TECHNICAL FIELD

The present disclosure relates to a binder composition, a hardenable mixture, a material or an article, and to methods for preparing the same.

BACKGROUND

Concrete based on Portland cement, although very widely used, typically has a relatively high en vironmental impact, and its production typically leads to high CO2 emissions. There has therefore been inter est in replacing traditional cement to at least some extent with more environmentally friendly components, and in reducing the environmental impact of concrete and concrete-like materials and binders used in them.

SUMMARY

A binder composition is disclosed. The binder composition may comprise Si<¾ and AI2O3, such that a weight ratio of Si02:Al ₂ 03 is in the range of about 10:1 to about 1:2. A hardenable mixture is also disclosed,

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the embodiments and constitute a part of this specification, illustrate various embodiments . In the drawings :

Fig. 1A and B illustrate silicon (S1O2) separated from coal bottom ash as particles having a substantially spherical structure. DETAILED DESCRIPTION

A binder composition is disclosed. The binder composition may be for preparing a hardenable mixture.

In the context of this specification, the term "binder composition" may refer to a composition that is suitable for preparing a hardenable mixture or mass, in particular when mixed with an aggregate material and optionally with a solvent, such as water or an aqueous solution.

The binder composition may comprise Si0 ₂ and

Al ₂ 0 ₃ , optionally in admixture with one or more other components. The components of the binder composition, such as the Si0 ₂ and the Al ₂ 0 ₃ , may react and harden, and upon hardening, bind to the aggregate, thereby forming a hardened material.

The binder composition may be cementitious. It may be used in a manner similar to traditional cement, or it can be used to replace traditional cement (e.g. Portland cement) at least partially in concrete or mortar mixtures.

The binder compositions described herein may have a low carbon footprint, and their manufacture may require a relatively low amount of energy, in particular when compared with traditional cement. Hardened materials and articles obtained using the binder composition may be relatively tolerant of salts and/or high temperatures during their manufacture and even their entire life cycle.

Not to be bound by theory, it may be that the Si0 ₂ and the Al ₂ 0 ₃ in the binder composition may react together when present in a hardenable mixture and form polymer chains or structures similar to polymer chains. These structures may be created e.g. when the binder composition contains ash or fly ash. However, in some embodiments, silicon-oxygen-silicon bonds and/or silicon-oxygen-aluminium bonds may additionally or instead be created. In embodiments where the hardenable mixture contains a solvent which is an aqueous solution including salts, such as an aqueous solution containing sodium chloride, or for instance seawater, sodium and/or chlorides or other salts may also participate in the reaction and/or be present in the structure . In embodiments where the binder composition contains ash that includes calcium, calcination may also take place.

Traditional Portland cement is considered to undergo a hydration reaction with water. However, the binder composition according to one or more embodiments described in this specification does not necessarily require the presence of water for the reaction and subsequent hardening; water or other suitable solvent may nevertheless facilitate the starting of the reaction. Water or other suitable solvent may also be mixed in the hardenable mixture to obtain a paste-like or a mass-like hardenable mixture that is suitable for casting.

Furthermore, it has now been found that the hardenable mixture may be hardened even in conditions in which no additional activator is added, and/or when the pH of the hardenable mixture is not strongly alkaline. For example, there may not be a need to add an alkali activator, such as an alkali hydroxide component. Therefore the need to additionally use an activator, such as a strongly alkaline hydroxide activator, may be reduced, or the need for an activator may even be avoided altogether, which may render processing and preparation of the binder composition and the hardenable mixture much simpler and safer, and also reduce costs. Thus, in some embodiments there is no additional activator present in the binder composition and/or the hardenable mixture .

The binder composition may have a weight ra tio of Si0 ₂ :Al ₂ 0 ₃ in the range of about 10:1 to about 1:2. Increasing the relative amount of Si0 ₂ may in crease the compression strength of the hardened mate rial obtainable with the binder composition. Increasing the relative amount of Al ₂ 0 _3/ on the other hand, may increase the tensile strength and/or thermal re sistance of the hardened material obtainable with the binder composition. A well-suited binder composition may have, for example, a weight ratio of Si02:Al ₂ 03 in the range of about 5:1 to about 1:1, or of about 4:1 to about 2:1.

