Acid-treated product 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 a hydraulic composition capable of sufficiently reducing an amount of carbon dioxide generated, as well as an acid-treated product suitable for use in the production of such a hydraulic composition and capable of being easily prepared, and a method for producing the same.SOLUTION: A hydraulic composition contains an acid-treated product and an alkali-stimulating material. The acid-treated product is obtained by treating an inorganic substance containing allophane with an acidic solution containing an inorganic acid. A method for producing the acid-treated product includes a step of mixing an inorganic substance containing allophane with an acidic solution containing an inorganic acid to obtain a mixture, and a step of separating an acid-treated inorganic substance from the mixture to obtain the acid-treated product.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to an acid-treated product and a method for producing the same, a hydraulic composition and a method for producing the same, and a hardened product 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 and a method for producing the same, as well as a hardened product and a method for producing the same, which can sufficiently reduce the amount of carbon dioxide generated. It also provides an acid-treated product that can be suitably used in the production of such a hydraulic composition and can be easily prepared, as well as a method for producing the same. [Means for solving the problem]

[0005] An acid-treated product according to one aspect of the present disclosure is obtained by treating an inorganic substance containing allophane with an acidic solution containing an inorganic acid. This acid-treated product can be a substitute for cement clinker, and because it is obtained by treating an inorganic substance containing allophane with an inorganic acid, it is possible to further reduce the amount of carbon dioxide generated during production compared to products obtained by calcination. Therefore, it is possible to easily prepare the acid-treated product, and it is possible to sufficiently reduce the amount of carbon dioxide generated. Furthermore, hydraulic compositions produced using such inorganic substances have excellent strength development.

[0006] A hydraulic composition according to one aspect of the present disclosure contains the acid-treated product and an alkaline activator. This hydraulic composition can be used as a substitute for cement clinker and contains the acid-treated product, which can reduce the amount of carbon dioxide generated during production, so the amount of carbon dioxide generated can be sufficiently reduced. Furthermore, the acid-treated product has excellent reactivity with the alkaline activator, so it has excellent strength development.

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

[0008] A method for producing an acid-treated product according to one aspect of the present disclosure includes the steps of mixing an inorganic substance containing allophane with an acidic solution containing an inorganic acid to obtain a mixture, and separating the acid-treated inorganic substance from the mixture to obtain the acid-treated product. The acid-treated product obtained by this production method can be a substitute for cement clinker. In addition, since the acid-treated product is obtained by mixing an inorganic substance containing allophane with an inorganic acid and then separating it, it can be prepared more easily than methods that require calcination, and the amount of carbon dioxide generated during production can be further reduced. Furthermore, hydraulic compositions produced using the acid-treated product obtained by this production method 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 acid-treated product obtained by the above-described production method with an alkaline activator to obtain a hydraulic composition containing the acid-treated product and the alkaline activator. This production method uses the acid-treated product, 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 acid-treated product 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 product according to one aspect of the present disclosure includes at least a step of hardening the hydraulic composition obtained by the above-described method. Since the hydraulic composition obtained by the acid treatment is used in this method, the amount of carbon dioxide generated can be sufficiently reduced. Furthermore, the hardened product 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 and a method for producing the same, as well as a hardened product and a method for producing the same, which can sufficiently reduce the amount of carbon dioxide generated. It is also possible to provide an acid-treated product that can be suitably used in the production of such a hydraulic composition and can be easily prepared, as well as a method for producing the same. [Brief explanation of the drawings]

[0012] [Figure 1] (a) shows the results of X-ray diffraction measurements of an alkali-treated material obtained by treating an inorganic material containing allophane with an aqueous sodium hydroxide solution. (b) shows the results of X-ray diffraction measurements of an alkali-treated material obtained by treating an inorganic material containing allophane with an aqueous sodium carbonate solution. [Figure 2] 1 shows the results of X-ray diffraction measurements of an acid-treated product obtained by treating an inorganic substance 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] <Acid-treated product and method for producing same> Acid-treated materials are obtained by treating inorganic materials, including allophane, with an acidic solution containing inorganic acids. Allophane is formed when volcanic ash and feldspar in volcanic ejecta deposits are altered over a long period of time by weathering and hydrothermal action. For example, it has a particle diameter of 0.05 to 0.2 μm and a hollow spherical structure, with an octahedral sheet of Al2O3 on the outside of the hollow sphere (shell) and a tetrahedral sheet of SiO2 on the inside of the hollow sphere (shell).

