METHOD OF MANUFACTURING SUCH AN OBJECT

FIELD OF THE INVENTION

The present invention relates to a method of manufacturing a cement-based composite object. In particular the present invention relates to such a method in which the composite comprises a large amount of aggregate which is made from recycled material that has been prepared by breakdown, such as crushing, of scrapped products.

BACKGROUND OF THE INVENTION

The group of materials called cement-based composites can also be referred to as concrete. They have been used for a very long time for the construction of e.g. buildings, walls, and bridges. Such materials typically comprise aggregates in the form of sand and stones of different sizes, cement, additional binder, water, and additives. The cement is a part of the binder which is mixed with water and additives to form the cement paste. It may also be possible to consider the smallest aggregates as being part of the cement paste. The additional binder may e.g. be fly ash or micro silica. Since most of these materials are natural products which exist in limited amounts, the cost of obtaining them increases - especially if it becomes necessary to transport them over long distances to a site of use. Therefore, the development of alternatives have taken place for several years. It has e.g. been found possible to replace some of the larger aggregates by recycled crushed blocks or bricks made of concrete that have already been used for another purpose.

Concrete comprising recycled material is sometimes referred to as "green concrete" indicating that it is manufactured in a way that saves resources with respect to consumption of natural materials or energy. However, the amount of recycled materials included is typically relatively low so that the inclusion of new materials is not avoided. Another issue in relation to the present invention is the increasing amount of waste piling up from scrapped products, such as wind turbine blades. Scrapped products which can neither be re-used, e.g. after melting, nor burnt to generate energy are typically deposited on landfills where they remain for decades or even centuries.

OBJECT OF THE INVENTION

It is an object of the present invention to provide a method of manufacturing so- called "green concrete" with which a high amount of the feedstock components is obtained from scrapped products.

It is another object of the present invention to provide a method of manufacturing a cement-based composite object with which feedstock components from scrapped products that are normally not recycled can find a second valuable use.

It is a further object of the present invention to provide an alternative to the prior art.

In particular, it may be seen as an object of the present invention to provide a method of manufacturing a cement-based composite object which method solves the above mentioned problems of the prior art.

SUMMARY OF THE INVENTION

Thus, the above described object and several other objects are intended to be obtained in a first aspect of the invention by providing a method of manufacturing a cement-based composite object, the method comprising the following steps: - providing the following feedstock components:

- aggregate with a size of at least 4 mm in an amount of 5 to 70 weight% of the total weight of the feedstock,

- aggregate with a size of 0 to 4 mm in an amount of 5 to 70 weight% of the total weight of the feedstock,

- cement in an amount of 3 to 20 weight%, such as 5 to 15 weight%, such as 10 to 15 weight%, of the total weight of the feedstock, - additives in an amount of 1 to 15 weight%, such as 2 to 15 weight% of the weight of the cement, and

- a balance of water,

- mixing the feedstock components to obtain a mouldable concrete,

- pouring the concrete into a mould or onto a moulding surface, and

- allowing the concrete to cure, wherein at least 70 weight%, such as at least 80 weight%, such as at least 90 weight%, of the total weight of the aggregate, is made from recycled material that has been prepared by breakdown, such as crushing, of scrapped products.

The terms "cement-based composite" and "concrete" can be used interchangeably here and in the following. The invention is related to materials comprising cement which acts as part of the binder, possibly in combination with additional binder.

The size of the aggregate is typically determined by use of a set of standardized sieves. However, other methods such as laser diffraction, dynamic light scattering and direct imaging techniques may also be used. It will be well-known to a person skilled in the art, what is meant by the size of aggregate within the technical field of the invention. At least for some types, shapes and sizes of objects, it will be necessary or advantageous to set an upper limit on the size of the aggregates. Such an upper limit may e.g. be set to 62 mm, such as 30 mm, such as 22 mm.

By "weight%", reference is made to the weights of the materials at the time just before mixing; i.e. when the feedstock material is provided and ready for use. After mixing, different chemical reactions as well as evaporation of the water will take place and influence the actual percentages.

The additives can be either dry or liquid before the mixing with the other feedstock components.

