Artificial aggregate and method for its production

Abstract

This invention relates to an artificial aggregate and its preparation method, belonging to the technical field of radiation-shielding concrete raw material preparation. The artificial aggregate comprises a metal shell, a porous structure, and a water-based liquid. The metal shell is a sealed structure used to contain the porous structure. The porous structure is formed by mixing ceramsite raw material with 1%–10% by weight of powdered B4C or Gd2O3, wherein B4C accounts for 20%–80% of the total weight of the powder, the powder particle size is 10 micrometers, and the mixture is shaped into a specified form, dried, and then fired. The water-based liquid is natural water, tap water, or boric acid solution contained within the pores of the porous structure. This artificial aggregate is readily available, its preparation process is simple, and the production process is highly industrialized. It can produce a new type of concrete with superior moisture content, workability, fast neutron moderation capability, and thermal neutron absorption capability compared to existing concrete, meeting the needs of nuclear radiation, especially neutron shielding structures, in special nuclear facilities.

Description

Technical Field

[0001] This invention belongs to the field of radiation-proof concrete raw material preparation technology, and specifically relates to an artificial aggregate and its preparation method. Background Technology

[0002] In the construction of facilities such as nuclear power plants, concrete structures are an important component of radiation shielding. Water is the best moderator for fast neutrons produced by nuclear reactions. Using serpentine (a mineral containing approximately 13% bound water by weight) as aggregate in concrete materials can provide good neutron shielding and is currently being used in a few nuclear facilities.

[0003] However, as a natural mineral, serpentine aggregate has many impurities and high production costs. The resulting serpentine concrete has poor workability and its moisture content is difficult to increase further, which cannot meet the needs of large-scale application in nuclear facilities.

[0004] Therefore, there is an urgent need to provide an artificial aggregate and its preparation method to meet the needs of large-scale application in nuclear facilities. Summary of the Invention

[0005] This invention provides an artificial aggregate and its preparation method, which can achieve large-scale production and is especially suitable for the preparation of high water content concrete.

[0006] To solve the above technical problems, the present invention includes the following technical solutions:

[0007] An artificial aggregate, comprising:

[0008] A metal casing, which is a sealed structure, is used to accommodate a porous structure;

[0009] A porous structure, wherein the porous structure is formed by mixing ceramsite raw material with 1% to 10% by weight of powdered B4C or Gd2O3, wherein the weight of B4C accounts for 20% to 80% of the total weight of the powder, the particle size of the powder is about 10 micrometers, the mixture is shaped into a specified shape, and the resulting shaped body is dried and then fired; and

[0010] A water-based liquid, wherein the water-based liquid is natural water, tap water or boric acid solution contained in the pores of the porous structure.

[0011] Furthermore, the porosity of the porous structure is >30%, and the cylinder compressive strength is >10MPa.

[0012] Furthermore, the ceramsite is selected from at least one of alumina particles, silicon oxide particles, silicon carbide particles, and silicon nitride particles.

[0013] Furthermore, the metal outer shell is a metal spherical shell or other hollow, irregularly shaped closed structure, and the metal is made of stainless steel.

[0014] Furthermore, the outer radius of the metal spherical shell is R, and the thickness is t, where the value of R ranges from 1.5 mm to 20 mm. In the formula, α is the safety factor, ranging from 1.5 to 2.0; p = 1.55 MPa is the critical boiling pressure of water at 200℃; σ y =360MPa is the yield stress of the metal material. This condition is based on the formula for membrane stress generated by internal pressure on a spherical shell in theoretical mechanics, and the membrane stress must be less than the yield stress of the metal spherical shell material. It is obtained through conversion.

[0015] The present invention also provides a method for preparing artificial aggregate, the method comprising the following steps:

[0016] Step S1: Use natural clay, blast furnace slag powder and other industrial solid waste and engineering waste soil as basic raw materials, and add 1% to 10% by weight of powdered B4C or Gd2O3, add water and foaming agent to make spherical particles. The specific mass ratio is as follows.

[0017]

[0018] The firing temperature is controlled at 1300℃ for 3 hours.

[0019] The particles are expanded by foaming agents and fired to allow internal moisture to escape, resulting in porous ceramsite. Finally, the ceramsite is sieved and classified according to its size, cylinder compressive strength, and porosity.

[0020] Step S2: Soak the ceramsite prepared in step S1 in water until it is saturated with liquid;

[0021] Step S3: The ceramsite soaked in step S2 is grouped according to its size, and the grouped ceramsite is placed in a freezer to freeze the outer liquid and lock in the inner liquid.

[0022] Step S4: Place the frozen ceramsite from step S3 into a high-temperature resistant net, immerse it in molten metal, coat the surface with a metal shell, and then remove it to obtain liquid-coated ceramsite.

