Ceramic composition, method for its preparation and use thereof

Abstract

A cementitious composition comprising a cement composition comprising Ordinary Portland Cement (OPC) and a finely divided ceramic obtained from waste ceramic items. The finely divided ceramic material

Description

The present invention relates to a ceramic composition and a method for the preparation thereof. The present invention also relates to uses of the ceramic composition. It is estimated that between 75,000 and 150,000 tonnes of ceramic waste materials are disposed of each year in the United Kingdom alone. The ceramic waste material is generally disposed of by way of land fill, with a small portion of the waste being used in low grade applications, such as being blended with other materials for road making. This amount is a small fraction of the total amount of ceramic waste material produced globally each year. It would be a significant advantage if a use could be found for the ceramic waste material. Huseien, G.F., et al. conducted a series of studies: ‘Waste ceramic powder incorporated alkali activated mortars exposed to elevated Temperatures: Performance evaluation’, Construction and Building Materials, 2018, 187, pages 307 to 317; ‘Performance of sustainable alkali activated mortars containing solid waste ceramic powder’, Chemical Engineering Transactions, 2018, 63, pages 673 to 678; ‘Evaluation of alkali-activated mortars containing high volume waste ceramic powder and fly ash replacing GBFS’, Construction and Building Materials, 2019, 210, pages 78 to 92; ‘Properties of ceramic tile waste based alkali-activated mortars incorporating GBFS and fly ash’, Construction and Building Materials, 2019, 214, pages 355 to 368; ‘Effects of ceramic tile powder waste on properties of self-compacted alkali-activated concrete’, Construction and Building Materials, 2020, 236, page 117574. Huseien and colleagues investigated extensively the use of ceramic waste as slag substitute in alkali activated mixes. The impact of substituting high-volume waste ceramic powder (CP) into slag alone or in conjunction with fly ash in the manufacture of alkali activated mortars was explored by assessing the fresh (workability, setting time) and hardened properties of mortar mixes (compressive strength, flexural strength, and water absorption), at room temperature as well as after exposure to high temperatures. Results showed that, even if a linear strength reduction was observed by replacing slag with CP, substitution rates of 50 to 70% were able to deliver satisfactory compressive strength of about 50 MPa. Fresh properties (setting time and workability were also observed to be improved with CP substitution, as well as a range of durability properties such as resistance to acid and sulfate attack, freeze-thaw, wet-dry cycles. A final strength of 40 MPa was recorded for substitution rate of 70%. Reig, L, et al. conducted a series of studies: ‘Alkaline activation of ceramic waste materials’, Waste and Biomass Valorization, 2013, 4, pages 729 to 736; ‘Influence of the activator concentration and calcium hydroxide addition on the properties of alkali-activated porcelain stoneware’, Construction and Building Materials, 2014, 63, pages 214 to 222; and ‘Compressive strength and microstructure of alkali-activated mortars with high ceramic waste content’, Ceramics International, 43(16), 2017, pages 13622 to 13634. Reig and colleagues investigated the suitability of ceramic waste as an alkali activated precursor. The study involved both “red” ceramic (brick waste) and “white ceramic” (porcelain stoneware), with size D50 = 10 pm. Porcelain powder was substituted with 2% Ca(OH)2, activated with NaOH and sodium silicate solution, and cured at 65°. Up to 30 MPa were obtained with 100% porcelain powder. In a further study, improved strength >35MPa was obtained by tuning the Ca(OH)2 and activation parameters. The use of ceramic waste as binder as well as aggregate was then investigated, with compressive strength of an all-waste mortar achieving >50 MPa when cured at 65°C, and 10 MPa when cured at room temperature. The same research group recently published a literature review on reusing ceramic waste as a precursor in alkali activated cements. The results indicated that ceramic powder can be an effective precursor, although it might need additional sources of Ca to react at room temperature, otherwise heat curing is needed. This alternative reuse option helps reducing CO2 emissions, embodied energy, Portland cement consumption, and ceramic waste accumulation in landfills, contributing to sustainable development. El-Dieb, et al., ‘The use of ceramic waste powder (CWP) in making eco-friendly concretes’, Ceramic Materials: Synthesis, Characterization, Applications and Recycling, 2019, pages 1 to 35, investigated the impact of ceramic waste powder produced during final polishing process of ceramic tiles. The researchers investigated the use of the powder both in conventional Portland cement-based concrete as well as in alkali activated concrete production. For this latter work, an optimised mix proportion with NaOH and KOH as activator, 40% slag inclusion and 24-hour curing at 60°C was suggested to achieve compressive strength of about 40 MPa after 7 days (with 28-day strength in the same range). Hwang et al., ‘Development of high-strength alkali-activated pastes containing high volumes of waste brick and ceramic powders. Construction and Building Materials, 2019, 218, pages 519 to 529, investigated the potential use of waste ceramic and red clay brick powders in the production of alkali-activated cement. Whilst 100% ceramic powder did not set at room temperature, dosage of 60% in conjunction with a blend of slag and fly ash delivered satisfactory compressive strength, in excess of 55 MPa after 28 days when the slag was dosed at 30%. It was observed that brick powder was more reactive than ceramic powder. Rashad and Essa, ‘Effect of ceramic waste powder on alkali-activated slag pastes cured in hot weather after exposure to elevated temperature’, Cement and Concrete Composites, 2020, 111, page 103617, explored the incorporation of up to 50% of ceramic waste powder into alkali-activated slag pastes cured in hot weather and exposed to elevated temperatures. The research examined the effect of ceramic powder inclusion on workability, water absorption, and compressive strength, and analysed the results using microstructural techniques. The study found that the inclusion of ceramic powder had a negative effect on workability but a positive effect on water absorption and compressive strength (>45MPa at 28 days) before and after exposure to elevated temperatures. Pommer et al., ‘Alkali-activated waste ceramics: Importance of precursor particle size distribution’, Ceramics International, 2021, 47(22), pages 31574 to 31582, studied the impact of particle size distribution on the performance of waste red brick ceramic materials as geopolymer precursors, finding that removing particles retained on a 0.5 mm sieve improves the mechanical performance and geopolymerization rate. The presence of coarser particles in the precursor leads to increased porosity, resulting in lower thermal conductivity and faster moisture transport in the activated material. Strength up to 35 MPa were recorded at room temperature curing for samples produced with fine red brick powder precursor. Zhang, et al.: ‘Effect of waste ceramic powder on properties of alkali-activated blastfurnace slag paste and mortar’, Polymers, 2021, 13(16), page2817 and ‘Effect of waste ceramic powder on the properties of alkali-activated slag and fly ash pastes exposed to high temperature’, 2021, Polymers, 13(21), page 3797, investigated the use of waste ceramic tiles substituting slag in alkali activated materials. Experimental results with substitution rate in the range 0 - 30% showed that as the rate of replacement of ceramic powder increases, the fluidity of the paste slightly increases. The strength of the mortar sample decreases in the early period but no significant decrease is observed in the later period. The durability under sulfuric acid attack improves with an increase in WCP content. The diffusion coefficient of chloride ions increases, and the resistivity decreases with an increase in ceramic powder content. In another study, the researchers studied the impact of ceramic waste powder substituting slag in the range 0 - 20% on the performance of alkali-activated slag and fly ash blends when exposed