Construction product

Abstract

A construction product in the form of an internal lining board. The board is formed from a mixture comprising: a binder and a bio-aggregate. The mixture further comprises a retarder and an accelerator, wherein the ratio by weight of the accelerator to the binder is 1:10000 to 5:100. Planar lining material is provided on one or both outer faces of the mixture.

Description

[0001] TITLE

[0002] Construction Product

[0003] TECHNOLOGICAL FIELD

[0004] Examples of the disclosure relate to a construction product. Some relate to a construction product in the form of an internal lining board.

[0005] BACKGROUND

[0006] In 2009, the construction sector was found to be responsible for producing 23% of global carbon emissions. There is therefore a continuing movement to improve the energy efficiency of buildings and reduce the carbon dioxide emissions associated with the built environment, in order to meet global carbon dioxide emissions targets.

[0007] Current interventions to produce more energy efficient buildings often lead to poor management of moisture within the building, caused for instance by increasing the thermal resistivity and air tightness of buildings. This can lead to degradation of the building, unhealthy living environments and occupant health issues. The increasing of air tightness and thermal resistivity of buildings can lead to increased condensation, and hence cause mould growth.

[0008] The most commonly used internal lining product is traditional plasterboard. The material of this product however has a very poor hygroscopic ability, i.e. , the ability to absorb and desorb water vapours, and is not thermally insulating. Furthermore, gypsum used to make plasterboard is a finite resource. Once plasterboard is finished with, it does not produce a useful product for reuse or for instance composting. It is therefore desirable to provide a compostable alternative to traditional plasterboard with good hygroscopic, strength and / or surface finish characteristics.

[0009] BRIEF SUMMARY According to various, but not necessarily all, examples there is provided a construction product in the form of an internal lining board, the board being formed from a mixture comprising: a binder; a bio-aggregate; an accelerator, wherein the ratio by weight of the accelerator to the binder is 1 :10000 to 5:100; and a retarder, wherein planar lining material is provided on one or both outer faces of the mixture.

[0010] The binder may comprise an alkaline earth-based binding agent and a cementitious material. The alkaline earth-based binding agent may be lime. The cementitious material may be cement. The ratio of alkaline earth-based binding agent to cementitious material by weight may be at least 50:50. The ratio of alkaline earthbased binding agent to cementitious material by weight may be at least 60:40. The ratio of alkaline earth-based binding agent to cementitious material by weight may be 70:30 to 90:10.

[0011] The ratio by weight of the accelerator to the binder may be 1 : 100 to 2: 100.

[0012] The accelerator may comprise calcium chloride, calcium nitrate, calcium nitrite, calcium formate, potassium aluminate, sodium silicate, sodium carbonate, sodium bicarbonate, sodium aluminate, diethanolamine, and / or aluminium sulfate. The accelerator may comprise an ionic compound. The accelerator may comprise sodium carbonate.

[0013] The ratio by weight of the retarder to the binder may be 1 : 10000 to 5: 100. The ratio by weight of the retarder to the binder may be 1 : 1000 to 1 : 100.

[0014] The retarder may comprise a sugar, phosphoric acid, a phosphate, boric acid, a borate, a lignosulfonate and / or citric acid. The retarder may comprise citric acid.

[0015] The alkaline earth-based binding agent may comprise hydrated lime.

[0016] The mixture may further comprise cellulose. The cellulose may comprise methylated cellulose. The cementitious material may comprise blast furnace slag, alkali activated binders, white cement, natural cement, calcium aluminate cement, and / or Portland cement.

[0017] The planar lining material may comprise paper.

[0018] The bio-aggregate may comprise pyrolyzed bio-aggregate.

[0019] The bio-aggregate may comprise a crop by-product. The bio-aggregate may comprise hemp shiv.

[0020] The ratio by weight of bio-aggregate to binder in the mixture may be 10:90 to 30:70.

[0021] According to various, but not necessarily all, examples there is provided a construction product in the form of an internal lining board, the board being formed from a mixture comprising: a bio-aggregate; and a binder, wherein the binder comprises an alkaline earth-based binding agent and a cementitious material and the ratio of alkaline earthbased binding agent to cementitious material by weight is at least 50:50, and wherein planar lining material is provided on one or both outer faces of the mixture.

[0022] The alkaline earth-based binding agent may be lime. The cementitious material may be cement. The ratio of alkaline earth-based binding agent to cementitious material by weight may be at least 60:40. The ratio of alkaline earth-based binding agent to cementitious material by weight may be 70:30 to 90:10.

[0023] The mixture may further comprise an accelerator. The ratio by weight of the accelerator to the binder may be 1 :10000 to 5:100. The ratio by weight of the accelerator to the binder may be 1 :100 to 2:100.

[0024] The accelerator may comprise calcium chloride, calcium nitrate, calcium nitrite, calcium formate, potassium aluminate, sodium silicate, sodium carbonate, sodium bicarbonate, sodium aluminate, diethanolamine, and / or aluminium sulfate. The accelerator may comprise an ionic compound. The accelerator may comprise sodium carbonate. The mixture may further comprise a retarder. The ratio by weight of the retarder to the binder may be 1 : 10000 to 5: 100. The ratio by weight of the retarder to the binder may be 1 :1000 to 1 :100.

[0025] The retarder may comprise a sugar, phosphoric acid, a phosphate, boric acid, a borate, a lignosulfonate and / or citric acid. The retarder may comprise citric acid.

[0026] The alkaline earth-based binding agent may comprise hydrated lime.

[0027] The mixture may further comprise cellulose. The cellulose may comprise methylated cellulose.

