A near zero magnetic concrete mixing system and a near zero magnetic concrete production method

Abstract

The application discloses a near-zero magnetic concrete mixing system and a near-zero magnetic concrete production method. The near-zero magnetic concrete mixing system comprises a concrete mixing device, a first magnetic shielding composite layer, a second magnetic shielding composite layer, an ultrasonic oscillation device, a phase angle detection device and a control device. The concrete mixing device comprises an equipment support, a stirring drum is installed on the equipment support, and a power input terminal of a stirring motor is connected with a motor power supply wire. The first magnetic shielding composite layer is arranged on the outside of the concrete mixing device. The second magnetic shielding composite layer is arranged on the outside of the stirring motor and the motor power supply wire. A waveguide rod of the ultrasonic oscillation device is installed in the stirring drum. A test probe of the phase angle detection device is installed in the stirring drum. The control device controls the operation state of the ultrasonic oscillation device according to the phase angle detected by the phase angle detection device. The system and the method can realize the production of an extremely low residual magnetic concrete (less than 0.5 nT).

Description

Technical Field

[0001] This invention belongs to the field of near-zero magnetic concrete preparation technology, and in particular relates to a near-zero magnetic concrete mixing system and a near-zero magnetic concrete production method. Background Technology

[0002] Concrete, a common building material, is widely used in various architectural and structural engineering projects. It is mainly composed of cementitious materials (such as cement), aggregates (such as sand and stone), and water, mixed in a specific ratio. While traditional concrete research and production technologies have matured, scientific research places higher demands on experimental environments. Some high-precision experimental facilities impose stringent limitations on the magnetic properties of materials, with "zero magnetic" or "near-zero magnetic" environments becoming a new requirement for many basic scientific studies. Against this backdrop, near-zero magnetic concrete has emerged as a concrete material for special applications, becoming an important material foundation for constructing low-magnetic-field spaces.

[0003] "Near-zero magnetic concrete" typically refers to concrete with a remanence value controlled within an extremely low range (less than 0.5 nT), providing a near-magnetically-free spatial environment for nuclear magnetic resonance imaging, precision magnetic sensor calibration, and basic physics experiments. However, traditional concrete raw materials generally contain ferromagnetic substances such as iron, cobalt, nickel, and their compounds. These materials retain a certain degree of hysteresis after molding, resulting in a high overall remanence value for the concrete structure, making it difficult to meet the requirements of the aforementioned near-zero magnetic environment. Even with optimized aggregates and low-magnetic mix design, the remanence value of ordinary commercial concrete is generally between several hundred and several thousand nT, far exceeding the control target of 0.5 nT.

[0004] Some literature and patents have explored methods for optimizing the mix proportions of low-magnetic concrete, such as replacing ordinary raw materials with low-magnetic materials (e.g., quartz stone, quartz sand) and white cement, and adjusting the water-cement ratio and admixture ratio to reduce remanence. However, even under optimal conditions, the lowest remanence value of concrete prepared by existing research is only about 3nT, which still cannot achieve a truly "near-zero magnetism" effect. Furthermore, physical processes such as mixing, vibration, and aggregate wear during concrete production may introduce new magnetic contamination, making the final remanence value uncontrollable and highly volatile even when using low-magnetic materials. At the equipment level, traditional concrete mixing equipment is generally made of ordinary carbon steel or stainless steel, which has high magnetic permeability and is itself a strong magnetic source. Simultaneously, electromagnetic interference generated by motors, cables, and electronic control systems during operation is difficult to shield, further increasing the background magnetic field in the mixing environment. Research shows that even with a low external magnetic field strength, the additional magnetic field generated by the mixer itself can affect the formation process of the concrete's internal microstructure, thus affecting its final magnetic characteristics. Currently, there is no complete mixing device or production method for preparing near-zero magnetic concrete. Summary of the Invention

[0005] The purpose of this invention is to provide a near-zero magnetic concrete mixing system and a near-zero magnetic concrete production method to solve the problem that there is currently no complete set of mixing equipment and production method for preparing near-zero magnetic concrete.

