High-early-strength material, high-early-strength cement composition, high-early-strength mortar, high-early-strength concrete, high-early-strength mortar cured product, high-early-strength concrete cured product

Abstract

The present invention provides a high-early-strength material comprising a calcium formate-based powder in which the particle size (D90) at which cumulation reaches 90% is not more than 1,200 μm in a volume-based cumulative particle size distribution measured by a laser diffraction scattering method.

Description

High-early-strength materials, high-early-strength cement compositions, high-early-strength mortar, high-early-strength concrete, hardened high-early-strength mortar, hardened high-early-strength concrete

[0001] The present invention relates to an early strength admixture, an early strength cement composition containing the early strength admixture, an early strength mortar and early strength concrete containing the early strength cement composition, and hardened products of the early strength mortar and early strength concrete.

[0002] Hydraulic materials such as cement used in civil engineering and construction fields are usually mixed with water and allowed to harden by standing for a certain period of time. The hardening speed of hydraulic materials can be affected by the ratio of the material to water, the ambient temperature, and the curing method, but the time it takes for hydraulic materials to harden can be shortened by using specific admixtures.

[0003] Reducing the time it takes for hydraulic materials to harden leads to improved productivity at work sites. For example, hardened concrete used in precast construction methods for reinforced concrete buildings and the like can generally be obtained by pouring a cement composition into a formwork, leaving it to stand for a predetermined time, and then further curing it by steam curing or the like. However, the use of a hardening accelerator can reduce the time it takes for the concrete to reach an initial strength that allows it to be removed from the form, allowing for efficient production of hardened concrete.

[0004] For example, Patent Document 1 discloses a hardening accelerator for hydraulic materials containing predetermined amounts of inorganic sulfate, calcium sulfoaluminate, and inorganic hydroxide. Patent Document 2 discloses a hardening accelerator for hydraulic materials having a Blaine specific surface area of ​​4000 cm ２ The document discloses a cement admixture containing calcium sulfoaluminate in an amount of 1 / g or more and one or more salts selected from the group consisting of formates, acetates and lactates.

[0005] JP 2014-19618 A JP 2010-235399 A

[0006] However, hydraulic materials using the above-mentioned admixtures may lose their fluidity immediately after being mixed with water, and may result in poor finish.

[0007] In view of the above, an object of the present invention is to provide a high-early-strength cement that can improve fluidity retention, setting properties, and finish properties.

[0008] As a result of intensive research into solving the above-mentioned problems, the present inventors have found that the problems can be solved by using a high-early-strengthening material containing calcium formate-based powder having a specific particle size distribution, and have arrived at the present invention.

[0009] [1] An early-high strength admixture comprising a calcium formate-based powder having a cumulative 90% particle diameter (D90) of 1,200 μm or less in a volume-integrated particle size distribution measured by a laser diffraction scattering method. [2] An early-high strength cement composition comprising the early-high strength admixture according to [1] above and cement. [3] The early-high strength cement composition according to [2] above, further comprising at least one selected from the group consisting of slag, silica fume, metakaolin, allophane, and fly ash. [4] An early-high strength mortar comprising the early-high strength cement composition according to [2] or [3] above. [5] An early-high strength concrete comprising the early-high strength cement composition according to [2] or [3] above. [6] A hardened early-high strength mortar obtained by hardening the early-high strength mortar according to [4] above. [7] A hardened early-high strength concrete obtained by hardening the early-high strength concrete according to [5] above. [8] A method for producing a hardened body, comprising hardening an early strength cement composition containing the early strength additive according to the above [1] by steam curing at a maximum temperature of 40 to 80°C for 2 to 8 hours.

[0010] According to the present invention, it is possible to provide a high-early-strength cement that can improve fluidity retention, setting properties, and finish properties.

[0011] Hereinafter, one embodiment of the present invention (the present embodiment) will be described in detail, but the present invention is not limited to this embodiment. In addition, "%" and "parts" in this specification are based on mass unless otherwise specified.

