Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B28—WORKING CEMENT, CLAY, OR STONE
  • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
  • B28B1/00—Producing shaped prefabricated articles from the material
  • B28B1/50—Producing shaped prefabricated articles from the material specially adapted for producing articles of expanded material, e.g. cellular concrete
• • 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
  • C04B28/18—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 mixtures of the silica-lime type
  • C04B28/186—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 mixtures of the silica-lime type containing formed Ca-silicates before the final hardening step
  • C04B28/188—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 mixtures of the silica-lime type containing formed Ca-silicates before the final hardening step the Ca-silicates being present in the starting mixture
• • 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
  • Y02P40/18—Carbon capture and storage [CCS]
• • 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 invention generally relates to a composite material and a process of production of the same. More particularly, the present invention relates to a novel lightweight aerated composite material made from a carbonatable calcium silicate composition, and
• the lightweight aerated composite material is comprised of calcium carbonate (CaC0 3 ) and Silica (S1O 2 ) , as cured products of carbonatable calcium silicate compositions.
• ordinary AAC is one example of lightweight precast concrete which is formed under a high temperature and high pressure (for example, 190°C, 12 atm) cured for 6 to 8 hours using raw materials such as calcareous materials of cement and lime (CaO) , siliceous materials such as silica (S1O2) , silica sand (S1O2) , and other materials such as gypsum (CaSO-i) , recycled materials produced in manufacturing such as fly ash, metal aluminum and other aerating agents, surfactants for stabilizing the bubbles, and other fillers.
• the aerating agent causes air voids to form in the matrix and increases the porosity of the material.
• Ordinary AAC products offer a number of advantages over conventional concretes such as good strength-to-weight ratio, resistance to fire, corrosion, termites and molds, as well as good thermal insulation and sound deadening properties. Due to their lightweight and dimensional accuracy, ordinary AAC products can be assembled with minimal waste thereby reducing the need for additional equipment in construction and assembling. They offer high durability and require minimum
• the lightweight of an ordinary AAC also helps with lowering shipping costs.
• compressive strength of an ordinary AAC depends on its total void volume, commercially available ordinary AAC achieve about 5 N/mm 2 at an absolute dry density of 0.50 g/cm 3 . These properties sufficiently meet the strength requirements for building materials.
• AAC are prepared by processes that commonly suffer from a number of deficiencies.
• the manufacturing process of ordinary AAC involves special equipment, large energy consumption, and excessive carbon dioxide emission, leaving unfavorable carbon footprint.
• Ordinary AAC are typically cured in autoclaves at temperatures ranging from 150°C to 190°C and at pressures ranging from 0.8 MPa to 1.2 MPa. These conditions lead to the creation of a stable form of tobermorite, which is the primary bonding element in ordinary AAC. In addition, they are relatively expensive due to high finishing costs and are also difficult to recycle.
• ordinary AAC panels use either reinforcing structures (for example, iron rods) embedded inside them or non-reinforcing structures.
• Such ordinary AAC also consist of large number of pores and bubbles that can simultaneously hold some amount of water. This water is found to be present even when the ordinary AAC is in a usual usage environment. Since ordinary AAC have a large number of air bubbles inside them, carbon dioxide from the air can infiltrate inside the ordinary AAC over time. The infiltrated carbon dioxide can also dissolve into such water, where calcium derived from various components is also present.
• 310480A describes ordinary AAC as a structure where air bubbles are connected to form innumerable pores that extend from the surface to the inside, allowing water to be easily absorbed from the surface. Since the absorbed water contains dissolved carbon dioxide gas, it reacts with the tobermorite crystals and CSH gel in the ordinary AAC to form calcium carbonate and cause the so-called carbonation phenomenon.
• Japanese Patent Publ. No. 5- 310480A also describes the general practice of making ordinary AAC panels that include cage-like iron
• iron reinforcement or other reinforcement When iron reinforcement or other reinforcement is used in case of ordinary AAC it has a tendency to absorb water right to its center, necessitating rust- prevention .
• WO2012/122031A discloses an improved bonding matrix in place of conventional cement, concrete, or other ceramic material such as CaO ⁇ 2S1O 2 ⁇ 43 ⁇ 40 and CaO ⁇ 3 ⁇ 40 or other weak hydrated Portland cement.
• the bonding element of such a bonding matrix is, for example, comprised of a precursor particle comprised of calcium silicate (CaSiOs) . This precursor particle can react with the carbon dioxide dissolved in water. Calcium cations are leached from calcium silicate particles and transform the peripheral portion of the calcium silicate particle core into calcium-deficient.
• the first layer and the second layer are formed from the precursor particle by a
• This bonding element can be formed by the method of gas-assisted hydrothermal liquid phase sintering. In such a method, a porous solid body
• a gas comprising a reactant of carbon dioxide is introduced into the partially
• solvent dissolves the reactant.
• the dissolved reactant is depleted from the solvent due to the reaction, but the gas comprising the reactant continues to be introduced into the partially saturated pores to supply additional reactant to the solvent.
• the particle is transformed into the first layer and the second layer.
• the presence of the first layer at the periphery of the core eventually hinders further reaction by separating the reactant and the at least first
• the core has a shape
• the first layer and the second layer partially or
• the resulting bonding element includes the core, the first layer and the second layer, and is generally larger in size than the precursor particle, filling in the surrounding porous regions of the porous solid body and possibly bonding with adjacent materials in the porous solid body.
