Carbonatable calcium silicate-based cement and concrete containing mineral additive and production method thereof
阅读说明：本技术 一种含有矿物质添加剂的可碳酸化硅酸钙基水泥和混凝土及其生产方法 (Carbonatable calcium silicate-based cement and concrete containing mineral additive and production method thereof ) 是由 艾哈迈德·居内伊特·塔什 迪帕克·拉维库玛 杰森·E·布赖恩特 于 2018-03-22 设计创作，主要内容包括：本发明提供一种新的方法和新的添加剂组合物及其在混凝土生产中(如干铸或湿铸)的广泛应用,用于改善混凝土材料的性能,如耐久性和美观性质。本发明的方法和组合物可用在基础设施、建筑、路面和景观美化行业中使用的多种水泥和混凝土组分中。(The present invention provides a novel method and novel additive composition and its broad application in the production of concrete (e.g. dry or wet casting) for improving the properties of concrete materials, such as durability and aesthetic properties. The methods and compositions of the present invention can be used in a variety of cement and concrete components used in the infrastructure, construction, pavement and landscaping industries.)
1. A carbonatable composition comprising:
calcium silicate, wherein the calcium silicate comprises one or more discrete calcium silicate phases of CS (wollastonite or pseudo-wollastonite), C3S2 (wollastonite), or C2S (dicalcium silicate, belite, whitish limestone), and
one or more minerals, wherein the one or more minerals are selected from the group consisting of magnesium, magnesium oxide, magnesium nitrate, magnesium sulfate, magnesium chloride, magnesium acetate, ground dolomite, ground limestone, magnesium hydroxide suspension, and combinations thereof,
ca element and Si element are present in the composition in a molar ratio of from about 0.5 to about 1.5, and
the metal oxides of Al, Fe and Mg are present in the composition at about 30% or less by mass, and the composition is suitable for carbonation with CO2 at a temperature of about 10 ℃ to about 90 ℃ to form CaCO with a mass gain of about 10% or more3。
2. The carbonatable composition according to claim 1, wherein the calcium silicate further comprises an amorphous calcium silicate phase comprising about 10% or more by mass of the total phase.
3. The carbonatable composition according to claim 1 or 2, wherein the one or more minerals comprise about 0.02% to about 20% by weight of the carbonatable composition.
4. Carbonatable according to any one of claims 1 to 3Composition comprising one or more residual SiO2Or a CaO phase.
5. The carbonatable composition according to any one of claims 1-4, comprising one or more compounds having the general formula (Ca, Na, K)2[(Mg,Fe2+,Fe3+,Al,Si)3O7]Of melilite type phase or of the general formula Ca2(Al，Fe3+)2O5A ferrite-type phase of (1).
6. The carbonatable composition according to any one of claims 1-5, comprising about 20% or less of metal oxides of Al, Fe and Mg by mass of total oxides.
7. The carbonatable composition according to any one of claims 1-6, wherein the reactive phase is present at 50% or more by mass.
8. The carbonatable composition according to any one of claims 1-7, further comprising a dispersant or a high range water reducer.
9. The carbonatable composition according to claim 8, wherein the dispersant or high range water reducer comprises a polycarboxylic acid based polymer.
10. The carbonatable composition according to any one of claims 1-9, further comprising a colorant.
11. The carbonatable composition according to claim 10, wherein the colorant comprises one or more of iron oxide, cobalt oxide, chromium oxide.
12. A method of forming a concrete product comprising:
adding an admixture to the concrete mixture prior to curing the cement to form a concrete product, the admixture comprising one or more minerals; and
curing the cement to form a concrete product, wherein,
the cement is a carbonatable calcium silicate-based cement, and
the one or more minerals are selected from the group consisting of magnesium, magnesium oxide, magnesium nitrate, magnesium sulfate, magnesium chloride, magnesium acetate, ground dolomite, ground limestone, magnesium hydroxide suspension, and combinations thereof.
13. The method of claim 12, wherein the one or more minerals comprise from about 0.02% to about 20% of the carbonatable calcium silicate-based cement.
14. The method of claim 12 or 13, further comprising adjusting the pH of the concrete mixture prior to curing the cement to form the concrete product.
15. The method of any one of claims 12-14, wherein the carbonatable calcium silicate-based cement comprises calcium silicate, wherein the calcium silicate comprises one or more discrete calcium silicate phases of CS (wollastonite or pseudo-wollastonite), C3S2 (wollastonite), or C2S (dicalcium silicate, xonotlite, whitlaite).
16. The method of claim 15, wherein the calcium silicate further comprises an amorphous calcium silicate phase comprising 10% or more by mass of the total phase.
17. The method of any one of claims 12-16, wherein in the carbonatable calcium silicate-based cement, the Ca element and the Si element are present in the composition in a molar ratio of from about 0.8 to about 1.2, and
the metal oxides of Al, Fe, and Mg are present in the composition at about 30% by mass or less.
18. The method of any one of claims 12-17, wherein the concrete mixture further comprises a dispersant or a high range water reducer.
19. The method of claim 18, wherein the dispersant or high range water reducer comprises a polycarboxylic acid based polymer.
20. The method of any one of claims 12-19, wherein the concrete mixture further comprises a colorant.
21. The method of claim 20, wherein the colorant comprises one or more of iron oxide, cobalt oxide, and chromium oxide.
22. The method of any one of claims 12-21, wherein magnesium oxide comprises from about 0.02% to about 20% by weight of the carbonatable composition.
23. A concrete product produced by the method of any one of claims 12-22.
24. The concrete product of claim 23 comprising one or more CaCO3 phases selected from the group consisting of ulexite-aragonite, calcite-aragonite-dolomite, calcite-dolomite, aragonite-dolomite and dolomite.
25. The concrete product of claim 24 comprising one or more CaCO3 phases selected from calcite-aragonite-dolomite, calcite-dolomite, aragonite-dolomite and dolomite.
26. A composite material, comprising:
a plurality of bonding units, wherein each bonding unit comprises:
a core consisting essentially of calcium silicate, a silicon-rich inner layer and a calcium carbonate-rich outer layer; and
a plurality of filler particles, wherein
The plurality of binding units and the plurality of filler particles collectively form one or more interlocking needle-shaped polymorphs.
27. The composite material of claim 26, wherein the filler particles are made of a silica-rich material.
28. The composite material of claim 26 or 27, wherein the plurality of filler particles comprise one or more of quartz, mica, and feldspar.