The feedstock components will typically be mixed in a predetermined order found suitable for obtaining a homogenous concrete depending on the actual recipe used for a given application; this will typically be determined by experimentation in combination with knowledge gained from previous work on similar materials. However, the scope of protection also covers methods in which all the feedstock components are added to the mixing equipment before the mixing step is initiated.

By "moulding" is meant that the concrete is in a state which allows for a transfer of the concrete from a container in which it is mixed to a mould or a mould surface without significantly influencing the mechanical and chemical properties of the materials. This transfer may take place by pouring or by use of a suitable tool, such as a spoon, a shovel, or a bucket. The transfer may also take place by pumping.

By "scrapped product" is meant a product which has had a first use which has been discontinued, e.g. because the product no longer fulfils the required purpose and therefore has been replaced by a new one. A difference between at least some naturally occurring materials traditionally used as aggregates and aggregates obtained by breakdown of scrapped products is the surface conditions of the two types of aggregates. Some of the surfaces of the aggregates obtained by breakdown correspond to the former outer surfaces of the scrapped products, and they are typically significantly smoother than naturally occurring aggregates, such as stones. Therefore it would be expected that it would be significantly harder to ensure a strong bonding between the aggregates and the material binding them together. Furthermore, the breakdown process often results in aggregates with surfaces having a plurality of straight sides meeting along relatively sharp edges. This will influence both the mixing process and the ability of the feedstock components to pack together in a dense manner while still being mouldable. The experimental work leading to the present invention has shown that despite these challenges, it is possible manufacture cement-based composite objects containing a significantly larger amount of recycled material than what is known from prior art without compromising the demands with respect to the mechanical properties, such as the compression strength. Examples of recipes and results of the manufacturing will be given in the detailed description of the invention. The concrete solidifies and hardens through a chemical process called "hydration"; this term could therefore also have been used instead of "cure" here and in the following.

In some embodiments of the invention, at least 95 weight%, such as at least 98 weight%, of the aggregate with a size of at least 4 mm is made from recycled material that has been prepared by breakdown, such as crushing, of scrapped products.

In some embodiments of the invention, at least 95 weight%, such as at least 98 weight%, of the aggregate with a size of 0 to 4 mm is made from recycled material that has been prepared by breakdown, such as crushing, of scrapped products.

By at least some of the above-mentioned types of embodiments, a very large amount of feedstock components from scrapped products that are normally not recycled can find a second valuable use. This is advantageous both because it is hereby possible to cut down on the use of natural resources available in limited amounts, and because depositing of the scrapped products can be avoided or at least limited. Thus, the invention is valuable both with respect to protection of the nature and with respect to cost-savings. Furthermore, the use of the scrapped products for the manufacturing of new composite objects provides the material with a significantly higher value than what might be obtainable from alternatively using them as landfill. This could also be referred to as the objects being higher in the hierarchy of scrap.

The scrapped products may comprise sanitary components made from vitreous china, such as washbasins, toilet pans, and cisterns. Vitreous china is a special clay which is a mix of several kinds of clay, called ball clay and china clay, silica, and a fluxing agent. The clays are hardened by first drying in air, then being fired baked in a very hot oven called a kiln. Such materials have a very long time of decomposition, and therefore keep filling up waste deposits for generations.

The scrapped products may comprise fibre reinforced plastic, such as wind turbine parts, such as wind turbine blades. Another example is boat hulls. Such products are often made from materials which are very hard or impossible to separate and to use for other purposes after scrapping. Furthermore, they may constitute a risk of contamination of areas where they are deposited - especially if they are deposited in areas without strict control of the handling and storage over time. For these types of scrapped products, it may be necessary to remove some elements, such as metal parts or foamed polymer parts, before the rest is crushed or ground into smaller sizes ready for use as aggregates. In principle these normally removed parts, could also remain and be moulded into the new object. However, it would have to be ensured that this will not negatively influence the long-term properties of the object for a given application.

In the above-mentioned embodiments where the scrapped products comprise sanitary components and/or fibre reinforced plastic, a part of the aggregates should preferably be based on aggregates traditionally used in concrete, such as stone and sand. This part of the aggregates may be new or recycled material or a combination thereof. An example of such a combination of feedstock components will be given in the detailed description.

