Preparation method of lightweight thermal-insulation cement-based material for aquaculture

Abstract

The invention discloses a preparation method of a lightweight thermal-insulation cement-based material for aquaculture, which comprises the following steps: (1) placing expanded vermiculite particles in alkali liquor, and keeping the temperature under a heating condition; and cleaning and drying the obtained expanded vermiculite particles to obtain the modified thermal insulation aggregate. (2) dispersing nano silicon dioxide in water to form a dispersion liquid, then adding a polycarboxylate superplasticizer, uniformly stirring, then adding sodium borohydride, uniformly stirring, and standing; and drying to remove redundant moisture, and grinding to obtain the chromium-reducing admixture. (3) taking the following raw materials: Portland cement, the modified thermal insulation aggregate, glass beads, a filler, the chromium-reducing admixture and fibers; the raw materials are uniformly mixed, water is added, and the mixture is uniformly stirred to obtain the thermal-insulation cement-based material. According to the invention, high-toxicity hexavalent chromium can be reduced into low-toxicity trivalent chromium, and the chromium element can be cured, so that the water-soluble chromium element in the material is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of marine engineering concrete preparation, and in particular to a method for preparing a lightweight thermal insulation cement-based material for aquaculture. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Cement-based materials are essential building materials for the aquaculture industry. Concrete-based aquaculture ponds are widely used due to their low cost, durability, ease of construction, and maintenance. In low ambient temperatures, heating equipment is often required to maintain the water temperature within the pond. In such situations, aquaculture ponds constructed with insulating cement-based materials can effectively reduce heat loss and maintain the water temperature.

[0004] At present, the thermal insulation cement-based materials used to build aquaculture ponds mainly use ordinary Portland cement as the gelling component, but the raw materials for the production of this cement are mainly ores and industrial solid waste, resulting in the obtained cement clinker usually containing soluble hexavalent chromium elements / Cr(VI). In addition, in the process of crushing and grinding the raw materials and the obtained cement clinker, the metal powder worn off from the metal parts of the equipment will also introduce some chromium elements. my country's national standard "Limits and Determination Methods of Water-soluble Chromium (VI) in Cement" (GB31893-2015) clearly stipulates that the water-soluble chromium (VI) in cement shall not exceed 10 mg / kg. However, when using this cement clinker to build aquaculture ponds, it is still easy for water-soluble chromium (VI) to migrate into the pond and affect the water quality. Therefore, it is necessary to take measures to reduce the water-soluble chromium (VI) in the prepared thermal insulation cement-based materials as much as possible. Summary of the Invention

[0005] To address these issues, the present invention provides a method for preparing a lightweight, thermally insulating cement-based material for aquaculture. This method not only reduces highly toxic hexavalent chromium to less toxic trivalent chromium, but also solidifies the chromium, effectively reducing the water-soluble chromium content in the material, making it more suitable for constructing aquaculture ponds. Specifically, the technical solution of the present invention is as follows.

[0006] A method for preparing a lightweight thermal insulation cement-based material for aquaculture, comprising the following steps: (1) Place the expanded vermiculite particles in an alkali solution and keep them warm under heating conditions. After completion, wash the expanded vermiculite particles to remove the residual alkali solution, dry them, and obtain the modified insulation aggregate for later use.

[0007] (2) Disperse nano-silica in water to form a dispersion, then add polycarboxylate water reducer and stir evenly, then add sodium borohydride and stir evenly and let it stand. After completion, dry to remove excess water, grind to obtain chromium-reducing admixture, and set aside.

[0008] (3) Take the following raw materials: Portland cement, the modified thermal insulation aggregate, glass beads, filler, the chromium-reducing admixture, and fiber. Mix the above raw materials and add water to stir evenly to obtain the thermal insulation cement-based material.

[0009] Furthermore, in step (1), the ratio of the expanded vermiculite particles to the alkali solution is 1 g: 25-50 ml. Optionally, the particle size of the expanded vermiculite particles is 2-6 mm.

[0010] Furthermore, in step (1), the concentration of the alkali solution is 1-3 mol / L. Optionally, the alkali solution includes at least one of a sodium hydroxide solution and a potassium hydroxide solution.

