Concrete composition, method for producing concrete composition, and precast concrete product

Abstract

To provide a concrete composition capable of obtaining a hardened body relatively excellent in development of initial strength without performing steam curing under a winter environment, a method for producing the concrete composition, and a precast concrete product.SOLUTION: The concrete composition includes cement, water, fine aggregate, coarse aggregate, glycerin and an accelerator, wherein the accelerator is one or more selected from calcium chloride, sodium carbonate, sodium thiosulfate, triethanolamine, diethanolisopropanolamine, triisopropanolamine and aluminum sulfate.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a concrete composition, a method for making a concrete composition, and a precast concrete product. [Background technology]

[0002] From the viewpoint of productivity, precast concrete products manufactured in factories, etc., are required to have sufficient initial strength (strength after removal from the formwork). For this reason, in the manufacture of precast concrete products, steam curing has traditionally been carried out, in which steam generated in a boiler is vented into a curing chamber to heat and humidify the concrete poured into the formwork, thereby accelerating the development of concrete strength. Steam curing is particularly essential in winter environments.

[0003] However, with the recent rise in awareness of environmental issues, research is being conducted into technologies that can ensure the early strength of concrete early without steam curing, with the aim of reducing greenhouse gas emissions and energy consumption.As a method for obtaining concrete that has excellent early strength development without steam curing, for example, Patent Document 1 discloses a method for producing concrete by kneading cement, water, fine aggregate, coarse aggregate, and glycerin, in which the temperature of the water immediately before mixing and the temperature of the mixture immediately after mixing are adjusted within predetermined ranges to improve the early strength of the concrete. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-151146 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the hardened concrete obtained using a concrete composition containing cement, water, fine aggregate, coarse aggregate, and glycerin exhibits a small increase in early strength in winter environments, and there is room for improvement.

[0006] In view of the above circumstances, an object of the present invention is to provide a concrete composition that can produce a hardened concrete product that exhibits relatively excellent early strength development in a winter environment without steam curing, a method for producing a concrete composition, and a precast concrete product. [Means for solving the problem]

[0007] The concrete composition according to the present invention comprises cement, water, fine aggregate, coarse aggregate, glycerin, and an accelerator, wherein the accelerator is one or more selected from calcium chloride, sodium carbonate, sodium thiosulfate, triethanolamine, diethanolisopropanolamine, triisopropanolamine, and aluminum sulfate.

[0008] With this constitution, the concrete composition can give a hardened body that exhibits relatively excellent early strength development in a winter environment without steam curing.

[0009] In the concrete composition according to the present invention, the content of the accelerator may be 0.002% by mass or more and 1.0% by mass or less relative to the cement.

[0010] With this constitution, the concrete composition can give a hardened product that exhibits excellent early strength.

[0011] In the concrete composition according to the present invention, the accelerator may be sodium thiosulfate, and the content of the sodium thiosulfate may be 0.2 mass % or more and 1.0 mass % or less with respect to the cement.

[0012] With this constitution, the concrete composition can give a hardened product that exhibits excellent early strength.

[0013] In the concrete composition according to the present invention, the accelerator may be triethanolamine, and the content of the triethanolamine may be 0.002% by mass or more and 0.01% by mass or less with respect to the cement.

[0014] With this constitution, the concrete composition can give a hardened product that exhibits excellent early strength.

[0015] In the concrete composition according to the present invention, the accelerator may be aluminum sulfate, and the content of the aluminum sulfate may be 0.1% by mass or more and 1.0% by mass or less with respect to the cement.

[0016] With this constitution, the concrete composition can give a hardened product that exhibits excellent early strength.

[0017] In the concrete composition according to the present invention, the content of the glycerin may be 0.1% by mass or more and 1.0% by mass or less relative to the cement.

[0018] With this constitution, the concrete composition can give a hardened product that exhibits excellent early strength.

