Patent Description:
Hydrothermally cured materials have the advantage that the required energy input is considerable lower compared to processes including firing or thermal pre-treatment of the precursor materials. In the last years, publications on the production of hydrothermally cured bauxite residue (BR) based bricks, which are either cementitious composites or from alkali-activated precursors, were released in the open literature.

In <CIT> a suggestion is made for the preparation of autoclaved cementitious bricks containing up to <NUM> wt% BR. Dicalcium silicate (C<NUM>S) containing BR was used in combination with other industrial by-products, such as fly ash, CaO-containing carbide slag and calcined phosphogypsum. After mixing with water the pastes were shaped using a hydraulic press (<NUM> - <NUM> MPa) and after a precuring step of <NUM> at <NUM>, samples were autoclaved at <NUM>-<NUM> bar for <NUM> up to <NUM>. Strengths of <NUM> to <NUM> MPa were achieved.

<CIT> describes the production of BR based (<NUM>-<NUM> wt%) concrete bricks in combination with cementitious materials (cement, lime), ground granulated blast furnace slag (GGBFS) and sand among other silica rich materials, such as fly ash. The mixes were pressed in shape and cured under hydrothermal conditions obtaining <NUM> bars for <NUM>-<NUM>. Bricks with compressive strengths between <NUM> and <NUM> MPa are reported, with satisfying results in durability tests, such as carbonation resistance and frost resistance.

<CIT> describes the production of autoclaved cementitious bricks consisting of <NUM> - <NUM> wt% BR in mix with <NUM> - <NUM> wt% of fly ash, <NUM> - <NUM> wt% sand, <NUM> - <NUM> wt% gypsum, <NUM> - <NUM> wt% lime. <NUM> - <NUM> wt% of BaSO<NUM> were added in order to decrease any potential radioactivity of BR. After a pre-curing step, green bodies were subjected to hydrothermal conditions of <NUM> and <NUM> bar for <NUM>.

Hydrothermal curing was applied in <CIT> who produced various kinds of cementitious composite bricks with a compositional range of <NUM> - <NUM> wt% of BR, <NUM> - <NUM> wt% fly ash, <NUM> - <NUM> wt% slags, <NUM> - <NUM> wt% carbide slag, <NUM> - <NUM> wt% cement and <NUM> - <NUM> wt% gypsum. Different samples types were produced by varying the shaping pressure (<NUM> - <NUM> MPa) and the curing regimes ranging from <NUM> to <NUM> bar and <NUM> to <NUM>. Compressive strengths up to <NUM> MPa are reported.

In (<NPL>), fine gibbsite (mean particle size of <NUM>) and amorphous microsilica were used as precursors along with an activating solution composed of potassium hydroxide. After curing for <NUM> at <NUM>, the resulting products were analysed using XRD and <NUM>Al and <NUM>Si MAS NMR. Unreacted gibbsite was detected in <NUM>Al MAS NMR spectra, with a peak at <NUM>-<NUM> ppm, which is characteristic for the octahedral configuration of aluminium in the mineral. Unreacted gibbsite is also detected in the XRD spectra, next to quartz (which was present in microsilica), while no zeolites were formed.

Autoclaved inorganic polymer bricks were synthesised in <CIT> who used a maximum fraction of <NUM> wt% of BR in combination with other reactive materials, such as GGBFS, basic oxygen furnace slag, kaolin tailings, coal gangue or <NUM> - <NUM> wt% silica fume. The samples were activated using <NUM> - <NUM> wt% of soluble sodium or potassium silicate. The material was extruded and cured in an autoclave at <NUM> - <NUM> bar for <NUM> to <NUM>. The samples showed good resistance to freeze-thaw, no efflorescence and strengths about <NUM> MPa. Information about the chemical composition of the used BR was not provided in the patent but in view of its origin it has been identified as the high-iron diaspore red mud of the alumina plant of the Quangxi region (<NPL>).

<NPL>) used raw as well as calcined bauxite residue as main component for inorganic polymers with the major goal to transform BR into a stable products that can be safely stored. Varying contents of amorphous silica fume (<NUM> - <NUM> wt%) and rho-alumina (<NUM> - <NUM> wt%) in the solid mix were used to adjust the composition of BR. Hairi discloses a method for manufacturing a building element comprising subjecting NaOH/Nasilicate to <NUM>) alkaline activation <NUM>) mixing and <NUM>) putting the mixture into a mould. The raw material precursor is a red mud residue derived from a Bayer process containing Gibbsite. The products obtained herein are achieving a compressive strength of up to <NUM> MPa.

<CIT> discloses a building comprising a shaped and cured element obtained by geopolymerisation, which can be used in building construction.

<CIT> discloses a non-fired, water insoluble inorganic polymer object, comprising less than <NUM> wt % gibbsite. The object is made from a material containing <NUM> wt. -% Al<NUM>O<NUM> and <NUM> wt. % Fe<NUM>O<NUM>. The object contains more than <NUM> wt. -% of the combination of Al<NUM>O<NUM> and Fe<NUM>O<NUM>. The object also contains an amorphous hydrated
aluminium silicate.

None of the cited prior art discloses a method, where a source rich in gibbsite-containing bauxite or bauxite residue or thermally treated bauxite or bauxite residue was subjected to hydrothermal curing, resulting to dissolution of the phases initially present and the formation of new reaction products, and as a result, a material that is water insoluble and can bear load.

The present application describes a process to convert inter alia a formulation containing bauxite residue (BR), also known as red mud, into a monolithic, water insoluble, material.

