Mortar mixture

Abstract

A mixture of pyrolyzed bio-aggregate, and a binder comprising alkaline earth metal oxide and / or alkaline earth metal hydroxide, and cementitious material in a ratio of at least 50:50, preferably 75:25

Description

TECHNOLOGICAL FIELD Examples of the disclosure relate to a mortar mixture. Some relate to low-carbon or carbon-negative mortar mixtures comprising a pyrolyzed bio-aggregate. BACKGROUND A mortar is a construction product that is a workable paste which hardens to form a solid. In some examples, the mortar is a structural mortar and can be used to bind building blocks such as bricks. In some examples, the mortar is a plaster or render and can be used for protective or decorative coating of walls and ceilings. A mortar mixture is used to create the mortar. The mortar mixture may constitute of a dry mix, before water has been added, or a wet mix after water has been added to the dry mix. A mortar mixture may be a mixture for a plaster, render, or structural mortar. Conventional mortars and mortar mixtures release greenhouse gases during one or more of: the manufacturing process, transportation, customer use and end of life. The manufacture of most mortars and mortar mixtures involves the generation of greenhouse gas emissions by using raw materials which have been mined or manufactured using fossil fuels and / or by transporting the product and / or the reagents. There is therefore a need for a mortar mixture which is capable of removing carbon dioxide from the atmosphere. BRIEF SUMMARY According to various, but not necessarily all, examples there is provided a mortar mixture comprising a pyrolyzed bio-aggregate and a binder. The binder comprises alkaline earth metal oxide and / or alkaline earth metal hydroxide and cementitious material. The ratio by weight of alkaline earth metal oxide and / or alkaline earth metal hydroxide to cementitious material is at least 50:50. In some but not necessarily all examples, the ratio by weight of alkaline earth metal oxide and / or alkaline earth metal hydroxide to cementitious material is at least 60:40. The ratio by weight of alkaline earth metal oxide and / or alkaline earth metal hydroxide to cementitious material may be 70:30 to 90:10. The ratio by weight of alkaline earth metal oxide and / or alkaline earth metal hydroxide to cementitious material may be 75:25 to 85:15. The alkaline earth metal oxide and / or alkaline earth metal hydroxide may comprise hydraulic lime. The ratio by weight of pyrolyzed bio-aggregate to binder may be 40:100 to 80:100. The pyrolyzed bio-aggregate may have been pyrolyzed by heating bio-aggregate to between 500°C and 1000°C. At least 50% by weight of the particles of the pyrolyzed bio-aggregate may have a maximum extent in any dimension of up to 10 mm. At least 50% by weight of the particles of the pyrolyzed bio-aggregate may have a maximum extent in any dimension of up to 0.5 mm. The mortar mixture may further comprise a non-biological aggregate. The non-biological aggregate may comprise sand, gravel, limestone, glass, perlite, vermiculite, crushed stone, and / or slag. The ratio by weight of non-biological aggregate to binder may be 1:100 to 180:100. The mortar mixture may comprise at least 20 wt.% non-biological aggregate. The mortar mixture may further comprise a water reducing agent. The water reducing agent may be a superplasticizer. The superplasticizer may be a steric effect superplasticizer. The ratio by weight of water reducing agent to binder may be 3:1000 to 7:1000. The mortar mixture may comprise less than 0.30 wt.% superplasticizer. The mortar mixture may further comprise cellulose. The mortar mixture may further comprise an air entrainer. The mortar mixture may be a mixture for a plaster or render. According to various, but not necessarily all, examples there is provided a set mortar formed from water and the mortar mixture. According to various, but not necessarily all, examples there is provided a method of manufacturing comprising: dry mixing pyrolyzed bio-aggregate, alkaline earth metal oxide and / or alkaline earth metal hydroxide and cementitious material to form a mortar mixture, wherein the ratio by weight of alkaline earth metal oxide and / or alkaline earth metal hydroxide to cementitious material is at least 50:50. According to various, but not necessarily all, examples there is provided a method of use comprising: mixing the mortar mixture of any one of claims 1 to 20 with water to form a wet mixture. The method may further comprise: applying the wet mixture to a surface. According to various, but not necessarily all, embodiments there is provided examples as claimed in the appended claims. 