Hydraulic components, hardeners, and methods for manufacturing hydraulic components

Abstract

To provide a low-carbon type hydraulic composition that is manufactured using an inorganic mineral other than kaolin and has sufficient compressive strength.SOLUTION: A hydraulic water-curing composition contains 30-70 mass% of inorganic minerals (except kaolin) having SiO2 content of 30-40 mass% and Al2O3 content of 30-40 mass%, and 30-70 mass% of alkali stimulants, and in the inorganic minerals, a ratio of a peak area of at least one of four-coordinated Al and five-coordinated Al is 30-50% when the sum of the peak areas of four-coordinated Al, five-coordinated Al and six-coordinated Al analyzed by 27Al-NMR is 100%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a hydraulic composition, a hardened product, and a method for producing a hydraulic composition. [Background technology]

[0002] Limestone Calcined Clay Cement (LC3) is known as a technology that uses inorganic minerals to calcinate them to increase their pozzolanic reactivity and then replace cement admixtures such as blast furnace slag and fly ash (see, for example, Non-Patent Document 1). This cement can be called a low-carbon cement, and compared to regular Portland cement, it can reduce carbon dioxide emissions (CO2) associated with its production. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Karen Scrivener et al.: Calcined clay limestone cements (LC3), Cement and Concrete Research,Vol.114,pp.49-56 (2018) Summary of the Invention [Problem to be solved by the invention]

[0004] Regarding the above technology, it has been shown that a material containing metakaolin, which is calcined kaolin as an inorganic mineral, can achieve good strength development. However, since kaolin is produced in limited regions and countries, the search for a material to replace kaolin has become an issue.

[0005] The present invention has been made in view of the above circumstances, and aims to provide a low-carbon hydraulic composition that is produced using an inorganic mineral other than kaolin and that exhibits sufficient compressive strength development. Another aim of the present invention is to provide a hardened product obtained from the hydraulic composition, and a method for producing the hydraulic composition. [Means for solving the problem]

[0006] The inventors focused on minerals such as allophane, which is usually said to inhibit the reaction of cement, as a material other than kaolin, and discovered that hydraulic compositions containing such minerals may have properties equivalent to or superior to those containing kaolin, and that the amount of cement to be blended as an alkali activator when preparing a hydraulic composition may be reduced, leading to the completion of the present invention.

[0007] One aspect of the present invention is a method for producing a slag cement paste comprising: 30 to 70 mass% of an inorganic mineral (excluding kaolin) having an SiO2 content of 30 to 40 mass% and an Al2O3 content of 30 to 40 mass%; and 30 to 70 mass% of an alkaline irritant, wherein the inorganic mineral is 27 Provided is a hydraulic composition in which the ratio of the peak area of ​​at least one of tetracoordinated Al and pentacoordinated Al is 30 to 50% when the sum of the peak areas of tetracoordinated Al, pentacoordinated Al, and hexacoordinated Al analyzed by Al-NMR is taken as 100%. The inventors have discovered the following inorganic minerals (clay minerals) with high pozzolanic reactivity and their calcined products as substitutes for kaolin: 27 It was found that inorganic minerals having a specific relationship of Al coordination numbers in structural analysis by Al-NMR are suitable for the production of low-carbon cement.The hydraulic composition containing inorganic minerals having the above-mentioned specific relationship of Al coordination numbers can be said to be a low-carbon hydraulic composition produced using inorganic minerals other than kaolin and having sufficient compressive strength development.

[0008] One embodiment of the hydraulic composition may contain 15% by mass or less of carbonate.

[0009] In one embodiment of the hydraulic composition, the inorganic mineral may be a clay mineral calcined at 500 to 950°C.

[0010] In one embodiment of the hydraulic composition, the alkaline irritant may include tricalcium silicate (3CaO·SiO2, denoted as C3S).

[0011] In one embodiment of the hydraulic composition, the inorganic mineral may include allophane.

[0012] One aspect of the present invention provides a hardened body obtained by hardening a paste containing the hydraulic composition and water. Such a hardened product obtained from the hydraulic composition can be said to be a low-carbon hardened product having sufficient compressive strength.

