A composite cement comprising carbonated olivine and a mineral-based carbonate

Abstract

The present disclosure relates to a composite cement comprising carbonated olivine and a mineral-based carbonate, in particular the present disclosure relates to a composite cement that comprises carbonated olivine and limestone. The present disclosure also relates to methods of forming a composite cement comprising carbonated olivine and a mineral-based carbonate, in particular the present disclosure relates to a method of forming a composite cement comprising carbonated olivine and limestone.

Description

[0001] Title: A composite cement comprising carbonated olivine

[0002] and a mineral-based carbonate

[0003] FIELD OF THE INVENTION

[0004] The present disclosure relates to a composite cement comprising carbonated olivine and a mineral-based carbonate, in particular the present disclosure relates to a composite cement that comprises carbonated olivine and limestone. The present disclosure also relates to methods of forming a composite cement comprising carbonated olivine and a mineral-based carbonate, in particular the present disclosure relates to a method of forming a composite cement comprising carbonated olivine and limestone.

[0005] BACKGROUND OF THE INVENTION

[0006] Cement based materials make up more than half of all the materials used by humankind worldwide and account for approximately eight percent of global carbon dioxide emissions. There is a need to reduce global carbon dioxide emissions associated with cement based materials.

[0007] An example of a cement based material is concrete. Concrete traditionally comprises cement, aggregates and water. Concrete is a fundamental building material and is a widely used man-made material. The cement in the concrete is the mineral glue that binds the different components in the concrete together.

[0008] Some types of cement, such as Ordinary Portland cement (also known as CEM I), contain a material called “cement clinker”. Cement clinker is usually present at a high amount in the cement. For example, Ordinary Portland cement contains more than 90 percent by weight of cement clinker. Cement clinker is made from an abundant raw material, such as clay, that is cheaply available almost worldwide. The cement clinker production process requires grinding and calcining up to a temperature of 1450 °C a mixture of limestone, clays and other minor components. The mixture is then mixed with 3 to 5 percent by weight of gypsum to form Ordinary Portland cement. The predominant source of carbon dioxide emissions in the production ofcement (and cement based materials generally) is the production of the cement clinker. For example, cement clinker production typically generates approximately 850 kg of carbon dioxide per ton of cement clinker produced. Typically, fossil fuel combustion and limestone decomposition in calcination during the production of the cement clinker are responsible for the majority, or all, of the carbon dioxide emissions.

[0009] Cement can be mixed with various supplements in different ratios and blends as established by the regulation UNI EN 197-1. In recent years, supplementary cementitious materials (SCMs) have been used in addition to or as a partial replacement of the cement clinker to reduce the carbon dioxide emissions associated with cement based materials. SCMs include materials such as ground granulated blast furnace slag (GGBFS), fly ash (FA), limestone filler, glass powder, natural pozzolana, calcined clays, silica fume, pumice, opaline rock, metakaolin and burnt shale. The use of SCMs is advantageous from an environmental and energy conservation viewpoint. By partly replacing cement clinker with SCMs, the environmental impact of cement based materials is improved. This is because the carbon dioxide emissions associated with cement clinker production, and thus cement based material production, is reduced. SCMs can also be formed as byproducts in industrial processes, and the reuse of SCMs further improves the energy efficiency of the cement based materials.

[0010] The use of SCMs in cement based materials is further advantageous because SCMs improve the durability, reduce the permeability and enhance the strength of cement based materials. For example, SCMs contribute to the properties of cement based materials through hydraulic or pozzolanic activity. The pozzolanic reaction is a chemical reaction that can take place between calcium and a silicate, such as calcium hydroxide and silica oxide, in the presence of water to form calcium silicate hydrate. Calcium silicate hydrate has favourable cementitious properties and can be the main binding phase in cement based materials. As a further example, SCMs also affect the chemical and physical properties of cement based materials. SCMs improve the physical properties of cement based materials by reducing the water absorption and apparent porosity, thus increasing the durability of the cement based materials.Unfortunately, the increasing demand for SCMs is misaligned with the availability of high quality SCMs (such as fly ash (FA) and ground granulated blast furnace slags (GGBFS)). To address this issue, limestone has been added to cement. Typically, limestone has been added to cement by inter-grinding with cement clinker.

[0011] Generally, when limestone is added to Ordinary Portland cement, limestone is added at up to 5 weight percent of the total weight of limestone and Ordinary Portland cement combined (according to current cement regulations) and when limestone is added to Portland-Limestone cement (PLC), limestone is added at up to 35 weight percent of the total weight of limestone and Portland-Limestone cement (PLC) combined (according to current cement regulations).

[0012] Advantageously, the addition of limestone improves the particle size distribution of the cement, enhances workability of the cement and reduces water demand of the cement. Further advantageously, when present at 5 weight percent or less of the total weight of the limestone and cement combined, the limestone can improve the strength and reduce the risk of segregation and bleeding in fresh concrete.

[0013] High limestone content in cement (for example, up to 15 weight percent of the total weight percent of the limestone and cement) is now common in Europe and North America. Such cements can match the performance of traditional cement in terms of strength and durability.

[0014] Limestone is often used alongside SCMs. Advantageously, the use of limestone optimises particle packing and the porous structure of the cement. Further advantageously, the use of limestone accelerates C3S hydration by providing a nucleation site and also stabilises ettringite.

[0015] However, limestone is a filler (not a SCM) and has limited pozzolanic behaviour. Further disadvantageously, the amount of limestone that can be used as a replacement to cement clinker is limited (i.e., no more than 15-20 weight percent replacement of the total weight of limestone and cement) before the mechanical properties of the cement and the resultant cement based material are impacted.There is therefore a continued need for finding new types of materials that can replace clinker and / or cement.

[0016] SUMMARY OF THE INVENTION

[0017] The present disclosure relates to a composite cement comprising carbonated olivine and a mineral-based carbonate, in particular the present disclosure relates to a composite cement that comprises carbonated olivine and limestone. The present disclosure also relates to methods of forming a composite cement comprising carbonated olivine and a mineral-based carbonate, in particular the present disclosure relates to a method of forming a composite cement comprising carbonated olivine and limestone.

[0018] The present invention is as set out in the following clauses:

[0019] 1. A composite cement comprising:

[0020] cement clinker;

[0021] carbonated olivine; and

[0022] a mineral-based carbonate.

[0023] 2. The composite cement of clause 1 , wherein the composite cement consists of: cement clinker;

[0024] carbonated olivine; and

[0025] a mineral-based carbonate.

[0026] 3. The composite cement of clause 1 or clause 2, wherein the mineral-based carbonate is: limestone; or, calcite; or, aragonite; or, vaterite; or, magnesium carbonate; or, dolomite; or, cement kiln dust; or, gypsum; or, a combination thereof.

[0027] 4. The composite cement of any one of clauses 1 to 3, wherein the mineral-based carbonate is limestone.

[0028] 5. The composite cement of any one of clauses 1 to 4, wherein the mineral-based carbonate comprises calcium oxide at: from 35 weight percent or greater; or, from 40weight percent or greater; or, from 44 weight percent or greater of the total weight of the mineral-based carbonate.

[0029] 6. The composite cement of any one of clauses 1 to 5, wherein the mineral-based carbonate comprises clay at: from 1.5 g per 100 g or less; or, from 1.4 g per 100 g or less; or, from 1.3 g per 100 g or less; or, from 1.2 g per 100 g of the mineral-based carbonate.

[0030] 7. The composite cement of any one of clauses 1 to 6, wherein the mineral-based carbonate has a total organic carbon (TOC) content (in terms of LL) of: 0.3 mass percentage or less; or, 0.25 mass percentage or less; or, 0.2 mass percentage or less of the total mass of the mineral-based carbonate.

[0031] 8. The composite cement of any one of clauses 1 to 7, wherein the mineral-based carbonate has a total organic carbon (TOC) content (in terms of L) of: 0.6 mass percentage or less; or, 0.55 mass percentage or less; or, 0.5 mass percentage or less of the total mass of the mineral-based carbonate.

