Low-magnetism concrete and preparation method thereof

Abstract

The invention relates to the field of civil engineering materials, in particular to low-magnetism concrete and a preparation method thereof. The invention relates to low-magnetism concrete, which is prepared from the following components in percentage by mass: 7 to 12 percent of special cement, 2.8 to 5.0 percent of silica fume, 4.5 to 7.5 percent of blast furnace slag powder, 45 to 60 percent of coarse aggregate, 15 to 25 percent of fine aggregate, 0.2 to 0.4 percent of functional additive, 4.5 to 7.0 percent of deionized water and 0.04 to 0.08 percent of water reducing agent. The special cement comprises a protein foaming agent and non-magnetic cement, the coarse aggregate and the fine aggregate are raw materials subjected to magnetic separation, and the functional additive is nano SiO2 modified by a titanate coupling agent. The problems that in the prior art, concrete has magnetism, precision instruments or facilities with requirements for magnetism can be affected, and normal work of the precision instruments or the facilities is affected are solved.

Description

Technical Field

[0001] This invention relates to the field of civil engineering materials, and more particularly to a low-magnetic concrete and its preparation method. Background Technology

[0002] Concrete is a fundamental material in modern construction, composed of cement, water, sand (fine aggregate), and gravel (coarse aggregate). In most buildings, its strength, durability, and cost-effectiveness are primary considerations. However, a minor "defect" in ordinary concrete is often overlooked: it contains extremely weak magnetism. This magnetism primarily originates from unavoidable trace amounts of ferromagnetic mineral impurities, such as magnetite (Fe3O4) particles, found in natural aggregates (sand and gravel).

[0003] Although these impurities may be present in quantities of only a few parts per ten thousand or even lower, completely undetectable in daily life and having no impact on building structures or the human body, such weak magnetism becomes a significant source of interference for some precision scientific and medical equipment that requires extremely stringent magnetic field conditions. For example, in particle accelerators (such as the Large Hadron Collider LHC), detectors need to capture extremely weak signals generated by particle collisions. Even the slightest magnetic interference from surrounding building materials can drown out crucial experimental signals like noise.

[0004] With the rapid development of magnetic detection technology, precision instrument manufacturing, and defense technology, the demand for special facilities such as geomagnetic observatories, high-precision magnetic laboratories, and specific defense projects has increased significantly. These facilities all require a building environment with a low magnetic background and a highly stable magnetic field distribution to avoid interference from external or internal material magnetism on precision measurements and equipment operation. This necessitates the development of a low-magnetic concrete. Summary of the Invention

[0005] In view of this, the present invention provides a low-magnetic concrete to solve the problem that the magnetic properties of concrete in the prior art can affect precision instruments or facilities that require magnetic properties, thus affecting their normal operation; the present invention also provides a method for preparing low-magnetic concrete to solve the above-mentioned technical problems.

[0006] A low-magnetic concrete comprises special cement, silica fume, blast furnace slag powder, coarse aggregate, fine aggregate, functional additives, deionized water, and water-reducing agent. The mass percentages of each component are as follows: special cement 7-12%, silica fume 2.8-5.0%, blast furnace slag powder 4.5-7.5%, coarse aggregate 45-60%, fine aggregate 15-25%, functional additives 0.2-0.4%, deionized water 4.5-7.0%, and water-reducing agent 0.04-0.08%. The special cement contains a protein-based foaming agent and non-magnetic cement. The coarse and fine aggregates are raw materials that have undergone magnetic separation. The functional additive is nano-SiO2 modified with a titanate coupling agent.

[0007] Furthermore, the coarse aggregate is magnetically separated quartzite aggregate with an Fe content of <0.01%; the fine aggregate is recycled ceramic fine aggregate with a magnetic susceptibility of ≤0.5×10⁻⁶. -8 m 3 / kg.

[0008] Furthermore, the special cement contains a protein-based foaming agent content of 0.5-1.2% of the weight of the low-magnetic concrete.

[0009] Furthermore, the Fe content in the non-magnetic cement is <0.01%.

[0010] Furthermore, the silica fume is silica fume containing ≥95% amorphous SiO2.

[0011] Furthermore, the blast furnace slag is blast furnace slag after magnetic separation, with an Fe content ≤0.08%.

