A method for producing different magnetic concretes based on magnetic field control

Abstract

The application discloses a production method of different magnetic concrete based on magnetic field control, and relates to a near-zero magnetic concrete mixing system which 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 outside the concrete mixing device; the second magnetic shielding composite layer is arranged outside 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; and 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 method can realize the production of extremely low remanence 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 production method of different magnetic concretes based on magnetic field control. Background Technology

[0002] Concrete, as one of the most commonly used structural materials in construction engineering, directly affects the safety and functionality of building structures. Traditional concrete uses silicate cement as a binder, mixed with sand, stone, water, and necessary admixtures, and solidifies through physical mixing and hydration reactions. Generally, ordinary commercial concrete meets most building requirements by satisfying conventional performance indicators such as strength, workability, and durability. However, in specific high-end engineering applications, such as astronomical observatories, precision instrument laboratories, geological exploration stations, and military facilities, the magnetic characteristics of concrete become a key performance indicator. Low-magnetic concrete refers to a special type of building material with a significantly lower remanent magnetization value than ordinary concrete. Its design goal is to maximize the shielding or reduction of magnetic interference from the concrete itself, providing an ideal background magnetic environment for weakly magnetically sensitive equipment or environments.

[0003] Existing methods for controlling the magnetism of concrete mainly focus on the selection of raw materials and optimization of mix proportions. Studies have shown that the magnetism of concrete is mainly determined by the ferromagnetic components it contains, especially the content of minerals such as iron oxides and magnetite in cement and aggregates. To reduce the remanence value, some technical solutions use special low-magnetic cement, non-magnetic aggregates, or even pre-treat materials through chemical means. However, these methods have several shortcomings: (1) the material cost is high and the supply channels are limited, which restricts their large-scale engineering applications; (2) the remanence value of concrete is significantly affected by cement batches, aggregate sources, etc., and has poor stability; (3) even if low-magnetic materials are used, the remanence value is often difficult to be lower than 2.5 nT, and it is even more impossible to meet the requirements of near-zero magnetic (<0.5 nT) environments. In addition, some inventions have attempted to reduce magnetism by optimizing the mixing process and adding shielding additives, but their control effect is limited. The lowest remanence value of concrete that can be obtained by the currently published invention patents is generally not lower than 3 nT, which is still unable to meet the stringent requirements of precision scientific research for extremely low magnetic environments. Summary of the Invention

[0004] The purpose of this invention is to provide a method for producing concrete with different magnetic properties based on magnetic field control, so as to solve the problem that the existing technology cannot achieve controllable, adjustable, stable and low-cost preparation of concrete with a remanent magnetization value of less than 2.5nT or even 0.5nT.

[0005] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A method for producing different magnetic concretes based on magnetic field control, comprising the following steps:

[0006] Step 1: Construct a concrete mixing construction space. The concrete mixing construction space consists of a first magnetic shielding composite layer and a space constructed using aluminum square tubes located inside the first magnetic shielding composite layer. Before preparing concrete, use a magnetic field strength testing device to test the environmental magnetic field value within the concrete mixing construction space. If the environmental magnetic field value meets the minimum design requirements and remains stable, proceed to Step 2.

[0007] Step 2: Place the concrete raw materials in the concrete mixing and construction space in advance; the concrete raw materials include cement, coarse aggregate, fine aggregate and organic water-reducing agent;

[0008] Step 3: Mix the concrete raw materials and water processed in Step 2 in the concrete mixing construction space and form concrete.

[0009] Step 4: After the concrete is formed, it continues to be placed in the concrete mixing and construction space. When the concrete phase angle is less than or equal to 10 degrees, the concrete can be moved to the conventional environment.

[0010] The production method of different magnetic concretes based on magnetic field control as described above, preferably, the minimum design requirements in step 1 are: when preparing 25nT concrete, the environmental magnetic field value is kept no higher than 200nT; when preparing 2.5nT concrete, the environmental magnetic field value is kept no higher than 80nT; when preparing 0.5nT concrete, the environmental magnetic field value is kept no higher than 30nT; and when preparing 0.05nT concrete, the environmental magnetic field value is kept no higher than 10nT.

[0011] The method for producing different magnetic concretes based on magnetic field control as described above, preferably, 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 on the inner side of the zero-magnetic steel plate.