[0015] The allophane-containing inorganic material may be a mineral, a volcanic ejecta deposit, or a mineral or deposit whose particle size has been adjusted. The allophane-containing inorganic material may be one that has been treated to such an extent that all of the allophane is not altered into other substances. The volcanic ejecta deposit may be a commercially available product, or a commercially available product that has been subjected to the above-mentioned 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, 50% by mass or more, or 60% by mass or more, from the viewpoint of improving strength development.

[0016] The allophane-containing inorganic material may contain at least one element selected from the group consisting of Al, Si, Na, K, Fe, Ca, and Mg. These elements may be contained as oxides. Examples of oxides that may be included include SiO2, Al2O3, Na2O, KO, Fe2O3, CaO, and MgO.

[0017] The SiO2 content in the inorganic substance may be 30 to 80 mass%, or 35 to 75 mass%. The Al2O3 content in the inorganic substance may be 5 to 45 mass%, or 10 to 40 mass%. The Na2O content in the inorganic substance may be 0.1 to 5 mass%, or 0.3 to 4 mass%. The K2O content in the inorganic substance may be 0.1 to 5 mass%, or 0.2 to 4 mass%. The R2O content in the inorganic substance may be 0.1 to 10 mass%, or 0.4 to 8 mass%. The R2O content in the present disclosure is the alkali content, calculated as the Na2O content + 0.658K2O content.

[0018] The Fe2O3 content in the inorganic substance may be 0.5 to 7 mass%, or 1 to 5 mass%. The CaO content in the inorganic substance may be 0.3 to 5 mass%, or 0.5 to 3 mass%. The MgO content in the inorganic substance 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 the oxide. When volcanic ejecta deposits weather, the SiO2 content, Na2O content, K2O content, and R2O content tend to decrease, and the Al2O3 content tends to increase.

[0019] 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 4 or less, 3 or less, 2 or less, or less than 1. If a hydraulic composition is prepared using an acid-treated product obtained by treatment with an acidic solution having a pH of less than 1, it is possible to improve long-term strength development. If a hydraulic composition is prepared using an acid-treated product obtained by treatment with an acidic solution having a pH of 3 to 5, it is possible to improve short-term strength development. In the present disclosure, long-term strength development is evaluated by compressive strength at 91 days, and short-term strength development is evaluated by compressive strength at 7 days.

[0020] 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 obtain a well-balanced and excellent short-term and long-term strength development of the hydraulic composition. -5 mol / L ~ 20 mol / L, 3 × 10 -5 mol / L to 10 mol / L, or 5×10 -5 The acid concentration may be 5 mol / L to 5 mol / L. One of the reasons why the strength development is improved by treatment with an acidic solution is that treating an inorganic material with such an acidic solution destabilizes the crystalline structure of allophane contained in the inorganic material, improving the reactivity with the alkaline activator contained in the hydraulic composition, thereby improving both the short-term and long-term strength development of the hydraulic composition. This action makes it possible to obtain a hydraulic composition and a hardened product that have a good balance between short-term and long-term strength development.

[0021] Increasing the concentration of the inorganic acid in the acidic solution tends to improve the long-term strength development. Therefore, when preparing a hydraulic composition that is particularly excellent in long-term strength development, the concentration of the inorganic acid in the acidic solution is 2×10 -2 mol / L, and may be 0.1 mol / L or more, 0.5 mol / L or more, 1 mol / L or more, or 2 mol / L or more.

[0022] On the other hand, when prioritizing short-term strength development, the concentration of inorganic acid in the acidic solution should be 2 x 10 -2 mol / L or less, 1×10 -3 mol / L or less, or 1×10 -4 mol / L or less.

[0023] The BET specific surface area of ​​the acid-treated product is 230m 2 / g, and 240m 2 / g or more. If a hydraulic composition is prepared using such an acid-treated product, the long-term strength development can be further improved. The BET specific surface area of ​​the acid-treated product is 230 m 2 / g or less, 220m 2 / g or less, 200m 2 / g or less, or 190m2 / g or less. If a hydraulic composition is prepared using such an acid-treated product, the short-term strength development can be further improved.

