Quick setting material and quick setting cement

Abstract

A quick setting material containing a calcium aluminate, gypsum, and particles A that contain sodium carbonate, wherein the particles A have an average particle size of 30 µm or larger in an observation image captured by a scanning electron microscope.

Description

Rapid hardening materials and rapid hardening cement

[0001] The present invention relates to a rapid hardening agent and a rapid hardening cement.

[0002] Hardening accelerators are sometimes used to accelerate the hardening of cement. Accelerator-hardening accelerators can improve the usability of cement by accelerating the hardening of cement. For this reason, various researches on hardening accelerators have been conducted. Examples of technologies related to hardening accelerators include those described in Patent Document 1 and Patent Document 2.

[0003] Patent Document 1 describes a method for producing a rapid-hardening cement composition containing γ-2CaO.SiO2, with the objective of providing a rapid-hardening admixture and a rapid-hardening cement composition that can suppress the development of short-term strength and the penetration of deterioration factors. ２ , 3CaO・2SiO ２ , α-CaO.SiO ２ and calcium magnesium silicate, and a rapid-hardening admixture containing calcium aluminates and gypsums, wherein the non-hydraulic compound contains Li and the Li content is 0.001 to 1.0 mass % in terms of oxide.

[0004] Patent Document 2 describes a method for providing a rapid hardening agent and a rapid hardening cement composition that are excellent in early strength development without impairing the long-term strength development and aesthetics of cement concrete, and a method for producing a rapid hardening agent and a rapid hardening cement composition that are excellent in early strength development without impairing the long-term strength development and aesthetics of cement concrete, comprising mixing 100 parts by mass of calcium aluminate clinker with a mixture of the following compounds: ｎ Disclosed is a cement quick-hardening additive characterized by containing ground calcium aluminate clinker obtained by pulverizing the clinker in the presence of 0.2 to 3.0 parts by mass of a fatty acid compound represented by X (R is a saturated or unsaturated hydrocarbon, n is 1 or 2, and X is hydrogen, an alkali metal, or an alkaline earth metal), gypsum, a setting retarder, and an alkali metal carbonate.

[0005] JP 2023-28444 A International Publication No. 2016 / 208277

[0006] The present invention provides a rapid-hardening agent capable of producing rapid-hardening cement having an improved performance balance between workable time and hardening properties, and a rapid-hardening cement having an improved performance balance between workable time and hardening properties.

[0007] According to the present invention, there are provided the following rapid hardening materials, rapid hardening cement, hardened rapid hardening cement, mortar, hardened mortar, concrete, hardened concrete, a method for producing rapid hardening cement, and a method for accelerating the hardening of cement.

[0008] [1] A hardening agent comprising calcium aluminate, gypsum, and particles A containing sodium carbonate, wherein the particles A have an average particle diameter of 30 μm or more in an image observed with a scanning electron microscope. [2] The hardening agent according to [1], wherein the particles A include primary particles composed of sodium carbonate. [3] The hardening agent according to [2], wherein the primary particles have an average particle diameter of 5 μm or less in an image observed with a scanning electron microscope. [4] The hardening agent according to [2] or [3], wherein the particles A include secondary particles formed by aggregation of the primary particles. [5] The hardening agent has a volume-based median diameter D of the hardening agent measured by a laser diffraction scattering method. ５０is 1 μm or more and 30 μm or less. [6] The hardening agent according to any one of [1] to [5], wherein the particle size distribution of the hardening agent on a volume basis measured by a laser diffraction scattering method has a peak in the particle size range of 50 μm or more and 1000 μm or less. [7] The hardening agent according to any one of [1] to [6], wherein the total amount of particles having a particle size in the range of 90 μm or more and 1000 μm or less in the volume basis particle size distribution of the hardening agent on a volume basis measured by a laser diffraction scattering method is 0.1 vol% or more and 20 vol% or less, when the total amount of the hardening agent is 100 vol%. [8] The hardening agent according to any one of [1] to [7], wherein the gypsum includes gypsum dihydrate. [9] The hardening agent according to [8], wherein the content of the gypsum dihydrate is 0.1 mass% or more and 20 mass% or less, when the total amount of the hardening agent is 100 mass%.

[10] The hardening accelerator according to [8] or [9], wherein the gypsum further contains anhydrous gypsum, and the content of the dihydrate gypsum is 5 parts by mass or more and 50 parts by mass or less when the content of the anhydrous gypsum is 100 parts by mass.

[11] The calcium aluminate is 12CaO.7Al ２ O ３ , 2CaO·Al ２ O ３ SiO ２ , and CaO·Al ２ O ３

[12] The rapid hardening material according to any one of [1] to

[10] , which contains one or more compounds selected from the group consisting of 12CaO.7Al. ２ O ３ , the 2CaO.Al ２ O ３ SiO ２ and the CaO.Al ２ O ３The hardening agent according to

[11] , wherein the total content of the above is 3% by mass or more and 15% by mass or less, when the total amount of the hardening agent is taken as 100% by mass.

[13] The hardening agent according to any one of [1] to

[12] , wherein the content of the sodium carbonate is 0.01% by mass or more and 0.50% by mass or less, when the total amount of the hardening agent is taken as 100% by mass.

[14] The hardening agent according to any one of [1] to

[13] , wherein the content of the calcium aluminate is 20% by mass or more and 80% by mass or less, when the total amount of the hardening agent is taken as 100% by mass.

[15] The hardening agent according to [1] to

[14] , wherein the pot life is more than 30 minutes, when measured by the <Pot Life Measurement Method> below. <Method for measuring pot life> 112.5 g of the rapid hardening agent, 337.5 g of cement, 1,350 g of standard sand, 3.6 g of a setting modifier (product name: D200, manufactured by Denka Co., Ltd.), and 207 g of water were mixed, and the time until the temperature rose by 1.0°C from the mixing temperature was measured as the pot life.

[16] According to the <Method for measuring compressive strength after 3 days> described below, the compressive strength after 3 days was 40 N / mm ２The rapid hardening additive according to any one of [1] to

[15] above is described above. <Method for measuring compressive strength after 3 days> 112.5 g of the rapid hardening additive, 337.5 g of cement, 1350 g of standard sand, 3.6 g of a set adjuster (product name: D200, manufactured by Denka Corporation), and 207 g of water are mixed to prepare a 4 x 4 x 16 cm test specimen, and the compressive strength after 3 days is measured using the test specimen in accordance with JIS R 5201:2015.

[17] A rapid hardening cement comprising the rapid hardening additive according to any one of [1] to

[16] above and cement.

[18] A hardened product of the rapid hardening cement according to

[17] above.

