Inorganic material containing allophane and method for producing the same, hydraulic composition and method for producing the same, as well as hardened body and method for producing the same

Abstract

To provide an inorganic material containing allophane capable of reducing an amount of carbon dioxide generated when used in the preparation of a hydraulic composition, and a method for producing the same.SOLUTION: An inorganic material containing allophane has a mass ratio of the Si content in terms of SiO2 to the Al content in terms of Al2O3 (SiO2 / Al2O3) exceeding 1.6. A method for producing an inorganic material containing allophane includes a step of mixing a raw material containing allophane and having a mass ratio of the Si content in terms of SiO2 to the Al content in terms of Al2O3 (SiO2 / Al2O3) of 1.6 or less with an acidic solution containing an inorganic acid to obtain a mixture, and a step of separating solid components from the mixture to obtain an inorganic material having a mass ratio of the Si content in terms of SiO2 to the Al content in terms of Al2O3 (SiO2 / Al2O3) exceeding 1.6.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to an allophane-containing inorganic substance and a method for producing the same, a hydraulic composition and a method for producing the same, and a hardened body and a method for producing the same. [Background technology]

[0002] Cement clinker, which is blended into Portland cement, is produced by burning raw materials in a kiln. This production process generates carbon dioxide. In order to reduce carbon dioxide emissions, attempts have been made to prepare low-carbon hydraulic compositions using inorganic minerals. For example, Patent Document 1 shows that compressive strength can be improved by calcining a mineral containing allophane, which is more readily available than metakaolin, and using this in a hydraulic composition. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-127724 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a hydraulic composition capable of reducing the amount of carbon dioxide generated, a method for producing the same, and a hardened product and a method for producing the same. It also provides an allophane-containing inorganic substance that can reduce the amount of carbon dioxide generated by using the same in the preparation of a hydraulic composition. It also provides a production method that allows such an allophane-containing inorganic substance to be easily prepared. [Means for solving the problem]

[0005] An allophane-containing inorganic material according to one aspect of the present disclosure has a mass ratio (SiO / AlO) of the Si content calculated as SiO of greater than 1.6. Such an inorganic material has excellent reactivity with alkaline activators, making it suitable for use in preparing hydraulic compositions. Thus, this inorganic material can be used as a substitute for cement clinker, and because it contains allophane derived from minerals, it can reduce the amount of carbon dioxide generated.

[0006] A hydraulic composition according to one aspect of the present disclosure contains the above-described inorganic substance and an alkaline activator. Because this hydraulic composition contains an inorganic substance that is excellent in long-term strength development, the amount of cement clinker blended can be reduced. Furthermore, because this inorganic substance contains allophane derived from minerals, by replacing cement clinker, the amount of carbon dioxide generated can be reduced.

[0007] A hardened product according to one aspect of the present disclosure is obtained by hardening the hydraulic composition. Because this hardened product is obtained by hardening the hydraulic composition, it is possible to sufficiently reduce the amount of carbon dioxide generated. In addition, the hardened product has high compressive strength.

[0008] A method for producing an allophane-containing inorganic material according to one aspect of the present disclosure includes the steps of: mixing a raw material containing allophane, the raw material having a mass ratio (SiO2 / Al2O3) of the Si content in terms of SiO2 to the Al content in terms of Al2O3 of 1.6 or less, with an acidic solution containing an inorganic acid to obtain a mixture; and separating a solid fraction from the mixture to obtain an inorganic material having a mass ratio (SiO2 / Al2O3) of the Si content in terms of SiO2 to the Al content in terms of Al2O3 of greater than 1.6. In this production method, the allophane-containing raw material is treated with an acidic solution containing an inorganic acid to obtain the allophane-containing inorganic material. This inorganic material can be used as a substitute for cement clinker, and because it is obtained by treating the allophane-containing raw material with an inorganic acid, it is possible to further reduce the amount of carbon dioxide generated during production compared to methods that require calcination. Therefore, the method can be easily prepared, and the amount of carbon dioxide generated can be sufficiently reduced. Furthermore, hydraulic compositions produced using such an inorganic material exhibit excellent strength development.

[0009] A method for producing a hydraulic composition according to one aspect of the present disclosure includes a step of blending at least the inorganic substance obtained by the above-described production method with an alkaline activator to obtain a hydraulic composition containing the inorganic substance and the alkaline activator. This production method uses the inorganic substance, which can be used as a substitute for cement clinker and can reduce the amount of carbon dioxide generated during production, thereby sufficiently reducing the amount of carbon dioxide generated. Furthermore, the inorganic substance has excellent reactivity with the alkaline activator. Therefore, this production method allows for the production of a hydraulic composition with excellent strength development.