The compression strength of the material or article obtained by hardening the hardenable mixture may be measured e.g. in MPa. The compression strength may be measured e.g. according to the standards EN 12350-1, EN 12390-2 and/or EN 12390-3.

Various starting materials may be used to prepare the binder composition. For example, the bind er composition may comprise essentially pure Si0 ₂ and essentially pure Al ₂ 0 ₃ in admixture in a desired weight ratio. Essentially pure Si0 ₂ may comprise at least 90 wt-%, or at least 95 wt-% of Si0 ₂ . Essentially pure AI2O3 may comprise at least 90 wt-%, or at least 95 wt- % of AI2O3. However, additionally or alternatively, various industrial by-products and/or recycled materi als may be used. Such industrial by-products and/or recycled materials may comprise Si0 ₂ and/or Al ₂ 0 ₃ . If desired, they may be processed, fractionated, and/or blended before forming the binder composition to pro vide the binder composition as intended.

To ensure that the S1O2 reacts with the A1 ₂ 0 ₃ , it may be included in the binder composition at least partly in a reactive form. At least part of the sili con in the binder composition may be in a reactive form. In an embodiment the material comprising the silicon or the Si0 ₂ is at least partly in the form of particles having a substantially spherical structure (Fig. 1A and IB) . This type of silicon is obtained for example by separating silicon containing particles from coal bottom ash or other suitable material and by grinding the silicon containing particles to a desired particle size e.g. by a pin mill or by jet pulveriza tion. So-called reactive silicon can be generated for example by heating i.a. blast furnace slag to 1100 de grees. In an embodiment, the Si0 ₂ or the whole binder composition may be in the form of particles, the par ticle diameter of the particles being less than or equal to about 20 pm. In an embodiment the particle diameter of the particles may be in the range of 1 to 20 pm. In such particles, the silicon may be in a re active form. When the silicon is in a reactive form, the hardening reaction may be efficiently initiated.

The binder composition may comprise at least one Si(¾- and/or Al ₂ C> ₃ -containing material selected from Si0 ₂ , AI ₂ O ₃ , ash, fly ash, slag, a Si0 ₂ -containing mineral, an Al ₂ 0 ₃ -containing mineral, tailings, a side stream material from a chemical pulping process, bed- sand obtainable from a power boiler, bottom ash ob tainable from the combustion of coal, red mud (baux ite) , ponded ash, and any mixtures and combinations thereof .

The binder composition may comprise two or more Si0 ₂ - and/or Al ₂ 0 ₃ -containing materials. These ma terials may be combined to obtain a desired composi tion .

The ash may be ash obtainable from the com bustion or incineration of coal, biomass (for example, wood-based biomass) and/or waste, for example munici pal waste. The ash may comprise Si0 ₂ and/or Al ₂ 0 ₃ .

The fly ash may be obtainable from the com bustion of coal, biomass (for example, wood-based bio mass) or oil shale and/or waste, for example municipal waste. The fly ash may comprise Si0 ₂ and/or Al ₂ 0 ₃ . In embodiments in which the binder composition comprises fly ash, it may comprise for example at least 40 wt-%, or at least 50 wt-%, or at least 60 wt-%, or at least 70 wt-%, or at least 80 wt-% of fly ash or a frac tion/f actions obtainable from fly ash.

The slag may be slag obtainable as a by product of iron or steel-making. For example, the slag may comprise or be ground-granulated blast furnace slag (GGBS) . GGBS may be obtained e.g. by quenching molten iron slag from a blast furnace in water or steam. Such a slag may be obtainable as a glassy, granular product, which may be dried or ground or oth erwise comminuted. The slag may comprise S1O ₂ and/or AI ₂ O ₃ .

The Si0 ₂ -containing mineral and/or the Al ₂ 0 ₃ - containing mineral, or in some embodiments the Si0 ₂ - and Al ₂ 0 ₃ -containing mineral, may comprise or be, for example, belite, alite, clinker, a calcium silicate, or any mixtures or combinations thereof. However, it may be desirable to use a mineral that does not con tain large amounts of CaO.

The tailings may comprise or be materials left over after the process of separating the valuable fraction from gangue of an ore. The tailings may com prise Si0 ₂ and/or AI ₂ O ₃ .

