Organic acid calcium, additive composition, and cement composition

Abstract

To provide organic acid calcium enabled to improve its initial strength and long-term strength when used in combination with amorphous aluminosilicate powder.SOLUTION: The organic acid calcium is used in combination with a curable composition including amorphous aluminosilicate powder of a BET specific surface area of 1.0 m2 / g or above. The amorphous aluminosilicate preferably includes at least one of metakaolin and allophane.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention mainly relates to calcium organic acids, additive compositions, and cement compositions used in the civil engineering and construction industries.

Background Art

[0002] Since a large amount of cement is used as a raw material for concrete, it is regarded as a material with a large CO2 emission. This is mainly due to the fact that, in the production process of cement, in addition to using a large amount of fossil fuel to obtain the combustion energy of the furnace, the decarbonation reaction of limestone (CaCO3 → CaO + CO2) occurs. Reducing the CO2 emission as concrete is an important theme as part of the measures against global warming.

[0003] In order to reduce the total amount of CO2 emitted when manufacturing concrete products, it is effective to reduce the amount of cement used by blending a large amount of industrial by-products (such as blast furnace slag fine powder and fly ash) as cement substitutes, and various studies are being carried out.

[0004] On the other hand, hydraulic materials such as cement usually harden by mixing with water and standing for a predetermined time. The hardening rate of the hydraulic material can be affected by the ratio of the material to water, the ambient temperature, and the curing method, but the time until the hydraulic material hardens can be shortened by using a hardening accelerator.

[0005] Regarding hardening accelerators, for example, Patent Document 1 below describes a hardening accelerator for hydraulic materials containing a predetermined amount of inorganic sulfate, calcium sulfoaluminate, and inorganic hydroxide. Patent Document 2 describes a cement admixture containing calcium sulfoaluminate having a Blaine specific surface area value of 4000 cm 2 / g or more and one or more selected from the group consisting of formate, acetate, and lactate.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] In recent years, when using a curing accelerator, it has been desired to further improve the initial strength and long-term strength. Further, when manufacturing concrete, it is desired to suppress the CO2 emission amount, and even when using an alternative material for cement, it is desired to have high initial strength and long-term strength.

[0008] The present invention has been made in view of such circumstances, and an organic acid calcium capable of improving the initial strength and long-term strength of a cured body produced by being used together with an amorphous aluminosilicate powder, an additive composition containing the organic acid calcium, and a cement composition containing the additive composition are provided.

Means for Solving the Problems

[0009] As a result of intensive studies to solve the above problems, the present inventors have found that the problem can be solved by an organic acid calcium used together with a curable composition containing an amorphous aluminosilicate powder having a predetermined BET specific surface area, and have arrived at the present invention. That is, the present invention is as follows. [1] An organic acid calcium used together with a curable composition containing an amorphous aluminosilicate powder having a BET specific surface area of 1.0 m 2 2 / g or more. [2] The organic acid calcium according to [1], wherein the amorphous aluminosilicate contains at least one of metakaolin and allophane. [3] An additive composition containing the organic acid calcium according to [1] or [2] and an inorganic sulfate. [4] The additive composition according to [3], wherein the inorganic sulfate contains at least one selected from gypsum, mirabilite, aluminum sulfate, sodium thiosulfate, and potassium alum. [5] The additive composition according to [3] or [4], further containing at least one of an expansion agent and an inorganic calcium compound. [6] Further, the additive composition according to any one of [3] to [5], containing an amorphous aluminosilicate powder having a BET specific surface area of 1.0 m 2 / g or more. [7] A cement composition comprising cement, an amorphous aluminosilicate powder having a BET specific surface area of 1.0 m 2 / g or more, and the additive composition according to any one of [3] to [6]. [8] The cement composition according to [7], wherein the amount of the amorphous aluminosilicate powder is 5 to 90 parts by mass with respect to 100 parts by mass of the cement. [Advantages of the Invention]

[0010] According to the present invention, an organic acid calcium capable of improving the initial strength and long-term strength of a cured product produced by using it together with an amorphous aluminosilicate powder, an additive composition containing the organic acid calcium, and a cement composition containing the additive composition can be provided. [Embodiments for Carrying Out the Invention]

[0011] Hereinafter, the organic acid calcium, additive composition, and cement composition of the present invention will be described in detail, but the present invention is not limited to the embodiments. In the present specification, “%” and “parts” are based on mass unless otherwise specified. In addition, a numerical range defined using the symbol “~” includes the numerical values at both ends (upper limit and lower limit) of “~”.