[0012] [Early-Hardening Material] The early-harvesting material according to this embodiment contains calcium formate powder having a particle diameter (D90) at 90% of the cumulative total in a volumetric particle size distribution measured by a laser diffraction scattering method of 1,200 μm or less. This early-harvesting material not only promotes the hardening of hydraulic substances such as cement when mixed with water and hardens, but may also harden while promoting the hardening process. The volumetric particle size distribution can be measured using a particle measuring device (such as the LA-960 series laser diffraction / scattering particle size distribution measuring device manufactured by Horiba, Ltd.).

[0013] (Calcium formate-based powder) The calcium formate-based powder contained in the early hardening material of the present invention has a particle size (D90) at 90% cumulative volume in a volumetric particle size distribution measured by a laser diffraction scattering method of 1,200 μm or less. In the present invention, calcium formate-based powder refers to a powder in which the main component per particle is calcium formate. If the D90 of the calcium formate-based powder exceeds 1,200 μm, the fluidity retention, setting property, and finish may be poor. Furthermore, the D90 of the calcium formate-based powder is preferably 1,000 μm or less, more preferably 800 μm or less, and even more preferably 500 μm or less. When the D90 of the calcium formate-based powder is within the above range, the fluidity retention, setting property, and finish are likely to be good.

[0014] The calcium formate powder preferably has a particle diameter at 50% cumulative volume (D50: median diameter) of 100 to 400 μm, more preferably 120 to 300 μm, and even more preferably 150 to 250 μm in a volume-integrated particle size distribution measured by a laser diffraction scattering method. When the median diameter of the calcium formate powder is within the above range, good fluidity retention, coagulation resistance, and finish are likely to be achieved.

[0015] The calcium formate-based powder contained in the early-strengthening material of the present invention preferably contains 0.001 to 0.1 mass% of SrO as a chemical component, more preferably 0.01 to 0.08 mass%, and even more preferably 0.02 to 0.05 mass%. When the SrO content in the calcium formate-based powder is within the above range, good fluidity retention is likely to be achieved. Examples of SrO raw materials include, but are not limited to, celestite, strontianite, strontium oxide, and strontium carbonate, and the SrO content can be adjusted by using these. In this specification, "as a chemical component" refers to a state in which SrO is solid-dissolved in calcium formate, which can be confirmed using X-ray fluorescence analysis (XRF) and X-ray diffraction (XRD). If no peak corresponding to SrO is observed in XRD but a peak corresponding to SrO is observed in XRF, it can be determined that SrO is solid-dissolved in calcium formate, and the content can be further measured. XRF can be performed using an X-ray fluorescence analyzer (such as the ZSX100e X-ray fluorescence analyzer manufactured by Rigaku Corporation), and XRD can be performed using an X-ray powder diffractometer (such as the SmartLab manufactured by Rigaku Corporation).

[0016] The calcium formate powder preferably contains 0.001 to 0.1 mass % of MnO as a chemical component, more preferably 0.01 to 0.08 mass %, and even more preferably 0.02 to 0.05 mass %. When the MnO content in the calcium formate powder is within the above range, it is easy to improve the fluidity retention. The MnO raw material is not particularly limited, but examples include hausmannite, rhodochrosite, tephroite, manganese blende, and rhodonite, and the MnO content can be adjusted by using these.

[0017] The high-early-strengthening material preferably contains 0.01 to 5.0 mass %, more preferably 0.1 to 4.0 mass %, and even more preferably 0.5 to 3.0 mass % of calcium formate powder. When the content of the calcium formate powder is within the above range, good fluidity retention, setting properties, and finish are likely to be achieved.

[0018] The early strength material preferably further contains an inorganic calcium compound. Examples of inorganic calcium compounds that can be used include calcium sulfate, calcium hydroxide, calcium carbonate, and calcium oxide. From the viewpoint of early strength development, calcium sulfate, calcium hydroxide, and / or calcium oxide are preferably used, and calcium sulfate is more preferably used. When calcium sulfate is used, it is preferably anhydrous.