The side stream material from a chemical pulping process may be e.g. dregs from the handling of black liquor.

The bottom ash obtainable from the combustion of coal may be understood as being the ash forming at the bottom of a coal furnace. The bottom ash obtaina ble from the combustion of coal may comprise Si0 ₂ and/or Al ₂ 0 ₃ . Si0 ₂ may also be separated or concentrat ed from it. Fig 1A and IB illustrate scanning electron microscope images of particles comprising S1O ₂ , which have been sieved, purified and ground from the bottom ash obtainable from the combustion of coal. These par ticles have a substantially spherical shape. In these particles, silicon has been found to be in a reactive form.

In this specification, the term "ponded ash" may refer to ash which is e.g. bottom ash, boiler slag and/or power plant ash, which may optionally include fly ash. The fly ash may be so-called lower-grade fly ash. Such ponded ash may have been collected for stor age and/or heaped in ponds . It may have been stored moist or wet, and/or it may have been moistened before or during storage. It may also have been dried during or after the storage, or it may be dried before being included in the binder composition.

The at least one SiCh- and/or Al203-containing material, or any mixtures or combinations thereof, may be comminuted. For example, it may be comminuted by at least one of grinding, milling (for example by a pin mill or by jet pulverization), crushing, or cutting. By the comminuting, particles of desired particle siz es or of a desired particle size distribution may be obtained. The at least one Si0 ₂ - and/or Al ₂ 0 ₃ - containing material may, alternatively or additional ly, be fractionated into two or more fractions, for example by particle size e.g. by sieving. For example, the particles may be separated or concentrated into a fraction enriched with Si0 ₂ and/or a second fraction enriched with Al ₂ 0 ₃ . Such fractions, or generally two or more materials, may then be mixed at such propor tions that a desired weight ratio of Si02:Al203, or otherwise a desired composition for the binder, is ob tained.

The binder composition may further comprise other components or admixtures, for example an accel erator, a retarder, an air entraining agent, a defoamer, a plasticizer, a pigment, a corrosion inhib itor, a bonding agent, a pumping aid, or any mixtures or combinations thereof. The raw material or materials of the binder composition may be selected such that a desired compo sition is achieved. If desired, one or more secondary raw materials may be used. A skilled person can select suitable raw materials and, if included, secondary raw materials, to achieve a suitable composition.

The binder composition may comprise at most about 40 wt-% of clinker. The clinker may refer to Portland clinker. It may be desirable to minimize the amount of clinker and/or CaO in the binder composi tion, for example to reduce the carbon footprint of the manufacture of the binder composition. Further more, the presence of CaO in the binder composition is typically not necessary for obtaining a hardenable mixture. In an embodiment, the binder composition com prises at most about 30 wt-%, or at most about 25 wt- %, or at most about 20 wt-%, or at most about 15 wt-%, or at most about 10 wt-% of clinker.

In the context of this specification, the term "wt-%" may be understood as weight percentage by the total dry weight, for example the total dry weight of the binder composition.

The binder composition may comprise at most about 40 wt-% of CaO. In an embodiment, the binder composition comprises at most about 30 wt-%, or at most about 25 wt-%, or at most about 20 wt-%, or at most about 15 wt-%, or at most about 10 wt-% of CaO.

The Si0 ₂ and the AI ₂ O ₃ may constitute at least about 40 wt-% of the binder composition. In other words, at least about 40 wt-% of the binder composi tion may consist of the S1O ₂ and the AI ₂ O ₃ present in the composition. In an embodiment, the S1O ₂ and the Al ₂ 0 ₃ may constitute at least about 50 wt-%, or at least about 60 wt-%, or at least about 70 wt-%, or at least about 80 wt-%, or at least about 90 wt-%, or at least about 95 wt-% of the binder composition. The binder composition may also consist of the Si0 ₂ and the Al ₂ 0 ₃ .

The Si0 ₂ and/or the Al ₂ 0 ₃ , or the entire binder composition may be present as particles, the particle diameters of the particles being smaller or equal to about 20 pm. The particles may, in an embodiment, have particle diameters in the range of 1 to 20 pm.

The Si0 ₂ and/or the Al ₂ 0 ₃ , or the entire binder composition may be present as particles, the particles having a mean particle diameter of at most about 20 pm, or at most about 15 pm. In such particles, silicon may be in a reactive form.

