Method for producing a crystalline tobermorite-containing hardened body

Abstract

To provide a method of manufacturing a hardened body containing crystalline tobermorite in a high content by effective utilization of fly ash.SOLUTION: A manufacturing method of a crystalline tobermorite-containing hardened body includes applying autoclave curing to a kneading material containing a siliceous raw material containing alkanolamine-blended fly ash and cement.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a hardened body, and more specifically, to a method for manufacturing a hardened body with an increased content of crystalline tobermorite.

Background Art

[0002] As a conventional technology for manufacturing a hardened body, there is known a method including a vacuum degassing step of vacuum degassing a material containing cement and an extrusion step of extruding the vacuum degassed material, such as the manufacturing method disclosed in Patent Document 1. Specifically, this manufacturing method has a kneading step of adding water to a mixed material containing cement and kneading to obtain a material, a vacuum degassing step of vacuum degassing the material containing cement, an extrusion molding step of extruding the vacuum degassed material to obtain a molded body, and a curing step of curing this molded body to obtain a hardened body.

[0003] The material used in such a manufacturing method contains cement, and if necessary, contains a siliceous material, reinforcing fiber, aggregate, extender, thickener, dispersant, and other materials. By adding water to such a material containing cement and kneading, a liquid or highly viscous and fluid kneaded material, which is a hydraulic material, is obtained.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The hardened material obtained by the manufacturing technology described in Patent Document 1 contains fly ash. From the perspective of promoting the utilization of industrial by-products and addressing the constraints of disposal sites, it is desirable to actively increase the proportion of fly ash that is effectively utilized, which is discharged in large quantities from thermal power plants and other sources. It is possible to effectively utilize fly ash by substituting a portion of the silicate raw material with fly ash, but if a large amount of fly ash is added, the tobermorite content of the resulting hardened material decreases.

[0006] Therefore, the present invention aims to provide a method for producing a hardened body containing a large amount of crystalline tobermorite by effectively utilizing fly ash. [Means for solving the problem]

[0007] In the method for producing a crystalline tobermorite-containing hardened body according to the present invention, a mixed material containing a siliceous raw material including fly ash mixed with an alkanolamine and cement is subjected to autoclave curing. The proportion of the alkanolamine is 0.05% by mass or more and 0.7% by mass or less based on 100% by mass of the fly ash mixed with the alkanolamine. The proportion of the fly ash mixed with the alkanolamine is 10% by mass or more and 95% by mass or less based on 100% by mass of the silicate raw material.

[0010] Preferably, the silica-based raw material comprises a crystalline silica raw material, fly ash mixed with the alkanolamine, and fly ash without the alkanolamine, wherein the proportion of the crystalline silica raw material is 9% by mass or more relative to 100% by mass of the silica-based raw material, and the proportion of the fly ash mixed with the alkanolamine is less than 47% by mass relative to 100% by mass of the silica-based raw material.

[0011] Preferably, the alkanolamine contains triethanolamine, and the proportion of triethanolamine in the alkanolamine is 90% by mass or more. [Effects of the Invention]

[0012] According to the present invention, a hardened body containing a large amount of crystalline tobermorite can be obtained. Since this hardened body contains a large amount of fly ash, fly ash discharged in large quantities from thermal power plants and the like can be effectively utilized. [Modes for carrying out the invention]

[0013] The following describes a method for producing a crystalline tobermorite-containing hardened body (hereinafter also referred to as a tobermorite-high content hardened body) according to an embodiment of the present invention (hereinafter also referred to as this embodiment).

[0014] To achieve the aforementioned objectives, the inventors conducted various studies and experiments and discovered that by replacing a portion of the silica-based material, such as silica powder, in a cement-containing material with fly ash pre-mixed with alkanolamine, and then curing the resulting material in a steam autoclave at a temperature of 160°C or higher and under high pressure, almost all of the large amount of added fly ash functions as a silica (SiO2) source and reacts with calcium hydroxide in the cement, resulting in the synthesis of a large amount of crystalline tobermorite, a calcium-silica hydrate compound.

[0015] The present invention provides a method for producing a crystalline tobermorite-containing hardened body, which involves curing a mixture of cement and a siliceous raw material containing fly ash mixed with alkanolamine. Specifically, this method involves, for example, blending cement and a siliceous raw material, blending fly ash pre-mixed with alkanolamine as the siliceous raw material, and, if necessary, blending in reinforcing fibers, lightweight aggregates, bulking agents, etc. to obtain a mixture, and then, after adding water, curing it in a steam autoclave at a curing temperature of 160°C or higher.

