Admixture, admixture production method, concrete, concrete production method, and calcium-containing material production method

Abstract

Provided are: an admixture for concrete that eliminates the need for dedicated equipment for carbon dioxide fixation; a production method therefor; concrete that includes the admixture; and a production method therefor.　An admixture according to the present invention is produced by reacting a by-product obtained in a quicklime production step with water and carbon dioxide and contains calcium in an amount of not more than 35 mass%. A method for producing the admixture comprises: a first step for reacting water with a raw material which is a by-product obtained in a quicklime production step; and a second step for reacting, with carbon dioxide, a product obtained in the first step.

Description

Admixture, method for manufacturing admixture, concrete, method for manufacturing concrete, and method for manufacturing calcium-containing material

[0001] The present invention relates to an admixture for concrete and a method for producing the same, concrete containing the admixture and a method for producing the same, and a method for producing a calcium-containing substance.

[0002] Carbon dioxide (CO ２ CO is produced during the production of cement, a powder that hardens when reacted with water and is used to make mortar and concrete. ２ In order to reduce the amount of generated carbon dioxide, it has been proposed to produce concrete using blast furnace slag or fly ash instead of cement.

[0003] Also, CO ２ As a material in which calcium carbonate (CaCO ３ ) and biochar, and CO generated during the manufacturing process ２ Concrete in which the viscosity is reduced to substantially zero or less is also known (see, for example, Patent Document 1).

[0004] CaCO ３ Concrete containing CaCO3 has been studied for a long time and can be manufactured using existing technology. ３ A large amount of energy is required to burn limestone in the production of ３ In the process of ２ Although the carbon dioxide is fixed, CO ２ occurs.

[0005] For this reason, CaCO ３ It has been proposed to use magnesium hydroxide produced not by burning limestone but by supplying carbon dioxide to calcium contained in concrete sludge generated in ready-mix concrete factories and the like (see, for example, Patent Documents 2 and 3). It has also been proposed to use magnesium hydroxide produced by adding CO2 from factory waste gases and the atmosphere to waste seawater containing calcium after producing magnesium hydroxide from seawater. ２ It has been proposed to use a material produced by supplying the above (see, for example, Patent Document 3).

[0006] JP 2023-160056 A JP 2023-96668 A JP 2023-127648 A

[0007] The calcium sources described in Patent Documents 2 and 3 are derived from waste materials, but in certain factories such as ready-mixed concrete factories and magnesium manufacturing factories, CO ２ However, there was a problem in that special equipment was required to fix the

[0008] The present invention has been made in view of the above-mentioned problems, and provides an admixture for concrete, which is produced by reacting a by-product obtained in a process for producing quicklime with water and carbon dioxide, and which contains 5% by mass or more and 37% by mass or less of calcium.

[0009] Also provided is a method for producing an admixture for concrete containing 5% by mass or more and 37% by mass or less of calcium, the method comprising a first step of reacting a by-product obtained in a step of producing quicklime as a raw material with water, and a second step of reacting the product obtained in the first step with carbon dioxide.

[0010] According to the present invention, CO ２ This eliminates the need for dedicated equipment to secure the

[0011] 1 is a diagram for explaining a process for producing quicklime; 2 is a diagram showing product CaO powder and calcined dust; 3 is a diagram showing an example of the configuration of an apparatus for producing calcium carbonate from quicklime; 4 is a diagram showing an example of a production flow of an admixture for concrete; 5 is a diagram showing the relationship between sieve openings and passing mass percentages; 6 is a diagram showing an example of a production flow of concrete;

[0012] Quicklime (calcium oxide: CaO) is obtained by burning limestone and is used in steel, soil improvement, desiccant, building material raw material, etc. Limestone is mainly composed of calcium carbonate (CaCO ３ ), which decomposes at about 900°C to form carbon dioxide (CO ２ ) to produce CaO.

[0013] The manufacturing process of CaO will be described with reference to Figure 1. In step 100, limestone mined from a mountain or the like is crushed into small pieces by a crusher. In step 101, the crushed limestone is classified using a sieve. In step 102, the classified limestone is placed in a furnace and burned at 900 to 1000°C. When the limestone is burned, the reaction of the following formula (1) occurs, producing quicklime: CaCO ３ →CaO+CO ２ (1)

[0014] The composition and crystalline structure of quicklime vary depending on where it is mined. The calcination method also affects the degree of shrinkage (consolidation), which in turn affects its reactivity and properties. The calcination method also depends on the type of furnace used to calcine the limestone. The type of furnace is determined by the method of heat exchange between the limestone and combustion gases produced by burning fuel such as heavy oil, and includes vertical furnaces such as the Maerz furnace and Beckenbach furnace, and horizontal furnaces such as the rotary kiln.

[0015] A Mertz furnace consists of two furnace tubes connected by a passage at the bottom. Limestone is alternately charged into each of the two furnace tubes from the top, and while one furnace tube is firing, the other furnace tube is preheating. After passing through a cooling zone below, the limestone is discharged from the bottom of the furnace as quicklime.

[0016] The Beckenbach kiln consists of an outer casing and an inner casing inserted inside it. Limestone is charged into the space between the inner and outer casings from the top of the furnace, passes through a preheating zone, a calcination zone, and a cooling zone, and is discharged from the bottom of the furnace as quicklime.

[0017] A rotary kiln has a preheating section, a calcining section, and a cooling section. After preheating to the temperature at which thermal decomposition begins in the preheating section, the material is burned while moving in the calcining section due to a gentle incline and rotation, becoming quicklime. The quicklime is then discharged from the furnace through the cooling section.

[0018] The main component of limestone is calcium carbonate, but other components include aluminum oxide (Al ２ O ３ ), iron oxide (Fe ２ O ３ ), silica (SiO２ ) etc.

[0019] In the process of calcining limestone in the production of quicklime, by-products are generated in the production of the quicklime product. The by-products are, for example, calcination dust, which is fine particles floating in the furnace, and are collected by a dust collector such as a bag filter. The calcination dust is powdered by the introduction of limestone into the furnace or by friction with the furnace, and is calcined, containing fine CaO particles generated according to the above formula (1).