In embodiments of the methods of the present invention, the starting solid raw material for the synthesis of the said monolith, consists of bauxite residue, from <NUM> to <NUM> wt%, the remaining fraction being (i) a source containing Al in the form of an oxide, hydroxide, oxyhydroxide, silicate, sulphide, sulphate, sulphite, halide, carbonate, phosphate, borate, and mineraloid, or a mixture of them, (ii) a source containing Si in the form of an oxide, hydroxide, oxyhydroxide, silicate, sulphide, sulphate, sulphite, halide, carbonate, phosphate, borate, and mineraloid, or a mixture of them; (iii) a source containing Ca, in the form of an oxide, hydroxide, oxyhydroxide, silicate, sulphide, sulphate, sulphite, halide, carbonate, phosphate, borate, and mineraloid, or a mixture of them.

The aforementioned sources, at the respective fractions, and optionally a solution containing alkalis and water are all intermixed.

In specific embodiments of the methods of the present invention, there is no additional alkali introduced, when the alkaline conditions result from water-soluble constituents present in the initial blend of precursors. In this case, only water needs to be added.

The resulting mixture is then shaped, and the shaped product is cured at a pressure higher than <NUM> bar and lower than <NUM> bar and at a temperature ranging from <NUM> to <NUM>, <NUM> and <NUM>, between <NUM> and <NUM>, between <NUM> and <NUM>, or between <NUM> and <NUM>. The resulting products are water insoluble, have a compressive strength between <NUM> MPa to <NUM> MPa, preferably higher than <NUM> MPa, or between <NUM> MPa to <NUM> MPa, or between <NUM> MPa to <NUM> MPa or between <NUM> MPa to <NUM> MPa and can be used in civil and industrial applications.

The present disclosure also describes in general a process and method of manufacturing hydrothermally-cured materials, generally understood as inorganic polymers or alkali-activated materials, from a gibbsitic precursor, such as lateritic bauxite, the derivable products, and their use. More particular the present disclosure also describes a non-fired inorganic polymer with compressive strengths between <NUM> MPa to <NUM> MPa, preferably higher than <NUM> MPa, or between <NUM> MPa to <NUM> MPa, or between <NUM> MPa to <NUM> MPa or between <NUM> MPa to <NUM> MPa, and comprises less than <NUM> wt% of diaspore [α-AlO(OH)] and/or less than <NUM> wt% boehmite (or böhmite) [γ-AlO(OH)]. It furthermore concerns obtaining such non-fired inorganic polymer by modifying the gibbsitic precursor by alkaline activation, press shaping and curing at a temperate temperature between <NUM> to <NUM>, <NUM> and <NUM>, between <NUM> and <NUM>, between <NUM> and <NUM>, or between <NUM> and <NUM>, whereby the precursor comprises gibbsite (γ-Al(OH)<NUM>) mineral. The gibbsite in such gibbsitic precursor is in an amount above <NUM> wt%, between <NUM> to <NUM> wt%, between <NUM> to about <NUM> wt%, or between <NUM> to about <NUM> wt%. Such inorganic polymer has been achieved without the need of subjecting the precursor to a shear such as extrusion. The resulting material is a non-fired monolith.

The invention differs from the disclosure of Hairi (cited above). As these authors point out: ". in the case of the samples derived from red mud, the crystalline components of the starting materials are relatively unreactive, and are present as inert fillers rather than reactants. "It seems that especially silica fume contributes to the strength development of the resulting prior art products whereas the alumina addition does not have a positive effect. The crystalline phases (for instance, gibbsite) do not participate in any reaction and also no newly formed crystalline products were detected in these prior art products.

The invention is directed to a method for manufacturing an inorganic polymer object from a precursor of claim <NUM>.

The following detailed description of the invention refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. Also, the following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims.

Several documents are cited throughout the text of this specification; however, there is no admission that any document cited is indeed prior art of the present invention.

Thus, the scope of the expression "a device comprising means A and B" should not be limited to the devices consisting only of components A and B.

Similarly it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding the understanding of one or more of the various inventive aspects.

LOI stand for loss on ignition. Loss on ignition is a test used in analytical chemistry, particularly in the analysis of minerals. It comprises strongly heating ("igniting") a sample of the material at a specified temperature, allowing volatile substances to escape, until its mass ceases to change.

A mineral in the meaning of this application is a naturally occurring chemical compound, usually of crystalline form and abiogenic in origin. Such mineral in the meaning of this application has one specific chemical composition, whereas a rock in the meaning of this application is an aggregate of different minerals or mineraloids.

Silica fume is also known as microsilica, (such as silica fume with <NPL>, EINECS number <NUM>-<NUM>-<NUM>) is an amorphous (non-crystalline) polymorph of silicon dioxide, silica. Mostly is an ultrafine powder collected as a byproduct of the silicon and ferrosilicon alloy production and comprises spherical particles with an average particle diameter of <NUM>.

Waterglass is in the meaning of sodium silicate, the common name for compounds with the formula (Na<NUM>SiO<NUM>)nO, such as for instance sodium metasilicate, Na<NUM>SiO<NUM>. These materials are available in aqueous solution and in solid form. The pure compositions are colourless or white, but commercial samples are often greenish or blue owing to the presence of iron-containing impurities.

As disclosed herein the invention is broadly drawn to the low temperature production of an inorganic polymer from a gibbsite containing (γ-Al(OH)<NUM>) precursor, shaped it into a monolith. It was found that materials containing only diaspore [(α-AlO(OH)] and/or boehmite (or böhmite) [γ-AlO(OH)] were less preferable. The material used has practically no fluoride in its composition. Moreover, we found there is no need to subject the material in shear processing, such as extrusion and additives such as silica fume or water glass may assist the process but are not required to obtain the effect of present invention.