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 BRIEF DESCRIPTION Some examples will now be described with reference to the accompanying drawings in which: FIG. 1 shows a graph illustrating the effect of varying the ratio by weight of alkaline earth metal oxide and / or alkaline earth metal hydroxide to cementitious material on the density and compressive load of construction materials; and FIG. 2 shows a graph illustrating the effect of varying the ratio by weight of alkaline earth metal oxide and / or alkaline earth metal hydroxide to cementitious material on the flexural load of construction materials. DETAILED DESCRIPTION The present disclosure provides mortars and mortar mixtures, as well as methods for manufacturing and using the mortars and mortar mixtures. The mortars and mortar mixtures, and the associated methods, of the present disclosure utilise pyrolyzed bioaggregate. The term “low-carbon” is used herein to refer to a product which, when manufactured, causes a smaller amount of carbon dioxide to be released into the atmosphere than a corresponding conventional product. The term “carbon-negative” is used herein to refer to a product which removes a greater amount of carbon dioxide from the atmosphere than enters the atmosphere during manufacture of the product. The mortars and mortar mixtures of the present invention described herein utilise carbon as a resource and as a result the manufacture of the mortars and mortar mixtures, may reduce carbon dioxide in the atmosphere. The mortars and mortar mixtures of the present invention described herein may have a net effect of removing carbon dioxide from the atmosphere (when measured from resource extraction until completion i.e., whole life cycle). The mortars and mortar mixtures of the present invention may therefore be used to mitigate global warming. According to a first aspect of the disclosure a mortar mixture is provided which comprises: a pyrolyzed bio-aggregate and a binder. The binder comprises: an alkaline earth metal oxide and / or an alkaline earth metal hydroxide; and cementitious material. The ratio by weight of alkaline earth metal oxide and / or alkaline earth metal hydroxide to cementitious material is at least 50:50. The mortar mixture can be used to form a mortar. 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. The bio-aggregate may be provided by a broad range of plant types. The mortar mixture may be prepared from low value, readily (and preferably locally) available, highly voluminous plant material. Furthermore, the mortar mixture may be produced on a large scale at low cost with low associated energy costs. 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. Bio aggregate may also be selected from wood chips, from any locally derived woodstream, possibly as a byproduct from wood milling, or the timber processing industry. This woodchips may be derived from renewable softwood (i.e., wood derived from sustainably managed coniferous trees). Alternatively, the wood chips may be derived from a hardwood waste stream. 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. 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 (such as hemp shiv); or any combination thereof. 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%. 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 improve the strength of the mortar through the use of bio-aggregate. The increased strength of the mortar therefore reduces the reliance on high carbon intensity binders. Furthermore, the mortar 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. 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. 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. In some examples the bio-aggregate may comprise milled post-consumer and / or postindustrial waste of biological origin, such as waste cotton clothing, waste wooden furniture or waste wooden doors. In some examples the bio-aggregate comprise engineered wood products. For example wood-based panel products such as plywood, medium-density fibreboard (MDF), particle board, or oriented strand board (OSB); or structural composite lumber (SCL) such as laminated veneer lumber (LVL), cross laminated timber (CLT), gluelam, parallel strand lumber (PSL) or laminated strand lumber (LSL). The term “pyrolysis” is used herein to refer 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 char / biocharand combustible gases. The combustible gases may be condensed to provide a combustible liquid referred to as pyrolysis oil or bio-oil. 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 bio-aggregate. 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. 