[0012] [Organic Acid Calcium] The organic acid calcium of the present invention has a BET specific surface area of 1.0 m 2It is used together with a curable composition containing amorphous aluminosilicate powder of 1.0 m² / g or more (hereinafter simply referred to as "amorphous aluminosilicate powder"). As such calcium organic acids, for example, calcium formate, calcium acetate, calcium lactate, etc. can be used, and only one kind or two or more kinds can be used. In the present embodiment, from the viewpoints of initial strength development property and long-term strength development property, it is preferable to use calcium formate and / or calcium acetate, and it is more preferable to use calcium formate.

[0013] The calcium organic acid of the present invention is preferably in powder form. The powder of calcium organic acid preferably has a passing fraction through a sieve with an opening of 0.6 mm of 95% or more. By making the calcium organic acid into a powder with a passing fraction through a sieve with an opening of 0.6 mm of 95% or more, the fluidity of the curable composition used together can be maintained, and the initial strength development property can be improved.

[0014] When using the calcium organic acid of the present invention with amorphous aluminosilicate powder, the amorphous aluminosilicate powder may be contained in the additive composition described later, or may be contained in the cement composition. Also, it may be contained in both.

[0015] (Curable composition) The curable composition used together with the calcium organic acid of the present invention has a BET specific surface area of 1.0 m² / g or more and contains amorphous aluminosilicate powder. 2 The BET specific surface area of the amorphous aluminosilicate powder is more preferably 5.0 m² / g or more, and even more preferably 10.0 m² / g or more. By using a curable composition containing amorphous aluminosilicate powder with a BET specific surface area of 1.0 m² / g or more, the initial strength and long-term strength of the cured body produced can be improved. 2 / g or more, and even more preferably 10.0 m² / g or more. By using a curable composition containing amorphous aluminosilicate powder with a BET specific surface area of 1.0 m² / g or more, the initial strength and long-term strength of the cured body produced can be improved. 2 / g or more. By using a curable composition containing amorphous aluminosilicate powder with a BET specific surface area of 1.0 m² / g or more, the initial strength and long-term strength of the cured body produced can be improved. 2 / g or more, the initial strength and long-term strength of the cured body produced can be improved.

[0016] The BET specific surface area of the amorphous aluminosilicate powder is a value measured by the BET single-point method using nitrogen gas in accordance with the method described in JIS Z 8803:2013 "Method for Measuring Specific Surface Area of Powder (Solid) by Gas Adsorption".

[0017] The amorphous aluminosilicate powder is derived from clay minerals and is not particularly limited as long as it is an aluminosilicate containing an amorphous part, and any of them can be used. Examples of the clay minerals as raw materials include (1) kaolin minerals, (2) mica clay minerals, (3) smectite-type minerals, and mixed-layer minerals formed by mixing these. The amorphous aluminosilicate can be obtained by, for example, firing and dehydrating these crystalline aluminosilicates to make them amorphous. From the viewpoint of further excellent reactivity, those derived from kaolin minerals such as kaolinite, halloysite, and dickite are preferable as the amorphous aluminosilicate, and metakaolin obtained by firing kaolinite is more preferable. Also, allophane can be used as the amorphous aluminosilicate. Allophane (Al2O3·(1~2)SiO2·5H2O) is an amorphous clay-like mineral. The amorphous aluminosilicate may be used alone or in combination of two or more.

[0018] In this specification, "amorphous" means that in the measurement by a powder X-ray diffractometer, the peaks derived from the clay minerals as raw materials are hardly seen. The amorphous aluminosilicate powder according to this embodiment only needs to have an amorphous ratio of 70% by mass or more, preferably 90% by mass or more, more preferably 100% by mass, that is, those in which no peaks are seen at all in the measurement by a powder X-ray diffractometer are most preferable. Here, the amorphous ratio is a value obtained by the standard addition method. Aluminosilicates with a high amorphous ratio, that is, aluminosilicates with a low crystalline ratio, tend to have better strength development at the same mixing amount compared to aluminosilicates with a low amorphous ratio. Examples of the heating for the amorphization of aluminosilicates include firing using an external-heat kiln, an internal-heat kiln, an electric furnace, etc., and melting using a melting furnace.