The process allowed producing a new inorganic polymer with adequate compressive strength for a range of applications, that is between <NUM> MPa to <NUM> MPa, preferably higher than <NUM> MPa, or between <NUM> MPa to <NUM> MPa, or between <NUM> MPa to <NUM> MPa or between <NUM> MPa to <NUM> MPa. As diaspore and boehmite do not help substantially the process this inorganic polymer disclosed herein contains less than <NUM> wt% diaspore and/or less than <NUM> wt% boehmite.

In an embodiment of the invention, the precursor gibbsitic materials comprising gibbsite is in an amount above <NUM> wt%, for instance between <NUM> to <NUM> wt%, preferably between <NUM> to about <NUM> wt% and more preferably between <NUM> to about <NUM> wt%, of the precursor where in order to obtain the inorganic polymer with the above described characteristics subjected to alkaline activation, press shaping and curing at a low temperate temperature between <NUM> to <NUM> or <NUM> to <NUM>, preferably between <NUM> and <NUM>. Such inorganic polymer can be pressed-shape into non-fired monoliths that are suitable for construction, building, bridging or supporting a structure.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only. Inorganic polymers disclosed herein are obtainable by modifying of a precursor by alkaline activation, press shaping and curing at a low temperate temperature between <NUM> to <NUM> or <NUM> to <NUM>, between <NUM> and <NUM>, between <NUM> and <NUM>, or between <NUM> and <NUM>, whereby the precursor comprises gibbsite γ-Al(OH)<NUM>) and whereby this gibbsite is in an amount above <NUM> wt%, between <NUM> to <NUM> wt%, between <NUM> to about <NUM> wt%, or between <NUM> to about <NUM> wt%, of the precursor and that the inorganic polymer has a compressive strength of this inorganic polymer between <NUM> MPa to <NUM> MPa, between <NUM> MPa to <NUM> MPa, between <NUM> MPa to <NUM> MPa, between <NUM> MPa to <NUM> MPa or between <NUM> MPa to <NUM> MPa. This inorganic polymer has been pressed into a non-fired monolith. This inorganic polymer comprises less than <NUM> wt% of diaspore [(α-AlO(OH)] and/or less than <NUM> wt% boehmite (or böhmite) [γ-AlO(OH)] or comprises no diaspore and/or no boehmite, comprising less than <NUM> wt% fluoride or comprises no fluoride. Alternatively this inorganic polymer has been press-shaped at a pressure of at least <NUM> MPa, preferably at least <NUM> MPa, yet more preferably at least <NUM> MPa for instance at a pressure in the range of to <NUM> to <NUM> MPa and by pressing for a time between <NUM> sec and <NUM>, between <NUM> sec and <NUM>, between <NUM> sec and <NUM>, between <NUM> sec and <NUM>, between <NUM> sec and <NUM>, for a time between <NUM> sec and <NUM> or between <NUM> sec and <NUM>. Preferably this precursor is processed without extrusion, but has been obtained by pressing of the precursor or by casting. The above inorganic polymer has a normalised chemical composition of the precursor expressed as oxides and in the range of Fe<NUM>O<NUM> <NUM> - <NUM> or <NUM>-<NUM> wt%, Al<NUM>O<NUM> <NUM> - <NUM> wt%, SiO<NUM> <NUM> - <NUM> wt%, TiO<NUM> <NUM> - <NUM> wt%, Na<NUM>O <NUM> - <NUM> wt%, CaO <NUM> - <NUM> wt%. This inorganic polymer can have the particular characteristic that the loss on ignition or volatile substances of the precursor is in the range of <NUM> to <NUM> wt%, <NUM> to <NUM> wt%, <NUM> to <NUM> wt% or <NUM> to <NUM> wt% as defined or definable by thermogravimetric analysis carried out at a temperature between <NUM> to <NUM>. The mineral mix is in specific embodiments of the methods of the present invention in total or in part from an ore, a naturally occurring mineral, or a rock for instance a rock of the group consisting of granite, gneiss and basalt or the mineral mix is from an ore, a naturally occurring mineral, or a rock without additional additives or the mineral mix is from an ore, a naturally occurring mineral, or a rock without additional additives other than kaolinite in a range of <NUM> - <NUM> wt% or <NUM> - <NUM> wt% or the mineral mix is from an ore, a naturally occurring mineral, or a rock without additional additives other than a ceramic clays or mineral clay in a range of <NUM> - <NUM> wt% or <NUM> - <NUM> wt% or it comprises any one of the group consisting of anatase, rutile, gibbsite, hematite, kaolinite and quartz or a combination thereof. The inorganic polymer can be characterised in that it comprises anatase, rutile, hematite, goethite, kaolinite and quartz. Typically if the inorganic polymer comprises anatase, rutile, hematite, kaolinite and quartz, for instance it comprises anatase and rutile each independently from each other in an amount between <NUM> wt% to <NUM> wt%, <NUM> wt% to <NUM> wt% or <NUM> to <NUM> wt%, hematite and goethite each independently from each other in an amount between <NUM> wt% to <NUM> wt%, <NUM> wt% to <NUM> wt%, <NUM> wt% to <NUM> wt%, <NUM> wt% to <NUM> wt% or <NUM> wt% to <NUM> wt%, kaolinite in an amount between <NUM> wt% to <NUM> wt%, <NUM> wt% to <NUM> wt%, <NUM> wt% to <NUM> wt%, <NUM> wt% to <NUM> wt% or <NUM> wt% to <NUM> wt%, quartz in an amount between <NUM> wt% to <NUM> wt%, <NUM> wt% to <NUM> wt%, <NUM> wt% to <NUM> wt%, <NUM> wt% to <NUM> wt%, <NUM> wt% to <NUM> wt% or <NUM> wt% to <NUM> wt%, comprises amorphous substances in an amount between between <NUM> to about <NUM> wt% or <NUM> to <NUM> wt% or <NUM> to <NUM> wt% or <NUM> to <NUM> wt%.

