METHODS OF PRODUCING A POLYMER CONCRETE, AND A POLYMER

CONCRETE

FIELD

The present invention relates to polymer concrete and methods for making it.

BACKGROUND

Concrete is a composite material that is widely used in the construction of buildings, bridges, roads, dams, paving and more. The popularity of concrete stems from its cheap and easy means of manufacture as well as its inherent strength, durability and formability. However, the widespread use of concrete has had significant environmental consequences. Traditional concrete requires combining water with cement to form a paste. As a result, vast quantities of fresh water are spent on concrete manufacture, particularly in regions already experiencing water shortages.

Polymer composite concretes, which are those made from mixtures of aggregates and polymers, may be manufactured using far lower quantities of water than traditional concrete whilst retaining, or even improving, its strength properties. Therefore, polymer concretes can have a lower environmental impact than traditional concrete without compromising on product quality.

The use of polymer concrete has, to date, been limited by the relatively high cost as compared to traditional concretes. Accordingly, ways to reduce its cost have been widely sought.

The present invention has been devised in light of the above considerations.

BRIEF DESCRIPTION OF THE INVENTION

2D materials has been subject to extensive research since graphene was first isolated in 2004. One of the extraordinary properties of 2D materials is their mechanical strength, with graphene having the highest tensile strength of any material ever measured. As a result, graphene has been considered as an additive for reinforcing composites to enhance their strength and durability. However, a commonly faced problem in the field of 2D material composites is in the dispersion of the 2D material within the composite matrix. For example, graphene tends to agglomerate, leading to an uneven distribution throughout the composite.

This would be a particular problem for a construction material such as concrete as it is critical to its application that its structural properties are even throughout the material. Evenly dispersing graphene and other 2D materials within concrete, which may contain multiple solid phases, is particularly challenging.

It has been found that adding graphene to concrete and polymer-based concrete may provide increases to compressive strength of up to ~40%; of flexural strength up to ~60%; of tensile strength up to ~70%; of energy absorption up to ~150%; of fracture energy up to ~1700%, as well as improved resistance against water and chloride ingress.

A further advantage to using graphene or other 2D materials in the formation of concrete, is therefore, that this allows the incorporation of other “non-traditional” materials into the concrete mixture.

The inventors have determined that by using a material such as graphene to reinforce the strength and durability of the concrete being used, this provides opportunity to incorporate (potentially large) amounts of plastic (or other materials) into the concrete mixture without adversely affecting the overall durability and strength of the resulting concrete. Even with large volumes of plastic products being recycled, there remains a huge volume of plastic waste that is not recycled. Having the option to incorporate large amounts of materials such as plastic, or other widely available materials such as hemp, jute, or the like, into the mixture, provides choice over the type of concrete that is produced. This provides the ability to offset the strength and durability of the concrete being manufactured against the availability of materials, depending on the intended use for the concrete. For example, it is essential for a load-bearing wall of a building to be formed of a very high strength and highly durable concrete. However, for other walls, which do not bear load, it may not be necessary for those walls to have the same strength, and for that purpose a different concrete mixture may be used. In this way, a lower-strength concrete may be manufactured, incorporating a relatively larger volume of materials of which there may be a plentiful supply - such as plastics requiring recycling - and by incorporating graphene (or another 2D material) into the mixture a baseline strength may still be met.

At its broadest, the present invention relates to a polymer concrete and a method of producing a polymer concrete.

An object of the invention is to provide a method of producing a polymer concrete, and a polymer concrete itself, throughout which 2D material is distributed substantially uniformly.

The inventors have found that polymer concrete manufactured to comprise 2D material enhances at least the strength property of the polymer concrete. It was identified that when the polymer concrete was manufactured by a method that distributed 2D material uniformly through the polymer concrete, at least the strength property of the polymer concrete was further improved.

According to a first aspect of the invention, the method of producing the polymer concrete comprises the steps of: (i-1) dispersing 2D material in a resin to form a 2D material resin dispersion, then (ii-1) mixing the 2D material resin dispersion with the hardener to form a 2D material pre mixture; or alternatively (i-2) dispersing 2D material in a hardener to form a 2D material hardener dispersion, then (ii-2) mixing the 2D material hardener dispersion with the resin to form the 2D material pre mixture. Then, having conducted either steps (i-1 ) and (ii-1 ) or steps (i-2) and (ii-2), (iii) combining the 2D material pre mixture with a filler composition to form the polymer concrete.

It will be recognised that in some embodiments steps (i-1) and (i-2) are carried out and steps (ii-1) and (ii-2) are not. Similarly, in other embodiments steps (ii-1) and (ii-2) are carried out and steps (i-1) and (i-2) are not. As an alternative to the above steps, a single step (i-3) may replace (i-1 ), (ii-1 ), (i- 2) and (ii-2), of dispersing 2D material in a thermoplastic polymer melt to form a 2D material premixture. Then, having conducted step (i-3), a step (iii) is carried out, combining the 2D material pre mixture with a filler composition to form the polymer concrete.

The inventors have found that it is advantageous to prepare the 2D material premixture before combining it with the filler composition, for example by mixing, as it helps achieve a more homogeneous distribution of 2D material within the resultant mixture.

The inventors also found that introducing the 2D material pre mixture to the filler composition releases fewer airborne 2D material particles than when 2D material is introduced to the filler composition as a solid or as a dispersion in either the resin or the hardener alone. This has advantages relating to the safety of manufacturing the polymer concrete.

In some embodiments, the step of mixing to form the 2D material pre-mixture is carried out by using a mechanical mixer, the mechanical mixer including at least one of: a screw mixer to rotate the materials; or a static mixer having multiple blades promoting mixing of the materials.

In some embodiments, the step of mixing to form the 2D material pre-mixture is carried out by using an acoustic mixer using high-frequency sound waves to mix the materials. It has been found to be advantageous to use a frequency of between 10kHz and 100kHz, and more preferably between 20kHz and 60kHz, and most preferably at around 40kHz.

