Preparation method of non-magnetic ceramsite, low-magnetic concrete and preparation method of low-magnetic concrete

Abstract

The invention provides a preparation method of non-magnetic ceramsite, low-magnetic concrete and a preparation method thereof.The non-magnetic ceramsite is prepared by the steps that activated ceramsite is placed in a rare earth ion solution, ferromagnetic ions in the activated ceramsite are replaced through rare earth ion exchange, and modified ceramsite is obtained; the preparation method comprises the following steps: preparing modified ceramsite, soaking the modified ceramsite in nano SiO2 sol to form a nano SiO2 protective layer on the surface of the modified ceramsite, and carrying out aging, gradient drying and calcining treatment to prevent the nano SiO2 coating layer from cracking and falling off. The invention also provides low-magnetism concrete taking the non-magnetic ceramsite as aggregate, the low-magnetism concrete is matched with low-magnetism cement, a water reducing agent and the like, mineral admixtures can be selectively added, and the low-magnetism concrete is prepared through graded dry mixing and batch wet mixing, so that the excellent performance that the residual magnetism intensity is only 1.6 nT and the 28-day compressive strength is greater than 48 MPa is realized; the method is suitable for high-requirement engineering scenes sensitive to magnetic field interference, such as superconducting magnetic suspension guide rails, non-magnetic laboratories, precise instrument bases and the like.

Description

Technical Field

[0001] This invention belongs to the field of building construction technology, specifically relating to a method for preparing non-magnetic ceramsite, low-magnetic concrete and its preparation method. Background Technology

[0002] With the development of modern technology, the construction scale and technical requirements of precision instruments and facilities (such as nuclear magnetic resonance spectrometers and superconducting magnetic levitation equipment), national defense and security engineering (including special protective buildings), and special electromagnetic environment laboratories are constantly being upgraded, placing near-"low magnetic interference" standards on the magnetic background of building structural materials. In these scenarios, even a weak residual magnetic field can lead to deviations in the measurement accuracy of precision instruments, limitations in the performance of national defense equipment, and distortion of experimental data. Therefore, "extremely low magnetic field" has become an indispensable core indicator for such engineering materials.

[0003] However, traditional concrete has always struggled to overcome the magnetic bottleneck because the ordinary silicate cement and natural sand and gravel aggregates it uses generally contain ferromagnetic minerals. These impurities cause residual magnetism in the hardened concrete, making it difficult to meet the needs of highly sensitive electromagnetic environments or special protective engineering projects. Although existing technologies control the magnetic field strength of concrete below 60 nT by using low-magnetic cement and strictly screening aggregate sources, this method is still insufficient in controlling the magnetic sensitivity of the coarse aggregate itself. Natural crushed stone or ordinary ceramsite may contain weakly magnetic minerals such as magnetite and hematite, which limits its use in terms of material sourcing and magnetic stability.

[0004] Expanded clay aggregate, widely recognized as an ideal lightweight aggregate in the construction field, has advantages such as weight reduction, heat insulation, and vibration reduction. However, its application in low-magnetic engineering faces a dilemma: on the one hand, the raw materials for expanded clay aggregate production (such as fly ash and clay) and the calcination process themselves are prone to introducing magnetic impurities (such as fly ash-based expanded clay aggregate containing incompletely converted magnetite phase), resulting in natural expanded clay aggregate or ordinary modified expanded clay aggregate generally having weak magnetism; on the other hand, the modification methods used in existing technologies to endow expanded clay aggregate with electromagnetic shielding function, such as iron powder filling and magnetic coating, will actually greatly enhance its magnetism, which runs counter to the core requirement of low magnetism. Summary of the Invention

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing non-magnetic ceramic particles includes: placing activated ceramic particles in a rare earth ion solution, and replacing ferromagnetic ions in the ceramic particles with rare earth ions through ion exchange to obtain modified ceramic particles; wetting the modified ceramic particles in nano-SiO2 sol, and coating the surface of the modified ceramic particles with the nano-SiO2 sol by stirring; and subjecting the modified ceramic particles coated with the nano-SiO2 sol to aging, drying and calcining treatments in sequence to obtain the non-magnetic ceramic particles.