According to another exemplary embodiment of the methods of the present invention the inorganic polymer according to any one of the previous statements is hydrothermally cured at a temperature between <NUM> and <NUM>, <NUM> and <NUM>, between <NUM> and <NUM>, between <NUM> and <NUM>, or between <NUM> and <NUM>. Particularly the starting material to obtain such inorganic polymer is a precursor composition with particle size smaller than <NUM>, preferably between <NUM> and <NUM> size. A particular property of such precursor composition is that it comprises less than <NUM> wt% of diaspore [(α-AlO(OH)] and less than <NUM> wt% boehmite (or böhmite) [γ-AlO(OH)] or comprises no diaspore and/or no boehmite, it comprises less than <NUM> wt% of silica fume or comprises no silica fume, it comprises less than <NUM> wt% water glass or comprises no water glass, it comprises less than <NUM> wt% fluoride or comprises no fluoride. Yet another particular property of such precursor mineral composition is that it does not comprise diaspore [α-AlO(OH)] and/or boehmite [γ-AlO(OH)] and/or it does not comprise silica fume.

The above-mentioned inorganic polymer can be characterised in that the mineralogical composition of the inorganic polymer or its precursor is defined or definable as a X-ray diffractogram by using X-ray Powder Diffraction (XRD) and/or the above-mentioned inorganic polymer can be characterised in that the inorganic polymer or its precursor is defined or definable as a X-ray diffractogram recorded for instance by a D2 Phaser (Bruker AXS), the software DiffracPlus EVA in combination with data of the ICCD-PDF-<NUM> database and/or the normalised chemical composition of the precursor or the inorganic polymer is defined or definable by sequential wavelength-dispersive XRF spectrometer, for instance an automatic PW <NUM> sequential wavelength-dispersive XRF spectrometer and further software analysis, for instance by Uniquant <NUM>. The above-mentioned inorganic polymer can be characterised in that the alkaline activation is by an alkaline solution for instance by an alkaline mixture of sodium of a <NUM> to <NUM> (mol/l) or that the alkaline activation has a total molar ratio of SiO<NUM>/Na<NUM>O in the range of <NUM> to <NUM> and H<NUM>O/Na<NUM>O in the range of <NUM> - <NUM> or <NUM> - <NUM>. The above-mentioned inorganic polymer can be characterised in that the alkaline activation is by an alkaline solution for instance by an alkaline mixture of potassium of a <NUM> to <NUM> (mol/l) or that the alkaline activation has a total molar ratio of SiO<NUM>/K<NUM>O in the range of <NUM> to <NUM> and H<NUM>O/Na<NUM>O in the range of <NUM> - <NUM> or <NUM> - <NUM>. Mixtures of Na and K hydroxides and silicates are also included, in combination with sulphates, sulphides, sulphites, carbonates and Ca-hydroxides and Ca-silicates, spent Bayer liquor, sodium aluminate solution, slurry of bauxite residue. The above-mentioned inorganic polymers are suitable for construction, building, bridging, supporting a structure and are manufactured as a non-fired building material comprising the inorganic polymer disclosed herein.

It is intended that the specification and examples be considered as exemplary only. Each and every claim is incorporated into the specification as an embodiment of the present invention. Thus, the claims are part of the description and are a further description and are in addition to the preferred embodiments of the present invention.

Each of the claims set out a particular embodiment of the invention. The following terms are provided solely to aid in the understanding of the invention.

By bauxite, it is implied a naturally occurring, heterogeneous weathering product composed primarily of one or more aluminum hydroxide minerals, plus various compounds containing Si, Fe, Ti, and other impurities in minor or trace amounts. The principal aluminum hydroxide minerals found in varying proportions within bauxite are gibbsite γ-Al(OH)<NUM>, and the polymorphs diaspore and boehmite, being [α-AlO(OH)] and [γ-AlO(OH)], respectively. The content of equivalent Al<NUM>O<NUM> is ><NUM> wt%. By bauxite residue, also known as red mud, it is implied the insoluble slurry residue generated during the digestion of bauxite in the alumina producing Bayer process. Bauxite residue slurries are strongly alkaline, and have a reasonably high electrical conductivity and ionic strength. In the process herein, the bauxite residue has ><NUM> wt% Fe<NUM>O<NUM>, ><NUM> wt% Al<NUM>O<NUM>, and <<NUM> wt% free H<NUM>O. The major minerals found in bauxite residue are listed in Table <NUM> of <NPL>. Among others, the bauxite residue has gibbsite as one of the minerals present, at a level ><NUM> wt%. Bauxite residue can be used after dewatering or after being already disposed, with subsequent drying and/or farming and/or thermal treatment. Upon thermal treatment, the gibbsite content may well be < 2wt%.

By source of Al, an oxide, hydroxide, oxyhydroxide, silicate, sulphide, sulphate, sulphite, halide, carbonate, phosphate, borate, and mineraloid, or a mixture of the above, found in rocks, minerals, by-products and residues, belonging to the following group, is implied: bauxite, containing ><NUM> wt% gibbsite, ideally ><NUM> wt%; clays, as found in nature or thermally or chemically or mechanically activated, preferably containing ><NUM> wt% kaolinite, ideally ><NUM> wt%; fly ash from bituminous coal, subbituminous coal or lignite, preferably containing ><NUM> wt% Al<NUM>O<NUM> equivalent, ideally ><NUM> wt%; aluminium salt slag (also known as aluminium salt cake); gibbsite-containing electrostatic precipitation dust (ESP dust), preferably containing ><NUM> wt% Al<NUM>O<NUM> equivalent, ideally ><NUM> wt%, as well as processed aluminium dross, preferably containing ><NUM> wt% Al<NUM>O<NUM> equivalent, ideally ><NUM> wt%.