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. The pyrolysis of the bio-aggregate enables carbon to be sequestered from the atmosphere and locked within the resultant pyrolyzed bio-aggregate indefinitely. Further, the pyrolysis increases the density of the carbon within the mortar and the mortar mixture. Pyrolyzed bio-aggregate particles I granulates are hydrophobic and therefore provide for improved contact between the binder and the bio-aggregate resulting in improved mechanical strength of the resultant mortar. Pyrolysis of the bio-aggregate 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 mortar. Pyrolysis of bio-aggregate also provides a source of bio-oil and / or bio-gas for further downstream processing. Pyrolyzed bio-aggregate may comprise biochar. 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. Pyrolyzed bio-aggregate particles have improved size regularity which results in a mortar with an improved surface finish due to a more regular particle size distribution. Pyrolysis of the bio-aggregate preferably produces pyrolyzed bio-aggregate particles with a reduced water content (preferably a uniform water content). 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. Pyrolyzed bio-aggregate comprises fewer volatile components than non-pyrolyzed bioaggregate. Therefore, a mortar 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 mortar can be used externally without the need for a further treatment or coating. Mortars containing pyrolyzed bio-aggregate have been found to have a lower thermal conductivity, which may be based at least in parton their lower density. Therefore, they may be useful as insulating materials. For example a render comprising pyrolyzed bioaggregate applied to the outside of a building helps to insulate the building. In another example, a plaster comprising pyrolyzed bio-aggregate would be used internally as an internal wall insulation. Both examples may remain vapour open providing a lower build-up of condensation. In some embodiments, the negative carbon mortar may comprise inert, non-biodegradable pyrolyzed bio-aggregate which has indefinitely sequestered biogenic carbon within the pyrolyzed bio-aggregate. In some but not necessarily all examples the ratio by weight of pyrolyzed bio-aggregate to binder in the mortar mixture is 30:100 to 100:100, such as 40:100 to 80:100, 40:100 to 65:100, 45:100 to 60:100 or substantially 50:100. The ratio by weight of pyrolyzed bio-aggregate (wt.%) to binder (wt.%) is preferably at least 10:100, preferably at least 30:100, for example at least 40:100. The ratio by weight of pyrolyzed bio-aggregate to binder is preferably no more than 150:100, preferably no more than 100:100, for example no more than 80:100, or no more than 65:100. 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 pyrolyzed bio-aggregate have a maximum extent in any dimension of 0.1 mm to 25 mm. Substantially all of the particles of the pyrolyzed bio-aggregate may have a maximum extent in any dimension of 0.5 mm to 15 mm, 0.5 mm to 10 mm, 1 mm to 7 mm, 2 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 pyrolyzed bio-aggregate may have a maximum extent in any dimension of at least 0.001 mm, at least 0.005 mm, at least 0.01 mm, at least 0.1 mm, at least 0.5 mm, at least 1 mm, at least 2 mm, or at least 3 mm. Substantially all of the particles of the pyrolyzed bio-aggregate have a maximum extent in any dimension of up to 25 mm, up to 15 mm, up to 10 mm, up to 5 mm, up to 3 mm, up to 2 mm, up to 1 mm, up to 0.5 mm, or up to 0.1 mm. In some examples, at least 50% by weight of the particles of the pyrolyzed bioaggregate have a maximum extent in any dimension of 0.1 mm to 25 mm. At least 50% by weight of the particles of the pyrolyzed bio-aggregate may have a maximum extent in any dimension of 0.5 mm to 15 mm, 0.5 mm to 10 mm, 1 mm to 7 mm, 2 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 pyrolyzed bioaggregate have a maximum extent in any dimension of at least 0.001 mm, at least 0.005 mm, at least 0.01 mm, at least 0.1 mm, at least 0.5 mm, at least 1 mm, at least 2 mm, or at least 3 mm. At least 50% by weight of the particles of the pyrolyzed bioaggregate may have a maximum extent in any dimension of up to 25 mm, up to 15 mm, up to 10 mm, up to 5 mm, up to 3 mm, up to 2 mm, up to 1 mm, up to 0.5 mm, or up to 0.1 mm. 