Foamed concrete compositions, methods of preparation and uses thereof

Abstract

A method of preparation of a foamed concrete, comprising the steps of; providing a cementitious slurry, comprising in wt% relative to the wt of the slurry, 60-70% of a cementitious material, 0.5-5% in

Description

Field of the Invention The present invention relates to foamed concrete compositions, methods of preparation and uses thereof, 5 and particularly, although not exclusively, to lightweight foamed concretes having a density of 400 kg / m3 or less. Background Foamed concrete materials are known in the art. A foam concrete is classified as a highly air entrained 10 sand / cement or cement only slurry, typically with greater than 20% air by volume. In known methods of forming foamed concretes, air is mechanically entrained into a cementitious base material slurry to produce a lighter density, mixed material. Typically, foamed concretes have densities ranging from 400kg / m3to 1800kg / m3 with (yield) strengths ranging from 0.5N / mm2to 12N / mm2. Foamed concretes may also be referred to in the art as “foamed mortar”, “foamed grout”, “aerated lightweight concrete” and 15 “cellular lightweight concrete”. "d" Foamed concrete is used primarily as a void filler as its high rate of expansion and fluid properties can make it a much more economical filling material than stiff low cement concrete, or hardcore and loose materials that require compaction. There is a general desire for foamed concrete having improved properties. The present invention has been devised in light of the above considerations. Summary of the Invention The present inventors have found that by employing particular methods of production, foamed concrete having a particularly low density, good flowability prior to curing, and suitable properties for use in 25 construction applications can be produced. Accordingly, in a first aspect, the present invention provides a method of preparation of a foamed concrete, the method comprising steps of: providing a cementitious slurry, the cementitious slurry comprising (in wt% relative to wt of slurry): from 60 to 70% of a cementitious material; 30 from 0.5 to 5% inorganic particles; from 5 to 10% water-soluble calcium salt; from 0.1 to 2% water-reducing agent, plasticizer or superplasticizer; from 10 to 30% water; 35 providing a protein-stabilised aqueous foam; mixing the slurry with the protein-stabilised aqueous foam in predetermined volume ratio to form an aerated slurry mixture, the mixing ratio of the cementitious slurry and the protein-stabilised aqueous foam being selected such that the overall density of the aerated slurry mixture is 400 kg / m3 or less; and allowing the aerated slurry mixture to cure to form the foamed concrete, wherein the cementitious material comprises cement and the inorganic particles comprise one or 5 more of: fly ash, ground granulated blast-furnace slag, limestone, silica, natural pozzolana, natural calcined pozzolana, metakaolin and mixtures thereof. The present inventors have found that methods as defined above can advantageously allow for 10 15 production of particularly low density foamed concretes. In particular, for production of foamed concretes having a suitable balance of low density and strength to allow for improved thermal insulation performance compared to known foamed concrete arrangements. In particular, the inventors have found that providing a method in which a cementitious slurry is mixed with a protein-stabilised aqueous foam in a predetermined mixing ratio (rather than, for example, a mixing method in which all dry ingredients are mixed with water alone and subsequently aerated in bulk) is particularly advantageous in this regard -specifically, by controlling the amount of air in the aerated slurry mixture by adding the foam to the cementitious slurry separately (vs aerating / foaming the slurry directly), improved control over the density of the aerated slurry and resultant foamed concrete can be achieved. Furthermore, the specific ratio of non-aqueous ingredients in the slurry (cementitious material, inorganic particles, water-soluble calcium salt and super plasticiser) as noted above can provide for formation of a foamed concrete having good performance in specific applications such as when used as an insulating material in construction application. The protein-stabilised aqueous foam may comprise water and a foaming agent or foaming agent mixture, wherein the foaming agent or foaming agent mixture comprises protein. The term “foaming agent” is used to refer to a material that facilitates the formation of foam, e.g. by reducing surface tension of a liquid, or increasing the colloidal stability of a foam by