Unfired brick and method for producing same

Abstract

In the present invention, a solidifying material that binds together particles of a brick raw material containing moisture is composed of an aluminum silicate powder, sodium metasilicate nonahydrate, and nanobubble water. The particles of the brick raw material and the solidifying material are uniformly dispersed and kneaded by the action of the nanobubble water, and the resulting kneaded product is pressure-molded and naturally dried to produce an unfired brick.

Description

Non-fired bricks and method for producing the same

[0001] The present invention relates to non-fired bricks and a method for producing the same, and more particularly to non-fired bricks produced by kneading a brick raw material containing moisture and a solidifying material that solidifies the particles of the raw material together, filling the kneaded mixture into a brick mold, and subjecting the filled mixture to pressure molding and then natural drying.

[0002] As a typical example of bricks, fired bricks can be produced by adding water to natural soil containing clay content, kneading the mixture, filling the kneaded mixture into a brick mold, forming the filled mixture into green bricks, and firing the green bricks at a high temperature to obtain bricks having the required strength. Moreover, since fired bricks are excellent in airtightness and heat insulation properties, there is a high demand for them as wall materials for medium- and high-rise buildings such as reinforced concrete or steel frame concrete. However, since the firing of bricks emits a large amount of CO2 gas, which is one of the factors contributing to global warming, and greenhouse gases, there is a growing movement to prohibit or restrict the production of fired bricks.

[0003] On the other hand, if non-fired bricks can be produced using dredged soil deposited in estuaries or the like as a brick raw material, it is possible to replace the demand for fired bricks and to effectively utilize the dredged soil. Focusing on this point, Patent Document 1 proposes using cement as a solidifying material for solidifying particles of dredged soil and / or desert soil.

[0004] However, since cement emits a large amount of CO2 gas, which is one of the factors contributing to global warming, and greenhouse gases during its production process, there is a movement to restrict the production of cement, and the development of a solidifying material that solidifies particles of a brick raw material to replace cement is desired.

[0005] On the other hand, as an alternative material for cement, the development of geopolymers has been studied (Non-Patent Documents 1, 2, etc.). A geopolymer is an amorphous condensation polymer that hardens by the reaction of an aluminum silicate powder and an alkali silicate solution, and since this reaction is a so-called endothermic reaction, it needs to be heat-cured.

[0006] In this regard, Non-Patent Document 1 reports an experiment aimed at slow hardening (for example, within 10 hours) of geopolymers, similar to general cement, instead of heat hardening. According to the same document, a method for producing geopolymers is being investigated using a mixture of blast furnace slag powder and fly ash as aluminum silicate powder, and mixing it with water glass as an alkali silica solution. In particular, the composition of the geopolymer and the mixing ratio of these components have been studied in order to meet the compressive strength and hardening requirements of general cement. As a result, it has been reported that the water glass is No. 2 stock solution (Na₂O / SiO₂, molar ratio: 2.5), the weight ratio of blast furnace slag powder and fly ash is 1:1, and the mass mixing ratio of No. 2 stock solution water glass to blast furnace slag powder and fly ash is 0.6.

[0007] On the other hand, Non-Patent Document 2 reports a method for producing unfired ceramics for use in tiles and the like by using New Zealand kaolin, which has been calcined and made amorphous, as aluminum silicate powder, dry-mixing this with sodium metasilicate nonahydrate, which is an alkali silica solution, and then heating the mixture at 10 to 100°C for, for example, several tens of hours, followed by dehydration and drying. According to this report, hardening did not occur at 10 to 30°C during the heating process, but hardened at 40°C or higher. Furthermore, it is inferred that sodium metasilicate nonahydrate dissolved in its own crystal water at 47°C, and the sodium ions reacted with the amorphous New Zealand kaolin, forming a geopolymer through dehydration condensation.

[0008] WO2022 / 208853A1

[0009] Paper "Basic Study on the Condensation Properties and Compressive Strength Development of Geopolymer Paste," Keigo Ichikawa, Naoki Mishima, Akihiro Maekawa, Shigemitsu Hatanaka, Proceedings of the Annuals of the Concrete Engineering Society, Vol. 37, No. 1, 2015. Paper "Establishment of Solidification Technology for Unfired Materials," Toru Fukuhara, Hayato Mizunawa, Aichi Industrial Science and Technology General Center Research Report 2016.

