Early strength material, early strength cement composition, early strength mortar, early strength concrete, early strength mortar cured product, early strength concrete cured product

Abstract

The present invention provides an early strength material comprising calcium formate powder, wherein, in the volume cumulative particle size distribution of the calcium formate powder determined by laser diffraction scattering method, 90% of the particles have a particle size (D90) of less than 1200 μm.

Description

Technical Field

[0001] This invention relates to an early-strength material, an early-strength cement composition comprising the early-strength material, an early-strength mortar and early-strength concrete comprising the early-strength cement composition, and cured products of the early-strength mortar and early-strength concrete. Background Technology

[0002] Hydraulic materials such as cement used in civil engineering and construction typically cure by mixing with water and allowing it to stand for a specified time. The curing speed of hydraulic materials can also be affected by the ratio of material to water, the ambient temperature, and the curing method. However, by using specific mixing materials, it is possible to shorten the time it takes for hydraulic materials to cure.

[0003] Shortening the curing time of hydraulic materials is crucial for improving productivity at work sites. For example, in precast construction methods for reinforced concrete buildings, cured concrete is typically produced by pouring a cementitious mixture into a formwork, allowing it to stand for a specified time, and then further curing it using methods such as steam curing. However, by using curing accelerators, the time until the material reaches its initial demolding strength can be shortened, thus enabling efficient production of cured concrete.

[0004] For example, Patent Document 1 discloses a curing accelerator for hydraulic materials containing a specified amount of inorganic sulfate, calcium sulfoaluminate, and inorganic hydroxide. Patent Document 2 discloses a material containing a Blaine surface area of ​​4000 cm². 2 A cementitious mixture consisting of calcium sulfoaluminate of 1 g or more and one or more of formate, acetate and lactate.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2014-19618

[0008] Patent Document 2: Japanese Patent Application Publication No. 2010-235399 Summary of the Invention

[0009] However, hydraulic materials using the mixtures described above may lose fluidity immediately after being mixed with water and may have poor processability.

[0010] Based on the above, the purpose of this invention is to provide an early-strength material that can maintain fluidity, coagulation, and processability.

[0011] The inventors conducted in-depth research to solve the problem described above, and discovered that an early-strength material containing calcium formate powder with a specific particle size distribution could solve this problem, thus completing the present invention. That is, the present invention is as follows.

[0012] [1] An early strength material comprising calcium formate powder, wherein, in the volume cumulative particle size distribution of the calcium formate powder determined by laser diffraction scattering method, 90% of the particles have a particle size (D90) of less than 1200 μm.

[0013] [2] An early-strength cement composition comprising the early-strength material described in [1] above and cement.

[0014] [3] The early-strength cement composition according to [2] above further comprises at least one selected from slag, silica fume, metakaolin, diatomite and fly ash.

[0015] [4] An early-strength mortar comprising the early-strength cement composition described in [2] or [3] above.

[0016] [5] An early-strength concrete comprising the early-strength cement composition described in [2] or [3] above.

[0017] [6] An early-strength mortar curing product is formed by curing the early-strength mortar described in [4] above.

[0018] [7] An early-strength concrete curing product is formed by curing the early-strength concrete described in [5] above.

[0019] [8] A method for manufacturing a cured material, wherein an early-strength cement composition containing the early-strength material described above [1] is cured by steam curing at a maximum temperature of 40 to 80°C for 2 to 8 hours.

[0020] According to the present invention, an early-strength material that can maintain fluidity, cohesiveness, and processability can be provided. Detailed Implementation

[0021] The following describes one embodiment of the present invention (this embodiment) in detail, but the present invention is not limited to this embodiment. It should be noted that, unless otherwise specified, "%" and "parts" in this specification refer to mass measurements.