[0006] The technical solution of this invention to solve the above-mentioned technical problems is as follows: a near-zero magnetic concrete mixing system and a near-zero magnetic concrete production method, comprising: a concrete mixing device, a first magnetic shielding composite layer, a second magnetic shielding composite layer, an ultrasonic oscillation device, a phase angle detection device, and a control device; the concrete mixing device includes an equipment support, on which a mixing drum is mounted, and the drive shaft of a mixing motor is connected to the mixing drum via gears; the power input terminal of the mixing motor is connected to a motor power supply line; the concrete mixing device is made of low-magnetic materials; the first magnetic shielding composite layer is disposed on the outside of the concrete mixing device, forming a concrete mixing construction space; the second magnetic shielding composite layer is disposed outside the mixing motor and the motor power supply line; the waveguide rod of the ultrasonic oscillation device is installed inside the mixing drum; the test probe of the phase angle detection device is installed inside the mixing drum; the control device is electrically connected to the mixing motor, the ultrasonic oscillation device, and the phase angle detection device, and the control device controls the operating state of the ultrasonic oscillation device according to the phase angle detected by the phase angle detection device.

[0007] The near-zero magnetic concrete mixing system of the present invention, as described above, further includes a first magnetic shielding composite layer comprising a zero-magnetic steel plate, an insulating protective layer, and a permalloy layer; a demagnetizing coil is provided inside the zero-magnetic steel plate.

[0008] The near-zero magnetic concrete mixing system of the present invention, as described above, further comprises, from the outside to the inside, a zero-magnetic steel plate, a demagnetizing coil, a first insulating protective layer, a first permalloy layer, a second insulating protective layer, a second permalloy layer, a third insulating protective layer, a third permalloy layer, and a fourth insulating protective layer.

[0009] The near-zero magnetic concrete mixing system of the present invention, as described above, further includes a second magnetic shielding composite layer comprising a zero-magnetic steel plate, an insulating protective layer, and a permalloy layer; a demagnetizing coil is provided inside the zero-magnetic steel plate.

[0010] The near-zero magnetic concrete mixing system of the present invention, as described above, further comprises, from the outside to the inside, a zero-magnetic steel plate, a demagnetizing coil, a first insulating protective layer, a first permalloy layer, a second insulating protective layer, a second permalloy layer, a third insulating protective layer, and a third permalloy layer.

[0011] The near-zero magnetic concrete mixing system of the present invention, as described above, further includes a mixing motor connected to an equipment bracket via a motor mounting base, and a fourth insulating protective layer provided between the motor mounting base and the third permalloy layer of the second magnetic shielding composite layer; and a fourth insulating protective layer provided between the outer wall of the motor power supply line and the third permalloy layer of the second magnetic shielding composite layer.

[0012] The near-zero magnetic concrete mixing system of the present invention, as described above, further includes a concrete mixing and construction space with a rectangular structure constructed using aluminum square tubes inside the first magnetic shielding composite layer.

[0013] The present invention also provides a method for producing near-zero magnetic concrete, which utilizes the near-zero magnetic concrete mixing system described in any of the above claims to produce near-zero magnetic concrete, comprising the following steps:

[0014] Step 1: Prepare concrete raw materials, which include cement, coarse aggregate, fine aggregate, municipal water, and organic water-reducing agent; the remanence of the coarse and fine aggregates is less than or equal to 1 nT.

[0015] Step 2: The demagnetizing coil is energized to demagnetize the magnetic shielding material of the magnetic shielding composite layer. Then, the magnetic field strength of the concrete mixing construction space inside the first magnetic shielding composite layer is tested. The magnetic field strength is less than or equal to 30 nT.

[0016] Step 3: Pour cement, water and water-reducing agent into the feed inlet of the concrete mixing device in sequence, start the mixing drum, and mix the materials for 10 to 15 seconds.

[0017] Step 4: Turn on the ultrasonic oscillation device to perform ultrasonic treatment on the cement slurry. Two seconds after the ultrasonic treatment ends, use a phase angle detection device to detect the phase angle of the cement slurry. If the phase angle is greater than or equal to 85 degrees, proceed to the next step. If the phase angle is less than 85 degrees, increase the frequency of the ultrasonic oscillation device and continue ultrasonic treatment on the cement slurry until the phase angle is greater than or equal to 85 degrees. Preferably, in Step 4, the specific parameters for ultrasonic treatment of the cement slurry are: ultrasonic frequency of 10 to 40 kHz, operating for 3 to 8 seconds. Preferably, in Step 4, increasing the frequency of the ultrasonic oscillation device means increasing the ultrasonic frequency successively in units of Δf; Δf = k × (85 - θ), where k = 0.5 kHz / °, and θ is the measured phase angle.