[0010] A method for producing a hardened body according to one aspect of the present disclosure includes at least a step of hardening the hydraulic composition obtained by the above-described method. This method uses the hydraulic composition obtained using the inorganic substance, and therefore can sufficiently reduce the amount of carbon dioxide generated. Furthermore, the hardened body obtained by this method has high compressive strength. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to provide a hydraulic composition capable of reducing the amount of carbon dioxide generated, a method for producing the same, and a hardened body and a method for producing the same. It is also possible to provide an allophane-containing inorganic substance that can reduce the amount of carbon dioxide generated by using the same in the preparation of a hydraulic composition. It is also possible to provide a production method that can easily prepare such an allophane-containing inorganic substance. [Brief explanation of the drawings]

[0012] [Figure 1] (a) shows the results of X-ray diffraction measurements of an alkali-treated product obtained by treating an allophane-containing raw material with a sodium hydroxide aqueous solution. (b) shows the results of X-ray diffraction measurements of an alkali-treated product obtained by treating an allophane-containing raw material with a sodium carbonate aqueous solution. [Figure 2] 1 shows the results of X-ray diffraction measurements of an acid-treated product obtained by treating a raw material containing allophane with hydrochloric acid. DETAILED DESCRIPTION OF THE INVENTION

[0013] Embodiments of the present disclosure are described below. However, the following embodiments are merely examples for explaining the present disclosure and are not intended to limit the present disclosure to the following content. In the description, the numerical ranges exemplified as "a to b" are numerical ranges inclusive of a and b, with a as the lower limit and b as the upper limit. The present disclosure also includes cases in which the upper or lower limit of each numerical range is replaced with the numerical value of any of the examples. When multiple materials are exemplified, one of the materials may be used alone, or multiple materials may be used in combination.

[0014] <Allophane-containing inorganic material and its manufacturing method> An inorganic material containing allophane (hereinafter sometimes simply referred to as "inorganic material") contains Al and Si. The mass ratio α (SiO2 / Al2O3) of the content of Si contained in the inorganic material in terms of SiO2 to the content of Al contained in the inorganic material in terms of Al2O3 exceeds 1.6.

[0015] From the viewpoint of further improving the strength development when a hydraulic composition is prepared using this inorganic material, the mass ratio α (SiO2 / Al2O3) of the content of Si contained in the inorganic material in terms of SiO2 to the content of Al contained in the inorganic material in terms of Al2O3 is preferably 1.7 or more, more preferably 1.8 or more, and even more preferably 1.9 or more. The mass ratio α may be, for example, less than 3.0 or less than 2.0.

[0016] The BET specific surface area of ​​inorganic materials is 230m 2 / g, and 240m 2 / g or more. If a hydraulic composition is prepared using such an inorganic substance, the long-term strength development can be further improved. The BET specific surface area of ​​the inorganic substance is 300 m 2 / g or less than 280m 2 / g or less.

[0017] The Si and Al in the inorganic material may be contained as oxides. The Si content in the inorganic material, calculated as SiO2, may be 44 to 60 mass%, 46 to 54 mass%, or 48 to 53 mass%. The Al2O3 content in the inorganic material may be 15 to 33 mass%, 20 to 31 mass%, or 25 to 30 mass%.

[0018] The inorganic substance may contain, in addition to Al and Si, at least one element selected from the group consisting of Na, K, Fe, Ca, and Mg. These elements may be contained as oxides. Examples of oxides include Na2O, KO, Fe2O3, CaO, and MgO. The Na content in the inorganic substance, calculated as Na2O, may be 0.1 to 4 mass%, or 0.3 to 3 mass%. The K content in the inorganic substance, calculated as KO, may be 0.1 to 4 mass%, or 0.2 to 3 mass%. The RO content in the inorganic substance may be 0.1 to 8 mass%, or 0.4 to 6 mass%. The RO content in the present disclosure is the alkali content, calculated as the Na2O content + 0.658KO content.

[0019] The content of Fe in the inorganic substance, calculated as Fe2O3, may be 0.5 to 7 mass%, or 1 to 5 mass%. The content of Ca in the inorganic substance, calculated as CaO, may be 0.3 to 5 mass%, or 0.5 to 3 mass%. The content of Mg in the inorganic substance, calculated as MgO, may be 0.05 to 1 mass%, or 0.1 to 0.5 mass%. The content of each oxide can be determined by quantifying each metal element by X-ray fluorescence analysis and converting it to its oxide.

[0020] The inorganic material containing allophane may be treated to such an extent that all of the allophane is not altered into other substances. The allophane content in the inorganic material may be 10% by mass or more, 30% by mass or more, 40% by mass or more, 50% by mass or more, or 60% by mass or more. By increasing the allophane content, it is possible to further improve the long-term strength development. The allophane content in the inorganic material may be 90% by mass or less, or 80% by mass or less. The allophane content can be determined by the acid-alkali alternating dissolution method described in the Examples.

[0021] The inorganic substance may be obtained by acid treatment. Natural allophane is produced by long-term weathering and hydrothermal alteration of volcanic ash and feldspar in volcanic deposits. For example, it has a particle diameter of 0.05 to 0.2 μm and a hollow spherical structure, with octahedral sheets of Al2O3 on the outer part of the hollow sphere (shell) and tetrahedral sheets of SiO2 on the inner part of the hollow sphere (shell). The allophane contained in the inorganic substance may be a natural allophane having such a structure that has been partially altered. The allophane contained in the inorganic substance is sufficient as long as the allophane skeleton is maintained. In this specification, any substance that can be quantified as allophane using the above-mentioned acid-alkali alternating dissolution method is considered to be "allophane" even if its structure has been altered.

[0022] The inorganic substance may not contain either or both of zeolite and dawsonite. A hydraulic composition prepared using such an inorganic substance is particularly excellent in long-term strength development.