inhibiting coalescent of bubbles. Foaming agents 25 are typically surfactants. The term “foaming agent mixture” is used herein to define a mixture of compounds that includes at least one foaming agent, but which may include plural foaming agents. The protein-stabilised aqueous foam may comprise the foaming agent or foaming agent mixture in an amount of from 0.1 wt% to 10 wt%, e.g. 0.5 wt% to 5 wt%, based on total weight of the foam. For example in some embodiments, protein-stabilised aqueous foam may comprise the foaming agent or 30 foaming agent mixture in an amount of 0.1 wt% or more, 0.5 wt% or more, 1 wt% or more, 2 wt% or more, 3 wt% or more, 4 wt% or more or 5 wt% or more. The balance of the protein-stabilised aqueous foam may comprise water. That is, the protein-stabilised aqueous foam may comprise water in an amount of from 95 to 99.99 wt%. In other words, the foam may consist essentially of, or consist of, the water and the foaming agent or foaming agent mixture. In some 35 embodiments, the relative amounts of foaming agent mixture may be expressed as a vol%. The foaming agent or foaming agent mixture may comprise protein in an amount of from 1 to 100 wt% based on total weight of the foaming agent mixture, more preferably 5 to 50 wt%, or 10 wt% to 20 wt% e.g. in an amount of 10 wt% or more or 15 wt% or more. In some embodiments, the foaming agent mixture may comprise protein in an amount of from 15-18 wt%. In other words, in view of the abovedescribed addition amounts of the foaming agent mixture to form the protein-stabilised aqueous foam, it will be understood that the protein-stabilised aqueous foam may comprise protein in an amount of from 0.01 wt% to 10 wt%. Typically, the protein content of the protein-stabilised aqueous foam may be less 5 than 5 wt%, or less than 1 wt% - for example it may be in a range of from about 0.05 wt% to 1 wt%. The protein may comprise a vegetable-derived protein or an animal-derived protein. The protein is preferably a structural fibrous protein. For example, the protein may comprise keratin, collagen, elastin, fibrin, or mixtures thereof. It has been found that the use of structural fibrous proteins may provide suitable structural properties for the foamed concrete. In some embodiments, the protein may be a 10 hydrolysed protein, e.g. it may comprise hydrolysed keratin, hydrolysed collagen, hydrolysed elastin, hydrolysed fibrin, or mixtures thereof. Where a foaming agent mixture is used, this may comprise one or more non-protein-based foaming agents / surfactants. The one or more further foaming agents / surfactants may be provided in an amount of from 1 to 50 wt% based on total weight of the foaming agent mixture. For example, the one or more 15 further foaming agents / surfactants may be provided in an amount of 2 wt% or more, 3 wt% or more, 4 wt% or more, 5 wt% or more, 10 wt% or more, or 20 wt% or more. The non-protein-based foaming agents / surfactants may comprise: sodium lauryl sulphate (SLS), coca amido propyl betaine (CAPB), alkyl C\J dimethyl hydroxyl ethyl ammonium chloride (HYPR), cocamide DEA(LM), sodium dodecyl benzene sulphonates (SDBS), and mixtures thereof. ’ 20 Where a foaming agent mixture is used, this may comprise a solvent. The solvent may be provided in an amount of from 1 to 20 wt% based on total weight of the foaming agent mixture, e.g. 2 to 6 wt%. For example, the solvent may be provided in an amount of 2 wt% or more, 3 wt% or more, 4 wt% or more or 5 wt% or more. The solvent may comprise hexylene glycol, trimethyl-trimethylene glycol, or any other suitable solvents. 25 Where a foaming agent mixture is used, this may comprise a stabiliser. The stabiliser may be provided in an amount of from 0.01 to 10 wt% based on total weight of the foaming agent mixture, e.g. 0.01 to 5wt%, e.g. 0.01 wt% or more, 0.02 wt% or more, 0.05 wt% or more, or 1 wt% or more. The stabiliser may comprise carboxymethyl cellulose, cellulose ether, methyl cellulose, ethyl cellulose, sodium dodecylbenzene sulfonate, trolamine, lauryl alcohol, amine oxide, lauryl dimethyl amine oxide, xantham 30 gum, refined glycerine, and mixtures thereof. The protein stabilised aqueous foam may be formed by mixing the water and foaming agent mixture, and then aerating the mixture. The mixture may be aerated in any suitable manner. One suitable method for aerating the mixture to form the protein stabilised aqueous foam includes injecting the mixture with compressed air through a mesh at a predetermined back pressure. 