29. The composite material of any one of claims 26-28, wherein the plurality of binding units are chemically converted from ground wollastonite or ground pseudowollastonite.
30. The composite material of any one of claims 26-28, wherein the plurality of binding elements are chemically converted from a calcium silicate precursor other than wollastonite.
31. The composite material of any one of claims 26-30, further comprising a colorant.
32. The composite material of claim 31, wherein the colorant comprises one or more of iron oxide, cobalt oxide, chromium oxide.
33. The composite material of claim 31 or 32, wherein the colorant is present in an amount from about 0% to about 10% by weight.
34. The composite material of claims 26-33, further comprising a discoloration control additive.
35. The composite material of claim 34, wherein the discoloration control additive comprises one or more of magnesium, magnesium oxide, magnesium nitrate, magnesium sulfate, magnesium chloride, and magnesium acetate.
36. The composite of claim 34 or 35, wherein the discoloration control additive constitutes from about 0.02 to about 20% by weight of the bonded unit.
37. A composite material formed by carbonation of carbonatable calcium silicate with CO2, comprising interlocked needle-shaped polymorphs of calcium carbonate.
Technical Field
The present invention relates to calcium silicate-based cements and concretes. More particularly, the present invention relates to novel additive compositions and their broad use in the production of concrete (e.g., dry casting or wet casting) for improving the properties, such as durability and aesthetic properties, of concrete materials. The methods and compositions of the present invention can be used in a variety of cement and concrete components used in the infrastructure, construction, pavement and landscaping industries.
Background
Concrete is the most consumed man-made material in the world. Concrete is typically formed by mixing portland cement, water and aggregates, such as sand, crushed stone, and the like. Portland cement is a synthetic material made by calcining a mixture of ground limestone and clay or a material of similar composition in a rotary kiln at a sintering temperature of around 1450 ℃. The manufacture of portland cement is not only an energy consuming process, but also a process that releases large amounts of greenhouse gases (CO 2). The carbon dioxide emissions from the cement industry account for about 5% of the global anthropogenic carbon dioxide emissions. More than 60% of these CO2 comes from the chemical decomposition or calcination of limestone.
Recently, a revolutionary cement based on carbonatable calcium silicate materials has been produced and is expected to be a replacement for traditional cements. The production of carbonatable calcium silicate based cements significantly reduces carbon dioxide emissions and energy consumption. In addition, this new cement sequesters CO2 when cured into a concrete product because CO2 is required to react with the carbonatable calcium silicate material to form the concrete product during the curing process.
Precast concrete is widely used in many different applications, including the pouring of concrete into a reusable form, which typically cures under controlled conditions. In many applications, aesthetic properties are as important as the physical or mechanical properties of the product. As a result, a large portion of the value of many prefabricated products, such as wallboard, block, paving and stone casting products, is based on meeting stringent and often very demanding aesthetic standards.
Thus, in the field of concrete production, in particular precast concrete produced using carbonatable calcium silicate based cements, there is a need for low cost materials and reliable and efficient methods to obtain concrete products with excellent mechanical and durability properties, while having high aesthetic properties.
Disclosure of Invention
The present invention provides a novel method and composition for improving the aesthetic properties and physical properties (e.g., mechanical and durability properties) of carbonatable calcium silicate-based cement and concrete products.
The carbonatable calcium silicate-based cement compositions of the present invention include selected mineral additives, typically in the form of coarse, fine and ultrafine particles or powders, for improving the durability and aesthetic properties of concrete products, particularly in various prefabricated applications. For example, the use of magnesium oxide (MgO) powder, refines or changes the pore structure, improves the particle size, and induces crystal morphology, thereby changing the water permeability of precast concrete products made from carbonatable calcium silicate-based cements. Ultrafine magnesium oxide can also be used to accelerate the carbonation curing process to stabilize specific calcium carbonate polymorphs, such as aragonite, and even dolomite, and to improve the durability of calcium silicate based adhesives by stabilizing the matrix and increasing water resistance or permeability.
In one aspect, the present invention generally relates to a carbonatable composition. The carbonatable composition comprises: calcium silicate; one or more discrete calcium silicate phases selected from CS (wollastonite or pseudo-wollastonite), C3S2 (wollastonite), C2S (belite, whitise), and an amorphous calcium silicate phase comprising 10% or more of the total phase mass; one or more minerals, wherein said minerals comprise magnesium, magnesium oxide, magnesium nitrate, magnesium sulfate, magnesium chloride, magnesium acetate, ground dolomite, ground limestone, magnesium hydroxide suspension, and combinations thereof, wherein said minerals comprise from about 0.02% to about 20% by weight of the carbonatable composition. The molar ratio of the Ca element and the Si element in the composition is generally about 0.5 to about 1.5. The metal oxides of Al, Fe, and Mg in the composition usually account for 30% by mass or less. The carbonatable composition is adapted to carbonate with CO2 as the reactive component at a temperature of about 30 ℃ to about 90 ℃ to form CaCO3 with a mass gain of about 10% or more.
In another aspect, the present disclosure is generally directed to a method of forming a concrete product. The method comprises the following steps: adding to the concrete mixture, prior to curing the cement to form a concrete product, an admixture comprising one or more minerals, wherein the minerals comprise magnesium, magnesium oxide, magnesium nitrate, magnesium sulfate, magnesium chloride, magnesium acetate, ground dolomite, ground limestone, magnesium hydroxide suspension, and mixtures thereof; the cement is cured into a concrete product. The cement is a carbonatable calcium silicate based cement. The above minerals in the concrete mixture comprise from about 0.02% to about 20% by weight of the carbonatable calcium silicate-based cement of the present invention.
In another aspect, the present invention is generally directed to a concrete product produced by the above method.
In another aspect, the present invention is generally directed to a composite material produced by the carbonation reaction of calcium silicate with CO2, comprising interlocked calcium carbonate needle-tip polymorphs.
In another aspect, the present disclosure is generally directed to a composite material. The composite material comprises: a plurality of bonded units, wherein each bonded unit comprises a core consisting essentially of calcium silicate, a silicon-rich inner layer, and a calcium carbonate-rich outer layer. The composite material comprises a plurality of filler particles. The plurality of binding units and the plurality of filler particles collectively form one or more interlocking needle-shaped polymorphs.
Drawings
The objects and features of the present invention may be better understood with reference to the drawings described below and the claims. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the drawings, like reference numerals are used to indicate like parts in the various views.
FIG. 1 shows a reversible reaction
FIG. 2 shows a reversible reaction
FIG. 3 is a phase diagram of a CaO-SiO2-CO2 system at a pressure of 1 kbar.