[0018] Step 5: Pour coarse and fine aggregates into the feed inlet of the concrete mixing plant, start the mixing drum, and mix the materials for about 30 to 90 seconds. Use a phase angle detection device to detect the phase angle of the fresh concrete. When the phase angle is less than 10 degrees, pour the concrete out of the discharge outlet of the concrete mixing plant.

[0019] The beneficial effects of this invention are:

[0020] 1. Achieving ultra-low remanent magnetization concrete production: Through the synergistic effect of multiple magnetic shielding composite layers (including zero-magnetic steel plates, permalloy layers, and demagnetizing coils), the external environmental magnetic field and electromagnetic interference from the mixing equipment itself (such as motors and power lines) are effectively shielded, ensuring that the background magnetic field strength in the mixing and construction space is ≤30nT. Combined with low-magnetic raw materials (aggregate remanent magnetization ≤1nT), the final concrete remanent magnetization can be controlled below 0.5nT, overcoming the limitation of existing technologies that can only reach a minimum of 3nT, and providing reliable materials for high-precision magnetically sensitive applications (such as basic physics experiments).

[0021] 2. Optimizes the microstructure of concrete and reduces magnetic defects; the cavitation and acoustic flow effects of the ultrasonic oscillation device strongly disperse cement particle agglomerates; phase angle detection provides real-time feedback (a phase angle ≥ 85 degrees in the cement paste indicates good dispersion). This reduces the aggregation of internal magnetic impurities and uneven hydration, improves the density and uniformity of concrete, thereby reducing residual magnetism and enhancing mechanical properties. Attached Figure Description

[0022] The advantages of the present invention, both above and / or other aspects, will become clearer and more readily understood through the following detailed description taken in conjunction with the accompanying drawings, which are merely illustrative and do not limit the invention, wherein:

[0023] Figure 1 This is a top view schematic diagram of a near-zero magnetic concrete mixing system according to an embodiment of the present invention;

[0024] Figure 2 for Figure 1 A magnified view of part A in the middle;

[0025] Figure 3 for Figure 1 A magnified view of part B in the middle;

[0026] Figure 4 This is a side view of a near-zero magnetic concrete mixing system according to an embodiment of the present invention;

[0027] Figure 5 for Figure 4 A magnified view of part C in the middle;

[0028] Figure 6 for Figure 4 A magnified view of part D in the middle;

[0029] Figure 7 This is a flowchart of a near-zero magnetic concrete production method according to an embodiment of the present invention.

[0030] The attached diagram lists the components represented by each number as follows:

[0031] 10. First magnetic shielding composite layer; 11. Zero-magnetic steel plate; 12. First insulating protective layer; 13. First permalloy layer; 14. Second insulating protective layer; 15. Second permalloy layer; 16. Third insulating protective layer; 17. Third permalloy layer; 18. Fourth insulating protective layer; 19. Demagnetizing coil; 20. Concrete mixing device; 21. Equipment support; 22. Mixing drum; 23. Mixing motor; 24. Motor power supply line; 25. Motor mounting base; 30. Second magnetic shielding composite layer; 40. Low-magnetic concrete layer; 50. Aluminum square tube. Detailed Implementation

[0032] In the following description, embodiments of the near-zero magnetic concrete mixing system and near-zero magnetic concrete production method of the present invention will be described with reference to the accompanying drawings.

[0033] The embodiments described herein are specific implementations of the present invention, used to illustrate the concept of the invention, and are illustrative and exemplary, and should not be construed as limiting the implementation or scope of the invention. In addition to the embodiments described herein, those skilled in the art can employ other obvious technical solutions based on the content disclosed in the claims and specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0034] The accompanying drawings in this specification are schematic diagrams used to illustrate the concept of the invention, showing the shapes of the various parts and their interrelationships. Please note that, to clearly demonstrate the structure of the components in the embodiments of the invention, the drawings are not drawn to the same scale. The same reference numerals are used to denote the same parts.