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 thickness of the applied mortar. The particle size of the pyrolyzed bio-aggregate will affect the density and thermal and / or hygroscopic properties of the resultant mortar. It has been found that too large a particle size leads to a mortar that lacks workability. As well as the pyrolyzed bio-aggregate, the mortar mixture also comprises a binder. The binder comprises an alkaline earth metal oxide and / or an alkaline earth metal hydroxide and cementitious material. An alkaline earth metal oxide may be, for example, magnesium oxide and / or calcium oxide. An alkaline earth metal hydroxide may be, for example, calcium hydroxide and / or magnesium oxide. For instance, the alkaline earth metal oxide and / or alkaline earth metal hydroxide may comprise lime, such as lime oxide, hydrated lime, natural hydraulic lime, or any combination thereof. Preferably, the an alkaline earth metal oxide and / or an alkaline earth metal hydroxide comprises hydraulic lime, such as natural hydraulic lime (NHL). For example, natural hydraulic lime 3.5. In some examples the alkaline earth metal oxide and / or alkaline earth metal hydroxide may comprise natural hydraulic lime 2, and / or natural hydraulic lime 5. In some examples the cementitious material comprises cement. For example, the cementitious material may comprise, natural cement, Portland cement, white cement, calcium sulphate aluminate cement, alkali activated binders and / or blast furnace slags. The cementitious material may comprise clinker minerals. 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) 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. 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. In the binder, the ratio by weight of alkaline earth metal oxide and / or alkaline earth metal hydroxide to cementitious material is at least 50:50. In some examples, the ratio by weight of alkaline earth metal oxide and / or alkaline earth metal hydroxide to cementitious material is 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 metal oxide and / or alkaline earth metal hydroxide 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 metal oxide and / or alkaline earth metal hydroxide to cementitious material may be 60:40 to 95:5, such as 70:30 to 90:10, 75:25 to 85:15, or 80:20 to 85:15. In some examples, the ratio by weight of alkaline earth metal oxide and / or alkaline earth metal hydroxide to cementitious material is substantially 84:16. It has been found that the ratio of alkaline earth metal oxide and / or alkaline earth metal hydroxide to cementitious material optimises binding properties, setting rate and mechanical properties. This ratio is different to that typically used for mortars and is a surprising effect. In some but not necessarily all examples the mortar mixture further comprises a non-biological aggregate. The non-biological aggregate may be an inorganic aggregate such as a mineral aggregate. The non-biological aggregate may comprise fine aggregate materials which have an average particle size of less than 3 mm. In some examples, the non-biological aggregate comprises sand, gravel, limestone such as limestone fines, glass such as glass bubbles, perlite, vermiculite, crushed stone, crushed mineral waste plastic and / or slag. In some examples the ratio by weight of non-biological aggregate to binder is 1:100 to 180:100, such as 10:100 to 180:100, 30:100 to 160:100, or 100:100 to 160:100. The ratio by weight of non-biological aggregate to binder may be at least 1:100, such as at least 10:100, at least 30:100, or at least 100:100. The ratio by weight of non-biological aggregate to binder may be at most 180:100, such as at most 160:100. In some examples the mortar mixture comprises at least 20 wt.% non-biological aggregate. Higher proportions of non-biological aggregate can lead to a stronger mortar, but can reduce the flow and binding properties of the mortar. In some but not necessarily all examples the mortar mixture further comprises a water reducing agent / plasticizer. The water reducing agent may be a superplasticizer. In some examples a plasticizer can enable the production of the mortar with at least approximately 15% less water content, and superplasticizers allow reduction in water content by 30% or more. In some examples the water reducing agent comprises a polycarboxylate ether, a lignosulfonate, a sulfonated synthetic polymer, galactomannan polysaccharides non-galactomannan polysaccharides comprising, agar; pectin; and / or gelatin. Preferably the superplasticizer is a steric effect superplasticizer. Most preferably the superplasticizer is a polycarboxylate. In some examples, the ratio by weight of superplasticizer to binder is 1:10000 to 3:100, such as 1:1000 to 3:100, or 3:1000 to 7:1000. In some examples the mortar mixture comprises less than 0.30 wt.% superplasticizer, such as 0.01 wt.% to 0.30 wt.% superplasticizer. It has been found that too much water reducing agent leads to air bubbles forming in the wet mix mortar, which leads to a non-smooth finish. In some but not necessarily all examples the mortar mixture further comprises cellulose. For example the cellulose may comprises methylated cellulose. In some examples the ratio of cellulose to binder is 1:1000 to 3:100. In some examples the mortar mixture comprises more than 0.03 wt.