[0019] The method for producing a concrete composition according to the present invention is the method for producing the above-mentioned concrete composition, and includes a step of kneading cement, water, fine aggregate, coarse aggregate, glycerin, and an accelerator, wherein the accelerator is one or more selected from calcium chloride, sodium carbonate, sodium thiosulfate, triethanolamine, diethanolisopropanolamine, triisopropanolamine, and aluminum sulfate.

[0020] With this configuration, the method for producing a concrete composition can produce a hardened body that exhibits relatively excellent early strength development in a winter environment without steam curing.

[0021] Precast concrete products according to the present invention are made from the hardened concrete compositions described above.

[0022] Due to this configuration, the precast concrete product exhibits excellent early strength development even in winter environments without steam curing. [Effects of the Invention]

[0023] According to the present invention, it is possible to provide a concrete composition that can produce a hardened body that exhibits relatively excellent early strength development without steam curing, a method for producing a concrete composition, and a precast concrete product. DETAILED DESCRIPTION OF THE INVENTION

[0024] The concrete composition, the method for producing the concrete composition, and the precast concrete product according to this embodiment will be described below.

[0025] <Concrete composition> The concrete composition according to this embodiment contains cement, water, fine aggregate, coarse aggregate, glycerin, and an accelerator.

[0026] The accelerator is at least one selected from calcium chloride, sodium carbonate, sodium thiosulfate, triethanolamine, diethanolisopropanolamine, triisopropanolamine, and aluminum sulfate, preferably at least one selected from sodium thiosulfate, triethanolamine, and aluminum sulfate, more preferably triethanolamine or aluminum sulfate. One accelerator may be used alone, or two or more accelerators may be used in combination.

[0027] The content of the accelerator is preferably 0.002% by mass or more and 1.0% by mass or less, more preferably 0.006% by mass or more and 0.6% by mass or less, based on the cement. When two or more accelerators are used, the content is the total content of the accelerators.

[0028] In one embodiment, the accelerator is sodium thiosulfate. In this embodiment, the content of sodium thiosulfate is preferably 0.2 mass% or more relative to the cement in order to improve the early strength development of the hardened body. In addition, the content of sodium thiosulfate is preferably 0.2 mass% or more relative to the cement in order to improve the total alkali content of 3.0 kg / m 3 From the viewpoint of the following, the content of sodium thiosulfate is preferably 1.0 mass % or less, and more preferably 0.6 mass % or less, relative to the cement: Sodium thiosulfate improves the early strength of the hardened body, which is thought to be due to accelerating the hydration of alite (CS), a constituent compound of cement.

[0029] In another embodiment, the accelerator is triethanolamine. In this embodiment, the content of triethanolamine is preferably 0.002% by mass or more and 0.01% by mass or less, and more preferably 0.002% by mass or more and 0.006% by mass or less, based on the cement, from the viewpoint of improving the early strength development of the hardened body. Note that triethanolamine improves the early strength of the hardened body, and this is thought to be due to accelerating the hydration of the aluminate (CA) phase, which is a constituent compound of cement, and accelerating the formation of ettringite (3CaO·Al2O3·3CaSO4·32H2O).

[0030] In yet another embodiment, the accelerator is aluminum sulfate. In this embodiment, the content of aluminum sulfate is preferably 0.1 mass% or more and 1.0 mass% or less, and more preferably 0.1 mass% or more and 0.6 mass% or less, based on the cement, from the viewpoint of improving the early strength development of the hardened body. Aluminum sulfate improves the early strength of the hardened body, and this is thought to be due to the fact that the supply of aluminum ions and sulfate ions increases the amount of ettringite (3CaO·Al2O3·3CaSO4·32H2O) produced.

[0031] When the accelerator is calcium chloride, its content is preferably 0.05 mass% or more relative to the cement in order to improve the early strength development of the hardened body, and the chloride content is preferably 0.30 kg / m 3 From the viewpoint of the following, the content of calcium chloride is preferably 0.15% by mass or less, and more preferably 0.1% by mass or less, relative to the cement: Calcium chloride improves the early strength of the hardened body, which is thought to be due to the promotion of hydration of alite (CS), a constituent compound of cement.

