A radiation-shielding aggregate, its preparation method, and high-strength, crack-resistant, radiation-shielding concrete.

Abstract

This invention discloses a radiation-shielding aggregate, its preparation method, and a high-strength, crack-resistant, radiation-shielding concrete, belonging to the field of concrete technology. The process includes the following steps: S1. Mixing lead powder, iron ore powder, and barium cement evenly, adding hydrogen peroxide and water, granulating, and curing and heating at high temperature to obtain the aggregate core; S2. Immersing the aggregate core in a mixed solution of sodium alginate and boron fiber, then spraying it with a calcium chloride aqueous solution to obtain aggregate particles; S3. Mixing red mud and graphite powder evenly, calcining at 800-900℃, grinding and sieving, mixing evenly with an alkaline activator, adding water to obtain a slurry, then mixing the slurry with the aggregate particles, and molding to obtain the final product. The radiation-shielding aggregate of this invention can attenuate the radiation energy gradient, exhibiting excellent deceleration, weakening, and absorption effects on radiation rays. Simultaneously, the radiation-shielding aggregate of this invention has relatively low apparent density and high strength, which can prevent concrete segregation and improve the workability and mechanical properties of concrete.

Description

Technical Field

[0001] This invention belongs to the field of concrete technology, specifically relating to a radiation-shielding aggregate and its preparation method, and high-strength, crack-resistant, radiation-shielding concrete. Background Technology

[0002] With the development of the nuclear industry, nuclear technology is increasingly widely used in energy, agriculture, military, and medical fields. Nuclear facilities such as nuclear reactors and high-energy particle accelerators generate highly penetrating radiation during operation. People working in such environments for extended periods can suffer radiation damage, leading to a decline in the human immune system. Therefore, when constructing buildings with radiation sources, proper shielding is essential. Nuclear radiation generally includes alpha, beta, gamma, X-rays, and neutrons. Alpha, beta, and X-rays have low transmission capabilities and are easily absorbed, so they are not the primary targets for protection. Gamma rays and neutrons are the most important targets for radiation protection. Gamma rays are high-energy, high-frequency electromagnetic waves composed of strong photon streams, with extremely strong penetrating power. Shielding against gamma rays typically uses materials with high atomic numbers and high densities. Neutrons are also uncharged and have extremely strong penetrating power. Lighter elements have a higher neutron absorption cross-section, increasing the probability of reaction with neutrons. Materials with a high hydrogen content are commonly used as neutron absorbers.

[0003] Radiation-shielding concrete, as a radiation shielding material, has been applied in nuclear power plants, medical buildings for radiation therapy, nuclear research facilities, and the storage of radioactive waste. Compared with radiation shielding materials such as steel plates and lead plates, radiation-shielding concrete has a series of advantages, including high technical and economic benefits, good structural characteristics, and excellent radiation shielding effect. Currently, there are two main technologies for large-volume radiation-shielding concrete: one is to select high-density aggregates such as magnetite, limonite, or barite to increase the apparent density of the concrete and use the material properties to shield radiation. However, these coarse aggregates are heavy and have relatively low strength, leading to easy segregation and poor mechanical properties in the concrete. The other is to use high-performance concrete to improve the density and crack resistance of the concrete. However, since high-density materials are not selected, the main method of radiation shielding relies on increasing the thickness of the concrete slab. Due to the increased structural volume, the internal temperature of the concrete rises during construction, which easily leads to temperature cracks. Moreover, radiation-shielding concrete is mostly used in high-temperature environments, which can easily cause the concrete to crack during operation, thus directly reducing the radiation shielding capacity of the concrete.

[0004] The current common problem is that most radiation-shielding concrete is based on high-density aggregates such as barite, resulting in heavy concrete structures, easy segregation, and generally poor radiation protection. Therefore, there is an urgent need to develop a radiation-shielding aggregate that can improve the radiation resistance of concrete while reducing its weight, solving the problem of easy segregation, and improving the workability and mechanical properties of concrete. Summary of the Invention

[0005] In view of the shortcomings of the prior art, one of the objectives of this invention is to provide a method for preparing radiation-shielding aggregate. The radiation-shielding aggregate prepared by this invention can attenuate the radiation energy gradient and has excellent deceleration, weakening and absorption effects on radiation rays. In addition, the radiation-shielding aggregate prepared by this invention has the characteristics of relatively low apparent density and high strength, which can avoid segregation and stratification of concrete and improve the workability and mechanical properties of concrete.

[0006] To achieve the above objectives, the specific technical solution of the present invention is as follows:

[0007] A method for preparing radiation-shielding aggregate includes the following steps:

[0008] S1. After mixing lead powder, iron ore powder and barium cement evenly, add hydrogen peroxide and water, mix evenly and then granulate. The wet particles are steam cured and heated at high temperature to obtain the aggregate core.

