process

Abstract

The present invention relates to a process for the manufacture of a granulated and glassy blast furnace slag analogue. Such granulated blast furnace slag analogue can subsequently be ground to produce a ground granulated blast furnace slag analogue. Such materials are suitable for use as supplementary cementitious materials.

Description

[0001] PROCESS

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a process for the manufacture of a granulated and glassy blast furnace slag analogue. Such granulated blastfurnace slag analogue can subsequently be ground to produce a ground granulated blast furnace slag analogue. Such materials are suitable for use as supplementary cementitious materials.

[0004] BACKGROUND

[0005] Ground granulated blast furnace slag (GGBFS) is a common supplementary cementitious materials (SCM) produced as a by-product of the iron industry and coal power plants. Blast furnace slags are being fully utilized in cements and are a key ingredient of resistant blends. Concretes exposed to aggressive environments (marine, sewers) require the use of SCM for durability. Today, SCMs are also the main means of reducing concrete’s carbon footprint, as these low carbon materials can replace Portland cement one to one, 70-90% in the case of GGBFS. In a net-zero future, coal power and blast furnaces will be retired, thus the production of blast furnace slag will reduce just as demand increases.

[0006] The growing demand for a dwindling supply of SCM both to reduce CO2 emissions from cement production and to improve durability will make the production of resistant concrete more difficult, and will impair the formulation of a range of specialist cement blends that are crucial for the construction industry - in particular to build offshore wind turbines, sewers, bridges, foundations, and any construction exposed to marine environments. Routes to lower concrete’s environmental impact without diminishing its value to society are crucial to enable the transition to a low-carbon society. Producing GGBFS analogues economically in a low emissions process is therefore a critical factor in building a sustainable, prosperous net-zero society and is currently an engineering challenge.

[0007] The present invention has been devised in light of the above considerations.

[0008] SUMMARY OF THE INVENTION

[0009] The present inventors have developed an alternative route to reduce emissions linked to cement production.

[0010] The present invention is based on the insight of the present inventors that materials that are conventionally known to be unsuitable for use as starting materials for the production ofsupplementary cementitious materials (SCM) can be used to form a granulated blast furnace slag analogue using the process of the invention.

[0011] Accordingly, in a first aspect, the present invention provides a process for the manufacture of a granulated blastfurnace slag analogue, the process including the steps:

[0012] (i) providing a first material, the first material providing at least one conductive metal or an alloy thereof;

[0013] (ii) heating the first material in a furnace to form a first heated material;

[0014] (iii) providing a second material, wherein the second material comprises:

[0015] (a) CaO

[0016] (b) SiO2

[0017] (c) optionally MgO

[0018] wherein the ratio by mass of (CaO + MgO) / SiO2is less than about 2;

[0019] (iv) contacting a surface of the first heated material with the second material to form a molten slag;

[0020] (v) quenching the molten slag to form the granulated blast furnace slag analogue;

[0021] (vi) separating the granulated blast furnace slag analogue from the first material;

[0022] (viii) removing the granulated blast furnace slag analogue from the furnace; and

[0023] (ix) repeating process steps (ii) to (viii) at least once.

[0024] In a second aspect, the present invention provides a granulated blast furnace slag analogue obtained by or obtainable by a process according to the first aspect.

[0025] In a third aspect, the present invention provides cement obtained by or obtainable by grinding the granulated blast furnace slag analogue of the second aspect and adding one or more cementitious materials, supplementary cementitious materials, or binders.

[0026] The invention includes the combination of the aspects and optional features described except where such a combination is clearly impermissible or expressly avoided.

[0027] SUMMARY OF THE DRAWINGS

[0028] Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying drawings in which:

[0029] Fig. 1 shows a ternary plot of different materials with respect to CaO, SiO2, AI2O3.

[0030] Fig. 2 shows an XRD scan of a legacy slag.

[0031] Fig. 3 shows an XRD scan of granulated blast furnace slag analogue produced by the process of the invention, wherein a legacy slag was used as the second material.CEC004WC

[0032] Fig 4. shows an XRD scan of granulated blast furnace slag analogue produced by the process of the invention, wherein recovered cement paste (RCP) was used as the second material.

[0033] Fig. 5 shows XRDs scan of further granulated blast furnace slag analogues produced by the process of the invention, wherein a legacy slag was used as the second material.

[0034] Fig. 6 shows the results of a Standard R3test measuring the heat release of various slags using an isothermal calorimeter operated at 40 °C. The pastes were prepared with 30% Ca(OH)2, 10% slags, 5% CaCOs and 54% of KOH-K2SO4 solution (4.00 g / L KOH and 20.0 g / L K2SO4 dissolved in de-ionised water) as per ASTM standard C1897-20.

[0035] Fig. 7 shows the mean compressive strength results of granulated blast furnace slag analogues after 2, 7, 28 and 56 days on 2 cm mortar cubes.

[0036] DETAILED DESCRIPTION OF THE INVENTION

[0037] Aspects and embodiments of the present invention will now be discussed with reference to the accompanying drawings. Further aspects and embodiments will be apparent to those skilled in the art. All documents mentioned in this text are incorporated herein by reference.

[0038] A first aspect of the invention is a process for the manufacture of a granulated blast furnace slag analogue, the process including the steps:

[0039] (i) providing a first material, the first material providing at least one conductive metal or an alloy thereof;

[0040] (ii) heating the first material in a furnace to form a first heated material;

[0041] (iii) providing a second material, wherein the second material comprises:

[0042] (a) CaO

[0043] (b) SiO2

[0044] (c) optionally MgO

[0045] wherein the ratio by mass of (CaO + MgO) / SiO2 is less than about 2;

[0046] (iv) contacting a surface of the first heated material with the second material to form a molten slag;

[0047] (v) quenching the molten slag to form the granulated blast furnace slag analogue;

[0048] (vi) separating the granulated blast furnace slag analogue from the first material;

[0049] (viii) removing the granulated blast furnace slag analogue from the furnace; and

[0050] (ix) repeating process steps (ii) to (viii) at least once.

[0051] First material

[0052] The first material provides at least one conductive metal or an alloy thereof.As used herein, the term “conductive metal” means a metal that is thermally conductive and / or electrically conductive under the process conditions of the first aspect of the invention. For example, metals that have a resistivity (expressed as p (Q*m) at 20 °C) of between about 1.5x1 O'8to about 7.5x1 O'7may be suitable for use in the process of the first aspect of the invention. For example, metals that have a conductivity (expressed as o (S / m) at 20 °C) of between about 1.0x106and about 7.0x107may be suitable for use in the process of the first aspect of the invention.

[0053] Non-limiting examples of conductive metals suitable for use in the process of the first aspect of the invention include iron (Fe), copper (Cu), titanium (Ti), tantalum (Ta), and alloys thereof.

[0054] The first material may provide iron (Fe) or an alloy thereof. The first material may be, but is not limited to, a material comprising iron oxides, iron oxyhydroxides, iron sulfides, calcium ferrites, iron-containing nesosilicates, iron-containing sorolicates, iron-containing ionosilicates and iron-containing phyllosilicates. The first material may be, or may comprise, iron oxides such as hematite (Fe2Os) or magnetite (FesC ) as well as ferrites containing these oxides and iron-containing neosilicates. The first material may preferably provide Fe2Os and / or the other compounds comprising the elements of this oxide selected from Fe2Os, FesC , Fayalite, Andradite Staurolite, Datolite, Titanite, Humite, Chloritoid, (Mg,Fe)?(SiO4)3(OH)2and ((Mg,Fe)7(SiO4)3(F,OH)2).

