Calcium organic acid, 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] This invention relates primarily to calcium organic acid, additive compositions, and cement compositions used in the civil engineering and construction industries. [Background technology]

[0002] Concrete is considered a material with high CO2 emissions because it uses a large amount of cement as a raw material. This is mainly due to the large amount of fossil fuels used to obtain combustion energy for the furnace during the cement production process, as well as the decarboxylation reaction of limestone (CaCO3 → CaO + CO2). Reducing CO2 emissions from concrete is an important issue as part of measures to combat global warming.

[0003] To reduce the total amount of CO2 emitted during the manufacturing of concrete products, it is effective to reduce the amount of cement used by incorporating large amounts of industrial by-products (such as blast furnace slag powder and fly ash) as a cement substitute, and various studies are underway to achieve this.

[0004] On the other hand, hydraulic materials such as cement typically harden when mixed with water and left to stand for a predetermined time. The hardening rate of hydraulic materials can be affected by the ratio of material to water, the ambient temperature, and the curing method, but the time it takes for hydraulic materials 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 Blaine specific surface area value of 4000 cm². 2 The description includes a cement admixture containing calcium sulfoaluminate in amounts of 1 / 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] Japanese Patent Publication No. 2014-19618 [Patent Document 2] Japanese Patent Publication No. 2010-235399 [Overview of the project] [Problems that the invention aims to solve]

[0007] In recent years, there has been a desire to further improve the initial and long-term strength when using hardening accelerators. Furthermore, there is a desire to reduce CO2 emissions during concrete production, and even when using cement substitute materials, it is desirable to have high initial and long-term strength.

[0008] The present invention has been made in view of these circumstances, and aims to provide an organic acid calcium that can improve the initial strength and long-term strength of the hardened body produced when used together with amorphous aluminosilicate powder, an additive composition containing the organic acid calcium, and a cement composition containing the additive composition. [Means for solving the problem]

[0009] The present inventors conducted intensive research to solve the above-mentioned problems and found that the problems can be solved by using calcium organic acid in combination with a curable composition containing amorphous aluminosilicate powder having a predetermined BET specific surface area, leading to the present invention. That is, the present invention is as follows. [1] BET specific surface area is 1.0 m 2 Calcium organic acid to be used with a curable composition containing amorphous aluminosilicate powder of 1 / g or more. [2] The amorphous aluminosilicate comprises at least one of metakaolin and allophene, the organic calcium acid according to [1]. An additive composition comprising the organic acid calcium described in [3] [1] or [2] and an inorganic sulfate. [4] The additive composition according to [3], wherein the inorganic sulfate comprises 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 comprising at least one of a leavening agent and an inorganic calcium compound. [6] Furthermore, the BET specific surface area is 1.0 m² 2 An additive composition according to any one of [3] to [5], comprising amorphous aluminosilicate powder in quantities of 1 / g or more. [7] Cement and a BET specific surface area of ​​1.0 m 2 A cement composition comprising amorphous aluminosilicate powder in amounts of 1 / g or more and an additive composition according to any one of [3] to [6]. [8] The cement composition according to [7], wherein the amount of amorphous aluminosilicate powder is 5 to 90 parts by mass per 100 parts by mass of cement. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide calcium organic acid, an additive composition containing calcium organic acid, and a cement composition containing the additive composition, which can improve the initial strength and long-term strength of the cured product when used together with amorphous aluminosilicate powder. [Modes for carrying out the invention]

[0011] The present invention will be described in detail below regarding the calcium organic acid, additive composition, and cement composition, but the present invention is not limited to these embodiments. In this specification, "%" and "parts" refer to mass unless otherwise specified. Furthermore, numerical ranges defined using the symbol "~" include the values ​​at both ends of "~" (upper and lower limits).