[0019] Examples of the curable composition used together with the calcium organic acid of the present invention include an additive composition or a cement composition, which will be described later. That is, the calcium organic acid of the present invention can be used together with an additive composition containing amorphous aluminosilicate powder. It can also be used together with a cement composition containing amorphous aluminosilicate powder. When used together with a cement composition containing amorphous aluminosilicate powder, the additive composition added to the cement composition may not contain amorphous aluminosilicate powder. By using the calcium organic acid of the present invention together with amorphous aluminosilicate powder, the initial strength and long-term strength of the cured body produced can be improved.

[0020] [Additive composition] The additive composition of the present embodiment includes the above calcium organic acid and inorganic sulfate.

[0021] (Calcium organic acid) As the calcium organic acid contained in the additive composition of the present embodiment, the above calcium organic acid can be used. The content of calcium organic acid in the additive composition is preferably 20 to 80% by mass, more preferably 30 to 70% by mass, and even more preferably 40 to 65% by mass in the additive composition excluding amorphous aluminosilicate powder. By setting the content of calcium organic acid within the above range and using it together with amorphous aluminosilicate powder, the initial strength and long-term strength of the cured body produced can be improved.

[0022] (Inorganic sulfate) As the inorganic sulfate contained in the additive composition of the present embodiment, it is preferable to use sulfate and / or thiosulfate from the viewpoints of initial strength and long-term strength development, and gypsum, mirabilite, aluminum sulfate, sodium thiosulfate, potassium alum, etc. can be used. Among them, mirabilite and aluminum sulfate are preferable, and mirabilite is more preferable. When using gypsum or mirabilite, it is more preferable that they are anhydrous.

[0023] The inorganic sulfate is preferably contained in the additive composition excluding the amorphous aluminosilicate powder in an amount of 0.5 to 75.0% by mass, more preferably 1.0 to 65.0% by mass, and still more preferably 3.0 to 50.0% by mass. By the content of the inorganic sulfate being within the above range, the initial strength and long-term strength can be improved.

[0024] (Inorganic calcium compound) The additive composition of the present embodiment may further contain an inorganic calcium compound. As the inorganic calcium compound, calcium hydroxide, calcium carbonate, calcium oxide, etc. can be used, and from the viewpoint of the initial strength and long-term strength development property, it is preferable to use calcium hydroxide and / or calcium oxide.

[0025] When the inorganic calcium compound is contained in the additive composition, it is preferably contained in the additive composition excluding the amorphous aluminosilicate powder in an amount of 15.0 to 70.0% by mass, more preferably 18.0 to 60.0% by mass, and still more preferably 20.0 to 40.0% by mass. By the content of the inorganic calcium compound being within the above range, the initial strength and long-term strength of the produced hardened body can be improved.

[0026] (Calcium sulfoaluminate) The additive composition of this embodiment can further contain calcium sulfoaluminate as an expansive agent. Calcium sulfoaluminate is a general term for hydraulic substances and hydrated salts represented by the chemical formula xCaO·yAl2O3·zCaSO4·mH2O (x, y, and z are positive real numbers other than 0, and m is 0 or a positive real number). For example, in addition to ye'elimite (3CaO·3Al2O3·CaSO4), there are the AFt phase represented by ettringite (3CaO·Al2O3·3CaSO4·32H2O), the AFm phase represented by monosulfate (3CaO·Al2O3·CaSO4·12H2O), and those in which the AFt phase and the AFm phase coexist. Calcium sulfoaluminate may be amorphous. Also, a part of Al2O3 may be substituted with a small amount of Fe2O3 or SiO2, etc., and a part of CaSO4 may be substituted with Ca(OH)2 or CaCO3, etc. In the present invention, in the above chemical formula xCaO·yAl2O3·zCaSO4·mH2O, z cannot be set to 0 because of the viewpoint of fluidity retention and the possibility that the strength during hardening may decrease due to phase transition.

[0027] When calcium sulfoaluminate is contained in the additive composition, it is preferably contained in an amount of 4.5 to 65.0% by mass, more preferably 15.0 to 60.0% by mass, and even more preferably 30.0 to 50.0% by mass in the additive composition excluding the amorphous aluminosilicate powder. By the calcium sulfoaluminate content being within the above range, cracking of the produced hardened body can be prevented, and the long-term strength can be improved.

[0028] Also, in this embodiment, it is preferable that the additive composition contains both calcium sulfoaluminate and an inorganic calcium compound. By the additive composition containing both calcium sulfoaluminate and an inorganic calcium compound, the initial strength and long-term strength of the produced hardened body can be improved.