35 The protein-stabilised aqueous foam may have an expanded weight of 25-40 grams per litre, e.g. 30-35 grams per litre. The cementitious slurry may be formed by mixing the slurry precursor components (cementitious material, inorganic particles, water-soluble calcium salt, and water-reducing agent, plasticizer or superplasticizer) with water in any suitable manner. In some methods, the cementitious material, inorganic particles, and water-soluble calcium salt may be mixed to form a precursor powder mixture, which is subsequently 5 mixed with the water + water-reducing agent, plasticizer or superplasticizer. For example, in one method, the water-reducing agent, plasticizer or superplasticizer may be added to the water for the slurry, and a precursor powder mixture comprising the cementitious material, inorganic particles, water-soluble calcium salt may be added to the water and super plasticiser to form the cementitious slurry. In another method, the cementitious material, inorganic particles, water-soluble calcium salt, and water-reducing 10 agent, plasticizer or superplasticizer may be mixed to form a precursor powder mixture, which is subsequently mixed with the water. This method may be preferred, as it means that all the non-water slurry components can be dry-packed and shipped together before being mixed with water on-site to form the cementitious slurry. Mixing of the slurry precursor components with water to form the slurry may conveniently be performed in a colloidal mixer, or any other suitable mixing apparatus. 15 The cementitious slurry may have a viscosity defined by a flow time of from 30 to 60 seconds for 3 litres of material passing through a modified March cone. Provision of a slurry having this viscosity may allow for suitable mixing of the foam with the cementitious slurry, thereby allowing for improved homogeneity of the aerated slurry mixture. The cementitious material comprises cement, e.g. Portland cement (CEM I). The cementitious material 20 is provided in an amount of from 60 to 70 wt% based on total weight of the slurry, however the specific addition amount may be selected based on the desired properties of the foamed concrete material. In some arrangements, the cementitious material may be provided in an amount of from e.g. 63 to 69 wt%, for example around 64 wt%, around 67 wt%, or around 69 wt%. The inorganic particles comprise one or more secondary cementitious materials including one or more of 25 fly ash, ground granulated blast-furnace slag (GGBS), limestone, silica, natural pozzolana, natural calcined pozzolana, metakaolin (including high reactive metakaolin). Preferably, the inorganic particles comprise silica and / or high reactive metakaolin. The inorganic particles are provided in an amount of from 0.5 to 5 wt% based on total weight of the slurry, however the specific addition amount may be selected based on the desired properties of the foamed 30 concrete material. In some arrangements, the inorganic particles may be provided in an amount of from e.g. 0.5 to 5 wt%, for example around 0.5 wt%, or around 3 wt%. The inorganic particles may be added to the slurry as a dry powder. Alternatively, the inorganic particles may be added to the slurry in the form of a suspension of the particles (e.g. in some examples, a nano-silica suspension may be used). The use of inorganic particles comprising silica may be particularly preferred - e.g. the use of silica alone, 35 or the use of a mixture of inorganic particles, wherein at least some of the particles are silica particles. This is because when water is added to cementitious materials such as CEM1, hydration occurs forming calcium hydroxide. Silicon dioxide from the silica can react with the calcium hydroxide to produce more Calcium Silicate Hydrates (CSH). The CSH can act to bind the particles together to form a stronger structure. Where silica is used, at least some of the particles may be in the form of micro-silica, or nano-silica. Micro-silica and nano-silica may be differentiated by their particle size and by their BET specific surface area. For example, a suitable micro-silica material may have an average particle size of around 150 nm (e.g. 100-200 nm) and a specific BET surface area of typically 20 m2 / g (e.g. 10-30 m2 / g). In comparison, a suitable nano-silica material may have an average particle size of less than 100 nm (e.g. 10-50 nm) and a specific BET surface area of typically 200 m2 / g (e.g. 175-225 m2 / g). The inorganic particles may have a diameter in a range of 5 mm or less, 4 mm or less, 3 mm or less, 2 mm or less, or 1 mm or less, e.g. they may have a diameter in a range of from 0.001 mm - 5 mm. Providing particle having a diameter of 5 mm or less can help to ensure good distribution of the particles within the slurry and allows the inorganic particles to be kept in suspension around the foam as the cementitious material hydrates and cures. When the aerated slurry is