[0019] The early hardening material preferably contains 15.0 to 70.0 mass %, more preferably 18.0 to 60.0 mass %, and even more preferably 20.0 to 40.0 mass % of an inorganic calcium compound. When the content of the inorganic calcium compound is within the above range, good fluidity retention, setting properties, and finish are easily achieved.

[0020] The early strength material preferably further contains an inorganic sulfate. Examples of inorganic sulfates that can be used include sodium sulfate, aluminum sulfate, sodium thiosulfate, and potassium alum. From the viewpoint of early strength development, it is preferable to use sulfate and / or thiosulfate, more preferably sodium sulfate, aluminum sulfate, sodium thiosulfate, and / or potassium alum, and even more preferably sodium sulfate and / or aluminum sulfate. Among these, it is even more preferable to use sodium sulfate from the viewpoint of improving fluidity retention. When sodium sulfate is used, it is preferably anhydrous.

[0021] The early hardening material preferably contains 0.5 to 30.0 mass %, more preferably 1.0 to 25.0 mass %, and even more preferably 3.0 to 15.0 mass % of inorganic sulfate. When the content of inorganic sulfate is within the above range, fluidity retention, setting properties, and finish properties are likely to be good.

[0022] The high-early-strength alloy preferably further contains calcium sulfoaluminate, which has the chemical formula xCaO·yAl ２ O ３ zCaSO ４ ・mH ２O (x, y, z are non-zero positive real numbers, m is 0 or a positive real number), and is a general term for hydraulic substances and hydrated salts. For example, hauyne (3CaO.3Al ２ O ３ CaSO ４ ), as well as ettringite (3CaO·Al ２ O ３ 3CaSO ４ ・32H ２ O), AFt phase, represented by monosulfate (3CaO.Al ２ O ３ CaSO ４ ・12H ２ Calcium sulfoaluminate may be amorphous. ２ O ３ A small amount of Fe is included in part of ２ O ３ or SiO ２ etc., and CaSO ４ Part of Ca(OH) ２ or CaCO ３ In the present invention, the above chemical formula xCaO.yAl may be substituted. ２ O ３ zCaSO ４ ・mH ２ In O, z cannot be 0 from the viewpoint of fluidity retention and because there is a risk of strength decreasing during curing due to phase transition.

[0023] The high-early-strength material preferably contains 4.5 to 65.0 mass% of calcium sulfoaluminate, more preferably 15.0 to 60.0 mass%, and even more preferably 30.0 to 50.0 mass%. When the calcium sulfoaluminate content is within the above range, good fluidity retention, setting properties, and finish are likely to be achieved.

[0024] [Early-Strength Cement Composition] The early-strength cement composition according to the present embodiment contains the early-strength additive of the present invention and cement. The cement is not particularly limited, and examples include various Portland cements, such as normal, early-strength, ultra-high-early-strength, low-heat, and moderate-heat cements; various blended cements obtained by mixing these Portland cements with blast furnace slag, fly ash, silica fume, metakaolin, allophane, and the like; environmentally friendly cements (ecocements) produced using municipal waste incineration ash and sewage sludge incineration ash as raw materials; commercially available fine cements; and white cements. Various cements can also be finely powdered and used. Furthermore, cements prepared by increasing or decreasing the amount of components (e.g., gypsum) typically used in cements can also be used. Furthermore, combinations of two or more of these cements can also be used. From the viewpoint of enhancing early strength development, it is preferable to select normal Portland cement or high-early-strength Portland cement. However, blast furnace cement or fly ash cement, which exhibits low early strength development, can also be used.

[0025] From the viewpoint of production cost and strength development, the cement should have a Blaine specific surface area of ​​2,500 to 7,000 cm ２ / g, and 2,750 to 6,000 cm ２ / g, and more preferably 3,000 to 4,500 cm ２ In the present invention, the Blaine specific surface area is determined in accordance with JIS R 5201:2015 "Physical testing methods for cement."

[0026] The content of the early strength admixture in the early strength cement composition is preferably 0.1 to 10 mass%, more preferably 0.3 to 5.0 mass%, and even more preferably 0.5 to 3.0 mass%. When the content of the early strength admixture in the early strength cement composition is within the above range, the fluidity retention, setting properties, and finish properties of the hydraulic material can be improved.

