A dual-response grouting material with magnetically controlled thixotropic properties and a preparation method thereof

Abstract

The application discloses a kind of dual-response grouting materials with magnetically controlled thixotropy and preparation method thereof, belong to grouting material technical field.The material is composed of cementitious matrix, high magnetic susceptibility soft magnetic particles, high remanence hard magnetic particles, functional admixture and mixing water.The core lies in the synergistic effect of soft magnetic and hard magnetic particles under different magnetic field modes, realizes the two-way active regulation of slurry viscosity: under static or low-frequency magnetic field, particles form chain together, slurry viscosity increases significantly, realizes fixed-point anchoring;Under the medium-frequency alternating magnetic field (1~100 Hz), hard magnetic particles regular flip and soft magnetic particles lag flip produce asynchronous oscillation, destroy magnetic chain structure, reduce slurry viscosity, maintain high fluidity to penetrate fine cracks.The application also provides the preparation process of the material, by switching magnetic field mode, solve the contradiction that high permeability and high retention rate are difficult to consider in grouting engineering, without evacuation can realize continuous construction, significantly improve grouting efficiency and quality.

Description

Technical Field

[0001] This invention belongs to the field of grouting materials technology, and particularly relates to a dual-response grouting material with magnetron thixotropic properties and its preparation method. Background Technology

[0002] In grouting projects, the rheological properties of the grout (especially its viscosity) are the core factors determining the grouting effect. Ideally, the grout should maintain a low viscosity under grouting pressure to penetrate fine cracks over long distances, and then rapidly thicken upon reaching the target area to retain it at a fixed point and prevent loss.

[0003] In recent years, introducing magnetic particles into grouting materials to impart magnetic field responsiveness has become a technological development trend. Existing patented technologies mainly include the following: CN109626942A discloses a magnetorheological intelligent shield tunneling grouting material, comprising, by weight: 400-1000 parts magnetic particles, 200-400 parts water, 50-100 parts expansive clay, 600-1200 parts sand, 400-800 parts fly ash, 100-200 parts cement, 100-200 parts water glass, and 30-100 parts admixtures. The magnetic particles are multi-domain materials of iron, cobalt, nickel, or their alloys with a particle size of 1-10 micrometers. This technology exhibits good grout fluidity even without an external magnetic field. During actual construction, different intensities of external magnetic fields can be applied according to different geological conditions to adjust the grout viscosity within the shield tail gap. Its core mechanism is that under the action of a static or quasi-static magnetic field, the magnetic particles align into a chain-like structure along the magnetic field lines, causing the grout viscosity to increase with increasing magnetic field strength.

[0004] CN120465523A discloses a device and method for adaptive repair of non-straight cracks using magnetic mortar. The magnetic mortar is composed of oil-based epoxy resin, magnetic materials, curing agent, fly ash, cement, etc. By nailing micro-magnetic anchors into the cracks, the micro-magnetic anchors attract the magnetic mortar and make it uniformly fill the cracks.

[0005] All the aforementioned patented technologies share a common limitation: their response to magnetic fields is unidimensional, only able to regulate viscosity by changing the magnetic field strength, and the direction of viscosity change is one-way (increased magnetic field strength → increased viscosity, decreased magnetic field strength → decreased viscosity). This unidirectional response mode presents the following contradictions under complex grouting conditions: ① To penetrate fine cracks, the grout needs to maintain a low viscosity; however, low-viscosity grout is easily lost when it encounters large voids and cannot be retained at a fixed point.

[0006] ② In order to prevent loss, the magnetic field is increased to thicken the slurry, which will also hinder the slurry from continuing to diffuse to distant places and fine cracks.

[0007] ③ Traditional magnetorheological slurries reduce viscosity by removing the magnetic field, but the chain structure of magnetic particles disintegrates after the magnetic field is removed, which takes a certain amount of time and cannot be actively accelerated.

