Cementitious compositions comprising de-lithiated beta-spodumene and methods for their application

Abstract

The present invention relates to methods of applying cementitious compositions comprising de-lithiated beta-spodumene by injecting, by spraying, or by layer-by- layer deposition, to cementitious compositions comprising de-lithiated beta-spodumene, and to the use of de-lithiated beta-spodumene to increase the shear modulus G of a cementitious composition.

Description

CEMENTITIOUS COMPOSITIONS COMPRISING DE-LITHIATED BETA-SPODUMENE AND METHODS FOR THEIR APPLICATIONTechnical FieldThe present invention relates to methods of applying cementitious compositions comprising de-lithiated beta-spodumene and to cementitious compositions comprising de-lithiated beta-spodumene.Background of the inventionVarious aluminosilicates are known as suitable supplementary cementitious materials. The use of such aluminosilicates is especially appealing where they are obtained as a by-product or waste stream from industrial processes and / or where their environmental footprint, especially carbon footprint, is lower as compared to cement clinker. In particular, the replacement of Portland cement by supplementary cementitious materials is of interest to reduce the environmental footprint of hydraulic binder compositions. Aluminosilicates are interesting replacement materials for Portland cement because they typically have pozzolanic properties and can therefore contribute to the mechanical strength of a cured hydraulic binder composition.An aluminosilicate material that has become available more recently is de-lithiated beta-spodumene, sometimes also referred to as lithium slag. Spodumene is a lithium-bearing mineral of the approximate chemical formula LiAISi2Oe that may exist in an alpha- and in a beta-form. While the alpha-form occurs naturally, the beta-form is formed by heating of alpha-spodumene to high temperatures. The betaspodumene has a more open structure and therefore allows for easier lithium extraction for example by acid or alkaline leaching. The material remaining after lithium has been extracted is referred to as de-lithiated beta-spodumene. De-lithiated beta-spodumene has become more available in recent years, because demand for lithium, for example for use in batteries, has largely increased.It is known to use de-lithiated beta-spodumene as supplementary cementitious material in concrete or cementitious mortar. For example, US 11 ,685,689 B2 (Nemaska Lithium Inc) discloses a process to obtain de-lithiated aluminosilicate from spodumene and its use in concrete and cementitious mortar. However, the concrete or cementitious mortars of US 11 ,685,689 B2 comprising de-lithiated spodumenehave a lower mechanical strength when cured as compared to concrete or mortar entirely based on Portland cement. The mechanical strength decreasing with increasing content of de-lithiated spodumene. However, to reduce the environmental footprint of cementitious compositions, high replacement levels of Portland cement by de-lithiated beta-spodumene are required.It is therefore desirable to find suitable materials and methods that can increase the mechanical strength of cured hydraulic binder compositions comprising de-lithiated beta-spodumene, especially at high contents of de-lithiated beta-spodumene. It is likewise desirable to find applications where de-lithiated beta-spodumene can replace cement to a large extent.Summary of the inventionIt is an object of the present invention to provide methods and uses of cementitious compositions comprising de-lithiated beta-spodumene. In particular, to provide methods and uses of cementitious compositions where cement, especially Portland cement, is replaced to a large extent by de-lithiated beta-spodumene.It has surprisingly been found that the shear modulus G at early age of a cementitious composition can be improved, when cement is replaced by de-lithiated beta-spodumene. Such increased shear modulus G is particularly desirable in applications where cementitious compositions are to be applied by injection, by spraying, or by layer-by-layer deposition.The increase of the shear modulus G also came as a surprise because other mechanical properties, especially the compressive strength of cementitious compositions are known to be lowered when de-lithiated beta-spodumene is present.The object of the present invention is therefore solved by a method as claimed in claim 1 .Further aspects of the present invention are the subject matter of independent claims. Preferred embodiments of the present invention are the subject matter of dependent claims.Detailed WaysIn a first aspect the present invention relates to a method of applying a cementitious composition comprising the steps of(i) preparing a cementitious composition comprising at least one cement, de-lithiated beta-spodumene, and optionally fillers and / or aggregates, and(ii) applying the cementitious composition by injecting, by spraying, or by layer-by- layer deposition.A cementitious composition within the present context comprises at least one cement, de-lithiated beta-spodumene (DBS), and optionally fillers and / or aggregates.According to embodiments, the cement is a cement according to standard EN 197-1 or EN 197-5. For example, the cement can be chosen from CEM I, CEM II, CEM III, CEM IV, or CEM V according to standard EN 197-1 , or from CEM II or CEM VI according to standard EN 197-5. Cements according to other standards, for example ASTM C150-07, is also suitable. A very preferred cement is Ordinary Portland cement or CEM I according to standard EN 197-1.According to embodiments, the cement is a calcium aluminate cement. Calcium aluminate cement is a material comprising one or more of the mineral phases CA, CA2, and C12A7 (with C: CaO, A: AI2O3). Further mineral and / or amorphous phases may additionally be present. The phase composition may be evaluated by XRD. For example, calcium aluminate