[0027] The high-early-strength cement composition according to the present embodiment preferably further contains at least one substance selected from the group consisting of slag, silica fume, metakaolin, allophane, and fly ash. The above substances are generally called supplementary cementitious materials (SCMs).

[0028] The high-early-strength cement composition preferably contains 20 to 100 mass %, more preferably 30 to 60 mass %, and even more preferably 40 to 50 mass % of the SCMs relative to the cement in the high-early-strength cement composition. When the SCM content is within the above range, good fluidity retention, setting properties, and finish are likely to be achieved.

[0029] The high-early-strength cement composition preferably further contains a water-reducing agent. The water-reducing agent is not particularly limited, but examples thereof include naphthalene-based water-reducing agents, melamine-based water-reducing agents, aminosulfonic acid-based water-reducing agents, and polycarboxylic acid-based water-reducing agents. One or more of these water-reducing agents can be used in the present invention.

[0030] The content of the water reducing agent is preferably 0.1 to 3.0 parts by mass, more preferably 0.3 to 2.5 parts by mass, and even more preferably 0.5 to 2.0 parts by mass, per 100 parts by mass of the high-early-strength cement composition.

[0031] The high-early-strength cement composition may contain calcium aluminate clinker. When the high-early-strength cement composition contains calcium aluminate clinker, it is easy to improve the setting property. Calcium aluminate clinker contains CaO and Al ２ O ３ It has hydration activity and contains CaO and / or Al ２ O ３ or a compound in which a part of the above is replaced with an alkali metal oxide, an alkaline earth metal oxide, silicon oxide, titanium oxide, iron oxide, an alkali metal halide, an alkaline earth metal halide, an alkali metal sulfate, an alkaline earth metal sulfate, or the like, or a compound in which CaO and Al ２ O ３It is a substance in which these are dissolved in small amounts as a solid solution in a substance mainly composed of these, and calcium aluminate may be either crystalline or amorphous.

[0032] The content of calcium aluminate clinker is preferably 0.1 to 10 parts by mass, and more preferably 0.3 to 5.0 parts by mass, per 100 parts by mass of cement in the high-early-strength cement composition. When the content of calcium aluminate clinker is within the above range, it is easy to achieve better setting properties.

[0033] The high-early-strength cement composition may contain an alkali metal carbonate. When the high-early-strength cement composition contains an alkali metal carbonate, it is easy to improve fluidity retention and early strength development. Examples of the alkali metal carbonate include sodium carbonate, potassium carbonate, lithium carbonate, sodium bicarbonate, potassium bicarbonate, and lithium bicarbonate, and these may also be combined.

[0034] The content of the alkali metal carbonate is preferably 1 to 6 parts by mass, and more preferably 2 to 5 parts by mass, in terms of solid content per 100 parts by mass of cement in the high-early-strength cement composition. When the content of the alkali metal carbonate is within the above range, it is easy to improve fluidity retention and early strength development.

[0035] The high-early-strength cement composition may contain a siliceous fine powder. When the high-early-strength cement composition contains a siliceous fine powder, it is easy to improve fluidity retention and early strength development. Examples of the siliceous fine powder include latent hydraulic substances such as ground granulated blast furnace slag, fly ash, and pozzolanic substances such as silica fume, and among these, silica fume is preferred. The type of silica fume is not limited, but from the viewpoint of fluidity, it is preferable to use silica fume containing ZrO as an impurity. ２ It is more preferable to use silica fume containing 10% or less of the above-mentioned compound or acidic silica fume. Acidic silica fume is a silica fume that, when 1 g of silica fume is added to 100 cc of pure water and stirred, the supernatant liquid has an acidic pH of 5.0 or less.

[0036] The fineness of the silica fine powder is not particularly limited, but typically, the fine powder of granulated blast furnace slag and fly ash has a Blaine specific surface area of ​​3,000 to 9,000 cm ２ / g, and silica fume has a BET specific surface area of ​​20,000 to 300,000 cm ２ / g range.