[0010] According to the geopolymers described in Non-Patent Documents 1 and 2, there is potential for them to be used as a substitute material for conventional cement. However, geopolymers cannot be used as a hardening agent for unfired bricks.

[0011] In other words, the unfired bricks according to the present invention use desert soil, dredged soil, or natural soil as raw materials. Generally, these raw materials contain a large amount of moisture because they originally contain moisture and are stored in open piles. It is unclear how the moisture contained in the raw materials affects the solidification process of the geopolymer. For example, drying these raw materials requires heating at 100°C or higher for several hours to evaporate the moisture, so it appears that moisture is bound to the particles of the raw materials. Moreover, separating the water contained in the raw materials requires heating and drying equipment, energy, and time, making it impractical.

[0012] The first problem that the present invention aims to solve is to provide a solidifying agent that can solidify particles of brick raw materials containing moisture together.

[0013] A second problem that the present invention aims to solve, in addition to the first problem, is to provide a method for producing unfired bricks by mixing a brick raw material containing moisture with the solidifying agent of the present invention, filling the mixture into a brick mold, forming the bricks, and then allowing the resulting raw bricks to air dry.

[0014] In order to solve the first problem, the inventors of the present invention have diligently studied the solidifying agent used in unfired bricks, which are produced by mixing a brick raw material containing moisture with a solidifying agent that binds the particles of the brick raw material together, filling the mixture into a brick mold, press-molding the raw brick, and then air-drying the resulting raw brick.

[0015] As a result, we propose a solidifying agent composed of aluminum silicate powder, sodium metasilicate nonahydrate, and nanobubble water. We found that the action of nanobubble water uniformly disperses and mixes the moisture-containing brick raw material particles with the solidifying agent, allowing the brick raw material particles to be uniformly solidified together.

[0016] Here, we will explain the effects of nanobubble water according to the present invention. Various methods for producing nanobubbles are widely known. As is well known, nanobubble water is water containing bubbles smaller than 1 μm and larger than 1 nm. The nanobubbles in this invention may be air bubbles, but are not limited to this. Also, the water is not limited to purified water, but may be seawater.

[0017] Because the bubbles in nanobubble water are one to three orders of magnitude smaller in diameter than microbubbles, their surfaces become negatively charged, causing them to repel each other and move apart. While attractive forces act when bubbles are far apart relative to their diameter, they essentially behave in water through Brownian motion. Therefore, nanobubbles are uniformly dispersed in water, making nanobubble water appear transparent. Furthermore, because nanobubbles in water are difficult to break, they can generally be retained for long periods of time, typically several months or more.

[0018] When sodium metasilicate nonahydrate is dissolved in this nanobubble water, a strongly alkaline solution is formed. When this solution is added to a mixture of aluminum silicate powder, which is the core of the solidifying agent, and brick raw materials, the strongly alkaline solution and the aluminum silicate powder react and undergo condensation polymerization, producing a geopolymer with solidifying properties.

[0019] As the generated geopolymer hardens while in contact with multiple particles of the brick raw material, these particles are solidified together by the geopolymer. As the number of brick raw material particles solidified by the geopolymer increases, the fluidity between the brick raw material and the aluminum silicate powder decreases, making smooth mixing difficult and hindering the uniform mixing of the solidifying agent.

[0020] Therefore, it is preferable to thoroughly mix the brick raw materials and the aluminum silicate powder, which is the core of the solidifying agent, and then add a solution of nanobubble water in which sodium metasilicate nonahydrate is dissolved and mix. This causes nanobubbles to adhere to the entire surface of the brick raw material particles and aluminum silicate powder, and the action of these bubbles reduces the contact resistance during mixing between the brick raw material particles and aluminum silicate powder, allowing the powders to be mixed smoothly and uniformly.

[0021] In this invention, it is preferable to use a mixture of blast furnace slag powder and fly ash powder as the aluminum silicate powder contained in the solidifying agent. This makes it possible to effectively utilize blast furnace slag powder and fly ash powder, which have traditionally been difficult to dispose of as waste. Generally, fly ash discharged from coal-fired power plants and the like is in a uniform powder form. However, ash discharged from furnaces that burn not only coal but also other waste may contain lumpy ash, so when applying this invention, it is essential to grind it into a powder beforehand. In addition, since blast furnace slag is often in the form of lumps, it is essential to grind it into a powder beforehand.