[19] Mortar comprising the rapid hardening cement according to

[17] above.

[20] A hardened product of the mortar according to

[19] above.

[21] Concrete comprising the rapid hardening cement according to

[17] above.

[22] A hardened product of the concrete according to

[21] above.

[23] A method for producing rapid hardening cement, comprising a step of mixing the hardening accelerator according to any one of [1] to

[16] with cement to obtain rapid hardening cement.

[24] A method for accelerating the hardening of cement, comprising a step of mixing the hardening accelerator according to any one of [1] to

[16] with cement to obtain a cement composition, and a step of hardening the cement composition.

[0009] According to the present invention, it is possible to provide a rapid hardening agent that can produce rapid hardening cement with an improved performance balance between workable time and hardening properties, and a rapid hardening cement with an improved performance balance between workable time and hardening properties.

[0010] In the present embodiment, each component may be used alone or in combination of two or more. Furthermore, the expression "A to B" regarding a numerical range means A or more and B or less unless otherwise specified.

[0011] The present invention will be described below based on embodiments.

[0012] (Hardening agent) The hardening agent of this embodiment contains calcium aluminate, gypsum, and particles A containing sodium carbonate. In the hardening agent of this embodiment, the particles A have an average particle diameter of 30 μm or more as measured in an image observed with a scanning electron microscope. By having the above-described configuration, the hardening agent of this embodiment can improve the performance balance between usable time and hardenability.

[0013] The reason for this is not entirely clear, but the following reason is presumed. It is believed that the inclusion of particles A containing sodium carbonate in the hardening agent of this embodiment promotes ettringite formation in the rapid-hardening cement containing the hardening agent, thereby improving the hardening properties of the rapid-hardening cement. Furthermore, in the hardening agent of this embodiment, particles A are in the form of clumps with an average particle diameter of 30 μm or more as measured by a predetermined method, which means that the initial stage of ettringite formation in the rapid-hardening cement containing the hardening agent progresses slowly, making it less likely that the usable life of the rapid-hardening cement will be shortened.

[0014] The form of the hardening agent is not particularly limited, but the hardening agent is preferably in a powder form from the viewpoint of suitability for mixing with cement.

[0015] Next, each component of the rapid hardening material of this embodiment will be described with specific examples.

[0016] <Calcium aluminate> The rapid hardening agent of the present embodiment contains calcium aluminate. Calcium aluminate is a mixture of calcium oxide (CaO) and aluminum oxide (Al ２ O ３ The calcium aluminate preferably comprises one or more selected from the group consisting of crystalline calcium aluminate and amorphous calcium aluminate, and more preferably comprises both crystalline calcium aluminate and amorphous calcium aluminate.

[0017] From the viewpoint of further improving the performance balance between pot life and hardenability, the content of calcium aluminate in the hardening agent of this embodiment is preferably 20% by mass or more and 80% by mass or less, more preferably 30% by mass or more and 78% by mass or less, even more preferably 35% by mass or more and 76% by mass or less, even more preferably 40% by mass or more and 74% by mass or less, even more preferably 45% by mass or more and 72% by mass or less, and even more preferably 50% by mass or more and 70% by mass or less, when the total amount of the hardening agent is taken as 100% by mass.

[0018] From the viewpoint of further improving the performance balance between pot life and hardenability, the content of crystalline calcium aluminate in the hardening agent of this embodiment is preferably 0 parts by mass or more and 45 parts by mass or less, more preferably 5 parts by mass or more and 40 parts by mass or less, even more preferably 10 parts by mass or more and 35 parts by mass or less, even more preferably 12 parts by mass or more and 33 parts by mass or less, and even more preferably 15 parts by mass or more and 30 parts by mass or less, based on 100 parts by mass of amorphous calcium aluminate.

[0019] (Crystalline calcium aluminate) The crystalline calcium aluminate of the present embodiment is, for example, 3CaO·Al ２ O ３ , 12CaO・7Al ２ O ３ , 11CaO・7Al ２ O ３ CaF ２ , CaO.Al ２ O ３ , 2CaO·Al ２ O ３ SiO ２ , CaO.Al ２ O ３ 2SiO ２ , CaO.TiO ２ , 3CaO·3Al ２ O ３ CaF ２ , and 3CaO·2Na ２ O.5Al ２ O ３The crystalline calcium aluminate preferably contains 12CaO.7Al from the viewpoint of further improving the balance between the working time and the hardenability. ２ O ３ (hereinafter also referred to as C12A7), 2CaO.Al ２ O ３ SiO ２ (hereinafter also referred to as C2AS), and CaO·Al ２ O ３ (hereinafter also referred to as CA), more preferably comprises one or more selected from the group consisting of C2AS and CA, even more preferably comprises both C2AS and CA, and even more preferably comprises all of C12A7, C2AS, and CA.

[0020] 12CaO · 7Al in the rapid hardening material of this embodiment ２ O ３ From the viewpoint of further improving the performance balance between pot life and curability, the content of (C12A7) is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.1% by mass or more and 4% by mass or less, even more preferably 0.5% by mass or more and 3.5% by mass or less, even more preferably 1% by mass or more and 3% by mass or less, and even more preferably 1.5% by mass or more and 2.5% by mass or less, when the total amount of the rapid hardening agent is taken as 100% by mass.

[0021] 2CaO·Al in the rapid hardening material of this embodiment ２ O ３ SiO ２ From the viewpoint of further improving the performance balance between pot life and curability, the content of (C2AS) is preferably 0.1% by mass or more and 10% by mass or less, more preferably 1% by mass or more and 7% by mass or less, even more preferably 2% by mass or more and 6% by mass or less, even more preferably 2.5% by mass or more and 5.5% by mass or less, and even more preferably 3% by mass or more and 5% by mass or less, when the total amount of the rapid hardening agent is taken as 100% by mass.

[0022] CaO · Al in the rapid hardening material of this embodiment ２ O ３From the viewpoint of further improving the performance balance between pot life and curability, the content of (CA) is preferably 0.1% by mass or more and 10% by mass or less, more preferably 1% by mass or more and 7% by mass or less, even more preferably 2% by mass or more and 6.5% by mass or less, even more preferably 4% by mass or more and 6% by mass or less, and even more preferably 4.5% by mass or more and 5.5% by mass or less, when the total amount of the rapid hardening agent is taken as 100% by mass.

[0023] From the viewpoint of further improving the performance balance between pot life and curability, the total content of C12A7, C2AS, and CA in the hardening agent of this embodiment is preferably 3% by mass or more and 15% by mass or less, more preferably 5% by mass or more and 14% by mass or less, even more preferably 7% by mass or more and 13% by mass or less, even more preferably 9% by mass or more and 12% by mass or less, and even more preferably 8.5% by mass or more and 11.5% by mass or less, when the total amount of the hardening agent is taken as 100% by mass.

