High-early-strength material, high-early-strength cement composition, high-early-strength mortar, high-early-strength concrete, hardened high-early-strength mortar body, hardened high-early-strength concrete body

Abstract

To provide a high-early-strength material that can improve fluidity retention, setting property and finish property.SOLUTION: The high-early-strength material contains calcium formate-based powder having a particle diameter at cumulative 90% (D90) of 1,200 μm or less in a volume cumulative particle size distribution measured by a laser diffraction scattering method.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to early-strength agents, early-strength cement compositions containing early-strength agents, early-strength mortars and early-strength concretes containing early-strength cement compositions, and hardened bodies of early-strength mortars and early-strength concretes.

Background Art

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

[0003] Shortening the time until the hydraulic material hardens leads to an improvement in productivity at the work site. For example, a hardened concrete body used in a precast method for use in a reinforced concrete building or the like can generally obtain a hardened body by placing a cement composition in a formwork, standing for a predetermined time, and then further curing by steam curing or the like. However, by using a hardening accelerator, the time until the initial strength at which demolding is possible is reached can be shortened, so that the hardened body can be produced efficiently.

[0004] For example, Patent Document 1 discloses a hardening accelerator for hydraulic materials containing a predetermined amount of inorganic sulfate, calcium sulfoaluminate, and inorganic hydroxide. In Patent Document 2, a cement admixture containing calcium sulfoaluminate having a Blaine specific surface area value of 4000 cm 2 / g or more and one or more selected from the group consisting of formate, acetate, and lactate is shown.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] However, a hydraulic material using the above admixture may lose its fluidity immediately after being kneaded with water, or may have poor finishability.

[0007] From the above, an object of the present invention is to provide an early-strength material capable of improving fluidity retention, setting property, and finishability.

MEANS FOR SOLVING THE PROBLEMS

[0008] As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by an early-strength material containing a calcium formate-based powder having a specific particle size distribution, and have arrived at the present invention. That is, the present invention is as follows.

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

Advantages of the Invention

[0010] According to the present invention, it is possible to provide an early-strength agent that can improve fluidity retention, setting properties, and finishability.

Embodiments for Carrying Out the Invention

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

[0012] [Early-strength agent] The early-strength agent according to this embodiment contains a calcium formate-based powder in which the particle diameter (D90) at which the cumulative volume is 90% is 1,200 μm or less in the volume integral particle size distribution measured by the laser diffraction scattering method. The early-strength agent not only accelerates the curing when a hydraulic substance such as cement is kneaded with water and cured, but may also cure itself while accelerating the curing. The volume integral particle size distribution can be measured using a particle measuring device (manufactured by Horiba, Ltd.: laser diffraction / scattering type particle size distribution measuring device LA-960 series, etc.).

[0013] (Calcium formate-based powder) The calcium formate-based powder contained in the early-strength material of the present invention has a particle diameter (D90) at which the cumulative volume is 90% of 1,200 μm or less in the volume-based particle size distribution measured by the laser diffraction scattering method. In the present invention, the calcium formate-based powder is a powder in which the main component in one particle is calcium formate. If the D90 of the calcium formate-based powder exceeds 1,200 μm, the fluidity retention, cohesiveness, and finish may be poor. Further, 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, it is easy to improve the fluidity retention, cohesiveness, and finish.

[0014] In the volume-based particle size distribution measured by the laser diffraction scattering method, the calcium formate-based powder preferably has a particle diameter (D50: median diameter) at which the cumulative volume is 50% of 100 to 400 μm, more preferably 120 to 300 μm, and even more preferably 150 to 250 μm. When the median diameter of the calcium formate-based powder is within the above range, it is easy to improve the fluidity retention, cohesiveness, and finish.

[0015] The calcium formate-based powder contained in the early strength agent 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. When the SrO content in the calcium formate-based powder is within the above range, it is easy to maintain good fluidity. The SrO raw material is not particularly limited, and examples include celestine, strontianite, strontium oxide, strontium carbonate, etc. By using these, the SrO content can be adjusted. In the present invention, "as a chemical component" refers to the state of being dissolved in calcium formate and can be confirmed by using fluorescence X-ray analysis (XRF) and X-ray diffraction method (XRD). When no peak corresponding to SrO is confirmed by XRD and a peak corresponding to SrO is confirmed by XRF, it can be determined that SrO is in a state of being dissolved in calcium formate, and the content can be further measured. Note that XRF can be carried out using a fluorescence X-ray analyzer (manufactured by Rigaku: fluorescence X-ray analyzer ZSX100e, etc.), and XRD can be carried out using a powder X-ray diffractometer (manufactured by Rigaku: SmartLab, etc.).