[0008] In existing magnetic grouting patent technologies, the applied magnetic field is always static or quasi-static. No patents have yet addressed the regulation of the rheological properties of magnetic grout by alternating magnetic fields (especially medium-frequency alternating magnetic fields, 1~100 Hz). In related technologies, it is known that magnetic particles will experience magnetic moment reversal under the action of an alternating magnetic field, but this effect is generally considered to lead to energy dissipation and heat generation. No one has yet proposed using the frequency effect of an alternating magnetic field to actively reduce the grout viscosity to resolve the aforementioned construction contradictions.

[0009] In summary, there is an urgent need for a smart material solution that can actively select whether to thicken or reduce the viscosity of the slurry by switching the magnetic field mode (static / alternating) under the same magnetic field device, according to construction needs. Summary of the Invention

[0010] To address the aforementioned technical problems, this invention proposes a dual-response grouting material with magnetotropic thixotropic properties and its preparation method. Two functional components with different magnetic properties—high magnetic susceptibility soft magnetic particles and high remanence hard magnetic particles—are simultaneously introduced into the grouting substrate. Utilizing the difference in their magnetic moment reversal rates under an alternating magnetic field, the viscosity of the grout can be bidirectionally controlled with "frequency selectivity."

[0011] To achieve the above objectives, the present invention provides the following technical solution: A dual-response grouting material with magnetron thixotropic properties, comprising the following components in parts by weight: 100 parts of cementitious substrate; 5-20 parts of high magnetic susceptibility soft magnetic particles; 3-12 parts of high remanence hard magnetic particles; 0.5-3 parts of functional additives; 30-60 parts of mixing water; Among them, the coercivity Hc of the high magnetic susceptibility soft magnetic particles is <200 Oe, and the saturation magnetization Ms is >80 emu / g; The coercivity Hc of the high remanence hard magnetic particles is greater than 1 kOe, and the remanence Mr is greater than 30 emu / g. Under the action of a static or low-frequency magnetic field (f ≤ 0.1 Hz), soft magnetic particles and hard magnetic particles are arranged into chains along the direction of the magnetic field, and the viscosity of the slurry increases significantly. Under the action of a medium-frequency alternating magnetic field (f = 1~100 Hz), the regular flipping of hard magnetic particles and the hysteretic flipping of soft magnetic particles generate asynchronous oscillations, which destroy the magnetic flux structure and reduce the viscosity of the slurry.

[0012] Beneficial Effects: Addressing the limitations of existing technologies that rely solely on a single magnetic response dimension and can only achieve unidirectional thickening through increased magnetic field strength, this invention introduces both high-magnetic-susceptibility soft magnetic particles and high-remanence hard magnetic particles into the grouting substrate, constructing a unique two-phase particle synergistic system. This enables bidirectional active control of rheological properties. Utilizing the differentiated responses of soft and hard magnetic particles under different magnetic field modes, this system endows the material with the ability to actively choose between thickening and viscosity reduction by switching modes within the same magnetic field environment. When a static or low-frequency magnetic field is applied, the two types of particles synergistically align along the magnetic field lines to form a dense chain structure, significantly increasing the slurry viscosity. However, when switching to a medium-frequency alternating magnetic field, the regular flipping of the hard magnetic particles and the hysteretic flipping of the soft magnetic particles generate asynchronous oscillations. This "micro-stirring" effect actively disrupts the established magnetic flux network, reducing the slurry viscosity and restoring fluidity, fundamentally overcoming the limitation of traditional magnetorheological slurry viscosity only increasing unidirectionally.

[0013] This invention eliminates the contradiction between high permeability and high retention rate of grouting materials through the aforementioned bidirectional control mechanism, achieving intelligent switching between "long-distance penetration → targeted sealing". In the initial stage of grouting, operators can apply a medium-frequency alternating magnetic field to maintain the grout in a low-viscosity state, allowing it to easily penetrate deep into minute cracks under grouting pressure, completing long-distance diffusion. Once the grout reaches the target sealing area, simply switching the magnetic field mode to a static magnetic field causes the grout to rapidly thicken and anchor, forming a high-strength sealing body, effectively preventing grout loss in large cavities or non-target areas. This ability to actively adjust the rheological state according to the construction process ensures that the grouting material can both flow far and remain effectively, greatly improving the accuracy and effectiveness of grouting repair.