[0012] [Calcium organic acid] The organic acid calcium of the present invention has a BET specific surface area of ​​1.0 m². 2It is used together with a curable composition containing amorphous aluminosilicate powder of 1 / g or more (hereinafter simply referred to as "amorphous aluminosilicate powder"). As such calcium organic acid, for example, calcium formate, calcium acetate, calcium lactate and the like 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 more preferably 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 a mesh size 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 a mesh size 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 the calcium organic acid of the present invention is used 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 m 2 / g or more and contains amorphous aluminosilicate powder. The BET specific surface area of the amorphous aluminosilicate powder is more preferably 5.0 m 2 / g or more, and further preferably 10.0 m 2 / g or more. By using a curable composition containing amorphous aluminosilicate powder with a BET specific surface area of 1.0 m 2 / g or more, the initial strength and long-term strength of the produced hardened body can be improved.

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

[0017] Amorphous aluminosilicate powder is derived from clay minerals and is not particularly limited as long as it contains an amorphous portion; any such aluminosilicate can be used. Examples of clay minerals used as raw materials include (1) kaolin minerals, (2) mica clay minerals, (3) smectite-type minerals, and mixed layer minerals formed by mixing these. Amorphous aluminosilicate can be obtained by amorphousizing these crystalline aluminosilicates, for example, by calcination and dehydration. From the viewpoint of superior reactivity, amorphous aluminosilicates derived from kaolin minerals such as kaolinite, halosite, and dickite are preferred, and metakaolin obtained by calcining kaolinite is even more preferred. Allophane can also be used as an amorphous aluminosilicate. Allophane (Al2O3·(1~2)SiO2·5H2O) is an amorphous clay quasi-mineral. Amorphous aluminosilicates may be used individually or in combination of two or more types.

[0018] In this specification, "amorphous" means that, as measured by a powder X-ray diffractometer, peaks originating from the clay mineral raw material are almost completely absent. The amorphous aluminosilicate powder according to this embodiment only needs to have an amorphous content of 70% by mass or more, preferably 90% by mass or more, and more preferably 100% by mass, i.e., it is most preferable that no peaks are observed at all when measured by a powder X-ray diffractometer. Here, the amorphous content is a value obtained by the standard addition method. Aluminosilicate with a high amorphous content, i.e., aluminosilicate with a low crystalline content, tends to have better strength development at the same amount of mixing compared with aluminosilicate with a low amorphous content. Heating for amorphousization of aluminosilicate can be performed by firing in an external kiln, internal kiln, electric furnace, etc., and melting in a melting furnace.

[0019] Examples of curable compositions used with the calcium organic acid of the present invention include additive compositions or cement compositions, as described later. Specifically, the calcium organic acid of the present invention can be used with an additive composition containing amorphous aluminosilicate powder. It can also be used with a cement composition containing amorphous aluminosilicate powder. When used with a cement composition containing amorphous aluminosilicate powder, the additive composition added to the cement composition does not need to 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 product can be improved.

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

[0021] (Organic calcium acid) The above-mentioned calcium organic acid can be used as the calcium organic acid contained in the additive composition of this embodiment. 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 product can be improved.

[0022] (Inorganic sulfates) In this embodiment, the inorganic sulfates included in the additive composition are preferably sulfates and / or thiosulfates from the viewpoint of initial strength and long-term strength development. Examples include gypsum, Glauber's salt, aluminum sulfate, sodium thiosulfate, and potassium alum. Among these, Glauber's salt and aluminum sulfate are preferred, with Glauber's salt being more preferred. When using gypsum or Glauber's salt, it is even more preferable that they be anhydrous.

[0023] Inorganic sulfates are preferably present in the additive composition, excluding amorphous aluminosilicate powder, at a concentration of 0.5 to 75.0% by mass, more preferably 1.0 to 65.0% by mass, and even more preferably 3.0 to 50.0% by mass. By having an inorganic sulfate content within the above range, both initial strength and long-term strength can be improved.

