WO2007049136A2

WO2007049136A2 - Method of making constructional elements

Info

Publication number: WO2007049136A2
Application number: PCT/IB2006/003017
Authority: WO
Inventors: Mogamat Kamedien
Original assignee: Mogamat Kamedien
Priority date: 2005-10-26
Filing date: 2006-10-26
Publication date: 2007-05-03
Also published as: WO2007049136A3

Abstract

A method of making a building or constructional element comprises the steps of dispersing rubber in particulate form in a settable matrix material such as a mixture of cement, water, sand and/or aggregate and forming the settable matrix material in which the rubber has been dispersed into building or constructional elements. The rubber particles are preferably obtained by shredding used vehicle tyres and may be dust sized particles or elongate shreds or fibres. The method includes the step of dispersing a bonding agent in the matrix material before the elements are formed so that the bonding agent, in the cured or set matrix material of the elements, adhesively bonds the rubber particles to the set matrix material. The bonding agent is preferably a synthetic latex product. The matrix material may be relatively stiff and be extruded to form bricks, for example, or may be relatively wet and be cast in moulds. Once the settable matrix material has been formed into the required shape it is allowed to cure.

Description

METHOD OF MAKING CONSTRUCTIONAL ELEMENTS

BACKGROUND OF THE INVENTION

THIS invention relates to a method of making building or constructional elements such as bricks, building blocks, and cast constructional elements. More particularly, the method is suitable for the elimination from the environment of solid waste material which is otherwise stored in unsightly dumps or tips. The invention extends also to building or constructional elements when made in accordance with the method of the present invention, and which contain said waste material.

SUMMARY OF THE INVENTION

According to one aspect of the invention there is provided, broadly, a method making building or constructional elements, the method comprising the steps of:

dispersing rubber in particulate form in a settable matrix material;

forming the settable matrix material in which the rubber has been dispersed into building or constructional elements; and

causing or allowing the settable matrix material of the building or constructional elements to cure or set,

the method including the step of dispersing a bonding agent in the matrix material before the elements are formed so that the bonding agent, in the cured or set matrix material of the elements, adhesively bonds the rubber particles to the set matrix material. The rubber will typically be vulcanised rubber, which is available as a waste material in the form of used vehicle tyres from waste dumps or tips which are environmentally unsightly and unattractive. The waste tyres will be subjected to comminution to achieve size reduction to obtain the rubber in particulate form. This size reduction will typically be by shredding the tyres in known fashion and using known shredding devices used for the shredding of tyres.

In one embodiment of the invention, the shredding may be so as to obtain rubber particles falling within the size range of dust, i.e. a few microns, up to 20 mesh. Preferably the particles have a maximum size of at most 30 mesh, typically at most 50 mesh. The shredded rubber particles will usually be subjected to size classification, for example by screening, after the shredding and before being dispersed in the settable matrix material, to obtain a desired particle size distribution, which can be established by routine experimentation.

When the particulate rubber has been dispersed in the settable matrix material, it may form 1 - 60% by mass, on a dry basis, of the settable mixture so obtained, which is formed into the elements. Preferably this proportion is 15 - 50% on a dry basis, more preferably 30 - 40% by mass.

In another embodiment, the shredding may be so as to obtain elongate shreds or fibres.

Rubber particles which are somewhat elongated in shape are preferred to more cubic or spherical granular particles in some embodiments. Routine experimentation can be employed to establish a suitable length:diameter ratio of such shreds or fibres. This ratio may be in the range 1 :1 - 10:1 , typically 3:1 - 7:1. In this regard the Applicant has successfully employed particles with a length of 1 - 4mm and a diameter of at most 1 mm, i.e. a length:diameter ratio of at least 1 :1 and up to 4:1 or more. In the case of bricks, shreds or fibres of up to 25mm in length can be used, preferably in conjunction with an extrusion process. The building or constructional elements may be of baked or burnt clay, being for example clay bricks produced in the usual way by firing in a brick kiln at the usual temperatures and according to the usual production cycle. The applicant has found that no unacceptable burning of the rubber takes place in the interiors of the building elements. There is, naturally, a slight drop in their compressive strength, depending on the rubber content, coupled with a somewhat reduced brittleness. Furthermore, the applicant has found that the method of making bricks according to the method of the invention can involve a somewhat faster burning cycle, and a somewhat shorter .hardening period, than those used for bricks made in the same fashion and from the same materials but omitting the bonding agent and the rubber. Clay bricks are typically extruded, the extrusions being cut into lengths which form bricks, and the rubber particles should be of a size and be present in a proportion which is determined by routine experimentation not to interfere with such extrusion or cutting.