[0024] In the calcium aluminate in the hardening accelerator of this embodiment, the mass ratio C12A7 / C2AS of the C12A7 content to the C2AS content is, from the viewpoint of further improving the performance balance between pot life and curability, preferably 0.45 or more and 0.85 or less, more preferably 0.48 or more and 0.82 or less, even more preferably 0.51 or more and 0.79 or less, even more preferably 0.54 or more and 0.76 or less, even more preferably 0.57 or more and 0.73 or less, and even more preferably 0.60 or more and 0.70 or less.

[0025] In the calcium aluminate in the hardening accelerator of this embodiment, the mass ratio C2AS / CA of the C2AS content to the CA content is preferably 0.35 or more and 0.85 or less, more preferably 0.38 or more and 0.82 or less, even more preferably 0.41 or more and 0.79 or less, even more preferably 0.44 or more and 0.76 or less, even more preferably 0.47 or more and 0.73 or less, and even more preferably 0.50 or more and 0.70 or less, from the viewpoint of further improving the performance balance between pot life and hardenability.

[0026] In the calcium aluminate in the hardening accelerator of this embodiment, the mass ratio CA / C12A7 of the CA content to the C12A7 content is preferably 1.8 or more and 3.4 or less, more preferably 1.9 or more and 3.3 or less, even more preferably 2.0 or more and 3.2 or less, and even more preferably 2.1 or more and 3.1 or less, from the viewpoint of further improving the performance balance between the pot life and the hardenability.

[0027] (Amorphous calcium aluminate) From the viewpoint of further improving the performance balance between pot life and hardenability, the content of amorphous calcium aluminate in the hardening agent of this embodiment is preferably 20% by mass or more and 80% by mass or less, more preferably 25% by mass or more and 75% by mass or less, even more preferably 30% by mass or more and 70% by mass or less, even more preferably 35% by mass or more and 65% by mass or less, and even more preferably 40% by mass or more and 60% by mass or less, when the total amount of the hardening agent is taken as 100% by mass.

[0028] <Method for Producing Calcium Aluminate> The method for producing calcium aluminate according to the present embodiment is not particularly limited, and known methods such as a melting method or a calcination method can be used. Calcium aluminate can be obtained, for example, by melting the raw materials at 1200 to 1900°C using an electric furnace or a kiln, followed by rapid cooling.

[0029] <Gypsum> The rapid hardening material of the present embodiment includes gypsum.

[0030] The gypsum of the present embodiment is preferably anhydrous gypsum (calcium sulfate anhydrous: CaSO ) from the viewpoint of further improving the performance balance between the pot life and the hardening property. ４ ), hemihydrate gypsum (calcium sulfate hemihydrate: CaSO ４ ・1 / 2H ２ O), and dihydrate gypsum (calcium sulfate dihydrate: CaSO ４ ・2H ２ O), more preferably, it contains one or two or more selected from the group consisting of gypsum anhydride and gypsum dihydrate, and even more preferably, it contains both gypsum anhydride and gypsum dihydrate. Note that gypsum dihydrate may be referred to as GY hereinafter.

[0031] From the viewpoint of further improving the performance balance between pot life and hardenability, the content of gypsum in the hardening accelerator of the present embodiment is preferably 40 parts by mass or more and 100 parts by mass or less, more preferably 45 parts by mass or more and 99 parts by mass or less, even more preferably 46 parts by mass or more and 98 parts by mass or less, even more preferably 47 parts by mass or more and 97 parts by mass or less, and even more preferably 48 parts by mass or more and 96 parts by mass or less, when the content of calcium aluminate in the hardening accelerator is taken as 100 parts by mass.

[0032] From the viewpoint of further improving the performance balance between pot life and hardening property, the content of gypsum in the hardening agent of this embodiment is preferably 10% by mass or more and 70% by mass or less, more preferably 20% by mass or more and 60% by mass or less, even more preferably 25% by mass or more and 55% by mass or less, even more preferably 30% by mass or more and 50% by mass or less, and even more preferably 32% by mass or more and 49% by mass or less, when the total amount of the hardening agent is taken as 100% by mass.

[0033] From the viewpoint of further improving the performance balance between pot life and hardenability, the content of anhydrous gypsum in the hardening accelerator of the present embodiment is preferably 20 parts by mass or more and 100 parts by mass or less, more preferably 25 parts by mass or more and 95 parts by mass or less, even more preferably 30 parts by mass or more and 90 parts by mass or less, even more preferably 35 parts by mass or more and 85 parts by mass or less, and even more preferably 40 parts by mass or more and 80 parts by mass or less, when the content of calcium aluminate in the hardening accelerator is taken as 100 parts by mass.

[0034] From the viewpoint of further improving the performance balance between pot life and hardening property, the content of anhydrous gypsum in the hardening agent of the present embodiment is preferably 15% by mass or more and 50% by mass or less, more preferably 20% by mass or more and 45% by mass or less, even more preferably 25% by mass or more and 43% by mass or less, even more preferably 26% by mass or more and 42% by mass or less, and even more preferably 27% by mass or more and 41% by mass or less, when the total amount of the hardening agent is taken as 100% by mass.

[0035] From the viewpoint of further improving the performance balance between pot life and hardenability, the content of gypsum dihydrate in the hardening accelerator of the present embodiment is preferably 1 part by mass or more and 20 parts by mass or less, more preferably 5 parts by mass or more and 20 parts by mass or less, even more preferably 6 parts by mass or more and 19 parts by mass or less, even more preferably 7 parts by mass or more and 18 parts by mass or less, and even more preferably 8 parts by mass or more and 17 parts by mass or less, when the content of calcium aluminate in the hardening accelerator is taken as 100 parts by mass.

[0036] From the viewpoint of further improving the performance balance between pot life and hardening property, the content of gypsum dihydrate in the hardening accelerator of the present embodiment is preferably 0.1% by mass or more and 20% by mass or less, more preferably 1% by mass or more and 15% by mass or less, even more preferably 3% by mass or more and 12% by mass or less, even more preferably 4% by mass or more and 10% by mass or less, and even more preferably 5% by mass or more and 9% by mass or less, when the total amount of the hardening accelerator is taken as 100% by mass.

[0037] From the viewpoint of further improving the performance balance between pot life and hardenability, the content of gypsum dihydrate in the hardening accelerator of the present embodiment is preferably 5 parts by mass or more and 50 parts by mass or less, more preferably 5 parts by mass or more and 40 parts by mass or less, even more preferably 10 parts by mass or more and 35 parts by mass or less, even more preferably 15 parts by mass or more and 30 parts by mass or less, and even more preferably 20 parts by mass or more and 25 parts by mass or less, when the content of anhydrous gypsum in the hardening accelerator is taken as 100 parts by mass.