[0024] (Inorganic calcium compounds) The additive composition of this embodiment may further contain an inorganic calcium compound. Examples of inorganic calcium compounds include calcium hydroxide, calcium carbonate, and calcium oxide. From the viewpoint of initial strength and long-term strength development, calcium hydroxide and / or calcium oxide are preferred.

[0025] When an inorganic calcium compound is included in the additive composition, it is preferable that it be present in 15.0 to 70.0% by mass, more preferably 18.0 to 60.0% by mass, and even more preferably 20.0 to 40.0% by mass, in the additive composition excluding the amorphous aluminosilicate powder. By having the inorganic calcium compound content within the above range, the initial strength and long-term strength of the cured product can be improved.

[0026] (Calcium sulfoaluminate) The additive composition of this embodiment may further include calcium sulfoaluminate as an expanding agent. Calcium sulfoaluminate is a general term for hydraulic substances and hydrated salts represented by the chemical formula xCaO·yAl2O3·zCaSO4·mH2O (where x, y, and z are non-zero positive real numbers, and m is 0 or a positive real number). Examples include hauyne (3CaO·3Al2O3·CaSO4), the AFt phase represented by ettringite (3CaO·Al2O3·3CaSO4·32H2O), the AFm phase represented by monosulfate (3CaO·Al2O3·CaSO4·12H2O), and substances in which the AFt and AFm phases coexist. Calcium sulfoaluminate may be amorphous. Furthermore, some of the Al2O3 may be substituted with trace amounts of Fe2O3 or SiO2, and some of the CaSO4 may be substituted with Ca(OH)2 or CaCO3. In this 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 risk of reduced strength during curing due to phase transition.

[0027] When calcium sulfoaluminate is included in the additive composition, it is preferable that it be present 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 amorphous aluminosilicate powder. Having the calcium sulfoaluminate content within the above range prevents cracking of the cured product and improves its long-term strength.

[0028] Furthermore, in this embodiment, it is preferable that the additive composition contains both calcium sulfoaluminate and an inorganic calcium compound. By including both calcium sulfoaluminate and an inorganic calcium compound in the additive composition, the initial strength and long-term strength of the cured product can be improved.

[0029] (Amorphous aluminosilicate powder) The additive composition of this embodiment may contain amorphous aluminosilicate powder. Including amorphous aluminosilicate powder in the additive composition can improve the initial strength and long-term strength of the cured product produced. As the amorphous aluminosilicate powder, the amorphous aluminosilicate powder described above can be used. When amorphous aluminosilicate powder is included in the additive composition, the amount 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 BET specific surface area of ​​1.0 m². 2 The additive composition comprises amorphous aluminosilicate powder in amounts of 1 / g or more. Furthermore, if the additive composition contains amorphous aluminosilicate powder, it is not necessary to include amorphous aluminosilicate powder separately from the additive composition.

[0031] The additive composition described above can be used as the additive composition included in the cement composition of the present invention.

[0032] The cement included in the cement composition of the present invention is not particularly limited and includes various types of Portland cement such as ordinary, rapid-hardening, ultra-rapid-hardening, low-heat, and moderate-heat cements; various blended cements obtained by mixing these Portland cements with blast furnace slag, fly ash, silica fume, etc.; 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. It is also possible to use various types of cement after they have been finely powdered. Furthermore, cements that have been adjusted by increasing or decreasing the amount of components commonly used in cement (e.g., gypsum) can also be used. In addition, combinations of two or more of these can also be used. From the viewpoint of improving initial strength and long-term strength, it is preferable to select ordinary Portland cement or rapid-hardening Portland cement.

[0033] From the perspective of manufacturing cost and strength development, cement has a Blaine specific surface area of ​​2,500 cm². 2 / g~7,000cm 2 It is preferable that the value is / g, and 2,750 cm 2 / g~6,000cm 2 It is more preferable that it be / g, and 3,000 cm 2 / g~4,500cm 2 It is even more preferable that the value is / g. In this invention, the Blaine specific surface area is determined in accordance with JIS R 5201:2015 (Physical Testing Methods for Cement).

