Organic calcium acid, additive composition, and cement composition

Abstract

The purpose of the present invention is to provide an organic calcium acid that, when used with an amorphous aluminosilicate powder, is capable of improving initial strength and long-term strength. The organic calcium acid is used with a curable composition containing amorphous aluminosilicate powder having a BET specific surface area of 1.0 m2 / g or greater. The amorphous aluminosilicate preferably contains at least one of metakaolin and allophane.

Description

Organic acid calcium, additive composition, and cement composition

[0001] The present invention relates to an organic acid calcium, an additive composition, and a cement composition that are mainly used in the civil engineering and construction industries.

[0002] Concrete uses a large amount of cement as a raw material, so CO ２ This is mainly due to the large amount of fossil fuels used to generate combustion energy in the furnace during the cement production process, as well as the decarbonation reaction of limestone (CaCO ３ →CaO+CO ２ ) is generated. ２ Reducing emissions has become an important theme as part of measures to combat global warming.

[0003] CO emitted during the production of concrete products ２ In order to reduce the total amount of cement used, it is effective to reduce the amount of cement used by incorporating large amounts of industrial by-products (ground granulated blast furnace slag, fly ash, etc.) as cement substitutes, and various research projects are being conducted on this.

[0004] On the other hand, hydraulic materials such as cement are usually mixed with water and allowed to stand for a predetermined time to harden. The hardening speed of hydraulic materials can be affected by the ratio of the material to water, the ambient temperature, and the curing method, but the time required for the hydraulic material to harden 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 predetermined amounts of inorganic sulfate, calcium sulfoaluminate, and inorganic hydroxide. Patent Document 2 describes a hardening accelerator for hydraulic materials having a Blaine specific surface area of ​​4000 cm ２ The document describes a cement admixture containing calcium sulfoaluminate in an amount of 1 / g or more and one or more salts selected from the group consisting of formates, acetates and lactates.

[0006] JP 2014-19618 A JP 2010-235399 A

[0007] In recent years, when a hardening accelerator is used, it is desired to further improve the early strength and long-term strength. ２ It is desirable to reduce the amount of carbon dioxide emitted, and even when a cement substitute material is used, it is desirable that the material have high early strength and long-term strength.

[0008] The present invention has been made in view of the above circumstances, and aims to provide an organic acid calcium salt that can improve the initial strength and long-term strength of a hardened body produced by using it together with an amorphous aluminosilicate powder, an additive composition containing the organic acid calcium salt, and a cement composition containing the additive composition.

[0009] The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result have found that the problems can be solved by using an organic acid calcium compound together with a curable composition containing an amorphous aluminosilicate powder having a predetermined BET specific surface area, thereby completing the present invention. That is, the present invention is as follows: [1] A BET specific surface area of ​​1.0 m ２

[0013] An organic acid calcium used together with a hardenable composition containing an amorphous aluminosilicate powder having a specific surface area of ​​1.0 m / 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 comprising 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, sodium sulfate, aluminum sulfate, sodium thiosulfate, and potassium alum. [5] The additive composition according to [3] or [4], further containing at least one of an expanding agent and an inorganic calcium compound. [6] The additive composition according to [3] or [4], further containing at least one of an expanding agent and an inorganic calcium compound. [7] The additive composition according to [6], wherein the BET specific surface area is 1.0 m ２ [7] The additive composition according to any one of [3] to [5], which contains an amorphous aluminosilicate powder having a BET specific surface area of ​​1.0 m / g or more. ２[8] A cement composition comprising an amorphous aluminosilicate powder having a solubility of 10 ...

[0010] According to the present invention, it is possible to provide an organic acid calcium salt that can improve the initial strength and long-term strength of a hardened product produced by using it together with an amorphous aluminosilicate powder, an additive composition containing the organic acid calcium salt, and a cement composition containing the additive composition.

[0011] The organic acid calcium, additive composition, and cement composition of the present invention will be described in detail below, but the present invention is not limited to these embodiments. In this specification, "%" and "parts" are based on mass unless otherwise specified. Furthermore, a numerical range defined using the symbol "to" includes both the upper and lower limits of the range.

[0012] [Organic Acid Calcium] The organic acid calcium of the present invention has a BET specific surface area of ​​1.0 m ２ / g or more of an amorphous aluminosilicate powder (hereinafter simply referred to as "amorphous aluminosilicate powder"). As such organic acid calcium, for example, calcium formate, calcium acetate, calcium lactate, etc. can be used, and one or more of them can be used. In this embodiment, from the viewpoint of early strength development and long-term strength development, it is preferable to use calcium formate and / or calcium acetate, and it is more preferable to use calcium formate.

