WO2023009783A1 - Béton à activation alcaline présentant une finition de surface vitreuse, et procédés et produits associés à ce béton - Google Patents

Béton à activation alcaline présentant une finition de surface vitreuse, et procédés et produits associés à ce béton Download PDF

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Publication number
WO2023009783A1
WO2023009783A1 PCT/US2022/038796 US2022038796W WO2023009783A1 WO 2023009783 A1 WO2023009783 A1 WO 2023009783A1 US 2022038796 W US2022038796 W US 2022038796W WO 2023009783 A1 WO2023009783 A1 WO 2023009783A1
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Prior art keywords
alkali
substrate
mixture
activated
concrete
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PCT/US2022/038796
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English (en)
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Kevin ROUFF
Luis Paco BOECKLEMANN
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Rouff Kevin
Boecklemann Luis Paco
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Publication of WO2023009783A1 publication Critical patent/WO2023009783A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
    • C04B28/006—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing mineral polymers, e.g. geopolymers of the Davidovits type
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
    • C04B2103/10—Accelerators; Activators
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/20—Resistance against chemical, physical or biological attack
    • C04B2111/28—Fire resistance, i.e. materials resistant to accidental fires or high temperatures
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P40/00—Technologies relating to the processing of minerals
    • Y02P40/10—Production of cement, e.g. improving or optimising the production methods; Cement grinding
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/91—Use of waste materials as fillers for mortars or concrete

Definitions

  • the present invention generally relates to alkali-activated concrete and to methods and products for use in the manufacturing of alkali-activated concrete.
  • the invention particularly relates to methods and products for manufacturing alkali -activated concrete having a glassy surface finish, and to alkali-activated concrete obtained therefrom.
  • Alkali activated materials including geopolymers and inorganic polymers, are a class of materials that are researched and used as alternative cementitious binders to more common binders such as ordinary Portland cement (OPC). “Geopolymers” were initially discovered in the late 1970’s, and they have since been considered a subclass of the wider class of “inorganic polymers” and even wider “alkali-activated materials”.
  • AAC alkali-activated concretes
  • Ceramic glazing is an age-old process of vitrifying a mixture of minerals on the surface of ceramic-ware, typically in the ranges of 900C-1300C.
  • the glaze typically includes a silica (glass former), alumina (refractory), flux, colorants (metallic oxides) and modifiers.
  • Glazes are often applied to the surface of ceramic-ware (or any other ceramic substrate) after the first “bisquette” firing of ceramics, and subsequently fired again (i.e., “glaze firing”), although industrial manufacturing processes will fire from the unfired (“greenware”) state directly to the glaze state, and often at a much quicker rate.
  • glazes can also be applied to volcanic stone, typically with an engobe layer (a ceramic liquid) applied beforehand. The narrow range of substrates is mostly because very few materials can withstand those temperatures, and the expansion coefficients of the glaze and substrate do not easily match.
  • enameling is a process by which a glass powder or frit, often combined with a flux, is applied to a surface of a substrate, and the substrate is thermally treated, as a nonlimiting example, at a temperature of about 700°C to about 900°C, causing the glass to melt and fuse to the substrate.
  • Enameling is a broader term within which are various other terms that differ by base ingredients, application techniques (wet, dry, spray, etc.), substrates onto which the enamels are applied (steel, copper, aluminum, stone, etc.), and temperatures at which the bodies are fired.
  • “Vitreous enamel” more specifically refers to the glass-like layer applied to a substrate (primarily metallic) and fused through firing, although the term “porcelain enamel” is also commonly used. Misleadingly, the term “enamel” is also incorrectly used to refer to certain paints, but these are not true enamels. Confusions also surround enamels as the word for enamel in languages such as French are the same for both ceramic glaze and vitreous enamel- “emaille”- despite them being different.
  • Vitreous enamels can be applied in powder form (“dry”), or in “wet” form through brushing, dipping, or spraying. Sometimes, the vitreous enamel is combined with bonding agents to assist in application (such as organic binders) that will burn away, or a liquid adhesive is added to the substrate to assist with adhesion between enamel and substrate. Unlike ceramic glaze firing, which can take many hours to fire, enamel firing happens in a matter of minutes, the speed depending on the system. Also, unlike ceramic glazes, vitreous enamels are typically applied to metalware, such as jewelry, decorative items, kitchen appliances, kitchenware, technical components, industrial machinery, commercial signs, house lettering signs, billboards, and more. Enamel improves durability and impact resistance of metallic substrates, creates a corrosion- resistant and water-resistant surface, and virtually any color is possible.
  • vitreous enamels only work on metallic substrates, they have been shown to work on volcanic stone and some forms of natural stone, such as granite. As mentioned with ceramic glazes, this narrow range of viable substrates on which enamels can be applied is due to the thermal shock, and mismatched expansion coefficients between glassy layer and underlying substrate.
  • a mixture for an alkali-activated concrete suitable for having a glassy surface finish formed thereon through a firing process is provided.
  • the alkali-activated concrete includes a cementitious binder, an aqueous alkali activator solution containing an alkali activator that activates and hardens the binder upon curing, and an aggregate dispersed in the cementitious binder.
  • the cementitious binder takes part in chemical reactions to harden when activated by the alkali activator.
  • the alkali-activated concrete has a high thermal resistance that is able to withstand the temperatures and thermal shock required for minerals of glazes and enamels thereon to vitrify and adhere to a surface of the alkali-activated concrete without cracking, crawling, peeling, or breaking apart.