[0023] Step S5: The liquid-coated particles obtained in step S4 are subjected to post-processing. The adhered artificial aggregates are cut and separated. The defects of the metal shell are reduced by tempering. The obtained ceramsite is subjected to heating test and pressure test. Qualified products are screened to obtain artificial aggregates.

[0024] Further, step S3 includes:

[0025] The size groups are separated according to a radius difference of 0.5 mm; and the average radius R of each group is determined in advance through experiments. 平均 The freezing time T that allows the outer layer of liquid to freeze while the inner layer remains unfrozen. 冷冻 (R 平均 To avoid the entire liquid freezing and cracking, which would damage the porous structure, the freezing time for this group was uniformly set as T. 冷冻 (R 平均 For example, using a freezer at -20°C, R 平均 = 10mm group freezing time T 冷冻 It is 0.5h.

[0026] Further, step S4 includes:

[0027] Based on the different size groups, the average radius R corresponding to each group is determined in advance through experiments. 平均 Minimum soaking time T for ceramsite 浸泡 (R 平均 To ensure that its surface is covered with a metal shell of thickness t; the uniform immersion time for this group is taken as T. 浸泡 (R 平均 For example, in molten steel at 1500°C, R 平均 =10mm group, soaking time T 浸泡 It lasts for 15 seconds.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] This invention provides an artificial aggregate comprising a metal shell, a porous structure, and water. The metal shell is a sealed structure designed to contain the porous structure. The porous structure is formed by mixing ceramsite raw material with 1%–10% by weight of powdered B4C or Gd2O3, shaping it into a specified form, drying the resulting molded body, and then firing it. The water-based liquid is natural water, tap water, or boric acid solution contained within the pores of the porous structure. This artificial aggregate is readily available, its preparation process is simple, and the production process can be highly industrialized. Furthermore, it can produce a new type of concrete with superior moisture content, workability, fast neutron moderation capability, and thermal neutron absorption capability compared to existing concrete, meeting the needs of nuclear radiation, particularly neutron shielding structures, in special nuclear facilities. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of an artificial aggregate according to an embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram showing the relationship between the thickness of the metal outer shell and the outer radius of the spherical shell in an artificial aggregate according to an embodiment of the present invention;

[0032] Figure 3This is a flowchart of a method for preparing artificial aggregate according to an embodiment of the present invention.

[0033] In the picture:

[0034] 1-Metal shell, 2-Porous structure, 3-Water-based liquid. Detailed Implementation

[0035] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a more detailed explanation of the artificial aggregate and its preparation method provided by the present invention. The advantages and features of the present invention will become clearer from the following description. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention. For ease of description, the terms "upper" and "lower" used below are consistent with the upper and lower directions in the accompanying drawings, but this should not be construed as a limitation of the technical solution of the present invention.

[0036] Example 1

[0037] The following is combined with Figures 1 to 3 The structure and composition of the artificial aggregate of the present invention will be described in detail.

[0038] Please continue to refer to this. Figure 1 and Figure 2 An artificial aggregate comprises a metal shell 1, a porous structure 2, and water. The metal shell 1 is a sealed structure used to contain the porous structure 2. The porous structure 2 is formed by mixing ceramsite raw material with 1% to 10% by weight of powdered B4C or Gd2O3, wherein the weight of B4C accounts for 20% to 80% of the total weight of the powder, the powder particle size is 10 micrometers, and the mixture is shaped into a specified shape, dried, and then fired. The water-based liquid 3 is natural water, tap water, or boric acid solution contained in the pores of the porous structure 2. The water-based liquid 3 is the main component for moderating fast neutrons generated by nuclear facilities.

[0039] In this embodiment, more preferably, the porosity of the porous structure 2 is >30%, and the cylinder compressive strength is >10MPa. The porous structure serves two purposes: firstly, it supports the spherical shell, preventing plastic deformation or buckling under normal working pressure; secondly, it contains liquid; and finally, the B and Gd elements can effectively absorb neutrons.

[0040] In this embodiment, more preferably, the ceramsite is selected from at least one of alumina particles, silicon oxide particles, silicon carbide particles, and silicon nitride particles.

[0041] In this embodiment, more preferably, the metal outer shell is a metal spherical shell or other hollow, irregularly shaped closed structure, and the metal is made of stainless steel. The metal outer shell is used to enclose the porous structure 2; therefore, the shape of the metal outer shell is determined by the forming shape of the porous structure 2. The forming body of the porous structure 2 can be any structure; therefore, the shape of the metal outer shell is not limited here, as long as it satisfies the effect of enclosing the porous structure 2 and completely sealing it.