[0029] (Amorphous aluminosilicate powder) The additive composition of the present embodiment can contain amorphous aluminosilicate powder. By including amorphous aluminosilicate powder in the additive composition, the initial strength and long-term strength of the produced hardened body can be improved. As the amorphous aluminosilicate powder, the above-described amorphous aluminosilicate powder can be used. When the amorphous aluminosilicate powder is included in the additive composition, the content is preferably 100 to 2000 parts by mass, more preferably 500 to 2000 parts by mass, still more preferably 700 to 1800 parts by mass, and even more preferably 900 to 1600 parts by mass with respect to 100 parts by mass of the additive composition excluding the amorphous aluminosilicate powder.

[0030] [Cement composition] The cement composition of the present invention includes cement, amorphous aluminosilicate powder having a BET specific surface area of 1.0 m 2 / g or more, and the above additive composition. Further, when the additive composition contains amorphous aluminosilicate powder, it may not contain amorphous aluminosilicate powder separately from the additive composition.

[0031] As the additive composition contained in the cement composition of the present invention, the above additive composition can be used.

[0032] The cement contained in the cement composition of the present invention is not particularly limited, and various Portland cements such as ordinary, early strength, ultra-early strength, low heat, and moderate heat Portland cements, and various blended cements obtained by mixing blast furnace slag, fly ash, silica fume, etc. with these Portland cements, environmentally friendly cements (eco-cements) manufactured using municipal solid waste incineration ash and sewage sludge incineration ash as raw materials, commercially available fine particle cements, white cements, etc. may be mentioned, and it is also possible to use various cements in a finely powdered form. Further, those obtained by adjusting the amount of components (for example, gypsum, etc.) usually used in cement can also be used. Furthermore, those obtained by combining two or more of these can also be used. From the viewpoint of improving the initial strength and long-term strength, it is preferable to select ordinary Portland cement or early strength Portland cement.

[0033] From the viewpoint of manufacturing cost and strength development property, the Blaine specific surface area of the cement is preferably 2,500 cm 2 / g to 7,000 cm 2 / g, more preferably 2,750 cm 2 / g to 6,000 cm 2 / g, and even more preferably 3,000 cm 2 / g to 4,500 cm 2 / g. In the present invention, the Blaine specific surface area is determined in accordance with JIS R 5201:2015 (Physical test methods for cement).

[0034] Further, in the cement composition of the present invention, a part of the cement can be made into an amorphous aluminosilicate powder having a BET specific surface area of 1.0 m 2 / g or more. The addition amount of the amorphous aluminosilicate powder is preferably added so as to be 5 to 90 parts by mass, more preferably 7.5 to 70 parts by mass, and even more preferably 10 to 60 parts by mass with respect to 100 parts by mass of the above cement.

[0035] By adding amorphous aluminosilicate powder instead of cement, the amount of cement can be reduced, and the amount of CO2 emissions due to the decarbonation reaction of limestone (CaCO3 → CaO + CO2) can be suppressed. As the amorphous aluminosilicate powder, the above-described amorphous aluminosilicate powder can be used, and in particular, it is preferable to use metakaolin. Metakaolin is obtained by firing kaolin, but since kaolin can be fired at a temperature lower than the temperature at which cement is fired, the amount of CO2 generated can be suppressed. Furthermore, since metakaolin is produced when iron is purified (produced), CO2 is not generated as in the case of firing cement, and CO2 emissions can be suppressed.

[0036] When the additive composition contained in the cement composition does not contain amorphous aluminosilicate powder, it is preferably contained in an amount of 5 to 100 parts by mass, more preferably 7.5 to 90 parts by mass, and even more preferably 10 to 85 parts by mass with respect to 100 parts by mass of the amorphous aluminosilicate powder. When the additive composition contains amorphous aluminosilicate powder, the additive composition is preferably contained in an amount of 35 to 65 parts by mass, more preferably 40 to 60 parts by mass, and even more preferably 45 to 55 parts by mass with respect to 100 parts by mass of cement. At this time, it is preferable to contain the additive composition so that the content of calcium organic acid in the additive composition is 0.3 to 8.0 parts by mass with respect to 100 parts by mass of cement. When the content of the additive composition in the cement composition is within the above range, the initial strength and long-term strength of the hardened hardened body can be improved.

[0037] The cement composition preferably further contains a water reducing agent. The water reducing agent is not particularly limited, and examples thereof include naphthalene-based water reducing agents, melamine-based water reducing agents, amino sulfonic acid-based water reducing agents, and polycarboxylic acid-based water reducing agents. In the present invention, one or more of these water reducing agents can be used.