  • an alkali-activated concrete suitable for having a glassy surface finish formed thereon through a firing process is provided.
  • the alkali-activated concrete is manufactured from the mixture.
  • a method of forming a glassy surface finish on a substrate comprising an alkali -activated concrete includes the steps of covering, at least partly, a surface of the substrate with a glass-finish material, firing the substrate with the applied glass-finish material to vitrify the glass-finish material, and cooling the substrate and the melted glass-finish material to harden the vitrified glass-finish material into the glassy surface finish.
  • the method may include providing and/or manufacturing the substrate.
  • a method of manufacturing the alkali- activated concrete includes mixing the cementitious binder, the alkali- activator solution, and the aggregate to form a wet concrete mixture, forming an object with the wet concrete mixture into a desired shape, curing the formed object, and drying the cured object.
  • a product includes a substrate including the alkali -activated concrete, and a glassy surface finish covering the substrate.
  • the glassy surface finish is vitrified and adheres to the substrate.
  • the methods, materials, compositions, and/or products disclosed herein in some arrangements provide the ability to apply glassy surface finishes, including ceramic glazes and vitreous enamels, to an alkali-activated material, inorganic polymer, or geopolymer bodies, with a wide range of mixture-designs.
  • the methods, materials, compositions, and/or products in some arrangements provide the ability to have a glassy finish on a concrete/stone-like substrate, and do so with a substrate that can be made using industrial wastes/byproducts.
  • FIG. 1 is a schematic diagram of a method of making an alkali-activated concrete object according to aspects of the invention.
  • FIG. 2 is a schematic diagram of a method of forming a glassy surface finish to the alkali- activated concrete object of FIG. 1 using a glaze according to aspects of the invention.
  • FIG. 3 is a schematic diagram of a method of forming a glassy surface finish to the alkali- activated concrete object of FIG. 1 using a vitreous enamel according to aspects of the invention.
  • FIG. 4 shows examples of vitreous enamel applied to geopolymer tiles in accordance with aspects of the invention.
  • FIG. 5 shows examples of slag-based AAC tiles with various vitreous enamels applied in accordance with aspects of the invention.
  • FIG. 6 shows examples of various tiles enameled in an industrial tunnel-furnace in accordance with aspects of the invention.
  • FIG. 7 shows an alkali -activated concrete tile during various stages of production in accordance with aspects of the invention.
  • FIG. 8 shows alkali -activated concrete substrates in the shape of tiles made with various different aggregate mixtures.
  • FIG. 9 shows an alkali-activated concrete substrate prepared with steel fibers and enameled in a tunnel furnace in accordance with aspects of the invention.
  • FIG. 10 shows another alkali -activated concrete substrate enameled in a tunnel furnace in accordance with aspects of the invention.
  • FIG. 11 shows various shapes and sizes of objects made of alkali-activated concrete and having a glassy surface finish in accordance with aspects of the invention.
  • FIG. 12 shows various objects made of alkali -activated concrete and having glassy surface finishes with various aesthetic features in accordance with aspects of the invention.
  • FIG. 13 shows objects made of alkali -activated concrete with various layers and stages of glassy surface finishes in accordance with aspects of the invention.
  • This application describes a process of forming a glassy surface finish, such as by enameling or glazing, on an alkali-activated concrete (AAC) substrate (piece, body, article, etc.), including inorganic polymers and geopolymers. Due to the lack of commercially available AAC products, the present disclosure also describes a process of preparing AAC substrates for the aim of enameling/glazing.
  • AAC alkali-activated concrete
  • an alkali-activated material such as an AAC, is a material that includes an alkali-activated cementitious binder (cement), for example, as the cement in an alkali-activated concrete.
  • AACs have been tested, all with successes, and therefore the disclosure refers broadly to AACs for the substrate onto which the enamels/glazes are applied, including the use of inorganic polymer and geopolymer concretes as substrates, given they are subclasses to alkali-activated materials.
  • Common base materials for geopolymers and inorganic polymers include, but are not limited to, metakaolin (calcined kaolin), various ashes such as those from coal (“fly ash”), municipal solid waste incineration ash (“bottom ash”), rice husk ash, volcanic ash, ground granulated blast furnace slag (GGBFS), other non-ferrous slags, and more recently, iron-rich (“fayalitic”) slags.
  • GGBFS ground granulated blast furnace slag
  • the inventors have tested alkali-activated concretes using GGBFS, copper slag, mixed metal recycling slag, and metakaolin for the purpose of enameling, and also believe that other alkali-activated ingredients would also work with the application of glazes and enamels.
  • This disclosure discloses both ceramic glazing and vitreous enamels as two separate processes with different system, but that both can be applied as a glassy layer surface finish to AAC.
  • glass-finish material is used herein to refer to both glazing materials and vitreous enamel materials that are applied to substrates and subsequently fired to form the glassy surface finish.
  • a method of forming a glassy surface finish on a substrate formed of an alkali- activated concrete includes at least partly covering a surface of the substrate with a glass-finish material.
  • the substrate may define or be a portion of an object or article have almost any shape, size, or form factor. Some examples shown herein are tiles and bricks. However, the substrate may have an infinite variety of other and/or more complex shapes, sizes, and form factors and are not limited to any specific shape, size, or form factor.
  • the glass- finish material may be a glaze material or a vitreous enamel material or combinations and/or mixtures thereof in any suitable form for applying to the surface of the object, such as a powder, paste, or liquid.