to high temperature up to 900°C. Results suggested that ceramic powder inclusion increased the strength both at 45°C curing (reaching >80MPa for 20% substitution) as well as after exposure, with residual strength of about 30 MPa after 900°C. Awoyera, P.O., etal., ‘Characterization of ceramic waste aggregate concrete’, HBRC Journal (2016), propose the use of ceramic tiles as aggregate in concrete formulations. The ceramic tiles were sieved into fine and coarse aggregates in line with standards. Other materials used to form the concrete were gravel, river sand, cement and potable water. CN115490448 discloses crushing waste sintered ceramics to form a waste ceramic reclaimed sand. The sand is used to prepare concrete and mortar by using the waste ceramic reclaimed sand as all or part of fine aggregate. Steiner, L.R., et al., ‘Effectiveness of ceramic tile polishing residues as supplementary cementitious materials for cement mortars’, Sustainable Materials and Technologies, 4 (2015), pages 30 to 35 describe experiments to use the sludge produced by the polishing of ceramic tiles. Polishing residue was recovered from the sludge and tested for its ability to replace a portion of the cement used in mortar comprising cement, sand and water. The polishing residue had a Dsc of from 5 to 12 microns. The polishing residue was used to replace 0, 10, 20, 25, 30 and 40% of the cement on a weight basis. The results indicate that polishing residue may be used to replace a portion of the cement in mortar, with the compressive strength of the mortar varying with the amount of polishing residue replacement employed. The use of ceramic tile waste to replace Portland cement was also investigated by Mas, M.A., et al., ‘Ceramic tile waste as replacement material in Portland cement’, Advances in Cement Research, 2015, 00(00), pages 1 to 12. Wall, stoneware and porcelain stoneware tile waste was crushed to particles of less than 2 mm and then ground in a ball mill to produce particles having a mean diameter of about 17.25 microns, with a Dgo under 43 microns. The resulting material was used to replace Portland cement in amounts of 15, 25, 35 and 50% by weight in paste and mortar samples. The results showed that increasing the amount of cement replacement decreased the strength activity index of the mortars. Lasseuguette, E., et al., ‘Recycling ceramic waste to produce green concrete’, 1st International Conference on Construction Materials for Sustainable Future, 19 to 21 April 2017, Zadar, Croatia, investigated a cement mortar mix employing a 15% by weight replacement of cement with ground ceramic tiles. The ceramic material had a particle size ranging from about 0.4 to 200 microns. The mortar mix comprised water, sand, cement and ceramic replacement. The use of ceramic replacement reduced the compressive strength of the mortar, compared with a control, in which no replacement was employed. CN113233835A discloses a concrete composition comprising cement, natural coarse aggregate, recycled coarse aggregate, natural fine aggregate, recycled ceramic fine aggregate, water, a ceramic admixture and a polycarboxylic acid superplasticizer. More recently, CN116283158A discloses a concrete composition comprising a waste ceramic component, in particular perlite, as a replacement for a portion of the cement. There is a continuing need for an improved manner to dispose of ceramic waste materials, such as those generated on construction and demolition sites. It would be very advantageous if a use could be found for ceramic waste materials that has a reduced environmental impact. It would be particularly advantageous if a use for waste and recycled ceramic and porcelain tiles could be found. In a first aspect, the present invention provides a cementitious composition comprising a cement composition, the cement composition comprising: Ordinary Portland Cement (OPC); and a finely divided ceramic material obtained from waste ceramic items. The composition of the present invention comprises a cement composition. The cement composition comprises Ordinary Portland Cement (OPC). OPC is a well-known cement in the art and is commercially available. OPC is defined in ASTM C150 as a hydraulic cement (cement that not only hardens by reacting with water but also forms a water-resistant product) produced by pulverizing clinkers which consist essentially of hydraulic calcium silicates, usually containing one or more of the forms of calcium sulphate as an inter-ground addition. The European Standard EN 197-1 defines OPC as a hydraulic material which shall consist of at least two-thirds by mass of calcium silicates, (3 CaOSiO2, and 2 CaOSiO2), the remainder consisting of aluminium- and iron-containing clinker phases and other compounds. The ratio of CaO to SiO2 shall not be less than 2.0. The magnesium oxide content (MgO) shall not exceed 5.0% by mass. OPC is provided in a number of different types, as follows: Type I - for general purpose; Type IA- same as Type I, for when air entrainment is desired; Type II - for moderate sulfate resistance; Type HA - same as Type II, for when air entrainment is desired; Type ll(MH) - similar to Type II, for when moderate heat of hydration is desired; Type H(MH)A - same as Type ll(MH), for when air entrainment is desired; Type III - for high early strength; Type IHA - same as Type HI, for when air entrainment is desired; Type IV - for low heat of hydration; and Type V - for high sulfate resistance. The composition may comprise any of one or a mixture of two or more of the aforementioned types of OPC. OPC may be present in the composition in any suitable amount and such amounts will be known in the art and understood by the skilled person. However, in the present invention, the cement composition comprises both OPC and a finely divided ceramic material. It can be considered that a portion of the OPC used in known or standard formulations is replaced or substituted by the finely divided ceramic material. The cement composition further comprises a finely divided ceramic material. The ceramic material is obtained from waste ceramic items. Suitable waste ceramic items as sources for this ceramic material are abundantly available and include items found in kitchens and bathrooms, such as toilets, urinals, sinks including both wall mounted and pedestal mounted, sink pedestals, b-days and bath tubs. In a preferred embodiment, the cement composition comprises finely divided ceramic material is derived from ceramic tiles. The ceramic items may be waste produced as part of the manufacturing process. Generally, these waste items are produced during the manufacturing process, for example after the ceramic items have been (ie. post-kiln). Generally, these items cannot be recycled within the manufacturing process and must be disposed of, for example by way of land-fill. Other sources of waste ceramic items are in the distribution, wholesale and retail chain, for example as a result of damage to items during transport or storage. An alternative source of the waste ceramic items is from the refitting of existing installations or as a result of demolition and construction. As noted above, in one preferred embodiment, the finely divided ceramic material is derived from waste ceramic tiles. Typical raw materials used in the production of ceramic tiles include clay, feldspar, pottery stone, silica sand and talc. Generally, the most important component of ceramic tile bodies is clay. Clay is a term for naturally occurring mineral aggregates consisting mainly of the hydrous silicate of alumina. Ceramic tiles in the UK are commonly composed of clays, silica (milled to a desired particle size) and limestone which are mixed together with water to produce a slurry, or "slip". The slip is then spray dried to produce a homogeneous, free flowing granulate. The tiles are formed in a press and then dried and fired in a kiln, with a typical firing cycle of around four days. The fired tiles, known as "bisque", are then ready for the glazing cycle. The glazed product can be fired in a kiln with cycles from 12 to 20 hours, or in a single layer roller kiln with cycles of 30 to 45 minutes. The resultant tiles comprise a tile body with a fired glaze coating, typically on a major surface and possibly one or more edge surfaces. The finely divided ceramic material may comprise one or a mixture of different ceramic materials. In one embodiment, the finely divided ceramic material consists essentially of or comprises porcelain. Porcelain is a