[0011] Furthermore, in step (1), the heating temperature is 60-80° C., and the insulation time is 4-5 hours.

[0012] Furthermore, in step (2), the polycarboxylate water reducer is 0.4-0.75% of the mass of the nano-silica.

[0013] Furthermore, in step (2), the mass ratio of sodium borohydride to nano-silicon dioxide is 1.8-2.3:1.

[0014] Furthermore, in step (2), the drying method includes at least one of heating, freeze drying, etc. Optionally, the heating temperature is 70-90°C.

[0015] Furthermore, in step (3), the proportions of the components in the raw materials are: 215-240 parts by weight of silicate cement, 450-530 parts by weight of the modified thermal insulation aggregate, 32-48 parts by weight of glass beads, 20-30 parts by weight of filler, 0.4-0.8 parts by weight of the chromium-reducing admixture, and 10-15 parts by weight of fiber.

[0016] Furthermore, in step (3), water is added according to a water-cement ratio of 0.42 to 0.48.

[0017] Furthermore, in step (3), the filler includes at least one of calcium carbonate powder, mica powder, quartz powder, etc. Optionally, the fineness of the filler is 300-500 mesh.

[0018] Furthermore, in step (3), the fiber comprises at least one of polyethylene fiber, polypropylene fiber, polyacrylonitrile fiber, basalt fiber, etc. Optionally, the length of the fiber is 5 to 20 mm.

[0019] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects: The present invention treats expanded vermiculite with alkali liquor to form a modified thermal insulation aggregate. This not only imparts good thermal insulation properties to the cement-based material of the present invention, but also depolymerizes the silicon-oxygen tetrahedrons in the expanded vermiculite under the action of alkali liquor to form products containing silanol groups, such as -Si(OH)3. Furthermore, due to the porous nature of the expanded vermiculite, the modified vermiculite can utilize its large specific surface area to provide a large amount of silanol groups. When added to Portland cement, the chromium element can not only be enriched in the pores of the aggregate by utilizing its adsorption capacity, but the chromium element in the cement can also be complexed by utilizing the silanol groups. Simultaneously, the calcium hydroxide generated by the cement hydration enters the aggregate, prompting the -Si(OH)3 to be converted into calcium silicate hydrate. After solidification, this cemented product can fix the complexed chromium element therein, effectively preventing the dissolution of the chromium element.

[0020] Furthermore, the chromium-reducing admixture of the present invention can not only reduce highly toxic hexavalent chromium to low-toxic trivalent chromium, but also solidify the chromium element, further reducing the water-soluble chromium element in the material. To this end, the present invention first utilizes a polycarboxylate water-reducing agent to perform surface modification on nano-silica, utilizing the electrostatic adsorption provided by the main chain of the polycarboxylate water-reducing agent to load a large amount of water-reducing agent molecules on the surface of the nano-silica. Then, the present invention uses sodium borohydride to reduce the carboxyl groups on the water-reducing agent molecules to hydroxyl groups. Since the polycarboxylate water-reducing agent contains a large number of carboxyl groups, the surface of the resulting nano-silica particles is loaded with a large amount of hydroxyl groups. Simultaneously, the remaining sodium borohydride and the nano-silica jointly form the chromium-reducing admixture. After being added to the thermal insulation cement-based material of the present invention, the hydroxyl groups on the surface of the nano-silica particles can complex and capture chromium, and on the other hand, the sodium borohydride can reduce hexavalent chromium to trivalent chromium or even a simple substance, thereby reducing the toxicity of the chromium element. At the same time, these chromium-captured nano-silica particles can further react with the calcium hydroxide produced by the hydration of the Portland cement to form calcium silicate hydrate. After solidification, this cementitious product can fix the complexed chromium within it, preventing its dissolution. This makes the thermal insulation cement-based material of the present invention more suitable for the construction of aquaculture ponds and reduces the impact on water quality. Furthermore, the calcium silicate hydrate formed in this process increases the content of the cementitious product in the thermal insulation cement-based material of the present invention, helping to improve the mechanical strength of the mortar. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0022] Figure 1 This is a picture of the modified thermal insulation aggregate sample prepared in the following Example 1.