[0022] [Early Strength Materials]

[0023] The early-strength material of this embodiment comprises calcium formate-based powder, wherein, in the volumetric cumulative particle size distribution measured by laser diffraction scattering, 90% of the particles have a diameter (D90) of 1200 μm or less. This early-strength material not only promotes the curing of hydraulic materials such as cement when mixed with water, but sometimes also promotes the curing of the early-strength material itself. It should be noted that the volumetric cumulative 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 Corporation).

[0024] (Calcium formate powder)

[0025] The early-strength material of the present invention contains calcium formate-based powder, and in the volumetric cumulative particle size distribution determined by laser diffraction scattering, 90% of the particles have a diameter (D90) of 1200 μm or less. In the present invention, calcium formate-based powder refers to powder in which calcium formate is the main component of a single particle. If the D90 of the calcium formate-based powder exceeds 1200 μm, poor flowability, agglomeration, and processability may occur. Furthermore, the D90 of the calcium formate-based powder is preferably 1000 μm or less, more preferably 800 μm or less, and even more preferably 500 μm or less. By keeping the D90 of the calcium formate-based powder within the above range, good flowability, agglomeration, and processability are easily achieved.

[0026] In the volumetric cumulative particle size distribution of calcium formate powder determined by laser diffraction scattering, the particle size that constitutes 50% (D50: median particle size) is preferably 100–400 μm, more preferably 120–300 μm, and even more preferably 150–250 μm. By keeping the median particle size of the calcium formate powder within the above range, it is easy to achieve good flowability, coagulation, and processability.

[0027] The early-strength material of the present invention preferably contains 0.001 to 0.1% by mass of SrO as a chemical component, more preferably 0.01 to 0.08% by mass, and even more preferably 0.02 to 0.05% by mass. If the SrO content in the calcium formate powder is within the above range, good flowability is easily maintained. There are no particular limitations on the SrO raw material; for example, lapis lazuli, strontium sapphire, strontium oxide, and strontium carbonate can be used, and the SrO content can be adjusted by using these. It should be noted that in the present invention, "as a chemical component" refers to a state of solid solution in calcium formate, which can be confirmed using X-ray fluorescence (XRF) and X-ray diffraction (XRD). If a peak corresponding to SrO is not confirmed in XRD but is confirmed in XRF, it can be determined that SrO is in a state of solid solution in calcium formate, and its content can be further determined. It should be noted that XRF can be performed using a fluorescence X-ray analysis apparatus (Rigaku Corporation: fluorescence X-ray analysis apparatus ZSX100e, etc.), and XRD can be performed using a powder X-ray diffraction apparatus (Rigaku Corporation: SmartLab, etc.).

[0028] Calcium formate-based powders preferably contain 0.001 to 0.1% by mass of MnO as a chemical component, more preferably 0.01 to 0.08% by mass, and even more preferably 0.02 to 0.05% by mass. If the MnO content in the calcium formate-based powder is within the above range, it is easier to maintain good flowability. There are no particular limitations on the MnO raw material; examples include rhodochrosite, rhodochrosite, manganese olivine, pyroxene, and rhodochrosite. By using these, the MnO content can be adjusted.

[0029] The early-strength material preferably contains 0.01 to 5.0% by mass of calcium formate powder, more preferably 0.1 to 4.0% by mass, and even more preferably 0.5 to 3.0% by mass. By keeping the content of calcium formate powder within the above range, it is easy to achieve good flowability, coagulation and processability.

[0030] The early-strength material preferably further contains an inorganic calcium compound. As the inorganic calcium compound, calcium sulfate, calcium hydroxide, calcium carbonate, calcium oxide, etc., can be used. From the viewpoint of initial strength performance, calcium sulfate, calcium hydroxide, and / or calcium oxide are preferred, and calcium sulfate is even more preferred. Furthermore, when using calcium sulfate, an anhydrous form is preferred.

[0031] The early-strength material preferably contains 15.0 to 70.0% by mass of inorganic calcium compound, more preferably 18.0 to 60.0% by mass, and even more preferably 20.0 to 40.0% by mass. By keeping the content of inorganic calcium compound within the above range, it is easy to maintain good flowability, coagulation and processability.