[0013] One aspect of the present invention is to provide an inorganic mineral (excluding kaolin) having an SiO2 content of 30 to 40 mass% and an Al2O3 content of 30 to 40 mass%. 27 The present invention provides a method for producing a hydraulic composition, comprising: a selection step of selecting an inorganic mineral in which, when analyzed by Al-NMR and the sum of the peak areas of tetracoordinated Al, pentacoordinated Al, and hexacoordinated Al is taken as 100%, the proportion of the peak area of ​​at least one of tetracoordinated Al and pentacoordinated Al is 30 to 50%; and a mixing step of mixing the selected inorganic mineral and an alkaline activator to prepare a hydraulic composition containing 30 to 70 mass% of the inorganic mineral and 30 to 70 mass% of the alkaline activator. According to this production method, it is possible to produce a low-carbon hydraulic composition that is produced using an inorganic mineral other than kaolin and that has sufficient compressive strength development.

[0014] One embodiment of the method for producing a hydraulic composition may further include a calcination step of heating the inorganic mineral at 500 to 950°C prior to the selection step. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a low-carbon hydraulic composition that is produced using an inorganic mineral other than kaolin and that exhibits sufficient compressive strength development. Furthermore, according to the present invention, it is possible to provide a hardened body obtained from the hydraulic composition and a method for producing the hydraulic composition. DETAILED DESCRIPTION OF THE INVENTION

[0016] Preferred embodiments of the present disclosure will be described in detail below, but the present disclosure is not limited to the following embodiments. In the following description, when "X to Y" (X and Y are arbitrary numbers) is written, it means "greater than or equal to X and less than or equal to Y" unless otherwise specified. Unless otherwise specified, the materials exemplified in this specification can be used singly or in combination of two or more. When multiple substances corresponding to each component are present in the composition, the content of each component in the composition means the total amount of the multiple substances present in the composition, unless otherwise specified.

[0017] <Hydraulic composition> The hydraulic composition contains an inorganic mineral (excluding kaolin) having an SiO2 content of 30 to 40 mass % and an Al2O3 content of 30 to 40 mass %, and an alkali activator.

[0018] (inorganic minerals) Inorganic minerals having an SiO2 content of 30 to 40 mass% and an Al2O3 content of 30 to 40 mass% include, in addition to kaolin, allophane, illite, montmorillonite, pyrophyllite, etc. Among these, from the viewpoint of reactivity with the alkaline stimulant, the inorganic mineral preferably contains allophane, and more preferably is allophane. The inorganic mineral may also be a clay mineral.

[0019] The SiO2 content in the inorganic mineral is preferably 32 mass % or more and 38 mass % or less from the viewpoint of reactivity with the alkaline irritant. The Al2O3 content in the inorganic mineral is preferably 32 mass % or more and 38 mass % or less from the viewpoint of reactivity with the alkaline stimulant.

[0020] In inorganic minerals, 27 When the sum of the peak areas of tetracoordinated Al, pentacoordinated Al, and hexacoordinated Al analyzed by Al-NMR is taken as 100%, the proportion of the peak area of ​​at least one of tetracoordinated Al and pentacoordinated Al is 30 to 50%. In inorganic minerals, tetracoordinated Al and pentacoordinated Al have unstable frameworks, which are thought to contribute to increased reactivity with alkaline irritants. When the peak area ratio of at least one of tetracoordinated Al and pentacoordinated Al is 30% or more, the effect of this action can be fully enjoyed. On the other hand, if the ratio of tetracoordinated Al and pentacoordinated Al is too high, there is a risk that the reaction with alkaline irritants will proceed too rapidly. When the peak area ratio of at least one of tetracoordinated Al and pentacoordinated Al is 50% or less, such a phenomenon can be easily suppressed. From these viewpoints, the peak area ratio of at least one of tetracoordinated Al and pentacoordinated Al is preferably 30 to 45%, more preferably 35 to 45%. From the viewpoint of easily achieving the above-mentioned effects, the peak area ratios of both tetracoordinated Al and pentacoordinated Al may be 30 to 50%, preferably 30 to 45%, and more preferably 35 to 45%.