  • the substrate with the applied glass-finish material thereon is fired, i.e., heated, for a selected period of time to vitrify the glass-finish material.
  • the substrate and the vitrified glass-finish material is cooled to harden the melted glass-finish material into the glassy surface finish.
  • FIGS. 1-3 illustrate basic non-limiting example processes of the invention.
  • an AAC substrate (piece, body, article, etc.) 20 is prepared.
  • an alkali-activated mortar (cement) 22 is prepared at 100, formed into a shape (e.g., cast) at 102, cured (typically at least 24 hours) at 104, and dried at 106.
  • a pre-existing AAC substrate 20 is commercially available, then one can simply proceed to the next step without having to create the AAC substrate 20 via the first step.
  • glaze or enamel is applied to the substrate.
  • FIG. 2 illustrates the process when using a glaze 24.
  • FIG. 3 illustrates the process when using a vitreous enamel.
  • ceramic glazing material 24 is applied at 110 in wet form, for example by dipping, brushing, pouring, spraying, or any other suitable method, as shown at 110.
  • Glaze material can be applied directly to the AAC substrate 20, or first on an engobe layer formed from engobe 28 for optimal results.
  • the substrates coated with the glaze or enamel are fired.
  • the fired substrates are cooled.
  • firing for a glaze has a slow temperature ramp (about 2 hours to about 48 hours), with a target temperature often in the higher temperature ranges (as nonlimiting examples, about 800 °C to about 1300 °C).
  • Cooling at 114 is also preferably gradual.
  • the enamel material 26 is applied onto the AAC substrate 20 in any suitable manner, for example as a powder, a wet slurry, or sprayed.
  • firing is short with a fast temperature ramp (e.g., about five minutes to about forty-five minutes), and a lower target temperature (as nonlimiting examples, about 450 °C to about 900 °C).
  • the substrates are cooled at 124, preferably including being annealed, but annealing is not necessary.
  • An AAC substrate 20 may be produced by preparing an alkali- activated mortar (cement) mixture 22, which may further include aggregates and, optionally if needed or desired, other additives, such as strengthening fibers. As illustrated at 102 in FIG. 1, the resulting mixture 22 is then cast into a mold or otherwise formed into a desired shape through any method of formgiving (forming) suitable for resulting in an object having a desired form factor. The mixture design depends on the use and can be selected accordingly as discussed in additional detail hereinafter. After forming, the mold is left to cure at 104, and the resulting forms are then dried at 106 to ensure minimal water content.
  • substrate refers to an object of any shape, size, and/or form factor with a surface to which the coatings and surface finishes disclosed herein are applied.
  • the substrate 20 may include only a surface portion of an object, a portion of the surface of the object, or the entire object itself including some or all of the surface of the object.
  • the tiles and bricks disclosed herein, as well as objects of essentially any other shape are substrates as used herein insofar as they have surfaces to which the coatings and surface finishes disclosed herein are applied and/or cover.
  • mixtures used for the AAC substrate 20 include a cementitious binder, such as a powder cementitious material, that will act as the primary binding matrix, an aqueous alkali activator solution containing an alkali activator to trigger the reaction of the cementitious binder, and some form of aggregate as filler and for mechanical enhancement.
  • a cementitious binder such as a powder cementitious material
  • an aqueous alkali activator solution containing an alkali activator to trigger the reaction of the cementitious binder
  • some form of aggregate as filler and for mechanical enhancement.
  • the cementitious binder material combined with the alkali activator are the main constituent factors that make the alkali -activated cement, and, when combined with the aggregates and cured, result in an alkali-activated concrete (AAC) suitable for being provided with a glassy surface finish as described herein.
  • AAC alkali-activated concrete
  • the mixture designs used for AAC substrates disclosed herein are specifically developed to suit desired parameters relative to shrinkage mitigation, target firing temperature, cracking, workability, and aesthetic considerations.
  • One goal of the mixtures is to achieve a strong cast that, when fired, is resistant enough to the thermal shock such that it does not crack, warp, or break apart.
  • Another goal is to maximize the use of secondary or waste materials, given the environmental considerations.
  • a further goal is to achieve a mixture that affords a homogenous surface and adhered bond to either enamel or glaze.
  • FIG. 10 shows how a similarly good result for enameling is achieved with a substantially different mixture design to the rest of the samples, as the primary principle of an alkali-activated substrate remains.
  • the sample in FIG 10 was prepared with a different composition of main ingredients, using majority GGBFS, and utilizing a maximum of commercially marketed materials as aggregates (minimized recycled material use, for ease-to- market or areas of strict regulations) and enameled using a tunnel furnace with equally successful result.
  • a specific selection of materials was used primarily because of their local availability, environmental incentives, and relevance to the Benelux regions in which experiments were conducted, though the invention is not limited to these materials and a wide variety of these and other materials would work.
  • fly ash both type F and C
  • other mining and/or metallurgical byproducts such as tungsten mine waste, calcined natural clays, other slags, and any other materials undergoing alkali activation of aluminosilicate base ingredients. Variations of the ingredients and more details of the ingredients constituting the mixture design, are detailed hereinafter.
  • Binder ingredients A variety of materials have been shown to work as the core cementitious agent in alkali-activation, inorganic polymer, and geopolymers. The main aspect of the cementitious ingredient is that it contains sufficient amorphous silica, alumina, and, in some cases, iron-oxide, that will take part in the reactions when activated by the alkali activator solution.