[0034] Furthermore, the cement composition of the present invention includes a portion of the cement with a BET specific surface area of ​​1.0 m². 2 It can be an amorphous aluminosilicate powder of 1g or more. 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, per 100 parts by mass of the cement.

[0035] By adding amorphous aluminosilicate powder instead of cement, the amount of cement can be reduced, and CO2 emissions from the decarboxylation reaction of limestone (CaCO3 → CaO + CO2) can be suppressed. As the amorphous aluminosilicate powder, the amorphous aluminosilicate powder described above can be used, and metakaolin is particularly preferred. Metakaolin is obtained by calcining kaolin, but since kaolin can be calcined at a lower temperature than that used for firing cement, the amount of CO2 emitted can be suppressed. Furthermore, since metakaolin is produced during the refining (production) of iron, CO2 is not generated as when cement is fired, thus suppressing CO2 emissions.

[0036] The amount of 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 amorphous aluminosilicate powder, when the additive composition does not contain amorphous aluminosilicate powder. Furthermore, 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, per 100 parts by mass of cement. In this case, it is preferable that the additive composition contains 0.3 to 8.0 parts by mass of organic acid calcium per 100 parts by mass of cement. When the content of additives 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 include naphthalene-based water-reducing agents, melamine-based water-reducing agents, aminosulfonic acid-based water-reducing agents, and polycarboxylic acid-based water-reducing agents, and in the present invention, one or more of these water-reducing agents can be used.

[0038] The water-reducing agent content 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, relative to the total mass of the cement, amorphous aluminate silicate powder, and additive composition.

[0039] Furthermore, the cement composition of the present invention may contain alkali metal carbonates. The inclusion of alkali metal carbonates in the cement composition facilitates improved initial and long-term strength development. Examples of alkali metal carbonates include sodium carbonate, potassium carbonate, lithium carbonate, sodium bicarbonate, potassium bicarbonate, and lithium bicarbonate, and combinations of these are also possible.

[0040] The alkali metal carbonate content is preferably 1 to 6 parts by mass, and more preferably 2 to 5 parts by mass, in terms of solid content, per 100 parts by mass of the total amount of cement and amorphous aluminosilicate powder in the cement composition. Having the alkali metal carbonate content within this range makes it easier to achieve good initial and long-term strength development.

[0041] The cement composition of the present invention may contain silicate fine powder. The inclusion of silicate fine powder in the cement composition facilitates good initial and long-term strength development. Examples of silicate fine powder include latent hydraulic materials such as blast furnace granulated slag powder, fly ash, and pozzolanic materials such as silica fume. Among these, silica fume is preferred from the viewpoint of both initial and long-term strength development.

[0042] The fineness of silica-based fine powder is not particularly limited, but typically blast furnace granulated slag powder and fly ash have a Blaine specific surface area of ​​3,000 to 9,000 cm². 2 The silica fume is in the range of / g, with a BET specific surface area of ​​20,000 to 300,000 cm². 2 It is within the range of / g.

[0043] The content of 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, based on 100 parts by mass of the total of cement and amorphous aluminosilicate powder in the cement composition. A silica fine powder content above the lower limit tends to improve initial and long-term strength development. Furthermore, a silica fine powder content below the upper limit also tends to improve initial and long-term strength development.

[0044] Cement compositions may contain defoaming agents to the extent that they do not adversely affect performance. The defoaming agent is used to suppress the amount of air incorporated during mixing. The type of defoaming agent is not particularly limited as long as it does not significantly adversely affect the strength characteristics of the hardened material, and both liquid and powder forms can be used. Examples include polyether-based defoaming agents, polyhydric alcohol-based defoaming agents such as esterified polyhydric alcohols and alkyl ethers, alkyl phosphate-based defoaming agents, and silicone-based defoaming agents.