[0038] The content of the water reducing agent is preferably 0.1 to 5.0% by mass, more preferably 0.3 to 4.0% by mass, and even more preferably 0.5 to 3.0% by mass based on the total mass of the cement, the amorphous aluminosilicate powder, and the additive composition.

[0039] In addition, the cement composition of the present invention can contain an alkali metal carbonate. By containing an alkali metal carbonate in the cement composition, it is easy to improve the initial strength development property and the long-term strength development property. Examples of the alkali metal carbonate include sodium carbonate, potassium carbonate, lithium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, lithium hydrogen carbonate, etc., and it is also possible to combine these.

[0040] The content ratio of the alkali metal carbonate is preferably 1 to 6 parts by mass in terms of solid content, more preferably 2 to 5 parts by mass, based on 100 parts by mass in total of the cement and the amorphous aluminosilicate powder in the cement composition. By the content ratio of the alkali metal carbonate being within the above range, it is easy to improve the initial strength development property and the long-term strength development property.

[0041] The cement composition of the present invention can contain a siliceous fine powder. By containing a siliceous fine powder in the cement composition, it is easy to improve the initial strength development property and the long-term strength development property. Examples of the siliceous fine powder include latent hydraulic substances such as granulated blast furnace slag fine powder, pozzolanic substances such as fly ash and silica fume. Among them, from the viewpoints of initial strength development property and long-term strength development property, it is preferable to use silica fume.

[0042] The fineness of the siliceous fine powder is not particularly limited, but usually, granulated blast furnace slag powder and fly ash are in the range of 3,000 to 9,000 cm 2 / g in terms of Blaine specific surface area, and silica fume is in the range of 20,000 to 300,000 cm 2 / g in terms of BET specific surface area.

[0043] The content ratio of the silica fine powder is preferably 1 to 20 parts by mass, more preferably 2 to 15 parts by mass, and even more preferably 3 to 12 parts by mass with respect to a total of 100 parts by mass of the cement and the amorphous aluminosilicate powder in the cement composition. When the content ratio of the silica fine powder is at least the above lower limit value, it is easy to improve the initial strength development property and the long-term strength development property. Furthermore, when the content ratio of the silica fine powder is at most the above upper limit value, it is easy to improve the initial strength development property and the long-term strength development property.

[0044] The cement composition can also contain an antifoaming agent as long as it does not adversely affect the performance. The antifoaming agent is used for the purpose of suppressing the amount of air entrained during mixing. The type of the antifoaming agent is not particularly limited as long as it does not significantly adversely affect the strength characteristics of the hardened body, and either a liquid or a powder can be used. For example, polyether-based antifoaming agents, polyhydric alcohol-based antifoaming agents such as esterified products of polyhydric alcohols and alkyl ethers, alkyl phosphate-based antifoaming agents, silicone-based antifoaming agents, and the like can be mentioned.

[0045] The content ratio of the antifoaming agent is preferably 0.002 to 0.5 parts by mass, more preferably 0.005 to 0.45 parts by mass, and even more preferably 0.01 to 0.4 parts by mass with respect to a total of 100 parts by mass of the cement and the amorphous aluminosilicate powder in the cement composition. When the content ratio of the antifoaming agent is at least the above lower limit value, the defoaming effect can be sufficiently exhibited. Also, when the content ratio of the antifoaming agent is at most the above upper limit value, it is easy to improve the fluidity retention property.

[0046] In addition, the cement composition can use one or more of a gas foaming substance, an AE agent, a rust preventive agent, a water repellent, an antibacterial agent, a coloring agent, an antifreeze agent, fine limestone powder, fine granulated blast furnace slag, incineration ash of sewage sludge and its molten slag, incineration ash of municipal waste and its molten slag, and incineration ash of pulp sludge, a thickening agent, and a shrinkage reducing agent, a polymer, and an anion exchanger such as hydrotalcite, etc. within a range that does not substantially inhibit the object of the present invention.

[0047] [Hardened body] The hardened body according to this embodiment is obtained by hardening a cement composition. Usually, when the cement composition and water are kneaded, the cement, which is a hydraulic material, undergoes a hydration reaction and hardens. The amount of water for kneading is not particularly limited, but it is preferably 10 to 70 parts by mass, more preferably 14 to 65 parts by mass, and even more preferably 16 to 60 parts by mass with respect to 100 parts by mass of the cement composition. When the amount of water for kneading is within the above range, it is easy to improve the initial strength development property of the hydraulic material.