[0022] Furthermore, the brick raw materials of the present invention may include desert soil and / or dredged soil. This allows for the effective use of desert soil or dredged soil, which are essentially waste materials, to produce unfired bricks. However, the present invention is not limited to this, and natural soil can be used as the brick raw material for unfired bricks.

[0023] Furthermore, when mixing the moisture-containing brick raw material with the solidifying agent of the present invention, if the mixing is not smooth or uniform, it is preferable to add nanobubble water. In other words, the lubricating effect of the added nanobubble water makes contact between the particles being mixed smoother, and uniform mixing can be achieved by giving a certain degree of fluidity to the mixed material. Alternatively, instead of adding nanobubble water, ordinary water or seawater may be added to adjust the fluidity of the mixed material.

[0024] Furthermore, the brick raw material containing moisture may be desert soil, dredged soil, or a mixture of both as appropriate. In addition, natural soil may be used alone, or a mixture of desert soil and dredged soil as appropriate.

[0025] On the other hand, the method for manufacturing unfired bricks according to the present invention, which solves the second problem, sets the mixing ratio of brick raw materials and solidifying agent based on the premise that the brick raw materials contain moisture. In other words, the dry weight of the moisture-containing brick raw materials is used as the basis, and the mixing ratios of the solidifying agent components other than nanobubble water are set as they are normally in a dry state. For example, the mixing ratio of brick raw materials is set to 60% by dry weight, and the solidifying agent components are set to 7% by dry weight of the blast furnace slag powder, 13% by dry weight of the fly ash powder, 12% by dry weight of the sodium metasilicate nonahydrate, and 8% by dry weight of the nanobubble water. However, the present invention is not limited to this example. It is preferable to conduct manufacturing method tests for each brick raw material used and determine the mixing ratio of each component.

[0026] Thus, in this invention, considering practical convenience, the mixing ratio of brick raw materials containing moisture is used as a basis, and the mixing ratio of the solidifying agent components and nanobubble water is increased according to the moisture content of the raw materials. In this regard, questions may arise regarding the idea of ​​adding a solidifying agent even to the moisture content of the brick raw materials. However, since the moisture contained in the raw materials behaves substantially bound to the raw materials and is thought to act as a solution of sodium metasilicate necessary for the hardening reaction of the geopolymer, it is considered preferable to proceed as in this invention.

[0027] Based on the above, the method for manufacturing the unfired brick of the present invention will be explained by dividing it into a preparation step and a manufacturing step. First, the preparation step includes the step of putting blast furnace slag powder and fly ash powder into a stirrer and mixing them, and the step of dissolving sodium metasilicate nonahydrate in nanobubble water at a predetermined mixing ratio of 1 / 3 to produce a solution. The manufacturing step begins with step 1, in which brick raw materials containing water are put into a stirrer and mixed until there are no lumps.

[0028] Next, the process includes step 2, in which the mixture of blast furnace slag powder and fly ash powder mixed in the preparation step is added to the mixture of brick raw materials in the agitator of step 1, and the solution prepared in the preparation step is gradually added and mixed; and step 3, in which the remaining two-thirds of the nanobubble water is added to the mixture of materials from step 2 and mixed.

[0029] Thus, the process is characterized by comprising the steps of: in step 3, all the constituent materials are uniformly mixed; in step 4, the mixture is divided into lumps of a certain amount and left to rest on a workbench at intervals for a certain period of time; in step 5, the lumps of mixture that have been left to rest in step 4 are filled one by one into brick molds and pressure molded; and in step 6, the raw bricks formed by the brick molds are removed and allowed to air dry.

[0030] Because of these characteristics, in step 1, a mixture of blast furnace slag powder and fly ash powder, which are aluminum silicate powders, is uniformly mixed with the brick raw materials. Then, in the next step 2, a solution of sodium metasilicate nonahydrate dissolved in nanobubble water is added. As a result, in step 2, a slow hardening reaction occurs between the mixture of blast furnace slag powder and fly ash powder and the sodium metasilicate nonahydrate, generating a geopolymer, which then solidifies the brick raw materials.

[0031] Furthermore, in step 3, the addition of nanobubble water at a remaining 2 / 3 of the set value enhances the fluidity of the mixture due to the lubricating effect of the nanobubble water. This makes it easier to divide the mixture into fixed-quantity lumps and place them at intervals on the workbench in the next step 4. As a result, the process of filling the brick molds with the lumps of mixture in step 5 can be carried out smoothly, allowing for pressure molding. The raw bricks thus pressure-molded are then removed from the brick molds in step 6 and transported to a drying area for several days to obtain unfired bricks with sufficient strength.