[0012] The beneficial effects of the low-magnetic concrete in this invention are as follows: This invention uses a certain amount of special cement, silica fume, blast furnace slag powder, coarse aggregate, fine aggregate, functional additives, deionized water, and water-reducing agent to prepare low-magnetic concrete. By adding a protein-based foaming agent to the cement, an effective closed-cell structure is ensured, blocking the continuous conduction of magnetic domains and reducing remanent magnetization. Simultaneously, the iron content in the cement is controlled to facilitate further reduction of the magnetic properties of the concrete after molding. By assembling the special cement, silica fume, and blast furnace slag into a cementitious material system, the path to ferromagnetic phase formation can be blocked, reducing Fe... 3+ Solid solution; by using nano-SiO2 modified with titanate coupling agent, residual magnetic particles can be encapsulated, blocking the formation of magnetic domains. At the same time, the compressive strength and durability are improved through the interfacial reinforcement effect of nano-SiO2. In addition, by magnetically separating coarse and fine aggregates, the magnetism within the coarse and fine aggregates is reduced. Since aggregates account for the majority of the concrete composition, the magnetism of the finished concrete product can be significantly reduced. This solves the problem in the prior art that the presence of magnetism in concrete can affect precision instruments or facilities with magnetic requirements, thus affecting their normal operation.

[0013] A method for preparing low-magnetic concrete involves using the raw material components of the aforementioned low-magnetic concrete. Special cement, silica fume, and blast furnace slag powder are mixed and stirred evenly to obtain gel material A. Deionized water is magnetized, and the magnetized deionized water, functional additives, and water-reducing agent are mixed and stirred evenly to obtain admixture B. Admixture B is added to gel material A and mixed and stirred evenly to obtain mixture C. Then, coarse aggregate and fine aggregate are added to mixture C and mixed and stirred evenly to obtain concrete. Finally, a demagnetization process is performed to obtain low-magnetic concrete.

[0014] Furthermore, when magnetizing deionized water, the deionized water is passed through a neodymium iron boron magnetic field, keeping the water flow direction perpendicular to the direction of the magnetic field lines.

[0015] Furthermore, when magnetizing deionized water, the magnetic field strength is controlled at 0.5-0.8T, the water flow rate is controlled at 1.5-2.0m / s, and the process is repeated three times.

[0016] Furthermore, during the demagnetization process, an alternating decaying magnetic field of 50Hz→0Hz is applied to the concrete.

[0017] The beneficial effects of the low-magnetic concrete preparation method of this invention are as follows: This method uses the aforementioned raw material components of low-magnetic concrete, employing a certain amount of special cement, silica fume, blast furnace slag powder, coarse aggregate, fine aggregate, functional additives, deionized water, and water-reducing agent to prepare low-magnetic concrete. By adding a protein-based foaming agent to the cement, an effective closed-cell structure is ensured, blocking the continuous conduction of magnetic domains and reducing remanent magnetization. Simultaneously, controlling the iron content in the cement facilitates further reduction of the magnetic properties of the concrete after molding. By assembling the special cement, silica fume, and blast furnace slag into a cementitious material system, the path to ferromagnetic phase formation can be blocked, reducing Fe... 3+ Solid solution; nano-SiO modified by using titanate coupling agent π This process can encapsulate residual magnetic particles, blocking magnetic domain formation, and simultaneously enhance compressive strength and durability through the interface reinforcement effect of nano-SiO2. Furthermore, magnetic separation of coarse and fine aggregates reduces their magnetism; since aggregates constitute the majority of concrete, this significantly reduces the magnetism of the finished concrete product. Additionally, magnetizing deionized water before mixing disrupts hydrogen bonds in water molecules, reducing the magnetic order of hydration products. Separately manufacturing gel material A and admixture B allows for thorough mixing of gel material A, which, after mixing, better blocks the ferromagnetic phase formation pathway and reduces Fe... 3+The role of solid solutions: After obtaining concrete, a demagnetization process is performed to further reduce the magnetism of the concrete, thereby solving the problem in existing technologies where the presence of magnetism in concrete can affect precision instruments or facilities that require magnetic properties, thus affecting their normal operation. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below through specific embodiments. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0019] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0020] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various information, such information should not be limited to these terms and should not be construed as indicating or implying relative importance. These terms are used only to distinguish information of the same type from one another. For example, without departing from the scope of this disclosure, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0021] In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two components. They can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0022] In the following description, suffixes such as "module," "part," or "unit" used to denote elements are used only for the convenience of the description of the invention and have no specific meaning in themselves. Therefore, "module" and "part" can be used interchangeably.

[0023] To better understand the technical solution of the present invention, the present invention will be described in detail below.