[0048] The hardened body is obtained by hardening after kneading the cement composition and water and then allowing it to stand. However, after kneading, it can be more efficiently obtained by filling (casting) it into a mold, curing it, or directly pouring it, spraying it, or applying it to the construction site.

[0049] [Manufacturing method of hardened body] The manufacturing method of the hardened body according to this embodiment is a method of hardening a cement composition containing an additive composition, cement, water, and amorphous aluminosilicate powder by steam curing at a maximum temperature of 40 to 80°C for 2 to 8 hours. When the additive composition contains amorphous aluminosilicate powder, it is not necessary to add the amorphous aluminosilicate powder separately. The manufacturing method of the hardened body preferably includes, in this order, a kneading step of kneading the additive composition, cement, amorphous aluminosilicate powder, and water, a casting step of filling the kneaded cement composition into a mold, and a curing step of curing the cement composition filled in the mold.

[0050] The kneading method in the kneading step is not particularly limited, and each material may be mixed during construction, or a part or all of them may be mixed in advance. As the mixing device, any existing device, for example, a tilting drum mixer, an omnimixer, a Henschel mixer, a V-type mixer, a Proshear mixer, and a Nauta mixer can be used.

[0051] The placing method in the placing process can be carried out by a known method. The temperature of the cement composition during placing is preferably 0 to 50 °C, more preferably 10 to 40 °C. When the temperature of the cement composition during placing is within the above range, it is easier to enable early demolding of the hardened body.

[0052] The method for manufacturing the hardened body preferably further includes a compaction process after the placing process. As the compaction method, a known method can be used, but from the viewpoint of workability, it is preferable to use a vibrator.

[0053] As the curing method used in the curing process, from the viewpoint of productivity improvement, it is preferable to use steam curing using a curing chamber, a heating sheet, etc. Steam curing usually raises the atmosphere around the object and cures while maintaining a certain temperature while maintaining an appropriate humidity. As the conditions for steam curing, the maximum temperature is preferably 40 to 80 °C, the curing time is preferably 2 to 8 hours, more preferably the maximum temperature is 40 to 75 °C, the curing time is 2.5 to 7.5 hours, and further preferably the maximum temperature is 45 to 60 °C, and the curing time is 3 to 7 hours. When steam curing is carried out with the maximum temperature of the atmosphere around the cement composition during steam curing within the above range and the curing time within the above range, the initial strength and long-term strength of the hardened body are likely to be improved.

[0054] The relative humidity around the cement composition during steam curing is preferably 50%RH or more, more preferably 75%RH or more, and further preferably 90%RH or more. The upper limit is not limited, but it may be 100%RH. When the relative humidity around the cement composition during steam curing is within the above range, the initial strength and long-term strength of the hardened body are likely to be improved.

[0055] The curing process preferably includes a pre-curing process. As the conditions for pre-curing, it is preferable to maintain the temperature at a constant level for about 1 to 3 hours at a temperature of 10 to 50 °C. By including the pre-curing process in the curing process, the temperature inside the placed cement composition can be made uniform, and it is easy to prevent temperature cracks due to the temperature difference between the inside and the outside.

[0056] The curing process preferably includes a heating process. As the heating method, known methods can be used, and it is preferable to heat at a temperature rising rate of 10 to 30 °C / hour, more preferably at a temperature rising rate of 12 to 28 °C / hour, and even more preferably at a temperature rising rate of 15 to 25 °C. When the temperature rising rate in the heating process is within the above range, it is possible to further promote curing while preventing temperature cracking due to a rapid temperature rise of the cement composition.

[0057] The curing process preferably includes a temperature holding process. As the temperature holding method, known methods can be used, and preferably, a constant temperature is maintained in the range of 40 to 80 °C for 1 to 8 hours, more preferably in the range of 40 to 75 °C for 1 to 6 hours, and even more preferably in the range of 45 to 65 °C for 2.5 to 5 hours. By maintaining a constant temperature within the above numerical range in the temperature holding process, the placed cement composition can be uniformly cured, and the initial strength and long-term strength of the cured body are likely to be improved.

[0058] The method for manufacturing a cured body preferably includes a natural cooling process after the curing process. In the natural cooling process, the cured body obtained by the curing process is naturally cooled in a normal temperature atmosphere. The cooling time is not particularly limited, but it is sufficient if the cured body can be cooled to a temperature at which it can be easily demolded, and about 0.5 to 2 hours is sufficient. By including the natural cooling process after the curing process, temperature cracking of the cured body can be prevented.