relatively low density, use of inorganic particles having a diameter of larger than 5mm may result in some unwanted settling of the particles within the aerated slurry. The water-soluble calcium salt may comprise calcium hydroxide (hydrated lime), calcium formate, or mixtures thereof. Inclusion of lime can allow for suitable water retention that allows for maximum early curing of the cementitious materials in the cementitious slurry. Addition of calcium formate may accelerate setting of the cementitious slurry, and may boost workability at low temperatures. The water-soluble calcium salt(s) are provided in an amount of from 5 to 10 wt% based on total weight of the slurry, however the specific addition amount may be selected based on the desired properties of the foamed concrete material. In some arrangements, the water-soluble calcium salt(s) may be provided in an amount of from e.g. 6 to 8wt%, for example around 7 wt%, or around 8 wt%. The water-reducing agent, plasticizer or superplasticizer may be selected from: lignosulfonates, sulfonated synthetic polymers, polycarboxylated ethers, and mixtures thereof. Preferably, the waterreducing agent, plasticizer or superplasticizer is selected to be a polycarboxylated ether, and preferably this is used alone and not in combination with other plasticisers such as lignosulfonates. The water-reducing agent, plasticizer or superplasticizer are provided in an amount of from 0.1 to 2 wt% based on total weight of the slurry, however the specific addition amount may be selected based on the desired properties of the foamed concrete material. In some arrangements, water-reducing agent, plasticizer or superplasticizer may be provided in an amount of from e.g. 0.1 to 1 wt%, for example around 0.13 wt%, around 0.5 wt%, or around 0.7 wt%. The water is provided in an amount of from 10 to 30 wt% based on total weight of the slurry - in practice, water may provide the balance of the cementitious slurry in addition to the solid slurry component. The water may be provided in an amount of from 20 wt% to 25 wt%, for example around 22 wt%, or around 25 wt%. The cementitious slurry and the protein-stabilised aqueous foam may be mixed in a predetermined (volume) ratio of from 5:95 to 20:80. That is, the aerated slurry mixture may comprise 5 vol% or more, 6 vol% or more, 7 vol % or more, 8 vol% or more, 9 vol% or more, 10 vol% or more, 15 vol% or more, or up to 20 vol% cementitious slurry. The aerated slurry mixture may comprise 95 vol% or less, 90 vol% or 5 less, 85 vol% or less, or down to 80 vol% foam. The precise mixing ratio may be varied depending on the properties of the cementitious slurry and the protein-stabilised aqueous foam - as noted above, the mixing ratio of the cementitious slurry and the protein-stabilised aqueous foam is selected such that the overall density of the aerated slurry mixture is 400 kg / m3 or less. For example, in one embodiment, about 918 litres of protein-stabilised aqueous foam may be combined with about 82 litres of cementitious slurry 10 in order to form an aerated slurry mixture (and thus resulting foamed concrete) having a density of around 200 kg / m3. The slurry and the protein-stabilised aqueous foam may be mixed in a predetermined ratio by pumped delivery of the slurry and foam to a static mixer at predetermined relative flow rates. In a second aspect, the present invention provides a foamed concrete having a density of 400 kg / m3 or 15 less, the foamed concrete being obtained or obtainable according to the method of the first aspect. The density of the foamed concrete may be 350 kg / m3 or less, 300 kg / m3 or less, 250 kg / m3 or less, 200 kg / m3 or less, 150 kg / m3 or less, or 100 kg / m3 or less. Foamed concretes having a density of 200 kg / m3 or less, C\J 150 kg / m3 or less, or 100 kg / m3 or less may be particularly preferred in view of their superior insulation properties. ’ 20 The density may be a dry density of the foamed concrete measured at 28 days from mixing. The foamed concrete will necessarily be porous (by its nature of being foamed). That is, the foamed I- concrete comprises a plurality of pores. The pores may have an average pore size in a range of from 0.1 mm to 3 mm„ e.g. 1mm to 2 mm as determined e.g. by SEM analysis or visual analysis, with the average pore size being taken as the average diameter of at least 10 pores measured in a cross-section through 25 the foamed concrete. Providing a foamed concrete with a pore size in this range can provide for suitable thermal performance (e.g. thermal insulation performance) of the foamed concrete. The foamed concrete may have a fire resistance which satisfies Euroclass A1 rating under BS EN 13501- 1. The foamed concrete may have a water vapour resistance of 0.5 MNs / g or less, 0.4 MNs / g or less, 0.3 30 MNs / g or less, 0.2 MNs / g or less, or 0.1 MNs / g or less. Foamed concrete having a water vapour resistance in these ranges may be particularly suitable for use as insulation materials in building construction, as they can allow for suitable ‘breathability’ (i.e. transmission of water vapour through the material). The water vapour resistance may be determined following the methodology given in BS EN ISO 12572 using test condition ‘B’, i.e. using a ‘dry cup’ test with desiccant in the test cups and 85 % 35 relative humidity in the cabinet. 