• the net- shape of the products that may be formed have more or less the same size and shape as their original forms but a higher density than the porous solid body.
• WO2014/165252A discloses a carbonation-cured material constituted by an aerated composite material using a carbonatable calcium silicate composition and a process of production of the same.
• ordinary AAC utilizes the hydrothermal reaction due to autoclaving at the time of production so as to form tobermorite crystals and cure the material, followed by a reduction in temperature and pressure to respectively ordinary temperature and ordinary pressure. The material is then taken out from the autoclave for processing its surfaces and end-parts as per the product specifications before supplying it for practical use.
• carbonation cured ACC the carbonation occurs when the calcium and carbon dioxide are reacted.
• This novel method of replacing conventional Portland cement for producing AAC can significantly reduce energy requirement and CO 2 emissions.
• the disclosed carbonatable calcium silicate compositions are made from widely available, low-cost raw materials by a process suitable for large-scale production with flexible equipment and production requirements. This unique approach is also accompanied by a remarkable proficiency for permanently and safely sequestrating CO 2 .
• WO2014/165252A describes an aerated composite material made from calcium silicate compositions where a plurality of voids comprise bubble-shaped and/or
• interconnected channels account for 50 vol% to 80 vol% of the composite material and where the composite material exhibits a density of approximately 300 kg/m 3 to 1500 kg/m 3 , exhibits a compressive strength of approximately 2.0 MPa to approximately 8.5 MPa (N/mm 2 ) , and exhibits a flexural strength of approximately 0.4 MPa to
• the compressive strength of an aerated composite material depends on the density and further the density depends on the void volume.
• the void volume can more particularly be divided into the bubble volume and the pore volume.
• the bubble volume depends on the amount of addition of the foaming agent (aerating agent) such as metal aluminum (aluminum powder) . Changing the amount of addition of this foaming agent can easily control the bubble volume.
• the pore volume can be controlled by the water content present at the time of mixing of the raw materials (water/solids (W/S) ratio) and the degree of advance of carbonation at the time of curing. That is, in principle, these factors can be changed to control the density-strength property.
• W/S water/solids
• the literature does not specifically disclose or teach at all what kind of compressive strength can be achieved at a specific void volume and a specific density much less specifically disclose, teach, or suggest the void volume and more particularly the bubble volume and pore volume.
• An aerated composite material prepared from calcium silicate compositions has several advantages compared to ordinary AAC. However, while a commercially available ordinary AAC realizes a higher compressive strength of approximately 5 N/mm 2 at an absolute dry density of 0.50 g/cm 3 and adequately satisfies the strength requirements as a building material, it remains a challenge to produce an aerated composite material from calcium silicate compositions that achieves a compressive strength similar to ordinary AAC at the same amount of bubbles when compared with the latter at the current state of the art. Under the circumstances, the technical problem of the present invention is to provide an aerated composite material that is prepared from calcium silicate compositions, which has a compressive strength equivalent to ordinary AAC at substantially the same density. [0021] The inventors engaged in intensive studies and repeated experiments to solve this problem and as a result discovered that of the pores having radius from 0.004 ⁇ to 10.0 ⁇ are mostly saturated by water before carbonation. As the carbonatable calcium silicate
• the pores in the bubble volume having radius 10.0 ⁇ or more are not saturated by water before carbonation, so at these bubbles the calcium carbonate precipitates only inside the adsorbed water layer.
• the bubble volume can also be easily controlled by the dosage of the foaming agent (aerating agent), e.g., metal aluminum.
• the foaming agent e.g., metal aluminum.
• the present invention is as outlined below:
• the invention generally relates to a composite material, which includes: a plurality of bonding elements, each including a core comprising
• the plurality of bonding elements and plurality of filler particles together form a bonding matrix and are
• the plurality of voids are bubble-shaped and/or interconnected channels; a pore volume with a radius of 0.004 ⁇ to 10.0 ⁇ in the plurality of voids is 0.30 ml/composite material 1 g or less; and an
• the pore volume with a radius of 0.004 ⁇ to 10.0 ⁇ in the composite material is 0.24 ml/composite material 1 g or less and the
• estimated compressive strength is 2.5 N/mm 2 or more.
• the pore volume with a radius of 0.004 ⁇ to 10.0 ⁇ in the composite material is 0.19 ml/composite material 1 g or less and the
• estimated compressive strength is 3.7 N/mm 2 or more.
• the pore volume with a radius of 0.004 ⁇ to 10.0 ⁇ in the composite material is 0.17 ml/composite material 1 g or less and the
• estimated compressive strength is 4.5 N/mm 2 or more.
• the pore volume with a radius of 0.004 ⁇ to 10.0 ⁇ in the composite material is 0.15 ml/composite material 1 g or less and the
• the plurality of bonding elements is chemically transformed from ground calcium silicate.
• the ground calcium silicate comprises one or more of a group of calcium silicate phases selected from CS (wollastonite or pseudowollastonite ) , C3S2 (rankinite) , C2S (belite, larnite, bredigite) , an amorphous calcium silicate phase, each of which material optionally comprises one or more metal ions or oxides, or blends thereof.