It may be desirable to reduce or minimize the amount of carbon in the binder composition. Not to be bound by theory, the carbon may interfere with the re actions between the Si0 ₂ and the Al ₂ 0 ₃ . For example, the binder composition may comprise at most about 10 wt-%, or at most about 5 wt-%, of carbon. The amount of car bon in the binder composition may be determined for example by determining its loss on ignition. If neces sary, carbon may be removed from the materials of the binder composition. Said carbon may be incombustible carbon, i.e. residual carbon. In an embodiment, said carbon does not include activated carbon.

A hardenable mixture comprising the binder composition according to one or more embodiments de scribed in this specification is also disclosed. The binder composition may be in admixture with an aggre gate material and optionally with a solvent in the hardenable mixture. However, this does not necessarily mean that the hardenable mixture would be exclusively obtainable by mixing the (previously prepared) binder composition with the aggregate material and/or the solvent, but the hardenable mixture may also be ob tainable by separately mixing one or more components of the binder compostion with the aggregate material and/or the solvent. The hardenable mixture may be a hardenable mass, in particular when it contains a solvent in admixture with the binder composition and the aggregate. For example, it may be a cementitious hardenable mixture or mass, such as a cementitious hardenable concrete mixture or mass .

The hardenable mixture may be a concrete, mortar or grout mixture. It may also be a concrete- type mixture, for example a polymer concrete mixture.

The hardenable mixture may be a dry mixture, for example a dry concrete mix or other dry product. E.g. a solvent may be added in a desired proportion to this type of dry mixture before hardening.

The aggregate material may be any suitable aggregate or filler material. The aggregate material may, for example, comprise or be at least one of sand, gravel, grit, crushed stone, filler, slag, an artifi cial (man-made) aggregate material, or any mixtures or combinations thereof. The aggregate material may be fine, coarse or any mixture or combination thereof. The aggregate material and its coarseness may be se lected e.g. on the basis of the intended use of the hardenable mixture, the exact composition of the bind er composition, the conditions for hardening the har denable mixture, etc.

The solvent may comprise or be, for example, water, an aqueous solution containing one or more salts, or any mixture or combination thereof. The har denable mixture is not necessarily particularly sensi tive to the presence of salts, unlike e.g. traditional concrete. For example, salt water, such as sea water, could be contemplated. The aqueous solution containing the one or more salts may have a salinity of at least 0.5 ppt (salinity corresponding to brackish water), or at least 10 ppt, or at least 30 ppt (salinity corre sponding to saline water) . The salinity of the aqueous solution containing the one or more salts may be at most or at least 10 ¾. However, the salinity is not specifically limited, but the aqueous solution may in some embodiments be even saturated or close to saturation in terms of salt or salts.

The salts are not particularly limited - they may include chlorides such as NaCl, KCl, Mgd ₂ and CaCl ₂ , sulfates such as MgS0 ₄ -7H ₂ 0, CuS0 ₄ -5H ₂ 0, ZnS0 ₄ ·7¾0 and FeS0 ₄ -7H ₂ 0, NaH ₂ P0 ₄ , KH ₂ P0 ₄ and other soluble phos phate, hydrogen phosphate and dihydrogen phosphate salts, bicarbonates such as NaHC0 ₃ , nitrates such as Ca(N0 ₃ ) ₂ and Fe (N0 ₃ ) ₃ -9H ₂ 0, ammonium salts such as NH ₄ C1, citrates such as sodium citrate, acetates, and so on.

The salt/salts may additionally or alterna tively be carbonates, such as Na ₂ CQ ₃ , K ₂ C0 ₃ , CaC0 ₃ , or any mixtures or combinations thereof. These may have a reinforcing effect, particularly in the initial stages of hardening.

The aqueous solution may contain e.g. an acid or a base. In some embodiments, the aqueous solution contains a base. The base may, in some embodiments, act as an activator. In some embodiments, the aqueous solution does not contain a base that may act as an activator. The acid may be e.g. one or more fulvic ac ids, humic acids, citric acids, tartaric acids and/or any mixtures or combinations thereof, or some other organic acid. These acids may provide positive ef fects, e.g. facilitate the hardening of the hardenable mixture and/or increase the strength, e.g. flexural strength, of the hardened mixture.