In some embodiments, after the step of dispersing the 2D material, and before the step of mixing to form the 2D material pre-mixture, the method may involve testing the composition of the 2D material-hardener/resin dispersion to determine whether it is sufficiently mixed, and if not, recirculating the 2D material-hardener/resin dispersion, for a further step of mixing the 2D material-hardener/resin dispersion.

In some embodiments, the step of dispersing the 2D material is carried out by at least one of: a screw mixer to rotate the materials; or a static mixer having multiple blades promoting mixing of the materials. Alternatively, or in addition, high- frequency sound waves may be used to mix (or assist in mixing) the materials. As before, a suitable frequency may be between 10kHz and 100kHz, or more preferably between 20kHz and 60kHz, and most preferably around 40kHz.

In some embodiments, the filler composition comprises at least (a) an aggregate material, and (b) at least one of sand, hemp, or jute, and optionally (c) a further polymer, wherein the further polymer may optionally be a thermoset polymer.

In some preferred embodiments of the present invention the 2D material comprises graphene. In some embodiments the 2D material is unfunctionalized graphene.

In some embodiments, the aggregate material comprises fine aggregate and coarse aggregate, wherein the fine aggregate has an average particle diameter of 4 mm to 8 mm and the coarse aggregate has an average particle diameter of 16 mm to 24 mm. The inventors found that the presence of fine and coarse aggregates improved the strength property of the polymer concrete.

In some embodiments the aggregate material comprises at least one of stone, rubber and carbon fibre.

In some embodiments, the 2D material pre-mixture is combined with the filler composition by spraying the 2D material pre-mixture onto the filler composition, for example while the filler composition is stirred or subject to mixing or other agitation, or by adding the 2D material pre-mixture to the filler composition dropwise, again for example while the filler composition is stirred or subject to mixing or other agitation. The inventors have found that a spray or dropwise technique is advantageous at least because it improves the homogeneity of distribution of the 2D material pre-mixture, and hence also the 2D material therein, amongst the filler composition.

In some embodiments, in step (i-1) the 2D material is dispersed incrementally into the resin, if using the alternative methods, in step (i-2) the 2D material is dispersed incrementally into the hardener, or into the thermoplastic polymer melt in step (i-3), respectively. The inventors have found that the gradual introduction of 2D material into either the resin or hardener or thermoplastic polymer melt, improves the evenness of distribution of the 2D material within the dispersion.

In some embodiments, 2D material is present in the 2D material pre mixture in an amount no more than 5 wt%. The inventors have found that when 2D material is present in the 2D material pre mixture in amounts in excess of 5 wt%, 2D material particles are more prone to agglomeration which reduces the homogeneity of distribution of 2D material within the 2D material pre mixture. In some preferred embodiments, 2D material is present in the 2D material pre mixture in an amount 1 wt% to 5 wt%. [Herein, “wt%” is used to refer to the amount of a component present in a composition by total weight of the composition. All composition ratios are provided as dry weight %, as no liquid is lost in the process so the ratio remains constant during the process].

In some embodiments, 2D material is present in the polymer concrete in an amount no more than 0.05 wt%. The inventors have found that when 2D material is present in the polymer concrete in amounts in excess of 0.05 wt%, 2D material particles are more prone to agglomeration which reduces the homogeneity of distribution of 2D material within the polymer concrete. In some preferred embodiments, 2D material is present in the polymer concrete in an amount 0.005 wt% to 0.05 wt%.

In some embodiments, the resin comprises at least one of a virgin thermoset polymer and a thermoplastic polymer. The skilled person would be aware of suitable hardeners, such as silica-based hardeners. A second aspect of the present invention relates to a polymer concrete manufactured by the method according to the first aspect of the present invention.

A third aspect of the present invention relates to a polymer concrete comprising (a) a binder, wherein the binder is formed from a resin and a hardener, or alternatively is formed from a thermoplastic polymer melt; (b) a filler composition, wherein the filler composition comprises at least (i) an aggregate material and (ii) at least one of sand, hemp or jute, and optionally (iii) a further polymer; and (c) a 2D material.

In some preferred embodiments, the 2D material comprises graphene. In some embodiments the 2D material is unfunctionalized graphene.

In some embodiments the resin comprises at least one of a virgin thermoset polymer and a thermoplastic polymer.

In some embodiments, 2D material is present in the polymer concrete in an amount no more than 0.05 wt%. The inventors have found that when 2D material is present in the polymer concrete in amounts in excess of 0.05 wt%, 2D material particles are more prone to agglomeration which reduces the homogeneity of distribution of 2D material within the polymer concrete. In some preferred embodiments, 2D material is present in the polymer concrete in an amount 0.005 wt% to 0.05 wt%.

In some embodiments, the aggregate material comprises fine aggregate and coarse aggregate, wherein the fine aggregate has an average particle diameter of 4 mm to 8 mm and the coarse aggregate has an average particle diameter of 16 mm to 24 mm. The inventors found that the presence of fine and coarse aggregate improved the strength property of the polymer concrete.

A fourth aspect of the present invention relates to a method of forming a structural element comprising conducting the present method of producing a polymer concrete and then the steps of (iv) heating and consolidating the polymer concrete to form a desired shape of the structural element, and (v) cooling the polymer concrete.

In some embodiments, the polymer concrete is consolidated by at least one of 3D printing, moulding, continuous hot pressing or extrusion. The extrusion may suitably be single screw extrusion or twin screw extrusion.

Another aspect of the present invention relates to a structural element manufactured by the method according to the fourth aspect of the present invention.

BRIEF DESCRIPTION OF THE FIGURES

In order that the present disclosure may be more readily understood, preferable embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIGURE 1 is a diagrammatic view of a method of mixing a 2D material premixture, by mixing a 2D material - resin dispersion;

FIGURE 2 is a diagrammatic view of a further method of mixing the 2D material premixture, by mixing a 2D material - hardener dispersion;

FIGURE 3 is a diagrammatic view of a further method of mixing the 2D material premixture, by mixing a 2D dispersion - thermoplastic dispersion;

FIGURE 4 illustrates schematically a method of producing the polymer concrete and subsequently the structural element according to some generalised embodiments of the present invention;

FIGURE 5 is a flow diagram showing the steps of a method of mixing a 2D material with a thermoset resin to form a polymer concrete; and

FIGURE 6 is a flow diagram showing the steps of a method of mixing a 2D material with a thermoplastic resin to form a polymer concrete.