FIG. 4 shows a reversible reactionPressure-temperature phase diagram of the relevant phases.
FIG. 5 shows a reversible reactionAccording to the equilibrium curve of the carbon dioxide in the inert gas as a function of the proportion.
FIG. 6 is a temperature-composition phase diagram showing the stable region of the various phases in the CaCO3-MgCO3 system.
FIG. 7 is a tetrahedral diagram showing the phase relationship between the compounds CaO, MgO, SiO2 and CO2, showing the CO2 deficient region below the Cc-Di-Wo and CC-Wo-Mo planes (shaded), where Cc represents calcite, Wo represents wollastonite, Ak represents akermanite, Di represents diopside and Mo represents forsterite (CaMgSiO 4).
FIG. 8 is a pressure-temperature phase diagram showing the phase relationship between compounds CaO, MgO, SiO2 and CO2, including a monotropic curve derived from quaternary invariant points involving calcite (Cc), diopside (Di), forsterite (Fo), forsterite (Mo), akermanite (Ak) and
Fig. 9 is a schematic diagram of a curing chamber for providing humidified CO2 composite material in accordance with the principles of the present invention.
FIG. 10 is a schematic of a curing chamber having multiple humidity control methods and the ability to control and replenish CO2 with constant flow or pressure regulation, and the ability to control temperature, in accordance with the principles of the present invention.
FIG. 11 shows the results of a mortar cube test with magnesium acetate tetrahydrate additive.
Fig. 12 shows the results of a mortar cube test using MagCet solution (an acetic acid solution of MgO).
FIG. 13 shows the observed discoloration of the pavement surface (middle light areas) upon exposure to simulated service life conditions.
FIG. 14 shows an exemplary SEM surface image of a paving material prior to exposure to simulated service life conditions.
FIG. 15 shows an exemplary SEM surface image of the deposits observed in the light colored areas of the paving produced without the addition of magnesium oxide.
FIG. 16 is an exemplary SEM surface image of aragonite crystals observed in a paving material produced with magnesium oxide.
FIG. 17(A) shows that the paving material without added magnesium oxide exhibits color non-uniformity due to the development of light colored areas on the paving material surface; (ii) a (B) The surface of the paving produced with the addition of magnesium oxide showed no discoloration.
FIG. 18 shows a reference paving material (A) and a paving material with added magnesium oxide (B) immediately after 1 hour of exposure to simulated rain; reference paving material (C) and paving material with added magnesium oxide (D) presented after drying for 1 hour at atmospheric pressure.
Detailed Description
The present invention provides a novel method for improving the strength, durability and aesthetic properties of carbonatable calcium silicate-based cement and concrete products.
The carbonatable calcium silicate-based cement compositions of the present invention comprise coarse, fine, and ultra-fine mineral additives for enhancing the strength, durability, and aesthetic properties of concrete products in a variety of prefabricated applications.
Carbonatable calcium silicate-based cements and concretes are revolutionary alternatives to traditional cement and concrete products. The production and use of these materials can significantly reduce energy requirements and carbon dioxide emissions. The carbonatable calcium silicate composition is widely available and low cost raw materials, and is prepared by a production process which has flexible equipment and production requirements and is suitable for large-scale production. This unique process also has a tolerance to CO2Excellent ability to perform permanent and secure isolation. Thanks to the invention, a wider range of applications ranging from construction, pavement and beautification, to infrastructure and transportation is obtained by improving energy consumption and a more ideal carbon footprint.
Particular applications of the invention include obtaining the strength of calcium silicate based cements by a carbonation reaction process, wherein carbon dioxide is sequestered in the presence of water. While water is necessary for certain preparatory steps such as dispersion and shaping, it is not a major component of the final reaction product. In some instances, this may form a porous matrix that may allow water to penetrate, thereby causing aesthetic defects and surface deposits.
As described herein, it has been unexpectedly discovered that the addition of specific mineral components (e.g., magnesium oxide) to concrete mixtures can mitigate or reduce aesthetic defects and surface deposits.
The formation of needles or whisker-like crystals of aqueous or anhydrous magnesium carbonate, calcium magnesium carbonate and/or magnesium hydroxycarbonate is not bound by theory. When they are formed within open capillaries or orifices of a paving or construction material binding unit-rich area, the nature and extent of water transport therein will be altered. Water can readily penetrate and pass through capillaries, orifices and interconnected channels of sizes greater than 1.4 μm under ambient pressure and temperature conditions, but these submicron-sized crystals formed in such channels will drastically alter the water flow regime and make the situation more similar to that of common portland cement (OPC) -based paving materials.
Furthermore, it has been surprisingly found that the addition of specific mineral components (e.g., magnesium oxide) to the concrete mix can also significantly improve the mechanical properties and durability of the product.
Without being bound by theory, strength is developed during carbonation of a calcium silicate powder that does not contain the hydraulic mineral xonotlite (C3S) and contains a much lower Ca/Si molar ratio than ordinary portland cement, wherein strength development is carried out in two steps: (i) forming an X-ray-amorphous layer of a silicate-rich (or Ca-deficient) gel by which step Ca2+Must diffuse to the calcium silicate particles and CO2(g) A contacting outer surface, and (ii) a separate CaCO formed on the X-ray-amorphous gel layer3The crystal, and the independent CaCO3 crystal further evolve into three-dimensional interconnected, CaCO3A mixture network of (a).
As described herein, deliberately adding ions with radii less than Ca2+(114pm) alkaline earth cations, e.g. Mg2+(86pm) was found to be effective in reducing the residual unreacted calcium silicate at the end of carbonation, resulting in a significant increase in strength. Mg (magnesium)2+First CO capable of being formed on the surface of the silico-calcium based cement particles2Diffuse a greater distance into the cured (i.e., weathered) product (Ca-deficient, X-ray amorphous silicate-based gel layer).
Also, without being bound by theory, magnesium oxide may be susceptible to being subjected to CO due to its high affinity for the dynamic water film or water molecules that appear through the pores and pore channels of the body2The carbonated building materials and blocks are subjected to in situ internal dehumidification.