  • the core cementitious ingredient which is the main source of amorphous silica and alumina for the AAC, iron-rich slags (both from primary and secondary production of metals like copper), synthetic slags (derived from bauxite residue), ground granulated blast furnace slag
  • hybrid geopolymers/ AACs often allow for easier workability and “just-add-water” mixing.
  • a small percentage of OPC is combined with powdered forms of alkali hydroxides, among other inorganic ingredients, allowing the user to add water and rely on the alkalinity of the OPC itself and its ability to bond to water.
  • Enameling on these hybrids were utilized, also with success, albeit less than the “pure” AAC, and it is believed that these hybrid geopolymers/ AACs also can work more reliably at scale as substrates for enameling and glazing in accordance with the present disclosure with further modifications to the mixture design.
  • Alkali activator solution The primary alkali activator solutions used in alkali-activated materials are aqueous sodium or potassium-based silicate solutions, often modified with sodium or potassium hydroxide, respectively. Experiments were conducted with combinations of these activator solutions, which resulted in achieving different aesthetic results. Other sources of these activator solutions may also be possible, particularly with the aim to achieve a secondary/recycled source of the activator, which may be particularly desirable if/when a majority of the other core ingredients are waste materials.
  • the main dependent factor for the activator solution is the alkali to silica ratio, as well as the water content. This factor can impact the amount of solution needed for workability, as well as the effectiveness of the polymerization reaction itself.
  • any alkali activator suitable to produce a desirable AAC object substrate may be used.
  • Our tests were primarily carried out with an alkali oxide to silica ratio (K 2 0:Si0 2 ) of about 1.75 in a solution containing about 65 wt.% water.
  • activator solutions have been used with success, including sodium-silicate/sodium hydroxide-based activator solutions.
  • the aggregates used in the mixture can vary greatly, depending on costs, availability, casting mechanics/ rheology, and the performance desired, for example in a high- temperature environment. Given the thermal firing process for enameling and/or glazing, preference is given to aggregates with low expansion phase (e.g., minimizing quartz content), or refractories. However, the firing sequence in enameling is so short that even a high quartz content and non-refractory materials did not prevent the system from working, and are viable options. In the case of glazing (a slow firing schedule), as long as firing schedules typical of ceramics (e.g., a slowing of the temperature ramp around 700 °C, as a nonlimiting example) are followed, a wide multitude of aggregates also works.
  • glazing a slow firing schedule
  • lime-containing materials be avoided, or thoroughly milled and/or screened.
  • Aggregates that have been successfully investigated include, but are not limited to, silica sand (of varying particle sizes), builder’s sand (often called “silver sand”, “bird sand”, and any other names), quartz flour/powder, marble powder, calcined alumina, chamotte/grog, calcined bauxite, recycled refractories, sintered bauxite residue, unmilled or partly milled slags (e.g., GGBFS, ferrous slags from metal recycling), crushed glass, and more.
  • any structurally and chemically suitable aggregate may be used, although the choice of aggregate will influence the target temperature, surface aesthetic, shrinkage, and workability of the AAC.
  • FIG. 8 shows variations to the resulting enamel with different aggregates in the substrate.
  • the images in FIG. 8 show that a variety of aggregate mixtures can be used within the mixture design of the AAC substrate, with varying effects.
  • the amount of aggregate used in the concrete mixture depends on the geometry and the rheology of the rest of the ingredients, as well as the firing methods and whether the substrates will have a ceramic glaze or a vitreous enamel applied.
  • One goal in adding aggregates is to maximize particle density and particle packing to prevent shrinkage, while allowing for adequate workability and casting.
  • With regards to the firing schedule given that ceramic glaze firing is much longer, one should bear in mind the expansion phases, as well as other internal effects with certain aggregates, particularly if the glaze has a fluxing effect in the body. For example, it was found that some AAC substrates react poorly with a specific glaze with excess fluxes, bloating the body. Another AAC substrate exhibited bloating in reaction with high temperatures of ceramic glazing, likely due to the aggregate selection.
  • a further AAC substrate exhibited poor adhesion of a glaze to the AAC substrate, which appeared to be caused by the AAC mixture, the application techniques, and other factors.
  • aggregates for the AAC should be selected, if glazing, according to similar principles as ceramics (e.g., grogs/chamottes), although other factors may also be influential to obtaining a particular desired glassy surface finish or for particular usage needs.
  • Strengthening fibers may optionally be integrated into the mortar mixture for the AAC. When used, fibers are typically added after the stage of adding the aggregates. The fibers may be used to provide added strength after curing, and, in this process, strength during and after firing. Due to the alkalinity of the activation process in the creation of the substrate bodies, it is preferable to select the fiber type so as to avoid unwanted reactions with the alkali (e.g., aluminum releasing hydrogen gas), corrosion, or gradual dissolution (as with some glass fibers).
  • the alkali e.g., aluminum releasing hydrogen gas
  • corrosion e.g., aluminum releasing hydrogen gas
  • gradual dissolution as with some glass fibers.
  • the strengthening fibers recommended in alkali -activated concretes are polymers, such as polypropylene (PP) or polyethylene (PE), metallic fibers, such as stainless steel, brass or other plated steel, and steel, basalt fibers, carbon fibers, and others.
  • PP polypropylene
  • PE polyethylene
  • metallic fibers such as stainless steel, brass or other plated steel, and steel
  • basalt fibers carbon fibers, and others.
  • fiber usage in the preparation of the substrates is preferably in line with the same principles for adequate fiber usage in regular portland cement-based concrete casting, based on many factors including the size of the formwork, the geometry, and the rheology.