DETAILED DESCRIPTION OF THE DISCLOSURE 2D Materials

Initially it is worth discussing the meaning of various terms of art that are used herein. “2D material” is used to refer to not only solids whose monolayers consist of a single layer of atoms, such as graphene and hexagonal boron nitride, but also to solids whose monolayers are a few atoms thick, such as MXenes and transition metal dichalcogenides.

“2D material” is also used to refer to not only monolayer materials but also to those that consist of a few layers (for example, 10 or fewer). For example, “graphene” is used to refer not only to monolayer graphene but also to few layer graphene.

“2D material” is also used to refer to not only a single type of 2D material but also to a plurality of 2D materials present together.

In preferred embodiments of the present invention, the 2D material comprises graphene. In certain embodiments the 2D material is >50 wt% graphene, and in some further embodiments >90 wt% graphene.

Named 2D materials refer not only to their unfunctionalized state but also to their functionalized derivatives. For example, “Graphene” is used to refer not only to unfunctionalized graphene but also to functionalized graphene.

Unfunctionalized 2D materials are 2D materials that are substantially free of chemical functionalization. For example, unfunctionalized graphene has a close to 100% carbon composition. In an embodiment the graphene is unfunctionalized graphene.

2D materials meeting these criteria are readily commercially available, and various methods of making 2D materials are well known.

Method

Techniques for dispersing 2D materials in a liquid phase to form a 2D material dispersion include, for example, mechanical stirring techniques. These techniques can be readily applied to the present invention, wherein 2D material 12 is dispersed either in a resin 14 to form a 2D-material resin dispersion 16 (see Figure 1 , for example). Alternatively, and as shown in Figure 2, the 2D material 12 is dispersed in a hardener 20’ to form a 2D material-hardener dispersion 16’. The resin 14 or the hardener 20’ are suitably in a liquid state at the time that 2D material 12 is dispersed in them.

Looking at Figure 1 , in which a 2D material-resin dispersion 16 is formed, subsequently, the 2D material-resin dispersion 16 is mixed with a hardener 20 in order to polymerise the resin 14 component of the dispersion, forming a 2D material pre-mixture 22. In the alternative of Figure 2, the 2D material-hardener dispersion 16’ is mixed with a resin 14’, in order to achieve the polymerisation of the resin component, forming the 2D material pre-mixture 22.

In either case, the specific mix ratio of the components depends on the type of resin system used and on the instructions of its manufacturer.

In more detail, Figure 1 illustrates the equipment and process involved in the method 10 for forming a 2D material-resin dispersion 16, of a 2D material 12 within a thermosetting resin 14. In embodiments of the technology, the 2D material 12 is placed into or onto a conveying apparatus. In the embodiment described, the conveying apparatus comprises a metering screw 24. The screw transports the 2D material 12 to a weighing device 26 (such as a set of scales). The metering screw 24 is stopped once the desired weight of 2D material 12 is measured. This allows the 2D material 12 to be accurately dispensed, preventing over or under dosing. The weighed 2D material 12 passes into a mixing vessel 32. The resin 14 is transferred to the mixing vessel 32 using a pump 28a (for example).

In embodiments of the technology, and as illustrated, a flow meter 30a is used to monitor the amount of resin 14 passing to the mixing vessel 32. The pump 28a is deactivated once the correct amount of resin 14 is transferred. A first ‘dispersing’ step, (i-1 ), takes place, in which the resin 14 and 2D material 12 are mixed to form a 2D material-resin dispersion 16. In some embodiments the mixing is performed by a static mixer (i.e. , the mixing vessel 32 may be such a static mixer). A static mixer consists of a series of fixed mixing elements, such as blades or baffles, which are arranged within a housing. The 2D materials 12 and polymeric materials are forced against/between the mixing elements, and as the materials pass through, they are subjected to a combination of shear and extensional forces that promote mixing and homogenisation.

In other embodiments of the described technology, the mixing is performed by a screw mixing technique (i.e., the mixing vessel 32 may be a screw mixer). The screw mixing technique is used to achieve uniform distribution of the 2D materials 12 and a homogeneous mixture, which can then be shaped into a final product using various processing techniques. The screw mixing process typically involves feeding polymer pellets into the screw, where they are melted by the heat generated by the friction between the pellets and the screw. As the mixture is transported along the length of the screw, the 2D materials 12 are added at positions spaced along the screw barrel. The screw mixing action ensures that the 2D materials 12 and fillers are uniformly distributed throughout the polymer melt.

In other embodiments, an acoustic mixing process is used (i.e., the mixing vessel 32 is an acoustic mixer). Acoustic mixing is a process that uses high-frequency sound waves to mix or disperse materials in a liquid medium. This technique is often used in the production of polymers, where it can be used to enhance the mixing of 2D materials 12 into the polymer matrix. Typically, the acoustic mixing of the 2D material dispersion 16 takes place at a frequency of between 10kHz and 100kHz, and more preferably between 20kHz and 60 kHz, and most preferably at around 40kHz.

In further embodiments a combination of the mixing techniques may be used. For example, a static mixer or screw mixer may be modified to allow acoustic mixing to take place simultaneously. Alternatively, the mixing steps may take place sequentially. For instance, an acoustic mixing process may be carried out as a first step, before a subsequent mechanical mixing process.

In some embodiments of the technology, the 2D material-resin dispersion 16 may be recirculated through the mixing vessel 32 one or more times. A first mixing step is performed to form the 2D material-resin dispersion 16. In the first step the materials are passed through the mixing vessel 32. A pump 28b is activated to draw the partially-mixed 2D material-resin dispersion out of the mixer 32. A multi directional valve 34 is operated to direct the dispersion partially mixed dispersion back into the mixer 32, where a subsequent mixing step is performed. An increase in the homogeneity of the dispersion can be achieved by repeating the mixing process.