[0028] The cementitious material may comprise blast furnace slag, alkali activated binders, white cement, natural cement, calcium aluminate cement, and / or Portland cement.

[0029] The planar lining material may comprise paper.

[0030] The bio-aggregate may comprise pyrolyzed bio-aggregate.

[0031] The bio-aggregate may comprise a crop by-product. The bio-aggregate may comprise hemp shiv.

[0032] The ratio by weight of bio-aggregate to binder in the mixture may be 10:90 to 30:70.

[0033] According to various, but not necessarily all, examples there is provided a method of manufacturing a construction product in the form of an internal lining board, the method comprising: producing the mixture of any of the preceding paragraphs; and providing a planar lining material on one or more outer faces of the mixture.

[0034] The method may further comprise forming the mixture into a predetermined geometric shape using extrusion moulding. The forming the mixture into a predetermined geometric shape using extrusion moulding may comprise forming the mixture into a predetermined geometric shape using continuous extrusion moulding. The method may further comprise adding water to the mixture, wherein the water is preheated to at least 15°C prior to adding the water to the mixture.

[0035] According to various, but not necessarily all, examples there is provided a method of manufacturing a construction product in the form of an internal lining board, the method comprising: producing a mixture of a bio-aggregate and a binder, wherein the binder comprises an alkaline earth-based binding agent and a cementitious material and the ratio of alkaline earth-based binding agent to cementitious material by weight is at least 50:50; and providing a planar lining material on one or more outer faces of the mixture.

[0036] The alkaline earth-based binding agent may be lime. The cementitious material may be cement.

[0037] The method may further comprise forming the mixture into a predetermined geometric shape using extrusion moulding. The forming the mixture into a predetermined geometric shape using extrusion moulding may comprise forming the mixture into a predetermined geometric shape using continuous extrusion moulding.

[0038] The method may further comprise adding water to the mixture, wherein the water is preheated to at least 15°C prior to adding the water to the mixture.

[0039] According to various, but not necessarily all, examples there is provided a method of manufacturing a construction product in the form of an internal lining board, the method comprising: producing a mixture of a binder; a bio-aggregate; a retarder; and an accelerator, wherein the ratio by weight of the accelerator to the binder is 1 :10000 to 5: 100; and providing a planar lining material on one or more outer faces of the mixture.

[0040] The binder may comprise an alkaline earth-based binding agent and a cementitious material. The alkaline earth-based binding agent may be lime. The cementitious material may be cement.

[0041] The method may further comprise forming the mixture into a predetermined geometric shape using extrusion moulding. The forming the mixture into a predetermined geometric shape using extrusion moulding may comprise forming the mixture into a predetermined geometric shape using continuous extrusion moulding.

[0042] The method may further comprise adding water to the mixture, wherein the water is preheated to at least 15°C prior to adding the water to the mixture.

[0043] According to various, but not necessarily all, embodiments there is provided examples as claimed in the appended claims.

[0044] While the above examples of the disclosure and optional features are described separately, it is to be understood that their provision in all possible combinations and permutations is contained within the disclosure. It is to be understood that various examples of the disclosure can comprise any or all the features described in respect of other examples of the disclosure, and vice versa. Also, it is to be appreciated that any one or more or all the features, in any combination, may be implemented by / comprised in / performable by an apparatus, a method, and / or computer program instructions as desired, and as appropriate. The description of a function should additionally be considered to also disclose any means suitable for performing that function.

[0045] BRIEF DESCRIPTION

[0046] Some examples will now be described with reference to the accompanying figures in which:

[0047] FIG. 1 shows images illustrating the effects of the amount of accelerator on the surface finish of construction materials;

[0048] FIG. 2 shows a graph with depth of surface deviation on the x-axis (pm) and the proportion of the surface with a given surface deviation on the y-axis across a first internal lining board without an accelerator in the mixture (lighter bars) and a second internal lining board with an accelerator in the mixture (darker bars);

[0049] FIG. 3 shows a graph illustrating the effect of varying the ratio by weight of alkaline earth-based binding agent to cementitious material on the density and compressive load of construction materials; FIG. 4 shows a graph illustrating the effect of varying the ratio by weight of alkaline earth-based binding agent to cementitious material on the flexural load of construction materials; and

[0050] FIG. 5 shows images illustrating the effects of varying the ratio by weight of alkaline earth-based binding agent to cementitious material on the surface finish of construction materials.

[0051] DETAILED DESCRIPTION

[0052] In examples of the disclosure, a construction product in the form of an internal lining board is provided. Furthermore, examples of the disclosure also provide a method of manufacturing an internal lining board.

[0053] In examples of the disclosure, the internal lining board is formed from a mixture comprising: a binder; a bio-aggregate; an accelerator, wherein the ratio by weight of the accelerator to the binder is 1 :10000 to 5:100; and a retarder, wherein planar lining material is provided on one or both outer faces of the mixture.

[0054] In some examples, the binder comprises an alkaline earth-based binding agent and a cementitious material. The alkaline earth-based binding agent could also be referred to as an alkaline earth metal-based binding agent. The alkaline earth-based binding agent may comprise an alkaline earth metal oxide (for example magnesium oxide and / or calcium oxide) and / or an alkaline earth metal hydroxide (for example calcium hydroxide and / or magnesium oxide). For instance, the alkaline earth-based binding agent may comprise lime, such as lime oxide, hydrated lime, natural hydraulic lime, or any combination thereof.

[0055] In some examples, the cementitious material may comprise blast furnace slag, alkali activated binders, white cement, natural cement, calcium aluminate cement, and / or Portland cement. The cementitious material may comprise cement. The cementitious material may comprise clinker minerals.

