Mixture for slab production   

Abstract: A method for producing a cementitious slab including mixing together cement with other materials with the combined mixture of materials having physical particle sizes sufficiently small to allow the material to be cut with a vibrating cutting tool when the material is a semi-set state.

FIELD OF THE INVENTION

The present invention relates generally to slab products and methods of manufacturing same.

Presently, the process of manufacturing cementitious products such as tiles in small individual moulds remains substantially the same as production methods that have been employed for the past 50 years and is still popular throughout the world.

However, over the past twenty years, the production of tiles has developed resulting in tiles with a greater contemporary appearance in response to the fashion and trends of modern architecture and interior design.

Presently, commercially available cementitious slab products are produced from a mix which typically comprises cement, silica sand, large (or coarse) aggregate pieces, a water reducing admixture and water. The large aggregate pieces are included to make up mass and may vary in size from approximately 3 mm to 10 mm or larger. Stone chips are often used as large aggregate pieces. The water reducing admixture may be a plasticizer based on Polycarboxylatic Ether Polymer.

The strength of material used in tile production has increased in relatively recent times, allowing tiles to be produced from a single large and thin slab, similar to marble or granite slabs, which can be cut to produce square or rectangular tiles of a desired size.

Large slabs are formed in individual moulds which are then subject to a vibration process. This causes the finest particles to move to the bottom of the mould. A slab takes the form or shape of the surface of the mould. This is known as “off-form” material.

Such production methods have allowed for greater flexibility in variation of sizes and thicknesses of square and/or rectangular tiles. Cutting tiles from a single slab allows for the production of square and/or rectangular tiles of differing sizes, which would previously have been produced in small individual moulds. Flexibility in production allows tiles to be made to a size at the request of a client without significant re-tooling or maintaining a large number of different mould sizes in stock. Additionally, precision machinery allows for a more accurate and superior finishing for the tiles.

In addition to the abovementioned advantages, cutting a large slab into smaller tiles takes advantage of the inherent natural aesthetic qualities of the large format slab. When separated, the smaller tiles have a unique appearance which increases the visual appeal of large surfaces such as walls and floors when covered with the smaller tiles

After the material is mixed it is placed into large moulds where the mix is vibrated into place. For mixes where fluid is added in order to activate the bonding process, the mix is poured into the mould and allowed to cure to a sufficient extent to allow the slab to be removed from the mould. For dry mixes where the bonding process is commenced by subjecting the mix to heat, the mix is poured and pressed into the mould. Dry mixes usually include resins that have a relatively high melting point and once sufficient heat is applied, the resin melts and bonds the remaining materials in the dry mix together. Cooling the material in the mould then sets the liquefied resin and allows the slab to be extracted from the mould.

The moulds are generally stored in a location where the material is allowed to set and harden prior to cutting. The storage period for wet mixed slabs is approximately one to four weeks before the slab is sufficiently cured for cutting of the material.

For naturally cured large slabs, once hardened sufficiently they are de-moulded and stacked for curing. Curing may require up to 4 weeks depending on the method and effectiveness of the curing process.

Of course, the need to allow the slab material sufficient time to cure prior to the cutting process requires the poured slabs to be shifted from the pouring line to a storage area. Generally, the slabs rest on frames after removal from their mould and are packaged for curing. This requires an interruption to the manufacturing process and the provision of sufficient storage space to store the slabs for curing in addition to the manually intensive processes associated with the removal of the slabs from their moulds and placing into storage for curing.

Slabs are calibrated for thickness before being cut into tiles. Following cutting, tiles are “rectified” to produce more accurate sides, the edges of the tiles are chamfered or arrised to erase chipping damage that is usually caused during the cutting process. Individual tiles are then processed including cleaning, drying and packing before being dispatched for sale.

The cutting process and subsequent operations are commonly performed on a continuous automated production line.

As a result, cement or concrete tiles may be ordered and installed in a similar manner to marble, granite and/or porcelain tiles. Further, tiles processed in this manner generally result in a higher quality installation outcome.

However, present production methods of tiles have a number of significant problems.