[0037] The content of the siliceous fine powder is preferably 1 to 20 parts by mass, more preferably 2 to 15 parts by mass, and even more preferably 3 to 12 parts by mass, per 100 parts by mass of cement in the high-early-strength cement composition. When the content of the siliceous fine powder is equal to or greater than the lower limit, fluidity retention and early strength development are likely to be improved. Furthermore, when the content of the siliceous fine powder is equal to or less than the upper limit, fluidity retention is likely to be improved.

[0038] The high-early-strength cement composition may contain an antifoaming agent to the extent that it does not adversely affect performance. Antifoaming agents are used to reduce the amount of air entrained during mixing. The type of antifoaming agent is not particularly limited as long as it does not significantly adversely affect the strength properties of the hardened mortar, and both liquid and powder forms can be used. Examples include polyether-based antifoaming agents, polyhydric alcohol-based antifoaming agents such as polyhydric alcohol esters and alkyl ethers, alkyl phosphate-based antifoaming agents, and silicone-based antifoaming agents.

[0039] The content of the antifoaming agent is preferably 0.002 to 0.5 parts by mass, more preferably 0.005 to 0.45 parts by mass, and even more preferably 0.01 to 0.4 parts by mass, per 100 parts by mass of cement in the high-early-strength cement composition. When the content of the antifoaming agent is equal to or greater than the lower limit, the antifoaming effect can be sufficiently exhibited, and when the content of the antifoaming agent is equal to or less than the upper limit, good fluidity retention can be easily achieved.

[0040] Furthermore, the early strength cement composition may contain one or more of the following additives, within a range that does not adversely affect performance: gas foaming substances, air-enhancing agents, rust inhibitors, water repellents, antibacterial agents, colorants, antifreeze agents, admixtures such as fine limestone powder, slowly cooled blast furnace slag powder, sewage sludge incineration ash and its molten slag, municipal waste incineration ash and its molten slag, and pulp sludge incineration ash; thickeners; shrinkage-reducing agents; polymers; and anion exchangers such as hydrotalcite.

[0041] [High-early-strength mortar] The high-early-strength mortar according to this embodiment contains the high-early-strength cement composition of the present invention. The fine aggregate used in the high-early-strength mortar is not particularly limited, and examples thereof include river sand, mountain sand, sea sand, lime sand, and silica sand.

[0042] The content of the fine aggregate is preferably 40 to 600 parts by mass, more preferably 50 to 500 parts by mass, and even more preferably 60 to 450 parts by mass, per 100 parts by mass of cement in the high-early-strength cement composition. By keeping the content of the fine aggregate within the above range, it is possible to improve fluidity retention and early strength development.

[0043] The high-early-strength mortar can be prepared by kneading a high-early-strength cement composition, fine aggregate, and water. The water content in the high-early-strength mortar is preferably 10 to 70%, more preferably 14 to 65%, and even more preferably 16 to 60%, in terms of water / cement ratio.

[0044] [High-Early-Strength Concrete] The high-early-strength concrete according to this embodiment contains the high-early-strength cement composition of the present invention. The aggregate used in the high-early-strength concrete is not particularly limited, and examples of fine aggregate that can be used include river sand, mountain sand, sea sand, lime sand, and silica sand, and examples of coarse aggregate that can be used include river gravel, mountain gravel, and lime gravel, as well as crushed sand and crushed stone.

[0045] The aggregate content is preferably 40 to 600 parts by mass, more preferably 50 to 500 parts by mass, and even more preferably 60 to 450 parts by mass, per 100 parts by mass of cement in the high-early-strength cement composition. Having the aggregate content within the above ranges can improve fluidity retention and early strength development. The fine aggregate ratio (the ratio of fine aggregate to total aggregate) is preferably 25 to 65%, more preferably 35 to 55%, and even more preferably 40 to 50%.

[0046] High-early-strength concrete can be prepared by mixing a high-early-strength cement composition, aggregate, and water. The water content in the concrete is preferably 10 to 70%, more preferably 14 to 65%, and even more preferably 16 to 60%, in terms of water / cement ratio.