% cellulose. The cellulose has been found to improve the strength of the mortar. The inclusion of cellulose also improves the interface between the binder and the pyrolyzed bioaggregate, creating a more structurally homogeneous composite. It has been found that too much cellulose leads to air bubbles forming in the wet mix mortar, which leads to a non-smooth finish. In some but not necessarily all examples the mortar mixture further comprises an air entrainer such as lignin sulfonate. The ratio by weight of air entrainer to binder may be 1:10000 to 3:100, such as 1:1000 to 2:1000. The mixture may further comprise one or more additives selected from: viscosity modifying agents; and / or coupling agents. The density of the mortar mixture may be at least 200 kg / m3 Preferably the density of the mortar mixture is at least 250 kg / m3, such as 325 kg / m3. The density of the mortar mixture may be up to 1500 kg / m3. Preferably the density of the mortar mixture is up to 1000 kg / m3, or up to 750 kg / m3. Most preferably the density of the mortar mixture is up to 500 kg / m3. The density of the mortar mixture may be between 200 kg / m3 and 1500 kg / m3, such as between 250 kg / m3 and 750 kg / m3, or between 250 kg / m3 and 500 kg / m3. In some examples, the mortar mixture is a dry mix. In other examples, the mortar mixture is a wet mix and comprises water. The wet mix may be considered a paste or slurry. The wet mix may be considered a mortar. In some examples the water might not be pure water. For example, the water may be rain water or seawater. In some examples the ratio of water to binder is between 80:100 and 200:100. Preferably the ratio of water to binder is between 120:100 and 220:100, such as between 150:100 and 200:100. The addition of water allows the mortar mixture to set I cure. In some examples, a set mortar is formed from water and the mortar mixture. In some examples the mortar is non-loadbearing and may be a plaster or a render formed by the mortar mixture described herein. The plaster may be an internal plaster that is for use on the internal walls of a building. The render may be an external render that is for use on the external walls of a building. In some examples the mortar is a load bearing mortar or a structural mortar. In some examples the mortar is type m, s, n or o as defined by ASTM C 270. The mortar may be any of the types as defined by EN 998. In one instance a mortar with a pyrolyzed feedstock, such as a pyrolyzed bioaggregate, can have fine surface finish, being durable and smooth in appearance, used predominantly as in internal plaster to provide a fine aesthetic finish whilst storing carbon. This variant may have a fine max particle size distribution and narrow distribution of particles. The correct ratio, covered by the ranges herein, of binder to aggregate and the correct coupling agents are required to ensure that the finish is not friable. This product may be applied in a thin sub 8 mm application, and could be applied on to any number of substrates. It could be finished in a standard manner with paint. In some instances a fixative may be required interstitially. In some instance this fixative would be required to be vapor open, potentially silicate based. In another instance a mortar has a low thermal conductivity, producing an insulative effect. In this instance the mortar may have a larger max particle size and a distribution of particle sizes with a higher mean, but the correct distribution to allow for application. This product would be made to be highly light weight, maximizing the volumetric binder to aggregate ratio. It would be applied in excess of 10 mm as a minimum, more likely to be applied thicker than 25mm, ideally in excess of 50mm. In the first instance a thermally insulative plaster could be applied internally. The pyrolysis process modifies the bio matter to the extent that the thermally insulative plaster could be applied externally. The reduction in presence of the sugars, and pectin, the cellulose and hemi cellulose that would ordinarily be metabolized by microbes, forming rot or fungal degradation dramatically reduces the effects of decay ordinarily experienced by bio matter in an external application. According to an aspect of the disclosure a method of manufacturing comprises: dry mixing pyrolyzed bio-aggregate, alkaline earth metal oxide and / or alkaline earth metal hydroxide and cementitious material to form a mortar mixture, wherein the ratio by weight of alkaline earth metal oxide and / or alkaline earth metal hydroxide to cementitious material is at least 50:50. According to an aspect of the disclosure a method of use comprises: mixing the dry mix with water to form a wet mixture. In some examples the method further comprises applying the wet mixture to a surface, such as a wall. In some examples applying the wet mixture using a trowel and / or roller. In some examples applying the wet mixture comprises spraying the wet mixture onto the surface. Mixing of the dry mix and wet mix may occur using 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 comprise a padel mixer. The mixer may be at a temperature between 15°C and 70°C, such as substantially room temperature (25°C). The mortar mixture may be mixed using the mixer for a predetermined time period. In some examples the components of the dry mortar mixture are mixed together dry and then mixed with the water to form a wet mix. In other examples all of the components, including the water, are mixed together at simultaneously. 