ceramic material formed by heating raw materials, generally including kaolinite, in a kiln to temperatures between 1,200 and 1,400 °C. References herein to ‘ceramic material’ include references to materials that consist of or comprise porcelain, unless otherwise stated. As described above, the cement composition comprises a combination of OPC and the finely divided ceramic material. The amounts of the OPC and finely divided ceramic material may be any suitable amounts and the relative amounts of these components may be varied according to such factors as, for example, the end use of the composition and the required properties of the composition once cured, such as compressive strength. Preferably, the OPC is present in the cement composition as the major component (that is greater than 50% by weight), with the finely divided ceramic material being present as the minor component (that is less than 50% by weight). The OPC may be present in the cement composition in an amount of from 20% by weight, preferably from 30%, more preferably from 40%, still more preferably from 50%, more preferably still from 55%, especially from 60% by weight. The OPC may be present in the cement composition in an amount of up to 98% by weight, preferably up to 95%, more preferably up to 90% by weight. In some embodiments, the OPC is present in an amount of up to 85%, preferably up to 80%, more preferably up to 75% especially up to 70% by weight. In one embodiment, the cement composition comprises the OPC in an amount of from 90 to 98% by weight, preferably from 91 to 97%, more preferably from 92 to 96%, still more preferably from 93 to 95% by weight. In one embodiment, the cement composition comprises the OPC in an amount of from 80 to 98% by weight, preferably from 82 to 96%, more preferably from 84 to 96%, still more preferably from 85 to 95% by weight. The finely divided ceramic material may be present in the cement composition in an amount of from 1 % by weight, preferably from 2%, more preferably from 4%, still more preferably from 5%, more preferably still from 7.5%, especially from 8% by weight. The finely divided ceramic material may be present in the cement composition in an amount of up to 80% by weight, preferably up to 75%, more preferably up to 70%, still more preferably up to 65%, more preferably still up to 60%, especially up to 55%, more especially up to 50%, still more especially up to 45% by weight. In some embodiments, the finely divided ceramic material is present in an amount of up to 35% by weight, preferably up to 30%, more preferably up to 25% especially up to 20% by weight. In one embodiment, the cement composition comprises the finely divided ceramic material in an amount of from 2 to 15% by weight, preferably from 3 to 13%, more preferably from 4 to 12%, still more preferably from 5 to 10% by weight. In one embodiment, the cement composition comprises the finely divided ceramic material in an amount of from 4 to 30% by weight, preferably from 6 to 25%, more preferably from 8 to 22%, still more preferably from 10 to 20% by weight. The OPC and the finely divided ceramic material may be present in the cement composition in any suitable weight ratio. As noted above, in one preferred embodiment, OPC is present in excess of the amount of the finely divided ceramic material. The weight ratio of OPC and finely divided ceramic material in the cement composition may be from 1:1, preferably from 1.2:1, more preferably from 1.5:1, still more preferably from 1.7:1, more preferably still from 2:1. The weight ratio of OPC and finely divided ceramic material in the cement composition may be up to 50:1, preferably up to 45:1, more preferably up to 40:1, still more preferably up to 35:1, more preferably still up to 30:1, especially up to 25:1, more especially up to 20:1, still more especially up to 15:1, for example up to 10:1. The weight ratio of OPC and finely divided ceramic material in the cement composition may be from 1:1 to 30:1, preferably from 2:1 to 25:1, more preferably from 3:1 to 20:1, still more preferably from 5:1 to 15:1, more preferably still from 7:1 to 12:1, especially from 8:1 to 10:1. In some embodiments, the weight ratio of the OPC and the finely divided ceramic material is from 2.5:1 to 20:1, for example from 3:1 to 15:1 or from 4:1 to 12:1. As noted above, the finely divided ceramic material is derived from waste ceramic items. In a particularly preferred embodiment, the waste ceramic items are ceramic tiles. The finely divided ceramic material may be prepared from the waste ceramic items by any suitable process, for example crushing, grinding or milling or a combination of one or more techniques. Suitable equipment for preparing the finely divided ceramic material is known in the art and is commercially available. The finely divided ceramic material may have any suitable particle size. For example, the finely divided ceramic material may have a Dso of from 1 micron, preferably from 2 microns, more preferably from 5 microns, still more preferably from 7.5 microns. The finely divided ceramic material may have a Dso of up to 50 microns, preferably up to 45 microns, more preferably up to 40 microns, still more preferably up to 35 microns, more preferably still up to 30 microns, for example up to 25 microns or up to 20 microns. A Dso of from 5 to 30 microns is suitable for many embodiments, preferably from 6 to 25 microns, more preferably from 8 to 22 microns, especially from 10 to 20 microns. The finely divided ceramic material may have a bi-modal size distribution, that is with two different size fractions. For example, the first fraction may have a Dso of from 0.01 micron, preferably from 0.02 microns, more preferably from 0.03 microns, still more preferably from 0.04 microns. The first fraction may have a Dso of up to 2 microns, preferably up to 1.5 microns, more preferably up to 1 micron, still more preferably up to 0.5 microns, more preferably still up to 0.3 microns, for example up to 0.2 microns or up to 0.1 microns. A Dso of from 5 to 30 microns is suitable for many embodiments, preferably from 0.01 to 0.1 microns, especially from 0.02 to 0.06 microns. For example, the second fraction may have a Dso of from 1 micron, preferably from 2 microns, more preferably from 5 microns, still more preferably from 7.5 microns. The second fraction may have a Dso of up to 50 microns, preferably up to 45 microns, more preferably up to 40 microns, still more preferably up to 35 microns, more preferably still up to 30 microns, for example up to 25 microns or up to 20 microns. A Dso of from 5 to 30 microns is suitable for many embodiments, preferably from 6 to 25 microns, more preferably from 8 to 22 microns, especially from 10 to 20 microns. The amount of cement composition employed will depend upon the type of cementitious composition and such factors as the intended use of the cured composition after combination with water. For example, in one embodiment, the cementitious composition may be for use as a cementitious paste, in which case the composition may comprise 100% by weight of the cement composition. In a further aspect, the present invention provides a cementitious paste comprising a cementitious composition as hereinbefore described and water. Any suitable amount of water may be combined with the cementitious composition to form the paste and suitable amounts will be known to the skilled person. The amount of water that may be added to the cementitious composition to form the paste, based on the amount of the cement composition, may be from 10% by weight, preferably from 15%, more preferably from 20%, still more preferably from 25%, more preferably still from 30%, especially from 35%, more especially from 40%. The amount of water that may be added to the cementitious composition to form the paste, based on the amount of the cement composition, may be up to 70% by weight, preferably up to 65%, more preferably up to 60%, still more preferably up to 55%. Water in an amount, based on the amount of cement composition, may in many embodiments be from 30 to 70% by weight, preferably from 35 to 65%, more preferably from 40 to 60%, still more preferably from 45 to 55% by weight. The cementitious paste is allowed to cure after being applied or used. The paste may be allowed to cure at ambient temperatures, that is without the addition of heat from an external source. Alternatively, the paste may be cured at an elevated temperature, that is with heat added to the paste from an external