[0020] For example, in a Beckenbach furnace, limestone and lump coke are mixed and fed into the furnace to reduce fuel costs, and the limestone is burned by burning the coke. ２ O ３ , Fe ２ O ３ , SiO ２ The ash contains ash components such as calcium carbonate, calcium iodide (CaO), and magnesium oxide (MgO), which remain after combustion. The ash adheres to the CaO produced by calcination, adheres to the CaO particles that make up the retained dust, scatters in the exhaust gas, remains in the furnace, or is discharged from the bottom of the furnace. These components are generally treated by surface treatment and separation (Reference 1: Michitaka Fujio, "Establishment of Operating Technology for Beckenbach-Type Lime Kilns," Journal of the Society of Inorganic Materials, Japan 7, pp. 220-226 (2000)). These components constitute the by-products or calcination dust obtained in the limestone manufacturing process.

[0021] Since calcination dust is a powder containing not only fine CaO particles but also ash and the like, it exhibits colors such as brown, gray, black, etc., whereas the CaO product is white. The colors vary depending on the type of furnace, the components of the fuel, etc., and include colors such as sand, chalk, off-white, ivory, silver gray, brown gray, gray, Rikyu gray, lead, gray, soot bamboo, dark brown, ink, black, iron black, silver, ivory, sky gray, pearl gray, silver gray, ash gray, rose gray, gray, steel gray, straight gray, charcoal gray, lamp black, and black, as specified in Appendix 1 of Japanese Industrial Standards (JIS) Z 8102:2001 (Color names of colors of objects).

[0022] In addition, JIS Z 8102:2001 allows the addition of modifier names to the above-mentioned conventional colors using the terms specified in 7.2 Table 3 and 7.3 Table 4 of the same standard, and includes colors modified by any of the above-mentioned conventional color names with "light," "strong," "dark," "light," "soft," "dull," "dark," "very light," "light grayish," "grayish," "dark grayish," "very dark," and "medium" as specified in JIS Z 8102:2001.7.2 Table 3 and 7.3 Table 4 (JIS Z 8102:2001.11.2 and 7.2 Table 3 and 7.3 Table 4).

[0023] Figure 2 shows the color of the CaO product and the color of the calcined dust. Figure 2(a) shows the CaO powder product, which is white, and Figure 2(b) shows the calcined dust, which is gray.

[0024] Although the calcination dust contains CaO, the content is small and it does not have a consistent color, so it is a waste Ca content containing CaO and is usually discarded.

[0025] The results of X-ray fluorescence analysis and particle size distribution measurement of the calcined dust obtained by calcining limestone in a Beckenbach furnace are shown below. The X-ray fluorescence analysis was performed using an X-ray fluorescence analyzer ZSX Primus II (manufactured by Rigaku Corporation).

[0026] The results of X-ray fluorescence analysis showed that the main components were 48.2% by mass of oxygen, 29.9% by mass of calcium, 10.4% by mass of carbon, 4.8% by mass of silicon (silica), and 4.1% by mass of aluminum. Other components of the calcined dust included 0.9% by mass of sulfur, 0.6% by mass of iron, 0.3% by mass of magnesium, 0.2% by mass of titanium, and 0.2% by mass of sodium.

[0027] The particle size distribution was measured using a laser diffraction / scattering particle size distribution analyzer (Beckman Coulter, Inc. LS 13 320XR: Universal Liquid Module / Wet Measurement Unit: Dispersion Medium / Ion Exchange Water: Particle Size / Volume). The cumulative fraction of volume-based particle sizes below a certain value was calculated. The cumulative fraction of volume-based particle sizes measured by the laser diffraction / scattering method was 99.0% for particle sizes below 600 μm, 79.3% for particle sizes below 150 μm, and 60.8% for particle sizes below 75 μm.

[0028] The by-product or calcined dust obtained in the process for producing quicklime according to the present invention may have a cumulative fraction of particles having a volumetric particle size of 600 μm or less as measured by a laser diffraction / scattering method of 70% or more, and more preferably 75% or more, 80% or more, 85% or more, 90% or more, 95% or more, or 97% or more.

[0029] The cumulative fraction of particles having a volumetric particle size of 150 μm or less, as measured by a laser diffraction / scattering method, may be 50% or more, or may be 55% or more, 60% or more, 65% or more, 70% or more, or 75% or more. The upper limit may be 95% or less, 90% or less, or 85% or less.

[0030] Furthermore, the cumulative fraction of particle diameters of 75 μm or less on a volume basis measured by a laser diffraction / scattering method may be 30% or more, 35% or more, 40% or more, 45% or more, 50% or more, or 55% or more, and the upper limit may be 95% or less, 90% or less, 85% or less, 80% or less, 75% or less, 70% or less, or 65% or less.

[0031] The quality of commercially available industrial lime (CaO) is specified in Japanese Industrial Standards (JIS) R9001:2006. JIS R9001:2006 specifies that special grade lime must contain 93% or more by mass of CaO, grade 1 lime must contain 90% or more by mass of CaO, and grade 2 lime must contain 80% or more by mass of CaO. Even if the CaO content is 80% or more by mass, the Ca content exceeds 57% by mass.

[0032] Furthermore, when producing Grade 1 quicklime, it is necessary to produce quicklime with a CaO content of 90% by mass or more and a Ca content exceeding 64% by mass, and when producing Special Grade quicklime, it is necessary to produce quicklime with a CaO content of 93% by mass or more and a Ca content exceeding 66% by mass. Therefore, to produce quicklime that satisfies both grades, it is necessary to produce quicklime with a CaO content of 93% by mass or more and a Ca content exceeding 66% by mass.

[0033] In contrast, the Ca content of by-products or calcined dust obtained in the process of producing quicklime may be 57% by mass or less as determined by X-ray fluorescence analysis. Furthermore, the Ca content of by-products or calcined dust for the purpose of producing Grade 1 quicklime may be 64% by mass or less. Furthermore, the Ca content of by-products or calcined dust for the purpose of producing Special Grade quicklime may be 66% by mass or less. For this reason, the CaO content of by-products or calcined dust may not exceed 93% by mass or 66% by mass, which satisfies the requirements for both grades.

[0034] Furthermore, the Ca content of the by-product or calcined dust obtained in the process for producing quicklime of the present invention, as determined by X-ray fluorescence analysis, may be 66% by mass or less, 64% by mass or less, 62% by mass or less, 60% by mass or less, 59% by mass or less, 57% by mass or less, less than 57% by mass, 56% by mass or less, 55% by mass or less, 50% by mass or less, 48% by mass or less, 45% by mass or less, 40% by mass or less, or 35% by mass or less. The preferred lower limit is 5% by mass or more, 10% by mass or more, or 15% by mass or more, more preferably 20% by mass or more, or 25% by mass or more.