[0024] In Example 1 of the low-magnetic concrete of this invention:

[0025] In this embodiment, the low-magnetic concrete includes special cement, silica fume, blast furnace slag powder, coarse aggregate, fine aggregate, functional additives, deionized water, and water-reducing agent. The mass percentages of each component are as follows: special cement 7-12%, silica fume 2.8-5.0%, blast furnace slag powder 4.5-7.5%, coarse aggregate 45-60%, fine aggregate 15-25%, functional additives 0.2-0.4%, deionized water 4.5-7.0%, and water-reducing agent 0.04-0.08%. Since the coarse and fine aggregates constitute a large proportion by weight, their magnetic properties directly affect the magnetic properties of the concrete. Therefore, magnetic separation is required for both coarse and fine aggregates. Specifically, in this embodiment, the coarse aggregate is magnetically separated quartzite aggregate with an Fe content <0.01%; the fine aggregate is recycled ceramic fine aggregate with a magnetic susceptibility ≤0.5×10⁻⁶. -8 m 3 / kg. By reducing the iron content in the aggregates that make up a large proportion of concrete, the iron content in the finished concrete can be significantly reduced, thereby reducing magnetism. At the same time, the addition of ceramic fine aggregates can reduce Cl- permeability, thus reducing the rate of electrochemical corrosion.

[0026] In addition, the special cement contains protein-based foaming agents and non-magnetic cement. The protein-based foaming agent content is 0.5-1.2%, and the Fe content in the non-magnetic cement is <0.01%. Adding protein-based foaming agents to the cement ensures the formation of an effective closed-cell structure, blocking the continuous conduction of magnetic domains and reducing remanence. The blast furnace slag is magnetically separated blast furnace slag with an Fe content ≤0.08%. The silica fume is amorphous silica fume with SiO2 ≥95%. The special cement, silica fume, and blast furnace slag can form a gel material system, thereby blocking the ferromagnetic phase formation pathway and reducing Fe content. 3+ Solid solutions, which in turn reduce the magnetism of concrete.

[0027] The functional additive is nano-SiO2 modified with a titanate coupling agent, which can encapsulate residual magnetic particles, block the formation of magnetic domains, and improve compressive strength and durability through the interfacial reinforcement effect of nano-SiO2. Water and a water-reducing agent are also required during concrete mixing. In this embodiment, the water-reducing agent is a polycarboxylate water-reducing agent with a water reduction rate ≥30%. The water used is deionized water that has undergone magnetization treatment. After treatment, the hydrogen bond clusters of water molecules in the deionized water are destroyed, thereby reducing the magnetic order of the water splash product.

[0028] Specifically, in this embodiment, the concrete comprises the following components by mass fraction: 9.6% special cement, 3.8% silica fume, 5.8% blast furnace slag powder, 53.5% coarse aggregate, 22.9% fine aggregate, 0.29% functional additives, 5.0% deionized water, and 0.06% water-reducing agent. The special cement contains 0.5% protein-based foaming agent. The mass fraction refers to the mass fraction of the material in the concrete. The deionized water is circulated three times through a neodymium iron boron magnetic field with a magnetic field strength of 0.6T, and the water flow velocity is 1.8m / s with the water flow perpendicular to the magnetic field lines.

[0029] The fluidity of low-magnetic concrete was tested according to JGJ / T70-2009, the compressive strength according to GB / T50081-2019, and the remanence strength according to EN50147-3. The results showed that the fluidity of the low-magnetic concrete was 175 mm, the 28-day compressive strength was 69.7 MPa, and the remanence strength was 5.3 nT.

[0030] In Example 2 of the low-magnetic concrete of this invention:

[0031] The proportions of each component in this embodiment differ from those in Embodiment 1. In this embodiment, the special cement is 8.2%, silica fume is 3.3%, blast furnace slag powder is 6.8%, coarse aggregate is 48.7%, fine aggregate is 26.3%, functional additives are 0.23%, deionized water is 6.2%, and water-reducing agent is 0.05%. The amount of protein foaming agent in the special cement is 0.8%. The mass fraction refers to the mass fraction of the material in the concrete. The deionized water is circulated three times through a neodymium iron boron magnetic field with a magnetic field strength of 0.7T, the water flow rate is 1.6m / s, and the water flow is perpendicular to the magnetic field lines.

[0032] The fluidity of low-magnetic concrete was tested according to JGJ / T70-2009, the compressive strength according to GB / T50081-2019, and the remanence strength according to EN50147-3. The results showed that the fluidity of the low-magnetic concrete was 190 mm, the 28-day compressive strength was 62.4 MPa, and the remanence strength was 7.8 nT.

[0033] In Example 3 of the low-magnetic concrete of this invention:

[0034] The proportions of each component in this embodiment differ from those in Embodiment 1. In this embodiment, the special cement is 11.5%, silica fume is 4.6%, blast furnace slag powder is 4.5%, coarse aggregate is 58.2%, fine aggregate is 19.3%, functional additives are 0.38%, deionized water is 5.1%, and water-reducing agent is 0.08%. The protein foaming agent in the special cement is 1.2%. The mass fraction refers to the mass fraction of the material in the concrete. The deionized water is circulated three times through a neodymium iron boron magnetic field with a magnetic field strength of 0.5T, the water flow rate is 2.0m / s, and the water flow is perpendicular to the magnetic field lines.