[0013] The organic acid calcium of the present invention is preferably in powder form. It is preferable that 95% or more of the organic acid calcium powder passes through a sieve with a mesh size of 0.6 mm. By making the organic acid calcium powder such that 95% or more of the organic acid calcium passes through a sieve with a mesh size of 0.6 mm, the fluidity of the curable composition used together can be maintained, and the early strength development can be improved.

[0014] When the organic acid calcium of the present invention is used together with an amorphous aluminosilicate powder, the amorphous aluminosilicate powder may be contained in an additive composition described below, or in a cement composition, or may be contained in both.

[0015] (Hardenable Composition) The hardenable composition used together with the organic acid calcium salt of the present invention has a BET specific surface area of ​​1.0 m ２ The amorphous aluminosilicate powder has a BET specific surface area of ​​5.0 m / g or more. ２ / g or more, and 10.0m ２ It is more preferable that the BET specific surface area is 1.0 m / g or more. ２ By using a curable composition containing an amorphous aluminosilicate powder in an amount of 1 / 2 g or more, the initial strength and long-term strength of the produced cured body 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 not particularly limited as long as it is an aluminosilicate derived from a clay mineral and contains an amorphous portion, and any can be used. Examples of clay minerals as raw materials include (1) kaolin minerals, (2) mica clay minerals, (3) smectite minerals, and mixed-layer minerals formed by mixing these. Amorphous aluminosilicates can be obtained by amorphizing these crystalline aluminosilicates, for example, by calcining and dehydrating them. As amorphous aluminosilicates, those derived from kaolin minerals such as kaolinite, halloysite, and dickite are preferred from the viewpoint of even better reactivity, and metakaolin obtained by calcining kaolinite is more preferred. Furthermore, allophane can be used as the amorphous aluminosilicate. Allophane (Al ２ O ３ (1-2) SiO ２ ・5H ２O) is an amorphous clay mineral. The amorphous aluminosilicate may be used alone or in combination of two or more.

[0018] As used herein, "amorphous" refers to a state in which peaks derived from the raw clay mineral are almost completely absent when measured using a powder X-ray diffractometer. The amorphous aluminosilicate powder according to this embodiment may have an amorphous content of 70% by mass or more, preferably 90% by mass or more, and more preferably 100% by mass, i.e., most preferably no peaks are observed when measured using a powder X-ray diffractometer. Here, the amorphous content is a value determined by the standard addition method. Aluminosilicates with a high amorphous content, i.e., aluminosilicates with a low crystalline content, tend to exhibit better strength development at the same mixing amount than aluminosilicates with a low amorphous content. Examples of heating methods for amorphizing aluminosilicate include firing using an externally heated kiln, an internally heated kiln, an electric furnace, etc., and melting using a melting furnace.

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

[0020] [Additive Composition] The additive composition of the present embodiment contains the organic acid calcium and an inorganic sulfate.

[0021] (Organic Calcium Acid) The organic calcium acid contained in the additive composition of this embodiment can be any of the above-described organic calcium acids. The content of the organic calcium acid in the additive composition, excluding the amorphous aluminosilicate powder, is preferably 20 to 80 mass %, more preferably 30 to 70 mass %, and even more preferably 40 to 65 mass %. By using the organic calcium acid in the above-described range together with the amorphous aluminosilicate powder, the initial strength and long-term strength of the produced hardened body can be improved.

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

[0023] The inorganic sulfate is preferably contained in an amount of 0.5 to 75.0 mass %, more preferably 1.0 to 65.0 mass %, and even more preferably 3.0 to 50.0 mass %, in the additive composition excluding the amorphous aluminosilicate powder. By containing the inorganic sulfate in the above range, it is possible to improve the initial strength and long-term strength.

[0024] (Inorganic calcium compound) The additive composition of the present embodiment may further contain an inorganic calcium compound. Examples of the inorganic calcium compound that can be used include calcium hydroxide, calcium carbonate, and calcium oxide. From the viewpoints of early strength and long-term strength development, it is preferable to use calcium hydroxide and / or calcium oxide.