[0023] Figure 2 This is a sample of the chromium-reducing admixture prepared in Example 1 below.

[0024] Figure 3 This is a compressive strength test diagram of the following Example 1.

[0025] Figure 4 This is a picture of the modified thermal insulation aggregate sample prepared in the following Example 2.

[0026] Figure 5 This is a sample of the chromium-reducing admixture prepared in Example 2 below.

[0027] Figure 6 This is a compressive strength test diagram of the following Example 2.

[0028] Figure 7 This is a sample of the chromium-reducing admixture prepared in Example 3 below.

[0029] Figure 8 This is a compressive strength test diagram of the following Example 3.

[0030] Figure 9 This is a compressive strength test diagram of the following Example 4. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present invention only and are not intended to limit the scope of the invention. The experimental methods in the following examples, for which specific conditions are not specified, are generally performed under conventional conditions or as recommended by the manufacturer.

[0032] Unless otherwise defined, all professional and scientific terms used in the present invention have the same meaning as those familiar to those skilled in the art. The reagents or raw materials used in the present invention can be purchased through conventional channels. Unless otherwise specified, the reagents or raw materials used in the present invention are used in a conventional manner in the art or according to the product instructions. In addition, any method and material similar to or equivalent to the described content can be applied to the inventive method. Now, the technical solution of the present invention is further described in conjunction with the accompanying drawings and specific examples.

[0033] Example 1 A method for preparing a lightweight thermal insulation cement-based material for aquaculture, comprising the following steps: (1) Add expanded vermiculite particles with a particle size distribution between 2 and 6 mm to a 1.5 mol / L sodium hydroxide solution and stir evenly. The ratio of the two is 1 g: 30 ml. Then heat to 75 ° C and keep warm for 4 hours. After completion, filter out the expanded vermiculite particles, wash with clean water and dry them to obtain modified insulation aggregate (such as Figure 1 as shown), and keep it as a standby.

[0034] (2) Add nano-silica to water and ultrasonically treat for 10 minutes to form a dispersion, then add polycarboxylic acid water reducer with a mass of 0.5% of nano-silica and stir evenly, then add sodium borohydride powder with a mass of 2 times that of nano-silica and stir evenly, then heat the obtained mixture to 80°C and keep it warm until the water evaporates, then disperse the product to obtain a chromium-reducing admixture (such as Figure 2 as shown), and keep it as a standby.

[0035] (3) Weigh the raw materials in the following proportions: 225 parts by weight of Portland cement (PO 42.5), 490 parts by weight of the modified thermal insulation aggregate of this embodiment, 38 parts by weight of glass beads, 23 parts by weight of filler (calcium carbonate powder with a fineness of 500 mesh), 0.6 parts by weight of the chromium-reducing admixture of this embodiment, 12 parts by weight of polyethylene fibers with a length of 10 mm, and 99 parts by weight of water.

[0036] (4) Dry-mix the silicate cement, modified thermal insulation aggregate, glass beads, filler, and fiber in a mixer for 5 minutes to obtain a mixture. Then, add the chromium-reducing admixture to water, stir evenly, and then add the admixture to the mixture and stir for 3 minutes to obtain the thermal insulation cement-based material.

[0037] Performance test: 1. The thermal insulation cement-based material prepared in this embodiment was prepared into a test piece and cured for 28 days. The test piece was then immersed in deionized water for 7 days. The amount of chromium (VI) dissolved was tested and the chromium (VI) removal rate was calculated. (2) The thermal insulation cement-based material prepared in this embodiment was prepared into a test piece and cured for 28 days. The compressive strength of the test piece was tested according to the "Standard for Test Methods of Physical and Mechanical Properties of Concrete" (GBT 50081-2019). Figure 3 The results are as follows: chromium (VI) dissolution amount = 0.013 mg / kg, chromium (VI) removal rate = 99.21%, and compressive strength = 4.06 MPa.

[0038] Example 2 A method for preparing a lightweight thermal insulation cement-based material for aquaculture, comprising the following steps: (1) Add expanded vermiculite particles with a particle size distribution between 2 and 6 mm to a 3 mol / L sodium hydroxide solution and stir evenly. The ratio of the two is 1 g: 25 ml. Then heat to 60 ° C and keep warm for 5 hours. After completion, filter out the expanded vermiculite particles, wash with clean water and dry them to obtain modified insulation aggregate (such as Figure 4 as shown), and keep it as a standby.