[0012] The production method of different magnetic concrete based on magnetic field control described above is preferably wherein the first magnetic shielding composite layer consists of, 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.

[0013] The method for producing different magnetic concretes based on magnetic field control as described above is preferably implemented in step 3 by using a concrete mixing device. The mixing motor and power supply line of the concrete mixing device are provided with a second magnetic shielding composite layer. The second magnetic shielding composite layer includes a zero-magnetic steel plate, an insulating protective layer, and a permalloy layer. A demagnetizing coil is provided inside the zero-magnetic steel plate. The concrete mixing device is made of low-magnetic materials.

[0014] The production method of different magnetic concrete based on magnetic field control described above is preferably wherein the second magnetic shielding composite layer consists of 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, from the outside to the inside.

[0015] The production method of different magnetic concrete based on magnetic field control as described above, preferably, the specific process of step 3 is as follows: cement, water and water-reducing agent are poured into the feed inlet of the concrete mixing device in sequence, the mixing drum is started and the materials are mixed for 10-15 seconds; the ultrasonic oscillation device is turned on to perform ultrasonic treatment on the cement paste; 2 seconds after the ultrasonic treatment ends, the phase angle of the cement paste is detected by the phase angle detection device; wherein, when the phase angle is greater than or equal to 85 degrees, the next step is performed, and when the phase angle is less than 85 degrees, the frequency of the ultrasonic oscillation device is increased and the cement paste is subjected to ultrasonic treatment until the phase angle is greater than or equal to 85 degrees; coarse aggregate and fine aggregate are poured into the feed inlet of the concrete mixing device, the mixing drum is started and the materials are mixed for 30-90 seconds; the phase angle of the fresh concrete is detected by the phase angle detection device, and when the phase angle is less than 10 degrees, the concrete is poured out from the discharge outlet of the concrete mixing device.

[0016] The production method of different magnetic concrete based on magnetic field control described above is preferably characterized by the following specific parameters for ultrasonic treatment of cement slurry: ultrasonic frequency of 10 to 40 kHz, working time of 3 to 8 seconds; increasing the frequency of the ultrasonic oscillation device means increasing the ultrasonic frequency in units of Δf; Δf = k × (85 - θ), where k = 0.5 kHz / °, and θ is the measured phase angle.

[0017] The beneficial effects of this invention are:

[0018] 1. Achieving near-zero magnetic properties (<0.5nT) in concrete materials: This invention effectively suppresses the magnetization behavior of cement particles by constructing a stable, low magnetic field environment throughout the concrete mixing process, and by combining a magnetic shielding layer and ultrasonic technology. This allows the final residual magnetic value of the concrete to be controllably reduced to 0.5nT or even lower, meeting the stringent requirements of astronomical observation, precision instrument installation, military engineering, and other applications for extremely low magnetic environments.

[0019] 2. For the first time, an ultrasonic excitation + phase angle feedback mechanism is introduced to optimize the mixing process; by monitoring the phase angle changes of cement paste and fresh concrete in real time, and adjusting the ultrasonic oscillation frequency based on this parameter, the microstructure inside the paste gradually tends to a non-directional, low remanent magnetization state, improving the uniformity of cement particle distribution and magnetic randomness, and ensuring the consistency of low magnetic performance molding.

[0020] 3. The effectiveness of magnetic shielding can be controlled by adjusting the number of layers in the first magnetic shielding composite layer. For example, a single magnetic shielding layer can control the ambient magnetic field to 200 nT, while five layers can control it to 10 nT (this control can also be achieved using active shielding coils). Through such adjustments, and by using coarse and fine aggregates with different magnetic properties, concrete with varying magnetic properties can be produced. This has significant practical implications because different construction scenarios require different residual magnetic values ​​in the concrete. Attached Figure Description

[0021] 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:

[0022] Figure 1 This is a top view schematic diagram of a near-zero magnetic concrete mixing system;

[0023] Figure 2 for Figure 1 A magnified view of part A in the middle;

[0024] Figure 3 for Figure 1 A magnified view of part B in the middle;

[0025] Figure 4 This is a side view of a near-zero magnetic concrete mixing system.