[0055] In the present invention, it is thought that the first material providing at least one conductive metal or an alloy thereof functions primarily as a heat source for the formation of a molten slag when combined with a second material as described herein.

[0056] In some cases, the first material may also act as a source of the requisite balance of elements for the formation of a molten slag when combined with a second material as described herein. The requisite balance of elements may include calcium (Ca) or silicon (Si), including oxides thereof (e.g. CaO, SiC>2).

[0057] The first material may therefore be any material that is suitable of providing this dual functionality in the process of the first aspect of the invention. However, any material that is suitable to provide the primary function of the first material, i.e. heat transfer to the second material to form a molten slag, may be used in the process of the first aspect of the invention.The first material may comprise, consist essentially of, or consist of iron flakes, such as electrolytic iron flakes.

[0058] The first material may comprise, consist essentially of, or consist of pure iron flakes. By “pure” in this context it is meant that the iron flakes, when analysed by optical emission spectroscopy, do not contain any element other than iron up to the detection limit of the optical emission spectroscopy analysis.

[0059] The first material may comprise, consist essentially of, or consist of an iron-containing alloy. Preferably the first material is an iron-containing alloy.

[0060] The iron-containing alloy may comprise one or more additional elements, or compounds (such as oxides, hydroxides, carbonates, nitrates, sulphates, phosphates, and the like) of one or more additional elements. These one or more additional elements are preferably metals, selected from the list comprising manganese, silicon, phosphorous, aluminium, nickel, chromium, vanadium, and cobalt.

[0061] The iron-containing alloy may further comprise carbon. The iron-containing alloy may comprise carbon in an amount of between 0.001 and 10 wt%, preferably between 0.001 and 5 wt%, such as between about 0.01 and 5.0 wt%, or between about 0.01 and 4.5 wt%, or between about 0.01 and 4.0 wt%, or between about 0.01 and 3.5 wt%, or between about 0.01 and 3.0 wt%, or between about 0.01 and 2.5 wt%, or between about 0.01 and 2.0 wt%, or between about 0.01 and 1.5 wt%, or between about 0.01 and 1.0 wt%, or between about 0.01 and 0.5 wt%.

[0062] The iron-containing alloy further comprising carbon may be cast iron or pig iron.

[0063] The iron-containing alloy further comprising carbon may be steel. Examples of steels suitable for use in the present invention include, but are not limited to, stainless steel and scrap steel. The steel may be a high purity steel.

[0064] In one embodiment, the iron-containing alloy does not comprise, consist essentially of, or consist of scrap steel.

[0065] The iron-containing alloy further comprising carbon may further comprise one or more additional elements, or compounds (such as oxides, hydroxides, carbonates, nitrates, sulphates, phosphates, and the like) of one or more additional elements. These one or more additional elements are preferably metals, and are preferably selected from the list comprising manganese,silicon, phosphorous, aluminium, nickel, chromium, vanadium, and cobalt, more preferably selected from the list comprising manganese, silicon, phosphorous, aluminium, nickel, and chromium.

[0066] The iron-containing alloy further comprising carbon (e.g. a steel) preferably has a sulphur content of less than about 0.1 wt% and more preferably less than about 0.05 wt%.

[0067] The iron-containing alloy further comprising carbon (e.g. a steel) may, when analysed by optical emission spectroscopy, have the following elemental composition in mass%:

[0068] C: 0.651; Si: 0.233; Mn: 0.691; P: 0.0132; S: 0.0106; Cr: 0.139; Mo: 0.00099; Ni: 0.0251; Al: 0.0023; N2: 0.0051; Fe: balance

[0069] The iron-containing alloy further comprising carbon (e.g. a steel) may, when analysed by optical emission spectroscopy, have the following elemental composition in mass%:

[0070] C: 0.102; Si: 0.200; Mn: 1.180; P: 0.0150; S: 0.002; Cr: 0.280; Mo: 0.000; Ni: 0.0500; Al: 0.0390; N2: 0.0070; Fe: balance

[0071] In some embodiments of the invention, the first material may be, consist of, consist essentially of, or comprise scrap steel. The terms “scrap steel” and “steel scraps” are used interchangeably herein to refer to materials that are typically used as an input for steel recycling methods known in the art.

[0072] In some preferred embodiments of the invention, the first material is a ferromagnetic material.

[0073] Heating the first material

[0074] The first aspect of the present invention includes the step of heating the first material (i.e. the first material as hereinbefore described) in a furnace to form a first heated material.

[0075] The function of the furnace is to heat the first material to a sufficient temperature to allow the formation of a slag, preferably a molten slag, from the combination of the first material and the second material. Preferably the furnace functions to heat the first material to a sufficient temperature that at least a surface of the first material is at least partially molten, and more preferably to a sufficient temperature that the first material is mostly, or substantially, or entirely molten. Accordingly the furnace may be any furnace that is suitable for enabling the process of the first aspect of the invention. Preferably the furnace is suitable for heating the first material, or at least a surface of the first material, to at least the liquidus temperature of the first material.Preferably, the furnace is capable of heating the first material, or at least a surface of the first material, to a temperature at least 1100 °C, at least 1200 °C, at least 1300 °C, at least 1350 °C, at least 1500 °C, more typically at least 1550 °C, at least 1600 °C, at least 1650 °C or at least 1700 °C.

[0076] Preferably, the furnace is not a conventional cement kiln.

[0077] The furnace will typically comprise a lining. Alternatively, or additionally, the furnace may contain a crucible, the crucible comprising a lining. In the case of a crucible, the lining may simply be the surface of the crucible that is in contact with at least one of the materials used in, or produced by (including intermediate products), the process described herein.

[0078] The lining may be any lining that is suitable for carrying out the process described herein. Nonlimiting examples of such a lining include those comprising aluminium, carbon (e.g. graphite), magnesium carbide, magnesiochromite, or magnesium oxide. Preferably the lining comprises, or consists of, a refractory material.

[0079] The furnace is preferably an induction furnace, an electric arc furnace (EAF), or an electric smelting furnace (ESF). More preferably, the furnace is an induction furnace or an electric arc furnace.

[0080] The skilled person well understands what an electric arc furnace (EAF) is. That is, a furnace whereby material is heated by means of an electrical arc. The electrical arc may be produced by electrical breakdown of a suitable gas. In use, material in the EAF is heated by contact with the electrical arc, and the passing of current through the material.