[0009] S2. The aggregate core obtained in step S1 is immersed in a mixed solution of sodium alginate and boron fiber, and then sprayed with calcium chloride aqueous solution to obtain aggregate particles.

[0010] S3. After mixing red mud and graphite powder evenly, calcining at 800~900℃, grinding and sieving to obtain powder, mixing the powder evenly with alkaline activator, adding water to obtain slurry, then mixing the slurry with the aggregate particles obtained in step S2, molding the aggregate and curing it to obtain the radiation-proof aggregate.

[0011] Lead (Pb) powder is a high-density material with excellent deceleration, refraction, and absorption capabilities for gamma rays. Iron ore powder contains a large amount of iron oxide, which has good absorption capabilities for gamma rays and strong elastic scattering capabilities for neutron radiation (which can be used to scatter and dissipate neutron radiation that penetrates the middle layer of aggregates), while also improving the strength of the core aggregate. Barium ions in barium cement have good radiation protection capabilities. Barium cement and water form a binding agent, which acts as a binder for lead powder and iron ore powder, further improving the strength of the core aggregate. At the same time, it provides an alkaline environment, and hydrogen peroxide decomposes in the alkaline environment to produce oxygen (O2) gas. The gas is interconnected and steam-cured and shaped. After high-temperature evaporation, a porous structure is formed inside the aggregate. The pores are randomly and irregularly distributed, which can effectively reduce the self-weight of the aggregate and reduce segregation of radiation-proof concrete. This invention utilizes lead powder, iron powder, and barium cement to prepare a high-density aggregate core with irregular channels. When radiation enters the concrete, low-, medium-, and some high-energy radiation rays can be absorbed by other auxiliary materials or aggregate layers, while higher-energy gamma and neutron rays enter the aggregate interior. The irregular channels with a certain degree of roughness cause the rays to be reflected in different directions. On the one hand, this prolongs the path length of the radiation inside the aggregate, increasing the energy attenuation of the rays. On the other hand, the radiation is reflected and refracted multiple times at different angles and on the surface. Each reflection reduces the energy, eventually reducing the energy of the rays until they are absorbed and cannot penetrate the aggregate smoothly.

[0012] Sodium alginate is rich in hydrogen, with each carbon atom in its molecule bonded to several hydrogen atoms. Besides the main chain of the sugar molecule, it also contains many hydroxyl groups (-OH). Sodium alginate possesses excellent water absorption and gelling properties; it reacts with calcium ions to form a gel and retain moisture. Due to the abundant hydrogen in sodium alginate and the absorbed water (H), the hydrogen nucleus and neutron have equal mass, resulting in a significantly reduced neutron velocity upon collision, converting rapid neutrons into thermal neutrons. Simultaneously, the boron (B) element introduced from the boron fibers can capture thermal neutrons, absorbing them and converting them into other particles, thus effectively reducing and absorbing neutron radiation energy. The intermediate structural layer of the aggregate serves to bond the upper and lower aggregate layers, buffer stress, and provide curing. Sodium alginate solution reacts with calcium chloride to form calcium alginate gel. Its three-dimensional network structure provides a certain degree of bonding and reinforcement. Simultaneously, boron fibers distributed within the gel can insert into the core layer of the radiation-shielding aggregate (the gel penetrates the pores of the core layer, and the fibers subsequently insert into the core layer) and the outer structure, acting as an interlocking connection between the upper, middle, and lower layers, effectively improving the interlayer bonding and strength of the aggregate structure. Furthermore, the calcium alginate gel possesses a certain degree of flexibility and elasticity, helping to disperse stress in the inner and outer layers, reducing shrinkage stress that could lead to aggregate cracking or deformation. In addition, the sodium alginate gel can slowly release water through its gel network structure in the later stages, enhancing the hydration of the barium cement in the core layer and the hydration of the geopolymer in the outer layer, effectively improving the overall strength of the aggregate.

[0013] Red mud contains relatively abundant silica, alumina, and iron oxide. During high-temperature calcination, graphite is added as a reducing agent, reacting with the iron oxides in the red mud to reduce iron ions and produce metallic iron. This enhances the outer layer of the aggregate's ability to block radiation. Simultaneously, some graphite is retained in the calcined red mud; its layered and crystalline structure allows it to effectively absorb and scatter radiation, especially gamma rays and neutron rays, slowing their penetration depth. The activity of the red mud is significantly enhanced after high-temperature calcination. Reacting it with an alkali activator to prepare a geopolymer cementitious material forms the outermost coating layer of the aggregate, improving its density and strength. Furthermore, when the aggregate is added to concrete, the alkali activator in the outermost layer also acts as an activator, effectively strengthening the transition zone between the radiation-shielding aggregate and the cementitious base, improving the overall density and mechanical properties of the concrete.