[0032] 9. The composite cement of any one of clauses 1 to 8, wherein the ratio of carbonated olivine to mineral-based carbonate (carbonated olivine: mineral-based carbonate) is: from 6:0.1 to 1 :1 by weight; or, from 6:01 to 1 :1 by weight; or, from 3:0.2 to 2:0.2 by weight.

[0033] 10. The composite cement of any one of clauses 1 to 9, wherein the mineral-based carbonate and carbonated olivine are present as a component of the composite cement at a combined weight of: from 15 to 99 weight percent; or, from 20 to 99 weight percent; or, from 25 to 97 weight percent; or, from 30 to 95 weight percent of the total weight of the composite cement.

[0034] 11. The composite cement of any one of clauses 1 to 10, wherein the cement clinker is: Ordinary Portland cement clinker; or, sulfate resistant cement clinker; or, low heat cement clinker; or, white cement clinker; or, low-alkali cement clinker; or, belite calciumsulfoaluminate ternesite (BCT) cement clinker; or, a combination thereof.12. The composite cement of any one of clauses 1 to 11 , wherein the composite cement comprises the cement clinker at: from 1 to 95 weight percent; or, from 3 to 75 weight percent; or, from 5 to 70 weight percent of the total weight of the composite cement.

[0035] 13. The composite cement of any one of clauses 1 to 12, wherein the composite cement comprises, or consists of:

[0036] cement clinker at from 5 to 70 weight percent of the total weight of the composite cement; and

[0037] mineral-based carbonate and carbonated olivine at a combined weight of from 30 to 95 weight percent of the total weight of the composite cement.

[0038] 14. The composite cement of any one of clauses 1 to 13, wherein the composite cement comprises a further supplementary cementitious material (SCM).

[0039] 15. The composite cement of clause 14, wherein the further supplementary cementitious material (SCM) is: ground granulated blast furnace slag (GGBFS); or, fly ash (FA); or, burnt shale; or, glass powder; or silica fume; or, natural pozzolana; or, pumice; or, opaline rock; or, metakaolin; or, olivine; or; calcined clay; or, a combination thereof.

[0040] 16. The composite cement of clause 14 or clause 15, wherein the further supplementary cementitious material (SCM) is present at: from 1 to 30 weight percent; or, from 1.5 to 25 weight percent; or, from 2 to 20 weight percent of the total weight of the composite cement.

[0041] 17. The composite cement of any one of clauses 1 to 16, wherein the composite cement comprises a further filler.

[0042] 18. The composite cement of clause 17, wherein the composite cement comprises the further filler at: from less than 10 weight percent; or, from less than 5 weight percent; or, from less than 1 weight percent of the total weight of the composite cement.19. The composite cement of clause 17 or clause 18, wherein the further filler is gypsum.

[0043] 20. The composite cement of any one of clauses 1 to 19, wherein the composite cement comprises: admixtures; or, additives; or, a combination thereof.

[0044] 21. The composite cement of clause 20, wherein the admixtures are: water reducing agents; or, plasticizers; or, air entering agents; or, retarders; or, setting accelerators; or, rheology modifiers; or, a combination thereof.

[0045] 22. The composite cement of clause 20 or clause 21 , wherein the additives are: pigments; or, fibers; or, reinforcing elements; or, self-healing agents; or, a combination thereof.

[0046] 23. A method of preparing the composite cement of any one of clauses 1 to 22, the method comprising the steps of:

[0047] (a) providing cement clinker;

[0048] (b) providing a mineral-based carbonate;

[0049] (c) providing carbonated olivine; and

[0050] (d) combining the cement clinker, mineral-based carbonate and carbonated olivine.

[0051] 24. The method of clause 23, wherein the mineral-based carbonate is limestone.

[0052] 25. The method of clause 23 or clause 24, wherein the carbonated olivine is prepared by reacting olivine with carbon dioxide in the presence of water; optionally, (i) wherein the olivine is reacted with the carbon dioxide in the presence of water at a pressure of: from 10 to 300 bar; or, 25 to 250 bar; or, from 50 to 200 bar; and / or,

[0053] (ii) wherein the olivine is reacted with the carbon dioxide in the presence of water at a temperature of: from 50 to 350 °C; or, from 125 to 325 °C; or, from 150 to 300 °C; and / or,

[0054] (iii) wherein the olivine is reacted with the carbon dioxide in the presence of water at a pressure of from 50 to 200 bar and a temperature of 150 to 300 °C.26. The method of any one of clauses 23 to 25, wherein the method further comprises the steps of:

[0055] (e) providing admixtures and / or additives; and / or

[0056] (f) grinding the cement clinker, carbonated olivine and / or mineral-based carbonate.

[0057] 27. The method of clause 26, wherein the admixtures and / or additives are:

[0058] (i) combined with the olivine during the preparation of carbonated olivine; (ii) combined with the cement clinker, mineral-based carbonate and carbonated olivine in step (d);

[0059] (iii) combined with the cement clinker, mineral-based carbonate and carbonated olivine in step (f); and / or

[0060] (iv) combined independently from each other.

[0061] 28. A cement based material comprising the composite cement of any one of clauses 1 to 22.

[0062] 29. Use of the composite cement of any one of clauses 1 to 22 for improving carbon dioxide performance of cement and / or cement based materials.

[0063] The present invention is also as set out in the following clauses:

[0064] 1 A. A composite cement comprising:

[0065] cement clinker;

[0066] carbonated olivine; or, a mixture of carbonated olivine and olivine; and a mineral-based carbonate.

[0067] 2A. The composite cement of clause 1 A, wherein the composite cement consists of:

[0068] cement clinker;

[0069] carbonated olivine; or, a mixture of olivine and carbonated olivine; and a mineral-based carbonate.3A. The composite cement of clause 1 A or clause 2A, wherein the mineral-based carbonate is: limestone; or, calcite; or, aragonite; or, vaterite; or, magnesium carbonate; or, dolomite; or, cement kiln dust; or, gypsum; or, a combination thereof; and / or,

[0070] wherein the mineral-based carbonate is limestone; and / or,

[0071] wherein the mineral-based carbonate comprises calcium oxide at: from 35 weight percent or greater; or, from 40 weight percent or greater; or, from 44 weight percent or greater of the total weight of the mineral-based carbonate.

[0072] 4A. The composite cement of any one of clauses 1 A to 3A, wherein the mineralbased carbonate comprises clay at: from 1.5 g per 100 g or less; or, from 1.4 g per 100 g or less; or, from 1.3 g per 100 g or less; or, from 1.2 g per 100 g of the mineral-based carbonate; and / or,

[0073] wherein the mineral-based carbonate has a total organic carbon (TOC) content (in terms of LL) of: 0.3 mass percentage or less; or, 0.25 mass percentage or less; or, 0.2 mass percentage or less of the total mass of the mineral-based carbonate; and / or,

[0074] wherein the mineral-based carbonate has a total organic carbon (TOC) content (in terms of L) of: 0.6 mass percentage or less; or, 0.55 mass percentage or less; or, 0.5 mass percentage or less of the total mass of the mineral-based carbonate.

[0075] 5A. The composite cement of any one of clauses 1 A to 4A, wherein the ratio of carbonated olivine to mineral-based carbonate (carbonated olivine: mineral-based carbonate); or, the ratio of the mixture of olivine and carbonated olivine to mineralbased carbonate (mixture of olivine and carbonated olivine: mineral-based carbonate), is: from 6:0.1 to 1 :1 by weight; or, from 3:0.2 to 2:0.2 by weight; and / or,

[0076] wherein the mineral-based carbonate and carbonated olivine; or, the mineral-based carbonate and the mixture of olivine and carbonated olivine, are present as a component of the composite cement at a combined weight of: from 15 to 99 weightpercent; or, from 20 to 99 weight percent; or, from 25 to 97 weight percent; or, from 30 to 95 weight percent of the total weight of the composite cement; and / or,

[0077] wherein the cement clinker is: Ordinary Portland cement clinker; or, sulfate resistant cement clinker; or, low heat cement clinker; or, white cement clinker; or, low-alkali cement clinker; or, belite calciumsulfoaluminate ternesite (BCT) cement clinker; or, cement; or, a combination thereof.