source. It is an advantage of the paste that curing at ambient temperatures without the addition of heat from an external source is possible and the cured paste exhibiting a high compressive strength. The time required for the paste to cure may vary, for example depending upon the composition of the paste. The time required for the paste to fully cure may be from 5 days, for example 7 days, 10 days, 15 days, 20 days or longer. In many embodiments, the compressive strength of the paste will increase as the paste cures. For example, the compressive strength may increase for a period of 28 days or longer. In a further aspect, the present invention provides a cured cementitious paste prepared by combining the cementitious composition hereinbefore described with water and allowing the resulting mixture to cure. The cementitious composition of the present invention may be used in a range of other applications, for example in a mortar composition and a concrete composition. In a further aspect, the present invention provides a mortar composition comprising: an aggregate; and a cementitious composition as hereinbefore described. The mortar composition comprises an aggregate. The aggregate is typically a finely divided material. Sand is a particularly suitable aggregate for use in mortar compositions, as is well known in the art. The amount of aggregate present in the mortar composition may be any suitable amount, which may vary depending upon the use to be made of the mortar composition. The aggregate may be present in an amount, based on the amount of the mortar composition, of from 10% by weight, preferably from 15%, more preferably from 20%, still more preferably from 25%, more preferably still from 30%, especially from 35%, more especially from 40%, still more especially from 45% by weight. The aggregate may be present in an amount of up to 95% by weight, preferably up to 90%, more preferably up to 85%, still more preferably up to 80%. An amount of aggregate of from 10 to 90% by weight is suitable for many embodiments, preferably from 15 to 85%, more preferably from 20 to 80%, still more preferably from 30 to 80%, more preferably still from 40 to 80% by weight of the mortar composition. An amount of about 75% by weight is preferred for many embodiments. The amount of the cementitious composition present in the mortar composition may be any suitable amount, which may vary depending upon the use to be made of the mortar composition. The cementitious composition may be present in an amount, based on the amount of the mortar composition, of from 5% by weight, preferably from 7.5%, more preferably from 10%, still more preferably from 12.5%, more preferably still from 15%, especially from 17.5%, more especially from 20%, still more especially from 22.5% by weight. The cementitious composition may be present in an amount of up to 90% by weight, preferably up to 85%, more preferably up to 80%, still more preferably up to 75%, more preferably still up to 70%, especially up to 65%, more especially up to 60%, still more especially up to 55%, for example up to 50% by weight. An amount of cementitious composition of from 5 to 50% by weight is suitable for many embodiments, preferably from 10 to 40%, more preferably from 15 to 35%, still more preferably from 20 to 30% by weight of the mortar composition. An amount of about 25% by weight is preferred for many embodiments. The weight ratio of the aggregate to the cementitious composition in the mortar composition may be any suitable ratio, as determined, for example, by the intended use of the mortar composition. The weight ratio of the aggregate to the cementitious composition in the mortar composition may be from 10:1 to 1:10, preferably from 8:1 to 1:8, more preferably from 6:1 to 1:6. Preferably, the weight ratio of the aggregate to the cementitious composition in the mortar composition is from 10:1 to 1:2, more preferably from 10:1 to 1:1, still more preferably from 8:1 to 1:1, more preferably still from 6:1 to 1:1. A weight ratio of from 5:1 to 1:1 is suitable for many embodiments. In general, it is preferred that the aggregate is present in the mortar composition in excess of the amount of the cementitious composition. Examples of suitable weight ratios of aggregate and cementitious composition for particular end uses are as follows: Laying bricks: weight ratio of aggregate to cementitious composition of 4:1; Pointing: weight ratio of aggregate to cementitious composition of 3:1; External render: weight ratio of aggregate to cementitious composition of 3.5:1; Screed for flooring: weight ratio of aggregate to cementitious composition of 4:1; Application in chimneys: weight ratio of aggregate to cementitious composition of 5:1; Joints in paving: weight ratio of aggregate to cementitious composition of 3:1; and Construction of retaining walls: weight ratio of aggregate to cementitious composition of 3:1. In use, the mortar composition is combined with water and applied or used, after which the composition is allowed to cure. Any suitable amount of water may be combined with the mortar composition and suitable amounts will be known to the skilled person. Increasing the amount of water present can reduce the compressive strength of the final, cured composition. Reducing the amount of water, while still providing sufficient for complete curing of the composition, can increase the compressive strength of the final cured composition. These effects are known in the art. The amount of water that may be added to the mortar composition paste, based on the amount of the mortar composition, may be from 2% by weight, preferably from 3%, more preferably from 5%, still more preferably from 7.5%, more preferably still from 10%, especially from 12%. The amount of water that may be added to the mortar composition, based on the amount of the cement composition, may be up to 30% by weight, preferably up to 25%, more preferably up to 20%, still more preferably up to 15%. Water in an amount, based on the amount of cement composition, may in many embodiments be from 5 to 25% by weight, preferably from 7.5 to 20%, more preferably from 10 to 15%, still more preferably from 12 to 14% by weight. The mortar composition may further comprise one or more components, for example a component to modify the physical properties of the composition. Such components are known in the art and their use is known to the skilled person. For example, the mortar composition may further comprise one or more plasticiser. Plasticisers provide the composition with an improved the flow characteristics and increased flexibility before the composition cures. Plasticisers can allow the amount of water employed to be reduced. This in turn can act to increase the compressive strength of the composition once cured and / or improve resistance to degradation, for example from freezing temperatures. Suitable plasticisers are commercially available and include lignosulfonates, sulfonated synthetic polymers (naphthalene, or melamine, formaldehyde condensates), and polycarboxylates-ether (PCE) synthetic polymers. The mortar composition is allowed to cure after being applied or used. The mortar composition may be allowed to cure at ambient temperatures, that is without the addition of heat from an external source. Alternatively, the mortar composition may be cured at an elevated temperature, that is with heat added to the mortar composition from an external source. It is an advantage of the mortar composition that curing at ambient temperatures without the addition of heat from an external source is possible and the cured mortar exhibiting a high compressive strength. The time required for the mortar composition to cure may vary, for example depending upon the composition of the mortar. The time required for the mortar composition to fully cure may be from 5 days, for example 7 days, 10 days, 15 days, 20 days or longer. In many embodiments, the compressive strength of the mortar composition will increase as the composition cures. For example, the compressive strength may increase for a period of 28 days or longer. In a further aspect, the present invention provides a cured mortar prepared by combining the mortar composition hereinbefore described with water and allowing the resulting mixture to cure. In a further aspect, the present invention provides a concrete composition comprising: an aggregate; and a cementitious composition as hereinbefore described. The concrete composition comprises an aggregate. The