[0038] In the calcium aluminate in the hardening accelerator of this embodiment, the mass ratio C12A7 / GY of the C12A7 content to the gypsum dihydrate content is preferably 0.15 or more and 0.45 or less, more preferably 0.17 or more and 0.42 or less, even more preferably 0.19 or more and 0.39 or less, even more preferably 0.21 or more and 0.36 or less, even more preferably 0.23 or more and 0.33 or less, and even more preferably 0.25 or more and 0.30 or less, from the viewpoint of further improving the performance balance between the pot life and the hardenability.

[0039] In the calcium aluminate in the hardening accelerator of this embodiment, the mass ratio C2AS / GY of the C2AS content to the gypsum dihydrate content is preferably 0.25 or more and 0.60 or less, more preferably 0.28 or more and 0.58 or less, even more preferably 0.31 or more and 0.56 or less, even more preferably 0.34 or more and 0.54 or less, even more preferably 0.37 or more and 0.52 or less, and even more preferably 0.40 or more and 0.50 or less, from the viewpoint of further improving the performance balance between the pot life and the hardenability.

[0040] In the calcium aluminate in the hardening accelerator of this embodiment, the mass ratio CA / GY of the CA content to the gypsum dihydrate content is preferably 0.4 or more and 1.1 or less, more preferably 0.45 or more and 1.05 or less, even more preferably 0.5 or more and 1.0 or less, even more preferably 0.55 or more and 0.95 or less, and still more preferably 0.6 or more and 0.9 or less, from the viewpoint of further improving the performance balance between the pot life and the hardenability.

[0041] <Additives> The additives are components added to the hardening agent for the purpose of improving the performance of the hardening agent. The hardening agent of the present embodiment contains particles A containing sodium carbonate from the viewpoint of improving the performance balance between pot life and hardenability.

[0042] The hardening accelerator of this embodiment may contain components other than particles A. Examples of components other than particles A include setting regulators, expansion agents, water reducing agents, air entraining (AE) agents, AE water reducing agents, high-performance water reducing agents, high-performance AE water reducing agents, thickeners, rust inhibitors, antifreeze agents, hydration heat inhibitors, polymer emulsions, clay minerals, ion exchangers, oxides, sulfates, phosphates, boric acid, fluorite, wollastonite, silica fume, shrinkage reducers, and fluidizing agents. Examples of clay minerals include bentonite and montmorillonite. Examples of ion exchangers include zeolite, hydrotalcite, and hydrocalumite. Examples of oxides include calcium oxide, silicon dioxide, and titanium oxide. Examples of sulfates include alum, aluminum sulfate, and sodium sulfate.

[0043] The method for blending the additives of this embodiment is not particularly limited. For example, pre-ground calcium aluminate, gypsum, and additives may be uniformly mixed using a mixer, or calcium aluminate, gypsum, and additives may be blended and mixed and ground in a grinder. Examples of mixers include a V-type blender, a cone blender, a Nauta mixer, a pan mixer, and an Omni mixer. Examples of grinders include a vibration mill, a tube mill, a ball mill, and a roller mill.

[0044] <Particles A> Particles A of this embodiment are particles containing sodium carbonate. The average particle diameter of particles A, as determined by an image observed with a scanning electron microscope, is 30 μm or more, from the viewpoint of improving the balance between usable time and curability. Here, the average particle diameter of particles A can be measured, for example, by the method described in the examples.

[0045] In the particles A of this embodiment, the average particle size as determined by an image observed with a scanning electron microscope is preferably 50 μm or more and 1,000 μm or less, more preferably 70 μm or more and 500 μm or less, even more preferably 80 μm or more and 300 μm or less, even more preferably 90 μm or more and 200 μm or less, and even more preferably 100 μm or more and 180 μm or less, from the viewpoint of improving the performance balance between the pot life and the curability.

[0046] From the viewpoint of further improving the performance balance between pot life and curability, the particles A of the present embodiment preferably contain one or more types selected from the group consisting of primary particles constituted by sodium carbonate and secondary particles formed by aggregation of primary particles, and more preferably contain secondary particles formed by aggregation of primary particles.

[0047] The primary particles of particle A of this embodiment have an average particle diameter, as determined by an image observed with a scanning electron microscope, of preferably 5 μm or less, more preferably 0.01 μm or more and 5 μm or less, even more preferably 0.05 μm or more and 4 μm or less, even more preferably 0.1 μm or more and 3 μm or less, even more preferably 0.3 μm or more and 2 μm or less, and even more preferably 0.5 μm or more and 1.5 μm or less, from the viewpoint of further improving the performance balance between pot life and curability. Here, the average particle diameter of the primary particles of particle A can be measured, for example, by the method described in the Examples.

[0048] From the viewpoint of further improving the performance balance between pot life and hardenability, the content of sodium carbonate in the hardening accelerator of this embodiment is preferably 0.005 parts by mass or more and 2.5 parts by mass or less, more preferably 0.01 parts by mass or more and 1.0 parts by mass or less, even more preferably 0.05 parts by mass or more and 0.5 parts by mass or less, and even more preferably 0.1 parts by mass or more and 0.4 parts by mass or less, when the content of calcium aluminate in the hardening accelerator is taken as 100 parts by mass.

[0049] From the viewpoint of further improving the performance balance between pot life and hardenability, the content of sodium carbonate in the hardening agent of this embodiment is preferably 0.01% by mass or more and 0.50% by mass or less, more preferably 0.02% by mass or more and 0.45% by mass or less, even more preferably 0.03% by mass or more and 0.40% by mass or less, even more preferably 0.04% by mass or more and 0.35% by mass or less, and even more preferably 0.05% by mass or more and 0.30% by mass or less, when the total amount of the hardening agent is taken as 100% by mass.

[0050] The method for producing particles A of this embodiment is not particularly limited, and for example, particles A may be produced by sieving raw materials for particles A, by pulverizing raw materials for particles A by a known pulverization method, or by dissolving raw materials for particles A in a solvent (e.g., water) and subjecting them to a recrystallization method. More specifically, particles A can be obtained by the methods described in the examples.

[0051] <Method for manufacturing hardening agent> The method for manufacturing the hardening agent of this embodiment is not particularly limited. The hardening agent of this embodiment can be obtained by mixing particles A containing calcium aluminate, gypsum, and sodium carbonate, and, if necessary, other additives, etc., by a conventionally known method. Note that the method for manufacturing the hardening agent, more specifically, the method described in the examples, can be adopted.