[0056] The cementitious material may comprise a hydraulic cement. The cementitious material may have a hydraulicity of more than two times the hydraulicity of natural hydraulic lime 3.5; such as more than three times, more than four times the hydraulicity of natural hydraulic lime 3.5, or more than five times the hydraulicity of natural hydraulic lime 3.5. For instance, the initial setting time of the cementitious material as determined using a Vicat needle test (e.g., in accordance with ASTM C191-21) may be less than half the initial setting time of natural hydraulic lime 3.5, such as less than a third of the initial setting time of natural hydraulic lime 3.5, less than a quarter of the initial setting time of natural hydraulic lime 3.5, or less than a less than a fifth of the initial setting time of natural hydraulic lime 3.5.

[0057] Often hydraulicity is increased through the presence of impurities. These elements are often silicious, ferrous or aluminate in nature. Oxides may also be present. In the case where silicious compounds (e.g., silicates such as a belite) are present, the silicious compounds (e.g., dicalcium silicate) can form calcium silicate hydrates once reacted with water.

[0058] In some examples, the ratio by weight of alkaline earth-based binding agent to cementitious material is at least 50:50 (i.e., the amount by weight of alkaline earthbased binding agent is the same as or higher than the amount of cementitious material). The ratio by weight of alkaline earth-based binding agent to cementitious material may be at least 60:40, at least 70:30; at least 75:25, or at least 80:20. In some examples, the ratio by weight of alkaline earth-based binding agent to cementitious material is at most 95:5; such as at most 90:10 or at most 85:15. The ratio by weight of alkaline earth-based binding agent to cementitious material may be 60:40 to 95:5, such as 70:30 to 90:10, 70:35 to 90:15, 75:25 to 85:15, or 80:25 to 80:20. In some examples, the ratio by weight of alkaline earth-based binding agent to cementitious material is substantially 80:20. It has been found that the ratio of alkaline earth-based binding agent to cementitious material can optimise binding properties, setting rate and mechanical properties, as further described later in the specification.

[0059] The mixture for forming the internal lining board may be substantially gypsum-free.

[0060] In some but not necessarily all examples the ratio by weight of bio-aggregate to binder in the mixture is 5:95 to 50:50, such as 5:95 to 35:65 or 10:90 to 30:70. The ratio by weight of bio-aggregate (wt.%) to binder (wt.%) is preferably at least 5:95, preferably at least 10:90, for example at least 15:85. The ratio by weight of bio-aggregate to binder is preferably no more than 50:50, preferably no more than 40:60, for example no more than 30:70.

[0061] The term "bio-aggregate" is used herein to refer to granulates formed from non-animal living organisms, such as plant material. The bio-aggregate may be lignocellulosic. The bio-aggregate may be formed from any suitable part of a plant. Preferably, the bioaggregate is formed from the stem of a plant. In some examples the bio-aggregate may be formed from other living organisms such as algae and / or fungi. The bioaggregate may for example comprise milled bio-aggregate. The bio-aggregate may be milled using any conventional milling mechanism, such as for example a knife, hammer, rotary or ball mill. The milled bio-aggregate may be passed through a screen or sieve having predetermined pores to enable milled bio-aggregate having predetermined dimensions to pass therethrough. The bio-aggregate is preferably formed from chemically unprocessed plant material. The term "chemically unprocessed" is used herein to refer to plant material in which the cell architecture within the plant material remains unchanged.

[0062] Particle size distribution is conventionally defined by the method by which it is determined. One suitable method is sieve analysis, where powder is separated on sieves of different sizes. The maximum extent of the particles and particle size distributions described herein may be determined by sieve analysis. The particle size distribution is therefore determined in terms of discrete size ranges based on the sizes of sieves used. In some examples, substantially all of the particles of the bio-aggregate have a maximum extent in any dimension of 0.5 mm to 15 mm. Substantially all of the particles of the bio-aggregate may have a maximum extent in any dimension of 1 mm to 10 mm, 2 mm to 7 mm, 3 mm to 6 mm, or 3 mm to 5 mm, such as substantially 4 mm. In some examples, substantially all of the particles of the bio-aggregate have a maximum extent in any dimension of up to 15 mm, up 10 mm, up to 7 mm, up to 6 mm, or up to 5 mm. Substantially all of the particles of the bio-aggregate may have a maximum extent in any dimension of at least 0.5 mm, at least 1 mm, at least 2 mm, such as at least 3 mm.

[0063] In some examples, at least 50% by weight of the particles of the bio-aggregate have a maximum extent in any dimension of 0.5 mm to 15 mm. At least 50% by weight of the particles of the bio-aggregate may have a maximum extent in any dimension of 1 mm to 10 mm, 2 mm to 7 mm, 3 mm to 6 mm, or 3 mm to 5 mm, such as substantially 4 mm. In some examples, at least 50% by weight of the particles of the bio-aggregate have a maximum extent in any dimension of up to 15 mm, up 10 mm, up to 7 mm, up to 6 mm, or up to 5 mm. At least 50% by weight of the particles of the bio-aggregate may have a maximum extent in any dimension of at least 0.5 mm, at least 1 mm, at least 2 mm, such as at least 3 mm.

[0064] In some embodiments, at least 50% by weight of the particles have a maximum extent in any dimension of less than one third of the construction product thickness, for example where the construction product is manufactured as a planar sheet, such as an internal lining board / plasterboard (as measured between opposing surfaces of the mixture optionally lined with planar lining material). In some embodiments, substantially none of the particles may have a maximum extent in any dimension of greater than one third of the construction product thickness, for example where the construction product is manufactured as a planar sheet, such as an internal lining board / plasterboard (as measured between opposing surfaces of the mixture optionally lined with planar lining material).