The ratio of the total amount of water to the total dry weight of all dry materials in the harden able mixture may be in the range of 0.1-0.3, or 0.12- 0.28, or 0.15-0.25, or 0.18-0.22, or about 0.2. This type of hardenable mixture may provide a stronger hardened material or article. With a lower amount of water, the hardenable mixture may also be more diffi cult to process.

This proportion of the total amount of water may be particularly suitable e.g. when the Si0 ₂ - and/or Al203-containing material comprises or is blast furnace slag.

On the other hand, the Si0 ₂ - and/or AI ₂ O ₃ - containing material (s) may, in some embodiments, con tain water per se. In this case, its/their amount and the amount of solvent may be adjusted such that a de sired ratio of the total amount of water to the total dry weight of all dry materials is obtained.

The hardenable mixture may also comprise for example fibre, such as steel fibre, aramid fibre, bas alt fibre, carbon fibre or synthetic fibre, e.g. poly mer or polypropene fibre or glass fibre. For example basalt fibre is not sensitive to salt stress, whereby the solvent used in the hardenable mixture may contain one or more salts.

The hardenable mixture, in particular when in admixture with the solvent, may have a pH e.g. in the range of 0 to 14. The pH may depend e.g. on the raw material and/or the composition of the binder composi tion. If an alkali activator is included in the binder composition or included in the hardenable mixture sep arately, the pH of the hardenable mixture may be rela tively high. The pH of the hardenable mixture may, for example, be greater than 11 or 12. However, in embodi ments in which no additional activator is added, the hardenable mixture may have a lower pH. The pH of the hardenable mixture may, for example, be a pH of up to 11, or up to 10, or up to 9, or up to 8, or in the range of 6 to 11, or in the range of 6 to 9. The pH of the hardenable mixture may be one of the pH values mentioned herein in the initial stage of hardening of the hardenable mixture. In embodiments in which the binder composition is itself basic to some extent, such as binder compositions comprising e.g. ash, fly ash, bottom ash obtainable from the combustion of coal, the raw material of the binder composition may as such raise the pH of the hardenable mixture. In these embodiments the pH of the hardenable mixture may be for example at most 13.

In an embodiment, the binder composition or the hardenable mixture does not comprise an additional activator. The term "additional activator" may be understood as referring to a component or substance added in addition to the raw material (s) and optionally the secondary raw material (s) of the binder composition, the aggregate material, and/or the solvent, and intended to activate the binder composition, for example by raising the pH of the hardenable mixture, thereby activating the reactions causing the hardening of the mixture. It is also possible that the activator affects the reactivity of the reactants through the ions it contains .

Such an additional activator may, at least in some embodiments, be understood as referring to an alkali activator. Examples of alkali activators may include lye, hydroxides, e.g. sodium hydroxide (NaOH) , potassium hydroxide (KOH) , lithium hydroxide (LiOH) , or any mixtures and combinations thereof. An alkali activator may comprise or be an aqueous solution of a hydroxide .

Such an additional activator may, at least in some embodiments, be understood as referring to sodium sulphate (Na ₂ S0 ₄ ), sodium carbonate (Na ₂ C0 ₃ ) , potassium sulphate (K2SO4) , potassium carbonate (K ₂ C0 ₃ ) , or any mixtures or combinations thereof.

Particle diameters and their distributions may be measured for example based on laser diffrac tion, for instance using a Coulter LS particle analyz er. In laser diffraction, a group of particles is il ^¬ luminated with monochromic light. The particles cause scattering of light. The scattering and its nature may depend on the size and refractive index of the parti cles. The particle size distribution may be calculated based on the scatter pattern detected.

A method for preparing the hardenable mixture according to one or more embodiments described in this specification is also disclosed. The method may com prise mixing the binder composition according to one or more embodiments described in this specification with an aggregate and optionally with a solvent.

The aggregate and the solvent may be any ag gregate or solvent described in this specification.

The solvent, e.g. water or aqueous solution, may be added such that the ratio of the total amount of water to the total dry weight of all dry materials in the hardenable mixture may be in the range of 0.1- 0.3, or 0.12-0.28, or 0.15-0.25, or 0.18-0.22, or about 0.2.