[0035] The following combination Figures 1 to 6 This invention describes a near-zero magnetic concrete mixing system according to an embodiment of the present invention, comprising:

[0036] The concrete mixing device 20 includes an equipment support 21, on which a mixing drum 22 is mounted. The drive shaft of a mixing motor 23 is connected to the mixing drum 22 via gears. The power input terminal of the mixing motor 23 is connected to a motor power supply line 24. In a preferred embodiment, the entire concrete mixing device is made of low-magnetic materials, such as 316L stainless steel, which can achieve a remanent magnetization value of less than 0.5 nT. Furthermore, low-magnetic materials have high wear resistance, preventing wear and chipping during concrete mixing. The mixing speed of the mixer is approximately 20–60 rpm.

[0037] A first magnetic shielding composite layer 10 and a second magnetic shielding composite layer 30 are used. The first magnetic shielding composite layer 10 is disposed on the outside of the concrete mixing device 20, forming the concrete mixing construction space. In a preferred embodiment of a near-zero magnetic concrete mixing system, the first magnetic shielding composite layer 10 includes a zero-magnetic steel plate 11, an insulating protective layer, and a permalloy layer. A demagnetizing coil 19 is provided inside the zero-magnetic steel plate 11. Figure 2 and Figure 5 As shown, the first magnetic shielding composite layer 10 consists of a zero-magnetic steel plate 11, a demagnetizing coil 19, a first insulating protective layer 12, a first permalloy layer 13, a second insulating protective layer 14, a second permalloy layer 15, a third insulating protective layer 16, a third permalloy layer 17, and a fourth insulating protective layer 18, from the outside to the inside.

[0038] The second magnetic shielding composite layer 30 is disposed outside the mixing motor 23 and the motor power supply line 24; in a preferred embodiment of a near-zero magnetic concrete mixing system, the second magnetic shielding composite layer 30 includes a zero-magnetic steel plate 11, an insulating protective layer, and a permalloy layer; a demagnetizing coil 19 is provided inside the zero-magnetic steel plate 11. Figure 3 Figure 6 As shown, the second magnetic shielding composite layer 30, from the outside to the inside, consists of a zero-magnetic steel plate 11, a demagnetizing coil 19, a first insulating protective layer 12, a first permalloy layer 13, a second insulating protective layer 14, a second permalloy layer 15, a third insulating protective layer 16, and a third permalloy layer 17. In a further preferred embodiment of the near-zero magnetic concrete mixing system, as... Figure 3 As shown, the stirring motor 23 is connected to the equipment bracket 21 via the motor mounting base 25. A fourth insulating protective layer 18 is also provided between the motor mounting base 25 and the third permalloy layer 17 of the second magnetic shielding composite layer 30; Figure 6 As shown, a fourth insulating protective layer 18 is also provided between the outer wall of the motor power supply line 24 and the third permalloy layer 17 of the second magnetic shielding composite layer 30.

[0039] In a further preferred embodiment of the near-zero magnetic concrete mixing system, such as Figure 1 and Figure 4 As shown, a rectangular concrete mixing and construction space is constructed inside the first magnetic shielding composite layer 10 using aluminum square tubes 50. Figure 4 As shown, a low-magnetic concrete layer 40 is provided on the mounting bottom surface of the concrete mixing device 20, and a second magnetic shielding composite layer 30 is provided below the low-magnetic concrete layer 40.

[0040] An ultrasonic oscillation device, with its waveguide rod installed inside the mixing drum 22, utilizes the cavitation and acoustic flow effects generated by ultrasound in the liquid to powerfully disperse the initial cement particle agglomerates. The ultrasonic oscillation device comprises an ultrasonic generator, a transducer, and a waveguide rod. The ultrasonic generator converts industrial frequency AC power into a high-frequency electrical signal, with adjustable frequency and waveform. The transducer is a piezoelectric ceramic transducer that converts the high-frequency electrical signal into mechanical vibration of the same frequency. The waveguide rod, made of high-strength titanium alloy, can be stepped, exponential, or conical in shape, effectively amplifying and transmitting the vibration generated by the transducer to the mixing area, producing a cavitation effect. The ultrasonic frequency is 10–40 kHz. Multiple waveguide rod working ends are embedded in the central area at the bottom of the mixing drum and on the side wall approximately one-third of the way up from the bottom. The working ends are evenly distributed, and the number is determined based on the drum size, concrete mixing volume, and preliminary experiments, approximately 2–4. The working end of the waveguide rod is covered with a wear-resistant alumina ceramic liner to prevent the aggregate from directly impacting and wearing the waveguide rod. The ultrasonic generator, transducer, and wiring on the outside of the mixing drum are covered with the same magnetic shielding material as the first magnetic shielding composite layer 10.