[0035] Commercially available industrial lime (CaO) has a sieve permeability of 100% when passing through a sieve with 600 μm openings, and a sieve permeability of 95% or more when passing through a sieve with 150 μm openings.

[0036] For this reason, the Ca content of the by-product, calcination dust, is less than the Ca content of commercially available industrial lime (CaO).

[0037] Concrete is produced by measuring cement, water, aggregate, etc. in a predetermined ratio, pouring them into a concrete mixer, and kneading them. When producing concrete, admixtures such as water-reducing agents and quick-setting agents are added as needed.

[0038] Cement is produced by placing raw materials such as limestone, clay, silica, and iron in a kiln such as a rotary kiln, firing them at a temperature of approximately 1500°C, and then rapidly cooling them to produce a clinker, to which gypsum is then added and crushed.

[0039] In the firing process to make clinker, CO ２ A large amount of fuel is burned to reach a firing temperature of approximately 1500°C, and a large amount of CO ２ CO is generated. ２ is one of the greenhouse gases that causes global warming, and there is a need to reduce emissions. ２ absorbs and hardens CO ２ Absorbent concrete is attracting attention. By using this technology, CO ２ The amount of absorption of CO ２ It is possible to achieve carbon negative emissions, exceeding the current level.

[0040] To achieve carbon negative, materials containing CO, such as CaO, ２ It is necessary to use a material that can adsorb or absorb the

[0041] In addition, CO ２ The absorption of CaO is realized by a hydration reaction with water according to the following formula (2) and a carbonation reaction with carbon dioxide according to the following formula (3): ２ O → Ca(OH) ２ (2) Ca(OH) ２ +CO ２ →CaCO ３ +H ２ O (3)

[0042] Conventionally, concrete sludge generated in ready-mix concrete factories and waste seawater after producing magnesium hydroxide from seawater have been used as materials containing CaO, and CO ２ By supplying CaCO ３ and CaCO ３ is used to manufacture concrete.

[0043] However, in certain factories such as ready-mix concrete factories and magnesium manufacturing factories, CO ２ However, there is a problem in that special equipment is required to fix the

[0044] In the production of concrete, CaCO3, also known as calcium carbonate, ３ An example of calcium carbonate used as an admixture for concrete is Calfinder (https: / / www.omi-mining.co.jp / business / calcium-carbonate / calfinder / ) manufactured by Omi Mining Co., Ltd., which contains CaCO ３ The content of CaCO is 90% by mass or more. ３ When the Ca content is calculated for a content of 90 mass%, the Ca content is 36 mass%. ３ is limestone (CaCO ３ ), and is so-called "ground calcium carbonate." Ground calcium carbonate is a type of calcium carbonate produced by grinding limestone (CaCO ３ ) is calcium carbonate produced by crushing it. ２ There is no reaction step with atmospheric CO ２ It has no effect of fixing the

[0045] Ecotancal (registered trademark) manufactured by Nippon Concrete Industries Co., Ltd. (https: / / www.ncic.co.jp / products / environment / ecocaco3.html) is an admixture that can be used for concrete. ３ The purity of CaCO is 97-99% and some have high whiteness. ３is calcium carbonate known as "light calcium carbonate (also called "precipitated calcium carbonate"). ３ is CO ２ This precipitated calcium carbonate is produced by reacting with CaCO ３ The content is 95% by mass or more, and the Ca content is 38% by mass or more.

[0046] Furthermore, Reference 2 (Haruki Sato and Kazuyoshi Ozone, "Distinguishing between Natural and Artificial Calcium Carbonate," Report of the Central Customs Analysis Laboratory, No. 59, pp. 101-112) analyzes many commercially available calcium carbonates using fluorescent X-rays, and states that the "C, O, and Ca" values ​​are 97% by mass or more. ３ Calcium carbonate with a Ca content of less than 90% by mass, i.e., a material with a Ca content of less than 36% by mass, has not been used as an admixture to produce concrete. Furthermore, only materials with high whiteness have been used as concrete admixtures up to now. In particular, calcium carbonate produced by reacting with CO2 (light calcium carbonate (precipitated calcium carbonate)) has a high whiteness of CaCO ３ The content is 95% by mass or more, and the Ca content is 38% by mass or more.

[0047] Furthermore, commercially available calcium carbonate used as an admixture for concrete has a sieve permeability of 100% for passing through a sieve with 600 μm openings, a sieve permeability of 90% or more for passing through a sieve with 150 μm openings, and a sieve permeability of 70% or more for passing through a sieve with 75 μm openings.

[0048] The calcined dust has a Ca content of approximately 30% by mass, and is either 66% by mass or less, or 57% by mass or less. Even if the calcined dust is hydrated and carbonated according to the above formulas (2) and (3), only a Ca content of less than 38% by mass or less than 36% by mass is produced. Incidentally, when the calcined dust with a Ca content of approximately 30% by mass is hydrated and carbonated according to the above formulas (2) and (3), a Ca content of approximately 22% by mass is produced. Furthermore, the calcined dust is not expected to be white. For these reasons, calcined dust has not been used in the production of concrete.

[0049] The inventors of the present invention have ２ The main component is CaCO3 without using dedicated equipment for fixing the ３ While investigating the raw materials for producing the admixture, concrete was produced using materials made from calcined dust, which is normally discarded, and the compressive strength (N / mm) at 7 and 28 days of age was measured. ２ The results of measuring the porosity of slag from the calcined dust were better than those of commercially available calcium carbonate or ground granulated blast furnace slag, and it was found that the material produced from the calcined dust can be used as an admixture. The present invention was made based on this finding.

[0050] The above measurements were conducted in accordance with JIS A 1108:2018. The case using only ordinary Portland cement as the binder was referred to as a normal mix, with a water-to-binder mass ratio (W / B) of 50%. The case using high-early-strength Portland cement and blast furnace slag was referred to as a slag mix, with the high-early-strength Portland cement and blast furnace slag in a mass ratio of 1:9 and a W / B of 47%. The case using commercially available calcium carbonate was referred to as a calcium carbonate mix, with the same amounts of high-early-strength Portland cement, blast furnace slag, and water as the slag mix, with the high-early-strength Portland cement and blast furnace slag in a mass ratio of 3:2 and a W / B of 47%. The case where the material made from the calcined dust was used was designated as the calcined dust manufacturing material blend, and the calcined dust in the calcined dust blend was replaced with the material made from the calcined dust. The same high-early-strength Portland cement and the material made from the blast furnace slag and the calcined dust were used in a mass ratio of 3:2, with a W / B ratio of 47%. The material made from the calcined dust was produced by reacting the calcined dust with water to produce CO2, as explained below. ２ The main component is CaCO ３ It is a material that is.