[0014] Optionally, the high magnetic susceptibility soft magnetic particles are selected from one or more of Fe3O4 microspheres, carbonyl iron powder, and iron-nickel alloy particles, with a particle size range of 1~30 μm.

[0015] Optionally, the high remanence hard magnetic particles are selected from one or more of neodymium iron boron nanoparticles, samarium cobalt nanoparticles, and barium ferrite nanoparticles, with a particle size range of 50~500 nm.

[0016] Optionally, the functional additive is at least one of polycarboxylate water-reducing and dispersing agents and naphthalene sulfonate water-reducing and dispersing agents.

[0017] Optionally, the cementitious substrate is selected from cement or geopolymer.

[0018] Furthermore, the cement is selected from any one of ordinary Portland cement (PO 42.5), sulfoaluminate cement, and ultrafine cement.

[0019] Furthermore, when the cementitious substrate is cement, the dual-response grouting material with magnetotropic thixotropic properties comprises the following components: The mixture comprises cement, soft magnetic particles with high magnetic susceptibility, hard magnetic particles with high remanence, functional admixtures, and mixing water, wherein the functional admixtures are polycarboxylate water-reducing and dispersing agents, naphthalene sulfonate water-reducing and dispersing agents, or a mixture of both.

[0020] Furthermore, when the gelling substrate is a geopolymer, the dual-response grouting material with magnetron thixotropic properties comprises the following components: Blast furnace slag powder, fly ash, sodium metasilicate pentahydrate powder (alkali activator), high magnetic susceptibility soft magnetic particles, high remanence hard magnetic particles, naphthalene sulfonate water-reducing dispersant and mixing water.

[0021] The preparation method of the above-mentioned dual-response grouting material with magnetron thixotropic properties includes the following steps: (1) Pre-magnetize the high remanence hard magnetic particles; (2) Dry mix the cementitious substrate, high magnetic susceptibility soft magnetic particles, and pre-magnetized high remanence hard magnetic particles evenly; (3) Dissolve the functional additives in the mixing water, add the mixed powder from step (2), stir until uniform, and obtain the slurry, which is the dual-response grouting material.

[0022] Optionally, the pre-magnetization process in step (1) uses a pulsed magnetic field device with a magnetic field strength of 1~3 T and a pulse count of 1~5.

[0023] The above-mentioned dual-response grouting material was used in a transparent model box to simulate the grouting of fractures in underground engineering.

[0024] Optionally, the process of simulating underground engineering fracture grouting in the transparent model box is as follows: (1) In the initial stage of grouting, a medium-frequency alternating magnetic field with a frequency of 1~100 Hz and a magnetic induction intensity of 20~80 mT is applied to keep the grout at a low viscosity so as to penetrate the fine cracks. (2) After the grout reaches the target area, switch to a static magnetic field or a low-frequency magnetic field with a magnetic induction intensity of 50~300mT to thicken the grout and anchor it for sealing.

[0025] Beneficial Effects: This invention enables continuous construction without the need for site relocation, significantly improving engineering efficiency. Switching between all rheological states requires only altering the electrical parameters of the electromagnetic coil (such as frequency and amplitude), without moving or removing the external magnetic field device. This non-contact remote control method allows construction personnel to flexibly switch between "penetration mode" and "anchoring mode" without interrupting the grouting process, adapting to complex and ever-changing underground fracture environments. This technology not only simplifies the operation process but also avoids delays caused by equipment disassembly and assembly, providing an efficient, intelligent, and reliable solution for underground fracture grouting.

[0026] Compared with the prior art, the present invention has the following advantages and technical effects: (1) Existing magnetorheological grouting materials (such as CN109626942A) only have a single response to magnetic field strength (H↑→viscosity↑). This invention introduces magnetic field frequency as a second control dimension for the first time, realizing bidirectional active control of static magnetic field thickening + medium frequency alternating magnetic field viscosity reduction, fundamentally breaking through the limitation that the viscosity of traditional magnetorheological grout can only increase in one direction.