[0025] When the additive composition contains an inorganic calcium compound, the content of the inorganic calcium compound in the additive composition excluding the amorphous aluminosilicate powder is preferably 15.0 to 70.0 mass%, more preferably 18.0 to 60.0 mass%, and even more preferably 20.0 to 40.0 mass%. By having the content of the inorganic calcium compound 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 the present embodiment may further contain calcium sulfoaluminate as an expanding agent. Calcium sulfoaluminate has the chemical formula xCaO.yAl ２ O ３ zCaSO ４ ・mH ２ O (x, y, z are non-zero positive real numbers, m is 0 or a positive real number), and is a general term for hydraulic substances and hydrated salts. For example, hauyne (3CaO.3Al ２ O ３ CaSO ４ ), as well as ettringite (3CaO·Al ２ O ３ 3CaSO ４ ・32H ２ O), AFt phase, represented by monosulfate (3CaO.Al ２ O ３ CaSO ４ ・12H ２ Calcium sulfoaluminate may be amorphous. ２ O ３ A small amount of Fe is included in part of ２ O ３ or SiO ２ etc., and CaSO ４ Part of Ca(OH) ２ or CaCO ３ In the present invention, the above chemical formula xCaO.yAl may be substituted. ２ O ３ zCaSO ４ ・mH ２In O, z cannot be 0 from the viewpoint of fluidity retention and because there is a risk of strength decreasing during curing due to phase transition.

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

[0028] In this embodiment, the additive composition preferably contains both calcium sulfoaluminate and an inorganic calcium compound, which can improve the initial strength and long-term strength of the resulting hardened body.

[0029] (Amorphous aluminosilicate powder) The additive composition of this embodiment may contain an amorphous aluminosilicate powder. By including the 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 amorphous aluminosilicate powder described above 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, even more preferably 700 to 1800 parts by mass, and even more preferably 900 to 1600 parts by mass, per 100 parts by mass of the additive composition excluding the amorphous aluminosilicate powder.

[0030] [Cement Composition] The cement composition of the present invention comprises cement and a cement having a BET specific surface area of ​​1.0 m ２ / g or more of amorphous aluminosilicate powder, and the additive composition. When the additive composition contains the amorphous aluminosilicate powder, it is not necessary to contain the amorphous aluminosilicate powder separately from the additive composition.

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

[0032] The cement contained in the cement composition of the present invention is not particularly limited, and examples thereof include various Portland cements such as normal, high-early-strength, ultra-high-early-strength, low-heat, and medium-heat; various mixed cements obtained by mixing these Portland cements with blast furnace slag, fly ash, silica fume, etc.; environmentally friendly cements (ecocements) produced using municipal waste incineration ash or sewage sludge incineration ash as raw materials; commercially available fine particle cements; and white cements. Various cements can also be finely powdered and used. Furthermore, cements prepared by increasing or decreasing the amount of components (e.g., gypsum) normally used in cements can also be used. Furthermore, combinations of two or more of these can also be used. From the viewpoint of improving early strength and long-term strength, it is preferable to select normal Portland cement or high-early-strength Portland cement.

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

[0034] In addition, the cement composition of the present invention is prepared by mixing a part of the cement with a BET specific surface area of ​​1.0 m ２ The amount of amorphous aluminosilicate powder added is preferably 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, relative to 100 parts by mass of the cement.

[0035] By adding amorphous aluminosilicate powder instead of cement, the amount of cement can be reduced, and the decarbonation reaction of limestone (CaCO ３ →CaO+CO ２ ) by CO ２ As the amorphous aluminosilicate powder, the above-mentioned amorphous aluminosilicate powder can be used, and it is particularly preferable to use metakaolin. Metakaolin can be obtained by firing kaolin, and since kaolin can be fired at a temperature lower than the temperature at which cement is fired, CO ２ Furthermore, metakaolin is produced during the refining (production) of iron, so it does not generate CO2, as occurs when burning cement. ２ No CO is generated. ２ can reduce emissions.

[0036] When the additive composition does not contain an amorphous aluminosilicate powder, the content of the additive composition contained in the cement composition is preferably 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, per 100 parts by mass of the amorphous aluminosilicate powder. When the additive composition contains an amorphous aluminosilicate powder, the content of the additive composition is preferably 35 to 65 parts by mass, more preferably 40 to 60 parts by mass, and even more preferably 45 to 55 parts by mass, per 100 parts by mass of cement. In this case, the additive composition is preferably contained so that the content of organic acid calcium in the additive composition is 0.3 to 8.0 parts by mass per 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 body can be improved.