[0065] The particle size of the bio-aggregate can affect the density and thermal and / or hygroscopic properties of the resultant construction product. The bio-aggregate may be provided by a broad range of plant types. The construction product may be prepared from low value, readily (and preferably locally) available, highly voluminous plant material. Furthermore, the construction product of the present disclosure may be produced on a large scale at low cost with low associated energy costs.

[0066] Suitable plant material for use as the bio-aggregate may include for example perennial plant(s), such as for example processed perennial plant(s) and / or by-products of processing of perennials plant(s). The bio-aggregate may comprise softwood or hardwood. Suitable plant material for use as the bio-aggregate includes both softwood and hardwood timber particles. The bio-aggregate may comprise forestry waste.

[0067] The bio-aggregate may comprise wood chips. The wood chips may be derived from a local timber source. The wood chips may be a biproduct of wood milling or the timber processing industry. The woodchips may be derived from renewable softwood (i.e., wood derived from sustainably managed coniferous trees).

[0068] The bio-aggregate is preferably an agricultural product or by-product, such as a crop by-product. The bio-aggregate could be for example a farm crop, fiber crop, farm crop by-product, food crop or food crop by-product.

[0069] The bio-aggregate is preferably selected from one or more of: maize; wheat (for example common wheat (Triticum aestivum); rice; barley; millet; grasses (for example horsetail); rice husk; wheat straw; tomato stalk, squash; pumpkin; watermelon; cucumber; melon; hops; cannabis; celtis tress; nettles; wildflowers; rape straw; algae; seaweed; bamboo; rapeseed (Brassica napus); barley (Hordeum vulgare); oats (Avena sativa); flax; rice straw; corn straw; giant miscanthus (Miscanthus giganteus); sugarcane bagasse; sisal straw; hemp (for example hemp shiv); or any combination thereof.

[0070] Preferably, the bio-aggregate consists of one or more moderate silica contentcontaining plants, and / or one or more high silica content-containing plants. The bio-aggregate preferably comprises at least one moderate (preferably a high) silica content-containing plant. Preferably, the at least one moderate (preferably high) silica content-containing plant comprises a silica content of equal to or above 2%, for example a silica content of equal to or above 4%.

[0071] The moderate to high silica content of the plant(s) forming the bio-aggregate is able to react with alkaline earth metals (for example calcium) within the binder to form a strong, durable crystalline, alkaline earth metal silica hydrate, for example calcium silica hydrate. This crystalline structure has been found to be the same as the crystalline structure of calcium silica hydrate found within cement. The alkaline earth metal silica hydrate (for example calcium silica hydrate) formed has been found to provide a pozzolanic effect which improves the strength of the construction product through the use of bio-aggregate. The increased strength of the construction product therefore reduces the reliance on high carbon intensity binders. Furthermore, the construction product of the present disclosure has increased strength without requiring the use of other mineral based pozzolans such as metakaolin and silica fume or requiring a lower amount of such mineral based pozzolans.

[0072] Preferably, the bio-aggregate comprises one or more high silica content-containing plants, selected for example from one or more of: the Poaceae, Equisetaceae, and / or Cyperaceae families or any combination thereof; and / or one or more moderate silica content-containing plants, selected for example from one or more of the Cucurbitales, Urticales and / or Commelinaceae families, or any combination thereof. The Poaceae plant family includes for example maize, wheat, rice, barley, and millet.

[0073] The bio-aggregate may comprise organic by-products of food processing. The organic by-products of food or drink processing may be selected from nutshells, fruit stones, coffee grounds, spent hops, spent grain, or pomace.

[0074] In some examples the bio-aggregate may comprise milled post-consumer and / or postindustrial waste of biological origin, such as waste cotton clothing.

[0075] In some examples, the bio-aggregate comprises pyrolyzed bio-aggregate. Pyrolyzed bio-aggregate may comprise biochar. The term “pyrolysis” is used herein to thermal decomposition of bio-aggregate in the absence or near absence of oxygen. Pyrolysis is usually carried out at temperatures at or above 500°C to enable enough heat to be provided to deconstruct biopolymers within the bio-aggregate. As no oxygen (or almost no oxygen) is present, combustion of the bio-aggregate does not occur and the matter thermally decomposes into biochar and combustible gases. The combustible gases may be condensed to provide a combustible liquid referred to as pyrolysis oil or biooil. Gases generated during pyrolysis such as carbon dioxide, carbon monoxide and light hydrocarbons may be combusted to provide heat for the process. Pyrolysis conditions such as the temperature and heating rate may vary. Variations in the pyrolysis conditions may alter the yields of pyrolyzed bio-aggregate obtained. In some embodiments, slow heating rates are used to increase the production of pyrolyzed bioaggregate. In some embodiments, the pyrolysis of the bio-aggregate may be self- sufficient by utilising the combustible gases obtained during the process to provide the thermal energy. Any of the bio-aggregates described herein could be pyrolyzed to provide the pyrolyzed bio-aggregate. The bio-aggregate described herein may be made up entirely of pyrolyzed bio-aggregate, a combination of pyrolyzed bio-aggregate and unpyrolyzed bio-aggregate, or entirely of unpyrolyzed bio-aggregate.