[0078] 6A. The composite cement of any one of clauses 1 A to 5A, wherein the composite cement comprises the cement clinker at: from 1 to 95 weight percent; or, from 3 to 75 weight percent; or, from 5 to 70 weight percent of the total weight of the composite cement; and / or,

[0079] wherein the composite cement comprises, or consists of:

[0080] cement clinker at from 5 to 70 weight percent of the total weight of the composite cement; and

[0081] mineral-based carbonate and carbonated olivine at a combined weight of from 30 to 95 weight percent of the total weight of the composite cement; or, mineral-based carbonate and the mixture of olivine and carbonated olivine at a combined weight of from 30 to 95 weight percent of the total weight of the composite cement.

[0082] 7A. The composite cement of any one of clauses 1 A to 6A, wherein the composite cement comprises a further supplementary cementitious material (SCM); optionally,

[0083] wherein the further supplementary cementitious material (SCM) is: ground granulated blast furnace slag (GGBFS); or, fly ash (FA); or, burnt shale; or, glass powder; or silica fume; or, natural pozzolana; or, pumice; or, opaline rock; or, metakaolin; or, olivine; or; calcined clay; or, a combination thereof; and / or,

[0084] wherein the further supplementary cementitious material (SCM) is present at: from 1 to 30 weight percent; or, from 1.5 to 25 weight percent; or, from 2 to 20 weight percent of the total weight of the composite cement.8A. The composite cement of any one of clauses 1 A to 7A, wherein the composite cement comprises a further filler; optionally,

[0085] wherein the composite cement comprises the further filler at: from less than 10 weight percent; or, from less than 5 weight percent; or, from less than 1 weight percent of the total weight of the composite cement; and / or,

[0086] wherein the further filler is gypsum.

[0087] 9A. The composite cement of any one of clauses 1 A to 8A, wherein the composite cement comprises: admixtures; or, additives; or, a combination thereof; optionally,

[0088] wherein the admixtures are: water reducing agents; or, plasticizers; or, air entering agents; or, retarders; or, setting accelerators; or, rheology modifiers; or, a combination thereof; and / or,

[0089] wherein the additives are: pigments; or, fibers; or, reinforcing elements; or, self-healing agents; or, a combination thereof.

[0090] 10A. A method of preparing the composite cement of any one of clauses 1 A to 9A, the method comprising the steps of:

[0091] (a) providing cement clinker;

[0092] (b) providing a mineral-based carbonate;

[0093] (c) providing carbonated olivine; or, providing a mixture of olivine and carbonated olivine; and

[0094] (d) combining the cement clinker, mineral-based carbonate and carbonated olivine; or, combining the cement clinker, mineral-based carbonate and the mixture of olivine and carbonated olivine.

[0095] 11 A. The method of clause 10A, wherein the mineral-based carbonate is limestone.

[0096] 12A. The method of clause 10A or clause 11A, wherein the carbonated olivine is prepared by reacting olivine with carbon dioxide in the presence of water; optionally,(i) wherein the olivine is reacted with the carbon dioxide in the presence of water at a pressure of: from 10 to 300 bar; or, 25 to 250 bar; or, from 50 to 200 bar; and / or,

[0097] (ii) wherein the olivine is reacted with the carbon dioxide in the presence of water at a temperature of: from 50 to 350 °C; or, from 125 to 325 °C; or, from 150 to 300 °C; or, from 100 to 300 °C; or, from 100 to 250 °C; and / or,

[0098] (iii) wherein the olivine is reacted with the carbon dioxide in the presence of water at a pressure of from 50 to 200 bar and a temperature of 150 to 300 °C.

[0099] 13A. The method of any one of clauses 10A to 12A, wherein the carbonated olivine has a carbonation degree of: from 10 to 99 weight percent; or, from 40 to 99 weight percent; or, from 60 to 95 weight percent; or, from 75 to 90 weight percent of the total weight of the carbonated olivine based on the total amount of carbon dioxide released during thermal decomposition of the carbonated olivine as determined by thermogravimetric analysis (TGA).

[0100] 14A. The method of any one of clauses 10A to 13A, wherein the method further comprises the steps of:

[0101] (e) providing admixtures and / or additives; and / or

[0102] (f) grinding the cement clinker, carbonated olivine and / or mineral-based carbonate; or, grinding the cement clinker, the mixture of olivine and carbonated olivine, and / or mineral-based carbonate; optionally,

[0103] wherein the admixtures and / or additives are:

[0104] (i) combined with the olivine during the preparation of carbonated olivine; (ii) combined with the cement clinker, mineral-based carbonate and carbonated olivine in step (d); or, combined with the cement clinker, mineralbased carbonate and the mixture of olivine and carbonated olivine in step (d); (iii) combined with the cement clinker, mineral-based carbonate and carbonated olivine in step (f); or, combined with the cement clinker, mineralbased carbonate and the mixture of olivine and carbonated olivine in step (f); and / or

[0105] (iv) combined independently from each other.15A. A cement based material comprising the composite cement of any one of clauses 1 A to 9A.

[0106] 16A. Use of the composite cement of any one of clauses 1 A to 9A for improving carbon dioxide performance of cement and / or cement based materials while maintaining the mechanical properties, as compressive strength.

[0107] 17A. The use of the composite cement of clause 16A, wherein the cement exhibits an eco-efficiency greater than 1 , indicating improved environmental performance relative to cement based materials based on only Portland cement (CEM I).

[0108] DETAILED DESCRIPTION

[0109] The present disclosure relates to a composite cement comprising carbonated olivine and a mineral-based carbonate, in particular the present disclosure relates to a composite cement that comprises carbonated olivine and limestone. The present disclosure also relates to methods of forming a composite cement comprising carbonated olivine and a mineral-based carbonate, in particular the present disclosure relates to a method of forming a composite cement comprising carbonated olivine and limestone.

[0110] Embodiments of the invention are described below with reference to the accompanying drawings. The accompanying drawings illustrate various embodiments of systems, methods, and embodiments of various other aspects of the disclosure. Any person with ordinary skills in the art will appreciate that the illustrated element boundaries (e.g., boxes, groups of boxes, or other shapes) in the figures represent one example of the boundaries. It may be that in some examples one element may be designed as multiple elements or that multiple elements may be designed as one element. In some examples, an element shown as an internal component of one element may be implemented as an external component in another and vice versa. Furthermore, elements may not be drawn to scale. Nonlimiting and non-exhaustive descriptions are described with reference to the following drawings. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating principles.Embodiments of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings in which like numerals represent like elements throughout the several figures, and in which example embodiments are shown. Embodiments of the claims may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0111] The words "comprising," "having," "containing," and "including," and other forms thereof, are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. It must also be noted that as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Although any systems and methods similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present disclosure, the preferred systems and methods are now described.

[0112] Some of the terms used to describe the present invention are set out below:

[0113] “Mineral-based carbonate” refers to a mineral that comprises carbonate. Example mineral-based carbonates include, but are not limited to, limestone; or, calcite; or, aragonite; or, vaterite; or, magnesium carbonate; or, dolomite; or, cement kiln dust; or, gypsum; or, a combination thereof.

[0114] “Carbonated olivine” refers to a mix of magnesium carbonate defined by the chemical formula MgCOaand amorphous silica defined by the chemical formula SiO2. For example, carbonated olivine is a material obtained from the carbonation of natural olivine, as defined in the following description. During the carbonation, part of the magnesium in the natural olivine reacts with carbon dioxide to form magnesium carbonate (MgCOa) and part of the silica from the crystal structure in the natural olivine is released to form amorphous silica (SiC ). Carbonated olivine may contain residual unreacted olivine.“Carbonation” refers to a wet process of introducing carbon dioxide, within a high-pressure reactor, to transform magnesium and silica present in natural olivine into magnesium carbonate (MgCO3) and amorphous silica (SiO2), wherein the combination of the magnesium carbonate and amorphous silica is carbonated olivine. When the carbonation reaction does not reach full conversion, the resulting material contains unreacted olivine.