By source of Si, an oxide, hydroxide, oxyhydroxide, silicate, sulphide, sulphate, sulphite, halide, carbonate, phosphate, borate, and mineraloid, or a mixture of the above, found in rocks, minerals, by-products and residues, belonging to the following group is implied: quartz sand, silica fume, precipitated silica; clays, as found in nature or thermally or chemically activated, preferably containing ><NUM> wt% kaolinite, ideally ><NUM> wt%; fly ash from bituminous coal, subbituminous coal or lignite, preferably containing ><NUM> wt% Al<NUM>O<NUM> equivalent; soda-lime-silica glass and any other type of glass, including vitreous slags, containing ><NUM> wt% SiO<NUM> equivalent.

By source of Ca, an oxide, hydroxide, oxyhydroxide, silicate, sulphide, sulphate, sulphite, halide, carbonate, phosphate, borate, and mineraloid, or a mixture of the above, found in rocks, minerals, by-products and residues, belonging to the following group is implied: CaCO<NUM>, CaO and Ca(OH)<NUM>, cement of any kind, including blended cements as defined in EN <NUM>-<NUM> and residues produced during the cement making process, for example cement kiln dust, as well as iron, steel and stainless steel slags. Where by defining wt% equivalent, it is implied the weight percent of that particular element, as calculated by XRF measurements and converted to oxides.

And where wt% of phases are mentioned, it is implied the weight percent of that particular phase, as calculated by quantitative XRD, or comparable methodologies. By a solution containing alkalis, the following solutions are implied: sodium or potassium - silicate, -carbonate, -sulphate, -sulphide, -sulphite or a mixture of any of the above, including solutions without any silicates present.

As all skilled in the art would acknowledge, in each of the three streams mentioned above, next to the element specified (Al, Si, Ca) a range of other components is introduced as well. Thus, the list above is not exhaustive, and mixed streams including (but not limited to) thermally processed bauxite residue, construction and demolition wastes, ashes from municipal solid waste treatment facilities and other incineration processes, landfill mining residues, processed or not, metallurgical slags originating from copper, lead, zinc, tin, nickel, phosphorous, as well as from the production of alloys of these metals disclosed herewith.

The production process comprises the following steps: mixing, dewatering/drying, alkali-activation, shaping, and curing. The steps of mixing, dewatering/drying and alkali-activation are sequential and can be in the order above or any other order, where for example the dewatering/drying precedes that of mixing, or where the alkali-activation precedes mixing and dewatering/drying.

Mixing takes place in a vessel where the bauxite residue, and the streams containing Si, Al and Ca are blended together in order to homogenise them. This can occur by the mechanical action of one of more shafts, auger screw, or other rotational, planetary, etc. mechanisms that will induce convective and/or intensive mixing. Mixing can take place at a state where the H<NUM>O content does not exceed <NUM> wt%, or at a slurry state, where water exceeds <NUM> wt%. Examples of mixer include, but are not limited to, paddle, ploughshare, roller pan, planetary and high shear ones. The solution containing the alkalis is introduced herein. Aggregates can be also introduced herein, that being defined as a material with particle sizes exceeding <NUM> microns, preferably <NUM> microns, with a part exceeding <NUM> microns.

After the mixing step, dewatering or drying may be necessary, depending on the water content in the mixing step. This can occur, but not limited to, by a filter-press, a drum filter, a belt filter, or other similar configurations, followed by any of the known drying methods. This step produces the right consistency for the next step, that of shaping.

In the process variable where dewatering/drying preceded the step of mixing, similar apparatus to the ones described above are used. In this process, the alkaline solution is introduced while mixing.

In one embodiment, the step that follows concerns a semi-dry shaping process. In this approach, the blend that has resulted before is dried to a water level not exceeding <NUM> wt%, milled and then pressed in a hydraulic, or a mechanical press. Additional water or alkali solution can be introduced while mixing, preferably by spray nozzles. In another embodiment, the step that follows concerns a semi-liquid shaping process. In this approach, the blend that has resulted before is dried to a water level not exceeding <NUM> wt%, and is then casted, extruded or pressed in a vibrating press. Additional water or alkali solution can be introduced while mixing. In both embodiments mentioned above, shaping can take place by any of the established techniques in the fields of concrete shaping, ceramic shaping, and aggregate shaping, such as by the so-called intensive mixers, and is not limited to the ones mentioned before.

In both embodiments mentioned above, the principles of ultra-high strength concrete design are followed, for example, coarse aggregates are excluded and the particle size distribution is designed in a way aiming to achieve high particle packing. In certain embodiments, one or more fine and/or ultrafine reactive fillers may be used having a particle size of between about <NUM> to <NUM>, whereas in other embodiments, submicron fillers with a particle size ranging from about <NUM> to about <NUM> may be used.

The resulting material is subsequently cured at elevated temperature and pressure. This is occurring at an autoclave vessel. The temperature ranges from <NUM> to <NUM> or <NUM> and <NUM>, between <NUM> and <NUM>, between <NUM> and <NUM>, or between <NUM> and <NUM> and the pressure ranges from higher than <NUM> bar to <NUM> bar. As an atmosphere in the autoclave, a concentration of CO<NUM> ><NUM> vol% will be satisfactory.