[0006] In some embodiments, the preparation steps of the rare earth ion solution are as follows: weigh lanthanum nitrate hexahydrate and cerium nitrate hexahydrate, add them to deionized water and dissolve them to obtain the rare earth ion solution; in the rare earth ion solution, La 3+ With Ce 3+ The molar ratio is 1:1, and the total molar concentration of the lanthanum nitrate hexahydrate and the cerium nitrate hexahydrate is 0.8–1.2 mol / L.

[0007] In some embodiments, the solid-liquid ratio of the modified ceramsite to the rare earth ion solution is 1:10 to 1:15 (kg / L).

[0008] In some embodiments, the preparation steps of the nano-SiO2 sol are as follows: Tetraethyl orthosilicate, anhydrous ethanol, and deionized water are weighed in a molar ratio of 1:4:(4~10); the tetraethyl orthosilicate and anhydrous ethanol are mixed in a volume ratio of 1:4 and stirred until clear and homogeneous to obtain solution A; the deionized water and anhydrous ethanol are mixed in a volume ratio of 9:40, and hydrochloric acid or ammonia is added to adjust the pH to obtain solution B; solution B is added dropwise to solution A and stirred until homogeneous, controlling the pH of the mixed solution between 2 and 4; the mixed solution is placed in a water bath at 60~70℃ and refluxed for 1~2 hours to obtain the nano-SiO2 sol, which is slightly turbid or translucent.

[0009] In some embodiments, the thickness of the coating layer formed by the nano-SiO2 sol on the surface of the modified ceramic particles is 200~300nm.

[0010] In some embodiments, the drying process employs a gradient heating process: first, the drying is carried out at 50°C for 2 hours, and then the temperature is increased to 80-100°C for 4 hours; and / or, the calcination temperature is 400-600°C, and the calcination time is 2-4 hours.

[0011] The present invention also provides a low-magnetic concrete, comprising the above-mentioned non-magnetic ceramsite, as well as low-magnetic cement, water-reducing agent and mixing water.

[0012] In some embodiments, the non-magnetic ceramsite includes small-diameter non-magnetic ceramsite and large-diameter non-magnetic ceramsite, wherein the particle size of the small-diameter non-magnetic ceramsite is 0-5 mm and the particle size of the large-diameter non-magnetic ceramsite is 5-20 mm; in each cubic meter of the low-magnetic concrete, the mass of each component is as follows: 200-450 kg of the low-magnetic cement, 600-900 kg of small-diameter non-magnetic ceramsite, 900-1400 kg of large-diameter non-magnetic ceramsite, 4-10 kg of water-reducing agent and 130-180 kg of mixing water.

[0013] In some embodiments, the low-magnetic concrete further includes mineral admixtures, wherein the amount of mineral admixtures in each cubic meter of the low-magnetic concrete is 0 to 100 kg.

[0014] The present invention also provides a method for preparing the above-mentioned low-magnetic concrete, the steps of which include: putting the non-magnetic ceramsite and the low-magnetic cement into a mixer for dry mixing; dissolving the water-reducing agent in the mixing water in advance to form a water-reducing agent solution; adding the water-reducing agent solution into the mixer in 2 to 3 portions for wet mixing; the wet mixing time is not less than 180 seconds, thereby obtaining the low-magnetic concrete.