[0026] Figure 5 for Figure 4 A magnified view of part C in the middle;

[0027] Figure 6 for Figure 4 A magnified view of part D in the middle;

[0028] Figure 7 Flowcharts of different magnetic concrete production methods based on magnetic field control;

[0029] Figure 8 This is a schematic diagram of the particle structure of cement powder.

[0030] Figure 9 A schematic diagram illustrating the stable flocculated overlapping structure of cement particles.

[0031] The attached diagram lists the components represented by each number as follows:

[0032] 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

[0033] In the following description, embodiments of the near-zero magnetic concrete mixing system and the production method of different magnetic concretes based on magnetic field control of the present invention will be described with reference to the accompanying drawings.

[0034] 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.

[0035] The accompanying drawings in this specification are schematic diagrams to aid in illustrating the concept of the invention, and schematically show the shapes of the various parts and their interrelationships. Please note that, in order 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 indicate the same parts.

[0036] Combined with appendix Figure 7 This invention describes a method for producing different magnetic concretes based on magnetic field control, comprising the following steps:

[0037] Step 1: Construct a concrete mixing construction space. The concrete mixing construction space consists of a first magnetic shielding composite layer 10 and a space constructed using aluminum square tubes 50 located inside the first magnetic shielding composite layer 10. Before preparing concrete, use a magnetic field strength testing device to test the environmental magnetic field value in the concrete mixing construction space. When the environmental magnetic field value meets the minimum design requirements and remains stable, proceed to Step 2.

[0038] In a preferred embodiment, the minimum design requirements in step 1 are as follows: when preparing 25nT concrete, the ambient magnetic field value is kept no higher than 200nT; when preparing 2.5nT concrete, the ambient magnetic field value is kept no higher than 80nT; when preparing 0.5nT concrete, the ambient magnetic field value is kept no higher than 30nT; and when preparing 0.05nT concrete, the ambient magnetic field value is kept no higher than 10nT.

[0039] In a preferred embodiment, 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. In a preferred embodiment, as... Figure 2 and Figure 5 As shown, the first magnetic shielding composite layer 10 consists of, from the outside to the inside, 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. Before testing the ambient magnetic field value, the demagnetizing coil 19 is first energized to demagnetize the magnetic shielding material of the magnetic shielding composite layer.

[0040] Step 2: Place the concrete raw materials in the concrete mixing and construction space in advance; the concrete raw materials include cement, coarse aggregate, fine aggregate and organic water-reducing agent;

[0041] Step 3: Mix the concrete raw materials and water processed in Step 2 in the concrete mixing construction space and form concrete.

[0042] In a preferred embodiment, in step 3, the mixing operation is performed using a concrete mixing device 20. The mixing motor 23 and motor power supply line 24 of the concrete mixing device 20 are externally provided with a second magnetic shielding composite layer 30. 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. In a preferred embodiment, as... Figure 3 and Figure 6 As shown, 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.

[0043] In a preferred embodiment, step 3 is as follows: cement, water, and water-reducing agent are sequentially poured into the inlet of the concrete mixing device 20; the mixing drum 22 is started to mix the materials for 10-15 seconds; the ultrasonic oscillation device is turned on to perform ultrasonic treatment on the cement slurry; 2 seconds after the ultrasonic treatment ends, the phase angle of the cement slurry is detected using a phase angle detection device; if the phase angle is greater than or equal to 85 degrees, the next step is performed; if the phase angle is less than 85 degrees, the frequency of the ultrasonic oscillation device is increased, and the cement slurry is continued to be ultrasonically treated until the phase angle is greater than or equal to 85 degrees; coarse aggregate and fine aggregate are poured into the inlet of the concrete mixing device 20; the mixing drum 22 is started to mix the materials for 30-90 seconds; the phase angle of the freshly mixed concrete is detected using a phase angle detection device; if the phase angle is less than 10 degrees, the concrete is poured out from the outlet of the concrete mixing device 20. In one specific embodiment, the specific parameters for ultrasonic treatment of cement slurry are as follows: ultrasonic frequency of 10 to 40 kHz, working time of 3 to 8 seconds; increasing the frequency of the ultrasonic oscillation device means increasing the ultrasonic frequency in units of Δf; Δf = k × (85 - θ), where k = 0.5 kHz / °, and θ is the measured phase angle.

[0044] Step 4: After the concrete is formed, it continues to be placed in the concrete mixing and construction space. When the concrete phase angle is less than or equal to 10 degrees, the concrete can be moved to a normal environment.