Instead, the building or constructional elements may be of cementitious construction, a suitable mix being made of cement powder such as Portland cement powder, water and, optionally, sand and/or aggregate, the rubber particles and adhesive bonding agent being dispersed in the mix which forms the settable matrix. Once again, the applicant has found that conventional production cycles used to make cementitious building or constructional elements may be used, with conventional proportions of constituents other than the rubber and bonding agent, thereby to obtain elements which again are somewhat less brittle and are of somewhat reduced compressive strength, compared with those omitting the rubber and bonding agent.

Routine experimentation can again be used to establish acceptable or indeed optimum formulations, constituents and production cycles. In this regard the applicant has successfully used fibrous rubber particles of the lengtfrdiameter ratios set forth above and having a length in the range of 0.5mm or less, up to 50mm or more, the elements being formed by moulding under pressure and a slight swelling being observed after the moulding, arising from the resilience of the rubber.

In one embodiment of the method, typically used to produce constructional elements such as kerbs, channels, paving slabs, fence panels and other cast or moulded elements, a wet mixture of the settable matrix material is produced and poured into a mould or form, subjected to agitation, and allowed to set in the mould or form.

The mixture may include cement powder, water, sand and/or aggregate, and the rubber particles.

The mixture may further include crushed building or constructional elements of the same or a similar nature as those being produced.

Preferably, the mould or form is vibrated with the wet mixture therein.

The building or constructional elements are preferably removed from the mould or form once set and allowed to cure.

The curing time may be in the range 24 - 120 hours.

The bonding agent may be liquid or at least flowable, to aid in its dispersal in the settable matrix material. The applicant has found that various so-called tile-bonding or tile-grouting liquids, which are used as adhesive bonding agents in the adhesive securing of tiles in place, are suitable for this purpose, and are readily available from hardware stores in South Africa. In a preferred embodiment of the method, the bonding agent comprises an acrylic latex-based product. Once again, routine experimentation is expected to be used in the selection of a particular bonding agent for a particular application in accordance with the present invention, and in selection of the amount of bonding agent used. The applicant has found that bonding agentrubber volume/mass ratios in the range 1 :100 - 1 :5 are suitable. A typical preferred ratio is approximately 1 liter of bonding agent to 50kg of rubber.

The invention extends also to building or constructional elements when made in accordance with the method of the present invention.

Advantages of building or constructional elements according to the present invention, compared with conventional clay-based or cementitious elements, include lighter weight and attractive properties with regard to heat-insulation, sound-absorption, bullet-proofing, reduced breakage and good water-repellency, bricks in accordance with the invention being suitable for use in damp courses. A particular advantage, however, is the potential for eliminating, in a useful and productive fashion, dumps or tips of used vehicle tyres.

DESCRIPTION OF PREFERRED EMBODIMENTS

The invention will now be described, by way of non-limiting illustrative example, with reference to the following worked Examples and to a description of further embodiments.

In the Examples below, burnt clay-based bricks were produced, and cementitious or so-called cement bricks. In each case the rubber was shredded from used vehicle tyres and had a particle size in the range 30 mesh - 20 mesh when used for clay-based bricks, and when used for cement bricks, it comprised fibrous particles having a diameter of about 1 mm and a length in the range 30 - 50mm. For the clay bricks a conventional brick-making clay was used; and for the cement bricks ordinary Portland cement and a silica sand were used.

In each case the bonding agent was the tile-bonding liquid available in South Africa from Adhesive Manufacturing CC under the trade mark "EZEEBOND". The liquid is an acrylic latex-based product used in the described method as a cement additive, and contains Savinex (trade mark) Acticide (trade mark) and water. The Savinex product used comprises a synthetic latex which provides enhanced adhesion between the constituents of the building elements, while the Acticide product is a biocide used for preservation of the wet state product.

EXAMPLE 1 - CLAY BRICKS

A conventional brick clay or brick earth, used in the making of clay bricks, was employed, together with rubber particles obtained by the shredding of scrap used vehicle tyres, screened to be in the particle range 30 - 20 mesh. The proportion of rubber used amounted to 20% of the clay used, by volume, on a dry basis.

The clay was mixed with the conventional amount of water used in the making of ordinary clay bricks, and the rubber particles were admixed therein, together with a liquid bonding agent as referred to above. The bonding agent was used in a proportion of 1 litre bonding agent/metre³ of rubber.