[0014] Preferably, in step S1, the mass ratio of lead powder, iron ore powder and barium cement is (70~75):(5~10):(10~15).

[0015] Preferably, the mass of the hydrogen peroxide is 3% to 5% of the total mass of lead powder, iron ore powder, and barium cement.

[0016] Preferably, in step S1, the high-temperature heating temperature is 200~300℃ and the time is 20~40min.

[0017] Preferably, in step S2, the mass ratio of sodium alginate, water, and boron fiber in the mixed solution is (1~2):30:2.

[0018] Preferably, in step S2, the boron fiber has a boron content of 35%-40%, a length of 2-3 mm, a diameter of 5-10 μm, and a tensile modulus of 300-400 GPa.

[0019] Preferably, in step S3, the mass ratio of red mud to graphite powder is 10:(0.5~2).

[0020] Preferably, in step S3, the mass of the alkaline surfactant is 7% to 8% of the powder mass.

[0021] Preferably, the alkaline activator includes Na2SiO3 and NaOH.

[0022] Another object of the present invention is to provide a radiation-shielding aggregate prepared by the preparation method described above, wherein the apparent density of the radiation-shielding aggregate is 2800~3000 kg / m³.

[0023] In view of the problems that most existing radiation-shielding concrete technologies are based on high-density aggregates such as barite, the concrete structure is heavy, the radiation protection effect is generally poor, and it is impossible to take into account shielding performance, working and mechanical properties, and crack resistance. Another objective of this invention is to provide a high-strength crack-resistant radiation-shielding concrete made of the aforementioned radiation-shielding aggregate, comprising the following components in parts by weight: 300-350 parts cement, 50-60 parts fly ash, 40-50 parts lithium slag powder, 500-600 parts sand, 150-200 parts xenotime ore sand, 220-260 parts radiation-shielding aggregate, 810-850 parts crushed stone, 2-4 parts brucite composite fiber, 6-9 parts water-reducing agent, and 155-170 parts water; wherein the brucite composite fiber is obtained by melting, extruding, and spinning brucite fiber, polyethylene, and nano-tungsten oxide.

[0024] This invention uses lithium slag powder, yttrium phosphate sand, and radiation-resistant aggregate to form a multi-level radiation energy attenuation protection system. At the same time, it combines magnesia composite fiber to enhance radiation protection and crack resistance and toughening effect. This comprehensively improves the radiation protection performance of concrete while taking into account its workability, mechanical properties and crack resistance, which can effectively improve the safety of radiation protection engineering structures and extend their service life.

[0025] Lithium slag contains relatively abundant lithium oxide and silicon dioxide. When added to concrete, the silicate components in lithium slag react with calcium hydroxide to generate more hydrated calcium silicate, thereby improving the density and strength of the concrete. Lithium slag contains lithium (Li), and when the lithium isotope (Li-6) reacts with neutrons, it absorbs neutrons and converts them into tritium (T) and helium-4 (He-4), thus absorbing neutron radiation. Lithium slag has a porous structure and readily absorbs water. When added to concrete as an admixture, it absorbs and stores water, which serves two purposes: firstly, it provides internal curing and enhances the strength of the concrete; secondly, the porous structure formed in the cementitious material increases the total water content of the concrete to a certain extent, and the hydrogen atoms in the water can collide with neutrons, effectively slowing down their velocity.

[0026] Yttrium phosphate sand forms cement-based mortar that coats coarse aggregates and fills pores. Yttrium phosphate has a high density, which increases the density of cement paste, reduces the density difference between radiation-shielding aggregates and cement paste, and lowers the segregation rate of concrete mixtures. Simultaneously, the phosphate minerals abundant in Yttrium phosphate can react with calcium hydroxide in concrete to form calcium phosphate minerals, enhancing the cohesion and strength of the concrete. Yttrium phosphate is also rich in yttrium (Y, atomic number 39) and rare earth elements such as cerium and lanthanum. The nuclei of these high atomic number elements can effectively weaken the radiation intensity of gamma rays and X-rays through Compton scattering and the photoelectric effect. Furthermore, the rare earth oxides in Yttrium phosphate can absorb some neutron energy through nuclear reactions and by slowing down neutrons, thereby reducing their penetrability.