[0032] When the accelerator is sodium carbonate, its content is preferably 0.02% by mass or more and 0.1% by mass or less relative to the cement, from the viewpoint of improving the early strength development of the hardened body. Sodium carbonate improves the early strength of the hardened body, which is thought to be due to accelerating the hydration of alite (CS), a constituent compound of cement.

[0033] When the accelerator is diethanol isopropanolamine, its content is preferably 0.002% by mass or more and 0.01% by mass or less, and more preferably 0.002% by mass or more and 0.006% by mass or less, based on the cement, from the viewpoint of improving the early strength development of the hardened body. Note that diethanol isopropanolamine improves the early strength of the hardened body, and this is thought to be due to the fact that it promotes the hydration of the aluminate (C3A) phase and ferrite (C4AF) phase, which are constituent compounds of cement, and promotes the formation of ettringite (3CaO·Al2O3·3CaSO4·32H2O).

[0034] When the accelerator is triisopropanolamine, its content is preferably 0.002% by mass or more and 0.01% by mass or less, and more preferably 0.002% by mass or more and 0.006% by mass or less, based on the cement, from the viewpoint of improving the early strength development of the hardened body. Note that triisopropanolamine improves the early strength of the hardened body, which is thought to be due to increasing the solubility of iron hydroxide generated with the hydration of the ferrite (C4AF) phase and accelerating hydration.

[0035] Glycerin is a compound with the chemical formula C3H8O3 and the chemical names glycerin, glycerol, or 1,2,3-propanetriol. Glycerin improves the early strength of hardened bodies, which is thought to be due to promoting the hydration of the aluminate (C3A) phase, a component compound of cement, and accelerating the formation of ettringite (3CaO·Al2O3·3CaSO4·32H2O).

[0036] From the viewpoint of improving the early strength development of the hardened body, the content of glycerin is preferably 0.1 mass % or more and 1.0 mass % or less, more preferably 0.1 mass % or more and 0.6 mass % or less, and even more preferably 0.1 mass % or more and 0.2 mass % or less, based on the cement.

[0037] Examples of cement include Portland cements such as ordinary Portland cement, high-early-strength Portland cement, ultra-high-early-strength Portland cement, moderate-heat Portland cement, low-heat Portland cement, sulfate-resistant Portland cement, and white Portland cement, as specified in JIS R 5210, ultra-high-early-strength cement, and alumina cement. Various blended cements obtained by mixing fly ash, blast furnace slag, or the like with the Portland cement can also be used. Among these, it is preferable to use high-early-strength Portland cement in order to improve the early strength development of the hardened body. One type of cement may be used alone, or two or more types may be used in combination.

[0038] The amount of cement mixed is, for example, unit amount (kg / m 3 : 1m of concrete composition 3 Mass per unit mass) is 270 kg / m 3 More than 500kg / m 3 When two or more cements are contained, the above blending amount is the total blending amount of the cements.

[0039] The water is not particularly limited, and examples of water that can be used include tap water, industrial water, recycled water, groundwater, river water, and rainwater.

[0040] The amount of water to be mixed is, for example, a unit amount (kg / m 3 : 1m of concrete composition 3 Mass per unit mass) is 135 kg / m 3 More than 175kg / m 3 It can be as follows:

[0041] Fine aggregate refers to aggregate that passes entirely through a 10 mm mesh sieve and at least 85% by mass through a 5 mm mesh sieve (JIS A 0203:2019). Examples of fine aggregate include naturally occurring sand such as mountain sand, river sand, land sand, sea sand, crushed sand, and crushed limestone sand, as specified in Appendix A (Aggregates for Ready-Mixed Concrete) of JIS A 5308 (Ready-Mixed Concrete), sand derived from slag such as blast furnace slag, electric furnace oxidized slag, and ferro-nickel slag, recycled aggregate, artificial lightweight aggregate, and recovered aggregate. These fine aggregates may be used alone or in combination of two or more types.