[0051] The test specimens were cast into the formwork and removed the next day, and then subjected to standard curing (underwater curing at 20°C). The measurement results showed that the compressive strength of the normal mix at 7 days was 39 N / mm ２ , the compressive strength at 28 days is 51 N / mm ２The compressive strength of the slag mixture at 7 days is 21 N / mm ２ , the compressive strength at 28 days is 26 N / mm ２ In the case of the Calcium carbonate mixture, the compressive strength at 7 days is 42 N / mm ２ , the compressive strength at 28 days is 56N / mm ２ In contrast, the compressive strength of the calcined dust manufacturing material mixture at 7 days was 53 N / mm ２ , the compressive strength at 28 days is 64N / mm ２ The compressive strength exceeded that of the normal mix, slag mix, and calcium carbonate mix. This demonstrates that the material made from calcined dust can be fully utilized as an admixture for concrete.

[0052] Calcination dust is a by-product obtained from the process of calcining limestone and is a waste Ca component containing CaO. Therefore, it is reacted with water as shown in the above formula (2) to produce slaked lime (Ca(OH) ２ ) can be generated. Then, CO ２ It is fixed by adsorption, absorption and reaction, and is used as an admixture for concrete (main component: CaCO ３ ) can be generated.

[0053] By using the resulting admixture in concrete production, CO in the atmosphere and exhaust gases can be reduced. ２ The main component of limestone is CaCO ３ Therefore, even if limestone is used as an admixture, CO ２ Although it is not considered to be fixed or stored, by using the calcination dust, ２ can be immobilized and stored.

[0054] Calcination dust, a by-product obtained from the process of calcining limestone, contains CaO, and CaCO3, the main component of concrete admixtures, is obtained from CaO. ３ To produce the above, known hydration processes and known carbonation processes can be used.

[0055] For example, a dry method can be used as a method of hydration and carbonation. Reference 3 (Kiyoji Itaya and seven others, "Preparation of Granular Slaked Lime by Hydration of Quicklime", Gypsum & Lime No. 234, pp. 306-314 (1991)) describes a method in which deionized water is sprayed onto CaO powder from above, the mixture is stirred with a scrubber, and Ca(OH) is produced by the hydration reaction of CaO. ２ Furthermore, Reference 4 ("On the Slake of Limestone," Inorganic Materials Society, Gypsum and Lime, Vol. 1957, No. 29, pp. 1434-1335 (1957)) describes that the method of piling CaO on the floor or in a container and pouring water over it to hydrate it is adopted by the majority of small and medium-sized industries in Japan. Reference 4 also mentions that dry mechanical methods of hydrating CaO by adding water include Anker-type automatic hydrators and Schnlthess-type automatic hydrators, and that CaO naturally hydrates when exposed to moisture in the air, so that it naturally absorbs moisture in the air to produce Ca(OH). ２ and Ca(OH) ２ is the CO in the air ２ Absorbs CaCO ３ It is also described that there is a method of carrying out a hydration / carbonation reaction by natural weathering to produce CaCO3, which is the main component of concrete admixtures, from CaO. Reference 5 (Yasue Nin and two others, "Research Trends in Lime", Inorganic Materials, Vol. 1, No. 252, pp. 370-381 (1994)) also describes that there have been many studies on carbonation. As described above, the dry method is widely used as a hydration / carbonation method, and CaCO3, the main component of concrete admixtures, is produced from CaO. ３ To produce the above, known dry hydration and carbonation methods can be used.

[0056] The hydration and carbonation method may be a dry method or a wet method. Fig. 3 is a diagram showing an example of a known wet hydration and carbonation process. In the hydration and carbonation process shown in Fig. 3, CaO is hydrated and carbonated to give CaCO ３ Since the calcination dust contains CaO, a conventional method for producing CaCO3 by hydrating and carbonated CaO is used. ３The same apparatus and method for producing the same product can be used.

[0057] CaCO ３ The manufacturing apparatus 10 includes a digester 11, a dissolving tank 12, a filter 13, a reaction tank 14, an aging tank 15, a washer 16, a dehydrator / dryer 17, and a filler 18. Calcination dust, which is waste Ca containing CaO, and water are fed into the digester 11. In the digester 11, the CaO in the calcination dust reacts with water as shown in the above formula (2) to form Ca(OH) ２ Generate.

[0058] The reaction vessel 14 is ２ is supplied, and CO is ２ Reacts with CaCO ３ Generate.

[0059] The dehydrator / dryer 17 is a CaCO ３ The filling machine 18 dehydrates and dries the dried CaCO ３ The packed CaCO ３ is shipped as a product.

[0060] The main component is CaCO3, which is produced by hydrating and carbonating calcination dust. ３ The admixture has a Ca content of 37% by mass or less, or 35% by mass or less, unlike commercially available calcium carbonate, which has a Ca content of 36% by mass or more, and in particular, commercially available light calcium carbonate (precipitated calcium carbonate), which has a Ca content of 38% by mass or more. ３ Therefore, it is desirable that the Ca content is 5 mass % or more.

[0061] Therefore, concrete admixtures are made by mixing the by-products obtained in the CaO manufacturing process with water and CO ２and contains 37% by mass or less of Ca. The preferred lower limit of the Ca content of the concrete admixture is 5% by mass as described above, but 10% by mass is more preferred, and 15% by mass is even more preferred. The lower limit is preferably 17% by mass rather than 15% by mass, and more preferably 20% by mass. The upper limit of the Ca content of the concrete admixture is 37% by mass as described above, but may be 36% by mass or less, 35% by mass or less, 34% by mass or less, 33% by mass or less, 32% by mass or less, 30% by mass or less, 28% by mass or less, or 25% by mass or less.

[0062] The by-product may be, but is not limited to, calcined dust obtained in the step of calcining limestone in the step of producing CaO. The by-product has a Ca content of 66% by mass or less, and may also have a Ca content of 57% by mass or less.