[0023] Such inorganic substances can replace materials such as cement clinker or Portland cement. By replacing these materials, inorganic substances can reduce the amount of carbon dioxide generated. Furthermore, when used as materials for hydraulic compositions, they can improve long-term strength development.

[0024] A method for producing an allophane-containing inorganic material according to one embodiment includes a mixing step of mixing a raw material containing allophane, the raw material having a mass ratio β (SiO2 / Al2O3) of the Si content in terms of SiO2 to the Al content in terms of Al2O3 of 1.6 or less, with an acidic solution containing an inorganic acid to obtain a mixture, and a separation step of separating a solid content from the mixture to obtain an inorganic material having a mass ratio α (SiO2 / Al2O3) of the Si content in terms of SiO2 to the Al content in terms of Al2O3 of greater than 1.6. The method for mixing the allophane-containing raw material and the acidic solution in the mixing step is not particularly limited, and for example, a known stirrer or kneader may be used. The blending ratio of the two is not particularly limited, and for example, 100 to 400 parts by mass or 150 to 300 parts by mass of the acidic solution may be blended with 100 parts by mass of the inorganic material.

[0025] The allophane-containing raw material may be a mineral, a volcanic ejecta deposit, or a mineral or deposit whose grain size has been adjusted. When volcanic ejecta deposits are weathered, the SiO2, Na2O, KO, and RO contents tend to decrease, and the Al2O3 content tends to increase. The volcanic ejecta deposits may be commercially available products, or may be commercially available products that have been subjected to the above-described treatment. Examples of commercially available products include Kanuma soil, Satsuma soil, Kuroboku soil, and SEKADO P1 (trade name, manufactured by Shinagawa General Co., Ltd.). The allophane content in the inorganic material may be 10% by mass or more, 30% by mass or more, 40% by mass or more, 50% by mass or more, or 60% by mass or more, from the viewpoint of improving strength development.

[0026] The mass ratio β (SiO2 / Al2O3) of the Si content in the raw material containing allophane, calculated as SiO2, to the Al content in the raw material containing allophane, calculated as Al2O3, is smaller than the mass ratio α of the final inorganic material. The mass ratio β is 1.6 or less, and may be 1.5 or less, 1.4 or less, or 1.3 or less. From the viewpoint of obtaining a hydraulic composition that exhibits excellent long-term strength development when used as a material for a hydraulic composition, the ratio of the mass ratio α to the mass ratio β, i.e., mass ratio α / mass ratio β, may be 1.2 or more, 1.3 or more, or 1.4 or more. From the same viewpoint, the mass ratio α / mass ratio β may be 4.0 or less, 3.0 or less, or 2.0 or less.

[0027] The Si content, calculated as SiO2, in the allophane-containing raw material may be smaller than the Si content, calculated as SiO2, in the finally obtained allophane-containing inorganic material. The Si content, calculated as SiO2, in the allophane-containing raw material may be 30 to 55 mass%, 35 to 50 mass%, or 40 to 45 mass%. The Al content, calculated as Al2O3, in the allophane-containing raw material may be larger than the Al content, calculated as Al2O3, in the finally obtained allophane-containing inorganic material. The Al content, calculated as Al2O3, in the allophane-containing raw material may be 25 to 45 mass%, or 30 to 40 mass%.

[0028] Examples of inorganic acids include hydrochloric acid, nitric acid, sulfuric acid, carbonic acid, phosphoric acid, boric acid, and hydrofluoric acid. One of these may be used alone, or two or more may be used in combination. The acidic solution containing an inorganic acid may be an aqueous solution, and may have a pH of less than 2 or less than 1. By preparing a hydraulic composition using an inorganic substance obtained by treatment with an acidic solution having a pH of less than 1, it is possible to improve long-term strength development. In the present disclosure, long-term strength development is evaluated by compressive strength at a material age of 91 days, and short-term strength development is evaluated by compressive strength at a material age of 7 days.

[0029] When preparing a hydraulic composition using an inorganic substance, the concentration of the inorganic acid in the acidic solution is set to 1×10 in order to sufficiently improve the long-term strength development of the hydraulic composition. -1mol / L or more, 5×10 -1 The concentration of the inorganic acid in the acidic solution may be, for example, 5 mol / L or less. One of the reasons why strength development is improved by treatment with an acidic solution is that treating a raw material containing allophane with such an acidic solution destabilizes the crystalline structure of the allophane contained in the raw material, thereby improving its reactivity with the alkaline activator contained in the hydraulic composition. This reaction proceeds slowly over time, which is thought to improve the long-term strength development of the hydraulic composition. This action makes it possible to obtain a hydraulic composition and a hardened product that are excellent in long-term strength development.

[0030] The temperature at which the mixture is prepared in the mixing step may be 20 to 80°C, 30 to 70°C, or 35 to 60°C. This allows the acid treatment to proceed smoothly. The curing period within this temperature range may be 1 day or more, 3 days or more, or 5 days or more. This allows the acid treatment to proceed sufficiently. From the viewpoint of shortening the process, the curing period may be 30 days or less, or 20 days or less. In this way, a slurry-like mixture is obtained.