[0115] “Carbonation degree” refers to the proportion of a starting material (natural olivine) that is converted into carbonate-containing phases during reaction with carbon dioxide. The carbonation degree of olivine feedstock is determined by thermogravimetric analysis (TGA) based on the mass loss recorded between approximately 450 °C and 900 °C with release of carbon dioxide. Owing to the magnitude of the mass loss being directly proportional to the quantity of carbonate formed, the mass loss provides a quantitative measure of the extent of carbonation. For example, a carbonated olivine having a carbonation degree of 90 weight percent indicates that approximately 90 weight percent of the carbonated product is composed of magnesium carbonate (MgCO3) and amorphous silica (SiO2) and the remaining fraction consists of unreacted or partially reacted constituents such as magnesium orthosilicate (Mg2SiO4) and iron oxide (FeO and / or Fe2O3).

[0116] “Cement based materials” refers to a material that comprises cement and water. Cement based materials can further comprise aggregates (such as sand, gravel, crushed rocks, lightweight aggregates and / or a combination thereof), admixtures (such as water reducing agents, plasticizers, air entering agents, retarders, setting accelerators, rheology modifiers and / or a combination thereof), additives (such as pigments, fibers, fillers, reinforcing elements, self-healing agents and / or a combination thereof) and / or a combination thereof. Examples of cement based materials include, but are not limited to, concrete, mortars, plasters and known construction chemical products such as screed and / or tile adhesives.

[0117] “Cement clinker” refers to an intermediary product produced in the manufacture of cement. The cement clinker may be present in the form of “cement clinker” (i.e., not grounded). Alternatively or additionally, the cement clinker may be present in theform of “cement” (i.e., grounded and optionally mixed with gypsum; or, additives; or, admixtures; or, a combination thereof).

[0118] “Composite cement” refers to a cement that comprises a supplementary cementitious material. The composite cement may be used in cement based materials such as, but not limited to, concrete, mortars and known construction chemical products such as screed and / or tile adhesives.

[0119] “Olivine” refers to a magnesium iron silicate and is defined by the chemical formula: (Mg,Fe)2SiO4. The ratio of magnesium to iron varies between the two endmembers of the solid solution states for olivine: forsterite (Mg endmember: Mg2SiO4) and fayalite (Fe endmember: Fe2SiO4). Other names for olivine include chrysolite, serpentine, dunite, forsterite, magnesium iron silicate, magnesium iron solid solution silicate, forsterite-fayalite solid solution, nesosilicate, orthosilicate, ultramafic, alkali earth silicate, and, magnesium silicate.

[0120] “Portland cement” refers to a finely ground hydraulic binder made exclusively from Portland cement clinker and a small, controlled amount of calcium sulfate (such as gypsum) added only to regulate the setting time. In its 100% pure form, it contains no fillers, supplementary cementitious materials, pigments, or chemical additives, consisting solely of the characteristic clinker minerals — tricalcium silicate (C3S), dicalcium silicate (C2S), tricalcium aluminate (C3A), and tetracalcium aluminoferrite (C4AF) — formed by heating a precise mixture of limestone and clay-derived materials to clinkering temperature.

[0121] “Pozzolanic activity” refers to how quicky a mineral, such as a silicate (such as silica and / or alumina), reacts with calcium (Ca2+) or calcium hydroxide (Ca(OH)2) in the presence of water to form compounds having cementitious properties. The compounds having cementitious properties include, but are not limited to, calcium silicate hydrates, calcium aluminate hydrates and calcium silicate aluminate hydrates. Pozzolanic activity can be measured by any method known in the art, such as the “activity index test” or the “Frattini test”.“Supplementary cementitious materials” or “SCMs” refers to a material that partially replaces cement clinker in cement. SCMs can have pozzolanic properties. Materials with pozzolanic properties are characterised by a content of reactive silica and / or alumina which form strength providing calcium silicate hydrates, calcium hydrates and / or calcium silicate aluminate hydrates when water is added. SCMs includes both latent hydraulic and pozzolanic materials. However, unreactive or only slightly reactive materials, such as but not limited to limestone, are differentiated from SCMs. SCMs improve the durability and strength of the final product and reduce the permeability of the final product. Examples of SCMs include, but are not limited to, ground granulated blast furnace slag (GGBFS), fly ash (FA), burnt shale, glass powder, silica fume, natural pozzolana, calcined clays, pumice, opaline rock, metakaolin, olivine and / or carbonated olivine.

[0122] “Weight percent” refers to the percentage weight in grams of a component of a composition in every 100 grams of a composition. For example, if a composite cement contains carbonated olivine at 10 weight percent, then there is 10 g of carbonated olivine for every 100 g of the composite cement.

[0123] A composite cement

[0124] In one example of the present disclosure, the composite cement comprises cement clinker, carbonated olivine and a mineral-based carbonate. Alternatively, the composite cement comprises cement clinker, a mixture of olivine and carbonated olivine, and a mineral-based carbonate.

[0125] Preferably, the composite cement consists of cement clinker, carbonated olivine and a mineral-based carbonate. Alternatively, the composite cement consists of cement clinker, a mixture of olivine and carbonated olivine, and a mineral-based carbonate.

[0126] The mineral-based carbonate can be limestone; or, calcite; or, aragonite; or, vaterite; or, magnesium carbonate; or, dolomite; or, cement kiln dust; or, gypsum; or, a combination thereof. Preferably, the mineral-based carbonate is limestone.Preferably, the mineral-based carbonate comprises calcium oxide at: from 35 weight percent or greater; or, from 40 weight percent or greater; or, from 44 weight percent or greater of the total weight of the mineral-based carbonate. More preferably, the mineral-based carbonate is limestone and comprises calcium oxide at from 44 weight percent or greater of the total weight of the mineral-based carbonate.

[0127] Preferably, the calcium oxide content is measured as set out in EN 197-1.

[0128] Preferably, the mineral-based carbonate comprises clay at: from 1.5 g per 100 g or less; or, from 1.4 g per 100 g or less; or, from 1.3 g per 100 g or less; or, from 1.2 g per 100 g of the mineral-based carbonate. More preferably, the mineral-based carbonate is limestone and comprises clay at from 1.2 g per 100 g of the mineralbased carbonate. Preferably, the clay content is measured by the methylene blue test in accordance with EN 933-9, wherein the mineral-based carbonate was ground to a fineness of 5000 cm2 / g as measured as specific surface in accordance with MS 1062-6.

[0129] Preferably, the mineral-based carbonate has a total organic carbon (TOC) content (in terms of LL) of: 0.3 mass percentage or less; or, 0.25 mass percentage or less; or, 0.2 mass percentage or less of the total mass of the mineral-based carbonate. More preferably, the mineral-based carbonate is limestone and has a total organic carbon (TOC) content (in terms of LL) of 0.2 mass percentage or less of the total mass of the mineral-based carbonate. Preferably, the total organic content (TOC) is measured by the method set out in EN 13639.

[0130] Preferably, the mineral-based carbonate has a total organic carbon (TOC) content (in terms of L) of: 0.6 mass percentage or less; or, 0.55 mass percentage or less; or, 0.5 mass percentage or less of the total mass of the mineral-based carbonate. More preferably, the mineral-based carbonate is limestone and has a total organic carbon (TOC) content (in terms of L) of 0.5 mass percentage or less of the total mass of the mineral-based carbonate. Preferably, the total organic content (TOC) is measured by the method set out in EN 13639.

[0131] Preferably, the ratio of carbonated olivine to mineral-based carbonate (carbonated olivine: mineral-based carbonate) is: from 6:0.1 to 1 :1 by weight; or, from 3:0.2 to2:0.2 by weight. More preferably, the ratio of carbonated olivine to mineral-based carbonate (carbonated olivine: mineral-based carbonate) is from 3:0.2 to 2:0.2 by weight.

[0132] Preferably, the ratio of the mixture of olivine and carbonated olivine to mineral-based carbonate (mixture of olivine and carbonated olivine: mineral-based carbonate) is: from 6:0.1 to 1 :1 by weight; or, from 3:0.2 to 2:0.2 by weight. More preferably, the ratio of the mixture of olivine and carbonated olivine to mineral-based carbonate (mixture of olivine and carbonated olivine: mineral-based carbonate) is from 3:0.2 to 2:0.2 by weight.