Magnesium hydroxide (brucite, Mg (OH)2) Formed initially in concreteIn the preparation of the mixture, magnesium hydroxide is added to CO after adding magnesium, magnesium oxide or magnesium salt to the liquid admixture portion of the concrete mixture2Carbonating itself in situ during the curing process to form magnesite (MgCO)3) Dolomite (CaMg (CO)3)2) Magalcite (magnesium), hydromagnesite (MgS (CO)3)4(OH)2·4H2O), magnesite trihydrate (Mg (HCO)3)(OH)·2H2O or MgCO3·3H2O), magnesium steatite (Mg)5(CO3)4(OH)2·5H2O), Celite (Mg)2CO3(OH)2·3H2O), dimagnesite (MgCO)3·2H2O) or magnesium carbonate pentahydrate (MgCO)3·5H2O) is used. These are the phases present in the ternary MgO-CO2-H2O system. The formation of these phases requires the removal of water from the surrounding environment in an in situ, real-time, dynamic manner. These fundamental (i.e., having an intrinsic pH above neutral) phases typically crystallize in a needle-like or needle-like morphology, and the interlocking or intermixing of these needles with one another further contributes to the strength in the product (e.g., composite building materials such as wallboard, blocks, pavers, and stone castings). The formation of such acicular or whisker-like crystals of magnesium carbonate, calcium magnesium carbonate and/or magnesium hydroxycarbonate can alter the properties and water transport range of the water therein, since these phases are immediately increased with respect to the use of CO2The surface roughness of the water channels inherent to the cured concrete product.
The presence of acetate ions and/or acetic acid in small amounts in the formation water of the concrete and mortar batches was also shown to increase the average strength of the calcium silicate based samples after carbonation (figure 11).
With CaO-CO2-H2In sharp contrast to the O system, MgO-CO2-H2Many phases containing water and carbonation appear in the O-triad diagram (e.g. magnesite, hydromagnesite, sphenesite, dimorphite, protohydromagnesite, fibromagnesite and hydromagnesite).
Adding different grades of particle size distribution, e.g. flatA homogeneous particle size of about 100nm, 10 μm or 50 μm, and different reactive magnesium oxide powders into moist batches of pastes, mortars and concrete samples, has been found to be useful in moist environments after carbonation by forming one or more of the above mentioned MgO-CO2-H2The phase in the O system to produce the intensity. To the forming water of the paste, mortar or concrete samples, a small amount of magnesium acetate (Mg (CH)3COO)2·4H2O) or a pH-controlled solution formed by dissolving a specified amount of magnesium oxide powder in a specified volume of dilute acetic acid, with the result that the strength after carbonation is significantly increased. (FIG. 12)
Magnesium, even in low concentrations: (<1%) when present as free CaCO3In nucleated water systems, the aragonite promoter proved to be strong regardless of the process temperature.
In certain embodiments of the present invention, ultra-fine (e.g., having an average particle size of about 100nm) magnesium oxide powder is added to the liquid admixture to increase the pH of the solution, for example: increasing the pH to about 9 (e.g., from about 8.5 to about 9.5, from about 8.7 to about 9.3, from about 8.8 to about 9.2) facilitates the in situ formation of magnesium hydroxide, or brucite, to increase the availability of magnesium to various beneficial ternary phases. Wherein the magnesium oxide powder is added in an amount of about 0.02% to about 20% (e.g., about 0.1% to about 20%, about 0.5% to about 20%, about 1% to about 20%, about 5% to about 20%, about 0.02% to about 10%, about 0.02% to about 5%, about 0.02% to about 1%, about 0.02% to about 0.1%), the liquid admixture is typically an acidic solution because the superplasticizer/dispersant used has a pH of less than 5.
In certain embodiments of the invention, the viscosity of the paste or slurry is adjusted by adding magnesium oxide, which forms magnesium hydroxide molecules in aqueous solution.
In certain embodiments of the invention, the magnesium ions in solution are enabled by the addition of magnesium oxide to increase the reactivity of the calcium-containing silicate phase by deforming or modifying the crystals of the calcium-containing orthosilicate or disilicate network.
In certain embodiments of the invention, magnesium oxide is added to a carbonatable calcium silicate-based cement mixture to reduce or eliminate the appearance of metastable polymorphic forms of calcium carbonate, and to reduce or prevent the formation of aesthetic surface defects due to precipitation of metastable phases such as spherulite.
In certain embodiments of the invention, a small percentage of magnesium oxide is added to the carbonatable calcium silicate-based cement mixture to promote the formation of a magnesium calcite phase, such as magnesian. The magnesium oxide is present in an amount of about 0.02% to about 20% (e.g., about 0.1% to about 20%, about 0.5% to about 20%, about 1% to about 20%, about 5% to about 20%, about 0.02% to about 10%, about 0.02% to about 5%, about 0.02% to about 1%, about 0.02% to about 0.1%).
In certain embodiments of the present invention, magnesium oxide is added to the carbonatable calcium silicate-based cement mixture to promote the formation of a acicular calcium carbonate phase, such as aragonite, in an amount from about 0.02% to about 20% (e.g., from about 0.1% to about 20%, from about 0.5% to about 20%, from about 1% to about 20%, from about 5% to about 20%, from about 0.02% to about 10%, from about 0.02% to about 5%, from about 0.02% to about 1%, from about 0.02% to about 0.1%).
In certain embodiments of the invention, magnesia is added to the carbonatable calcium silicate-based cement mixture to promote the formation of dolomite in an amount of about 0.02% to 20% (e.g., about 0.1% to about 20%, about 0.5% to about 20%, about 1% to about 20%, about 5% to about 20%, about 0.02% to about 10%, about 0.02% to about 5%, about 0.02% to about 1%, about 0.02% to about 0.1%).
In certain embodiments of the invention, magnesia is added to the carbonatable calcium silicate-based cement mixture to stabilize the magalcite and/or aragonite and to minimize the formation of spherulite, the magnesia being present in an amount from about 0.02% to 20% (e.g., from about 0.1% to about 20%, from about 0.5% to about 20%, from about 1% to about 20%, from about 5% to about 20%, from about 0.02% to about 10%, from about 0.02% to about 5%, from about 0.02% to about 1%, from about 0.02% to about 0.1%).
In certain embodiments of the invention, magnesium oxide is added to the carbonatable calcium silicate-based cement mixture to enrich the microstructural diversity of the binder matrix and reduce the incidence of structural and aesthetic damage due to water ingress, in an amount of about 0.02% to 10% (e.g., about 0.1% to about 10%, about 0.5% to about 10%, about 1% to about 10%, about 5% to about 10%, about 0.02% to about 5%, about 0.02% to about 2%, about 0.02% to about 1%, about 0.02% to about 0.1%).