aggregate is typically a divided material. The aggregate may comprise two or more different aggregate components. For example, the aggregate may comprise a finely divided material, such as sand. The aggregate may comprise a coarse, granular material, such as a coarse sand, gravel or crushed rock. A mixture of two or more granular materials may be used. In one preferred embodiment, the aggregate comprises a finely divided material, preferably sand, and a coarse aggregate material, preferably gravel or crushed rock. The amount of aggregate present in the concrete composition may be any suitable amount, which may vary depending upon the use to be made of the concrete composition. The aggregate may be present in an amount of from 10% by weight, preferably from 20%, more preferably from 30%, still more preferably from 40%, more preferably still from 50%, especially from 55%, more especially from 60%, still more especially from 65% by weight. The aggregate may be present in an amount of up to 95% by weight, preferably up to 90%, more preferably up to 85%, still more preferably up to about 80%. An amount of aggregate of from 10 to 90% by weight is suitable for many embodiments, preferably from 20 to 85%, more preferably from 40 to 80% by weight of the concrete composition. An amount of from about 60 to 85% by weight is preferred for many embodiments, with an amount of from 75 to 85% by weight being particularly suitable for many embodiments. The amount of the cementitious composition present in the concrete composition may be any suitable amount, which may vary depending upon the use to be made of the concrete composition. The cementitious composition may be present in an amount of from 5% by weight, preferably from 7.5%, more preferably from 10%, still more preferably from 12.5%, more preferably still from 15%, especially from 17.5%. The cementitious composition may be present in an amount of up to 90% by weight, preferably up to 85%, more preferably up to 80%, still more preferably up to 75%, more preferably still up to 70%, especially up to 65%, more especially up to 60%, still more especially up to 55%, for example up to 50% by weight. An amount of cementitious composition of from 5 to 50% by weight is suitable for many embodiments, preferably from 10 to 40%, more preferably from 15 to 30%, still more preferably from 15 to 25% by weight of the concrete composition. An amount of about 20% by weight is preferred for many embodiments. The weight ratio of the aggregate to the cementitious composition in the concrete composition may be any suitable ratio, as determined, for example, by the intended use of the concrete composition. The weight ratio of the aggregate to the cementitious composition in the concrete composition may be from 10:1 to 1:10, preferably from 8:1 to 1:8, more preferably from 6:1 to 1:6. Preferably, the weight ratio of the aggregate to the cementitious composition in the concrete composition is from 10:1 to 1:2, more preferably from 10:1 to 1:1, still more preferably from 8:1 to 1:1, more preferably still from 6:1 to 1:1. A weight ratio of from 5:1 to 1:1 is suitable for many embodiments, especially a weight ratio of from 3:1 to 5:1. In general, it is preferred that the aggregate is present in the concrete composition in excess of the amount of the cementitious composition. Examples of suitable weight ratios of aggregate and cementitious composition for particular grades of concrete are as follows. The ratios indicated are the ratios of cementitious composition : fine aggregate (for example sand): coarse aggregate (for example gravel): M5 1:5:10; M7.5 1:4:8; M10 1:3:6; M15 1:2:4; M20 1:1.5:3; and M25 1:1:2. In use, the concrete composition is combined with water and applied or used, after which the composition is allowed to cure. Any suitable amount of water may be combined with the concrete composition and suitable amounts will be known to the skilled person. Increasing the amount of water present can reduce the compressive strength of the final, cured composition. Reducing the amount of water, while still providing sufficient for complete curing of the composition, can increase the compressive strength of the final cured composition. These effects are known in the art. The amount of water that may be added to the concrete composition paste, based on the amount of the concrete composition, may be from 2% by weight, preferably from 3%, more preferably from 5%, still more preferably from 7.5%. The amount of water that may be added to the concrete composition, based on the amount of the concrete composition, may be up to 30% by weight, preferably up to 25%, more preferably up to 20%, still more preferably up to 15%. Water in an amount, based on the amount of cement composition, may in many embodiments be from 5 to 25% by weight, preferably from 7.5 to 20%, more preferably from 7.5 to 15%, still more preferably from 8 to 12% by weight. The concrete composition may further comprise one or more components, for example a component to modify the physical properties of the composition. Such components are known in the art and their use is known to the skilled person. For example, the mortar composition may further comprise one or more plasticiser, as discussed above with respect to the mortar compositions. Other components that may be added, as known in the art, include corrosion inhibitors, colouring agents, agents for increasing (retarding) or decreasing (accelerating) the curing time, agents to promote air entrainment, and agents to reduce shrinking. The concrete composition is allowed to cure after being applied or used. The concrete composition may be allowed to cure at ambient temperatures, that is without the addition of heat from an external source. Alternatively, the concrete composition may be cured at an elevated temperature, that is with heat added to the composition from an external source. It is an advantage of the concrete composition that curing at ambient temperatures without the addition of heat from an external source is possible and the cured concrete exhibiting a high compressive strength. The time required for the composition to cure may vary, for example depending upon the composition of the concrete. The time required for the concrete composition to fully cure may be from 5 days, for example 7 days, 10 days, 15 days, 20 days or longer. In many embodiments, the compressive strength of the concrete composition will increase as the composition cures. For example, the compressive strength may increase for a period of 28 days or longer. In a further aspect, the present invention provides a cured concrete prepared by combining the concrete composition hereinbefore described with water and allowing the resulting mixture to cure. Embodiments of the present invention will now be described, for illustrative purposes only, by way of the following working examples. Percentages indicated are weight percent, unless otherwise stated. Reference will be made to the accompanying figures, in which: Figure 1 is an XRD diffractogram of GGBS, OPC and ceramic tile powders; Figure 2 is a graph of the FT-IR spectra of GGBS, OPC and ceramic tile powders; Figure 3 is a graph of the particle size distributions of a porcelain tile powder; Figure 4 is a graph of the particle size distribution of a ceramic tile powder; Figure 5 shows SEM micrographs of the porcelain and ceramic tile powders of Figures 3 and 4; Figure 6 is a graph showing the results of compressive strength tests for OPC mortars; Figure 7 is a graph showing the results of compressive tests for OPC concrete compositions; Figure 8 is a graph showing the results of slump tests for OPC concrete compositions; Figure 9 is an XRD diffractogram of cement pastes; Figure 10 is a graph of the FT-IR spectra of cement pastes; and Figure 11 shows SEM micrographs of cement pastes. EXAMPLES A range of experiments were conducted as described in detail below. Unused, new ceramic and porcelain tiles were supplied by Paignton Tile Company Ltd, labelled as non-marketable materials due to damages. References in these examples to ‘ceramic’ (CER) are to ceramic tile materials that do not contain porcelain. Porcelain is identified separately as POR. Powders were produced by pre-crushing the tiles in a drum cement mixer for one hour with metal weights, followed by sieving of the debris to 600 microns. The sieved powder was then ball milled for 10 minutes in a Retsch PM100 ball mill at 300 rpm. Ordinary Portland Cement (OPC) powder was supplied by Tarmac and used as supplied. The oxide composition of the ceramic and porcelain powders was obtained by X-ray Fluorescence Spectroscopy (XRF) using a Rigaku SuperMini 200 Wavelength Dispersive XRF spectrometer. The powders were dried overnight at 80°C then calcined at 1050°C for 1 hour. The calcined sample was fused with lithium borate flux using a Vulcan Automatic Fusion Machine to produce glass bead. Quantitative data was obtained using an empirical application calibrated with 52 certified reference materials. 