[0015] Compared with the prior art, the preparation method of non-magnetic ceramsite, low-magnetic concrete and its preparation method provided by the present invention have the following beneficial effects: 1. This invention innovatively employs a dual modification technology of "rare earth ion exchange + SiO2 coating," overcoming the limitations of existing technologies that only reduce magnetism by screening raw materials. Through a high-temperature hydrothermal reaction, rare earth ions are driven to interact with Fe inside and on the surface of the ceramic particles. 2+ / Fe 3+ Ferromagnetic ion replacement destroys the magnetically ordered structure at the atomic level; the outer layer forms a dense nonmagnetic SiO2 protective layer with a thickness of 200~300nm through the sol-gel process. The dual effect achieves the demagnetization of ceramsite, providing core support for low magnetic concrete to finally achieve ultra-low remanent magnetic strength, and completely solves the pain point of ordinary ceramsite introducing magnetic impurities due to raw materials or calcination process. 2. The SiO2 coating layer of the non-magnetic ceramic particles is subjected to gradient drying and calcination at 400~600℃ to form a strong Si-O-Si covalent bond network, which forms a chemical bond with the ceramic particle substrate, effectively avoiding the problem of easy cracking and peeling of the ceramic particle coating layer. 3. The low-magnetic concrete provided by this invention uses non-magnetic ceramsite to replace traditional aggregates, forming a synergistic and compatible low-magnetic cementitious system with low-magnetic cement and mineral admixtures (such as slag powder). The remanence of the final product is only 1.6~2.6 nT, which is far superior to the level of less than 60 nT in the prior art. It can meet the needs of scenarios that are extremely sensitive to the disturbance of the geomagnetic field, such as nuclear magnetic resonance imaging, superconducting magnetic levitation train tracks, and non-magnetic laboratories, and avoid measurement deviations of precision instruments and distortion of experimental data. Detailed Implementation

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the specific implementation methods of the present invention will be described below.

[0017] In the following description of embodiments, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. It should be understood that, as used in this specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, and / or sets thereof.

[0018] References to "one embodiment" or "some embodiments" in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," "in some implementations," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0019] This invention provides a method for preparing non-magnetic ceramic particles, comprising the following steps: modifying activated ceramic particles in a rare earth ion solution, wherein the rare earth ions replace the ferromagnetic ions in the ceramic particles to obtain modified ceramic particles; fully impregnating the modified ceramic particles in nano-SiO2 sol, stirring to ensure complete surface coating of the modified ceramic particles; and then subjecting the modified ceramic particles coated with nano-SiO2 sol to aging, drying, and calcining sequentially to obtain non-magnetic ceramic particles.

[0020] The specific steps include: S1. Screening and Cleaning of Expanded Ceramsite: First, according to the concrete aggregate gradation design requirements, the raw expanded ceramsite is graded and screened to accurately select qualified expanded ceramsite of different particle sizes, ensuring that the aggregate gradation meets the proportion requirements for subsequent concrete preparation. Then, the screened expanded ceramsite is placed in deionized water and treated with ultrasonic cleaning for 15-20 minutes. The cavitation effect of ultrasound efficiently removes dust, loose debris, and trace impurities adhering to the surface of the expanded ceramsite, clearing surface obstacles for subsequent acid washing, activation, and modification treatments.

[0021] S2. Acid washing and activation of ceramsite: After screening and cleaning, the raw ceramsite is completely immersed in dilute nitric acid (recommended concentration: 1 mol / L) or dilute hydrochloric acid solution for 1-2 hours at room temperature. On the one hand, the acid solution dissolves and removes stubborn impurities, oxide layers, and trace ferromagnetic deposits from the surface of the ceramsite, further purifying the aggregate surface. On the other hand, the acid etching activates the surface structure of the ceramsite, promoting the generation of more hydroxyl (-OH) active groups on its surface, creating sufficient active sites for subsequent rare earth ion exchange reactions, and improving the efficiency and uniformity of ion exchange.

[0022] After pickling, the ceramsite is repeatedly rinsed with a large amount of deionized water, and the pH value of the effluent is continuously monitored until the effluent is neutral to ensure that the residual acid and reaction products on the surface of the ceramsite are completely removed, so as to avoid secondary reactions during subsequent modification.