[0045] The content of the defoaming 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, based on 100 parts by mass of the total amount of cement and amorphous aluminosilicate powder in the cement composition. A content of defoaming agent above the lower limit allows for sufficient defoaming effect. Furthermore, a content of defoaming agent below the upper limit facilitates good fluidity retention.

[0046] Furthermore, the cement composition may use one or more of the following materials, to the extent that they do not adversely affect performance: gas foaming substances, air-entraining agents, rust inhibitors, water repellents, antibacterial agents, colorants, antifreezes, admixtures such as limestone fine powder, blast furnace slow-cooling slag fine powder, sewage sludge incineration ash and its molten slag, municipal solid waste incineration ash and its molten slag, and pulp sludge incineration ash, as well as thickeners, shrinkage reducing agents, polymers, and anion exchangers such as hydrotalcite, to the extent that they do not substantially hinder the objectives of the present invention.

[0047] [Cured body] The hardened body according to this embodiment is obtained by hardening a cement composition. The hardened body is usually formed when the cement composition and water are mixed, causing the cement, which is a hydraulic material, to undergo a hydration reaction and harden. The amount of mixing water 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 mixing water is within the above range, it is easier to achieve good initial strength development of the hydraulic material.

[0048] The hardened material is obtained by mixing a cement composition with water and then allowing it to harden. However, it can be obtained more efficiently by filling (casting) the mixture into a formwork and curing it, or by pouring, spraying, or coating it directly onto the construction site.

[0049] [Method for manufacturing a hardened body] The method for manufacturing a hardened body according to this embodiment is to harden 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. If amorphous aluminosilicate powder is included in the additive composition, it is not necessary to add amorphous aluminosilicate powder separately. The method for manufacturing a hardened body preferably includes, in this order, a mixing step of mixing 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 process is not particularly limited; the materials may be mixed at the time of application, or some or all of them may be mixed in advance. Any existing mixing equipment can be used, such as tilting drum mixers, omni mixers, Henschel mixers, V-type mixers, Proscher mixers, and Nauta mixers.

[0051] The placement method in the placement process can be carried out using known methods. The temperature of the cement composition at the time of placement is preferably 0 to 50°C, and more preferably 10 to 40°C. When the temperature of the cement composition at the time of placement is within the above range, it becomes easier to enable early demolding of the hardened body.

[0052] The manufacturing method for the hardened body preferably includes a compaction step after the concrete placement step. While known methods can be used for compaction, it is preferable to use a vibrator from the viewpoint of workability.

[0053] From the viewpoint of improving productivity, it is preferable to use steam curing, such as curing rooms or heated sheets, as the curing method used in the curing process. Steam curing usually involves raising the temperature of the atmosphere around the target object and maintaining a constant temperature while keeping appropriate humidity. Preferably, the conditions for steam curing are 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. When steam curing is performed with the maximum temperature of the atmosphere around the cement composition within the above range and the curing time within the above range, the initial strength and long-term strength of the hardened body tend to improve.

[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 tend to improve.

[0055] The curing process preferably includes a pre-curing process. The conditions for pre-curing are preferably a temperature of 10-50°C, maintained at a constant temperature for approximately 1-3 hours. Including a pre-curing process in the curing process makes it possible to equalize the temperature inside the poured cement composition, thus preventing temperature cracks caused by temperature differences between the inside and outside.

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

[0057] The curing process preferably includes a temperature holding process. Known methods can be used for temperature holding, preferably maintaining a constant temperature 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 during the temperature holding process, the cast cement composition can be hardened uniformly, and the initial strength and long-term strength of the hardened body are more easily improved.

[0058] The method for manufacturing the cured body preferably includes a natural cooling step after the curing step. In the natural cooling step, the cured 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 to cool the cured body to a temperature at which it can be easily demolded, and a time of about 0.5 to 2 hours is sufficient. Including a natural cooling step after the curing step can prevent temperature cracking of the cured body. [Examples]

[0059] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples and comparative examples without departing from its spirit.