[0076] In some examples, pyrolyzed bio-aggregate is pyrolyzed by heating bio-aggregate to between 500°C and 1000°C. The pyrolysis may comprise heating the bio-aggregate to between 500°C and 800°C. The pyrolysis may comprise heating the bio-aggregate to between 500°C and 700°C. The bio-aggregate may be heated from substantially room temperature to between 500°C and 1000°C in a time period of 5 minutes to 1 hour. The bio-aggregate may be heated from substantially room temperature to between 500°C and 1000°C in a time period of 15 minutes to 1 hour. The bio-aggregate may be heated from substantially room temperature to between 500°C and 800°C in a time period of 5 minutes to 1 hour. The bio-aggregate may be heated from substantially room temperature to between 500°C and 800°C in a time period of 15 minutes to 1 hour. The bio-aggregate may be heated at a temperature ramp rate of between 10°C per minute and 125°C per minute, such as 30°C per minute.

[0077] The pyrolysis of the bio-aggregate enables carbon to be sequestered from the atmosphere and locked within the resultant pyrolyzed bio-aggregate / biochar indefinitely. Further, the pyrolysis increases the density of the carbon within the construction product.

[0078] Pyrolyzed bio-aggregate particles / granulates are hydrophobic and therefore provide for improved contact between the binder and the bio-aggregate resulting in improved mechanical strength of the resultant construction product. Pyrolysis of the bioaggregate chemically alters the structure of the bio-aggregate resulting in increased mechanical properties, inclusive of for example compressive modulus and / or strength and flexural modulus / strength of the bio-aggregate and then in turn the resultant construction product. Pyrolysis of bio-aggregate also provides a source of bio-oil and / or bio-gas for further downstream processing.

[0079] Pyrolysis of the bio-aggregate preferably homogenises the bio-aggregate. Pyrolysis of the bio-aggregate preferably produces pyrolyzed bio-aggregate particles with a narrower particle size distribution compared to non-pyrolyzed bio-aggregate. Bioaggregate is highly siliceous and has a fibrous nature, which may make it difficult / non cost effective to grind to a small particle size. Pyrolyzed bio-aggregate, due in part to the high carbon content, is far more brittle in character and therefore easier to grind.

[0080] Pyrolyzed bio-aggregate particles have improved size regularity which results in a construction product with an improved surface finish due to a more regular particle size distribution.

[0081] Pyrolysis of the bio-aggregate preferably produces pyrolyzed bio-aggregate particles with a reduced water content (preferably a uniform water content).

[0082] Pyrolyzed bio-aggregate has an improved ability to sequester volatile organic components (VOCs) out of the atmosphere due to the ionic nature of the particle surface and the increased surface area compared to non-pyrolyzed particles.

[0083] In some embodiments, the negative carbon construction product may comprise inert, non-biodegradable pyrolyzed bio-aggregate which has indefinitely sequestered biogenic carbon within the pyrolyzed bio-aggregate. Pyrolyzed bio-aggregate comprises less volatile components than non-pyrolyzed bioaggregate. Therefore, a construction product comprising the pyrolyzed bio-aggregate is more resistant to rot and decay as these volatile components are not available to microbes. As a result the construction product can be used externally without the need for a further treatment or coating.

[0084] Construction products containing pyrolyzed bio-aggregate have been found to have a lower thermal conductivity, which may be based at least in part on their lower density. Therefore, they may be useful as insulating materials.

[0085] The accelerator may comprise calcium chloride, calcium nitrate, calcium nitrite, calcium formate potassium aluminate, sodium silicate, sodium carbonate, sodium bicarbonate, sodium aluminate, diethanolamine, and / or aluminium sulfate. The accelerator may be an ionic compound. The accelerator decreases the setting time of the binder.

[0086] In some examples, the ratio by weight of the accelerator to the binder is 2:1000 to 5:100. The ratio by weight of the accelerator to the binder may be 3:1000 to 4:100, 5:1000 to 3:100, or 1 :100 to 2:100.

[0087] In some examples, the ratio by weight of the accelerator to the binder is at most 4:100; such as at most 3:100 or at most 2:100. The ratio by weight of the accelerator to the binder may be at least 2:1000, such as at least 3:1000, at least 5:1000, or at least 1 :100.

[0088] The retarder may comprise a sugar, phosphoric acid, a phosphate, boric acid, a borate, a lignosulfonate and / or citric acid. The retarder increases the setting time of the binder.

[0089] In some examples, the ratio by weight of the retarder to the binder is 1 :10000 to 5:100. The ratio by weight of the retarder to the binder may be 5: 10000 to 2: 100, 1 :1000 to 1 :100, 2:1000 to 8:1000, or 1 :10000 to 3:1000.

[0090] In some examples, the ratio by weight of the retarder to the binder is at most 5:100; such as at most 2:100, at most 1 :100, or at most 3:1000. The ratio by weight of the retarder to the binder may be at least 1 :10000, such as at least 3:10000, at least 5: 10000, or at least 1 : 1000.

[0091] Without being bound by theory, it is believed that the inclusion of both an accelerator and a retarder in the mixture causes, during curing, regions of material that are in a more advanced stage of curing and regions of material that are in a less advanced stage of curing. The regions in a less advanced stage of curing are more flowable and thus maintain workability of the overall mixture during processing to allow the mixture to be formed into a desired shape, whilst a faster overall setting time is provided. It has been found that a faster setting time improves the surface finish of the construction product, as further described later in the specification. Faster setting times also improve the dimensional stability of the construction product, allowing the product to retain tighter geometrical tolerance during cure. An improved surface finish is particularly important when bio-aggregate is included in the mixture. The hygroscopic nature of bio-aggregate can cause variable shrinkage of the construction product across its surface, which causes difficulties in achieving a good surface finish.