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

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

[0039] The cement composition of the present invention can also contain an alkali metal carbonate. When the cement composition contains an alkali metal carbonate, it is easy to improve the early strength development and long-term strength development. Examples of the alkali metal carbonate include sodium carbonate, potassium carbonate, lithium carbonate, sodium bicarbonate, potassium bicarbonate, and lithium bicarbonate, and these can also be combined.

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

[0041] The cement composition of the present invention can contain a siliceous fine powder. When the cement composition contains a siliceous fine powder, it is easy to improve the early strength development and long-term strength development. Examples of the siliceous fine powder include latent hydraulic substances such as ground granulated blast furnace slag, fly ash, and pozzolanic substances such as silica fume. Among these, it is preferable to use silica fume from the viewpoint of early strength development and long-term strength development.

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

[0043] The content of the siliceous 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, per 100 parts by mass of the total of the cement and amorphous aluminosilicate powder in the cement composition. When the content of the siliceous fine powder is equal to or greater than the above-mentioned lower limit, it is easy to improve the early strength development and long-term strength development. Furthermore, when the content of the siliceous fine powder is equal to or less than the above-mentioned upper limit, it is easy to improve the early strength development and long-term strength development.

[0044] The cement composition may contain an antifoaming agent to the extent that it does not adversely affect performance. Antifoaming agents are used to reduce the amount of air entrained during mixing. The type of antifoaming agent is not particularly limited as long as it does not significantly adversely affect the strength properties of the hardened body, and both liquid and powder forms can be used. Examples include polyether-based antifoaming agents, polyhydric alcohol-based antifoaming agents such as polyhydric alcohol esters and alkyl ethers, alkyl phosphate-based antifoaming agents, and silicone-based antifoaming agents.

[0045] The content 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, relative to 100 parts by mass of the total of the cement and amorphous aluminosilicate powder in the cement composition. When the content of the antifoaming agent is equal to or greater than the above-mentioned lower limit, the antifoaming effect can be fully exerted. Furthermore, when the content of the antifoaming agent is equal to or less than the above-mentioned upper limit, the fluidity retention can be easily improved.

[0046] Furthermore, the cement composition may contain one or more of the following additives, within a range that does not adversely affect performance: gas foaming substances, air-entraining agents, rust inhibitors, water repellents, antibacterial agents, colorants, antifreeze agents, admixtures such as fine limestone powder, slowly cooled blast furnace slag powder, sewage sludge incineration ash and its molten slag, municipal waste incineration ash and its molten slag, and pulp sludge incineration ash; thickeners; shrinkage-reducing agents; polymers; and anion exchangers such as hydrotalcite.

[0047] [Hardened product] The hardened product according to this embodiment is obtained by hardening a cement composition. The hardened product is usually produced by kneading the cement composition with water, causing the cement, which is a hydraulic material, to undergo a hydration reaction and harden. The amount of water used for mixing is not particularly limited, but 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, per 100 parts by mass of the cement composition. When the amount of water used for mixing is within the above range, it is easy to improve the initial strength development of the hydraulic material.

[0048] The hardened product is obtained by mixing the cement composition with water and then leaving it to harden, but it can also be obtained more efficiently by filling (casting) the mixture into a formwork after mixing and curing it, or by pouring it directly into the application area, or by spraying or painting it on.

[0049] [Method for Producing Hardened Body] The method for producing a hardened body according to this embodiment is a method in which a cement composition containing an additive composition, cement, water, and amorphous aluminosilicate powder is hardened by steam curing at a maximum temperature of 40 to 80°C for 2 to 8 hours. Note that when the additive composition contains amorphous aluminosilicate powder, it is not necessary to add the amorphous aluminosilicate powder separately. The method for producing a 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 a formwork with the mixed cement composition; and a curing step of curing the cement composition filled in the formwork.

[0050] The mixing method in the mixing step is not particularly limited, and the materials may be mixed at the time of construction, or some or all of them may be mixed in advance. As a mixing device, any existing device such as a tilting mixer, an omni mixer, a Henschel mixer, a V-type mixer, a Plosser mixer, or a Nauta mixer can be used.

[0051] The casting method in the casting step can be performed by a known method. The temperature of the cement composition during casting is preferably 0 to 50°C, more preferably 10 to 40°C. When the temperature of the cement composition during casting is within the above range, it becomes easier to quickly demold the hardened body.

[0052] The method for producing the hardened body preferably further includes a compaction step after the casting step. Although a known method can be used for the compaction, it is preferable to use a vibrator from the viewpoint of workability.