In certain embodiments of the invention, magnesium oxide is added to the carbonatable calcium silicate-based cement mixture to promote the formation of a ternary phase that is resistant to potential structural and aesthetic degradation in specific applications involving exposure to acidic chemicals (e.g., acidic precipitation), the magnesium oxide being present in an amount of about 0.02% to 20% (e.g., about 0.1% to about 20%, about 0.5% to about 20%, about 1% to about 20%, about 5% to about 20%, about 0.02% to about 10%, about 0.02% to about 5%, about 0.02% to about 1%, about 0.02% to about 0.1%).
In certain embodiments of the invention, the pore structure of the carbonated calcium silicate-based cement is modified by the formation of needle-like or needle-point shaped calcium carbonate polymorphs by the addition of magnesium oxide to the carbonatable calcium silicate-based cement mixture at a level. Such pore structure modification can inhibit the transport of aqueous phases containing salts, organic residues, minerals, and other contaminants that may reduce the aesthetic properties and durability of carbonatable calcium silicate-based concrete, the magnesium oxide being present in an amount of about 0.02% to 20% (e.g., about 0.1% to about 20%, about 0.5% to about 20%, about 1% to about 20%, about 5% to about 20%, about 0.02% to about 10%, about 0.02% to about 5%, about 0.02% to about 1%, about 0.02% to about 0.1%).
In certain embodiments of the invention, magnesium oxide is added to the carbonatable calcium silicate-based cement mixture to reduce drying shrinkage due to flash-dry conditions or high moisture/solids mixtures, the magnesium oxide being present in an amount of about 0.02% to about 20% (e.g., about 0.1% to about 20%, about 0.5% to about 20%, about 1% to about 20%, about 5% to about 20%, about 0.02% to about 10%, about 0.02% to about 5%, about 0.02% to about 1%, about 0.02% to about 0.1%).
In certain embodiments of the invention, magnesium oxide is added to the carbonatable calcium silicate-based cement mixture to increase the carbonation and sequestration of carbon dioxide at a level of about 0.02% to 20% (e.g., about 0.1% to about 20%, about 0.5% to about 20%, about 1% to about 20%, about 5% to about 20%, about 0.02% to about 10%, about 0.02% to about 5%, about 0.02% to about 1%, about 0.02% to about 0.1%).
In certain embodiments of the present invention, ground limestone or dolomite limestone is added to the carbonatable calcium silicate-based cement mixture in an amount of about 0.02% to 10% (e.g., about 0.1% to about 10%, about 0.5% to about 10%, about 1% to about 10%, about 5% to about 10%, about 0.02% to about 5%, about 0.02% to about 2%, about 0.02% to about 1%, about 0.02% to about 0.1%) to improve the pore structure of the carbonated calcium silicate-based binder and to inhibit the transport of an aqueous phase containing salts, organic residues, minerals and other contaminants that may reduce the aesthetic properties and durability of the carbonatable calcium silicate-based concrete.
In certain embodiments of the present invention, ground dolomite is added to the carbonatable calcium silicate-based cement mixture to improve the pore structure of the carbonated calcium silicate-based binder and to inhibit the transport of an aqueous phase containing salts, organic residues, minerals, and other contaminants that may reduce the aesthetic properties and durability of the carbonatable calcium silicate-based concrete, the ground dolomite being present in an amount of about 0.02% to 20% (e.g., about 0.1% to about 20%, about 0.5% to about 20%, about 1% to about 20%, about 5% to about 20%, about 0.02% to about 10%, about 0.02% to about 5%, about 0.02% to about 1%, about 0.02% to about 0.1%).
In certain embodiments of the invention, a magnesium hydroxide suspension or a magnesium oxide emulsion is added to the carbonatable calcium silicate-based cement mixture to modify the pore structure of the carbonated calcium silicate-based binder and inhibit the transport of an aqueous phase containing salts, organic residues, minerals, and other contaminants that may reduce the aesthetic properties and durability of the carbonatable calcium silicate-based concrete, the magnesium hydroxide suspension or the magnesium oxide emulsion being present in an amount of about 0.02% to 20% (e.g., about 0.1% to about 20%, about 0.5% to about 20%, about 1% to about 20%, about 5% to about 20%, about 0.02% to about 10%, about 0.02% to about 5%, about 0.02% to about 1%, about 0.02% to about 0.1%).
In certain embodiments of the invention, the addition of a combination of coarse and fine ground limestone having different particle size distributions to a carbonatable calcium silicate-based cement mixture to improve particle packing of the carbonatable calcium silicate-based cement and reduce permeability of the slurry to inhibit water ingress, which may be useful in inhibiting the transport of salts, organic residues, minerals and other contaminants that may reduce the aesthetic properties and durability of the carbonatable calcium silicate-based concrete. The composition is present in an amount of about 0.02% to 20% (e.g., about 0.1% to about 20%, about 0.5% to about 20%, about 1% to about 20%, about 5% to about 20%, about 0.02% to about 10%, about 0.02% to about 5%, about 0.02% to about 1%, about 0.02% to about 0.1%).
Accordingly, in one aspect, the present invention generally relates to a carbonatable composition. The carbonatable composition comprises calcium silicate; one or more discrete calcium silicate phases selected from CS (wollastonite or pseudo-wollastonite), C3S2 (wollastonite), C2S (dicalcium silicate, belite, whitish wollastonite); an amorphous calcium silicate phase comprising about 10% or more of the total phase by mass; one or more magnesium oxide-containing minerals, wherein the magnesium oxide comprises from about 0.02% to about 20% by weight of the carbonatable composition. The Ca element and the Si element of the composition are present in the composition in a molar ratio of about 0.5 to about 1.5. Metal oxides of Al, Fe, and Mg are present in the composition in a mass of 30% or less. The composition is suitable for use with CO2Carbonating at a temperature of about 10 ℃ to about 90 ℃ to form CaCO having a mass gain of about 10% or more3。
In some embodiments, the carbonatable composition comprises one or more residual SiO2And a CaO phase.
In some embodiments, the carbonatable composition comprises one or more melilite-type phases having the general formula (C)a,Na,K)2[(Mg,Fe2+,Fe3+,Al,Si)3O7]Or a ferrite phase of the formula Ca2(Al,Fe3+)2O5。
In some embodiments, the carbonatable composition includes about 20% (e.g., 15%, 10%, 5%) or less metal oxides of Al, Fe, and Mg by mass of the total oxides.
In some embodiments, the carbonatable composition includes about 50% or more by mass of the reactive phase.
In some embodiments, the one or more minerals further comprise one or more of magnesium, magnesium nitrate, magnesium sulfate, magnesium chloride, and magnesium acetate.