[0035] The fluidity of low-magnetic concrete was tested according to JGJ / T70-2009, the compressive strength according to GB / T50081-2019, and the remanence strength according to EN50147-3. The results showed that the fluidity of the low-magnetic concrete was 190 mm, the 28-day compressive strength was 72.1 MPa, and the remanence strength was 4.9 nT.

[0036] In Example 1 of the method for preparing low-magnetic concrete in this invention (hereinafter referred to as the preparation method):

[0037] The preparation method of this invention uses the raw material ratio of any one of Examples 1-3 of the above-mentioned low-magnetic concrete, and specifically includes the following steps.

[0038] S1, special cement, silica fume and blast furnace slag powder are mixed and stirred evenly to obtain gel material A. The stirring time in this embodiment is not less than 2 minutes. At the same time, deionized water is magnetized. During the treatment, the deionized water is circulated three times and subjected to a neodymium iron boron magnetic field with a magnetic field strength of 0.5T.

[0039] S2, mix water, functional additives and water-reducing agent and stir evenly to obtain additive B, pour water-reducing agent B into gel material A and mix and stir evenly to obtain mixture C, stir evenly, and the stirring time in this embodiment is not less than 1 minute;

[0040] S3, pour the coarse aggregate and fine aggregate into the mixture C and mix and stir evenly for no less than 2 minutes to obtain concrete;

[0041] S4. Apply an alternating decaying magnetic field of 50Hz→0Hz to the concrete and perform a demagnetization process to obtain low-magnetic concrete.

[0042] It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A low-magnetic concrete, characterized in that: The product comprises special cement, silica fume, blast furnace slag powder, coarse aggregate, fine aggregate, functional additives, deionized water, and water-reducing agent. The mass percentages of each component are as follows: special cement 7-12%, silica fume 2.8-5.0%, blast furnace slag powder 4.5-7.5%, coarse aggregate 45-60%, fine aggregate 15-25%, functional additives 0.2-0.4%, deionized water 4.5-7.0%, and water-reducing agent 0.04-0.08%. The special cement contains protein-based foaming agents and non-magnetic cement. The coarse and fine aggregates are raw materials that have undergone magnetic separation. The functional additive is nano-SiO2 modified with titanate coupling agent.

2. The low-magnetic concrete according to claim 1, characterized in that: The coarse aggregate is magnetically separated quartzite aggregate with an Fe content of <0.01%; the fine aggregate is recycled ceramic fine aggregate with a magnetic susceptibility of ≤0.5×10⁻⁶. -8 m 3 / kg.

3. The low-magnetic concrete according to claim 1 or 2, characterized in that: The special cement contains protein as a foaming agent, with a content of 0.5-1.2% of the weight of the low-magnetic concrete.

4. The low-magnetic concrete according to claim 1 or 2, characterized in that: The Fe content in the non-magnetic cement is <0.01%.

5. The low-magnetic concrete according to claim 1 or 2, characterized in that: The silica fume is amorphous SiO2 ≥ 95% silica fume.

6. The low-magnetic concrete according to claim 1 or 2, characterized in that: The blast furnace slag is blast furnace slag after magnetic separation, with an Fe content of ≤0.08%.

7. A method for preparing low-magnetic concrete, characterized in that: Using the raw material components of the low-magnetic concrete according to any one of claims 1-6, special cement, silica fume, and blast furnace slag powder are mixed and stirred evenly to obtain gel material A; deionized water is magnetized, and the magnetized deionized water, functional additives, and water-reducing agent are mixed and stirred evenly to obtain admixture B; admixture B is poured into gel material A and mixed and stirred evenly to obtain mixture C; then, coarse aggregate and fine aggregate are poured into mixture C and mixed and stirred evenly to obtain concrete; finally, a demagnetization process is performed to obtain low-magnetic concrete.

8. The method for preparing low-magnetic concrete according to claim 7, characterized in that: When magnetizing deionized water, the water is passed through a neodymium iron boron magnetic field, keeping the direction of water flow perpendicular to the direction of the magnetic field lines.

9. The method for preparing low-magnetic concrete according to claim 8, characterized in that: When magnetizing deionized water, the magnetic field strength is controlled at 0.5-0.8T, the water flow rate is controlled at 1.5-2.0m / s, and the water is treated in three cycles.

10. The method for preparing low-magnetic concrete according to any one of claims 7-9, characterized in that: During the demagnetization process, an alternating decaying magnetic field of 50Hz→0Hz is applied to the concrete.