[0027] This invention utilizes brucite fiber, polyethylene, and nano-tungsten oxide to prepare a brucite composite fiber with high strength, toughness, crack resistance, water dispersibility, and radiation resistance, effectively improving the mechanical, crack-resistant, and radiation-resistant properties of concrete. Brushcite fiber exhibits good strength, water dispersibility, and alkali resistance, and has excellent compatibility with cement-based materials. Furthermore, the high hydrogen content in brucite fiber further enhances the neutron radiation protection of concrete. Polyethylene (PE) possesses good toughness and ductility, improving the toughness and fracture resistance of the composite fiber, compensating for the brittleness of brucite fiber, and enhancing the overall ductility and fatigue resistance of the composite fiber. Simultaneously, the molecular structure of polyethylene is mainly composed of CH bonds, with a high hydrogen content, further supplementing the hydrogen content in the composite fiber. Tungsten oxide has a high electronic band gap; when exposed to radiation, the generation and migration of electron-hole pairs help disperse and slow down the energy transfer of radiation. Simultaneously, the ultra-high surface area, surface energy, and density of nano-tungsten oxide increase the interface with radiation rays, achieving efficient absorption of radiation through the photoelectric effect and Compton scattering.

[0028] Preferably, the brucite composite fiber has a diameter of 40~50μm, a length of 15~25mm, a tensile strength of 320~350MPa, and a Young's modulus of 2.5GPa~2.7Gpa.

[0029] Preferably, the preparation method of the magnesia composite fiber is as follows: nano-tungsten oxide is pretreated with a silane coupling agent and set aside; polyethylene particles are heated to a molten state, and then magnesia fiber and pretreated nano-tungsten oxide are added, mixed evenly, and then extruded, spun, and cooled to obtain the magnesia composite fiber.

[0030] More preferably, the mass ratio of the magnesium hydroxide fiber, polyethylene and nano-tungsten oxide is (50~70):(35~45);(15~25).

[0031] Compared with the prior art, the advantages of the present invention are:

[0032] (1) The radiation-shielding aggregate prepared by the present invention has a three-layer structure, which can attenuate the energy of radiation rays in layers and ultimately absorb the radiation energy. The core of the aggregate has irregular channels, which can reflect the high-energy gamma and neutron rays that ultimately enter the interior of the aggregate in different directions. By extending the path, attenuating the energy, and ultimately absorbing the radiation, the middle layer is based on the rich hydrogen element of sodium alginate itself and the H element of absorbed water. At the same time, boron fibers are introduced to reduce the absorption of neutron radiation energy and play a role in bonding the upper and lower layers of the aggregate, buffering stress and curing. The outermost layer is wrapped with red mud geopolymer. The metallic iron produced by the calcination and reduction of red mud and the graphite added in the process improve the weakening and absorption of radiation rays in the outermost layer, while improving the density and strength of the aggregate and strengthening the transition zone between the aggregate and the cementitious base.

[0033] (2) The present invention uses lithium slag to improve the density and strength of concrete, which has the effect of internal curing. At the same time, the lithium slag itself and the pore structure formed in the concrete to increase the water content can both slow down neutron rays. Yttrium phosphate sand reduces the segregation rate of the mixture of radiation-proof aggregate concrete, enhances the cohesion, density and strength of concrete. At the same time, yttrium phosphate is rich in rare earth elements such as yttrium and cerium, which can weaken the intensity of γ radiation and slow down neutrons. The brucite composite fiber has a series of characteristics such as high strength, toughness and radiation resistance. While improving the mechanical and crack resistance of concrete, it is cross-distributed in the concrete to further improve the radiation protection performance.

[0034] (3) In this invention, radiation protection design is carried out in cementitious materials, sand and aggregates. A multi-level radiation energy attenuation protection system is formed by using lithium slag powder, yttrium phosphate sand and radiation-proof aggregates. At the same time, the radiation protection and crack resistance are enhanced by the use of magnesia composite fiber. The radiation protection performance of concrete is comprehensively improved while taking into account its workability, mechanical properties and crack resistance. Detailed Implementation

[0035] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] The method for preparing the radiation-shielding aggregate of the present invention includes the following steps:

[0037] S1. After mixing lead powder, iron ore powder and barium cement evenly, add hydrogen peroxide and water, mix evenly and then granulate. The wet particles are steam cured and heated at high temperature to obtain the aggregate core.

[0038] S2. The aggregate core obtained in step S1 is immersed in a mixed solution of sodium alginate and boron fiber, and then sprayed with calcium chloride aqueous solution to obtain aggregate particles.

[0039] S3. After mixing red mud and graphite powder evenly, calcining at 800~900℃, grinding and sieving to obtain powder, mixing the powder evenly with alkaline activator, adding water to obtain slurry, then mixing the slurry with the aggregate particles obtained in step S2, molding the aggregate and curing it to obtain the radiation-proof aggregate.