The specific mentioning of sanitary components made from vitreous china as well as parts made from fibre reinforced plastic does not exclude the use of scrapped product being made from other types of products and materials as long as these products can be broken into smaller fractions suitable for incorporation in a cement-based composite material which can be moulded in accordance with the present invention. Such products include, but are not limited to, fibre cement, roof tiles, bricks, gypsum, eternit (preferably without asbestos), and concrete. The concrete may comprise gas concrete also referred to a porous concrete. Eternit can also be referred to as fibre cement.

The scrapped products may comprise building insulation material, such as mineral wool or glass wool. Mineral wool may also be referred to as stone wool or rock wool.

The scrapped products may comprise recycled material that has been prepared by breakdown of building constructions, typically after removal of combustable material and metal parts. This kind of scrapped material typically contains e.g. roof tiles, bricks, and concrete. It is traditionally used as ballast and hard core e.g. under road surfaces. By instead using it in the manufacturing of cement-based composite objects in accordance with the present invention, it results in a more valuable use. In other words, it can move up in the hierarchy of scrap.

In some embodiments of the invention, the aggregate with a size of 0 to 4 mm comprises sand that is a residue from a washing or filtering process. This may be the case for all or substantially all of this size of aggregates, or it may be only a part thereof. What is referred to as "residue" could also be called a "bi-product", a "waste product", a "spent product" or a "decay product". Sand is typically defined as ranging from 0.05 to 2.0 mm. Particles larger than 2.0 mm are typically called gravel or stones. Sand used for washing and filtering processes was typically originally provided as a natural raw material, but due to the use in potentially contaminating processes, it is at present considered as a product which has to be deposited after use. Such a contaminating process could e.g. be in a sand filter in swimming pools. However, during the work on the present invention, it has been found that by incorporation in an object manufactured by a method according to the present invention, such sand can find a second valuable use.

The aggregate with a size of 0 to 4 mm may comprise glass fibres, glass, rock wool, or paint sediment, and this part of the aggregate may be obtained by breakdown of scrapped products. Hereby such scrapped products can find a second and valuable use as described above for some of the other feedstock components. Glass waste may also be used as aggregate with a size of at least 4 mm.

In any of the embodiments as described above, at least some of the water may be re-used from a previous corresponding manufacturing process cycle after removal of sludge, if present. Hereby the total water consumption can be lowered, since the water is re-used instead of being led into the wastewater discharge.

At least a part of the water may be demineralised water. Such demineralised water can be used to activate the accelerator in the cement. Furthermore, studies performed during the development of the present invention have shown that in embodiments comprising building insulation material as described above, the use of demineralised water will remove the surface tension and will thereby facilitate the mixing of the building insulation material with the other feedstock components. Furthermore it has been found that by using demineralised water, the small pieces of broken-down building insulation material can be dispersed throughout the concrete instead of gathering in small clumps or cakes as may otherwise happen.

For embodiments comprising building insulation material, it has been found advantageous to add an air entrainment agent, which could also be referred to as a soap, to the concrete. The agent used in the experiments made during the development of the present invention was UFAPORE LC from the company Unger Fabrikker AS. It is an air entraining agent for light weight concrete which consists of a mixture of anionic surfactants. This has resulted in the building insulation material being easier to mix with the other feedstock components, including that it does not float on the surface of the water.

The step of providing the feedstock components may further comprise providing additional binder in an amount of 0.5 to 5 weight% of the total weight of the feedstock. As mentioned above, the cement also forms a part of the binder, as it will establish at least some of the coherence in the mixture. The additional binder may be selected from the group consisting of: fly ash, micro silica particles, calcium oxide, lime stone, or a combination thereof. When the additional binder comprises fly ash, this fly ash may be without minerals. This may have been obtained by removing the minerals from the fly ash so that both the minerals and the remaining fly ash can be used for different purposes.

The specific mentioning of the different feedstock components does not exclude the presence of small amounts of further material not intended to be included, such as small pieces of plastic, paper or metal just happening to be present during the breakdown of the scrapped products e.g. because they were fastened to the product before it was scrapped.