Once the dispersion is sufficiently mixed, the resulting 2D material-resin dispersion 16 passed from the mixing vessel 32 to a further mixing vessel 33 to be mixed with a hardener 20. The pump 28b and flow meter 30b are used, as described above for the transfer of the resin 14, to ensure an appropriate volume of 2D materialresin dispersion 16 is provided to the further mixing vessel 33. In a similar manner a pump 28c and flow meter 30c are used to dispense the hardener 20 accurately. The hardener 20 and 2D material-resin dispersion 16 are mixed to form a 2D material pre-mixture 22. The 2D material pre-mixture 22 is used in subsequent processing to form polymer concrete.

The resin 14 may be any suitable reactive resin prepolymer. The hardener 20 may be any catalyst or co-reactant suitable for use with the resin prepolymer. In some embodiments the resin 14 is an epoxy resin and the hardener 20 may be any polyfunctional amine, acid, phenols, alcohols, or thiols. Epoxy resin has been found to provide excellent mechanical performance, and allows easy handling. In other embodiments the resin 14 is a polyester resin and the hardener may be any catalyst or initiator suitable for use with the polyester resin, such as benzoyl peroxide or methyl ethyl ketone peroxide. For some resin systems it is desirable to heat the resin and/or hardener during processing. Increasing the temperature of the components of a viscous resin system leads to a reduction in viscosity. This results in increased homogeneity of the dispersion of the 2D materials 12 in the resin 14 and/or hardener 20.

Typically, a suitable ratio of resin to hardener is 100:30 by weight, for example where an LN2 epoxy resin is used.

Figure 2 shows the equipment involved in a method 10’ similar to the method 10 described above in relation to Figure 1. The difference between the method of Figure 2 and the method of Figure 1 is that the 2D materials 12 are dispersed in the hardener 20’ in an initial mixing stage, in place of the resin 14, forming a 2D material-hardener dispersion 16’ in place of the 2D material-resin dispersion 16 produced from the earlier-described method. The method is then otherwise the same, although the second mixing stage taking place in the further mixing vessel 33 involves the addition of resin 14’ to the 2D material-hardener dispersion 16’.

The viscosity of the resin 14 and hardener components of various thermosetting polymer systems can vary considerably. For instance it may be that for one thermosetting polymer system, the resin 14 may be of a viscosity that is favourable for mixing with 2D materials 12. In other systems it may be the hardener 20 that is most suitable for mixing at the first step. The present invention allows the preferred resin component to be selected for mixing with the 2D materials 12. The 2D material 12 dispersion can therefore be optimised depending on the characteristics of the components of the resin system.

The method steps corresponding to the methods 10, 10’ and equipment outlined in Figures 1 and 2, are set out in Figure 5 of the drawings. It can be seen that the 2D material is weighed 64, and either resin 14 or hardened 20’ metered accordingly, to create a dispersion 68 of 2D material in either the resin 14’ or hardener 20’.

The resulting 2D dispersion is tested 70 using one or more sensors as known to the skilled person, and if the composition is found not to be sufficiently homogeneous, the 2D dispersion is recirculated 72 back to the mixing vessel 32 for a further step of mixing.

Once the 2D dispersion is found to be sufficiently homogeneous, the dispersion is mixed 74 with the other of the resin 14’ or hardener 20, forming the 2D material premixture 22.

Figure 3 illustrates the process and equipment used in a further alternative method 10”, in which the resin and hardener are replaced by a thermoplastic material 21. In this embodiment, illustrated in Figure 3, a 2D material 12 is dispersed in a thermoplastic material 21 to form a 2D material thermoplastic melt dispersion 16”. In such embodiments, the 2D material thermoplastic melt dispersion 16” itself forms the 2D material pre-mixture 22 suitable for forming the polymer concrete. The thermoplastic material 21 may be provided in the form of pellets. The pellet material is typically heated in order to melt the thermoplastic material 21 ready for mixing. In this embodiment, a heat source 23 is provided for carrying out the heating step; for example, using electrical heating via electrical heating elements. Heating may also (or alternatively) occur from mechanical processes; for example, heat may be generated by the shear forces acting on the polymeric material in a screw extruder.

The steps of the method 10” outlined for the layout of Figure 3 are set out in Figure 6 of the drawings. As before, It can be seen that the 2D material is weighed 64, and thermoplastic polymer is metered 66’ (and may be heated at this step). A dispersion is created 68’ of 2D material in thermoplastic polymer melt. The resulting 2D dispersion is tested 70, as before, and recirculated 72 back to the mixing vessel 32 for a further step of mixing if found not to be sufficiently homogeneous.

In any of the above-described methods 10, 10’, 10”, the 2D material 12 is preferably dispersed in whichever component it is to be mixed with, at the first step, incrementally. In other words, fractions of the 2D material 12 are dispersed in the resin 14 / hardener 20’ / thermoplastic material 21 periodically (over an appropriate amount of time). It has been found that an incremental dispersion of 2D material 12 into the resin 14 / hardener 20’ I thermoplastic material 21 over time results in the 2D material 12 being more homogeneously distributed within the 2D material resin dispersion or alternatively the 2D material-hardener dispersion. For example, the 2D material 12 might be dispersed in the resin 14 / hardener 20’ I thermoplastic material 21 in ten equally-sized fractions at regular intervals over 30 minutes, while the resin 14 (or hardener 20’ or thermoplastic material 21) undergoes continuous stirring. In this way the concentration of 2D material 12 in the resin 14 or hardener is gradually increased, reducing the likelihood of agglomeration.

The skilled person in this technical field would certainly be aware of methods for mixing a resin 14 and a hardener 20 together, which can be readily applied to the present invention, wherein a 2D material resin dispersion is mixed with hardener to form a 2D material 12 pre mixture or alternatively a 2D-material hardener dispersion is mixed with resin 14 to form the 2D material pre mixture. Suitable mixing methods include, for example, mechanical mixing and ultrasonic mixing techniques, as described above.