[0040] In the embodiments and comparative examples of this invention, the lead powder has a particle size of 20-45 μm and a lead content of ≥99%; the iron ore powder has an iron content of ≥70% and a specific surface area of ​​2000-2500 cm². 2 / g; the density of barium cement is 3.5~3.7g / cm³. 3 The composition of the red mud includes: barium sulfate content ≥90%; boron fiber with boron content of 35%-40%, length of 2-3mm, diameter of 5-10μm, and tensile modulus of 300-400GPa; red mud composition of SiO2≥20%, Fe2O3≥30%, Al2O3≥20%, and TiO2≥5%; brucite fiber produced by Jihong Mineral Products Processing Plant in Lingshou County, Hebei Province, with tensile strength of 892.4~1283.7MPa; silane coupling agent KH570 produced by Guangzhou Yihuisheng Chemical Co., Ltd.; nano tungsten oxide particles with a particle size of 40~50nm produced by Shanghai Pantian Powder Materials Co., Ltd.; polyethylene particles with a particle size of 35~50μm produced by Taixing Chunfen Plastic Products Co., Ltd.

[0041] The high-strength, crack-resistant, and radiation-proof concrete of the present invention comprises the following components in parts by weight: 300-350 parts cement, 50-60 parts fly ash, 40-50 parts lithium slag powder, 500-600 parts sand, 150-200 parts xenotime ore sand, 220-260 parts radiation-proof aggregate, 810-850 parts crushed stone, 2-4 parts brucite composite fiber, 6-9 parts water-reducing agent, and 155-170 parts water; wherein the brucite composite fiber is obtained by melting, extruding, and spinning brucite fiber, polyethylene, and nano-tungsten oxide.

[0042] The cement used is ordinary Portland cement P•O 42.5; the fly ash is Grade I fly ash; and the specific surface area of ​​the lithium slag is 400~500 m². 2 / kg; the fineness modulus of natural sand is 2.8~3.2; the fineness modulus of yttrium phosphate sand is 1.4~2.5; the water-reducing agent is polycarboxylate water-reducing agent, with a water reduction rate of 35% and a solid content of 37%.

[0043] Example 1

[0044] This embodiment provides a method for preparing radiation-shielding aggregate, including the following steps:

[0045] S1. Lead powder, iron ore powder and barium cement are mixed evenly in a mass ratio of 70:10:15 to obtain a mixed powder. 5% hydrogen peroxide and 15% water by mass of the mixed powder are added and mixed evenly. The mixture is then granulated to prepare spherical wet particles with a particle size of 2~8mm. The wet particles are then steam-cured at 80℃ for 10h, and then heated at 200℃ for 30min. After being removed and cooled to room temperature, the aggregate core is obtained.

[0046] S2. The aggregate core obtained in step S1 is immersed in a mixed solution of sodium alginate and boron fiber for 30 minutes. The mass ratio of sodium alginate, water and boron fiber in the mixed solution is 2:30:2. After taking it out, it is sprayed with 0.5wt% calcium chloride solution. The mass ratio of calcium chloride solution to aggregate core is 100:1. Then it is left to stand at room temperature for 30 minutes to obtain aggregate particles with a particle size of 3~10mm.

[0047] S3. Mix red mud and graphite powder evenly at a mass ratio of 10:1, calcine in a 900℃ high-temperature furnace for 100 minutes, cool and grind into uniform powder with a particle size of less than 75μm, then mix the powder with 8% of the powder mass of alkaline activator evenly, add 40% of the powder mass of water, stir evenly to obtain a slurry, the alkaline activator is composed of NaOH and Na2SiO3 at a mass ratio of 1:5; then mix the slurry with the aggregate particles obtained in step S2, use a pelletizing machine to form aggregate, let stand for 1 day, and then cure under standard curing environment for 7 days to obtain radiation-resistant aggregate with a particle size of 5-20mm.

[0048] Example 2

[0049] This embodiment provides a method for preparing radiation-shielding aggregate, including the following steps:

[0050] S1. Lead powder, iron ore powder and barium cement are mixed evenly in a mass ratio of 75:5:10 to obtain a mixed powder. 3% hydrogen peroxide and 10% water by mass of the mixed powder are added and mixed evenly. The mixture is then granulated to prepare spherical wet particles with a particle size of 2~8mm. The wet particles are then steam-cured at 90℃ for 8 hours, and then heated at 300℃ for 20 minutes. After being removed and cooled to room temperature, the aggregate core is obtained.

[0051] S2. The aggregate core obtained in step S1 is immersed in a mixed solution of sodium alginate and boron fiber for 20 minutes. The mass ratio of sodium alginate, water and boron fiber in the mixed solution is 1:30:2. After taking it out, it is sprayed with a 1.0 wt% calcium chloride solution. The mass ratio of calcium chloride solution to aggregate core is 80:1. Then it is left to stand at room temperature for 20 minutes to obtain aggregate particles with a particle size of 3~10 mm.

[0052] S3. Mix red mud and graphite powder evenly at a mass ratio of 10:2, calcine in a high-temperature furnace at 800℃ for 120 minutes, cool and grind into uniform powder with a particle size of less than 75μm, then mix the powder with 7% of the powder mass of alkaline activator evenly, add 38% of the powder mass of water, stir evenly to obtain a slurry, the alkaline activator is composed of NaOH and Na2SiO3 at a mass ratio of 1:6; then mix the slurry with the aggregate particles obtained in step S2, use a pelletizing machine to form aggregate, let stand for 1 day, and then cure under standard curing environment for 4 days to obtain radiation-resistant aggregate with a particle size of 5-20mm.