In some embodiments of the invention, the step of pouring comprises pouring the concrete into a mould being dimensioned and shaped to manufacture an object in the form of a building block configured to be joined with similar building blocks for the establishment of a building construction, such as a wall or a part of a house. The concrete may alternatively be moulded to form different products without the need for assembly from blocks. Examples of such products are crash barriers and retaining walls.

A method according to the invention may further comprise the following step subsequent to the step of pouring:

- adding an identification element to the concrete, the identification element comprising information about the object being moulded.

Such an identification element may e.g. be an electronic chip or a QR code. Hereby it will be possible to provide the object with information relating to both the origin of the feedstock components used and potentially also information about required ways of handling the material when the object is to be scrapped in the future. An example of such information could be results of a standardised leaching test. Other types of relevant information can also be included.

The first and second aspects of the present invention may be combined. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE FIGURES

The method of manufacturing a cement-based composite object according to the invention will now be described in more detail with regard to the accompanying figures. The figures show one way of implementing the present invention and is not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

Figure 1 is a flow diagram of a method according to the invention.

Figures 2. a and 2.b schematically show how scrapped products in the form of sanitary components and fibre reinforced plastics, respectively, are broken down to aggregates for subsequent use in the manufacturing of cement-based composite objects. Figure 3 schematically shows the manufacturing of objects in the form of building blocks suitable for joining with similar building blocks.

DETAILED DESCRIPTION OF AN EMBODIMENT

As described above, an overall object of the present invention is to provide a method of manufacturing a cement-based composite object with which at least 70 weight%, of the total weight of the aggregate, is made from recycled material that has been prepared by breakdown, such as crushing, of scrapped products. The overall steps of the method resemble those of a known way of preparing a similar material in which all or most of the materials are provided as new materials. These steps are schematically shown in figure 1:

A: Providing the following feedstock components.

B: Mixing the feedstock components to obtain a mouldable concrete.

C: Pouring the concrete into a mould or onto a moulding surface. D: Allowing the concrete to cure.

The feedstock components are the following as schematically shown in figure 1:

- aggregate 1 with a size of at least 4 mm in an amount of 5 to 70 weight% of the total weight of the feedstock,

- aggregate 2 with a size of 0 to 4 mm in an amount of 5 to 70 weight% of the total weight of the feedstock,

- cement 3 in an amount of 3 to 20 weight%, such as 5 to 15 weight%, such as 10 to 15 weight%, of the total weight of the feedstock,

- additives 4 in an amount of 1 to 15 weight%, such as 2 to 15 weight% of the weight of the cement, and

- a balance of water 5.

As described above, the feedstock components may further comprise additional binder 6 in an amount of 0.5 to 5 weight% of the total weight of the feedstock. Since such an additional binder 6 is an optional feature, the corresponding circle in figure 1 is shown with broken lines.

In some embodiments of the invention, at least 95 weight%, such as at least 98 weight%, of the aggregate 1 with a size of at least 4 mm is made from recycled material that has been prepared by breakdown, such as crushing, of scrapped products. Furthermore, at least 95 weight%, such as at least 98 weight%, of the aggregate 2 with a size of 0 to 4 mm may be made from recycled material that has been prepared by breakdown, such as crushing, of scrapped products. Figures

2. a and 2.b schematically show embodiments in which aggregate 1,2 to be used in the manufacturing process are prepared from scrapped products 7,8. In figure

2. a, the aggregates are prepared by breakdown of sanitary components 7 made from vitreous china, such as washbasins, toilet pans, and cisterns. In figure 2.b, the aggregates are prepared from scrapped products comprising fibre reinforced plastic 8. It will also be possible to use aggregates 1,2 from both sanitary components 7 and fibre reinforced plastic 8 in the same objects. The examples schematically shown in figure 2.b are wind turbine parts, wind turbine blades, and boat hulls. However, other types of scrapped products are also covered by the scope of protection. As previously mentioned, where the scrapped products comprise sanitary components and/or fibre reinforced plastic, a part of the aggregates should preferably be based on aggregates traditionally used in concrete, such as stone and sand. This part of the aggregates may be new or recycled material or a combination thereof. Further details of the other feedstock components were described above. In the same way as shown for sanitary components and fibre reinforced plastics, the aggregates could be prepared by breakdown of other types of scrapped products as described above. Such scrapped products could e.g. be parts of building structures.