• the plurality of bonding elements is chemically transformed from ground wollastonite or composite cement particles comprising calcium silicates by reacting the ground wollastonite, or composite cement particles comprising calcium silicates, with CO 2 via a controlled hydrothermal liquid phase sintering (HLPS) process.
• HLPS hydrothermal liquid phase sintering
• the filler particles are a CaO-rich material. In certain embodiments, the filler particles are selected from the group consisting of lime and quartz. In certain embodiments, the filler particles are selected from the group consisting of industrial waste, lime, different types of fly ash, slag, and silica fume.
• the plurality of voids is formed by hydrogen gas, which is generated by reacting an aerating agent in an alkali atmosphere.
• the aerating agent is a powder, which includes at least one of aluminum, iron, calcium carbonate, and blends of the same.
• the invention generally relates to a process of production of a composite
• the process includes: forming a wet mixture, wherein the wet mixture comprises water, filler particles comprising CaO or Si having a particle size of 0.1 ⁇ to 1000 ⁇ , ground calcium silicate particles, and an aerating agent, has a water/solid ratio (W/S) of 0.45 or less; casting the wet mixture in a mold; allowing the aerating agent to generate hydrogen gas thereby causing volume expansion of the wet mixture; pre-curing the obtained expanded mixture to a hardness enabling it to be taken out from the mold and moved; cutting the obtained pre-cured expanded mixture into a desired product shape; and causing the cut expanded mixture to cure at ordinary pressure, 60°C or more of temperature, a relative humidity of 65% or more, and an atmosphere of a CO 2 gas
• the ground calcium silicate particles comprise one or more of a group of calcium silicate phases selected from CS
• the temperature at the carbonation step is 80°C or more. In certain embodiments, the relative humidity at the carbonation step is 95% or more .
• carbonation step is 40 hours or more.
• the composite material according to the present invention is carbonation cured AAC, which has a
• the carbonation cured AAC therefore, can be suitably used as a building material. Furthermore, in the process of production of the composite material according to the present invention, massive energy consumption, excessive emission of carbon diode, and undesired carbon footprint can be suppressed.
• FIGs. 1(a) -1(c) are schematic illustrations of cross-sections of bonding elements according to exemplary embodiments, including three exemplary core morphologies:
• FIGs. 2-1 shows ID oriented fiber- shaped bonding elements in a dilute bonding matrix
• FIG. 2(b) shows 2D oriented platelet shaped bonding elements in a dilute bonding matrix (bonding elements are not touching)
• FIG. 2 (c) shows 3D oriented platelet shaped bonding elements in a dilute bonding matrix (bonding elements are not touching)
• FIG. 2(d) shows randomly oriented platelet shaped bonding elements in a dilute bonding matrix
• FIGs. 2-2 show a concentrated bonding matrix (with a volume fraction sufficient to establish a percolation network) of bonding elements where the matrix is 3D oriented and FIG. 2(f) shows a concentrated bonding matrix (with a volume fraction sufficient to establish a percolation network) of
• filler components such as polymers, metals, inorganic particles, aggregates, etc., may be included.
• FIG. 3 is a graph that shows the relationship between the absolute drying density and compressive strength of ordinary AAC and carbonation cured AAC.
• FIG. 7 is a graph that shows the relationship between the carbonate degree of carbonation cured AAC and the volume per composite material 1 g of a radius 0.004 ⁇ to 10.0 ⁇ porous region.
• FIG. 8 is a graph that shows the relationship between volume per composite material 1 g of a radius
• FIG. 9 is a graph that shows one example of particle size distributions of synthetic wollastonite
• FIG. 10 is a graph that shows one example of particle size distributions of lime and gypsum.
• FIG. 11 is a graph that shows one example of a particle size distribution of metal aluminum (Yamato #87) .
• This invention provides an aerated composite material produced from a carbonatable calcium silicate composition that has a compressive strength equivalent to ordinary AAC at substantially the same density.
• the composite material of the present invention is a composite material comprising: a plurality of bonding elements, each including a core comprising calcium silicate, a first layer which partially or fully surrounds the core and is rich in S1O 2 , and a second layer which partially or fully surrounds the first layer and is rich in CaCC>3, in certain instances the layers are not distinct;
• the plurality of bonding elements and plurality of filler particles together form a bonding matrix and are substantially evenly dispersed in the matrix and bonded together,
• the plurality of voids are bubble-shaped and/or interconnected channels, a pore volume with a radius of 0.004 ⁇ to 10.0 ⁇ (e.g., from 0.004 ⁇ to 5.0 ⁇ , from 0.004 ⁇ to 1.0 ⁇ , from 0.004 ⁇ to 0.5 ⁇ , from 0.004 ⁇ to 0.1 ⁇ , from 0.004 ⁇ to 0.05 ⁇ , from 0.004 ⁇ to 0.01 ⁇ , from 0.01 ⁇ to 10.0 ⁇ , from 0.05 ⁇ to 10.0 ⁇ , from 0.1 ⁇ to 10.0 ⁇ , from 0.5 ⁇ to 10.0 ⁇ , from 1.0 ⁇ to 10.0 ⁇ ) in the plurality of voids is 0.30 ml/composite material 1 g or less (e.g., 0.24 ml/composite material 1 g or less, 0.19 ml/composite material 1 g or less, 0.17 ml/composite material 1 g or less, 0.15 ml
• the invention provides a process of production of a composite material.