[0031] In the separation step, the acid-treated inorganic material is separated from the slurry mixture. Examples of separation methods include known methods for separating solids and liquids, such as centrifugation, filtration, standing, and drying. The liquid may be evaporated and distilled off under reduced pressure. These methods may be combined to separate the acid-treated inorganic material (acid-treated material). After drying, the inorganic material may be pulverized and sieved to adjust the particle size. The particle size of the inorganic material may be, for example, 1 mm or less, 500 μm or less, or 200 μm or less, from the viewpoint of smoothly proceeding with the reaction when mixed with the alkaline irritant.

[0032] In this manner, an inorganic material containing allophane can be prepared. The method for producing an inorganic material containing allophane may include any other steps in addition to those described above. However, it is not necessary to include a step of heating to 100°C or higher (for example, a calcination step or a firing step). This allows the amount of carbon dioxide generated in the production process of the inorganic material to be sufficiently reduced. The above production method can produce an inorganic material suitable for use in a hydraulic composition that is excellent in long-term strength development from a raw material containing allophane, even without including such a heating step.

[0033] <Hydraulic composition and method for producing the same> The hydraulic composition contains an inorganic substance containing allophane and an alkali activator. The hydraulic composition may be in powder form or may further contain water. Hydraulic compositions also include those that have fluidity before hardening. Examples of alkali activators include cement clinker, Portland cement, tricalcium silicate (3CaO·SiO2, represented by C3S), slaked lime, and alkali carbonates.

[0034] The content of the inorganic substance relative to the total solid content of the hydraulic composition may be 1% by mass or more, 3% by mass or more, 5% by mass or more, 10% by mass or more, 20% by mass or more, or 30% by mass or more, from the viewpoint of further reducing the amount of carbon dioxide generated by reducing the blending amount of alkaline activator. Furthermore, from the viewpoint of obtaining a hydraulic composition excellent in long-term strength development, the content of the inorganic substance relative to 100 parts by mass of alkaline activator may be 1 part by mass or more, 3 parts by mass or more, 5 parts by mass or more, 10 parts by mass or more, 20 parts by mass or more, or 30 parts by mass or more.

[0035] The content of the inorganic substance relative to the total solid content of the hydraulic composition may be 50% by mass or less, 40% by mass or less, or 30% by mass or less. If the content of the inorganic substance relative to the alkaline activator is reduced, the short-term strength development of the hydraulic composition tends to improve. From this perspective, the content of the inorganic substance in the hydraulic composition may be less than 60 parts by mass, less than 50 parts by mass, less than 30 parts by mass, or less than 20 parts by mass relative to 100 parts by mass of the alkaline activator.

[0036] The content of the inorganic substance relative to the total solid content of the hydraulic composition may be 1 to 50 mass%. Such a hydraulic composition reduces the amount of carbon dioxide generated and exhibits excellent, balanced short-term and long-term strength development. The ratio of the allophane content contained in the inorganic substance relative to the total solid content of the hydraulic composition may be 3 to 40 mass%, 5 to 35 mass%, or 6 to 30 mass%, from the viewpoint of achieving high, balanced short-term and long-term strength development.

[0037] The method for producing a hydraulic composition includes a blending step of blending the above-mentioned inorganic substance and alkaline activator to obtain a hydraulic composition containing the inorganic substance and alkaline activator. The blending step may be performed by adding water and kneading. The ratio of water to the alkaline activator (water-binder ratio) may be 30 to 70%, or 40 to 60%. Kneading may be performed using a known mixer. The hydraulic composition obtained in this manner can reduce the amount of carbon dioxide generated and is excellent in long-term strength development.

[0038] <Hardened body and its manufacturing method> The hardened product is obtained by hardening the hydraulic composition described above. When the hydraulic composition is in powder form, it may be hardened by blending with water and curing. Since this hardened product is obtained using the inorganic material described above as a raw material, the amount of carbon dioxide generated can be sufficiently reduced. Compared to when an inorganic material containing untreated allophane is used as a raw material, the long-term strength development can be improved.

[0039] The method for producing a hardened product includes a step of hardening the hydraulic composition described above. When the hydraulic composition is in powder form, it may be hardened by blending with water and curing. When the hydraulic composition is in slurry form, it may be hardened by curing. In this production method, the hydraulic composition produced using the inorganic substance described above is used, so the amount of carbon dioxide generated can be sufficiently reduced. Compared to when an inorganic substance containing untreated allophane is used as a raw material, long-term strength development can be improved.

[0040] Although several embodiments have been described above, the present disclosure is not limited to the above embodiments. For example, in the above embodiments, the case where an inorganic substance containing allophane is used in a hydraulic composition has been described, but it is not essential to use the inorganic substance in a hydraulic composition, and the inorganic substance may be used for other purposes. The present disclosure includes the following embodiments [1] to

[11] .