[0039] (2) Add nano-silica to water and ultrasonically treat for 15 minutes to form a dispersion, then add polycarboxylic acid water reducer with a mass of 0.4% of nano-silica and stir evenly, then add sodium borohydride powder with a mass of 1.8 times that of nano-silica and stir evenly, then heat the obtained mixture to 70°C and keep it warm until the water evaporates, then disperse the product to obtain a chromium-reducing admixture (such as Figure 5 as shown), and keep it as a standby.

[0040] (3) Weigh the raw materials in the following proportions: 215 parts by weight of Portland cement (PO 42.5), 450 parts by weight of the modified thermal insulation aggregate of this embodiment, 32 parts by weight of glass beads, 20 parts by weight of filler (quartz powder with a fineness of 300 mesh), 0.4 parts by weight of the chromium-reducing admixture of this embodiment, 15 parts by weight of polyethylene fibers with a length of 5 mm, and 90.3 parts by weight of water.

[0041] (4) Dry-mix the silicate cement, modified thermal insulation aggregate, glass beads, filler, and fiber in a mixer for 5 minutes to obtain a mixture. Then, add the chromium-reducing admixture to water, stir evenly, and then add the admixture to the mixture and stir for 3 minutes to obtain the thermal insulation cement-based material.

[0042] Performance test: 1. The thermal insulation cement-based material prepared in this embodiment was prepared into a test piece and cured for 28 days. The test piece was then immersed in deionized water for 7 days. The amount of chromium (VI) dissolved was tested and the chromium (VI) removal rate was calculated. (2) The thermal insulation cement-based material prepared in this embodiment was prepared into a test piece and cured for 28 days. The compressive strength of the test piece was tested according to the "Standard for Test Methods of Physical and Mechanical Properties of Concrete" (GBT 50081-2019). Figure 6 The results are as follows: chromium (VI) dissolution amount = 0.018 mg / kg, chromium (VI) removal rate = 98.91%, and compressive strength = 4.32 MPa.

[0043] Example 3 A method for preparing a lightweight thermal insulation cement-based material for aquaculture, comprising the following steps: (1) Add expanded vermiculite particles with a particle size distribution between 2 and 6 mm to a 1 mol / L sodium hydroxide solution and stir evenly, with the ratio of 1 g to 50 ml. Then heat to 80°C and keep warm for 4.5 hours. After completion, filter out the expanded vermiculite particles, rinse with clean water, and air-dry to obtain a modified thermal insulation aggregate for later use.

[0044] (2) Add nano-silica to water and ultrasonically treat for 10 minutes to form a dispersion, then add polycarboxylic acid water reducer with a mass of 0.75% of nano-silica and stir evenly, then add sodium borohydride powder with a mass of 2.3 times that of nano-silica and stir evenly, then heat the obtained mixture to 90°C and keep it warm until the water evaporates, then disperse the product to obtain a chromium-reducing admixture (such as Figure 7 as shown), and keep it as a standby.

[0045] (3) Weigh the raw materials in the following proportions: 240 parts by weight of Portland cement (PO 42.5), 530 parts by weight of the modified thermal insulation aggregate of this embodiment, 48 parts by weight of glass beads, 30 parts by weight of filler (mica powder with a fineness of 450 mesh), 0.8 parts by weight of the chromium-reducing admixture of this embodiment, 10 parts by weight of polypropylene fiber with a length of 20 mm, and 115.2 parts by weight of water.

[0046] (4) Dry-mix the silicate cement, modified thermal insulation aggregate, glass beads, filler, and fiber in a mixer for 5 minutes to obtain a mixture. Then, add the chromium-reducing admixture to water, stir evenly, and then add the admixture to the mixture and stir for 3 minutes to obtain the thermal insulation cement-based material.