[0042] The amount of fine aggregate mixed is, for example, unit amount (kg / m 3 : 1m of concrete composition 3 mass per unit mass), 600 kg / m 3 More than 1000kg / m 3 When two or more types of fine aggregate are contained, the above blending amount is the total blending amount of the fine aggregate.

[0043] Coarse aggregate refers to aggregate that retains 85% or more by mass on a 5 mm mesh sieve (JIS A 0203:2019). Examples of coarse aggregate include, but are not limited to, natural aggregates such as river gravel, mountain gravel, and sea gravel; artificial aggregates such as crushed stone such as sandstone, hard limestone, basalt, and andesite; and recycled aggregate. One type of coarse aggregate may be used alone, or two or more types may be used in combination.

[0044] The amount of coarse aggregate mixed is, for example, unit amount (kg / m 3 : 1m of concrete composition 3 mass per unit mass), 800 kg / m 3 More than 1250kg / m 3 When two or more types of coarse aggregate are contained, the above blending amount is the total blending amount of the coarse aggregate.

[0045] The concrete composition according to this embodiment may further contain an admixture. Examples of the admixture include air-entraining agents, air-entraining water-reducing agents, high-performance water-reducing agents, superplasticizers, separation-reducing agents, set retarders (e.g., tartaric acid), set accelerators (e.g., aluminum sulfate), quick-setting agents, shrinkage-reducing agents, foaming agents, foaming agents, waterproofing agents, and antifoaming agents. One type of admixture may be used alone, or two or more types may be used in combination.

[0046] The content of the admixture can be, for example, 0.4% by mass or more and 3.5% by mass or less relative to the cement. When two or more admixtures are contained, the content is the total content of the admixtures.

[0047] The concrete composition according to this embodiment may further contain an admixture. Examples of the admixture include inorganic fine powders such as silica fume, fly ash, ground granulated blast furnace slag, cement kiln dust, blast furnace fume, ground granulated converter slag, anhydrous gypsum, hemihydrate gypsum, dihydrate gypsum, expansive additives, limestone fine powder, quicklime fine powder, and dolomite fine powder, as well as inorganic fillers such as sodium bentonite, calcium bentonite, attapulgite, sepiolite, activated clay, acid clay, allophane, imogolite, shirasu (volcanic ash), shirasu balloons, kaolinite, metakaolin (calcined clay), synthetic zeolite, artificial zeolite, mordenite, and clinoptilolite. The admixtures may be used alone or in combination of two or more.

[0048] The content of the admixture can be, for example, 5% by mass or more and 60% by mass or less relative to the cement. When two or more types of admixtures are contained, the content is the total content of the other admixtures.

[0049] The total alkali content of the concrete composition according to this embodiment is preferably 3.0 kg / m 3 The total amount of alkali is 3.0 kg / m 3 If the total alkali content is less than this, the alkali-silica reaction in the hardened concrete can be suppressed. The total alkali content can be calculated using the method specified in Appendix B (Method for suppressing alkali-silica reaction) of JIS A 5308 (Ready-mixed concrete).

[0050] The chloride content of the concrete composition according to this embodiment is preferably 0.30 kg / m 3 Chloride content is less than 0.30 kg / m 3 If the chloride content is below this level, corrosion of the steel material in the hardened body can be suppressed. The chloride content can be calculated by the method specified in JIS A 5308 (ready-mixed concrete).

[0051] The concrete composition according to this embodiment contains cement, water, fine aggregate, coarse aggregate, glycerin, and an accelerator, and the accelerator is one or more selected from calcium chloride, sodium carbonate, sodium thiosulfate, triethanolamine, diethanolisopropanolamine, triisopropanolamine, and aluminum sulfate. This makes it possible to obtain a hardened body with relatively excellent early strength development in winter environments without steam curing.