[0027] (2) By switching the magnetic field mode (static / medium frequency alternation), the same grout can be freely switched between "high penetration mode" (low viscosity) and "anchoring mode" (high viscosity). In the early stage of grouting, the medium frequency mode is used to penetrate the fine cracks over a long distance. After reaching the target position, the static mode is switched to anchor the grout at a fixed point, which perfectly solves the industry problem of "both flowing far and staying in place".

[0028] (3) All rheological state switching only requires changing the electrical parameters (frequency and amplitude) of the electromagnetic coil, without moving or removing the magnetic field device, which greatly improves construction efficiency.

[0029] (4) This invention introduces the "asynchronous oscillation viscosity reduction of soft magnetic / hard magnetic dual-phase particles" mechanism into the field of grouting materials for the first time. By using the regular flipping of hard magnetic particles under alternating magnetic field as a "micro stirring paddle", the chain structure of soft magnetic particles is actively destroyed, and the "magnetic moment flipping hysteresis" which is usually regarded as a negative effect is transformed into a driving force for active viscosity reduction.

[0030] (5) The magnetic functional component dosage is reasonable (8%~32%), the preparation method is simple, no special equipment is required, and it can be directly produced and used in the existing grouting and mixing system. Attached Figure Description

[0031] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1This is a schematic diagram showing the microstructure changes of the dual-response grouting material prepared in this invention under different magnetic field modes. In the figure: (a) No magnetic field - particles are randomly dispersed, low viscosity; (b) Static magnetic field - soft and hard magnetic particles are chained together, high viscosity; (c) Medium frequency alternating magnetic field - hard magnetic particles are turned over and "stirred", destroying the magnetic chain and restoring low viscosity.

[0032] Figure 2 This is a flowchart illustrating the preparation process of the dual-response grouting material of the present invention.

[0033] Figure 3 This is a schematic diagram illustrating the application scenario of the dual-response grouting material of the present invention in grouting construction. In the figure, (a) represents the medium-frequency mode - grout penetration into micro-cracks; (b) represents the static mode - grout anchoring and sealing at cavities / large cracks; 1-structure to be repaired; 2-grouting hole; 3-grouting fluid containing magnetic particles; 4-micro-cracks; 5-cavities or large cracks; 6-electromagnetic coil; 7-anchoring and sealing body. Detailed Implementation

[0034] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0035] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0036] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0037] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0038] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0039] This invention provides a dual-response grouting material with magnetron thixotropic properties, composed of the following components in parts by mass: (1) Cementitious substrate: 100 parts; It is selected from one of ordinary Portland cement (PO 42.5), sulfoaluminate cement, ultrafine cement, or geopolymer. The base material provides the basic mechanical strength and flowability of the grouting material. For applications requiring penetration into fine cracks, ultrafine cement (specific surface area ≥ 800 m² / kg) is preferred.