In an embodiment, no additional activator is added to the hardenable mixture prior to the hardening of the hardenable mixture .

In an embodiment, no additional alkali acti vator, such as an alkali silicate activator and/or an alkali hydroxide activator, is added to the hardenable mixture prior to the hardening of the hardenable mix ture . In the context of the method or methods de scribed herein the additional activator/activator may be any activator described in this specification.

The pH of the hardenable mixture may be any pH described in this specification.

A hardened material or an article formed by hardening the hardenable mixture according to one or more embodiments described in this specification is also disclosed. A method for preparing the hardened material or article according to one or more embodiments de scribed in this specification is also disclosed. The method may comprise preparing the hardenable mixture according to one or more embodiments of the hardenable mixture or of the method described in this specifica tion, forming the material or article into a desired shape, and allowing the material or article to harden.

The hardening may be allowed to proceed at a suitable temperature. Depending e.g. on the exact com position of the binder composition and/or of the har denable mixture, the temperature may be equal to or greater than room temperature, or even lower. However, the temperature may be greater than room temperature. Such a temperature and/or warming of the hardenable mixture and/or of the material or article may acceler ate the hardening. The hardenable mixture may be warmed up e.g. to above 40 °C to accelerate the hard ening .

The hardening may be allowed to proceed for a desired period of time. Typically, concrete mixtures or concrete-type hardenable mixtures continue to hard en for a long time, even after full compression strength has been reached. The desired period of time may be e.g. at least 28 days. However, hardening of the hardenable mixture or article cast in a mould may be allowed to proceed for a shorter time before remov ing it from the mould, such that the hardening of the mixture or material may continue after it has been re moved from the mould.

In an embodiment, no additional activator is added to the hardenable mixture. No additional activa tor is added prior to the hardening of the hardenable mixture .

A material or an article obtainable by the method according to one or more embodiments described in this specification is also disclosed. The hardened article may be for example an element. The element may be for example a building el ement, such as a wall element, a hollow-core slab element, a fagade element, a column element or a beam el ement; or an infrastructure element, such as a road or a street construction element, a bridge element, a railing element, a retaining wall element, an edge beam, a tunnel element, a railroad tie, a pier ele ment, an agricultural element or a foundation element. The hardened article may also be for example a balco ny, a road structure, a base, a mine protection barri er, a foundation, a noise wall, a post, a container, a yard slab, or a cable trough.

Use of the binder composition according to one or more embodiments described in this specifica tion, or use of the hardenable mixture according to one or more embodiments described in this specifica tion, for preparing and optionally hardening a harden able mixture, a hardened material or a hardened arti cle without the addition of an additional activator is also disclosed.

EXAMPLES

Reference will now be made in detail to various embodiments, an example of which is illustrated in the accompanying drawing.

The description below discloses some embodiments in such a detail that a person skilled in the art is able to utilize the embodiments based on the disclosure. Not all steps or features of the embodiments are discussed in detail, as many of the steps or features will be obvious for the person skilled in the art based on this specification.

Example 1 Fly ash obtainable from the combustion of wood was comminuted by grinding it in a pin mill. The comminuted fly ash particles were sieved. If necessary, carbon was removed from the fly ash particles .

The fly ash particles were used as a binder composition for making a concrete-like hardenable mixture. 450 g of the fly ash particles were mixed with 1350 g of an aggregate, in this case with sand, and with 225 g of tap water. The pH of the mixture was 12.6. The hardenable mixture was poured into a mold and allowed to harden.

After 28 days, the compression strength of the hardened material was measured and was found to be over 30 MPa.

It is obvious to a person skilled in the art that with the advancement of technology, the basic idea may be implemented in various ways. The embodiments are thus not limited to the examples described above; instead they may vary within the scope of the claims .

The embodiments described hereinbefore may be used in any combination with each other. Several of the embodiments may be combined together to form a further embodiment. An article, a method, or a use, disclosed herein, may comprise at least one of the embodiments described hereinbefore. It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages . It will further be understood that reference to 'an' item may refer to one or more of those items. The term "comprising" is used in this specification to mean including the feature (s) or act(s) followed thereafter, without excluding the presence of one or more additional features or acts.