17 1024 The foamed concrete may have a thermal conductivity of 0.1 W / mK or less, 0.09 W / mK or less, 0.08 W / mK or less, or 0.07 W / mK or less, as determined via the Transient Hot Disk Method using Hot Disk M1 Thermal Conductivity Analyser. In a third aspect, the present invention provides the use of the foamed concrete of the second aspect as an insulation material, optionally as an insulating material within a light gauge steel frame structure. It has been found that this material can offer particular good performance in such application. The invention includes the combination of the aspects and preferred features described except where such a combination is clearly impermissible or expressly avoided. Summary of the Figures Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which: Figure 1. is an image showing a surface of a foamed concrete material according to the present invention. Figure 2. is a graph showing thermal conductivity against density for various foamed concrete samples according to the present invention. Examples EXAMPLE 1 A base mix cementitious slurry was produced, the slurry having the following composition (% by wt based on total weight of slurry) as follows: Constituent component Amount CEM1 (portland cement) 67% Micro silica powder 3.4% Hydrated lime (calcium hydroxide) 6.8% Super plasticiser (polycarboxylated ether) 0.7% Water 22.1% The slurry was produced according to the following protocol: a) CEM1, Micro silica powder and Hydrated lime (calcium hydroxide) were mixed to form a preblended dry powder mixture. b) Super plasticiser (polycarboxylated ether) was added to the water for the slurry in the mixing chamber of a colloidal mixer. c) The pre-blended dry powder mixture was gradually fed into the colloidal mixer to mix with the water and super plasticiser to form a slurry. 5 d) The slurry was mixed for a time of 3 minutes for each 100kg of material, to ensure homogenous mixing within the slurry. e) The slurry was sampled during the mixing process. When the slurry reached a viscosity defined by a flow time of from 30 to 60 seconds for 3 litres of material passing through a modified March cone it was pumped out of the mixing chamber to a holding tank with rotating agitator. 10 A protein-stabilised aqueous foam was also produced by mixing a foaming agent mixture in water (97 vol% water, 3 vol% foaming agent mixture, wherein the foaming agent mixture includes hydrolysed keratin protein in an amount of at least 15 wt% based on weight of the foaming agent mixture, and one or more optional further components including non-protein-based foaming agents, solvents and / or stabilisers) and injecting the mixture with compressed air through a lance with 4m2 of nylon mesh 15 confined in a tube to create a 4 bar back pressure. The resultant foam had a density of 35 g / litre. The slurry and the protein-stabilised aqueous foam were then mixed in a predetermined ratio to form an C\J aerated slurry mixture having a predetermined density by pumped delivery of the slurry and foam to a static mixer at predetermined relative flow rates. ’ Once mixed, the aerated slurry mixture exited the static mixer and travelled along a flexible placing hose ^^»20 to be placed for use. One or more samples of the aerated slurry mixture were extracted and weighed at T-“ this time to ensure that the correct density of aerated slurry mixture was being provided. The density of the aerated slurry mixture was adjusted for production of different samples by adjusting the relative flow rate of slurry and / or foam to the mixer, with the ratio of slurry:foam in the aerated slurry mixture being varied to enable the predetermined density of the aerated slurry mixture to be varied from about 100kg / m3 25 up to 400kg / m3. After placing the aerated slurry mixture, it was then allowed to cure to form the foamed concrete. EXAMPLE 2 A base mix cementitious slurry was produced, the slurry having the following composition (% by wt based 30 on total weight of slurry) as follows: Constituent component Amount CEM1 (portland cement) 69% Nano-silica