[0041] The phase angle detection device has a test probe installed inside the stirring drum 22. The test probe is made of high-strength titanium alloy and is installed at the bottom of the stirring drum.

[0042] The control device is electrically connected to the stirring motor 23, the ultrasonic oscillation device, and the phase angle detection device. The control device controls the operation of the ultrasonic oscillation device according to the phase angle detected by the phase angle detection device.

[0043] Combination Figure 7 This invention describes an embodiment of a near-zero magnetic concrete production method, which utilizes the near-zero magnetic concrete mixing system described in any of the above claims to produce near-zero magnetic concrete, and includes the following steps:

[0044] Step 1: Prepare concrete raw materials, which include cement, coarse aggregate, fine aggregate, municipal water, and organic water-reducing agent; the remanence of the coarse and fine aggregates is less than or equal to 1 nT.

[0045] Step 2: The demagnetizing coil 19 is energized to demagnetize the magnetic shielding material of the magnetic shielding composite layer. Then, the magnetic field strength of the concrete mixing construction space inside the first magnetic shielding composite layer 10 is tested. The magnetic field strength is less than or equal to 30 nT.

[0046] Step 3: Pour cement, water and water-reducing agent into the feed inlet of the concrete mixing device 20 in sequence, start the mixing drum 22 to mix the materials for 10 to 15 seconds;

[0047] Step 4: Turn on the ultrasonic oscillation device to perform ultrasonic treatment on the cement slurry. Two seconds after the ultrasonic treatment ends, use a phase angle detection device to detect the phase angle of the cement slurry. If the phase angle is greater than or equal to 85 degrees, proceed to the next step. If the phase angle is less than 85 degrees, increase the frequency of the ultrasonic oscillation device and continue ultrasonic treatment on the cement slurry until the phase angle is greater than or equal to 85 degrees. The specific parameters for ultrasonic treatment of the cement slurry in Step 4 are: ultrasonic frequency of 10 to 40 kHz, operating for 3 to 8 seconds. In Step 4, increasing the frequency of the ultrasonic oscillation device means increasing the ultrasonic frequency successively in units of Δf; Δf = k × (85 - θ), where k = 0.5 kHz / °, and θ is the measured phase angle.

[0048] Step 5: Pour coarse and fine aggregates into the feed inlet of the concrete mixing device 20, start the mixing drum 22 to mix the materials for about 30 to 90 seconds; use the phase angle detection device to detect the phase angle of the fresh concrete, and when the phase angle is less than 10 degrees, pour the concrete out from the discharge outlet of the concrete mixing device 20.

[0049] Effect Verification Example

[0050] The materials used in the following embodiments of the present invention are sourced as follows: the cement is P·O42.5 silicate cement (standard GB / T3813-2017) sold by Xi'an Linya Cement Sales Co., Ltd.; the admixture is organic polycarboxylate superplasticizer (model PCE-412) sold by Liaoning Hengda New Materials Co., Ltd.; both coarse and fine aggregates are purchased from Shijiazhuang Runfa Mineral Products Co., Ltd. The remanent magnetization detection method for coarse and fine aggregates is as follows: quartz stone or quartz sand is placed in a 100x100x100mm plastic box, and a fluxgate sensor is used to detect the remanent magnetization at a distance of 2cm from any surface of the plastic box; the coarse aggregate is quartz stone with a particle size greater than 4.75 mm, and the remanent magnetization value of the coarse aggregate is not higher than 0.86nT; the fine aggregate is quartz sand with a particle size less than 4.75 mm, and the remanent magnetization value of the coarse aggregate is not higher than 0.93nT.

[0051] Both the examples and the comparative examples were prepared by mixing concrete according to the mix proportions shown in Table 1. During concrete mixing, the examples used the near-zero magnetic concrete mixing system described above.

[0052] Table 1 Sample Mixing Ratio

[0053]

[0054] The mixed concrete was prepared into concrete test blocks, each measuring 100x100x100mm. After 28 days of hardening, its properties and remanent magnetization were tested. The remanent magnetization was measured using a fluxgate magnetometer at a distance of 2cm from any surface of the test block. Concrete performance was conducted according to the methods specified in GB / T50081-2019, "Standard for Test Methods of Physical and Mechanical Properties of Concrete". Specifically, for compressive strength testing, standard cubic specimens with sides of 150mm were prepared. For flexural strength testing, prism specimens with sides of 150mm*150mm*600mm were prepared.