[0023] The washed ceramsite is transferred to a forced-air drying oven and dried at 105±5℃ for 2-4 hours to completely remove the free moisture from the internal pores and surface of the ceramsite, resulting in a dry, clean ceramsite substrate with sufficient surface activity, which is then ready for subsequent modification treatment.

[0024] S3, rare earth ion modification Weigh out a certain mass of lanthanum nitrate hexahydrate (La(NO3)3·6H2O) and cerium nitrate hexahydrate (Ce(NO3)3·6H2O), and prepare a mixed rare earth ion solution using deionized water as the solvent. In the rare earth ion solution, La... 3+ With Ce 3+ The molar ratio of La(NO3)3·6H2O and Ce(NO3)3·6H2O in the solution is 1:1. At the same time, the total molar concentration of La(NO3)3·6H2O in the solution is adjusted to be in the range of 0.8~1.2 mol / L, and the mixture is stirred until the solute is completely dissolved to ensure uniform ion distribution.

[0025] The dried ceramsite obtained in step S2 is completely immersed in the prepared rare earth ion solution, and the solid-liquid ratio is controlled at 1:10~1:15 (kg / L) to ensure that the ceramsite and the rare earth ion solution are in full contact.

[0026] The mixture of ceramsite and exchange solution was then transferred to a high-pressure reactor lined with polytetrafluoroethylene (PTFE). The reactor was sealed to ensure a leak-free reaction system. The reactor was then placed in a forced-air drying oven and reacted at a constant temperature of 150–180°C for 12 hours to obtain modified ceramsite. This was achieved by driving the La... 3+ Ce 3+ Fe inside the ceramsite 2+ / Fe 3+ When ferromagnetic ions undergo efficient exchange, their magnetically ordered structure is destroyed at the source.

[0027] S4, nano-SiO2 outer coating S41. Preparation of nano-SiO2 sol According to the following order: tetraethyl orthosilicate (TEOS): anhydrous ethanol (EtOH): deionized water ( Weigh out the above raw materials in a molar ratio of 1:4:(4~10).

[0028] Measure TEOS and anhydrous ethanol in a volume ratio of 1:4. Slowly pour TEOS into the anhydrous ethanol and stir continuously until the mixture is uniform and transparent to obtain solution A.

[0029] In a separate clean container, add deionized water and anhydrous ethanol in a volume ratio of 9:40. After stirring and mixing, add a small amount of 0.1 mol / L hydrochloric acid or ammonia as a catalyst dropwise. Fine-tune the pH value of the system according to the reaction requirements to obtain solution B.

[0030] Under high-speed and vigorous stirring, solution B is slowly added dropwise to solution A. During the addition process, the pH value of the solution system is controlled in the acidic range of 2 to 4. The acid catalysis promotes the hydrolysis and condensation reaction of TEOS to form a dense and uniform thin-layer coating film.

[0031] After the addition is complete, place the mixed solution in a 60-70℃ water bath and continue stirring and reflux for 1-2 hours, continuously observing the solution state. When the mixed solution becomes slightly turbid or translucent, it indicates that a stable nano-SiO2 sol has been successfully prepared. Stop the reaction and... Cool the sol to room temperature.

[0032] S42, outer coating of expanded clay aggregate The modified ceramsite obtained in step S3 is completely immersed in the nano-SiO2 sol prepared in step S41, ensuring that the sol completely covers the ceramsite, and soaked for 10-30 minutes. During soaking, the ceramsite is gently stirred every 5-10 minutes to effectively remove air from the internal pores and surface of the ceramsite, allowing the nano-SiO2 sol to fully penetrate into the depths of the pores of the modified ceramsite, ensuring the integrity and uniformity of the coating.