[0024] The acid-treated product may contain at least one element selected from the group consisting of Al, Si, Na, K, Fe, Ca, and Mg. These elements may be contained as oxides. Examples of oxides include SiO2, Al2O3, Na2O, K2O, Fe2O3, CaO, and MgO. The SiO2 content in the acid-treated product may be 32 to 80 mass% or 38 to 75 mass%. The Al2O3 content in the inorganic material may be 5 to 42 mass% or 10 to 38 mass%. The Na2O content in the inorganic material may be 0.1 to 4 mass% or 0.3 to 3 mass%. The K2O content in the inorganic material may be 0.1 to 4 mass% or 0.2 to 3 mass%. The R2O content in the inorganic material may be 0.1 to 8 mass% or 0.4 to 6 mass%.

[0025] From the viewpoint of further improving the long-term strength development of a hydraulic composition containing an acid-treated product, the ratio α (SiO2 / Al2O3) of the content of Si contained in the acid-treated product in terms of SiO2 to the content of Al contained in the acid-treated product in terms of Al2O3 is preferably 1.4 or more, more preferably 1.5 or more, even more preferably more than 1.6, particularly preferably 1.7 or more, and even more particularly preferably 1.8 or more. The ratio α may be, for example, 5.0 or less or 4.0 or less.

[0026] From the viewpoint of further improving the long-term strength development of the hydraulic composition containing the acid-treated product, the ratio β (SiO2 / Al2O3) of the Si content calculated as SiO2 to the Al content calculated as Al2O3 in the inorganic material before the treatment with inorganic acid may be smaller than the ratio α. For example, α / β may be 1.2 or more, 1.3 or more, or 1.4 or more. α / β may be 4.0 or less, or 3.0 or less.

[0027] From the viewpoint of further improving the short-term strength development of the hydraulic composition containing the acid-treated product, the ratio α (SiO2 / Al2O3) of the content of Si contained in the acid-treated product in terms of SiO2 to the content of Al contained in the acid-treated product in terms of Al2O3 is preferably less than 1.4, more preferably 1.3 or less. The ratio α may be, for example, 1.0 or more, or 1.1 or more.

[0028] From the viewpoint of further improving the short-term strength development of the hydraulic composition containing the acid-treated product, the ratio β (SiO2 / Al2O3) of the content of Si converted to SiO2 to the content of Al converted to Al2O3 in the inorganic material before the treatment with inorganic acid may be equal to the ratio α. For example, α / β may be 0.8 or more and less than 1.2, or 0.9 to 1.1.

[0029] Such acid-treated products can replace materials such as cement clinker or Portland cement. Therefore, the amount of carbon dioxide generated can be reduced. Furthermore, since they can be produced without calcination, the amount of carbon dioxide generated can be significantly reduced. Furthermore, by changing the concentration of the inorganic acid in the acidic solution, the timing of strength development can be adjusted when the acid-treated products are used as materials for hydraulic compositions.

[0030] The method for producing the acid-treated product includes a mixing step of mixing the inorganic material containing allophane with an acidic solution containing the inorganic acid to obtain a mixture, and a separation step of separating the acid-treated inorganic material from the mixture to obtain the acid-treated product. The method for mixing the inorganic material and the acidic solution 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 per 100 parts by mass of the inorganic material.

[0031] 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.

[0032] 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 product). After drying, the acid-treated product may be pulverized and sieved to adjust the particle size. In this way, the particle size of the acid-treated product 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.

[0033] In this manner, an acid-treated product can be prepared. The method for producing an acid-treated product 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 acid-treated product to be sufficiently reduced. Even without including such a heating step, the above-mentioned production method can produce an acid-treated product from an inorganic substance containing allophane that is suitable for use in a hydraulic composition that is excellent in long-term or short-term strength development.

[0034] <Hydraulic composition and manufacturing method thereof> The hydraulic composition contains the above-mentioned acid-treated product and an alkaline activator. The hydraulic composition may be in powder form or may further contain water. The hydraulic composition also includes those that have fluidity before hardening. Examples of alkaline activators include cement clinker, Portland cement, tricalcium silicate (3CaO·SiO2, represented by C3S), slaked lime, and alkali carbonates.