[0092] In some examples, the mixture further comprises cellulose. The cellulose may comprise methylated / methyl cellulose. In some examples the ratio by weight of cellulose to binder is 1 :1000 to 3:100. In some examples, the mixture comprises more than 0.03 wt.% cellulose. The cellulose has been found to improve the strength of the board and create a bond between the lining material and the board materials. The inclusion of cellulose also improves the interface between the binder and the bioaggregate, creating a more structurally homogeneous composite.

[0093] In some examples, the mixture further comprises a filler. The filler may comprise fines. The filler may comprise limestone fines.

[0094] In some examples, the planar lining material is paper, such as recycled paper. In some examples, the paper has a weight of up to 250 gsm. The paper may have a weight of at least 150 gsm. The paper may have a weight of between 170 gsm and 200 gsm. In other examples, the planar lining material may be hessian. The construction product in the form of an internal lining board may be in the form of a planar sheet, with planar lining material being provided on one or both sides of the planar cured mixture. The internal lining board could also be referred to as plasterboard or drywall. The planar lining material may be provided on each outer face of a pair of opposed outer faces of the planar cured mixture. In some embodiments, the planar lining material may also extend beyond, and for example around at least a portion of, one or more edges of the outer face(s) of the planar shaped cured mixture. The planar lining material may help to form the edge(s) of one or more outer face(s) of the planar shaped board and to provide shape thereto.

[0095] The density of the construction product may be at least 400 kg / m3. Preferably the density of the construction product is at least at least 500 kg / m3, such as 650 kg / m3. The density of the construction product may be up to 900 kg / m3. Preferably the density of the construction product is up to 700 kg / m3. The density of the construction product may be between 500 kg / m3and 750 kg / m3, such as 650 kg / m3. Preferably, the density of the construction product is between 500 kg / m3and 700 kg / m3.

[0096] The construction product thickness (as measured between opposing surfaces of the mixture optionally lined with planar lining material), for example when in the form of a planar sheet (for example an internal lining board), may be at least 5 mm, preferably at least 9 mm, for example about 10 mm. The construction product thickness may be no more than 50mm. Preferably, the construction product thickness is between 5 mm and 50 mm, preferably between 9 mm and 50 mm, for example between 10 mm and 50 mm. Most preferably, the construction product thickness is between 8 mm and 15 mm.

[0097] To prepare the construction product, the bio-aggregate, accelerator, retarder and binder may be mixed together with water. The water may be preheated prior to mixing to at least 0°C, at least 5°C, at least 10°C, at least 15°C, or preferably at least 20°C.

[0098] In some examples, the alkaline earth-based binding agent and cementitious material may be mixed together to form a dry mix. The binder described herein may therefore comprise a mixture of alkaline earth-based binding agent (such as lime) and the cementitious material (such as cement). The mixture of the alkaline earth-based binding agent and the cementitious material can be referred to as a physical mixture of alkaline earth-based binding agent (such as lime) and the cementitious material (such as cement). Water may optionally be mixed with an air entraining agent such as lignin sulfonate to form a wet mix. The dry mix and wet mix / water can be mixed to form a slurry. The bio-aggregate may be added to the slurry to form a paste. The accelerator and / or retarder could be added at of these stages, i.e. , the accelerator or retarder could be added to the dry mix, the wet mix / water, the slurry, or the paste.

[0099] When water has been added to the bio-aggregate, accelerator, retarder and binder, the mixture is in the form of a paste. The paste may be formed in a mixer. The mixer may be at a pressure of between 0.5 bar and 1 .5 bar, such as substantially atmospheric pressure (1 bar). The mixer may be at a temperature between 15°C and 70°C, such as substantially room temperature (25°C). The ratio of binder to water may be between 1 :1 and 1 :2.5. The water may form 20 wt.% to 70 wt. % of the paste. Preferably, the water forms 30 wt.% to 60 wt.% of the paste, such as 40 to 50 wt.% of the paste. The paste may be subsequently dried. For example, the paste may be dried at a temperature of between 30°C to 100°C.

[0100] The mixture in the form of a paste may further comprise one or more additives selected from: viscosity modifying agents; and / or coupling agents; and / or water retention agents; and / or air entraining agents; and / or cellulose; and / or plasticizers; or any combination thereof. The one or more additives may comprise one or more carbohydrates, for example polysaccharides, such as for example methylated cellulose ether. The one or more additives are preferably plant-derived.

[0101] The mixture may be formed into a predetermined geometric shape, such as a planar sheet, for example by use of a mould or formwork. The mixture may be formed into a predetermined geometric shape using extrusion moulding, which could be continuous extrusion mounding, for instance by extruding the mixture (in the form of the paste) through a die. The predetermined geometric shape may be a substantially planar shape. The die could for instance be one or more rollers through which the mixture is continuously extruded. The construction product may be formed by continuously extruding the mixture on a conveyor, wherein the paste is provided on the conveyor, and the die is defined by a gap between the conveyor and a roller. In some examples a planar lining material is applied to an outer face of the mixture by the roller during continuous extrusion. The die may also include a static (i.e., non-rolling) element in conjunction with the roller. In other examples, the construction product might be cast or 3D-printed.

[0102] A planar lining material is preferably provided on one or both outer faces of the mixture. In some embodiments, the mixture may be introduced, for example pumped, in between two sheets of planar lining material on a conveyor between rollers to gauge the thickness of the resultant molded mixture.

[0103] In some examples, the mixture is exposed to a carbon dioxide feed stream comprising at least 0.1 % carbon dioxide by volume for a predetermined time period to accelerate curing. The step of exposing the mixture to a carbon dioxide feed stream may be carried out within a chamber. The chamber could be the mixer in which the paste is formed or an oven, for example a crossflow oven.