Once the mixture was homogeneous, it was extruded and cut into bricks, which were then dried and burnt in the fashion used to produce ordinary clay bricks.

EXAMPLE 2 - CEMENT BRICKS

A conventional mixture of water, cement, sand, crushed stone aggregate and crusher dust was employed, except that a portion of the crushed stone aggregate was replaced by fibrous shredded rubber. The crushed stone removed formed 10% by volume of the total volume of the conventional mixture. The volume of fibrous rubber used to replace the aggregate removed was twice that of the removed aggregate. The rubber comprised fibrous shredded particles of about 1 mm diameter and about 30 - 50mm in length. The rubber particles accordingly formed 20% by volume of the mixture, and were obtained by shredding scrap used vehicle tyres.

A volume of 500 litres of the mixture was admixed with 500ml of the liquid bonding agent in a mechanical mixer, from which 126 cement bricks were formed by moulding. These bricks were allowed to dry and cure to produce cement bricks.

In each of Examples 1 and 2 bricks were obtained which were somewhat less brittle and of somewhat reduced compressive strength, compared respectively with, on the one hand, conventional clay bricks, and, on the other hand, cement bricks. In each case, other than the use of the rubber and tile-bonding liquid as described in Example 1 and Example 2, the brick-making process employed was substantially conventional.

Brick making in different regions employs different raw materials and different brick-making techniques, using different types of plant and brick- making machines. It is expected that, accordingly, routine experimentation will be carried out to establish acceptable or preferably optimum techniques, raw materials and proportions thereof, bearing practical and economic considerations in mind, together with the requirements of the manufacturer with regard to the desired specifications of the product.

In the above two Examples, building elements in the form of bricks were produced, using a relatively dry or stiff mixture which was extruded and cut into bricks, or moulded into individual bricks. The invention also has application to the production of cast or moulded products, in which a wetter mixture is used. Such products include kerbs, channels, paving slabs, fence panels and other building elements. By way of example, the production of a kerb according to an embodiment of the invention will be described.

Typically, the production of a kerb requires the following steps:

1. Mixture of constituents to form a wet mixture.

2. Pouring of wet mixture into pre-cast mould.

3. Vibration of mould with wet mixture in situ.

4. A set curing time before kerb (or other building element) is removed from mould in cured, solid form.

5. In certain circumstances the kerb (or other building element) although set may not be completely cured and may require further curing time.

Step 1 : Mixture of constituents

A generally conventional mixture of water, cement, sand, stone and crushed kerbs was produced. To this, a volume of fibrous shredded rubber was added. The volume of rubber added was equal to 10% of the total combined volume of the conventional constituents. The reaction was catalysed chemically by adding an acrylic latex cement additive as referred to above and mechanically by rotation and stirring. The product of the reaction is ready for step 2 once it is of a uniform colour and texture, and once the correct viscosity is achieved. Typically, the product must be of a medium to low viscosity to facilitate its transfer to a mould and the vibration thereof.

Step 2: Transfer of mixture

Once the mixture is ready for step 2 it is then poured or shoveled into a precast mould. The mould will typically be made of wood, metal, rubber or plastics materials.

Step 3: Vibration

Following step 2, the mould, with the mixture in situ, is placed on a vibrating surface. This surface is typically a vibrating table. This step is typically complete when the mixture is once again of uniform texture and the meniscus of the mixture within the mould is as level as possible. Steps 4 and 5: Curing

The curing process begins with the mixture in the mould. Once the product has set or congealed sufficiently, it may removed from the mould. The product is typically not ready for application however, and may require more time to cure. The curing process typically takes 24 to 120 hours.

In one embodiment, a mass of 381kg of rubber shreds was used per cubic meter of the concrete mixture.

Conveniently, following the mixing of the constituents in step 1 , the wet mixture can be transported to a construction site and then poured into moulds and allowed to cure on site.

Apart from the production of constructional elements using moulds, the above described wet mixture can also be used in place of conventional concrete mixtures for pouring foundations and for forming columns and other structures using suitable shuttering or form work.

By contrast with the above described method of producing bricks, the method of producing cast building elements can make use of either particles or shreds/fibres of rubber, whereas in the case of bricks, the use of rubber shreds/fibres is generally preferred.

The viscosity of the wet mixture can vary over a relatively wide range, but must be sufficiently low to permit pouring of the mixture.