[0033] After soaking, remove the impregnated modified ceramsite and transfer it to a roller coating machine or a customized uniform rotating device. Adjust the rotation speed of the device to 20-30 rpm to continuously and gently tumble the ceramsite with nano-SiO2 sol on the surface, allowing excess nano-SiO2 sol to flow and spread evenly along the surface of the ceramsite, avoiding localized liquid accumulation that could lead to uneven coating thickness.

[0034] Continue rolling for about 1 hour until the nano-SiO2 sol on the surface of the modified ceramic particles is semi-dry and has no obvious adhesion, thus initially completing the coating.

[0035] The thickness of the nano-SiO2 sol coating layer is 200~300nm.

[0036] S43. Post-treatment: The preliminarily coated modified ceramic particles are then transferred to a sealed container with a lid and allowed to stand for aging at room temperature for 6 hours to promote further condensation and cross-linking of the gel network, thereby enhancing the structural integrity and mechanical stability of the coating layer.

[0037] After aging, the expanded clay aggregates are evenly spread on a tray and dried using a gradient temperature process: first, they are dried at 50℃ for 2 hours to slowly remove free solvent from the surface; then, the temperature is raised to 80~100℃ and dried continuously for 4 hours to completely remove residual moisture from the coating layer and the pores of the expanded clay aggregates. By gradually increasing the temperature, cracking and peeling of the coating layer due to rapid solvent evaporation can be avoided, ensuring the stability of the coating structure.

[0038] Subsequently, the dried ceramic particles were transferred to a muffle furnace for calcination: the temperature was increased to the target temperature of 400-600℃ at a rate of 1-2℃ / min, held for 2-4 hours, and then naturally cooled to room temperature with the furnace to obtain the non-magnetic ceramic particles. During calcination, not only were organic residues, physically adsorbed water, and residual solvents in the gel completely removed, but the formation of the Si-O-Si covalent network was also promoted, causing the amorphous nano-SiO2 coating layer to undergo a densification transformation. Simultaneously, a strong chemical bond was formed with the ceramic particle substrate, significantly improving the adhesion and weather resistance of the coating layer.

[0039] After the muffle furnace cools to room temperature, the non-magnetic ceramic particles are removed and repeatedly rinsed with deionized water. The conductivity of the washing solution is monitored in real time until it is essentially the same as that of the deionized water, ensuring thorough removal of physically adsorbed rare earth ions and other soluble impurities from the ceramic particle surface. Finally, the cleaned ceramic particles are placed in a forced-air drying oven and dried at 80-100℃ for 4-6 hours to completely remove pores and residual moisture from the surface, resulting in dense, stable, non-magnetic modified ceramic particles for later use.

[0040] Furthermore, based on the aforementioned non-magnetic ceramsite, the present invention also provides a low-magnetic concrete, comprising the aforementioned non-magnetic ceramsite, low-magnetic cement, polycarboxylate superplasticizer, and mixing water. The non-magnetic ceramsite replaces conventional aggregates in traditional concrete formulations and is classified into two categories based on particle size: small-diameter non-magnetic ceramsite and large-diameter non-magnetic ceramsite. Small-diameter non-magnetic ceramsite is continuously graded non-magnetic ceramsite with a particle size of 0-5 mm, serving as the fine aggregate in low-magnetic concrete; large-diameter non-magnetic ceramsite is continuously graded non-magnetic ceramsite with a particle size of 5-20 mm, serving as the coarse aggregate in low-magnetic concrete.

[0041] The mass of each component in low-magnetic concrete, calculated per cubic meter, is as follows: Low-magnetic cement 200~450kg Small-diameter non-magnetic ceramic aggregates, 600~900 kg Large-diameter non-magnetic ceramic granules: 900~1400 kg 4~10kg of polycarboxylate superplasticizer Mixing water 130~180kg The aforementioned low-magnetic cement is white silicate cement.

[0042] In some embodiments, low-magnetic concrete may also contain mineral admixtures, preferably at least one of fly ash and slag powder. The amount of mineral admixture is 0-100 kg per cubic meter of the low-magnetic concrete.