suspension 40% solids 1.4% Hydrated lime (calcium hydroxide) 6.9% Super plasticiser (polycarboxylated ether) 0.5% Water 22.2% A foamed concrete was produced using this base mix cementitious slurry following the method described above in relation to Example 1. EXAMPLE 3 5 A base mix cementitious slurry was produced, the slurry having the following composition (% by wt based on total weight of slurry) as follows: Constituent component Amount CEM1 (portland cement) 63.7% Micro silica powder 3.18% Hydrated lime (calcium hydroxide) 6.37% Calcium formate 1.23% Super plasticiser (polycarboxylated ether) 0.13% Water 25.4% 17 1024 A foamed concrete was produced using this base mix cementitious slurry following a method similar to that described above in relation to Example 1, other than all non-water ingredients of the cementitious 10 slurry (CEM1, micro silica, hydrated lime, calcium formate, superplasticiser) were mixed to form a preblended dry powder mixture, with this mixture being added to water alone in the colloidal mixer to form the cementitious slurry (in other words, the superplasticiser was not separately added to the water). It was found that the formulation of the cementitious slurry used in this example was particularly effective 15 for low-temperature use of the resulting foamed-concrete formulation: this formulation allowed for effecting curing and setting of the foamed concrete even in low winter temperatures of 10 °C or less. Characterisation of Examples Various samples of foamed concrete materials produced according to the above methods were then characterised. 20 Fig. 1 is an image showing a surface of a foamed concrete material according to the present invention. It can be seen that the foam includes pores having an average diameter of around 1.5 mm. Fig. 2 is a graph showing thermal conductivity against density for various foamed concrete samples according to the present invention. These samples were produced according to the method noted above, where the ratio of slurry:foam in the aerated slurry mixture was varies to produce samples of varying 25 densities, with samples having a density as low as 98 kg / m3, with the majority of the samples having a density of between 100 and 170 kg / m3 It can be seen that the thermal conductivity of the foamed concrete generally decreases with density - in other words, improved thermal insulating performance is provided with reduced density. All samples having a density of less than 200 kg / m3 were seen to demonstrate a thermal conductivity of 0.1 W / mK or less or 0.09 W / mK or less. Samples having a density 5 of around 100 kg / m3demonstrated particularly good insulating performance, having thermal conductivities of 0.07 W / mK or less. A number of samples were also assessed for water vapour resistance, and results given in the table below. Each of the 200 kg / m3, 250 kg / m3, 300 kg / m3 and 350 kg / m3 samples were tested following the methodology given in BS EN ISO 12572 using test condition ‘B’, i.e. using a ‘dry cup’ test with desiccant 10 in the test cups and 85 % relative humidity in the cabinet. The 150 kg / m3 sample was tested using test condition ‘E’, ie a ‘wet cup’ test with deionised water in the test cups and 50 % relative humidity in the cabinet. Material density kg / m3 150* 200 250 300 350 Calculated water vapour resistance 0.059 0.168 0.250 0.179 0.268 MNs / g CM .................................................................................................................................................................................................................................................... It can be seen from this table that all samples demonstrated water vapour resistance of 0.3 MNs / g or less, indicating good levels of breathability &suitability for use in construction application. ^^.15 The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof. While the invention has been described in conjunction with the exemplary embodiments described above, 20 many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention. For the avoidance of any doubt, any theoretical explanations provided herein are provided for the 25 purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations. Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described. Throughout this specification, including the claims which follow, unless the context requires otherwise, the 30 word “comprise” and “include”, and variations such as “comprises”, “comprising”, and “including” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed 5 herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment. The term “about” in relation to a numerical value is optional and means for example + / -10%. 10 CM 14 04 25