[0053] Comparative Example 1

[0054] The preparation method of the comparative radiation-shielding aggregate is basically the same as that of Example 1, except that step S1 is as follows: lead powder, iron ore powder and barium cement are mixed evenly in a mass ratio of 70:10:15 to obtain a mixed powder. Water of 15% by mass of the mixed powder is added and mixed evenly. Spherical wet particles with a particle size of 2~8mm are prepared by granulation. The wet particles are then steam-cured at 80℃ for 10h to obtain the aggregate core.

[0055] Comparative Example 2

[0056] The preparation method of the comparative radiation-shielding aggregate is basically the same as that of Example 1, except that boron powder of the corresponding weight is used to replace boron fibers in step S2.

[0057] Comparative Example 3

[0058] The preparation method of the comparative example radiation-shielding aggregate is basically the same as that of Example 1, except that step S3 is as follows: the aggregate particles obtained in step S2 are mixed with cement paste, the aggregate is formed by pelletizing machine, and after standing for 1 day, it is cured for 7 days under standard curing environment to obtain radiation-shielding aggregate with a particle size of 5-20 mm.

[0059] Referring to GB / T 14685-2022 "Construction Pebbles and Crushed Stone", the crushing value and apparent density of the radiation shielding aggregates in Examples 1-2 and Comparative Examples 1-3 were tested, and the test results are shown in Table 1.

[0060]

[0061] As can be seen from the test results in Table 1, the crushing values ​​of the radiation-shielding aggregates in Examples 1 and 2 are around 6.0% to 6.2%, which are generally low. The aggregates exhibit excellent compressive strength, and their apparent densities are 2880 kg / m³, respectively. 3 and 2910kg / m 3 It is far lower than that of traditional barite (4300-4600 kg / m³). 3The apparent density of magnetite aggregate (5000-5300 kg / m³) and magnetite ore aggregate. 3 In Comparative Example 1, no hydrogen peroxide was added or high-temperature heating was performed during the aggregate preparation process in step S1. As a result, no irregular porous structure was formed inside the aggregate. Although the compressive strength of the aggregate was improved, the apparent density was ultimately 3480 kg / m³. 3 The density of the aggregate in Example 2 was much higher than that in Example 1. Concrete with a higher aggregate density is prone to segregation, which affects the workability and mechanical properties of the concrete. In Comparative Example 2, boron powder was used to replace boron fibers with a corresponding weight. Compared with Example 1, the crushing value increased by 14.5%, but the aggregate strength decreased. This is because the boron powder is distributed in the sodium alginate gel and cannot provide interlayer bonding between the upper and lower layers of the aggregate to enhance the aggregate strength. This also shows that the boron fibers are distributed in the gel and can be inserted into the core layer and outer layer of the radiation-shielding aggregate structure, playing a role in interlocking connection between the upper, middle and lower layers, effectively improving the interlayer bonding and aggregate strength of the aggregate structure.

[0062] Example 3

[0063] This embodiment provides a high-strength, crack-resistant, radiation-proof concrete, comprising the following components in parts by weight: 350 parts cement, 60 parts fly ash, 40 parts lithium slag powder, 600 parts natural sand, 150 parts yttrium phosphate sand, 220 parts radiation-proof aggregate prepared in Example 1, 810 parts crushed stone, 4 parts magnesia composite fiber, 9 parts water-reducing agent, and 170 parts water.

[0064] The preparation method of magnesia composite fiber is as follows: (1) Weigh magnesia fiber, polyethylene particles and nano tungsten oxide in a mass ratio of 60:40:20. Treat the nano tungsten oxide with silane coupling agent KH570 and set aside. Heat the polyethylene particles to a molten state and keep the temperature at 190~200℃. (2) Then add magnesia fiber and nano tungsten oxide to the molten polyethylene. Use a twin-screw extruder to mix them evenly at 200~300 rpm. Push the mixed molten material out of the extruder. The outlet pressure of the extruder is 18~20 MPa. Use spinning technology to stretch it into fibers with a diameter of 40~50μm. Cool the fiber temperature through a cooling water tank to solidify and shape it. Then cut it to a length of 15~25mm to obtain magnesia composite fiber.

[0065] The preparation method of high-strength, crack-resistant, and radiation-proof concrete in this embodiment includes the following steps:

[0066] M1. Weigh each component according to the parts by weight;

[0067] M2. Dry mix radiation-proof aggregate, crushed stone, yttrium phosphate sand, natural sand, cement and fly ash for 10-15 seconds, then add 1 / 2 water-reducing agent and 1 / 2 water, mix for 40-60 seconds, then add lithium slag powder, magnesia composite fiber, the remaining 1 / 2 water-reducing agent and 1 / 2 water, mix evenly for 40-60 seconds to obtain concrete paste.