[0052] In the concrete composition according to this embodiment, the content of the accelerator is 0.002 mass % or more and 1.0 mass % or less relative to the cement, so that a hardened body having excellent early strength development can be obtained.

[0053] In the concrete composition according to this embodiment, the accelerator is sodium thiosulfate, and the content of sodium thiosulfate relative to the cement is 0.2 mass % or more and 1.0 mass % or less, so that a hardened body with excellent early strength can be obtained.

[0054] In the concrete composition according to this embodiment, the accelerator is triethanolamine, and the content of triethanolamine relative to the cement is 0.002% by mass or more and 0.01% by mass or less, so that a hardened body with excellent early strength can be obtained.

[0055] In the concrete composition according to this embodiment, the accelerator is aluminum sulfate, and the content of the aluminum sulfate relative to the cement is 0.1% by mass or more and 1.0% by mass or less, so that a hardened body with excellent early strength development can be obtained.

[0056] In the concrete composition according to the present embodiment, the content of the glycerin is 0.1 mass % or more and 1.0 mass % or less relative to the cement, so that a hardened body having excellent early strength development can be obtained.

[0057] <Method of manufacturing concrete composition> The method for producing a concrete composition according to this embodiment is the method for producing the above-described concrete composition, and includes a step of kneading cement, water, fine aggregate, coarse aggregate, glycerin, and an accelerator (hereinafter also referred to as the "kneading step"). The accelerator is one or more selected from calcium chloride, sodium carbonate, sodium thiosulfate, triethanolamine, diethanolisopropanolamine, triisopropanolamine, and aluminum sulfate.

[0058] In the kneading step, cement, water, fine aggregate, coarse aggregate, glycerin, an accelerator, and other materials as necessary are kneaded to obtain a kneaded product. The kneading method is not particularly limited, and kneading can be performed by a conventionally known method using, for example, a forced biaxial mixer, a forced uniaxial mixer, a tilting mixer, or a pan-type forced mixer.

[0059] The kneading temperature can be, for example, from 5° C. to 20° C. The kneading time can be, for example, from 30 seconds to 180 seconds.

[0060] The method for producing a concrete composition according to this embodiment may include a casting step of casting the kneaded mixture into a formwork, and a curing step of removing the mixture from the formwork and curing it after casting.

[0061] In the casting step, the kneaded material is cast into a formwork and subjected to vibration molding. The vibration molding method is not particularly limited, and conventionally known methods can be used. In the curing step, the hardened kneaded material is removed from the formwork and cured outdoors, etc. The curing method is not particularly limited, and conventionally known methods can be used.

[0062] The method for producing a concrete composition according to this embodiment includes a step of kneading cement, water, fine aggregate, coarse aggregate, glycerin, and an accelerator, and the accelerator is one or more selected from calcium chloride, sodium carbonate, sodium thiosulfate, triethanolamine, diethanolisopropanolamine, triisopropanolamine, and aluminum sulfate. This makes it possible to produce a hardened body that exhibits relatively excellent early strength development in winter environments without steam curing.

[0063] <Precast concrete products> The precast concrete product according to this embodiment is obtained by hardening the above-described concrete composition.

[0064] The precast concrete product according to this embodiment is produced by hardening the above-described concrete composition, and therefore exhibits relatively excellent early strength development even in winter environments without steam curing.

[0065] In this specification, "winter environment" refers to an ambient temperature of 5° C. or higher and 10° C. or lower. The concrete composition, method for manufacturing a concrete composition, and precast concrete product according to the present invention are capable of producing a hardened product with relatively good early strength development in a winter environment, i.e., an environment with an ambient temperature of 5° C. or higher and 10° C. or lower, but are not limited to winter environments, and can produce a hardened product with relatively good early strength development even in an environment of, for example, 20° C.