cement can be according to standard EN 14647:2005.According to embodiments, the at least one cement is a calcium sulfoaluminate cement. A calcium sulfoaluminate cement is a cement comprising C4(As-xFx)$ (with C: CaO; A: AI2O3; F: Fe2Os; $: SO3) where x is an integer of from 0 - 3.According to embodiments, the cementitious composition comprises a mixture of two, three, or more of Portland cements, calcium aluminate cement, and / or calcium sulfoaluminate cement.Preferably, the cement is Ordinary Portland cement.A cementitious composition of the present invention may additionally comprise pozzolanic and / or latent hydraulic materials different from de-lithiated betaspodumene. Additional pozzolanic and / or hydraulic materials in particular can be selected from steelmaking slag, ironmaking slag, rice husk ash, burnt oil shale, calcined clay, and volcanic ashes.Within the present context the at least one cement, the de-lithiated beta-spodumene, and optionally present additional pozzolanic and / or latent hydraulic materials together are also referred to as a hydraulic binder.De-lithiated beta-spodumene is a material resulting from the lithium extraction from the mineral spodumene having the approximate chemical formula LiAISi20e. Typically, beta-spodumene is formed by heating of alpha spodumene to high temperatures. The beta-spodumene has a more open structure and therefore allows for easier lithium extraction for example by acid or alkaline leaching. The material remaining after lithium has been extracted is referred to as de-lithiated betaspodumene.According to embodiments, the de-lithiated beta-spodumene comprises 20 - 35 w% of AI2O3, 60 - 70 w% of SiO2, 0.1 - 2 w% of Fe2Os, and up to 3 w% of SO3, in each case relative to the total dry weight of the de-lithiated beta-spodumene. The oxide composition of de-lithiated beta-spodumene can be determined by x-ray fluorescence (XRF).According to embodiments, de-lithiated beta-spodumene of the present invention has a particle size D10 of between 2 - 10 pm, especially between 2 - 4 pm, and a particle size D90 of between 30 - 100 pm, especially between 30 - 50 pm. The particle size D10 is the size in the particle size distribution where 10% of particles are smaller and 90% are bigger. The particle size D90 is the size in the particle size distribution where 90% of particles are smaller and 10% are bigger. The medium particle size D50 of a preferred de-lithiated beta-spodumene is between 5 - 30 pm, especially between 5 - 10 pm. The particle size can be determined by laser diffraction according to standard ISO 13320:2009.Very preferably, de-lithiated beta-spodumene has a low alkali content, especially a content of Na2O equivalents of not more than 1 .0 w%. Also very preferably, de- lithiated beta-spodumene has a low chloride content, especially a content of chlorides of not more than 0.01 w%.According to embodiments, the de-lithiated beta-spodumene contains not more than 30 w% of water, preferably 0 - 30 w% of water or 10 - 30 w% of water, relative to the total weight of the de-lithiated beta-spodumene. Water in this context is absorbed water. Absorbed water can be measured by drying a sample of de-lithiated beta-spodumene in an oven. It is possible to dry the de-lithiated beta-spodumene before use, for example by drying in an oven.Preferably, in a method of the present invention, the cementitious composition comprises at least 20 w%, preferably at least 30 w%, more preferably 20 - 50 w%, especially 20 - 30 w% or 30 - 40 w%, of de-lithiated beta-spodumene, relative to the total dry weight of cement and de-lithiated beta-spodumene. Thereby, the percentage is given in relation to the sum of cement and de-lithiated beta-spodumene, and, if present additional pozzolanic and / or latent hydraulic materials. In other words, the percentage is given in relation to the total dry weight of hydraulic binder.Aggregates are materials that are not reactive in the hydration reaction of the cementitious composition. Within the present context, aggregates are understood to be particulate materials, preferably with a particle size of more than 0.063 mm and up to several cm. One or more aggregates of different chemical composition and / or of different particle size distribution may be used. A very preferred aggregate is sand.Fillers are understood to be very finely divided particulate materials, preferably with a particle size of lower than 0.063 mm. One or more fillers of different chemical composition and / or of different particle size distribution may be used. Fillers, within the present context, are non-reactive in the hydration reaction of the cementitious composition but may have an accelerating effect as they can act as seeds for the precipitation of hydrate phases. A preferred filler within the present context is ground limestone.A cementitious composition of the present invention may be a dry composition. Dry means that the cementitious composition is in the form of a free flowing powder. If the cementitious composition is provided in the form of a free flowing powder, a method of the present invention very preferably additionally comprise a step of mixing the cementitious composition with water. It is preferred, that the mixing with water is done after the mixing of the at least one cement, de-lithiated beta-spodumene, and optionally fillers and / or aggregates, but before any step of application.It is likewise possible that the cementitious composition is in the form of a wet, preferably an aqueous, slurry or paste. In such cases, preferably, the cementitious composition additionally comprises water, especially with a weight ratio of water to hydraulic binder of 0.4 - 0.7.Methods and means for the preparation of a cementitious composition of the present invention are not particularly limited and are known to the skilled person. For example, a cementitious composition can be prepared by providing at least one cement, de-lithiated beta-spodumene, and