[0040] (2) High magnetic susceptibility soft magnetic particles: 5~20 parts; High magnetic susceptibility soft magnetic particles possess low coercivity (Hc < 200 Oe) and high saturation magnetization (Ms > 80 emu / g). They can be fully magnetized under relatively weak magnetic fields and exhibit extremely low remanence after the magnetic field is removed. High magnetic susceptibility soft magnetic particles are selected from one or more of the following: ① Fe3O4 microspheres: particle size 1~20 μm, saturation magnetization about 85~95 emu / g, coercivity about 50~100 Oe; ② Carbonyl iron powder: particle size 1~10 μm, saturation magnetization about 190~210 emu / g, coercivity about 0.05~2Oe; ③ Iron-nickel alloy particles: particle size 5~30 μm, saturation magnetization about 120~150 emu / g, coercivity about 1~10Oe; The role of high magnetic susceptibility soft magnetic particles: They can be rapidly magnetized under a static magnetic field and arranged into chains along the direction of the magnetic field, providing a basic thickening effect; Under a low-frequency alternating magnetic field, the magnetic moment can follow and flip, but the flipping speed is limited by the relaxation time. (3) High remanence hard magnetic particles: 3~12 parts; High remanence hard magnetic particles possess high coercivity (Hc>1 kOe) and high remanence (Mr>30 emu / g), and can maintain a strong remanence intensity once magnetized; high remanence hard magnetic particles are selected from one or more of the following: ① Neodymium iron boron (NdFeB) nanoparticles: particle size 50~500 nm, coercivity about 8~12 kOe, remanence about 60~80 emu / g; ② Samarium cobalt (SmCo) nanoparticles: particle size 50~500 nm, coercivity about 15~25 kOe, remanence about 50~70 emu / g; ③ Barium ferrite (BaFe) 12 O 19Nanoparticles: particle size 100~500 nm, coercivity about 3~5 kOe, remanence about 30~40 emu / g; The role of high-remanence hard magnetic particles is that they possess a stable magnetic moment direction after pre-magnetization; under low-frequency alternating magnetic fields, their magnetic moments can flip along the direction of the magnetic field (because although their coercivity is high, they can still flip when the amplitude of the applied alternating field is sufficient); while soft magnetic particles, due to their shorter relaxation time, exhibit a lag in flipping. This asynchronous flipping effect is the core of this invention for achieving frequency-selective viscosity reduction.

[0041] (4) Functional admixtures: 0.5~3 parts; Functional additives are selected based on different substrate systems: ① For cement-based systems: Polycarboxylate water-reducing dispersants, naphthalene sulfonate water-reducing dispersants, or mixtures of both are selected. The polar groups (such as carboxyl and sulfonic acid groups) and hydrophobic skeleton in their molecular structure can simultaneously play the following dual roles: First, they disperse cement particles through electrostatic repulsion and steric hindrance, releasing free water in the flocculated structure and improving the fluidity of the slurry (water-reducing function); Second, they adsorb onto the surface of magnetic particles, preventing irreversible agglomeration and sedimentation of magnetic particles (especially high remanence hard magnetic particles) in the slurry, ensuring the uniform dispersion of two-phase particles (dispersion stabilization function). ② For geopolymer-based systems: Naphthalene sulfonate water-reducing dispersant is selected, which is structurally stable in alkaline environments. In its molecular structure, the naphthalene ring is connected by methylene bridges to form a hydrophobic framework, and the side chain sulfonic acid groups (-SO3) - It provides hydrophilicity and electrostatic repulsion. When naphthalene-based water-reducing agents are added to the geopolymer system, the sulfonic acid groups are adsorbed onto the surface of the geopolymer precursor particles and magnetic particles through electrostatic action, so that the particle surface carries the same charge and the particles repel each other, releasing the free water trapped in the flocculation structure, thereby improving the fluidity of the slurry. (5) Mixing water: 30~60 parts.

[0042] The dual-response rheological modulation mechanism of the above-mentioned grouting material with magnetotropic thixotropic properties disclosed in this invention is as follows: The material of this invention can achieve the following three rheological states by switching magnetic field modes: State 1: Static / Low-frequency magnetic field (f = 0~0.1 Hz) — High-viscosity "anchoring" mode Under static or extremely low-frequency magnetic fields (50–300 mT), both soft and hard magnetic particles are magnetized along the magnetic field lines and arranged in chains. Together, these two types of particles form a dense magnetic flux network, significantly increasing the slurry viscosity (up to 10–30 times the initial viscosity) and substantially enhancing the yield stress. This method is used to rapidly thicken and anchor the slurry upon reaching the target area, preventing loss.

[0043] State 2: Medium-frequency alternating magnetic field (f = 1~100 Hz) – Low viscosity “penetration” mode Under a mid-frequency alternating magnetic field with a frequency of 1~100 Hz and an amplitude of 20~80 mT: ① Due to their high coercivity, hard magnetic particles (such as NdFeB and SmCo) can have their magnetic moments rotate regularly and periodically following the direction of an alternating magnetic field (the rotation frequency is equal to the magnetic field frequency).