[0035] The content of the acid-treated product 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 acid-treated product 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.

[0036] The content of the acid-treated product 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 acid-treated product 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 acid-treated product 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.

[0037] The ratio of the allophane content contained in the inorganic material 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 improving short-term and long-term strength development in a balanced manner.

[0038] The method for producing a hydraulic composition includes a blending step of blending the acid-treated product and an alkaline activator to obtain a hydraulic composition containing the acid-treated product and the alkaline activator. The blending step may include 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 not only generates less carbon dioxide but also exhibits excellent short-term and long-term strength development.

[0039] <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 acid-treated product 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 hardened product can exhibit improved short-term and long-term strength development.

[0040] 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 acid-treated product described above is used, so 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, short-term and long-term strength development can be improved.

[0041] 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 the acid-treated product is used in a hydraulic composition has been described, but it is not essential to use the acid-treated product in a hydraulic composition, and the acid-treated product may be used for other purposes. The present disclosure includes the following embodiments [1] to

[11] .

[0042] [1] An acid-treated product obtained by treating an inorganic material containing allophane with an acidic solution containing an inorganic acid. [2] The concentration of the inorganic acid in the acidic solution is 2 × 10 -2 mol / L or more. [3] The concentration of the inorganic acid in the acidic solution is 2 × 10 -2 mol / L or less. [4] BET specific surface area is 230m 2 / g or more of the acid-treated product according to any one of [1] to [3]. [5] The acid-treated product according to any one of [1] to [4], which contains Al and Si and has a ratio of the content of Si in terms of SiO2 to the content of Al in terms of Al2O3 (SiO2 / Al2O3) of more than 1.6. [6] A hydraulic composition comprising the acid-treated product according to any one of the above [1] to [5] and an alkaline activator. [7] The hydraulic composition according to [6], wherein the content of the acid-treated product is 50 mass % or less. [8] A hardened product obtained by hardening the hydraulic composition according to [6] or [7] above. [9] A step of mixing an inorganic substance containing allophane with an acidic solution containing an inorganic acid to obtain a mixture; and separating the acid-treated inorganic material from the mixture to obtain an acid-treated product.

[10] A method for producing a hydraulic composition, comprising a step of blending at least the acid-treated product obtained by the production method according to [9] with an alkaline activator to obtain a hydraulic composition containing the acid-treated product and the alkaline activator.

[11] A method for producing a hardened product, comprising a step of hardening the hydraulic composition obtained by the method according to

[10] above. [Example]

[0043] The present disclosure will be described in more detail with reference to examples, comparative examples, and reference examples, but the present disclosure is not limited to the following examples.

[0044] (Comparative Example 1-1) <Raw material preparation and analysis> SEKADO P-1 (trade name, manufactured by Shinagawa General Co., Ltd.) was prepared as an inorganic substance. 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.

[0045] 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.

[0046] 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%.

[0047] <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.

[0048] <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.

[0049] (Example 1-1) The SEKADO P1 used in Comparative Example 1-1 was pretreated 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 fraction that fell through the sieve was designated the acid-treated product of Example 1-1.

[0050] A hydraulic composition and a hardened product were prepared in the same manner as in Comparative Example 1-1, except that the acid-treated product prepared as described above was used as the inorganic substance instead of SEKADO P-1 (untreated), and the compressive strength was measured. The results are shown in Table 1.

[0051] (Comparative Example 1-2) Pretreatment 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 used as the alkali-treated product 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 alkali-treated product was used as the inorganic substance instead of SEKADO P-1 (untreated), and compressive strength was measured. The results are shown in Table 1.

[0052] (Comparative Examples 1-3) Pretreatment 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 alkali-treated product of Comparative Example 1-3. A hydraulic composition and a hardened product were prepared in the same manner as in Comparative Example 1-1, except that this alkali-treated product was used as the inorganic substance instead of SEKADO P-1 (untreated), and compressive strength was measured. The results are shown in Table 1.

[0053] (Comparative Examples 1-4) Pretreatment 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 alkali-treated product 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 alkali-treated product was used as the inorganic substance instead of SEKADO P-1 (untreated), and compressive strength was measured. The results are shown in Table 1.