[0104] Exposure of the mixture to the carbon dioxide containing feed stream has been found to increase the cure rate and resultant mechanical properties of the product. Furthermore, the resultant construction product has sequestered carbon during accelerated carbonation through exposure to the carbon dioxide containing feed stream. As a result, the product is removing carbon from the atmosphere and locking the carbon within the product indefinitely. Furthermore, when the product incorporates pyrolyzed bio-aggregate, even further carbon is sequestered from the atmosphere and locked away within the product. The manufacturing process has been found to be low- carbon or carbon-negative. The product is therefore an effective carbon dioxide removal product.

[0105] Examples

[0106] Some example and comparative example mixtures are provided in Table 1 below. Table 1

[0107] Fig. 1 shows images of internal lining boards with varying amounts of accelerator included in the mixture. The three example boards of Fig. 1 were prepared using the mixture of example 1 of Table 1 , though in two of the examples of Fig. 1 the mixture further comprises an accelerator (sodium carbonate in these examples), with differing amounts of accelerator in the two accelerator examples. Fig. 1 demonstrates the effects of the inclusion of an accelerator in the mixture on the surface finish of the construction material in the form of an internal lining board. Fig. 2 shows depth of surface deviation on the x-axis (pm) and the proportion of the surface with a given surface deviation on the y-axis across a cross section of two internal lining boards. The lighter bars of Fig. 2 illustrate a first example internal lining board prepared using example mixture 1 of Table 1 without an accelerator in the mixture. The darker bars of Fig. 2 illustrate a second example internal lining board prepared using example mixture

[0108] 1 of Table 1 but with an accelerator (sodium carbonate in this example) included in the mixture at a 2:100 ratio by weight of accelerator to binder. The surface deviation of Fig.

[0109] 2 is determined using laser imaging. As demonstrated by both Figs. 1 and 2, the accelerator significantly reduces large surface deviations and thus improves the surface finish.

[0110] It has been found that the inclusion of the accelerator provides an improved surface finish. An improved / flatter / smoother surface finish provides for an improved appearance, a smoother surface for application of finishing layers, improved tolerances when used in a building project. An improved surface finish also decreases the risk of damage to the internal lining boards, for instance when the boards are stacked.

[0111] Fig. 3 shows a graph illustrating the effects of varying the ratio by weight of the alkaline earth-based binding agent (lime in the example of Fig. 3) to the cementitious material (natural cement in the example of Fig. 3) on the density and compressive load of example internal lining boards. A first example board of Fig. 3 is prepared using example mixture 1 of Table 1 (80:20 lime to natural cement ratio by weight). The remaining example boards of Fig. 3 are the same as the first example board of Fig. 3 but have varying lime to natural cement ratios by weight (60:40, 70:30, and 75:25 lime to natural cement ratio by weight).

[0112] Fig. 4 shows a graph illustrating the effects of varying the amount of cementitious material (natural cement in the example of Fig. 4) relative to the amount of the alkaline earth-based binding agent (lime in the example of Fig. 4) on the ultimate flexural load of example internal lining boards. The example boards of Fig. 4 are the same as those of Fig.3.

[0113] As demonstrated in Figs. 3 and 4, the ratio by weight of the alkaline earth-based binding agent to the cementitious material of 80:20 provides the strongest construction product.

[0114] Fig. 5 shows images of internal lining boards with varying ratios by weight of the alkaline earth-based binding agent to the cementitious material. These images illustrate a degradation in surface finish when the ratio by weight of the alkaline earthbased binding agent to the cementitious material is beyond 80:20. The example boards of Fig. 5 are the same as those of Figs. 3 & 4, but with varying lime to natural cement ratios by weight.

[0115] There is thus described a construction product and a method of manufacturing a construction product with a number of advantages as described above and below. The construction product has an improved surface finish, whilst also maintaining workability of the wet mixture to form a desired shape. The construction product is strong and lightweight. The construction product can be produced efficiently and at large scale. The construction product uses compostable materials. The construction product sequesters carbon.

[0116] The term ‘comprise’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising Y indicates that X may comprise only one Y or may comprise more than one Y. If it is intended to use ‘comprise’ with an exclusive meaning then it will be made clear in the context by referring to ‘comprising only one...’ or by using ‘consisting.’

[0117] In this description, reference has been made to various examples. The description of features or functions in relation to an example indicates that those features or functions are present in that example. The use of the term ‘example’ or ‘for example’ or ‘can’ or ‘may’ in the text denotes, whether explicitly stated or not, that such features or functions are present in at least the described example, whether described as an example or not, and that they can be, but are not necessarily, present in some of or all other examples. Thus ‘example’, ‘for example’, ‘can’, or ‘may’ refers to a particular instance in a class of examples. A property of the instance can be a property of only that instance or a property of the class or a property of a sub-class of the class that includes some but not all the instances in the class. It is therefore implicitly disclosed that a feature described with reference to one example but not with reference to another example, can where possible be used in that other example as part of a working combination but does not necessarily have to be used in that other example.

[0118] As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or” mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

[0119] Although examples have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the claims. In some alternative examples, the internal lining boards described herein may be formed from a mixture that does not comprise an accelerator and / or a retarder.

[0120] Features described in the preceding description may be used in combinations other than the combinations explicitly described above.

[0121] Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

[0122] The description of a feature, such as an apparatus or a component of an apparatus, configured to perform a function, or for performing a function, should additionally be considered to also disclose a method of performing that function. For example, description of an apparatus configured to perform one or more actions, or for performing one or more actions, should additionally be considered to disclose a method of performing those one or more actions with or without the apparatus.