5 Examples Example and comparative example mortars were prepared, and properties of the mortars were recorded as shown in Table 1. For these example and comparative example mortar the ratio by weight of pyrolyzed bio-aggregate to binder was 0.5. Table 1 Exampl e Binders Mass ratio of binders Pyrolyzed bioaggregate Wet workability Dry finish Prism flexural strength (kN) Prism compress ive strength (kN) Density (kg / m3) 1 NHL3.5 : Natural cement 84:16 Superfine Smooth (suited to finishing plaster) Minimal dust, smooth, hard, no cracking 0.153 - 0.287 1.103 - 1.845 970- 1210 2 NHL2 100 Coarse Too much slump Shrinkage cracks - - 3 Hydrated lime : Portland cement 90:10 Superfine Smooth No dust, smooth, hard, no cracking 0.38 2.755 1001 It can be seen that for example mortars 1 and 2, where the ratio by weight of alkaline earth metal oxide and / or alkaline earth metal hydroxide to cementitious material was 15 84:16 and 90:10 respectively, that a workable mortar was produced with a good dry finish. However, for comparative example mortar 2, which contains no cementitious material, the mortar had too much slump and so was not workable. Table 2 Example 4 Hydrated Lime (kg) 450 Cementitious material (kg) 112.5 (natural cement) Methylated cellulose (kg) 7.029 4mm hemp shiv (kg) 145.7 Fig. 1 shows a graph illustrating the effects of varying the ratio by weight of the alkaline earth metal oxide and / or alkaline earth metal hydroxide to cementitious material lime in the example of Fig. 1) to the cementitious material (natural cement in the example of Fig. 1) on the density and compressive load of example construction products. A first example construction product of Fig. 1 is prepared using example mixture 4 of Table 2 (80:20 lime to natural cement ratio by weight). The remaining example construction products of Fig. 1 are the same as the first example construction products of Fig. 1 but have varying lime to natural cement ratios by weight (60:40, 70:30, and 75:25 lime to natural cement ratio by weight). Fig. 2 shows a graph illustrating the effects of varying the amount of cementitious material (natural cement in the example of Fig. 2) relative to the amount of alkaline earth metal oxide and / or alkaline earth metal hydroxide to cementitious material (lime in the example of Fig. 2) on the ultimate flexural load of example construction products. The example construction products of Fig. 2 are the same as those of Fig. 1. As demonstrated in Figs. 1 and 2, the ratio by weight of the alkaline earth metal oxide and / or alkaline earth metal hydroxide to the cementitious material of 80:20 provides the strongest construction product. For a fifth example mortar, with a NHL3.5 : Natural cement (84 : 16) binder and with a ratio by weight of pyrolyzed bio-aggregate to binder of 0.7, the following was observed when compared to example mortar 1 with a ratio by weight of pyrolyzed bioaggregate to binder of 0.5: • Higher water requirement (70 - 140 %) • Excess dust in the dry plaster • Friability significantly increased • Lower prism flexural strength (0.02 - 0.24 kN) • Lower prism compressive strength (0.071 - 2.135 kN) • Lower density (294 -1015 kg / m3) which is not favourable for strength As such, larger ratio by weight of pyrolyzed bio-aggregate to binder lead to less favourable mortar properties, including increased friability. 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.’ 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. 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. Features described in the preceding description may be used in combinations other than the combinations explicitly described above. Although features have been described with reference to certain examples, those features may also be present in other examples whether described or not. 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. 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. 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. Whilst endeavoring in the foregoing specification to draw attention to those features 5 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: 10