For example, the processing (cutting, calibrating, arising and/or rectification) of a slab is generally effected by use of diamond cutting tools, such as cutting blades, calibrating tools etc.

When cutting a slab, which is a very hard material, the edges of the cut are subject to varying degrees of chipping and rough edges. Further, the slabs and/or tiles are liable to crack or break during the cutting and calibrating process. The stresses can cause chips and breakages, particularly at corners where the cementitious slab or the tiles are weakest.

The chipping, cracking and/or breakages can result in wastage or the need to repair damaged material. This can be both costly and time consuming.

Another disadvantage is that the processing is difficult and requires care by skilled operators in order to ameliorate wastage due to chips, cracks and/or breakages. Such skilled operators are costly and the production of the tiles from the slab is time consuming and interrupts the production process.

Subsequent to the calibrating and cutting process, the slab products are generally stored again to fully cure which may require a further three to four weeks of storage in a controlled environment before dispatching the products to their installation destination. The further storage of slab products for final curing represents additional handling and storage costs.

Other disadvantages in present production techniques include the need for expensive equipment for cutting (including diamond tools and large capital equipment), large energy costs (for example, electricity) and a large amount of water, which is consumed during the processing of slabs into products. It is not unusual for a calibrating apparatus to cost $400,000 or more with a cutting line expected to cost approximately $700,000 to $1 million dollars.

The cutting and calibration processes also result in a large quantity of waste material, which is created when material is removed during the cutting and calibration processes. The waste must then be separated from the water used for the processing prior to re-use of that water. The separated waste material must be collected, treated and disposed of, which may be inconvenient and/or expensive. In this regard, the cost of a water filtration system is expected to be approximately $100,000 to $200,000. Further, the operational cost with respect to electrical energy consumption of all the equipment is generally significant as most of the equipment needs a multi-purpose power supply.

The cutting process can be particularly wasteful when cutting small tiles or mosaic pieces as the diamond cutting blade removes approximately 3 mm to 5 mm of material from each cut. When producing many tiles from slabs, the total volume of material removed during the cutting process is significant.

As a result of problems with existing processes, it has been considered that producing small tiles, mosaic pieces and tiles with curved or other non-quadrangular shapes is too problematic. In the case of mosaics, present production methods typically result in approximately 50% to 60% wastage of material thereby only generating a 40% to 50% yield. This is primarily due to the substantial amount of material that is wasted as a result of the cutting process producing relatively small tiles combined with the increased incidence of damage inflicted on the tiles. Unfortunately, the relatively small size of the tile leads to an increased incidence of chipping as the tile moves and vibrates as it is separated from the slab as compared with larger tiles that are not as susceptible to movement during separation due to their greater weight.

Furthermore, cutting other types of slab material, such as plasterboard, can be problematic as such materials are generally cut in a hardened state subsequent to manufacture. Typically, preparing a factory for production of slabs and tiles is an expensive undertaking requiring a great deal of planning, preparation, construction and installation time. A factory floor must be specially adapted in order to accommodate heavy purpose built equipment, with each plant requiring drainage systems and effluent tanks for collecting, separating and treating waste material from the water. In addition to all of the abovementioned disadvantages, the construction of a factory with special purpose drainage systems in itself represents a significant cost and hence an impediment to the establishment of a manufacturing facility.

Tiles produced by present processes are not suitable for applications such as creating mosaics, countertops, kitchen islands and/or furniture etc due to the rough edges and/or appearance of the large aggregate pieces at the sides or at the surface of the tiles. Currently, it is preferred to use other materials which are considered less problematic for these applications.

At least one further disadvantage exists with present slab and tile production, being that the products have a high flexural strength. The high flexural strength has the disadvantage that cracks in the tiles do not appear readily and may only become obvious after the product has been fixed in place. This may lead to the requirement for expensive replacement of products such as installed tiles.

Cracks do not readily appear in the product even in circumstances where the product has suffered a solid impact. Such cracks do not readily appear as the interlocking structures of the coarse aggregate pieces tend to hold the material of the product together.