Example

[0059] Hereinafter, the present invention will be described in more detail using examples and comparative examples. However, the present invention is not limited to the following examples and comparative examples as long as it does not depart from the gist thereof.

[0060] <Experimental Example 1> Using calcium formate, gypsum, and sodium sulfate, an additive composition having the composition shown in Table 1 was prepared by mixing with a tilted barrel mixer. Using the prepared additive composition, cement, sand, water reducer, water, and metakaolin or allophane as a cement substitute, a cement composition was prepared at the blending amounts shown in Table 1 (Test Nos. 1-1 to 6). Further, as comparative examples, a cement composition without substituting cement with metakaolin or allophane and without the additive composition (Test No. 1-7) and a cement composition without the additive composition (Test Nos. 1-8, 9) were prepared. Metakaolin and allophane having the BET specific surface areas shown in Table 1 were used. The obtained cement composition was cured in a mold at a temperature of 20°C until the age of 1 day, and after demolding, it was cured in water at a temperature of 20°C until the age of 28 days to produce a cement hardened body. For each of the obtained cement hardened bodies, the compressive strength after 1 day, 7 days, and 28 days of age was measured. The results are shown in Table 1.

[0061] (Materials Used) Calcium formate: Reagent Metakaolin: Manufactured by Imerys (Degree of amorphism: 90% or more) Allophane: Produced in Tochigi Prefecture (Degree of amorphism: 90% or more) Gypsum: Anhydrous, reagent Sodium sulfate: Anhydrous, reagent Cement: Ordinary Portland cement (commercial product) Sand: JIS standard sand Water reducer: Polycarboxylic acid (commercial product) Water: Tap water

[0062] (Measurement Items) Compressive strength: In accordance with the method specified in JIS R 5201; 2015 "Physical Test Methods for Cement", the compressive strength was measured.

[0063]

Table 1

[0064] From the results shown in Table 1, the cement hardened bodies (Test Nos. 1-2, 3, 5, 6) containing calcium formate in the additive composition and substituted with metakaolin or allophane having a BET specific surface area within the scope of the present invention showed high compressive strength both initially (after 1 and 7 days) and in the long term (after 28 days). The cement hardened bodies substituted with metakaolin or allophane not having a BET specific surface area within the scope of the present invention (Test Nos. 1-1, 4), and the cement hardened bodies using an additive composition not containing calcium formate (Test Nos. 1-7 to 9) had lower values for both initial strength and long-term strength compared with the examples.

[0065] <Experimental Example 2> The additive composition and the cement composition were adjusted in the same manner as in Experimental Example 1 so as to have the compositions shown in Table 2. Metakaolin and allophane having the BET specific surface areas shown in Table 2 were used. The obtained cement composition was molded using a mold, pre-cured in the mold at a temperature of 20°C for 1.5 hours, heated at a rate of 20°C / hour, held at a maximum temperature of 50°C for 3 hours, and then naturally cooled to room temperature (20°C) to perform steam curing. Thereafter, the mold was removed, and sealed curing was carried out until the age of 28 days. For each of the obtained cement hardened bodies, the compressive strength was measured immediately after the completion of steam curing (age of 6 hours), after 7 days, and after 28 days. The results are shown in Table 2.

[0066]

Table 2

[0067] As shown in Table 2, the cement hardened bodies (Test Nos. 2-2, 3, 5, 6) containing calcium formate in the additive composition and substituted with metakaolin or allophane having a BET specific surface area within the scope of the present invention showed high compressive strength both initially (after 6 hours and 7 days) and in the long term (after 28 days). Also, it was confirmed that high compressive strength could be obtained by performing steam curing as compared with Experimental Example 1. The cement hardened bodies (Test Nos. 2-1 and 4) substituted with metakaolin or allophane whose BET specific surface area is not within the scope of the present invention had lower values for both the initial strength and the long-term strength compared with the examples. Also, the cement hardened bodies (Test Nos. 2-7 to 9) using an additive composition not containing calcium formate showed low values, particularly in the initial strength, compared with the examples.