[0063] The concrete admixture can be manufactured by a method similar to the conventional method. Fig. 4 is a diagram showing the manufacturing flow of the concrete admixture. The following description will be given assuming that a known dry hydration and carbonation method is used. In step 200, the concrete admixture is made by using a by-product obtained in the CaO manufacturing process as a raw material, and water is sprayed onto the raw material to cause a reaction. Then, in step 201, the product produced by the reaction of the raw material with water is placed in a rotating cylindrical tube and air is passed through to remove CO2 from the air. ２ This reaction produces CaCO ３ and the resulting CaCO ３ As described above, the reaction with water can be carried out without being in solution, and the CO ２ Similarly, the reaction of the by-products obtained in the CaO production process with water can be carried out without being in solution. ２ The reaction with CO after the reaction with water can also be carried out without using a solution. ２ The reaction with may be a reaction in solution.

[0064] The admixture thus produced was subjected to a sieving test to measure the passing mass percentage. Particle size measurements were performed using a stainless steel sieve with a frame diameter of 200 mm manufactured by Nonaka Rikagakuki Seisakusho Co., Ltd., conforming to JIS Z 8801-1. The relationship between the sieve opening and the passing mass percentage (%) is as follows: 75 μm: 62.0%, 106 μm: 68.4%, 250 μm: 87.3%, 425 μm: 96.4%, 850 μm: 99.8%, 2 mm: 99.9%, 4.75 mm: 100%.

[0065] From the above passing mass percentage (%), a particle size accumulation curve was created in which the vertical axis represents passing mass percentage (%) and the horizontal axis represents particle diameter on a logarithmic scale. The created particle size accumulation curve is shown in Figure 5. When the passing mass percentage (%) values ​​for particle diameters of 600 μm, 150 μm, and 75 μm were read from the particle size accumulation curve shown in Figure 5, the passing mass percentage value for a particle diameter of 600 μm was 99%, the passing mass percentage value for a particle diameter of 150 μm was 76%, and the passing mass percentage value for a particle diameter of 75 μm was 62%.

[0066] The passing mass percentage value for particles with a particle diameter of 600 μm determined in this manner is 70% or more, the passing mass percentage value for particles with a particle diameter of 150 μm is 45% or more, and the passing mass percentage value for particles with a particle diameter of 75 μm is 30% or more. The passing mass percentage value for particles with a particle diameter of 600 μm determined in this manner is preferably 75% or more, more preferably 80% or more, and even more preferably 85% or more. The passing mass percentage value for particles with a particle diameter of 600 μm is preferably 90% or more, more preferably 95% or more, and even more preferably 97% or more.

[0067] The mass percentage of the admixture passing through a particle diameter of 150 μm determined as described above is preferably 50% or more, more preferably 55% or more, more preferably 60% or more, and even more preferably 65% ​​or more. The mass percentage of the admixture passing through a particle diameter of 150 μm is preferably 70% or more, more preferably 75% or more, than 65% or more. The upper limit of the mass percentage of the admixture passing through a particle diameter of 150 μm can be 95%, 90%, or 85%.

[0068] The mass percentage of the admixture passing through a particle diameter of 75 μm determined as described above is preferably 35% or more, more preferably 40% or more, and even more preferably 45% or more. The mass percentage of the admixture passing through a particle diameter of 75 μm is preferably 50% or more, more preferably 55% or more, rather than 45% or more. The upper limit of the mass percentage of the admixture passing through a particle diameter of 75 μm can be 95%, 90%, 85%, 80%, 75%, or 70%.

[0069] Furthermore, a portion of the admixture produced as described above was analyzed using an energy dispersive X-ray fluorescence analyzer manufactured by Rigaku Corporation (model number: EDXL300, measurement conditions: FP (fundamental parameter) method), and the Ca content was found to be 33% by mass. Even if the Ca content of the admixture is 35% by mass, the Ca content of the calcined dust used as the raw material will be 56.9% by mass, which is 57% by mass or less. Furthermore, if the Ca content of the admixture is 37% by mass, the Ca content of the calcined dust used as the raw material will be around 60% by mass (approximately 62% by mass), which is 66% by mass or less.

[0070] The admixture produced by hydration and carbonation was gray, similar to the fired dust in Figure 2(b). The admixture produced was not white, but rather brown, gray, black, etc. The colors were sand, chalk, natural, ivory, silver gray, brown gray, gray, Rikyu gray, lead, gray, soot bamboo, dark brown, ink, black, iron black, silver, ivory, sky gray, pearl gray, silver gray, ash gray, rose gray, gray, steel gray, straight gray, charcoal gray, lamp black, black, etc., as specified in Appendix 1 of Japanese Industrial Standards (JIS) Z 8102:2001 (Color Names of Object Colors). In addition, JIS Z 8102:2001 allows the addition of modifiers to the above-mentioned conventional colors using the terms specified in 7.2 Table 3 and 7.3 Table 4 of the same standard, and includes colors modified by any of the above-mentioned conventional color names with "light," "strong," "dark," "light," "soft," "dull," "dark," "very light," "light grayish," "grayish," "dark grayish," "very dark," and "medium" as specified in JIS Z 8102:2001.7.2 Table 3 and 7.3 Table 4 (JIS Z 8102:2001.11.2 and 7.2 Table 3, 7.3 Table 4). Admixtures are materials having the above-mentioned particle sizes, or materials having the above-mentioned colors, or both.

[0071] In addition, the whiteness W (L) of admixtures (calcium-containing materials) manufactured by hydration and carbonation according to the Lab color space established by the International Commission on Illumination (CIE) ＊ a ＊ b ＊ ) may be less than 95, 90 or less, 85 or less, 80 or less, 75 or less, 70 or less, 65 or less, 60 or less, 55 or less, 50 or less, 45 or less, or 40 or less. Furthermore, the lightness index L according to the Lab color space established by the CIE of the admixture (calcium-containing material) produced by hydration and carbonation may be ＊ may be measured as less than 95, 90 or less, 85 or less, 80 or less, 75 or less, 70 or less, 65 or less, 60 or less, 55 or less, 50 or less, 45 or less, or 40 or less.