[0042] In this embodiment, more preferably, the radial stress of the spherical shell satisfies the classical formula in theoretical mechanics:

[0043] The radial stress amplification factor is less than the yield stress of the spherical shell, i.e.

[0044] Through formula conversion, the thickness of the spherical shell satisfies the following formula:

[0045] In the formula, σ l For the radial stress of the spherical shell, water is chosen as the water-based liquid, and the highest operating temperature under design conditions is 200℃. At this temperature, the critical boiling pressure of water is p = 1.55MPa. Alternatively, if a metallic spherical shell is selected, its yield stress σ... y =360MPa; R ranges from 1.5mm to 20mm; α is the safety factor, ranging from 1.5 to 2.0. Taking a particle with an outer radius R = 10mm as an example, according to the formula... The calculated shell thickness t is at least 0.0323 mm; if the outer radius R of a particle is 20 mm, then the shell thickness t is at least 0.0646 mm. Therefore, if the metal material and the maximum operating temperature are determined, then p and σ... y Since both are constants, the thickness t of the metal spherical shell is linearly proportional to the outer radius R of the shell.

[0046] Please continue to refer to this. Figures 1 to 3 The present invention also provides a method for preparing artificial aggregate, the method comprising the following steps:

[0047] Step S1: Preparation of porous structure: Using natural clay, industrial solid waste, and engineering waste soil as basic raw materials, and adding 1% to 10% by weight of powdered B4C or Gd2O3, water and foaming agent are added to mix and form granules. The specific mass ratios are as follows:

[0048]

[0049] The firing temperature is controlled at 1300℃ for 3 hours. The particles are expanded by a foaming agent and the internal moisture is released during the firing at 1300℃ to obtain porous ceramsite. Finally, the ceramsite is sieved and classified according to its size, cylinder compressive strength and porosity to obtain a porous structure.

[0050] Step S2, Immersing the porous structure: The ceramsite prepared in step S1 is immersed in a water-based liquid. The open pores are the main channels for the ceramsite to absorb water. The liquid can enter the open pores through the action of surface tension and be transferred inside the ceramsite through the connectivity of the pores until the ceramsite absorbs the liquid to saturation. The volume of the water-based liquid can reach more than 25% of the total volume of the ceramsite.

[0051] Step S3, Freezing the porous structure: The ceramsite soaked in step S2 is grouped according to its size, and the grouped ceramsite is placed in a freezer to freeze the outer liquid and lock in the internal liquid.

[0052] Step S4, Coating with a metal shell: Place the frozen ceramic granules from step S3 in a high-temperature resistant net and immerse them in molten metal to coat the surface with a metal shell before removing them to obtain liquid-coated granules.

[0053] Step S5: Post-processing: The liquid-coated particles obtained in step S4 are subjected to post-processing, namely, the adhered artificial aggregates are cut and separated, the defects of the metal shell are reduced by tempering, and the obtained ceramsite is subjected to heating test and pressure test to screen qualified products, thereby obtaining artificial aggregates.

[0054] In this embodiment, more preferably, step S3 includes:

[0055] The size groups are separated by a radius difference of 0.5 mm; and the average radius R of each group is determined in advance through experiments. 平均 The freezing time T that allows the outer layer of liquid to freeze while the inner layer remains unfrozen. 冷冻 (R 平均 To prevent the entire liquid from freezing and cracking, thus damaging the porous structure, the unified freezing time for this group was set as T. 冷冻 (R 平均 ).

[0056] In this embodiment, more preferably, step S4 includes:

[0057] Based on the different size groups, the average radius R corresponding to each group is determined in advance through experiments. 平均 Minimum soaking time T for ceramsite 浸泡 (R 平均 Ensure that its surface is covered with a metal shell of thickness t; the uniform immersion time for this group is taken as T. 浸泡 (R平均 ).

[0058] Specifically, three types of concrete test blocks were prepared for testing: artificial aggregate concrete (prepared using the aforementioned method, with an internal natural water volume of approximately 28%), ordinary concrete, and serpentine concrete. The corresponding mix proportions are shown in the table below. The particle size of the artificial coarse aggregate, ordinary crushed stone, and serpentine was 5-10 mm in a continuous gradation. The fineness modulus of the artificial fine aggregate, river sand, and serpentine sand was controlled at approximately 2.3. PO 52.5 silicate cement was used, and the solids content of the water-reducing agent was 28%.

[0059]

[0060] Concrete was molded into cylindrical specimens with a diameter of 6 cm and a height of 4 cm, and tested after standard curing for 28 days. Three types of concrete were irradiated using an electron accelerator with neutrons at energies of approximately 0.01 eV, 1 eV, and 100 eV. The neutron shielding capability was determined by recording the flux of neutrons after penetrating the concrete. Each energy level was irradiated for approximately 5 hours, and the neutron emission flux from the electron accelerator was approximately 100,000 ns.