[0068] In step M2, 1 / 2 water-reducing agent refers to 1 / 2 of the total amount of water-reducing agent, and 1 / 2 water refers to 1 / 2 of the total amount of water.

[0069] Example 4

[0070] The high-strength, crack-resistant, radiation-proof concrete of Example 4 is basically the same as that of Example 3, except that it includes the following components in parts by weight: 300 parts cement, 50 parts fly ash, 50 parts lithium slag powder, 550 parts natural sand, 200 parts yttrium phosphate sand, 260 parts radiation-proof aggregate prepared in Example 1, 850 parts crushed stone, 2 parts magnesia composite fiber, 6 parts water-reducing agent, and 155 parts water.

[0071] Example 5

[0072] The difference between Example 5 and Example 3 is that the radiation-resistant aggregate of Example 2 is used instead of the radiation-resistant aggregate of Example 1.

[0073] Comparative Example 4

[0074] The difference between Comparative Example 4 and Example 3 is that the radiation-resistant aggregate of Comparative Example 1 is used instead of the radiation-resistant aggregate of Example 1.

[0075] Comparative Example 5

[0076] The difference between Comparative Example 5 and Example 3 is that the radiation-resistant aggregate of Comparative Example 2 is used instead of the radiation-resistant aggregate of Example 1.

[0077] Comparative Example 6

[0078] The difference between Comparative Example 6 and Example 3 is that the radiation-resistant aggregate of Comparative Example 3 is used instead of the radiation-resistant aggregate of Example 1.

[0079] Comparative Example 7

[0080] The difference between Comparative Example 7 and Example 3 is that an equal amount of slag powder was used to replace lithium slag powder.

[0081] Comparative Example 8

[0082] The difference between Comparative Example 8 and Example 3 is that an equal amount of brucite fiber was used to replace the brucite composite fiber.

[0083] The workability, mechanical properties, crack resistance and radiation protection properties of the high-strength crack-resistant and radiation-proof concrete of Examples 3-5 and Comparative Examples 4-8 were tested, and the test results are shown in Table 2.

[0084] According to the provisions of GB / T50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures", the workability of fresh concrete in the examples and comparative examples was tested. The larger the slump, the better the fluidity. The mechanical properties of concrete were tested according to GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Ordinary Concrete". The early crack resistance and impermeability of concrete were tested according to GB / T50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete". The early crack resistance of concrete was determined by the "crack resistance plate test". The test results are expressed as the calculated total crack area per unit area index. The smaller the value, the better the crack resistance.

[0085] The radiation protection performance of concrete was tested according to GB 18871-2002 "Basic Standards for Ionizing Radiation Protection and Radiation Source Safety". The linear attenuation coefficients (cm²) of concrete for gamma rays and neutron rays were measured. -1 The larger the linear attenuation coefficient, the better the radiation protection performance of the concrete; gamma ray measuring equipment: nuclear radiation detector; neutron ray measuring equipment: neutron source; irradiation energy 4MeV.

[0086]

[0087] As shown in Table 2, the test results indicate that, in terms of workability, the slump of all examples was greater than or equal to 200 mm, demonstrating high flowability. Furthermore, the cement paste and aggregate in the concrete were tightly bound together, exhibiting good cohesion and no segregation, thus ensuring excellent pumpability. Comparative Example 4 used the radiation-shielding aggregate from Comparative Example 1, which has a relatively high aggregate density of 3480 kg / m³. 3 The concrete slump was 180mm, its fluidity was reduced, and segregation occurred.

[0088] In terms of mechanical properties and crack resistance, the 28-day compressive strength of Examples 3-5 was generally between 56.8 MPa and 57.6 MPa, and the total crack area per unit area was 30-35 mm. 2 / m 2The concrete in Comparative Example 4 exhibited excellent crack resistance; however, Comparative Example 5 showed reduced flowability and segregation, leading to a decrease in both compressive strength and crack resistance of its hardened concrete. Comparative Example 5 showed increased crushing value of the radiation-shielding aggregate, resulting in decreased concrete compressive strength. Compared to Example 3, Comparative Example 6 used a cement-based outer layer for its radiation-shielding aggregate. Because it lacked alkali-activating materials, the transition zone between the aggregate and cement was not effectively strengthened, resulting in a slight decrease in concrete strength. While the pozzolanic activity of the slag powder in Comparative Example 7 was higher than that of lithium slag, lithium slag had a certain internal curing effect, so the compressive strength of the concrete from both examples was not significantly different. Furthermore, excessively high pozzolanic activity would increase the heat of hydration in the concrete, affecting crack resistance. Comparative Example 8 used ordinary magnesia fiber, which had relatively insufficient fiber toughness, resulting in poorer crack resistance compared to Example 3.