[0041] [1] An inorganic substance containing allophane, in which the mass ratio of the Si content converted to SiO2 to the Al content converted to Al2O3 (SiO2 / Al2O3) exceeds 1.6. [2] BET specific surface area is 230m 2 / g or more of the inorganic substance described in [1]. [3] The inorganic substance according to [1] or [2], wherein the content of Si in terms of SiO2 is 44 to 60 mass %. [4] A hydraulic composition containing the inorganic material according to any one of the above [1] to [3] and an alkali activator. [5] The hydraulic composition according to [4], wherein the content of the inorganic substance is 1 to 50 mass %. [6] A hardened product obtained by hardening the hydraulic composition described in [5] above. [7] A step of mixing a raw material containing allophane and having a mass ratio (SiO2 / Al2O3) of the content of Si converted to SiO2 to the content of Al converted to Al2O3 of 1.6 or less with an acidic solution containing an inorganic acid to obtain a mixture; and separating a solid content from the mixture to obtain an inorganic substance having a mass ratio (SiO2 / Al2O3) of the content of Si converted into SiO2 to the content of Al converted into Al2O3 exceeding 1.6. [8] A method for producing a hydraulic composition, comprising a step of blending at least the inorganic substance obtained by the production method according to [7] with an alkaline activator to obtain a hydraulic composition containing the inorganic substance and the alkaline activator. [9] A method for producing a hardened product, comprising a step of hardening the hydraulic composition obtained by the method according to [8] above. [Example]

[0042] The present disclosure will be described in more detail with reference to examples and comparative examples, but the present disclosure is not limited to the following examples.

[0043] (Comparative Example 1-1) <Raw material preparation and analysis> SEKADO P-1 (trade name, manufactured by Shinagawa General Co., Ltd.) was prepared as a raw material containing allophane. The allophane content of SEKADO P-1 was measured by the acid-alkali alternating dissolution method. Specifically, the measurement was carried out according to the following procedure.

[0044] First, organic matter was removed from SEKADO P-1 by the following method. Specifically, the sample was first sieved through a 0.425 mm sieve. 50 ml of 10% by mass hydrogen peroxide solution was added to the sample that passed through the sieve, and the mixture was heated in a water bath. Next, 20 ml of 30% by mass hydrogen peroxide solution was added, and the mixture was heated in a water bath for 24 hours. After that, a sufficient amount of distilled water was added to the sample, and the aqueous phase was separated by centrifugation (2800 rpm, 6 minutes), and the sample was washed. Washing was performed twice. The washed sample was dried at 105°C for 24 hours.

[0045] The dried sample was subjected to the following series of steps (1) to (7) five times. (1) 50 ml of 8 M hydrochloric acid was added to the sample and shaken for 30 minutes. (2) A sufficient amount of distilled water was added to the sample, and the sample was washed by separating the aqueous phase by centrifugation (2800 rpm, 6 minutes). (3) 50 ml of 0.5 M aqueous sodium hydroxide solution was added to the washed sample, and the sample was heated in a water bath at 60°C for 5 minutes. (4) The aqueous phase was separated by centrifugation (2800 rpm, 6 minutes) and the sample was washed. (5) A sufficient amount of distilled water was added to the sample, and the sample was washed by separating the aqueous phase by centrifugation (2800 rpm, 6 minutes). (6) After washing, the sample was dried at 105°C for 24 hours. (7) After drying, the weight of the sample was measured. By repeating the series of steps (1) to (7) five times, it was confirmed that the weight change of the sample due to leaching had almost completely disappeared. The allophane content was calculated based on the weight loss rate. The allophane content was found to be 72.5 mass%.

[0046] <Preparation of hydraulic composition and hardened product> Ordinary Portland cement (research cement, Cement Association) was prepared as an alkali activator. This ordinary Portland cement and SEKADO P-1 (untreated) were blended in a mass ratio of 70:30, and water was added to a water-cement ratio (W / C) of 50%. The mixture was then hand-mixed for 10 minutes to prepare a hydraulic composition. The allophane content in the hydraulic composition was calculated as 72.5% by mass x 0.3 = 21.75% by mass. The prepared hydraulic composition was filled into a 2 cm x 2 cm x 13 cm mold and cured in air for one day. After demolding, the composition was cured in water in a thermostatic chamber at 20°C for 7, 28, or 91 days. A hardened product was thus obtained.

[0047] <Compression strength measurement> The compressive strength of each hardened specimen was measured at ages of 7, 28, and 91 days. The compressive strength was measured in accordance with the method described in JIS R 5201:2015 "Physical Testing Methods for Cement." The results are shown in Table 1.

[0048] (Example 1-1) The SEKADO P1 used in Comparative Example 1-1 was pretreated (acid treatment) using hydrochloric acid (HCl concentration: 2 mol / L). Specifically, 100 g of SEKADO P1 was weighed into a beaker, and 200 g of hydrochloric acid was added to it. The mixture was aged at 40°C for 7 days while stirring with a stirrer. Thereafter, the solvent was removed using a centrifuge, and the solid matter was washed by repeatedly adding water and centrifuging. Washing was continued until the pH of the washing liquid reached 6 or higher. After washing, the solid matter was dried in a dryer at 105°C for 24 hours. The dried solid matter was pulverized in a ball mill and sieved using a sieve with 90 μm openings, and the undersieve fraction was taken as the inorganic substance of Example 1-1.

[0049] A hydraulic composition and a hardened product were prepared in the same manner as in Comparative Example 1-1, except that the inorganic material prepared as described above was used instead of SEKADO P-1 (untreated), and the compressive strength was measured. The results are shown in Table 1.