It was demonstrated in the present study that stable inorganic polymers with promising mechanical properties can be synthesised from bauxite and bauxite residue. The alkaline activator dissolves under hydrothermal conditions the alumina hydrates, reactive silicates and quartz, leading to a release of reactive aluminate and silicate species which form dense, inorganic polymers. The reaction products are amorphous in terms of crystalline structure and comprise zeolites, such as analcime, and/or carbonates, such as cancrinite.

The described process allows the use of raw materials which are available within alumina plants. Low-grade, high silica bauxites which are not suitable for alumina production are favoured as precursors in that context. Also bauxite residue has proven its potential to give inorganic polymers. Optional additions like clays or sand even improve the mechanical properties of the produced materials.

Herein disclosed is an inorganic polymer lacking fluoride or comprising only a trace of fluoride for instance less than <NUM> wt% fluoride and comprises less than <NUM> or less than <NUM> wt% of diaspore [(α-AlO(OH)] and less than <NUM> or less than <NUM> wt% boehmite (or böhmite) [γ-AlO(OH)] or comprises no diaspore and/or no boehmite. This is obtainable by modifying of a precursor by alkaline activation, press shaping and curing at a low temperate temperature between <NUM> to <NUM> or <NUM> to <NUM>, between <NUM> and <NUM>, between <NUM> and <NUM>, or between <NUM> and <NUM>, whereby the precursor comprises gibbsite (γ-Al(OH)<NUM>) minerals and whereby this gibbsite is in an amount above <NUM> wt%, between <NUM> to <NUM> wt%, between <NUM> to about <NUM> wt%, or between <NUM> to about <NUM> wt%, of the precursor and that the inorganic polymer has a compressive strength between <NUM> MPa and <NUM> MPa or between <NUM> and <NUM> MPa, between <NUM> MPa to <NUM> MPa, between <NUM> MPa to <NUM> MPa or between <NUM> MPa to <NUM> MPa. Such inorganic polymer can be achieved with the above process without the need of subjecting the shear. The material can be produced into non-fired monoliths.

The inorganic polymers disclosed herein comprises any one of the group consisting of anatase, rutile, gibbsite, hematite, goethite, kaolinite and quartz or a combination thereof or it is characterised in that it comprises anatase, rutile, hematite, kaolinite and quartz, for instance it comprises anatase and rutile each independently from each other in an amount between <NUM> wt% to <NUM> wt%, <NUM> wt% to <NUM> wt% or <NUM> to <NUM> wt%, hematite and goethite each independently from each other in an amount between <NUM> wt% to <NUM> wt%, <NUM> wt% to <NUM> wt%, <NUM> wt% to <NUM> wt% or <NUM> wt% to <NUM> wt%, kaolinite in an amount between <NUM> wt% to <NUM> wt%, <NUM> wt% to <NUM> wt%, <NUM> wt% to <NUM> wt%, <NUM> wt% to <NUM> wt% or <NUM> wt% to <NUM> wt%, quartz in an amount between <NUM> wt% to <NUM> wt%, <NUM> wt% to <NUM> wt%, <NUM> wt% to <NUM> wt%, <NUM> wt% to <NUM> wt%, <NUM> wt% to <NUM> wt% or <NUM> wt% to <NUM> wt%, comprises amorphous substances in an amount between <NUM> to about <NUM> wt% or between <NUM> to about <NUM> wt% Furthermore the inorganic polymers of disclosed herein have a normalised chemical composition of the precursor comprises oxides and in the range of Fe<NUM>O<NUM> <NUM> - <NUM> or <NUM> - <NUM> wt%, Al<NUM>O<NUM> <NUM> - <NUM> wt%, SiO<NUM> <NUM> - <NUM> wt%, TiO<NUM> wt% <NUM> - <NUM>, Na<NUM>O <NUM> - <NUM> wt%, CaO <NUM> - <NUM> wt% as can be analysed by normalised chemical composition of the precursor or the inorganic polymer is defined or definable by sequential wavelength-dispersive XRF spectrometer, for instance an automatic PW <NUM> sequential wavelength-dispersive XRF spectrometer and further Uniquant <NUM> software analysis.

One advantageously starts form a precursor mineral mix that is in total or in part from an ore, a naturally occurring mineral, or a rock for instance a rock of the group consisting of granite, gneiss and basalt for instance from an ore, a naturally occurring mineral, or a rock without additional additives; an ore, a naturally occurring mineral, or a rock without additional additives other than kaolinite in a range of <NUM> - <NUM> wt% or of <NUM> - <NUM> wt% or an ore, a naturally occurring mineral, or a rock without additional additives other than a ceramic clays or mineral clay in a range of <NUM> - <NUM> wt% or <NUM> - <NUM> wt%.

In yet another advantageous embodiment of the methods of the invention the precursor mineral composition used herein has a particle size smaller than <NUM>, preferably between <NUM> and <NUM> preferably the precursor mineral composition comprises less than <NUM> wt% of diaspore [(α-AlO(OH)] and/or less than <NUM> wt% boehmite (or böhmite) [γ-AlO(OH)], the precursor mineral composition comprises less than <NUM> wt% of silica fume or comprises no silica fume and/or the precursor mineral composition comprises less than <NUM> wt% water glass or comprises no water glass and /or the inorganic polymer according to any one of the previous claims, characterised in that the precursor mineral composition comprises less than <NUM> wt% fluoride or comprises no fluoride and/or the precursor mineral composition does not comprise diaspore [(α-AlO(OH)] and/or boehmite.