5 XRF results are shown in Table 1 below, along with the oxide composition of fly ash (sourced from Drax UK, reported for comparison purposes only). The (oxide) chemical composition of ceramic and porcelain was found to be broadly similar, apart from the CaO content, which was found to be >5% higher in ceramic than in porcelain. Other differences were measured in the range of about ±2%. io Table 1. Oxide composition and loss on ignition (LOI) in %wt of ceramic and porcelain powders from XRF analysis. Oxide Ceramic Porcelain Na2O 1.14 3.92 MgO 0.67 0.72 AI2O3 16.45 18.18 SiO2 66.34 68.39 P2O5 0.15 0.16 SO3 0.03 <0.01 K2O 2.25 1.84 CaO 7.26 1.23 TiO2 0.67 0.63 Mn2O3 0.03 0.03 Fe2O3 1.93 1.73 ZnO 0.40 0.15 SrO 0.02 0.04 ZrO2 0.51 0.36 BaO 0.12 0.14 LOI 0.6 0.9 The mineral composition of OPC, and the tile powders (TP) was determined using x-ray diffraction (XRD), using a Bruker D8 Advance diffractometer with a CuK 5 a, with a wavelength of 1.5418 A. The generator was adjusted to 40kV with a current of 40 mA and a goniometer speed of ~0.04° 29 / s over the range 10-70°8. The resulting XRD diffractograms are shown in Figure 1. The diffractograms show the expected peaks associated to the cement minerals in OPC (alite, belite, ferrite, gypsum, and aluminate species). The presence of amorphous materials in io TP was suggested by the broad hump of the baseline in the range 20-30° 20, which appears more pronounced in porcelain than in ceramic. The mineral composition of TP was predominantly quartz and mullite, with some presence of plagioclase feldspar, anorthite, and almandine. 15 Infrared spectroscopy characterisation of the tile powders was obtained through Fourier Transform Infrared Spectroscopy in the Attenuated Total Reflectance mode (ATR-FTIR). The test was carried out using a JASCO 4100 series FTIR spectrometer performing 16 scans per measurement across the range of 400-4000 cm-1 with a resolution of 2.0 cm-1. The FTIR spectra are shown in Figure 2. The interpretation of absorbance bands corresponding to vibrations of chemical bonds in specific compounds was performed based on available literature. The same equipment and settings were used to determine the infrared spectroscopy of the reaction products. Large peaks corresponding to Si-O-Si vibration could be observed in the materials, confirming the more crystalline nature of the silicates. A strong presence of calcium-based species was observed for OPC. The quartz distinctive peak was observed for the porcelain and ceramic powders. The grain size distribution of the tile powders (TP) was assessed using a Bettersizer S3 Plus device with water as a medium. The particle size distributions for porcelain tile powder and ceramic tile powder are shown in Figures 3 and 4 respectively. The size distribution for porcelain powder followed the expected trend, with a continuous and well-graded distribution, a D50 = 16 pm, and a large size D97 <70 pm, as shown in Figure 3. Unexpectedly, the ceramic powder showed a bi-modal distribution, with a substantial fraction (> 50%) of the powder having sub-micron size (D50 = 0.04 pm), whilst another fraction in the expected range centred around 15-20 pm, as shown in Figure 4. The test was repeated twice and gave very similar results. Visual appearance from SEM micrographs confirmed qualitatively the analysis, as shown in Figure 5. The sharp appearance of the surfaces of some of the powder grains indicates the vitreous (i.e., amorphous) nature of a fraction of the materials. Aggregate (sand and 10mm gravel) was supplied by Bradfords. Example 1 Tile Powder as an SCM in OPC-based cementitious compositions Experiments were conducted to examine the use of the ceramic and porcelain tile powders (TP) as supplementary cementitious materials (SCM) in 5 cementitious compositions containing Ordinary Portland Cement (OPC). In a first batch of experiments, a range of mortar mixes were prepared. The components used to prepare each of the mortar mixes are summarised in Table 2 below. Each mortar mix was formed from a mixture comprising Ordinary Portland Cement (OPC), sand and water. Porcelein tile powder (POR) and ceramic tile io powder (CER) were used as a substitute for a portion of the OPC, in the amounts indicated in Table 2. Examples 1Aand 1J employed OPC without substitution with tile powder and were used as comparative examples. 15 Table 2. Example No. Substitution (wt%) OPC (g) POR (g) CER (g) Sand (g) Water (g) 1A 0 500 0 0 1375 250 1B 10 450 50 0 1375 250 1C 20 400 100 0 1375 250 1D 30 350 150 0 1375 250 1E 10 450 0 50 1375 250 1F 20 400 0 100 1375 250 1G 30 350 0 150 1375 250 1H 20 400 40 60 1375 250 11 20 400 60 40 1375 250 1J 0 500 0 0 1375 230 1K 10 450 25 25 1375 230 1L 15 425 37.5 37.5 1375 230 1M 20 400 50 50 1375 230 In a second batch of experiments, a range of concrete mixes were prepared. The components used to prepare each of the concrete mixes are summarised in Table 3 below. Each concrete mix was formed from a mixture comprising Ordinary 5 Portland Cement (OPC), sand and water. Porcelein tile powder (POR) and ceramic tile powder (CER) were used as a substitute for a portion of the OPC, in the amounts indicated in Table 3. The quantity of water indicated in Table 3 refers to the total amount of water used in the mix, that is including the allowance for absorption of water by the aggregate. io Examples 1N and 1P employed OPC without substitution by tile powder and are for comparative purposes. 15 Table 3. Example No. Substitution (wt%) OPC (g) POR (g) CER (g) Sand (g) Gravel (g) Water (g) 1N 0 440 0 0 700 1050 220 10 10 396 44 0 700 1050 220 1P 0 400 0 0 700 1100 212 1Q 30 320 40 40 700 1100 212 The mortar and concrete samples of Examples 1A to 1Q were prepared and 5 cast in accordance with BS EN 206, BS EN 12390-1, and BS EN 12390-2. The appropriate quantities of dry material were weighed and placed in a clean, dry bowl. The dry material was then mixed ensuring lumps had been broken up to achieve a uniform consistency. The liquid components were weighed and added to the mix. The liquid was added to the dry material as it was being mixed. io Mortar mixes were prepared using a Quattro MXP004 planetary mixer. Concrete mixes were produced with a Creteangle PE / CL mixer. After mixing to a suitable texture the material was put into cube moulds: 50 mm cubes for mortar samples and 100 mm cube moulds for concrete. The moulds were clean and had a thin layer of lubricant applied to aid the process of de ls moulding. The filled moulds were vibrated on a Controls D0407B vibrating table to ensure the material filled the full volume of the mould. Once the samples had been suitably vibrated and flattened, these were wrapped in cling film. The samples were left at room temperature. The samples were demoulded approximately 24 hours later and re-wrapped in cling film. The resulting samples were kept at room temperature. In a third batch of experiments, a range of OPC pastes were prepared. The 5 components used to prepare each of the concrete mixes are summarised in Table 4 below. Each paste was formed from a mixture comprising Ordinary Portland Cement (OPC), sand and water. Porcelein tile powder (POR) and ceramic tile powder (CER) were used as a substitute for a portion of the OPC, in the amounts indicated in Table 4. io Example 1R employed OPC without substitution by tile powder and is for comparative purposes. Table 4 Example No. Substitution OPC (g) POR (g) CER (g) Water (ml) 1R 0% 5 0 0 2.5 1S 10% 4.5 0.5 0 2.5 1T 20% 4 1 0 2.5 1U 30% 3.5 1.5 0 2.5 1V 10% 4.5 0 0.5 2.5 1W 20% 4 0 1 2.5 1X 30% 3.5 0 1.5 2.5 1Y 20% 4 0.4 0.6 2.5 1Z 20% 4 0.6 0.4 2.5 Paste samples were mixed by hand from the components detailed in Table 4, cast into 4 cm3 silicon moulds and covered with cling film for 28 days curing at room temperature. Example 2 Compressive Tests on OPC-based mortar compositions Samples of the OPC-based mortar compositions of Examples 1Ato 1M were allowed to cure and their compressive strength was tested. Compressive