[0081] Typical temperatures in conventional cement kilns can reach up to 1450 °C. On the other hand, the typical maximum operating temperature in an EAF is significantly higher, for example at least 1350 °C, at least 1500 °C, more typically at least 1550 °C, at least 1600 °C, at least 1650 °C or at least 1700 °C. Industrial EAFs may have a typical maximum operating temperature of up to 1800 °C. EAFs for research purposes may of course reach significantly higher temperatures. Accordingly, the EAF may have a maximum operating temperature of up to 1900 °C, up to 2000 °C, up to 2100 °C, up to 2200 °C, or up to 2300 °C for example. A suitable maximum temperature for carrying out the process of the first aspect may therefore be in a range formed by selection of any one of these lower limits with any one of these upper limits, e.g. 1350 °C to 2300 °C, preferably 1500 °C to 2300 °C.Second material

[0082] The following descriptions of preferred second materials that are suitable for use in the present invention are to be understood as describing materials that can be used as the only second material in the present invention, or in combination with the other second materials described herein, unless explicitly stated otherwise.

[0083] In the first aspect of the invention as described herein, the process includes the step of providing a second material, wherein the second material comprises

[0084] (a) CaO

[0085] (b) SiO2

[0086] (c) optionally MgO

[0087] wherein the ratio by mass of (CaO + MgO) / SiO2 is less than about 2.

[0088] Preferably the ratio by mass of (CaO + MgO) / SiO2 in the second material is less than about 2.0, less than about 1.9, such as less than about 1.8, less than about 1.7, less than about 1.6, less than about 1.5, less than about 1.4, less than about 1.3, less than about 1.2, less than about 1.1, less than about 1.0, less than about 0.9, less than about 0.8, less than about 0.7, less than about 0.6, less than about 0.5, less than about 0.4, less than about 0.3, less than about 0.2, or less than about 0.1.

[0089] The ratio by mass of (CaO + MgO) / SiO2 in the second material may be in the range of from 0.01 to 2, such as 0.01 to 1.9, 0.05 to 1.8, 0.1 to 1.7, 0.2 to 1.6, 0.3 to 1.5, or 0.4 to 1.4, or 0.7 to 1.3, e.g. 0.8 to 1.2.

[0090] The ratio by mass of (CaO + MgO) / SiO2 in the second material is less than about 2 and may be greater than about 0.7, such as greater than about 0.8, greater than about 0.9, greater than about 1.0, greater than about 1.1, or greater than about 1.2.

[0091] The ratio by mass of (CaO + MgO) / SiO2 in the second material is therefore lower than that required for the production of Portland cement. This difference is indicative of the ability of the process of the present invention to utilise materials that are not conventionally used for the production of SCMs.

[0092] The second material may comprise, or may be selected from, calcium oxides, calcium hydroxides, calcium carbonates, calcium ferrite, calcium sulfates, calcium-containing aluminosilicates, calcium-containing nesosilicates, calcium-containing sorolicates, calcium-containing ionosilicates, and calcium-containing phyllosilicates. Examples of such material include, but arenot limited to, CaCOs, CaO, Ca(OH)2, CaSO4.2H2O, CaCh, CaFe2C>4, Ca2Fe20s, C2SH, afwiellite, xonotlite, tobermorite, wollastonite, olivine, basalt rock, amorphous glass, glass waste, gypsum, and calcium (aluminium) silicate hydrate (C-(A)-S — H).

[0093] The second material may be a decarbonated calcium source.

[0094] The second material may be a byproduct, or waste product, of an industrial process. The use of one or more waste products, or industrial byproducts, of this kind in the process of the invention provides an additional environmental and / or economic benefit, due to the reuse (e.g. recycling) of materials that would otherwise be considered to be waste products.

[0095] The second material may be a fly ash. Fly ash is typically produced as a byproduct of the combustion of coal, such as in a coal power plant. The fly ash may be Class C fly ash. Alternatively, the fly ash may be Class F fly ash. The fly ash may be a mixture of Class C fly ash and Class F fly ash. Preferably, the fly ash is Class F fly ash.

[0096] The second material may be a legacy slag, and in particular may be a legacy blast furnace slag. The person skilled in the art will understand that a “legacy slag” refers to an industrial waste byproduct, and in particular to an air cooled blast furnace slag. Further details of legacy slags, in particular in the context of iron and steel waste slags, is found in Journal of Geochemical Exploration Volume 219, December 2020, 106630 (https: / / doi.Org / 10.1016 / j.gexplo.2020.106630), the contents of which are incorporated herein by reference in their entirety.

[0097] One characteristic feature of such legacy slags is that their chemical oxide composition is similar to that of a blast furnace slag. An advantage of using legacy slag for the formation of a granulated blastfurnace slag analogue, as in the process of the first aspect of the invention, is that the legacy slag comprises all of the decarbonated calcium required to form a granulated blast furnace slag analogue. This is advantageous as there is no net increase in the amount of carbon dioxide produced by the process, particularly where the furnace used is an induction furnace or electric arc furnace which is itself powered by decarbonised electricity. As such, the process of the first aspect of the invention is a carbon-efficient way to produce a supplementary cementitious material from waste materials, such as industrial by-product waste materials.

[0098] The British Standards Institution standard EN 15167-1 sets the requirements for ground granulated blast furnace slag for use in concrete, mortar and grout. These are summarised as:

[0099] • Amorphous content >2 / 3rd(>66.67%)• MgO content < 18%

[0100] • Sulfide < 2.0 %

[0101] • Sulfate <2.5%

[0102] • Loss of ignition, corrected for sulfide < 3.0%

[0103] • Chloride < 0.1%

[0104] • Moisture content < 1.0 %

[0105] This standard also requires that the ground granulated blast furnace slag shall comprise at least two thirds by mass of the sum of calcium oxide (CaO), magnesium oxide (MgO), and silicon dioxide (SiO?), with the majority of the remainder being alumina (AI2O3). In addition, the standard requires that the ground granulated blast furnace slag has a ratio by mass of (CaO + MgO) / SiO2 of greater than 1.0.

[0106] Preferred second materials for use in the present invention have a chemical oxide composition that is similar to this standard for GGBFS for use in concrete.

[0107] The second material has a minimum aluminium content that is distinct from materials that are typically used for the production of cementitious materials or supplementary cementitious materials. In particular, the second material has a minimum aluminium content that is distinct from materials that are typically used for the production of Portland cement.

[0108] The second material preferably comprises aluminium (e.g. alumina) in an amount of at least about 4 wt% of the total weight of the second material. Preferably, the second material comprises aluminium (e.g. alumina) in an amount of at least about 5 wt% of the total weight of the second material, more preferably at least about 6 wt%, such as at least about 7 wt%, at least about 8 wt%, at least about 9 wt%, at least about 10 wt%, at least about 11 wt%, at least about 12 wt%, at least about 13 wt%, at least about 14 wt%, at least about 15 wt%, at least about 16 wt%, at least about 17 wt%, at least about 18 wt%, at least about 19 wt%, or at least about 20 wt%.

[0109] The second material preferably comprises aluminium (e.g. alumina) in an amount of between about 4 wt% and about 20 wt% of the total weight of the second material, more preferably between about 5 wt% and about 18 wt%, still more preferably between about 7 wt% and about 16 wt%, even more preferably between about 8 wt% and about 12 wt%.