In the embodiments described, the 2D material resin dispersion 16 is mixed with hardener 20 or alternatively the 2D material hardener dispersion 16’ is mixed with resin 14’ in the further mixing vessel 33 using mixing techniques as described above. For example, screw mixing techniques such as single screw mixing or twin screw mixing can be used to form the 2D material pre mixture. Recirculating the 2D material pre mixture 22 back through the screw mixing apparatus has been found to improve the evenness of distribution of 2D material throughout the 2D material pre mixture 22.

In the further embodiment illustrated in Figure 3, a 2D material 12 is dispersed in a thermoplastic material 21 to form a 2D material thermoplastic melt dispersion 16”. In such embodiments, the 2D material thermoplastic melt dispersion 16” itself forms the 2D material pre-mixture 22” suitable for forming the polymer concrete. Figure 4 provides an exemplary chart setting out the various components that may be used in producing the polymer concrete.

The methods 10, 10’, 10” of mixing the 2D material pre-mixture 22 are equivalent to the mixing steps described in Figures 1 to 3. While in this diagram the use of a thermoplastic 21 in which to disperse the 2D material is not shown, it should be understood that the method 10” involving that step equally applies here.

Once sufficiently homogeneous, the 2D material pre-mixture 22 is combined with further components to produce the polymer concrete material. In broad terms the steps of producing polymer concrete include: introducing the polymer matrix (i.e. resin 14 and hardener 20, or alternatively the thermoplastic material 21) to filler materials 50, 52, 54, mixing 56 the polymer matrix with the filler materials 50, 52, 54 to form the concrete, heating and consolidating 58 the concrete to produce a final cured product and cooling 60 the product to produce a final product. As discussed below, the final product is typically output as a structural element 62.

Methods of introducing a polymer matrix to a filler composition are well known to a person skilled in the art and include, for example, straightforward pouring techniques. These techniques can be readily applied to the present technology, wherein the 2D material pre mixture 22 is introduced to a filler composition to form the polymer concrete. When introducing the 2D material pre-mixture to the filler composition by pouring, a composition of around 17% polymer to 83% (by weight) of filler is required to ensure that the polymer evenly coats the filler material.

In some embodiments the 2D material pre mixture 22 may suitably be held in a liquid state under stirring, such as by mechanical or ultrasonic stirring techniques that are familiar to the skilled person, before combination with the filler composition. Preferably, the 2D material pre-mixture 22 is introduced to the filler composition while the 2D material pre mixture is in a liquid state. Of course it will be recognised that the 2D material-pre-mixture 22 may also be solidified, as an only partially cured composition, for example by cooling and then re-liquified for combination with the filler composition for example by heating. In some embodiments the filler composition is stirred whilst the 2D material pre mixture 22 is introduced to the filler composition. The inventors have found that this more homogeneously distributes the 2D material pre mixture amongst the filler composition.

In some preferred embodiments the 2D material pre mixture 22 is introduced to/mixed with the filler composition using a spraying or dropwise addition technique. It was found that using spraying or dropwise addition techniques to introduce the 2D material pre mixture 22 to the filler composition improved the evenness of distribution of the 2D material pre mixture amongst the filler composition. The skilled person would be aware of suitable spray or dropwise techniques for introducing a polymer to a filler composition. Such methods also reduce the chance of a thermal runaway reaction occurring.

When introducing the 2D material pre-mixture 22 to the filler composition by spraying, the composition may contain as little as 2%wt of the polymer material. Preferably, the composition contains 3%wt - 5%wt of 2D material pre-mixture 22, and 95%wt - 97%wt of filler, to ensure that the polymer evenly coats the filler material. An important advantage of using a spraying technique is that a smaller amount of polymer material is required. This has benefits in terms of process efficiency, as relatively smaller amounts of polymer materials need to be mixed in order to create a given amount of polymer concrete. Furthermore there are environmental benefits to using a reduced amount of polymeric material, as the amount of resources required to form the polymer concrete are reduced.

Methods of mixing a polymer matrix and a filler composition together are well known and a skilled person in this technical field would be aware at least of several mechanical mixing techniques, for example. In an embodiment, a screw mixing technique such as single screw mixing or twin screw mixing is used to mix the 2D material pre mixture and the filler composition together after the 2D material pre mixture is introduced to the filler composition.

The general combination and flow of these stages of the present method, along with some exemplary but non-limiting suggestions for the various ingredients and methods at the different stages, is illustrated schematically in Figure 4.

Components

“Resin” 14, 14’ is used to refer to the combination of one or more resins. The resin 14, 14’ may comprise any suitable polyester, vinylester, epoxy or polyurethane resin 14, 14’ or combination of resins 14, 14’. The skilled person would be aware of suitable resins 14, 14’ for forming a polymer composite. In some embodiments of the present invention the resin 14, 14’ comprises at least one of a virgin thermoset polymer and a thermoplastic polymer.

A “thermoset polymer” is used to refer to a polymer that irreversibly solidifies when it is cured. Heat may initiate the curing of a thermoset polymer but is not necessarily required. In some embodiments of the present invention, the presence of a hardener alone is sufficient to initiate the cross linking reaction, without external temperatures elevated above standard room temperature.

A “thermoplastic polymer” is used to refer to a polymer that is more pliable when heated to a temperature above a threshold value, and that will reversibly solidify upon cooling. Heating a solidified thermoplastic polymer above a threshold value restores its pliability without decomposing the polymer.

A “virgin thermoset polymer” is used to refer to a thermoset polymer that has never previously been cured prior to being mixed with the hardener as part of the method of the present invention.

In some embodiments the resin 14, 14’ comprises a virgin thermoplastic polymer, wherein the thermoplastic polymer has never previously been cured prior to being mixed with the hardener 20, 20’ as part of the method of the present invention. In some embodiments the resin 14, 14’ comprises a recycled thermoplastic polymer, wherein the thermoplastic polymer comprising the present invention has previously been (reversibly) cured prior to comprising the resin 14, 14’ of the present invention.

“Hardener” 20, 20’ is used to refer to any species or combination of one or more species that reacts or otherwise interacts with a resin 14, 14’ to harden the resin 14, 14’, for example those that catalyse the cross-linking reaction of a resin 14, 14’. The hardener 20, 20’ may be one or more suitable hardeners 20, 20’.