[0047] [Hardened product] The hardened early strength mortar according to this embodiment is obtained by hardening the high-early strength mortar of the present invention. Also, the hardened early strength concrete according to this embodiment is obtained by hardening the high-early strength concrete of the present invention.

[0048] The hardened body is obtained by allowing high-early-strength mortar or high-early-strength concrete to harden by standing, but it can be obtained more efficiently by filling (casting) the mixture into a formwork after mixing and curing, or by pouring it directly into the construction site, or by spraying or applying it.

[0049] The compressive strength of the hardened body is 11.0 N / mm 6 hours after casting, depending on the type of cement used. ２ It is preferable that the strength is 13.0 N / mm or more. ２ More preferably, it is 15.0 N / mm ２ More preferably, it is equal to or greater than this.

[0050] [Method for producing hardened body] The method for producing a hardened body according to this embodiment is a method for hardening an early strength cement composition containing an early strength admixture of the present invention by steam curing for 2 to 8 hours at a maximum temperature of 40 to 80° C. The method for producing a hardened body preferably includes, in this order: a mixing step of mixing the early strength admixture, cement, and water; a casting step of filling a formwork with the mixed early strength cement composition; and a curing step of curing the early strength cement composition filled in the formwork.

[0051] The mixing method in the mixing step is not particularly limited, and the materials may be mixed at the time of construction, or some or all of them may be mixed in advance. As a mixing device, any existing device such as a tilting mixer, an omni mixer, a Henschel mixer, a V-type mixer, a Plosser mixer, or a Nauta mixer can be used.

[0052] The casting method in the casting step can be a known method. The temperature of the early strength cement composition during casting is preferably 0 to 50°C, more preferably 10 to 40°C. When the temperature of the early strength cement composition during casting is within the above range, it is easy to quickly demold the hardened body.

[0053] The method for producing a hardened body preferably further includes a compaction step after the pouring step. Any known method can be used for compaction, but from the viewpoint of workability, it is preferable to use a vibrator. The early-high-early-strength cement composition containing the early-high-strength additive of the present invention maintains its fluidity well just before pouring, so compaction can be easily performed, the early-high-early-strength cement composition can be uniformly distributed within the formwork, and air bubbles that may have been mixed in during pouring can be removed.

[0054] From the viewpoint of improving productivity, steam curing using a curing chamber, a heating sheet, or the like is preferably used as the curing method used in the curing step. Steam curing is usually performed by raising the temperature of the atmosphere surrounding the target and maintaining a constant temperature while maintaining an appropriate humidity. Steam curing conditions are preferably a maximum temperature of 40 to 80°C and a curing time of 2 to 8 hours, more preferably a maximum temperature of 40 to 75°C and a curing time of 2.5 to 7.5 hours, and even more preferably a maximum temperature of 45 to 60°C and a curing time of 3 to 7 hours. Steam curing performed with the maximum temperature of the atmosphere surrounding the early strength cement composition within the above ranges during steam curing and with the curing time within the above ranges tends to enable the hardened body to be quickly demolded.

[0055] The relative humidity around the early strength cement composition during steam curing is preferably 50% RH or higher, more preferably 75% RH or higher, and even more preferably 90% RH or higher. There is no upper limit, but it may be 100% RH. When the relative humidity around the early strength cement composition during steam curing is within the above range, it is easy to enable the hardened body to be quickly demolded.

[0056] The curing step preferably includes a pre-curing step. The pre-curing conditions are preferably a temperature of 10 to 50°C, maintained constant for about 1 to 3 hours. By including the pre-curing step in the curing step, the temperature inside the cast high-early-strength cement composition can be made uniform, making it easier to prevent thermal cracking due to the temperature difference between the inside and outside.

[0057] The curing step preferably includes a heating step. Known heating methods can be used, and heating is preferably carried out at a temperature increase rate of 10 to 30°C / hour, more preferably at a temperature increase rate of 12 to 28°C / hour, and even more preferably at a temperature increase rate of 15 to 25°C. When the temperature increase rate in the heating step is within the above range, hardening can be further promoted while preventing thermal cracking due to a sudden temperature increase in the high-early-strength cement composition.