[0066] The present invention includes the following aspects. [1] A mixture comprising cement, water, fine aggregate, coarse aggregate, glycerin, and an accelerator; A concrete composition, wherein the accelerator is one or more selected from calcium chloride, sodium carbonate, sodium thiosulfate, triethanolamine, diethanolisopropanolamine, triisopropanolamine, and aluminum sulfate. [2] The concrete composition according to [1], wherein the content of the accelerator is 0.002% by mass or more and 1.0% by mass or less relative to the cement. [3] The concrete composition according to [1], wherein the accelerator is sodium thiosulfate, and the content of the sodium thiosulfate is 0.2% by mass or more and 1.0% by mass or less relative to the cement. [4] The concrete composition according to [1], wherein the accelerator is triethanolamine, and the content of the triethanolamine is 0.002% by mass or more and 0.01% by mass or less relative to the cement. [5] The concrete composition according to [1], wherein the accelerator is aluminum sulfate, and the content of the aluminum sulfate is 0.1% by mass or more and 1.0% by mass or less relative to the cement. [6] The concrete composition according to any one of [1] to [5], wherein the content of the glycerin is 0.1% by mass or more and 1.0% by mass or less relative to the cement. [7] A method for producing a concrete composition according to any one of [1] to [6], The method includes a step of kneading cement, water, fine aggregate, coarse aggregate, glycerin, and an accelerator, A method for producing a concrete composition, wherein the accelerator is one or more selected from calcium chloride, sodium carbonate, sodium thiosulfate, triethanolamine, diethanolisopropanolamine, triisopropanolamine, and aluminum sulfate. [8] A precast concrete product obtained by hardening the concrete composition according to any one of [1] to [6]. [Example]

[0067] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0068] <Materials used> The materials used in the concrete composition are listed below. Cement: High-early-strength Portland cement (abbreviation: C, Sumitomo Osaka Cement Co., Ltd.) Mixing water: Tap water (abbreviation: W, Funabashi City, Chiba Prefecture) Fine aggregate: mountain sand (abbreviation: S, produced in Kakegawa City, Shizuoka Prefecture) Coarse aggregate: Crushed hard sandstone 2005 (abbreviation: G, produced in Sakuragawa City, Ibaraki Prefecture) Admixture: High-performance water reducer, Mighty 21-LVS (abbreviation: SP, Kao Corporation) Glycerin: Reagent (Abbreviation: A1, Kanto Chemical Co., Ltd.) Calcium chloride: Reagent (Abbreviation: A2, Kanto Chemical Co., Ltd.) Sodium carbonate: Reagent (Abbreviation: A3, Kanto Chemical Co., Ltd.) Sodium thiosulfate: Reagent (Abbreviation: A4, Kanto Chemical Co., Ltd.) Triethanolamine: Reagent (Abbreviation: A5, Tokyo Chemical Industry Co., Ltd.) Diethanolisopropanolamine: Reagent (Abbreviation: A6, Tokyo Chemical Industry Co., Ltd.) Triisopropanolamine: Reagent (Abbreviation: A7, Tokyo Chemical Industry Co., Ltd.) Aluminum sulfate: Reagent (Abbreviation: A8, Kanto Chemical Co., Ltd.) Potassium sulfate: Reagent (Abbreviation: A9, Kanto Chemical Co., Ltd.) Calcium sulfate: Reagent (Abbreviation: A10, Kanto Chemical Co., Ltd.)

[0069] <Formulation> Concrete compositions of each example and comparative example were prepared according to the formulations shown in Table 1. Specifically, cement, fine aggregate, and coarse aggregate were mixed for 15 seconds using a forced biaxial mixer, and then mixing water containing admixtures, glycerin, and an accelerator was added, followed by mixing for 90 seconds to prepare the concrete compositions. The concrete compositions were mixed in an environment of 5°C, 10°C, or 20°C.

[0070] [Table 1]

[0071] <Total amount of alkali> The total alkali content of the concrete composition of each example and comparative example was calculated according to the method specified in Appendix B (method for inhibiting alkali-silica reaction) of JIS A 5308 (ready-mixed concrete). The calculated values ​​are shown in Tables 2 to 4.