• process includes: forming a wet mixture, wherein the wet mixture comprises water, filler particles comprising CaO or Si having a size of a particle size of 0.1 ⁇ to 1000 ⁇ (e.g., from 0.1 ⁇ to 500 ⁇ , from 0.1 ⁇ to 100 ⁇ , from 0.1 ⁇ to 50 ⁇ , from 0.1 ⁇ to 10 ⁇ , from 0.1 ⁇ to 5 ⁇ , from 0.1 ⁇ to 1 ⁇ , from 0.5 ⁇ to 1000 ⁇ , from 1 ⁇ to 1000 ⁇ , from 5 ⁇ to 1000 ⁇ , from 10 ⁇ m to 1000 ⁇ , from 50 ⁇ m to 1000 ⁇ , from 100 ⁇ to 1000 ⁇ ) , ground calcium silicate particles, and an aerating agent, has a water/solid ratio (W/S) of 0.45 or less (e.g., 0.4, 0.35, 0.3, 0.25); casting the wet mixture in a mold; allowing the aerating agent to generate hydrogen gas thereby causing volume expansion of the wet mixture
• the calcium silicate composition may include various calcium silicates.
• composition is from about 0.8 to about 1.2.
• composition is comprised of a blend of discrete
• crystalline calcium silicate phases selected from one or more of CS (wollastonite or pseudowollastonite ) , C3S2
• the calcium silicate compositions are characterized by having about 30% or less of metal oxides of Al, Fe and Mg by total oxide mass, and being suitable for carbonation with CO 2 at a temperature of about 30 °C to about 90 °C to form CaCC>3 with mass gain of about 10% or more.
• Calcium silicate compositions may include amorphous (non-crystalline) calcium silicate phases in addition to the crystalline phases described above.
• the amorphous phase may additionally incorporate Al, Fe and Mg ions and other impurity ions present in the raw materials.
• Each of these crystalline and amorphous calcium silicate phases is suitable for carbonation with C0 2 .
• the calcium silicate compositions may also include small quantities of residual CaO (lime) and S1O 2
• the calcium silicate composition may also include small quantities of C3S (alite, CasSiOs) .
• the C2S phase present within the calcium silicate composition may exist in any a-Ca 2 SiC>4, p-Ca 2 SiC>4 or y-Ca 2 Si0 polymorph or combination thereof.
• the calcium silicate compositions may also include quantities of inert phases such as melilite type minerals (melilite or gehlenite or akermanite) with the general formula (Ca, Na, K) 2 [ (Mg, Fe 2+ , Fe 3+ , Al , Si ) 3 0 7 ] and ferrite type minerals (ferrite or brownmillerite or C 4 AF) with the general formula Ca 2 (Al , Fe 3+ ) 2 ⁇ 5.
• the calcium silicate composition is
• the calcium silicate comprises only of crystalline phases. In certain embodiments, some of the calcium silicate composition exists in an amorphous phase and some exists in a crystalline phase.
• the term "calcium silicate composition” generally refers to naturally-occurring minerals or synthetic materials that are comprised of one or more of a group of calcium silicate phases including CS (wollastonite or pseudowollastonite, and sometimes formulated CaSiC>3 or CaO-SiC ⁇ ), C3S2 (rankinite, and sometimes formulated as Ca 3 Si2C>7 or 3CaO-2SiC>2), C2S
• the carbonatable calcium silicate composition does not hydrate.
• minor amounts of hydratable calcium silicate phases e.g., C2S, C3S and CaO may be present.
• C2S exhibits slow
• the calcium silicate phases included in the calcium silicate composition do not hydrate when exposed to water. Due to the composites produced using a calcium silicate composition as the binding agent do not generate significant strength when combined with water.
• calcium silicate compositions, phases and methods disclosed herein can be adopted to use magnesium silicate phases in place of or in addition to calcium silicate phases.
• magnesium silicate refers to naturally- occurring minerals or synthetic materials that are
• Mg 2 Si0 4 also known as “fosterite”
• Mg 3 Si 4 Oi 0 (OH) 2 also known as “talc”
• material may include one or more other metal ions and oxides (e.g., calcium, aluminum, iron or manganese oxides), or blends thereof, or may include an amount of calcium silicate in naturally- occurring or synthetic form(s) ranging from trace amount
• the plurality of bonding elements can preferably be chemically transformed from ground synthetic or naturally occurring calcium silicate composition, more preferably can be chemically transformed from ground calcium silicate composition by reacting the ground synthetic or natural occurring
• FIGs. 1(a) to 1(c) show exemplary embodiments of three types of bonding elements.
• the corresponding bonding elements and/or cores can include ones of spherical, elliptical, hexagonal or other polygonal shapes or numerous other shapes, but can be any of numerous morphologies not limited to these.
• the morphologies of the precursor particles and, according to the same, the corresponding bonding elements and/or cores may include equiaxed states or states where one axis is longer than the others such as with a wire or rod shape.
• the precursor particles can include single crystals (that is, be "monocrystalline" ) or a plurality of crystals
• the precursor particles can actually include a plurality of particles or include amorphous phases.
• both the anions and cations differ in the different layers.