[0052] <Physical Properties of Rapid Hardening Material> Next, the physical properties of the rapid hardening material of this embodiment will be described.

[0053] In this embodiment, the volume-based median diameter D of the rapid hardening material by the laser diffraction scattering method is ５０ From the viewpoint of further improving the performance balance between pot life and curability, the average particle size is preferably 1 μm or more and 30 μm or less, more preferably 2 μm or more and 25 μm or less, even more preferably 4 μm or more and 20 μm or less, and even more preferably 6 μm or more and 15 μm or less.

[0054] From the viewpoint of further improving the performance balance between usable time and hardening property, the rapid hardening additive of this embodiment has a particle size peak in the range of preferably 50 μm or more and 1000 μm or less, more preferably 70 μm or more and 700 μm or less, even more preferably 80 μm or more and 500 μm or less, even more preferably 90 μm or more and 400 μm or less, and even more preferably 100 μm or more and 300 μm or less in a volume-based particle size distribution measured by a laser diffraction scattering method.

[0055] In the volume-based particle size distribution of the rapid hardening agent of this embodiment measured by a laser diffraction scattering method, the total amount of particles having a particle diameter in the range of 90 μm to 1000 μm is, from the viewpoint of further improving the performance balance between usable time and hardenability, preferably 0.1% by volume to 20% by volume, more preferably 0.5% by volume to 15% by volume, even more preferably 1.0% by volume to 12% by volume, even more preferably 1.5% by volume to 11% by volume, even more preferably 2.0% by volume to 10% by volume, even more preferably 2.5% by volume to 8.0% by volume, even more preferably 2.5% by volume to 7.5% by volume, and even more preferably 2.5% by volume to 7.0% by volume.

[0056] <Characteristics of the rapid hardening material> Next, the characteristics of the rapid hardening material of this embodiment will be described.

[0057] In the rapid hardening additive of the present embodiment, the pot life measured by the <Method for measuring pot life> below is preferably more than 30 minutes, more preferably 31 minutes or more, even more preferably 32 minutes or more, even more preferably 33 minutes or more, even more preferably 34 minutes or more, and even more preferably 35 minutes or more, from the viewpoint of further improving the performance balance between pot life and hardenability.

[0058] <Method for Measuring Pot Life> 112.5 g of the rapid hardening additive of this embodiment, 337.5 g of cement, 1350 g of standard sand, 3.6 g of a setting modifier (product name: D200, manufactured by Denka Co., Ltd.), and 207 g of water are mixed. Then, the time until the temperature rises by 1.0°C from the kneading temperature is measured as the pot life.

[0059] In the rapid hardening material of this embodiment, the upper limit of the pot life measured by the above <Method for measuring pot life> is not particularly limited, but may be, for example, 90 minutes or less, 75 minutes or less, or 60 minutes or less.

[0060] In the rapid hardening additive of this embodiment, the pot life measured by the above <Method for measuring pot life> is preferably more than 30 minutes and not more than 90 minutes, more preferably 31 minutes or more and not more than 90 minutes, even more preferably 32 minutes or more and not more than 90 minutes, even more preferably 33 minutes or more and not more than 90 minutes, even more preferably 34 minutes or more and not more than 90 minutes, and even more preferably 35 minutes or more and not more than 90 minutes, from the viewpoint of further improving the performance balance between pot life and hardenability.

[0061] In the rapid hardening material of this embodiment, the compressive strength after 3 days measured by the <Method for measuring compressive strength after 3 days> described below is preferably 40 N / mm ２ More preferably, 41 N / mm ２ More preferably, 42 N / mm ２ More preferably, 43 N / mm ２ More preferably, 44 N / mm ２ That's all.

[0062] <Method for measuring compressive strength after 3 days> 112.5 g of the rapid hardening material of this embodiment, 337.5 g of cement, 1350 g of standard sand, 3.6 g of a setting modifier (product name: D200, manufactured by Denka Co., Ltd.), and 207 g of water were mixed to prepare a 4 × 4 × 16 cm test specimen. The compressive strength after 3 days was then measured using the test specimen in accordance with JIS R 5201:2015.

[0063] In the rapid hardening material of this embodiment, the upper limit of the compressive strength after 3 days according to the above <Method for measuring compressive strength after 3 days> is not particularly limited, but is, for example, 100 N / mm ２ The following is the result.

[0064] In the rapid hardening material of this embodiment, the compressive strength after 3 days measured by the above <Method for measuring compressive strength after 3 days> is preferably 40 N / mm ２ More than 100N / mm ２ or less, more preferably 41 N / mm ２ More than 100N / mm ２ or less, more preferably 42 N / mm ２ More than 100N / mm ２ or less, more preferably 43 N / mm ２ More than 100N / mm ２ or less, more preferably 44 N / mm ２ More than 100N / mm ２ The following is the result.

[0065] <Use of Rapid Hardening Material> Next, the use of the rapid hardening material of this embodiment will be described.

[0066] The hardening accelerator of this embodiment can improve the performance balance between the working life and hardening properties of a cement composition containing the hardening accelerator of this embodiment, and therefore can be mixed with various cements for use. Examples of cements to be mixed with the hardening accelerator of this embodiment include Portland cement, blended cement, ecocement, and special cement. Examples of Portland cement include ordinary Portland cement, early-strength Portland cement, ultra-early-strength Portland cement, moderate-heat Portland cement, low-heat Portland cement, sulfate-resistant Portland cement, and white Portland cement. Examples of blended cement include blast-furnace cement, silica cement, and fly ash cement. Examples of ecocement include ordinary ecocement and rapid-hardening ecocement. Examples of special cement include alumina cement, ultra-rapid-hardening cement, grout cement, oil well cement, and cement that does not meet JIS standards.

[0067] (Rapid-hardening cement) The rapid-hardening cement of this embodiment includes the rapid-hardening agent of this embodiment and cement. The cement used in the rapid-hardening cement of this embodiment is not particularly limited, and examples thereof include Portland cement, blended cement, ecocement, and special cement. The rapid-hardening cement may contain components other than the rapid-hardening agent and cement as necessary. Examples of components other than the rapid-hardening agent and cement include a setting adjuster.

[0068] From the viewpoint of further improving the performance balance between usable time and hardening property, the content of cement in the rapid-hardening cement of this embodiment is preferably 100 parts by mass or more and 500 parts by mass or less, more preferably 150 parts by mass or more and 450 parts by mass or less, even more preferably 200 parts by mass or more and 400 parts by mass or less, and even more preferably 250 parts by mass or more and 350 parts by mass or less, when the content of the rapid-hardening agent in the rapid-hardening cement is taken as 100 parts by mass.