[0032] The early-strength material preferably further contains an inorganic sulfate. As an inorganic sulfate, sodium sulfate, aluminum sulfate, sodium thiosulfate, potassium alum, etc., can be used. From the viewpoint of initial strength performance, sulfates and / or thiosulfates are preferred, sodium sulfate, aluminum sulfate, sodium thiosulfate and / or potassium alum are more preferred, and sodium sulfate and / or aluminum sulfate are even more preferred. From the viewpoint of maintaining good flowability, sodium sulfate is even more preferred. When using sodium sulfate, an anhydrous form is preferred.

[0033] The early-strength material preferably contains 0.5 to 30.0% by mass of inorganic sulfate, more preferably 1.0 to 25.0% by mass, and even more preferably 3.0 to 15.0% by mass. By keeping the content of inorganic sulfate within the above range, it is easy to maintain good flowability, coagulation and processability.

[0034] Early-strength materials preferably contain calcium sulfoaluminate. Calcium sulfoaluminate has the chemical formula xCaO. yAl2O3 zCaSO4 The term mH₂O (where x, y, and z are positive real numbers not equal to 0, and m is 0 or a positive real number) represents the general term for hydraulic substances and hydrated salts, for example, excluding chalcedony (3CaO). 3Al2O3 Besides CaSO4, ettringite (3CaO) can be cited as an example. Al2O3 3CaSO4 The AFt phase, represented by 32H2O, and the monosulfate (3CaO) Al2O3 CaSO4 Calcium sulfoaluminate, represented by AFm phase (12H2O) and coexisting with AFt and AFm phases, can be amorphous. Furthermore, a portion of Al2O3 can be replaced by trace amounts of Fe2O3 or SiO2, and a portion of CaSO4 can be replaced by Ca(OH)2 or CaCO3. It should be noted that in this invention, in the above chemical formula xCaO... yAl2O3 zCaSO4 In mH2O, based on the viewpoint of fluidity retention and the possibility of reduced strength during curing due to phase transfer, z cannot be set to 0.

[0035] The early-strength material preferably contains 4.5 to 65.0% by mass of calcium sulfoaluminate, more preferably 15.0 to 60.0% by mass, and even more preferably 30.0 to 50.0% by mass. By keeping the content of calcium sulfoaluminate within the above range, it is easy to maintain good flowability, coagulation and processability.

[0036] [Early-strength cement composition]

[0037] The early-strength cement composition of this embodiment contains the early-strength material and cement of the present invention.

[0038] As for cement, there are no particular limitations. Examples include various Portland cements such as ordinary, early-strength, ultra-early-strength, low-heat, and medium-heat cements; various blended cements obtained by mixing these Portland cements with blast furnace slag, fly ash, silica fume, metakaolin, and diaspore; environmentally friendly cements (eco-cement) made from municipal solid waste incineration ash and sewage sludge incineration ash; commercially available micronized cements; and white cements. Various cements can also be used by micronizing them. Furthermore, cements obtained by adjusting the amount of commonly used cement components (such as gypsum) can also be used. Moreover, cements obtained by combining two or more of these components can also be used. From the viewpoint of improving initial strength performance, ordinary Portland cement and early-strength Portland cement are preferred, but blast furnace cement and fly ash cement with low initial strength performance can also be used.

[0039] From the perspectives of manufacturing cost and strength performance, the optimal Blaine specific surface area for cement is 2500–7000 cm². 2 / g, more preferably 2750-6000cm 2 / g, more preferably 3000-4500cm 2 / g. It should be noted that in this invention, the Blaine surface area is determined according to JIS R 5201:2015 "Physical test method for cement".

[0040] The content of early-strength materials in the early-strength cement composition is preferably 0.1 to 10% by mass, more preferably 0.3 to 5.0% by mass, and even more preferably 0.5 to 3.0% by mass. If the content of early-strength materials in the early-strength cement composition is within the above range, the fluidity retention, setting properties, and processability of the hydraulic materials can be further improved.

