GB2608595A

GB2608595A - Cementitious composition

Info

Publication number: GB2608595A
Application number: GB2109455.2A
Authority: GB
Inventors: Wadley Natalie; Wadley Luke
Original assignee: Changemaker 3d Ltd
Current assignee: Changemaker 3d Ltd
Priority date: 2021-06-30
Filing date: 2021-06-30
Publication date: 2023-01-11
Also published as: GB202109455D0

Abstract

A cementitious composition comprising a mixture of a cement binder and a graphene based ink. The ink may include graphene based nanoplatelets dispersed in carrier liquid. The nanoplatelets may be few-layer graphene or graphene-graphite and may be present in 100-600 grams per litre of dispersion. The carrier liquid may be aqueous and include a stabilising agent, such as a polymer or surfactant. The composition may be concrete and include aggregate and water. A cementitious article, e.g. an architectural or structural article, may comprise the composition. The method of forming the article may comprise using an additive manufacturing machine. The graphene-based ink is intended to act as an accelerator to increase the rate of development of early strength and load-bearing capacity.

Description

CEMENTITIOUS COMPOSITION

The invention relates to a cementitious composition, a cementitious article, a method of preparing a cementitious composition and a method of manufacturing a cementitious article.

It is known to include admixtures and additives in cement, mortar and concrete to vary their properties.

According to a first aspect of the invention, there is provided a cementitious composition comprising a mixture, the mixture including a cement binder and a graphene-based ink.

The graphene-based ink acts as an accelerator that increases the rate of development of early strength, and therefore load-bearing capacity, in the cementitious composition in comparison to normal curing. In addition, the graphene-based ink enables the cementitious composition of the invention to exhibit a similar or higher compressive strength in comparison to the same cementitious composition without the graphenebased ink.

The graphene-based ink may be used to replace part of the water in the cementitious composition. This in turn provides environmental and cost benefits in the form of reduced water usage and reduced transportation needs. Furthermore, the graphenebased ink provides a more environmentally friendly solution than other chemical accelerators.

The graphene-based ink may be prepared in a number of different ways, non-limiting examples of which are described as follows.

Graphene is a two-dimensional material of sp2-bonded carbon atoms arranged in a hexagonal lattice. The graphene in the graphene-based ink may include monolayer graphene, bilayer graphene, trilayer graphene and/or few-layer graphene (10 layers of graphene). The graphene-based ink may include, but is not limited to, graphene flakes, graphene platelets, graphene nanoplatelets, graphene ribbons and/or graphene sheets. The graphene-based ink may include pristine graphene, chemically functionalised graphene and/or graphene derivatives.

In a preferred embodiment of the invention, the graphene-based ink may include graphene-based nanoplatelets dispersed in a carrier liquid. The graphene-based nanoplatelets may include few-layer graphene nanoplatelets and/or graphene-graphite nanoplatelets. A nanoplatelet is a high aspect ratio structure (i.e. length/thickness > 10) with a typical thickness of <100 nm and a typical length >500 nm. It is envisaged that the nanoplatelets in the graphene-based ink may have different geometrical characteristics.

Preferably the graphene-based nanoplatelets are present in the graphene-based ink in an amount of 100g to 600g per litre of dispersion, the dispersion including the graphene-based nanoplatelets and the carrier liquid. Other concentrations of the graphene-based nanoplatelets in the graphene-based ink are envisaged.

The carrier liquid may be aqueous. This results in a water-based graphene-based ink that is low in cost and more environmentally friendly. In other embodiments of the invention, the carrier liquid may be non-aqueous.

In embodiments of the invention, the graphene-based ink may include a stabilising agent. This further enhances the quality and condition of the resultant cementitious 20 composition.

The stabilising agent may include a polymer. The polymer may be selected from, but is not limited to, a group consisting of: carboxymethylcellulose; polyvinyl alcohol; and polyvinylpyrrolidone. Other polymers may be used as the stabilising agent in the invention.

The stabilising agent may include a surfactant. The surfactant may be sodium deoxycholate. Alternatively the surfactant may be selected from a group consisting of: an anionic surfactant; a cationic surfactant; a non-ionic surfactant; a zwitterionic surfactant; and a biosurfactant. Other surfactants may be used as the stabilising agent in the invention.