[0047] Performance test: 1. The thermal insulation cement-based material prepared in this embodiment was prepared into a test piece and cured for 28 days. The test piece was then immersed in deionized water for 7 days. The amount of chromium (VI) dissolved was tested and the chromium (VI) removal rate was calculated. (2) The thermal insulation cement-based material prepared in this embodiment was prepared into a test piece and cured for 28 days. The compressive strength of the test piece was tested according to the "Standard for Test Methods of Physical and Mechanical Properties of Concrete" (GBT 50081-2019). Figure 8 The results are as follows: chromium (VI) dissolution amount = 0.011 mg / kg, chromium (VI) removal rate = 99.33%, and compressive strength = 3.83 MPa.

[0048] Example 4 A method for preparing a lightweight thermal insulation cement-based material for aquaculture, comprising the following steps: (1) Add nano-silica to water and ultrasonically treat for 10 minutes to form a dispersion. Then add polycarboxylic acid water reducer with a mass of 0.5% of the nano-silica and stir evenly. Then add sodium borohydride powder with a mass of 2 times that of the nano-silica and stir evenly. Then heat the obtained mixture to 80°C and keep it warm until the water evaporates. Then disperse the product to obtain a chromium-reducing admixture for use.

[0049] (2) The raw materials were weighed in the following proportions: 225 parts by weight of Portland cement (PO 42.5), 490 parts by weight of expanded vermiculite particles (particle size distribution between 2 and 6 mm), 38 parts by weight of glass microspheres, 23 parts by weight of filler (calcium carbonate powder with a fineness of 500 mesh), 0.6 parts by weight of the chromium-reducing admixture of this embodiment, 12 parts by weight of polyethylene fibers with a length of 10 mm, and 99 parts by weight of water.

[0050] (3) Dry-mix the silicate cement, expanded vermiculite particles, glass beads, filler, and fiber in a blender for 5 minutes to obtain a mixture. Then, add the chromium-reducing admixture to water, stir evenly, and then add the admixture to the mixture and stir for 3 minutes to obtain the thermal insulation cement-based material.

[0051] Performance test: 1. The thermal insulation cement-based material prepared in this embodiment was prepared into a test piece and cured for 28 days. The test piece was then immersed in deionized water for 7 days. The amount of chromium (VI) dissolved was tested and the chromium (VI) removal rate was calculated. (2) The thermal insulation cement-based material prepared in this embodiment was prepared into a test piece and cured for 28 days. The compressive strength of the test piece was tested according to the "Standard for Test Methods of Physical and Mechanical Properties of Concrete" (GBT 50081-2019). Figure 9 The results are as follows: chromium (VI) dissolution amount = 0.326 mg / kg, chromium (VI) removal rate = 80.19%, and compressive strength = 3.41 MPa.

[0052] Example 5 A method for preparing a lightweight thermal insulation cement-based material for aquaculture, comprising the following steps: (1) Add expanded vermiculite particles with a particle size distribution between 2 and 6 mm to a 1 mol / L sodium hydroxide solution and stir evenly, with the ratio of 1 g to 50 ml. Then heat to 80°C and keep warm for 4.5 hours. After completion, filter out the expanded vermiculite particles, rinse with clean water, and air-dry to obtain a modified thermal insulation aggregate for later use.

[0053] (2) Weigh the raw materials in the following proportions: 240 parts by weight of Portland cement (PO 42.5), 530 parts by weight of the modified thermal insulation aggregate of this embodiment, 48 parts by weight of glass beads, 30 parts by weight of filler (mica powder with a fineness of 450 mesh), 0.8 parts by weight of nano-silica, 10 parts by weight of polypropylene fiber with a length of 20 mm, and 115.2 parts by weight of water.

[0054] (3) Dry-mix the silicate cement, modified thermal insulation aggregate, glass beads, filler, and fiber in a mixer for 5 minutes to obtain a mixture. Then, add the nano-silica to water, stir evenly, and then add the nano-silica to the mixture and stir for 3 minutes to obtain the thermal insulation cement-based material.

[0055] Performance test: 1. The thermal insulation cement-based material prepared in this embodiment was prepared into a test piece and cured for 28 days. The test piece was then immersed in deionized water for 7 days, and the chromium (VI) dissolution amount was tested, and the chromium (VI) removal rate was calculated. (2) The thermal insulation cement-based material prepared in this embodiment was prepared into a test piece and cured for 28 days. The compressive strength of the test piece was tested according to the "Standard for Test Methods of Physical and Mechanical Properties of Concrete" (GBT 50081-2019). The results were: chromium (VI) dissolution amount = 0.454 mg / kg, chromium (VI) removal rate = 72.38%, and compressive strength = 3.77 MPa.