  • Polymer fibers are sometimes used in cement-concrete mixtures in threat of fire to prevent spalling or failure by allowing the fibers to burn out, thereby providing channels for excess moisture to escape.
  • the same principle can be used in the case of glazing/enameling alkali- activated concretes. However, depending on the fiber, mixture density, and firing time, this can also lead to bubbles at the surface as the fibers bum out.
  • FIG. 9 shows evidence of a sample made incorporating steel fibers in the mixture. The sample was prepared with steel fibers in the mixture add enameled via tunnel furnace with good success.
  • Additional additives include network modifiers for the polymerization process, additional silica (either in silicates or silica fume) and others. It is assumed that these too should not substantially affect the result, so long as they are in minimal quantities in organic based, or integrating into the inorganic polymerization mechanisms (as with the amorphous silica).
  • Mixture example 1 One of the successful results in terms of the desired mechanical properties listed above were from a mixture that combined the following in parts by weight (pbw):
  • Iron-rich slag powder 100 pbw
  • GGBFS 15 pbw
  • alkali activator solution potassium silicate (fGCkSiC ratio of 1.75); 65 wt.% water): 40-50 pbw
  • Mixture example 2 Another mixture was designed to incorporate more materials that are easily available on the market. This was done to allow for ease to market and be more easily adopted in regions with more strict regulations, given that the other materials are from waste. See FIG. 9 below for visual evidence of the same similarly successful enameling result. This mixture combined the following in parts by weight (pbw):
  • Iron-rich slag powder 50 pbw
  • alkali activator solution alkali activator: potassium silicate (fGCkSiCh ratio of 1.75); 65 wt.% water): 45-55 pbw Aggregates: 272 pbw
  • the method for mixing the mixture to form the wet cement for casting may vary, particular to various mixture designs.
  • one non-limiting example method is the following.
  • wet components are first added to a mixer, followed by the powdered slag(s)/binder ingredients.
  • Recommended mixers are ones that include high-shear, high-speed mixing systems, such as vertical mixers, but other mixers also work.
  • the mixer is activated at high speed for about three minutes to incorporate the activator solution with the powderized binder.
  • the aggregates are gradually added with the mixer set to a slow/low speed, and subsequently mixed until fully incorporated (as a nonlimiting example, about one to about three minutes).
  • additives such as fibers
  • other additives such as fibers
  • the mortar (cement) is now ready for the next stage, formgiving.
  • the mortar (cement) mixture has been prepared, the mortar (cement) is then formed into a desired shape through formgiving methods common to any cement-based concrete working.
  • a mold as shown 102 in FIG. 1, 3D printing, or rendering onto a surface.
  • a wide variety of shapes and dimensions are possible in the process of enameling and glazing, however larger bodies become more difficult due to effects in firing. For example,
  • FIG. 11 shows larger bricks that are enameled, as well as thinner tiles, which show that a variety of shape sizes and mass, including large bricks, are also possible.
  • different shapes are shown (a large 40 cm x 40 cm x 1.5 cm thick tile, and a 2.5 x 2.5 x 2.5 cm cube) both of which demonstrate successful results of having a glassy surface finish formed thereon in accordance with the principles of this disclosure.
  • the preferred method of formgiving is to cast the mortar (cement) into a mold, due to production efficiency considerations and the consistency of surface onto which the glaze/enamels will be applied.
  • the mold can be made of a multitude of materials along the same principles of regular cement-based concrete casting, including wood, polyurethane, silicone, and any other suitable material for molding the AAC.
  • a suitable mold release may be used to make it easier to release the casting from the mold. Multiple mold releases were tested without noticeable impact on the resulting glaze/enamel adhesion. Suitable mold releases include a standard release spray, such as a silicone- based release spray, and a mold release oil applied in a thin single layer. Other mold releases may also be suitable.
  • the substrates are allowed to set and cure as illustrated at 104.
  • This can include the use of thermal curing, ranging from 23°C-80°C, or left at ambient temperature. Samples were prepared using both heat cure methods and ambient cure methods, with successful enameling/glazing in both. However, heat-curing, as nonlimiting examples, about 60 to about 80°C, may be more favorable due to the added mechanical strength and increased rate of internal polymerization.
  • the substrates are preferably cured in a high humidity environment, such as 100% humidity, to avoid early cracking. This is done either by closing and/or wrapping the molds in a film, or placing the molds in a high-humidity, heated chamber. In some cases, a shorter curing cycle led to a weak body and subsequent cracking or exploding in the firing stage, so it is preferred to cure the cement material in the mold for about twenty-four hours.
  • the resulting AAC substrate 20 is preferably left to dry by any suitable means to remove as much moisture as possible, as illustrated at 106.
  • the substrate 20 may be dried by open air, low-temperature oven/drying cabinet, or other ambient/low temperature means. Other drying means are also possible.
  • the time for drying depends on the environment and the size and quantity of the substrate 20. As a nonlimiting example, a minimum of three days may be preferred based on the local climate, but other times are also possible depending on many different factors.
  • the surface of the AAC substrate 20 may be prepared and/or treated prior to the application of the glass-finish material 24 or 26. Different results can be attained depending on how the surface of the substrate 20 is treated. Leaving the surface untreated from the casting process gives a different result from when the surface is sanded and/or cut, and also different from the result if the surface is fully polished. However, these differences appear to be primarily aesthetic.