In some embodiments, the precipitate-free solution of magnesium nitrate is prepared by dissolving magnesium oxide powder of any particle size in technical grade concentrated nitric acid diluted with water to produce Mg2+A stock solution of ions instead of adding a replacement powdered magnesium nitrate salt. The magnesium oxide powder typically has an average particle size in the range of about 0.05 to about 100 μm. Mg in the stock solution2+The concentration of the ions ranges from about 0.001 to about 1M (e.g., about 0.01 to about 1M, about 0.1 to about 1M, about 0.001 to about 0.1M, about 0.001 to about 0.01M).
In some embodiments, the precipitate-free solution of magnesium chloride is prepared by dissolving magnesium oxide powder of any particle size in concentrated technical grade hydrochloric acid diluted with water to produce Mg2+A stock solution of ions instead of adding a replacement powdered magnesium chloride salt. The magnesium oxide powder typically has an average particle size in the range of about 0.05 to about 100 μm. Mg in the stock solution2+The concentration of the ions ranges from about 0.001 to about 1M (e.g., about 0.01 to about 1M, about 0.1 to about 1M, about 0.001 to about 0.1M, about 0.001 to about 0.01M).
In some embodiments, the precipitate-free solution of magnesium sulfate is prepared by dissolving magnesium oxide powder of any particle size in technical grade concentrated sulfuric acid diluted with water2+Stock solutions of ions prepared instead of adding magnesium sulphate in place of the powdered magnesium sulphate, said magnesium oxide powder typically having an average particle size in the range of about 0.05 toAbout 100 μm. Mg in the stock solution2+The concentration of the ions ranges from about 0.001 to about 1M (e.g., about 0.01 to about 1M, about 0.1 to about 1M, about 0.001 to about 0.1M, about 0.001 to about 0.01M).
In some embodiments, the carbonatable composition further comprises a dispersant or a high range water reducer (e.g., a polycarboxylic acid-based polymer).
In some embodiments, the carbonatable composition further comprises a colorant (e.g., one or more of iron oxide, cobalt oxide, and chromium oxide).
The carbonatable compositions disclosed herein may be used in the production of concrete by dry casting or wet casting.
In another aspect, the present invention is generally directed to a method of forming a concrete product. The method comprises the following steps: adding an admixture comprising one or more minerals (including magnesium oxide) to the concrete mixture prior to curing the cement to form a concrete product; the cement is cured to form a concrete product. The cement is carbonatable calcium silicate-based cement. By weight, the magnesium oxide in the one or more minerals constitutes about 0.02% to about 20% (e.g., about 0.02% to about 10%, about 0.05% to about 7%, about 0.05% to about 6%, about 0.05% to about 5%, about 0.05% to about 4%, about 0.05% to about 3%, about 0.05% to about 2%, about 0.05% to about 1%, about 0.05% to about 0.5%, about 0.05% to about 0.25%, about 0.1% to about 8%, about 0.5% to about 8%, about 1% to about 8%, about 2% to about 8%, about 3% to about 8%, about 4% to about 8%, about 5% to about 8%, about 6% to about 8%, about 0.25% to about 1%, about 0.5% to about 2%) of the carbonatable calcium silicate-based cement.
In some embodiments, the method further comprises adjusting the pH of the concrete mixture prior to curing the cement to form the concrete product.
In another aspect, the present invention is generally directed to a concrete product produced by the method of the present invention.
In another aspect, the present invention relates generally to a composition comprising calcium silicate and CO2The carbonation of (c) to form a composite material comprising interlocked needle-tip polymorphs of calcium carbonate.
In another aspect, the present disclosure is generally directed to a composite material. The composite material comprises: a plurality of bonded units, wherein each bonded unit comprises a core comprising predominantly calcium silicate, a silicon-rich inner layer, and a calcium carbonate-rich outer layer. The composite material comprises a plurality of filler particles, the plurality of binding units and the plurality of filler particles collectively forming one or more interlocking needle-tip polymorphs.
In some embodiments, the filler particles are made of a silica-rich material. In some embodiments, the plurality of filler particles comprises one or more of quartz, mica, and feldspar.
In some embodiments, the plurality of binding units are chemically converted from ground wollastonite. In some embodiments, the plurality of binding units are chemically converted from a precursor calcium silicate rather than wollastonite.
In some embodiments, the composite further comprises a colorant, such as: one or more of iron oxide, cobalt oxide and chromium oxide. In some embodiments, the colorant is 0 to about 10% by weight of the composite.
In some embodiments, the composite further comprises a discoloration control additive, such as: one or more of magnesium, magnesium oxide, magnesium nitrate, magnesium sulfate, magnesium chloride and magnesium acetate. In some embodiments, the discoloration control additive comprises 0.02 to about 20% of the bonded unit by weight.
In some embodiments, the concrete product comprises a CaCO selected from one or more of calcite-aragonite, calcite-aragonite-dolomite, calcite-dolomite, aragonite-dolomite, and dolomite3And (4) phase(s).
In some embodiments, the concrete product has acid rain resistance.
In some embodiments, the concrete product comprises CaCO selected from one or more of calcite-aragonite-dolomite, calcite-dolomite, aragonite-dolomite, and dolomite3And (4) phase(s).
In some embodiments of the method, the cement is a carbonatable calcium silicate-based cement. In some embodiments of the method, the carbonatable calcium silicate-based cement comprises: calcium silicate; a discrete calcium silicate phase selected from one or more of CS (wollastonite or pseudo-wollastonite), C3S2 (wollastonite), C2S (dicalcium silicate, belite, whitish wollastonite); and an amorphous calcium silicate phase which accounts for 30% by mass or more of the total phase.
In certain preferred embodiments, the molar ratio of the Ca element to the Si element in the composition is from about 0.5 to about 1.5. In certain preferred embodiments, the molar ratio of the Ca element to the Si element in the composition is from about 0.5 to about 1.2. In certain preferred embodiments, the molar ratio of the Ca element to the Si element in the composition is from about 0.5 to about 1.15. In certain preferred embodiments, the molar ratio of the Ca element to the Si element in the composition is from about 0.8 to about 1.5. In certain preferred embodiments, the molar ratio of Ca element to Si element in the composition is from about 0.8 to about 1.2. In certain preferred embodiments, the molar ratio of the Ca element to the Si element in the composition is from about 0.8 to about 1.15. In certain preferred embodiments, the molar ratio of the Ca element to the Si element in the composition is from about 0.85 to about 1.15. In certain preferred embodiments, the molar ratio of the Ca element to the Si element in the composition is from about 0.90 to about 1.10. In certain preferred embodiments, the molar ratio of the Ca element to the Si element in the composition is from about 0.95 to about 1.05. In certain preferred embodiments, the molar ratio of the Ca element to the Si element in the composition is from about 0.98 to about 1.02. In certain preferred embodiments, the molar ratio of the Ca element to the Si element in the composition is from about 0.99 to about 1.01.