optionally fillers and / or aggregates and, in powder form to one or more weight hoppers. In some embodiments, fillers and / or aggregates are present and the de-lithiated beta-spodumene is intermixed with the fillers and / or aggregates in dry state before mixing with the cement. Powder materials can be dosed from weight hoppers into a mixer, such as an Auger mixer, and additionally water and optionally admixtures and accelerators can be added. It can be preferred to provide any admixtures and accelerators as a solution or dispersion in the mixing water. Mixing can be discontinuous or continuous. Continuous mixing has the advantage of high throughput.According to embodiments, the cementitious composition additionally comprises at least one of a superplasticizer, a retarder, and reinforcing fibers.The superplasticizer preferably is selected from polycarboxylate ethers, lignosulfonates, melamine formaldhyde resins, polyaryl ethers, and mixtures thereof. The retarder preferably is selected from sugar and sugar derivatives, hydroxycarboxylic acids, phosphates, and mixtures thereof. The reinforcing fiber preferably is selected from thermoplastic fibers, in particular polypropylene fibers, steel fibers, or mixtures thereof.According to embodiments, the cementitious composition additionally comprises at least one activator selected from the group consisting of alkali metal sulfate, alkali metal chloride, alkaline earth metal chloride, alkali metal silicate, aluminium sulfate, and mixtures thereof.It has been found that such activators increase the reactivity of de-lithiated betaspodumene in hydraulic reactions.Particularly preferably, the at least one activator is selected form the group consisting of sodium sulfate, potassium sulfate, magnesium sulfate, sodium chloride, potassium chloride, magnesium chloride, calcium chloride, sodium silicate, potassium silicate, aluminium sulfate, and mixtures thereof.It is preferred that the at least one activator is present in an amount of 0.5 - 5 w%, preferably 1 - 3 w%, relative to the total dry weight of de-lithiated beta-spodumene.A method of the present invention comprises a step of applying the cementitious composition by injecting, by spraying, or by layer-by-layer deposition.It is relevant in methods of applying of cementitious compositions by injecting, spraying, or layer-by-layer deposition that the cementitious compositions have a sufficiently high shear modulus G at early age. A suitable method and apparatus to measure shear modulus G of cementitious compositions at early age is described, for example, in EP 1726947 (Sika Technology AG). Thereby, the expression “early age” of a cementitious composition relates to a time of not more than 4 hours from the mixing of the dry cementitious composition with water.The shear modulus G is an intrinsic material property and describes the materials resistance to shear deformation under static or quasi-static loads. A high shear modulus G of a cementitious composition is linked to a high resistance of said cementitious composition when exposed to a given shear deformation. This is particularly relevant, if the cementitious composition is to be used under conditions where significant shear deformations are encountered. It is normally a requirement that cementitious compositions remain in place directly after application onto a substrate. This can be difficult to achieve where the cementitious composition is applied overhead or on substrates having a strong inclination such as for example a wall. This can also be difficult when the cementitious composition is intended to fill a void that extends substantially horizontally or when the cementitious composition is to be applied in subsequent layers that need to support each other. In all of these cases, a sufficiently high shear modulus G of the cementitious composition is required to ensure that said cementitious composition does not drip down, run down, or flow out under the forces of gravity, rebound when projected against a support, or collapse under the weight of subsequent layers.The addition of de-lithiated beta-spodumene to a cementitious composition, in particular the replacement of cement by de-lithiated beta-spodumene, allows to increase the shear modulus G at early age as compared to the same cementitious composition not comprising de-lithiated beta-spodumene.At the same time, the flow properties, such as slump and slump flow measured according to standards AS 1012.3.1 and AS 1012.3.5 or ASTM C143 and ASTM C1611of a cementitious composition comprising de-lithiated beta-spodumene can be easily adjusted to be on a level desirable for pumping.Application of a cementitious composition can be done as long as the cementitious composition is in a dry state. It is, however, preferred within the present context to apply a cementitious composition in the wet state, in particular in the form of an aqueous slurry or paste.It is possible to apply the cementitious composition on a substrate. A substrate can for example be a support element or a part of a building such as a wall, a floor, or a ceiling. A substrate can also be another layer of cementitious composition.It is possible to apply a cementitious composition of the present invention by injection. In particular injection means injection into a void, especially a void that extends substantially horizontally. It is an advantage of the present invention that flowing out of the cementitious composition is minimized. In particular, where a cementitious composition is applied by injection, the method of the present invention is a method of grouting. For example, grouting of an annulus in a tunneling application or backfilling of a mine. Equipment for annulus grouting or mine backfilling is known to the skilled person.It is possible to spray apply a cementitious composition of the present invention onto a substrate. Thereby, a layer of cementitious material on the substrate may be formed. In