[0016] The calcium formate-based powder preferably contains 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. When the MnO content in the calcium formate-based powder is within the above range, it is easy to maintain good fluidity. The MnO raw material is not particularly limited, and examples includehausmannite, rhodochrosite, teflorite, pyrolusite, baryte, etc. By using these, the MnO content can be adjusted.

[0017] The early strength agent preferably contains 0.01 to 5.0% by mass of the calcium formate-based powder, more preferably 0.1 to 4.0% by mass, and even more preferably 0.5 to 3.0% by mass. When the content of the calcium formate-based powder is within the above range, it is easy to maintain good fluidity, setting property, and finish.

[0018] The early strength agent 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 development property, it is preferable to use calcium sulfate, calcium hydroxide and / or calcium oxide, and calcium sulfate is more preferable. Further, when using calcium sulfate, it is more preferably an anhydride.

[0019] The early strength agent preferably contains 15.0 to 70.0% by mass of the inorganic calcium compound, more preferably contains 18.0 to 60.0% by mass, and even more preferably contains 20.0 to 40.0% by mass. When the content of the inorganic calcium compound is within the above range, it is easy to improve the fluidity retention, setting property, and finish property.

[0020] The early strength agent preferably further contains an inorganic sulfate. As the inorganic sulfate, sodium sulfate, aluminum sulfate, sodium thiosulfate, potassium alum, etc. can be used. From the viewpoint of initial strength development property, it is preferable to use sulfate and / or thiosulfate, more preferably sodium sulfate, aluminum sulfate, sodium thiosulfate, and potassium alum, even more preferably sodium sulfate and aluminum sulfate. Among them, from the viewpoint of improving the fluidity retention, sodium sulfate is even more preferable. When using sodium sulfate, it is more preferably an anhydride.

[0021] The early strength agent preferably contains 0.5 to 30.0% by mass of the inorganic sulfate, more preferably contains 1.0 to 25.0% by mass, and even more preferably contains 3.0 to 15.0% by mass. When the content of the inorganic sulfate is within the above range, it is easy to improve the fluidity retention, setting property, and finish property.

[0022] The early strength agent preferably further contains calcium sulfoaluminate. Calcium sulfoaluminate has the chemical formula xCaO·yAl 2 O 3 ·zCaSO 4 ·mH2 It is a general term for hydraulic substances and hydrates represented by O (where x, y, and z are positive real numbers other than 0, and m is 0 or a positive real number). For example, in addition to aluminate (3CaO·3Al 2 O 3 ·CaSO 4 ), there are also AFt phases represented by ettringite (3CaO·Al 2 O 3 ·3CaSO 4 ·32H 2 O), AFm phases represented by monosulfate (3CaO·Al 2 O 3 ·CaSO 4 ·12H 2 O), and those in which AFt and AFm coexist. Calcium sulfoaluminate may be amorphous. Also, a part of Al 2 O 3 may be substituted with a small amount of Fe 2 O 3 or SiO 2 etc., and a part of CaSO 4 may be substituted with Ca(OH) 2 or CaCO 3 etc. In the present invention, in the above chemical formula xCaO·yAl 2 O 3 ·zCaSO 4 ·mH 2 O, z cannot be set to 0 because of the fluidity retention and the risk of strength reduction during hardening due to phase transition.

[0023] The early strength agent 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. When the content of calcium sulfoaluminate is within the above range, it is easy to improve the fluidity retention, setting property, and finish.

[0024] [Early strength cement composition] The early strength cement composition according to this embodiment contains the early strength agent of the present invention and cement. The cement is not particularly limited, and examples include various Portland cements such as ordinary, early-strength, ultra-early-strength, low-heat, and moderate-heat Portland cements; various blended cements obtained by mixing blast furnace slag, fly ash, silica fume, metakaolin, allophane, etc. with these Portland cements; environment-friendly cement (eco-cement) manufactured using municipal waste incineration ash or sewage sludge incineration ash as raw materials; commercially available fine particle cement, white cement, etc. It is also possible to use various cements in a finely powdered form. In addition, those adjusted by increasing or decreasing the amount of components (such as gypsum, etc.) usually used in cement can also be used. Furthermore, combinations of two or more of these can also be used. From the perspective of enhancing the early strength development property, it is preferable to select ordinary Portland cement or early-strength Portland cement, but it is also possible to use blast furnace cement or fly ash cement with low early strength development property.