Figure 3 schematically shows an embodiment of the invention in which the concrete is poured into a mould 9 being dimensioned and shaped to manufacture an object in the form of a building block 10 configured to be joined with similar building blocks 10 for the establishment of a building construction 11, such as a wall or a part of a house. The shape of the building blocks 10 shown in figure 3 is just an example, and many other shapes are possible, such as building blocks having circular, hexagonal, or irregular cross-sections. An identification element 12 may be added to the concrete after it has been poured into the mould 9 or after the building block 10 has been removed from the mould 9 as shown in figure

3. Such an identification element 12 typically comprises information about the object being moulded. In figure 3, the identification element 12 is added after removal of the object from the mould 9, but it can also be added while the object is still in the mould. The identification element 12 can e.g. be an electronic chip or a QR code used to provide the object with information about e.g. the feedstock components used.

The following table 1 shows an example of a recipe which has been used for the manufacturing of a cement-based composite object as part of the work leading to the present invention. In one of the test cylinders, the aggregate consisted of crushed sanitary components, crushed concrete size 4-22 mm, and crushed concrete size 0-4 mm. In another test cylinder, the aggregate consisted of crushed wind turbine, crushed concrete size 4-22 mm, and crushed concrete size 0-4 mm. For the test cylinder comprising crushed wind turbine parts, the used and crushed parts included the blades, the nacelle, and the tower. The fibre reinforced plastic was glass-fibre reinforced epoxy. The manufactured objects with the above composition were tested according to standards normally used within this technical field for testing of ordinary concrete, i.e. concrete with non-recycled materials. The test used was DS/EN 206. The results showed a compression strength of 30 MPa. It is considered likely to be able to obtain a compression strength of 35 MPa by using a higher amount of cement.

When an object is to be made in which crushed wind turbine blades are used as aggregate, the crushing process may provide both the aggregate with a size of at least 4 mm and the aggregate with at size of 0-4 mm. The aggregates with a size of at least 4 mm and of 0-4 mm, respectively, are preferably mixed with aggregate of similar sizes obtained by crushing of recycled concrete. The aggregate from crushed recycled concrete with a size of 0-4 mm is often referred to as stone powder. The reactive properties and water-unsaturated surfaces of the stone powder has been found to be a satisfactory combination with the typically smooth and water-resistant surfaces of the crushed fibre reinforced polymer from which the wind turbine blades were made. Results have shown that by mixing these two components in a ratio of e.g. 70 weight% stone powder and 30 weight% aggregate from wind turbine blade and adding cement and additives, the chemical reactions taking place will result in the stone powder encapsulating the aggregates from wind turbine blades and thereby make them suitable for the formation of a composite material with satisfactory strength properties to find use in new objects made according to the present invention.

The development of the present invention has included the performance of leaching tests on cylindrical objects made from different material compositions as shown in table 1. The leaching tests were performed in accordance with EN12457- 1:2002. In the leaching test, the amount of 11 potentially critical materials was determined, and based thereon a category was assigned. The results showed that both types of materials were assigned the same category as concrete made from new (i.e. not recycled) feedstock materials. Therefore, objects made from these materials and in accordance with the present invention fulfil the requirements for being allowed to use as foundation material for building and construction work according to official regulations for the use of waste products.

The following table 2 shows another example of a recipe which has been used for the manufacturing of a cement-based composite object as part of the work leading to the present invention. In the test cylinders of this example, the aggregate included crushed building material in the form of a mixture of mineral wool and glass wool, crushed concrete size 4-22 mm, and crushed concrete size 0-4 mm. The inventor has realized that for the mixing of the material comprising insulation, it is advantageous to add an air entrainment agent which could also be referred to as a soap. The agent used in the present experiments was UFAPORE LC from the company Unger Fabrikker AS. It is an air entraining agent for light weight concrete which consists of a mixture of anionic surfactants. For table 2, the weight percentages have not been calculated, but they would be close to those in table 1.

Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. The mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.