[0053] From the viewpoint of improving productivity, steam curing using a curing chamber, a heating sheet, or the like is preferably used as the curing method used in the curing step. Steam curing is usually performed by raising the temperature of the atmosphere around the target and maintaining a constant temperature while maintaining an appropriate humidity. Steam curing conditions are preferably a maximum temperature of 40 to 80°C and a curing time of 2 to 8 hours, more preferably a maximum temperature of 40 to 75°C and a curing time of 2.5 to 7.5 hours, and even more preferably a maximum temperature of 45 to 60°C and a curing time of 3 to 7 hours. Steam curing performed with the maximum temperature of the atmosphere around the cement composition during steam curing within the above ranges and the curing time within the above ranges tends to improve the initial strength and long-term strength of the hardened body.

[0054] The relative humidity around the cement composition during steam curing is preferably 50% RH or higher, more preferably 75% RH or higher, and even more preferably 90% RH or higher. There is no upper limit, 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 step preferably includes a pre-curing step. The pre-curing conditions are preferably a temperature of 10 to 50°C, maintained constant for about 1 to 3 hours. By including the pre-curing step in the curing step, the temperature inside the poured cement composition can be made uniform, making it easier to prevent thermal cracking due to the temperature difference between the inside and outside.

[0056] The curing step preferably includes a heating step. As the heating method, a known method can be used, and heating is preferably performed at a temperature increase rate of 10 to 30°C / hour, more preferably at a temperature increase rate of 12 to 28°C / hour, and even more preferably at a temperature increase rate of 15 to 25°C. When the temperature increase rate in the heating step is within the above range, hardening can be further promoted while preventing thermal cracking due to a sudden temperature increase in the cement composition.

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

[0058] The method for producing a hardened body preferably includes a natural cooling step after the curing step. In the natural cooling step, the hardened body obtained in the curing step is naturally cooled in a room temperature atmosphere. The cooling time is not particularly limited, but it is sufficient that the hardened body is cooled to a temperature at which it can be easily demolded, and may be about 0.5 to 2 hours. By including the natural cooling step after the curing step, thermal cracking of the hardened body can be prevented.

[0059] The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited to the following examples and comparative examples as long as they do not deviate from the spirit of the present invention.

[0060] Experimental Example 1 Calcium formate, gypsum, and mirabilite were mixed using a tilting mixer to prepare an additive composition having the composition shown in Table 1. Using the prepared additive composition, cement, sand, a water-reducing agent, water, and metakaolin or allophane as a cement substitute, cement compositions were prepared in the amounts shown in Table 1 (Test Nos. 1-1 to 1-6). Furthermore, as comparative examples, a cement composition (Test No. 1-7) in which cement was not replaced with metakaolin or allophane and did not contain the additive composition, and a cement composition (Test Nos. 1-8 and 1-9) in which the additive composition was not contained were prepared. The metakaolin and allophane used had the BET specific surface areas shown in Table 1. The resulting cement composition was cured in a formwork at 20°C until it reached a material age of 1 day, and then removed from the formwork and cured in water at 20°C until it reached a material age of 28 days, producing a hardened cement body. The compressive strength of each of the hardened cement bodies obtained was measured after 1 day, 7 days, and 28 days. The results are shown in Table 1.

[0061] (Materials used) Calcium formate: Reagent Metakaolin: Manufactured by Imerys (amorphous degree: 90% or more) Allophane: Produced in Tochigi Prefecture (amorphous degree: 90% or more) Gypsum: Anhydrous, reagent Glauber's salt: Anhydrous, reagent Cement: Ordinary Portland cement (commercially available) Sand: JIS standard sand Water-reducing agent: Polycarboxylic acid (commercially available) Water: Tap water

[0062] (Measurement items) Compressive strength: Compressive strength was measured in accordance with the method specified in JIS R 5201; 2015 "Physical testing methods for cement."

[0063]

[0064] The results shown in Table 1 show that hardened cement pastes containing calcium formate in the additive composition and substituted with metakaolin or allophane whose BET specific surface area falls within the range of the present invention (Test Nos. 1-2, 3, 5, and 6) showed high compressive strength in the early stages (after 1 and 7 days) and long term (after 28 days). Hardened cement pastes containing metakaolin or allophane whose BET specific surface area falls outside the range of the present invention (Test Nos. 1-1 and 1-4), and hardened cement pastes using additive compositions that did not contain calcium formate (Test Nos. 1-7 to 1-9) showed lower values ​​for both early strength and long term strength compared to the Examples.