[0133] Preferably, the carbonated olivine and mineral-based carbonate are present as a component of the composite cement at a combined weight of: 15 to 99 weight percent; or, from 20 to 99 weight percent; or, from 25 to 97 weight percent; or, from 30 to 95 weight percent of the total weight of the composite cement. More preferably, the carbonated olivine and mineral-based carbonate are present as a component of the composite cement at a combined weight of from 30 to 95 weight percent of the total weight of the composite cement.

[0134] Preferably, the mixture of olivine and carbonated olivine and the mineral-based carbonate are present as a component of the composite cement at a combined weight of: 15 to 99 weight percent; or, from 20 to 99 weight percent; or, from 25 to 97 weight percent; or, from 30 to 95 weight percent of the total weight of the composite cement. More preferably, the mixture of olivine and carbonated olivine and the mineral-based carbonate are present as a component of the composite cement at a combined weight of from 30 to 95 weight percent of the total weight of the composite cement.

[0135] Preferably, the cement clinker is: Ordinary Portland cement clinker; or, sulfate resistant cement clinker; or, low heat cement clinker; or, white cement clinker; or, low-alkali cement clinker; or, belite calciumsulfoaluminate ternesite (BCT) cement clinker; or, a combination thereof. More preferably, the cement clinker is Ordinary Portland cement clinker.Preferably, the composite cement comprises the cement clinker at: from 1 to 95 weight percent; or, from 3 to 75 weight percent; or, from 5 to 70 weight percent of the total weight of the composite cement. More preferably, the composite cement comprises the cement clinker at 5 to 70 weight percent of the total weight of the composite cement.

[0136] Preferably, the composite cement comprises the Ordinary Portland cement clinker at 5 to 70 weight percent of the total weight of the composite cement.

[0137] Preferably, the composite cement comprises, or consists of, cement clinker at from 5 to 70 weight percent of the total weight of the composite cement and a combination of mineral-based carbonate and carbonated olivine at from 30 to 95 weight percent of the total weight of the composite cement. More preferably, the composite cement comprises, or consists of, cement clinker at from 5 to 70 weight percent of the total weight of the composite cement and a combination of limestone and carbonated olivine at from 30 to 95 weight percent of the total weight of the composite cement

[0138] Preferably, the composite cement comprises, or consists of, cement clinker at from 5 to 70 weight percent of the total weight of the composite cement and a combination of mineral-based carbonate and the mixture of olivine and carbonated olivine at from 30 to 95 weight percent of the total weight of the composite cement. More preferably, the composite cement comprises, or consists of, cement clinker at from 5 to 70 weight percent of the total weight of the composite cement and a combination of limestone and the mixture of olivine and carbonated olivine at from 30 to 95 weight percent of the total weight of the composite cement.

[0139] The composite cement may comprise a further supplementary cementitious material (SCM).

[0140] Preferably, the further supplementary cementitious material (SCM) is: ground granulated blast furnace slag (GGBFS); or, fly ash (FA); or, burnt shale; or, glass powder; or silica fume; or, natural pozzolana; or, pumice; or, opaline rock; or, metakaolin; or, olivine; or; calcined clay; or, a combination thereof.The SCM may be a material with pozzolanic properties. The material with pozzolanic properties may be: ground granulated blast furnace slag (GGBFS); and / or, fly ash (FA); and / or, burnt shale; and / or, glass powder; and / or, silica fume; and / or, natural pozzolana; and / or, calcined clays; and / or, pumice; and / or, opaline rock; and / or, metakaolin; and / or, carbonated olivine; and / or, a combination thereof.

[0141] Preferably, the further supplementary cementitious material (SCM) is present at: from 1 to 30 weight percent; or, from 1.5 to 25 weight percent; or, from 2 to 20 weight percent of the total weight of the composite cement. More preferably, the further supplementary cementitious material (SCM) is present at from 2 to 20 weight percent of the total weight of the composite cement.

[0142] The composite cement can comprise a further filler.

[0143] Preferably, the composite cement comprises the further filler at: from less than 10 weight percent; or, from less than 8 weight percent; or, from less than 6 weight percent; or, from 2 to 10 weight percent; or, from 3 to 5 weight percent; or, at 5 weight percent of the total weight of the composite cement. More preferably, the composite cement comprises the further filler at 5 weight percent of the total weight of the composite cement.

[0144] Preferably, the further filler is gypsum.

[0145] Preferably, the composite cement comprises gypsum at 5 weight percent of the total weight of the composite cement.

[0146] The composite cement may comprise, and / or be mixed with: admixtures; or, additives; or, a combination thereof. The admixtures can be: water reducing agents; or, plasticizers; or, air entering agents; or, retarders; or, setting accelerators; or, rheology modifiers; or, a combination thereof. The additives can be: pigments; or, fibers; or, reinforcing elements; or, self-healing agents; or, a combination thereof.

[0147] Advantageously, by replacing cement clinker with a mineral-based carbonate, such as limestone, and carbonated olivine (or a mixture of olivine and carbonated olivine) in the production of cement based materials, a cement based material can be formedthat has a reduced carbon dioxide footprint and that also has comparable physical properties to a cement based material that does not comprise a mineral-based carbonate, such as limestone, and carbonated olivine (or a mixture of olivine and carbonated olivine).

[0148] Further advantageously, carbonated olivine is a mix of magnesium carbonate defined by the chemical formula MgCOaand amorphous silica defined by the chemical formula SiO2. The characteristic morphology of carbonated olivine has a positive impact on the rheology of cement allowing a reduction in plasticiser and / or filler demand (of the cement based material).

[0149] Further advantageously, the low water demand of carbonated olivine as a SCM does not negatively impact the workability of the composite cement. This advantageously reduces the water demand and thus improves the overall climate footprint of the resultant cement based material.

[0150] When used alone, limestone can be used to replace only a low amount of cement or cement clinker because limestone is a filler and not a SCM. Advantageously, by combining limestone with carbonated olivine (or a mixture of olivine and carbonated olivine), a high amount of cement or cement clinker replacement of the cement based material can be achieved, further reducing the carbon dioxide footprint of the resultant cement based material.

[0151] A method of making the composite cement

[0152] In one example of the present disclosure, the composite cement is made by a method that comprises the following steps:

[0153] (a) providing cement clinker;

[0154] (b) providing a mineral-based carbonate;

[0155] (c) providing carbonated olivine; or, providing a mixture of olivine and carbonated olivine; and

[0156] (d) combining the cement clinker, mineral-based carbonate and carbonated olivine; or, combining the cement clinker, mineral-based carbonate and the mixture of olivine and carbonated olivine.The mineral-based carbonate can be limestone; or, calcite; or, aragonite; or, vaterite; or, magnesium carbonate; or, dolomite; or, cement kiln dust; or, gypsum; or, a combination thereof. Preferably, the mineral-based carbonate is limestone.

[0157] Preferably, the method includes the additional step of grinding the cement clinker in step (a). Alternatively or additionally, the method includes the additional step of grinding the cement clinker, mineral-based carbonate and carbonated olivine as step (f). Alternatively or additionally, the method includes the additional step of grinding the cement clinker, mineral-based carbonate and the mixture of olivine and carbonated olivine as step (f).

[0158] Preferably, the method of making the composite cement further comprises the additional step of providing admixtures and / or additives as step (e).

[0159] Preferably, when the composite cement includes an admixture(s) and / or an additive(s), the admixture(s) and / or additive(s) are:

[0160] (i) combined with the olivine during the preparation of carbonated olivine; (ii) combined with the cement clinker, mineral-based carbonate and carbonated olivine in step (d); or, combined with the cement clinker, mineralbased carbonate and the mixture of olivine and carbonated olivine in step (d); (iii) combined with the cement clinker, mineral-based carbonate and carbonated olivine in step (f); or, combined with the cement clinker, mineralbased carbonate and the mixture of olivine and carbonated olivine in step (f); and / or

[0161] (iii) combined independently from each other.