[0045] Mechanism of this invention:

[0046] Cement is one of the decisive factors affecting the remanence of concrete. The cement production process involves two grinding stages and one firing stage, resulting in identical composition of finished cement from the same batch after grinding. From a mineral composition perspective, cement particles contain a significant amount of ferromagnetic minerals, giving each cement particle a high remanence value. In terms of particle size, cement particles range from 0.1μm to 100μm, with a d50 value of approximately 10μm. Compared to sand and gravel aggregates, cement particles are extremely small and can be approximated as point masses. Morphologically, ground cement particles are irregular, three-dimensional bodies with sharp edges. When cement is in powder form, different particles are in close contact, with smaller particles filling the spaces between larger particles. The direction of the magnetic induction intensity of cement particles is initially random and disordered, with variations between different cement particles. When a large number of cement particles agglomerate together, the vector sum of the magnetic induction intensities of all cement particles is almost zero. Theoretically, under the influence of the Earth's magnetic field and other strong magnetic fields in the surrounding area, each cement particle would be magnetized, with its magnetic induction intensity pointing in the same direction as the surrounding strong magnetic fields. This would result in the vector sum of the magnetic induction intensities of the cement powder particles, giving the overall particle a high remanence value. However, due to the dense packing and irregular shape of the cement particles, each particle is constrained by several surrounding particles and cannot rotate towards the direction of the external strong magnetic field, maintaining its original position. Therefore, the overall remanence value of the cement powder is extremely low.

[0047] In concrete preparation, a large amount of water is added to the cement. Upon initial contact with water, cement particles form a solid-liquid suspension, where they disperse and their movement and rotation are no longer constrained by surrounding particles. Under the influence of the Earth's magnetic field or a strong surrounding magnetic field, each cement particle is rapidly magnetized, rotating towards the direction of magnetization. The magnetic induction intensity of the cement particles is vector-summed, resulting in a high remanence value in the concrete. Subsequently, the cement particles begin to dissolve and react chemically with water. After dissolution, the cement particles acquire positive and negative charges on their surfaces, leading to agglomeration. Simultaneously, the cement hydration reaction produces ettringite, CSH gel, etc., which gradually overlap between the cement particles. The cement particles gradually form a stable flocculated and overlapping structure, and their movement and rotation are again constrained. The system gradually stabilizes, and the high remanence value of the concrete remains unchanged.

[0048] When using the concrete preparation method described in this invention, a stable and low-level environmental magnetic field is first established, and concrete is prepared in this environment. After cement comes into contact with water and forms a solid-liquid suspension dispersion system, the cement particles are minimally affected by the surrounding environmental magnetic field and do not undergo significant magnetization. The cement particles do not move or rotate in a directional manner but maintain random motion. The magnetic induction intensity orientation of different cement particles varies, resulting in a disordered state. The remanent magnetization value after the superposition of the magnetic induction intensities of a large number of cement particles is very small. Simultaneously, this remanent magnetization value is affected by the established environmental magnetic field; the lower the environmental magnetic field value, the lower the overall remanent magnetization value of the cement. Subsequently, the cement particles begin to dissolve and react chemically with water. The charged cement particles exhibit agglomeration, and the ettringite, CSH gel, etc., produced by the cement hydration reaction gradually aggregate between the cement particles. Figure 8 It is in the form of cement granules and powder. For example... Figure 9 As cement particles gradually form a stable flocculated and overlapping structure, the system gradually stabilizes, and the remanent magnetic value of the concrete no longer changes. The time for cement particles to form a stable flocculated and overlapping structure is approximately 10 to 40 minutes. Therefore, the preparation method involved in this invention can prepare low-magnetic to near-zero-magnetic concrete using conventional ordinary cement, without the need for specific low-magnetic cement.

[0049] The following combination Figures 1 to 6 This invention describes the facilities and apparatus used in the above-described methods for producing different magnetic concretes based on magnetic field control. One embodiment of a near-zero magnetic concrete mixing system includes:

[0050] 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.

[0051] 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 5As shown, the first magnetic shielding composite layer 10 consists of, from the outside to the inside, a demagnetizing coil 19, a zero-magnetic steel plate 11, 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.

[0052] 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 and 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 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.