An alternative product to slabs and tiles produced therefrom is natural stone material. However, natural stone material has many variables which are difficult to control. The stone material may be too soft, too hard, too porous or may have too many veins to be useful for a particular purpose. Furthermore, such materials may not be aesthetically appealing for a customer or suitable for a particular application.

It is an object of the present invention to provide a process and product which at least ameliorates one or more of the above-mentioned disadvantages associated with slab and tile production.

The reference to any prior art or prior art techniques, in this specification is not, and should not be taken as, an acknowledgement or any suggestion that these references form part of the common general knowledge of persons skilled in the relevant field of technology of the invention as claimed herein.

SUMMARY

In one aspect, the present invention provides a method for producing a cementitious slab including mixing together cement with other materials with the combined mixture of materials having physical particle sizes sufficiently small to allow the material to be cut with a vibrating cutting tool when the material is in a semi-set state.

The mix may include fine and ultra fine aggregate material and a water reducing plasticizer, which may be a polycarboxylic ether polymer.

Further, the mix may also include at least one of a crushed aggregate material or flour and water.

In an embodiment, a buffer solution is added to the mixture to reduce surface tension. In this regard, one or more of vinegar and/or ethanol is added to the mixture which has the effect of reducing air contained in the mix. Of course, other fluids may be added for this purpose.

The addition of a buffer solution to reduce surface tension in the mix allows the material to be poured into a mould and for the poured material to release any entrapped air within the mixture without requiring vigorous vibration that is presently needed to agitate material to allow entrapped air to rise to the surface and escape the mixture prior to curing. Further, the inclusion of a water reducing plasticiser such as a polycarboxylic ether polymer has the effect of reducing the viscosity of the mixture such that it can “self level” and to a certain extent “self compact”.

In an embodiment, the fine aggregate material and/or an ultra fine aggregate material and/or the crushed aggregate (flour) material is a siliceous material. In one particular embodiment, the siliceous material is sand (silica sand).

In an embodiment, the material is mixed together thoroughly. As a result of the material only including relatively small sized particles (i.e. without any large aggregate that is usually included), the mixing may be performed with a standard commercial dough mixer (or similar device). This avoids the need for an extensive planetary mixer that is usually required when mixing cementitious materials, containing large aggregates and also assists to effect a more thorough mix of the materials.

Once thoroughly mixed, the material may be poured into a mould. In an embodiment, a mould is formed by creating retaining walls on a flat surface. The walls of the mould are prepared specifically for each pour of the material. In an embodiment, the flat surface is a pane, or sheet, of glass and the mould walls are formed with a quick drying acrylic material that is ejected under pressure from a container. In this embodiment, the acrylic material is a material commonly used for filling gaps prior to painting a surface.

Further, the material is ejected from the container and directed toward a removable mould forming wall that retains the acrylic material in place until it is sufficiently dry to remove the forming wall. The acrylic material is allowed to cure sufficiently until it is capable of retaining the poured material within the mould walls.

The present invention enables mould walls to be formed with quick drying acrylic material as there is a reduced requirement for vigorous shaking and/or vibrating in order to level the material and cause entrapped air to escape. Ordinarily, mould walls formed with a malleable acrylic material would not be sufficiently strong to retain the poured material during a shaking or vibrating process.

In another embodiment, the mould may include a sacrificial layer (or mould liner) that is applied prior to pouring the material into the mould and may be removed when de-moulding occurs. The mould lining may be a relatively thin sheet of plastic material and in one embodiment, the mould liner is applied to the mould surface with a device to reduce the likelihood of air being entrapped between the mould surface and the mould liner. A mould liner reduces wear on the mould surface in addition to substantially reducing the requirement for daily cleaning and/or maintenance therefore reducing wastage and/or costs and/or improving quality of the slab product.

In an embodiment, the fine aggregate material may be sized between approximately 355 microns and 700 microns, the ultrafine aggregate material may be sized less than 355 microns and the crushed aggregate material and/or flour may be sized less than 150 microns. The sizes of the particles described above have been found to allow a cementitious slab to be cut in a semi-set state without the material tearing or rippling either during or after the cutting process or melding back together once cut.

In another embodiment, the slab further includes a colouring agent that is added to the mixture.