particular, where a cementitious composition is applied by spraying, the method of the present invention is a method of shotcreting, for example shotcreting of the walls of a tunnel or of a mine. It is an advantage of the present invention that rebounding, dripping down, or running down of the cementitious composition is minimized. During shotcreting the cementitious composition is conveyed through a hose and pneumatically projected at high velocity onto a substrate. It is preferred, that an additional shotcrete accelerator is added during spray application, in particular a preparation of aluminium sulfate. Equipment for shotcreting is known to the skilled person.It is possible to apply a cementitious composition of the present invention by layer- by-layer deposition. Thereby, several consecutive layers of cementitious material may be formed. It is an advantage of the present invention that collapse of supporting layers of the cementitious composition is minimized. In particular, where a cementitious composition is applied layer-by-layer, the method of the present invention is a method of 3D printing. Equipment for 3D printing is known to the skilled person.In another aspect, the present invention relates to a cementitious composition for injecting, spraying, or layer-by-layer deposition comprising, in each case relative to the total dry weight of the composition, a) 10 - 20 w% of at least one cement, b) 2 - 10 w%, preferably 5 - 10 w%, of de-lithiated beta-spodumene, c) 65 - 75 w%, preferably 65 - 70 w%, of fillers and / or aggregates, d) optionally up to 0.3 w% of admixtures, d) optionally water in a weight ratio of water to hydraulic binder of 0.4 - 0.7.All features and embodiments as described for other aspects also apply to this aspect.According to embodiments, the cementitious composition of the present invention additionally comprises a concrete additive selected from the group consisting of silica fume, fly ash, and mixtures thereof.According to embodiments, the cementitious composition of the present invention additionally comprises 0.5 - 5 w%, preferably 1 - 3 w%, relative to the total dry weight of de-lithiated beta-spodumene, of at least one activator selected from the group consisting of alkali metal sulfate, alkali metal chloride, alkaline earth metal chloride, and mixtures thereof.Very preferably, a cementitious composition as described above is used in a method of the present invention as described above.In another aspect, the present invention relates to a hardened body, obtained by curing a cementitious composition as described above.All features and embodiments as described for other aspects also apply to this aspect.The hardened body can be part of a building, especially of a tunnel or of a mine. The Hardening of the cementitious composition starts with the addition of water and proceeds with time. Preferably, hardening is done at ambient conditions without the application of heat or pressure and without the addition of further chemicals. It is, however, also possible to heat cure a cementitious composition of the present invention, for example at temperatures above 40 °C and as high as 170 or 190 °C.When hardening at temperatures around 100 °C or higher, typically also increased pressure is applied, for example by autoclaving the cementitious composition. Steam curing of a cementitious composition of the present invention is also possible.It is also possible, even though not preferred, to increase the rate of hardening by supplying CO2 gas to the hardening cementitious composition.In another aspect the present invention relates to the use of de-lithiated betaspodumene to increase the shear modulus G of a cementitious composition.All features and embodiments as described for other aspects also apply to this aspect.The cementitious composition comprises water in a weight ratio of water to hydraulic binder of 0.4 - 0.7.In particular, de-lithiated beta-spodumene is used to replace cement in the cementitious composition. Thereby, the total amount of hydraulic binder is kept constant.Preferably, the shear modulus G is increased at early age, especially at an age of not more than 4 hours measured from mixing of the dry cementitious composition with water.The expression “increase” relates to an increase of the shear modulus G as compared to a cementitious composition not comprising de-lithiated beta-spodumene but comprising the same total amount of hydraulic binder.ExamplesIn a first set of experiments, hydraulic binders for cementitious compositions were prepared by mixing Ordinary Portland Cement with de-lithiated beta-spodumene. Thereby, four binders were produced having a content of 0 w%, 20 w%, 30 w%, and 40 w% of de-lithiated beta-spodumene, relative to the total dry weight of the respective binder.The de-lithiated beta-spodumene used had the following properties:■ XRF analysis: 69.2 w% SiO2, 29.4 w% AI2O3, 0.29 w% CaO, 0.28 w% Fe2Os, 0.19 w% K2O, 0.1 w% Na2O, 0.35 w% SO3■ Granulometry (measured according to standard ISO 13320:2020): D10: 2.5 pm, D50: 8.8 pm, D90: 36.4 pm■ Activity index (measured according to standard EN 15167-1 :2006): 45% @ 7days, 65% @ 28 days■ Moisture content (measured by oven drying): 23.9 w%In a first set of experiments, the hydraulic binders 1 - 4 were mixed with water in a weight ratio of water to binder of 0.46 to form cementitious pastes P1 - P4. The respective paste was then spray applied in a mini-shot application (see below) whereby 8 w% of aluminium sulfate based accelerator (50% solids) were added, relative to the total dry weight of hydraulic binder.The mini-shot application is a laboratory application simulating real shotcrete application. In the mini-shot application a cementitious paste is spray applied with a shotcrete gun, the accelerator is added to the paste in the spray gun. The set-up and measuring principles of a mini-shot are for examples described in EP 1726947 (Sika Technology AG), in particular in paragraphs