[0058] The curing step preferably includes a temperature holding step. A known method can be used as the temperature holding method, and a constant temperature is preferably maintained within the range of 40 to 80°C for 1 to 8 hours, more preferably within the range of 40 to 75°C for 1 to 6 hours, and even more preferably within the range of 45 to 65°C for 2.5 to 5 hours. By maintaining a constant temperature within the above-mentioned range in the temperature holding step, the cast high-early-strength cement composition can be hardened uniformly, which makes it easier to quickly remove the formwork.

[0059] The method for producing a hardened body preferably includes a natural cooling step after the curing step. In the natural cooling step, the hardened body obtained in the curing step is naturally cooled in a room temperature atmosphere. The cooling time is not particularly limited, but it is sufficient that the hardened body is cooled to a temperature at which it can be easily demolded, and may be about 0.5 to 2 hours. By including the natural cooling step after the curing step, thermal cracking of the hardened body can be prevented.

[0060] The present invention will be further explained below based on experimental examples, but the present invention is not limited to these.

[0061] Experimental Example 1: The calcium formate powder was prepared by grinding, sieving, and granulating the calcium formate powder so that its D90 was as shown in Table 1. The SrO content of the prepared calcium formate was measured by XRF using a ZSX100e X-ray fluorescence analyzer (Rigaku Corporation) and found to be 0.02%. The prepared calcium formate and cement were mixed to give a 2.0% by mass content of the calcium formate to prepare a high-early-strength cement composition. The resulting high-early-strength cement composition, fine aggregate, coarse aggregate, and water were mixed to give a water-to-cement ratio of 37.5% and a fine aggregate ratio of 42% to prepare high-early-strength concrete (Table 1, Nos. 1-2 to 1-6). Similarly, concrete without the high-early-strength additive was prepared by mixing cement, fine aggregate, coarse aggregate, and water to give a water-to-cement ratio of 35% (Table 1, No. 1-1). The air content, slump change, compressive strength, setting properties, and finish properties of each concrete were measured. The results are shown in Table 1 below.

[0062] (Materials used) Calcium formate: Reagent. Cement: Ordinary Portland cement (commercially available), Blaine specific surface area: 3,200 cm ２ / g, specific gravity 3.15g / cm ３ Water: Tap water. Fine aggregate: Sand from the Himekawa River system in Itoigawa City, Niigata Prefecture, maximum size 5 mm or less, density 2.62 g / cm ３ Coarse aggregate: Crushed stone from Itoigawa City, Niigata Prefecture, maximum size 25 mm, density 2.67 g / cm ３ .

[0063] (Measurement items) Air content: Measured in accordance with the method specified in JIS A 1116:2019 "Test method for unit volume mass of fresh concrete and test method for air content by mass (mass method)."

[0064] Slump change: In accordance with the method specified in JIS A 1101:2020 "Concrete slump test method," the slump immediately after mixing and after leaving to stand for 30 minutes after mixing were measured, and the change was calculated.

[0065] Compressive strength: Compressive strength was measured using a cylindrical specimen having a diameter of 100 cm and a length of 200 cm in accordance with the method specified in JIS A 1108:2018 "Test method for compressive strength of concrete."

[0066] Setting: According to the method specified in JIS A 1147:2019 "Test method for concrete setting time", the penetration resistance value is 1.0 N / mm ２ and 3.5 N / mm ２ The time at which each of these occurred was measured.

[0067] Finish: Concrete was poured into a container measuring 350 mm long x 245 mm wide x 90 mm high (approximately 7.7 L), and 60 minutes after pouring, the concrete was visually inspected for sagging at an angle of approximately 40° and rated on a three-point scale. A rating of good (◯) was given for no visible sagging (unevenness) or floating water, and no sagging occurred when the concrete was troweled; a rating of poor (△) was given for almost no sagging or floating water, but sagging occurred when the concrete was troweled; and a rating of poor (×) was given for visible sagging or floating water.