[0069] From the viewpoint of further improving the performance balance between usable time and hardening property, the content of the setting regulator in the rapid-hardening cement of this embodiment is preferably 0.1 parts by mass or more and 10 parts by mass or less, more preferably 1 part by mass or more and 6 parts by mass or less, even more preferably 2 parts by mass or more and 5 parts by mass or less, and even more preferably 3 parts by mass or more and 4 parts by mass or less, when the amount of the rapid-hardening agent in the rapid-hardening cement is 100 parts by mass.

[0070] From the viewpoint of further improving the performance balance between usable time and hardening property, the content of the set regulator in the rapid-hardening cement of this embodiment is preferably 0.1 parts by mass or more and 5 parts by mass or less, more preferably 0.2 parts by mass or more and 3 parts by mass or less, even more preferably 0.4 parts by mass or more and 2 parts by mass or less, and even more preferably 0.5 parts by mass or more and 1.5 parts by mass or less, when the cement in the rapid-hardening cement is taken as 100 parts by mass.

[0071] <Method for producing rapid hardening cement> The method for producing rapid hardening cement of this embodiment includes the following steps. Mixing step: The rapid hardening agent of this embodiment is mixed with cement to obtain rapid hardening cement. Because the method for producing rapid hardening cement of this embodiment has the configuration described above, it is possible to obtain rapid hardening cement with an improved performance balance between pot life and hardening properties.

[0072] In the mixing step, the hardening agent of this embodiment is mixed with cement to obtain a cement composition. The mixing method of this embodiment is not particularly limited. For example, the hardening agent of this embodiment and cement that have been previously pulverized may be uniformly mixed using a mixer, or the hardening agent of this embodiment and cement may be mixed and pulverized using a pulverizer. Examples of mixers include a V-type blender, a cone blender, a Nauta mixer, a pan mixer, and an Omni mixer. Examples of pulverizers include a vibration mill, a tube mill, a ball mill, and a roller mill. In the above mixing step, components other than the hardening agent of this embodiment and cement may be added as needed.

[0073] <Hardened product of rapid hardening cement> The hardened product of the rapid hardening cement of this embodiment is a hardened product of the rapid hardening cement of this embodiment. The hardened product of the rapid hardening cement of this embodiment is obtained by mixing the rapid hardening cement of this embodiment with water and hardening the mixture.

[0074] <Mortar> The mortar of this embodiment includes the rapid hardening cement of this embodiment. The mortar of this embodiment may further include fine aggregate. The fine aggregate may be, for example, a fine aggregate specified in JIS A 0203:2019. The fine aggregate used in the mortar of this embodiment is not particularly limited, and examples thereof include river sand, mountain sand, sea sand, lime sand, and silica sand.

[0075] In order to further improve the performance balance between usable time and hardening property, the content of the fine aggregate in the mortar of this embodiment is preferably 900 parts by mass or more and 1500 parts by mass or less, more preferably 1000 parts by mass or more and 1400 parts by mass or less, even more preferably 1100 parts by mass or more and 1300 parts by mass or less, and even more preferably 1150 parts by mass or more and 1250 parts by mass or less, when the content of the rapid hardening agent in the mortar is taken as 100 parts by mass.

[0076] From the viewpoint of further improving the performance balance between usable time and hardening property, the content of the fine aggregate in the mortar of this embodiment is preferably 100 parts by mass or more and 1,000 parts by mass or less, more preferably 200 parts by mass or more and 600 parts by mass or less, even more preferably 300 parts by mass or more and 500 parts by mass or less, and even more preferably 350 parts by mass or more and 450 parts by mass or less, when the content of cement in the mortar is taken as 100 parts by mass.

[0077] <Hardened Mortar> The hardened mortar of the present embodiment is a hardened product of the mortar of the present embodiment. The hardened mortar of the present embodiment can be obtained by mixing the mortar of the present embodiment with water and hardening the mixture.

[0078] <Concrete> The concrete of this embodiment includes the rapid hardening cement of this embodiment. The concrete of this embodiment may also include fine aggregate and coarse aggregate. The fine aggregate and coarse aggregate may be, for example, those specified in JIS A 0203:2019. The fine aggregate used in the concrete of this embodiment is not particularly limited, and examples thereof include river sand, mountain sand, sea sand, lime sand, and silica sand. The coarse aggregate used in the concrete of this embodiment is not particularly limited, and examples thereof include river gravel, mountain gravel, lime gravel, crushed stone, slag aggregate, and recycled aggregate.

[0079] <Hardened Concrete> The hardened concrete of the present embodiment is a hardened product of the concrete of the present embodiment. The hardened concrete of the present embodiment is obtained by mixing the concrete of the present embodiment with water and hardening the mixture.

[0080] <Method for accelerating hardening of cement> The method for accelerating hardening of cement of this embodiment includes the following steps. Mixing step: mixing the hardening accelerator of this embodiment with cement to obtain a cement composition. Hardening step: hardening the cement composition. Since the method for accelerating hardening of cement of this embodiment has the configuration described above, it is possible to improve the performance balance between the usable time and hardening properties of the cement composition mixed with the hardening accelerator. In this embodiment, the cement composition is a composition containing the hardening accelerator of this embodiment and cement. In addition, the cement composition of this embodiment is a concept that includes the above-mentioned hardening cement.

[0081] In the mixing step, the hardening agent of this embodiment is mixed with cement to obtain a cement composition. The mixing method of this embodiment is not particularly limited. For example, the hardening agent of this embodiment and cement that have been previously pulverized may be uniformly mixed using a mixer, or the hardening agent of this embodiment and cement may be mixed and pulverized using a pulverizer. Examples of mixers include a V-type blender, a cone blender, a Nauta mixer, a pan mixer, and an Omni mixer. Examples of pulverizers include a vibration mill, a tube mill, a ball mill, and a roller mill. In the above mixing step, components other than the hardening agent of this embodiment and cement may be added as needed.

[0082] In the hardening step, the cement composition is hardened. The hardening of the cement composition in this embodiment is carried out by mixing the cement composition with water and then leaving it to stand. The hardening of the cement composition may also be carried out by mixing the pre-pulverized rapid hardening agent of this embodiment with cement and water and leaving the mixture to stand.

[0083] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations may be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements that do not impair the effects of the present invention are included in the present invention.

[0084] The present embodiment will be described in detail below with reference to examples, etc. However, the present embodiment is not limited to the descriptions of these examples.