[0055] Example 1

[0056] The near-zero magnetic concrete production method includes the following steps:

[0057] Step 1, prepare concrete raw materials;

[0058] Step 2: The demagnetizing coil 19 is energized to demagnetize the magnetic shielding material of the magnetic shielding composite layer. Then, the magnetic field strength of the concrete mixing construction space inside the first magnetic shielding composite layer 10 is tested. The magnetic field strength is less than or equal to 30 nT.

[0059] Step 3: Pour cement, water and water-reducing agent into the feed inlet of the concrete mixing device 20 in sequence, start the mixing drum 22 to mix the materials for 15 seconds;

[0060] Step 4: Turn on the ultrasonic oscillation device to perform ultrasonic treatment on the cement slurry (ultrasonic frequency 20KHz, working for 5 seconds); 2 seconds after the ultrasonic treatment ends, use the phase angle detection device to detect the phase angle of the cement slurry, which is equal to 65 degrees; increase the frequency of the ultrasonic oscillation device and continue to perform ultrasonic treatment on the cement slurry (ultrasonic frequency 30KHz, working for 5 seconds); 2 seconds after the ultrasonic treatment ends, use the phase angle detection device to detect the phase angle of the cement slurry, which is equal to 80 degrees; increase the frequency of the ultrasonic oscillation device and continue to perform ultrasonic treatment on the cement slurry (ultrasonic frequency 32.5KHz, working for 5 seconds); 2 seconds after the ultrasonic treatment ends, use the phase angle detection device to detect the phase angle of the cement slurry, which is equal to 86 degrees; In Step 4, increasing the frequency of the ultrasonic oscillation device means increasing the ultrasonic frequency successively in units of Δf; Δf=k×(85-θ), where k=0.5kHz / °, and θ is the measured phase angle. In this embodiment of the invention, the inherent resonant frequency of cement particles (typically 15-40kHz) can be precisely matched by dynamic frequency adjustment, thereby exciting a larger amplitude to promote hydration. The ultrasonic power absorbed per unit volume of cement slurry is adjusted by the output power of the ultrasonic oscillation device and the volume of near-zero magnetic concrete; in Example 1, the ultrasonic power absorbed per unit volume of cement slurry is 500W / L.

[0061] Step 5: Pour coarse and fine aggregates into the feed inlet of the concrete mixing device 20, start the mixing drum 22 to mix the materials for about 30 to 90 seconds; use the phase angle detection device to detect the phase angle of the fresh concrete, and when the phase angle is less than 10 degrees, pour the concrete out from the discharge outlet of the concrete mixing device 20.

[0062] Example 2

[0063] Except for step 4, the rest is the same as in Example 1. Specifically: Step 4, turn on the ultrasonic oscillation device to perform ultrasonic treatment on the cement slurry (ultrasonic frequency is 20KHz, working for 5 seconds); 2 seconds after the ultrasonic treatment ends, use a phase angle detection device to detect the phase angle of the cement slurry, and the phase angle is equal to 65 degrees.

[0064] Example 3

[0065] Except for step 4, the rest is the same as in Example 1. Specifically: Step 4, turn on the ultrasonic oscillation device to perform ultrasonic treatment on the cement slurry (ultrasonic frequency of 20KHz, working for 5 seconds); 2 seconds after the ultrasonic treatment ends, use the phase angle detection device to detect the phase angle of the cement slurry, and the phase angle is equal to 65 degrees; increase the frequency of the ultrasonic oscillation device and continue to perform ultrasonic treatment on the cement slurry (ultrasonic frequency of 30KHz, working for 5 seconds); 2 seconds after the ultrasonic treatment ends, use the phase angle detection device to detect the phase angle of the cement slurry, and the phase angle is equal to 80 degrees.

[0066] Example 4

[0067] Except for step 4, the rest is the same as in Example 1. Specifically: In step 4, the ultrasonic power absorbed per unit volume of cement slurry is adjusted by the output power of the ultrasonic oscillation device and the volume of near-zero magnetic concrete. In this example, the ultrasonic power absorbed per unit volume of cement slurry is 520 W / L.