[0072] <Chloride content> The chloride content of the concrete composition of each example and each comparative example was calculated by the method specified in JIS A 5308 (ready-mixed concrete). The calculated values ​​are shown in Tables 2 to 4.

[0073] <Compression strength> The concrete compositions of each Example and Comparative Example were cast into a formwork measuring φ100 × 200 mm to prepare specimens for compressive strength testing. Compressive strength was measured for the specimens of each Example and Comparative Example at an age of 18 hours and one day using a method in accordance with JIS A 1108. The measured values ​​are shown in Tables 2 to 4.

[0074] Furthermore, the compressive strength of the test specimens of each Example and Comparative Examples 7 to 20 was evaluated based on the increase rate in comparison with the compressive strength of the test specimens of each Comparative Example 2 to 6, which had the same content of glycerin (A1), according to the following index. The results are shown in Tables 2 to 5. ◎: The increase in compressive strength is more than 30% and not more than 100%. ○: The increase rate of compressive strength is 0% or more and 30% or less. ×: The increase in compressive strength is less than 0%.

[0075] [Table 2]

[0076] [Table 3]

[0077] [Table 4]

[0078] [Table 5]

[0079] As can be seen from the results in Tables 2 to 5, the concrete compositions of each example that satisfy all of the constituent requirements of the present invention can produce hardened bodies with relatively excellent early strength (at 18 hours and 1 day ages) without steam curing in winter environments where the ambient temperature is between 5°C and 10°C.

[0080] Furthermore, the concrete compositions of Examples 18 to 20, which used sodium thiosulfate (A4), were able to obtain hardened bodies that exhibited relatively excellent early strength (at 18 hours and 1 day) compared to the concrete compositions of Comparative Examples 11 to 13, which used potassium sulfate (A9), and Comparative Examples 18 to 20, which used calcium sulfate (A10). Similarly, the concrete compositions of Examples 52 to 58, which used aluminum sulfate (A8), were able to obtain hardened bodies that exhibited relatively excellent early strength (at 18 hours and 1 day) compared to the concrete compositions of Comparative Examples 7 to 13, which used potassium sulfate (A9), and Comparative Examples 14 to 20, which used calcium sulfate (A10).

Claims

1. The mixture comprises cement, water, fine aggregate, coarse aggregate, glycerin, and an accelerator; A concrete composition, wherein the accelerator is one or more selected from calcium chloride, sodium carbonate, sodium thiosulfate, triethanolamine, diethanolisopropanolamine, triisopropanolamine, and aluminum sulfate.

2. The concrete composition according to claim 1, wherein the content of the accelerator is 0.002 mass % or more and 1.0 mass % or less relative to the cement.

3. the promoter is sodium thiosulfate, 2. The concrete composition according to claim 1, wherein the content of the sodium thiosulfate is 0.2 mass % or more and 1.0 mass % or less relative to the cement.

4. the accelerator is triethanolamine, 2. The concrete composition according to claim 1, wherein the content of the triethanolamine is 0.002 mass % or more and 0.01 mass % or less relative to the cement.

5. the promoter is aluminum sulfate, 2. The concrete composition according to claim 1, wherein the content of the aluminum sulfate is 0.1% by mass or more and 1.0% by mass or less relative to the cement.

6. The concrete composition according to any one of claims 1 to 5, wherein the content of the glycerin is 0.1% by mass or more and 1.0% by mass or less relative to the cement.

7. A method for producing a concrete composition according to any one of claims 1 to 5, The method includes a step of kneading cement, water, fine aggregate, coarse aggregate, glycerin, and an accelerator, A method for producing a concrete composition, wherein the accelerator is one or more selected from calcium chloride, sodium carbonate, sodium thiosulfate, triethanolamine, diethanolisopropanolamine, triisopropanolamine, and aluminum sulfate.

8. A precast concrete product obtained by hardening the concrete composition according to any one of claims 1 to 5.

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