[0085] First, the following materials were used in each example. <Materials used for the rapid hardening agent> Calcium aluminate: Synthesis Examples 1 and 2 synthesized by the methods described below Anhydrous gypsum (CaSO ４ ): Anhydrite (manufactured by Mitsubishi Materials Denshi Kasei Co., Ltd.) ・Dihydrate gypsum (CaSO ４ ・2H ２ O): Gypsum dihydrate (special grade, manufactured by Kishida Chemical Co., Ltd.) Sodium carbonate (Na ２ CO ３Particle A containing sodium carbonate, prepared by the method described below. <Materials used in rapid hardening cement> Cement: ordinary cement, manufactured by Denka Co., Ltd. Standard sand: standard sand for cement strength testing, manufactured by the Cement Association of Japan. Set adjuster: D200, manufactured by Denka Co., Ltd.

[0086] Synthesis Examples 1 and 2 Next, the synthesis methods of calcium aluminate Synthesis Examples 1 and 2 will be described. In each synthesis example, the following materials were used. Calcium oxide source (CaO source): calcium oxide (Kanto Chemical Co., Ltd. Grade 1) Aluminum oxide source (Al ２ O ３ Source): Aluminum oxide (α-type) (special grade, manufactured by Kanto Chemical Co., Ltd.) Silicon oxide source (SiO ２ Source): Silicon dioxide (special grade, manufactured by Kanto Chemical Co., Ltd.)

[0087] Calcium aluminate synthesis examples 1 and 2 were synthesized by the following method. ２ O ３ source, and SiO ２ The sources were mixed according to the formulations in Table 2 to obtain raw material mixtures. These raw material mixtures were melted at 1600°C for 30 minutes and then rapidly cooled to 20°C to synthesize clinkers. The clinkers were pulverized for 60 seconds using a disc mill to obtain calcium aluminate Synthesis Examples 1 and 2.

[0088] <Particles A containing sodium carbonate> Sodium carbonate (manufactured by Kanto Chemical Co., Inc.) was passed through a sieve having a nominal mesh size of 90 μm as specified in JIS Z8801-1: 2019. The residue remaining on the sieve was collected to obtain particles A containing sodium carbonate.

[0089] Examples 1 and 2, Comparative Example 1 The hardening agents of each example were obtained by mixing the components to obtain the formulations shown in Table 1. Note that Comparative Example 1 is a hardening agent that does not contain particles A containing sodium carbonate or gypsum dihydrate. The physical properties and characteristics of the hardening agents obtained in each example were measured by the following methods.

[0090] <Measurement of the average particle size of particles A containing sodium carbonate> Samples were prepared from the rapid hardening materials of each example by carrying out the following <pretreatment>. Using the samples, the average particle size of particles A containing sodium carbonate was measured based on images observed with a scanning electron microscope (SEM). The results are shown in Table 1. The average particle size was calculated using SEM images of particles photographed using an SEM / EDS device under the following <Photographing Condition 1>. Whether or not particles in the SEM images were particles A was determined based on the analysis results of the EDS device. If the analysis results of the EDS device showed that the particles contained all of carbon, oxygen, and sodium, they were determined to be particles A, and otherwise they were determined not to be particles A.

[0091] <Pretreatment> The hardening accelerator of each example was dispersed in a thermosetting epoxy resin (product name: G2, manufactured by Gatan Corporation). The thermosetting epoxy resin with the hardening accelerator dispersed therein was poured into a silicone mold. A cured product was obtained by curing the thermosetting epoxy resin with the hardening accelerator dispersed therein. The cured product was separated from the silicone mold. The surface of the separated cured product was cross-sectionally processed using an Ar ion polishing device (product name: SM-09010, manufactured by JEOL Ltd.) under conditions of an acceleration voltage of 6.0 kV and a processing time of 8 hours, thereby obtaining a sample.

[0092] <Photography Condition 1> Apparatus: SEM / EDS Apparatus: Combination of an SEM apparatus (product name: SU6000, manufactured by Hitachi High-Technologies Corporation) and an EDS apparatus (INCA X-act, manufactured by Oxford Instruments) Magnification: ×100 Acceleration voltage: 15.0 kV Image analysis software: Image J (National Institutes of Health, USA) From the photographed SEM image, 10 particles A (aggregates of primary particles of sodium carbonate) in which the particles did not overlap and the particle outlines were visible were randomly selected. The projected area equivalent circle diameter (Heywood diameter) of the selected particles was calculated using image processing software (Image J), ​​and the arithmetic mean value of the obtained projected area equivalent circle diameters was used as the average particle diameter.

[0093] <Measurement of Average Particle Size of Sodium Carbonate Primary Particles> Using the sample and measurement data obtained in the above <Measurement of Average Particle Size of Particle A Containing Sodium Carbonate>, the average particle size of the primary particles of sodium carbonate in Particle A (hereinafter referred to as primary particles) was measured based on images observed with a scanning electron microscope (SEM). The measurement results are shown in Table 1. The average particle size was calculated using SEM images of particles photographed using an SEM / EDS device under the following <Photographing Condition 2>. Whether or not particles in the SEM images were primary particles was determined based on the analysis results of the EDS device. If the analysis results of the EDS device showed that the particles contained all of carbon, oxygen, and sodium, they were determined to be primary particles, and otherwise they were determined not to be primary particles.

[0094] <Photography Condition 2> Apparatus: SEM / EDS Apparatus: Combination of an SEM apparatus (product name: SU6000, manufactured by Hitachi High-Technologies Corporation) and an EDS apparatus (INCA X-act, manufactured by Oxford Instruments) Magnification: ×1000 Acceleration voltage: 15.0 kV Image analysis software: Image J (National Institutes of Health, USA) Ten primary particles (fine particles constituting particle A) were randomly extracted from the captured SEM image. The projected area circle equivalent diameter (Heywood diameter) of the selected particles was calculated using image processing software (Image J), ​​and the arithmetic mean value of the obtained projected area circle equivalent diameters was used as the average particle diameter.

[0095] <Median diameter D of rapid hardening material ５０ Measurement of the median diameter D of each rapid hardening material using a particle size measuring device using the laser diffraction / scattering method (product name: LA-960, manufactured by Horiba Ltd.) ５０ The results are shown in Table 1. The rapid hardening materials of each example were ultrasonically dispersed in ethanol, and then the median diameter D ５０ was measured.