[0110] The second material preferably comprises at least 1 % by weight of magnesium, or an oxide thereof, as a percentage by weight of the second material. The presence of magnesium in these amounts in legacy slags may be characteristic of such materials. Preferably, the second materialcomprises at least about 1.0 wt% of magnesium, such as about 2.0 wt%, about 3.0 wt%, about 4.0 wt%, about 5.0 wt%, about 6.0 wt%, about 7.0 wt%, about 8.0 wt%, about 9.0 wt%, about 10.0 wt%, about 11.0 wt%, about 12.0 wt%, about 13.0 wt%, about 14.0 wt%, about 15.0 wt%, about 16.0 wt%, about 17.0 wt%, about 18.0 wt%, about 19.0 wt%, or about 20.0 wt%.

[0111] The second material preferably comprises magnesium (e.g. magnesium oxide) in an amount of between about 1 wt% and about 20 wt% of the total weight of the second material, more preferably between about 2 wt% and about 19 wt%, still more preferably between about 3 wt% and about 18 wt%, even more preferably between about 4 wt% and about 17 wt%.

[0112] In some preferred processes of the invention, the second material is pelletised before being added to the furnace. This improves the processability and ease of handling of some preferred second materials. In other preferred processes of the invention, however, pelletisation of the second material before it is added to the furnace is not required, particularly if the physical properties of the second material are such that pelletisation is not necessary to provide acceptable material handling properties.

[0113] In order to produce a granulated blast furnace slag analogue via the process of the first aspect of the invention, preferably the first material, the second material, or the first material and the second material further provide:

[0114] i) at least one source of silicon;

[0115] ii) at least one source of aluminium;

[0116] Preferably, the at least one source of silicon comprises SiO?.

[0117] Preferably the at least one source of aluminium comprises AI2O3.

[0118] The at least one source of silicon and or / aluminium may be a clay, such as bentonite or kaolin. The clay may be calcined. Such clays may provide a source of silicon, such as silicon oxide. Such clays may provide a source of aluminium, such as aluminium oxide.

[0119] The at least one source of silicon may be silica fume. Silica fume, or microsilica, is typically produced as a byproduct of silicon and ferrosilicon production. Silica fume may provide a source of silicon, such as silicon oxide.

[0120] The at least one source of silicon may be asbestos, such as asbestos fibres. Such asbestoscontaining materials were previously used as insulation materials in construction. Asbestos mayprovide a source of silicon, such as silicon oxide. Alternatively, or additionally, asbestos may have a protective effect on the furnace lining, or crucible lining, in which the process of the invention is carried out.

[0121] In some preferred processes according to the first aspect of the invention, no material or additive other than the first material and the second material is added to the furnace. In such processes, the balance of elements (such as Al and Si) required to form the granulated blast furnace slag analogue are provided entirely by the combination of the first material and the second material, and preferably substantially by the second material.

[0122] In some preferred processes according to the first aspect of the invention the balance of elements (such as Al and Si) required to form the granulated blast furnace slag analogue are provided by the second material. For example, greater than about 50 wt% of the balance of elements required to form the granulated blast furnace slag analogue are provided by the second material, such as greater than about 60 wt%, greater than about 70 wt%, greater than about 75 wt%, greater than about 80 wt%, greater than about 85 wt%, greater than about 90 wt%, greater than about 91 wt%, greater than about 92 wt%, greater than about 93 wt%, greater than about 94 wt%, greater than about 95 wt%, greater than about 96 wt%, greater than about 97 wt%, greater than about 98 wt%, or greater than about 99 wt%.

[0123] In processes of the invention wherein the balance of elements required to form the granulated blast furnace slag analogue are provided substantially (or entirely) by the second material, the function of the first material is to act as a heating source to transfer heat to the second material, e.g. by thermal conduction. Thus in processes according to the first aspect wherein the furnace is an induction furnace or an electric arc furnace, the furnace heats the first material, and the first material heats the second material, e.g. by thermal conduction. Without wishing to be bound by theory, it is thought that this means of heating the second material is more efficient (e.g. thermally efficient, or electrically efficient) than conventional means by which the second material is primarily heated by convection from the heated interior of a conventional furnace, such as a cement kiln or similar.

[0124] The process of the invention may be conducted under reducing conditions. The term “reducing conditions” is a term of the art that is well known to the person skilled in the art.

[0125] In the context of the present invention, the reducing conditions may be produced by one or more of the following: the process parameters; the gas mixture present in the furnace during the process; the presence of reducing agents in the first material; the presence of reducing agents inthe second material; the addition of reducing agents to the first material, second material, heated first material, or molten slag at any stage of the process; or leaching of reducing agents from the furnace walls, furnace lining, crucible walls, or crucible lining.

[0126] Some non-limiting examples of reducing agents suitable for use in the process described herein are coal, graphite, and other carbon-based reducing agents; gases such as carbon monoxide, methane, and hydrogen; metals such as aluminium, silicon, calcium; and alloys or compounds such as calcium carbide, ferro silicon, and ferro aluminium. For the avoidance of doubt, this list is merely an example of suitable reducing agents that may be used.

[0127] In processes where at least one reducing agent is present, the at least one reducing agent is preferably present in the furnace prior to the quenching of the molten slag to form the granulated blast furnace slag analogue.

[0128] The process of the first aspect of the invention comprises a step of quenching the molten slag to form the granulated blast furnace slag analogue. Any suitable means of quenching the molten slag may be used. For example, the molten slag may be quenched by adding the molten slag to water. Quenching in this way produces a granulated blast furnace slag analogue, where the particle size of the granulated blast furnace slag is in the order of a few millimetres, e.g. about 5 mm, about 4 mm, about 3 mm, about 2 mm, or about 1 mm.

[0129] The process according to the first aspect of the invention comprises a step of separating the granulated blast furnace slag analogue from the first material. Any suitable separation means may be used. If the first material is a ferromagnetic material, the first material may be separated from the second material by magnetic separation.

[0130] The process according to the first aspect of the invention comprises a step of removing the granulated blast furnace slag analogue from the furnace.

[0131] Preferably, at least about 60%, more preferably at least about 67% (i.e. about two thirds) of the granulated blast furnace slag analogue should be melted before it is removed from the furnace. In contrast, in conventional cement manufacturing processes, the melt content is less than about 30%.

[0132] In preferred processes according to the first aspect of the invention, the first material is not removed from the furnace. That is, the first material is not removed from the furnace before, simultaneously to, or subsequently to, the step of removing the granulated blast furnace slaganalogue from the furnace. Thus in some preferred processes, the first material remains in (i.e. is retained in) the furnace after the separation of the granulated blast furnace slag analogue from the first material. In some preferred processes, the first material remains in (i.e. is retained in) the furnace after the granulated blast furnace slag analogue is removed from the furnace.

[0133] In preferred processes according to the first aspect of the invention, after separation from the first material, the granulated blast furnace slag analogue is removed from the furnace and the first material remains in (i.e. is retained in) the furnace.

[0134] The first material may therefore be reused one or more times, such as one additional time, two additional times, three additional times, or as many additional times as is required. In this way, the first material is recycled and reused, primarily as a heating material for the process of the first aspect of the invention.

[0135] In preferred processes of the first aspect of the invention, at least steps (ii) to (viii) of the process, as described herein, are repeated at least once after the granulated blast furnace slag analogue is removed from the furnace. Steps (ii) to (viii) of the process, as described herein, may be repeated at least once, e.g. once, twice, three times, four times, or as many additional times are required. Preferably these repeated process cycles are conducted without removal of the first material from the furnace. That is, preferably these repeated process cycles are conducted using the same first material as the initial process cycle, without removal of the first material from the furnace.