[0016] Crystalline tobermorite is a calcium-silica hydrate compound that possesses moderate strength and does not undergo changes due to heating. Therefore, the resulting hardened material with a high tobermorite content exhibits improved heat resistance.

[0017] <Method for manufacturing a hardened product with a high tobermorite content> The method for producing the tobermorite-rich hardened body of this embodiment involves curing in an autoclave a mixture of a siliceous raw material containing fly ash mixed with an alkanolamine and cement.

[0018] [Mixing ingredients] The compounding material comprises a siliceous raw material containing fly ash mixed with alkanolamine and cement. That is, the compounding material comprises cement components and a siliceous raw material, and the siliceous raw material contains fly ash mixed with alkanolamine. "Fly ash mixed with alkanolamine" refers to fly ash obtained by pre-mixing it with alkanolamine, and the compounding material is obtained by mixing it with cement and other siliceous raw materials such as silica powder and fly ash without alkanolamine. The compounding material may contain other components besides the above components.

[0019] [Cement components] Examples of cement components that can be used include Portland cement, fly ash cement, blast furnace cement, alumina cement, high-brain cement, and silica fume cement. These may be used individually or in combination of two or more. Portland cement may include, for example, ordinary Portland cement, rapid-hardening Portland cement, moderate-heat Portland cement, and low-heat Portland cement. The mixing ratio of the cement components is preferably 15% to 70% by mass, and more preferably 25% to 60% by mass, based on 100% by mass of the mixed material.

[0020] [Silica-based raw materials] Silica-based raw materials play a role in generating tobermorite through a hydrothermal reaction during autoclave curing. Suitable silica-based raw materials include silica powder, fly ash, silica fume, diatomaceous earth, siliceous clay, and bentonite. These may be used individually or in combination of two or more. In particular, silica powder and fly ash are preferred for better tobermorite production. The blending ratio of silica-based raw materials is preferably 5% to 80% by mass, and more preferably 15% to 70% by mass, based on 100% by mass of the mixed material.

[0021] In relation to the present invention, it has been found that a hardened body with a high content of crystalline tobermorite can be produced by using fly ash to which alkanolamine has been pre-added as a silicate raw material. That is, in the present invention, it is important that the silicate raw material includes fly ash mixed with alkanolamine (hereinafter also referred to as alkanolamine-treated fly ash). In the kneading material used in the method for producing a hardened body with a high content of tobermorite of this embodiment, the silicate raw material includes alkanolamine-treated fly ash, and in addition thereto, as necessary, it may include, for example, fly ash without alkanolamine (hereinafter also referred to as untreated fly ash), silica powder, silica fume, diatomaceous earth, siliceous clay, bentonite, etc.

[0022] A higher percentage of fly ash by mass in the silica-based raw material (hereinafter also referred to as the fly ash replacement rate) is preferable. The higher this value, the more effectively the fly ash is utilized in the manufacturing method of this embodiment. Specifically, the fly ash replacement rate is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 85% by mass or more. The fly ash replacement rate can be calculated using the formula: (mass of alkanolamine-treated fly ash + mass of untreated fly ash) × 100 / (total mass of silica-based raw material) (mass%).

[0023] (Alkanolamine) Alkanolamines include triisopropanolamine, triethanolamine, diethanolamine, methyldiethanolamine, etc., and are diverse. As a result of experimental studies using various alkanolamines, more crystalline tobermorite was obtained when triethanolamine was used. That is, it is preferable that the alkanolamine contains triethanolamine. Also, if the active ingredient of the alkanolamine used is combined with fly ash, either the stock solution or the diluted product may be used.

[0024] It was found that when the alkanolamine is contained in an amount of 0.05% by mass or more based on 100% by mass of the alkanolamine-treated fly ash, the amount of crystalline tobermorite produced becomes larger. The ratio of the alkanolamine is preferably 0.05% by mass or more and 0.7% by mass or less based on 100% by mass of the alkanolamine-treated fly ash. When it is less than 0.05% by mass, the amount of crystalline tobermorite produced may be less than when only silica powder is used. Also, when it is more than 0.7% by mass, the setting rate of the cement becomes too high, the moldability of the kneaded material decreases, and a vacuum degassing extruded molded body may not be obtained.

[0025] The ratio of the alkanolamine-treated fly ash is preferably 95% by mass or less based on 100% by mass of the siliceous raw material. In this case, the amount of crystalline tobermorite produced can be increased more. This ratio is more preferably 70% by mass or less, even more preferably 60% by mass or less, and particularly preferably 50% by mass or less. This ratio is, for example, 10% by mass or more, and preferably 40% by mass or more.