Non-limiting examples of graphene-based inks and their production methods are described through this specification.

Different types of cement binders may be used in the cementitious composition of the invention. Preferably the cement binder includes, but is not limited to, a hydraulic cement (e.g. Portland cement), slag (e.g. ground granulated blast furnace slag) or a fly ash compound. Other materials may be used as the cement binder in the invention.

In the invention, the mixture may include water and/or aggregate.

Different types of aggregate may be used in the cementitious composition of the invention. Preferably the aggregate includes sand, rock and/or gravel. Different aggregate sizes may be used in the cementitious composition of the invention. For example, the aggregate may include aggregate particles with a grain size of 3 mm or less.

The invention is applicable to different cementitious compositions, such as cement compositions, concrete compositions and mortar compositions. The constituent parts of the cementitious composition may be provided in different proportions to produce a concrete or mortar composition. Coarser aggregate is typically used for concrete compositions, while finer aggregate is typically used for mortar compositions.

The graphene-based ink may be incorporated into the cementitious composition as an admixture or an additive.

Other admixtures or additives may be added to the cementitious composition of the invention to improve its working properties and durability. Such admixtures or additives include, but are not limited to, lime and plasticisers.

According to a second aspect of the invention, there is provided a method of preparing the cementitious composition of the first aspect of the invention or any one of its embodiments, the method comprising the step of mixing a cement binder and a graphene-based ink to produce the cementitious composition.

The features and advantages of the cementitious composition of the first aspect of the invention and its embodiments apply mutatis mutandis to the method of the second aspect of the invention and its embodiments.

According to a third aspect of the invention, there is provided a cementitious article comprising the cementitious composition of the first aspect of the invention or any one of its embodiments.

The features and advantages of the cementitious composition of the first aspect of the invention and its embodiments apply mutatis mutandis to the cementitious article of the third aspect of the invention and its embodiments.

The invention is applicable to a wide range of cementitious articles. In embodiments of the invention, the cementitious article may be a cementitious structure, such as a brick, a slab, a wall, a floor, a ceiling, a chamber, a storage unit, a foundation, a pillar, an arch, a pavement, a road and a bridge. The cementitious article may be used in architectural, structural, non-structural, industrial and design applications.

According to a fourth aspect of the invention, there is provided a method of manufacturing a cementitious article of the third aspect of the invention or any one of its embodiments, the method comprising the step of manufacturing the cementitious article from the cementitious composition of the first aspect of the invention or any one of its embodiments.

The features and advantages of the cementitious composition and the cementitious article of the first and third aspects of the invention and their embodiments apply mutatis mutandis to the method of the fourth aspect of the invention and its embodiments.

The method may include the step of pouring the cementitious composition into a mould to form the cementitious article as a casting inside the mould. The formed cementitious article is then removed from or broken out of the mould.

The method may include the step of manufacturing the cementitious article using an additive manufacturing machine comprising a dispensing head. The scope of the additive manufacturing machine includes a 3D printer. In such a step, the cementitious composition is dispensed from the dispensing head to print a plurality of layers of the cementitious composition in order to form the cementitious article. Movement and speed of the dispensing head may be controlled during the printing process to define the position and shape of each layer. Each subsequent layer may be printed on top of a prior-printed layer to form the cementitious article out of multiple layers stacked on top of each other.

The increase in rate of development of early strength, and therefore load-bearing capacity, in the cementitious composition due to the gra phene-based ink helps to speed up the overall additive manufacturing process. Otherwise additional time is required in waiting for each layer to cure and develop sufficient strength before the next layer can be printed. Moreover, the reduced water and transportation requirements simplifies the pre-manufacturing preparations and planning of the additive manufacturing process, especially when different cementitious articles are required and/or different sites are involved.

The method of the invention may include the steps of: mixing a cement binder and a graphene-based ink to produce the cementitious composition; and delivering the cementitious composition to the dispensing head.

The additive manufacturing machine may include a mixing container in which the cement binder and the graphene-based ink may be mixed.

In the invention, the mixing process may include mixing the cement binder and the graphene-based ink with aggregate and/or water to produce the cementitious composition.