[0136] The potential to reuse the first material in this way (i.e. by having the first material remain in the furnace after removal of the granulated blast furnace slag analogue from the furnace) is a significant advantage of the process described herein. By reusing the first material in this way, the process is a sustainable, low carbon way of converting waste materials and industrial byproducts, such as legacy slags, into useful cementitious materials (or supplementary cementitious materials) such as granulated blast furnace slag analogues with the efficient use of the first material as a means to heat the second material in a furnace, such as an induction furnace or an electric arc furnace, that can itself by powered using low carbon electricity sources. This is a substantial improvement over prior art processes for producing cementitious materials.

[0137] The process of the invention may preferably comprise a step of grinding the granulated blast furnace slag analogue to form a ground granulated blast furnace slag analogue. The granulated blast furnace slag may be ground, for example using a planetary ring mill or a ball mill with steelballs as charge, to form a granulated ground blast furnace slag analogue. For the avoidance of doubt, these are merely examples of suitable grinding methods that may be used.

[0138] In one embodiment of the first aspect of the invention, the second material may comprise, consist essentially of, or consist of a waste material or industrial by-product, such as a legacy slag as described herein.

[0139] Therefore, one example of the first aspect of the invention is a process for the manufacture of a granulated blastfurnace slag analogue, the process including the steps:

[0140] (i) providing a first material, the first material providing at least one conductive metal or an alloy thereof;

[0141] (ii) heating the first material in a furnace to form a first heated material;

[0142] (iii) providing a second material, wherein the second material comprises:

[0143] (a) CaO

[0144] (b) SiO2

[0145] (c) optionally MgO

[0146] wherein the ratio by mass of (CaO + MgO) / SiO2 is less than about 2, and

[0147] wherein the second material comprises, consists essentially of, or consists of a legacy slag;

[0148] (iv) contacting a surface of the first heated material with the second material to form a molten slag;

[0149] (v) quenching the molten slag to form the granulated blast furnace slag analogue;

[0150] (vi) separating the granulated blast furnace slag analogue from the first material;

[0151] (viii) removing the granulated blast furnace slag analogue from the furnace; and

[0152] (ix) repeating process steps (ii) to (viii) at least once.

[0153] In this embodiment, the first material and the furnace are preferably as hereinbefore described.

[0154] In one embodiment of the first aspect of the invention, the second material may comprise, consist essentially of, or consist of a cement paste, such as a cement paste derived from Construction and Demolition Waste (CDW). Examples of such cement pastes are hydrated cement paste (HCP), including HCP that has been saturated with chloride (HCP Cl), and recovered cement paste (RCP).

[0155] Therefore, one example of the first aspect of the invention is a process for the manufacture of a granulated blastfurnace slag analogue, the process including the steps:(i) providing a first material, the first material providing at least one conductive metal or an alloy thereof;

[0156] (ii) heating the first material in a furnace to form a first heated material;

[0157] (iii) providing a second material, wherein the second material comprises:

[0158] (a) CaO

[0159] (b) SiO2

[0160] (c) optionally MgO

[0161] wherein the ratio by mass of (CaO + MgO) / SiO2is less than about 2, and

[0162] wherein the second material comprises, consists essentially of, or consists of a cement paste derived from Construction and Demolition Waste (CDW);

[0163] (iv) contacting a surface of the first heated material with the second material to form a molten slag;

[0164] (v) quenching the molten slag to form the granulated blast furnace slag analogue;

[0165] (vi) separating the granulated blast furnace slag analogue from the first material;

[0166] (viii) removing the granulated blast furnace slag analogue from the furnace; and

[0167] (ix) repeating process steps (ii) to (viii) at least once.

[0168] In this embodiment, the first material and the furnace are preferably as hereinbefore described.

[0169] In one embodiment of the first aspect of the invention, the second material may comprise, consist essentially of, or consist of a mixture of a legacy slag as described herein and a cement paste derived from Construction and Demolition Waste (CDW) as described herein.

[0170] Therefore, one example of the first aspect of the invention is a process for the manufacture of a granulated blastfurnace slag analogue, the process including the steps:

[0171] (i) providing a first material, the first material providing at least one conductive metal or an alloy thereof;

[0172] (ii) heating the first material in a furnace to form a first heated material;

[0173] (iii) providing a second material, wherein the second material comprises:

[0174] (a) CaO

[0175] (b) SiO2

[0176] (c) optionally MgO

[0177] wherein the ratio by mass of (CaO + MgO) / SiO2is less than about 2, and

[0178] wherein the second material comprises, consists essentially of, or consists of a legacy slag and a cement paste derived from Construction and Demolition Waste (CDW);(iv) contacting a surface of the first heated material with the second material to form a molten slag;

[0179] (v) quenching the molten slag to form the granulated blast furnace slag analogue;

[0180] (vi) separating the granulated blast furnace slag analogue from the first material;

[0181] (viii) removing the granulated blast furnace slag analogue from the furnace; and

[0182] (ix) repeating process steps (ii) to (viii) at least once.

[0183] In this embodiment, the first material and the furnace are preferably as hereinbefore described.

[0184] In processes wherein the second material comprises a cement paste derived from Construction and Demolition Waste (CDW), the cement paste may be combined with one or more additional materials to assist with fluxing of the first material (e.g. steel) and / or to promote and preferably optimise the production of a molten slag with a chemical oxide composition that is suitable for the production of a granulated blast furnace slag analogue. For example, CaO may be one such additional material. Preferably the ratio of cement paste to additional material is in the range defined by 75wt% cement paste : 25wt% additional material at one limit to 99wt% cement paste : 1wt% additional material at the other limit. The upper end of the range may instead be:

[0185] 80wt% cement paste : 20wt% additional material

[0186] 85wt% cement paste : 15wt% additional material

[0187] 90wt% cement paste : 10wt% additional material

[0188] 95wt% cement paste : 5wt% additional material

[0189] The additional material may be CaO entirely. Alternatively it may not include CaO. Alternatively it may be CaO with one or more further materials. Examples of suitable further materials includes, but is not limited to, clays (such as A^Os-rich kaolin clay), reducing additives (such as aluminium metal and / or ferrosilicon), bauxite, silica sand, silica-rich clays (such as shales), and corundum. The function of such additives is to provide the necessary balance of elements for producing a granulated blast furnace slag analogue as further described herein, and / or to promote the formation of particularly desirable phases in the granulated blast furnace slag analogue as further described herein, and / or as processing aids for the process of the first aspect of the invention.

[0190] The additional material, where present, may comprise, consist essentially of, or consist of, lime.

[0191] Advantageously, the use of lime as an additional material means that the process of the first aspect of the invention can avoid the production of CO2 that results from the decomposition of calcium carbonate to oxides (and / or hydroxides) of calcium during conventional processes for the production of cementitious materials.Heating process

[0192] The process of the first aspect of the invention includes the steps of heating the first material as described herein in a furnace as described herein to form a first heated material, and contacting a surface of the first heated material with the second material as described herein to form a molten slag.