[0056] Example 6 A method for preparing a lightweight thermal insulation cement-based material for aquaculture, comprising the following steps: (1) Add expanded vermiculite particles with a particle size distribution between 2 and 6 mm to a 3 mol / L sodium hydroxide solution and stir evenly in a ratio of 1 g to 25 ml. Then heat to 60°C and keep warm for 5 hours. After completion, filter out the expanded vermiculite particles, rinse with clean water, and air-dry to obtain a modified thermal insulation aggregate for later use.

[0057] (2) Add nano-silica to water and ultrasonically treat for 15 minutes to form a dispersion, then add polycarboxylic acid water reducer (0.4% by weight of nano-silica) and stir evenly, then heat the resulting mixture to 70°C and keep it warm until the water evaporates, then disperse the product to obtain a chromium-reducing admixture for later use.

[0058] (3) Weigh the raw materials in the following proportions: 215 parts by weight of Portland cement (PO 42.5), 450 parts by weight of the modified thermal insulation aggregate of this embodiment, 32 parts by weight of glass beads, 20 parts by weight of filler (quartz powder with a fineness of 300 mesh), 0.4 parts by weight of the chromium-reducing admixture of this embodiment, 15 parts by weight of polyethylene fibers with a length of 5 mm, and 90.3 parts by weight of water.

[0059] (4) Dry-mix the silicate cement, modified thermal insulation aggregate, glass beads, filler, and fiber in a mixer for 5 minutes to obtain a mixture. Then, add the chromium-reducing admixture to water, stir evenly, and then add the admixture to the mixture and stir for 3 minutes to obtain the thermal insulation cement-based material.

[0060] Performance test: 1. The thermal insulation cement-based material prepared in this embodiment was prepared into a test piece and cured for 28 days. The test piece was then immersed in deionized water for 7 days, and the chromium (VI) dissolution amount was tested, and the chromium (VI) removal rate was calculated. (2) The thermal insulation cement-based material prepared in this embodiment was prepared into a test piece and cured for 28 days. The compressive strength of the test piece was tested according to the "Standard for Test Methods of Physical and Mechanical Properties of Concrete" (GBT 50081-2019). The results were: chromium (VI) dissolution amount = 0.641 mg / kg, chromium (VI) removal rate = 61.07%, and compressive strength = 4.46 MPa.

[0061] Example 7 A method for preparing a lightweight thermal insulation cement-based material for aquaculture, comprising the following steps: (1) Add expanded vermiculite particles with a particle size distribution between 2 and 6 mm to a 1 mol / L sodium hydroxide solution and stir evenly, with the ratio of 1 g to 50 ml. Then heat to 80°C and keep warm for 4.5 hours. After completion, filter out the expanded vermiculite particles, rinse with clean water, and air-dry to obtain a modified thermal insulation aggregate for later use.

[0062] (2) Add nano-silica to water and ultrasonically treat it for 10 minutes to form a dispersion. Then, add sodium borohydride powder (2.3 times the mass of the nano-silica) and stir evenly. Then, heat the resulting mixture to 90°C and keep it warm until the water evaporates. Then, disperse the product to obtain a chromium-reducing admixture for use.

[0063] (3) Weigh the raw materials in the following proportions: 240 parts by weight of Portland cement (PO 42.5), 530 parts by weight of the modified thermal insulation aggregate of this embodiment, 48 parts by weight of glass beads, 30 parts by weight of filler (mica powder with a fineness of 450 mesh), 0.8 parts by weight of the chromium-reducing admixture of this embodiment, 10 parts by weight of polypropylene fiber with a length of 20 mm, and 115.2 parts by weight of water.

[0064] (4) Dry-mix the silicate cement, modified thermal insulation aggregate, glass beads, filler, and fiber in a mixer for 5 minutes to obtain a mixture. Then, add the chromium-reducing admixture to water, stir evenly, and then add the admixture to the mixture and stir for 3 minutes to obtain the thermal insulation cement-based material.