[0162] A method of making carbonated olivine

[0163] In one example of the present disclosure, the composite cement comprises carbonated olivine. The carbonated olivine is prepared by reacting olivine with carbon dioxide in the presence of water. The reaction can be represented with the following equation:Mg2SiO4 + 2CO2 — 2MgC0a + S1O2

[0164] Preferably, the olivine is reacted with the carbon dioxide in the presence of water at a pressure of: from 10 to 300 bar; or, from 25 to 250 bar; or, from 50 to 200 bar.

[0165] Preferably, the olivine is reacted with the carbon dioxide in the presence of water at a temperature of: from 50 to 350 °C; or, from 125 to 325 °C; or, from 150 to 300 °C. Preferably, the olivine is reacted with the carbon dioxide in the presence of water at a temperature of: from 100 to 350 °C; or, from 100 to 300 °C; or, from 100 to 250 °C.

[0166] Preferably, the olivine is reacted with the carbon dioxide in the presence of water at a pressure of from 50 to 200 bar and a temperature of from 150 to 300 °C.

[0167] Preferably, the olivine is reacted with the carbon dioxide in the presence of water at a pressure of from 50 to 200 bar and a temperature of from 100 to 250 °C.

[0168] Preferably, the olivine carbonation has a carbonation degree of carbonated olivine of: from 10 to 100 weight percent; or, 40 to 99 weight percent; or, from 60 to 95 weight percent; or from 75 to 90 weight percent of the total weight of the carbonated olivine based on the total amount of carbon dioxide released during thermal decomposition of the carbonated product as determined by thermogravimetric analysis (TGA).

[0169] Preferably, the olivine is crushed and milled into fine particles prior to the reaction with the carbon dioxide in the presence of water. Preferably, the olivine is milled to a particle size of: from 700 mesh (20 pm) to 50 mesh (300 pm); or, from 600 mesh (23 pm) to 100 mesh (150 pm); or, from 500 mesh (25 pm) to 170 mesh (90 pm).

[0170] Preferably, the olivine is crushed to a particle size of from 500 mesh (25 pm) to 170 mesh (90 pm).

[0171] The olivine may be reacted with the carbon dioxide in the presence of water and a catalyst. The catalyst may be a chelating agent. The chelating agent may be: oxalic acid; and / or, citric acid; and / or, fulvic acid; and / or, ethylenediaminetetraacetic acid(EDTA); and / or, nitrilotriacetic acid (NTA); and / or, a combination thereof. Preferably, the chelating agent is oxalic acid.

[0172] The olivine may be reacted with the carbon dioxide in the presence of water and a salt. The salt may act as a catalyst. The salt may be: sodium bicarbonate; and / or, sodium carbonate; and / or, sodium chloride; and / or a combination thereof.

[0173] In one example of the present disclosure, the SCM carbonated olivine is prepared by a method set out in the paper titled “Kinetics and mechanism of mineral carbonation of olivine for CO2 sequestration” by F. Wang etal., Minerals Engineering 131 (2019), 185-197, which is hereby incorporated by reference in its entirety.

[0174] Cement based materials comprising the composite cement

[0175] In one example of the present disclosure, a cement based material comprises the composite cement.

[0176] Preferably, the cement based material is: concrete; or, mortar; or, plasters; or, screed; or, tile adhesives; or, a combination thereof.

[0177] EXAMPLES

[0178] The following are non-limiting examples that discuss, with reference to tables and figures, the advantages of the present invention. The examples set forth herein are merely examples among other possible examples.

[0179] Example 1: Determining the compressive strength of cement based materials wherein the cement is Cem I

[0180]

[0181] In this non-limiting example, the compressive strength of a cement based material (mortar) comprising the composite cement as presently claimed was determined. As a comparison, the compressive strength of comparable cement based materials (mortar) was also determined.Mortar was produced and tested following the EN 196-1 :2016 standard. According to EN 196-1 :2016, mortar prisms for compressive strength testing were produced with a mixture of 450 (± 2) g cement or blended cement, 225 (± 1 ) g of water and one bag of 1 ,350 (± 5) g CEN Standard Sand. Mortar workability and consistency was evaluated with a mini slump test and the support of a manual flow table (EN 1015-18:2002 standard).

[0182] The cement was partly replaced with limestone and carbonated olivine. The cement, limestone and carbonated olivine were combined and then water added to the combined materials to form the mortar.

[0183] The cement used was Ordinary Portland Cement Cem I 52.5 R and met the requirements set by the European standard EN 197-1 :2011 on cements. The cement contained Ordinary Portland Cement at from 95 to 100 weight percent by mass and minor additional constituents at from 0 to 5 weight % by mass of the total weight of the cement.

[0184] The limestone used was a commercial product (Ankerfill 125, Sibelco), with a particle size of less than 0.125 mm, comprising calcium carbonate at 90 weight percent or greater of the total weight of the limestone. The limestone was certified according to the European standard EN 13043.

[0185] The carbonated olivine was produced via a wet process using a high pressure reactor. The process was performed using a carbon dioxide purity of 99.7 percent for four hours at 200 °C and 180 bar in the presence of sodium bicarbonate (NaHCOa). The starting material (olivine) had a magnesium oxide (MgO) content of 49.3 weight percent, a silica (SiC ) content of 41.6 weight percent and an iron oxide (FeO) content of 7.6 weight percent of the total weight of the starting material (olivine) measured by X-ray fluorescence (XRF) (Axios, Malvern Panalytical). The starting material (olivine) had an olivine content of 89.4 weight percent of the total weight of the starting material (olivine) measured by XRD (Bruker D2 Phaser instrument). The starting material (olivine) had a D50 of 7pm (measured by laser diffraction, Sympatec Helos). The starting material (olivine) was reacted with the carbon dioxide. The achieved product had a conversion rate (carbonation degree) of 90 weight percent ofthe total weight of the carbonated olivine. .The carbonated olivine was a mix characterised by a magnesium carbonate (MgCO3) content of 60 weight percent and an amorphous silica (SiO2) content of 28.6 weight percent of the total weight of the carbonated olivine measured by XRD (Bruker D2 phaser instrument). The remaining part of the carbonated olivine included unreacted materials (such as olivine, and accessory minerals). The carbonated olivine had a D50 of 15.96 pm measured by laser diffraction.

[0186] The carbonation degree was calculated based on mass loss determined by Thermogravimetric analysis (TGA-Mettler Toledo TGA / DSC 3+) in the temperature range 450 °C to 900 °C. In this temperature range, magnesium carbonate in the solid carbonated product decomposes and carbon dioxide was released.

[0187] 2MgCOs + SiO2 -> 2MgO+ SiO2 + 2CO2

[0188] The release of carbon dioxide from the solid carbonated product resulted in a loss in mass of the solid material. The magnitude of the mass loss was directly proportional to the amount of carbonate formed, thereby providing a quantitative measure of the extent of carbonation.

[0189] The cement, limestone and carbonated olivine were used as a dry powder, wherein the moisture content for the limestone and the carbonated olivine was below 0.2 by weight the total weight of the limestone and carbonated olivine (as measured with a thermogravimetric analysis performed up to 200 °C).

[0190] Mineralogical measurements were performed with XRD analysis with quantification of the Rietveld method.

[0191] The composition of five different cement based materials (mortar) and the measured compressive strength (CS) after seven and twenty-eight days is shown in Table 1. The composition is shown relative to the amount of cement, limestone and carbonated olivine (without the standard sand).The reference (Frefl) is a mortar in which the binder consists of 100 weight percent Ordinary Portland Cement Cem I 52.5 R containing 5 weight percent gypsum of the total weight of the cement.

[0192] Table 1 : The composition of five different cement based materials (mortar) and the measured compressive strength (CS) after seven and twenty-eight days. The amount of each component is as a weight percentage of the total weight of the cement based material (mortar).

[0193] Component Frefl F1 F2 F3 F4

[0194] Cem 1 100 70 70 70 70 Limestone NA NA 30 7 10 Carbonated NA 30 NA 23 20 olivine

[0195] CS 7 days 56.5 41.3 35.8 43.4 44.1 (MPa)

[0196] CS 28 days 64.3 59.0 45.1 59.5 56.3

[0197] (MPa)

[0198]

[0199] The partial substitution of cement with carbonated olivine provides good results in terms of mechanical properties of the mortar at seven and twenty-eight days. When limestone is used alone at the same replacement level, the mechanical performance of the mortar drops. However, despite the lower contribution from limestone to the mechanical performance of the mortar, when limestone is used to partially replace the carbonated olivine, the mechanical strength of the mortar is increased at seven and twenty-eight days.