A nominal value for the proportion of bonding agent to rubber particles or fibres in the mixture is one liter to 50kg. A typical minimum ratio of bonding agent to rubber is one liter to 100kg, while a typical maximum value is one liter to 5kg.

Claims

1. A method of making a building or constructional element, the method comprising the steps of:

dispersing rubber in particulate form in a settable matrix material;

the method including the step of dispersing a bonding agent in the matrix material before the elements are formed so that the bonding agent, in the cured or set matrix material of the elements, adhesively bonds the rubber particles to the set matrix material.

2. A method according to claim 1 wherein the rubber is vulcanised rubber.

3. A method according to claim 2 wherein the vulcanised rubber is obtained from used vehicle tyres.

4. A method according to claim 2 or claim 3 including subjecting the rubber to comminution to achieve size reduction to obtain the rubber in particulate form.

5. A method according to claim 4 wherein the comminution is achieved by shredding the tyres.

6. A method according to claim 5 wherein the shredding is carried out so as to obtain rubber particles falling within the size range of dust, up to 20 mesh.

7. A method according to claim 6 wherein the rubber particles have a maximum size of 30 mesh.

8. A method according to claim 7 wherein the rubber particles have a maximum size of 50 mesh.

9. A method according to any one of claims 4 to 8 wherein the shredded rubber particles are subjected to size classification after the shredding and before being in the settable natural material, to obtain a desired particle size distribution.

10. A method according to any one of claims 1 to 9 wherein the particulate rubber, when it has been dispersed in the settable matrix material, forms 1 - 60% by mass, on a dry basis, of the settable mixture so obtained.

11. A method according to claim 10 wherein the particulate rubber forms 15 - 50% by mass of the settable mixture.

12. A method according to claim 11 wherein the particulate rubber forms 30 - 40% by mass of the settable mixture.

13. A method according to claim 5 wherein the rubber particles are elongated in shape, having a length:diameter ratio in the range 1 :1 - 10:1.

14. A method according to claim 13 wherein the rubber particles have a length:diameter ratio in the range 3:1 - 7:1.

15. A method according to claim 13 wherein the rubber particles have a length in the range 1 - 4mm and a diameter not exceeding 1 mm.

16. A method according to claim 13 wherein the rubber particles have a length not exceeding 25mm.

17. A method according to any one of claims 1 to 16 wherein the building or constructional elements comprise clay, the elements being formed as clay bricks and being fired in a kiln.

18. A method according to claim 17 wherein the clay bricks are formed by extrusion, the extrusions being cut into lengths which form bricks, and the size and proportion of the rubber particles being selected to minimize interference with such extrusion or cutting.

19. A method according to any one of claims 1 to 16 wherein the building or constructional elements are cementitious, comprising a mix of cement powder and water, the rubber particles and adhesive bonding agent being dispersed in the mix which forms the settable matrix.

20. A method according to claim 19 wherein the mix of cement powder and water further includes sand and/or aggregrate.

21. A method according to any one of claims 1 to 20 wherein the building or constructional elements are formed by moulding under pressure.

22. A method according to any one of claims 1 to 16 wherein a wet mixture of the settable matrix material is produced and poured into a mould or form, subjected to agitation, and allowed to set in the mould or form.

23. A method according to claim 22 wherein the mixture includes cement powder, water, sand and/or aggregate, and the rubber particles.

24. A method according to claim 23 wherein the mixture includes crushed building or constructional elements of the same or a similar nature as those being produced.

25. A method according to any one of claims 22 to 24 wherein the mould or form is vibrated with the wet mixture therein.

26. A method according to any one of claims 22 to 25 wherein the building or constructional elements are removed from the mould or form once set and allowed to cure.

27. A method according to claim 26 wherein the curing time is in the range 24 - 120 hours.

28. A method according to any one of claims 1 to 27 wherein the bonding agent is a flowable liquid, to aid in its dispersal in the settable matrix material.

29. A method according to claim 28 wherein the bonding agent comprises an acrylic latex-based product.

30. A method according to any one of claims 1 to 29 wherein the ratio of bonding agent to rubber in the building or constructional element is in the range 1 liter of bonding agent to 100kg of rubber - 1 liter of bonding agent to 5kg of rubber.

31. A method according to claim 30 wherein the ratio of bonding agent to rubber is about one liter of bonding agent to 50kg of rubber.

32. A method of making building or constructional elements substantially as herein described with reference to Example 1 or Example 2 herein, or with reference to other described embodiments.

33. A building or constructional element formed by the method of any one of claims 1 to 32.