[0060] <Experimental Example 1> Additive compositions with the compositions shown in Table 1 were prepared by mixing calcium formate, gypsum, and Glauber's salt using a tilting drum mixer. Cement compositions were prepared using the prepared additive composition, cement, sand, water-reducing agent, water, and metakaolin or allofen as a cement substitute, according to the proportions shown in Table 1 (Tests No. 1-1 to 1-6). For comparative examples, cement compositions without the substitution of cement with metakaolin or allofen, and without the additive composition (Test No. 1-7), and without the additive composition (Tests No. 1-8 and 1-9) were also prepared. Metakaolin and allofen with the BET specific surface area shown in Table 1 were used. The obtained cement composition was cured in a formwork at a temperature of 20°C until it reached 1 day of age. After demolding, it was cured in water at a temperature of 20°C until it reached 28 days of age to produce a hardened cement body. The compressive strength of each hardened cement was measured at 1 day, 7 days, and 28 days after formation. The results are shown in Table 1.

[0061] (Materials used) Calcium formate: Reagent Metakaolin: Manufactured by Imerys (amorphous: 90% or higher) Allophane: Produced in Tochigi Prefecture (Amorphous texture: 90% or higher) Gypsum: anhydrous, reagent Glauber's salt: anhydride, 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] [Table 1]

[0064] As shown in Table 1, cementitious bodies (Tests No. 1-2, 3, 5, 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 showed high compressive strength in the initial period (after 1 and 7 days) and in the long term (after 28 days). Cement hardened bodies substituted with metakaolin or allophane, whose BET specific surface area is not within the range of the present invention (Tests No. 1-1, 4), and cement hardened bodies using additive compositions that do not contain calcium formate (Tests No. 1-7 to 9) showed lower initial and long-term strengths compared to the examples.

[0065] <Experimental Example 2> The additive composition and 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 area shown in Table 2 were used. The obtained cement composition was molded using a formwork, and pre-cured in the formwork at 20°C for 1.5 hours. The temperature was then increased at a rate of 20°C / hour, and after being held at a maximum temperature of 50°C for 3 hours, steam curing was performed by allowing it to cool naturally to room temperature (20°C). After that, the formwork was removed and sealed and cured until the material was 28 days old. For each of the hardened cement bodies obtained, the compressive strength was measured immediately after steam curing (6 hours old), after 7 days, and after 28 days. The results are shown in Table 2.

[0066] [Table 2]

[0067] As shown in Table 2, cement hardened bodies (Tests No. 2-2, 3, 5, 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 showed high compressive strength in the initial (after 6 hours and 7 days) and long-term (after 28 days) stages. Furthermore, compared to Experimental Example 1, it was confirmed that higher compressive strength could be obtained by performing steam curing. Cement hardened materials substituted with metakaolin or allophane, whose BET specific surface area is not within the range of the present invention (Tests No. 2-1, 2-4), showed lower initial and long-term strengths compared to the examples. Furthermore, cement hardened materials using additive compositions that do not contain calcium formate (Tests No. 2-7 to 2-9) showed lower values ​​compared to the examples, particularly in initial strength.

[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 drum mixer. Cement compositions were prepared using the prepared additive composition, cement, sand, water-reducing agent, water, and metakaolin as a cement substitute, according to the proportions shown in Table 3 (Tests No. 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 using the same method as in Experimental Example 1. The compressive strength of the hardened cement body was measured at 1 day, 7 days, and 28 days of age. The results are shown in Table 3.