It was found that loss on ignition or volatile substances of such suitable precursor described above was in the range of <NUM> to <NUM> wt%, <NUM> to <NUM> wt% or <NUM> to <NUM> wt% as defined or definable by thermogravimetric analysis carried out at a temperature between <NUM> to <NUM>, for instance by a SDT Q600 thermogravimetric analysis instruments. It could be characterised that the amorphous substances comprise between, in approximation, <NUM> wt% to <NUM> wt%, <NUM> to <NUM>% or <NUM> wt% to <NUM> wt% or <NUM> wt% to <NUM> wt%.

The present invention relates to a suitable method of manufacture. In a particular embodiment the precursor has been shape-pressed at a pressure of at least <NUM> MPa; the precursor has been press-shaped at a pressure in the range of to <NUM> to <NUM> MPa and pressing time is between <NUM> sec and <NUM>, between <NUM> sec and <NUM>, between <NUM> sec and <NUM>, for a time between <NUM> sec and <NUM> or between <NUM> sec and <NUM>.

The present disclosure also provides that the inorganic polymer disclosed herein can be obtained from an alkaline activated and pressed precursor that has been hydrothermally cured at a temperature between <NUM> and <NUM>, <NUM> to <NUM>, between <NUM> and <NUM>, between <NUM> and <NUM>, or between <NUM> and <NUM>, whereby the shaping pressure was between <NUM> to <NUM> MPa, <NUM> to <NUM> MPa or <NUM> to <NUM> MPa and the alkaline activation is by an alkaline solution composed of Na- and/or K- and/or Ca- hydroxides, silicates, sulphates, sulphides, sulphite, carborates, and mixtures of them. In the afore mentioned solution, the sodium concentration in the solution ranges from <NUM> to <NUM> mol/l and the potassium concentration in the solution ranges from <NUM> to <NUM> mol/l, the total ratio of SiO<NUM>/(Na<NUM>O+K<NUM>O) is in the range of <NUM> to <NUM> and H<NUM>O/(Na<NUM>O+K<NUM>O) is in the range of <NUM> - <NUM> or <NUM> - <NUM>.

The inorganic polymer obtained in the present application can further be used for construction, building, bridging, supporting a structure.

One of the raw material used in this study was gibbsitic bauxite. After drying, it was milled in a ball mill (Retsch PM400) in order to pass a <NUM> mesh size.

Further, gibbsitic BR slurry was used. Before further processing the slurry was vacuum-filtered (under <NUM>) and the obtained cake was dried for <NUM> at <NUM> and milled in a disk mill (Fritsch Pulverisette) to break agglomerates.

Two kinds of clays, an industrial clay and a natural kaolin, originated from a deposit in south-west England were used in this study. Both clays were dried for <NUM> at <NUM>. The industrial clay was milled below <<NUM> using a vibratory disk mill (Retsch RS200).

The chemical composition of above-mentioned raw materials was measured using an automatic PW <NUM> sequential wavelength-dispersive XRF spectrometer (Phillips) and analyzed with the software Uniquant <NUM> (Omega Data Systems BV). X-ray diffractograms were recorded in order to determine the mineralogical composition using a D2 Phaser (Bruker AXS) and the software DiffracPlus EVA in combination with data of the ICCD-PDF-<NUM> database. Thermogravimetric Analysis, TGA (measurement of weight change) was carried out up to <NUM> using a SDT Q600 (TA Instruments) in order to determine the loss on ignition.

Five different mixes were prepared comprising different fractions of gibbsitic bauxite, gibbsitic BR, the industrial clay and kaolin (Table <NUM>). Examples using only composition A are not according to the invention.

Samples were mixed in ethanol using a Turbula Shaker (WAB, Switzerland). Before further processing, ethanol was removed by vacuum evaporation.

Two different types of activator were prepared to investigate the potential influence on the characteristics of the later products. Alkaline solution I was prepared by mixing <NUM> wt% sodium silicate solution (m SiO<NUM>/Na<NUM>O = <NUM>, <NUM> % H<NUM>O) and <NUM> wt% NaOH (<NUM>). The total ratio of SiO<NUM>/Na<NUM>O = <NUM> and H<NUM>O/Na<NUM>O = <NUM>.

Solution II was prepared by blending <NUM> wt% sodium silicate solution (m SiO<NUM>/Na<NUM>O = <NUM>, <NUM> % H<NUM>O) with <NUM> wt% NaOH (<NUM>) resulting in ratios of SiO<NUM>/Na<NUM>O = <NUM> and H<NUM>O/Na<NUM>O = <NUM>.

For the production of the samples, dry mixes were first sieved <<NUM> and subsequently mixed with the alkaline solution I according to a solution to solid ratio of <NUM>. Homogenization was carried out using an electric handheld mixer for <NUM> in total. Forming agglomerates were broken in between to assure homogenous distribution of the solution. The dry pastes were introduced in metallic moulds (dimensions: <NUM> x <NUM> x <NUM><NUM>) and pressed (hydraulic press: Carver, Inc, USA) maintaining a pressure of either <NUM> MPa, <NUM> MPa or <NUM> MPa for <NUM>. The choice of pressing the samples for shaping leads to a decreased requirement of alkaline solution compared to castable pastes. Potentially, a low degree of porosity, a higher degree of reaction and thus more stable products can be achieved compared to casting. The pressed articles were subsequently subjected to curing for <NUM> under hydrothermal conditions using an autoclave cell filled with distilled water which was positioned in a laboratory oven. Different temperatures and thus pressure regimes were screened. A compilation of the produced samples, moulding pressure and curing temperature are listed in Table <NUM>.

For the dry mix C, additional samples were produced using alkaline solution II applying a shaping pressure <NUM> MPa and a curing temperature of <NUM>.