[0068] Example 5

[0069] Except for step 4, the rest is the same as in Example 1. Specifically: In step 4, the ultrasonic power absorbed per unit volume of cement slurry is adjusted by the output power of the ultrasonic oscillation device and the volume of near-zero magnetic concrete. In this example, the ultrasonic power absorbed per unit volume of cement slurry is 560 W / L.

[0070] Example 6

[0071] Except for step 4, the rest is the same as in Example 1. Specifically: In step 4, the ultrasonic power absorbed per unit volume of cement slurry is adjusted by the output power of the ultrasonic oscillation device and the volume of near-zero magnetic concrete. In this example, the ultrasonic power absorbed per unit volume of cement slurry is 450 W / L.

[0072] Example 7

[0073] Except for step 4, the rest is the same as in Example 1. Specifically: In step 4, the ultrasonic power absorbed per unit volume of cement slurry is adjusted by the output power of the ultrasonic oscillation device and the volume of near-zero magnetic concrete. In this example, the ultrasonic power absorbed per unit volume of cement slurry is 400 W / L.

[0074] Example 8

[0075] Except for step 4, the rest is the same as in Example 1. Specifically: In step 4, the ultrasonic power absorbed per unit volume of cement slurry is adjusted by the output power of the ultrasonic oscillation device and the volume of near-zero magnetic concrete. In this example, the ultrasonic power absorbed per unit volume of cement slurry is 350W / L.

[0076] The inventors tested the temperature of the cement pastes in Examples 1 and 4-8 after ultrasonic treatment. The temperature rise of the pastes after treatment was as follows: Example 1, 2.0℃; Example 4, 3.2℃; Example 5, 3.5℃; Example 6, 1.7℃; Example 7, 1.5℃; Example 8, 1.3℃. The ultrasonic power absorbed per unit volume of cement paste was adjusted to ≤500W / L to control the temperature rise of the paste while ensuring uniform mixing, thus avoiding excessively rapid hydration and deterioration of concrete performance.

[0077] Comparative Example

[0078] This comparative example uses a conventional near-zero magnetic concrete mixing system for concrete mixing, and the rest of the process is the same as in Example 1.

[0079] Table 2 Performance Test Results

[0080]

[0081] Based on the data obtained from the above embodiments of the present invention, it is necessary to control the phase angle of the cement paste at 85 degrees in step 4 to avoid increasing the residual magnetism of the concrete in step 5 if the phase angle is too small. Simultaneously, in step 4, increasing the frequency of the ultrasonic oscillation device means progressively increasing the ultrasonic frequency in units of Δf; Δf = k × (85 - θ), where k = 0.5 kHz / °, and θ is the measured phase angle. Dynamic frequency adjustment can precisely match the inherent resonant frequency of the cement particles (typically 15-40 kHz), exciting a larger amplitude to promote hydration. Furthermore, by adjusting the output power of the ultrasonic oscillation device and the volume of near-zero magnetic concrete, the ultrasonic power absorbed per unit volume of cement paste is adjusted to ≤500 W / L, thereby avoiding undesirable changes in the residual magnetism and properties of the concrete.

[0082] The technical features disclosed above are not limited to the combinations of the disclosed features with other features. Those skilled in the art can also make other combinations of the technical features according to the purpose of the invention to achieve the purpose of the invention.