[0043] The preparation process of the above-mentioned low-magnetic concrete is as follows: Add the measured small-diameter and large-diameter non-magnetic ceramic granules into the mixer and dry mix for 30 seconds to ensure they are evenly mixed.

[0044] Add low-magnetic cement and non-magnetic mineral admixtures (add as needed or not), and continue dry mixing for 60 seconds to ensure that all solid materials are evenly distributed.

[0045] Dissolve the polycarboxylate superplasticizer in the mixing water beforehand, and add it slowly and evenly to the mixer in 2-3 batches during the mixing process.

[0046] Keep stirring and control the wet mixing time to be no less than 180 seconds until the mixture is uniform in color and texture, ensuring that all the ceramsite surfaces are fully coated with the slurry and that the overall mixture has no bleeding or segregation.

[0047] The performance of the low-magnetic concrete provided by the present invention will be further described in detail below with reference to the embodiments.

[0048] Example 1: This example provides a low-magnetic concrete that combines excellent load-bearing performance with anti-magnetic interference characteristics. It is suitable for precision engineering structures that need to withstand certain loads and are sensitive to magnetic field environments. Typical application scenarios include the sidewalls of superconducting magnetic levitation train guide rails and non-magnetic laboratory flooring.

[0049] The mass of each component in low-magnetic concrete, calculated per cubic meter, is as follows: Low-magnetic cement: 320kg Mineral admixture: 100kg (using S95 grade slag powder; the addition of mineral admixture can partially replace cement, effectively reducing heat of hydration and minimizing the risk of magnetic fluctuations in large-volume concrete caused by temperature rise). Small-diameter non-magnetic ceramic aggregate: 800kg Large-diameter non-magnetic ceramic aggregate: 1000kg Polycarboxylate superplasticizer: 6kg (using a slow-release, slump-retaining high-performance superplasticizer with a solid content of 40% to ensure that the low-magnetic concrete maintains good workability during long-term transportation and construction). Mixing water: 165kg The above-mentioned method for preparing low-magnetic concrete: Step 1, Pretreatment and Feeding: Put small-diameter non-magnetic ceramsite and large-diameter non-magnetic ceramsite into a forced mixer and dry mix for 30 seconds to make the coarse and fine aggregates evenly distributed.

[0050] Step 2: Mixing of cementitious materials: Add low-magnetic cement and S95 grade slag powder into the mixer and continue to dry mix for 60 seconds to ensure that all solid materials are fully mixed.

[0051] Step 3, Wet mixing process: Dissolve the polycarboxylate superplasticizer in the mixing water to prepare an aqueous solution; start the mixer and slowly add the above aqueous solution into the mixer in three batches, with the total wet mixing time controlled at about 200 seconds, until the mixture is uniformly mixed, the color is consistent, the surface of the non-magnetic ceramic particles is completely coated with the slurry, and there is no bleeding or segregation in the mixer.

[0052] Step 4, Molding and Curing: After discharge, test the slump of the low-magnetic concrete mixture and control the target value to 180±20mm; after pouring and molding, cover with plastic film for moisture retention and curing. Remove the mold after 24 hours and immediately move it into a standard curing room (temperature 20±2℃, relative humidity >95%) for curing until the specified age.

[0053] The key performance indicators of the obtained low-magnetic concrete were as follows: slump of 186 mm, 28-day compressive strength of 48.8 MPa, and remanent magnetic strength of only 2.6 nT.

[0054] Example 2: This example aims to provide a low-magnetic concrete with extremely low magnetic susceptibility and excellent volume stability, which is specifically adapted to the construction needs of ultra-precision instrument bases or shielding rooms that are extremely sensitive to geomagnetic field disturbances, such as nuclear magnetic resonance spectrometers and electron microscopes.