[0021] The sum of the peak areas of tetracoordinated Al and pentacoordinated Al is preferably 50% or more from the viewpoint of reactivity with an alkaline irritant, and is preferably 90% or less from the viewpoint of the reaction rate with an alkaline irritant. From these viewpoints, the sum of the peak areas of tetracoordinated Al and pentacoordinated Al is more preferably 60 to 90%, and even more preferably 70 to 80%. From the above, the peak area of ​​hexacoordinated Al is preferably 10 to 50%, more preferably 10 to 40%, and even more preferably 20 to 30%.

[0022] The peak areas of tetracoordinated Al, pentacoordinated Al, and hexacoordinated Al can be adjusted by a process such as the peak area adjustment process described below. For example, when calcination is performed to adjust the peak areas, the inorganic mineral may be a clay mineral calcined at 500 to 950°C.

[0023] The above peak area ratio is measured as follows. Nuclides of inorganic minerals 27 The chemical shift and coordination state of Al-NMR are analyzed using an NMR apparatus JNM-ECZ800R (manufactured by JEOL Ltd.). The analysis method is the MAS (Magic Angle Spinning) method, and a 3.2 mm sample tube is used. The analysis conditions are magnetic field strength: 18.79 T, frequency: 20 kHz, number of accumulations: 256, and pulse width: 90° (0.6 μs). obtained 27 For Al-NMR spectra, each peak is separated using a Voigt function, which is a convolution function of a Gaussian function and a Lorentzian function.The integrated values ​​of each separated peak are then used to calculate each peak area. In addition, inorganic minerals 27 In the Al-NMR spectrum, peak P1 is observed in the chemical shift range of -10 ppm to 15 ppm, peak P2 in the range of 50 ppm to 80 ppm, and peak P3 in the range of 30 ppm to 40 ppm. Peak P1 corresponds to 6-coordinated Al, which originates from the inorganic mineral framework. Peaks P2 and P3 originate from 4-coordinated Al and 5-coordinated Al, respectively, which are thought to be generated by partial collapse of the inorganic mineral framework (e.g., decomposition and dehydroxylation of the 6-coordinated Al structure due to heat treatment at high temperatures). From the obtained areas of the peaks P1 to P3, the sum of the area of ​​P1+P2+P3 and the ratios of the areas of P2 and P3 based on this sum are calculated.

[0024] The content of inorganic minerals in the hydraulic composition is 30% by mass or more based on the total amount of the hydraulic composition from the viewpoint of compressive strength, and 70% by mass or less from the viewpoint of easily maintaining good fluidity. From these viewpoints, the content is preferably 35 to 60% by mass, more preferably 40 to 55% by mass.

[0025] (Alkaline stimulant) Examples of alkaline stimulants include Portland cement clinker and tricalcium silicate (3CaO·SiO2, denoted as C3S).

[0026] The Portland cement clinker may be Portland cement clinker used to prepare various Portland cements specified in JIS R 5210:2003 "Portland Cement." Examples of the various Portland cements include ordinary Portland cement, high-early-strength Portland cement, moderate-heat Portland cement, and low-heat Portland cement. The Portland cement clinker may be Portland cement clinker used to prepare ordinary Portland cement and high-early-strength Portland cement.

[0027] The mineral composition of Portland cement clinker can be calculated using the Bogue formula. The Bogue formula is a widely used formula for calculating the content of major minerals in Portland cement clinker from the content ratio of their chemical composition. Using the Bogue formula shown below, the contents of tricalcium silicate (3CaO·SiO2, represented by C3S), dicalcium silicate (2CaO·SiO2, represented by C2S), and tricalcium aluminate (3CaO·Al2O3, represented by C3A) in Portland cement clinker can be calculated. Note that "%" in the formula below means "mass %." The chemical formula represents the content ratio (mass%) of each compound indicated by the chemical analysis value according to JIS R 5204:2019 "Fluorescent X-ray analysis method for cement."

[0028] <Bogue formula> C3S[%]=(4.07×CaO[%])-(7.60×SiO2[%])-(6.72×Al2O3[%])-(1.43×Fe2O3[%])-(2.85×SO3[%]) C2S[%]=(2.87×SiO2[%])-(0.754×C3S[%]) C3A[%]=(2.65×Al2O3[%])-(1.69×Fe2O3[%]) C4AF[%]=3.04×Fe2O3[%]

[0029] From the perspective of compressive strength, the content of the alkali activator in the hydraulic composition is 30% by mass or more based on the total amount of the hydraulic composition, while from the perspective of reducing CO2 emissions, it is 70% by mass or less. From these perspectives, the content is preferably 35 to 60% by mass, and more preferably 40 to 55% by mass.