[0044] ② Soft magnetic particles (such as Fe3O4 and carbonyl iron powder) have low coercivity and short magnetic moment relaxation time. In a rapidly changing magnetic field, the magnetic moment reversal is significantly delayed and cannot keep up with the rhythm of magnetic field changes.

[0045] ③ An asynchronous oscillation effect is generated between the regular flipping of hard magnetic particles and the hysteretic flipping of soft magnetic particles: the hard magnetic particles, like "miniature stirring paddles", generate local micro-disturbances in the slurry, disrupting the chain-like structure formed by the soft magnetic particles and destroying the magnetic flux network.

[0046] ④ The grout viscosity decreases instead of increasing, or remains at a low level similar to that in the absence of a magnetic field, maintaining good fluidity and permeability. This mode is used in the initial stage of grouting or when long-distance diffusion is required, to keep the grout viscosity low so as to penetrate fine cracks.

[0047] State 3: High-frequency magnetic field (f>1 kHz) – intrinsic viscosity mode When the magnetic field frequency exceeds approximately 1 kHz, all magnetic particles (including hard and soft magnetic particles) cannot follow the magnetic field's rotation due to inertial effects; the magnetic moment remains almost stationary, and the magnetic effect essentially disappears. The slurry viscosity returns to its intrinsic viscosity without an applied magnetic field. This mode can be used as a "standby" state.

[0048] like Figure 2 As shown, the present invention also provides a method for preparing a dual-response grouting material with magnetotropic thixotropic properties, comprising the following steps: Step 1: Pre-magnetization of hard magnetic particles (optional) High remanence hard magnetic particles are placed in a pulsed magnetic field device and pre-magnetized by applying a pulsed magnetic field of 1~3 T to give the hard magnetic particles initial remanence. This step is optional; the high remanence hard magnetic particles can also be magnetized when a static magnetic field is first applied at the grouting site.

[0049] Step 2: Dry powder premixing Weigh out the gelling substrate (including the alkali activator powder required for the geopolymer), high magnetic susceptibility soft magnetic particles, and pre-magnetized high remanence hard magnetic particles according to the mass ratio, and put them into the mixer and dry mix for 2-3 minutes to ensure that all solid components are fully and evenly mixed.

[0050] Step 3: Wet mixing and pulping Dissolve the functional additive (polycarboxylate water-reducing dispersant, naphthalene sulfonate water-reducing dispersant, or a mixture of both) in the mixing water, add the mixed powder from step two, and stir with a mechanical stirrer at a speed of 200~500 r / min for 3~5 minutes until the slurry is uniform, without lumps or sedimentation.

[0051] The application method of the above-mentioned dual-response grouting material with magnetron thixotropic properties is carried out in a transparent model box, and specifically includes the following steps: Simulated construction phase one (penetration and diffusion): Turn on the medium-frequency alternating magnetic field (f = 5~50 Hz, B = 20~50 mT) and inject grout; at this time, the grout maintains low viscosity and high fluidity, and penetrates long distances into the fine cracks under the driving force of grouting pressure; Simulated construction phase two (fixed-point anchoring): When the grout reaches the target area, the magnetic field is switched to a static strong magnetic field (B = 100~300 mT); the grout viscosity increases sharply and is fixed in the target area to prevent it from flowing to non-target areas; Phase 3 of the simulated construction (switching / waiting): If further diffusion is required, the system can be switched back to the medium-frequency alternating magnetic field mode; if a long standby period is required, the system can be switched to the high-frequency mode or the magnetic field can be turned off.

[0052] Unless otherwise specified, the term "parts" in this invention refers to parts by weight.

[0053] All raw materials used in this invention were purchased from the market. The powdered polycarboxylate superplasticizer was purchased from Shanghai Qishuo Industrial Co., Ltd., model QS-8011L; the powdered naphthalene sulfonate superplasticizer was purchased from Kaimet Technology Co., Ltd., model SNF-A.