[0025] From the perspective of manufacturing cost and strength development property, the cement preferably has a Blaine specific surface area of 2,500 to 7,000 cm 2 / g, more preferably 2,750 to 6,000 cm 2 / g, and even more preferably 3,000 to 4,500 cm 2 / g. In the present invention, the Blaine specific surface area is determined in accordance with JIS R 5201:2015 "Physical Testing Methods for Cement".

[0026] In the early-strength cement composition, the content of the early-strength agent 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. When the content of the early-strength agent in the early-strength cement composition is within the above range, the fluidity retention, setting property, and finishability of the hydraulic material can be made better.

[0027] The early-strength cement composition according to this embodiment preferably further contains at least one or more selected from the group consisting of slag, silica fume, metakaolin, allophane, and fly ash. The above substances are generally substances called Supplementary Cementitious Materials (SCMs).

[0028] The early-strength cement composition preferably contains 20 to 100% by mass of the above SCMs based on the cement in the early-strength cement composition, more preferably 30 to 60% by mass, and even more preferably 40 to 50% by mass. When the content ratio of SCMs is within the above range, it is easy to improve the fluidity retention, setting property, and finishability.

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

[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 with respect to 100 parts by mass of the early-strength cement composition.

[0031] The early-strength cement composition can contain calcium aluminate clinker. When the early-strength cement composition contains calcium aluminate clinker, it is easy to improve the setting property. Calcium aluminate clinker has CaO and Al 2 O 3 as main components and has hydration activity. A part of CaO and / or Al 2 O 3 is replaced by compounds such as alkali metal oxides, alkaline earth metal oxides, silicon oxide, titanium oxide, iron oxide, alkali metal halides, alkaline earth metal halides, alkali metal sulfates, and alkaline earth metal sulfates, or compounds of CaO and Al2 O 3 These are substances in which these are dissolved in small amounts in those having O and 3 as main components, and the calcium aluminate may be either crystalline or amorphous.

[0032] The content ratio of the calcium aluminate clinker is preferably 0.1 to 10 parts by mass, more preferably 0.3 to 5.0 parts by mass, based on 100 parts by mass of the cement in the early-strength cement composition. When the content ratio of the calcium aluminate clinker is within the above range, it is easier to improve the setting property.

[0033] The early-strength cement composition can contain an alkali metal carbonate. When the early-strength cement composition contains an alkali metal carbonate, it is easier to improve the fluidity retention and the initial strength development property. Examples of the alkali metal carbonate include sodium carbonate, potassium carbonate, lithium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, lithium hydrogen carbonate, etc., and it is also possible to combine these.

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

[0035] The early-strength cement composition can contain a silica fine powder. When the early-strength cement composition contains a silica fine powder, it is easier to improve the fluidity retention and the initial strength development property. Examples of the silica fine powder include latent hydraulic substances such as blast furnace granulated slag fine powder, pozzolanic substances such as fly ash and silica fume. Among them, silica fume is preferable. The type of silica fume is not limited, but from the viewpoint of fluidity, ZrO as an impurity 2It is more preferable to use silica fume or acidic silica fume containing 10% or less. Acidic silica fume refers to a substance that exhibits acidity with a pH of 5.0 or less in the supernatant when 1 g of silica fume is put into 100 cc of pure water and stirred.

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

[0037] The content ratio 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 with respect to 100 parts by mass of cement in the early-strength cement composition. When the content ratio of the siliceous fine powder is at or above the above lower limit value, it is easy to improve the fluidity retention and the initial strength development property. Furthermore, when the content ratio of the siliceous fine powder is at or below the above upper limit value, it is easy to make the fluidity retention better.