[0089] Regarding radiation protection performance, the linear attenuation coefficients for gamma rays and neutron rays in Examples 3-5 ranged from 0.72 to 0.76 cm⁻¹. -1 0.60-0.64cm -1 The concrete exhibited excellent radiation shielding performance. Compared to Example 3, although the radiation-shielding aggregate in Comparative Example 4 was denser, the concrete showed segregation, resulting in reduced density and a decrease in overall radiation shielding performance. The linear attenuation coefficients for γ-rays and neutron rays in Comparative Example 5 were 0.60 cm⁻¹. -1 0.52cm -1 The main reason for the decrease in radiation protection performance of concrete is the reduced density and strength of its radiation-shielding aggregate layers. In Comparative Example 6, the outermost layer of the radiation-shielding aggregate is cement paste. Compared with Example 3, which does not contain iron oxide and graphite anti-gamma-ray radiation materials, the linear attenuation coefficient of gamma rays in the concrete is reduced, while the linear attenuation coefficient of neutron rays does not show a significant decrease. The linear attenuation coefficient of neutron rays in Comparative Example 7 is 20% lower than that in Example 3, indicating that the addition of lithium slag to concrete can effectively slow down and absorb neutron rays. The test results of Comparative Example 8 prove that brucite composite fibers have an improving effect on the crack resistance of concrete, making the concrete more compact and with better radiation protection performance. At the same time, the anti-gamma-ray and neutron ray capabilities of brucite fibers themselves have a significant improving effect on the radiation protection performance of concrete.

[0090] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing radiation-shielding aggregate, characterized in that, Includes the following steps: S1. After mixing lead powder, iron ore powder and barium cement evenly, add hydrogen peroxide and water, mix evenly and then granulate. The wet particles are steam cured and heated at high temperature to obtain the aggregate core. S2. The aggregate core obtained in step S1 is immersed in a mixed solution of sodium alginate and boron fiber, and then sprayed with calcium chloride aqueous solution to obtain aggregate particles. S3. After mixing red mud and graphite powder evenly, calcining at 800~900℃, grinding and sieving to obtain powder, mixing the powder evenly with alkaline activator, adding water to obtain slurry, then mixing the slurry with the aggregate particles obtained in step S2, molding the aggregate and curing it to obtain the radiation-proof aggregate.

2. The method for preparing radiation-shielding aggregate according to claim 1, characterized in that, In step S1, the mass ratio of lead powder, iron ore powder and barium cement is (70~75):(5~10):(10~15).

3. The method for preparing radiation-shielding aggregate according to claim 1, characterized in that, The mass of the hydrogen peroxide is 3% to 5% of the total mass of lead powder, iron ore powder, and barium cement.

4. The method for preparing radiation-shielding aggregate according to claim 1, characterized in that, In step S1, the high-temperature heating temperature is 200~300℃ and the time is 20~40min.

5. The method for preparing radiation-shielding aggregate according to claim 1, characterized in that, In step S2, the mass ratio of sodium alginate, water and boron fiber in the mixed solution is (1~2):30:

2.

6. The method for preparing radiation-shielding aggregate according to claim 1, characterized in that, In step S3, the mass ratio of red mud to graphite powder is 10:(0.5~2).

7. Radiation-shielding aggregate prepared by the preparation method according to any one of claims 1 to 6.

8. A high-strength, crack-resistant, radiation-resistant concrete made from radiation-resistant aggregate prepared by the method according to any one of claims 1 to 6, characterized in that, The components include the following parts by weight: 300-350 parts cement, 50-60 parts fly ash, 40-50 parts lithium slag powder, 500-600 parts sand, 150-200 parts yttrium phosphate sand, 220-260 parts radiation-shielding aggregate, 810-850 parts crushed stone, 2-4 parts magnesia composite fiber, 6-9 parts water-reducing agent, and 155-170 parts water. The brucite composite fiber is obtained by melting, extruding and spinning brucite fiber, polyethylene and nano-tungsten oxide.

9. The high-strength, crack-resistant, radiation-proof concrete according to claim 8, characterized in that, The preparation method of the magnesia composite fiber is as follows: nano-tungsten oxide is pretreated with a silane coupling agent and set aside; polyethylene particles are heated to a molten state, and then magnesia fiber and pretreated nano-tungsten oxide are added, mixed evenly, and then extruded, spun, and cooled to obtain the magnesia composite fiber.

10. A high-strength, crack-resistant, radiation-proof concrete according to claim 9, characterized in that, The mass ratio of the magnesia fiber, polyethylene and nano-tungsten oxide is (50~70):(35~45);(15~25).

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