[0041] The early-strength cement composition of this embodiment preferably further comprises at least one selected from slag, silica fume, metakaolin, hydrated quartz, and fly ash. These substances are commonly referred to as Supplementary Cementitious Materials (SCMs).

[0042] Compared to the cement in the early-strength cement composition, the early-strength cement composition preferably contains 20-100% by mass of the above-mentioned SCMs, more preferably 30-60% by mass, and even more preferably 40-50% by mass. By keeping the content of SCMs within the above range, it is easy to achieve good fluidity retention, setting properties, and processability.

[0043] The early-strength cement composition preferably further contains a water-reducing agent. There are no particular limitations on the water-reducing agent, but examples include naphthalene-based water-reducing agents, melamine-based water-reducing agents, aminosulfonic acid-based water-reducing agents, and polycarboxylate-based water-reducing agents. In this invention, one or more of these water-reducing agents may be used.

[0044] The content of water-reducing agent is preferably 0.1 to 3.0 parts by weight relative to 100 parts by weight of the early-strength cement composition, more preferably 0.3 to 2.5 parts by weight, and even more preferably 0.5 to 2.0 parts by weight.

[0045] Early-strength cement compositions can contain calcium aluminate clinker. Including calcium aluminate clinker in early-strength cement compositions facilitates good setting properties. Calcium aluminate clinker is primarily composed of CaO and Al₂O₃ and possesses hydration activity. A portion of CaO and / or Al₂O₃ is replaced by compounds such as alkali metal oxides, alkaline earth metal oxides, silicon dioxide, titanium dioxide, iron oxide, alkali metal halides, alkaline earth metal halides, alkali metal sulfates, and alkaline earth metal sulfates, or these compounds are dissolved in small amounts in the composition primarily composed of CaO and Al₂O₃. Calcium aluminate can be either crystalline or amorphous.

[0046] The preferred content of calcium aluminate clinker is 0.1 to 10 parts by weight, more preferably 0.3 to 5.0 parts by weight, relative to 100 parts by weight of cement in the early-strength cement composition. By keeping the content of calcium aluminate clinker within the above range, it is easier to further improve the setting properties.

[0047] Early-strength cement compositions can contain alkali metal carbonates. Including alkali metal carbonates in early-strength cement compositions facilitates good fluidity retention and initial strength performance. Examples of alkali metal carbonates include sodium carbonate, potassium carbonate, lithium carbonate, sodium bicarbonate, potassium bicarbonate, and lithium bicarbonate, as well as combinations thereof.

[0048] The proportion of alkali metal carbonates in the early-strength cement composition, relative to 100 parts by weight of cement, is preferably 1 to 6 parts by weight, more preferably 2 to 5 parts by weight, based on the amount of solids. By keeping the proportion of alkali metal carbonates within the above range, it is easy to achieve good fluidity retention and initial strength performance.

[0049] Early-strength cement compositions may contain silica microparticles. By including silica microparticles in the early-strength cement composition, it is easier to maintain good flowability and initial strength performance. Examples of silica microparticles include potential hydraulic substances such as water-quenched blast furnace slag microparticles, and pozzolanic substances such as fly ash or silica fume, with silica fume being preferred. The type of silica fume is not limited, but from the viewpoint of flowability, silica fume containing less than 10% ZrO2 as an impurity, or acidic silica fume, is more preferred. Acidic silica fume refers to silica fume in which the pH of the supernatant after adding 1g of silica fume to 100cc of pure water and stirring is below 5.0.

[0050] There is no particular limitation on the fineness of silica micro powder, but generally, water-quenched blast furnace slag micro powder and fly ash have a Blaine specific surface area of ​​3000–9000 cm². 2 The silica fume ranges from 20,000 to 300,000 cm² in terms of BET specific surface area. 2 The range of / g.