[0055] The mass of each component in low-magnetic concrete, calculated per cubic meter, is as follows: Low-magnetic cement: 300kg Small-diameter non-magnetic ceramic aggregate: 760kg Large-diameter non-magnetic ceramic aggregate: 975kg Polycarboxylate superplasticizer: 4kg (40% solids content, slow-release, slump-retaining high-performance superplasticizer) Mixing water: 145kg The above-mentioned method for preparing low-magnetic concrete: Step 1: Environmental and Raw Material Pretreatment: All mixing and transportation equipment must be thoroughly cleaned and demagnetized before use. Aggregates must be inspected batch by batch with a metal detector before entering the warehouse to remove magnetic impurities.

[0056] Step 2, Mixing process: Add all dry materials in the order of "large-diameter non-magnetic ceramsite → small-diameter non-magnetic ceramsite → low-magnetic cement", and extend the dry mixing time to 90 seconds to ensure that the components are mixed extremely evenly; mix the polycarboxylate superplasticizer with the mixing water in advance to prepare an aqueous solution, and inject it into the mixer at a uniform speed within 2 minutes, with a total wet mixing time of not less than 240 seconds.

[0057] Step 3, Low-disturbance molding process: Use non-magnetic plastic or wooden molds for casting, and avoid high drop impacts during the casting process; use an immersion plastic vibrator to slowly vibrate, which ensures compaction and avoids introducing air bubbles or causing magnetic particles to oriented.

[0058] Step 4, Constant Temperature and Non-Magnetic Curing Process: After casting, the green body is placed in a constant temperature environment of 20±0.5℃ without strong electromagnetic interference for sealed curing, and the curing period is not less than 28 days.

[0059] The core performance indicators of the obtained low-magnetic concrete were as follows: the fluidity of the mixture was 176 mm, the 28-day compressive strength reached 50.2 MPa, and the remanent magnetic strength was only 1.6 nT.

[0060] Comparative Example 1 This comparative example provides a conventional method for preparing lightweight expanded clay concrete, which aims to contrast with the above embodiments and demonstrate the demagnetization effect of low-magnetic concrete prepared using modified expanded clay.

[0061] The mass of each component in lightweight expanded clay concrete, calculated per cubic meter of concrete, is as follows: Cement: 300kg Ceramics sand: 760kg (continuously graded ordinary ceramics sand with a particle size of 0~5mm) Expanded clay aggregate: 975kg (continuously graded ordinary expanded clay aggregate with a particle size of 5~20mm) Polycarboxylate superplasticizer: 4kg (40% solids content, slow-release, slump-retaining high-performance superplasticizer) Mixing water: 145kg The preparation method of the above-mentioned lightweight ceramsite concrete: Step 1: Equipment Cleaning: All mixing and transport equipment must be thoroughly cleaned before use.

[0062] Step 2, Mixing process: Add all dry materials in the order of "ceramsite → ceramsite sand → cement", and extend the dry mixing time to 90 seconds to ensure that the components are mixed extremely evenly; mix the polycarboxylate superplasticizer with the mixing water in advance to prepare an aqueous solution, and inject it into the mixer at a uniform speed within 2 minutes, with a total wet mixing time of not less than 240 seconds.

[0063] Step 3, Low-disturbance molding process: Casting is carried out using conventional molds, and immersion vibrators are used to slowly compact the material to ensure density.

[0064] Step 4, Curing process: The cast green body is placed in a constant temperature environment of 20±0.5℃ for curing, and the curing period is not less than 28 days.

[0065] The core performance indicators of the obtained lightweight ceramsite concrete are as follows: the fluidity of the mixture is 179 mm, the 28-day compressive strength reaches 52.6 MPa, and the remanent magnetic strength is 1078 nT.

[0066] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing non-magnetic ceramic particles, characterized in that, include: The activated ceramsite was placed in a rare earth ion solution, and the rare earth ions replaced the ferromagnetic ions in the ceramsite through ion exchange to obtain modified ceramsite. The modified ceramic particles are immersed in nano-SiO2 sol, and the surface of the modified ceramic particles is coated with nano-SiO2 sol by stirring. The modified ceramic particles coated with the nano-SiO2 sol were subjected to aging, drying and calcination treatments in sequence to obtain the non-magnetic ceramic particles.