• the core has Ca +2 , Si +4 , and 0 ⁇ 2 ions
• the second layer mainly has Si +4 and 0 ⁇ 2 and a small amount of Ca +2 ions, but the second layer has Ca +2 and C0 3 ⁇ 2 ions.
• the bonding matrix of the present embodiment includes the above plurality of bonding elements.
• the bonding matrix can be porous.
• the void volume depends on many variables, which can be used for controlling the porosity, such as: temperature, reactor design, precursor material, and amount of liquid that is introduced into the carbonation (transformation) step .
• the bonding matrix may incorporate filler particles, which are mixed with the precursor materials during the later explained transformation process to create the composite material.
• the filler particles may include any one of a number of types of materials that can be incorporated into the bonding matrix such as inert materials and active materials.
• inert materials any one of a number of types of materials that can be incorporated into the bonding matrix
• active materials An inert material does not go through any chemical reaction during the
• An active material can be comprised of a first type, which does not go through any chemical reaction during the transformation, but acts as a nucleation site and/or a second type, which chemically reacts with the bonding matrix during the transformation.
• the inert material may physically or mechanically interact with the bonding matrix, but does not go through any chemical reaction during the transformation and does not act as a
• the inert material may include polymers, metals, inorganic particles, aggregates, and the like.
• the first type of active material does not go through any chemical reaction during the transformation, but acts as a nucleation site. Further, it may physically or
• this type of active material may, for example, include limestone, marble powder, and other calcium carbonate-containing materials.
• the second type of active material chemically reacts with the bonding matrix during the transformation. For example, lime makes the pH alkaline in the wet mixing step and causes the generation of hydrogen gas by the addition of aluminum powder (metal aluminum) to contribute the formation of bubbles, then acts as a calcium source during the transformation.
• magnesium hydroxide can be used as a filler. It may chemically react with a dissolving calcium component phase from the bonding matrix to form magnesium calcium carbonate. Further, gypsum chemically reacts with the bonding matrix during the transformation and is sometimes added for the purpose of increasing the hardness at the time of pre-curing.
• the filler particles may, for example, be CaO-containing or silicon-containing materials.
• the filler particles may be, for example, lime, quartz (including sand), wollastonite, xonotlite, burned oil shale, fly or volcanic ash, stack dust from kilns, ground clay, pumice dust. Materials such as industrial waste materials, lime, slag, and silica fume may also be used.
• the filler may, for example, be CaO-containing or silicon-containing materials.
• the filler particles may be, for example, lime, quartz (including sand), wollastonite, xonotlite, burned oil shale, fly or volcanic ash, stack dust from kilns, ground clay, pumice dust. Materials such as industrial waste materials, lime, slag, and silica fume may also be used.
• the filler may, for example, lime, quartz (including sand), wollastonite, xonotlite, burned oil shale, fly
• particles may be light-weight aggregates such as pearlite or vermiculite, for example, may also be a CaO-rich
• the plurality of filler particles may have any suitable median particle size and size distribution dependent on the desired composite material. However, in the present embodiment, the plurality of filler particles may have a particle size 0.1 ⁇ to 1000 ⁇ of size.
• the composite material of the present embodiment may further contain one or more additives for correcting the appearance and physical or mechanical properties.
• FIG. 10 shows one example of the particle size distribution of lime and gypsum. Further, FIG. 11 shows one example of the
• the bonding elements may be positioned, relative to each other in any one of a number of orientations.
• the bonding matrix can exhibit any of numerous different patterns.
• the bonding elements can be aligned in one direction
• the bonding elements can be aligned in a random pattern (that is, "random"
• the concentration of bonding elements in the bonding matrix may vary.
• the concentration of bonding elements on a volume basis may be relatively high, wherein at least some of the bonding elements are in contact with one another. This situation may arise if filler material is incorporated into the bonding matrix, but the type of filler material and/or the amount of filler material is such that the level of volumetric dilution of the bonding element is relatively low.
• the concentration of bonding elements on a volume basis may be relatively low, wherein the bonding elements are more widely dispersed within the bonding matrix such that few, if any of the bonding
• the concentration of bonding elements on a volume basis may be one where all or substantially all of the bonding elements contact each other.
• FIGs. 2(a) to 2(d) illustrate bonding matrices that include fiber- or platelet-shaped bonding elements in different orientations possibly diluted by the
• FIG. 2(f) illustrates a bonding matrix that includes a relatively high concentration of platelet-shaped bonding elements that are aligned in a 3-D orientation, for example, the X-, y-, and z-directions .
• a relatively high concentration of bonding elements is shown by the lack of filler around the bonding elements, therefore, there is almost no or absolutely no dilution of bonding elements.
• FIG. 2(f) illustrates a bonding matrix that includes a relatively low concentration of platelet-shaped bonding elements that are situated in a random orientation.
• a relatively low concentration of bonding elements is shown by the presence of fillers around the bonding elements; therefore, there is at least a certain extent of dilution of bonding elements. Due to the concentration and
• the composite material can be called a percolation network.
• a one-level repeating hierarchic system generally is formed by blending two different sizes of one different order or ranges of particle sizes and can be described as a "composite material".
• Larger size particles are not limited to these, but these may be arranged in hexagonal dense packing or cubic dense packing or random packing or other such different types of packing and form a network including void spaces, while smaller size particles can be positioned in the voids of the larger size particles.