[0026] When the siliceous raw material contains fly ash untreated with alkanolamine, the ratio of the crystalline silica raw material such as silica powder is 9% by mass or more based on 100% by mass of the siliceous raw material, and the ratio of the alkanolamine-treated fly ash is preferably less than 47% by mass based on 100% by mass of the siliceous raw material.

[0027] When the alkanolamine contains triethanolamine, the proportion of triethanolamine in the alkanolamine is preferably 90% by mass or more. In this case, crystalline tobermorite is more easily formed, and the amount of crystalline tobermorite produced can be increased. This proportion is more preferably 95% by mass or more, and even more preferably 98% by mass. This proportion may also be 100% by mass.

[0028] [Other materials] The compounding material may include, for example, reinforcing fibers, lightweight aggregates, and bulking agents. Examples of reinforcing fibers include natural fibers such as pulp fibers; organic fibers such as vinylon fibers, polyester fibers, polyamide fibers, acrylic fibers, acetate fibers, polyethylene fibers, and polypropylene fibers; glass fibers; carbon fibers; ceramic fibers; and metal fibers. Examples of lightweight aggregates include inorganic lightweight aggregates such as shirasu balloons, glass balloons, perlite, calcined vermiculite, and fly ash balloons; and organic lightweight aggregates such as synthetic resin beads and synthetic resin foams. Examples of bulking agents include crushed inorganic boards. The compounding material may also include other materials such as thickeners, dispersants, pigments, and colorants.

[0029] By mixing these materials, adding water, and kneading, a kneading material can be obtained.

[0030] [Autoclave curing] By subjecting the aforementioned kneaded material to autoclave curing, a crystalline tobermorite-containing hardened body is obtained.

[0031] When the mixed material is cured in an autoclave, it is usually molded into the desired shape using a mold or the like to form a molded body (solidified body). It is preferable to perform a vacuum degassing treatment on the mixed material during this molding process, and it is preferable to perform this molding by extrusion molding. These processes can be carried out, for example, using a vacuum extrusion molding machine.

[0032] Furthermore, a primary curing (hardening curing before autoclave curing) may be performed on the mixed materials before autoclave curing (secondary curing). The primary curing can be adjusted as appropriate depending on the composition of the mixed materials, for example, by room temperature curing or steam curing. The primary curing is performed, for example, under normal pressure at a temperature of 40°C to 90°C for a period of 4 to 12 hours.

[0033] By subjecting the mixed material to autoclave curing, a hardened body with a high content of crystalline tobermorite can be obtained. Specifically, after curing before autoclave curing, the molded body is removed from the mold and subjected to steam autoclave curing (high-temperature, high-pressure steam curing) in a known or new steam autoclave apparatus under saturated steam at a pressure of approximately 10 to 30 atmospheres. By applying steam autoclave treatment, crystalline tobermorite that cannot be obtained at room temperature and atmospheric pressure can be produced.

[0034] The curing temperature in the steam autoclave is preferably 160°C or higher. More preferably, the curing temperature is in the range of 160°C to 200°C. It has been observed that the amount of tobermorite produced decreases when the curing temperature in the steam autoclave exceeds 210°C.

[0035] To ensure a sufficient yield of crystalline tobermorite, the curing time in a steam autoclave should ideally be 4 hours or longer when the curing temperature is around 160°C. While a longer curing time is generally advantageous from the standpoint of increasing the yield of crystalline tobermorite, it is preferable to set the curing time to, for example, between 5 and 12 hours, considering the burden on the steam autoclave operating under high temperature and pressure.

[0036] After autoclave curing, drying curing may be performed. Drying curing can be carried out by leaving the tobermorite-rich cured material obtained by autoclave curing to stand in ambient air at room temperature.

[0037] In the manufacturing method of the present invention, it is preferable to perform both curing before autoclave curing and drying curing after autoclave curing, or to perform only curing before autoclave curing.

[0038] The tobermorite-rich hardened body obtained by the manufacturing method of the present invention contains a large amount of fly ash, making it possible to effectively utilize fly ash discharged in large quantities from thermal power plants and the like. [Examples]

[0039] The present invention will be specifically described below with reference to examples.

[0040] [Examples 1-8 and Comparative Examples 1-5] To confirm the effectiveness of the method for producing a crystalline tobermorite-rich hardened material according to the present invention, test specimens of a crystalline tobermorite-rich hydraulic hardened material were actually produced. Specifically, these test specimens were produced as follows: First, the materials shown in Tables 1 and 2 were mixed and kneaded to obtain a kneaded material. At this time, triethanolamine was used as the alkanolamine species, and the alkanolamine-treated fly ash was used, obtained by adding triethanolamine to fly ash in an amount shown in Tables 1 and 2 (0.01% to 0.80% by mass) relative to 100% by mass of alkanolamine-treated fly ash, in the amount indicated by the triethanolamine addition rate (relative to alkanolamine-treated fly ash) in Tables 1 and 2.