The metal oxides of Al, Fe and Mg are typically included in the calcium silicate composition at levels controlled to less than about 30%. In certain preferred embodiments, the composition comprises about 20% or less of the metal oxides of Al, Fe, and Mg by total oxide mass. In certain preferred embodiments, the composition comprises about 15% or less of the metal oxides of Al, Fe, and Mg by total oxide mass. In certain preferred embodiments, the composition comprises about 12% or less of the metal oxides of Al, Fe, and Mg by total oxide mass. In certain preferred embodiments, the composition comprises about 10% or less of the metal oxides of Al, Fe, and Mg by total oxide mass. In certain preferred embodiments, the composition comprises about 5% or less of the metal oxides of Al, Fe, and Mg by total oxide mass.
In addition to the above crystalline phases, the calcium silicate composition may also comprise an amorphous (non-crystalline) calcium silicate phase. The amorphous phase may additionally bind Al, Fe and Mg ions as well as other impurity ions present in the starting material.
The calcium silicate composition may also contain small amounts of residual CaO (lime) and SiO2 (silica). The calcium silicate composition may also contain small amounts of C3S (tricalcium silicate, Ca)3SiO5)。
The C2S phase present in the calcium silicate composition may be alpha-Ca2SiO4、β-Ca2SiO4Or gamma-Ca2SiO4Polymorphs, or any combination thereof.
The calcium silicate composition may also comprise a plurality of inert phases, such as those having the general formula (Ca, Na, K)2[(Mg,Fe2+,Fe3 +,Al,Si)3O7]Of melilite-type minerals (melilite, gehlenite or akermanite) and of the general formula Ca2(Al,Fe3 +)2O5The ferrite mineral (ferrite, calcium-iron-aluminum or C4 AF). In certain embodiments, the calcium silicate composition consists only of the amorphous phase. In certain embodiments, some of the calcium silicate composition is present in the amorphous phase and some is present in the crystalline phase.
In certain embodiments, the carbonatable compositions include a reactive phase present at about 50% or more (e.g., about 55% or more, about 60% or more, about 65% or more, about 70% or more, about 75% or more, about 80% or more, about 85% or more, about 90% or more, about 95% or more) by mass.
In certain embodiments, the carbonatable composition includes about 20% or less of the metal oxides of Al, Fe, and Mg by total oxide mass.
Any suitable calcium silicate composition may be used as a precursor for the bonding unit. As used herein, the term "calcium silicate composition" generally refers to naturally occurring mineral or synthetic materials, consisting of a group of one or more calcium silicate phases comprising CS (wollastonite or pseudo-wollastonite, sometimes expressed as CaSiO3 or CaO · SiO2), C3S2 (wollastonite, sometimes expressed as Ca3Si2O7 or 3CaO · 2SiO2), C2S (dicalcium silicate, β -Ca2SiO4 or belite, β -Ca7Mg (SiO4)4 or whitise, α -Ca2SiO4 or γ -Ca2SiO4, sometimes expressed as Ca2SiO4 or 2CaO · SiO2), calcium silicate based amorphous phases (each of which may comprise one or more other metal ions and oxides (such as aluminium, magnesium, iron or manganese oxides) or mixtures thereof), or may contain some magnesium silicate, either naturally occurring or synthetic, in a range from trace amounts (1%) to about 50% by weight or more.
Notably, preferably, the carbonatable calcium silicate compositions of the present invention are not hydrated. However, minor amounts of hydratable calcium silicate phases (e.g., C2S, C3S, and CaO) may be present. When exposed to water, C2S shows slow kinetics of hydration and is in CO2Rapid conversion to CaCO during curing3. Upon exposure to water, C3S and CaO hydrate rapidly, and should therefore be limited in quality<5％。
It should be understood that the disclosed calcium silicate compositions, phases and methods may be employed in place of or in addition to the calcium silicate phase. As used herein, the term "magnesium silicate" refers to a naturally occurring mineral or synthetic material consisting of one or more of the group of magnesium-silicon containing compounds comprising: such as Mg2SiO4(also known as "forsterite"), (Mg, Fe)2SiO4 (also known as "olivine"), Mg3Si4O10(OH)2(also known as "talc"), CaMgSi2O6 (also known as "diopside"), and CaMgSiO4(also known as "calcium forsterite"), each of which may contain one or more other metal ions and oxides (e.g., aluminum, magnesium, iron, or manganese oxide), or mixtures thereof, or may contain some naturally occurring or syntheticCalcium silicate in a form ranging from a trace amount (1%) to about 50% by weight or more.
The main purpose of the carbonatable compositions of the present invention is that they can be carbonated to form composite materials that are beneficial in a variety of applications. For example, the carbonation may be reacted with CO2 by a controlled Hydrothermal Liquid Phase Sintering (HLPS) process to produce a bonded unit that bonds the various components of the composite together. For example, in a preferred embodiment, CO2 is used as the active reactive component that causes CO2 sequestration, and the resulting bonded units in the resulting composite have a carbon footprint that is not comparable to any existing production process. The thermodynamic driving force of the HLPS process is the free energy generated by the reduction of surface energy (area) caused by chemical reactions and crystal growth. The kinetics of the HLPS process are carried out at reasonable rates at low temperatures due to the use of solutions (aqueous or anhydrous) instead of high melting point fluids or high temperature solid media for transporting the active reaction components.