In other embodiments, materials are added to the mixture to provide the slab and/or any slab products separated therefrom with properties that are otherwise unknown for present slab products.

In this regard, the present invention allows relatively thin slabs 3.5 mm to 5 mm) to be manufactured as they retain the necessary structural integrity despite their reduced thickness. This allows material such as nano titanium dioxide, to be added to the mixture in sufficient quantities such that the external surface of the slab will display the desired properties. For example, nano titanium dioxide is a photocatalytic agent that is presently added to paint such that painted surfaces display the desired properties of the photocatalytic agent, namely, the breakdown of airborne pollutants and removal of same from the atmosphere. However, nano titanium dioxide is relatively expensive and it is presently only used in materials that are applied to surfaces as a thin layer. This enables the surface to embody the desired property of the photocatalytic agent at a reasonable cost. Cementitious slabs are generally manufactured with a significantly greater thickness to provide the required strengths and as a result, adding sufficient quantities of expensive material such as a photocatalytic agent is commercially infeasible as the amount required in the slab to render an outer surface with the desired properties results in an excessive cost of the slab products.

In other embodiments, aggregate such as limestone or marble chips can be used where the particle size is reduced sufficiently to allow a poured slab to be cut in a semi-set state without the slab deforming either during or subsequent to the cutting process. However, it is preferable to use an aggregate that doesn\'t exhibit a propensity to absorb water. In this regard, when a slab retains too much water in the mixture a phenomena known as “water bleed” or “fine particle bleed” occurs where the water carries fine particles away from a cut surface and it is difficult to cut with a vibrating cutting tool without the material deforming and re-joining around the cut. Accordingly, some aggregate materials will provide a better result for subsequent cutting of the material as compared with others.

Subsequent to pouring a slab of cementitious material, the material may be cut in a semi-set state prior to fully curing. Again, this is enabled as a result of the choice of materials in the mixture and further reduces stress that would otherwise be imparted to a slab during the cutting process. In an embodiment, the slab is cut with a vibrating cutting tool, which is another contributing factor that enables cementitious slabs to be manufactured with a reduced thickness as compared with present production techniques.

It will be recognised that the term “cure” is interchangeable with the term “set”. It will also be recognized that the term “semi-set” has a substantially similar meaning to “semi-plastic” or “semi-hardened”.

FIG. 1 is a diagrammatic illustration of a mixing vessel containing the component parts of a mixture prior to the mixing process;

FIG. 2 is a diagrammatic illustration of a mould substrate and a mould liner prior to fitting;

FIG. 3 is a diagrammatic illustration of a mould substrate and a mould liner during the fitting of same;

FIG. 4 is a diagrammatic illustration of the application of mould retaining walls to a substrate to which a mould liner has been fitted;

FIG. 5 is a diagrammatic illustration of pouring a mixture into a mould;

FIG. 6 is a diagrammatic illustration of a slab of material in a mould in a semi-set state during a cutting process;

FIG. 7 is a diagrammatic illustration of the slab products resulting from the cutting process illustrated in FIG. 6 with the mould retaining walls removed and the slab products de-moulded;

FIGS. 8A and 8B illustrate respectively the representative appearance of a prior art slab of material at a cut edge and a slab of material according to an embodiment of the invention; and

FIGS. 9A and 9B diagrammatically illustrate de-moulded slab products with the mould lining removed and retained fitted to the slab product respectively.

DETAILED DESCRIPTION

It should be noted that all of the discussion below, regardless of the particular embodiment being described, is exemplary in nature, rather than limiting.

The present invention is relevant to the manufacture of cementitious slabs and/or tiles produced therefrom, which may be used for tiles (internal, external, floor and wall; conventional and alternative type tiles); paving cladding for walls (both internally and externally) mosaics (including floor mosaics); kitchen bench tops; kitchen counters, benches and islands; table tops; integrally cast products for tilt-up panels, including scott systems; curtain walling and external cladding with optional accessories, including products containing fibre; insulation tiles; other slab products for the slab market; furniture; roof tiles or slab and/or tiles for other suitable applications.

An example method for producing a cementitious slab according to the present invention includes steps of mixing cement, a fine aggregate material, an ultra fine aggregate material and water.