[0072] The whiteness W (L) in the Lab color space established by the CIE＊ a ＊ b ＊ ) and the measured value L ＊ , a ＊ , b ＊ The relationship between L and L is as follows: ＊ is the lightness index in the Lab color space, and a ＊ , b ＊ are color coordinates in the Lab color space. ＊ a ＊ b ＊ )=100-[(100-L ＊ ) ２ + (a ＊ ) ２ +(b ＊ ) ２ ] １／２ (4)

[0073] The by-products generated in the calcination process for producing quicklime (CaO) are made from dust and other raw materials, and therefore have a lower whiteness W (L) in the Lab color space established by CLE than general light calcium carbonate (precipitated calcium carbonate). ＊ a ＊ b ＊ ) tends to be low. Similarly, the lightness index L in the Lab color space established by CLE ＊ also tends to be low.

[0074] As in the above, some of the admixtures (calcium-containing materials) produced by hydration and carbonation were measured as admixture A and admixture B using the following measuring device and conditions. The measurement results are shown in Table 1. Measuring device: Spectrophotometer SE7700 manufactured by Nippon Denshoku Industries Co., Ltd. Measurement conditions: Reflection, light source / field of view = C / 2, filled into a φ58 mm round cell and measured

[0075]

[0076] From the results in Table 1 above, the whiteness W (L ＊ a ＊ b ＊ ) is a low value of 36, and the brightness index L ＊ However, admixtures A and B had low values ​​of 36.03 and 35.90.

[0077] The admixture is CaCO ３ Since it contains the above, it is a calcium-containing substance, and the production flow shown in FIG. 4 is a production flow of an admixture for concrete, and also one of the production flows of a calcium-containing substance.

[0078] 6 is a diagram showing the concrete manufacturing flow. In step 300, a by-product obtained in the CaO manufacturing process is mixed with water and CO ２ The admixture is produced by reacting the above with the above to produce an admixture containing 35 mass % or less of Ca. Specifically, the admixture is produced by the production process shown in FIG.

[0079] Once the admixture is prepared, in step 301, Portland cement, aggregate, water, and admixture are weighed out according to a predetermined ratio. High-early-strength Portland cement can be used as the Portland cement, but ordinary Portland cement is also acceptable. The aggregate includes fine aggregate and coarse aggregate. Fine aggregate is aggregate in which all particles are 10 mm or less, with at least 85% by mass of particles being 5 mm or less. In contrast, coarse aggregate is aggregate in which particles 5 mm or larger account for at least 85% by mass. The volume ratio (s / a) of the fine aggregate to the total aggregate in the concrete can be, for example, in the range of 35 to 55% expressed as a percentage. The mass ratio of water to Portland cement can be, for example, 100:5 to 100:25. Furthermore, the mass of the admixture can be 5 to 10 times the mass of the Portland cement.

[0080] In step 302, the measured Portland cement, aggregate, water, and admixture are poured into a concrete mixer. Then, in step 303, the mixture is mixed with the mixing blades in the concrete mixer to produce fresh concrete (ready-mixed concrete), which is concrete that has not yet hardened.

[0081] The ready-mixed concrete is transported to the construction site in a vehicle such as a mixer truck, where it is poured into formwork. After pouring, it is cured for a specified period of time, and the formwork is removed, after which the concrete structure is constructed.

[0082] When producing concrete, in addition to admixtures derived from by-products produced in the production process of Portland cement, aggregate, water, and CaO, admixtures such as water-reducing agents can be used. Furthermore, in addition to the admixtures derived from the by-products and Portland cement, at least one of ground blast furnace slag, fly ash, silica fume, expansive agents, and waterproofing materials can also be mixed and used.

[0083] From the above, CO2 is not generated during production because it uses a by-product obtained from the limestone burning process. ２ The by-product of the admixture is CO ２ Since it is produced by simply reacting with the additives, it is a negative material. Also, since it uses by-products, it is possible to provide the additives at low cost.

[0084] The by-products are solid Ca-containing materials and CO ２ Since the location of the admixture can be selected, no large-scale dedicated equipment is required when manufacturing the admixture. ３ Because it contains CaCO3, it is not widely sold as a fertilizer or soil conditioner. ３ Like calcium carbonate, it can be used as a fertilizer for growing plants, a soil conditioner, a plant growth agent, and an agricultural material. It can also be used as a raw material for manufacturing these.

[0085] The admixture, the method for manufacturing an admixture, the concrete, the method for manufacturing a concrete, and the method for manufacturing a calcium-containing material of the present invention have been described in detail with reference to the embodiments shown in the drawings. However, the present invention is not limited to the above-described embodiments, and can be modified within the scope of what a person skilled in the art can conceive, such as other embodiments, additions, changes, deletions, etc., and any embodiment is within the scope of the present invention as long as it exhibits the functions and effects of the present invention.

[0086] 10... Manufacturing equipment 11... Digestion tank 12... Dissolution tank 13... Filter 14... Reaction tank 15... Maturation tank 16... Washing machine 17... Dehydration / drying machine 18... Filling machine

Claims

1. An admixture for concrete, produced by reacting a by-product obtained in the process of manufacturing quicklime with water and carbon dioxide, and containing 5% to 37% by mass of calcium.

2. The concrete admixture according to claim 1, wherein the by-product is calcined dust obtained in the step of calcining limestone in the step of producing quicklime.

3. The admixture for concrete according to claim 2, which is produced by reacting the calcined dust with the water and then reacting the carbon dioxide with the water.

4. The admixture for concrete according to any one of claims 1 to 3, wherein the by-product has a cumulative fraction of particles with a volumetric particle diameter of 600 μm or less of 70% or more, a cumulative fraction of particles with a volumetric particle diameter of 150 μm or less of 50% or more, and a cumulative fraction of particles with a volumetric particle diameter of 75 μm or less of 30% or more, as measured by a laser diffraction / scattering method.

5. The admixture for concrete according to any one of claims 1 to 3, wherein the by-product is a powder of a color specified in Appendix 1 of Japanese Industrial Standards (JIS) Z 8102:2001 (Color Names of Object Colors), which is sand, chalk, natural, ivory, silver gray, brown gray, gray, Rikyu gray, lead, gray, soot bamboo, dark brown, ink, black, iron black, silver, ivory, sky gray, pearl gray, silver gray, ash gray, rose gray, gray, steel gray, straight gray, charcoal gray, lamp black, black, or any of these colors modified by the terms "light," "strong," "dark," "light," "soft," "dull," "dark," "very light," "light grayish," "grayish," "dark grayish," "very dark," or "medium." 6. The by-product has a volumetric particle diameter of 600 μm or less, a volumetric particle diameter of 150 μm or less, and a volumetric particle diameter of 75 μm or less, measured by a laser diffraction / scattering method, of 70% or more, 50% or more, and 30% or more, and meets the requirements of Japanese Industrial Standards (JIS) Z 8102:2001 (Color Names of Object Colors) Appendix 1, which is sand, chalk, natural, ivory, silver gray, brown gray, gray, Rikyu gray, lead, gray, soot bamboo, black tea, ink, black, iron black, silver, ivory, sky gray, pearl gray, silver gray, ash gray, rose gray, gray, steel gray, straight gray, charcoal gray, lamp black, black, and any of these colors modified with the terms "light," "strong," "dark," "light," "soft," "dull," "dark," "very light," "light grayish," "grayish," "dark grayish," "very dark," and "medium." The admixture for concrete according to any one of claims 1 to 3 is a powder of any of the colors specified in Appendix 1.