  • the untreated surface results in a more homogenous finish than the sanded surface, which may be a result of exposed pores and holes after sanding, and the polished surface has more pockets/crazing (i.e., where the glaze/enamel pools into small globules), which may be a result of less adhesion and absorption into the polished substrate 20.
  • the surface treatment following the formgiving stage is not requirement in the process, and is more of a consideration of the desired aesthetic result of the finished product. For ease of manufacturing, it may be best to simply use the as-casted substrate surface as is, without additional treatment steps. For example, FIG. 7 shows the different surfaces, and evidence of different results after enameling.
  • FIG. 7 shows the different surfaces, and evidence of different results after enameling.
  • FIG. 7A shows an AAC tile with an untreated surface, directly from the casted mold.
  • FIG. 7B shows an AAC tile with a sanded surface.
  • FIG. 7C shows an AAC tile with polished surface.
  • FIGS. 7D and 7E show AAC tiles with one half of the substrate sanded, and the other left untreated, prior to enameling. These results show that both cases (untreated or treated) work, and can provide different aesthetic results.
  • a glassy surface finish 30, such as a glaze or vitreous enamel can be formed on a AAC substrate 20 by firing (heat treating) a glass-finish material, such as an unfired glaze material 24 or vitreous enamel material 26, such that the glass-finish material at least partly vitrifies into the glassy surface finish bonded to the surface of the substrate 20.
  • a glass-finish material such as a glaze or vitreous enamel material.
  • the substrate 20 is then loaded into furnaces and fired at the appropriate temperature to adequately vitrify and adhere to the substrate 20.
  • Some exemplary firing systems and ranges of temperatures are outlined below for ceramic glazes and vitreous enamels, though other temperatures and means to fire the substrate 20 may be implemented.
  • the substrate 20 is cooled to form the hardened, glassy surface finish 30 securely coupled to the exterior of the substrate 20, either with or without an annealing or other controlled cool down period.
  • additional layers and/or spot fixes for fixing imperfections in the glassy surface finish may optionally be added and the re-fired. More detailed description of this method for each of a glazing process and an enameling process is provided hereinafter.
  • FIG. 2 illustrates a non-limiting example method of forming a glassy surface finish on an AAC substrate 20 using ceramic glazes.
  • glazes are typically prepared in liquid form, and can be brushed, sprayed, poured or dipped to adhere directly on the surface of the substrate 20, which in this example is in the form of a tile or brick.
  • a standard ceramic engobe layer 28 can first be applied to the surface of the body, allowed to dry, and thereafter the glaze 24 can be coated onto the ceramic engobe layer.
  • One or more layers of the glaze 24 may be applied.
  • Engobes are similar to a ceramic slip, allowing application of a thin ceramic layer in liquid form to a substrate.
  • the glaze 24 is then applied directly over the engobe layer 28.
  • the use of engobe as a base layer is often used in the glazing of volcanic stones, and the same principle can be utilized with the AAC substrate 20 as a means to achieve a more uniform glazed finish.
  • the engobe layer 28 is not required, and the glaze 24 bonds to the AAC substrate 20 regardless, albeit with more texture and irregularities, which at times may be aesthetically desirable.
  • the glazes 24 selected can be whichever colors, effects, or textures that one desires, though they preferably are selected in accordance with the firing target, as discussed hereinafter in relation to firing.
  • the substrate 20 with the glaze thereon is fired to at least partially melt the glaze material and bond the glaze material to the substrate 20.
  • Ceramic glaze temperatures vary depending on the glaze used, and can fall in a range of, as a nonlimiting example, about 800 to about 1300 °C (about 1472 to about 2372 °F). Different mixture designs for the substrate 20 will allow or require different temperatures, and typically more refractory aggregates will enable a higher firing temperature to be implemented.
  • An oxidation firing atmosphere oxidation may be used to avoid reduction of the substrate 20, but it is possible that a reduction atmosphere may also work and be implemented at substantially lower temperatures.
  • the firing can be done in any heating device suitable for achieving and controlling the needed temperature, atmosphere, and time period, such as standard consumer or industrial ceramic kilns.
  • the firing schedules can vary from a few hours induration at large industrial scales to over twenty-four hours for smaller scale manufacturing systems. Testing by the inventors suggest that “low-fire” glazes (i.e., up to pyrometric cone 04) worked best, but even higher (up to cone 01) showed adequate results. Although tests of “mid-fire” and “high-fire” glazes caused over-firing and bloating of substrates, it is believed that higher temperature glazes would also work with the right refractories aggregate content.
  • the fired glazed substrate 20 is then allowed to cool.
  • the substrate 20 may be cooled within the kiln environment, for example, following the same methodology common to ceramics.
  • additional layers or spots of glazing may be applied and re-fired after the initial firing and cool down, for example by repeating portions of the process described herein.
  • ceramic glazing With ceramic glazing, re-glazing is possible but difficult due to the lack of porosity of the surface and differing shrink rates.
  • small fixes, or the application of overglazes or lusters is possible, following the same methodology common to regular ceramics. This can be accomplished generally, for example, by repeating the application, firing, and cooling steps 110, 112, and 114 or modifications thereof. It may also be desirable to retain some imperfections on the glassy surface finish for various reasons, such as for aesthetic reasons. For example, FIG. 12 shows sample tiles with various aesthetic results possible from altering aggregates, enamel techniques, and substrate preparation.
  • FIG. 13 shows the results of glazing on different AAC substrates.
  • the upper left and upper right samples are of an AAC tile with three different colored ceramic engobes applied on the left portion of the tile, and no engobe applied along the far right edge of the tile.