Claims

1. A method for producing near-zero magnetic concrete, characterized in that, Near-zero magnetic concrete is produced using a near-zero magnetic concrete mixing system. The near-zero magnetic concrete mixing system includes: A concrete mixing device (20) includes an equipment support (21), on which a mixing drum (22) is mounted. The drive shaft of a mixing motor (23) is connected to the mixing drum (22) via gears. The power input terminal of the mixing motor (23) is connected to a motor power supply line (24). The concrete mixing device is made of low-magnetic materials. The first magnetic shielding composite layer (10) and the second magnetic shielding composite layer (30) are provided. The first magnetic shielding composite layer (10) is disposed on the outside of the concrete mixing device (20) and forms a concrete mixing construction space. The second magnetic shielding composite layer (30) is disposed on the outside of the mixing motor (23) and the motor power supply line (24). An ultrasonic oscillation device, wherein the waveguide rod of the ultrasonic oscillation device is installed inside the stirring drum (22); A phase angle detection device, wherein the test probe of the phase angle detection device is installed inside the stirring drum (22); The control device is electrically connected to the stirring motor (23), the ultrasonic oscillation device and the phase angle detection device. The control device controls the operating state of the ultrasonic oscillation device according to the phase angle detected by the phase angle detection device. The near-zero magnetic concrete production method includes the following steps: Step 1: Prepare concrete raw materials, which include cement, coarse aggregate, fine aggregate, municipal water, and organic water-reducing agent; the remanence of the coarse and fine aggregates is less than or equal to 1 nT. Step 2: The demagnetizing coil (19) is energized to demagnetize the magnetic shielding material of the magnetic shielding composite layer. Then, the magnetic field strength of the concrete mixing construction space inside the first magnetic shielding composite layer (10) is tested. The magnetic field strength is less than or equal to 30nT. Step 3: Pour cement, water and water-reducing agent into the feed inlet of the concrete mixing device (20) in sequence, start the mixing drum (22) to mix the materials for 10 to 15 seconds; Step 4: Turn on the ultrasonic oscillation device to perform ultrasonic treatment on the cement slurry. Two seconds after the ultrasonic treatment ends, use a phase angle detection device to detect the phase angle of the cement slurry. If the phase angle is greater than or equal to 85 degrees, proceed to the next step. If the phase angle is less than 85 degrees, increase the frequency of the ultrasonic oscillation device and continue to perform ultrasonic treatment on the cement slurry until the phase angle is greater than or equal to 85 degrees. Increasing the frequency of the ultrasonic oscillation device means increasing the ultrasonic frequency successively in units of Δf; Δf=k×(85-θ), where k=0.5kHz / °, and θ is the measured phase angle. Step 5: Pour coarse and fine aggregates into the feed port of the concrete mixing device (20), start the mixing drum (22) to mix the materials for 30 to 90 seconds; use the phase angle detection device to detect the phase angle of the fresh concrete, and when the phase angle is less than 10 degrees, pour the concrete out from the discharge port of the concrete mixing device (20).

2. The near-zero magnetic concrete production method according to claim 1, characterized in that, In step 4, the specific parameters for ultrasonic treatment of the cement slurry are: ultrasonic frequency of 10 to 40 kHz, working time of 3 to 8 seconds.

3. The near-zero magnetic concrete production method according to claim 1, characterized in that, The first magnetic shielding composite layer (10) includes a zero-magnetic steel plate (11), an insulating protective layer and a permalloy layer; a demagnetizing coil (19) is provided inside the zero-magnetic steel plate (11).

4. The near-zero magnetic concrete production method according to claim 3, characterized in that, The first magnetic shielding composite layer (10) consists of a zero-magnetic steel plate (11), a demagnetizing coil (19), a first insulating protective layer (12), a first permalloy layer (13), a second insulating protective layer (14), a second permalloy layer (15), a third insulating protective layer (16), a third permalloy layer (17), and a fourth insulating protective layer (18) from the outside to the inside.

5. The near-zero magnetic concrete production method according to claim 1, characterized in that, The second magnetic shielding composite layer (30) includes a zero-magnetic steel plate (11), an insulating protective layer and a permalloy layer; a demagnetizing coil (19) is provided inside the zero-magnetic steel plate (11).

6. The near-zero magnetic concrete production method according to claim 5, characterized in that, The second magnetic shielding composite layer (30) consists of a zero-magnetic steel plate (11), a demagnetizing coil (19), a first insulating protective layer (12), a first permalloy layer (13), a second insulating protective layer (14), a second permalloy layer (15), a third insulating protective layer (16), and a third permalloy layer (17) from the outside to the inside.

7. The near-zero magnetic concrete production method according to claim 6, characterized in that, The stirring motor (23) is connected to the equipment bracket (21) via the motor mounting base (25). A fourth insulating protective layer (18) is provided between the motor mounting base (25) and the third permalloy layer (17) of the second magnetic shielding composite layer (30). A fourth insulating protective layer (18) is also provided between the outer wall of the motor power supply line (24) and the third permalloy layer (17) of the second magnetic shielding composite layer (30).

8. The near-zero magnetic concrete production method according to claim 1, characterized in that, A rectangular concrete mixing construction space is constructed inside the first magnetic shielding composite layer (10) using aluminum square tubes (50).

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