2. The method for preparing non-magnetic ceramic particles according to claim 1, characterized in that, The preparation steps of the rare earth ion solution are as follows: Weigh out lanthanum nitrate hexahydrate and cerium nitrate hexahydrate, add them to deionized water and dissolve them to obtain the rare earth ion solution; In the rare earth ion solution, La 3+ With Ce 3+ The molar ratio is 1:1, and the total molar concentration of the lanthanum nitrate hexahydrate and the cerium nitrate hexahydrate is 0.8–1.2 mol / L.

3. The method for preparing non-magnetic ceramic particles according to claim 1 or 2, characterized in that, The solid-liquid ratio of the modified ceramsite to the rare earth ion solution is 1:10 to 1:15 (kg / L).

4. The method for preparing non-magnetic ceramic particles according to claim 1, characterized in that, The preparation steps of the nano-SiO2 sol are as follows: Weigh out tetraethyl orthosilicate, anhydrous ethanol, and deionized water respectively in a molar ratio of 1:4:(4~10); The tetraethyl orthosilicate and the anhydrous ethanol were mixed at a volume ratio of 1:4 and stirred until clear and homogeneous to obtain solution A. The deionized water and anhydrous ethanol were mixed at a volume ratio of 9:40, and hydrochloric acid or ammonia was added to adjust the pH to obtain solution B. Add solution B dropwise to solution A and stir until homogeneous, controlling the pH of the mixed solution between 2 and 4; The mixed solution was placed in a water bath at 60-70°C and stirred and refluxed for 1-2 hours to obtain the nano-SiO2 sol, which was slightly turbid or semi-transparent.

5. The method for preparing non-magnetic ceramic particles according to claim 1, characterized in that, The thickness of the coating layer formed by the nano-SiO2 sol on the surface of the modified ceramic particles is 200~300nm.

6. The method for preparing non-magnetic ceramic particles according to claim 1, characterized in that, The drying process employs a gradient temperature increase: first, treatment at 50°C for 2 hours, followed by raising the temperature to 80–100°C for 4 hours; and / or, The calcination temperature is 400~600℃, and the calcination time is 2~4 hours.

7. A low-magnetic concrete, characterized in that, The mixture includes the non-magnetic ceramsite as described in any one of claims 1-6, and also includes low-magnetic cement, water-reducing agent, and mixing water.

8. The low-magnetic concrete according to claim 7, characterized in that, The non-magnetic ceramic particles include small-diameter non-magnetic ceramic particles and large-diameter non-magnetic ceramic particles. The particle size of the small-diameter non-magnetic ceramic particles is 0~5mm, and the particle size of the large-diameter non-magnetic ceramic particles is 5~20mm. The masses of each component in each cubic meter of the low-magnetic concrete are as follows: 200-450 kg of the low-magnetic cement, 600-900 kg of small-diameter non-magnetic ceramsite, 900-1400 kg of large-diameter non-magnetic ceramsite, 4-10 kg of water-reducing agent, and 130-180 kg of mixing water.

9. The low-magnetic concrete according to claim 7, characterized in that, The low-magnetic concrete also includes mineral admixtures, and the amount of mineral admixtures in each cubic meter of the low-magnetic concrete is 0~100kg.

10. A method for preparing low-magnetic concrete as described in any one of claims 7-9, characterized in that, step include: The non-magnetic ceramsite and the low-magnetic cement are put into a mixer and dry-mixed. The water-reducing agent is dissolved in the mixing water in advance to form a water-reducing agent solution. The water-reducing agent solution is added to the mixer in 2 to 3 batches for wet mixing. The wet mixing time is not less than 180 seconds to obtain the low magnetic concrete.