7. The admixture for concrete according to any one of claims 1 to 3, wherein the admixture is a powder of a color specified in Appendix 1 of Japanese Industrial Standards (JIS) Z 8102:2001 (Color names of object colors), which is sand, chalk, natural, ivory, silver gray, brown gray, gray, Rikyu gray, lead, gray, soot bamboo, dark brown, ink, black, iron black, silver, ivory, sky gray, pearl gray, silver gray, ash gray, rose gray, gray, steel gray, straight gray, charcoal gray, lamp black, black, or any of these colors modified by the terms "light," "strong," "dark," "light," "soft," "dull," "dark," "very light," "light grayish," "grayish," "dark grayish," "very dark," or "medium." 8. A method for producing an admixture for concrete containing 5% to 37% by mass of calcium, the method comprising: a first step of reacting a by-product obtained in a process for producing quicklime with water; and a second step of reacting the product obtained in the first step with carbon dioxide.

9. The method for producing a concrete admixture according to claim 8, wherein the by-product is calcined dust obtained in the step of calcining limestone in the step of producing quicklime.

10. A method for manufacturing an admixture for concrete according to claim 8 or 9, wherein the by-product has a cumulative fraction of particles with a volumetric particle diameter of 600 μm or less of 70% or more, a cumulative fraction of particles with a volumetric particle diameter of 150 μm or less of 50% or more, and a cumulative fraction of particles with a volumetric particle diameter of 75 μm or less of 30% or more, as measured by a laser diffraction / scattering method.

11. The method for producing a mineral admixture for concrete according to claim 8 or 9, wherein the by-product is a powder of any of the following colors as defined in Appendix 1 of Japanese Industrial Standards (JIS) Z 8102:2001 (Color names of object colors): sand, chalk, natural, ivory, silver gray, brown gray, gray, Rikyu gray, lead, gray, soot bamboo, dark brown, ink, black, iron black, silver, ivory, sky gray, pearl gray, silver gray, ash gray, rose gray, gray, steel gray, straight gray, charcoal gray, lamp black, black, and any of these colors modified by the terms "light," "strong," "dark," "light," "soft," "dull," "dark," "very light," "light grayish," "grayish," "dark grayish," "very dark," or "medium." 12. The by-product has a volumetric particle diameter of 600 μm or less, a volumetric particle diameter of 150 μm or less, and a volumetric particle diameter of 75 μm or less, measured by a laser diffraction / scattering method, of 70% or more, 50% or more, and 30% or more, and meets the requirements of Japanese Industrial Standards (JIS) Z 8102:2001 (Color Names of Object Colors) Appendix 1, which is sand, chalk, natural, ivory, silver gray, brown gray, gray, Rikyu gray, lead, gray, soot bamboo, dark brown, ink, black, iron black, silver, ivory, sky gray, pearl gray, silver gray, ash gray, rose gray, gray, steel gray, straight gray, charcoal gray, lamp black, black, and any of these colors modified by the terms "light," "strong," "dark," "light," "soft," "dull," "dark," "very light," "light grayish," "grayish," "dark grayish," "very dark," and "medium." 13. Concrete containing an admixture containing 5% to 37% by weight of calcium, the admixture being produced by reacting a by-product obtained in the process of producing quicklime with water and carbon dioxide.

14. The concrete according to claim 13, wherein the by-product is calcined dust obtained in the step of calcining limestone in the step of producing quicklime.

15. The concrete of claim 14, produced by reacting the calcined dust with the water and then reacting the carbon dioxide.

16. The concrete according to any one of claims 13 to 15, wherein the by-product has a cumulative fraction of particles with a volumetric particle diameter of 600 μm or less of 70% or more, a cumulative fraction of particles with a volumetric particle diameter of 150 μm or less of 50% or more, and a cumulative fraction of particles with a volumetric particle diameter of 75 μm or less of 30% or more, as measured by a laser diffraction / scattering method.

17. The concrete according to any one of claims 13 to 15, wherein the by-product is a powder of a color specified in Appendix 1 of Japanese Industrial Standards (JIS) Z 8102:2001 (Color Names of Object Colors), which is sand, chalk, natural, ivory, silver gray, brown gray, gray, Rikyu gray, lead, gray, soot bamboo, dark brown, ink, black, iron black, silver, ivory, sky gray, pearl gray, silver gray, ash gray, rose gray, gray, steel gray, straight gray, charcoal gray, lamp black, black, or any of these colors modified by the terms "light," "strong," "dark," "light," "soft," "dull," "dark," "very light," "light grayish," "grayish," "dark grayish," "very dark," or "medium." 18. Add 1 m of the admixture ３ The concrete according to any one of claims 13 to 15, wherein the concrete contains 400 kg or less of the sintered body.

19. The concrete according to any one of claims 13 to 15, comprising Portland cement, aggregate, water, and the admixture, wherein the mass of the admixture is in the range of 5 to 10 times the mass of the Portland cement.

20. A method for producing concrete, comprising the steps of: reacting a by-product obtained in a process for producing quicklime with water and carbon dioxide to produce an admixture containing 5% to 37% by mass of calcium; and kneading the produced admixture with aggregate and water to produce the concrete.

21. The method for producing concrete according to claim 20, wherein the by-product is calcined dust obtained in the step of calcining limestone in the step of producing quicklime.

22. The method for producing concrete according to claim 20 or 21, wherein the step of producing the admixture includes a first step of reacting the by-product with water, and a second step of reacting the product obtained by the first step with carbon dioxide.