[0054] (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.

[0055] [Table 1]

[0056] 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 "strength ratio." As shown in Table 1, up to an age of 28 days, Comparative Example 1-5, which was subjected to calcination as a pretreatment, showed the highest compressive strength. However, at an age of 91 days, Example 1-1, which was subjected to acid treatment, showed the highest compressive strength. Comparing acid treatment and alkali treatment, it was confirmed that acid treatment is more effective in improving compressive strength.

[0057] To investigate the factors behind the difference in strength development between alkali treatment and acid treatment, XRD measurements were performed on the untreated SEKADO P1 used in Comparative Example 1-1, the acid-treated product prepared in Example 1-1, and the alkali-treated products 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 alkali-treated product 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 alkali-treated product 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 acid-treated product of Example 1-1, and no difference was detected between the product before and after acid treatment by X-ray diffraction. This suggests that the crystalline structure of allophane is maintained during acid treatment. Next, we investigated the effects of changing the concentration of hydrochloric acid and the type of inorganic material used in the pretreatment.

[0058] (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%.

[0059] <Preparation of hydraulic composition and hardened product> Ordinary Portland cement (manufactured by UBE Mitsubishi Cement Corporation) was prepared as an alkali 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 allophane content in the inorganic matter 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.

[0060] <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.

[0061] Example 2-1 Pretreatment 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. The under-sieve fraction was designated as the acid-treated product of Example 2-1.

[0062] A hydraulic composition and a hardened body were prepared in the same manner as in Comparative Example 2-1, except that the acid-treated Kanuma clay was used as the inorganic substance instead of untreated Kanuma clay, and the compressive strength was measured. The results are shown in Table 2.

[0063] (Example 2-2) For pretreatment, hydrochloric acid (HCl concentration: 1.0 × 10 -4 The acid-treated product of Example 2-2 was obtained in the same manner as in Example 2-1, except that an acid-treated slag (mol / L, pH = approximately 4) was used. A hydraulic composition and a hardened product were prepared in the same manner as in Comparative Example 2-1, except that this acid-treated product was used as the inorganic substance, and compressive strength was measured. The results are shown in Table 2.

[0064] (Example 2-3) For pretreatment, hydrochloric acid (HCl concentration: 1.0 × 10 -2 The acid-treated product of Example 2-3 was obtained in the same manner as in Example 2-1, except that an acid-treated slag (mol / L, pH = approximately 2) was used. A hydraulic composition and a hardened product were prepared in the same manner as in Comparative Example 2-1, except that this acid-treated product was used as the inorganic substance, and compressive strength was measured. The results are shown in Table 2.

[0065] [Table 2]

[0066] Table 2 shows the relative strengths of Examples 2-1 to 2-3 as "strength ratios" when Comparative Example 2-1 is set as the standard (100). As shown in Table 2, even when the inorganic substance was changed, Example 2-1, which was pretreated with hydrochloric acid (HCl concentration: 2 mol / L, pH < 1), had the highest long-term strength at an age of 91 days. Furthermore, the short-term strength at an age of 7 days was higher in all of Examples 2-1 to 2-3 than in Comparative Example 2-1. Next, the mixing ratio of the inorganic substance and the alkaline activator was changed to examine the effect.

[0067] (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 inorganic matter 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.

[0068] (Example 3-1) An acid-treated product was obtained in the same manner as in Example 2-1. A hydraulic composition was prepared and a hardened product was obtained in the same manner as in Example 2-1, except that the blending ratio of ordinary Portland cement to the acid-treated product was 90:10 by mass. The compressive strength of the hardened product 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] (Example 3-2) An acid-treated product was obtained in the same manner as in Example 2-2. A hydraulic composition was prepared and a hardened product was obtained in the same manner as in Example 2-2, except that the blending ratio of ordinary Portland cement to the acid-treated product was 90:10 by mass. The compressive strength of the hardened product 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] (Example 3-3) An acid-treated product was obtained in the same manner as in Example 2-3. A hydraulic composition was prepared and a hardened product was obtained in the same manner as in Example 2-3, except that the blending ratio of ordinary Portland cement to the acid-treated product was 90:10 by mass. The compressive strength of the hardened product 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.