[0200] Example 2: Determining the compressive strength of cement based materials wherein the cement is Cem II

[0201]

[0202] In this non-limiting example, the compressive strength of a cement based material (mortar) comprising the composite cement as presently claimed was determined. As a comparison, the compressive strength of comparable cement based materials (mortar) was also determined.Mortar was produced and tested following the EN 196-1 standard. According to EN 196-1 , mortar prisms for compressive strength testing were produced with a mixture of 450 (± 2) g cement or blended cement, 225 (± 1) g of water and one bag of 1 ,350 (± 5) g CEN Standard Sand. Mortar workability and consistency was evaluated with a mini slump test and the support of a manual flow table (EN 1015 standard).

[0203] The cement was partly replaced with limestone and carbonated olivine. The cement, limestone and carbonated olivine were combined and then water added to the combined materials to form the mortar.

[0204] The cement used was Ordinary Portland Cement Cem IIA / LL 42.5N and met the requirements set by the European standard EN 197-1 on cements. The cement contained Ordinary Portland Cement at from 80 to 94 weight percent by mass and limestone at from 6 to 20 weight % by mass of the total weight of the cement.

[0205] The limestone used was a commercial product comprising calcium carbonate at 90 weight percent or greater of the total weight of the limestone. The limestone was certified according to the European standard EN 13043.

[0206] The carbonated olivine was produced via the method set out in Example 1.

[0207] The cement, limestone and carbonated olivine were used as a dry powder, wherein the moisture content for the limestone and the carbonated olivine was below 0.2 by weight the total weight of the limestone and carbonated olivine (as measured with a thermogravimetric analysis performed up to 200 °C).

[0208] Mineralogical measurements were performed with XRD analysis with quantification of the Rietveld method.

[0209] The composition of five different cement based materials (mortar) and the measured compressive strength (CS) after twenty-eight days is shown in Table 2. The composition is shown relative to the amount of cement, limestone and carbonated olivine (without the standard sand).The reference (Fref2) is a mortar in which the binder consists of 100 weight percent Ordinary Portland Cement Cem IIA / LL.

[0210] Table 2: The composition of two different cement based materials (mortar) and the measured compressive strength (CS) after twenty-eight days. The amount of each component is as weight percentage of the total weight of the cement based material (mortar).

[0211] Component Fref2 Fa

[0212] Cem IIA / LL 100 80

[0213] Carbonated olivine NA 20

[0214] CS 28 days 43.5 44.3

[0215] (MPa)

[0216]

[0217] The partial substitution of a blended cement with limestone with a carbonated olivine leads to a slight improvement of the mechanical properties of the mortar. This is because of the high reactivity of the carbonated olivine.

[0218] Examule 3: Measurement of the global warming potential of the cement based materials of Example 1 and a cement based material made from cement (only)

[0219] In this non-limiting example, the global warming potential (GWP) of the cement based materials Frefl and F1-F4 of Example 1 and Fref2 and Fa of Example 2 was measured.

[0220] The carbonation process may have a global warming potential associated with energy and material inputs. The resulting carbonated olivine exhibits a GWP in the range of -0.15 to -0.40 KgCO2 / Kg. In a specific example, the carbonated olivine has a GWP of -0.30 KgCO2 / Kg.

[0221] The value was calculated from considering the step of production (quarrying and crushing), shipping (from Norway to France), slurry preparation and handling (milling,mixing and preheating), reaction (heating), carbon dioxide preparation (carbon dioxide separation and compression) and post-processing (filtration and drying). A conversion rate of 90 percent from a starting olivine material that comprises 90 weight percent of the total weight of the starting olivine material is olivine (wherein 93 weight percent of the total weight of the starting olivine material is forsterite and 7 weight percent of the total weight of the starting olivine material is fayalite).

[0222] The GWP of Cem I, limestone and Cem II was determined from ICE Database V3.0 2019.

[0223] The GWP of each material present in the cement based materials (mortar) is set out in Table 3.

[0224] Table 3 The GWP of each material present in the cement based materials (mortar).

[0225] Component GWP (kgCO2 / kg)

[0226] Cem 1 0.912

[0227] Cem IIA / LL 0.799

[0228] Limestone 0.0157

[0229] Carbonated olivine -0.3

[0230]

[0231] The GWP of each cement based material is set out in Table 4.

[0232] Table 4: The GWP of each cement based material.

[0233] Component Frefl F1 F2 F3 F4 Fref2 Fa Cem 1 100 70 70 70 70 NA NA Limestone NA NA 30 7 10 NA NA Cem IIA / LL NA NA NA NA NA 100 80 Carbonated NA 30 NA 23 20 NA 20 olivine

[0234] GWP total 0.912 0.548 0.643 0.570 0.579 0.799 0.579 (kgCO2 / kg)

[0235]

[0236] As shown in Table 4, owing to the low GWP contribution of the limestone and the negative GWP contribution of the carbonated olivine, the cement based materials that comprise these replacements have a low carbon footprint (up to 40 % lower than cement based materials that do not contain the replacement materials). At the same time, the mechanical strength of the cement based material is the same or improved.

[0237] To enable a performance-based comparison between the cement based materials set out in Tables 2 and 4, two environmental-mechanical indicators were calculated:

[0238] (1) Strength-Normalized GWP ( )

[0239] GWP (kg CO2e per kg cement based material)

[0240] =fc (MPa)

[0241] Wherein fcis the compressive strength of the material and a lower indicates a more eco-efficient cement based materials.

[0242] (2) Relative Eco-Efficiency vs Reference

[0243] Q / c / / c, ref)

[0244] Eco-efficiency ratio =

[0245] (GWP / GWPref)

[0246] Wherein this ratio is dimensionless.

[0247] Values >1 indicate better performance per unit environmental burden compared to traditional CEM I.

[0248] The eco-efficiency index used herein is consistent with established

[0249] performance-based indicators such as strength-normalized GWP commonly applied in cement based material efficiency analysis.

[0250] The results are shown in Table 5. The environmental performances presented in Table 5 were calculated based on the mechanical results reported in examples 1 and 2 and the GWP values reported in example 3.Table 5: Environmental performance of the different cement based materials containing carbonated olivine and limestone in different amounts.

[0251] <p = GWP / Strength Eco-Efficiency Ratio vs Cement based material

[0252] (kg CO2 / (kg MPa)) Fret

[0253] Frefl 0.0142 1.00

[0254] F1 0.0093 1.53

[0255] F2 0.0143 0.99

[0256] F3 0.0096 0.48

[0257] F4 0.0103 1.38

[0258] Fref2 0.0184 1.00

[0259] Fa 0.0131 1.41

[0260]

[0261] The data in Table 5 shows that the cement based materials formulated with carbonated olivine (F1 , F3, F4, Fa) exhibited substantially improved eco-efficiency relative to the CEM reference cement based materials (Frefl , Fref2). Specifically, these mixes showed 38-53% lower strength-normalized GWP, demonstrating that they deliver significantly more compressive strength per unit CO2e emitted.

[0262] F2 achieved a reduced GWP but exhibited a proportional loss in compressive strength. As a result, the value for F2 was comparable to the reference cement based material, and its eco-efficiency ratio remained below unity, indicating no net gain in environmental efficiency.

[0263] The results demonstrate that the incorporation of carbonated olivine into blended cements provides a dual environmental and mechanical advantage, exceeding the benefits of clinker reduction alone. While any SCM decreases the clinker factor and thus lowers the GWP, the performance of carbonated olivine is particularly significant because it is inherently CO2-negative. This means that the addition of carbonated olivine not only prevents additional emissions but also introduces embodied carbon sequestration, contributing to a substantial reduction in the overall binder-level (cement based material- level) GWP even in the presence of other SCMs such as limestone.In parallel, the high pozzolanic reactivity of carbonated olivine contributes meaningfully to strength development. Despite the reduced clinker content, cement based materials containing carbonated olivine (F1, F3, F4, Fa) maintained high 28-day mechanical performance, outperforming what would be expected from clinker dilution alone. This behaviour contrasts with the limestone blend (F2), which, although effective in lowering GWP, experienced a proportionally larger decline in strength, leading to no overall gain in eco-efficiency.