With reference to FIG. 1, a mixing vessel (10) is illustrated containing materials such as cement (12), fine aggregate (14) an ultra-fine aggregate (16) and a crushed or ground (flour) material (17). In the exemplary embodiment of FIG. 1, the mixing vessel (10) is also illustrated containing three mounds of pigment (18) that are included in the mix to achieve the desired colour of the resulting slab of material.

The fine aggregate material (14) and/or the ultra fine aggregate material (16) and/or the crushed or ground (flour) material (17) may be a siliceous material, including sand. Further, the cementitious mix may also include a crushed aggregate material and/or flour, wherein the crushed aggregate material may also be sand.

In order to reduce water content of the cementitious mix, a water reducing plasticizer may be added, which may be a polycarboxylic ether polymer. The amount of water reducing plasticizer may be between approximately 1% to 5% of the mix by weight of cement. For example, should the cement content of the cementitious mix be 100 kilograms, the amount of water reducing plasticizer may be between approximately 1 kilogram and 5 kilograms. The water to cement ratio, where a water reducing plasticizer is used, may be approximately 0.24 to 0.26.

The ratio of cement (12) to fine aggregate material (14) to ultra fine aggregate material (16) may be 2:2:1. For example, the cementitious mix may contain 100 kilograms of cement, 100 kilograms of fine aggregate material and 50 kilograms of ultra fine aggregate material. Furthermore, in an embodiment where the cementitious mix includes either crushed aggregate material or flour, the ratio of cement to fine aggregate material to ultra fine aggregate material to crushed sand or flour may be 10:10:5:2. For example, the cementitious mix may contain 100 kilograms of cement, 100 kilograms of fine aggregate material, 50 kilograms of ultra fine aggregate material and 20 kilograms of crushed aggregate material or flour.

Of course, the precise ratios of materials in any mix that will produce the best result will depend upon the quality and suitability of the materials, the quality of any polycarboxylate admixture and the efficiency of the mixing apparatus.

In a further embodiment, a buffer solution is added to the cementitious mix to reduce surface tension such as vinegar and/or ethanol, which is included in order to reduce air content of the cementitious mix. The air content of the cementitious mix is generally in the form of air bubbles and it is intended for the vinegar and/or ethanol to reduce the air bubble content of the cementitious mix. The vinegar and/or alcohol to cement ratio may be approximately 0.075.

The cementitious mix may be mixed in a standard commercial dough mixer including a mixing vessel (10) and a mixing head (20) until thoroughly mixed into a wet consistency. The period of mixing may be approximately 3 to 5 minutes.

With reference to FIG. 2, a mould substrate (24) is provided in the form of a sheet of glass. A suitably sized sheet of mould liner (26) is removed from a roll of the liner material (28) and placed over the mould substrate (24). The liner (26) is then applied to the top surface of the mould substrate (24) as illustrated in FIG. 3. The liner (26) is applied to the substrate (24) firmly in order to prevent, or at least minimize, the possibility of air being trapped between the liner (26) and the mould substrate (24)

Once the mould liner (26) is applied to the mould substrate (24), an acrylic material is dispensed from a tubular container (28) to form a mould retaining wall (3D) (refer FIG. 4). The height of the mould retaining wall (3D) will depend upon the required depth of the slab. With reference to FIG. 5, slab material (32) is poured into the mould from a mixing vessel (34).

Moulds may be of varying shapes and sizes and may be made from various materials including aluminium, steel, timber, plastic, glass and/or acrylic etc.

The mould lining assists in preventing damage to the mould by the cutting tool and may discarded and replaced after the de-moulding process. The mould liner may be formed from plastic, waxed paper or any material suitable for this process.

When in the mould, the cementitious mix is allowed to substantially self-level. The self-leveling process may require approximately 2 minutes to 6 minutes in duration. Further, during self-leveling, air and air bubbles escape from the cementitious mix. Approximately 80% to 95% or greater of air and air bubbles are expected to escape from the mix during the self-leveling process without intervention.