The “2D material resin dispersion” 16 is used to refer to the product of dispersing the 2D material 12 in the resin 14. The “2D material-hardener dispersion” 16’ is used to refer to the product of dispersing the 2D material 12 in the hardener 20’.

“2D material pre mixture” 22 is used to refer to the product of mixing the 2D material-resin dispersion 16 with the hardener 20 or alternatively mixing the 2D material hardener dispersion 16’ with the resin 14’, or alternatively, the 2D material thermoplastic melt dispersion 16”. The 2D material pre mixture 22 is considered to be broadly similar whether it was formed by mixing the 2D material resin dispersion with the hardener or alternatively by mixing the 2D material hardener dispersion with the resin 14.

“The filler composition” is used to refer to those constituents of the polymer concrete that do not form part of the 2D material pre mixture 22. In some embodiments, the filler composition comprises at least (a) an aggregate material 52, and (b) at least one of sand, hemp or jute (preferably sand) 50, and optionally (c) a further polymer 54. In an embodiment, the further polymer 54 comprises a (cured) thermoset polymer, for example the further polymer is a thermoset polymer. In particular, here, a recycled thermoset polymer may be used. This has significant environmental benefits, as uses for post-use, cured thermoset polymers are much needed. From an environmental point of view, it is desirable to use increasing amounts of recycled materials. The mechanical properties of the polymer reinforced concrete are affected by the amount of recycled polymer used. Polymer concrete materials that have higher recycled polymer content are likely to have reduced mechanical properties. It is therefore possible to tailor the content of the recycled material in a given concrete component in order to provide a component that balances the required mechanical performance with the desire to use increasing amounts of recycled materials. For instance, a structural load bearing component would have a relatively lower content of recycled polymer in comparison to a concrete component that is not designed to bear a structural load.

Components of the filler composition may suitably be provided in a crushed or shredded state in order to control their particle size and/or to produce particles that have a more angular shape. Techniques for crushing such components will be well known to the skilled person, including mechanical crushing methods. Likewise, techniques for shredding polymers are extremely well known, for example granulating and milling methods.

In some embodiments, the sand (if used) may comprise at least one of sharp sand, river sand, sea sand and artificial sand. In some embodiments, the jute (if used) comprises at least one of white jute and tossa jute.

Surprisingly, the inventors have identified that the filler composition may suitably comprise unwashed sea sand. Sea sand, and particularly unwashed sea sand, has not been widely accepted as a material for producing concrete due to its high chloride content (derived from the salt water of the sea), which renders reinforcing members such as steel vulnerable to corrosion and hence causes long-term deterioration of reinforced concrete structures. The suitability of (unwashed) sea sand in the present polymer concrete is thought to be because the polymer concrete does not comprise an aqueous medium into which salts from sea sand can dissolve. The aggregate material 52 comprises one or more aggregates. In some embodiments, the aggregate material 52 comprises a fine aggregate and a coarse aggregate, wherein the fine aggregate has an average particle diameter that is smaller than the average particle diameter of the coarse aggregate. The fine aggregate may be the same type of material as the coarse aggregate.

Alternatively, the fine aggregate may be a different type of material to the coarse aggregate. The skilled person in this technical field would be aware of techniques for controlling aggregate particle diameter, for example sieve analysis techniques adhering to European protocol BS EN 933.

In an embodiment of the invention, the aggregate material 52 comprises a fine aggregate having an average particle diameter of 4 mm to 8 mm, preferably 5 mm to 7 mm and most preferably about 6 mm. In another embodiment the aggregate material comprises a coarse aggregate having an average particle diameter of 16 mm to 24 mm, preferably 18 mm to 22 mm and most preferably about 20 mm.

In a preferred embodiment, the aggregate material 52 comprises both a fine aggregate having an average particle diameter of 4 mm to 8 mm, preferably 5 mm to 7 mm and most preferably about 6 mm and a coarse aggregate having an average particle diameter of 16 mm to 24 mm, preferably 18 mm to 22 mm and most preferably about 20 mm.

In other embodiments of the invention Biochar may be used as an aggregate. Biochar is a highly porous, form of carbon that is produced by heating organic matter in a low-oxygen environment. The process of creating biochar, known as pyrolysis, transforms the organic matter into a form that can be used for a variety of applications. Using biochar as an aggregate allows the carbon to be trapped into the concrete structure. Adding sufficient biochar as aggregate allows the carbon emissions created during the manufacture to be offset resulting in a net removal of carbon from the atmosphere. The skilled person will be aware of suitable aggregate materials for a polymer concrete. In some embodiments the aggregate material 52 comprises at least one of stone, rubber and carbon fibre.

The term “further polymer” 54 is used to refer to an optional additional component of the filler composition material beyond the aggregate 52 and sand/hemp/jute 50. The further polymer 54 is not necessarily the same as any polymer(s) comprising the 2D material pre mixture 22, such as those comprising the resin 14, 14’, however in some embodiments it may be the same type of polymer(s) as those used in the resin 14, 14’. In some preferred embodiments, the further polymer 54 is a thermoset polymer, preferably a recycled thermoset polymer.

In some embodiments, 2D material 12 is present in the 2D material pre mixture 22 in an amount no more than 5 wt%. The inventors have found that when 2D material 12 is present in the 2D material pre mixture in amounts in excess of 5 wt%, 2D material 12 particles are more prone to agglomeration which reduces the homogeneity of distribution of 2D material 12 within the 2D material pre mixture. In some preferred embodiments, 2D material 12 is present in the 2D material pre mixture in an amount 1 wt% to 5 wt%, preferably 2 wt% to 4 wt% and most preferably about 3 wt%.

In some embodiments, 2D material 12 is present in the polymer concrete 36 in an amount no more than 0.05 wt%. The inventors have found that when 2D material 12 is present in the polymer concrete in amounts in excess of 0.05 wt%, 2D material 12 particles are more prone to agglomeration which reduces the homogeneity of distribution of 2D material 12 within the polymer concrete. In some preferred embodiments, 2D material 12 is present in the polymer concrete in an amount 0.01 wt% to 0.05 wt%, preferably 0.01 wt% to 0.04 wt% and most preferably 0.01 wt% to 0.02 wt%.