[0038] The early-strength cement composition can also contain an antifoaming agent within a range that does not adversely affect the performance. The antifoaming agent is used for the purpose of suppressing the amount of air entrained during mixing. The type of the antifoaming agent is not particularly limited as long as it does not significantly adversely affect the strength characteristics of the hardened mortar, and both liquid and powder forms can be used. For example, polyether-based antifoaming agents, polyhydric alcohol-based antifoaming agents such as esterified products of polyhydric alcohols and alkyl ethers, alkyl phosphate-based antifoaming agents, silicone-based antifoaming agents, etc. can be mentioned.

[0039] The content ratio of the defoaming agent is preferably 0.002 to 0.5 parts by mass, more preferably 0.005 to 0.45 parts by mass, and even more preferably 0.01 to 0.4 parts by mass with respect to 100 parts by mass of the cement in the early-strength cement composition. When the content ratio of the defoaming agent is at least the above lower limit value, the defoaming effect can be sufficiently exhibited. When the content ratio of the defoaming agent is at most the above upper limit value, it is easy to improve the fluidity retention property.

[0040] In addition, the early-strength cement composition can be used, within a range not adversely affecting the performance, one or more of gas foaming substances, AE agents, rust preventives, water repellents, antibacterial agents, colorants, antifreezing agents, fine limestone powder, fine powder of slowly cooled blast furnace slag, incineration ash of sewage sludge and its molten slag, incineration ash of municipal waste and its molten slag, and incineration ash of pulp sludge, etc., thickeners, shrinkage reducing agents, polymers, and anion exchangers such as hydrotalcite, etc., within a range not substantially inhibiting the object of the present invention.

[0041] [Early-strength mortar] The early-strength mortar according to the present embodiment contains the early-strength cement composition of the present invention. The fine aggregate used in the early-strength mortar is not particularly limited, and river sand, mountain sand, sea sand, lime sand, silica sand, etc. can be used.

[0042] The content ratio 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 with respect to 100 parts by mass of the cement in the early-strength cement composition. When the content ratio of the fine aggregate is within the above range, the fluidity retention property and the initial strength development property can be made better.

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

[0044] [Early-strength concrete] The early-strength concrete according to this embodiment contains the early-strength cement composition of the present invention. The aggregates used in the early-strength concrete are not particularly limited. As fine aggregates, river sand, mountain sand, sea sand, lime sand, silica sand, etc. can be used. As coarse aggregates, river gravel, mountain gravel, lime gravel, etc. can be used, and crushed sand and crushed stone can also be used.

[0045] The content ratio of the 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 with respect to 100 parts by mass of cement in the early-strength cement composition. By the content ratio of the aggregate being within the above range, the fluidity retention and the initial strength development can be made better. Also, 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] The early-strength concrete can be prepared by kneading the early-strength cement composition, the aggregate, and water. The water content in the concrete is preferably 10 to 70% in terms of the water / cement ratio, more preferably 14 to 65%, and even more preferably 16 to 60%.

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

[0048] The above hardened body is obtained by hardening the early-strength mortar or early-strength concrete by allowing it to stand. However, after kneading, it can be more efficiently obtained by filling (casting) it into a mold and curing it, or by directly pouring it, spraying it, or applying it to the construction site.

[0049] The compressive strength of the above-mentioned hardened body depends on the type of cement used, but is preferably 11.0 N / mm 2 or more, more preferably 13.0 N / mm 2 or more, and even more preferably 15.0 N / mm 2 or more, 6 hours after placement.

[0050] [Method for manufacturing hardened body] The method for manufacturing a hardened body according to the present embodiment is a method of curing a quick-setting cement composition containing the quick-setting material of the present invention by steam curing at a maximum temperature of 40 to 80°C for 2 to 8 hours. The method for manufacturing a hardened body preferably includes, in this order, a kneading step of kneading a quick-setting material, cement, and water, a placing step of filling the kneaded quick-setting cement composition into a mold, and a curing step of curing the quick-setting cement composition filled in the mold.

[0051] The kneading method in the kneading step is not particularly limited, and each material may be mixed during construction, or a part or all of them may be mixed in advance. As the mixing device, any existing device, for example, a tilting drum mixer, an omnimixer, a Henschel mixer, a V-type mixer, a proshear mixer, a Nauta mixer, etc. can be used.

[0052] The placing method in the placing step can be performed by a known method. The temperature of the quick-setting cement composition during placement is preferably 0 to 50°C, and more preferably 10 to 40°C. When the temperature of the quick-setting cement composition during placement is within the above range, it is easy to enable early demolding of the hardened body.