[0030] From the perspective of compressive strength, the content of the inorganic mineral and the alkali activator in the hydraulic composition is 60% by mass or more based on the total amount of the hydraulic composition, preferably 80% by mass or more, more preferably 85% by mass or more, and may even be 100% by mass (substantially consisting of the inorganic mineral and the alkali activator).

[0031] In addition to the inorganic mineral and the alkali activator, the hydraulic composition may contain other components. Examples of other components include inorganic fine powders, gypsum, carbonates, etc. The other components can be 40% by mass or less based on the total amount of the hydraulic composition, and may be 20% by mass or less, or may be 15% by mass or less.

[0032] The inorganic fine powder is added to the hydraulic composition for the purpose of improving the compressive strength. Examples of the inorganic fine powder include powdery materials such as silica and crushed stone. From the perspective of fluidity, the content of the inorganic fine powder in the hydraulic composition is 0% by mass or more based on the total amount of the hydraulic composition, while from the perspective of compressive strength, it is preferably 15% by mass or less.

[0033] Gypsum is added to the hydraulic composition for the purpose of adjusting the hydration reaction rate. Examples of gypsum include gypsum dihydrate, gypsum hemihydrate, and anhydrous gypsum. The gypsum content in the hydraulic composition may be the same as that in common Portland cement, and is preferably 0% by mass or more, based on the total amount of the hydraulic composition, and more preferably 5% by mass or less, from the viewpoint of easily maintaining a good hydration reaction rate.

[0034] Carbonates are added to hydraulic compositions to promote the hydration reaction of the alkaline activator C3S. Examples of carbonates include alkali metal carbonates and alkaline earth metal carbonates, such as sodium carbonate, calcium carbonate (limestone), and magnesium carbonate. As the limestone, for example, commercially available limestone powder and powders containing calcium carbonate as a main component, such as kansui stone powder, can be used. The limestone preferably includes limestone that conforms to the minor mixing components described in JIS R 5210 "Portland cement." The content of carbonate in the hydraulic composition is preferably 0% by mass or more based on the total amount of the hydraulic composition from the viewpoint of fluidity, and 15% by mass or less from the viewpoint of compressive strength.

[0035] <Cured body> The hardened product is obtained by hardening a paste containing the hydraulic composition and water. The hardening conditions are not particularly limited. The hardened product can be prepared in accordance with the method described in JIS R 5201:2015 "Physical Test Methods for Cement."

[0036] The amount of water in the paste is 35 parts by mass or more relative to 100 parts by mass of the total amount of the hydraulic composition from the viewpoint of fluidity, and 80 parts by mass or less from the viewpoint of easily making the pore structure of the hardened body dense. From these viewpoints, the amount of water is preferably 35 to 80 parts by mass, and more preferably 50 to 70 parts by mass.

[0037] <Method for producing hydraulic composition> The method for producing the hydraulic composition is to use an inorganic mineral (excluding kaolin) having an SiO2 content of 30 to 40 mass % and an Al2O3 content of 30 to 40 mass %. 27 The method includes a selection step of selecting an inorganic mineral in which the ratio of the peak area of ​​at least one of tetracoordinated Al and pentacoordinated Al is 30 to 50% when the sum of the peak areas of tetracoordinated Al, pentacoordinated Al, and hexacoordinated Al is taken as 100% by analyzing the inorganic mineral by Al-NMR, and a mixing step of mixing the selected inorganic mineral and an alkaline activator to prepare a hydraulic composition containing 30 to 70 mass% of the inorganic mineral and 30 to 70 mass% of the alkaline activator.

[0038] The method for producing a hydraulic composition may further include a peak area adjustment step prior to the selection step.