[0065] Experimental Example 2 An additive composition and a cement composition were prepared in the same manner as in Experimental Example 1 to have the compositions shown in Table 2. Metakaolin and allophane with the BET specific surface areas shown in Table 2 were used. The resulting cement composition was molded using a formwork, and pre-cured at 20°C for 1.5 hours in the formwork. The temperature was increased at a rate of 20°C / hour, and the maximum temperature was maintained at 50°C for 3 hours. After that, the composition was allowed to cool naturally to room temperature (20°C), whereby steam curing was performed. The composition was then demolded and subjected to sealed curing up to 28 days. The compressive strength of each of the resulting hardened cement bodies was measured immediately after steam curing (at an age of 6 hours), after 7 days, and after 28 days. The results are shown in Table 2.

[0066]

[0067] As shown in Table 2, hardened cement pastes (Test Nos. 2-2, 2-3, 2-5, and 2-6) containing calcium formate in the additive composition and substituted with metakaolin or allophane whose BET specific surface area falls within the range of the present invention exhibited high compressive strengths in the early stage (after 6 hours and 7 days) and long term (after 28 days). Furthermore, compared with Experimental Example 1, it was confirmed that high compressive strength can be obtained by steam curing. Hardened cement pastes (Test Nos. 2-1 and 2-4) substituted with metakaolin or allophane whose BET specific surface area falls outside the range of the present invention exhibited lower values ​​for both early strength and long term strength compared with the Examples. Furthermore, hardened cement pastes (Test Nos. 2-7 to 2-9) using additive compositions that did not contain calcium formate exhibited lower values, particularly for early strength, compared with the Examples.

[0068] Experimental Example 3: An additive composition was prepared by mixing calcium formate, gypsum, sodium sulfate, calcium sulfoaluminate, calcium hydroxide, calcium carbonate, and calcium oxide using a tilting mixer. Using the prepared additive composition, cement, sand, a water-reducing agent, water, and metakaolin as a cement substitute, cement compositions were prepared in the proportions shown in Table 3 (Test Nos. 3-1 to 3-6). The metakaolin used had the BET specific surface area shown in Table 3.

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

[0070] (Materials used) Calcium sulfoaluminate: trial product, Blaine specific surface area 3,500 cm ２ / g (CaO:CaSO using first-grade calcium carbonate, calcium sulfate dihydrate, and aluminum hydroxide) ４ :Al ２ O ３ The mixture was mixed in a molar ratio of 4:3:1, baked at 1,400°C for 2 hours, and allowed to cool to room temperature to obtain a powder with a Blaine specific surface area of ​​3,500 cm ２ / g.) Calcium hydroxide: reagent Calcium carbonate: reagent Calcium oxide: reagent Other materials used were the same as those in Experimental Example 1.

[0071]

[0072] As shown in Table 3, the addition of calcium sulfoaluminate or an inorganic calcium compound to the additive composition resulted in higher compressive strength in either or both the early (after 1 and 7 days) and long-term (after 28 days) periods than Test No. 1-3, which did not contain either of these additives.

[0073] Experimental Example 4 An additive composition was prepared by mixing calcium formate, gypsum, and sodium sulfate using a tilting mixer. Cement compositions were prepared using the prepared additive composition, cement, limestone fine powder, sand, a water-reducing agent, water, and metakaolin as a cement substitute (Test Nos. 4-1 to 4-5). Similarly, a cement composition not containing 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 hardened cement body in the same manner as in Experimental Example 1. The compressive strength of the obtained hardened cement body was measured after 1 day, 7 days, and 28 days of age. The results are shown in Table 3.

[0075] (Materials Used) Anhydrous gypsum: reagent Limestone fine powder: reagent Other materials used were the same as those in Experimental Examples 1 and 2.

[0076]

[0077] The results shown in Table 4 show that even when metakaolin was used as a cement substitute, hardened cement pastes (Test Nos. 4-2 to 4-5) made using metakaolin with a BET specific surface area falling within the range of the present invention and an additive composition containing calcium formate exhibited high compressive strength in the early stages (after 1 and 7 days) and long term (after 28 days).The hardened cement paste (Test No. 4-1) made using metakaolin with a BET specific surface area falling outside the range of the present invention, and the hardened cement pastes (Test Nos. 4-6 and 4-7) made using an additive composition that did not contain calcium formate exhibited lower values ​​for both early strength and long term strength compared to the Examples.

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

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. Further, 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, 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.

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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