[0051] Relative to 100 parts by weight of cement in the early-strength cement composition, the content of silica micropowder is preferably 1 to 20 parts by weight, more preferably 2 to 15 parts by weight, and even more preferably 3 to 12 parts by weight. By keeping the content of silica micropowder above the above-mentioned lower limit, it is easy to achieve good flowability retention and initial strength performance. Furthermore, by keeping the content of silica micropowder below the above-mentioned upper limit, it is easy to further improve flowability retention.

[0052] Early-strength cement compositions may also contain defoamers within a range that does not negatively impact performance. Defoamers are used to suppress the amount of air entrained during mixing. There are no particular limitations on the type of defoamer, as long as it does not significantly negatively affect the strength characteristics of the cured mortar; both liquid and powder forms can be used. Examples include polyether-based defoamers, polyol-based defoamers such as esters or alkyl ethers of polyols, alkyl phosphate-based defoamers, and silicone-based defoamers.

[0053] The defoamer content is preferably 0.002 to 0.5 parts by weight relative to 100 parts by weight of cement in the early-strength cement composition, more preferably 0.005 to 0.45 parts by weight, and even more preferably 0.01 to 0.4 parts by weight. By keeping the defoamer content above the lower limit, the defoaming effect can be fully demonstrated, and by keeping the defoamer content below the upper limit, good fluidity retention is easily achieved.

[0054] In addition, the early-strength cement composition may use one or more of the following, within the range that will not negatively affect the performance and does not substantially impair the purpose of the present invention: gas foaming material, AE agent, rust inhibitor, hydrophobic agent, antibacterial agent, colorant, antifreeze agent, limestone micro powder, blast furnace slow-cooling slag micro powder, sewage sludge incineration ash and its molten slag, municipal solid waste incineration ash and its molten slag, and pulp sludge incineration ash, thickener and shrinkage reducing agent, polymer, and anion exchanger such as hydrotalcite, etc.

[0055] [Early-strength mortar]

[0056] The early-strength mortar of this embodiment comprises the early-strength cement composition of the present invention.

[0057] There are no particular restrictions on the fine aggregates used in early-strength mortars; river sand, mountain sand, sea sand, lime sand, and silica sand, etc., can be used.

[0058] The proportion of fine aggregate relative to 100 parts by weight of cement in the early-strength cement composition is preferably 40 to 600 parts by weight, more preferably 50 to 500 parts by weight, and even more preferably 60 to 450 parts by weight. By keeping the proportion of fine aggregate within the above range, the fluidity retention and initial strength performance can be further improved.

[0059] Early-strength mortar can be prepared by mixing an early-strength cement composition, fine aggregate, and water. The water content in the early-strength mortar, based on the water / cement ratio, is preferably 10-70%, more preferably 14-65%, and even more preferably 16-60%.

[0060] [Early-strength concrete]

[0061] The early-strength concrete of this embodiment comprises the early-strength cement composition of the present invention.

[0062] There are no particular restrictions on the aggregates used in early-strength concrete. As fine aggregates, river sand, mountain sand, sea sand, lime sand, and silica sand can be used. As coarse aggregates, river gravel, mountain gravel, and lime gravel can be used, as well as crushed sand and crushed stone.

[0063] The aggregate content is preferably 40 to 600 parts by weight, more preferably 50 to 500 parts by weight, and even more preferably 60 to 450 parts by weight, relative to 100 parts by weight of cement in the early-strength cement composition. By keeping the aggregate content within the above range, the fluidity retention and initial strength performance can be further improved. Furthermore, the fine aggregate ratio (the proportion of fine aggregate relative to the total aggregate) is preferably 25 to 65%, more preferably 35 to 55%, and even more preferably 40 to 50%.

[0064] Early-strength concrete can be prepared by mixing an early-strength cement composition, aggregates, and water. The water content in the concrete, based on the water / cement ratio, is preferably 10-70%, more preferably 14-65%, and even more preferably 16-60%.