[0068]

[0069] Experimental Example 2: High-early-strength concrete was prepared and various measurements were carried out in the same manner as in Experimental Example 1, except that the cement in the high-early-strength cement composition was replaced with the SCMs shown below at the SCM replacement rates shown in Table 2 below to prepare high-early-strength cement compositions. The results are also shown in Table 2 below.

[0070] (Materials used) Slag: manufactured by Esment Kanto Co., Ltd. Silica fume: manufactured by Tomoe Engineering Co., Ltd. Metakaolin: manufactured by Imerys Co., Ltd. Allophane: Allophane (produced in Tochigi Prefecture) was baked in an electric furnace at 800°C for 1 hour and then rapidly cooled. Fly ash: manufactured by Kyushu Electric Power Co., Inc.

[0071]

[0072] Experimental Example 3: The high-early-strength cement composition was prepared by mixing the high-early-strength cement and cement prepared in Experimental Example 1 so that the high-early-strength cement was 2.0% by mass, and adding a water-reducing agent in an amount of 0.5% by mass based on the weight of the cement. Using the prepared high-early-strength cement composition, a high-early-strength mortar was prepared with a water / cement ratio of 35% and a cement / fine aggregate ratio of 1:1.5 (by mass). The prepared high-early-strength mortar was then filled into a 4 x 4 x 16 cm formwork and steam-cured to obtain a hardened high-early-strength mortar. The steam-curing conditions were 1 hour of pre-curing at 20°C, 1.5 hours of temperature increase at a rate of 20°C / hour, 3 hours of temperature hold at 50°C, and 0.5 hours of natural cooling. Various measurements were performed on the hardened high-early-strength mortar. The results are shown in Table 3 below.

[0073] (Materials used) Cement: Ordinary Portland cement (commercially available), Blaine specific surface area 3,200 cm ２ / g, specific gravity 3.15g / cm ３ Water: Tap water. Fine aggregate: River sand from the Himekawa River system in Niigata Prefecture. Water reducing agent: Polycarboxylic acid-based high-performance water reducing agent (commercially available).

[0074] (Measurement items) Mortar flow change rate: In accordance with the method specified in JIS R 5201:2015 "Physical testing methods for cement," the flow value of the mortar immediately after mixing and the flow value of the mortar after being left to stand for 30 minutes after mixing were measured, and the mortar flow change rate was calculated as (mortar flow change rate) = (1 - (flow value 30 minutes after mixing) / (flow value immediately after mixing)) × 100.

[0075] Compressive strength: Compressive strength was measured 6 hours after steam curing (immediately after demolding) in accordance with the method specified in JIS R 5201:2015 "Physical testing methods for cement."

[0076] Setting property: According to the method specified in JIS R 5201:2015 "Physical test method for cement", the penetration resistance value is 1.0 N / mm ２ and 3.5 N / mm ２ The time at which each of these occurred was measured.

[0077]

[0078] The early strength material of the present invention can be widely applied to civil engineering and construction fields, such as hardened concrete used in precast construction methods.

Claims

1. A high-early-strength material containing calcium formate powder having a cumulative 90% particle diameter (D90) of 1,200 μm or less in the volume-integrated particle size distribution measured by the laser diffraction scattering method.

2. A high-early-strength cement composition comprising the high-early-strength material according to claim 1 and cement.

3. The early strength cement composition according to claim 2, further comprising at least one selected from the group consisting of slag, silica fume, metakaolin, allophane, and fly ash.

4. A high-early-strength mortar comprising the high-early-strength cement composition according to claim 2 or 3.

5. A high-early-strength concrete comprising the high-early-strength cement composition according to claim 2 or 3.

6. A hardened early strength mortar obtained by hardening the early strength mortar according to claim 4.

7. A hardened early strength concrete product obtained by hardening the early strength concrete according to claim 5.

8. A method for producing a hardened product, comprising hardening an early strength cement composition containing the early strength additive according to claim 1 by steam curing at a maximum temperature of 40 to 80°C for 2 to 8 hours.

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