The step of delivering the cementitious composition to the dispensing head may involve pumping the cementitious composition to the dispensing head. The additive manufacturing machine may include a pump for pumping the cementitious composition to the dispensing head. A hose may be used to fluidly connect the mixing container to the dispensing head.

It will be appreciated that the use of the terms "first" and "second", and the like, in this patent specification is merely intended to help distinguish between similar features, and is not intended to indicate the relative importance of one feature over another feature, unless otherwise specified.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, and the claims and/or the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and all features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

Preferred embodiments of the invention will now be described, by way of non-limiting examples, with reference to the accompanying drawings in which: Figure 1 shows a flow chart illustrating a method of manufacturing a mortar-based article using an additive manufacturing machine; Figure 2 shows an additive manufacturing machine; and Figures 3 and 4 shows the additive manufacturing machine when in use.

The figures are not necessarily to scale, and certain features and certain views of the figures may be shown exaggerated in scale or in schematic form in the interests of clarity and conciseness.

The following embodiments of the invention are described with reference to a mortar composition. It will be appreciated that the following embodiments of the invention are applicable mutatis mutandis to other cementitious compositions such as cement compositions and concrete compositions.

Mortar composition A mortar composition according to an embodiment of the invention comprises a mixture of aggregate, a cement binder, water and a graphene-based ink.

The aggregate is in the form of sand with a grain size of 3 mm or less. Different types and sizes of aggregate may be used in other embodiments of the invention.

Different types of cement binders may be used. The cement binder may include a hydraulic cement (e.g. Portland cement), slag (e.g. ground granulated blast furnace slag) or a fly ash compound. The cement binder may include one or more of the following compounds: tricalcium silicate, dicalcium silicate, tricalcium aluminate, tetracalcium aluminoferrite and gypsum.

The graphene-based ink includes graphene-based nanoplatelets dispersed in an aqueous carrier liquid to form a water-based graphene-based ink. The graphene-based nanoplatelets are in the form of a mixture of few-layer graphene nanoplatelets and graphene-graphite nanoplatelets. The graphene-based nanoplatelets are present in the graphene-based ink in an amount of 100g to 600g per litre of dispersion, the dispersion including the graphene-based nanoplatelets and the carrier liquid.

The dimensions of each graphene-based nanoplatelet can vary. A lateral size of each graphene-based nanoplatelet may range from 100 nm to 5 pm, preferably from 0.5 pm to 2 pm. Each graphene-based nanoplatelet may have a structure that is monolayer, bilayer, trilayer, few-layer or more than 10 layers up to 100 layers.

Optionally the graphene-based ink may include a stabilising agent, such as a polymer or a surfactant. The polymer may be selected from, but is not limited to, a group consisting of: carboxymethylcellulose; polyvinyl alcohol; and polyvinylpyrrolidone. The surfactant may be sodium deoxycholate, or may be selected from a group consisting of: an anionic surfactant; a cationic surfactant; a non-ionic surfactant; a zwitterionic surfactant; and a biosurfactant.

Other graphene-based inks may be used in place of the graphene-based ink described hereinabove. For example, non-limiting examples of graphene-based inks and their production methods are disclosed in PCT application number PCT/EP2016/074106, which was filed on 7 October 2016 and published as WO 2017/060497A1 on 13 April 2017. Such graphene-based inks may be used as the graphene-based ink of the mortar composition of the invention and cementitious compositions of other embodiments of the invention.

Additive manufacturing An additive manufacturing machine 20 may be used to manufacture a mortar-based article from the mortar composition. Such an article may be, for example, an architectural or structural article. Other examples of articles are described through this specification.

Figure 1 shows a flow chart illustrating a method of manufacturing the mortar-based article using the additive manufacturing machine 20.

Figure 2 shows the additive manufacturing machine 20. The additive manufacturing machine 20 comprises a robotic arm 22, a dispensing head 24, a mixing container 26, a mortar pump 28 and a hose 30. The dispensing head 24 is in the form of a nozzle 24 measuring 40 mm by 20 mm. Other nozzle dimensions are envisaged.

Initially aggregate, a cement binder, water and the graphene-based ink is mixed inside the mixing container 26 to produce the mortar composition (Step 100 in Figure 1).