Claims

1. A method of preparation of a foamed concrete, the method comprising steps of:providing a cementitious slurry, the cementitious slurry comprising (in wt% relative to wt of slurry): from 60 to 70% of a cementitious material;5 from 0.5 to 5% inorganic particles;from 5 to 10% water-soluble calcium salt;from 0.1 to 2% water-reducing agent, plasticizer or superplasticizer;from 10 to 30% water;providing a protein-stabilised aqueous foam;10 mixing the slurry with the protein-stabilised aqueous foam in predetermined volume ratio to forman aerated slurry mixture, the mixing ratio of the cementitious slurry and the protein-stabilised aqueous foam being selected such that the overall density of the aerated slurry mixture is 400 kg / m3 or less; and allowing the aerated slurry mixture to cure to form the foamed concrete, wherein the cementitious material comprises cement and15 wherein the inorganic particles comprise one or more of: fly ash, ground granulated blast-furnaceslag, limestone, silica, natural pozzolana, natural calcined pozzolana, metakaolin and mixtures thereof.

2. The method according to claim 1 wherein the protein-stabilised aqueous foam comprises water and a foaming agent or foaming agent mixture, wherein the foaming agent or foaming agent mixture comprises protein.20 3. The method according to claim 2 wherein the protein-stabilised aqueous foam comprises thefoaming agent or foaming agent mixture in an amount of from 0.1 wt% to 10 wt%, based on total weight of the foam.

4. The method according to any one of claims 2 to 3 wherein the protein in the foaming agent or foaming agent mixture is a structural fibrous protein, optionally wherein the protein is selected from25 keratin, collagen, elastin, fibrin, or mixtures thereof.

5. The method according to any one of claims 2 to 4 wherein the foaming agent or foaming agent mixture comprises:from 1 to 100 wt% protein;optionally, from 1 to 20 wt% non-protein-based foaming agent;30 optionally, from 1 to 10 wt% solvent; andoptionally, from 1 to 20 wt% stabiliser.

6. The method according to any one of the preceding claims wherein the protein-stabilised aqueous foam has an expanded weight of 25-40 grams per litre.

7. The method according to any one of the preceding claims wherein the cementitious material35 comprises Portland cement (CEM1).14 04 258. The method according to any one of the preceding claims wherein the inorganic particles have a maximum diameter of 5mm.

9. The method according to any one of the preceding claims wherein the water-soluble calcium salt comprises calcium hydroxide (hydrated lime), calcium formate, or mixtures thereof.5 10. The method according to any one of the preceding claims wherein water-reducing agent,plasticizer or superplasticizer is selected from, lignosulfonates, sulfonated synthetic polymers, polycarboxylated ethers, and mixtures thereof.

11. The method according to any one of the preceding claims wherein the cementitious slurry and the protein-stabilised aqueous foam are mixed in a predetermined volume ratio of from 5:95 to 20:80.10 12. A foamed concrete obtained or obtainable according to the method of any one of claims 1 to 11.

13. The foamed concrete according to claim 12 wherein the foamed concrete comprises a plurality of pores, said pores having an average pore size in a range of from 0.1 mm to 3 mm.

14. The foamed concrete according to claim 12 or claim 13 wherein the foamed concrete has a fire resistance which satisfies Euroclass A1 rating under BS EN 13501-1.15 15. The foamed concrete according to any one of claims 12 to 14 wherein the vapour resistance ofthe foamed concrete is 0.5 MNs / g or less.

16. The foamed concrete according to any one of claims 12 to 15 wherein the thermal conductivity of the foamed concrete is 0.1 W / mK or less.

17. The foamed concrete according to any one of claims 12 to 16 wherein the foamed concrete has a20 dry density of 350 kg / m3 or less.

18. Use of the foamed concrete according to any one of claims 12 to 17 as an insulation material, optionally as an insulating material within a light gauge steel frame structure.

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