[0053] 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 using aluminum square tubes 50 inside the first magnetic shielding composite layer 10. Figure 4 As shown, a low-magnetic concrete layer 40 is provided on the installation bottom surface of the concrete mixing device 20, and a dual-magnetic shielding composite layer 30 is provided below the low-magnetic concrete layer 40.

[0054] An ultrasonic oscillation device, with its waveguide rod installed inside the mixing drum 22, utilizes the cavitation and acoustic flow effects of 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 AC power into a high-frequency electrical signal, with adjustable frequency and waveform. The transducer, a piezoelectric ceramic transducer, 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 sidewalls 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, typically ranging from 2 to 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.

[0055] 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.

[0056] 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.

[0057] Effect Verification Example

[0058] 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 remanence 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 remanence 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 remanence value of the coarse aggregate in Examples 1 to 8 is not higher than 0.86nT; the fine aggregate is quartz sand with a particle size less than 4.75 mm, and the remanence value of the fine aggregate in Examples 1 to 8 is not higher than 0.93nT.

[0059] 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.

[0060] Table 1 Sample Mixing Ratio

[0061]

[0062] 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 / T 50081-2019, "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.

[0063] Example 1

[0064] Step 1: Construct a concrete mixing and construction space. The concrete mixing and construction space consists of a first magnetic shielding composite layer and a space constructed using aluminum square tubes located inside the first magnetic shielding composite layer. Before preparing concrete, use a magnetic field strength testing device to test the environmental magnetic field value within the concrete mixing and construction space. If the environmental magnetic field value meets the minimum design requirements and remains stable, proceed to Step 2. The purpose of this embodiment is to prepare 0.5nT concrete with an environmental magnetic field value of 20nT.

[0065] Step 2: Place the concrete raw materials in the concrete mixing and construction space in advance; the concrete raw materials include cement, coarse aggregate, fine aggregate and organic water-reducing agent;

[0066] Step 3: Mix and mold the concrete in the concrete mixing construction space;

[0067] 3.1. Pour cement, water, and water-reducing agent sequentially into the feed inlet of the concrete mixing device 20. Start the mixing drum 22 to mix the materials for 15 seconds. 3.2. Turn on the ultrasonic oscillation device to perform ultrasonic treatment on the cement slurry (ultrasonic frequency 20kHz, operating for 5 seconds). Two seconds after the ultrasonic treatment ends, use a phase angle detection device to detect the phase angle of the cement slurry; the phase angle is equal to 65 degrees. Increase the frequency of the ultrasonic oscillation device and continue ultrasonic treatment on the cement slurry (ultrasonic frequency 30kHz, operating for 5 seconds). Two seconds after the treatment ends, the phase angle of the cement slurry is detected using a phase angle detection device, and the phase angle is equal to 80 degrees. The frequency of the ultrasonic oscillation device is increased, and the cement slurry is continued to undergo ultrasonic treatment (ultrasonic frequency of 32.5 kHz, working for 5 seconds). Two seconds after the ultrasonic treatment ends, the phase angle of the cement slurry is detected using a phase angle detection device, and the phase angle 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 = 0.5 kHz / °, and θ is the measured phase angle. In this embodiment of the invention, the inherent resonant frequency of cement particles (usually 15-40 kHz) can be accurately matched by dynamic frequency adjustment, 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 500 W / L. 3.3 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 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.

[0068] Step 4: After the concrete is formed, it continues to be placed in the concrete mixing and construction space. When the concrete phase angle is less than or equal to 10 degrees, the concrete can be moved to the conventional environment.

[0069] Example 2

[0070] Except for step 3.2, 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 the phase angle detection device to detect the phase angle of the cement slurry, and the phase angle is equal to 65 degrees.

[0071] Example 3

[0072] Except for step 3.2, 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.

[0073] Example 4

[0074] Except for step 3.2, 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 520W / L.

[0075] Example 5

[0076] Except for step 3.2, 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 560W / L.

[0077] Example 6

[0078] Except for step 3.2, 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 450W / L.

[0079] Example 7

[0080] Except for step 3.2, 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 400W / L.

[0081] Example 8

[0082] Except for step 3.2, 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.

[0083] Example 9

[0084] The purpose of this embodiment is to prepare 2.5nT concrete with an ambient magnetic field value of 60nT and a residual magnetic value of coarse and fine aggregates not exceeding 2.85nT; the rest is the same as in embodiment 1.