• these composite material Larger size particles are not limited to these, but these may be arranged in hexagonal dense packing or cubic dense packing or random packing or other such different types of packing and form a network including void spaces, while smaller size particles can be positioned in the voids of the larger size particles.
• hierarchic systems can be prepared using different size particles at the different levels.
• bonding elements constituted by spherical particles having 1 mm diameters fill the void spaces of packed spherical
• the plurality of bonding elements may have any suitable median particle size and size distribution
• the bonding elements can be made sizes suitable for this, for example, as shown in FIG. 9, about 2 ⁇ to 50 ⁇ in range. Further, as explained above, the particle size of the bonding element increases somewhat over the particle size of the precursor due to the presence of the Si0 2 -rich first layer that is produced by carbonation of the
• a plurality of bubbles is formed by the gas material, which is generated by the aerating agent.
• a plurality of bubble voids is formed by the hydrogen gas, which is generated by reaction of the aerating agent under alkali conditions.
• the aerating agent is preferably a powder containing at least one of aluminum, iron, calcium carbonate, and their mixtures, more preferably is a metal aluminum powder.
• the size of the bubbles is
• aerating agent may be utilized so long as it is able to form a plurality of voids constituting bubble-shaped and/or interconnected channels.
• the amount of pores is also depended on the initial water content of the mixture at the time of mixing the materials and by the degree of progress of carbonation at the time of carbonation. This is also related to the pore volume with pores having a radius of 0.004 ⁇ to 10.0 ⁇ (e.g., from 0.004 ⁇ to 5.0 ⁇ , from 0.004 ⁇ to 1.0 ⁇ , from 0.004 ⁇ to 0.5 ⁇ , from 0.004 ⁇ to 0.1 ⁇ , from 0.004 ⁇ to 0.05 ⁇ , from 0.004 ⁇ to 0.01 ⁇ , from 0.01 ⁇ to 10.0 ⁇ , from 0.05 ⁇ to 10.0 ⁇ , from 0.1 ⁇ to 10.0 ⁇ , from 0.5 ⁇ to 10.0 ⁇ , from 1.0 ⁇ to 10.0 ⁇ ) .
• the wet mixture comprises water, filler particles comprising CaO or Si having a size of a particle size of 0.1 ⁇ to 1000 ⁇ , particles of ground calcium silicate composition, and an aerating agent and has a water/solid ratio (W/S) of 0.45 or less; a step of casting the wet mixture in a mold;
• various ingredients are mixed in a specified order. For example, water is added; filler particles comprising CaO or Si having a particle size 0.1 ⁇ to 1000 ⁇ size and ground calcium silicate composition are added and mixed, then the aerating agent is added and mixed.
• the particles of ground calcium silicate composition are from about 0.5 ⁇ to 100 ⁇ in size and are ground particles of natural occurring or synthetic calcium silicate composition.
• the filler particles comprising CaO or Si having a particle size 1 ⁇ to 300 ⁇ size are ground lime
• the aerating agent may be aluminum powder.
• the particle-like composition may be about 80 wt% to about 95 wt% ground calcium silicate composition, about 5 wt% to about 20 wt% ground lime, and about 0.1 wt% to about 0.5 wt% of aluminum powder in terms of percent with respect to the solid content of ground calcium silicate composition, lime, and other filler particles (below, expressed as "to solids") .
• the carbonation step can be performed at ordinary pressure, but the present invention does not exclude pressurization . Further, in the present embodiment, the carbonation step can be performed in a CO 2 gas concentration 95% atmosphere, but the present invention does not exclude a less than 95% concentration.
• the particle size of the ground calcium silicate composition for example, can be about 2 ⁇ to 50 ⁇ in size. The particle size is the median particle size. Further, the bulk density of the particles of ground calcium silicate composition may be about 0.6 g/ml to about 1.2 g/ml .
• the calcium silicate composition can react with the carbon dioxide, which is dissolved in the water.
• the calcium cations are leached from the calcium silicate composition whereby the
• peripheral portion of the calcium silicate core is transformed to calcium-deficient calcium silicate.
• the calcium cations being leached from the
• the structure of the peripheral portion eventually becomes unstable and breaks down thereby transforming the calcium-deficient
• the first layer and second layer may be formed from the precursor particle of the bonding element according the following formula (1) :
• CO 2 is introduced as a gas phase that dissolves into an infiltration fluid such as water.
• the dissolution of CO 2 forms acidic carbonic species that results in a decrease of pH in solution.
• the weakly acidic solution dissolves a fixed amount of calcium species from CaSiC>3.
• the released calcium cations and the dissolved carbonate species lead to the precipitation of insoluble carbonates.
• the silica-rich first layers are thought to remain on the mineral particles as
• the first layer and second layer on the core act as a barrier to further reaction between calcium silicate and carbon dioxide, resulting in the bonding element having a core, first layer, and second layer.
• the CaCC>3 produced from the CO2 carbonation reactions disclosed herein may exist as one or more of several CaCC>3 polymorphs (e.g., calcite, aragonite, and vaterite) .