[0096] <Analysis of mineral composition of hardening accelerator> The mineral composition of each hardening accelerator was confirmed by X-ray diffraction analysis in accordance with the following <Condition 1>. The results are shown in Table 3. The hardening accelerator of Comparative Example 1 contained no components other than those listed in Table 3 (for example, CaF ２ , CaSiO ３ , SiO ２The rapid hardening material of Comparative Example 1 also contained 2CaO.Al, but these are not listed in Table 3. ２ O ３ SiO ２ (C2AS) and CaO·Al ２ O ３ (CA) was not detected. <Condition 1> - Model used: Miniflex (manufactured by Rigaku Corporation) - X-ray source: Cu Kα - Starting angle: 20° - Ending angle: 40° - Sampling width: 0.02° - Scan speed: 4.0° / min - Voltage: 30 kV - Current: 15 mA - Divergence slit: 1.25° - Scattering slit: 8.0 mm - Receiving slit: 0.3 mm - Crystal structure analysis software: PDXL (manufactured by Rigaku Corporation)

[0097] <Method for measuring pot life> 112.5 g of the hardening accelerator, 337.5 g of cement, 1350 g of standard sand, 3.6 g of set retarder, and 207 g of water were mixed for each example. The time required for the temperature to rise by 1.0°C from the as-mixed temperature was then measured as the pot life. The measurement results are shown in Table 1. The pot life was measured in indoor air at a temperature of 20°C and a relative humidity of 80%RH. The cement temperature was confirmed using a thermometer (manufactured by Chino Corporation). The as-mixed temperature was the temperature of the mixture measured immediately after mixing the hardening accelerator, cement, standard sand, set retarder, and water.

[0098] <Method for measuring compressive strength after 3 days> 112.5 g of the rapid hardening material of each example, 337.5 g of cement, 1350 g of standard sand, 3.6 g of setting modifier, and 207 g of water were mixed to prepare a 4 x 4 x 16 cm test specimen. The test specimen was then used to measure the compressive strength after 3 days in accordance with JIS R 5201:2015. The measurement results are shown in Table 1. The compressive strength after 3 days was measured in an indoor atmosphere at a temperature of 20°C. The compressive strength after 3 days was measured using a compressive strength measuring device (product name: 500 kN uniaxial compression tester, Marui Co., Ltd.).

[0099]

[0100]

[0101]

[0102] This application claims priority based on Japanese Patent Application No. 2024-150534, filed September 2, 2024, the disclosure of which is incorporated herein in its entirety by reference.

Claims

1. A rapid hardening material comprising particles A containing calcium aluminate, gypsum, and sodium carbonate, wherein the particles A have an average particle diameter of 30 μm or more as measured in an image observed with a scanning electron microscope.

2. The hardening accelerator according to claim 1, wherein the particles A include primary particles composed of sodium carbonate.

3. The rapid hardening material according to claim 2, wherein the primary particles have an average particle size of 5 μm or less as determined by an image observed with a scanning electron microscope.

4. The hardening accelerator according to claim 2, wherein the particles A include secondary particles formed by agglomeration of the primary particles.

5. The volume-based median diameter D of the rapid hardening material measured by the laser diffraction scattering method ５０ The rapid hardening material according to claim 1, wherein the average particle diameter is 1 μm or more and 30 μm or less.

6. The hardening agent according to claim 1, wherein the particle size distribution of the hardening agent on a volume basis measured by a laser diffraction scattering method has a peak in the particle diameter range of 50 μm or more and 1000 μm or less.

7. The hardening agent according to claim 1, wherein the total amount of particles having a particle diameter in the range of 90 μm or more and 1000 μm or less in a volume-based particle size distribution of the hardening agent as measured by a laser diffraction scattering method is 0.1 volume % or more and 20 volume % or less when the total amount of the hardening agent is taken as 100 volume %.

8. The rapid hardening material according to claim 1, wherein the gypsum comprises gypsum dihydrate.

9. The hardening agent according to claim 8, wherein the content of the gypsum dihydrate is 0.1% by mass or more and 20% by mass or less when the total amount of the hardening agent is 100% by mass.

10. The rapid hardening material according to claim 8, wherein the gypsum further contains anhydrous gypsum, and the content of the dihydrate gypsum is 5 parts by mass or more and 50 parts by mass or less when the content of the anhydrous gypsum is 100 parts by mass.

11. The calcium aluminate is 12CaO.7Al ２ O ３ , 2CaO·Al ２ O ３ SiO ２ , and CaO·Al ２ O ３ The hardening accelerator according to claim 1, comprising one or more compounds selected from the group consisting of:

12. Said 12CaO・7Al ２ O ３ , the 2CaO.Al ２ O ３ SiO ２ and the CaO.Al ２ O ３ The hardening agent according to claim 11, wherein the total content of the hardening agent is 3% by mass or more and 15% by mass or less when the total amount of the hardening agent is 100% by mass.

13. The hardening agent according to claim 1, wherein the content of the sodium carbonate is 0.01% by mass or more and 0.50% by mass or less when the total amount of the hardening agent is 100% by mass.

14. The hardening agent according to claim 1, wherein the content of the calcium aluminate is 20% by mass or more and 80% by mass or less when the total amount of the hardening agent is 100% by mass.

15. The hardening accelerator according to claim 1, whose pot life is more than 30 minutes according to the <Pot Life Measurement Method> below. <Pot Life Measurement Method> 112.5 g of the hardening accelerator, 337.5 g of cement, 1,350 g of standard sand, 3.6 g of setting modifier (product name: D200, manufactured by Denka Co., Ltd.), and 207 g of water are mixed, and the pot life is measured as the time until the temperature rises by 1.0°C from the mixed temperature.

16. The compressive strength after 3 days is 40 N / mm according to the method for measuring compressive strength after 3 days below. ２ The rapid hardening material according to claim 1, wherein the compressive strength after 3 days is measured in accordance with JIS R 5201:2015. <Method for measuring compressive strength after 3 days> 112.5 g of the rapid hardening material, 337.5 g of cement, 1350 g of standard sand, 3.6 g of a setting modifier (product name: D200, manufactured by Denka Co., Ltd.), and 207 g of water are mixed to prepare a test specimen measuring 4 × 4 × 16 cm. The compressive strength after 3 days is then measured using the test specimen in accordance with JIS R 5201:2015.

17. A rapid hardening cement comprising the rapid hardening agent according to any one of claims 1 to 16 and cement.

18. A hardened product of the rapid hardening cement according to claim 17.

19. A mortar comprising the rapid hardening cement of claim 17.

20. A hardened mortar according to claim 19.

21. Concrete comprising the rapid hardening cement of claim 17.

22. A hardened concrete product according to claim 21.

23. A method for producing rapid hardening cement, comprising the step of mixing the rapid hardening agent according to any one of claims 1 to 16 with cement to obtain rapid hardening cement.

24. A method for accelerating the hardening of cement, comprising the steps of: mixing the hardening accelerator according to any one of claims 1 to 16 with cement to obtain a cement composition; and hardening the cement composition.

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