[0193] The inventors have realised that it is possible to make use of the high temperatures (compared with temperatures available in conventional cement kilns) in furnaces as hereinbefore described (e.g. electric arc furnaces) to produce granulated blast furnace slag analogues.

[0194] As previously described, in the process of the invention, the furnace functions to heat the first material to a sufficient temperature that at least a surface of the first material is at least partially molten. Preferably the first material, or at least a surface of the first material, is heated to at least the liquidus temperature of the first material.

[0195] In this way, the formation of the molten slag on a surface of the heated first material can enable the production of zero carbon cement. This exploits the high temperatures reached by the furnace (e.g. induction furnace or EAF) without burning fuel for the purpose of making cementitious materials.

[0196] The combination of this heating means with the ability to reuse (i.e. recycle) the first material in the process of the first aspect of the invention as hereinbefore described is particularly advantageous, as it further enhances the sustainability and economic, material, and carbon efficiency of the process.

[0197] Granulated blastfurnace slag analogue

[0198] A second aspect of the invention is a granulated blast furnace slag analogue obtained by or obtainable by a process as hereinbefore described.

[0199] The granulated blast furnace slag may be characterised by comprising amorphous, or glassy, materials or phases. Preferably the granulated blast furnace slag comprises a higher proportion of amorphous or glassy materials or phases than that of the second material.

[0200] The term “amorphous” in this context is a term of the art, and its meaning is well known to the skilled person. It may be contrasted with materials or phases that are said to be “crystalline” or“possess a high degree of crystallinity”. That is, an amorphous material (or phase) is one in which little or no, preferably no, degree of long range order is observed, for example by XRD analysis.

[0201] Preferably, the granulated blast furnace slag analogue comprises at least 65% by mass of an amorphous material. More preferably, the granulated blast furnace slag analogue comprises at least 75% by mass of an amorphous material, such as at least 80%, at least 85%, at least 90%, or at least 95%. In some preferred granulated blast furnace slag analogues, the amorphous content is substantially 100%, i.e. there is no crystalline material present in the material, up to the detection level of the analytical method used to assess the level of amorphous or crystalline content in the granulated blast furnace slag analogue.

[0202] Preferably, the granulated blast furnace slag analogue comprises less than 35% by mass of crystalline materials. More preferably, the granulated blast furnace slag analogue comprises less than 25% by mass of crystalline materials, such as less than 20%, less than 15%, less than 10%, or less than 5%. In some preferred granulated blast furnace slag analogues, there is substantially no crystalline material present in the material, up to the detection level of the analytical method used to assess the level of amorphous or crystalline content in the granulated blast furnace slag analogue.

[0203] The British Standards Institution standard EN 15167-1 sets the requirements for ground granulated blast furnace slag for use in concrete, mortar and grout. One requirement is an amorphous content >2 / 3rd(>66.67%) Accordingly, the granulated blast furnace slag analogue obtained by or obtainable by the process of the first aspect of the invention may have a similar content of amorphous material or phases as a conventional granulated blast furnace slag for use in concrete, mortar and grout.

[0204] The granulated blast furnace slag analogue obtained by or obtainable by the process of the first aspect of the invention may have a calcium to silica ratio of less than about 2.5:1, such as less than about 2.0:1 , preferably less than about 1.5:1, more preferably less than about 1.0:1, such as less than about 0.9:1, less than about 0.8:1, less than about 0.7:1, less than about 0.6:1, less than about 0.5:1 , less than about 0.4:1 , or less than about 0.3:1.

[0205] The granulated blast furnace slag analogue obtained by or obtainable by the process of the first aspect of the invention may have a calcium to silica ratio in the range of from about 0.1 :1 to about 2.5.1, preferably about 0.3:1 to about 2.0:1, more preferably about 0.4:1 to about 1.8:1.The granulated blast furnace slag analogue obtained by or obtainable by the process of the first aspect of the invention may comprise a minimum of about 50% by mass of the total amount of the granulated blast furnace slag analogue of CaO + MgO + SiO? + AI2O3 . Preferably, the granulated blast furnace slag analogue obtained by or obtainable by the process of the first aspect of the invention comprises CaO + MgO + SiO? + AI2O3 (by mass of the total amount of the granulated blast furnace slag analogue) of at least about 55%, more preferably at least about 60%, still more preferably at least about 65%, such as at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or at least about 97%.

[0206] Portland cement is characterised by having, inter alia, a calcium to silica ratio of at least 3:1 (according to EN 197-1). The granulated blast furnace slag analogues obtained by or obtainable by the process of the first aspect of the invention are therefore distinct from materials that may be described as Portland cement, or Portland cement-like materials, for at least this reason.

[0207] Portland cement is highly crystalline. The granulated blastfurnace slag analogues obtained by or obtainable by the process of the first aspect of the invention are therefore distinct from materials that may be described as Portland cement, or Portland cement-like materials, in that they are glassy rather than crystalline.

[0208] Portland cement is also characterised by having, inter alia, a magnesium oxide (MgO) content of less than about 5%, and preferably less than about 4%.

[0209] The granulated blast furnace slag analogue obtained by or obtainable by the process of the first aspect of the invention may have a magnesium oxide (MgO) content of up to about 20%, such as in the range of from about 5% to about 20%, e.g. about 5% to about 19%, or about 6% to about 18%. Preferred granulated blast furnace slag analogue obtained by or obtainable by the process of the first aspect of the invention may have a magnesium oxide (MgO) content of greater than about 10%, preferably greater than about 15%, such as about 16%, about 17%, about 18%, about 19%, or about 20%.

[0210] Cement

[0211] A third aspect of the invention is a cement obtained by or obtainable by grinding the granulated blast furnace slag analogue of the second aspect of the invention and adding one or more cementitious materials, supplementary cementitious materials, or binders.The granulated blast furnace slag analogue of the second aspect of the invention may be used as a replacement for Portland cement for a number of applications. The degree of substitution that is possible is determined by various industrial standards. The granulated blast furnace slag analogue as described herein is suitable for use in place of ground granulated blast furnace slag in any such industrial standard.

[0212] In addition, the granulated blast furnace slag analogue of the second aspect of the invention may be used to produce alkali activated binders, by combination with a suitable activator, such as e.g. calcium hydroxide, calcium oxide, sodium hydroxide, potassium hydroxide, sodium silicate, potassium silicate, sodium sulfate, potassium sulfate, sodium carbonate, potassium carbonate, or combinations thereof. For the avoidance of doubt, this list of suitable activators is non-limiting.

[0213] EXPERIMENTAL SECTION

[0214] General methods

[0215] X-ray fluorescence (XRF) analyses were performed with a Rigaku ZSX Primus IV XRF spectrometer, using the quantitative Fluxana Raw calibration application.

[0216] X-ray diffraction (XRD) was performed with a Malvern Panalytical Empyrean spectrometer with cobalt anode (CoKai = 1.789 A) operated at 35 kV and 35 mA. A cobalt source was preferred over copper to minimise the fluorescence from Fe-K edge emissions. The samples were front-loaded and the scan range was 5-90 °20 with a step size of 0.01 °20 and time per step of 1 s. Each measurement took around 30 minutes. The Rietveld analysis to quantify the crystalline phase content was performed using Topas Academic v7 software. The lattice parameters and crystallite size were allowed to refine, while the atomic positions were not refined. The amorphous content of highly amorphous samples were determined by the external standard method using corundum as the standard.