[0050] (Comparative Example 1-2) Pretreatment (alkali treatment) of SEKADO P1 was carried out in the same manner as in Example 1-1, except that an aqueous sodium hydroxide solution (NaOH concentration: 5 mol / L) was used instead of hydrochloric acid. The solid matter was washed in the same manner as in Example 1-1, and washing was continued until the pH of the washing solution reached 6 to 7. After washing, drying, pulverization, and sieving were carried out in the same manner as in Example 1-1, and the undersieve fraction was taken as the inorganic substance of Comparative Example 1-2. A hydraulic composition and a hardened body were prepared in the same manner as in Comparative Example 1-1, except that this inorganic substance was used instead of SEKADO P-1 (untreated), and compressive strength was measured. The results are shown in Table 1.

[0051] (Comparative Examples 1-3) Pretreatment (alkali treatment) of SEKADO P1 was carried out in the same manner as in Example 1-1, except that an aqueous sodium hydroxide solution (NaOH concentration: 0.1 mol / L) was used instead of hydrochloric acid. The solid matter was washed in the same manner as in Example 1-1, and washing was continued until the pH of the washing solution reached 6 to 7. After washing, drying, pulverization, and sieving were carried out in the same manner as in Example 1-1, and the undersieve fraction was taken as the inorganic substance of Comparative Example 1-3. A hydraulic composition and a hardened body were prepared in the same manner as in Comparative Example 1-1, except that this inorganic substance was used instead of SEKADO P-1 (untreated), and compressive strength was measured. The results are shown in Table 1.

[0052] (Comparative Examples 1-4) Pretreatment (alkali treatment) of SEKADO P1 was carried out in the same manner as in Example 1-1, except that a saturated aqueous solution of sodium carbonate (Na2CO3 concentration: 20 g / 100 L) was used instead of hydrochloric acid. The solid matter was washed in the same manner as in Example 1-1, and washing was continued until the pH of the washing solution reached 6 to 7. After washing, drying, pulverization, and sieving were carried out in the same manner as in Example 1-1, and the undersieve fraction was taken as the inorganic substance of Comparative Example 1-4. A hydraulic composition and a hardened body were prepared in the same manner as in Comparative Example 1-1, except that this inorganic substance was used instead of SEKADO P-1 (untreated), and compressive strength was measured. The results are shown in Table 1.

[0053] (Comparative Examples 1-5) The SEKADO P1 used in Comparative Example 1-1 was calcined in air at 800°C for 3 hours in a calcination furnace. After cooling, the calcined product was removed from the calcination furnace. A hydraulic composition and a hardened product were prepared in the same manner as in Comparative Example 1-1, except that this calcined product was used as the inorganic substance, and compressive strength was measured. The results are shown in Table 1.

[0054] [Table 1]

[0055] Table 1 shows the relative strengths of Example 1-1 and each comparative example, with Comparative Example 1-1 set as the reference (100), as the "strength ratio." As shown in Table 1, up to an age of 28 days, Comparative Example 1-5, which underwent calcination as a pretreatment, showed the highest compressive strength. However, at an age of 91 days, Example 1-1, which underwent acid treatment, showed the highest compressive strength. Comparing acid treatment and alkali treatment as pretreatments, it was confirmed that acid treatment was more effective in improving compressive strength.

[0056] To investigate the factors behind the difference in strength development between alkali treatment and acid treatment, XRD measurements were performed on the SEKADO P1 used in Comparative Example 1-1, the inorganic material prepared in Example 1-1, and the inorganic materials prepared in Comparative Examples 1-2 to 1-4. A Bruker D2 PHASE (instrument name) was used as the measurement device. The measurement results are shown in Figures 1(a), 1(b), and 2. As shown in Figure 1(a), zeolite (A in Figure 1(a)) was formed in the inorganic material of Comparative Example 1-2, which was prepared by treatment with a 5 mol / L aqueous sodium hydroxide solution. As shown in Figure 1(b), dawsonite (D in Figure 1(b)) was formed in the inorganic material of Comparative Example 1-4, which was prepared by treatment with an aqueous sodium carbonate solution. On the other hand, as shown in Figure 2, no foreign matter was formed in the inorganic material of Example 1-1, and X-ray diffraction revealed that there was no significant difference in the crystal structure between the raw material before acid treatment and the inorganic material obtained by acid treatment. This confirms that the skeleton of the allophane crystal structure is maintained during acid treatment, and that the inorganic matter obtained by acid treatment contains allophane.Next, the effects of changing the concentration of hydrochloric acid used in the acid treatment and the type of raw material containing allophane were examined.

[0057] (Comparative Example 2-1) <Raw material preparation and analysis> Kanuma soil (manufactured by Akagi Engei Co., Ltd.) was prepared as an inorganic substance. The allophane content of Kanuma soil was measured using the same acid-alkali alternate dissolution method as in Comparative Example 1-1. As a result, the allophane content was 63.2 mass%.

[0058] <Preparation of hydraulic composition and hardened product> Ordinary Portland cement (manufactured by UBE Mitsubishi Cement Corporation) was prepared as an alkaline activator. This ordinary Portland cement and Kanuma clay (untreated) were mixed in a mass ratio of 70:30, water was added at a water-to-cement ratio (W / C) of 50%, and the mixture was kneaded for 1 minute and 30 seconds using a three-one motor to prepare a hydraulic composition. The ratio of the allophane content in the raw materials to the total solid content of the hydraulic composition was calculated as 63.2 mass% x 0.3 = 18.96 mass%. The prepared hydraulic composition was filled into a 1 cm x 1 cm x 6 cm mold and cured in air for 1 day. After demolding, the composition was cured in water in a thermostatic chamber at 20°C for 7, 28, or 91 days. A hardened product was obtained in this manner.