[0061] The neutron flux data obtained after penetrating concrete are shown in the table below:

[0062] 0.01eV 1eV 100eV Artificial aggregate concrete 9253 13856 16966 Ordinary concrete 23698 35065 39745 Serpentine concrete 13959 22129 25678

[0063] As can be seen from the table, the neutron shielding ability of artificial aggregate concrete is better than that of ordinary concrete and serpentine concrete at three energies: 0.01eV, 1eV, and 100eV. The neutron shielding rate of artificial aggregate concrete can be increased by about 25% and 10% compared with that of ordinary concrete and serpentine concrete, respectively.

[0064] The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. The above embodiments only illustrate several implementations of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. An artificial aggregate, characterized in that, include: A metal casing, which is a sealed structure, is used to accommodate a porous structure; The porous structure is formed by mixing ceramsite raw material with 1% to 10% by weight of powdered B4C or Gd2O3, the powder having a particle size of 10 micrometers, shaping it into a specified shape, and then drying and firing the resulting shaped body. as well as A water-based liquid, wherein the water-based liquid is natural water, tap water or boric acid solution contained in the pores of the porous structure.

2. The artificial aggregate according to claim 1, characterized in that, The porosity of the porous structure is >30%, and the cylinder compressive strength is >10MPa.

3. The artificial aggregate according to claim 1, characterized in that, The metal outer shell is a metal spherical shell or other hollow, irregularly shaped closed structure, and the metal is made of stainless steel.

4. The artificial aggregate according to claim 3, characterized in that, The outer radius of the metal spherical shell is R, and the thickness is t, where the value of R ranges from 1.5 mm to 20 mm. In the formula, α is the safety factor, which takes a value of 1.5~2.0; p=1.55MPa is the critical boiling pressure of water at 200℃; σ y =360 MPa is the yield stress of the metal material.

5. The method for preparing artificial aggregate according to claim 4, characterized in that, Includes the following steps: Step S1: Use natural clay, industrial solid waste, and engineering waste soil as base raw materials, and mix in 1%~10% by weight of powdered B4C or Gd2O3, add water and foaming agent to form granules. The specific mass ratios are as follows: 30%~40% natural clay Industrial solid waste 10%~20% Construction waste soil accounts for 10% to 15% of the total. B4C or Gd2O3 1%~10% Water 10%~30% Foaming agent 1%~5%; The firing temperature is controlled at 1300℃ for 3 hours. The particles are expanded by a foaming agent and the internal moisture is released by firing at 1300℃ to obtain porous ceramsite. Finally, the ceramsite is screened and classified according to its size, cylinder compressive strength and porosity. Step S2: Soak the ceramsite prepared in step S1 in a water-based liquid. The open pores are the main channels for the ceramsite to absorb water. The liquid can enter the open pores through the action of surface tension and be transferred inside the ceramsite through the connectivity of the pores until the ceramsite absorbs the liquid to saturation. The volume of the water-based liquid reaches more than 25% of the total volume of the ceramsite. Step S3: The ceramsite soaked in step S2 is grouped according to its size, and the grouped ceramsite is placed in a freezer to freeze the outer liquid and lock in the inner liquid. Step S4: Place the frozen ceramsite from step S3 into a high-temperature resistant net and immerse it in molten metal. After the surface is coated with a metal shell, remove the ceramsite to obtain liquid-coated granules. Step S5: The liquid-coated particles obtained in step S4 are subjected to post-processing. The adhered artificial aggregates are cut and separated. The defects of the metal shell are reduced by tempering. The obtained ceramsite is subjected to heating test and pressure test. Qualified products are screened to obtain artificial aggregates.

6. The preparation method according to claim 5, characterized in that, Step S3 includes: The size groups are separated by a radius difference of 0.5 mm; and the average radius R of each group is determined in advance through experiments. 平均 The freezing time T that allows the outer layer of liquid to freeze while the inner layer remains unfrozen. 冷冻 (R 平均 To prevent the entire liquid from freezing and cracking, thus damaging the porous structure, the unified freezing time for this group was set as T. 冷冻 (R 平均 ).

7. The preparation method according to claim 5, characterized in that, Step S4 includes: Based on the different size groups, the average radius R corresponding to each group is determined in advance through experiments. 平均 Minimum soaking time T for ceramsite 浸泡 (R 平均 To ensure that its surface is covered with a metal shell of thickness t; the uniform immersion time for this group is taken as T. 浸泡 (R 平均 ).

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