[0217] Example 1: Production of granulated blastfurnace slag analogue from waste legacy blastfurnace slag deposit.

[0218] In this process, a legacy slag collected from old slag deposits from Carnforth, UK was used. The X-ray fluorescence (XRF) analysis of the legacy slag is shown in Table 1.

[0219]

[0220] Table 1 : Oxide composition of the legacy slag usedCEC004WC

[0221] Upon characterization, this slag was found to be naturally cooled by air, and hence to have high crystallinity (i.e. low amorphous content). The XRD scan of the legacy slag is shown in Figure 2. The legacy slag was found to mainly contain phases such as Gehlenite, Rankinite, and Anorthite, which are not reactive phases. As a result, the legacy slag is not suitable to use as a supplementary cementitious material (SCM) in cement.

[0222] A medium size graphite crucible (GC80) of dimensions 300 mm height and 100 mm diameter was loaded with 12 kg of carbon steel balls and placed in an induction furnace powered by 3 phase 50 Hz electricity, generating single phase output power of 112 kW, 1200 / 600 V and 220 / 440 A at 2-3.3 kHz. The furnace was equipped with a 750 L capacity water tank for cooling, operated between 2.8 to 6.2 bar pressure, providing IP54 degree of protection.

[0223] The steel was heated to 1600 °C, forming molten steel. Crushed legacy slag (about 1 kg; particle size of less than 4 mm) was added to the top of the molten steel. This heating process occurred under reducing conditions, due to the leaching of carbon from the graphite crucible.

[0224] During the process, the molten slag thus formed was stirred with long steel rods. To quench the molten slag and thus granulate it, the molten slag was poured into a bucket of water, forming granulated slag with a particle size in the order of a few mm. The process time from adding the legacy slag to the furnace to removal of the granulated blast furnace slag analogue from the funeral was about 15 minutes.

[0225] Addition of new crushed legacy slag was then added to the molten steel, and the process above repeated.

[0226] The XRD scan of the granulated slag is shown in Figure 3. Analysis of the granulated slag by XRD showed it to be highly amorphous (>95% amorphous content), similar to typical ground granulated blast furnace slag. The granulated slag is therefore a granulated blast furnace slag analogue. The granulated slag could be ground, for example using a planetary ring mill or a ball mill with steel balls as charge, to form a granulated ground blast furnace slag analogue.

[0227] Example 2: Production of granulated blast furnace slag analogue using recovered cement paste RCP (RCP)

[0228] In this method, instead of using legacy slag as in Example 1 , recovered cement paste (RCP) from construction demolition waste was used. The RCP used was of low quality, with only 20% CaO, around 65% SiO?, and around 5% AI2O3. To compensate for this, extra lime and alumina (bauxite,CEC004WC

[0229] pure) were added. The composition added to the molten steel in the crucible in the induction furnace was as follows:

[0230] RCP - 750 g

[0231] Lime - 225 g

[0232] Alumina - 85 g

[0233] The XRF analysis of the oxide composition of the RCP is shown in Table 2.

[0234]

[0235] Table 2: Oxide composition of the RCP used

[0236] The process described in Example 1 was then carried out, using this composition in place of the legacy slag.

[0237] The XRD scan of the granulated slag is shown in Figure 4. Analysis of the granulated slag formed in this process by XRD showed it to be highly amorphous, similar to typical ground granulated blast furnace slag. The granulated slag is therefore a granulated blast furnace slag analogue. The granulated slag could be ground, for example using a planetary ring mill or a ball mill with steel balls as charge, to form a granulated ground blast furnace slag analogue.

[0238] Example 3: Production of granulated blast furnace slag analogue using different flux recipes Four granulated blast furnace slag analogues were produced using a variety of flux recipes.

[0239] Each of the granulated blast furnace slag analogues were produced in an induction furnace equipped with a graphite crucible. Around 12 kg of carbon steel balls were added, which provided the heat source for producing the slag analogues. For each slag, after heating, the slag was tapped into water to quench and granulate.

[0240] The feedstock composition used in the production of each of the slag analogues is shown below in Table 3.

[0241]

[0242]

[0243] Table 3: Composition of the various feedstocks used for producing blast furnace slag analogues

[0244] The composition of each of the feedstocks that were used was measured using a quantitative XRF using fused beads, and are shown in Table 4.

[0245]

[0246] Table 4: XRF analysis of the composition of the various feedstocks used for producing blast furnace slag analogues

[0247] The legacy slags were collected from a slag bank in Carnforth which is believed to be air cooled blast furnace slag and is several decades, or even centuries, old. RCP (recovered cement paste) was a fine fraction (below 250pm) sieved from crushed construction and demolition concrete. HCP (hydrated cement paste) was prepared by mixing Portland cement (CEM I) with water at a water to cement ratio of 0.6 and was cured for at least 1 month and subsequently dried to remove free moisture. Kaolin was a raw kaolinitic clay sourced from the UK. Silica sand was construction sand. Lime was powdered lime used for steelmaking operations. Corundum (AI2O3) and calcium fluoride (CaF2) were commercially available, analytical grade materials.

[0248] The oxide composition of the slags produced from the compositions described above were measured using XRF, and the results shown in Table 5. A reference, commercially obtained, ground granulated blast furnace slag procured is also shown in Table 5 for comparison.

[0249]

[0250]

[0251] Table 5: XRF analysis of the composition of the various blast furnace slag analogues

[0252] A key difference between the granulated blast furnace slag analogues produced in this process and the reference blast furnace slag are higher Fe2Os (it is in fact FeO, as XRF is carried out after fully oxidizing), higher manganese, and slightly higher C^C content. The reason for these differences are thought to be due to partial oxidation of the steel present, and this could be avoided by either ensuring that the steel is not in contact with air / O? or by ensuring sufficient reducing conditions are used - as is the case for the production of a blast furnace slag. In addition, the MgO content in the blast furnace slag analogues was found to be considerably lower than in the reference blast furnace slag. Older methods of producing blast furnace slags did not use much dolomite, and mostly used limestone. Several studies have noted that higher MgO content is beneficial for higher reactivity. For producing slag analogues, MgO content can be further increased by using raw materials containing MgO, or by using small amounts of corrective additions of more concentrated MgO sources.

[0253] The ratios of major oxides of the blast furnace slag analogues are shown in Table 6. It can be seen that all of the slags produced had i) a lower CaO / SiO? ratio and ii) a lower (CaO+MgO) / SiO2 ratio compared to the reference slag. A higher ratio of CaO / SiO2 is expected to result in improvement in performance of the blastfurnace slag analogues. It is possible to produce higher ratios by altering the feedstock composition in order to achieve these ratios.

[0254] >

[0255]

[0256] Table 6: Oxide ratios for the blast furnace slag analogues

[0257] The XRD scans of the granulated slags is shown in Figure 5. Analysis of the granulated slags by XRD showed them to be highly amorphous (>90% amorphous content), similar to typical ground granulated blast furnace slag. The granulated slags are therefore a granulated blast furnace slaganalogues. The granulated slags could be ground, for example using a planetary ring mill or a ball mill with steel balls as charge, to form a granulated ground blast furnace slag analogue.