Discussion of various characteristics of HLPS, carbonatable calcium silicate based cements, formation and carbonation of cementitious units, equipment and processes thereof and related subject matter can be found in: U.S. patent No. 8,114,367, U.S. publication No. US 2009/0143211 (application serial No. 12/271,566), U.S. publication No. US 2011/0104469 (application serial No. 12/984,299), U.S. publication No. 2009/0142578 (application serial No. 12/271,513), U.S. publication No. 2013/0122267 (application serial No. 13/411,218), U.S. publication No. 2012/0312194 (application serial No. 13/491,098), WO20091102360(PCT/US2008/083606), WO2011/053598(PCT/US2010/054146), WO2011/090967(PCT/US2011/021623), U.S. provisional patent application serial No. 61/708,423 filed on 1/10/2012, and U.S. publication 2014/0127450 (application serial No. 14/045,758), U.S. publication No. 2015/0266778 (application serial No. 14/045,519), U.S. publication No. 2014/0127458 (application serial No. 14/045,766, U.S. publication No. 2014/0342124 (application serial No. 14/045,540), U.S. publication No. 2014/0272216 (application serial No. 14/207,413), U.S. publication No. 2014/0263683 (application serial No. 14/207,421), U.S. publication No. 2014/0314990 (application serial No. 14/207,920), U.S. publication No. 9,221,027 (application serial No. 14/209,238), U.S. publication No. 2014/0363665 (application serial No. 14/295,601), U.S. publication No. 2014/0361471 (application serial No. 14/295,402), U.S. publication No. 2016/0355439 (application serial No. 14/506,079), U.S. publication No. 2015/0225295 (application serial No. 14/602,313), U.S. publication No. 2015/0056437 (application serial No. 14/463,901), U.S. publication No. 2016/0168720 (application serial No. 82, U.S. publication No. 2016/0031757 (application serial No. 14/817,193), U.S. publication No. 2016/0272544 (application serial No. 15/074,659), U.S. publication No. 2016/0096773 (application serial No. 14/874,350), U.S. publication No. 2016/0340261 (application serial No. 14/715,497), U.S. publication No. 2016/0272545 (application serial No. 15/074,692), U.S. publication No. 2017/0102373 (application serial No. 15/290,328), U.S. publication No. 2017/0121223 (application serial No. 15/335,520), U.S. publication No. 2017/0204010 (application serial No. 15/409,352), U.S. publication No. 2017/0253530 (application serial No. 15/449,736), U.S. publication No. 2017/0260096 (application serial No. 15/451,344), U.S. publication No. 2017/0320781 (application serial No. 82, United states application serial No. 15/716,392 filed on 26.9.2017 and united states application serial No. 15/831,135 filed on 4.12.2017, each of which is, in fact, incorporated herein by reference in its entirety.
Fig. 1-8 show phase diagrams of various phase interrelationships between some of the described materials. FIG. 9 illustrates CO providing humidification in accordance with the principles of the present invention2Schematic representation of a composite curing chamber. In fig. 9, a water source is provided and water vapor is added to the air circulating within the curing chamber. FIG. 10 illustrates a control and replenishment of CO with various humidity control methods and with constant flow or pressure regulation in accordance with the principles of the present invention2And a schematic of a curing chamber capable of controlling temperature. The system is an example of a system capable of providing closed loop control or control using feedback, in which a set time requirement, such as CO, in a process cycle is provided2Set values of operating parameters such as concentration, humidity and temperature, and taking measurements to look upWhether the actual value of the controlled parameter is the desired value.
In an exemplary embodiment of carbonation of the composition of the present invention, a ground calcium silicate composition is used. The ground calcium silicate composition has an average particle size of from about 1 μm to about 100 μm (e.g., from about 1 μm to about 80 μm, from about 1 μm to about 60 μm, from about 1 μm to about 50 μm, from about 1 μm to about 40 μm, from about 1 μm to about 30 μm, from about 1 μm to about 20 μm, from about 1 μm to about 10 μm, from about 5 μm to about 90 μm, from about 5 μm to about 80 μm, from about 5 μm to about 70 μm, from about 5 μm to about 60 μm, from about 5 μm to about 50 μm, from about 5 μm to about 40 μm, from about 10 μm to about 80 μm, from about 10 μm to about 70 μm, from about 10 μm to about 60 μm, from about 10 μm to about 50 μm, from about 10 μm to about 40 μm, from about 10 μm to about 30 μm, from about 10 μm to about 20 μm, from about 1 μm to about 20 μm, from about 20 μm, about 30 μm, or more, or, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm), bulk density of about 0.5g/ml to about 3.5g/ml (loose, as: 0.5g/mL, l.0g/mL, l.5g/mL, 2.0g/mL, 2.5g/mL, 2.8g/mL, 3.0g/mL, 3.5g/mL) and from about 1.0g/mL to about 1.2g/mL (tapped), a Blaine surface area from about 150m2/kg to about 700m2Kg (e.g. 150 m)2/kg、200m2/kg、250m2/kg、300m2/kg、350m2/kg、400m2/kg、450m2/kg、500m2/kg、550m2/kg、600m2/kg,、650m2/kg、700m2In kg). In an exemplary embodiment of carbonation of the calcium silicate composition of the present invention, a cumulative 10% of the ground calcium silicate particles used have a particle size greater than 1 μm in the volume distribution of the particle size distribution.
Any suitable aggregate material may be used to form the composite material from the carbonatable compositions of the present invention, for example, calcium oxide-containing or silicon-containing materials. Exemplary aggregates include inert materials such as darkrock, building sand, gravel beans, and the like. In certain preferred embodiments, lightweight aggregate such as perlite or vermiculite may also be used as aggregate. Materials such as industrial waste (e.g., fly ash, slag, silica fume) may also be used as good fillers.
The various aggregates can have any suitable average particle size and size distribution. In certain embodiments, the average particle size of the plurality of aggregates ranges from about 0.25mm to about 25mm (e.g., about 5mm to about 20mm, about 5mm to about 18mm, about 5mm to about 15mm, about 5mm to about 12mm, about 7mm to about 20mm, about 10mm to about 20mm, about 1/8 ", about 1/4", about 3/8 ", about 1/2", about 3/4 ").
The composite material may also contain chemical admixtures such as plasticizers, set retarders, accelerators, dispersants and other rheology modifiers, and may also contain certain commercial chemical admixtures such as Glenium from BASF chemicalsTM7500 and Acumer of Dow chemical CoTM. In certain embodiments, the one or more pigments may be uniformly dispersed or substantially non-uniformly dispersed in the bonding matrix, depending on the desired composite material. The pigment can be any suitable pigment including, for example, various metal oxides (e.g., black iron oxide, cobalt oxide, and chromium oxide). The pigment may be any color or colors, such as selected from black, white, blue, gray, pink, green, red, yellow, and brown. The pigment may be present in any suitable dosage, such as in a dosage range of from about 0.0% to about 10% by weight, depending on the desired composite.
The carbonatable calcium silicate compositions of the present invention can be used to produce a variety of composite products by processes that do not require autoclaves and are suitable for continuous, large-scale production. This production method is a great improvement over conventional concrete in terms of economic and environmental impact.
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