Polymer Concrete

Putting into practise the presently described method produces a polymer concrete 36, wherein the polymer concrete comprises the components as set out above. Another aspect of the described technology relates to a polymer concrete 36 comprising (a) a binder, wherein the binder is formed from a resin 14, 14’, and a hardener 20, 20’, or alternatively the binder is a thermoplastic material 21 ; (b) a filler composition, wherein the filler composition comprises at least (i) an aggregate material 52 and (ii) at least one of sand, hemp or jute 50, and optionally (iii) a further polymer 54; and (c) 2D material 12.

In some embodiments the 2D material 12 comprises graphene, preferably unfunctionalized graphene.

In some embodiments the resin 14, 14’ comprises at least one of a virgin thermoset polymer and a thermoplastic polymer.

In some embodiments, 2D material 12 is present in the polymer concrete in an amount no more than 0.05 wt%. The inventors have found that when 2D material 12 is present in the polymer concrete in amounts in excess of 0.05 wt%, 2D material 12 is present in the polymer concrete in amounts in excess of 0.05 wt%, 2D material 12 particles are more prone to agglomeration which reduces the homogeneity of distribution of 2D material 12 within the polymer concrete. In some embodiments, 2D material 12 is present in the polymer concrete in an amount 0.005 wt% to 0.05 wt%, preferably 0.01 wt% to 0.04 wt% and most preferably 0.01 wt% to 0.02 wt%.

The aggregate material 52 comprises one or more aggregates. In some embodiments, the aggregate material 52 comprises a fine aggregate and a coarse aggregate, wherein the fine aggregate has an average particle diameter that is smaller than the average particle diameter of the coarse aggregate. The fine aggregate may be the same type of material as the coarse aggregate.

Alternatively, the fine aggregate may be a different type of material to the coarse aggregate. In an embodiment, the aggregate material comprises a fine aggregate having an average particle diameter of 4 mm to 8 mm, preferably 5 mm to 7 mm and most preferably about 6 mm. In another embodiment the aggregate material comprises a coarse aggregate having an average particle diameter of 16 mm to 24 mm, preferably 18 mm to 22 mm and most preferably about 20 mm.

In a preferred embodiment, the aggregate material 52 comprises both a fine aggregate having an average particle diameter of 4 mm to 8 mm, preferably 5 mm to 7 mm and most preferably about 6 mm and a coarse aggregate having an average particle diameter of 16 mm to 24 mm, preferably 18 mm to 22 mm and most preferably about 20 mm.

In some embodiments the aggregate material 52 comprises at least one of stone, rubber and carbon fibre.

In some embodiments, 2D material 12 is present in the polymer concrete in an amount no more than 0.05 wt%. The inventors have found that when 2D material 12 is present in the polymer concrete in amounts in excess of 0.05 wt%, 2D material 12 particles are more prone to agglomeration which reduces the homogeneity of distribution of 2D material 12 within the polymer concrete. In some preferred embodiments, 2D material 12 is present in the polymer concrete in an amount 0.01 wt% to 0.05 wt%, preferably 0.01 wt% to 0.04 wt% and most preferably 0.01 wt% to 0.02 wt%.

Uses of the polymer concrete

A particular usage of the polymer concrete as according to the present technology is as a construction material. This requires the polymer concrete to be formed into a structural element 62 suitable for use in construction.

Hence, another aspect of the present technology regards a method of forming a structural element 62, comprising the steps of producing a polymer concrete 36 as set out above, and then the steps of heating and consolidating 58 the polymer concrete to form the structural element, and cooling 60 the polymer concrete 36 to form the final product.

The polymer concrete 36 may suitably be consolidated using at least one of 3D printing, moulding, continuous hot pressing or extrusion techniques. Extrusion may optionally be screw extrusion, such as single screw extrusion or twin screw extrusion.

Moulding is a traditional method of forming concrete and involves simply pouring the mixed concrete into moulds before the material cures. Once in the mould the concrete can be hot pressed by using heat and pressure to compact and shape the concrete within the mould. This technique is commonly used in the production of concrete bricks, pathing slabs other products that require a high degree of precision and durability. Extrusion of concrete involves forcing the liquid polymer concrete through a die. This is particularly useful in the manufacture of long components of uniform section, such as concrete pipes.

3D printing of concrete involves the depositing layers of concrete material to build up the structure in a pre-defined pattern. This technique allows for the creation of complex designs and shapes that would be difficult or impossible to achieve using traditional construction methods. The benefits of 3D printing of concrete include increased speed and efficiency of construction and leads to reduced waste.

At any stage before the polymer concrete 36 is settled by cooling 60 to form the structural element 62, reinforcement members may be introduced within the polymer concrete. The skilled person would certainly be familiar with suitable reinforcing members for concrete, which may comprise for example steel, polymer or alternate composite materials, any of which may optionally be provided in conjunction with rebar.

Putting into practice the presently described method produces a structural element 62 that forms another aspect of the present invention, wherein the structural element 62 comprises the components as set out above. When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

The invention may also broadly consist in the parts, elements, steps, examples and/or features referred to or indicated in the specification individually or collectively in any and all combinations of two or more said parts, elements, steps, examples and/or features. In particular, one or more features in any of the embodiments described herein may be combined with one or more features from any other embodiment(s) described herein.

Protection may be sought for any features disclosed in any one or more published documents referenced herein in combination with the present disclosure.

Although certain example embodiments of the invention have been described, the scope of the appended claims is not intended to be limited solely to these embodiments. The claims are to be construed literally, purposively, and/or to encompass equivalents.

Comparative testing results

The inventors produced and tested a Polymer-Graphene (0.1 wt% of Graphene) concrete under compression, to compare its relative performance against a more standard concrete mix under the same conditions.