[0059] <Compression strength measurement> The compressive strength of each hardened specimen was measured at ages of 7, 28, and 91 days. The compressive strength was measured in accordance with the method described in JIS R 5201:2015 "Physical Testing Methods for Cement." The results are shown in Table 2.

[0060] Example 2-1 Pretreatment (acid treatment) was carried out using hydrochloric acid (HCl concentration: 2 mol / L, pH <1) in the same manner as in Example 1-1, except that the Kanuma soil used in Comparative Example 2-1 was used instead of SEKADO P1. Specifically, 100 g of Kanuma soil was weighed into a beaker, and 200 g of hydrochloric acid was added to it. The mixture was aged at 40°C for 7 days while stirring with a stirrer. The solvent was then removed using a centrifuge, and the solid matter was washed by repeatedly adding water and centrifuging. Washing was continued until the pH of the washing solution reached 6 or higher. After washing, the solid matter was dried in a dryer at 105°C for 24 hours. The dried solid matter was pulverized in a ball mill and sieved using a sieve with 90 μm openings, and the undersieve fraction was designated as the inorganic matter of Example 2-1.

[0061] A hydraulic composition and a hardened body were prepared in the same manner as in Comparative Example 2-1, except that this inorganic substance was used instead of Kanuma soil (untreated), and the compressive strength was measured. The results are shown in Table 2.

[0062] (Comparative Example 2-2) For pretreatment, hydrochloric acid (HCl concentration: 1.0 × 10 -4 The inorganic substance of Comparative Example 2-2 was obtained in the same manner as in Example 2-1, except that ammonium hydroxide (NaOH, HCl, pH = approx. 4) was used instead of Kanuma soil (untreated). A hydraulic composition and a hardened body were prepared in the same manner as in Comparative Example 2-1, except that this inorganic substance was used instead of Kanuma soil (untreated), and compressive strength was measured. The results are shown in Table 2.

[0063] (Comparative Example 2-3) For pretreatment, hydrochloric acid (HCl concentration: 1.0 × 10 -2 The inorganic substance of Comparative Example 2-3 was obtained in the same manner as in Example 2-1, except that ammonium hydroxide (NaOH, pH = approx. 2) was used instead of Kanuma soil (untreated). A hydraulic composition and a hardened body were prepared in the same manner as in Comparative Example 2-1, except that this inorganic substance was used instead of Kanuma soil (untreated), and compressive strength was measured. The results are shown in Table 2.

[0064] [Table 2]

[0065] Table 2 shows the relative strength ratios of Example 2-1 and Comparative Examples 2-2 and 2-3, with Comparative Example 2-1 set as the standard (100). As shown in Table 2, even when the type of raw material containing allophane was changed, the long-term strength at 91 days was highest in Example 2-1, which was pretreated with hydrochloric acid (HCl concentration: 2 mol / L, pH < 1). Next, the blending ratio of the raw material containing allophane and the alkaline activator was changed to examine the effect.

[0066] (Comparative Example 3-1) A hydraulic composition was prepared in the same manner as in Comparative Example 2-1, except that the blending ratio of ordinary Portland cement to Kanuma clay (untreated) was 90:10 by mass, and a hardened body was obtained. The ratio of the allophane content contained in the raw materials to the total solid content of the hydraulic composition was calculated to be 63.2 mass% x 0.1 = 6.32 mass%. The compressive strength of the hardened body was measured at ages of 7 days, 28 days, and 91 days in the same manner as in Comparative Example 2-1. The results are shown in Table 3.

[0067] Example 3-1 The inorganic material was obtained in the same manner as in Example 2-1. A hydraulic composition was prepared and a hardened body was obtained in the same manner as in Example 2-1, except that the blending ratio of ordinary Portland cement to the inorganic material was 90:10 by mass. The compressive strength of the hardened body was measured at ages of 7 days, 28 days, and 91 days in the same manner as in Comparative Example 2-1. The results are shown in Table 3.

[0068] (Comparative Example 3-2) The inorganic material was obtained in the same manner as in Comparative Example 2-2. A hydraulic composition was prepared and a hardened body was obtained in the same manner as in Comparative Example 2-2, except that the blending ratio of ordinary Portland cement to the inorganic material was 90:10 by mass. The compressive strength of the hardened body was measured at ages of 7 days, 28 days, and 91 days in the same manner as in Comparative Example 2-1. The results are shown in Table 3.

[0069] (Comparative Example 3-3) The inorganic material was obtained in the same manner as in Comparative Example 2-3. A hydraulic composition was prepared and a hardened body was obtained in the same manner as in Comparative Example 2-3, except that the blending ratio of ordinary Portland cement to the inorganic material was 90:10 by mass. The compressive strength of the hardened body was measured at ages of 7 days, 28 days, and 91 days in the same manner as in Comparative Example 2-1. The results are shown in Table 3.

[0070] (Reference example 3-1) A hardened body was obtained in the same manner as in Comparative Example 3-1, except that Kanuma soil was not added, i.e., ordinary Portland cement used in Comparative Example 3-1 was used as the hydraulic composition. The compressive strength of the hardened body was measured at ages of 7, 28, and 91 days in the same manner as in Comparative Example 2-1. The results are shown in Table 3.