[0053] The method for manufacturing a hardened body preferably further includes a compaction step after the placing step. As the compaction method, a known method can be used, but from the viewpoint of workability, it is preferable to use a vibrator. Since the quick-setting cement composition containing the quick-setting material of the present invention maintains good fluidity immediately before placement, compaction can be easily performed, the quick-setting cement composition can be evenly distributed in the mold, and air bubbles mixed in during placement can be removed.

[0054] As a curing method used in the curing process, from the perspective of productivity improvement, it is preferable to use steam curing using a curing chamber, a heating sheet, or the like. Steam curing usually raises the temperature of the atmosphere around the object and cures while maintaining a certain temperature while keeping an appropriate humidity. As the conditions for steam curing, it is preferably at a maximum temperature of 40 to 80°C and a curing time of 2 to 8 hours, more preferably at a maximum temperature of 40 to 75°C and a curing time of 2.5 to 7.5 hours, and even more preferably at a maximum temperature of 45 to 60°C and a curing time of 3 to 7 hours. When steam curing is performed with the maximum temperature of the atmosphere around the early-strength cement composition during steam curing within the above range and the curing time within the above range, it is easy to enable early demolding of the hardened body.

[0055] The relative humidity around the early-strength cement composition during steam curing is preferably 50%RH or more, more preferably 75%RH or more, and even more preferably 90%RH or more. The upper limit is not limited, and 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 early demolding of the hardened body.

[0056] The curing process preferably includes a pre-curing process. As the conditions for pre-curing, it is preferable to keep the temperature constant at 10 to 50°C for about 1 to 3 hours. By including the pre-curing process in the curing process, the temperature inside the placed early-strength cement composition can be made uniform, and it is easy to prevent temperature cracking due to the temperature difference between the inside and the outside.

[0057] The curing process preferably includes a heating process. As the heating method, a known method can be used, and it is preferable to heat at a heating rate of 10 to 30°C / hour, more preferably at a heating rate of 12 to 28°C / hour, and even more preferably at a heating rate of 15 to 25°C. When the heating rate in the heating process is within the above range, it is possible to promote curing while preventing temperature cracking due to a rapid temperature rise of the early-strength cement composition.

[0058] The curing process preferably includes a temperature maintenance process. As the temperature maintenance method, known methods can be used. Preferably, the temperature is 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 to maintain a constant temperature. By maintaining a constant temperature within the above numerical range in the temperature maintenance process, the placed early-strength cement composition can be uniformly cured, making early demolding easier.

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

Examples

[0060] Hereinafter, the present invention will be further described based on experimental examples, but the present invention is not limited thereto.

[0061] <Experimental Example 1> The following calcium formate was used as a calcium formate-based powder, and various early-strengthening materials were prepared by adjusting through pulverization, sieving, and granulation so that the D90 of the calcium formate-based powder would be the values shown in Table 1 below. When the SrO content of the prepared early-strengthening material was measured by XRF using a fluorescence X-ray analyzer ZSX100e (manufactured by Rigaku Corporation), it was 0.02%. Using the prepared early-strength agent and cement, they were mixed so that the early-strength agent was 2.0% by mass to prepare an early-strength cement composition. Using the obtained early-strength cement composition, fine aggregate, coarse aggregate, and water, they were mixed so that the water / cement ratio was 37.5% and the fine aggregate ratio was 42% to prepare early-strength concrete (Table 1 No. 1-2 to 6). Similarly, using cement, fine aggregate, coarse aggregate, and water, they were mixed so that the water / cement ratio was 35% to prepare concrete without an early-strength agent (Table 1 No. 1-1). For each of the obtained concretes, measurements of air content, slump change, compressive strength, setting property, and finishability were carried out. The results are shown together in Table 1 below.

[0062] (Materials Used) Calcium formate: Reagent. Cement: Ordinary Portland cement (commercial product), Blaine specific surface area 3,200 cm 2 / g, specific gravity 3.15 g / cm 3 . Water: Tap water. Fine aggregate: Sand from the Himekawa River system in Iwafune City, Niigata Prefecture, maximum size 5 mm or less, density 2.62 g / cm 3 . Coarse aggregate: Crushed stone from Iwafune 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 by Mass of Air Content (Mass Method)".