  • the surface is then glazed with a regular commercial transparent ceramic glaze, and fired.
  • the lower left sample shows a different glaze containing high metal oxide content, with varying layers.
  • the resulting glaze on all portions were successful, with the most homogenous glaze surface finish on the three engobe layers.
  • FIG. 3 illustrates a non-limiting example method of forming a glassy surface finish on an AAC substrate 20 using a vitreous enamel 26.
  • the types of enamels 26 that can be used are manifold. Producers of enamel powders typically have their own recipes in making enamel, and typically they all work to some degree, some with more desirable effects than others. Some enamels are marketed as “jeweler’s enamels”, which are typically more glassy and translucent, and significantly more expensive than others. The more common enamel, often used in metal signage, enamelware, and on kitchen furniture/utensils is “steel enamel”, which is generally more opaque and satin than the jeweler’s enamel.
  • vitreous enamels exist, and it is believed that they would all fuse and adhere on an AAC substrate in a similarly suitable manner.
  • This disclosure includes all vitreous enamels that could be successfully applied to an AAC substrate so as to form a suitable glassy surface finish.
  • Vitreous enamels 26 can be applied to the surface as a liquid paste (“wet” application) by brushing, spraying, dipping, etc., as shown 120.
  • This enamel paste is prepared either with commercially available enamel adhesives, or simply water.
  • An organic-based mixture can also be prepared to aid in adhesion and application with the enamel, such as the addition of gum arabic.
  • Enamel 26 can also be applied simply in dry powder form directly on the surface of the AAC by sprinkling it on, which is typically how jewelers apply enamel to substrates, with the help of a sieve for even distribution.
  • An adhesive solution layer can also be applied to the substrate beforehand, followed by the powdered enamel, to ensure better adhesion to the substrate when handling.
  • a thickness of about one to about three mm (about 1/25 to about 1/10 inch) is believed optimal for some applications, but the enamel can work at a variety of thicknesses. Multiple layers of enamel can be subsequently added before firing if needed or desired. Further layers of enamel can be added even after the first firing, for example to fix mistakes or provide other effects.
  • the firing process 122 of the enamels on the AAC substrate 20 is much quicker than that of ceramics, primarily because the fumaces/kilns do not heat up with the substrate 20, but rather are already at target temperatures when the substrate 20 enters the firing environment.
  • a substrate 20 can be heated from ambient temperature to target temperature within the fumace/kiln at a fast rate, but can also be place directly from ambient temperature to a furnace at temperature elevated temperatures. In the latter case, it may be preferably to first allow the substrate 20 to dwell at an elevated temperature, as a nonlimiting example, about 450°C (about 842° F), for about ten to thirty minutes to de-gas, followed by firing it at target temperature.
  • the firing time at target temperature may be, as a nonlimiting example, about five to about forty -five minutes, depending on the size of the substrate 20 and the furnace.
  • the “tunnel furnace” system is more common, whereby a substrate can be moved on a conveyor belt directly through the furnace.
  • the substrate 20 is moved first by a conveyor to mid way temperature, as a nonlimiting example, about 450° C.
  • the substrate 20 moves through this environment, as a nonlimiting example, about five to fifteen minutes, before moving into the target temperature environment (depending on the enamel, a nonlimiting example is a range of about 750 °C - 1000 °C), through which the substrate 20 may be moved for another five to fifteen minutes.
  • FIG. 6 shows various enameled tiles that were enameled in an industrial tunnel-furnace with excellent results of the final glassy surface finish and overall end product. Three of the enameled tiles were fired in one industrial furnace, while a fourth enameled tile was fired in a different industrial furnace and with a different firing schedule. All four samples show similar end results, which indicates that equipment and firing schedules are flexible and that various different firing equipment and firing schedules may be implemented.
  • the fired enameled substrate 20 is then allowed to cool.
  • the cooling can be much quicker than with glazing.
  • the fired substrate 20 can be removed from the furnace environment and allowed to anneal at a mid-way temperature or cooled directly at ambient temperature. Because cooling directly at ambient temperature can add strain to a substrate, a mid way annealing environment is typically preferred.
  • the substrate 20 can also be allowed to cool within the kiln, for example as is often done with ceramic glazing, although this may obviate some of the time advantages over glazing.
  • substrates may be moved directly from the target temperature to a cooling/annealing section of the tunnel furnace, as a nonlimiting example, about five to fifteen minutes, and finally out of the furnace environment to ambient temperature.
  • the rate of firing and cooling of tunnel furnace systems depends largely on the manufacturer, but they are typically quick and reliable in comparison to front or top loading systems that might be more practiced at the small scale.
  • Other methods are also possible for heating ("firing") substrates with enamels applied to their surfaces for the purpose of vitrifying the enamels and bonding them to the substrate surfaces, including methods that may not be yet commercially practiced or tested.
  • Glassy layers could be applied and fused to large AAC substrates in a manner similar to how roofing tar is applied, with the aid of a torch. This has clear energy saving implications given that the entire AAC substrate does not need to be heated, as well as new possibilities for how the application of colored glass layers to large concrete bodies may change architecture or design. All such modifications for applying an enamel layer while preventing the enamel layer from being blown away by a torch are within the scope of the invention.
  • additional layers or spots of enamel may be applied and re-fired after the initial firing and cool down, for example by repeating portions of the process described herein.