The normal concrete mix: normal concrete, a dry mixing was carried out for fine aggregate, and then a proposed amount of cement was added to the fine aggregate and mixed for another 3 minutes by manual mixing. The required quantity of tap water was then added and the constituents were mixed for a further five minutes, with 1 minute of rest to avoid the forming of air bubbles as recommended by the ACI Committee (American Concrete Institute). The constituent parts (dry weight, each rounded to a single decimal place) of this “normal” concrete mix were cement (17.2 wt%): sand (27.5 wt%): coarse stone (36.7 wt%): fine stone (18.4 wt%): graphene (0.1 wt%).

The polymer-graphene concrete: the casting moulds were thoroughly cleaned, and mould release agent was used to ready the mould for concrete casting. The concrete was cast in layers for all specimens; each layer was compacted by a rod then all specimens were wet-cured by covering the finished surface and moulds with polyethylene sheet for one day. The constituent parts of this polymer- graphene concrete mix were polymer (17.2 wt%): sand (27.5 wt%): coarse stone (36.7 wt%): fine stone (18.4 wt%): graphene (0.1 wt%).

The compressive strength test was determined according to B.S.1881 , part 116. This test was made on 50mm cubes using an electrical testing machine with a capacity of 2000 KN. The compressive strength of the specimen was calculated by dividing the maximum load applied on the specimen during the test (to obtain the final failure) by the average cross-sectional area of the specimen.

Results show that the polymer-graphene concrete presents much higher compressive modulus results (83 GPa) compared to cement concrete (30 GPa) and higher compressive strength (34.3 MPa) compared to cement concrete (28 MPa).

These results show that GIM concrete has an improvement of 281% for compressive modulus and 22.7% for compressive strength.

Representative features

Certain representative features of the described technology are set out in the following clauses, which stand alone or may be combined, in any combination, with one or more features disclosed in the text and/or drawings of the specification.

1. A method of producing a polymer concrete comprising the steps of: (i-1) dispersing 2D material in a resin to form a 2D material resin dispersion, then (ii-1) mixing the 2D material resin dispersion with the hardener to form a 2D material pre-mixture; or alternatively

(i-2) dispersing 2D material in a hardener to form a 2D material hardener dispersion, then

(ii-2) mixing the 2D material hardener dispersion with the resin to form the 2D material pre mixture, and then, having conducted either steps (i-1) and (ii-1) or steps (i-2) and (ii- 2),

(iii) combining the 2D material pre-mixture with a filler composition to form the polymer concrete.

2. The method according to clause 1, wherein the filler composition comprises at least (a) an aggregate material, and (b) at least one of sand, hemp or jute, and optionally (c) a further polymer, wherein the further polymer, if present, is optionally a thermoset polymer.

3. The method according to clause 1 or 2, wherein the 2D material comprises graphene.

4. The method according to clause 2 or 3, wherein the aggregate material comprises a fine aggregate and a coarse aggregate, and wherein the fine aggregate has an average particle diameter of 4 mm to 8 mm, preferably 5 mm to 7 mm and most preferably about 6 mm, and the coarse aggregate has an average particle diameter of 16 mm to 24 mm, preferably 18 mm to 22 mm and most preferably about 20 mm.

5. The method according to any one of clauses 2 to 4, wherein the aggregate material comprises at least one of stone, rubber and carbon fibre.

6. The method according to any one of clauses 1 to 5, wherein in step (iii) the 2D material pre-mixture is combined with the filler composition by spraying the 2D material pre-mixture onto the filler composition or by adding the 2D material premixture to the filler composition dropwise.

7. The method according to any one of clauses 1 to 6, wherein in step (i-1) 2D material is dispersed incrementally into the resin or alternatively in step (i-2) 2D material is dispersed incrementally into the hardener. 8. The method according to any one of clauses 1 to 7, wherein the 2D material is present in the 2D material pre-mixture in an amount 1 wt% to 5 wt%, preferably 2 wt% to 4 wt% and most preferably about 3 wt%.

9. The method according to any one of clauses 1 to 8, wherein the 2D material is present in the polymer concrete in an amount 0.005 wt% to 0.05 wt%, preferably 0.01 wt% to 0.04 wt% and most preferably 0.01 wt% to 0.02 wt%.

10. The method according to any one of clauses 1 to 9, wherein the resin comprises at least one of a virgin thermoset polymer and a thermoplastic polymer.

11. The method according to any one of clauses 1 to 10, wherein the 2D material comprises unfunctionalized graphene.

12. A polymer concrete manufactured by the method according to any one of clauses 1 to 11.

13. A polymer concrete, comprising:

(a) a binder, wherein the binder is formed from a resin, and a hardener;

(b) a filler composition, wherein the filler composition comprises at least (i) an aggregate material and (ii) at least one of sand, hemp or jute, and optionally (iii) a further polymer; and

(c) 2D material.

14. The polymer concrete according to clause 13, wherein the 2D material comprises graphene.

15. The polymer concrete according to clause 13 or 14, wherein the resin comprises at least one of a virgin thermoset polymer and a thermoplastic polymer.

16. The polymer concrete according to any one of clauses 13 to 15, wherein the 2D material is present in the polymer concrete in an amount 0.005 wt% to 0.05 wt%, preferably 0.01 wt% to 0.04 wt% and most preferably 0.01 wt% to 0.02 wt%.

17. The polymer concrete according to any one of clauses 13 to 16, wherein the aggregate material comprises a fine aggregate and a coarse aggregate, and wherein the fine aggregate has an average particle diameter of 4 mm to 8 mm, preferably 5 mm to 7 mm and most preferably about 6 mm, and the coarse aggregate has an average particle diameter of 16 mm to 24 mm, preferably 18 mm to 22 mm and most preferably about 20 mm. 18. A method of forming a structural element, comprising conducting the method of producing a polymer concrete according to any one of clauses 1 to 11 , and then the steps of:

(iv) heating and consolidating the polymer concrete to form a desired shape of the structural element, and (v) cooling the polymer concrete.

19. The method of forming a structural element according to clause 18, wherein the polymer concrete is consolidated by at least one of 3D printing, moulding, continuous hot pressing or extrusion, wherein the extrusion is optionally screw extrusion, such as single screw extrusion or twin screw extrusion.

20. A structural element manufactured by the method according to clause 18 or 19.