[0068] <Experimental Example 3> An additive composition was prepared by mixing calcium formate, gypsum, mirabilite, calcium sulfoaluminate, calcium hydroxide, calcium carbonate, and calcium oxide using a tilted drum mixer. Using the prepared additive composition, cement, sand, water reducing agent, water, and metakaolin as a cement substitute, a cement composition was prepared at the blending amounts shown in Table 3 (Test Nos. 3-1 to 6). The metakaolin having the BET specific surface area shown in Table 3 was used.

[0069] The obtained cement composition was used to produce a cement hardened body in the same manner as in Experimental Example 1. For the obtained cement hardened body, the compressive strength after 1 day, 7 days, and 28 days of age was measured. The results are shown in Table 3.

[0070] (Materials Used) Calcium sulfoaluminate: Prototype, Blaine specific surface area 3,500 cm 2 / g (Using reagent grade calcium carbonate, calcium sulfate dihydrate, and aluminum hydroxide, mixed at a molar ratio of CaO:CaSO4:Al2O3 of 4:3:1, fired at 1,400 °C for 2 hours, left to cool to room temperature, and ground until the Blaine specific surface area reached 3,500 cm 2 / g.) Calcium hydroxide: Reagent Calcium carbonate: Reagent Calcium oxide: Reagent For the other materials, the same materials as in Experimental Example 1 were used.

[0071]

Table 3

[0072] As shown in Table 3, by containing calcium sulfoaluminate or an inorganic calcium compound in the additive composition, high compressive strength was shown either at the initial stage (after 1 and 7 days), or in the long term (after 28 days), or both, compared to Test Nos. 1-3 that did not contain any of them.

[0073] <Experimental Example 4> Using calcium formate, gypsum, and mirabilite, the additive composition was prepared by mixing with a tilted drum mixer. Using the prepared additive composition, a cement composition was prepared with cement, limestone fine powder, sand, water reducing agent, water, and metakaolin as a cement substitute (Test Nos. 4-1 to 5). Similarly, a cement composition without the additive composition (Test No. 4-6) and a cement composition containing anhydrous gypsum instead of the additive composition (Test No. 4-7) were prepared. The blending amounts of each material are shown in Table 4. Metakaolin with the BET specific surface area shown in Table 4 was used.

[0074] The obtained cement composition was used to produce a cement hardened body in the same manner as in Experimental Example 1. For the obtained cement hardened body, the compressive strength after 1 day, 7 days, and 28 days of age was measured. The results are shown in Table 3.

[0075] (Materials Used) Anhydrous gypsum: reagent Limestone fine powder: reagent For the other materials, the same materials as in Experimental Example 1 and Experimental Example 2 were used.

[0076]

Table 4

[0077] From the results shown in Table 4, even when metakaolin is used as a cement substitute, the cement hardened bodies (Test Nos. 4-2 to 5) using metakaolin with a BET specific surface area within the scope of the present invention and an additive composition containing calcium formate exhibited high compressive strength in the initial stage (after 1 and 7 days) and the long term (after 28 days). The cement hardened body (Test No. 4-1) substituted with metakaolin whose BET specific surface area is not within the scope of the present invention, and the cement hardened body (Test Nos. 4-6 and 7) using an additive composition not containing calcium formate had lower values for both the initial strength and the long term strength compared to the examples.

Industrial Applicability

[0078] The calcium organic acid of the present invention can improve the initial strength and the long term strength of the hardened body produced by being used together with an amorphous aluminosilicate powder, and thus can be effectively used in the civil engineering and construction industries.

Claims

1. An organic acid calcium used together with a curable composition containing an amorphous aluminosilicate powder having a BET specific surface area of 1.0 m ２ / g or more.

2. The calcium organic acid according to claim 1, wherein the amorphous aluminosilicate contains at least one of metakaolin and allophane.

3. An additive composition comprising the calcium organic acid according to claim 1 or 2 and an inorganic sulfate.

4. The additive composition according to claim 3, wherein the inorganic sulfate contains at least one selected from gypsum, mirabilite, aluminum sulfate, sodium thiosulfate, and potassium alum.

5. The additive composition according to claim 3, further containing at least one of an expansive agent and an inorganic calcium compound.

6. Furthermore, the additive composition according to claim 3, comprising an amorphous aluminosilicate powder having a BET specific surface area of 1.0 m ２ / g or more.

7. Cement, an amorphous aluminosilicate powder having a BET specific surface area of 1.0 m ２ / g or more, and the additive composition according to claim 3, a cement composition comprising the same.

8. The cement composition according to claim 7, wherein the amount of the amorphous aluminosilicate powder is 5 to 90 parts by mass with respect to 100 parts by mass of the cement.

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