Water may be introduced into the mixing container 26 automatically using a water pump or manually by hand. The mixing of the aggregate, the cement binder, the water and the graphene-based ink inside the mixing container 26 may be carried out automatically, e.g. using an electric mixer, or manually by hand. The use of the graphene-based ink not only makes it easy to mix the graphene-based nanoplatelets uniformly with the aggregate, the cement binder and the water, without requiring any specialised equipment, but also makes it easy to properly quantify the amount of graphene-based nanoplatelets that is added to the mixture. Uniform dispersion of the graphene-based nanoplatelets in the mortar composition is important to ensure uniform properties throughout the mortar composition, which is readily achieved using the graphene-based ink.

The hose 30 is arranged to fluidly connect the mixing container 26 to the nozzle 24. The mortar pump 28 is controlled to pump the mortar composition through the hose 30 from the mixing container 26 to the nozzle 24 (Step 102 in Figure 1). In use, the mortar composition is dispensable from the nozzle 24.

The nozzle 24 is mounted onto the robotic arm 22 that is movable in multiple axes and is controlled by a control unit. Exemplary technical details of the robotic arm 22 are as follows: Position repeatability: 0.15 mm Path repeatability at 1 m/s: 1.5 mm Layer resolution: 10 mm to 50 mm Print speed: 50 mm/s to 600 mm/s Print precision: 1/1/1 mm As the mortar composition is pumped to and dispensed from the nozzle 24, the robotic arm 22 guides the movement of the nozzle 24 to follow a pre-programmed printing path and speed to print a layer of the mortar composition at a pre-defined location and with a pre-defined shape (Step 104 in Figure 1). Each subsequent layer of the mortar composition is printed in a similar fashion, with its own pre-programmed printing path and speed, so that the multiple layers together form a 3D mortar-based article (Step 106 in Figure 1). Figure 3 shows the use of the additive manufacturing machine 20 to print a first layer 32, and Figure 4 shows the use of the additive manufacturing machine 20 to print a second layer 34 on top of the first layer 32.

The robotic arm 22 may be configured to be movable so as to add an additional axis of movement to the pre-programmed printing path. For example, the robotic arm 22 may be mounted onto wheels or tracks, or may be mounted to move along a rail.

Alternatively the robotic arm 22 may be suspended from a gantry. Further alternatively the nozzle 24 itself may be suspended from a gantry, with the robotic arm 22 being omitted from the additive manufacturing machine 20.

Non-limiting examples of additive manufacturing machines for printing the mortar-based article can be found at: haps://cv e.eu/technolocaybes ir?tersi Casting Alternatively the mortar-based article may be manufactured by first mixing aggregate, a cement binder, water and the graphene-based ink inside a mixing container to produce the mortar composition and then by pouring the mortar composition into a mould so that the mortar-based article is formed as a casting inside the mould. The mortar-based article is then removed from or broken out of the mould.

Testing To illustrate the improvements arising from the inclusion of the graphene-based ink in the mortar composition, samples were prepared using the additive manufacturing and casting processes. The samples included tasted cubes and printed cubes measuring approximately 10 cm by 10 cm by 10 cm, with each sample formed of a mortar composition with the graphene-based ink.

The mortar composition used for testing is CyBe mortar, although it will be appreciated that other mortar compositions can be used. CyBe mortar comprises 70% aggregate with a grain size of 3mm or less, is non-metallic with a very low chloride and sulphate content, and can be printed at speeds up to 600 mm/s and layer heights up to 50 mm. Further details of the CyBe mortar can be found at: bStoa;LL mortar/.

The CyBe mortar with the graphene-based ink is prepared by using the graphenebased ink to replace part of the water in the CyBe mortar without the graphene-based ink. Specifically, the volumetric quantity of the graphene-based ink used in the CyBe mortar with the graphene-based ink is the same as the volumetric quantity of water that is replaced. Other volumetric ratios between the graphene-based ink and the replaced water may be used. Replacing part of the water in the mortar composition with the graphene-based ink provides environmental and cost benefits in the form of reduced water usage and reduced transportation needs and also simplifies the pre-manufacturing preparations and planning of the additive manufacturing process.

The testing of the casted cubes and printed cubes was carried out in accordance with EN 12390-3:2019 "Testing hardened concrete. Compressive strength of test specimens" and EN 12390-7:2019 "Testing hardened concrete. Density of hardened concrete". Prior to testing, the cubes were stored in a climate-controlled room at a temperature of 20 ± 2°C and a humidity 95%. The surfaces of the cubes were clean and dry at the start of the test.