[0065] Performance test: 1. The thermal insulation cement-based material prepared in this embodiment was prepared into a test piece and cured for 28 days. The test piece was then immersed in deionized water for 7 days. The chromium (VI) dissolution amount was tested and the chromium (VI) removal rate was calculated. (2) The thermal insulation cement-based material prepared in this embodiment was prepared into a test piece and cured for 28 days. The compressive strength of the test piece was tested according to the "Standard for Test Methods of Physical and Mechanical Properties of Concrete" (GBT 50081-2019). The results were: chromium (VI) dissolution amount = 0.272 mg / kg, chromium (VI) removal rate = 83.47%, and compressive strength = 3.62 MPa.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a lightweight thermal insulation cement-based material for aquaculture, characterized in that: The steps include: (1) placing expanded vermiculite particles in an alkali solution and keeping the solution warm under heating conditions; after completion, washing the obtained expanded vermiculite particles, drying them to obtain a modified thermal insulation aggregate for later use; (2) Dispersing nano-silica in water to form a dispersion, then adding polycarboxylate water reducer and stirring evenly, then adding sodium borohydride and stirring evenly and letting it stand; after completion, drying to remove excess water, grinding to obtain chromium-reducing admixture, and setting aside; (3) Take the following raw materials: Portland cement, the modified thermal insulation aggregate, glass beads, filler, the chromium-reducing admixture, and fiber; mix the above raw materials and add water and stir evenly to obtain the thermal insulation cement-based material.

2. The method for preparing a lightweight thermal insulation cement-based material for aquaculture according to claim 1, characterized in that: In step (1), the ratio of the expanded vermiculite particles to the alkali solution is 1 g: 25-50 ml; optionally, the particle size of the expanded vermiculite particles is 2-6 mm.

3. The method for preparing a lightweight thermal insulation cement-based material for aquaculture according to claim 1, characterized in that: In step (1), the concentration of the alkali solution is 1-3 mol / L.

4. The method for preparing a lightweight thermal insulation cement-based material for aquaculture according to claim 1, characterized in that: In step (1), the alkali solution includes: at least one of sodium hydroxide solution and potassium hydroxide solution; optionally, in step (1), the heating temperature is 60-80° C., and the insulation time is 4-5 hours.

5. The method for preparing a lightweight thermal insulation cement-based material for aquaculture according to claim 1, characterized in that: In step (2), the polycarboxylate water reducer is 0.4-0.75% of the mass of the nano-silica.

6. The method for preparing a lightweight thermal insulation cement-based material for aquaculture according to claim 1, characterized in that: In step (2), the mass ratio of sodium borohydride to nano-silicon dioxide is 1.8-2.3:1; Optionally, in step (2), the drying method includes at least one of heating and freeze-drying; optionally, the heating temperature is 70-90°C.

7. The method for preparing a lightweight thermal insulation cement-based material for aquaculture according to any one of claims 1 to 6, characterized in that: In step (3), the proportions of the components in the raw materials are: 215-240 parts by weight of silicate cement, 450-530 parts by weight of the modified thermal insulation aggregate, 32-48 parts by weight of glass beads, 20-30 parts by weight of filler, 0.4-0.8 parts by weight of the chromium-reducing admixture, and 10-15 parts by weight of fiber.

8. The method for preparing a lightweight thermal insulation cement-based material for aquaculture according to any one of claims 1 to 6, characterized in that: In step (3), water is added according to a water-cement ratio of 0.42 to 0.

48.

9. The method for preparing a lightweight thermal insulation cement-based material for aquaculture according to any one of claims 1 to 6, characterized in that: In step (3), the filler includes at least one of calcium carbonate powder, mica powder, and quartz powder; optionally, the fineness of the filler is 300-500 mesh.

10. The method for preparing a lightweight thermal insulation cement-based material for aquaculture according to any one of claims 1 to 6, characterized in that: In step (3), the fiber includes: at least one of polyethylene fiber, polypropylene fiber, polyacrylonitrile fiber, and basalt fiber; optionally, the length of the fiber is 5 to 20 mm.

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