[0071] [Table 3]

[0072] Table 3 shows the relative strengths of Example 3-1, Comparative Examples 3-2, and 3-3 as "strength ratios" with Comparative Example 3-1 set as the standard (100). As shown in Table 3, even when the blending ratio of inorganic material to binder in the hydraulic composition was 10 / 90, Example 3-1, which was pretreated with hydrochloric acid (HCl concentration: 2 mol / L), had the highest long-term strength at 91 days. Example 3-1 had compressive strength almost equivalent to that of Reference Example 3-1, in which a hardened body was prepared using only ordinary Portland cement. Furthermore, Example 3-1 also had higher short-term strength at 7 days than Comparative Example 3-1.

[0073] In Examples 1-1, 2-1, and 3-1, the long-term strength was high at an age of 91 days. The reason for this is thought to be that treating raw materials containing allophane with inorganic acid destabilizes the crystalline structure of allophane, increasing its reactivity with the alkaline activator, and that this reaction progresses over time.

[0074] When preparing the inorganic substances in Example 2-1, Comparative Example 2-2, and Comparative Example 2-3, the initial washing solution used to wash the solids was subjected to ICP atomic emission spectroscopy to measure the amount of Al elution. The washing solution obtained by washing Kanuma clay with water without acid treatment was also subjected to ICP atomic emission spectroscopy to measure the amount of Al elution. The measurement device used was a Hitachi PS3520UVDD2 (device name). Furthermore, the BET specific surface area of ​​the Kanuma clay (untreated) used in Comparative Example 2-1 and the inorganic substances (acid-treated) prepared in Example 2-1, Comparative Example 2-2, and Comparative Example 2-3 were measured, and X-ray fluorescence analysis (XRF) was performed. Furthermore, X-ray fluorescence analysis (XRF) was performed on the calcined product used in Comparative Example 1-5.

[0075] The BET specific surface area was measured by heating and drying Kanuma soil or acid-treated inorganic material at 105°C for 1 hour under a nitrogen gas atmosphere, and then measuring the amount of nitrogen gas adsorption using a Microtrac-Bell BELSORPMINI. The BET specific surface area was calculated based on the measurement results. X-ray fluorescence analysis (XRF) was performed using a Rigaku Simultix15 (instrument name) to measure the contents of Si, Al, Fe, Ca, Na, and K. These were then converted to their respective oxides to determine the SiO2, Al2O3, Fe2O3, CaO, Na2O, and K2O contents. The respective results are shown in Tables 4 and 5.

[0076] [Table 4]

[0077] [Table 5]

[0078] According to the results of ICP atomic emission spectroscopy shown in Table 4, the cleaning solution obtained by washing Kanuma soil with water and the Kanuma soil with an HCl concentration of 1 × 10 -4 mol / L and 1×10 -2 While almost no Al was eluted into the cleaning solutions of Comparative Examples 2-2 and 2-3 after acid treatment with 2 mol / L hydrochloric acid, the amount of eluted Al was significantly increased in the cleaning solution of Example 2-1 after acid treatment with hydrochloric acid having an HCl concentration of 2 mol / L. The XRF results shown in Table 5 also indicate that the inorganic material of Example 2-1 obtained by acid treatment with 2 mol / L hydrochloric acid had a higher SiO2 / Al2O3 ratio than the other samples. This is presumably due to the destabilization of the crystalline structure of the allophane contained in the inorganic material of Example 2-1, resulting in an increased amount of eluted Al. The BET specific surface area was the largest for the inorganic material of Example 2-1, which was acid treated with 2 mol / L hydrochloric acid. This also indicates that the crystalline structure of the allophane was destabilized. This destabilization of the crystalline structure is thought to contribute to the improvement of long-term strength.

Claims

1. Al's Al ２ O ３ The content of Si in SiO ２ Mass ratio of converted content (SiO ２ / Al ２ O ３ ) is more than 1.

6.

2. BET specific surface area is 230m ２ The inorganic material according to claim 1, wherein the inorganic material has a molecular weight of more than 1000 kJ / g.

3. Si SiO ２ The inorganic substance according to claim 1, wherein the content in terms of the total mass is 44 to 60 mass%.

4. A hydraulic composition comprising the inorganic material according to any one of claims 1 to 3 and an alkaline activator.

5. The hydraulic composition according to claim 4, wherein the content of the inorganic substance is 1 to 50 mass %.

6. A hardened product obtained by hardening the hydraulic composition according to claim 5.

7. Contains allophane and Al ２ O ３ The content of Si in SiO ２ Mass ratio of converted content (SiO ２ / Al ２ O ３ ) is 1.6 or less, and an acidic solution containing an inorganic acid to obtain a mixture; A solid content of Al is separated from the mixture. ２ O ３ The content of Si in SiO ２ Mass ratio of converted content (SiO ２ / Al ２ O ３ and obtaining an inorganic substance having a molecular weight of 1.6 or more.

8. A method for producing a hydraulic composition, comprising a step of blending at least the inorganic substance obtained by the production method according to claim 7 with an alkaline activator to obtain a hydraulic composition containing the inorganic substance and the alkaline activator.

9. A method for producing a hardened product, comprising a step of hardening the hydraulic composition obtained by the method according to claim 8.

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