[0064] Slump change: In accordance with the method specified in JIS A 1101:2020 "Test Method for Slump of Concrete", the slump immediately after mixing and the slump after standing for 30 minutes after mixing were measured, and the change amount was calculated.

[0065] Compressive strength: Measured in accordance with the method specified in JIS A 1108:2018 "Test Method for Compressive Strength of Concrete" using a cylindrical specimen of φ100×200 cm.

[0066] Coagulability: In accordance with the method specified in JIS A 1147:2019 "Test Method for Setting Time of Concrete", the time when the penetration resistance value reaches 1.0 N / mm 2 and 3.5 N / mm 2 was measured respectively.

[0067] Workability: Concrete was placed in a container with dimensions of 350 mm in length × 245 mm in width × 90 mm in height (approx. 7.7 L). After 60 minutes of placement, the slope was set to approximately 40°, and the sag of the concrete was visually confirmed and evaluated in three grades. Those with no sag (bias) or floating of moisture in the concrete and no sag occurring in the concrete even when troweled were rated as good (〇), those with almost no sag or floating of moisture in the concrete but sag occurring in the concrete when troweled were rated as poor (△), and those with visible sag or floating of moisture in the concrete were rated as unacceptable (×).

[0068]

Table 1

[0069] <Example 2> Except that the cement in the early-strength cement composition was replaced with SCMs shown in the following Table 2 at the SCMs replacement ratio using the SCMs shown below, early-strength concrete was prepared and various measurements were carried out in the same manner as in Example 1. The results are also shown in Table 2 below.

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

[0071]

Table 2

[0072] <Experimental Example 3> Using the accelerating agent and cement prepared in Experimental Example 1, they were mixed so that the accelerating agent was 2.0% by mass, and a water reducing agent was added so as to be 0.5% with respect to the weight of the cement to prepare an early strength cement composition. Using the prepared early strength cement composition, an early strength mortar was prepared such that the water / cement ratio was 35% and the ratio of cement to fine aggregate was 1:1.5 (mass ratio). Further, after filling the prepared early strength mortar into a mold having dimensions of 4×4×16 cm, steam curing was performed to obtain a hardened body of the early strength mortar. The steam curing conditions were pre-curing at 20°C for 1 hour, heating at a rate of 20°C / hour for 1.5 hours, maintaining the temperature at 50°C for 3 hours, and natural cooling for 0.5 hour. Various measurements were performed on the obtained hardened body of the early strength mortar. The results are shown in Table 3 below.

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

[0074] (Measurement Items) Mortar flow change rate: In accordance with the method specified in JIS R 5201:2015 "Physical Test Methods for Cement", the flow value of the mortar immediately after remixing and the flow value of the mortar after standing for 30 minutes after remixing were measured, and (mortar flow change rate) = (1 - (flow value after 30 minutes from kneading) / (flow value immediately after kneading)) × 100 was used to calculate the mortar flow change rate.

[0075] Compressive strength: In accordance with the method specified in JIS R 5201:2015 "Physical Test Methods for Cement", the compressive strength at an age of 6 hours (immediately after demolding) after the completion of steam curing was measured.

[0076] Coagulability: In accordance with the method specified in JIS R 5201:2015 "Methods of Physical Tests for Cement", the times when the penetration resistance values become 1.0 N / mm 2 and 3.5 N / mm 2 were measured respectively.

[0077]

Table 3

Industrial Applicability

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

Claims

1. A quick-setting material comprising a calcium formate-based powder in which the particle diameter (D90) at which the cumulative percentage becomes 90% is 1,200 μm or less in the volume-integrated particle size distribution measured by the laser diffraction scattering method.

2. A quick-setting cement composition comprising the quick-setting material according to Claim 1 and cement.

3. The quick-setting 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 quick-setting mortar comprising the quick-setting cement composition according to Claim 2 or 3.

5. A quick-setting concrete comprising the quick-setting cement composition according to Claim 2 or 3.

6. A hardened quick-setting mortar obtained by hardening the quick-setting mortar according to Claim 4.

7. A hardened quick-setting concrete obtained by hardening the quick-setting concrete according to Claim 5.

8. A method for producing a hardened body, wherein a quick-setting cement composition containing the quick-setting material according to Claim 1 is hardened by steam curing at a maximum temperature of 40 to 80°C for 2 to 8 hours.

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