[0065] [Cured product]

[0066] The early-strength mortar cured product of this embodiment is formed by curing the early-strength mortar of the present invention. Furthermore, the early-strength concrete cured product of this embodiment is formed by curing the early-strength concrete of the present invention.

[0067] The aforementioned solidified material is obtained by allowing early-strength mortar or early-strength concrete to stand and cure. After mixing, it can be obtained more efficiently by filling (pouring) it into the template and curing it, or by directly pouring, spraying or coating it onto the construction site.

[0068] The compressive strength of the cured material depends on the type of cement used, but is preferably 11.0 N / mm² 6 hours after pouring. 2 The above, more preferably 13.0 N / mm 2 The above is further preferred to be 15.0 N / mm. 2 above.

[0069] [Method for manufacturing cured products]

[0070] The method for manufacturing the cured product in this embodiment is a method for curing an early-strength cement composition containing the early-strength material of the present invention by steam curing at a maximum temperature of 40-80°C for 2-8 hours. The method for manufacturing the cured product preferably includes, in sequence: a mixing step of mixing the early-strength material, cement and water; a casting step of filling the mixed early-strength cement composition into a mold; and a curing step of curing the early-strength cement composition after it has been filled into the mold.

[0071] There are no particular limitations on the mixing method in the mixing process. The materials can be mixed during construction, or some or all of them can be mixed in advance. As for the mixing equipment, any existing equipment can be used, such as tilting mixers, universal mixers, Henschel mixers, V-type mixers, plow mixers, and Notta mixers.

[0072] The casting method in the casting process can be carried out using known techniques. The temperature of the early-strength cement composition during casting is preferably 0 to 50°C, more preferably 10 to 40°C. If the temperature of the early-strength cement composition during casting is within the above range, the cured material can be easily demolded as early as possible.

[0073] The method for producing the solidified material preferably includes a compaction step after the casting process. Known compaction methods can be used, but from an operational point of view, a vibrator is preferred. The early-strength cement composition containing the early-strength material of the present invention maintains good fluidity just before casting, thus allowing for easy compaction, uniform distribution of the early-strength cement composition within the mold, and removal of air bubbles introduced during casting.

[0074] From a productivity standpoint, steam curing using a curing chamber, heating elements, or similar equipment is preferred as a curing method. Steam curing typically involves heating the atmosphere surrounding the object while maintaining appropriate humidity and a consistent temperature. Preferred steam curing conditions are a maximum temperature of 40–80°C and a curing time of 2–8 hours; more preferably, a maximum temperature of 40–75°C and a curing time of 2.5–7.5 hours; and even more preferably, a maximum temperature of 45–60°C and a curing time of 3–7 hours. If the maximum temperature of the atmosphere surrounding the early-strength cement composition during steam curing is within the above-mentioned range and the curing time is within the above-mentioned range, the cured material can be easily demolded earlier.

[0075] 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, and it can be 100% RH. If the relative humidity around the early-strength cement composition during steam curing is within the above range, the cured material can be easily demolded earlier.

[0076] The curing process preferably includes a pre-curing process. As a pre-curing condition, it is preferable to maintain a constant temperature of 10–50°C for approximately 1–3 hours. By including a pre-curing process, the curing process ensures uniform internal temperature of the poured early-strength cement composition, easily preventing temperature cracks caused by temperature differences between the internal and external environments.

[0077] The curing process preferably includes a heating process. As a heating method, known methods can be used, preferably with a heating rate of 10–30°C / hour, more preferably 12–28°C / hour, and even more preferably 15–25°C. If the heating rate in the heating process is within the above range, temperature cracking caused by a rapid temperature rise in the early-strength cement composition can be prevented, and curing can be further promoted.

[0078] The curing process preferably includes a temperature holding process. As a temperature holding method, known methods can be used to maintain a certain temperature, preferably within the range of 40–80°C for 1–8 hours, more preferably within the range of 40–75°C for 1–6 hours, and even more preferably within the range of 45–65°C for 2.5–5 hours. In the temperature holding process, by maintaining a certain temperature within the above-mentioned range, the early-strength cement composition after pouring can be uniformly cured, facilitating early demolding.