After the curing duration of <NUM>, samples were allowed to cool down slowly in order to suppress the formation of cracks due to a thermal shock. After removing from the autoclave cell, specimens of every sample type were boiled for <NUM> in water in order to visually investigate their water stability.

The compressive strength of the produced samples was tested on an Instron <NUM> (load cell <NUM> kN), applying a crosshead speed of <NUM>/min. Four specimens were measured for each sample type.

Selected samples were analysed using X-ray diffraction as described in "Characterization of raw materials" and compared with spectra of the respective dry mixes. The samples were further analysed using Al MAS NMR spectroscopy.

Bauxite comprises as expected mostly of alumina, a substantial amount of iron oxide next to silica and minor titania (Table <NUM>).

The mineralogical composition and the recorded diffractogram of gibbsitic bauxite are displayed in <FIG>.

The gibbsitic bauxite residue is dominated by Fe<NUM>O<NUM> and still a relatively high content of undigested alumina is present, besides silica, titania and minor sodium oxide and calcia (Table <NUM>).

As regards the mineralogy, main phases are hematite (<NUM> wt%) and goethite (<NUM> wt%), followed by cancrinite (<NUM> wt%), gibbsite (<NUM> wt%), katoite (<NUM> wt%), rutile (<NUM> wt%), quartz (<NUM> wt%) and boehmite (<NUM> wt%), next to amorphous phases.

The industrial clay is characterized by a high content of silica and alumina (Table <NUM>), which is also reflected in the mineralogical composition with quartz (<NUM> wt%), micas (<NUM> wt%), <NUM>:<NUM> clays (<NUM> wt%) and <NUM>:<NUM> clays (<NUM> wt%) next to calcite (<NUM> wt%) and rutile (<NUM> wt%).

Kaolin comprises mainly of kaolinite (<NUM> wt%) and <NUM>:<NUM> clays (<NUM> wt%), next to K-felspar (<NUM> wt%) and quartz (<NUM> wt%). Its chemistry is thus dominated by silica (<NUM> wt%) and alumina (<NUM> wt%) with minor quantities of K<NUM>O (<NUM> wt%) and Fe<NUM>O<NUM> (<NUM> wt%).

The synthesised materials were all water stable after boiling in water for <NUM>.

The mechanical properties of the tested samples are shown in Table <NUM>.

The compressive strengths of mix C, prepared with alkaline solution II, shaping pressure <NUM> MPa and curing temperature <NUM>, show similar values as the samples activated with alkaline solution I, reaching <NUM> ± <NUM> MPa.

All tested mixes have proven their suitability as precursor materials for inorganic polymer materials with adequate strengths for a range of applications. The higher the content of reactive silica in the precursor material, the higher the compressive strength of the final product. The highest compressive strength is achieved in sample A1, but it has to be noted that a higher shaping pressure was applied for that mix.

In <FIG>, representative XRD scans of the reaction products are compared qualitatively in the range of <NUM> to <NUM> °2ϑ with the respective dry precursor.

<FIG> indicates that the changes between the precursor mix B and the IP B2 are mainly concentrated on the phases cancrinite, gibbsite, quartz and katoite. After the hydrothermal curing neither gibbsite nor quartz are detected and also the intensity of the katoite peaks are significantly decreased, which suggests the dissolution of these phases after the autoclaving process. The peak intensities of cancrinite increased and while pectolite peaks appear.

A similar trend can be seen for precursor C and IP C3 (<FIG>), where cancrinite intensities raised, while gibbsite and quartz peaks disappeared. In contrast to system B, intensities of boehmite increased while katoite remained constant.

In system D (<FIG>), an increase in cancrinite, boehmite can be observed after activation, while gibbsite is again consumed. Further, the zeolite phases analcime and gismondine are formed.

The XRD data suggest that gibbsite, present in BR and bauxite is digested during autoclaving either releasing aluminates in the pore solution or dehydrating to boehmite. Cancrinite peak intensity is increased in all samples, suggesting the formation of cancrinite in all investigated samples. In the present case, cancrinite formation can possibly be explained by the release of aluminate species (originating from gibbsite dissolution), silicates (from the activation solution or quartz dissolution) and sodium from the activation solution. The formation of the crystalline phases, such as zeolithes (i.e. analcime and gismondine), and potentially amorphous structures are believed to be responsible for the setting and the strength development in the hydrothermally cured materials.

Claim 1:
A method for manufacturing an inorganic polymer object from a precursor
wherein the precursor comprises gibbsite-containing residue of the Bayer process or thermally processed gibbsite-containing residue of the Bayer process, wherein the precursor is free from, or comprises less than <NUM> wt% of one or more species selected from the group consisting of ground granulated blast furnace slag, basic oxygen furnace slag, kaolin tailings, coal gangue and silica fume,
the method comprising the steps of:
- alkaline-activating said precursor,
- mixing the precursor,
- shaping the mixed precursor and
- hydrothermally curing the shaped precursor at a temperature between <NUM> and <NUM>, and under a pressure higher than <NUM> bar and less than <NUM> bar, whereby the precursor comprises up to <NUM> wt% one or more of a component selected from the group consisting of quartz sand, precipitated silica, natural clay, calcareous sand, thermally-activated clay, chemically-activated clay, mechanically-activated clay, fly ash from bituminous coal, subbituminous coal or lignite, gibbsite-containing electrostatic precipitation dust (ESP dust), aluminium salt cake, processed aluminium dross, CaCO<NUM>, CaO and Ca(OH)<NUM>, mono-, di- and tricalcium silicate, metallurgical slag, EN <NUM>-<NUM> blended cement, cement kiln dust, soda-lime-silica glass or other glass compositions, thermally processed bauxite residue and vitreous slag.