zinc stearate and magnesium stearate or mixtures thereof.

13. The compositions according to claim 11 or 12 wherein the amount of stearate or stearates added to the dry powdered pre-mix is within the range of 1% and 30% by weight.

14. The compositions according to claim 13 wherein the amount of stearate added is 3% by weight. The compositions according to any preceding claim wherein from 1% to 99% by weight hard-setting types of plaster and cement are added to softer-setting types of plaster and cement to increase strength.

16. The compositions according to claim 15 wherein from 10% to by weight of hard-setting types of plaster and cement are added to soft-setting types of plaster and cement.

17. The compositions according to any preceding claim wherein sand or granite dust or mixtures thereof is added to increase wear strength of final set products.

18. The compositions according to any preceding claim wherein fibres comprising cellulosic material such as paper fibres and sisal, and glass fibres are added to the water slurry to prevent vertical running down or sagging of the slurry during application.

19. The compositions according to claim 18 wherein the fibres used vary in length from 5mm to A method of manufacturing crushed and chopped pre-formed expanded foam polystyrene chips from waste material for use in the compositions of any one of claims 1 to 19 which comprises the following steps: 1) crushing waste or discarded fruit and vegetable boxes or packing of rigid expanded foam polystyrene to form chips, 2) compressing the crushed chips to compact the polystyrene and reduce the entrained air content, flailing the crushed or compressed chips to produce a chip of deformed structure having a plurality of interlinkable fibrous tufts extending from external surfaces thereof.

21. The method according to claim 20 wherein a particle size reduction of from 7 to 10mm down to 300 to 500 micron is obtained by flailing.

22. The method according to claim 20 or 21 wherein heat is generated by friction when a swing hammer mill is used which activates elastic memory cells of foam polystyrene to restore part of the originally-entrained air.

23. The method according to claim 22 wherein air is restored into the cells up to a content of between 20% to 30% by weight.

24. Lightweight settable cement or plaster compositions formed of heterogeneous materials substantially as hereinbefore described. A method of manufacturing lightweight settable cement and/or plaster compositions formed of heterogeneous materials substantially as hereinbefore described.

26. A method of manufacturing crushed and chopped pre-formed expanded foam polystyrene chips from waste material for use in the lightweight settable cement or plaster compositions formed of heterogeneous materials substantially as hereinbefore described. Dated this 5th day of Febuary 2001 MICHAEL MORRISON and PAUL DONAHUE By Our Patent Attorney JOHN L.DAVIES CO