[0070] (Materials used) Calcium sulfoaluminate: Prototype, Blaine specific surface area 3,500 cm² 2 / g (A mixture of reagent-grade calcium carbonate, calcium sulfate dihydrate, and aluminum hydroxide is prepared in a molar ratio of CaO:CaSO4:Al2O3 in a ratio of 4:3:1, fired at 1,400°C for 2 hours, and left to stand at room temperature until the Blaine specific surface area reaches 3,500 cm².) 2 It was ground down to a weight of / 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, the inclusion of calcium sulfoaluminate or an inorganic calcium compound in the additive composition resulted in higher compressive strength in either the initial (after 1 and 7 days) or long-term (after 28 days) timeframes, or both, compared to Test No. 1-3, which did not contain either.

[0073] <Experimental Example 4> Additive compositions were prepared by mixing calcium formate, gypsum, and Glauber's salt using a tilting drum mixer. Cement compositions were prepared using the prepared additive compositions, cement, limestone powder, sand, water-reducing agent, water, and metakaolin as a cement substitute (Tests No. 4-1 to 4-5). Similarly, cement compositions without additive compositions (Test No. 4-6) and cement compositions containing anhydrous gypsum instead of additive compositions (Test No. 4-7) were prepared. The proportions 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 using the same method as in Experimental Example 1. The compressive strength of the hardened cement body was measured at 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 For the other materials, the same materials as those used in Experimental Examples 1 and 2 were employed.

[0076] [Table 4]

[0077] As shown in Table 4, even when metakaolin was included as a substitute for cement, the cement hardened bodies (Tests No. 4-2 to 4-5) using metakaolin whose BET specific surface area falls within the range of the present invention, along with an additive composition containing calcium formate, showed high compressive strength in the initial period (after 1 and 7 days) and the long term (after 28 days). The cementitious body in which metakaolin was substituted with a material whose BET specific surface area is not within the scope of the present invention (Test No. 4-1), and the cementitious body using an additive composition that does not contain calcium formate (Tests No. 4-6, 7), showed lower initial strength and long-term strength compared to the examples. [Industrial applicability]

[0078] The calcium organic acid of the present invention, when used together with amorphous aluminosilicate powder, can improve the initial strength and long-term strength of the resulting hardened body, making it effective for use in the civil engineering and construction industries.

Claims

1. BET specific surface area is 1.0 m² ２ An additive composition comprising an organic acid calcium, an inorganic sulfate, and a calcium sulfoaluminate, to be used together with amorphous aluminosilicate powder at a concentration of 1 / g or more, The aforementioned calcium organic acid is at least one of calcium formate, calcium acetate, and calcium lactate. The content of the aforementioned organic acid calcium is 30 to 70% by mass in the additive composition excluding the amorphous aluminosilicate powder. The content of the inorganic sulfate is 3.0 to 50.0% by mass in the additive composition excluding the amorphous aluminosilicate powder. The additive composition wherein the calcium sulfoaluminate content is 15.0 to 60.0% by mass in the additive composition excluding the amorphous aluminosilicate powder.

2. The additive composition according to claim 1, wherein the amorphous aluminosilicate powder is at least one of metakaolin and allophane.

3. The additive composition according to claim 1 or 2, wherein the inorganic sulfate comprises at least one selected from gypsum, sodium sulfate, aluminum sulfate, sodium thiosulfate, and potassium alum.

4. Furthermore, the additive composition according to claim 1 or 2 contains an inorganic calcium compound.

5. Furthermore, the BET specific surface area is 1.0 m². ２ The additive composition according to claim 1 or 2, comprising 700 to 1800 parts by mass of amorphous aluminosilicate powder at a concentration of 1 / g or more, per 100 parts by mass of the additive composition excluding the amorphous aluminosilicate powder.

6. Cement and a BET specific surface area of ​​1.0 m² ２ The composition comprises amorphous aluminosilicate powder at a concentration of 1 / g or more, and the additive composition described in claim 1 or 2. A cement composition wherein the amorphous aluminosilicate powder content is 10 to 60 parts by mass per 100 parts by mass of cement, and the amount of the additive composition excluding the amorphous aluminosilicate powder is 1 to 51 parts by mass.

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