strength was tested on cubes of the mortar compositions at 1, 7 and 28 days in accordance with BS EN 12390-3 and BS EN 12390-4. The tests were conducted using a load-controlled press Controls MCC 8 Testing System with the machine set to a loading rate of 0.6 MPa / s. Two cubes were tested for each mix and each curing age. The results are shown in Figure 6. Referring to the results shown in Figure 6, the use of neat ceramic powder as SCM resulted in the highest compressive strengths. Samples with 10% OPC substitution had compressive strength very similar to the cubes of the comparative examples. Increasing the substitution rate resulted in a decrease in the compressive strength. Compressive strength increases over time were notable for the samples with 20% ceramic TP substitution with improvement of compressive strength by nearly 84% at 7 days and nearly 40% at 28 days. This evidence indicates that longer curing times would have allowed the compressive strength of compositions with TPs to match the compressive strength of the comparative examples produced using OPC without substitution. Samples produced using neat porcelain tile powder as a substitute for OPC showed a general reduction of mean compressive strength in comparison with the comparative examples. The mix with 10% porcelain substitution performed similar to the comparative examples, as at 28 days the mean compressive strength of the comparative example was 28.7MPa and the 10% porcelain substitution mix strength was 26.6MPa (about 7% reduction). The reduction of water in the compositions had the effect of improving the strength of the samples. Whilst the compressive strength of the comparative examples exceeded 35 MPa at 28 days, the substitution of 10% OPC resulted in a strength reduction of less than 10%, and strengths higher than 30 MPa were recorded for samples with a substitution rate of 20%. While some reduction in compressive strength may be observed when substituting OPC with porcelain and ceramic tile powders, the resulting compositions are useful and mortars. Example 3 Flowability test on OPC-based mortar compositions Flow table tests were carried out on fresh mortar compositions of Examples 1J to 1M according to EN 1015-3:1999. The observed spread of the mortar compositions was within the range of 95 to 100 mm on the table after 10 shocks. The inclusion of significant amounts of tile powder did not affect the flowability of the composition. Example 4 Compressive Tests on OPC-based concrete compositions Samples of the OPC-based concrete compositions of Examples 1N to 1Q were allowed to cure and their compressive strength was tested. Compressive strength was tested on cubes of the concrete compositions at 1, 7 and 28 days in accordance with BS EN 12390-3 and BS EN 12390-4. The tests were conducted using a load-controlled press Controls MCC 8 Testing System with the machine set to a loading rate of 0.6 MPa / s. Two cubes were tested for each mix and each curing age. The results are shown in Figure 7. The results of the compressive strength tests show that, with a 10% substitution of ceramic-only powder, the compressive strength increased compared with the comparative example, with 28-day values of about 30 MPa. Compositions with lower water showed higher strength (> 35 MPa), and the substitution of 20% OPC with blended TPs delivered strength comparable to the comparative examples. The results indicate that the 10% substitution of OPC by tile powder is clearly suitable, with a 20% substitution rate also being achievable without significant reduction in compressive strength. Example 5 Slump Tests on OPC-based concrete compositions Samples of the OPC-based concrete compositions of Examples 1N to 1Q were tested to determine their tendency to slump. The slump tests were carried out on fresh concrete samples to determine the workability in accordance with BS EN 12350-2. The tests were carried out immediately after mixing. The compositions with reduced water (Examples 1P and 1Q) were rather stiff, and no slump fall was recorded. The compositions of Example 1N and 10 with standard water content exhibit satisfactory slump falling in class S4. The results are shown in Figure 8. Example 6 Characterisation of OPC-based cement pastes The properties of the cement pastes of Examples 1R to 1Z were analysed. In particular, the physical structure of the reacted pastes was analysed using x-ray diffraction. The analysis was conducted using a Bruker D8 Advance diffractometer with a CuK a, with a wavelength of 1.5418 A. The generator was adjusted to 40kV with a current of 40 mA and a goniometer speed of ~0.04° 29 / s over the range 1O-7O°0. Infrared spectroscopy characterisation of the cement pastes was obtained through Fourier Transform Infrared Spectroscopy in the Attenuated Total Reflectance mode (ATR-FTIR). The tests were carried out using a JASCO 4100 series FTIR spectrometer performing 16 scans per measurement across the range of 400-4000 cm-1 with a resolution of 2.0 cm-1. The cements pastes were further analysed using Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM / EDX). Figure 9 shows the XRD diffractograms for the cement pastes of Examples 1Rto 1Z. Referring to Figure 9, the diffractograms show that no new crystalline reaction product (i.e., identified by newly identified peaks) were observed when blending OPC with TPs. The main differences between neat OPC and blended pastes are the presence of quartz and the slight reduction of peaks corresponding to typical reaction products, such as Portlandite, calcium hydroxide, and CSH. Comparing the results shown in Figure 9 with the diffractogram of the raw TPs of Figure 1, it is noted that peaks previously attributed to anorthite (a Ca-based plagioclase feldspar), and almandine (an iron aluminosilicate) are not present in Figure 9. This is as result of these components being consumed during the reaction. This indicates a chemical contribution of the TPs to the reaction processes. It is also noted that abundant portlandite was available in the system after 28 days, thus indicating that strength increases using longer curing times can be achieved. Figure 10 shows the FT-IR spectra obtained for the pastes of Examples 1R to 1Z. Referring to Figure 10, there is shown a broad hump centred at about 3500 cm-1. This indicates the extent of hydration of the samples. The hump is more pronounced in the Comparative Example 1R and Examples 1V and 1W (10% and 20% ceramic substitution), indicating a more developed hydration and thus increased strength. It is further noted that the peak associated with the Si-0 vibrations for reacted pastes was found at wavenumbers lower than 1000 cm-1, whereas the same peak for raw ceramic and porcelain powder was detected at higher wavenumbers (see Figure 2). Shifts of such peaks to a lower wavenumber are typically associated with a change of microstructure and formation of the amorphous reaction products, in which SiO4 units are partially replaced by tetrahedral AIO4 units. Figure 11 shows SEM images of the cement pastes of Examples 1R, 1V, 1W and 1X. The scale of the images is in the range of from 50 to 100pm. The images in Figure 11 show overall homogeneous morphologies and elemental maps with expected distributions. It is noted that the images show a significant improvement in the presence of Al in the paste when ceramic TP was included in the composition. The experimental results show the following: It is possible to use powder obtained from waste and recycled ceramic tiles, including porcelain tiles, as a substitute for Ordinary Portland Cement (OPC). Substitution rates of 10% by weight resulted in little to no change in the compressive strength of the final material. Higher amounts of tile powder may also be used. The compressive strength of mortar and concrete compositions using tile powder as a substitute for OPC increased with longer curing times. Curing times in excess of 28 days may still provide increases in compressive strength. With a 10% by weight substitution of OPC with ceramic tile powder, the compressive strength of concrete compositions increased compared with the same concrete composition comprising OPC alone, with 28-day values of about 30 MPa being achieved. Compositions employing lower amounts of water showed higher strength (> 35 MPa), and the substitution of 20% OPC with tile powder, including a blend of ceramic and porcelain powder, exhibited a compressive strength comparable to the comparative example using OPC alone.