[0071] (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.

[0072] [Table 3]

[0073] Table 3 shows the relative strength of each Example, with Comparative Example 3-1 set as the standard (100), as the "strength ratio." 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 an age of 91 days. Example 3-1 had compressive strength almost equivalent to that of Reference Example 3-4, in which a hardened body was prepared using only ordinary Portland cement. Furthermore, the short-term strength at an age of 7 days was higher in all of Examples 3-1 to 3-3 than in Comparative Example 3-1.

[0074] Examples 1-1, 2-1, and 3-1 all had higher long-term strength at a material age of 91 days than Comparative Examples 1-1, 2-1, and 3-1. This is thought to be due to the fact that acid treatment of the inorganic material destabilizes the crystalline structure of allophane contained in the inorganic material, improving its reactivity with the alkaline activator, and that this reaction progresses over time. Furthermore, Examples 2-1 to 2-3 and Examples 3-1 to 3-3 all had higher short-term strength at a material age of 7 days than Comparative Examples 2-1 and 3-1.

[0075] When preparing the acid-treated Kanuma soil in Examples 2-1, 2-2, and 2-3, the initial washing solution used to wash the solids was subjected to ICP emission spectroscopy to measure the amount of Al elution. The washing solution obtained by washing Kanuma soil with water without acid treatment was also subjected to ICP 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 untreated Kanuma soil used in Comparative Example 2-1 and the acid-treated products prepared in Examples 2-1, 2-2, and 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.

[0076] The BET specific surface area was measured by heating and drying Kanuma clay or its acid-treated product in a nitrogen gas atmosphere at 105°C for one hour, 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 results are shown in Tables 4 and 5.

[0077] [Table 4]

[0078] [Table 5]

[0079] 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 -2While almost no Al was eluted into the cleaning solutions of Examples 2-2 and 2-3 after treatment with 2 mol / L hydrochloric acid, the amount of Al eluted from the cleaning solution of Example 2-1 after treatment with 2 mol / L hydrochloric acid significantly increased. The XRF results shown in Table 5 also indicate that the acid-treated product of Example 2-1, obtained by 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, resulting in an increased amount of Al elution. The BET specific surface area was also the largest for the acid-treated product of Example 2-1, obtained by treatment with 2 mol / L hydrochloric acid. This also indicates that the crystalline structure of the allophane contained in Kanuma soil was destabilized. This destabilization of the crystalline structure is thought to contribute to the improvement in the strength of the hardened product.

Claims

1. An acid-treated product obtained by treating an inorganic material containing allophane with an acidic solution containing an inorganic acid.

2. The concentration of the inorganic acid in the acidic solution is 2×10 －２ 2. The acid-treated product according to claim 1, wherein the acid-treated product has a pH of more than 1.

0.

3. The concentration of the inorganic acid in the acidic solution is 2×10 －２ 2. The acid-treated product according to claim 1, wherein the acid concentration is 0.05 mol / L or less.

4. BET specific surface area is 230m ２ The acid-treated product according to claim 1, wherein the acid-treated product has a hydroxyl group content of more than 1000 ppm / g.

5. Contains Al and Si, and Al ２ O ３ The content of Si in SiO ２ Ratio of converted content (SiO ２ / Al ２ O ３ 2. The acid-treated product according to claim 1, wherein the β-amino acid group is β-amino acid group, and the β-amino acid group is β-amino acid group.

6. A hydraulic composition comprising the acid-treated product according to any one of claims 1 to 5 and an alkaline activator.

7. The hydraulic composition according to claim 6 , wherein the content of the acid-treated product is 50% by mass or less.

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

9. a step of mixing an inorganic substance containing allophane with an acidic solution containing an inorganic acid to obtain a mixture; and separating the acid-treated inorganic material from the mixture to obtain an acid-treated product.

10. A method for producing a hydraulic composition, comprising a step of blending at least the acid-treated product obtained by the production method according to claim 9 with an alkaline activator to obtain a hydraulic composition containing the acid-treated product and the alkaline activator.

11. A method for producing a hardened product, comprising a step of hardening the hydraulic composition obtained by the method according to claim 10.

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