A further reduction in air and air bubbles may be achieved by gently vibrating the mould containing the cementitious mix. A cementitious mix may be vibrated until air and air bubbles substantially no longer appear to be escaping the surface of the cementitious mix. In this regard, the gentle vibration may be of approximately 3 to 10 seconds duration.

Following leveling and vibrating of the cementitious mix, it is allowed to set until it is in a substantially semi-set (or substantially semi-hardened) state. When in a semi-set state, the cementitious material or cementitious slab is cut in to tiles or other desired products. As it is in a semi-set state, the cementitious material may be cut with a knife or other sharp cutting tool vibrated at a preselected frequency.

The preselected frequency may be an ultrasonic frequency, which may be in the range of 20 kHz to 40 kHz. The ultrasonic cutting tool may be a hand held type or may be incorporated into automated machinery, such as computer controlled automated cutting machinery.

It will be appreciated that an embodiment using a blade vibrating at an ultrasonic frequency should result in very little or substantially no cementitious material adhering to the blade when cutting. This should result in the blade not requiring cleaning and should also result in little or substantially no cementitious material being removed from the slab during the cutting process.

With reference to FIG. 6, a diagrammatic illustration of the cutting process is provided wherein the slab material (32) has cured to a semi-set state and a cutting device (36) controlled by a robotic arm passes a vibrating cutting tool (38) through the slab material (32). A path 40 is cut through the slab material (32).

With reference to FIG. 7, a diagrammatic illustration of the slab products (42, 44) resulting from the cut 40 through the slab of material is provided. Further, in FIG. 7, the mould retaining walls (3D) have been removed and this can be effected by trimming the mould retaining walls (3D) off the slab. In this regard, selecting a material for the mould retaining wall (3D) that is sufficiently malleable allows same to be cut by the vibrating cutting tool (38).

The ultrasonic cutting tool (38) may be a thin blade, capable of cutting but substantially not removing cementitious material from the slab. Further, cutting of the material may occur at a rate of approximately 300 to 800 mm per second.

It should be understood that, when the cementitious slab is in a semi-set state, other cutting techniques may be employed as an alternative to ultrasonic cutting.

The cementitious material may cure into a substantially semi-set state following self-leveling and/or vibration. This part of the curing process may be approximately 30 minutes to 1 hour in an ambient temperature of approximately 21 degrees Celsius. A higher ambient temperature may accelerate the curing time. It is important to understand that cutting of the cementitious slab may occur at any time after the placement of the cementitious material into a mould, however, the cementitious material should be leveled and, air allowed to escape or be removed with further time allowed for the cementitious material to sufficiently cured so as to be in a semi-set state.

The cementitious material may be assessed for suitability for cutting by applying the cutter to the cementitious material and observing that when the material is cut it substantially does not move and/or meld back together over the cut.

It will be recognised that, as the cementitious slab is cut whilst in a substantially semi-set state, there is substantially reduced stress on the cementitious material as compared with previous methods of cutting where a cementitious slab is in a substantially hardened state. Accordingly, due to reduced stress on the cementitious material, chipping and breaking of the cementitious slab should be substantially reduced or eliminated. Further, little or substantially no cementitious material is removed from the cementitious slab during the cutting process of the present invention.

The cementitious slab may be cut into tiles having a range of sizes and shapes. The shapes may include curved and rounded shapes and the tiles may also be produced with sharp corners. Further, cutting a cementitious slab whilst in a semi-set state does not require the use of expensive cutting equipment, such as diamond tools, and reduces cutting time. Also, the amount of water required for cutting is substantially reduced or may be eliminated altogether. This has a further advantage in that little or no effluence is produced, which previously required expensive treatment and/or disposal.

The method of the present invention may be used to prepare a slab material from which it is possible to cut shapes, angles and sizes which have previously been considered as either not possible or too problematic.

As the process does not require high pressure water during cutting and calibrating, stress imparted upon the slab is substantially reduced, which in turn reduces damage. This allows a slab with a reduced thickness (as compared with present production processes) to be cut into separate slab products.

The cementitious slab may be poured to thicknesses of between approximately 3 mm to 5 mm and subsequently cut into slab products which may create possibilities for new and innovative products.