[0041] The mixed material after kneading was subjected to vacuum degassing and extrusion molding to obtain a molded body.

[0042] (Evaluation of the moldability of the compounding material) To evaluate the moldability of the compounding material, the material hardness of the molded body was measured using a needle penetration hardness tester from the start of compounding up to 2 hours later. The evaluation criteria are as follows.

[0043] (Evaluation criteria for moldability) ○: Needle penetration hardness is less than 12 even after more than 2 hours. △: Needle penetration hardness exceeds 12 between 1 hour and 2 hours. ×: Needle penetration hardness exceeds 12 within 1 hour.

[0044] The results of the moldability evaluation showed that adding 0.80% by mass or more of triethanolamine to 100% by mass of triethanolamine-treated fly ash reduced the moldability.

[0045] The molded bodies that received a "○" rating in the moldability evaluation were subjected to primary curing at 65°C for 11 hours under normal pressure, followed by autoclave curing at 170°C for 5 hours to obtain a cured body.

[0046] Powder X-ray diffraction analysis was performed on the obtained cured material to confirm the amount of crystalline tobermorite produced. The amount of crystalline tobermorite produced (relative value determined from the powder X-ray diffraction analysis results) is shown in Tables 1 and 2 below.

[0047] [Table 1]

[0048] In the results shown in Table 1, by comparing the fly ash substitution rate, which was high, with that of Comparative Example 2, which was the same 85% by mass, it can be seen that in Examples 1 to 6, using alkanolamine-treated fly ash resulted in a larger amount of crystalline tobermorite being produced. Furthermore, in Examples 2 to 5, setting the triethanolamine content to between 0.05% by mass and 0.70% by mass further increased the amount of crystalline tobermorite produced.

[0049] [Table 2]

[0050] In the results shown in Table 2, "Silica powder content" is the content (mass%) of silica powder relative to 100% by mass of the silica raw material, and "Alkanolamine-treated fly ash substitution rate" is the substitution rate (mass%) of alkanolamine-treated fly ash relative to 100% by mass of the silica raw material. From Comparative Examples 1 to 4, it can be seen that when a portion of the silica powder, which is a crystalline silica raw material, is substituted with untreated fly ash, increasing the substitution rate reduces the amount of crystalline tobermorite produced. However, from Examples 4, 7, and 8, it can be seen that increasing the substitution rate of alkanolamine-treated fly ash in the silica raw material increases the amount of crystalline tobermorite produced. However, as can be seen from Comparative Example 5, when the proportion of silica powder is less than 9% by mass relative to 100% by mass of the silica raw material, and the proportion of alkanolamine-treated fly ash is 47% by mass or more relative to 100% by mass of the silica raw material, the amount of crystalline tobermorite produced decreases. Therefore, when the silica-based raw material contains untreated fly ash with alkanolamine, it is preferable that the proportion of crystalline silica raw material such as silica powder is 9% by mass or more relative to 100% by mass of the silica-based raw material, and the proportion of alkanolamine-treated fly ash is less than 47% by mass relative to 100% by mass of the silica-based raw material.

Claims

1. A method for producing a crystalline tobermorite-containing hardened body, comprising applying autoclave curing to a mixed material containing a siliceous raw material including fly ash mixed with alkanolamine and cement, The proportion of the alkanolamine is 0.05% by mass or more and 0.7% by mass or less, relative to 100% by mass of the fly ash mixed with the alkanolamine. A method for producing a crystalline tobermorite-containing cured body, wherein the proportion of fly ash mixed with the alkanolamine is 10% by mass or more and 95% by mass or less based on 100% by mass of the siliceous raw material.

2. In claim 1, The siliceous raw material comprises a crystalline silica raw material, fly ash mixed with the alkanolamine, and fly ash without the alkanolamine. The proportion of the crystalline silica raw material is 9% by mass or more relative to 100% by mass of the siliceous raw material. A method for producing a crystalline tobermorite-containing cured body, wherein the proportion of fly ash mixed with the alkanolamine is less than 47% by mass relative to 100% by mass of the siliceous raw material.

3. In claim 1 or 2, A method for producing a crystalline tobermorite-containing cured product, wherein the alkanolamine contains triethanolamine, and the proportion of triethanolamine in the alkanolamine is 90% by mass or more.

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