[0079] The preferred method for manufacturing the cured product includes a natural cooling process after the curing process. In the natural cooling process, the cured product obtained from the curing process is allowed to cool naturally in a room temperature atmosphere. The cooling time is not particularly limited, as long as it cools to a temperature that allows for easy demolding of the cured product; this can be approximately 0.5 to 2 hours. By including a natural cooling process after the curing process, temperature cracking of the cured product can be prevented.

[0080] Example

[0081] The present invention will be further described below with reference to experimental examples, but the present invention is not limited thereto.

[0082] <Experimental Example 1>

[0083] The following calcium formate was used as a calcium formate-based powder. The powder was pulverized, sieved, and granulated to adjust the D90 value to the value listed in Table 1 below, thus preparing various early-strength materials. The SrO content of the prepared early-strength materials was determined using XRF analysis with a ZSX100e fluorescence X-ray analyzer (manufactured by Rigaku Corporation), and the result was 0.02%.

[0084] Early-strength cementitious compositions were prepared by mixing the prepared early-strength material and cement at a concentration of 2.0% by mass of the early-strength material. Early-strength concrete (Tables 1 No. 1-2 to 6) was prepared by mixing the obtained early-strength cement composition, fine aggregate, coarse aggregate, and water at a water / cement ratio of 37.5% and a fine aggregate ratio of 42%. Similarly, concrete without early-strength materials was prepared by mixing cement, fine aggregate, coarse aggregate, and water at a water / cement ratio of 35% (Table 1 No. 1-1). The air content, slump change, compressive strength, setting properties, and workability of each concrete were measured. The results are recorded in Table 1 below.

[0085] (Materials used)

[0086] Calcium formate: a reagent.

[0087] Cement: Ordinary Portland cement (commercially available), Blaine surface area 3200 cm² 2 / g, specific gravity 3.15g / cm³3 .

[0088] Water: tap water.

[0089] Fine aggregate: Himekawa River system sand from Itaogawa City, Niigata Prefecture, with a maximum size of less than 5mm and a density of 2.62g / cm³. 3 .

[0090] Coarse aggregate: Crushed stone from Itogawa City, Niigata Prefecture, maximum size 25mm, density 2.67g / cm³ 3 .

[0091] (Measurement Items)

[0092] Air volume: The air volume was determined according to the method specified in JIS A 1116:2019 "Test method for the volumetric mass of fresh concrete and test method based on the mass of air volume (mass method)".

[0093] Slump change: The slump immediately after mixing and the slump after standing for 30 minutes are measured according to the method specified in JIS A 1101:2020 "Test method for slump of concrete", and the change is calculated.

[0094] Compressive strength: The compressive strength was determined using a cylindrical specimen with a diameter of φ100×200cm, according to the method specified in JIS A 1108:2018 "Test method for compressive strength of concrete".

[0095] Setting properties: According to the method specified in JIS A 1147:2019 "Test method for setting time of concrete", the penetration resistance value was measured to reach 1.0 N / mm. 2 and 3.5 N / mm 2 The time.

[0096] Workability: Concrete is poured into a container measuring 350mm (length) x 245mm (width) x 90mm (height) (approximately 7.7L). 60 minutes after pouring, the concrete is visually inspected for edge collapse at an angle of approximately 40°, and evaluated on a three-tiered scale. A good (〇) condition is characterized by no visible edge collapse (deviation) or water seepage, and no edge collapse even when a trowel is touched. A poor (△) condition is characterized by almost no edge collapse or water seepage, but edge collapse occurs when a trowel is touched. A bad (×) condition is characterized by visible edge collapse and water seepage.