Furthermore, as a result of there being less stress caused to the product during processing, the material may be substantially stronger. The strength of the material is further enhanced by the use of flour materials and an emphasis upon reduction of the water content of the slab mixture. In turn, this may result in fewer problems, such as broken corners etc, during installation of the product.

Moreover, as no large aggregate pieces are used in producing the cementitious material, there may be a reduction in post-installation issues associated with the slow development cracks (including hair-line cracks). It is expected that slab products produced according to the present invention will provide a more pleasant aesthetic appearance along cut edges as compared with previous products that included large aggregate in the mix. With reference to FIG. 8A, an example profile of a cut edge of a slab product according to present production methods is illustrated in which the size and shape of the large aggregate dominates the appearance. This appearance has had a limiting effect when considering whether or not to use existing slab products for various applications. In contrast, FIG. 8B illustrates an example profile of a cut edge of a slab product according to the present invention which is expected to be more widely accepted for use in instances where the cut edge will be visible.

The cementitious slab may also be assessed and/or calibrated for consistency of thickness whilst in a semi-set state. Any areas of the cementitious slab which are thicker (higher) than desired may be removed.

Removal may be effected by a cheese grater type device. However, it will be recognised that any requirement for assessing and/or calibrating the thickness of the cementitious slab and/or removing material from thicker areas of the slab should be substantially minimised due to the method of production of the slab according to the present invention.

Assessing and/or calibrating the thickness and/or removing cementitious material in order to achieve an even thickness may occur before the slab is cut or after the slab is cut into tiles. However, calibration and/or assessing and/or removing cementitious material should occur whilst the cementitious slab is in a semi-hardened (semi-set) state.

Following cutting of the cementitious slab, the tiles are stored for approximately 20 to 24 hours, which allows for further hardening of the tiles. The tiles are hardened such that they may be taken from the mould.

The de-moulded tiles are then packaged and allowed to completely cure.

With reference to FIGS. 9A and 9B, de-moulded slab products are illustrated. In the instance of FIG. 9A, the mould liner has been removed from the slab product (46). This may occur at the time of de-moulding where the slab product (46) is removed whilst the liner is retained in place. Alternatively, as illustrated in FIG. 9B, the mould liner is cut at the time the slab product is cut and thus the liner (50) remains attached to the slab product (48) subsequent to de-moulding. The liner (50) may then be removed from the slab product (48) or retained in place to protect the slab product (48) during subsequent handling and transport.

The present invention embodies various advantages and in particular, enables the efficient and less costly manufacture of slab products as compared with existing processes. For example, the cutting of slab material in a semi-set state avoids the need to allow the slab to harden to a sufficient extent to withstand the stress and impact of cutting the slab with a diamond tipped blade. This has the combined advantages of avoiding the requirement to interrupt the processing of the slab between pouring and cutting and obviates the need for expensive mixing and calibrating/cutting equipment that is normally used in present day manufacturing processes.

Further, by reducing, or virtually eliminating, the amount of material removed from the slab during the cutting process, the manufacturing process avoids any need to use water to capture and carry the excess material away from the cutting surface. This avoids any requirement for a water filtration plant and the on-going maintenance that is usually required for such a system.

Obviating the need for large and heavy equipment, or the need for water drainage and treatment systems, avoids the need to manufacture slab products in a purpose built facility. In contrast, manufacturing slab products in accordance with the present invention may be performed in any facility capable of housing the necessary equipment to effect cutting of slab material in a semi-set state. In this regard, the electrical power consumption to operate such equipment is substantially less than present requirements. Further, by enabling the cutting process to be effected shortly after the pouring process avoids the manually intensive handling associated with interim storage of slabs for curing and also avoids the need to store slabs until such time as they may be cut.

While certain exemplary embodiments have been described, it is to be understood that such embodiments are merely illustrative of and not restrictive on the invention, and that this invention is not limited to the specific constructions and arrangements described since various other changes, combinations, omissions, modifications and substitutions, in addition to those set forth in the above paragraphs, are possible. Those skilled in the art will appreciate that various adaptations and modifications of the described embodiments can be configured without departing from the scope and spirit of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.