[0032] The present invention provides a solidifying agent that can solidify particles of brick raw materials containing moisture together.

[0033] Furthermore, it is possible to manufacture unfired bricks by effectively utilizing desert soil or dredged soil, which are essentially waste materials.

[0034] Furthermore, the present invention provides a method for producing unfired bricks, which involves mixing a brick raw material containing moisture with the solidifying agent of the present invention, filling the mixture into a brick mold, and then naturally drying the resulting raw brick.

[0035] Figure 1 is a flowchart showing the procedure for manufacturing an unfired brick according to one embodiment of the present invention.

[0036] Table 1 shows the names of the materials and their mixing ratios for the brick raw materials and solidifying agent components related to the unfired brick of one embodiment of the present invention. The brick raw material in this embodiment is dredged soil with a moisture content of approximately 30%. The solidifying agent is a mixture of blast furnace slag powder and fly ash powder as aluminum silicate powder, and sodium metasilicate nonahydrate dissolved in nanobubble water is used as the alkali silica solution. The blast furnace slag powder is obtained by grinding blast furnace slag into a powder, with an average particle size of approximately 13 to 14 μm, and the fly ash powder has an average particle size of approximately 12.3 μm. However, these average particle sizes are just examples, and the present invention is not limited to these average particle sizes.

[0037] The mixing ratios of these constituent materials will now be explained. The mixing ratios in Table 1 are determined by the ratio of the solidifying agent constituent materials to the dry weight of the brick raw materials. In contrast, the water contained in dredged soil is difficult to physically separate, like bound water. Therefore, in this embodiment, the weight of the other constituent materials is measured and used according to the mixing ratios shown in Table 1, corresponding to the weight of the dredged soil containing water.

[0038] Regarding this point, as mentioned above, a hardening agent is mixed in even with respect to the moisture content of the brick raw materials. However, since the moisture contained in the brick raw materials is considered to be substantially bound to the brick raw materials, it is preferable to mix in a weight of hardening agent corresponding to the moisture content of the brick raw materials.

[0039]

[0040] Based on the embodiments shown in Table 1, Figure 1 shows a flowchart illustrating the procedure for manufacturing a non-fired brick according to one embodiment of the present invention. In this embodiment, the weight of each component is measured and used based on the mixing ratio of the component materials shown in Table 1. The manufacturing procedure is basically divided into a preparation step P and a manufacturing step S. In preparation step P1, blast furnace slag powder and fly ash powder, which form the core of the solidifying agent, are put into a stirrer and mixed until the degree of mixing is uniform. In preparation step P2, sodium metasilicate nonahydrate is measured and dissolved in nanobubble water at a ratio of 1 / 3. The remaining 2 / 3 nanobubble water is left in a container or the like. It is optional whether the mixed material and solution from the preparation step are transferred to a stirrer or another container for storage.

[0041] After these preparations are complete, the production of unfired bricks begins. In the production process S1, dredged soil, which is the raw material for the bricks, is put into a different mixer than the one used in the preparation process P1 and mixed until there are no lumps. In the production process S2, the mixture of blast furnace slag powder and fly ash powder from the mixer used in the preparation process P1 is added to the mixture of dredged soil from the mixer used in S1, and the solution from the preparation process P2 is gradually added and mixed. As a result, the blast furnace slag powder and fly ash powder, which form the core of the fixing material, are uniformly mixed in the production process S1. When the solution from the preparation process P2 is gradually added and mixed, the hardening reaction of the geopolymer begins at the point where the mixture of blast furnace slag powder and fly ash powder comes into contact with the solution. Gradually, the hardening reaction of the geopolymer spreads throughout the mixture, and the solidifying action of the hardening agent spreads throughout the entire brick raw material.

[0042] In manufacturing step S3, the mixture from manufacturing step S2 is further mixed while gradually adding the remaining two-thirds of the nanobubble water from preparation step P2. By gradually adding the remaining two-thirds of the nanobubble water in this way, the lubricating effect of the nanobubble water makes the mixing of the brick raw materials and the solidifying agent smoother, allowing for uniform and even mixing of the powder and granules. If necessary, the fluidity can be adjusted by adding or substituting ordinary water for the nanobubble water added in this step. Furthermore, the fluidity can be adjusted using seawater instead of ordinary water.