[0264] The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilized for realizing the invention in diverse forms thereof.

[0265] Although certain example aspects of the invention have been described, the scope of the appended claims is not intended to be limited solely to these examples.

Claims

1. CLAIMS1. A composite cement comprising:cement clinker;carbonated olivine; or, a mixture of carbonated olivine and olivine; and a mineral-based carbonate.

2. The composite cement of claim 1 , wherein the composite cement consists of: cement clinker;carbonated olivine; or, a mixture of olivine and carbonated olivine; and a mineral-based carbonate.

3. The composite cement of claim 1 or claim 2, wherein the mineral-based carbonate is: limestone; or, calcite; or, aragonite; or, vaterite; or, magnesium carbonate; or, dolomite; or, cement kiln dust; or, gypsum; or, a combination thereof; and / or,wherein the mineral-based carbonate is limestone; and / or,wherein the mineral-based carbonate comprises calcium oxide at: from 35 weight percent or greater; or, from 40 weight percent or greater; or, from 44 weight percent or greater of the total weight of the mineral-based carbonate.

4. The composite cement of any one of claims 1 to 3, wherein the mineral-based carbonate comprises clay at: from 1.5 g per 100 g or less; or, from 1.4 g per 100 g or less; or, from 1.3 g per 100 g or less; or, from 1.2 g per 100 g of the mineral-based carbonate; and / or,wherein the mineral-based carbonate has a total organic carbon (TOC) content (in terms of LL) of: 0.3 mass percentage or less; or, 0.25 mass percentage or less; or, 0.2 mass percentage or less of the total mass of the mineral-based carbonate;and / or,wherein the mineral-based carbonate has a total organic carbon (TOC) content (in terms of L) of: 0.6 mass percentage or less; or, 0.55 mass percentage or less; or, 0.5 mass percentage or less of the total mass of the mineral-based carbonate.

5. The composite cement of any one of claims 1 to 4, wherein the ratio of carbonated olivine to mineral-based carbonate (carbonated olivine: mineral-based carbonate); or, the ratio of the mixture of olivine and carbonated olivine to mineral-based carbonate (mixture of olivine and carbonated olivine: mineral-based carbonate), is: from 6:0.1 to 1 :1 by weight; or, from 3:0.2 to 2:0.2 by weight; and / or,wherein the mineral-based carbonate and carbonated olivine; or, the mineral-based carbonate and the mixture of olivine and carbonated olivine, are present as a component of the composite cement at a combined weight of: from 15 to 99 weight percent; or, from 20 to 99 weight percent; or, from 25 to 97 weight percent; or, from 30 to 95 weight percent of the total weight of the composite cement; and / or,wherein the cement clinker is: Ordinary Portland cement clinker; or, sulfate resistant cement clinker; or, low heat cement clinker; or, white cement clinker; or, low-alkali cement clinker; or, belite calciumsulfoaluminate ternesite (BCT) cement clinker; or, cement; or, a combination thereof.

6. The composite cement of any one of claims 1 to 5, wherein the composite cement comprises the cement clinker at: from 1 to 95 weight percent; or, from 3 to 75 weight percent; or, from 5 to 70 weight percent of the total weight of the composite cement; and / or,wherein the composite cement comprises, or consists of:cement clinker at from 5 to 70 weight percent of the total weight of the composite cement; andmineral-based carbonate and carbonated olivine at a combined weight of from 30 to 95 weight percent of the total weight of the composite cement; or, mineral-based carbonate and the mixture of olivine and carbonated olivine at a combined weight of from 30 to 95 weight percent of the total weight of the composite cement.

7. The composite cement of any one of claims 1 to 6, wherein the composite cement comprises a further supplementary cementitious material (SCM); optionally,wherein the further supplementary cementitious material (SCM) is: ground granulated blast furnace slag (GGBFS); or, fly ash (FA); or, burnt shale; or, glass powder; or silica fume; or, natural pozzolana; or, pumice; or, opaline rock; or, metakaolin; or, olivine; or; calcined clay; or, a combination thereof; and / or,wherein the further supplementary cementitious material (SCM) is present at: from 1 to 30 weight percent; or, from 1.5 to 25 weight percent; or, from 2 to 20 weight percent of the total weight of the composite cement.

8. The composite cement of any one of claims 1 to 7, wherein the composite cement comprises a further filler; optionally,wherein the composite cement comprises the further filler at: from less than 10 weight percent; or, from less than 5 weight percent; or, from less than 1 weight percent of the total weight of the composite cement; and / or,wherein the further filler is gypsum.

9. The composite cement of any one of claims 1 to 8, wherein the composite cement comprises: admixtures; or, additives; or, a combination thereof; optionally,wherein the admixtures are: water reducing agents; or, plasticizers; or, air entering agents; or, retarders; or, setting accelerators; or, rheology modifiers; or, a combination thereof; and / or,wherein the additives are: pigments; or, fibers; or, reinforcing elements; or, self-healing agents; or, a combination thereof.

10. A method of preparing the composite cement of any one of claims 1 to 9, the method comprising the steps of:(a) providing cement clinker;(b) providing a mineral-based carbonate;(c) providing carbonated olivine; or, providing a mixture of olivine and carbonated olivine; and(d) combining the cement clinker, mineral-based carbonate and carbonated olivine; or, combining the cement clinker, mineral-based carbonate and the mixture of olivine and carbonated olivine.

11. The method of claim 10, wherein the mineral-based carbonate is limestone.

12. The method of claim 10 or claim 11 , wherein the carbonated olivine is prepared by reacting olivine with carbon dioxide in the presence of water; optionally,(i) wherein the olivine is reacted with the carbon dioxide in the presence of water at a pressure of: from 10 to 300 bar; or, 25 to 250 bar; or, from 50 to 200 bar; and / or,(ii) wherein the olivine is reacted with the carbon dioxide in the presence of water at a temperature of: from 50 to 350 °C; or, from 125 to 325 °C; or, from 150 to 300 °C; or, from 100 to 300 °C; or, from 100 to 250 °C; and / or,(iii) wherein the olivine is reacted with the carbon dioxide in the presence of water at a pressure of from 50 to 200 bar and a temperature of 150 to 300 °C.

13. The method of any one of claims 10 to 12, wherein the carbonated olivine has a carbonation degree of: from 10 to 99 weight percent; or, from 40 to 99 weight percent; or, from 60 to 95 weight percent; or, from 75 to 90 weight percent of the total weight of the carbonated olivine based on the total amount of carbon dioxide released during thermal decomposition of the carbonated olivine as determined by thermogravimetric analysis (TGA).

14. The method of any one of claims 10 to 13, wherein the method further comprises the steps of:(e) providing admixtures and / or additives; and / or(f) grinding the cement clinker, carbonated olivine and / or mineral-based carbonate; or, grinding the cement clinker, the mixture of olivine and carbonated olivine, and / or mineral-based carbonate; optionally,wherein the admixtures and / or additives are:(i) combined with the olivine during the preparation of carbonated olivine; (ii) combined with the cement clinker, mineral-based carbonate and carbonated olivine in step (d); or, combined with the cement clinker, mineralbased carbonate and the mixture of olivine and carbonated olivine in step (d); (iii) combined with the cement clinker, mineral-based carbonate and carbonated olivine in step (f); or, combined with the cement clinker, mineralbased carbonate and the mixture of olivine and carbonated olivine in step (f); and / or(iv) combined independently from each other.

15. A cement based material comprising the composite cement of any one of claims 1 to 9.

16. Use of the composite cement of any one of claims 1 to 9 for improving carbon dioxide performance of cement and / or cement based materials while maintaining the mechanical properties, as compressive strength.

17. The use of the composite cement of claim 16, wherein the cement exhibits an eco-efficiency greater than 1 , indicating improved environmental performance relative to cement based materials based on only Portland cement (CEM I).

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