[0054] The technical solution of the present invention will be further illustrated by the following embodiments.

[0055] Example 1: Ultrafine cement-based magnetron thixotropic dual-response grouting material (1) Material ratio: ultrafine cement (specific surface area 850 m²) 2 100 parts of Fe3O4 microspheres (5-15 μm particle size); 5 parts of neodymium iron boron nanoparticles (100-300 nm particle size, pre-magnetized); 1.5 parts of polycarboxylate water-reducing dispersant; 45 parts of mixing water.

[0056] (2) Preparation method, including the following steps: ① Place neodymium iron boron nanoparticles in a pulsed magnetic field device and pre-magnetize them three times with a 2 T pulsed magnetic field.

[0057] ② Add ultrafine cement, Fe3O4 microspheres, and pre-magnetized NdFeB particles to the mixer and dry mix for 2 minutes.

[0058] ③ Dissolve the polycarboxylate water-reducing dispersant in the mixing water, add the mixed powder, and stir at 300 r / min for 4 min to obtain the ultrafine cement-based magnetron thixotropic dual-response grouting material.

[0059] Verification method for dual-response rheological properties: The following tests were conducted using a rotational rheometer with a self-made electromagnetic coil accessory: ① Static mode (B = 150 mT, f = 0): The measured slurry viscosity is significantly increased compared to when there is no magnetic field, and obvious yield stress appears, showing "solid-like" characteristics.

[0060] ② Medium frequency alternating mode (B = 30 mT, f = 10 Hz): The measured slurry viscosity decreased significantly, recovering to a fluidity level close to that of the absence of a magnetic field.

[0061] ③ High-frequency mode (B = 30 mT, f = 2 kHz): The viscosity is basically the same as that in the absence of a magnetic field.

[0062] The above phenomena verify that the material of the present invention has frequency-selective rheological control capabilities of "static thickening, mid-frequency viscosity reduction, and high-frequency restoration".

[0063] Application simulation verification: A transparent fracture simulation device (with fracture opening gradually changing from 0.1 to 2 mm) was used, and an electromagnetic coil was installed near the grouting port.

[0064] ① When the medium frequency mode (B = 30 mT, f = 10 Hz) is turned on and the grout is injected, it can be observed that the grout smoothly penetrates into the depths of the fine cracks (aperture < 0.2 mm) under low pressure and diffuses over a long distance.

[0065] ② After the slurry reaches the target area, switch to a static magnetic field (B = 200 mT, f = 0). It can be observed that the viscosity of the slurry increases rapidly, forming a tight seal in the target area and no longer flowing into non-target areas.

[0066] Example 2: Geopolymer-based Magnetron Thixotropic Dual-Response Grouting Material (1) Material proportions: Blast furnace slag powder (S95 grade, specific surface area ≥ 400 m²) 2 50 parts ( / kg); 35 parts Class I fly ash; 15 parts sodium metasilicate pentahydrate powder; 15 parts iron-nickel alloy particles (particle size 5~15 μm); 4 parts samarium cobalt nanoparticles (particle size 200~400nm, pre-magnetized); 1.5 parts naphthalene sulfonate water-reducing dispersant; 45 parts mixing water.

[0067] (2) The preparation method is the same as in Example 1.

[0068] Application simulation verification: A transparent fracture simulation device (with fracture opening gradually changing from 2 cm to 1 mm) was used, and an electromagnetic coil was installed near the grouting port.

[0069] ① Static mode (B = 200 mT, f = 0): The slurry rapidly forms a magnetic flux network, and the viscosity increases significantly. It can resist gravity and prevent sagging and loss in inclined or vertical fracture surfaces.

[0070] ② Medium-frequency alternating mode (B = 25 mT, f = 15 Hz): The slurry regains good fluidity and can be injected into fine cracks under low pressure.

[0071] ③ Switching response time: After switching from static to medium frequency mode, the viscosity begins to decrease within 5 seconds and reaches a stable low viscosity state within 15 seconds.