[0039] (Selection process) In the selection step, inorganic minerals with high pozzolanic reactivity and calcined products thereof are selected as materials suitable for low-carbon cement to replace kaolin. If the inorganic minerals selected have the above-mentioned specific relationship in terms of peak area, they can be subjected to the mixing step. On the other hand, if the inorganic minerals do not have the above-mentioned specific relationship in terms of peak area, they can be subjected to the peak area adjustment step described below.

[0040] (Mixing process) In the mixing step, the inorganic mineral and the alkaline activator selected as described above are mixed. When mixing the two, the other components described above may also be mixed. The blending amounts of each raw material are as described above.

[0041] In the mixing step, each raw material may be pulverized. When pulverization is performed, the order of mixing and pulverization is not particularly limited. That is, the raw materials may be mixed and then pulverized, or the raw materials may be individually pulverized and then mixed, or the raw materials may be mixed and pulverized simultaneously. The mixing may be performed using a mixer such as a pan mixer, a tilting mixer, or a ribbon mixer, or may be mixed and pulverized using a pulverizer such as a ball mill, a vertical roller mill, or a roller press, or each raw material may be pulverized separately and then mixed using a mixer such as a mechanical mixer.

[0042] (Peak area adjustment step) If the area of ​​the peak P1 of hexacoordinated Al derived from the inorganic mineral framework is too large, the inorganic mineral will not have the above-mentioned specific relationship in terms of peak area. In this case, adjusting the peak area of ​​the inorganic mineral may make it suitable for practical use.

[0043] As described above, peaks P2 and P3, which are derived from tetrahedral Al and pentahedral Al, respectively, are thought to be generated by partial collapse of the inorganic mineral framework. Partial collapse of the inorganic mineral framework can be achieved, for example, by calcination, acid-base treatment, or grinding of the inorganic mineral.

[0044] In the case where calcination of the inorganic mineral is carried out, the method for producing a hydraulic composition can be said to further comprise a calcination step of heating the inorganic mineral prior to the selection step. The calcination temperature is preferably 500°C or higher from the viewpoint of increasing tetracoordinated Al and pentacoordinated Al, which contribute to an increase in compressive strength, and is preferably 950°C or lower from the viewpoint of suppressing the use of the tetracoordinated Al and pentacoordinated Al in the formation of other minerals (for example, the formation of mullite in the case of allophane).From these viewpoints, the calcination temperature is more preferably 600 to 900°C. The calcination time is not particularly limited, but may be 0.5 to 5 hours, or may be 1 to 4 hours, in view of the effect on the crystal structure.

[0045] After the peak area adjustment step, the selection step is carried out again, and the selection results are fed back to the peak area adjustment step to adjust various conditions (for example, calcination temperature, calcination time, etc.) in the peak area adjustment step. [Example]

[0046] The present invention will be described in more detail by the following examples, but the present invention is not limited to these examples.

[0047] <Raw materials for hydraulic compositions> (inorganic minerals) The types of inorganic minerals (clay minerals) used are shown in Table 1. [Table 1]

[0048] (Alkaline stimulant) C3S (3CaO SiO2) was prepared as an alkaline irritant by mixing silicon dioxide (Wako Pure Chemical Industries, Ltd.) and calcium carbonate (Wako Pure Chemical Industries, Ltd.) in a molar ratio of 1:3, kneading the mixture with water, and firing it in an electric furnace at 1500°C for 1 hour.

[0049] (Other ingredients) Limestone: Ube Material Industries, Ltd. (limestone fine powder, 325 mesh) Anhydrite: natural anhydrite

[0050] <Preparation of hydraulic composition> Various inorganic minerals were calcined under the conditions shown in Table 2. The calcination time was 1 hour. Next, the calcined inorganic minerals, the alkali activator and other components were mixed according to the formulation shown in Table 2 to prepare hydraulic compositions.

[0051] <Preparation of hardened body> The hydraulic composition obtained in each example and water were mixed in a mass ratio of 100:70, and a paste was prepared using a Three-One Motor (manufactured by HEIDEN) at a rotation speed of 300 rpm for a mixing time of 1 minute 30 seconds. The prepared paste was filled into a 1 cm x 1 cm x 6 cm mold and left to stand in air at 20°C and 60 RH for 1 day, after which it was demolded to obtain a hardened body.