[0072] -

[0076] ,The following table 1 shows the measurement results of shear modulus G over time.Table 1: Results of shear modulus for cementitious pastes P1 (comparative) and P2- P4 (inventive)* w% relative to sum of OPC and de-lithiated beta-spodumeneIt can be seen from the results of table 1 that the shear modulus at early time is increased where de-lithiated beta-spodumene is present. An increased shear modulus is indicative of reduced sagging or rebounding of the cementitious composition in spray applications.In a second set of experiments, shotcrete compositions were prepared from the hydraulic binders 1 - 4 as described above. Thereby, 460 kg of the respective binder, 484 kg of fine sand (0.15 - 0.6 mm), 724 kg of coarse sand (0.15 - 6.7 mm), and 465 kg of aggregate (2.36 - 9.5 mm) were dry mixed until visually homogeneous. Total batch water of 210 kg was added. Together with the batch water polycarboxylate ether based superplasticizer, sugar-acid based retarder, and polypropylene fiber with length 65 mm and cross section of 1 .37 x 0.34 mm were added in the respective amounts indicated in below table 2. Mixing was continued for 3 minutes.Slump and slump flow of the resulting shotcrete compositions S1 - S4 was measured according to standards AS 1012.3.1 and AS 1012.3.5 directly after mixing and after 3 h of mixing.Heat release was measured in an isothermal process as described in standard ASTM C1702-17 using an instrument Semament. The open time is the time at the point of inflection of the cumulative heat flow curve. It was measured on the heat flow curve as the time where the heat flow curve starts to increase.Table 2: Examples S1 (comparative) and S2 - S4 (inventive)* w% relative to sum of OPC and de-lithiated beta-spodumeneIt can be seen from the results of above table 2 that the introduction of de-lithiated beta-spodumene in a cementitious composition for spray application leads to a faster reaction. While superplasticizer dosages of the mixes were adjusted to achieve the same initial slump for all mixes, results in table 2 show that at essentially the same initial slump, the slump retention and the initial slump flow both are improved when de-lithiated beta-spodumene is present, and the slump flow retention is improved for examples S2 and S3. In addition the compressive strength at late age is improved for examples S2 and S3.