[0072] Example 3: Sulfoaluminate cement-based rapid-curing dual-response grouting material (1) Material ratio: 100 parts of sulfoaluminate cement (SAC 42.5); 10 parts of hydroxyl iron powder (particle size 3~8 μm); 6 parts of barium ferrite nanoparticles (particle size 150~400 nm, pre-magnetized); 0.8 parts of naphthalene sulfonate water-reducing dispersant; 0.5 parts of polycarboxylate water-reducing dispersant; 40 parts of mixing water.

[0073] (2) The preparation method is the same as in Example 1, and the verification method is the same as in Example 2.

[0074] The features of this embodiment 3 are: short setting time (initial setting time of about 20 minutes), which is suitable for water inrush cracks that require rapid sealing.

[0075] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A dual-response grouting material with magnetron thixotropic properties, characterized in that, It consists of the following components in parts by weight: 100 parts of cementitious substrate; 5-20 parts of high magnetic susceptibility soft magnetic particles; 3-12 parts of high remanence hard magnetic particles; 0.5-3 parts of functional additives; 30-60 parts of mixing water; Among them, the coercivity Hc of the high magnetic susceptibility soft magnetic particles is < 200 Oe, and the saturation magnetization Ms is > 80 emu / g; The coercivity Hc of the high remanence hard magnetic particles is > 1 kOe, and the remanence Mr is > 30 emu / g.

2. The dual-response grouting material with magnetron thixotropic properties according to claim 1, characterized in that, The high magnetic susceptibility soft magnetic particles are selected from one or more of Fe3O4 microspheres, carbonyl iron powder, and iron-nickel alloy particles, with a particle size of 1~30μm.

3. The dual-response grouting material with magnetron thixotropic properties according to claim 1, characterized in that, The high remanence hard magnetic particles are selected from one or more of neodymium iron boron nanoparticles, samarium cobalt nanoparticles, and barium ferrite nanoparticles, with a particle size of 50~500 nm.

4. The dual-response grouting material with magnetron thixotropic properties according to claim 1, characterized in that, The functional additives include at least one of polycarboxylate water-reducing and dispersing agents and naphthalene sulfonate water-reducing and dispersing agents.

5. A dual-response grouting material with magnetron thixotropic properties according to claim 4, characterized in that, The cementitious substrate is selected from cement or geopolymer; When the cementitious substrate is cement, the dual-response grouting material with magnetotropic thixotropic properties comprises the following components: Cement, high magnetic susceptibility soft magnetic particles, high remanence hard magnetic particles, functional admixtures and mixing water, wherein the functional admixtures are polycarboxylate water-reducing and dispersing agents, naphthalene sulfonate water-reducing and dispersing agents or a mixture of the two. When the cementitious substrate is a geopolymer, the dual-response grouting material with magnetron thixotropic properties comprises the following components: Blast furnace slag powder, fly ash, sodium metasilicate pentahydrate powder, high magnetic susceptibility soft magnetic particles, high remanence hard magnetic particles, naphthalene sulfonate water-reducing dispersant and mixing water.

6. The dual-response grouting material with magnetron thixotropic properties according to claim 5, characterized in that, The cement is selected from any one of PO 42.5 silicate cement, sulfoaluminate cement and ultrafine cement.

7. A method for preparing a dual-response grouting material with magnetron thixotropic properties as described in any one of claims 1-6, characterized in that, Includes the following steps: (1) Pre-magnetize the high remanence hard magnetic particles; (2) Dry mix the cementitious substrate, high magnetic susceptibility soft magnetic particles, and pre-magnetized high remanence hard magnetic particles evenly; (3) Dissolve the functional additives in the mixing water, add the mixed powder obtained in step (2), stir until uniform, and obtain the slurry, which is the dual-response grouting material.

8. The method for preparing a dual-response grouting material with magnetron thixotropic properties according to claim 7, characterized in that, The conditions for the pre-magnetization treatment in step (1) are: magnetic field strength of 1~3T and pulse number of 1~5 times.

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