  • vitreous enamels it is possible to add multiple layers and/or to fix and adjust the enamel in multiple firings when using an AAC substrate. This can be accomplished by repeating the application and firing steps of the enameling process described herein.
  • FIGS 4 and 5 show various samples of AAC substrates that were successfully finished with an enamel surface finish in accordance with the materials and methods described herein.
  • FIG 4. shows various examples of vitreous enamel applied to geopolymer tiles of various thickness and shapes.
  • FIG. 5 shows tile samples of slag-based AAC substrates, with various vitreous enamels applied. The substrates were fired at about 800 °C, and the enamel was applied as a dry powder. These samples exemplify a small portion of the variety of aesthetic results possible with different enamel choice and application techniques.
  • the glazing and enameling of a cast alkali -actuated concrete substrate and the use of a waste-based material as substrate in vitreous enameling, are disclosed. Due to the thermal resistance and mechanical characteristics of the inorganic polymers, the AAC substrates are able to withstand the high temperatures and thermal shock required for the minerals of glazes and enamels to vitrify and adhere to the inorganic polymer body. This is unique, given that ceramic glazes only typically work on ceramic bodies, and occasionally on lava-stone, whereas enamels by contrast typically only work on metallic bodies, with the exception of some volcanic stones and some granites. It is believed that up until now, no concrete could be glazed or enameled successfully.
  • the methods, materials, compositions, and products of the present disclosure demonstrate that it is possible to melt and fuse the finishing glassy layer to the underlying AAC substrate in a matter of minutes, as opposed to the many hours required for previously known ceramic glazing.
  • volcanic stone which can be enameled or glazed and is sought after as a luxury surface product.
  • volcanic stone is very arduously mined and sourced from unique, often at-risk, environments, such as Mt. Etna of Italy and the Auvergne region of France. Further, finding large slabs of intact volcanic stone, shipping them around the world, and then cutting them to size (with inevitable off-cut waste) also results in a high environmental and monetary cost. Further, volcanic stone cannot be formed and molded into virtually and shape, size, and form factor in the way concretes can be formed, and thus does not lend itself to large scale production of a large variety of useful objects of varying shapes and sizes.
  • the methods, materials, compositions, and products of the present disclosure enable one to apply aesthetically pleasing and durable finishes to virtually any shape and size AAC substrate, whether it is casted, printed, or shaped by other means, without the need for mining virgin materials, all the while making use of more local secondary resources, and at less of the environmental footprint of other OPC counterparts.
  • This also means a similar product to enameled/glazed lava stone can be made at greatly reduced cost.
  • the substrate has been shown to undergo a sintering process that partially transition from an inorganic polymer to a ceramic internal structure, whereby the substrates effectively switch from being a concrete to a ceramic body. This is particularly the case in the event of applying ceramic glaze to the substrate given the longer firing times which allow the sintering process to occur. In the event of transitioning to a ceramic, the result is an even stronger body than before, particularly in tensile/flexural strength.

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Abstract

Béton à activation alcaline présentant une finition de surface vitreuse, et procédés et produits associés à ce béton. Un substrat comprenant le béton à activation alcaline est fini par une finition de surface vitreuse qui est vitrifiée et adhère au substrat, par exemple par glaçage ou émaillage avec un processus de cuisson approprié. Un mélange destiné au béton à activation alcaline possède un liant cimentaire, un activateur alcalin et un agrégat. Le béton à activation alcaline formé à partir du mélange présente une résistance thermique élevée qui est apte à résister aux températures et au choc thermique requis pendant un processus de cuisson approprié pour que les minéraux de glaçures et d'émaux sur ce béton vitrifient une surface du béton à activation alcaline et adhèrent à cette surface sans se fissurer ou se briser. Le béton à activation alcaline peut comporter des géopolymères et/ou des polymères inorganiques.
PCT/US2022/038796 2021-07-29 2022-07-29 Béton à activation alcaline présentant une finition de surface vitreuse, et procédés et produits associés à ce béton WO2023009783A1 (fr)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0632681A (ja) * 1992-07-16 1994-02-08 Sansou:Kk ガラス化表面をもつセメント硬化物
US20070221100A1 (en) * 2006-03-22 2007-09-27 Sanjay Kumar Process for the preparation of self-glazed geopolymer tile from fly ash and blast furnace slag
WO2007109862A1 (fr) * 2006-03-29 2007-10-04 Zeobond Research Pty Ltd composition de ciment DE mélange à sec, procédés et systèmes englobant ladite composition
WO2020056470A1 (fr) * 2018-09-21 2020-03-26 Ahmed Redha Saleem Graytee Compositions et articles géopolymères frittés
CN111302682A (zh) * 2019-12-17 2020-06-19 李韦皞 一种含有碱活化液及无机粉体的碱活化浆料

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0632681A (ja) * 1992-07-16 1994-02-08 Sansou:Kk ガラス化表面をもつセメント硬化物
US20070221100A1 (en) * 2006-03-22 2007-09-27 Sanjay Kumar Process for the preparation of self-glazed geopolymer tile from fly ash and blast furnace slag
WO2007109862A1 (fr) * 2006-03-29 2007-10-04 Zeobond Research Pty Ltd composition de ciment DE mélange à sec, procédés et systèmes englobant ladite composition
WO2020056470A1 (fr) * 2018-09-21 2020-03-26 Ahmed Redha Saleem Graytee Compositions et articles géopolymères frittés
CN111302682A (zh) * 2019-12-17 2020-06-19 李韦皞 一种含有碱活化液及无机粉体的碱活化浆料

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