[0043] In manufacturing process S4, a certain amount of the kneaded material in the stirrer of manufacturing process S3 is taken out one by one, formed into lumps, arranged at intervals on a workbench (for example, a belt conveyor), and left to stand for a certain period of time. Next, in manufacturing process S5, the lumps of the kneaded material on the workbench after a certain period of time have elapsed are filled into the brick mold one by one and pressure-molded, for example, at 3 tons.

[0044] When the molding is completed, in manufacturing process S6, the green bricks are taken out from the brick mold, transported to a drying area, arranged on shelves in an indoor warehouse, etc., and naturally dried. Thereby, unfired bricks with the required strength can be obtained.

[0045] Note that the embodiments in Table 1 and FIG. 1 show an example of using dredged soil as the brick raw material, but the present invention is not limited thereto. For example, unfired bricks of the present invention can be similarly manufactured using desert soil. Also, unfired bricks with a strength equal to or higher than that of the unfired bricks of the present invention can be manufactured using natural soil. Furthermore, dredged soil and desert soil may be mixed and used as the brick raw material.

[0046] Furthermore, 20% of silt clay can be kneaded with respect to the raw material weight ratio of the dredged soil. Thereby, unfired bricks having a strength higher than that in the case of using only dredged soil can be manufactured.

[0047] Since the polycondensation reaction of this geopolimer is an endothermic reaction, in order to promote the reaction, it is preferable to heat the nanobubble water to, for example, 40°C to 70°C and dissolve the sodium metasilicate nonahydrate for use. The nanobubble water will not have its bubbles destroyed even when heated to 40°C to 70°C, and the above-described action of the nanobubble water is maintained. In the case of an area where the ambient temperature is 30 to 50°C, the polycondensation reaction of the geopolimer proceeds without heating the nanobubble water.

[0048] As described above, the present invention has been described based on the embodiments, but it is obvious to those skilled in the art that the present invention is not limited thereto and can be implemented in a modified or changed form within the scope of the gist of the present invention. Needless to say, such a modified or changed form belongs to the scope of the claims of the present application.

Claims

1. A non-fired brick manufactured by mixing a brick raw material containing moisture with a solidifying agent that binds the particles of the brick raw material together, filling the mixture into a brick mold, press-molding the resulting raw brick, and then air-drying the resulting brick, wherein the solidifying agent is composed of aluminum silicate powder, sodium metasilicate notahydrate, and nanobubble water.

2. The unfired brick according to claim 1, characterized in that the aluminum silicate powder of the solidifying agent is a mixture of blast furnace slag powder and fly ash powder.

3. An unfired brick according to claim 2, characterized in that the brick raw material comprises desert soil and / or dredged soil.

4. An unfired brick according to claim 2, characterized in that the brick raw material comprises natural soil.

5. An unfired brick according to claim 2, characterized in that the blending ratio is 7% of the blast furnace slag powder, 13% of the fly ash powder, 12% of the sodium metasilicate nonahydrate, and 8% of the nanobubble water, based on 60% of the dry weight of the brick raw materials.

6. A method for producing unfired bricks according to claim 5, comprising: a preparation step P1 of mixing the blast furnace slag powder and the fly ash powder; a preparation step P2 of dissolving the sodium metasilicate nonahydrate in 1 / 3 of a predetermined mixing ratio of nanobubble water to produce a solution; a manufacturing step S1 of mixing the brick raw materials until there are no lumps; a manufacturing step S2 of adding the mixture from the preparation step P1 to the mixture from the manufacturing step S1 and gradually adding the solution from the preparation step P2 and mixing; a manufacturing step S3 of gradually adding the remaining 2 / 3 of the nanobubble water to the mixture from the manufacturing step S2 and mixing; a manufacturing step S4 of forming the mixture from the manufacturing step S3 into lumps of a certain amount and letting them rest on a workbench at intervals for a certain period of time; a manufacturing step S5 of filling the lumps from the manufacturing step S4 into a brick mold and press-molding them; and a manufacturing step S6 of removing the raw bricks formed by the mold and air-drying them.

7. A method for producing unfired bricks according to claim 6, characterized in that in the manufacturing step S3, the amount of nanobubble water added is adjusted to control the fluidity of the mixture.

8. A method for producing unfired bricks according to claim 7, characterized in that in the production step S3, in addition to adjusting the amount of nanobubble water added, or instead, the amount of water or seawater added is adjusted.

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