• the CaC0 3 are
• calcite preferably in the form of calcite but may also be present as aragonite or vaterite or as a combination of two or three of the polymorphs (e.g., calcite/aragonite,
• gas-assisted HLPS processes utilize partially infiltrated pore space so as to enable gaseous diffusion to rapidly infiltrate the expanded mixture after the pre-curing step and saturate thin liquid interfacial solvent films in the pores with dissolved CO2 .
• CO2 species have low solubility in pure water (1.5 g/liter at 25°C, 1 atm) .
• CO2 must be continuously supplied to and distributed throughout the expanded mixture after the pre-curing step to enable significant carbonate conversion.
• Utilizing gas phase diffusion offers a huge (about 100-fold) increase in diffusion length over that of diffusing soluble CO2 an equivalent time in a liquid phase.
• the expanded mixture after the pre-curing step comprising a plurality of precursor particles is cut to a predetermined shape, and is then placed in a carbonation curing chamber and heated.
• Water as a solvent is introduced into the pores in the expanded mixture by vaporizing the water in the chamber.
• a cooling plate above the expanded mixture condenses the evaporated water that then drips onto the expanded mixture and into the pores, thus partially saturating the pores.
• the water can be heated and sprayed.
• the reactant carbon dioxide is pumped into the chamber, and the carbon dioxide diffuses into the partially saturated pores of the expanded mixture after the pre-curing step. Once in the pores, the carbon dioxide dissolves in the water, thus allowing the reaction between the precursor
• the reactant continues to react with the first layer, transforming the peripheral portion of the first layer into the second layer.
• the formation of the second layer may be by the exo-solution of a component in the first layer, and such a second layer may be a gradient layer, wherein the concentration of one of the chemical elements (cations) making up the second layer varies from high to low as you move from the core particle surface to the end of the first layer.
• the presence of the second layer at the periphery of the precursor core eventually hinders further reaction by separating the reactant and the first layer, causing the reaction to effectively stop, leaving a bonding element having the core, the first layer at a periphery of the core, and a second layer on the first layer.
• the resulting bonding element is generally larger in size than the original precursor particle, thereby filling in the surrounding porous regions of the expanded mixture after the pre-curing step and bonding with
• the method allows for net-shape formation of products having substantially the same shape as but a higher density than the original expanded
• the bonding elements and matrices can be formed with minimal distortion and residual stresses.
• the carbonation step water vapor is given to the expanded mixture after the pre-curing step together with the CO 2 .
• the carbonation step is generally performed at about 60°C at ordinary pressure for 18 to 19 hours.
• the temperature at the carbonation step was a temperature of 60°C or more, but in some cases 80°C or more is preferable. Further, the relative humidity in the carbonation step was 65% or more, but in some cases, 95% or more is preferable. Further, the time in the
• carbonation step was 6 hours to 60 hours, but in some cases 40 hours or more is preferable.
• the inventors discovered that the pores having radius from 0.004 ⁇ to 10.0 ⁇ are mostly saturated by water before carbonation. As the carbonatable calcium silicate composition undergoes carbonation, these pores are effectively filled by precipitation of calcium carbonate. The pores in the bubble volume having radius 10.0 ⁇ or more are not saturated by water before
• the bubble volume can also be easily controlled by the dosage of the foaming agent (aerating agent), e.g., metal aluminum.
• the foaming agent e.g., metal aluminum.
• the pore volume with a radius of 0.004 ⁇ to 10.0 ⁇ in the composite material is 0.24 ml/composite material 1 g or less and the estimated compressive strength is 2.5 N/mm 2 or more, more preferably the pore volume with a radius of 0.004 ⁇ to 10.0 ⁇ in the composite material is 0.19 ml/composite material 1 g or less and the estimated compressive strength is 3.7 N/mm 2 or more, still more preferably the pore volume with a radius of 0.004 ⁇ to 10.0 ⁇ in the composite material is 0.17 ml/composite material 1 g or less and the estimated compressive strength is 4.5 N/mm 2 or more, and particularly preferably the pore volume with a radius of 0.004 ⁇ to 10.0 ⁇ in the composite material is 0.15 ml/composite material 1 g or less and the estimated compressive strength is 5.0 N/mm 2 or more.
• the water reducer, sucrose, and Solidia cement were added to a predetermined amount of water, then the mixture was continuously stirred for about 2.5 minutes to form a slurry.
• lime was added to this and stirred for 30 seconds while forming a uniform slurry, and then Aluminum powder which was dispersed in phosphoric acid diluted in advance 100 fold and had been allowed to stand for at least 1 hour was added to the slurry which was then stirred for 30 seconds to prepare a wet mixture.
• the wet mixture was cast into a mold up to a height of about half of the mold.
• the wet mixture was pre-cured for about 3 to 4 hours in a
• the pre-cured expanded mixture was taken out from the mold.