Table 1 sets out the production method, the dimensions, the mass and the density of each casted cube and each printed cube. Table 1 also shows the age of each sample in days, where the age is the time period between the manufacture of the sample and the testing of the sample. Table 2 shows the measured compressive strength of each sample.

Table 1

Sample Production method Age (days) Length (mm) Width (mm) Height (mm) Mass (g) Density (kg/m3) 1 Casting 3 100.1 100.0 100.6 2067 2050 2 Casting 3 100.2 100.2 102.4 2120 2060 3 Casting 3 100.0 100.6 100.5 2081 2060 4 Casting 7 100.7 100.6 101.1 2086 2040 Casting 7 100.3 100.8 102.4 2128 2050 6 Casting 7 100.3 100.4 100.8 2081 2050 7 Casting 28 101.6 100.8 100.6 2139 2070 8 Casting 28 101.6 101.2 101.4 2175 2090 9 Casting 28 102.0 102.0 100.8 2101 2000 Casting 56 100.5 100.2 101.1 2088 2050 11 Additive manufacturing 3 96.1 101.8 100.3 2010 2050 12 Additive manufacturing 3 101.2 100.3 100.8 2094 2050 13 Additive manufacturing 3 95.8 99.8 100.9 1975 2050 14 Additive manufacturing 7 96.9 101.6 102.2 2025 2010 Additive manufacturing 7 97.0 103.1 98.3 1998 2030 16 Additive manufacturing 7 99.4 102.9 100.4 2083 2030 17 Additive manufacturing 36 90.1 81.2 90.2 1336 2030 18 Additive manufacturing 56 87.6 87.3 90.8 1401 2020 19 Additive manufacturing 56 93.3 93.7 91.8 1614 2010

Table 2

Sample Flatness deviation (mm) Cross-sectional area length (mm) Cross-sectional area width (mm) Force (kN) Compressive strength (N/mm2) 1 0.1 100.6 100.0 288.8 28.7 2 0.1 102.4 100.2 291.1 28.4 3 0.1 100.5 100.6 290.7 28.8 4 0.1 101.1 100.6 301.0 29.6 0.1 102.4 100.8 314.0 30.4 6 0.1 100.8 100.4 324.6 32.1 7 <0.1 100.6 100.8 345.4 34.0 8 0.1 101.4 101.2 354.9 34.6 9 0.1 100.8 102.0 314.0 30.5 0.1 101.1 100.2 303.7 30.0 11 0.1 100.3 101.8 315.2 30.9 12 0.1 100.8 100.3 307.0 30.4 13 0.1 100.9 99.8 312.9 31.1 14 0.1 102.2 101.6 331.6 31.9 0.1 98.3 103.1 326.7 32.2 16 0.1 100.4 102.9 331.0 32.0 17 0.1 90.2 81.2 242.7 33.2 18 0.1 90.8 87.3 259.0 32.7 19 0.1 91.8 93.7 303.7 35.3 The CyBe mortar without the graphene-based ink exhibits a compressive strength of approximately 20 N/mm2 after 5 hours, approximately 25 N/mm2 after 1 day, approximately 30 N/mm2 after 7 days and approximately 40 N/mm2 after 28 days.

In comparison, it can be seen from Tables 1 and 2 that the samples based on the CyBe mortar with the gra phene-based ink exhibits an increased rate of development of early strength in comparison to the CyBe mortar without the graphene-based ink. In particular, the printed cubes demonstrate 3-day compressive strengths that are comparable to or higher than the 7-day compressive strength of the CyBe mortar without the graphene-based ink.

Furthermore, the printed cubes demonstrate further increases in compressive strength during the 4 days between the 3-day and 7-day tests, with the 7-day compressive strengths of the printed cubes remaining above the 7-day compressive strengths of N/mm2 of the CyBe mortar without the graphene-based ink. Generally the data in Tables 1 and 2 shows a general trend of increasing compressive strength with sample age.