Claims

1. A cementitious composition comprising a cement composition, the cement composition comprising:Ordinary Portland Cement (OPC); anda finely divided ceramic material obtained from waste ceramic items.

2. The cementitious composition according to claim 1, wherein the cement composition comprises finely divided ceramic material derived from ceramic tiles.

3. The cementitious composition according to either of claims 1 or 2, wherein the cement composition comprises finely divided porcelain material.

4. The cementitious composition according to any preceding claim, wherein Ordinary Portland Cement (OPC) is present in an amount up to 95% by weight.

5. The cementitious composition according to any preceding claim, wherein the Ordinary Portland Cement (OPC) is Type I, Type IA, Type II, Type HA, Type Il(MH), Type ll(MH)A, Type III, Type IHA, Type IV, Type V or a mixture of two or more thereof.

6. The cementitious composition according to any preceding claim, wherein the finely divided ceramic material is present in an amount up to 30% by weight.

7. The cementitious composition according to any preceding claim, wherein the finely divided ceramic material has a Dso of up to 50 microns.

8. The cementitious composition according to any preceding claim, wherein the finely divided ceramic material has a bi-modal size distribution.

9. A cementitious paste comprising a cementitious composition according to any preceding claim and water.

10. A cured cementitious paste prepared by combining the cementitious composition according to any of claims 1 to 9 with water and allowing the resulting mixture to cure.

11. A mortar composition comprising:an aggregate; anda cementitious composition according to any of claims 1 to 9.

12. The mortar composition according to claim 11, wherein the weight ratio of the aggregate to the cementitious composition is from 8:1 to 1:

813. A cured mortar prepared by combining the mortar composition of either of claims 11 or 12 with water and allowing the resulting mixture to cure.

14. A concrete composition comprising:an aggregate; anda cementitious composition according to any of claims 1 to 9.

15. The concrete composition according to claim 14, wherein the weight ratio of the aggregate to the cementitious composition is from 8:1 to 1:8.

16. The concrete composition according to either of claims 14 or 15, wherein the composition when cured provides a concrete of grade M5, M7.5, M10, M15, M20, or M25.

17. A cured concrete prepared by combining the concrete composition according to any of claims 14 to 17 with water and allowing the resulting mixture to cure.

18. The cured concrete of claim 17, wherein the concrete is of grade M5, M7.5, M10, M15, M20, or M25.

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