[0123] Although features have been described with reference to certain examples, those features may also be present in other examples whether described or not.

[0124] The term ‘a’, ‘an’ or ‘the’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising a / an / the Y indicates that X may comprise only one Y or may comprise more than one Y unless the context clearly indicates the contrary. If it is intended to use ‘a’, ‘an’ or ‘the’ with an exclusive meaning then it will be made clear in the context. In some circumstances the use of ‘at least one’ or ‘one or more’ may be used to emphasis an inclusive meaning but the absence of these terms should not be taken to infer any exclusive meaning.

[0125] The presence of a feature (or combination of features) in a claim is a reference to that feature or (combination of features) itself and to features that achieve substantially the same technical effect (equivalent features). The equivalent features include, for example, features that are variants and achieve substantially the same result in substantially the same way. The equivalent features include, for example, features that perform substantially the same function, in substantially the same way to achieve substantially the same result. In this description, reference has been made to various examples using adjectives or adjectival phrases to describe characteristics of the examples. Such a description of a characteristic in relation to an example indicates that the characteristic is present in some examples exactly as described and is present in other examples substantially as described.

[0126] The above description describes some examples of the present disclosure however those of ordinary skill in the art will be aware of possible alternative structures and method features which offer equivalent functionality to the specific examples of such structures and features described herein above and which for the sake of brevity and clarity have been omitted from the above description. Nonetheless, the above description should be read as implicitly including reference to such alternative structures and method features which provide equivalent functionality unless such alternative structures or method features are explicitly excluded in the above description of the examples of the present disclosure.

[0127] Whilst endeavoring in the foregoing specification to draw attention to those features believed to be of importance the Applicant may seek protection via the claims in respect of any patentable feature or combination of features hereinbefore referred to and / or shown in the drawings whether or not emphasis has been placed thereon. l / we claim:

Claims

CLAIMS1. A construction product in the form of an internal lining board, the board being formed from a mixture comprising: a binder, wherein the binder comprises lime and cement; a bio-aggregate; an accelerator, wherein the ratio by weight of the accelerator to the binder is 1 : 10000 to 5: 100; and a retarder, wherein planar lining material is provided on one or both outer faces of the mixture.

2. The construction product of claim 1 , wherein the ratio of lime to cement by weight is at least 50:50.

3. The construction product of claim 2, wherein the ratio of lime to cement by weight is at least 60:40.

4. The construction product of claim 3, wherein the ratio of lime to cement by weight is 70:30 to 90:10.

5. The construction product of any of the preceding claims, wherein the ratio by weight of the accelerator to the binder is 1 : 100 to 2: 100.

6. The construction product of any of the preceding claims, wherein the accelerator comprises calcium chloride, calcium nitrate, calcium nitrite, calcium formate, potassium aluminate, sodium silicate, sodium carbonate, sodium bicarbonate, sodium aluminate, diethanolamine, and / or aluminium sulfate.

7. The construction product of any of the preceding claims, wherein the accelerator comprises an ionic compound.

8. The construction product of any of the preceding claims, wherein the accelerator comprises sodium carbonate.

9. The construction product of any of the preceding claims, wherein the ratio by weight of the retarder to the binder is 1 : 10000 to 5: 100.

10. The construction product of any of the preceding claims, wherein the ratio by weight of the retarder to the binder is 1 : 1000 to 1 : 100.

11. The construction product of any of the preceding claims, wherein the retarder comprises a sugar, phosphoric acid, a phosphate, boric acid, a borate, a lignosulfonate and / or citric acid.

12. The construction product of any of the preceding claims, wherein the retarder comprises citric acid.

13. The construction product of any of the preceding claims, wherein the mixture further comprises cellulose.

14. The construction product of claim 13, wherein the cellulose comprises methylated cellulose.

15. The construction product of any of the preceding claims, wherein the lime comprises hydrated lime.

16. The construction product of any of the preceding claims, wherein the cement comprises white cement, natural cement, calcium aluminate cement, and / or Portland cement.

17. The construction product of any of the preceding claims, wherein the planar lining material is paper.

18. The construction product of any of the preceding claims, wherein the bioaggregate comprises pyrolyzed bio-aggregate.

19. The construction product of any of the preceding claims, wherein the bioaggregate comprises a crop by-product.

20. The construction product of any of the preceding claims, wherein the ratio by weight of bio-aggregate to binder in the mixture is 10:90 to 30:70.

21. A method of manufacturing a construction product in the form of an internal lining board, the method comprising: producing a mixture of a binder, wherein the binder comprises lime and cement; a bio-aggregate; a retarder; and an accelerator, wherein the ratio by weight of the accelerator to the binder is 1 : 10000 to 5: 100; and providing a planar lining material on one or more outer faces of the mixture.

22. The method according to claim 21 , wherein the method further comprises forming the mixture into a predetermined geometric shape using extrusion moulding.

23. The method according to claim 22, wherein the method further comprises forming the mixture into a predetermined geometric shape using continuous extrusion moulding.

24. The method according to claim 21 or any claim dependent thereon, wherein the method further comprises adding water to the mixture, wherein the water is preheated to at least 15°C prior to adding the water to the mixture.

25. A construction product in the form of an internal lining board, the board being formed from a mixture comprising: a binder; a bio-aggregate; an accelerator, wherein the ratio by weight of the accelerator to the binder is 1 : 10000 to 5: 100; and a retarder,wherein planar lining material is provided on one or both outer faces of the mixture.

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