[0052] [Table 2]

[0053] <Peak area ratio calculation> Nuclides of inorganic minerals 27 The chemical shifts and coordination states of Al-NMR were analyzed using an NMR apparatus JNM-ECZ800R (manufactured by JEOL Ltd.). The analysis was performed using the MAS (Magic Angle Spinning) method, with a 3.2 mm sample tube. The analysis conditions were magnetic field strength: 18.79 T, frequency: 20 kHz, number of integrations: 256, and pulse width: 90° (0.6 μs). obtained 27 For the Al-NMR spectrum, the waveform of each peak was separated using the Voigt function, which is a convolution function of a Gaussian function and a Lorentzian function. 27 In the Al-NMR spectrum, peak P1 in the chemical shift range of −10 ppm to 15 ppm corresponds to 6-coordinated Al, peak P2 in the chemical shift range of 50 ppm to 80 ppm corresponds to 4-coordinated Al, and peak P3 in the chemical shift range of 30 ppm to 40 ppm corresponds to 5-coordinated Al. The area of ​​each peak was calculated using the integral value of each separated peak. From the obtained peak areas, the sum of the areas of P1+P2+P3 and the ratio (%) of the areas of P1 to P3 based on this sum were calculated. The results are shown in Table 3.

[0054] <Compression strength measurement> The compressive strength of the hardened specimens obtained in each example was measured according to the following method. Specifically, the compressive strength was measured in accordance with the method described in JIS R 5201:2015 "Physical Testing Methods for Cement." Two hardened specimens were used, with N=4 for each measurement. The results are shown in Table 3.

[0055] [Table 3]

[0056] As shown in Table 3, in the examples, a low-carbon hydraulic composition having sufficient compressive strength development was produced using inorganic minerals other than kaolin. This indicates that the use of inorganic minerals other than kaolin 27 This is evidence that by analyzing using Al-NMR and selecting an inorganic mineral based on the ratio of the peak areas of tetrahedral Al and pentahedral Al, and mixing this with an alkaline activator, it is possible to produce a low-carbon hydraulic composition that exhibits sufficient compressive strength.

Claims

1. SiO ２ The content is 30 to 40 mass % and Al ２ O ３ The inorganic mineral (excluding kaolin) is contained in an amount of 30 to 40% by mass, and the alkali irritant is contained in an amount of 30 to 70% by mass. In the inorganic mineral, ２７ A hydraulic composition, wherein, when the sum of the peak areas of tetracoordinated Al, pentacoordinated Al, and hexacoordinated Al analyzed by Al-NMR is taken as 100%, the ratio of the peak area of ​​at least one of the tetracoordinated Al and the pentacoordinated Al is 30 to 50%, and the sum of the peak areas of the tetracoordinated Al and the pentacoordinated Al is 60 to 90%.

2. The hydraulic composition according to claim 1 , wherein the hydraulic composition contains 15% by mass or less of a carbonate.

3. 3. The hydraulic composition according to claim 1, wherein the inorganic mineral is a clay mineral calcined at 500 to 950°C.

4. The alkaline irritant is C ３ The hydraulic composition according to any one of claims 1 to 3, comprising S.

5. The hydraulic composition according to any one of claims 1 to 4, wherein the inorganic mineral comprises allophane.

6. A hardened body obtained by hardening a paste containing the hydraulic composition according to any one of claims 1 to 5 and water.

7. SiO ２ The content is 30 to 40 mass % and Al ２ O ３ Inorganic minerals (excluding kaolin) with a content of 30 to 40 mass% ２７ a selecting step of selecting an inorganic mineral analyzed by Al-NMR, in which, when the sum of the peak areas of tetracoordinated Al, pentacoordinated Al, and hexacoordinated Al is taken as 100%, a ratio of the peak area of ​​at least one of the tetracoordinated Al and the pentacoordinated Al is 30 to 50% and the sum of the peak areas of the tetracoordinated Al and the pentacoordinated Al is 60 to 90%; a mixing step of mixing the selected inorganic mineral and alkaline activator to prepare a hydraulic composition containing 30 to 70 mass% of the inorganic mineral and 30 to 70 mass% of the alkaline activator.

8. The method according to claim 7, further comprising a calcination step of heating the inorganic mineral at 500 to 950°C prior to the selection step.

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