23. A method for manufacturing concrete according to claim 20 or 21, wherein the by-product has a cumulative fraction of particles with a volumetric particle diameter of 600 μm or less of 70% or more, a cumulative fraction of particles with a volumetric particle diameter of 150 μm or less of 50% or more, and a cumulative fraction of particles with a volumetric particle diameter of 75 μm or less of 30% or more, as measured by a laser diffraction / scattering method.

24. Add 1 m of the admixture ３ 22. The method for producing concrete according to claim 20 or 21, wherein the amount of the additive is 400 kg or less relative to the concrete.

25. A method for producing concrete according to claim 20 or 21, wherein the concrete contains Portland cement, aggregate, water, and an admixture, and the mass of the admixture is in the range of 5 to 10 times the mass of the Portland cement.

26. A method for producing a calcium-containing material, comprising a first step of reacting a by-product obtained in the calcination process for producing quicklime with water, and a second step of reacting the product obtained in the first step with carbon dioxide.

27. A method for producing a calcium-containing material having a calcium content of 37% by mass or less, comprising a first step of reacting the contents of the raw material with water using a by-product obtained in the calcination process for producing quicklime as a raw material, and a second step of reacting the product obtained in the first step with carbon dioxide.

28. A method for producing a calcium-containing material described in claim 26 or 27, wherein the by-product has a cumulative fraction of particle diameters of 600 μm or less, a cumulative fraction of particle diameters of 150 μm or less, and a cumulative fraction of particle diameters of 75 μm or less, measured by a laser diffraction / scattering method, of 70% or more, 50% or more, and 30% or more, on a volume basis.

29. The method for producing a calcium-containing substance according to claim 26 or 27, wherein the by-product is a powder of any of the colors specified in Appendix 1 of Japanese Industrial Standards (JIS) Z 8102:2001 (Color names of objects), including sand, chalk, natural, ivory, silver gray, brown gray, gray, Rikyu gray, lead, gray, soot bamboo, dark brown, ink, black, iron black, silver, ivory, sky gray, pearl gray, silver gray, ash gray, rose gray, gray, steel gray, straight gray, charcoal gray, lamp black, and black, as well as any of these colors modified by the terms "light," "strong," "dark," "light," "soft," "dull," "dark," "very light," "light grayish," "grayish," "dark grayish," "very dark," and "medium." 30. The by-products have a volumetric particle size of 600 μm or less, a volumetric particle size of 150 μm or less, and a volumetric particle size of 75 μm or less, measured by a laser diffraction / scattering method, of 70% or more, 50% or more, and 30% or more, respectively, and comply with the Japanese Industrial Standards (JIS) Z 8102:2001 (Color Names of Colors of Objects) Appendix 1, which is sand, chafun, natural, ivory, silver gray, brown gray, gray, Rikyu gray, lead, gray, soot bamboo, dark brown, ink, black, iron black, silver, ivory, sky gray, pearl gray, silver gray, ash gray, rose gray, gray, steel gray, straight gray, charcoal gray, lamp black, black, and any of these colors modified by the terms "light," "strong," "dark," "light," "soft," "dull," "dark," "very light," "light grayish," "grayish," "dark grayish," "very dark," and "medium." 31. A method for producing a calcium-containing substance according to claim 26 or 27, wherein the calcium content of the by-product is 66% by mass or less.

32. A method for producing a calcium-containing material as described in claim 26 or 27, wherein the calcium content of the by-product is 66 mass% or less, and the by-product has a cumulative fraction of particle diameters of 600 μm or less, measured by laser diffraction / scattering method, on a volume basis, of 70% or more, a cumulative fraction of particle diameters of 150 μm or less, and a cumulative fraction of particle diameters of 75 μm or less, measured by laser diffraction / scattering method.

33. A method for producing a calcium-containing material according to claim 26 or 27, wherein the calcium content of the by-product is 66% by mass or less, and the by-product is a powder of any of the following colors as defined in Appendix 1 of Japanese Industrial Standards (JIS) Z 8102:2001 (Color names of colors of objects): sand, chalk, natural, ivory, silver gray, brown gray, gray, Rikyu gray, lead, gray, soot bamboo, dark brown, ink, black, iron black, silver, ivory, sky gray, pearl gray, silver gray, ash gray, rose gray, gray, steel gray, straight gray, charcoal gray, lamp black, black, and any of these colors modified by the terms "light," "strong," "dark," "light," "soft," "dull," "dark," "very light," "light grayish," "grayish," "dark grayish," "very dark," and "medium." 34. The calcium content of the by-product is 66% by mass or less, and the by-product has a volume-based cumulative fraction of particles with a diameter of 600 μm or less, a cumulative fraction of particles with a diameter of 150 μm or less, and a cumulative fraction of particles with a diameter of 75 μm or less, measured by a laser diffraction / scattering method, of 70% or more, 50% or more, and 30% or more, and meets the requirements of Japanese Industrial Standards (JIS) Z 8102:2001 (Color Names of Colors of Objects) Appendix 1, which is sand, chafun, natural, ivory, silver gray, brown gray, gray, Rikyu gray, lead, gray, soot bamboo, dark brown, ink, black, iron black, silver, ivory, sky gray, pearl gray, silver gray, ash gray, rose gray, gray, steel gray, straight gray, charcoal gray, lamp black, black, and any of these colors modified by the terms "light," "strong," "dark," "light," "soft," "dull," "dark," "very light," "light grayish," "grayish," "dark grayish," "very dark," and "medium." 35. The method for producing a calcium-containing material according to claim 26 or 27, wherein the by-product is calcination dust obtained in the step of calcining limestone in the step of producing quicklime.

36. The admixture has a whiteness W (L) in the Lab color space established by the International Commission on Illumination (CIE). ＊ a ＊ b ＊ 4. The admixture for concrete according to any one of claims 1 to 3, wherein the powder has a viscosity of less than 95.

37. The admixture has a lightness index L in the Lab color space established by the International Commission on Illumination (CIE). ＊ The admixture for concrete according to any one of claims 1 to 3, wherein the powder has a viscosity of less than 95.

38. The calcium-containing material has a whiteness W (L) in the Lab color space established by the International Commission on Illumination (CIE). ＊ a ＊ b ＊ 28. A method for producing a calcium-containing substance according to claim 26 or 27, wherein the calcium stearate is less than 95.

39. The calcium-containing material has a lightness index L in the Lab color space established by the International Commission on Illumination (CIE). ＊ A method for producing a calcium-containing substance according to claim 26 or 27, wherein the calcium saturation index is less than 95.

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