• the pre-cured expanded mixture which was taken out was placed in a carbonation curing chamber where the pre-cured expanded mixture was caused to cure by carbonation at a
• FIG. 3 shows the relationship between the absolute drying density and compressive strength of ordinary 7AAC and carbonation cured 7AAC . It was learned that in carbonation cured AAC, by using Solidia cement (SC-L-) and reducing the W/S ratio to 0.45 or less and further, in the carbonation step, raising the temperature from 60°C to 80°C, raising the relative humidity RH from 65% to 95%, or extending the carbonation time from 18 hours to 40 or 48 hours, the compressive strength
• W2 (g) is the weight when drying a sample after measurement of the later explained compressive strength in a convection dryer at 110°C for a minimum of 4 days until the weight no longer changed
• D (mm) is the
• the compressive strength of the composite material is found in the following way. From the part of the composite materials, a core sample of a diameter 50mm(
• Pore A region the region having 0.004 ⁇ to
• Pore B region the region having 0.2 ⁇ to 3.0 ⁇ pore radius, that is, the pores of this region still present before carbonation step, sealed by water, and filled with bonding elements due to active carbonation,
• Pore C region the region having 3.0 ⁇ to 10.0 ⁇ pore radius, that is, the pores of this region present before carbonation step, and is not sealed by water, and filled with bonding elements due to carbonation only inside adsorbed water layer,
• Bubble region the region having over 10.0 ⁇ pore radius, that is, the pores of this region present before carbonation step, and is not sealed by water, and filled with bonding elements due to carbonation only inside adsorbed water layer, for example, the region where production can be controlled by the aerating agent of aluminum powder.
• the "pore volume” means the total amount of pore volume in the range of a
• predetermined pore radius for example radius 0.004 ⁇ to 10.0 ⁇
• the "mercury intrusion method” measures the pore diameter distribution from the relationship between the intrusion pressure and intrusion amount when pressing mercury to the inside of a porous material such as
• the measurable range of pore size was 0.004 ⁇ to 80 ⁇ or so, but the measurement value is not one which expresses the actual pore radius, but is used as an indicator which expresses the size of gaps present between component materials and is an extremely effective means for
• the part of the composite materials was crushed and sized to obtain a 2 to 4 mm part. This was dried at 105 ⁇ 5°C until reaching a constant weight and rendered an absolute dry state for use as a measurement sample.
• This measurement sample was measured for pore size distribution using a "Pore Master-33"" made by Yuasa Ionics. At this time, the contact angle of the mercury and sample was 130° and the surface tension of the mercury was calculated as 484 dyn/cm.
• the pore volume was found from the obtained pore size distribution as the pore volume in the range of a pore diameter of 0.004 ⁇ to 10.0 ⁇ to a unit mass (1 g) of the solids of the measurement sample (total pore amount) .
• the present inventors based on the discovery that by decreasing the W/S ratio to 0.45 or less and, in the carbonation step, raising the temperature from 60°C to 80°C, raising the relative humidity RH from 65% to 95%, or extending the carbonation time from 18 hours to 40 or 48 hours, the compressive strength increases, studied the relationship of the pore volume per composite material 1 g of the mainly carbonated porous region of the "region having a 0.004 ⁇ to 10.0 ⁇ pore radius", carbonation degree, and compressive strength.
• FIG. 7 is a graph which shows the relationship between the carbonation degree of carbonation cured AAC and the pore volume per composite material 1 g of the radius 0.004 ⁇ to 10.0 ⁇ pore region. From FIG. 7, it was confirmed that in carbonation cured AAC with a volume per composite material 1 g of the "region having a 0.004 ⁇ to 10.0 ⁇ pore radius" less than 0.30 ml/composite material 1 g, by raising the temperature from 60°C to 80°C, raising the relative humidity RH from 65% to 95%, or extending the carbonation time from 18 hours to 40 or 48 hours, the carbonation degree increases.
• the “carbonation degree” means the ratio of the calcium component that actually reacts with the carbon dioxide in the composite material and is present in the composite material as calcium carbonate to the total calcium component that can react with carbon
• V carbon dioxide which is produced when dissolving the composite material in acid.
• the amount of the total calcium component which can react with the carbon dioxide can be obtained by grounding up the composite, then calculating the CaO content in the composite by fluorescent X-ray analysis by the glass bead method, then calculating the amount of CO 2 gas (v) of an equivalent molar quantity with this.
• v is the amount of gas (ml) which is obtained by drying the composite at 105°C for 24 hours, then grounding it up, precisely measuring 100 to 500 mg as a sample, then dissolving it in a 5N hydrochloric acid aqueous solution, measuring the amount of carbon dioxide gas generated, and converting this to 1 g of sample.
• V is the amount of gas (ml) which is obtained by drying the composite at 105°C for 24 hours, then grounding it up, precisely measuring 100 to 500 mg as a sample, then dissolving it in a 5N hydrochloric acid aqueous solution, measuring the amount of carbon dioxide gas generated, and converting
• V (ml) CaO content (wt% ) x22400/ ( 100x56 ) .
• the carbonation degree (%) is expressed by the following formula:
• FIG. 8 is a graph which shows the relationship between the pore volume per composite material 1 g of the radius 0.004 ⁇ to 10.0 ⁇ pore region and the estimated compressive strength at an absolute dry density 0.50 in the carbonation cured AAC of the examples according to the present invention.
• the estimated compressive strength at an absolute dry density 0.50 represented by the following formula:
• composite material 1 g that is, the volume of the bubble region, and evaluating the effect on the compressive strength of only the volume per composite material 1 g of the "region having a pore radius of 0.004 ⁇ to 10.0 ⁇ " .
• present invention is carbonation cured AAC which has a compressive strength substantially equal to that of ordinary AAC, so avoids the problems of carbonation in ordinary AAC while realizing a strength substantially equal to the strength of ordinary AAC and therefore can be suitably used as a building material.

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