[0258] Example 4: heat release measurements

[0259] The granulated slags produced according to Example 3 were milled to a fine powder and the heat release measured. The results are shown in Figure 6. It can be seen that the reference slag had a higher heat release than the other slags. This is due to two factors: firstly, the reference slag has a higher CaO / SiO? ratio compared to the other samples, and also has a higher MgO content, and both favours faster hydration of the reference slag. Secondly, the reference slag was ground in an industrial mill which achieved good fineness, whereas the slags produced in the present Examples were milled in a lab scale ball mill, which is less effective in generating fine particles.

[0260] Example 5: compressive strength testing

[0261] The performance of the GGBS analogues produced according to Example 3 was determined using compressive strength measurements. For this, mortar mixes were prepared with standard sand and a cement blend which consists of 50% Portland cement and 50% slags. The sand to cement blend ratio was 3:1. A water to binder ratio of 0.5 was used. The mortars were prepared by mixing with hand, and were then cast on a 2x2x2 cube mould, and subsequently cured at 20 °C. For the first day, the slags were cured in lab conditions after covering with a plastic film. After the first day, the slags were demoulded then transferred to a water bath at a fixed temperature of 20 °C.

[0262] The results of the compressive strength testing are shown in Figure 7. By 28 days, the reference slag showed better performance, which is thought to be due to the better milling, higher CaO / SiO? ratio and higher MgO content, and possibly also lower FeO content. Notably, however, by 56 days, Slag 1 and Slag 2 showed comparable strength to the reference slag, and in particular Slag 1 has similar strength to the reference slag.

[0263] Example 6: theoretical slag compositions

[0264] From the results shown above, it is clear that there can be improvements made to the slag chemistry by controlling the oxide composition and making the slags finer. It is possible to produce composition similar the reference blast furnace slag used in the reference by correctly proportioning various feedstocks. Several examples of theoretical slags produced by using the same feedstocks used in Example 3, and further adding the two decarbonated and readily available materials shown in Table 7.

[0265]

[0266] Table 7: Oxide composition of a ladle slag collected from UK measured using XRF and olivine, which was reported in a journal publication (doi.org / 10.1016 / j.conbuildmat.2022.127378).

[0267] Theoretical Slag 1 - with flux composition of: Ladle slag 54.3%, RCP 29.3%, Kaolin 5.4%, olivine 10.9%; results in a slag with composition: CaO 42.8%, SiO235.7%, AI2O38.3%, MgO 8.3%

[0268] This has a CaO / SiO2 = 1.2, and (CaO+MgO) / SiO2 = 1.43

[0269] Theoretical Slag 2 - with flux composition of: Ladle slag 53.5%, RCP 35.8%, olivine 10.7%; results in a slag with composition: CaO 43.8%, SiO236.3%, AI2O36.6%, MgO 8.2%

[0270] This has a CaO / SiO2 = 1.2, and (CaO+MgO) / SiO2 = 1.43

[0271] Theoretical slag 3 - with flux composition of: Ladle slag 14.3%, Legacy blast furnace slag 71.4%, olivine 14.3%; results in a slag with composition: CaO 42.8%, SiO235.6%, AI2O38.2%, MgO 8.1%

[0272] This has a CaO / SiO2 = 1.2, and (CaO+MgO) / SiO2 = 1.43

[0273] These theoretical slags show that it is possible to produce slag compositions similar to the reference blast furnace slag described above, without using carbon intensive material such as limestone or lime or dololime, by correctly choosing the feedstock.

[0274] The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

[0275] While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forthabove are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

[0276] For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

[0277] Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0278] Throughout this specification, including the claims which follow, unless the context requires otherwise, the word “comprise” and “include”, and variations such as “comprises”, “comprising”, and “including” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment. The term “about” in relation to a numerical value is optional and means for example + / - 10%

Claims

CEC004WCCLAIMS1. A process for the manufacture of a granulated blast furnace slag analogue, the process including the steps:(i) providing a first material, the first material providing at least one conductive metal or an alloy thereof;(ii) heating the first material in a furnace to form a first heated material;(iii) providing a second material, wherein the second material comprises:(a) CaO(b) SiO2(c) optionally MgOwherein the ratio by mass of (CaO + MgO) / SiO2is less than about 2;(iv) contacting a surface of the first heated material with the second material to form a molten slag;(v) quenching the molten slag to form the granulated blast furnace slag analogue;(vi) separating the granulated blast furnace slag analogue from the first material;(viii) removing the granulated blast furnace slag analogue from the furnace; and (ix) repeating process steps (ii) to (viii) at least once.

2. The process according to claim 1 , wherein the second material further comprises alumina (AI2Os).

3. The process according to claim 2, wherein the second material comprises at least 4% by mass of alumina (AI2Os),4. The process according to any preceding claim, wherein the second material is a waste product or an industrial byproduct.

5. The process according to any preceding claim, wherein the second material comprises a legacy slag.

6. The process according to any preceding claim, wherein the second material comprises a cement paste derived from Construction and Demolition Waste (CDW).

7. The process according to claim 6, wherein the cement paste is selected from the group consisting of hydrated cement paste (HCP), including HCP that has been saturated with chloride (HCP Cl), and recovered cement paste (RCP).

8. The process according to any preceding claim, wherein the first material is an iron-containing alloy.

9. The process according to claim 8, wherein the iron-containing alloy further comprises carbon.

10. The process according to any preceding claim, wherein the first material is a steel.

11. The process according to any preceding claim, wherein the process is conducted under reducing conditions.

12. The process according to any preceding claim, wherein at least one reducing agent is present in the furnace prior to the quenching of the molten slag to form the granulated blast furnace slag analogue.

13. The process according to any preceding claim, further comprising grinding the granulated blast furnace slag analogue to form a ground granulated blast furnace slag analogue.

14. The process according to any preceding claim, wherein the second material is pelletised before being added to the furnace.

15. The process according to any of claims 1 to 14, further comprising the step of providing one or more further materials and contacting a surface of the first heated material or the molten slag with the one or more further materials, wherein the one or more further materials comprise a clay, a sand, corundum, or mixtures thereof.

16. The process according to any preceding claim, wherein the furnace is an induction furnace, an electric arc furnace, or an electric smelting furnace.

17. The process according to any preceding claim, wherein the maximum operating temperature experienced by the granulated blast furnace slag analogue in the furnace is at least 1100 °C.

18. Granulated blast furnace slag analogue obtained by or obtainable by a process according to any one of claims 1 to 17.

19. The granulated blast furnace slag analogue according to claim 18, wherein the granulated blast furnace slag analogue comprises at least 65% by mass of an amorphous material.

20. The granulated blast furnace slag analogue according to claim 18 or claim 19, wherein the granulated blast furnace slag analogue comprises less than 35% by mass of crystalline materials.

21. The granulated blast furnace slag analogue according to any of claims 18 to 20, wherein the ratio of calcium to silica of the granulated blast furnace slag analogue is less than about 2:1.

22. Cement obtained by or obtainable by grinding the granulated blast furnace slag analogue of any of claims 18 to 21 and adding one or more cementitious materials, supplementary cementitious materials, or binders.

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