[0097]

[0098] <Experimental Example 2>

[0099] Early-strength cement compositions were prepared by replacing cement in the early-strength cement composition with the SCMs shown below at the SCMs substitution rates shown in Table 2 below. Otherwise, early-strength concrete was prepared in the same manner as in Experimental Example 1, and various measurements were performed. The results are recorded in Table 2 below.

[0100] (Materials used)

[0101] Slag: Made by Esment Kanto.

[0102] Silica ash: Produced by Pakistan Industries.

[0103] Metakaolin: manufactured by Imerys.

[0104] Boehmite: Boehmite (produced in Tochigi Prefecture) is placed in an electric furnace and fired at 800°C for 1 hour, followed by rapid cooling.

[0105] Fly ash: manufactured by Kyushu Electric Power Company.

[0106]

[0107] <Experimental Example 3>

[0108] The early-strength material prepared in Example 1 and cement were mixed at a weight of 2.0% by mass, and a water-reducing agent was added to make the weight of the early-strength material relative to the cement 0.5% to prepare an early-strength cement composition. Using the prepared early-strength cement composition, early-strength mortar was prepared with a water / cement ratio of 35% and a cement-to-fine aggregate ratio of 1:1.5 (by mass).

[0109] In addition, the prepared early-strength mortar was filled into a template with dimensions of 4×4×16cm and then steam-cured to obtain the cured early-strength mortar. The steam curing conditions were set as follows: pre-curing at 20℃ for 1 hour, heating at a rate of 20℃ / hour for 1.5 hours, holding at 50℃ for 3 hours, and then natural cooling for 0.5 hours. Various measurements were performed on the obtained cured early-strength mortar. The results are shown in Table 3 below.

[0110] (Materials used)

[0111] Cement: Ordinary Portland cement (commercially available), Blaine surface area 3200 cm² 2 / g, specific gravity 3.15g / cm³ 3 .

[0112] Water: tap water.

[0113] Fine aggregate: River sand from the Himekawa River system in Niigata Prefecture.

[0114] Water-reducing agent: Polycarboxylate-based high-performance water-reducing agent (commercially available).

[0115] (Measurement Items)

[0116] Mortar flow change rate: According to the method specified in JIS R 5201:2015 "Physical test method for cement", the flow value of mortar immediately after mixing and the flow value of mortar after standing for 30 minutes after mixing are measured. The flow change rate of mortar is set as (mortar flow change rate) = (1 - (flow value after 30 minutes of mixing) / (flow value immediately after mixing)) × 100. The mortar flow change rate is calculated.

[0117] Compressive strength: The compressive strength of the cement was determined according to the method specified in JIS R 5201:2015 "Physical test method for cement" at 6 hours after steam curing (just after demolding).

[0118] Setting properties: Penetration resistance was measured according to the methods specified in JIS R 5201:2015 "Physical Test Methods for Cement" to reach 1.0 N / mm. 2 and 3.5 N / mm 2 The time.

[0119]

[0120] Industrial availability

[0121] The early strength material of this invention can be widely used in civil engineering and construction fields, such as concrete curing materials used in prefabrication construction methods.

Claims

1. An early-strength material comprising calcium formate powder, wherein, in a volumetric cumulative particle size distribution determined by laser diffraction scattering, 90% of the calcium formate powder has a particle size (D90) of less than 1200 μm.

2. An early-strength cement composition comprising the early-strength material as described in claim 1 and cement.

3. The early-strength cement composition according to claim 2, wherein, It further includes at least one of the following: slag, silica fume, metakaolin, diatomite, and fly ash.

4. An early-strength mortar comprising the early-strength cement composition of claim 2 or 3.

5. An early-strength concrete comprising the early-strength cement composition of claim 2 or 3.

6. A cured early-strength mortar, which is formed by curing the early-strength mortar as described in claim 4.

7. A cured early-strength concrete product, which is formed by curing the early-strength concrete as described in claim 5.

8. A method for manufacturing a cured material, wherein an early-strength cement composition containing the early-strength material of claim 1 is cured by steam curing at a maximum temperature of 40-80°C for 2-8 hours.

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