[0085] Example 10

[0086] The purpose of this embodiment is to prepare 25nT concrete with an ambient magnetic field value of 150nT and a remanent magnetic value of coarse and fine aggregates not exceeding 28.50nT; the rest is the same as in embodiment 1.

[0087] Example 11

[0088] The purpose of this embodiment is to prepare 0.05nT concrete with an ambient magnetic field value of 5nT and a residual magnetic value of coarse and fine aggregates not exceeding 0.1nT; the rest is the same as in embodiment 1.

[0089] 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.

[0090] Comparative Example

[0091] 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.

[0092] Table 2 Performance Test Results

[0093]

[0094] 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.

[0095] 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 concrete with different magnetic properties based on magnetic field control, characterized in that, Includes the following steps: Step 1: Construct a concrete mixing construction space. The concrete mixing construction space consists of a first magnetic shielding composite layer and a space constructed using aluminum square tubes located inside the first magnetic shielding composite layer. Before preparing concrete, use a magnetic field strength testing device to test the environmental magnetic field value within the concrete mixing construction space. If the environmental magnetic field value meets the minimum design requirements and remains stable, proceed to Step 2. Step 2: Place the concrete raw materials in the concrete mixing and construction space in advance; the concrete raw materials include cement, coarse aggregate, fine aggregate and organic water-reducing agent; Step 3: In the concrete mixing and construction space, mix the concrete raw materials and water processed in Step 2 and form concrete. The specific process of Step 3 is as follows: 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 10-15 seconds; turn on the ultrasonic oscillation device to perform ultrasonic treatment on the cement paste; 2 seconds after the ultrasonic treatment ends, use a phase angle detection device to detect the phase angle of the cement paste; 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 paste. Continue mixing until the phase angle is greater than or equal to 85 degrees; pour coarse and fine aggregates into the feed inlet of the concrete mixing plant, start the mixing drum, and mix the materials for 30 to 90 seconds; use a phase angle detection device to detect the phase angle of the fresh concrete, and pour the concrete out from the discharge outlet of the concrete mixing plant when the phase angle is less than 10 degrees; the specific parameters for ultrasonic treatment of cement paste are: ultrasonic frequency of 10 to 40 kHz, working for 3 to 8 seconds; increasing the frequency of the ultrasonic oscillation device means increasing the ultrasonic frequency step by step in units of Δf; Δf=k×(85-θ), where k=0.5kHz / °, and θ is the measured phase angle; Step 4: After the concrete is formed, it continues to be placed in the concrete mixing and construction space. When the concrete phase angle is less than or equal to 10 degrees, the concrete can be moved to the conventional environment.

2. The method for producing different magnetic concretes based on magnetic field control according to claim 1, characterized in that, The minimum design requirements mentioned in step 1 are as follows: when preparing 25nT concrete, the ambient magnetic field value should not exceed 200nT; when preparing 2.5nT concrete, the ambient magnetic field value should not exceed 80nT; when preparing 0.5nT concrete, the ambient magnetic field value should not exceed 30nT; and when preparing 0.05nT concrete, the ambient magnetic field value should not exceed 10nT.

3. The method for producing different magnetic concretes based on magnetic field control according to claim 1, characterized in that, The first magnetic shielding composite layer includes a zero-magnetic steel plate, an insulating protective layer, and a permalloy layer; a demagnetizing coil is provided on the inner side of the zero-magnetic steel plate.

4. The method for producing different magnetic concretes based on magnetic field control according to claim 3, characterized in that, The first magnetic shielding composite layer consists of, 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.

5. The method for producing different magnetic concretes based on magnetic field control according to claim 1, characterized in that, In step 3, the mixing operation is carried out using a concrete mixing device. The mixing motor and the motor power supply line of the concrete mixing device are provided with a second magnetic shielding composite layer. The second magnetic shielding composite layer includes a zero-magnetic steel plate, an insulating protective layer, and a permalloy layer. A demagnetizing coil is provided inside the zero-magnetic steel plate. The concrete mixing device is made of low-magnetic materials.

6. The method for producing different magnetic concretes based on magnetic field control according to claim 5, characterized in that, The second magnetic shielding composite layer consists of, 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.

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