Claims

Claims1 . Method of applying a cementitious composition comprising the steps of(i) preparing a cementitious composition comprising at least one cement, de- lithiated beta-spodumene, and optionally fillers and / or aggregates, and(ii) applying the cementitious composition by injecting, by spraying, or by layer- by-layer deposition.

2. The method as claimed in claim 1 , wherein the cementitious composition comprises at least 20 w%, preferably at least 30 w%, more preferably 20 - 50 w%, especially 20 - 30 w% or 30 - 40 w%, of de-lithiated beta-spodumene, relative to the total dry weight of cement and de-lithiated beta-spodumene.

3. The method as claimed in at least one of the previous claims, wherein the de- lithiated beta-spodumene contains not more than 30 w% of water, preferably 0 - 30 w% of water, relative to the total weight of the de-lithiated beta-spodumene.

4. The method as claimed in at least one of the previous claims, wherein the cementitious composition additionally comprises at least one of a superplasticizer, a retarder, and a reinforcing fiber.

5. The method as claimed in at least one of the previous claims, wherein the cementitious composition additionally comprises water.

6. The method as claimed in at least one of the previous claims, wherein the cementitious composition additionally comprises at least one activator selected from the group consisting of alkali metal sulfate, alkali metal chloride, alkaline earth metal chloride, alkali metal silicate, aluminium sulfate, and mixtures thereof.

7. The method as claimed in claim 6, wherein the at least one activator is present in an amount of 0.5 - 5 w%, preferably 1 - 3 w%, relative to the total dry weight of de-lithiated beta-spodumene.

8. The method as claimed in at least one of claims 6 - 7, wherein the at least one activator is selected form the group consisting of sodium sulfate, potassiumsulfate, magnesium sulfate, sodium chloride, potassium chloride, magnesium chloride, calcium chloride, aluminium sulfate, and mixtures thereof.

9. The method as claimed in at least one of the previous claims, wherein fillers and / or aggregates are present and the de-lithiated beta-spodumene is intermixed with the fillers and / or aggregates in dry state before mixing with the cement.

10. A cementitious composition for injecting, spraying, or layer-by-layer deposition comprising, in each case relative to the total dry weight of the composition, a) 10 - 20 w% of at least one cement, b) 2 - 10 w%, preferably 5 - 10 w%, of de-lithiated beta-spodumene, c) 65 - 75 w%, preferably 65 - 70 w%, of fillers and / or aggregates, d) optionally up to 0.3 w% of admixtures, d) optionally water in a weight ratio of water to hydraulic binder of 0.4 - 0.7.11 . The cementitious composition as claimed in claim 9, wherein it additionally comprises a concrete additive selected from the group consisting of silica fume, fly ash, and mixtures thereof.

12. The cementitious composition as claimed in at least one of claims 10 - 11 , wherein it additionally comprises 0.5 - 5 w%, preferably 1 - 3 w%, relative to the total dry weight of de-lithiated beta-spodumene, of at least one activator selected from the group consisting of alkali metal sulfate, alkali metal chloride, alkaline earth metal chloride, and mixtures thereof.

13. A hardened body, obtained by curing a cementitious composition as claimed in at least one of claims 10 - 12.

14. Use of de-lithiated beta-spodumene to increase the shear modulus G of a cementitious composition.

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