Claims

1. A mortar mixture comprising:a pyrolyzed bio-aggregate; anda binder comprising:an alkaline earth metal oxide and / or an alkaline earth metal hydroxide; andcementitious material,wherein the ratio by weight of alkaline earth metal oxide and / or alkaline earth metal hydroxide to cementitious material is at least 50:50.

2. The mortar mixture of claim 1, wherein the ratio by weight of alkaline earth metal oxide and / or alkaline earth metal hydroxide to cementitious material is at least 60:40.

3. The mortar mixture of claim 2, wherein the ratio by weight of alkaline earth metal oxide and / or alkaline earth metal hydroxide to cementitious material is 70:30 to 90:10.

4. The mortar mixture of claim 3, wherein the ratio by weight of alkaline earth metal oxide and / or alkaline earth metal hydroxide to cementitious material is 75:25 to 85:15.

5. The mortar mixture of any of the preceding claims, wherein the alkaline earth metal oxide and / or alkaline earth metal hydroxide comprises hydraulic lime.

6. The mortar mixture of any of the preceding claims, wherein the ratio by weight of pyrolyzed bio-aggregate to binder is 40:100 to 80:100.

7. The mortar mixture of any of the preceding claims, wherein the pyrolyzed bioaggregate has been pyrolyzed by heating bio-aggregate to between 500°C and 1000°C.

8. The mortar mixture of any of the preceding claims, wherein at least 50% by weight of the particles of the pyrolyzed bio-aggregate have a maximum extent in any dimension of up to 10 mm.

9. The mortar mixture of claims 1 to 7, wherein at least 50% by weight of the particles of the pyrolyzed bio-aggregate have a maximum extent in any dimension of up to 0.5 mm.

10. The mortar mixture of any of the preceding claims, further comprising a non-biological aggregate.

11. The mortar mixture of claim 10, wherein the non-biological aggregate comprises sand, gravel, limestone, glass, perlite, vermiculite, crushed stone, and / or slag.

12. The mortar mixture of claim 10 or 11, wherein the ratio by weight of non-biological aggregate to binder is 1:100 to 180:100.

13. The mortar mixture of any of claims 10 to 12, wherein the mortar mixture comprises at least 20 wt.% non-biological aggregate.

14. The mortar mixture of any of the preceding claims, further comprising a water reducing agent.

15. The mortar mixture of claim 13, wherein the water reducing agent is a superplasticizer.

16. The mortar mixture of claim 14, wherein the superplasticizer is a steric effect superplasticizer.

17. The mortar mixture of any of claims 13 to 15, wherein the ratio by weight of water reducing agent to binder is 3:1000 to 7:1000.

18. The mortar mixture of any of claims 13 to 15, wherein the mortar mixturecomprises less than 0.30 wt.% superplasticizer.

19. The mortar mixture of any of the preceding claims, further comprisingcellulose.

20. The mortar mixture of any of the preceding claims, further comprising an air entrainer.

21. The mortar mixture of any of the preceding claims, wherein the mortar mixture is a mixture for a plaster or render.

22. A set mortar formed from water and the mortar mixture of any one of claims 1 to 20.

23. A method of manufacturing comprising:dry mixing pyrolyzed bio-aggregate, alkaline earth metal oxide and / or alkaline earth metal hydroxide and cementitious material to form a mortar mixture, wherein the ratio by weight of alkaline earth metal oxide and / or alkaline earth metal hydroxide to cementitious material is at least 50:50.

24. A method of use comprising:mixing the mortar mixture of any one of claims 1 to 20 with water to form a wet mixture.

25. The method according to claim 24 further comprising: applying the wet mixture to a surface.

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