The inclusion of the graphene-based ink as an accelerator in the mortar composition therefore not only results in an increased rate of development of early strength, and therefore load-bearing capacity, in the mortar composition and the mortar-based article in comparison to normal curing, but also enables the resultant mortar composition and the mortar-based article to exhibit a similar or higher compressive strength in comparison to the same mortar composition and the same mortar-based article without the graphene-based ink. The increased rate of development of early strength is particularly advantageous for speeding up the additive manufacturing process by reducing the amount of required wait time between consecutive printing steps.

It will be appreciated that the above numerical values are intended to help illustrate the working of the invention but are not intended to be limiting on the scope of the invention.

The listing or discussion of an apparently prior-published document or apparently prior-published information in this specification should not necessarily be taken as an acknowledgement that the document or information is part of the state of the art or is common general knowledge.

Preferences and options for a given aspect, feature or parameter of the invention should, unless the context indicates otherwise, be regarded as having been disclosed in combination with any and all preferences and options for all other aspects, features and parameters of the invention.

Claims

CLAIMS1. A cementitious composition comprising a mixture, the mixture including a cement binder and a graphene-based ink.
2. A cementitious composition according to Claim 1 wherein the graphene-based ink includes graphene-based nanoplatelets dispersed in a carrier liquid.
3. A cementitious composition according to Claim 2 wherein the graphene-based nanoplatelets include few-layer graphene nanoplatelets and/or graphene-graphite nanoplatelets.
4. A cementitious composition according to Claim 2 or Claim 3 wherein the graphene-based nanoplatelets are present in the graphene-based ink in an amount of 100g to 600g per litre of dispersion, the dispersion including the graphene-based nanoplatelets and the carrier liquid.
5. A cementitious composition according to any one of Claims 2 to 4 wherein the carrier liquid is aqueous.
6. A cementitious composition according to any one of the preceding claims wherein the graphene-based ink includes a stabilising agent.
7. A cementitious composition according to Claim 6 wherein the stabilising agent includes a polymer.
8. A cementitious composition according to Claim 7 wherein the polymer is selected from a group consisting of: carboxymethylcellulose; polyvinyl alcohol; and polyvinylpyrrolidone.
9. A cementitious composition according to any one of Claims 6 to 8 wherein the stabilising agent includes a surfactant.
10. A cementitious composition according to Claim 9 wherein the surfactant is sodium deoxycholate.
11. A cementitious composition according to Claim 9 wherein the surfactant is selected from a group consisting of: an anionic surfactant; a cationic surfactant; a nonionic surfactant; a zwitterionic surfactant; and a biosurfactant.
12. A cementitious composition according to any one of the preceding claims wherein the cement binder includes a hydraulic cement, slag or a fly ash compound.
13. A cementitious composition according to any one of the preceding claims wherein the mixture includes water.
14. A cementitious composition according to any one of the preceding claims wherein the mixture includes aggregate.
15. A cementitious composition according to Claim 14 wherein the aggregate includes sand, rock and/or gravel.
16. A cementitious composition according to any one of the preceding claims wherein the cementitious composition is a concrete composition.
17. A cementitious composition according to any one of Claims 1 to 15 wherein the cementitious composition is a mortar composition.
18. A method of preparing a cementitious composition of any one of the preceding claims, the method comprising the step of mixing a cement binder and a graphene-based ink to produce the cementitious composition.
19. A cementitious article comprising a cementitious composition of any one of Claims 1 to 17.
20. A cementitious article according to Claim 19 wherein the cementitious article is an architectural or structural article.
21. A method of manufacturing a cementitious article of Claim 19 or Claim 20, the method comprising the step of manufacturing the cementitious article from the cementitious composition of any one of Claims 1 to 17.
22. A method according to Claim 21 including the step of manufacturing the cementitious article using an additive manufacturing machine comprising a dispensing head, wherein the cementitious composition is dispensed from the dispensing head to print a plurality of layers of the cementitious composition in order to form the cementitious article.
23. A method according to Claim 22 including the steps of: mixing a cement binder and a graphene-based ink to produce the cementitious composition; and delivering the cementitious composition to the dispensing head.
24. A method according to Claim 23 wherein the additive manufacturing machine includes a mixing container in which the cement binder and the graphene-based ink may be mixed.
25. A method according to Claim 23 or Claim 24 wherein the step of delivering the cementitious composition to the dispensing head involves pumping the cementitious composition to the dispensing head.